File: reader.go

package info (click to toggle)
golang-github-phpdave11-gofpdi 1.0.13-1
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, sid
  • size: 144 kB
  • sloc: makefile: 2
file content (1632 lines) | stat: -rw-r--r-- 42,040 bytes parent folder | download
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
package gofpdi

import (
	"bufio"
	"bytes"
	"compress/zlib"
	"encoding/binary"
	"fmt"
	"github.com/pkg/errors"
	"io"
	"io/ioutil"
	"math"
	"os"
	"strconv"
)

type PdfReader struct {
	availableBoxes []string
	stack          []string
	trailer        *PdfValue
	catalog        *PdfValue
	pages          []*PdfValue
	xrefPos        int
	xref           map[int]map[int]int
	xrefStream     map[int][2]int
	f              io.ReadSeeker
	nBytes         int64
	sourceFile     string
	curPage        int
	alreadyRead    bool
	pageCount      int
}

func NewPdfReaderFromStream(rs io.ReadSeeker) (*PdfReader, error) {
	length, err := rs.Seek(0, 2)
	if err != nil {
		return nil, errors.Wrapf(err, "Failed to determine stream length")
	}
	parser := &PdfReader{f: rs, nBytes: length}
	if err := parser.init(); err != nil {
		return nil, errors.Wrap(err, "Failed to initialize parser")
	}
	if err := parser.read(); err != nil {
		return nil, errors.Wrap(err, "Failed to read pdf from stream")
	}
	return parser, nil
}

func NewPdfReader(filename string) (*PdfReader, error) {
	var err error
	f, err := os.Open(filename)
	if err != nil {
		return nil, errors.Wrap(err, "Failed to open file")
	}
	info, err := f.Stat()
	if err != nil {
		return nil, errors.Wrap(err, "Failed to obtain file information")
	}

	parser := &PdfReader{f: f, sourceFile: filename, nBytes: info.Size()}
	if err = parser.init(); err != nil {
		return nil, errors.Wrap(err, "Failed to initialize parser")
	}
	if err = parser.read(); err != nil {
		return nil, errors.Wrap(err, "Failed to read pdf")
	}

	return parser, nil
}

func (this *PdfReader) init() error {
	this.availableBoxes = []string{"/MediaBox", "/CropBox", "/BleedBox", "/TrimBox", "/ArtBox"}
	this.xref = make(map[int]map[int]int, 0)
	this.xrefStream = make(map[int][2]int, 0)
	err := this.read()
	if err != nil {
		return errors.Wrap(err, "Failed to read pdf")
	}
	return nil
}

type PdfValue struct {
	Type       int
	String     string
	Token      string
	Int        int
	Real       float64
	Bool       bool
	Dictionary map[string]*PdfValue
	Array      []*PdfValue
	Id         int
	NewId      int
	Gen        int
	Value      *PdfValue
	Stream     *PdfValue
	Bytes      []byte
}

// Jump over comments
func (this *PdfReader) skipComments(r *bufio.Reader) error {
	var err error
	var b byte

	for {
		b, err = r.ReadByte()
		if err != nil {
			return errors.Wrap(err, "Failed to ReadByte while skipping comments")
		}

		if b == '\n' || b == '\r' {
			if b == '\r' {
				// Peek and see if next char is \n
				b2, err := r.ReadByte()
				if err != nil {
					return errors.Wrap(err, "Failed to read byte")
				}
				if b2 != '\n' {
					r.UnreadByte()
				}
			}
			break
		}
	}

	return nil
}

// Advance reader so that whitespace is ignored
func (this *PdfReader) skipWhitespace(r *bufio.Reader) error {
	var err error
	var b byte

	for {
		b, err = r.ReadByte()
		if err != nil {
			if err == io.EOF {
				break
			}
			return errors.Wrap(err, "Failed to read byte")
		}

		if b == ' ' || b == '\n' || b == '\r' || b == '\t' {
			continue
		} else {
			r.UnreadByte()
			break
		}
	}

	return nil
}

// Read a token
func (this *PdfReader) readToken(r *bufio.Reader) (string, error) {
	var err error

