File: channel.c

package info (click to toggle)
starlink-ast 8.0.2%2Bdfsg-2
  • links: PTS, VCS
  • area: main
  • in suites: jessie, jessie-kfreebsd
  • size: 25,004 kB
  • ctags: 13,896
  • sloc: ansic: 167,825; sh: 11,448; makefile: 640; perl: 158
file content (6458 lines) | stat: -rw-r--r-- 228,082 bytes parent folder | download | duplicates (2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982
3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
4121
4122
4123
4124
4125
4126
4127
4128
4129
4130
4131
4132
4133
4134
4135
4136
4137
4138
4139
4140
4141
4142
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
4153
4154
4155
4156
4157
4158
4159
4160
4161
4162
4163
4164
4165
4166
4167
4168
4169
4170
4171
4172
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4183
4184
4185
4186
4187
4188
4189
4190
4191
4192
4193
4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
4209
4210
4211
4212
4213
4214
4215
4216
4217
4218
4219
4220
4221
4222
4223
4224
4225
4226
4227
4228
4229
4230
4231
4232
4233
4234
4235
4236
4237
4238
4239
4240
4241
4242
4243
4244
4245
4246
4247
4248
4249
4250
4251
4252
4253
4254
4255
4256
4257
4258
4259
4260
4261
4262
4263
4264
4265
4266
4267
4268
4269
4270
4271
4272
4273
4274
4275
4276
4277
4278
4279
4280
4281
4282
4283
4284
4285
4286
4287
4288
4289
4290
4291
4292
4293
4294
4295
4296
4297
4298
4299
4300
4301
4302
4303
4304
4305
4306
4307
4308
4309
4310
4311
4312
4313
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
4332
4333
4334
4335
4336
4337
4338
4339
4340
4341
4342
4343
4344
4345
4346
4347
4348
4349
4350
4351
4352
4353
4354
4355
4356
4357
4358
4359
4360
4361
4362
4363
4364
4365
4366
4367
4368
4369
4370
4371
4372
4373
4374
4375
4376
4377
4378
4379
4380
4381
4382
4383
4384
4385
4386
4387
4388
4389
4390
4391
4392
4393
4394
4395
4396
4397
4398
4399
4400
4401
4402
4403
4404
4405
4406
4407
4408
4409
4410
4411
4412
4413
4414
4415
4416
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
4427
4428
4429
4430
4431
4432
4433
4434
4435
4436
4437
4438
4439
4440
4441
4442
4443
4444
4445
4446
4447
4448
4449
4450
4451
4452
4453
4454
4455
4456
4457
4458
4459
4460
4461
4462
4463
4464
4465
4466
4467
4468
4469
4470
4471
4472
4473
4474
4475
4476
4477
4478
4479
4480
4481
4482
4483
4484
4485
4486
4487
4488
4489
4490
4491
4492
4493
4494
4495
4496
4497
4498
4499
4500
4501
4502
4503
4504
4505
4506
4507
4508
4509
4510
4511
4512
4513
4514
4515
4516
4517
4518
4519
4520
4521
4522
4523
4524
4525
4526
4527
4528
4529
4530
4531
4532
4533
4534
4535
4536
4537
4538
4539
4540
4541
4542
4543
4544
4545
4546
4547
4548
4549
4550
4551
4552
4553
4554
4555
4556
4557
4558
4559
4560
4561
4562
4563
4564
4565
4566
4567
4568
4569
4570
4571
4572
4573
4574
4575
4576
4577
4578
4579
4580
4581
4582
4583
4584
4585
4586
4587
4588
4589
4590
4591
4592
4593
4594
4595
4596
4597
4598
4599
4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614
4615
4616
4617
4618
4619
4620
4621
4622
4623
4624
4625
4626
4627
4628
4629
4630
4631
4632
4633
4634
4635
4636
4637
4638
4639
4640
4641
4642
4643
4644
4645
4646
4647
4648
4649
4650
4651
4652
4653
4654
4655
4656
4657
4658
4659
4660
4661
4662
4663
4664
4665
4666
4667
4668
4669
4670
4671
4672
4673
4674
4675
4676
4677
4678
4679
4680
4681
4682
4683
4684
4685
4686
4687
4688
4689
4690
4691
4692
4693
4694
4695
4696
4697
4698
4699
4700
4701
4702
4703
4704
4705
4706
4707
4708
4709
4710
4711
4712
4713
4714
4715
4716
4717
4718
4719
4720
4721
4722
4723
4724
4725
4726
4727
4728
4729
4730
4731
4732
4733
4734
4735
4736
4737
4738
4739
4740
4741
4742
4743
4744
4745
4746
4747
4748
4749
4750
4751
4752
4753
4754
4755
4756
4757
4758
4759
4760
4761
4762
4763
4764
4765
4766
4767
4768
4769
4770
4771
4772
4773
4774
4775
4776
4777
4778
4779
4780
4781
4782
4783
4784
4785
4786
4787
4788
4789
4790
4791
4792
4793
4794
4795
4796
4797
4798
4799
4800
4801
4802
4803
4804
4805
4806
4807
4808
4809
4810
4811
4812
4813
4814
4815
4816
4817
4818
4819
4820
4821
4822
4823
4824
4825
4826
4827
4828
4829
4830
4831
4832
4833
4834
4835
4836
4837
4838
4839
4840
4841
4842
4843
4844
4845
4846
4847
4848
4849
4850
4851
4852
4853
4854
4855
4856
4857
4858
4859
4860
4861
4862
4863
4864
4865
4866
4867
4868
4869
4870
4871
4872
4873
4874
4875
4876
4877
4878
4879
4880
4881
4882
4883
4884
4885
4886
4887
4888
4889
4890
4891
4892
4893
4894
4895
4896
4897
4898
4899
4900
4901
4902
4903
4904
4905
4906
4907
4908
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
4934
4935
4936
4937
4938
4939
4940
4941
4942
4943
4944
4945
4946
4947
4948
4949
4950
4951
4952
4953
4954
4955
4956
4957
4958
4959
4960
4961
4962
4963
4964
4965
4966
4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
4986
4987
4988
4989
4990
4991
4992
4993
4994
4995
4996
4997
4998
4999
5000
5001
5002
5003
5004
5005
5006
5007
5008
5009
5010
5011
5012
5013
5014
5015
5016
5017
5018
5019
5020
5021
5022
5023
5024
5025
5026
5027
5028
5029
5030
5031
5032
5033
5034
5035
5036
5037
5038
5039
5040
5041
5042
5043
5044
5045
5046
5047
5048
5049
5050
5051
5052
5053
5054
5055
5056
5057
5058
5059
5060
5061
5062
5063
5064
5065
5066
5067
5068
5069
5070
5071
5072
5073
5074
5075
5076
5077
5078
5079
5080
5081
5082
5083
5084
5085
5086
5087
5088
5089
5090
5091
5092
5093
5094
5095
5096
5097
5098
5099
5100
5101
5102
5103
5104
5105
5106
5107
5108
5109
5110
5111
5112
5113
5114
5115
5116
5117
5118
5119
5120
5121
5122
5123
5124
5125
5126
5127
5128
5129
5130
5131
5132
5133
5134
5135
5136
5137
5138
5139
5140
5141
5142
5143
5144
5145
5146
5147
5148
5149
5150
5151
5152
5153
5154
5155
5156
5157
5158
5159
5160
5161
5162
5163
5164
5165
5166
5167
5168
5169
5170
5171
5172
5173
5174
5175
5176
5177
5178
5179
5180
5181
5182
5183
5184
5185
5186
5187
5188
5189
5190
5191
5192
5193
5194
5195
5196
5197
5198
5199
5200
5201
5202
5203
5204
5205
5206
5207
5208
5209
5210
5211
5212
5213
5214
5215
5216
5217
5218
5219
5220
5221
5222
5223
5224
5225
5226
5227
5228
5229
5230
5231
5232
5233
5234
5235
5236
5237
5238
5239
5240
5241
5242
5243
5244
5245
5246
5247
5248
5249
5250
5251
5252
5253
5254
5255
5256
5257
5258
5259
5260
5261
5262
5263
5264
5265
5266
5267
5268
5269
5270
5271
5272
5273
5274
5275
5276
5277
5278
5279
5280
5281
5282
5283
5284
5285
5286
5287
5288
5289
5290
5291
5292
5293
5294
5295
5296
5297
5298
5299
5300
5301
5302
5303
5304
5305
5306
5307
5308
5309
5310
5311
5312
5313
5314
5315
5316
5317
5318
5319
5320
5321
5322
5323
5324
5325
5326
5327
5328
5329
5330
5331
5332
5333
5334
5335
5336
5337
5338
5339
5340
5341
5342
5343
5344
5345
5346
5347
5348
5349
5350
5351
5352
5353
5354
5355
5356
5357
5358
5359
5360
5361
5362
5363
5364
5365
5366
5367
5368
5369
5370
5371
5372
5373
5374
5375
5376
5377
5378
5379
5380
5381
5382
5383
5384
5385
5386
5387
5388
5389
5390
5391
5392
5393
5394
5395
5396
5397
5398
5399
5400
5401
5402
5403
5404
5405
5406
5407
5408
5409
5410
5411
5412
5413
5414
5415
5416
5417
5418
5419
5420
5421
5422
5423
5424
5425
5426
5427
5428
5429
5430
5431
5432
5433
5434
5435
5436
5437
5438
5439
5440
5441
5442
5443
5444
5445
5446
5447
5448
5449
5450
5451
5452
5453
5454
5455
5456
5457
5458
5459
5460
5461
5462
5463
5464
5465
5466
5467
5468
5469
5470
5471
5472
5473
5474
5475
5476
5477
5478
5479
5480
5481
5482
5483
5484
5485
5486
5487
5488
5489
5490
5491
5492
5493
5494
5495
5496
5497
5498
5499
5500
5501
5502
5503
5504
5505
5506
5507
5508
5509
5510
5511
5512
5513
5514
5515
5516
5517
5518
5519
5520
5521
5522
5523
5524
5525
5526
5527
5528
5529
5530
5531
5532
5533
5534
5535
5536
5537
5538
5539
5540
5541
5542
5543
5544
5545
5546
5547
5548
5549
5550
5551
5552
5553
5554
5555
5556
5557
5558
5559
5560
5561
5562
5563
5564
5565
5566
5567
5568
5569
5570
5571
5572
5573
5574
5575
5576
5577
5578
5579
5580
5581
5582
5583
5584
5585
5586
5587
5588
5589
5590
5591
5592
5593
5594
5595
5596
5597
5598
5599
5600
5601
5602
5603
5604
5605
5606
5607
5608
5609
5610
5611
5612
5613
5614
5615
5616
5617
5618
5619
5620
5621
5622
5623
5624
5625
5626
5627
5628
5629
5630
5631
5632
5633
5634
5635
5636
5637
5638
5639
5640
5641
5642
5643
5644
5645
5646
5647
5648
5649
5650
5651
5652
5653
5654
5655
5656
5657
5658
5659
5660
5661
5662
5663
5664
5665
5666
5667
5668
5669
5670
5671
5672
5673
5674
5675
5676
5677
5678
5679
5680
5681
5682
5683
5684
5685
5686
5687
5688
5689
5690
5691
5692
5693
5694
5695
5696
5697
5698
5699
5700
5701
5702
5703
5704
5705
5706
5707
5708
5709
5710
5711
5712
5713
5714
5715
5716
5717
5718
5719
5720
5721
5722
5723
5724
5725
5726
5727
5728
5729
5730
5731
5732
5733
5734
5735
5736
5737
5738
5739
5740
5741
5742
5743
5744
5745
5746
5747
5748
5749
5750
5751
5752
5753
5754
5755
5756
5757
5758
5759
5760
5761
5762
5763
5764
5765
5766
5767
5768
5769
5770
5771
5772
5773
5774
5775
5776
5777
5778
5779
5780
5781
5782
5783
5784
5785
5786
5787
5788
5789
5790
5791
5792
5793
5794
5795
5796
5797
5798
5799
5800
5801
5802
5803
5804
5805
5806
5807
5808
5809
5810
5811
5812
5813
5814
5815
5816
5817
5818
5819
5820
5821
5822
5823
5824
5825
5826
5827
5828
5829
5830
5831
5832
5833
5834
5835
5836
5837
5838
5839
5840
5841
5842
5843
5844
5845
5846
5847
5848
5849
5850
5851
5852
5853
5854
5855
5856
5857
5858
5859
5860
5861
5862
5863
5864
5865
5866
5867
5868
5869
5870
5871
5872
5873
5874
5875
5876
5877
5878
5879
5880
5881
5882
5883
5884
5885
5886
5887
5888
5889
5890
5891
5892
5893
5894
5895
5896
5897
5898
5899
5900
5901
5902
5903
5904
5905
5906
5907
5908
5909
5910
5911
5912
5913
5914
5915
5916
5917
5918
5919
5920
5921
5922
5923
5924
5925
5926
5927
5928
5929
5930
5931
5932
5933
5934
5935
5936
5937
5938
5939
5940
5941
5942
5943
5944
5945
5946
5947
5948
5949
5950
5951
5952
5953
5954
5955
5956
5957
5958
5959
5960
5961
5962
5963
5964
5965
5966
5967
5968
5969
5970
5971
5972
5973
5974
5975
5976
5977
5978
5979
5980
5981
5982
5983
5984
5985
5986
5987
5988
5989
5990
5991
5992
5993
5994
5995
5996
5997
5998
5999
6000
6001
6002
6003
6004
6005
6006
6007
6008
6009
6010
6011
6012
6013
6014
6015
6016
6017
6018
6019
6020
6021
6022
6023
6024
6025
6026
6027
6028
6029
6030
6031
6032
6033
6034
6035
6036
6037
6038
6039
6040
6041
6042
6043
6044
6045
6046
6047
6048
6049
6050
6051
6052
6053
6054
6055
6056
6057
6058
6059
6060
6061
6062
6063
6064
6065
6066
6067
6068
6069
6070
6071
6072
6073
6074
6075
6076
6077
6078
6079
6080
6081
6082
6083
6084
6085
6086
6087
6088
6089
6090
6091
6092
6093
6094
6095
6096
6097
6098
6099
6100
6101
6102
6103
6104
6105
6106
6107
6108
6109
6110
6111
6112
6113
6114
6115
6116
6117
6118
6119
6120
6121
6122
6123
6124
6125
6126
6127
6128
6129
6130
6131
6132
6133
6134
6135
6136
6137
6138
6139
6140
6141
6142
6143
6144
6145
6146
6147
6148
6149
6150
6151
6152
6153
6154
6155
6156
6157
6158
6159
6160
6161
6162
6163
6164
6165
6166
6167
6168
6169
6170
6171
6172
6173
6174
6175
6176
6177
6178
6179
6180
6181
6182
6183
6184
6185
6186
6187
6188
6189
6190
6191
6192
6193
6194
6195
6196
6197
6198
6199
6200
6201
6202
6203
6204
6205
6206
6207
6208
6209
6210
6211
6212
6213
6214
6215
6216
6217
6218
6219
6220
6221
6222
6223
6224
6225
6226
6227
6228
6229
6230
6231
6232
6233
6234
6235
6236
6237
6238
6239
6240
6241
6242
6243
6244
6245
6246
6247
6248
6249
6250
6251
6252
6253
6254
6255
6256
6257
6258
6259
6260
6261
6262
6263
6264
6265
6266
6267
6268
6269
6270
6271
6272
6273
6274
6275
6276
6277
6278
6279
6280
6281
6282
6283
6284
6285
6286
6287
6288
6289
6290
6291
6292
6293
6294
6295
6296
6297
6298
6299
6300
6301
6302
6303
6304
6305
6306
6307
6308
6309
6310
6311
6312
6313
6314
6315
6316
6317
6318
6319
6320
6321
6322
6323
6324
6325
6326
6327
6328
6329
6330
6331
6332
6333
6334
6335
6336
6337
6338
6339
6340
6341
6342
6343
6344
6345
6346
6347
6348
6349
6350
6351
6352
6353
6354
6355
6356
6357
6358
6359
6360
6361
6362
6363
6364
6365
6366
6367
6368
6369
6370
6371
6372
6373
6374
6375
6376
6377
6378
6379
6380
6381
6382
6383
6384
6385
6386
6387
6388
6389
6390
6391
6392
6393
6394
6395
6396
6397
6398
6399
6400
6401
6402
6403
6404
6405
6406
6407
6408
6409
6410
6411
6412
6413
6414
6415
6416
6417
6418
6419
6420
6421
6422
6423
6424
6425
6426
6427
6428
6429
6430
6431
6432
6433
6434
6435
6436
6437
6438
6439
6440
6441
6442
6443
6444
6445
6446
6447
6448
6449
6450
6451
6452
6453
6454
6455
6456
6457
6458
/*
*class++
*  Name:
*     Channel

*  Purpose:
*     Basic (textual) I/O channel.

*  Constructor Function:
c     astChannel
f     AST_CHANNEL

*  Description:
*     The Channel class implements low-level input/output for the AST
*     library.  Writing an Object to a Channel will generate a textual
*     representation of that Object, and reading from a Channel will
*     create a new Object from its textual representation.
*
*     Normally, when you use a Channel, you should provide "source"
c     and "sink" functions which connect it to an external data store
f     and "sink" routines which connect it to an external data store
*     by reading and writing the resulting text. By default, however,
*     a Channel will read from standard input and write to standard
*     output. Alternatively, a Channel can be told to read or write from
*     specific text files using the SinkFile and SourceFile attributes,
*     in which case no sink or source function need be supplied.

*  Inheritance:
*     The Channel class inherits from the Object class.

*  Attributes:
*     In addition to those attributes common to all Objects, every
*     Channel also has the following attributes:
*
*     - Comment: Include textual comments in output?
*     - Full: Set level of output detail
*     - Indent: Indentation increment between objects
*     - ReportLevel: Selects the level of error reporting
*     - SinkFile: The path to a file to which the Channel should write
*     - Skip: Skip irrelevant data?
*     - SourceFile: The path to a file from which the Channel should read
*     - Strict: Generate errors instead of warnings?

*  Functions:
c     In addition to those functions applicable to all Objects, the
c     following functions may also be applied to all Channels:
f     In addition to those routines applicable to all Objects, the
f     following routines may also be applied to all Channels:
*
c     - astWarnings: Return warnings from the previous read or write
c     - astPutChannelData: Store data to pass to source or sink functions
c     - astRead: Read an Object from a Channel
c     - astWrite: Write an Object to a Channel
f     - AST_WARNINGS: Return warnings from the previous read or write
f     - AST_READ: Read an Object from a Channel
f     - AST_WRITE: Write an Object to a Channel

*  Copyright:
*     Copyright (C) 1997-2006 Council for the Central Laboratory of the
*     Copyright (C) 2009 Science & Technology Facilities Council.
*     All Rights Reserved.
*     Research Councils

*  Licence:
*     This program is free software: you can redistribute it and/or
*     modify it under the terms of the GNU Lesser General Public
*     License as published by the Free Software Foundation, either
*     version 3 of the License, or (at your option) any later
*     version.
*     
*     This program is distributed in the hope that it will be useful,
*     but WITHOUT ANY WARRANTY; without even the implied warranty of
*     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*     GNU Lesser General Public License for more details.
*     
*     You should have received a copy of the GNU Lesser General
*     License along with this program.  If not, see
*     <http://www.gnu.org/licenses/>.

*  Authors:
*     RFWS: R.F. Warren-Smith (Starlink)

*  History:
*     12-AUG-1996 (RFWS):
*        Original version.
*     6-SEP-1996:
*        Finished initial implementation.
*     11-DEC-1996 (RFWS):
*        Added support for foreign language source and sink functions.
*     28-APR-1997 (RFWS):
*        Prevent "-0" being written (use "0" instead).
*     27-NOV-2002 (DSB):
*        Added astWriteInvocations.
*     8-JAN-2003 (DSB):
*        - Changed private InitVtab method to protected astInitChannelVtab
*        method.
*        - Modified to use protected Vtab initialisation methods when
*        loading an Object.
*     1-NOV-2003 (DSB):
*        Change the initialiser so that it accepts source and sink
*        wrapper functions as arguments (for use by derived classes).
*     16-AUG-2006 (DSB):
*        - Document non-destructive nature of unsuccessful astRead calls
*        on a FitsChan.
*     3-OCT-2008 (DSB):
*        Added "Strict" attribute.
*     11-DEC-2008 (DSB):
*        Added astPutChannelData and astChannelData functions.
*     16-JAN-2009 (DSB):
*        Added astAddWarning and astWarnings.
*     11-JUN-2009 (DSB):
*        Enable astChannelData to be used from within astRead.
*     7-DEC-2009 (DSB):
*        Added Indent attribute.
*     12-FEB-2010 (DSB):
*        Represent AST__BAD externally using the string "<bad>".
*     23-JUN-2011 (DSB):
*        Added attributes SinkFile and SourceFile.
*     2-OCT-2012 (DSB):
*        Report an error if an Inf or NaN value is read from the external
*        source.
*class--
*/

/* Module Macros. */
/* ============== */
/* Set the name of the class we are implementing. This indicates to
   the header files that define class interfaces that they should make
   "protected" symbols available. */
#define astCLASS Channel

/* Define a string containing the maximum length of keywords used to
   identify values in the external representation of data. This is
   deliberately kept small so as to simplify integration with
   standards such as FITS. */
#define MAX_NAME "8"

/* Max length of string returned by GetAttrib */
#define GETATTRIB_BUFF_LEN 50

/* String used to represent AST__BAD externally. */
#define BAD_STRING "<bad>"

/* Include files. */
/* ============== */
/* Interface definitions. */
/* ---------------------- */

#include "globals.h"             /* Thread-safe global data access */
#include "error.h"               /* Error reporting facilities */
#include "memory.h"              /* Memory allocation facilities */
#include "object.h"              /* Base Object class */
#include "channel.h"             /* Interface definition for this class */
#include "loader.h"              /* Interface to the global loader */
#include "keymap.h"              /* Storing arbitrary data in an AST Object */
#include "pointset.h"            /* For AST__BAD */

/* Error code definitions. */
/* ----------------------- */
#include "ast_err.h"             /* AST error codes */

/* C header files. */
/* --------------- */
#include <ctype.h>
#include <errno.h>
#include <float.h>
#include <limits.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>

/* Module Variables. */
/* ================= */

/* Address of this static variable is used as a unique identifier for
   member of this class. */
static int class_check;

/* Pointers to parent class methods which are extended by this class. */
static const char *(* parent_getattrib)( AstObject *, const char *, int * );
static int (* parent_testattrib)( AstObject *, const char *, int * );
static void (* parent_clearattrib)( AstObject *, const char *, int * );
static void (* parent_setattrib)( AstObject *, const char *, int * );

/* Define macros for accessing each item of thread specific global data. */
#ifdef THREAD_SAFE

/* Define how to initialise thread-specific globals. */
#define GLOBAL_inits \
   globals->Class_Init = 0; \
   globals->AstReadClassData_Msg = 0; \
   globals->GetAttrib_Buff[ 0 ] = 0; \
   globals->Items_Written = 0; \
   globals->Current_Indent = 0; \
   globals->Nest = -1; \
   globals->Nwrite_Invoc = 0; \
   globals->Object_Class = NULL; \
   globals->Values_List = NULL; \
   globals->Values_Class = NULL; \
   globals->Values_OK = NULL; \
   globals->End_Of_Object = NULL; \
   globals->Channel_Data  = NULL;

/* Create the function that initialises global data for this module. */
astMAKE_INITGLOBALS(Channel)

/* Define macros for accessing each item of thread specific global data. */
#define class_init astGLOBAL(Channel,Class_Init)
#define class_vtab astGLOBAL(Channel,Class_Vtab)
#define astreadclassdata_msg astGLOBAL(Channel,AstReadClassData_Msg)
#define getattrib_buff astGLOBAL(Channel,GetAttrib_Buff)
#define items_written  astGLOBAL(Channel,Items_Written)
#define current_indent astGLOBAL(Channel,Current_Indent)
#define nest           astGLOBAL(Channel,Nest)
#define nwrite_invoc   astGLOBAL(Channel,Nwrite_Invoc)
#define object_class   astGLOBAL(Channel,Object_Class)
#define values_list    astGLOBAL(Channel,Values_List)
#define values_class   astGLOBAL(Channel,Values_Class)
#define values_ok      astGLOBAL(Channel,Values_OK)
#define end_of_object  astGLOBAL(Channel,End_Of_Object)
#define channel_data   astGLOBAL(Channel,Channel_Data)



static pthread_mutex_t mutex2 = PTHREAD_MUTEX_INITIALIZER;
#define LOCK_MUTEX2 pthread_mutex_lock( &mutex2 );
#define UNLOCK_MUTEX2 pthread_mutex_unlock( &mutex2 );

static pthread_mutex_t mutex3 = PTHREAD_MUTEX_INITIALIZER;
#define LOCK_MUTEX3 pthread_mutex_lock( &mutex3 );
#define UNLOCK_MUTEX3 pthread_mutex_unlock( &mutex3 );

/* If thread safety is not needed, declare and initialise globals at static
   variables. */
#else

/* Contextual error message reported in astReadClassData? */
static int astreadclassdata_msg = 0;

/* Buffer returned by GetAttrib. */
static char getattrib_buff[ GETATTRIB_BUFF_LEN + 1 ];

/* Count of the number of output items written since the last "Begin"
   or "IsA" item. */
static int items_written = 0;

/* Amount of indentation to be applied to the next output item. */
static int current_indent = 0;

/* Nesting level, used to keep track of data associated with building
   Objects when they contain other Objects. */
static int nest = -1;

/* The number of times astWrite has been invoked. */
static int nwrite_invoc = 0;

