File: ar_io.c

package info (click to toggle)
pax 1:20201030-1
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, sid
  • size: 736 kB
  • sloc: ansic: 10,222; sh: 1,567; makefile: 41
file content (1328 lines) | stat: -rw-r--r-- 33,460 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
/*	$OpenBSD: ar_io.c,v 1.62 2017/03/11 12:55:47 tb Exp $	*/
/*	$NetBSD: ar_io.c,v 1.5 1996/03/26 23:54:13 mrg Exp $	*/

/*-
 * Copyright (c) 2012, 2016, 2017, 2019
 *	mirabilos <m@mirbsd.org>
 * Copyright (c) 1992 Keith Muller.
 * Copyright (c) 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Keith Muller of the University of California, San Diego.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/ioctl.h>
#if HAVE_SYS_MTIO_H
#include <sys/mtio.h>
#endif
#include <sys/stat.h>
#include <sys/wait.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#if HAVE_STRINGS_H
#include <strings.h>
#endif
#include <unistd.h>

#include "pax.h"
#include "extern.h"

__RCSID("$MirOS: src/bin/pax/ar_io.c,v 1.28 2019/02/10 21:50:06 tg Exp $");

#ifndef PAX_SAFE_PATH
#define PAX_SAFE_PATH "/bin:/usr/bin"
#endif

/*
 * Routines which deal directly with the archive I/O device/file.
 */

#define DMOD		0666		/* default mode of created archives */
#define EXT_MODE	O_RDONLY	/* open mode for list/extract */
#define AR_MODE		(O_WRONLY | O_CREAT | O_TRUNC)	/* mode for archive */
#define APP_MODE	O_RDWR		/* mode for append */
#define STDO		"<STDOUT>"	/* pseudo name for stdout */
#define STDN		"<STDIN>"	/* pseudo name for stdin */
int arfd = -1;				/* archive file descriptor */
static char artyp = ISREG;		/* archive type: file/FIFO/tape */
static int arvol = 1;			/* archive volume number */
static int lstrval = -1;		/* return value from last i/o */
static char io_ok;			/* i/o worked on volume after resync */
static char did_io;			/* did i/o ever occur on volume? */
static char done;			/* set via tty termination */
static struct stat arsb;		/* stat of archive device at open */
static char invld_rec;			/* tape has out of spec record size */
static char wr_trail = 1;		/* trailer was rewritten in append */
static char can_unlnk = 0;		/* do we unlink null archives?  */
const char *arcname;			/* printable name of archive */
static char *arcname_alloc = NULL;	/* this is so we can free(3) it */
const char *compress_program;		/* name of compression program */
static pid_t zpid = -1;			/* pid of child process */
char force_one_volume;			/* 1 if we ignore volume changes */

#if HAVE_SYS_MTIO_H
static int get_phys(void);
#endif
extern sigset_t s_mask;
static void ar_start_compress(int, int);

/*
 * ar_open()
 *	Opens the next archive volume. Determines the type of the device and
 *	sets up block sizes as required by the archive device and the format.
 *	Note: we may be called with name == NULL on the first open only.
 * Return:
 *	-1 on failure, 0 otherwise
 */

int
ar_open(const char *name)
{
#if HAVE_SYS_MTIO_H
	struct mtget mb;
#endif

	if (arfd != -1)
		(void)close(arfd);
	arfd = -1;
	can_unlnk = did_io = io_ok = invld_rec = 0;
	artyp = ISREG;
	flcnt = 0;

	/*
	 * open based on overall operation mode
	 */
	switch (act) {
	case LIST:
	case EXTRACT:
		if (name == NULL) {
			arfd = STDIN_FILENO;
			arcname = STDN;
		} else if ((arfd = binopen3(0, name, EXT_MODE, DMOD)) < 0)
			syswarn(1, errno, "Failed open to read on %s", name);
		if (arfd != -1 && compress_program != NULL)
			ar_start_compress(arfd, 0);
		break;
	case ARCHIVE:
		if (name == NULL) {
			arfd = STDOUT_FILENO;
			arcname = STDO;
		} else if ((arfd = binopen3(0, name, AR_MODE, DMOD)) < 0)
			syswarn(1, errno, "Failed open to write on %s", name);
		else
			can_unlnk = 1;
		if (arfd != -1 && compress_program != NULL)
			ar_start_compress(arfd, 1);
		break;
	case APPND:
		if (name == NULL) {
			arfd = STDOUT_FILENO;
			arcname = STDO;
		} else if ((arfd = binopen3(0, name, APP_MODE, DMOD)) < 0)
			syswarn(1, errno, "Failed open to read/write on %s",
				name);
		break;
	case COPY:
		/*
		 * arfd not used in COPY mode
		 */
		arcname = "<NONE>";
		lstrval = 1;
		return(0);
	}
	if (arfd < 0)
		return(-1);