	// If there is a token available on the stack, pop it out and return it.
	if len(this.stack) > 0 {
		var popped string
		popped, this.stack = this.stack[len(this.stack)-1], this.stack[:len(this.stack)-1]
		return popped, nil
	}

	err = this.skipWhitespace(r)
	if err != nil {
		return "", errors.Wrap(err, "Failed to skip whitespace")
	}

	b, err := r.ReadByte()
	if err != nil {
		if err == io.EOF {
			return "", nil
		}
		return "", errors.Wrap(err, "Failed to read byte")
	}

	switch b {
	case '[', ']', '(', ')':
		// This is either an array or literal string delimeter, return it.
		return string(b), nil

	case '<', '>':
		// This could either be a hex string or a dictionary delimiter.
		// Determine the appropriate case and return the token.
		nb, err := r.ReadByte()
		if err != nil {
			return "", errors.Wrap(err, "Failed to read byte")
		}
		if nb == b {
			return string(b) + string(nb), nil
		} else {
			r.UnreadByte()
			return string(b), nil
		}

	case '%':
		err = this.skipComments(r)
		if err != nil {
			return "", errors.Wrap(err, "Failed to skip comments")
		}
		return this.readToken(r)

	default:
		// FIXME this may not be performant to create new strings for each byte
		// Is it probably better to create a buffer and then convert to a string at the end.
		str := string(b)

	loop:
		for {
			b, err := r.ReadByte()
			if err != nil {
				return "", errors.Wrap(err, "Failed to read byte")
			}
			switch b {
			case ' ', '%', '[', ']', '<', '>', '(', ')', '\r', '\n', '\t', '/':
				r.UnreadByte()
				break loop
			default:
				str += string(b)
			}
		}
		return str, nil
	}

	return "", nil
}

// Read a value based on a token
func (this *PdfReader) readValue(r *bufio.Reader, t string) (*PdfValue, error) {
	var err error
	var b byte

	result := &PdfValue{}
	result.Type = -1
	result.Token = t
	result.Dictionary = make(map[string]*PdfValue, 0)
	result.Array = make([]*PdfValue, 0)

	switch t {
	case "<":
		// This is a hex string

		// Read bytes until '>' is found
		var s string
		for {
			b, err = r.ReadByte()
			if err != nil {
				return nil, errors.Wrap(err, "Failed to read byte")
			}
			if b != '>' {
				s += string(b)
			} else {
				break
			}
		}

		result.Type = PDF_TYPE_HEX
		result.String = s

	case "<<":
		// This is a dictionary

		// Recurse into this function until we reach the end of the dictionary.
		for {
			key, err := this.readToken(r)
			if err != nil {
				return nil, errors.Wrap(err, "Failed to read token")
			}
			if key == "" {
				return nil, errors.New("Token is empty")
			}

			if key == ">>" {
				break
			}

			// read next token
			newKey, err := this.readToken(r)
			if err != nil {
				return nil, errors.Wrap(err, "Failed to read token")
			}

			value, err := this.readValue(r, newKey)
			if err != nil {
				return nil, errors.Wrap(err, "Failed to read value for token: "+newKey)
			}

			if value.Type == -1 {
				return result, nil
			}

			// Catch missing value
			if value.Type == PDF_TYPE_TOKEN && value.String == ">>" {
				result.Type = PDF_TYPE_NULL
				result.Dictionary[key] = value
				break
			}

			// Set value in dictionary
			result.Dictionary[key] = value
		}

		result.Type = PDF_TYPE_DICTIONARY
		return result, nil

	case "[":
		// This is an array

		tmpResult := make([]*PdfValue, 0)