/* Pointer to a user-supplied block of memory to be made available to
   source or sink functions via the astChannelData function. */
static void *channel_data = NULL;

/***
   The following items are all pointers to dynamically allocated
   arrays (stacks) that grow as necessary to accommodate one element
   for each level of nesting (one more than the value of "nest").
***/

/* Stack of pointers to null-terminated character strings giving the
   names of the classes of the Objects being built at each nesting
   level. */
static char **object_class = NULL;

/* Stack of pointers to the elements designated as the "heads" of
   circular, doubly linked lists of name-value associations. */
static AstChannelValue **values_list = NULL;

/* Stack of pointers to null-terminated character strings giving the
   names of the classes for which the values held in the values lists
   are intended. */
static char **values_class = NULL;

/* Stack of flags indicating whether the values held in the values
   lists are intended for the class loaders currently executing to
   build Objects at each nesting level. */
static int *values_ok = NULL;

/* Stack of flags indicating whether "End" items have been read for
   the Objects being built at each nesting level. */
static int *end_of_object = NULL;


/* Define the class virtual function table and its initialisation flag
   as static variables. */
static AstChannelVtab class_vtab;   /* Virtual function table */
static int class_init = 0;       /* Virtual function table initialised? */
#define LOCK_MUTEX2
#define UNLOCK_MUTEX2
#define LOCK_MUTEX3
#define UNLOCK_MUTEX3

#endif

/* External Interface Function Prototypes. */
/* ======================================= */
/* The following functions have public prototypes only (i.e. no
   protected prototypes), so we must provide local prototypes for use
   within this module. */
AstChannel *astChannelForId_( const char *(*)( void ),
                              char *(*)( const char *(*)( void ), int * ),
                              void (*)( const char * ),
                              void (*)( void (*)( const char * ),
                                        const char *, int * ),
                              const char *, ... );
AstChannel *astChannelId_( const char *(*)( void ), void (*)( const char * ), const char *, ... );

/* Prototypes for Private Member Functions. */
/* ======================================== */
static AstObject *Read( AstChannel *, int * );
static AstObject *ReadObject( AstChannel *, const char *, AstObject *, int * );
static AstChannelValue *FreeValue( AstChannelValue *, int * );
static AstChannelValue *LookupValue( const char *, int * );
static AstKeyMap *Warnings( AstChannel *, int * );
static char *GetNextText( AstChannel *, int * );
static char *InputTextItem( AstChannel *, int * );
static char *ReadString( AstChannel *, const char *, const char *, int * );
static char *SourceWrap( const char *(*)( void ), int * );
static const char *GetAttrib( AstObject *, const char *, int * );
static double ReadDouble( AstChannel *, const char *, double, int * );
static int GetComment( AstChannel *, int * );
static int GetFull( AstChannel *, int * );
static int GetSkip( AstChannel *, int * );
static int GetStrict( AstChannel *, int * );
static int ReadInt( AstChannel *, const char *, int, int * );
static int TestAttrib( AstObject *, const char *, int * );
static int TestComment( AstChannel *, int * );
static int TestFull( AstChannel *, int * );
static int TestSkip( AstChannel *, int * );
static int TestStrict( AstChannel *, int * );
static int Use( AstChannel *, int, int, int * );
static int Write( AstChannel *, AstObject *, int * );
static void AddWarning( AstChannel *, int, const char *, const char *, int * );
static void AppendValue( AstChannelValue *, AstChannelValue **, int * );
static void ClearAttrib( AstObject *, const char *, int * );
static void ClearComment( AstChannel *, int * );
static void ClearFull( AstChannel *, int * );
static void ClearSkip( AstChannel *, int * );
static void ClearStrict( AstChannel *, int * );
static void ClearValues( AstChannel *, int * );
static void Copy( const AstObject *, AstObject *, int * );
static void Delete( AstObject *, int * );
static void Dump( AstObject *, AstChannel *, int * );
static void GetNextData( AstChannel *, int, char **, char **, int * );
static void OutputTextItem( AstChannel *, const char *, int * );
static void PutChannelData( AstChannel *, void *, int * );
static void PutNextText( AstChannel *, const char *, int * );
static void ReadClassData( AstChannel *, const char *, int * );
static void RemoveValue( AstChannelValue *, AstChannelValue **, int * );
static void SetAttrib( AstObject *, const char *, int * );
static void SetComment( AstChannel *, int, int * );
static void SetFull( AstChannel *, int, int * );
static void SetSkip( AstChannel *, int, int * );
static void SetStrict( AstChannel *, int, int * );
static void SinkWrap( void (*)( const char * ), const char *, int * );
static void Unquote( AstChannel *, char *, int * );
static void WriteBegin( AstChannel *, const char *, const char *, int * );
static void WriteDouble( AstChannel *, const char *, int, int, double, const char *, int * );
static void WriteEnd( AstChannel *, const char *, int * );
static void WriteInt( AstChannel *, const char *, int, int, int, const char *, int * );
static void WriteIsA( AstChannel *, const char *, const char *, int * );
static void WriteObject( AstChannel *, const char *, int, int, AstObject *, const char *, int * );
static void WriteString( AstChannel *, const char *, int, int, const char *, const char *, int * );

static int GetReportLevel( AstChannel *, int * );
static int TestReportLevel( AstChannel *, int * );
static void ClearReportLevel( AstChannel *, int * );
static void SetReportLevel( AstChannel *, int, int * );

static int GetIndent( AstChannel *, int * );
static int TestIndent( AstChannel *, int * );
static void ClearIndent( AstChannel *, int * );
static void SetIndent( AstChannel *, int, int * );

static const char *GetSourceFile( AstChannel *, int * );
static int TestSourceFile( AstChannel *, int * );
static void ClearSourceFile( AstChannel *, int * );
static void SetSourceFile( AstChannel *, const char *, int * );

static const char *GetSinkFile( AstChannel *, int * );
static int TestSinkFile( AstChannel *, int * );
static void ClearSinkFile( AstChannel *, int * );
static void SetSinkFile( AstChannel *, const char *, int * );

/* Member functions. */
/* ================= */
static void AddWarning( AstChannel *this, int level, const char *msg,
                        const char *method, int *status ) {
/*
*+
*  Name:
*     astAddWarning

*  Purpose:
*     Add a warning to a Channel.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     void astAddWarning( AstChannel *this, int level, const char *msg,
*                         const char *method, int status, ... )

*  Class Membership:
*     Channel method.

*  Description:
*     This function stores a warning message inside a Channel. These
*     messages can be retirieved using astWarnings.

*  Parameters:
*     this
*        Pointer to the Channel.
*     level
*        Ignore the warning if the ReportLevel attribute value is less
*        than "level".
*     msg
*        The wanting message to store. It may contain printf format
*        specifiers. If a NULL pointer is supplied, all warnings
*        currently stored in the Channel are removed.
*     method
*        The method name.
*     status
*        Inherited status value.
*     ...
*        Extra values to substitute into the message string as
*        replacements for the printf format specifiers.
*-

*  Note: The expansion of the printf format specifiers is done in the
*     astAddWarning_ wrapper function. The AddWarning functions defined by
*     each class receives the fully expanded message and does not have a
*     variable argument list. The variable argument list is included in the
*     above prologue in order to document the wrapper function.

*/

/* Local Variables: */
   int i;          /* Message index */
   char *a;        /* Pointer to copy of message */

/* If a NULL pointer was supplied, free all warnings currently in the
   Channel. Do this before checking the inherited status so that it works
   even if an error has occurred. */
   if( !msg ) {
      for( i = 0; i < this->nwarn; i++ ) {
         (this->warnings)[ i ] = astFree( (this->warnings)[ i ] );
      }
      this->warnings = astFree( this->warnings );
      this->nwarn = 0;
      return;
   }

/* Check the global error status. */
   if ( !astOK ) return;

/* Only proceed if the message level is sufficiently important. */
   if( astGetReportLevel( this ) >= level ) {

/* If we are being strict, issue an error rather than a warning. */
      if( astGetStrict( this ) ) {
         if( astOK ) {
            astError( AST__BADIN, "%s(%s): %s", status, method,
                      astGetClass( this ), msg );
         }

/* Otherwise, we store a copy of the message in the Channel. */
      } else {

/* Allocate memory and store a copy of th supplied string in it. */
         a = astStore( NULL, msg, strlen( msg ) + 1 );

/* Expand the array of warning pointers in ther Channel structure. */
         this->warnings = astGrow( this->warnings, this->nwarn + 1,
                                   sizeof( char * ) );

/* If all is OK so far, store the new warning pointer, and increment the
   number of warnings in the Channel. */
         if( astOK ) {
            (this->warnings)[ (this->nwarn)++ ] = a;

/* Otherwise, attempt to free the memory holding the copy of the warning. */
         } else {
            a = astFree( a );
         }
      }
   }
}

static void AppendValue( AstChannelValue *value, AstChannelValue **head, int *status ) {
/*
*  Name:
*     AppendValue

*  Purpose:
*     Append a Value structure to a list.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     void AppendValue( AstChannelValue *value, AstChannelValue **head, int *status )

*  Class Membership:
*     Channel member function.

*  Description:
*     This function appends a Value structure to a doubly linked
*     circular list of such structures. The new list element is
*     inserted just in front of the element occupying the "head of
*     list" position (i.e. it becomes the new last element in the
*     list).

*  Parameters:
*     value
*        Pointer to the new element. This must not already be in the
*        list.
*     head
*        Address of a pointer to the element at the head of the list
*        (this pointer should be NULL if the list is initially
*        empty). This pointer will only be updated if a new element is
*        being added to an empty list.
*     status
*        Pointer to the inherited status variable.

*  Notes:
*     - This function does not perform error chacking and does not
*     generate errors.
*/

/* If the list is initially empty, the sole new element points at
   itself. */
   if ( !*head ) {
      value->flink = value;
      value->blink = value;

/* Update the list head to identify the new element. */
      *head = value;

/* Otherwise, insert the new element in front of the element at the
   head of the list. */
   } else {
      value->flink = *head;
      value->blink = ( *head )->blink;
      ( *head )->blink = value;
      value->blink->flink = value;
   }
}

void *astChannelData_( void ) {
/*
c++
*  Name:
*     astChannelData

*  Purpose:
*     Return a pointer to user-supplied data stored with a Channel.

*  Type:
*     Public macro.

*  Synopsis:
*     #include "channel.h"
*     void *astChannelData

*  Class Membership:
*     Channel macro.

*  Description:
*     This macro is intended to be used within the source or sink
*     functions associated with a Channel. It returns any pointer
*     previously stored in the Channel (that is, the Channel that has
*     invoked the source or sink function) using astPutChannelData.
*
*     This mechanism is a thread-safe alternative to passing file
*     descriptors, etc, via static global variables.

*  Returned Value:
*     astChannelData
*        The pointer previously stored with the Channel using
*        astPutChannelData. A NULL pointer will be returned if no such
*        pointer has been stored with the Channel.

*  Applicability:
*     Channel
*        This macro applies to all Channels.

*  Notes:
*     - This routine is not available in the Fortran 77 interface to
*     the AST library.
c--
*/
   astDECLARE_GLOBALS
   astGET_GLOBALS(NULL);
   return channel_data;
}

static void ClearAttrib( AstObject *this_object, const char *attrib, int *status ) {
/*
*  Name:
*     ClearAttrib

*  Purpose:
*     Clear an attribute value for a Channel.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     void ClearAttrib( AstObject *this, const char *attrib, int *status )

*  Class Membership:
*     Channel member function (over-rides the astClearAttrib protected
*     method inherited from the Object class).

*  Description:
*     This function clears the value of a specified attribute for a
*     Channel, so that the default value will subsequently be used.

*  Parameters:
*     this
*        Pointer to the Channel.
*     attrib
*        Pointer to a null terminated string specifying the attribute
*        name.  This should be in lower case with no surrounding white
*        space.
*     status
*        Pointer to the inherited status variable.
*/

/* Local Variables: */
   AstChannel *this;              /* Pointer to the Channel structure */

/* Check the global error status. */
   if ( !astOK ) return;

/* Obtain a pointer to the Channel structure. */
   this = (AstChannel *) this_object;

/* Check the attribute name and clear the appropriate attribute. */

/* Comment. */
/* -------- */
   if ( !strcmp( attrib, "comment" ) ) {
      astClearComment( this );

/* Full. */
/* ----- */
   } else if ( !strcmp( attrib, "full" ) ) {
      astClearFull( this );

/* Indent. */
/* ------- */
   } else if ( !strcmp( attrib, "indent" ) ) {
      astClearIndent( this );

/* ReportLevel. */
/* ------------ */
   } else if ( !strcmp( attrib, "reportlevel" ) ) {
      astClearReportLevel( this );

/* Skip. */
/* ----- */
   } else if ( !strcmp( attrib, "skip" ) ) {
      astClearSkip( this );

/* SourceFile. */
/* ----------- */
   } else if ( !strcmp( attrib, "sourcefile" ) ) {
      astClearSourceFile( this );

/* SinkFile. */
/* --------- */
   } else if ( !strcmp( attrib, "sinkfile" ) ) {
      astClearSinkFile( this );

/* Strict. */
/* ------- */
   } else if ( !strcmp( attrib, "strict" ) ) {
      astClearStrict( this );

/* If the attribute is still not recognised, pass it on to the parent
   method for further interpretation. */
   } else {
      (*parent_clearattrib)( this_object, attrib, status );
   }
}

static void ClearValues( AstChannel *this, int *status ) {
/*
*  Name:
*     ClearValues

*  Purpose:
*     Clear the current values list.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     void ClearValues( AstChannel *this, int *status )

*  Class Membership:
*     Channel member function.

*  Description:
*     This function clears any (un-read) Value structures remaining in
*     the current values list (i.e. at the current nesting level). It
*     should be invoked after all required values have been read.
*
*     If the values list has not been read, or if any remaining values
*     are found (i.e. the list is not empty) then this indicates an
*     unrecognised input class or an input value that has not been
*     read by a class loader. This implies an error in the loader, or
*     bad input data, so an error is reported.
*
*     All resources used by any remaining Value structures are freed
*     and the values list is left in an empty state.

*  Parameters:
*     this
*        Pointer to the Channel being read. This is only used for
*        constructing error messages. It must not be NULL.
*     status
*        Pointer to the inherited status variable.

*  Notes:
*     - This function attempts to execute even if the global error
*     status is set on entry, although no further error report will be
*     made if it subsequently fails under these circumstances.
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   AstChannelValue **head;       /* Address of pointer to values list */
   AstChannelValue *value;       /* Pointer to value list element */

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this);

/* If "values_class" is non-NULL, then the values list has previously
   been filled with Values for a class. */
   if ( values_class[ nest ] ) {

/* If "values_ok" is zero, however, then these Values have not yet
   been read by a class loader. This must be due to a bad class name
   associated with them or because the class data are not available in
   the correct order. If we are using strict error reporting, then report
   an error (unless the error status is already set). */
      if ( astGetStrict( this ) && !values_ok[ nest ] && astOK ) {
         astError( AST__BADIN,
                   "astRead(%s): Invalid class structure in input data.", status,
                   astGetClass( this ) );
         astError( AST__BADIN,
                   "Class \"%s\" is invalid or out of order within a %s.", status,
                   values_class[ nest ], object_class[ nest ] );
      }

/* Free the memory holding the class string. */
      values_class[ nest ] = astFree( values_class[ nest ] );
   }

/* Reset the "values_ok" flag. */
   values_ok[ nest ] = 0;

/* Now clear any Values remaining in the values list. Obtain the
   address of the pointer to the head of this list (at the current
   nesting level) and loop to remove Values from the list while it is
   not empty. */
   head = values_list + nest;
   while ( *head ) {

/* Obtain a pointer to the first element. */
      value = *head;

/* Issue a warning. */
      if ( value->is_object ) {
         astAddWarning( this, 1, "The Object \"%s = <%s>\" was "
                        "not recognised as valid input.", "astRead", status,
                        value->name, astGetClass( value->ptr.object ) );
      } else {
         astAddWarning( this, 1, "The value \"%s = %s\" was not "
                        "recognised as valid input.", "astRead", status,
                        value->name, value->ptr.string );
      }

/* Remove the Value structure from the list (which updates the head of
   list pointer) and free its resources. */
      RemoveValue( value, head, status );
      value = FreeValue( value, status );
   }
}

static AstChannelValue *FreeValue( AstChannelValue *value, int *status ) {
/*
*  Name:
*     FreeValue

*  Purpose:
*     Free a dynamically allocated Value structure.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     AstChannelValue *FreeValue( AstChannelValue *value, int *status )

*  Class Membership:
*     Channel member function.

*  Description:
*     This function frees a dynamically allocated Value structure,
*     releasing all resources used by it. The structure contents must
*     have been correctly initialised.

*  Parameters:
*     value
*        Pointer to the Value structure to be freed.
*     status
*        Pointer to the inherited status variable.

*  Returned Value:
*     A NULL pointer is always returned.

*  Notes:
*     - This function attempts to execute even if the global error
*     status is set on entry, although no further error report will be
*     made if it subsequently fails under these circumstances.
*/

/* Check that a non-NULL pointer has been supplied. */
   if ( value ) {

/* If the "name" component has been allocated, then free it. */
      if ( value->name ) value->name = astFree( value->name );

/* If the "ptr" component identifies an Object, then annul the Object
   pointer. */
      if ( value->is_object ) {
         if ( value->ptr.object ) {
            value->ptr.object = astAnnul( value->ptr.object );
         }

/* Otherwise, if it identifies a string, then free the string. */
      } else {
         if ( value->ptr.string ) {
            value->ptr.string = astFree( value->ptr.string );
         }
      }

/* Free the Value structure itself. */
      value = astFree( value );
   }

/* Return a NULL pointer. */
   return NULL;
}

static const char *GetAttrib( AstObject *this_object, const char *attrib, int *status ) {
/*
*  Name:
*     GetAttrib

*  Purpose:
*     Get the value of a specified attribute for a Channel.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     const char *GetAttrib( AstObject *this, const char *attrib, int *status )

*  Class Membership:
*     Channel member function (over-rides the protected astGetAttrib
*     method inherited from the Object class).

*  Description:
*     This function returns a pointer to the value of a specified
*     attribute for a Channel, formatted as a character string.

*  Parameters:
*     this
*        Pointer to the Channel.
*     attrib
*        Pointer to a null terminated string containing the name of
*        the attribute whose value is required. This name should be in
*        lower case, with all white space removed.
*     status
*        Pointer to the inherited status variable.

*  Returned Value:
*     - Pointer to a null terminated string containing the attribute
*     value.

*  Notes:
*     - The returned string pointer may point at memory allocated
*     within the Channel, or at static memory. The contents of the
*     string may be over-written or the pointer may become invalid
*     following a further invocation of the same function or any
*     modification of the Channel. A copy of the string should
*     therefore be made if necessary.
*     - A NULL pointer will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   AstChannel *this;             /* Pointer to the Channel structure */
   const char *result;           /* Pointer value to return */
   int comment;                  /* Comment attribute value */
   int full;                     /* Full attribute value */
   int indent;                   /* Indent attribute value */
   int report_level;             /* ReportLevel attribute value */
   int skip;                     /* Skip attribute value */
   int strict;                   /* Report errors insead of warnings? */

/* Initialise. */
   result = NULL;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this_object);

/* Obtain a pointer to the Channel structure. */
   this = (AstChannel *) this_object;

/* Compare "attrib" with each recognised attribute name in turn,
   obtaining the value of the required attribute. If necessary, write
   the value into "getattrib_buff" as a null terminated string in an appropriate
   format.  Set "result" to point at the result string. */

/* Comment. */
/* -------- */
   if ( !strcmp( attrib, "comment" ) ) {
      comment = astGetComment( this );
      if ( astOK ) {
         (void) sprintf( getattrib_buff, "%d", comment );
         result = getattrib_buff;
      }

/* Full. */
/* ----- */
   } else if ( !strcmp( attrib, "full" ) ) {
      full = astGetFull( this );
      if ( astOK ) {
         (void) sprintf( getattrib_buff, "%d", full );
         result = getattrib_buff;
      }

/* Indent. */
/* ------- */
   } else if ( !strcmp( attrib, "indent" ) ) {
      indent = astGetIndent( this );
      if ( astOK ) {
         (void) sprintf( getattrib_buff, "%d", indent );
         result = getattrib_buff;
      }

/* ReportLevel. */
/* ------------ */
   } else if ( !strcmp( attrib, "reportlevel" ) ) {
      report_level = astGetReportLevel( this );
      if ( astOK ) {
         (void) sprintf( getattrib_buff, "%d", report_level );
         result = getattrib_buff;
      }

/* Skip. */
/* ----- */
   } else if ( !strcmp( attrib, "skip" ) ) {
      skip = astGetSkip( this );
      if ( astOK ) {
         (void) sprintf( getattrib_buff, "%d", skip );
         result = getattrib_buff;
      }

/* SourceFile. */
/* ----------- */
   } else if ( !strcmp( attrib, "sourcefile" ) ) {
      result = astGetSourceFile( this );

/* SinkFile. */
/* --------- */
   } else if ( !strcmp( attrib, "sinkfile" ) ) {
      result = astGetSinkFile( this );

/* Strict. */
/* ------- */
   } else if ( !strcmp( attrib, "strict" ) ) {
      strict = astGetStrict( this );
      if ( astOK ) {
         (void) sprintf( getattrib_buff, "%d", strict );
         result = getattrib_buff;
      }

/* If the attribute name was not recognised, pass it on to the parent
   method for further interpretation. */
   } else {
      result = (*parent_getattrib)( this_object, attrib, status );
   }

/* Return the result. */
   return result;

}

static void GetNextData( AstChannel *this, int skip, char **name,
                         char **val, int *status ) {
/*
*+
*  Name:
*     astGetNextData

*  Purpose:
*     Read the next item of data from a data source.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     void astGetNextData( AstChannel *this, int skip, char **name,
*                          char **val )

*  Class Membership:
*     Channel method.

*  Description:
*     This function reads the next item of input data from a data
*     source associated with a Channel and returns the result.
*
*     It is layered conceptually on the astGetNextText method, but
*     instead of returning the raw input text, it decodes it and
*     returns name/value pairs ready for use. Note that in some
*     derived classes, where the data are not stored as text, this
*     function may not actually use astGetNextText, but will access
*     the data directly.

*  Parameters:
*     this
*        Pointer to the Channel.
*     skip
*        A non-zero value indicates that a new Object is to be read,
*        and that all input data up to the next "Begin" item are to be
*        skipped in order to locate it. This is useful if the data
*        source contains AST objects interspersed with other data (but
*        note that these other data cannot appear inside AST Objects,
*        only between them).
*
*        A zero value indicates that all input data are significant
*        and the next item will therefore be read and an attempt made
*        to interpret it whatever it contains. Any other data
*        inter-mixed with AST Objects will then result in an error.
*     name
*        An address at which to store a pointer to a null-terminated
*        dynamically allocated string containing the name of the next
*        item in the input data stream. This name will be in lower
*        case with no surrounding white space.  It is the callers
*        responsibilty to free the memory holding this string (using
*        astFree) when it is no longer required.
*
*        A NULL pointer value will be returned (without error) to
*        indicate when there are no further input data items to be
*        read.
*     val
*        An address at which to store a pointer to a null-terminated
*        dynamically allocated string containing the value associated
*        with the next item in the input data stream. No case
*        conversion is performed on this string and all white space is
*        potentially significant.  It is the callers responsibilty to
*        free the memory holding this string (using astFree) when it
*        is no longer required.
*
*        The returned pointer will be NULL if an Object data item is
*        read (see the "Data Representation" section).

*  Data Representation:
*     The returned data items fall into the following categories:
*
*     - Begin: Identified by the name string "begin", this indicates
*     the start of an Object definition. The associated value string
*     gives the class name of the Object being defined.
*
*     - IsA: Identified by the name string "isa", this indicates the
*     end of the data associated with a particular class structure
*     within the definiton of a larger Object. The associated value
*     string gives the name of the class whose data have just been
*     read.
*
*     - End: Identified by the name string "end", this indicates the
*     end of the data associated with a complete Object
*     definition. The associated value string gives the class name of
*     the Object whose definition is being ended.
*
*     - Non-Object: Identified by any other name string plus a
*     non-NULL "val" pointer, this gives the value of a non-Object
*     structure component (instance variable). The name identifies
*     which instance variable it is (within the context of the class
*     whose data are being read) and the value is encoded as a string.
*
*     - Object: Identified by any other name string plus a NULL "val"
*     pointer, this identifies the value of an Object structure
*     component (instance variable).  The name identifies which
*     instance variable it is (within the context of the class whose
*     data are being read) and the value is given by subsequent data
*     items (so the next item should be a "Begin" item).