	if (chdname != NULL)
		if (chdir(chdname) != 0) {
			syswarn(1, errno, "Failed chdir to %s", chdname);
			return(-1);
		}
	/*
	 * set up is based on device type
	 */
	if (fstat(arfd, &arsb) < 0) {
		syswarn(1, errno, "Failed stat on %s", arcname);
		(void)close(arfd);
		arfd = -1;
		can_unlnk = 0;
		return(-1);
	}
	if (S_ISDIR(arsb.st_mode)) {
		paxwarn(0, act == LIST || act == EXTRACT ?
		    "Cannot read an archive from a directory %s" :
		    "Cannot write an archive on top of a directory %s",
		    arcname);
		(void)close(arfd);
		arfd = -1;
		can_unlnk = 0;
		return(-1);
	}

	if (S_ISCHR(arsb.st_mode))
#if HAVE_SYS_MTIO_H
		artyp = ioctl(arfd, MTIOCGET, &mb) ? ISCHR : ISTAPE;
#else
		artyp = ISCHR;
#endif
	else if (S_ISBLK(arsb.st_mode))
		artyp = ISBLK;
	else if ((lseek(arfd, 0, SEEK_CUR) == -1) && (errno == ESPIPE))
		artyp = ISPIPE;
	else
		artyp = ISREG;

	/*
	 * make sure beyond any doubt that we can unlink only regular files
	 * we created
	 */
	if (artyp != ISREG)
		can_unlnk = 0;
	/*
	 * if we are writing, we are done
	 */
	if (act == ARCHIVE) {
		blksz = rdblksz = wrblksz;
		lstrval = 1;
		return(0);
	}

	/*
	 * set default blksz on read. APPNDs writes rdblksz on the last volume
	 * On all new archive volumes, we shift to wrblksz (if the user
	 * specified one, otherwise we will continue to use rdblksz). We
	 * must set blocksize based on what kind of device the archive is
	 * stored.
	 */
	switch (artyp) {
	case ISTAPE:
		/*
		 * Tape drives come in at least two flavors. Those that support
		 * variable sized records and those that have fixed sized
		 * records. They must be treated differently. For tape drives
		 * that support variable sized records, we must make large
		 * reads to make sure we get the entire record, otherwise we
		 * will just get the first part of the record (up to size we
		 * asked). Tapes with fixed sized records may or may not return
		 * multiple records in a single read. We really do not care
		 * what the physical record size is UNLESS we are going to
		 * append. (We will need the physical block size to rewrite
		 * the trailer). Only when we are appending do we go to the
		 * effort to figure out the true PHYSICAL record size.
		 */
		blksz = rdblksz = MAXBLK;
		break;
	case ISPIPE:
	case ISBLK:
	case ISCHR:
		/*
		 * Blocksize is not a major issue with these devices (but must
		 * be kept a multiple of 512). If the user specified a write
		 * block size, we use that to read. Under append, we must
		 * always keep blksz == rdblksz. Otherwise we go ahead and use
		 * the device optimal blocksize as (and if) returned by stat
		 * and if it is within pax specs.
		 */
		if ((act == APPND) && wrblksz) {
			blksz = rdblksz = wrblksz;
			break;
		}

		if ((arsb.st_blksize > 0) && (arsb.st_blksize < MAXBLK) &&
		    ((arsb.st_blksize % BLKMULT) == 0))
			rdblksz = arsb.st_blksize;
		else
			rdblksz = DEVBLK;
		/*
		 * For performance go for large reads when we can without harm
		 */
		if ((act == APPND) || (artyp == ISCHR))
			blksz = rdblksz;
		else
			blksz = MAXBLK;
		break;
	case ISREG:
		/*
		 * if the user specified wrblksz works, use it. Under appends
		 * we must always keep blksz == rdblksz
		 */
		if ((act == APPND) && wrblksz && ((arsb.st_size%wrblksz)==0)){
			blksz = rdblksz = wrblksz;
			break;
		}
		/*
		 * See if we can find the blocking factor from the file size
		 */
		for (rdblksz = MAXBLK; rdblksz > 0; rdblksz -= BLKMULT)
			if ((arsb.st_size % rdblksz) == 0)
				break;
		/*
		 * When we cannot find a match, we may have a flawed archive.
		 */
		if (rdblksz <= 0)
			rdblksz = FILEBLK;
		/*
		 * for performance go for large reads when we can
		 */
		if (act == APPND)
			blksz = rdblksz;
		else
			blksz = MAXBLK;
		break;
	default:
		/*
		 * should never happen, worst case, slow...
		 */
		blksz = rdblksz = BLKMULT;
		break;
	}
	lstrval = 1;
	return(0);
}