		// Recurse into this function until we reach the end of the array
		for {
			key, err := this.readToken(r)
			if err != nil {
				return nil, errors.Wrap(err, "Failed to read token")
			}
			if key == "" {
				return nil, errors.New("Token is empty")
			}

			if key == "]" {
				break
			}

			value, err := this.readValue(r, key)
			if err != nil {
				return nil, errors.Wrap(err, "Failed to read value for token: "+key)
			}

			if value.Type == -1 {
				return result, nil
			}

			tmpResult = append(tmpResult, value)
		}

		result.Type = PDF_TYPE_ARRAY
		result.Array = tmpResult

	case "(":
		// This is a string

		openBrackets := 1

		// Create new buffer
		var buf bytes.Buffer

		// Read bytes until brackets are balanced
		for openBrackets > 0 {
			b, err := r.ReadByte()

			if err != nil {
				return nil, errors.Wrap(err, "Failed to read byte")
			}

			switch b {
			case '(':
				openBrackets++

			case ')':
				openBrackets--

			case '\\':
				nb, err := r.ReadByte()
				if err != nil {
					return nil, errors.Wrap(err, "Failed to read byte")
				}

				buf.WriteByte(b)
				buf.WriteByte(nb)

				continue
			}

			if openBrackets > 0 {
				buf.WriteByte(b)
			}
		}

		result.Type = PDF_TYPE_STRING
		result.String = buf.String()

	case "stream":
		return nil, errors.New("Stream not implemented")

	default:
		result.Type = PDF_TYPE_TOKEN
		result.Token = t

		if is_numeric(t) {
			// A numeric token.  Make sure that it is not part of something else
			t2, err := this.readToken(r)
			if err != nil {
				return nil, errors.Wrap(err, "Failed to read token")
			}
			if t2 != "" {
				if is_numeric(t2) {
					// Two numeric tokens in a row.
					// In this case, we're probably in front of either an object reference
					// or an object specification.
					// Determine the case and return the data.
					t3, err := this.readToken(r)
					if err != nil {
						return nil, errors.Wrap(err, "Failed to read token")
					}

					if t3 != "" {
						switch t3 {
						case "obj":
							result.Type = PDF_TYPE_OBJDEC
							result.Id, _ = strconv.Atoi(t)
							result.Gen, _ = strconv.Atoi(t2)
							return result, nil

						case "R":
							result.Type = PDF_TYPE_OBJREF
							result.Id, _ = strconv.Atoi(t)
							result.Gen, _ = strconv.Atoi(t2)
							return result, nil
						}

						// If we get to this point, that numeric value up there was just a numeric value.
						// Push the extra tokens back into the stack and return the value.
						this.stack = append(this.stack, t3)
					}
				}

				this.stack = append(this.stack, t2)
			}

			if n, err := strconv.Atoi(t); err == nil {
				result.Type = PDF_TYPE_NUMERIC
				result.Int = n
				result.Real = float64(n) // Also assign Real value here to fix page box parsing bugs
			} else {
				result.Type = PDF_TYPE_REAL
				result.Real, _ = strconv.ParseFloat(t, 64)
			}
		} else if t == "true" || t == "false" {
			result.Type = PDF_TYPE_BOOLEAN
			result.Bool = t == "true"
		} else if t == "null" {
			result.Type = PDF_TYPE_NULL
		} else {
			result.Type = PDF_TYPE_TOKEN
			result.Token = t
		}
	}

	return result, nil
}

// Resolve a compressed object (PDF 1.5)
func (this *PdfReader) resolveCompressedObject(objSpec *PdfValue) (*PdfValue, error) {
	var err error

	// Make sure object reference exists in xrefStream
	if _, ok := this.xrefStream[objSpec.Id]; !ok {
		return nil, errors.New(fmt.Sprintf("Could not find object ID %d in xref stream or xref table.", objSpec.Id))
	}