*  Notes:
*     - NULL pointer values will be returned if this function is
*     invoked with the global error status set, or if it should fail
*     for any reason.
*     - This method is provided primarily so that derived classes may
*     over-ride it in order to read from alternative data sources. It
*     provides a higher-level interface than astGetNextText, so is
*     suitable for classes that either need to read textual data in a
*     different format, or to read from non-textual data sources.
*-
*/

/* Local Variables: */
   char *line;                   /* Pointer to input text line */
   int done;                     /* Data item read? */
   int i;                        /* Loop counter for string characters */
   int len;                      /* Length of input text line */
   int nc1;                      /* Offset to start of first field */
   int nc2;                      /* Offset to end of first field */
   int nc3;                      /* Offset to start of second field */
   int nc;                       /* Number of charaters read by "astSscanf" */

/* Initialise the returned values. */
   *name = NULL;
   *val = NULL;

/* Check the global error status. */
   if ( !astOK ) return;

/* Read the next input line as text (the loop is needed to allow
   initial lines to be skipped if the "skip" flag is set). */
   done = 0;
   while ( !done && ( line = InputTextItem( this, status ) ) && astOK ) {

/* If OK, determine the line length. */
      len = strlen( line );

/* Non-Object value. */
/* ----------------- */
/* Test for lines of the form " name = value" (or similar), where the
   name is no more than MAX_NAME characters long (the presence of a
   value on the right hand side indicates that this is a non-Object
   value, encoded as a string). Ignore these lines if the "skip" flag
   is set. */
      if ( nc = 0,
           ( !skip
             && ( 0 == astSscanf( line,
                               " %n%*" MAX_NAME "[^ \t=]%n = %n%*[^\n]%n",
                               &nc1, &nc2, &nc3, &nc ) )
             && ( nc >= len ) ) ) {

/* Note we have found a data item. */
         done = 1;

/* Extract the name and value fields. */
         *name = astString( line + nc1, nc2 - nc1 );
         *val = astString( line + nc3, len - nc3 );

/* If OK, truncate the value to remove any trailing white space. */
         if ( astOK ) {
            i = len - nc3 - 1;
            while ( ( i >= 0 ) && isspace( ( *val )[ i ] ) ) i--;
            ( *val )[ i + 1 ] = '\0';

/* Also remove any quotes from the string. */
            Unquote( this, *val, status );
         }

/* Object value. */
/* ------------- */
/* Test for lines of the form " name = " (or similar), where the name
   is no more than MAX_NAME characters long (the absence of a value on
   the right hand side indicates that this is an Object, whose
   definition follows on subsequent input lines). Ignore these lines
   if the "skip" flag is set. */
      } else if ( nc = 0,
                  ( !skip
                    && ( 0 == astSscanf( line,
                                      " %n%*" MAX_NAME "[^ \t=]%n = %n",
                                      &nc1, &nc2, &nc ) )
                    && ( nc >= len ) ) ) {

/* Note we have found a data item. */
         done = 1;

/* Extract the name field but leave the value pointer as NULL. */
         *name = astString( line + nc1, nc2 - nc1 );

/* Begin. */
/* ------ */
/* Test for lines of the form " Begin Class " (or similar). */
      } else if ( nc = 0,
             ( ( 0 == astSscanf( line,
                             " %*1[Bb]%*1[Ee]%*1[Gg]%*1[Ii]%*1[Nn] %n%*s%n %n",
                              &nc1, &nc2, &nc ) )
               && ( nc >= len ) ) ) {

/* Note we have found a data item. */
         done = 1;

/* Set the returned name to "begin" and extract the associated class
   name for the value. Store both of these in dynamically allocated
   strings. */
         *name = astString( "begin", 5 );
         *val = astString( line + nc1, nc2 - nc1 );

/* IsA. */
/* ---- */
/* Test for lines of the form " IsA Class " (or similar). Ignore these
   lies if the "skip" flag is set. */
      } else if ( nc = 0,
                  ( !skip
                    && ( 0 == astSscanf( line,
                                      " %*1[Ii]%*1[Ss]%*1[Aa] %n%*s%n %n",
                                      &nc1, &nc2, &nc ) )
                    && ( nc >= len ) ) ) {

/* Note we have found a data item. */
         done = 1;

/* Set the returned name to "isa" and extract the associated class
   name for the value. */
         *name = astString( "isa", 3 );
         *val = astString( line + nc1, nc2 - nc1 );

/* End. */
/* ---- */
/* Test for lines of the form " End Class " (or similar). Ignore these
   lines if the "skip" flag is set. */
      } else if ( nc = 0,
                  ( !skip
                    && ( 0 == astSscanf( line,
                                      " %*1[Ee]%*1[Nn]%*1[Dd] %n%*s%n %n",
                                      &nc1, &nc2, &nc ) )
                    && ( nc >= len ) ) ) {

/* Note we have found a data item. */
         done = 1;

/* If found, set the returned name to "end" and extract the associated
   class name for the value. */
         *name = astString( "end", 3 );
         *val = astString( line + nc1, nc2 - nc1 );

/* If the input line didn't match any of the above and the "skip" flag
   is not set, then report an error. */
      } else if ( !skip ) {
         astError( AST__BADIN,
                   "astRead(%s): Cannot interpret the input data: \"%s\".", status,
                   astGetClass( this ), line );
      }

/* Free the memory holding the input data as text. */
      line = astFree( line );
   }

/* If successful, convert the name to lower case. */
   if ( astOK && *name ) {
      for ( i = 0; ( *name )[ i ]; i++ ) {
         ( *name )[ i ] = tolower( ( *name )[ i ] );
      }
   }

/* If an error occurred, ensure that any memory allocated is freed and
   that NULL pointer values are returned. */
   if ( !astOK ) {
      *name = astFree( *name );
      *val = astFree( *val );
   }
}

static char *GetNextText( AstChannel *this, int *status ) {
/*
*+
*  Name:
*     GetNextText

*  Purpose:
*     Read the next line of input text from a data source.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     char *astGetNextText( AstChannel *this )

*  Class Membership:
*     Channel method.

*  Description:
*     This function reads the next "raw" input line of text from the
*     data source associated with a Channel.
*
*     Each line is returned as a pointer to a null-terminated string
*     held in dynamic memory, and it is the caller's responsibility to
*     free this memory (using astFree) when it is no longer
*     required. A NULL pointer is returned if there are no more input
*     lines to be read.

*  Parameters:
*     this
*        Pointer to the Channel.

*  Returned Value:
*     Pointer to a null-terminated string containing the input line
*     (held in dynamically allocated memory, which must be freed by
*     the caller when no longer required). A NULL pointer is returned
*     if there are no more input lines to be read.

*  Notes:
*     - A NULL pointer will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*     - This method is provided primarily so that derived classes may
*     over-ride it in order to read from alternative (textual) data
*     sources.
*-
*/

/* Local Constants: */
#define MIN_CHARS 81             /* Initial size for allocating memory */
#define ERRBUF_LEN 80

/* Local Variables: */
   FILE *fd;                     /* Input file descriptor */
   char *errstat;                /* Pointer for system error message */
   char *line;                   /* Pointer to line data to be returned */
   char errbuf[ ERRBUF_LEN ];    /* Buffer for system error message */
   const char *sink_file;        /* Path to output sink file */
   const char *source_file;      /* Path to source file */
   int c;                        /* Input character */
   int len;                      /* Length of input line */
   int readstat;                 /* "errno" value set by "getchar" */
   int size;                     /* Size of allocated memory */

/* Initialise. */
   line = NULL;

/* Check the global error status. */
   if ( !astOK ) return line;

/* If the SourceFile attribute of the Channel specifies an input file,
   but no input file has yet been opened, open it now. Report an error if
   it is the same as the sink file. */
   if( astTestSourceFile( this ) && !this->fd_in ) {
      source_file = astGetSourceFile( this );

      if( this->fd_out ) {
         sink_file = astGetSinkFile( this );
         if( astOK && !strcmp( sink_file, source_file ) ) {
            astError( AST__RDERR, "astRead(%s): Failed to open input "
                      "SourceFile '%s' - the file is currently being used "
                      "as the output SinkFile.", status, astGetClass( this ),
                      source_file );
         }
      }

      if( astOK ) {
         this->fd_in = fopen( source_file, "r" );
         if( !this->fd_in ) {
            if ( errno ) {
#if HAVE_STRERROR_R
               strerror_r( errno, errbuf, ERRBUF_LEN );
               errstat = errbuf;
#else
               errstat = strerror( errno );
#endif
               astError( AST__RDERR, "astRead(%s): Failed to open input "
                         "SourceFile '%s' - %s.", status, astGetClass( this ),
                         source_file, errstat );
            } else {
               astError( AST__RDERR, "astRead(%s): Failed to open input "
                         "SourceFile '%s'.", status, astGetClass( this ),
                         source_file );
            }
         }

      }
   }

/* Source function defined, but no input file. */
/* ------------------------------------------- */
/* If no active input file descriptor is stored in the Channel, but
   a source function (and its wrapper function) is defined for the
   Channel, use the wrapper function to invoke the source function to
   read a line of input text. This is returned in a dynamically
   allocated string. */
   if ( !this->fd_in && this->source && this->source_wrap ) {

/* About to call an externally supplied function which may not be
   thread-safe, so lock a mutex first. Also store the channel data
   pointer in a global variable so that it can be accessed in the source
   function using macro astChannelData. */
      astStoreChannelData( this );
      LOCK_MUTEX3;
      line = ( *this->source_wrap )( this->source, status );
      UNLOCK_MUTEX3;

/* Input file defined, or no source function. */
/* ------------------------------------------ */
/* Read the line from the input file or from standard input. */
   } else if( astOK ) {
      c = '\0';
      len = 0;
      size = 0;

/* Choose the file descriptor to use. */
      fd = this->fd_in ? this->fd_in : stdin;

/* Loop to read input characters, saving any "errno" value that may be
   set by "getchar" if an error occurs. Quit if an end of file (or
   error) occurs or if a newline character is read. */
      while ( errno = 0, c = getc( fd ), readstat = errno,
              ( c != EOF ) && ( c != '\n' ) ) {

/* If no memory has yet been allocated to hold the line, allocate some
   now, using MIN_CHARS as the initial line length. */
         if ( !line ) {
            line = astMalloc( sizeof( char ) * (size_t) MIN_CHARS );
            size = MIN_CHARS;

/* If memory has previously been allocated, extend it when necessary
   to hold the new input character (plus a terminating null) and note
   the new size. */
         } else if ( ( len + 2 ) > size ) {
            line = astGrow( line, len + 2, sizeof( char ) );
            if ( !astOK ) break;
            size = (int) astSizeOf( line );
         }

/* Store the character just read. */
         line[ len++ ] = c;
      }

/* If the above loop completed without setting the global error
   status, check the last character read and use "ferror" to see if a
   read error occurred. If so, report the error, using the saved
   "errno" value (but only if one was set). */
      if ( astOK && ( c == EOF ) && ferror( fd ) ) {
         if ( readstat ) {
#if HAVE_STRERROR_R
            strerror_r( readstat, errbuf, ERRBUF_LEN );
            errstat = errbuf;
#else
            errstat = strerror( readstat );
#endif
            astError( AST__RDERR,
                      "astRead(%s): Read error on standard input - %s.", status,
                      astGetClass( this ), errstat );
         } else {
            astError( AST__RDERR,
                      "astRead(%s): Read error on standard input.", status,
                      astGetClass( this ) );
         }
      }

/* If an empty line has been read, allocate memory to hold an empty
   string. */
      if ( !line && ( c == '\n' ) ) {
         line = astMalloc( sizeof( char ) );
      }

/* If memory has been allocated and there has been no error,
   null-terminate the string of input characters. */
      if ( line ) {
         if ( astOK ) {
            line[ len ] = '\0';

/* If there has been an error, free the allocated memory. */
         } else {
            line = astFree( line );
         }
      }
   }


/* Return the result pointer. */
   return line;

/* Undefine macros local to this function. */
#undef MIN_CHARS
#undef ERRBUF_LEN
}

static AstKeyMap *Warnings( AstChannel *this, int *status ){
/*
*++
*  Name:
c     astWarnings
f     AST_WARNINGS

*  Purpose:
*     Returns any warnings issued by the previous read or write operation.

*  Type:
*     Public virtual function.

*  Synopsis:
c     #include "channel.h"
c     AstKeyMap *astWarnings( AstChannel *this )
f     RESULT = AST_WARNINGS( THIS, STATUS )

*  Class Membership:
*     Channel member function.

*  Description:
*     This function returns an AST KeyMap object holding the text of any
*     warnings issued as a result of the previous invocation of the
c     astRead or astWrite
f     AST_READ or AST_WRITE
*     function on the Channel. If no warnings were issued, a
c     a NULL value
f     AST__NULL
*     will be returned.
*
*     Such warnings are non-fatal and will not prevent the
*     read or write operation succeeding. However, the converted object
*     may not be identical to the original object in all respects.
*     Differences which would usually be deemed as insignificant in most
*     usual cases will generate a warning, whereas more significant
*     differences will generate an error.
*
*     The "Strict" attribute allows this warning facility to be switched
*     off, so that a fatal error is always reported for any conversion
*     error.

*  Parameters:
c     this
f     THIS = INTEGER (Given)
*        Pointer to the Channel.
f     STATUS = INTEGER (Given and Returned)
f        The global status.

*  Returned Value:
c     astWarnings()
f     AST_WARNINGS = INTEGER
*        A pointer to the KeyMap holding the warning messages, or
c        NULL
f        AST__NULL
*        if no warnings were issued during the previous read operation.

*  Applicability:
*     Channel
*        The basic Channel class generates a warning when ever an
*        un-recognised item is encountered whilst reading an Object from
*        an external data source. If Strict is zero (the default), then
*        unexpected items in the Object description are simply ignored,
*        and any remaining items are used to construct the returned
*        Object. If Strict is non-zero, an error will be reported and a
*        NULL Object pointer returned if any unexpected items are
*        encountered.
*
*        As AST continues to be developed, new attributes are added
*        occasionally to selected classes. If an older version of AST is
*        used to read external Object descriptions created by a more
*        recent version of AST, then the Channel class will, by default,
*        ignore the new attributes, using the remaining attributes to
*        construct the Object. This is usually a good thing. However,
*        since external Object descriptions are often stored in plain
*        text, it is possible to edit them using a text editor. This
*        gives rise to the possibility of genuine errors in the
*        description due to finger-slips, typos, or simple
*        mis-understanding. Such inappropriate attributes will be ignored
*        if Strict is left at its default zero value. This will cause the
*        mis-spelled attribute to revert to its default value,
*        potentially causing subtle changes in the behaviour of
*        application software. If such an effect is suspected, the Strict
*        attribute can be set non-zero, resulting in the erroneous
*        attribute being identified in an error message.
*     FitsChan
*        The returned KeyMap will contain warnings for all conditions
*        listed in the Warnings attribute.
*     XmlChan
*        Reports conversion errors that result in what are usally
*        insignificant  changes.

*  Notes:
*     - The returned KeyMap uses keys of the form "Warning_1",
*     "Warning_2", etc.
*     - A value of
c     NULL will be returned if this function is invoked with the AST
c     error status set,
f     AST__NULL will be returned if this function is invoked with STATUS
f     set to an error value,
*     or if it should fail for any reason.
*--
*/

/* Local Variables: */
   AstKeyMap *result;
   char key[ 20 ];
   int i;

/* Check the global status, and supplied keyword name. */
   result = NULL;
   if( !astOK ) return result;

/* Check there are some warnings to return. */
   if( this->nwarn && this->warnings ) {

/* Create the KeyMap. */
      result = astKeyMap( "", status );

/* Loop round all warnings, adding them into the KeyMap. */
      for( i = 0; i < this->nwarn; i++ ){
         sprintf( key, "Warning_%d", i + 1 );
         astMapPut0C( result, key, (this->warnings)[ i ], " " );
      }
   }

/* Return the KeyMap. */
   return result;
}

AstChannel *astInitChannel_( void *mem, size_t size, int init,
                             AstChannelVtab *vtab, const char *name,
                             const char *(* source)( void ),
                             char *(* source_wrap)( const char *(*)( void ), int * ),
                             void (* sink)( const char * ),
                             void (* sink_wrap)( void (*)( const char * ),
                                                 const char *, int * ), int *status ) {
/*
*+
*  Name:
*     astInitChannel

*  Purpose:
*     Initialise a Channel.

*  Type:
*     Protected function.

*  Synopsis:
*     #include "channel.h"
*     AstChannel *astInitChannel( void *mem, size_t size, int init,
*                                 AstChannelVtab *vtab, const char *name,
*                                 const char *(* source)( void ),
*                                 char *(* source_wrap)( const char *(*)( void ), int * ),
*                                 void (* sink)( const char * ),
*                                 void (* sink_wrap)( void (*)( const char * ),
*                                                     const char *, int * ) )

*  Class Membership:
*     Channel initialiser.

*  Description:
*     This function is provided for use by class implementations to
*     initialise a new Channel object. It allocates memory (if
*     necessary) to accommodate the Channel plus any additional data
*     associated with the derived class.  It then initialises a
*     Channel structure at the start of this memory. If the "init"
*     flag is set, it also initialises the contents of a virtual
*     function table for a Channel at the start of the memory passed
*     via the "vtab" parameter.

*  Parameters:
*     mem
*        A pointer to the memory in which the Channel is to be
*        initialised.  This must be of sufficient size to accommodate
*        the Channel data (sizeof(Channel)) plus any data used by the
*        derived class. If a value of NULL is given, this function
*        will allocate the memory itself using the "size" parameter to
*        determine its size.
*     size
*        The amount of memory used by the Channel (plus derived class
*        data).  This will be used to allocate memory if a value of
*        NULL is given for the "mem" parameter. This value is also
*        stored in the Channel structure, so a valid value must be
*        supplied even if not required for allocating memory.
*     init
*        A boolean flag indicating if the Channel's virtual function
*        table is to be initialised. If this value is non-zero, the
*        virtual function table will be initialised by this function.
*     vtab
*        Pointer to the start of the virtual function table to be
*        associated with the new Channel.
*     name
*        Pointer to a constant null-terminated character string which
*        contains the name of the class to which the new object
*        belongs (it is this pointer value that will subsequently be
*        returned by the astGetClass method).
*     source
*        Pointer to a "source" function which will be used to obtain
*        lines of input text. Generally, this will be obtained by
*        casting a pointer to a source function which is compatible
*        with the "source_wrap" wrapper function (below). The pointer
*        should later be cast back to its original type by the
*        "source_wrap" function before the function is invoked.
*
*        If "source" is NULL, the Channel will read from standard
*        input instead.
*     source_wrap
*        Pointer to a function which can be used to invoke the
*        "source" function supplied (above). This wrapper function is
*        necessary in order to hide variations in the nature of the
*        source function, such as may arise when it is supplied by a
*        foreign (non-C) language interface.
*
*        The single parameter of the "source_wrap" function is a
*        pointer to the "source" function, and it should cast this
*        function pointer (as necessary) and invoke the function with
*        appropriate arguments to obtain the next line of input
*        text. The "source_wrap" function should then return a pointer
*        to a dynamically allocated, null terminated string containing
*        the text that was read. The string will be freed (using
*        astFree) when no longer required and the "source_wrap"
*        function need not concern itself with this. A NULL pointer
*        should be returned if there is no more input to read.
*
*        If "source_wrap" is NULL, the Channel will read from standard
*        input instead.
*     sink
*        Pointer to a "sink" function which will be used to deliver
*        lines of output text. Generally, this will be obtained by
*        casting a pointer to a sink function which is compatible with
*        the "sink_wrap" wrapper function (below). The pointer should
*        later be cast back to its original type by the "sink_wrap"
*        function before the function is invoked.
*
*        If "sink" is NULL, the Channel will write to standard output
*        instead.
*     sink_wrap
*        Pointer to a function which can be used to invoke the "sink"
*        function supplied (above). This wrapper function is necessary
*        in order to hide variations in the nature of the sink
*        function, such as may arise when it is supplied by a foreign
*        (non-C) language interface.
*
*        The first parameter of the "sink_wrap" function is a pointer
*        to the "sink" function, and the second parameter is a pointer
*        to a const, null-terminated character string containing the
*        text to be written.  The "sink_wrap" function should cast the
*        "sink" function pointer (as necessary) and invoke the
*        function with appropriate arguments to deliver the line of
*        output text. The "sink_wrap" function then returns void.
*
*        If "sink_wrap" is NULL, the Channel will write to standard
*        output instead.

*  Returned Value:
*     A pointer to the new Channel.

*  Notes:
*     - A null pointer will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*-
*/

/* Local Variables: */
   AstChannel *new;              /* Pointer to new Channel */

/* Check the global status. */
   if ( !astOK ) return NULL;

/* If necessary, initialise the virtual function table. */
   if ( init ) astInitChannelVtab( vtab, name );

/* Initialise an Object structure (the parent class) as the first
   component within the Channel structure, allocating memory if
   necessary. */
   new = (AstChannel *) astInitObject( mem, size, 0,
                                       (AstObjectVtab *) vtab, name );

   if ( astOK ) {

/* Initialise the Channel data. */
/* ---------------------------- */
/* Save the pointers to the source and sink functions and the wrapper
   functions that invoke them. */
      new->source = source;
      new->source_wrap = source_wrap;
      new->sink = sink;
      new->sink_wrap = sink_wrap;

/* Indicate no input or output files have been associated with the
   Channel. */
      new->fd_in = NULL;
      new->fn_in = NULL;
      new->fd_out = NULL;
      new->fn_out = NULL;

/* Set all attributes to their undefined values. */
      new->comment = -INT_MAX;
      new->full = -INT_MAX;
      new->indent = -INT_MAX;
      new->report_level = -INT_MAX;
      new->skip = -INT_MAX;
      new->strict = -INT_MAX;
      new->data = NULL;
      new->warnings = NULL;
      new->nwarn = 0;

/* If an error occurred, clean up by deleting the new object. */
      if ( !astOK ) new = astDelete( new );
   }

/* Return a pointer to the new object. */
   return new;
}

void astInitChannelVtab_(  AstChannelVtab *vtab, const char *name, int *status ) {
/*
*+
*  Name:
*     astInitChannelVtab

*  Purpose:
*     Initialise a virtual function table for a Channel.

*  Type:
*     Protected function.

*  Synopsis:
*     #include "channel.h"
*     void astInitChannelVtab( AstChannelVtab *vtab, const char *name )

*  Class Membership:
*     Channel vtab initialiser.

*  Description:
*     This function initialises the component of a virtual function
*     table which is used by the Channel class.

*  Parameters:
*     vtab
*        Pointer to the virtual function table. The components used by
*        all ancestral classes will be initialised if they have not already
*        been initialised.
*     name
*        Pointer to a constant null-terminated character string which contains
*        the name of the class to which the virtual function table belongs (it
*        is this pointer value that will subsequently be returned by the Object
*        astClass function).
*-
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
   AstObjectVtab *object;        /* Pointer to Object component of Vtab */

/* Check the local error status. */
   if ( !astOK ) return;

/* Get a pointer to the thread specific global data structure. */
   astGET_GLOBALS(NULL);

/* Initialize the component of the virtual function table used by the
   parent class. */
   astInitObjectVtab( (AstObjectVtab *) vtab, name );

/* Store a unique "magic" value in the virtual function table. This
   will be used (by astIsAChannel) to determine if an object belongs
   to this class.  We can conveniently use the address of the (static)
   class_check variable to generate this unique value. */
   vtab->id.check = &class_check;
   vtab->id.parent = &(((AstObjectVtab *) vtab)->id);

/* Initialise member function pointers. */
/* ------------------------------------ */
/* Store pointers to the member functions (implemented here) that
   provide virtual methods for this class. */
   vtab->AddWarning = AddWarning;
   vtab->ClearComment = ClearComment;
   vtab->ClearFull = ClearFull;
   vtab->ClearSkip = ClearSkip;
   vtab->ClearStrict = ClearStrict;
   vtab->GetComment = GetComment;
   vtab->GetFull = GetFull;
   vtab->GetNextData = GetNextData;
   vtab->GetNextText = GetNextText;
   vtab->GetSkip = GetSkip;
   vtab->GetStrict = GetStrict;
   vtab->Warnings = Warnings;
   vtab->PutNextText = PutNextText;
   vtab->Read = Read;
   vtab->ReadClassData = ReadClassData;
   vtab->ReadDouble = ReadDouble;
   vtab->ReadInt = ReadInt;
   vtab->ReadObject = ReadObject;
   vtab->ReadString = ReadString;
   vtab->SetComment = SetComment;
   vtab->SetFull = SetFull;
   vtab->SetSkip = SetSkip;
   vtab->SetStrict = SetStrict;
   vtab->TestComment = TestComment;
   vtab->TestFull = TestFull;
   vtab->TestSkip = TestSkip;
   vtab->TestStrict = TestStrict;
   vtab->Write = Write;
   vtab->WriteBegin = WriteBegin;
   vtab->WriteDouble = WriteDouble;
   vtab->WriteEnd = WriteEnd;
   vtab->WriteInt = WriteInt;
   vtab->WriteIsA = WriteIsA;
   vtab->WriteObject = WriteObject;
   vtab->WriteString = WriteString;
   vtab->PutChannelData = PutChannelData;

   vtab->ClearReportLevel = ClearReportLevel;
   vtab->GetReportLevel = GetReportLevel;
   vtab->SetReportLevel = SetReportLevel;
   vtab->TestReportLevel = TestReportLevel;

   vtab->ClearIndent = ClearIndent;
   vtab->GetIndent = GetIndent;
   vtab->SetIndent = SetIndent;
   vtab->TestIndent = TestIndent;

   vtab->ClearSourceFile = ClearSourceFile;
   vtab->GetSourceFile = GetSourceFile;
   vtab->SetSourceFile = SetSourceFile;
   vtab->TestSourceFile = TestSourceFile;

   vtab->ClearSinkFile = ClearSinkFile;
   vtab->GetSinkFile = GetSinkFile;
   vtab->SetSinkFile = SetSinkFile;
   vtab->TestSinkFile = TestSinkFile;

/* Save the inherited pointers to methods that will be extended, and
   replace them with pointers to the new member functions. */
   object = (AstObjectVtab *) vtab;

   parent_clearattrib = object->ClearAttrib;
   object->ClearAttrib = ClearAttrib;
   parent_getattrib = object->GetAttrib;
   object->GetAttrib = GetAttrib;
   parent_setattrib = object->SetAttrib;
   object->SetAttrib = SetAttrib;
   parent_testattrib = object->TestAttrib;
   object->TestAttrib = TestAttrib;

/* Declare the destructor and copy constructor. */
   astSetDelete( (AstObjectVtab *) vtab, Delete );
   astSetCopy( (AstObjectVtab *) vtab, Copy );

/* Declare the Dump function for this class. There is no destructor or
   copy constructor. */
   astSetDump( vtab, Dump, "Channel", "Basic I/O Channel" );

/* If we have just initialised the vtab for the current class, indicate
   that the vtab is now initialised, and store a pointer to the class
   identifier in the base "object" level of the vtab. */
   if( vtab == &class_vtab ) {
      class_init = 1;
      astSetVtabClassIdentifier( vtab, &(vtab->id) );
   }
}

static char *InputTextItem( AstChannel *this, int *status ) {
/*
*  Name:
*     InputTextItem

*  Purpose:
*     Read the next item from a data source as text.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     char *InputTextItem( AstChannel *this )

*  Class Membership:
*     Channel member function.