/*
 * ar_close(int int_sig)
 *	closes archive device, increments volume number, and prints i/o summary
 *	If in_sig is set we're in a signal handler and can't flush stdio.
 */
void
ar_close(int in_sig)
{
	int status;

	if (arfd < 0) {
		did_io = io_ok = flcnt = 0;
		if (vfpart) {
			(void)write(listfd, "\n", 1);
			vfpart = 0;
		}
		return;
	}
	if (!in_sig)
		fflush(listf);

	/*
	 * Close archive file. This may take a LONG while on tapes (we may be
	 * forced to wait for the rewind to complete) so tell the user what is
	 * going on (this avoids the user hitting control-c thinking pax is
	 * broken).
	 */
	if (vflag && (artyp == ISTAPE)) {
		(void)dprintf(listfd,
		    "%s%s: Waiting for tape drive close to complete...",
		    vfpart ? "\n" : "", argv0);
	}

	/*
	 * if nothing was written to the archive (and we created it), we remove
	 * it
	 */
	if (can_unlnk && (fstat(arfd, &arsb) == 0) && (S_ISREG(arsb.st_mode)) &&
	    (arsb.st_size == 0)) {
		(void)unlink(arcname);
		can_unlnk = 0;
	}

	/*
	 * for a quick extract/list, pax frequently exits before the child
	 * process is done
	 */
	if ((act == LIST || act == EXTRACT) && nflag && zpid > 0) {
		kill(zpid, SIGINT);
		zpid = -1;
	}

	(void)close(arfd);

	/* Do not exit before child to ensure data integrity */
	if (zpid > 0) {
		waitpid(zpid, &status, 0);
		if (!WIFEXITED(status) || WEXITSTATUS(status))
			exit_val = 1;
	}

	if (vflag && (artyp == ISTAPE)) {
		(void)write(listfd, "done.\n", sizeof("done.\n")-1);
		vfpart = 0;
	}
	arfd = -1;

	if (!io_ok && !did_io) {
		flcnt = 0;
		return;
	}
	did_io = io_ok = 0;

	/*
	 * The volume number is only increased when the last device has data
	 * and we have already determined the archive format.
	 */
	if (frmt != NULL)
		++arvol;

	/* Vflag can cause this to have been set */
	if (vfpart) {
		(void)write(listfd, "\n", 1);
		vfpart = 0;
	}

	/* nothing to do any more, unless vflag */
	if (!vflag) {
		flcnt = 0;
		return;
	}

	/*
	 * Print out a summary of I/O for this archive volume.
	 */

	/*
	 * If we have not determined the format yet, we just say how many bytes
	 * we have skipped over looking for a header to id. there is no way we
	 * could have written anything yet.
	 */
	if (frmt == NULL) {
		(void)dprintf(listfd,
		    "%s: unknown format, %" OT_FMT " bytes skipped.\n", argv0, rdcnt);
		flcnt = 0;
		return;
	}

	if (op_mode == OP_PAX)
		(void)dprintf(listfd, "%s: %s vol %d, %lu files,"
		    " %" OT_FMT " bytes read, %" OT_FMT " bytes written.\n",
		    argv0, frmt->name, arvol-1, flcnt, rdcnt, wrcnt);
	else if (op_mode == OP_CPIO)
		(void)dprintf(listfd, "%" OT_FMT " blocks\n",
		    (rdcnt ? rdcnt : wrcnt) / 5120);
	flcnt = 0;
}

/*
 * ar_drain()
 *	drain any archive format independent padding from an archive read
 *	from a socket or a pipe. This is to prevent the process on the
 *	other side of the pipe from getting a SIGPIPE (pax will stop
 *	reading an archive once a format dependent trailer is detected).
 */
void
ar_drain(void)
{
	int res;
	char drbuf[MAXBLK];

	/*
	 * we only drain from a pipe/socket. Other devices can be closed
	 * without reading up to end of file. We sure hope that pipe is closed
	 * on the other side so we will get an EOF.
	 */
	if ((artyp != ISPIPE) || (lstrval <= 0))
		return;

	/*
	 * keep reading until pipe is drained
	 */
	while ((res = read(arfd, drbuf, sizeof(drbuf))) > 0)
		continue;
	lstrval = res;
}

/*
 * ar_set_wr()
 *	Set up device right before switching from read to write in an append.
 *	device dependent code (if required) to do this should be added here.
 *	For all archive devices we are already positioned at the place we want
 *	to start writing when this routine is called.
 * Return:
 *	0 if all ready to write, -1 otherwise
 */

int
ar_set_wr(void)
{
	off_t cpos;

	/*
	 * we must make sure the trailer is rewritten on append, ar_next()
	 * will stop us if the archive containing the trailer was not written
	 */
	wr_trail = 0;