	// Get object id and index
	objectId := this.xrefStream[objSpec.Id][0]
	objectIndex := this.xrefStream[objSpec.Id][1]

	// Read compressed object
	compressedObjSpec := &PdfValue{Type: PDF_TYPE_OBJREF, Id: objectId, Gen: 0}

	// Resolve compressed object
	compressedObj, err := this.resolveObject(compressedObjSpec)
	if err != nil {
		return nil, errors.Wrap(err, "Failed to resolve compressed object")
	}

	// Verify object type is /ObjStm
	if _, ok := compressedObj.Value.Dictionary["/Type"]; ok {
		if compressedObj.Value.Dictionary["/Type"].Token != "/ObjStm" {
			return nil, errors.New("Expected compressed object type to be /ObjStm")
		}
	} else {
		return nil, errors.New("Could not determine compressed object type.")
	}

	// Get number of sub-objects in compressed object
	n := compressedObj.Value.Dictionary["/N"].Int
	if n <= 0 {
		return nil, errors.New("No sub objects in compressed object")
	}

	// Get offset of first object
	first := compressedObj.Value.Dictionary["/First"].Int

	// Get length
	//length := compressedObj.Value.Dictionary["/Length"].Int

	// Check for filter
	filter := ""
	if _, ok := compressedObj.Value.Dictionary["/Filter"]; ok {
		filter = compressedObj.Value.Dictionary["/Filter"].Token
		if filter != "/FlateDecode" {
			return nil, errors.New("Unsupported filter - expected /FlateDecode, got: " + filter)
		}
	}

	if filter == "/FlateDecode" {
		// Decompress if filter is /FlateDecode
		// Uncompress zlib compressed data
		var out bytes.Buffer
		zlibReader, _ := zlib.NewReader(bytes.NewBuffer(compressedObj.Stream.Bytes))
		defer zlibReader.Close()
		io.Copy(&out, zlibReader)

		// Set stream to uncompressed data
		compressedObj.Stream.Bytes = out.Bytes()
	}

	// Get io.Reader for bytes
	r := bufio.NewReader(bytes.NewBuffer(compressedObj.Stream.Bytes))

	subObjId := 0
	subObjPos := 0

	// Read sub-object indeces and their positions within the (un)compressed object
	for i := 0; i < n; i++ {
		var token string
		var _objidx int
		var _objpos int

		// Read first token (object index)
		token, err = this.readToken(r)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to read token")
		}

		// Convert line (string) into int
		_objidx, err = strconv.Atoi(token)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to convert token into integer: "+token)
		}

		// Read first token (object index)
		token, err = this.readToken(r)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to read token")
		}

		// Convert line (string) into int
		_objpos, err = strconv.Atoi(token)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to convert token into integer: "+token)
		}

		if i == objectIndex {
			subObjId = _objidx
			subObjPos = _objpos
		}
	}

	// Now create an io.ReadSeeker
	rs := io.ReadSeeker(bytes.NewReader(compressedObj.Stream.Bytes))

	// Determine where to seek to (sub-object position + /First)
	seekTo := int64(subObjPos + first)

	// Fast forward to the object
	rs.Seek(seekTo, 0)

	// Create a new io.Reader
	r = bufio.NewReader(rs)

	// Read token
	token, err := this.readToken(r)
	if err != nil {
		return nil, errors.Wrap(err, "Failed to read token")
	}

	// Read object
	obj, err := this.readValue(r, token)
	if err != nil {
		return nil, errors.Wrap(err, "Failed to read value for token: "+token)
	}

	result := &PdfValue{}
	result.Id = subObjId
	result.Gen = 0
	result.Type = PDF_TYPE_OBJECT
	result.Value = obj

	return result, nil
}

func (this *PdfReader) resolveObject(objSpec *PdfValue) (*PdfValue, error) {
	var err error
	var old_pos int64