*  Description:
*     This function reads the next input data item as text from the
*     data source associated with a Channel. It is similar to the
*     astGetNextText method (which it invokes), except that it strips
*     off any comments along with leading and trailing white
*     space. Input lines which are empty or do not contain significant
*     characters (e.g. all comment) are skipped, so that only
*     significant lines are returned.
*
*     Each line is returned as a pointer to a null-terminated string
*     held in dynamic memory, and it is the caller's responsibility to
*     free this memory (using astFree) when it is no longer
*     required. A NULL pointer is returned if there are no more input
*     lines to be read.

*  Parameters:
*     this
*        Pointer to the Channel.

*  Returned Value:
*     Pointer to a null-terminated string containing the input line
*     (held in dynamically allocated memory, which must be freed by
*     the caller when no longer required). A NULL pointer is returned
*     if there are no more input lines to be read.

*  Notes:
*     - A NULL pointer will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*/

/* Local Variables: */
   char *line;                   /* Pointer to line data to be returned */
   int i;                        /* Loop counter for line characters */
   int j;                        /* Counter for characters */
   int len;                      /* Length of result line */
   int nonspace;                 /* Non-space character encountered? */
   int quoted;                   /* Character is inside quotes? */

/* Initialise. */
   line = NULL;

/* Check the global error status. */
   if ( !astOK ) return line;

/* Loop to read input lines until one is found which contains useful
   characters or end of file is reached (or a read error occurs). */
   while ( !line && ( line = astGetNextText( this ) ) && astOK ) {

/* Loop to remove comments and leading and trailing white space. */
      len = 0;
      nonspace = 0;
      quoted = 0;
      for ( i = j = 0; line[ i ]; i++ ) {

/* Note quote characters and ignore all text after the first unquoted
   comment character. */
         if ( line[ i ] == '"' ) quoted = !quoted;
         if ( ( line[ i ] == '#' ) && !quoted ) break;

/* Note the first non-space character and ignore everything before
   it. */
         if ( ( nonspace = nonspace || !isspace( line[ i ] ) ) ) {

/* Move each character to its new position in the string. */
            line[ j++ ] = line[ i ];

/* Note the final length of the string (ignoring trailing spaces). */
            if ( !isspace( line[ i ] ) ) len = j;
         }
      }

/* If the string is not empty, terminate it. */
     if ( len ) {
        line[ len ] = '\0';

/* Otherwise, free the memory used for the string so that another
   input line will be read. */
      } else {
         line = astFree( line );
      }
   }

/* Return the result pointer. */
   return line;

/* Undefine macros local to this function. */
#undef MIN_CHARS
}

static AstChannelValue *LookupValue( const char *name, int *status ) {
/*
*  Name:
*     LookupValue

*  Purpose:
*     Look up a Value structure by name.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     AstChannelValue *LookupValue( const char *name )

*  Class Membership:
*     Channel member function.

*  Description:
*     This function searches the current values list (i.e. at the
*     current nesting level) to identify a Value structure with a
*     specified name. If one is found, it is removed from the list and
*     a pointer to it is returned. If no suitable Value can be found,
*     a NULL pointer is returned instead.

*  Parameters:
*     name
*        Pointer to a constant null-terminated character string
*        containing the name of the required Value. This must be in
*        lower case with no surrounding white space. Note that names
*        longer than NAME_MAX characters will not match any Value.

*  Returned value:
*     Pointer to the required Value structure, or NULL if no suitable
*     Value exists.

*  Notes:
*     - The returned pointer refers to a dynamically allocated
*     structure and it is the callers responsibility to free this when
*     no longer required. The FreeValue function must be used for this
*     purpose.
*     - A NULL pointer will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   AstChannelValue **head;       /* Address of head of list pointer */
   AstChannelValue *result;      /* Pointer value to return */
   AstChannelValue *value;       /* Pointer to list element */

/* Initialise. */
   result = NULL;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(NULL);

/* Check that the "values_ok" flag is set. If not, the Values in the
   values list belong to a different class to that of the current
   class loader, so we cannot return any Value. */
   if ( values_ok[ nest ] ) {

/* Obtain the address of the current "head of list" pointer for the
   values list (at the current nesting level). */
      head = values_list + nest;

/* Obtain the head of list pointer itself and check the list is not
   empty. */
      if ( ( value = *head ) ) {

/* Loop to inspect each list element. */
         while ( 1 ) {

/* If a name match is found, remove the element from the list, return
   a pointer to it and quit searching. */
            if ( !strcmp( name, value->name ) ) {
               RemoveValue( value, head, status );
               result = value;
               break;
            }

/* Follow the list until we return to the head. */
            value = value->flink;
            if ( value == *head ) break;
         }
      }
   }

/* Return the result. */
   return result;
}

static void OutputTextItem( AstChannel *this, const char *line, int *status ) {
/*
*  Name:
*     OutputTextItem

*  Purpose:
*     Output a data item formatted as text.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     void OutputTextItem( AstChannel *this, const char *line, int *status )

*  Class Membership:
*     Channel member function.

*  Description:
*     This function outputs a data item formatted as a text string to
*     a data sink associated with a Channel. It keeps track of the
*     number of items written.

*  Parameters:
*     this
*        Pointer to the Channel.
*     line
*        Pointer to a constant null-terminated string containing the
*        data item to be output (no newline character should be
*        appended).
*     status
*        Pointer to the inherited status variable.
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */

/* Check the global error status. */
   if ( !astOK ) return;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this);

/* Write out the line of text using the astPutNextText method (which
   may be over-ridden). */
   astPutNextText( this, line );

/* If successful, increment the count of items written. */
   if ( astOK ) items_written++;
}

static void PutChannelData( AstChannel *this, void *data, int *status ) {
/*
c++
*  Name:
*     astPutChannelData

*  Purpose:
*     Store arbitrary data to be passed to a source or sink function.

*  Type:
*     Public function.

*  Synopsis:
*     #include "channel.h"
*     void astPutChannelData( AstChannel *this, void *data )

*  Class Membership:
*     Channel method.

*  Description:
*     This function stores a supplied arbitrary pointer in the Channel.
*     When a source or sink function is invoked by the Channel, the
*     invoked function can use the astChannelData macro to retrieve the
*     pointer. This provides a thread-safe alternative to passing file
*     descriptors, etc, via global static variables.

*  Parameters:
*     this
*        Pointer to the Channel.
*     data
*        A pointer to be made available to the source and sink functions
*        via the astChannelData macro. May be NULL.

*  Applicability:
*     Channel
*        All Channels have this function.

*  Notes:
*     - This routine is not available in the Fortran 77 interface to
*     the AST library.
c--
*/

/* Check the global error status. */
   if ( !astOK ) return;

/* Store the pointer. */
   this->data = data;
}

static void PutNextText( AstChannel *this, const char *line, int *status ) {
/*
*+
*  Name:
*     astPutNextText

*  Purpose:
*     Write a line of output text to a data sink.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     void astPutNextText( AstChannel *this, const char *line )

*  Class Membership:
*     Channel method.

*  Description:
*     This function writes an output line of text to a data sink
*     associated with a Channel.

*  Parameters:
*     this
*        Pointer to the Channel.
*     line
*        Pointer to a constant null-terminated string containing the
*        line of output text to be written (no newline character
*        should be appended).

*  Notes:
*     - This method is provided primarily so that derived classes may
*     over-ride it in order to write to alternative (textual) data
*     sinks.
*-
*/

/* Local Constants: */
#define ERRBUF_LEN 80

/* Local Variables: */
   char *errstat;                /* Pointer for system error message */
   char errbuf[ ERRBUF_LEN ];    /* Buffer for system error message */
   const char *sink_file;        /* Path to output sink file */
   const char *source_file;      /* Path to output source file */

/* Check the global error status. */
   if ( !astOK ) return;

/* If the SinkFile attribute of the Channel specifies an output file,
   but no output file has yet been opened, open it now. Report an error
   if it is the same as the source file. */
   if( astTestSinkFile( this ) && !this->fd_out ) {
      sink_file = astGetSinkFile( this );

      if( this->fd_out ) {
         source_file = astGetSourceFile( this );
         if( astOK && !strcmp( sink_file, source_file ) ) {
            astError( AST__WRERR, "astWrite(%s): Failed to open output "
                      "SinkFile '%s' - the file is currently being used "
                      "as the input SourceFile.", status, astGetClass( this ),
                      sink_file );
         }
      }

      if( astOK ) {
         this->fd_out = fopen( sink_file, "w" );
         if( !this->fd_out ) {
            if ( errno ) {
#if HAVE_STRERROR_R
               strerror_r( errno, errbuf, ERRBUF_LEN );
               errstat = errbuf;
#else
               errstat = strerror( errno );
#endif
               astError( AST__WRERR, "astWrite(%s): Failed to open output "
                         "SinkFile '%s' - %s.", status, astGetClass( this ),
                         sink_file, errstat );
            } else {
               astError( AST__WRERR, "astWrite(%s): Failed to open output "
                         "SinkFile '%s'.", status, astGetClass( this ),
                         sink_file );
            }
         }
      }
   }

/* Check no error occurred above. */
   if( astOK ) {

/* If an active output file descriptor is stored in the channel, write
   the text to it, with a newline appended. */
      if( this->fd_out ) {
         (void) fprintf( this->fd_out, "%s\n", line );

/* Otherwise, if a sink function (and its wrapper function) is defined for
   the Channel, use the wrapper function to invoke the sink function to
   output the text line. Since we are about to call an externally supplied
   function which may not be thread-safe, lock a mutex first. Also store
   the channel data pointer in a global variable so that it can be accessed
   in the source function using macro astChannelData. */
      } else if ( this->sink && this->sink_wrap ) {
         astStoreChannelData( this );
         LOCK_MUTEX2;
         ( *this->sink_wrap )( *this->sink, line, status );
         UNLOCK_MUTEX2;

/* Otherwise, simply write the text to standard output with a newline
   appended. */
      } else {
         (void) printf( "%s\n", line );
      }
   }
}

static AstObject *Read( AstChannel *this, int *status ) {
/*
*++
*  Name:
c     astRead
f     AST_READ

*  Purpose:
*     Read an Object from a Channel.

*  Type:
*     Public function.

*  Synopsis:
c     #include "channel.h"
c     AstObject *astRead( AstChannel *this )
f     RESULT = AST_READ( THIS, STATUS )

*  Class Membership:
*     Channel method.

*  Description:
*     This function reads the next Object from a Channel and returns a
*     pointer to the new Object.

*  Parameters:
c     this
f     THIS = INTEGER (Given)
*        Pointer to the Channel.
f     STATUS = INTEGER (Given and Returned)
f        The global status.

*  Returned Value:
c     astRead()
f     AST_READ = INTEGER
*        A pointer to the new Object. The class to which this will
*        belong is determined by the input data, so is not known in
*        advance.

*  Applicability:
*     FitsChan
c        All successful use of astRead on a FitsChan is destructive, so that
f        All successful use of AST_READ on a FitsChan is destructive, so that
*        FITS header cards are consumed in the process of reading an Object,
*        and are removed from the FitsChan (this deletion can be prevented
*        for specific cards by calling the FitsChan
c        astRetainFits function).
f        AST_RETAINFITS routine).
*        An unsuccessful call of
c        astRead
f        AST_READ
*        (for instance, caused by the FitsChan not containing the necessary
*        FITS headers cards needed to create an Object) results in the
*        contents of the FitsChan being left unchanged.
*     StcsChan
*        The AST Object returned by a successful use of
c        astRead
f        AST_READ
*        on an StcsChan, will be either a Region or a KeyMap, depending
*        on the values of the StcsArea, StcsCoords and StcsProps
*        attributes. See the documentation for these attributes for further
*        information.

*  Notes:
*     - A null Object pointer (AST__NULL) will be returned, without
*     error, if the Channel contains no further Objects to be read.
*     - A null Object pointer will also be returned if this function
c     is invoked with the AST error status set, or if it should fail
f     is invoked with STATUS set to an error value, or if it should fail
*     for any reason.
*--
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   AstLoaderType *loader;        /* Pointer to loader for Object */
   AstObject *new;               /* Pointer to new Object */
   char *class;                  /* Pointer to Object class name string */
   char *name;                   /* Pointer to data item name */
   int skip;                     /* Skip non-AST data? */
   int top;                      /* Reading top-level Object definition? */

/* Initialise. */
   new = NULL;

/* Check the global error status. */
   if ( !astOK ) return new;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this);

/* Determine if we are reading a top-level (i.e. user-level) Object
   definition, as opposed to the definition of an Object contained
   within another Object. This is indicated by the current nesting
   level. */
   top = ( nest == -1 );

/* If reading a top-level object, determine if data lying in between
   Object definitions in the input data stream are to be skipped. */
   skip = ( top && astGetSkip( this ) );

/* Read the next input data item. If we are reading a top-level Object
   definition, skip any unrelated data beforehand. Otherwise read the
   data strictly as it comes (there should be no unrelated data
   embedded within Object definitions themselves). */
   astGetNextData( this, skip, &name, &class );

/* If no suitable data item was found (and no error occurred), we have
   reached the end of data. For a top-level Object a NULL Object
   pointer is simply returned, but for a nested Object this indicates
   that part of the Object definition is missing, so report an
   error. */
   if ( astOK ) {
      if ( !name ) {
         if ( !top ) {
            astError( AST__EOCHN,
                      "astRead(%s): End of input encountered while trying to "
                      "read an AST Object.", status, astGetClass( this ) );
         }

/* If a data item was found, check it is a "Begin" item. If not, there
   is a data item missing, so report an error and free all memory. */
      } else if ( strcmp( name, "begin" ) ) {
         astError( AST__BADIN,
                   "astRead(%s): Missing \"Begin\" when expecting an Object.", status,
                   astGetClass( this ) );
         name = astFree( name );
         if ( class ) class = astFree( class );

/* If the required "Begin" item was found, free the memory used for the
   name string. */
      } else {
         name = astFree( name );

/* Use the associated class name to locate the loader for that
   class. This function will then be used to build the Object. */
         loader = astGetLoader( class, status );

/* Extend all necessary stack arrays to accommodate entries for the
   next nesting level (this allocates space if none has yet been
   allocated). */
         end_of_object = astGrow( end_of_object, nest + 2, sizeof( int ) );
         object_class = astGrow( object_class, nest + 2, sizeof( char * ) );
         values_class = astGrow( values_class, nest + 2, sizeof( char * ) );
         values_list = astGrow( values_list, nest + 2, sizeof( AstChannelValue * ) );
         values_ok = astGrow( values_ok, nest + 2, sizeof( int ) );

/* If an error occurred, free the memory used by the class string,
   which will not now be used. */
         if ( !astOK ) {
            class = astFree( class );

/* Otherwise, increment the nesting level and initialise the new stack
   elements for this new level. This includes clearing the
   "end_of_object" flag so that ReadClassData can read more data, and
   storing the class name of the object we are about to read. */
         } else {
            nest++;
            end_of_object[ nest ] = 0;
            object_class[ nest ] = class;
            values_class[ nest ] = NULL;
            values_list[ nest ] = NULL;
            values_ok[ nest ] = 0;

/* Invoke the loader, which reads the Object definition from the input
   data stream and builds the Object. Supply NULL/zero values to the
   loader so that it will substitute values appropriate to its own
   class. */
            new = (*loader)( NULL, (size_t) 0, NULL, NULL, this, status );

/* Clear the values list for the current nesting level. If the list
   has not been read or any Values remain in it, an error will
   result. */
            ClearValues( this, status );

/* If no error has yet occurred, check that the "end_of_object" flag
   has been set. If not, the input data were not correctly terminated,
   so report an error. */
            if ( astOK && !end_of_object[ nest ] ) {
               astError( AST__BADIN,
                         "astRead(%s): Unexpected end of input (missing end "
                         "of %s).", status,
                         astGetClass( this ), object_class[ nest ] );
            }

/* If an error occurred, report contextual information. Only do this
   for top-level Objects to avoid multple messages. */
            if ( !astOK && top ) {
               astError( astStatus, "Error while reading a %s from a %s.", status,
                         class, astGetClass( this ) );
            }

/* Clear the Object's class string, freeing the associated memory
   (note this is the memory allocated for the "class" string
   earlier). */
            object_class[ nest ] = astFree( object_class[ nest ] );

/* Restore the previous nesting level. */
            nest--;
         }

/* Once the top-level Object has been built, free the memory used by
   the stack arrays. */
         if ( top ) {
            end_of_object = astFree( end_of_object );
            object_class = astFree( object_class );
            values_class = astFree( values_class );
            values_list = astFree( values_list );
            values_ok = astFree( values_ok );
         }
      }
   }

/* If an error occurred, clean up by deleting the new Object and
   return a NULL pointer. */
   if ( !astOK ) new = astDelete( new );

/* Return the pointer to the new Object. */
   return new;
}

static void ReadClassData( AstChannel *this, const char *class, int *status ) {
/*
*+
*  Name:
*     astReadClassData

*  Purpose:
*     Read values from a data source for a class loader.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     void astReadClassData( AstChannel *this, const char *class )

*  Class Membership:
*     Channel method.

*  Description:
*     This function reads the data for a class from the data source
*     associated with a Channel, so as to provide values for
*     initialising the instance variables of that class as part of
*     building a complete Object. This function should be invoked by
*     the loader for each class immediately before it attempts to read
*     these values.
*
*     The values read are placed into the current values list by this
*     function. They may then be read from this list by the class
*     loader making calls to astReadDouble, astReadInt, astReadObject
*     and astReadString. The order in which values are read by the
*     loader is unimportant (although using the same order for reading
*     as for writing will usually be more efficient) and values are
*     removed from the list as they are read.

*  Parameters:
*     this
*        Pointer to the Channel.
*     class
*        A pointer to a constant null-terminated string containing the
*        name of the class whose loader is requesting the data (note
*        this is not usually the same as the class name of the Object
*        being built). This value allows the class structure of the
*        input data to be validated.
*-
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   AstObject *object;            /* Pointer to new Object */
   AstChannelValue *value;       /* Pointer to Value structure */
   char *name;                   /* Pointer to data item name string */
   char *val;                    /* Pointer to data item value string */
   int done;                     /* All class data read? */

/* Check the global error status. */
   if ( !astOK ) return;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this);

/* If the "values_ok" flag is set, this indicates that the values list
   (at the current nesting level) has been filled by a previous
   invocation of this function and has then been read by the
   appropriate class loader. In this case, clear any entries which may
   remain in the current values list. If any such entries are found,
   they represent input data that were not read, so an error will
   result. */
   if ( values_ok[ nest ] ) ClearValues( this, status );

/* If "values_class" is non-NULL, this indicates that the values list
   (at the current nesting level) has been filled by a previous
   invocation of this function, but that the values belong to a class
   whose loader has not yet tried to read them. In this case, we must
   continue to keep the values until they are needed, so we do not
   read any more input data this time. */
   if ( values_class[ nest ] ) {

/* If the class to which the previously saved values belong matches
   the class we now want values for, set the "values_ok" flag. This
   then allows the values to be accessed (by LookupValue). */
      values_ok[ nest ] = !strcmp( values_class[ nest ], class );

/* If the current values list is empty, we must read in values for the
   next class that appears in the input data. However, first check
   that the "end_of_object" flag has not been set. If it has, we have
   already reached the end of this Object's data, so there is some
   kind of problem with the order in which class loaders have been
   invoked. This will probably never happen, but report an error if
   necessary. */
   } else if ( end_of_object[ nest ] ) {
      astError( AST__LDERR,
                "astRead(%s): Invalid attempt to read further %s data "
                "following an end of %s.", status,
                astGetClass( this ), class, object_class[ nest ] );
      astError( AST__LDERR,
                "Perhaps the wrong class loader has been invoked?" , status);

/* If we need new values, loop to read input data items until the end
   of the data for a class is reached. */
   } else {
      done = 0;
      while ( astOK && !done ) {

/* Read the next input data item. */
         astGetNextData( this, 0, &name, &val );
         if ( astOK ) {

/* Unexpected end of input. */
/* ------------------------ */
/* If no "name" value is returned, we have reached the end of the
   input data stream without finding the required end of class
   terminator, so report an error. */
            if ( !name ) {
               astError( AST__EOCHN,
                         "astRead(%s): Unexpected end of input (missing end "
                         "of %s).", status,
                         astGetClass( this ), object_class[ nest ] );

/* "IsA" item. */
/* ----------- */
/* Otherwise, if an "IsA" item was read, it indicates the end of the
   data for a class. Store the pointer to the name of this class in
   "values_class" and note whether this is the class whose data we
   wanted in "values_ok". If the data we have read do not belong to
   the class we wanted, they will simply be kept until the right class
   comes looking for them. */
            } else if ( !strcmp( name, "isa" ) ) {
               values_class[ nest ] = val;
               values_ok[ nest ] = !strcmp( val, class );

/* Free the memory holding the name string. */
               name = astFree( name );

/* Note we have finished reading class data. */
               done = 1;

/* "End" item. */
/* ----------- */
/* If an "End" item was read, it indicates the end of the data both
   for a class and for the current Object definition as a whole. Set
   the "end_of_object" flag (for the current nesting level) which
   prevents any further data being read for this Object. This flag is
   also used (by Read) to check that an "End" item was actually
   read. */
            } else if ( !strcmp( name, "end" ) ) {
               end_of_object[ nest ] = 1;

/* Check that the class name in the "End" item matches that of the
   Object being built. If so, store the pointer to the name of this
   class in "values_class" and note whether this is the class whose
   data we wanted in "values_ok". If the data we have read do not
   belong to the class we wanted, they will simply be kept until the
   right class comes looking for them. */
               if ( !strcmp( val, object_class[ nest ] ) ) {
                  values_class[ nest ] = val;
                  values_ok[ nest ] = !strcmp( class, val );

/* If the "End" item contains the wrong class name (i.e. not matching
   the corresponding "Begin" item), then report an error. */
               } else {
                  astError( AST__BADIN,
                            "astRead(%s): Bad class structure in input data.", status,
                            astGetClass( this ) );
                  astError( AST__BADIN,
                            "End of %s read when expecting end of %s.", status,
                            val, object_class[ nest ] );

/* Free the memory used by the class string, which will not now be
   used. */
                  val = astFree( val );
               }

/* Free the memory holding the name string. */
               name = astFree( name );

/* Note we have finished reading class data. */
               done = 1;

/* String value. */
/* ------------- */
/* If any other name is obtained and "val" is not NULL, we have read a
   non-Object value, encoded as a string. Allocate memory for a Value
   structure to describe it. */
            } else if ( val ) {
               value = astMalloc( sizeof( AstChannelValue ) );
               if ( astOK ) {

/* Store pointers to the name and value string in the Value structure
   and note this is not an Object value. */
                  value->name = name;
                  value->ptr.string = val;
                  value->is_object = 0;

/* Append the Value structure to the values list for the current
   nesting level. */
                  AppendValue( value, values_list + nest, status );

/* If an error occurred, free the memory holding the "name" and "val"
   strings. */
               } else {
                  name = astFree( name );
                  val = astFree( val );
               }

/* Object value. */
/* ------------- */
/* If "val" is NULL, we have read an Object item, and the Object
   definition should follow. Allocate memory for a Value structure to
   describe it. */
            } else {
               value = astMalloc( sizeof( AstChannelValue ) );

/* Invoke astRead to read the Object definition from subsequent data
   items and to build the Object, returning a pointer to it. This will
   result in recursive calls to the current function, but as these
   will use higher nesting levels they will not interfere with the
   current invocation. */
               astreadclassdata_msg = 0;
               object = astRead( this );
               if ( astOK ) {

/* Store pointers to the name and Object in the Value structure and
   note this is an Object value. */
                  value->name = name;
                  value->ptr.object = object;
                  value->is_object = 1;

/* Append the Value structure to the values list for the current
   nesting level. */
                  AppendValue( value, values_list + nest, status );

/* If an error occurred, report a contextual error maessage and set
   the "astreadclassdata_msg" flag (this prevents multiple messages if this function is
   invoked recursively to deal with nested Objects). */
               } else {
                  if ( !astreadclassdata_msg ) {
                     astError( astStatus,
                               "Failed to read the \"%s\" Object value.", status,
                               name );
                     astreadclassdata_msg = 1;
                  }

/* Free the memory holding the "name" string and any Value structure
   that was allocated. */
                  name = astFree( name );
                  value = astFree( value );
               }
            }
         }
      }
   }
}

static double ReadDouble( AstChannel *this, const char *name, double def, int *status ) {
/*
*+
*  Name:
*     astReadDouble

*  Purpose:
*     Read a double value as part of loading a class.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     double astReadDouble( AstChannel *this, const char *name, double def )

*  Class Membership:
*     Channel method.