	/*
	 * Add any device dependent code as required here
	 */
	if (artyp != ISREG)
		return(0);
	/*
	 * Ok we have an archive in a regular file. If we were rewriting a
	 * file, we must get rid of all the stuff after the current offset
	 * (it was not written by pax).
	 */
	if (((cpos = lseek(arfd, 0, SEEK_CUR)) < 0) ||
	    (ftruncate(arfd, cpos) < 0)) {
		syswarn(1, errno, "Unable to truncate archive file");
		return(-1);
	}
	return(0);
}

/*
 * ar_app_ok()
 *	check if the last volume in the archive allows appends. We cannot check
 *	this until we are ready to write since there is no spec that says all
 *	volumes in a single archive have to be of the same type...
 * Return:
 *	0 if we can append, -1 otherwise.
 */

int
ar_app_ok(void)
{
	if (artyp == ISPIPE) {
		paxwarn(1, "Cannot append to an archive obtained from a pipe.");
		return(-1);
	}

	if (!invld_rec)
		return(0);
	paxwarn(1,"Cannot append, device record size %d does not support %s spec",
		rdblksz, argv0);
	return(-1);
}

/*
 * ar_read()
 *	read up to a specified number of bytes from the archive into the
 *	supplied buffer. When dealing with tapes we may not always be able to
 *	read what we want.
 * Return:
 *	Number of bytes in buffer. 0 for end of file, -1 for a read error.
 */

int
ar_read(char *buf, int cnt)
{
	int res = 0;

	/*
	 * if last i/o was in error, no more reads until reset or new volume
	 */
	if (lstrval <= 0)
		return(lstrval);

	/*
	 * how we read must be based on device type
	 */
	switch (artyp) {
	case ISTAPE:
		if ((res = read(arfd, buf, cnt)) > 0) {
			/*
			 * CAUTION: tape systems may not always return the same
			 * sized records so we leave blksz == MAXBLK. The
			 * physical record size that a tape drive supports is
			 * very hard to determine in a uniform and portable
			 * manner.
			 */
			io_ok = 1;
			if (res != rdblksz) {
				/*
				 * Record size changed. If this happens on
				 * any record after the first, we probably have
				 * a tape drive which has a fixed record size
				 * (we are getting multiple records in a single
				 * read). Watch out for record blocking that
				 * violates pax spec (must be a multiple of
				 * BLKMULT).
				 */
				rdblksz = res;
				if (rdblksz % BLKMULT)
					invld_rec = 1;
			}
			return(res);
		}
		break;
	case ISREG:
	case ISBLK:
	case ISCHR:
	case ISPIPE:
	default:
		/*
		 * Files are so easy to deal with. These other things cannot
		 * be trusted at all. So when we are dealing with character
		 * devices and pipes we just take what they have ready for us
		 * and return. Trying to do anything else with them runs the
		 * risk of failure.
		 */
		if ((res = read(arfd, buf, cnt)) > 0) {
			io_ok = 1;
			return(res);
		}
		break;
	}

	/*
	 * We are in trouble at this point, something is broken...
	 */
	lstrval = res;
	if (res < 0)
		syswarn(1, errno, "Failed read on archive volume %d", arvol);
	else if (!frmt || !frmt->is_uar)
		paxwarn(1, "End of archive volume %d reached", arvol);
	return(res);
}

/*
 * ar_write()
 *	Write a specified number of bytes in supplied buffer to the archive
 *	device so it appears as a single "block". Deals with errors and tries
 *	to recover when faced with short writes.
 * Return:
 *	Number of bytes written. 0 indicates end of volume reached and with no
 *	flaws (as best that can be detected). A -1 indicates an unrecoverable
 *	error in the archive occurred.
 */

int
ar_write(char *buf, int bsz)
{
	int res;
	off_t cpos;

	/*
	 * do not allow pax to create a "bad" archive. Once a write fails on
	 * an archive volume prevent further writes to it.
	 */
	if (lstrval <= 0)
		return(lstrval);

	if ((res = write(arfd, buf, bsz)) == bsz) {
		wr_trail = 1;
		io_ok = 1;
		return(bsz);
	}
	/*
	 * write broke, see what we can do with it. We try to send any partial
	 * writes that may violate pax spec to the next archive volume.
	 */
	if (res < 0)
		lstrval = res;
	else
		lstrval = 0;