	// Create new bufio.Reader
	r := bufio.NewReader(this.f)

	if objSpec.Type == PDF_TYPE_OBJREF {
		// This is a reference, resolve it.
		offset := this.xref[objSpec.Id][objSpec.Gen]

		if _, ok := this.xref[objSpec.Id]; !ok {
			// This may be a compressed object
			return this.resolveCompressedObject(objSpec)
		}

		// Save current file position
		// This is needed if you want to resolve reference while you're reading another object.
		// (e.g.: if you need to determine the length of a stream)
		old_pos, err = this.f.Seek(0, os.SEEK_CUR)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to get current position of file")
		}

		// Reposition the file pointer and load the object header
		_, err = this.f.Seek(int64(offset), 0)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to set position of file")
		}

		token, err := this.readToken(r)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to read token")
		}

		obj, err := this.readValue(r, token)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to read value for token: "+token)
		}

		if obj.Type != PDF_TYPE_OBJDEC {
			return nil, errors.New(fmt.Sprintf("Expected type to be PDF_TYPE_OBJDEC, got: %d", obj.Type))
		}

		if obj.Id != objSpec.Id {
			return nil, errors.New(fmt.Sprintf("Object ID (%d) does not match ObjSpec ID (%d)", obj.Id, objSpec.Id))
		}

		if obj.Gen != objSpec.Gen {
			return nil, errors.New("Object Gen does not match ObjSpec Gen")
		}

		// Read next token
		token, err = this.readToken(r)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to read token")
		}

		// Read actual object value
		value, err := this.readValue(r, token)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to read value for token: "+token)
		}

		// Read next token
		token, err = this.readToken(r)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to read token")
		}

		result := &PdfValue{}
		result.Id = obj.Id
		result.Gen = obj.Gen
		result.Type = PDF_TYPE_OBJECT
		result.Value = value

		if token == "stream" {
			result.Type = PDF_TYPE_STREAM

			err = this.skipWhitespace(r)
			if err != nil {
				return nil, errors.Wrap(err, "Failed to skip whitespace")
			}

			// Get stream length dictionary
			lengthDict := value.Dictionary["/Length"]

			// Get number of bytes of stream
			length := lengthDict.Int

			// If lengthDict is an object reference, resolve the object and set length
			if lengthDict.Type == PDF_TYPE_OBJREF {
				lengthDict, err = this.resolveObject(lengthDict)

				if err != nil {
					return nil, errors.Wrap(err, "Failed to resolve length object of stream")
				}

				// Set length to resolved object value
				length = lengthDict.Value.Int
			}

			// Read length bytes
			bytes := make([]byte, length)

			// Cannot use reader.Read() because that may not read all the bytes
			_, err := io.ReadFull(r, bytes)
			if err != nil {
				return nil, errors.Wrap(err, "Failed to read bytes from buffer")
			}

			token, err = this.readToken(r)
			if err != nil {
				return nil, errors.Wrap(err, "Failed to read token")
			}
			if token != "endstream" {
				return nil, errors.New("Expected next token to be: endstream, got: " + token)
			}

			token, err = this.readToken(r)
			if err != nil {
				return nil, errors.Wrap(err, "Failed to read token")
			}

			streamObj := &PdfValue{}
			streamObj.Type = PDF_TYPE_STREAM
			streamObj.Bytes = bytes

			result.Stream = streamObj
		}

		if token != "endobj" {
			return nil, errors.New("Expected next token to be: endobj, got: " + token)
		}

		// Reposition the file pointer to previous position
		_, err = this.f.Seek(old_pos, 0)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to set position of file")
		}

		return result, nil

	} else {
		return objSpec, nil
	}

	return &PdfValue{}, nil
}

// Find the xref offset (should be at the end of the PDF)
func (this *PdfReader) findXref() error {
	var result int
	var err error
	var toRead int64

	toRead = 1500

	// If PDF is smaller than 1500 bytes, be sure to only read the number of bytes that are in the file
	fileSize := this.nBytes
	if fileSize < toRead {
		toRead = fileSize
	}