*  Description:
*     This function searches the current values list of a Channel to
*     identify a double value with a specified name. If such a value
*     is found, it is returned, otherwise a default value is returned
*     instead.
*
*     This function should only be invoked from within the loader
*     function associated with a class, in order to return a double
*     value to be assigned to an instance variable. It must be
*     preceded by a call to the astReadClassData function, which loads
*     the values associated with the class into the current values
*     list from the input data source.

*  Parameters:
*     this
*        Pointer to the Channel.
*     name
*        Pointer to a constant null-terminated character string
*        containing the name of the required value. This must be in
*        lower case with no surrounding white space. Note that names
*        longer than 6 characters will not match any value.
*     def
*        If no suitable value can be found (e.g. it is absent from the
*        data stream being read), then this value will be returned
*        instead.

*  Returned Value:
*     The required value, or the default if the value was not found.

*  Notes:
*     - A value of 0.0 will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*-
*/

/* Local Variables: */
   AstChannelValue *value;       /* Pointer to required Value structure */
   double result;                /* Value to be returned */
   int nc;                       /* Number of characters read by astSscanf */

/* Initialise. */
   result = 0.0;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Search for a Value structure with the required name in the current
   values list.*/
   value = LookupValue( name, status );
   if ( astOK ) {

/* If a Value was found, check that it describes a string (as opposed
   to an Object). */
      if ( value ) {
         if ( !value->is_object ) {

/* If so, then attempt to decode the string to give a double value,
   checking that the entire string is read (and checking for the magic string
   used to represent bad values). If this fails, then the wrong name has
   probably been given, or the input data are corrupt, so report an error. */
            nc = 0;
            if ( ( 0 == astSscanf( value->ptr.string, " " BAD_STRING " %n",
                                                      &nc ) )
                    && ( nc >= (int) strlen( value->ptr.string ) ) ) {
               result = AST__BAD;

            } else if ( !( ( 1 == astSscanf( value->ptr.string, " %lf %n",
                                                      &result, &nc ) )
                    && ( nc >= (int) strlen( value->ptr.string ) ) ) ) {
               astError( AST__BADIN,
                         "astRead(%s): The value \"%s = %s\" cannot "
                         "be read as a double precision floating point "
                         "number.", status, astGetClass( this ),
                         value->name, value->ptr.string );

            } else if( !astISFINITE( result ) ) {
               astError( AST__BADIN,
                         "astRead(%s): Illegal double precision floating "
                         "point value \"%s\" read for \"%s\".", status,
                         astGetClass( this ), value->ptr.string, value->name );

            }

/* Report a similar error if the Value does not describe a string. */
         } else {
            astError( AST__BADIN,
                      "astRead(%s): The Object \"%s = <%s>\" cannot "
                      "be read as a double precision floating point number.", status,
                      astGetClass( this ),
                      value->name, astGetClass( value->ptr.object ) );
         }

/* Free the Value structure and the resources it points at. */
         value = FreeValue( value, status );

/* If no suitable Value structure was found, then use the default
   value instead. */
      } else {
         result = def;
      }
   }

/* Return the result. */
   return result;
}

static int ReadInt( AstChannel *this, const char *name, int def, int *status ) {
/*
*+
*  Name:
*     astReadInt

*  Purpose:
*     Read an int value as part of loading a class.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     int astReadInt( AstChannel *this, const char *name, int def )

*  Class Membership:
*     Channel method.

*  Description:
*     This function searches the current values list of a Channel to
*     identify an int value with a specified name. If such a value is
*     found, it is returned, otherwise a default value is returned
*     instead.
*
*     This function should only be invoked from within the loader
*     function associated with a class, in order to return an int
*     value to be assigned to an instance variable. It must be
*     preceded by a call to the astReadClassData function, which loads
*     the values associated with the class into the current values
*     list from the input data source.

*  Parameters:
*     this
*        Pointer to the Channel.
*     name
*        Pointer to a constant null-terminated character string
*        containing the name of the required value. This must be in
*        lower case with no surrounding white space. Note that names
*        longer than 6 characters will not match any value.
*     def
*        If no suitable value can be found (e.g. it is absent from the
*        data stream being read), then this value will be returned
*        instead.

*  Returned Value:
*     The required value, or the default if the value was not found.

*  Notes:
*     - A value of zero will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*-
*/

/* Local Variables: */
   AstChannelValue *value;       /* Pointer to required Value structure */
   int nc;                       /* Number of characters read by astSscanf */
   int result;                   /* Value to be returned */

/* Initialise. */
   result = 0;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Search for a Value structure with the required name in the current
   values list.*/
   value = LookupValue( name, status );
   if ( astOK ) {

/* If a Value was found, check that it describes a string (as opposed
   to an Object). */
      if ( value ) {
         if ( !value->is_object ) {

/* If so, then attempt to decode the string to give an int value,
   checking that the entire string is read. If this fails, then the
   wrong name has probably been given, or the input data are corrupt,
   so report an error. */
            nc = 0;
            if ( !( ( 1 == astSscanf( value->ptr.string, " %d %n",
                                                      &result, &nc ) )
                    && ( nc >= (int) strlen( value->ptr.string ) ) ) ) {
               astError( AST__BADIN,
                         "astRead(%s): The value \"%s = %s\" cannot "
                         "be read as an integer.", status, astGetClass( this ),
                         value->name, value->ptr.string );
            }

/* Report a similar error if the Value does not describe a string. */
         } else {
            astError( AST__BADIN,
                      "astRead(%s): The Object \"%s = <%s>\" cannot "
                      "be read as an integer.", status, astGetClass( this ),
                      value->name, astGetClass( value->ptr.object ) );
         }

/* Free the Value structure and the resources it points at. */
         value = FreeValue( value, status );

/* If no suitable Value structure was found, then use the default
   value instead. */
      } else {
         result = def;
      }
   }

/* Return the result. */
   return result;
}

static AstObject *ReadObject( AstChannel *this, const char *name,
                              AstObject *def, int *status ) {
/*
*+
*  Name:
*     astReadObject

*  Purpose:
*     Read a (sub)Object as part of loading a class.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     AstObject *astReadObject( AstChannel *this, const char *name,
*                               AstObject *def )

*  Class Membership:
*     Channel method.

*  Description:
*     This function searches the current values list of a Channel to
*     identify an Object with a specified name. If such an Object is
*     found, a pointer to it is returned, otherwise a default pointer
*     is returned instead.
*
*     This function should only be invoked from within the loader
*     function associated with a class, in order to return an Object
*     pointer value to be assigned to an instance variable. It must be
*     preceded by a call to the astReadClassData function, which loads
*     the values associated with the class into the current values
*     list from the input data source.

*  Parameters:
*     this
*        Pointer to the Channel.
*     name
*        Pointer to a constant null-terminated character string
*        containing the name of the required Object. This must be in
*        lower case with no surrounding white space. Note that names
*        longer than 6 characters will not match any Object.
*     def
*        If no suitable Object can be found (e.g. the Object is absent
*        from the data stream being read), then a clone of this
*        default Object pointer will be returned instead (or NULL if
*        this default pointer is NULL).

*  Returned Value:
*     A pointer to the Object, or a clone of the default pointer if
*     the Object was not found.

*  Notes:
*     - A NULL pointer will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*-
*/

/* Local Variables: */
   AstObject *result;            /* Pointer value to return */
   AstChannelValue *value;       /* Pointer to required Value structure */

/* Initialise. */
   result = NULL;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Search for a Value structure with the required name in the current
   values list.*/
   value = LookupValue( name, status );
   if ( astOK ) {

/* If a Value was found, check that it describes an Object (as opposed to
   a string). */
      if ( value ) {
         if ( value->is_object ) {

/* If so, then extract the Object pointer, replacing it with NULL. */
            result = value->ptr.object;
            value->ptr.object = NULL;

/* If the Value does not describe an Object, then the wrong name has
   probably been given, or the input data are corrupt, so report an
   error. */
         } else {
            astError( AST__BADIN,
                      "astRead(%s): The value \"%s = %s\" cannot be "
                      "read as an Object.", status, astGetClass( this ),
                      value->name, value->ptr.string );
         }

/* Free the Value structure and the resources it points at. */
         value = FreeValue( value, status );

/* If no suitable Value structure was found, clone the default
   pointer, if given. */
      } else if ( def ) {
         result = astClone( def );
      }
   }

/* Return the result. */
   return result;
}

static char *ReadString( AstChannel *this, const char *name,
                         const char *def, int *status ) {
/*
*+
*  Name:
*     astReadString

*  Purpose:
*     Read a string value as part of loading a class.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     char *astReadString( AstChannel *this, const char *name,
*                          const char *def )

*  Class Membership:
*     Channel method.

*  Description:
*     This function searches the current values list of a Channel to
*     identify a string value with a specified name. If such a value
*     is found, a pointer to the string is returned, otherwise a
*     pointer to a copy of a default string is returned instead.
*
*     This function should only be invoked from within the loader
*     function associated with a class, in order to return a string
*     pointer value to be assigned to an instance variable. It must be
*     preceded by a call to the astReadClassData function, which loads
*     the values associated with the class into the current values
*     list from the input data source.

*  Parameters:
*     this
*        Pointer to the Channel.
*     name
*        Pointer to a constant null-terminated character string
*        containing the name of the required value. This must be in
*        lower case with no surrounding white space. Note that names
*        longer than 6 characters will not match any value.
*     def
*        If no suitable string can be found (e.g. the value is absent
*        from the data stream being read), then a dynamically
*        allocated copy of the null-terminated string pointed at by
*        "def" will be made, and a pointer to this copy will be
*        returned instead (or NULL if this default pointer is NULL).

*  Returned Value:
*     A pointer to a dynamically allocated null-terminated string
*     containing the value required, or to a copy of the default
*     string if the value was not found (or NULL if the "def" pointer
*     was NULL).

*  Notes:
*     - It is the caller's responsibility to arrange for the memory
*     holding the returned string to be freed (using astFree) when it
*     is no longer required.
*     - A NULL pointer will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*-
*/

/* Local Variables: */
   AstChannelValue *value;       /* Pointer to required Value structure */
   char *result;                 /* Pointer value to return */

/* Initialise. */
   result = NULL;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Search for a Value structure with the required name in the current
   values list.*/
   value = LookupValue( name, status );
   if ( astOK ) {

/* If a Value was found, check that it describes a string (as opposed
   to an Object). */
      if ( value ) {
         if ( !value->is_object ) {

/* If so, then extract the string pointer, replacing it with NULL. */
            result = value->ptr.string;
            value->ptr.string = NULL;

/* If the Value does not describe a string, then the wrong name has
   probably been given, or the input data are corrupt, so report an
   error. */
         } else {
            astError( AST__BADIN,
                      "astRead(%s): The Object \"%s = <%s>\" cannot "
                      "be read as a string.", status, astGetClass( this ),
                      value->name, astGetClass( value->ptr.object ) );
         }

/* Free the Value structure and the resources it points at. */
         value = FreeValue( value, status );

/* If no suitable Value structure was found, then make a dynamic copy
   of the default string (if given) and return a pointer to this. */
      } else if ( def ) {
         result = astStore( NULL, def, strlen( def ) + (size_t) 1 );
      }
   }

/* Return the result. */
   return result;
}

static void RemoveValue( AstChannelValue *value, AstChannelValue **head, int *status ) {
/*
*  Name:
*     RemoveValue

*  Purpose:
*     Remove a Value structure from a circular linked list.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     void RemoveValue( AstChannelValue *value, AstChannelValue **head, int *status );

*  Class Membership:
*     Channel member function.

*  Description:
*     This function removes a Value structure from a doubly linked
*     circular list of such structures. The "head of list" pointer is
*     updated to point at the element following the one removed.

*  Parameters:
*     value
*        Pointer to the structure to be removed (note that this must
*        actually be in the list, although this function does not
*        check).
*     head
*        Address of a pointer to the element at the head of the
*        list. This pointer will be updated to point at the list
*        element that follows the one removed. If the list becomes
*        empty, the pointer will be set to NULL.
*     status
*        Pointer to the inherited status variable.

*  Notes:
*     - This function does not perform error chacking and does not
*     generate errors.
*/

/* Remove the Value structure from the list by re-establishing links
   between the elements on either side of it. */
   value->blink->flink = value->flink;
   value->flink->blink = value->blink;

/* Update the head of list pointer to identify the following
   element. */
   *head = value->flink;

/* If the head of list identifies the removed element, then note that
   the list is now empty. */
   if ( *head == value ) *head = NULL;

/* Make the removed element point at itself. */
   value->flink = value;
   value->blink = value;
}

static void SetAttrib( AstObject *this_object, const char *setting, int *status ) {
/*
*  Name:
*     SetAttrib

*  Purpose:
*     Set an attribute value for a Channel.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     void SetAttrib( AstObject *this, const char *setting )

*  Class Membership:
*     Channel member function (over-rides the astSetAttrib protected
*     method inherited from the Object class).

*  Description:
*     This function assigns an attribute value for a Channel, the
*     attribute and its value being specified by means of a string of
*     the form:
*
*        "attribute= value "
*
*     Here, "attribute" specifies the attribute name and should be in
*     lower case with no white space present. The value to the right
*     of the "=" should be a suitable textual representation of the
*     value to be assigned and this will be interpreted according to
*     the attribute's data type.  White space surrounding the value is
*     only significant for string attributes.

*  Parameters:
*     this
*        Pointer to the Channel.
*     setting
*        Pointer to a null terminated string specifying the new attribute
*        value.
*/

/* Local Variables: */
   AstChannel *this;             /* Pointer to the Channel structure */
   int comment;                  /* Comment attribute value */
   int full;                     /* Full attribute value */
   int indent;                   /* Indent attribute value */
   int len;                      /* Length of setting string */
   int nc;                       /* Number of characters read by "astSscanf" */
   int report_level;             /* Skip attribute value */
   int skip;                     /* Skip attribute value */
   int sourcefile;               /* Offset of SourceFile string */
   int sinkfile;                 /* Offset of SinkFile string */
   int strict;                   /* Report errors instead of warnings? */

/* Check the global error status. */
   if ( !astOK ) return;

/* Obtain a pointer to the Channel structure. */
   this = (AstChannel *) this_object;

/* Obtain the length of the setting string. */
   len = (int) strlen( setting );

/* Test for each recognised attribute in turn, using "astSscanf" to parse
   the setting string and extract the attribute value (or an offset to
   it in the case of string values). In each case, use the value set
   in "nc" to check that the entire string was matched. Once a value
   has been obtained, use the appropriate method to set it. */

/* Comment. */
/* ---------*/
   if ( nc = 0,
        ( 1 == astSscanf( setting, "comment= %d %n", &comment, &nc ) )
        && ( nc >= len ) ) {
      astSetComment( this, comment );

/* Full. */
/* ----- */
   } else if ( nc = 0,
               ( 1 == astSscanf( setting, "full= %d %n", &full, &nc ) )
               && ( nc >= len ) ) {
      astSetFull( this, full );

/* Indent. */
/* ------- */
   } else if ( nc = 0,
               ( 1 == astSscanf( setting, "indent= %d %n", &indent, &nc ) )
               && ( nc >= len ) ) {
      astSetIndent( this, indent );

/* ReportLavel. */
/* ------------ */
   } else if ( nc = 0,
               ( 1 == astSscanf( setting, "reportlevel= %d %n", &report_level, &nc ) )
               && ( nc >= len ) ) {
      astSetReportLevel( this, report_level );

/* Skip. */
/* ----- */
   } else if ( nc = 0,
               ( 1 == astSscanf( setting, "skip= %d %n", &skip, &nc ) )
               && ( nc >= len ) ) {
      astSetSkip( this, skip );

/* SinkFile. */
/* --------- */
   } else if ( nc = 0,
               ( 0 == astSscanf( setting, "sinkfile=%n%*[^\n]%n", &sinkfile, &nc ) )
               && ( nc >= len ) ) {
      astSetSinkFile( this, setting + sinkfile );

/* SourceFile. */
/* ----------- */
   } else if ( nc = 0,
               ( 0 == astSscanf( setting, "sourcefile=%n%*[^\n]%n", &sourcefile, &nc ) )
               && ( nc >= len ) ) {
      astSetSourceFile( this, setting + sourcefile );

/* Strict. */
/* ------- */
   } else if ( nc = 0,
               ( 1 == astSscanf( setting, "strict= %d %n", &strict, &nc ) )
               && ( nc >= len ) ) {
      astSetStrict( this, strict );

/* If the attribute is still not recognised, pass it on to the parent
   method for further interpretation. */
   } else {
      (*parent_setattrib)( this_object, setting, status );
   }
}

static void SinkWrap( void (* sink)( const char * ), const char *line, int *status ) {
/*
*  Name:
*     SinkWrap

*  Purpose:
*     Wrapper function to invoke a C Channel sink function.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     void SinkWrap( void (* sink)( const char * ), const char *line, int *status )

*  Class Membership:
*     Channel member function.

*  Description:
*     This function invokes the sink function whose pointer is
*     supplied in order to write an output line to an external data
*     store.

*  Parameters:
*     sink
*        Pointer to a sink function, whose single parameter is a
*        pointer to a const, null-terminated string containing the
*        text to be written, and which returns void. This is the form
*        of Channel sink function employed by the C language interface
*        to the AST library.
*     status
*        Pointer to the inherited status variable.
*/

/* Check the global error status. */
   if ( !astOK ) return;

/* Invoke the sink function. */
   ( *sink )( line );
}

static char *SourceWrap( const char *(* source)( void ), int *status ) {
/*
*  Name:
*     SourceWrap

*  Purpose:
*     Wrapper function to invoke a C Channel source function.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     char *SourceWrap( const char *, int *status(* source)( void ) )

*  Class Membership:
*     Channel member function.

*  Description:
*     This function invokes the source function whose pointer is
*     supplied in order to read the next input line from an external
*     data store. It then returns a pointer to a dynamic string
*     containing a copy of the text that was read.

*  Parameters:
*     source
*        Pointer to a source function, with no parameters, that
*        returns a pointer to a const, null-terminated string
*        containing the text that it read. This is the form of Channel
*        source function employed by the C language interface to the
*        AST library.
*     status
*        Pointer to the inherited status variable.

*  Returned Value:
*     A pointer to a dynamically allocated, null terminated string
*     containing a copy of the text that was read. This string must be
*     freed by the caller (using astFree) when no longer required.
*
*     A NULL pointer will be returned if there is no more input text
*     to read.

*  Notes:
*     - A NULL pointer value will be returned if this function is
*     invoked with the global error status set or if it should fail
*     for any reason.
*/

/* Local Variables: */
   char *result;                 /* Pointer value to return */
   const char *line;             /* Pointer to input line */

/* Initialise. */
   result = NULL;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Invoke the source function to read the next input line and return a
   pointer to the resulting string. */
   line = ( *source )();

/* If a string was obtained, make a dynamic copy of it and save the
   resulting pointer. */
   if ( line ) result = astString( line, (int) strlen( line ) );

/* Return the result. */
   return result;
}

void astStoreChannelData_( AstChannel *this, int *status ) {
/*
*+
*  Name:
*     astStoreChannelData

*  Purpose:
*     Store the Channel's channel-data pointer in a thread-specific
*     global variable.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     astStoreChannelData( AstChannel *this )

*  Class Membership:
*     Channel method.

*  Description:
*     This function stores the Channel's channel-data pointer (if any)
*     established by the previous call to astPutChannelData, in a
*     thread-specific global variable from where the astChannelData macro
*     can access it.

*  Parameters:
*     this
*        Pointer to the Channel.
*-
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */

/* Check the global error status. */
   if ( !astOK ) return;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this);

/* Store the pointer int he global variable. */
   channel_data = this->data;
}

static int TestAttrib( AstObject *this_object, const char *attrib, int *status ) {
/*
*  Name:
*     TestAttrib

*  Purpose:
*     Test if a specified attribute value is set for a Channel.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     int TestAttrib( AstObject *this, const char *attrib, int *status )

*  Class Membership:
*     Channel member function (over-rides the astTestAttrib protected
*     method inherited from the Object class).

*  Description:
*     This function returns a boolean result (0 or 1) to indicate whether
*     a value has been set for one of a Channel's attributes.

*  Parameters:
*     this
*        Pointer to the Channel.
*     attrib
*        Pointer to a null terminated string specifying the attribute
*        name.  This should be in lower case with no surrounding white
*        space.
*     status
*        Pointer to the inherited status variable.

*  Returned Value:
*     One if a value has been set, otherwise zero.

*  Notes:
*     - A value of zero will be returned if this function is invoked
*     with the global status set, or if it should fail for any reason.
*/

/* Local Variables: */
   AstChannel *this;             /* Pointer to the Channel structure */
   int result;                   /* Result value to return */

/* Initialise. */
   result = 0;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Obtain a pointer to the Channel structure. */
   this = (AstChannel *) this_object;

/* Check the attribute name and test the appropriate attribute. */

/* Comment. */
/* -------- */
   if ( !strcmp( attrib, "comment" ) ) {
      result = astTestComment( this );

/* Full. */
/* ----- */
   } else if ( !strcmp( attrib, "full" ) ) {
      result = astTestFull( this );

/* Indent. */
/* ------- */
   } else if ( !strcmp( attrib, "indent" ) ) {
      result = astTestIndent( this );

/* ReportLevel. */
/* ------------ */
   } else if ( !strcmp( attrib, "reportlevel" ) ) {
      result = astTestReportLevel( this );

/* Skip. */
/* ----- */
   } else if ( !strcmp( attrib, "skip" ) ) {
      result = astTestSkip( this );

/* SourceFile. */
/* ----------- */
   } else if ( !strcmp( attrib, "sourcefile" ) ) {
      result = astTestSourceFile( this );

/* SinkFile. */
/* ----------- */
   } else if ( !strcmp( attrib, "sinkfile" ) ) {
      result = astTestSinkFile( this );

/* Strict. */
/* ------- */
   } else if ( !strcmp( attrib, "strict" ) ) {
      result = astTestStrict( this );

/* If the attribute is still not recognised, pass it on to the parent
   method for further interpretation. */
   } else {
      result = (*parent_testattrib)( this_object, attrib, status );
   }

/* Return the result, */
   return result;
}

static void Unquote( AstChannel *this, char *str, int *status ) {
/*
*  Name:
*     Unquote

*  Purpose:
*     Remove quotes from a (possibly) quoted string.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     void Unquote( AstChannel *this, char *str, int *status )

*  Class Membership:
*     Channel member function.

*  Description:
*     This function removes one layer of quote characters (") from a
*     string which is possibly quoted. Any quotes within quotes (which
*     should have been doubled when the string was originally quoted)
*     are also converted back to single quotes again.
*
*     The quotes need not start or end at the ends of the string, and
*     there may be any number of quoted sections within the string. No
*     error results if the string does not contain any quotes at all
*     (it is simply returned unchanged), but an error results if any
*     unmatched quotes are found.

*  Parameters:
*     this
*        Pointer to a Channel. This is only used for constructing error
*        messages and has no influence on the string processing.
*     str
*        Pointer to the null-terminated string to be processed. This
*        is modified in place. The new string starts at the same
*        location as the original but has a new null character
*        appended if necessary (it will usually be shorter than the
*        original).
*     status
*        Pointer to the inherited status variable.
*/

/* Local Variables: */
   int i;                        /* Loop counter for "input" characters */
   int j;                        /* Counter for "output" characters */
   int quoted;                   /* Inside a quoted string? */

/* Check the global error status. */
   if ( !astOK ) return;

/* Loop to inspect each character in the string. */
   quoted = 0;
   for ( i = j = 0; str[ i ]; i++ ) {

/* Non-quote characters are simply copied to their new location in the
   string. */
      if ( str[ i ] != '"' ) {
         str[ j++ ] = str[ i ];

/* If a quote character '"' is encountered and we are not already in a
   quoted string, then note the start of a quoted string (and discard
   the quote). */
      } else if ( !quoted ) {
         quoted = 1;

/* If a quote character is encountered inside a quoted string, then
   check if the next character is also a quote. If so, convert this
   double quote to a single one. */
      } else if ( str[ i + 1 ] == '"' ) {
         str[ j++ ] = '"';
         i++;

/* If a single quote character is encountered inside a quoted string,
   then note the end of the quoted string (and discard the quote). */
      } else {
         quoted = 0;
      }
   }

/* Append a null to terminate the processed string. */
   str[ j ] = '\0';

/* If the "quoted" flag is still set, then there were unmatched
   quotes, so report an error. */
   if ( quoted ) {
      astError( AST__UNMQT,
                "astRead(%s): Unmatched quotes in input data: %s.", status,
                astGetClass( this ), str );
   }
}

static int Use( AstChannel *this, int set, int helpful, int *status ) {
/*
*  Name:
*     Use

*  Purpose:
*     Decide whether to write a value to a data sink.

*  Type:
*     Private function.

*  Synopsis:
*     #include "channel.h"
*     int Use( AstChannel *this, int set, int helpful, int *status )

*  Class Membership:
*     Channel member function.

*  Description:
*     This function decides whether a value supplied by a class "Dump"
*     function, via a call to one of the astWrite... protected
*     methods, should actually be written to the data sink associated
*     with a Channel.
*
*     This decision is based on the settings of the "set" and
*     "helpful" flags supplied to the astWrite... method, plus the
*     attribute settings of the Channel.

*  Parameters:
*     this
*        A pointer to the Channel.
*     set
*        The "set" flag supplied.
*     helpful
*        The "helpful" value supplied.
*     status
*        Pointer to the inherited status variable.

*  Returned Value:
*     One if the value should be written out, otherwise zero.