	switch (artyp) {
	case ISREG:
		if ((res > 0) && (res % BLKMULT)) {
			/*
			 * try to fix up partial writes which are not BLKMULT
			 * in size by forcing the runt record to next archive
			 * volume
			 */
			if ((cpos = lseek(arfd, 0, SEEK_CUR)) < 0)
				break;
			cpos -= res;
			if (ftruncate(arfd, cpos) < 0)
				break;
			res = lstrval = 0;
			break;
		}
		if (res >= 0)
			break;
		/*
		 * if file is out of space, handle it like a return of 0
		 */
		if ((errno == ENOSPC) || (errno == EFBIG) || (errno == EDQUOT))
			res = lstrval = 0;
		break;
	case ISTAPE:
	case ISCHR:
	case ISBLK:
		if (res >= 0)
			break;
		if (errno == EACCES) {
			paxwarn(0, "Write failed, archive is write protected.");
			res = lstrval = 0;
			return(0);
		}
		/*
		 * see if we reached the end of media, if so force a change to
		 * the next volume
		 */
		if ((errno == ENOSPC) || (errno == EIO) || (errno == ENXIO))
			res = lstrval = 0;
		break;
	case ISPIPE:
	default:
		/*
		 * we cannot fix errors to these devices
		 */
		break;
	}

	/*
	 * Better tell the user the bad news...
	 * if this is a block aligned archive format, we may have a bad archive
	 * if the format wants the header to start at a BLKMULT boundary. While
	 * we can deal with the mis-aligned data, it violates spec and other
	 * archive readers will likely fail. if the format is not block
	 * aligned, the user may be lucky (and the archive is ok).
	 */
	if (res >= 0) {
		if (res > 0)
			wr_trail = 1;
		io_ok = 1;
	}

	/*
	 * If we were trying to rewrite the trailer and it didn't work, we
	 * must quit right away.
	 */
	if (!wr_trail && (res <= 0)) {
		paxwarn(1,"Unable to append, trailer re-write failed. Quitting.");
		return(res);
	}

	if (res == 0)
		paxwarn(0, "End of archive volume %d reached", arvol);
	else if (res < 0)
		syswarn(1, errno, "Failed write to archive volume: %d", arvol);
	else if (!frmt->blkalgn || ((res % frmt->blkalgn) == 0))
		paxwarn(0,"WARNING: partial archive write. Archive MAY BE FLAWED");
	else
		paxwarn(1,"WARNING: partial archive write. Archive IS FLAWED");
	return(res);
}

/*
 * ar_rdsync()
 *	Try to move past a bad spot on a flawed archive as needed to continue
 *	I/O. Clears error flags to allow I/O to continue.
 * Return:
 *	0 when ok to try i/o again, -1 otherwise.
 */

int
ar_rdsync(void)
{
	long fsbz;
	off_t cpos;
	off_t mpos;
#if HAVE_SYS_MTIO_H
	struct mtop mb;
#endif

	/*
	 * Fail resync attempts at user request (done) or if this is going to be
	 * an update/append to a existing archive. if last i/o hit media end,
	 * we need to go to the next volume not try a resync
	 */
	if ((done > 0) || (lstrval == 0))
		return(-1);

	if ((act == APPND) || (act == ARCHIVE)) {
		paxwarn(1, "Cannot allow updates to an archive with flaws.");
		return(-1);
	}
	if (io_ok)
		did_io = 1;

	switch (artyp) {
#if HAVE_SYS_MTIO_H
	case ISTAPE:
		/*
		 * if the last i/o was a successful data transfer, we assume
		 * the fault is just a bad record on the tape that we are now
		 * past. If we did not get any data since the last resync try
		 * to move the tape forward one PHYSICAL record past any
		 * damaged tape section. Some tape drives are stubborn and need
		 * to be pushed.
		 */
		if (io_ok) {
			io_ok = 0;
			lstrval = 1;
			break;
		}
		mb.mt_op = MTFSR;
		mb.mt_count = 1;
		if (ioctl(arfd, MTIOCTOP, &mb) < 0)
			break;
		lstrval = 1;
		break;
#endif
	case ISREG:
	case ISCHR:
	case ISBLK:
		/*
		 * try to step over the bad part of the device.
		 */
		io_ok = 0;
		if (((fsbz = arsb.st_blksize) <= 0) || (artyp != ISREG))
			fsbz = BLKMULT;
		if ((cpos = lseek(arfd, 0, SEEK_CUR)) < 0)
			break;
		mpos = fsbz - (cpos % fsbz);
		if (lseek(arfd, mpos, SEEK_CUR) < 0)
			break;
		lstrval = 1;
		break;
	case ISPIPE:
	default:
		/*
		 * cannot recover on these archive device types
		 */
		io_ok = 0;
		break;
	}
	if (lstrval <= 0) {
		paxwarn(1, "Unable to recover from an archive read failure.");
		return(-1);
	}
	paxwarn(0, "Attempting to recover from an archive read failure.");
	return(0);
}