	// 0 means relative to the origin of the file,
	// 1 means relative to the current offset,
	// and 2 means relative to the end.
	whence := 2

	// Perform seek operation
	_, err = this.f.Seek(-toRead, whence)
	if err != nil {
		return errors.Wrap(err, "Failed to set position of file")
	}

	// Create new bufio.Reader
	r := bufio.NewReader(this.f)
	for {
		// Read all tokens until "startxref" is found
		token, err := this.readToken(r)
		if err != nil {
			return errors.Wrap(err, "Failed to read token")
		}

		if token == "startxref" {
			token, err = this.readToken(r)
			// Probably EOF before finding startxref
			if err != nil {
				return errors.Wrap(err, "Failed to find startxref token")
			}

			// Convert line (string) into int
			result, err = strconv.Atoi(token)
			if err != nil {
				return errors.Wrap(err, "Failed to convert xref position into integer: "+token)
			}

			// Successfully read the xref position
			this.xrefPos = result
			break
		}
	}

	// Rewind file pointer
	whence = 0
	_, err = this.f.Seek(0, whence)
	if err != nil {
		return errors.Wrap(err, "Failed to set position of file")
	}

	this.xrefPos = result

	return nil
}

// Read and parse the xref table
func (this *PdfReader) readXref() error {
	var err error

	// Create new bufio.Reader
	r := bufio.NewReader(this.f)

	// Set file pointer to xref start
	_, err = this.f.Seek(int64(this.xrefPos), 0)
	if err != nil {
		return errors.Wrap(err, "Failed to set position of file")
	}

	// Xref should start with 'xref'
	t, err := this.readToken(r)
	if err != nil {
		return errors.Wrap(err, "Failed to read token")
	}
	if t != "xref" {
		// Maybe this is an XRef stream ...
		v, err := this.readValue(r, t)
		if err != nil {
			return errors.Wrap(err, "Failed to read XRef stream")
		}

		if v.Type == PDF_TYPE_OBJDEC {
			// Read next token
			t, err = this.readToken(r)
			if err != nil {
				return errors.Wrap(err, "Failed to read token")
			}

			// Read actual object value
			v, err := this.readValue(r, t)
			if err != nil {
				return errors.Wrap(err, "Failed to read value for token: "+t)
			}

			// If /Type is set, check to see if it is XRef
			if _, ok := v.Dictionary["/Type"]; ok {
				if v.Dictionary["/Type"].Token == "/XRef" {
					// Continue reading xref stream data now that it is confirmed that it is an xref stream

					// Check for /DecodeParms
					paethDecode := false
					if _, ok := v.Dictionary["/DecodeParms"]; ok {
						columns := 0
						predictor := 0

						if _, ok2 := v.Dictionary["/DecodeParms"].Dictionary["/Columns"]; ok2 {
							columns = v.Dictionary["/DecodeParms"].Dictionary["/Columns"].Int
						}
						if _, ok2 := v.Dictionary["/DecodeParms"].Dictionary["/Predictor"]; ok2 {
							predictor = v.Dictionary["/DecodeParms"].Dictionary["/Predictor"].Int
						}

						if columns > 4 || predictor > 12 {
							return errors.New("Unsupported /DecodeParms - only tested with /Columns <= 4 and /Predictor <= 12")
						}
						paethDecode = true
					}

					/*
						// Check to make sure field size is [1 2 1] - not yet tested with other field sizes
						if v.Dictionary["/W"].Array[0].Int != 1 || v.Dictionary["/W"].Array[1].Int > 4 || v.Dictionary["/W"].Array[2].Int != 1 {
							return errors.New(fmt.Sprintf("Unsupported field sizes in cross-reference stream dictionary: /W [%d %d %d]",
								v.Dictionary["/W"].Array[0].Int,
								v.Dictionary["/W"].Array[1].Int,
								v.Dictionary["/W"].Array[2].Int))
						}
					*/

					index := make([]int, 2)