*  Notes:
*     - A value of zero will be returned if this function is invoked
*     with the global error status set or if it should fail for any
*     reason.
*/

/* Local Variables: */
   int full;                     /* Full attribute value */
   int result;                   /* Result value to be returned */

/* Check the global error status. */
   if ( !astOK ) return 0;

/* If "set" is non-zero, then so is the result ("set" values must
   always be written out). */
   result = ( set != 0 );

/* Otherwise, obtain the value of the Channel's Full attribute. */
   if ( !set ) {
      full = astGetFull( this );

/* If Full is positive, display all values, if zero, display only
   "helpful" values, if negative, display no (un-"set") values. */
      if ( astOK ) result = ( ( helpful && ( full > -1 ) ) || ( full > 0 ) );
   }

/* Return the result. */
   return result;
}

static int Write( AstChannel *this, AstObject *object, int *status ) {
/*
*++
*  Name:
c     astWrite
f     AST_WRITE

*  Purpose:
*     Write an Object to a Channel.

*  Type:
*     Public function.

*  Synopsis:
c     #include "channel.h"
c     int astWrite( AstChannel *this, AstObject *object )
f     RESULT = AST_WRITE( THIS, OBJECT, STATUS )

*  Class Membership:
*     Channel method.

*  Description:
*     This function writes an Object to a Channel, appending it to any
*     previous Objects written to that Channel.

*  Parameters:
c     this
f     THIS = INTEGER (Given)
*        Pointer to the Channel.
c     object
f     OBJECT = INTEGER (Given)
*        Pointer to the Object which is to be written.
f     STATUS = INTEGER (Given and Returned)
f        The global status.

*  Returned Value:
c     astWrite()
f     AST_WRITE = INTEGER
*        The number of Objects written to the Channel by this
c        invocation of astWrite (normally, this will be one).
f        invocation of AST_WRITE (normally, this will be one).

*  Applicability:
*     FitsChan
*        If the FitsChan uses a foreign encoding (e.g. FITS-WCS) rather
*        than the native AST encoding, then storing values in the
*        FitsChan for keywords NAXIS1, NAXIS2, etc., before invoking
c        astWrite
f        AST_WRITE
*        can help to produce a successful write.

*  Notes:
*     - A value of zero will be returned if this function is invoked
c     with the AST error status set, or if it should fail for any
f     with STATUS set to an error value, or if it should fail for any
*     reason.
*     - Invoking this function will usually cause the sink function
*     associated with the channel to be called in order to transfer a
*     textual description of the supplied object to some external data
*     store. However, the FitsChan class behaves differently. Invoking
*     this function on a FitsChan causes new FITS header cards to be
*     added to an internal buffer (the sink function is not invoked).
*     This buffer is written out through the sink function only when the
*     FitsChan is deleted.
*--
*/

/* Check the global error status. */
   if ( !astOK ) return 0;

/* The work of this function is actually performed by the protected
   astDump method of the Object. The fact that this is further
   encapsulated within the astWrite method (which belongs to the
   Channel) is simply a trick to allow it to be over-ridden either by
   a derived Channel, or a derived Object (or both), and hence to
   adapt to the nature of either argument. */
   astDump( object, this );

/* Return the number of Objects written. */
   return astOK ? 1 : 0;
}

static void WriteBegin( AstChannel *this, const char *class,
                        const char *comment, int *status ) {
/*
*+
*  Name:
*     astWriteBegin

*  Purpose:
*     Write a "Begin" data item to a data sink.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     void astWriteBegin( AstChannel *this, const char *class,
*                         const char *comment )

*  Class Membership:
*     Channel method.

*  Description:
*     This function writes a "Begin" data item to the data sink
*     associated with a Channel, so as to begin the output of a new
*     Object definition.

*  Parameters:
*     this
*        Pointer to the Channel.
*     class
*        Pointer to a constant null-terminated string containing the
*        name of the class to which the Object belongs.
*     comment
*        Pointer to a constant null-terminated string containing a
*        textual comment to be associated with the "Begin"
*        item. Normally, this will describe the purpose of the Object.

*  Notes:
*     - The comment supplied may not actually be used, depending on
*     the nature of the Channel supplied.
*-
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   char *line;                   /* Pointer to dynamic output string */
   int i;                        /* Loop counter for indentation characters */
   int nc;                       /* Number of output characters */

/* Check the global error status. */
   if ( !astOK ) return;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this);

/* Start building a dynamic string with an initial space. Then add
   further spaces to suit the current indentation level. */
   line = astAppendString( NULL, &nc, " " );
   for ( i = 0; i < current_indent; i++ ) {
      line = astAppendString( line, &nc, " " );
   }

/* Append the "Begin" keyword followed by the class name. */
   line = astAppendString( line, &nc, "Begin " );
   line = astAppendString( line, &nc, class );

/* If required, also append the comment. */
   if ( astGetComment( this ) && *comment ) {
      line = astAppendString( line, &nc, " \t# " );
      line = astAppendString( line, &nc, comment );
   }

/* Write out the resulting line of text. */
   OutputTextItem( this, line, status );

/* Free the dynamic string. */
   line = astFree( line );

/* Increment the indentation level and clear the count of items written
   for this Object. */
   current_indent += astGetIndent( this );
   items_written = 0;
}

static void WriteDouble( AstChannel *this, const char *name,
                         int set, int helpful,
                         double value, const char *comment, int *status ) {
/*
*+
*  Name:
*     astWriteDouble

*  Purpose:
*     Write a double value to a data sink.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     void astWriteDouble( AstChannel *this, const char *name,
*                          int set, int helpful,
*                          double value, const char *comment )

*  Class Membership:
*     Channel method.

*  Description:
*     This function writes a named double value, representing the
*     value of a class instance variable, to the data sink associated
*     with a Channel. It is intended for use by class "Dump" functions
*     when writing out class information which will subsequently be
*     re-read.

*  Parameters:
*     this
*        Pointer to the Channel.
*     name
*        Pointer to a constant null-terminated string containing the
*        name to be used to identify the value in the external
*        representation. This will form the key for identifying it
*        again when it is re-read. The name supplied should be unique
*        within its class.
*
*        Mixed case may be used and will be preserved in the external
*        representation (where possible) for cosmetic effect. However,
*        case is not significant when re-reading values.
*
*        It is recommended that a maximum of 6 alphanumeric characters
*        (starting with an alphabetic character) be used. This permits
*        maximum flexibility in adapting to standard external data
*        representations (e.g. FITS).
*     set
*        If this is zero, it indicates that the value being written is
*        a default value (or can be re-generated from other values) so
*        need not necessarily be written out. Such values will
*        typically be included in the external representation with
*        (e.g.) a comment character so that they are available to
*        human readers but will be ignored when re-read. They may also
*        be completely omitted in some circumstances.
*
*        If "set" is non-zero, the value will always be explicitly
*        included in the external representation so that it can be
*        re-read.
*     helpful
*        This flag provides a hint about whether a value whose "set"
*        flag is zero (above) should actually appear at all in the
*        external representaton.
*
*        If the external representation allows values to be "commented
*        out" then, by default, values will be included in this form
*        only if their "helpful" flag is non-zero. Otherwise, they
*        will be omitted entirely. When possible, omitting the more
*        obscure values associated with a class is recommended in
*        order to improve readability.
*
*        This default behaviour may be further modified if the
*        Channel's Full attribute is set - either to permit all values
*        to be shown, or to suppress non-essential information
*        entirely.
*     value
*        The value to be written.
*     comment
*        Pointer to a constant null-terminated string containing a
*        textual comment to be associated with the value.
*
*        Note that this comment may not actually be used, depending on
*        the nature of the Channel supplied and the setting of its
*        Comment attribute.
*-
*/

/* Local Constants: */
#define BUFF_LEN 100             /* Size of local formatting buffer */

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   char *line;                   /* Pointer to dynamic output string */
   char buff[ BUFF_LEN + 1 ];    /* Local formatting buffer */
   int i;                        /* Loop counter for indentation characters */
   int nc;                       /* Number of output characters */

/* Check the global error status. */
   if ( !astOK ) return;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this);

/* Use the "set" and "helpful" flags, along with the Channel's
   attributes to decide whether this value should actually be
   written. */
   if ( Use( this, set, helpful, status ) ) {

/* Start building a dynamic string with an initial space, or a comment
   character if "set" is zero. Then add further spaces to suit the
   current indentation level. */
      line = astAppendString( NULL, &nc, set ? " " : "#" );
      for ( i = 0; i < current_indent; i++ ) {
         line = astAppendString( line, &nc, " " );
      }

/* Append the name string followed by " = ". */
      line = astAppendString( line, &nc, name );
      line = astAppendString( line, &nc, " = " );

/* Format the value as a string and append this. Make sure "-0" isn't
   produced. Use a magic string to represent bad values. */
      if( value != AST__BAD ) {
         (void) sprintf( buff, "%.*g", DBL_DIG, value );
         if ( !strcmp( buff, "-0" ) ) {
            buff[ 0 ] = '0';
            buff[ 1 ] = '\0';
         }
      } else {
         strcpy( buff, BAD_STRING );
      }
      line = astAppendString( line, &nc, buff );

/* If required, also append the comment. */
      if ( astGetComment( this ) && *comment ) {
         line = astAppendString( line, &nc, " \t# " );
         line = astAppendString( line, &nc, comment );
      }

/* Write out the resulting line of text. */
      OutputTextItem( this, line, status );

/* Free the dynamic string. */
      line = astFree( line );
   }

/* Undefine macros local to this function. */
#undef BUFF_LEN
}

static void WriteEnd( AstChannel *this, const char *class, int *status ) {
/*
*+
*  Name:
*     astWriteEnd

*  Purpose:
*     Write an "End" data item to a data sink.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     void astWriteEnd( AstChannel *this, const char *class )

*  Class Membership:
*     Channel method.

*  Description:
*     This function writes an "End" data item to the data sink
*     associated with a Channel. This item delimits the end of an
*     Object definition.

*  Parameters:
*     this
*        Pointer to the Channel.
*     class
*        Pointer to a constant null-terminated string containing the
*        class name of the Object whose definition is being terminated
*        by the "End" item.
*-
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   char *line;                   /* Pointer to dynamic output string */
   int i;                        /* Loop counter for indentation characters */
   int nc;                       /* Number of output characters */

/* Check the global error status. */
   if ( !astOK ) return;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this);

/* Decrement the indentation level so that the "End" item matches the
   corresponding "Begin" item. */
   current_indent -= astGetIndent( this );

/* Start building a dynamic string with an initial space. Then add
   further spaces to suit the current indentation level. */
   line = astAppendString( NULL, &nc, " " );
   for ( i = 0; i < current_indent; i++ ) {
      line = astAppendString( line, &nc, " " );
   }

/* Append the "End" keyword followed by the class name. */
   line = astAppendString( line, &nc, "End " );
   line = astAppendString( line, &nc, class );

/* Write out the resulting line of text. */
   OutputTextItem( this, line, status );

/* Free the dynamic string. */
   line = astFree( line );
}

static void WriteInt( AstChannel *this, const char *name, int set, int helpful,
                      int value, const char *comment, int *status ) {
/*
*+
*  Name:
*     astWriteInt

*  Purpose:
*     Write an integer value to a data sink.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     void astWriteInt( AstChannel *this, const char *name,
*                       int set, int helpful,
*                       int value, const char *comment )

*  Class Membership:
*     Channel method.

*  Description:
*     This function writes a named integer value, representing the
*     value of a class instance variable, to the data sink associated
*     with a Channel. It is intended for use by class "Dump" functions
*     when writing out class information which will subsequently be
*     re-read.

*  Parameters:
*     this
*        Pointer to the Channel.
*     name
*        Pointer to a constant null-terminated string containing the
*        name to be used to identify the value in the external
*        representation. This will form the key for identifying it
*        again when it is re-read. The name supplied should be unique
*        within its class.
*
*        Mixed case may be used and will be preserved in the external
*        representation (where possible) for cosmetic effect. However,
*        case is not significant when re-reading values.
*
*        It is recommended that a maximum of 6 alphanumeric characters
*        (starting with an alphabetic character) be used. This permits
*        maximum flexibility in adapting to standard external data
*        representations (e.g. FITS).
*     set
*        If this is zero, it indicates that the value being written is
*        a default value (or can be re-generated from other values) so
*        need not necessarily be written out. Such values will
*        typically be included in the external representation with
*        (e.g.) a comment character so that they are available to
*        human readers but will be ignored when re-read. They may also
*        be completely omitted in some circumstances.
*
*        If "set" is non-zero, the value will always be explicitly
*        included in the external representation so that it can be
*        re-read.
*     helpful
*        This flag provides a hint about whether a value whose "set"
*        flag is zero (above) should actually appear at all in the
*        external representaton.
*
*        If the external representation allows values to be "commented
*        out" then, by default, values will be included in this form
*        only if their "helpful" flag is non-zero. Otherwise, they
*        will be omitted entirely. When possible, omitting the more
*        obscure values associated with a class is recommended in
*        order to improve readability.
*
*        This default behaviour may be further modified if the
*        Channel's Full attribute is set - either to permit all values
*        to be shown, or to suppress non-essential information
*        entirely.
*     value
*        The value to be written.
*     comment
*        Pointer to a constant null-terminated string containing a
*        textual comment to be associated with the value.
*
*        Note that this comment may not actually be used, depending on
*        the nature of the Channel supplied and the setting of its
*        Comment attribute.
*-
*/

/* Local Constants: */
#define BUFF_LEN 50              /* Size of local formatting buffer */

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   char *line;                   /* Pointer to dynamic output string */
   char buff[ BUFF_LEN + 1 ];    /* Local formatting buffer */
   int i;                        /* Loop counter for indentation characters */
   int nc;                       /* Number of output characters */

/* Check the global error status. */
   if ( !astOK ) return;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this);

/* Use the "set" and "helpful" flags, along with the Channel's
   attributes to decide whether this value should actually be
   written. */
   if ( Use( this, set, helpful, status ) ) {

/* Start building a dynamic string with an initial space, or a comment
   character if "set" is zero. Then add further spaces to suit the
   current indentation level. */
      line = astAppendString( NULL, &nc, set ? " " : "#" );
      for ( i = 0; i < current_indent; i++ ) {
         line = astAppendString( line, &nc, " " );
      }

/* Append the name string followed by " = ". */
      line = astAppendString( line, &nc, name );
      line = astAppendString( line, &nc, " = " );

/* Format the value as a decimal string and append this. */
      (void) sprintf( buff, "%d", value );
      line = astAppendString( line, &nc, buff );

/* If required, also append the comment. */
      if ( astGetComment( this ) && *comment ) {
         line = astAppendString( line, &nc, " \t# " );
         line = astAppendString( line, &nc, comment );
      }

/* Write out the resulting line of text. */
      OutputTextItem( this, line, status );

/* Free the dynamic string. */
      line = astFree( line );
   }

/* Undefine macros local to this function. */
#undef BUFF_LEN
}

int astWriteInvocations_( int *status ){
/*
*+
*  Name:
*     astWriteInvocations

*  Purpose:
*     Returns the number of invocations of the astWrite method.

*  Type:
*     Protected function.

*  Synopsis:
*     #include "channel.h"
*     int astWriteInvocations

*  Class Membership:
*     Channel method.

*  Description:
*     This function returns the number of invocations of astWrite which
*     have been made so far, excluding those made from within the
*     astWriteObject method. An example of its use is to allow a Dump
*     function to determine if a sub-object has already been dumped
*     during the current invocation of astWrite. See the Dump method for
*     the AstUnit class as an example.
*-
*/
   astDECLARE_GLOBALS
   astGET_GLOBALS(NULL);
   return nwrite_invoc;
}

static void WriteIsA( AstChannel *this, const char *class,
                      const char *comment, int *status ) {
/*
*+
*  Name:
*     astWriteIsA

*  Purpose:
*     Write an "IsA" data item to a data sink.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     void astWriteIsA( AstChannel *this, const char *class,
*                       const char *comment )

*  Class Membership:
*     Channel method.

*  Description:
*     This function writes an "IsA" data item to the data sink
*     associated with a Channel. This item delimits the end of the
*     data associated with the instance variables of a class, as part
*     of an overall Object definition.

*  Parameters:
*     this
*        Pointer to the Channel.
*     class
*        Pointer to a constant null-terminated string containing the
*        name of the class whose data are terminated by the "IsA"
*        item.
*     comment
*        Pointer to a constant null-terminated string containing a
*        textual comment to be associated with the "IsA"
*        item. Normally, this will describe the purpose of the class
*        whose data are being terminated.

*  Notes:
*     - The comment supplied may not actually be used, depending on
*     the nature of the Channel supplied.
*-
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   char *line;                   /* Pointer to dynamic output string */
   int i;                        /* Loop counter for indentation characters */
   int indent_inc;               /* Indentation increment */
   int nc;                       /* Number of output characters */

/* Check the global error status. */
   if ( !astOK ) return;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this);

/* Output an "IsA" item only if there has been at least one item
   written since the last "Begin" or "IsA" item, or if the Full
   attribute for the Channel is greater than zero (requesting maximum
   information). */
   if ( items_written || astGetFull( this ) > 0 ) {

/* Start building a dynamic string with an initial space. Then add
   further spaces to suit the current indentation level, but reduced
   by one to allow the "IsA" item to match the "Begin" and "End" items
   which enclose it. */
      indent_inc = astGetIndent( this );
      line = astAppendString( NULL, &nc, " " );
      for ( i = 0; i < ( current_indent - indent_inc ); i++ ) {
         line = astAppendString( line, &nc, " " );
      }

/* Append the "IsA" keyword followed by the class name. */
      line = astAppendString( line, &nc, "IsA " );
      line = astAppendString( line, &nc, class );

/* If required, also append the comment. */
      if ( astGetComment( this ) && *comment ) {
         line = astAppendString( line, &nc, " \t# " );
         line = astAppendString( line, &nc, comment );
      }

/* Write out the resulting line of text. */
      OutputTextItem( this, line, status );

/* Free the dynamic string. */
      line = astFree( line );

/* Clear the count of items written for this class. */
      items_written = 0;
   }
}

static void WriteObject( AstChannel *this, const char *name,
                         int set, int helpful,
                         AstObject *value, const char *comment, int *status ) {
/*
*+
*  Name:
*     astWriteObject

*  Purpose:
*     Write an Object as a value to a data sink.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     void astWriteObject( AstChannel *this, const char *name,
*                          int set, int helpful,
*                          AstObject *value, const char *comment )

*  Class Membership:
*     Channel method.

*  Description:
*     This function writes an Object as a named value, representing
*     the value of a class instance variable, to the data sink
*     associated with a Channel. It is intended for use by class
*     "Dump" functions when writing out class information which will
*     subsequently be re-read.

*  Parameters:
*     this
*        Pointer to the Channel.
*     name
*        Pointer to a constant null-terminated string containing the
*        name to be used to identify the value in the external
*        representation. This will form the key for identifying it
*        again when it is re-read. The name supplied should be unique
*        within its class.
*
*        Mixed case may be used and will be preserved in the external
*        representation (where possible) for cosmetic effect. However,
*        case is not significant when re-reading values.
*
*        It is recommended that a maximum of 6 alphanumeric characters
*        (starting with an alphabetic character) be used. This permits
*        maximum flexibility in adapting to standard external data
*        representations (e.g. FITS).
*     set
*        If this is zero, it indicates that the value being written is
*        a default value (or can be re-generated from other values) so
*        need not necessarily be written out. Such values will
*        typically be included in the external representation with
*        (e.g.) a comment character so that they are available to
*        human readers but will be ignored when re-read. They may also
*        be completely omitted in some circumstances.
*
*        If "set" is non-zero, the value will always be explicitly
*        included in the external representation so that it can be
*        re-read.
*     helpful
*        This flag provides a hint about whether a value whose "set"
*        flag is zero (above) should actually appear at all in the
*        external representaton.
*
*        If the external representation allows values to be "commented
*        out" then, by default, values will be included in this form
*        only if their "helpful" flag is non-zero. Otherwise, they
*        will be omitted entirely. When possible, omitting the more
*        obscure values associated with a class is recommended in
*        order to improve readability.
*
*        This default behaviour may be further modified if the
*        Channel's Full attribute is set - either to permit all values
*        to be shown, or to suppress non-essential information
*        entirely.
*     value
*        A Pointer to the Object to be written.
*     comment
*        Pointer to a constant null-terminated string containing a
*        textual comment to be associated with the value.
*
*        Note that this comment may not actually be used, depending on
*        the nature of the Channel supplied and the setting of its
*        Comment attribute.
*-
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   char *line;                   /* Pointer to dynamic output string */
   int i;                        /* Loop counter for indentation characters */
   int indent_inc;               /* Indentation increment */
   int nc;                       /* Number of output characters */

/* Check the global error status. */
   if ( !astOK ) return;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this);

/* Use the "set" and "helpful" flags, along with the Channel's
   attributes to decide whether this value should actually be
   written. */
   if ( Use( this, set, helpful, status ) ) {

/* Start building a dynamic string with an initial space, or a comment
   character if "set" is zero. Then add further spaces to suit the
   current indentation level. */
      line = astAppendString( NULL, &nc, set ? " " : "#" );
      for ( i = 0; i < current_indent; i++ ) {
         line = astAppendString( line, &nc, " " );
      }

/* Append the name string followed by " =". The absence of a value on
   the right hand side indicates an Object value, whose definition
   follows. */
      line = astAppendString( line, &nc, name );
      line = astAppendString( line, &nc, " =" );

/* If required, also append the comment. */
      if ( astGetComment( this ) && *comment ) {
         line = astAppendString( line, &nc, " \t# " );
         line = astAppendString( line, &nc, comment );
      }

/* Write out the resulting line of text. */
      OutputTextItem( this, line, status );

/* Free the dynamic string. */
      line = astFree( line );

/* If the value is not a default, write the Object to the Channel as
   well, suitably indented (this is omitted if the value is commented
   out). */
      if ( set ) {
         indent_inc = astGetIndent( this );
         current_indent += indent_inc;
         (void) astWrite( this, value );
         current_indent -= indent_inc;
      }
   }
}

static void WriteString( AstChannel *this, const char *name,
                         int set, int helpful,
                         const char *value, const char *comment, int *status ) {
/*
*+
*  Name:
*     astWriteString

*  Purpose:
*     Write a string value to a data sink.

*  Type:
*     Protected virtual function.

*  Synopsis:
*     #include "channel.h"
*     void astWriteString( AstChannel *this, const char *name,
*                          int set, int helpful,
*                          const char *value, const char *comment )

*  Class Membership:
*     Channel method.

*  Description:
*     This function writes a named string value, representing the
*     value of a class instance variable, to the data sink associated
*     with a Channel. It is intended for use by class "Dump" functions
*     when writing out class information which will subsequently be
*     re-read.

*  Parameters:
*     this
*        Pointer to the Channel.
*     name
*        Pointer to a constant null-terminated string containing the
*        name to be used to identify the value in the external
*        representation. This will form the key for identifying it
*        again when it is re-read. The name supplied should be unique
*        within its class.
*
*        Mixed case may be used and will be preserved in the external
*        representation (where possible) for cosmetic effect. However,
*        case is not significant when re-reading values.
*
*        It is recommended that a maximum of 6 alphanumeric characters
*        (starting with an alphabetic character) be used. This permits
*        maximum flexibility in adapting to standard external data
*        representations (e.g. FITS).
*     set
*        If this is zero, it indicates that the value being written is
*        a default value (or can be re-generated from other values) so
*        need not necessarily be written out. Such values will
*        typically be included in the external representation with
*        (e.g.) a comment character so that they are available to
*        human readers but will be ignored when re-read. They may also
*        be completely omitted in some circumstances.
*
*        If "set" is non-zero, the value will always be explicitly
*        included in the external representation so that it can be
*        re-read.
*     helpful
*        This flag provides a hint about whether a value whose "set"
*        flag is zero (above) should actually appear at all in the
*        external representaton.
*
*        If the external representation allows values to be "commented
*        out" then, by default, values will be included in this form
*        only if their "helpful" flag is non-zero. Otherwise, they
*        will be omitted entirely. When possible, omitting the more
*        obscure values associated with a class is recommended in
*        order to improve readability.
*
*        This default behaviour may be further modified if the
*        Channel's Full attribute is set - either to permit all values
*        to be shown, or to suppress non-essential information
*        entirely.
*     value
*        Pointer to a constant null-terminated string containing the
*        value to be written.
*     comment
*        Pointer to a constant null-terminated string containing a
*        textual comment to be associated with the value.
*
*        Note that this comment may not actually be used, depending on
*        the nature of the Channel supplied and the setting of its
*        Comment attribute.
*-
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   char *line;                   /* Pointer to dynamic output string */
   int i;                        /* Loop counter for characters */
   int nc;                       /* Number of output characters */
   int quote;                    /* Quote character found? */
   int size;                     /* Size of allocated memory */

/* Check the global error status. */
   if ( !astOK ) return;

/* Get a pointer to the structure holding thread-specific global data. */
   astGET_GLOBALS(this);

/* Use the "set" and "helpful" flags, along with the Channel's
   attributes to decide whether this value should actually be
   written. */
   if ( Use( this, set, helpful, status ) ) {

/* Start building a dynamic string with an initial space, or a comment
   character if "set" is zero. Then add further spaces to suit the
   current indentation level. */
      line = astAppendString( NULL, &nc, set ? " " : "#" );
      for ( i = 0; i < current_indent; i++ ) {
         line = astAppendString( line, &nc, " " );
      }

/* Append the name string followed by " = " and an opening quote
   character (the string will be quoted to protect leading and
   trailing spaces). */
      line = astAppendString( line, &nc, name );
      line = astAppendString( line, &nc, " = \"" );

/* We now append the value string, but must inspect each character so
   that quotes (appearing inside quotes) can be doubled. Determine the
   current size of memory allocated for the dynamic string. */
      size = (int) astSizeOf( line );

/* Loop to inspect each character and see if it is a quote. */
      for ( i = 0; value[ i ]; i++ ) {
         quote = ( value[ i ] == '"' );

/* If more memory is required, extend the dynamic string (allowing for
   doubling of quotes and the final null) and save its new size. */
         if ( nc + 2 + quote > size ) {
            line = astGrow( line, nc + 2 + quote, sizeof( char ) );
            if ( astOK ) {
               size = (int) astSizeOf( line );

/* Quit if an error occurs. */
            } else {
               break;
            }
         }

/* Append the value character to the dynamic string, duplicating each
   quote character. */
         line[ nc++ ] = value[ i ];
         if ( quote ) line[ nc++ ] = '"';
      }

/* Append the closing quote. */
      line = astAppendString( line, &nc, "\"" );

/* If required, also append the comment. */
      if ( astGetComment( this ) && *comment ) {
         line = astAppendString( line, &nc, " \t# " );
         line = astAppendString( line, &nc, comment );
      }

/* Write out the resulting line of text. */
      OutputTextItem( this, line, status );

/* Free the dynamic string. */
      line = astFree( line );
   }
}

/* Functions which access class attributes. */
/* ---------------------------------------- */
/* Implement member functions to access the attributes associated with
   this class using the macros defined for this purpose in the
   "object.h" file. */

/*
*att++
*  Name:
*     SourceFile

*  Purpose:
*     Input file from which to read data.