/*
 * ar_fow()
 *	Move the I/O position within the archive forward the specified number of
 *	bytes as supported by the device. If we cannot move the requested
 *	number of bytes, return the actual number of bytes moved in skipped.
 * Return:
 *	0 if moved the requested distance, -1 on complete failure, 1 on
 *	partial move (the amount moved is in skipped)
 */

int
ar_fow(off_t sksz, off_t *skipped)
{
	off_t cpos;
	off_t mpos;

	*skipped = 0;
	if (sksz <= 0)
		return(0);

	/*
	 * we cannot move forward at EOF or error
	 */
	if (lstrval <= 0)
		return(lstrval);

	/*
	 * Safer to read forward on devices where it is hard to find the end of
	 * the media without reading to it. With tapes we cannot be sure of the
	 * number of physical blocks to skip (we do not know physical block
	 * size at this point), so we must only read forward on tapes!
	 */
	if (artyp != ISREG)
		return(0);

	/*
	 * figure out where we are in the archive
	 */
	if ((cpos = lseek(arfd, 0, SEEK_CUR)) >= 0) {
		/*
		 * we can be asked to move farther than there are bytes in this
		 * volume, if so, just go to file end and let normal buf_fill()
		 * deal with the end of file (it will go to next volume by
		 * itself)
		 */
		if ((mpos = cpos + sksz) > arsb.st_size) {
			*skipped = arsb.st_size - cpos;
			mpos = arsb.st_size;
		} else
			*skipped = sksz;
		if (lseek(arfd, mpos, SEEK_SET) >= 0)
			return(0);
	}
	syswarn(1, errno, "Forward positioning operation on archive failed");
	lstrval = -1;
	return(-1);
}

/*
 * ar_rev()
 *	move the i/o position within the archive backwards the specified byte
 *	count as supported by the device. With tapes drives we RESET rdblksz to
 *	the PHYSICAL blocksize.
 *	NOTE: We should only be called to move backwards so we can rewrite the
 *	last records (the trailer) of an archive (APPEND).
 * Return:
 *	0 if moved the requested distance, -1 on complete failure
 */

int
ar_rev(off_t sksz)
{
	off_t cpos;
#if HAVE_SYS_MTIO_H
	struct mtop mb;
	int phyblk;
#endif

	/*
	 * make sure we do not have try to reverse on a flawed archive
	 */
	if (lstrval < 0)
		return(lstrval);

	switch (artyp) {
	case ISPIPE:
		if (sksz <= 0)
			break;
		/*
		 * cannot go backwards on these critters
		 */
		paxwarn(1, "Reverse positioning on pipes is not supported.");
		lstrval = -1;
		return(-1);
	case ISREG:
	case ISBLK:
	case ISCHR:
	default:
		if (sksz <= 0)
			break;

		/*
		 * For things other than files, backwards movement has a very
		 * high probability of failure as we really do not know the
		 * true attributes of the device we are talking to (the device
		 * may not even have the ability to lseek() in any direction).
		 * First we figure out where we are in the archive.
		 */
		if ((cpos = lseek(arfd, 0, SEEK_CUR)) < 0) {
			syswarn(1, errno,
			   "Unable to obtain current archive byte offset");
			lstrval = -1;
			return(-1);
		}

		/*
		 * we may try to go backwards past the start when the archive
		 * is only a single record. If this happens and we are on a
		 * multi-volume archive, we need to go to the end of the
		 * previous volume and continue our movement backwards from
		 * there.
		 */
		if ((cpos -= sksz) < 0) {
			if (arvol > 1) {
				/*
				 * this should never happen
				 */
				paxwarn(1,"Reverse position on previous volume.");
				lstrval = -1;
				return(-1);
			}
			cpos = 0;
		}
		if (lseek(arfd, cpos, SEEK_SET) < 0) {
			syswarn(1, errno, "Unable to seek archive backwards");
			lstrval = -1;
			return(-1);
		}
		break;
#if HAVE_SYS_MTIO_H
	case ISTAPE:
		/*
		 * Calculate and move the proper number of PHYSICAL tape
		 * blocks. If the sksz is not an even multiple of the physical
		 * tape size, we cannot do the move (this should never happen).
		 * (We also cannot handle trailers spread over two vols.)
		 * get_phys() also makes sure we are in front of the filemark.
		 */
		if ((phyblk = get_phys()) <= 0) {
			lstrval = -1;
			return(-1);
		}

		/*
		 * make sure future tape reads only go by physical tape block
		 * size (set rdblksz to the real size).
		 */
		rdblksz = phyblk;

		/*
		 * if no movement is required, just return (we must be after
		 * get_phys() so the physical blocksize is properly set)
		 */
		if (sksz <= 0)
			break;

		/*
		 * ok we have to move. Make sure the tape drive can do it.
		 */
		if (sksz % phyblk) {
			paxwarn(1,
			    "Tape drive unable to backspace requested amount");
			lstrval = -1;
			return(-1);
		}