					// If /Index is not set, this is an error
					if _, ok := v.Dictionary["/Index"]; ok {
						if len(v.Dictionary["/Index"].Array) < 2 {
							return errors.Wrap(err, "Index array does not contain 2 elements")
						}

						index[0] = v.Dictionary["/Index"].Array[0].Int
						index[1] = v.Dictionary["/Index"].Array[1].Int
					} else {
						index[0] = 0
					}

					prevXref := 0

					// Check for previous xref stream
					if _, ok := v.Dictionary["/Prev"]; ok {
						prevXref = v.Dictionary["/Prev"].Int
					}

					// Set root object
					if _, ok := v.Dictionary["/Root"]; ok {
						// Just set the whole dictionary with /Root key to keep compatibiltiy with existing code
						this.trailer = v
					} else {
						// Don't return an error here.  The trailer could be in another XRef stream.
						//return errors.New("Did not set root object")
					}

					startObject := index[0]

					err = this.skipWhitespace(r)
					if err != nil {
						return errors.Wrap(err, "Failed to skip whitespace")
					}

					// Get stream length dictionary
					lengthDict := v.Dictionary["/Length"]

					// Get number of bytes of stream
					length := lengthDict.Int

					// If lengthDict is an object reference, resolve the object and set length
					if lengthDict.Type == PDF_TYPE_OBJREF {
						lengthDict, err = this.resolveObject(lengthDict)

						if err != nil {
							return errors.Wrap(err, "Failed to resolve length object of stream")
						}

						// Set length to resolved object value
						length = lengthDict.Value.Int
					}

					t, err = this.readToken(r)
					if err != nil {
						return errors.Wrap(err, "Failed to read token")
					}
					if t != "stream" {
						return errors.New("Expected next token to be: stream, got: " + t)
					}

					err = this.skipWhitespace(r)
					if err != nil {
						return errors.Wrap(err, "Failed to skip whitespace")
					}

					// Read length bytes
					data := make([]byte, length)

					// Cannot use reader.Read() because that may not read all the bytes
					_, err := io.ReadFull(r, data)
					if err != nil {
						return errors.Wrap(err, "Failed to read bytes from buffer")
					}

					// Look for endstream token
					t, err = this.readToken(r)
					if err != nil {
						return errors.Wrap(err, "Failed to read token")
					}
					if t != "endstream" {
						return errors.New("Expected next token to be: endstream, got: " + t)
					}

					// Look for endobj token
					t, err = this.readToken(r)
					if err != nil {
						return errors.Wrap(err, "Failed to read token")
					}
					if t != "endobj" {
						return errors.New("Expected next token to be: endobj, got: " + t)
					}

					// Now decode zlib data
					b := bytes.NewReader(data)

					z, err := zlib.NewReader(b)
					if err != nil {
						return errors.Wrap(err, "zlib.NewReader error")
					}
					defer z.Close()

					p, err := ioutil.ReadAll(z)
					if err != nil {
						return errors.Wrap(err, "ioutil.ReadAll error")
					}

					objPos := 0
					objGen := 0
					i := startObject

					// Decode result with paeth algorithm
					var result []byte
					b = bytes.NewReader(p)

					firstFieldSize := v.Dictionary["/W"].Array[0].Int
					middleFieldSize := v.Dictionary["/W"].Array[1].Int
					lastFieldSize := v.Dictionary["/W"].Array[2].Int

					fieldSize := firstFieldSize + middleFieldSize + lastFieldSize
					if paethDecode {
						fieldSize++
					}

					prevRow := make([]byte, fieldSize)
					for {
						result = make([]byte, fieldSize)
						_, err := io.ReadFull(b, result)
						if err != nil {
							if err == io.EOF {
								break
							} else {
								return errors.Wrap(err, "io.ReadFull error")
							}
						}