*  Type:
*     Public attribute.

*  Synopsis:
*     String.

*  Description:
*     This attribute specifies the name of a file from which the Channel
*     should read data. If specified it is used in preference to any source
*     function specified when the Channel was created.
*
*     Assigning a new value to this attribute will cause any previously
*     opened SourceFile to be closed. The first subsequent call to
c     astRead
f     AST_READ
*     will attempt to open the new file (an error will be reported if the
*     file cannot be opened), and read data from it. All subsequent call to
c     astRead
f     AST_READ
*     will read data from the new file, until the SourceFile attribute is
*     cleared or changed.
*
*     Clearing the attribute causes any open SourceFile to be closed. All
*     subsequent data reads will use the source function specified when the
*     Channel was created, or will read from standard input if no source
*     function was specified.
*
*     If no value has been assigned to SourceFile, a null string will be
*     returned if an attempt is made to get the attribute value.

*  Notes:
*     - Any open SourceFile is closed when the Channel is deleted.
*     - If the Channel is copied or dumped
c     (using astCopy or astShow)
f     (using AST_COPY or AST_SHOW)
*     the SourceFile attribute is left in a cleared state in the output
*     Channel (i.e. the value of the SourceFile attribute is not copied).

*  Applicability:
*     FitsChan
*        In the case of a FitsChan, the specified SourceFile supplements
*        the source function specified when the FitsChan was created,
*        rather than replacing the source function. The source file
*        should be a text file (not a FITS file) containing one header per
*        line. When a value is assigned to SourceFile, the file is opened
*        and read immediately, and all headers read from the file are
*        appended to the end of any header already in the FitsChan. The file
*        is then closed. Clearing the SourceFile attribute has no further
*        effect, other than nullifying the string (i.e. the file name)
*        associated with the attribute.

*att--
*/

/* Clear the SourceFile value by closing any open file, freeing the
   allocated memory and assigning a NULL pointer. */
astMAKE_CLEAR(Channel,SourceFile,fn_in,((this->fd_in=(this->fd_in?(fclose(this->fd_in),NULL):NULL)),astFree(this->fn_in)))

/* If the SourceFile value is not set, supply a default in the form of a
   pointer to the constant string "". */
astMAKE_GET(Channel,SourceFile,const char *,NULL,( this->fn_in ? this->fn_in : "" ))

/* Set a SourceFile value by closing any open file, freeing any previously
   allocated memory, allocating new memory, storing the string and saving
   the pointer to the copy. */
astMAKE_SET(Channel,SourceFile,const char *,fn_in,((this->fd_in=(this->fd_in?(fclose(this->fd_in),NULL):NULL)),astStore( this->fn_in, value, strlen( value ) + (size_t) 1 )))

/* The SourceFile value is set if the pointer to it is not NULL. */
astMAKE_TEST(Channel,SourceFile,( this->fn_in != NULL ))

/*
*att++
*  Name:
*     SinkFile

*  Purpose:
*     Output file to which to data should be written.

*  Type:
*     Public attribute.

*  Synopsis:
*     String.

*  Description:
*     This attribute specifies the name of a file to which the Channel
*     should write data. If specified it is used in preference to any sink
*     function specified when the Channel was created.
*
*     Assigning a new value to this attribute will cause any previously
*     opened SinkFile to be closed. The first subsequent call to
c     astWrite
f     AST_WRITE
*     will attempt to open the new file (an error will be reported if the
*     file cannot be opened), and write data to it. All subsequent call to
c     astWrite
f     AST_WRITE
*     will write data to the new file, until the SinkFile attribute is
*     cleared or changed.
*
*     Clearing the attribute causes any open SinkFile to be closed. All
*     subsequent data writes will use the sink function specified when the
*     Channel was created, or will write to standard output if no sink
*     function was specified.
*
*     If no value has been assigned to SinkFile, a null string will be
*     returned if an attempt is made to get the attribute value.

*  Notes:
*     - A new SinkFile will over-write any existing file with the same
*     name unless the existing file is write protected, in which case an
*     error will be reported.
*     - Any open SinkFile is closed when the Channel is deleted.
*     - If the Channel is copied or dumped
c     (using astCopy or astShow)
f     (using AST_COPY or AST_SHOW)
*     the SinkFile attribute is left in a cleared state in the output
*     Channel (i.e. the value of the SinkFile attribute is not copied).

*  Applicability:
*     FitsChan
*        When the FitsChan is destroyed, any headers in the FitsChan will be
*        written out to the sink file, if one is specified (if not, the
*        sink function used when the FitsChan was created is used). The
*        sink file is a text file (not a FITS file) containing one header
*        per line.

*att--
*/

/* Clear the SinkFile value by closing any open file, freeing the allocated
   memory and assigning a NULL pointer. */
astMAKE_CLEAR(Channel,SinkFile,fn_out,((this->fd_out=(this->fd_out?(fclose(this->fd_out),NULL):NULL)),astFree(this->fn_out)))

/* If the SinkFile value is not set, supply a default in the form of a
   pointer to the constant string "". */
astMAKE_GET(Channel,SinkFile,const char *,NULL,( this->fn_out ? this->fn_out : "" ))

/* Set a SinkFile value by closing any open file, freeing any previously
   allocated memory, allocating new memory, storing the string and saving
   the pointer to the copy. */
astMAKE_SET(Channel,SinkFile,const char *,fn_out,((this->fd_out=(this->fd_out?(fclose(this->fd_out),NULL):NULL)),astStore( this->fn_out, value, strlen( value ) + (size_t) 1 )))

/* The SinkFile value is set if the pointer to it is not NULL. */
astMAKE_TEST(Channel,SinkFile,( this->fn_out != NULL ))


/*
*att++
*  Name:
*     Comment

*  Purpose:
*     Include textual comments in output?

*  Type:
*     Public attribute.

*  Synopsis:
*     Integer (boolean).

*  Description:
*     This is a boolean attribute which controls whether textual
*     comments are to be included in the output generated by a
*     Channel. If included, they will describe what each item of
*     output represents.
*
*     If Comment is non-zero, then comments will be included. If
*     it is zero, comments will be omitted.

*  Applicability:
*     Channel
*        The default value is non-zero for a normal Channel.
*     FitsChan
*        The default value is non-zero for a FitsChan.
*     XmlChan
*        The default value is zero for an XmlChan.

*att--
*/

/* This is a boolean value (0 or 1) with a value of -INT_MAX when
   undefined but yielding a default of one. */
astMAKE_CLEAR(Channel,Comment,comment,-INT_MAX)
astMAKE_GET(Channel,Comment,int,0,( this->comment != -INT_MAX ? this->comment : 1 ))
astMAKE_SET(Channel,Comment,int,comment,( value != 0 ))
astMAKE_TEST(Channel,Comment,( this->comment != -INT_MAX ))

/*
*att++
*  Name:
*     Full

*  Purpose:
*     Set level of output detail.

*  Type:
*     Public attribute.

*  Synopsis:
*     Integer.

*  Description:
*     This attribute is a three-state flag and takes values of -1, 0
*     or +1.  It controls the amount of information included in the
*     output generated by a Channel.
*
*     If Full is zero, then a modest amount of
*     non-essential but useful information will be included in the
*     output. If Full is negative, all non-essential information will
*     be suppressed to minimise the amount of output, while if it is
*     positive, the output will include the maximum amount of detailed
*     information about the Object being written.

*  Applicability:
*     Channel
*        The default value is zero for a normal Channel.
*     FitsChan
*        The default value is zero for a FitsChan.
*     XmlChan
*        The default value is -1 for an XmlChan.
*     StcsChan
*        The default value is zero for an StcsChan. Set a positive value
*        to cause default values to be included in STC-S descriptions.

*  Notes:
*     - All positive values supplied for this attribute are converted
*     to +1 and all negative values are converted to -1.
*att--
*/

/* This ia a 3-state value (-1, 0 or +1) with a value of -INT_MAX when
   undefined but yielding a default of zero. */
astMAKE_CLEAR(Channel,Full,full,-INT_MAX)
astMAKE_GET(Channel,Full,int,0,( this->full != -INT_MAX ? this->full : 0 ))
astMAKE_SET(Channel,Full,int,full,( value > 0 ? 1 : ( value < 0 ? -1 : 0 ) ))
astMAKE_TEST(Channel,Full,( this->full != -INT_MAX ))

/*
*att++
*  Name:
*     Indent

*  Purpose:
*     Specifies the indentation to use in text produced by a Channel.

*  Type:
*     Public attribute.

*  Synopsis:
*     Integer (boolean).

*  Description:
*     This attribute controls the indentation within the output text produced by
f     the AST_WRITE function.
c     the astWrite function.
*     It gives the increase in the indentation for each level in the object
*     heirarchy. If it is set to zero, no indentation will be used. [3]

*  Applicability:
*     Channel
*        The default value is zero for a basic Channel.
*     FitsChan
*        The FitsChan class ignores this attribute.
*     StcsChan
*        The default value for an StcsChan is zero, which causes the entire
*        STC-S description is written out by a single invocation of the sink
*        function. The text supplied to the sink function will not contain
*        any linefeed characters, and each pair of adjacent words will be
*        separated by a single space. The text may thus be arbitrarily large
*        and the StcsLength attribute is ignored.
*
*        If Indent is non-zero, then the text is written out via multiple
*        calls to the sink function, each call corresponding to a single
*        "line" of text (although no line feed characters will be inserted
*        by AST). The complete STC-S description is broken into lines so that:
*
*        - the line length specified by attribute StcsLength is not exceeded
*        - each sub-phrase (time, space, etc.) starts on a new line
*        - each argument in a compound spatial region starts on a new line
*
*        If this causes a sub-phrase to extend to two or more lines, then the
*        second and subsequent lines will be indented by three spaces compared
*        to the first line. In addition, lines within a compound spatial region
*        will have extra indentation to highlight the nesting produced by the
*        parentheses. Each new level of nesting will be indented by a further
*        three spaces.
f
f        Note, the default value of zero is unlikely to be appropriate when
f        an StcsChan is used within Fortran code. In this case, Indent
f        should usually be set non-zero, and the StcsLength attribute set to
f        the size of the CHARACTER variable used to
f        receive the text returned by AST_GETLINE within the sink function.
f        This avoids the possibility of long lines being truncated invisibly
f        within AST_GETLINE.
*     XmlChan
*        The default value for an XmlChan is zero, which results in no
*        linefeeds or indentation strings being added to output text.
*        If any non-zero value is assigned to Indent, then extra linefeed and
*        space characters will be inserted as necessary to ensure that each
*        XML tag starts on a new line, and each tag will be indented by
*        a further 3 spaces to show its depth in the containment hierarchy.
*att--
*/

/* This is an integer value with a value of -INT_MAX when undefined,
   yielding a default of 3. Sub-classes may over-ride theis default. */
astMAKE_CLEAR(Channel,Indent,indent,-INT_MAX)
astMAKE_GET(Channel,Indent,int,3,( this->indent != -INT_MAX ? this->indent : 3 ))
astMAKE_SET(Channel,Indent,int,indent,value)
astMAKE_TEST(Channel,Indent,( this->indent != -INT_MAX ))

/*
*att++
*  Name:
*     ReportLevel

*  Purpose:
*     Determines which read/write conditions are reported.

*  Type:
*     Public attribute.

*  Synopsis:
*     Integer (boolean).

*  Description:
*     This attribute determines which, if any, of the conditions that occur
*     whilst reading or writing an Object should be reported. These
*     conditions will generate either a fatal error or a warning, as
*     determined by attribute Strict. ReportLevel can take any of the
*     following values:
*
*     0 - Do not report any conditions.
*
*     1 - Report only conditions where significant information content has been
*     changed. For instance, an unsupported time-scale has been replaced by a
*     supported near-equivalent time-scale. Another example is if a basic
*     Channel unexpected encounters data items that may have been introduced
*     by later versions of AST.
*
*     2 - Report the above, and in addition report significant default
*     values. For instance, if no time-scale was specified when reading an
*     Object from an external data source, report the default time-scale
*     that is being used.
*
*     3 - Report the above, and in addition report any other potentially
*     interesting conditions that have no significant effect on the
*     conversion. For instance, report if a time-scale of "TT"
*     (terrestrial time) is used in place of "ET" (ephemeris time). This
*     change has no signficiant effect because ET is the predecessor of,
*     and is continuous with, TT. Synonyms such as "IAT" and "TAI" are
*     another example.
*
*     The default value is 1. Note, there are many other conditions that
*     can occur whilst reading or writing an Object that completely
*     prevent the conversion taking place. Such conditions will always
*     generate errors, irrespective of the ReportLevel and Strict attributes.

*  Applicability:
*     Channel
*        All Channels have this attribute.
*     FitsChan
*        All the conditions selected by the FitsChan Warnings attribute are
*        reported at level 1.
*att--
*/

/* This is an integer value with a value of -INT_MAX when undefined,
   yielding a default of one. */
astMAKE_CLEAR(Channel,ReportLevel,report_level,-INT_MAX)
astMAKE_GET(Channel,ReportLevel,int,1,( this->report_level != -INT_MAX ? this->report_level : 1 ))
astMAKE_SET(Channel,ReportLevel,int,report_level,value)
astMAKE_TEST(Channel,ReportLevel,( this->report_level != -INT_MAX ))

/*
*att++
*  Name:
*     Skip

*  Purpose:
*     Skip irrelevant data?

*  Type:
*     Public attribute.

*  Synopsis:
*     Integer (boolean).

*  Description:
*     This is a boolean attribute which indicates whether the Object
*     data being read through a Channel are inter-mixed with other,
*     irrelevant, external data.
*
*     If Skip is zero (the default), then the source of input data is
*     expected to contain descriptions of AST Objects and comments and
*     nothing else (if anything else is read, an error will
*     result). If Skip is non-zero, then any non-Object data
*     encountered between Objects will be ignored and simply skipped
*     over in order to reach the next Object.

*  Applicability:
*     Channel
*        All Channels have this attribute.
*     FitsChan
*        The FitsChan class sets the default value of this attribute
*        to 1, so that all irrelevant FITS headers will normally be
*        ignored.
*att--
*/

/* This ia a boolean value (0 or 1) with a value of -INT_MAX when
   undefined but yielding a default of zero. */
astMAKE_CLEAR(Channel,Skip,skip,-INT_MAX)
astMAKE_GET(Channel,Skip,int,0,( this->skip != -INT_MAX ? this->skip : 0 ))
astMAKE_SET(Channel,Skip,int,skip,( value != 0 ))
astMAKE_TEST(Channel,Skip,( this->skip != -INT_MAX ))

/*
*att++
*  Name:
*     Strict

*  Purpose:
*     Report an error if any unexpeted data items are found?

*  Type:
*     Public attribute.

*  Synopsis:
*     Integer (boolean).

*  Description:
*     This is a boolean attribute which indicates whether a warning
*     rather than an error should be issed for insignificant conversion
*     problems. If it is set non-zero, then fatal errors are issued
*     instead of warnings, resulting in the
c     AST error status being set.
f     inherited STATUS variable being set to an error value.
*     If Strict is zero (the default), then execution continues after minor
*     conversion problems, and a warning message is added to the Channel
*     structure. Such messages can be retrieved using the
c     astWarnings
f     AST_WARNINGS
*     function.

*  Notes:
*     - This attribute was introduced in AST version 5.0. Prior to this
*     version of AST unexpected data items read by a basic Channel always
*     caused an error to be reported. So applications linked against
*     versions of AST prior to version 5.0 may not be able to read Object
*     descriptions created by later versions of AST, if the Object's class
*     description has changed.

*  Applicability:
*     Channel
*        All Channels have this attribute.
*att--
*/

/* This ia a boolean value (0 or 1) with a value of -INT_MAX when
   undefined but yielding a default of zero. */
astMAKE_CLEAR(Channel,Strict,strict,-INT_MAX)
astMAKE_GET(Channel,Strict,int,0,( this->strict != -INT_MAX ? this->strict : 0 ))
astMAKE_SET(Channel,Strict,int,strict,( value != 0 ))
astMAKE_TEST(Channel,Strict,( this->strict != -INT_MAX ))

/* Destructor. */
/* ----------- */
static void Delete( AstObject *obj, int *status ) {
/*
*  Name:
*     Delete

*  Purpose:
*     Destructor for Channel objects.

*  Type:
*     Private function.

*  Synopsis:
*     void Delete( AstObject *obj, int *status )

*  Description:
*     This function implements the destructor for Channel objects.

*  Parameters:
*     obj
*        Pointer to the object to be deleted.
*     status
*        Pointer to the inherited status variable.

*  Notes:
*     This function attempts to execute even if the global error status is
*     set.
*/

/* Local Variables: */
   AstChannel *this;               /* Pointer to Channel */

/* Obtain a pointer to the Channel structure. */
   this = (AstChannel *) obj;

/* Free memory used to store warnings. */
   astAddWarning( this, 0, NULL, NULL, status );

/* Close any open input or output files. */
   if( this->fd_in ) fclose( this->fd_in );
   if( this->fd_out ) fclose( this->fd_out );

/* Free file name memory. */
   this->fn_in = astFree( this->fn_in );
   this->fn_out = astFree( this->fn_out );
}

/* Copy constructor. */
/* ----------------- */
static void Copy( const AstObject *objin, AstObject *objout, int *status ) {
/*
*  Name:
*     Copy

*  Purpose:
*     Copy constructor for Channel objects.

*  Type:
*     Private function.

*  Synopsis:
*     void Copy( const AstObject *objin, AstObject *objout, int *status )

*  Description:
*     This function implements the copy constructor for Channel objects.

*  Parameters:
*     objin
*        Pointer to the object to be copied.
*     objout
*        Pointer to the object being constructed.
*     status
*        Pointer to the inherited status variable.

*  Notes:
*     -  This constructor makes a deep copy.
*/

/* Local Variables: */
   AstChannel *out;                /* Pointer to output Channel */

/* Check the global error status. */
   if ( !astOK ) return;

/* Obtain pointers to the input and output Channels. */
   out = (AstChannel *) objout;

/* Just clear any references to the input memory from the output Channel. */
   out->warnings = NULL;
   out->nwarn = 0;
   out->fd_in = NULL;
   out->fn_in = NULL;
   out->fd_out = NULL;
   out->fn_out = NULL;
}

/* Dump function. */
/* -------------- */
static void Dump( AstObject *this_object, AstChannel *channel, int *status ) {
/*
*  Name:
*     Dump

*  Purpose:
*     Dump function for Channel objects.

*  Type:
*     Private function.

*  Synopsis:
*     void Dump( AstObject *this, AstChannel *channel, int *status )

*  Description:
*     This function implements the Dump function which writes out data
*     for the Channel class to an output Channel.

*  Parameters:
*     this
*        Pointer to the Object whose data are being written.
*     channel
*        Pointer to the Channel to which the data are being written.
*     status
*        Pointer to the inherited status variable.
*/

/* Local Variables: */
   AstChannel *this;             /* Pointer to the Channel structure */
   const char *comment;          /* Pointer to comment string */
   int ival;                     /* Integer value */
   int set;                      /* Attribute value set? */

/* Check the global error status. */
   if ( !astOK ) return;

/* Obtain a pointer to the Channel structure. */
   this = (AstChannel *) this_object;

/* Write out values representing the instance variables for the
   Channel class.  Accompany these with appropriate comment strings,
   possibly depending on the values being written.*/

/* In the case of attributes, we first use the appropriate (private)
   Test...  member function to see if they are set. If so, we then use
   the (private) Get... function to obtain the value to be written
   out.

   For attributes which are not set, we use the astGet... method to
   obtain the value instead. This will supply a default value
   (possibly provided by a derived class which over-rides this method)
   which is more useful to a human reader as it corresponds to the
   actual default attribute value.  Since "set" will be zero, these
   values are for information only and will not be read back. */

/* Indent */
/* ------------ */
   set = TestIndent( this, status );
   ival = set ? GetIndent( this, status ) : astGetIndent( this );
   astWriteInt( channel, "Indnt", set, 0, ival, "Indentation increment" );

/* ReportLevel. */
/* ------------ */
   set = TestReportLevel( this, status );
   ival = set ? GetReportLevel( this, status ) : astGetReportLevel( this );
   astWriteInt( channel, "RpLev", set, 0, ival, "Error reporting level" );

/* Skip. */
/* ----- */
   set = TestSkip( this, status );
   ival = set ? GetSkip( this, status ) : astGetSkip( this );
   astWriteInt( channel, "Skip", set, 0, ival,
                ival ? "Ignore data between Objects" :
                       "No data allowed between Objects" );

/* Strict. */
/* ------- */
   set = TestStrict( this, status );
   ival = set ? GetStrict( this, status ) : astGetStrict( this );
   astWriteInt( channel, "Strict", set, 0, ival,
                ival ? "Report errors insead of warnings" :
                       "Report warnings instead of errors" );

/* Full. */
/* ----- */
   set = TestFull( this, status );
   ival = set ? GetFull( this, status ) : astGetFull( this );
   if ( ival < 0 ) {
      comment = "Suppress non-essential output";
   }else if ( ival == 0 ) {
      comment = "Output standard information";
   } else {
      comment = "Output maximum information";
   }
   astWriteInt( channel, "Full", set, 0, ival, comment );

/* Comment. */
/* -------- */
   set = TestComment( this, status );
   ival = set ? GetComment( this, status ) : astGetComment( this );
   astWriteInt( channel, "Comm", set, 0, ival,
                ival ? "Display comments" :
                       "Omit comments" );
}

/* Standard class functions. */
/* ========================= */
/* Implement the astIsAChannel and astCheckChannel functions using the
   macros defined for this purpose in the "object.h" header file. */
astMAKE_ISA(Channel,Object)
astMAKE_CHECK(Channel)

AstChannel *astChannel_( const char *(* source)( void ),
                         void (* sink)( const char * ),
                         const char *options, int *status, ...) {
/*
*+
*  Name:
*     astChannel

*  Purpose:
*     Create a Channel.

*  Type:
*     Protected function.

*  Synopsis:
*     #include "channel.h"
*     AstChannel *astChannel( const char *(* source)( void ),
*                             void (* sink)( const char * ),
*                             const char *options, ..., int *status )

*  Class Membership:
*     Channel constructor.

*  Description:
*     This function creates a new Channel and optionally initialises
*     its attributes.
*
*     A Channel implements low-level input/output for the AST library.
*     Writing an Object to a Channel (using astWrite) will generate a
*     textual representation of that Object, and reading from a
*     Channel (using astRead) will create a new Object from its
*     textual representation.
*
*     Normally, when you use a Channel, you should provide "source"
*     and "sink" functions which connect it to an external data store
*     by reading and writing the resulting text. By default, however,
*     a Channel will read from standard input and write to standard
*     output.

*  Parameters:
*     source
*        Pointer to a "source" function that takes no arguments and
*        returns a pointer to a null-terminated string.
*
*        This function will be used by the Channel to obtain lines of
*        input text. On each invocation, it should return a pointer to
*        the next input line read from some external data store, and a
*        NULL pointer when there are no more lines to read.
*
*        If "source" is NULL, the Channel will read from standard
*        input instead.
*     sink
*        Pointer to a "sink" function that takes a pointer to a
*        null-terminated string as an argument and returns void.
*
*        This function will be used by the Channel to deliver lines of
*        output text. On each invocation, it should deliver the
*        contents of the string supplied to some external data store.
*
*        If "sink" is NULL, the Channel will write to standard output
*        instead.
*     options
*        Pointer to a null-terminated string containing an optional
*        comma-separated list of attribute assignments to be used for
*        initialising the new Channel. The syntax used is identical to
*        that for the astSet function and may include "printf" format
*        specifiers identified by "%" symbols in the normal way.
*     status
*        Pointer to the inherited status variable.
*     ...
*        If the "options" string contains "%" format specifiers, then
*        an optional list of additional arguments may follow it in
*        order to supply values to be substituted for these
*        specifiers. The rules for supplying these are identical to
*        those for the astSet function (and for the C "printf"
*        function).

*  Returned Value:
*     astChannel()
*        A pointer to the new Channel.