		/*
		 * move backwards the requested number of bytes
		 */
		mb.mt_op = MTBSR;
		mb.mt_count = sksz/phyblk;
		if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
			syswarn(1,errno, "Unable to backspace tape %d blocks.",
			    mb.mt_count);
			lstrval = -1;
			return(-1);
		}
		break;
#endif
	}
	lstrval = 1;
	return(0);
}

#if HAVE_SYS_MTIO_H
/*
 * get_phys()
 *	Determine the physical block size on a tape drive. We need the physical
 *	block size so we know how many bytes we skip over when we move with
 *	mtio commands. We also make sure we are BEFORE THE TAPE FILEMARK when
 *	return.
 *	This is one really SLOW routine...
 * Return:
 *	physical block size if ok (ok > 0), -1 otherwise
 */

static int
get_phys(void)
{
	int padsz = 0;
	int res;
	int phyblk;
	struct mtop mb;
	char scbuf[MAXBLK];

	/*
	 * move to the file mark, and then back up one record and read it.
	 * this should tell us the physical record size the tape is using.
	 */
	if (lstrval == 1) {
		/*
		 * we know we are at file mark when we get back a 0 from
		 * read()
		 */
		while ((res = read(arfd, scbuf, sizeof(scbuf))) > 0)
			padsz += res;
		if (res < 0) {
			syswarn(1, errno, "Unable to locate tape filemark.");
			return(-1);
		}
	}

	/*
	 * move backwards over the file mark so we are at the end of the
	 * last record.
	 */
	mb.mt_op = MTBSF;
	mb.mt_count = 1;
	if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
		syswarn(1, errno, "Unable to backspace over tape filemark.");
		return(-1);
	}

	/*
	 * move backwards so we are in front of the last record and read it to
	 * get physical tape blocksize.
	 */
	mb.mt_op = MTBSR;
	mb.mt_count = 1;
	if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
		syswarn(1, errno, "Unable to backspace over last tape block.");
		return(-1);
	}
	if ((phyblk = read(arfd, scbuf, sizeof(scbuf))) <= 0) {
		syswarn(1, errno, "Cannot determine archive tape blocksize.");
		return(-1);
	}

	/*
	 * read forward to the file mark, then back up in front of the filemark
	 * (this is a bit paranoid, but should be safe to do).
	 */
	while ((res = read(arfd, scbuf, sizeof(scbuf))) > 0)
		continue;
	if (res < 0) {
		syswarn(1, errno, "Unable to locate tape filemark.");
		return(-1);
	}
	mb.mt_op = MTBSF;
	mb.mt_count = 1;
	if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
		syswarn(1, errno, "Unable to backspace over tape filemark.");
		return(-1);
	}

	/*
	 * set lstrval so we know that the filemark has not been seen
	 */
	lstrval = 1;

	/*
	 * return if there was no padding
	 */
	if (padsz == 0)
		return(phyblk);

	/*
	 * make sure we can move backwards over the padding. (this should
	 * never fail).
	 */
	if (padsz % phyblk) {
		paxwarn(1, "Tape drive unable to backspace requested amount");
		return(-1);
	}

	/*
	 * move backwards over the padding so the head is where it was when
	 * we were first called (if required).
	 */
	mb.mt_op = MTBSR;
	mb.mt_count = padsz/phyblk;
	if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
		syswarn(1,errno,"Unable to backspace tape over %d pad blocks",
		    mb.mt_count);
		return(-1);
	}
	return(phyblk);
}
#endif

/*
 * ar_next()
 *	prompts the user for the next volume in this archive. For some devices
 *	we may allow the media to be changed. Otherwise a new archive is
 *	prompted for. By pax spec, if there is no controlling tty or an eof is
 *	read on tty input, we must quit pax.
 * Return:
 *	0 when ready to continue, -1 when all done
 */

int
ar_next(void)
{
	char *buf;
	sigset_t o_mask;

	/*
	 * WE MUST CLOSE THE DEVICE. A lot of devices must see last close, (so
	 * things like writing EOF etc will be done) (Watch out ar_close() can
	 * also be called via a signal handler, so we must prevent a race.
	 */
	if (sigprocmask(SIG_BLOCK, &s_mask, &o_mask) < 0)
		syswarn(0, errno, "Unable to set signal mask");
	ar_close(0);
	if (sigprocmask(SIG_SETMASK, &o_mask, NULL) < 0)
		syswarn(0, errno, "Unable to restore signal mask");

	if (done || !wr_trail || force_one_volume || op_mode == OP_TAR)
		return(-1);

	tty_prnt("\nATTENTION! %s archive volume change required.\n", argv0);

	/*
	 * if i/o is on stdin or stdout, we cannot reopen it (we do not know
	 * the name), the user will be forced to type it in.
	 */
	if (strcmp(arcname, STDO) && strcmp(arcname, STDN) && (artyp != ISREG)
	    && (artyp != ISPIPE)) {
		if (artyp == ISTAPE) {
			tty_prnt("%s ready for archive tape volume: %d\n",
				arcname, arvol);
			tty_prnt("Load the NEXT TAPE on the tape drive");
		} else {
			tty_prnt("%s ready for archive volume: %d\n",
				arcname, arvol);
			tty_prnt("Load the NEXT STORAGE MEDIA (if required)");
		}

		if ((act == ARCHIVE) || (act == APPND))
			tty_prnt(" and make sure it is WRITE ENABLED.\n");
		else
			tty_prnt("\n");

		for (;;) {
			tty_prnt("Type \"y\" to continue, \".\" to quit %s,",
				argv0);
			tty_prnt(" or \"s\" to switch to new device.\nIf you");
			tty_prnt(" cannot change storage media, type \"s\"\n");
			tty_prnt("Is the device ready and online? > ");

			if ((buf = tty_rd()) == NULL || !strcmp(buf, ".")) {
				free(buf);
				done = 1;
				lstrval = -1;
				tty_prnt("Quitting %s!\n", argv0);
				vfpart = 0;
				return(-1);
			}

			if ((buf[0] == '\0') || (buf[1] != '\0'))
				goto eunknown;

			switch (buf[0]) {
			case 'y':
			case 'Y':
				/*
				 * we are to continue with the same device
				 */
				free(buf);
				if (ar_open(arcname) >= 0)
					return (0);
				tty_prnt("Cannot re-open %s, try again\n",
				    arcname);
				continue;
			case 's':
			case 'S':
				/*
				 * user wants to open a different device
				 */
				free(buf);
				tty_prnt("Switching to a different archive\n");
				break;
			default:
 eunknown:
				tty_prnt("%s unknown command, try again\n", buf);
				free(buf);
				continue;
			}
			break;
		}
	} else
		tty_prnt("Ready for archive volume: %d\n", arvol);

	/*
	 * have to go to a different archive
	 */
	for (;;) {
		tty_prnt("Input archive name or \".\" to quit %s.\n", argv0);
		tty_prnt("Archive name > ");

		if ((buf = tty_rd()) == NULL || !strcmp(buf, ".")) {
			free(buf);
			done = 1;
			lstrval = -1;
			tty_prnt("Quitting %s!\n", argv0);
			vfpart = 0;
			return(-1);
		}
		if (buf[0] == '\0') {
			tty_prnt("Empty file name, try again\n");
			free(buf);
			continue;
		}
		if (!strcmp(buf, "..")) {
			tty_prnt("Illegal file name '..', try again\n");
			free(buf);
			continue;
		}
		if (strlen(buf) > PAXPATHLEN) {
			tty_prnt("File name too long, try again\n");
			free(buf);
			continue;
		}

		/*
		 * try to open new archive
		 */
		if (ar_open(buf) >= 0) {
			free(arcname_alloc);
			arcname = arcname_alloc = buf;
			break;
		}
		tty_prnt("Cannot open %s, try again\n", buf);
		free(buf);
		continue;
	}
	return (0);
}

/*
 * ar_start_compress()
 * starts the compression/decompression process as a child, using magic
 * to keep the fd the same in the calling function (parent).
 */
void
ar_start_compress(int fd, int wr)
{
	int fds[2];
	const char *compress_flags;

	guess_compress_program(wr);
	if (compress_program == NULL)
		return;

	if (pipe(fds) < 0)
		err(1, "pipe");
	zpid = fork();
	if (zpid < 0)
		err(1, "fork");

	/* parent */
	if (zpid) {
		dup2(fds[wr ? 1 : 0], fd);
		close(fds[0]);
		close(fds[1]);

#if HAVE_PLEDGE
		if (pmode == 0 || (act != EXTRACT && act != COPY)) {
		    if (pledge("stdio rpath wpath cpath fattr dpath getpw proc tape",
			NULL) == -1)
				err(1, "pledge");
		}
#endif
	} else {
		if (wr) {
			dup2(fds[0], STDIN_FILENO);
			dup2(fd, STDOUT_FILENO);
			compress_flags = "-c";
		} else {
			dup2(fds[1], STDOUT_FILENO);
			dup2(fd, STDIN_FILENO);
			compress_flags = "-dc";
		}
		close(fds[0]);
		close(fds[1]);

		/* System compressors are more likely to use pledge(2) */
		putenv("PATH=" PAX_SAFE_PATH);

		if (execlp(compress_program, compress_program,
		    compress_flags, (char *)NULL) < 0)
			err(1, "exec(%s)", compress_program);
		/* NOTREACHED */
	}
}