*  Notes:
*     - A NULL pointer value will be returned if this function is
*     invoked with the global error status set, or if it should fail
*     for any reason.
*-

*  Implementation Notes:
*     - This function implements the basic Channel constructor which
*     is available via the protected interface to the Channel class.
*     A public interface is provided by the astChannelId_ function.
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
   AstChannel *new;              /* Pointer to new Channel */
   va_list args;                 /* Variable argument list */

/* Get a pointer to the thread specific global data structure. */
   astGET_GLOBALS(NULL);

/* Check the global status. */
   if ( !astOK ) return NULL;

/* Initialise the Channel, allocating memory and initialising the
   virtual function table as well if necessary. Supply pointers to
   (local) wrapper functions that can invoke the source and sink
   functions with appropriate arguments for the C language. */
   new = astInitChannel( NULL, sizeof( AstChannel ), !class_init, &class_vtab,
                         "Channel", source, SourceWrap, sink, SinkWrap );

/* If successful, note that the virtual function table has been
   initialised. */
   if ( astOK ) {
      class_init = 1;

/* Obtain the variable argument list and pass it along with the
   options string to the astVSet method to initialise the new
   Channel's attributes. */
      va_start( args, status );
      astVSet( new, options, NULL, args );
      va_end( args );

/* If an error occurred, clean up by deleting the new object. */
      if ( !astOK ) new = astDelete( new );
   }

/* Return a pointer to the new Channel. */
   return new;
}

AstChannel *astChannelId_( const char *(* source)( void ),
                           void (* sink)( const char * ),
                           const char *options, ... ) {
/*
*++
*  Name:
c     astChannel
f     AST_CHANNEL

*  Purpose:
*     Create a Channel.

*  Type:
*     Public function.

*  Synopsis:
c     #include "channel.h"
c     AstChannel *astChannel( const char *(* source)( void ),
c                             void (* sink)( const char * ),
c                             const char *options, ... )
f     RESULT = AST_CHANNEL( SOURCE, SINK, OPTIONS, STATUS )

*  Class Membership:
*     Channel constructor.

*  Description:
*     This function creates a new Channel and optionally initialises
*     its attributes.
*
*     A Channel implements low-level input/output for the AST library.
c     Writing an Object to a Channel (using astWrite) will generate a
f     Writing an Object to a Channel (using AST_WRITE) will generate a
*     textual representation of that Object, and reading from a
c     Channel (using astRead) will create a new Object from its
f     Channel (using AST_READ) will create a new Object from its
*     textual representation.
*
*     Normally, when you use a Channel, you should provide "source"
c     and "sink" functions which connect it to an external data store
f     and "sink" routines which connect it to an external data store
*     by reading and writing the resulting text. By default, however,
*     a Channel will read from standard input and write to standard
*     output. Alternatively, a Channel can be told to read or write from
*     specific text files using the SinkFile and SourceFile attributes,
*     in which case no sink or source function need be supplied.

*  Parameters:
c     source
f     SOURCE = SUBROUTINE (Given)
c        Pointer to a source function that takes no arguments and
c        returns a pointer to a null-terminated string.  If no value
c        has been set for the SourceFile attribute, this function
c        will be used by the Channel to obtain lines of input text. On
c        each invocation, it should return a pointer to the next input
c        line read from some external data store, and a NULL pointer
c        when there are no more lines to read.
c
c        If "source" is NULL and no value has been set for the SourceFile
c        attribute, the Channel will read from standard input instead.
f        A source routine, which is a subroutine which takes a single
f        integer error status argument.   If no value has been set
f        for the SourceFile attribute, this routine will be used by
f        the Channel to obtain lines of input text. On each
f        invocation, it should read the next input line from some
f        external data store, and then return the resulting text to
f        the AST library by calling AST_PUTLINE. It should supply a
f        negative line length when there are no more lines to read.
f        If an error occurs, it should set its own error status
f        argument to an error value before returning.
f
f        If the null routine AST_NULL is suppied as the SOURCE value,
f        and no value has been set for the SourceFile attribute,
f        the Channel will read from standard input instead.
c     sink
f     SINK = SUBROUTINE (Given)
c        Pointer to a sink function that takes a pointer to a
c        null-terminated string as an argument and returns void.
c        If no value has been set for the SinkFile attribute, this
c        function will be used by the Channel to deliver lines of
c        output text. On each invocation, it should deliver the
c        contents of the string supplied to some external data store.
c
c        If "sink" is NULL, and no value has been set for the SinkFile
c        attribute, the Channel will write to standard output instead.
f        A sink routine, which is a subroutine which takes a single
f        integer error status argument.  If no value has been set
f        for the SinkFile attribute, this routine will be used by
f        the Channel to deliver lines of output text. On each
f        invocation, it should obtain the next output line from the
f        AST library by calling AST_GETLINE, and then deliver the
f        resulting text to some external data store.  If an error
f        occurs, it should set its own error status argument to an
f        error value before returning.
f
f        If the null routine AST_NULL is suppied as the SINK value,
f        and no value has been set for the SinkFile attribute,
f        the Channel will write to standard output instead.
c     options
f     OPTIONS = CHARACTER * ( * ) (Given)
c        Pointer to a null-terminated string containing an optional
c        comma-separated list of attribute assignments to be used for
c        initialising the new Channel. The syntax used is identical to
c        that for the astSet function and may include "printf" format
c        specifiers identified by "%" symbols in the normal way.
f        A character string containing an optional comma-separated
f        list of attribute assignments to be used for initialising the
f        new Channel. The syntax used is identical to that for the
f        AST_SET routine.
c     ...
c        If the "options" string contains "%" format specifiers, then
c        an optional list of additional arguments may follow it in
c        order to supply values to be substituted for these
c        specifiers. The rules for supplying these are identical to
c        those for the astSet function (and for the C "printf"
c        function).
f     STATUS = INTEGER (Given and Returned)
f        The global status.

*  Returned Value:
c     astChannel()
f     AST_CHANNEL = INTEGER
*        A pointer to the new Channel.

*  Notes:
c     - Application code can pass arbitrary data (such as file
c     descriptors, etc) to source and sink functions using the
c     astPutChannelData function. The source or sink function should use
c     the astChannelData macro to retrieve this data.
f     - The names of the routines supplied for the SOURCE and SINK
f     arguments should appear in EXTERNAL statements in the Fortran
f     routine which invokes AST_CHANNEL. However, this is not generally
f     necessary for the null routine AST_NULL (so long as the AST_PAR
f     include file has been used).
*     - A null Object pointer (AST__NULL) will be returned if this
c     function is invoked with the AST error status set, or if it
f     function is invoked with STATUS set to an error value, or if it
*     should fail for any reason.
f     - Note that the null routine AST_NULL (one underscore) is
f     different to AST__NULL (two underscores), which is the null Object
f     pointer.
*--

*  Implementation Notes:
*     - This function implements the external (public) interface to
*     the astChannel constructor function. It returns an ID value
*     (instead of a true C pointer) to external users, and must be
*     provided because astChannel_ has a variable argument list which
*     cannot be encapsulated in a macro (where this conversion would
*     otherwise occur).
*     - The variable argument list also prevents this function from
*     invoking astChanel_ directly, so it must be a re-implementation
*     of it in all respects, except for the final conversion of the
*     result to an ID value.
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
   AstChannel *new;              /* Pointer to new Channel */
   va_list args;                 /* Variable argument list */

   int *status;                  /* Pointer to inherited status value */

/* Get a pointer to the inherited status value. */
   status = astGetStatusPtr;

/* Get a pointer to the thread specific global data structure. */
   astGET_GLOBALS(NULL);

/* Check the global status. */
   if ( !astOK ) return NULL;

/* Initialise the Channel, allocating memory and initialising the
   virtual function table as well if necessary. Supply pointers to
   (local) wrapper functions that can invoke the source and sink
   functions with appropriate arguments for the C language. */
   new = astInitChannel( NULL, sizeof( AstChannel ), !class_init, &class_vtab,
                         "Channel", source, SourceWrap, sink, SinkWrap );

/* If successful, note that the virtual function table has been
   initialised. */
   if ( astOK ) {
      class_init = 1;

/* Obtain the variable argument list and pass it along with the
   options string to the astVSet method to initialise the new
   Channel's attributes. */
      va_start( args, options );
      astVSet( new, options, NULL, args );
      va_end( args );

/* If an error occurred, clean up by deleting the new object. */
      if ( !astOK ) new = astDelete( new );
   }

/* Return an ID value for the new Channel. */
   return astMakeId( new );
}

AstChannel *astChannelForId_( const char *(* source)( void ),
                              char *(* source_wrap)( const char *(*)( void ), int * ),
                              void (* sink)( const char * ),
                              void (* sink_wrap)( void (*)( const char * ),
                                                  const char *, int * ),
                              const char *options, ... ) {
/*
*+
*  Name:
*     astChannelFor

*  Purpose:
*     Initialise a Channel from a foreign language interface.

*  Type:
*     Public function.

*  Synopsis:
*     #include "channel.h"
*     AstChannel *astChannelFor( const char *(* source)( void ),
*                                char *(* source_wrap)( const char *(*)
*                                                       ( void ), int * ),
*                                void (* sink)( const char * ),
*                                void (* sink_wrap)( void (*)( const char * ),
*                                                    const char *, int * ),
*                                const char *options, ... )

*  Class Membership:
*     Channel constructor.

*  Description:
*     This function creates a new Channel from a foreign language
*     interface and optionally initialises its attributes.
*
*     A Channel implements low-level input/output for the AST library.
*     Writing an Object to a Channel (using astWrite) will generate a
*     textual representation of that Object, and reading from a
*     Channel (using astRead) will create a new Object from its
*     textual representation.
*
*     Normally, when you use a Channel, you should provide "source"
*     and "sink" functions which connect it to an external data store
*     by reading and writing the resulting text. This function also
*     requires you to provide "wrapper" functions which will invoke
*     the source and sink functions. By default, however, a Channel
*     will read from standard input and write to standard output.

*  Parameters:
*     source
*        Pointer to a "source" function which will be used to obtain
*        lines of input text. Generally, this will be obtained by
*        casting a pointer to a source function which is compatible
*        with the "source_wrap" wrapper function (below). The pointer
*        should later be cast back to its original type by the
*        "source_wrap" function before the function is invoked.
*
*        If "source" is NULL, the Channel will read from standard
*        input instead.
*     source_wrap
*        Pointer to a function which can be used to invoke the
*        "source" function supplied (above). This wrapper function is
*        necessary in order to hide variations in the nature of the
*        source function, such as may arise when it is supplied by a
*        foreign (non-C) language interface.
*
*        The single parameter of the "source_wrap" function is a
*        pointer to the "source" function, and it should cast this
*        function pointer (as necessary) and invoke the function with
*        appropriate arguments to obtain the next line of input
*        text. The "source_wrap" function should then return a pointer
*        to a dynamically allocated, null terminated string containing
*        the text that was read. The string will be freed (using
*        astFree) when no longer required and the "source_wrap"
*        function need not concern itself with this. A NULL pointer
*        should be returned if there is no more input to read.
*
*        If "source_wrap" is NULL, the Channel will read from standard
*        input instead.
*     sink
*        Pointer to a "sink" function which will be used to deliver
*        lines of output text. Generally, this will be obtained by
*        casting a pointer to a sink function which is compatible with
*        the "sink_wrap" wrapper function (below). The pointer should
*        later be cast back to its original type by the "sink_wrap"
*        function before the function is invoked.
*
*        If "sink" is NULL, the Channel will write to standard output
*        instead.
*     sink_wrap
*        Pointer to a function which can be used to invoke the "sink"
*        function supplied (above). This wrapper function is necessary
*        in order to hide variations in the nature of the sink
*        function, such as may arise when it is supplied by a foreign
*        (non-C) language interface.
*
*        The first parameter of the "sink_wrap" function is a pointer
*        to the "sink" function, and the second parameter is a pointer
*        to a const, null-terminated character string containing the
*        text to be written.  The "sink_wrap" function should cast the
*        "sink" function pointer (as necessary) and invoke the
*        function with appropriate arguments to deliver the line of
*        output text. The "sink_wrap" function then returns void.
*
*        If "sink_wrap" is NULL, the Channel will write to standard
*        output instead.
*     options
*        Pointer to a null-terminated string containing an optional
*        comma-separated list of attribute assignments to be used for
*        initialising the new Channel. The syntax used is identical to
*        that for the astSet function and may include "printf" format
*        specifiers identified by "%" symbols in the normal way.
*     ...
*        If the "options" string contains "%" format specifiers, then
*        an optional list of additional arguments may follow it in
*        order to supply values to be substituted for these
*        specifiers. The rules for supplying these are identical to
*        those for the astSet function (and for the C "printf"
*        function).

*  Returned Value:
*     astChannelFor()
*        A pointer to the new Channel.

*  Notes:
*     - A null Object pointer (AST__NULL) will be returned if this
*     function is invoked with the global error status set, or if it
*     should fail for any reason.
*     - This function is only available through the public interface
*     to the Channel class (not the protected interface) and is
*     intended solely for use in implementing foreign language
*     interfaces to this class.
*-

*  Implememtation Notes:
*     - This function behaves exactly like astChannelId_, in that it
*     returns ID values and not true C pointers, but it has two
*     additional arguments. These are pointers to the "wrapper
*     functions" which are needed to accommodate foreign language
*     interfaces.
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Declare the thread specific global data */
   AstChannel *new;              /* Pointer to new Channel */
   va_list args;                 /* Variable argument list */
   int *status;                  /* Pointer to inherited status value */

/* Get a pointer to the inherited status value. */
   status = astGetStatusPtr;

/* Check the global status. */
   if ( !astOK ) return NULL;

/* Get a pointer to the thread specific global data structure. */
   astGET_GLOBALS(NULL);

/* Initialise the Channel, allocating memory and initialising the
   virtual function table as well if necessary. */
   new = astInitChannel( NULL, sizeof( AstChannel ), !class_init, &class_vtab,
                         "Channel", source, source_wrap, sink, sink_wrap );

/* If successful, note that the virtual function table has been
   initialised. */
   if ( astOK ) {
      class_init = 1;

/* Obtain the variable argument list and pass it along with the
   options string to the astVSet method to initialise the new
   Channel's attributes. */
      va_start( args, options );
      astVSet( new, options, NULL, args );
      va_end( args );

/* If an error occurred, clean up by deleting the new object. */
      if ( !astOK ) new = astDelete( new );
   }

/* Return an ID value for the new Channel. */
   return astMakeId( new );
}

AstChannel *astLoadChannel_( void *mem, size_t size,
                             AstChannelVtab *vtab, const char *name,
                             AstChannel *channel, int *status ) {
/*
*+
*  Name:
*     astLoadChannel

*  Purpose:
*     Load a Channel.

*  Type:
*     Protected function.

*  Synopsis:
*     #include "channel.h"
*     AstChannel *astLoadChannel( void *mem, size_t size,
*                                 AstChannelVtab *vtab, const char *name,
*                                 AstChannel *channel )

*  Class Membership:
*     Channel loader.

*  Description:
*     This function is provided to load a new Channel using data read
*     from a Channel. It first loads the data used by the parent class
*     (which allocates memory if necessary) and then initialises a
*     Channel structure in this memory, using data read from the input
*     Channel.
*
*     If the "init" flag is set, it also initialises the contents of a
*     virtual function table for a Channel at the start of the memory
*     passed via the "vtab" parameter.


*  Parameters:
*     mem
*        A pointer to the memory into which the Channel is to be
*        loaded.  This must be of sufficient size to accommodate the
*        Channel data (sizeof(Channel)) plus any data used by derived
*        classes. If a value of NULL is given, this function will
*        allocate the memory itself using the "size" parameter to
*        determine its size.
*     size
*        The amount of memory used by the Channel (plus derived class
*        data).  This will be used to allocate memory if a value of
*        NULL is given for the "mem" parameter. This value is also
*        stored in the Channel structure, so a valid value must be
*        supplied even if not required for allocating memory.
*
*        If the "vtab" parameter is NULL, the "size" value is ignored
*        and sizeof(AstChannel) is used instead.
*     vtab
*        Pointer to the start of the virtual function table to be
*        associated with the new Channel. If this is NULL, a pointer
*        to the (static) virtual function table for the Channel class
*        is used instead.
*     name
*        Pointer to a constant null-terminated character string which
*        contains the name of the class to which the new object
*        belongs (it is this pointer value that will subsequently be
*        returned by the astGetClass method).
*
*        If the "vtab" parameter is NULL, the "name" value is ignored
*        and a pointer to the string "Channel" is used instead.

*  Returned Value:
*     A pointer to the new Channel.

*  Notes:
*     - A null pointer will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*-
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
   AstChannel *new;              /* Pointer to the new Channel */

/* Initialise. */
   new = NULL;

/* Check the global error status. */
   if ( !astOK ) return new;

/* Get a pointer to the thread specific global data structure. */
   astGET_GLOBALS(channel);

/* If a NULL virtual function table has been supplied, then this is
   the first loader to be invoked for this Channel. In this case the
   Channel belongs to this class, so supply appropriate values to be
   passed to the parent class loader (and its parent, etc.). */
   if ( !vtab ) {
      size = sizeof( AstChannel );
      vtab = &class_vtab;
      name = "Channel";

/* If required, initialise the virtual function table for this class. */
      if ( !class_init ) {
         astInitChannelVtab( vtab, name );
         class_init = 1;
      }
   }

/* Invoke the parent class loader to load data for all the ancestral
   classes of the current one, returning a pointer to the resulting
   partly-built Channel. */
   new = astLoadObject( mem, size, (AstObjectVtab *) vtab, name,
                        channel );

   if ( astOK ) {

/* Read input data. */
/* ================ */
/* Request the input Channel to read all the input data appropriate to
   this class into the internal "values list". */
      astReadClassData( channel, "Channel" );

/* Set the pointers to the source and sink functions, and their
   wrapper functions, to NULL (we cannot restore these since they
   refer to process-specific addresses). */
      new->source = NULL;
      new->source_wrap = NULL;
      new->sink = NULL;
      new->sink_wrap = NULL;

/* We do not have any data to pass to the source and sink functions. */
      new->data = NULL;

/* No warnings yet. */
      new->warnings = NULL;
      new->nwarn = 0;

/* Indicate no input or output files have been associated with the
   Channel. */
      new->fd_in = NULL;
      new->fn_in = NULL;
      new->fd_out = NULL;
      new->fn_out = NULL;

/* Now read each individual data item from this list and use it to
   initialise the appropriate instance variable(s) for this class. */

/* In the case of attributes, we first read the "raw" input value,
   supplying the "unset" value as the default. If a "set" value is
   obtained, we then use the appropriate (private) Set... member
   function to validate and set the value properly. */

/* Indent. */
/* ------- */
      new->indent = astReadInt( channel, "indnt", -INT_MAX );
      if ( TestIndent( new, status ) ) SetIndent( new, new->indent, status );

/* ReportLevel. */
/* ------------ */
      new->report_level = astReadInt( channel, "rplev", -INT_MAX );
      if ( TestReportLevel( new, status ) ) SetReportLevel( new,
                                                            new->report_level,
                                                            status );

/* Skip. */
/* ----- */
      new->skip = astReadInt( channel, "skip", -INT_MAX );
      if ( TestSkip( new, status ) ) SetSkip( new, new->skip, status );

/* Strict. */
/* ------- */
      new->strict = astReadInt( channel, "strict", -INT_MAX );
      if ( TestStrict( new, status ) ) SetStrict( new, new->strict, status );

/* Full. */
/* ----- */
      new->full = astReadInt( channel, "full", -INT_MAX );
      if ( TestFull( new, status ) ) SetFull( new, new->full, status );

/* Comment. */
/* -------- */
      new->comment = astReadInt( channel, "comm", -INT_MAX );
      if ( TestComment( new, status ) ) SetComment( new, new->comment, status );

/* If an error occurred, clean up by deleting the new Channel. */
      if ( !astOK ) new = astDelete( new );
   }

/* Return the new Channel pointer. */
   return new;
}

/* Virtual function interfaces. */
/* ============================ */
/* These provide the external interface to the virtual functions
   defined by this class. Each simply checks the global error status
   and then locates and executes the appropriate member function,
   using the function pointer stored in the object's virtual function
   table (this pointer is located using the astMEMBER macro defined in
   "object.h").

   Note that the member function may not be the one defined here, as
   it may have been over-ridden by a derived class. However, it should
   still have the same interface. */
void astGetNextData_( AstChannel *this, int begin, char **name, char **val, int *status ) {
   *name = NULL;
   *val = NULL;
   if ( !astOK ) return;
   (**astMEMBER(this,Channel,GetNextData))( this, begin, name, val, status );
}
char *astGetNextText_( AstChannel *this, int *status ) {
   if ( !astOK ) return NULL;
   return (**astMEMBER(this,Channel,GetNextText))( this, status );
}
void astPutNextText_( AstChannel *this, const char *line, int *status ) {
   if ( !astOK ) return;
   (**astMEMBER(this,Channel,PutNextText))( this, line, status );
}
AstObject *astRead_( AstChannel *this, int *status ) {
   if ( !astOK ) return NULL;
   astAddWarning( this, 0, NULL, NULL, status );
   return (**astMEMBER(this,Channel,Read))( this, status );
}
void astReadClassData_( AstChannel *this, const char *class, int *status ) {
   if ( !astOK ) return;
   (**astMEMBER(this,Channel,ReadClassData))( this, class, status );
}
double astReadDouble_( AstChannel *this, const char *name, double def, int *status ) {
   if ( !astOK ) return 0.0;
   return (**astMEMBER(this,Channel,ReadDouble))( this, name, def, status );
}
int astReadInt_( AstChannel *this, const char *name, int def, int *status ) {
   if ( !astOK ) return 0;
   return (**astMEMBER(this,Channel,ReadInt))( this, name, def, status );
}
AstObject *astReadObject_( AstChannel *this, const char *name,
                           AstObject *def, int *status ) {
   if ( !astOK ) return NULL;
   return (**astMEMBER(this,Channel,ReadObject))( this, name, def, status );
}
char *astReadString_( AstChannel *this, const char *name, const char *def, int *status ) {
   if ( !astOK ) return NULL;
   return (**astMEMBER(this,Channel,ReadString))( this, name, def, status );
}
void astWriteBegin_( AstChannel *this, const char *class,
                     const char *comment, int *status ) {
   if ( !astOK ) return;
   (**astMEMBER(this,Channel,WriteBegin))( this, class, comment, status );
}
void astWriteDouble_( AstChannel *this, const char *name, int set, int helpful,
                      double value, const char *comment, int *status ) {
   if ( !astOK ) return;
   (**astMEMBER(this,Channel,WriteDouble))( this, name, set, helpful, value,
                                            comment, status );
}
void astWriteEnd_( AstChannel *this, const char *class, int *status ) {
   if ( !astOK ) return;
   (**astMEMBER(this,Channel,WriteEnd))( this, class, status );
}
void astWriteInt_( AstChannel *this, const char *name, int set, int helpful,
                   int value, const char *comment, int *status ) {
   if ( !astOK ) return;
   (**astMEMBER(this,Channel,WriteInt))( this, name, set, helpful, value,
                                         comment, status );
}
void astWriteIsA_( AstChannel *this, const char *class, const char *comment, int *status ) {
   if ( !astOK ) return;
   (**astMEMBER(this,Channel,WriteIsA))( this, class, comment, status );
}
void astWriteString_( AstChannel *this, const char *name, int set, int helpful,
                      const char *value, const char *comment, int *status ) {
   if ( !astOK ) return;
   (**astMEMBER(this,Channel,WriteString))( this, name, set, helpful, value,
                                            comment, status );
}
void astPutChannelData_( AstChannel *this, void *data, int *status ) {
   if ( !astOK ) return;
   (**astMEMBER(this,Channel,PutChannelData))( this, data, status );
}

AstKeyMap *astWarnings_( AstChannel *this, int *status ){
   if( !astOK ) return NULL;
   return (**astMEMBER(this,Channel,Warnings))( this, status );
}

/* Because of the variable argument list, we need to work a bit harder on
   astAddWarning. Functions that provide implementations of the
   astAddWarning method recieve the fully expanded message and so do not
   need a variable argument list. */

void astAddWarning_( void *this_void, int level, const char *fmt,
                     const char *method, int *status, ... ) {
   AstChannel *this;
   char buff[ 201 ];
   va_list args;
   int nc;

   this = astCheckChannel( this_void );

   if( fmt ) {
      if( astOK ) {
         va_start( args, status );
         nc = vsprintf( buff, fmt, args );
         va_end( args );
         if( nc > 200 ) {
            astError( AST__INTER, "astAddWarning(%s): Message buffer size "
                      "exceeded (internal AST programming error).",
                      status, astGetClass( this ) );
         } else {
            (**astMEMBER(this,Channel,AddWarning))( this, level, buff, method, status );
         }
      }
   } else {
      (**astMEMBER(this,Channel,AddWarning))( this, level, NULL, method, status );
   }
}

/* Count the number of times astWrite is invoked (excluding invocations
   made from within the astWriteObject method - see below). The count is
   done here so that invocations of astWrite within a sub-class will be
   included. */
int astWrite_( AstChannel *this, AstObject *object, int *status ) {
   astDECLARE_GLOBALS
   if ( !astOK ) return 0;
   astGET_GLOBALS(this);
   nwrite_invoc++;
   astAddWarning( this, 0, NULL, NULL, status );
   return (**astMEMBER(this,Channel,Write))( this, object, status );
}

/* We do not want to count invocations of astWrite made from within the
   astWriteObject method. So decrement the number of invocations first
   (this assumes that each invocation of astWriteObject will only invoke
   astWrite once). */
void astWriteObject_( AstChannel *this, const char *name, int set,
                      int helpful, AstObject *value, const char *comment, int *status ) {
   astDECLARE_GLOBALS
   if ( !astOK ) return;
   astGET_GLOBALS(this);
   nwrite_invoc--;
   (**astMEMBER(this,Channel,WriteObject))( this, name, set, helpful, value,
                                            comment, status );
}