						if paethDecode {
							filterPaeth(result, prevRow, fieldSize)
							copy(prevRow, result)
						}

						objectData := make([]byte, fieldSize)
						if paethDecode {
							copy(objectData, result[1:fieldSize])
						} else {
							copy(objectData, result[0:fieldSize])
						}

						if objectData[0] == 1 {
							// Regular objects
							b := make([]byte, 4)
							copy(b[4-middleFieldSize:], objectData[1:1+middleFieldSize])

							objPos = int(binary.BigEndian.Uint32(b))
							objGen = int(objectData[firstFieldSize+middleFieldSize])

							// Append map[int]int
							this.xref[i] = make(map[int]int, 1)

							// Set object id, generation, and position
							this.xref[i][objGen] = objPos
						} else if objectData[0] == 2 {
							// Compressed objects
							b := make([]byte, 4)
							copy(b[4-middleFieldSize:], objectData[1:1+middleFieldSize])

							objId := int(binary.BigEndian.Uint32(b))
							objIdx := int(objectData[firstFieldSize+middleFieldSize])

							// object id (i) is located in StmObj (objId) at index (objIdx)
							this.xrefStream[i] = [2]int{objId, objIdx}
						}

						i++
					}

					// Check for previous xref stream
					if prevXref > 0 {
						// Set xrefPos to /Prev xref
						this.xrefPos = prevXref

						// Read preivous xref
						xrefErr := this.readXref()
						if xrefErr != nil {
							return errors.Wrap(xrefErr, "Failed to read prev xref")
						}
					}
				}
			}

			return nil
		}

		return errors.New("Expected xref to start with 'xref'.  Got: " + t)
	}

	for {
		// Next value will be the starting object id (usually 0, but not always) or the trailer
		t, err = this.readToken(r)
		if err != nil {
			return errors.Wrap(err, "Failed to read token")
		}

		// Check for trailer
		if t == "trailer" {
			break
		}

		// Convert token to int
		startObject, err := strconv.Atoi(t)
		if err != nil {
			return errors.Wrap(err, "Failed to convert start object to integer: "+t)
		}

		// Determine how many objects there are
		t, err = this.readToken(r)
		if err != nil {
			return errors.Wrap(err, "Failed to read token")
		}

		// Convert token to int
		numObject, err := strconv.Atoi(t)
		if err != nil {
			return errors.Wrap(err, "Failed to convert num object to integer: "+t)
		}

		// For all objects in xref, read object position, object generation, and status (free or new)
		for i := startObject; i < startObject+numObject; i++ {
			t, err = this.readToken(r)
			if err != nil {
				return errors.Wrap(err, "Failed to read token")
			}

			// Get object position as int
			objPos, err := strconv.Atoi(t)
			if err != nil {
				return errors.Wrap(err, "Failed to convert object position to integer: "+t)
			}

			t, err = this.readToken(r)
			if err != nil {
				return errors.Wrap(err, "Failed to read token")
			}

			// Get object generation as int
			objGen, err := strconv.Atoi(t)
			if err != nil {
				return errors.Wrap(err, "Failed to convert object generation to integer: "+t)
			}

			// Get object status (free or new)
			objStatus, err := this.readToken(r)
			if err != nil {
				return errors.Wrap(err, "Failed to read token")
			}
			if objStatus != "f" && objStatus != "n" {
				return errors.New("Expected objStatus to be 'n' or 'f', got: " + objStatus)
			}

			// Append map[int]int
			this.xref[i] = make(map[int]int, 1)

			// Set object id, generation, and position
			this.xref[i][objGen] = objPos
		}
	}

	// Read trailer dictionary
	t, err = this.readToken(r)
	if err != nil {
		return errors.Wrap(err, "Failed to read token")
	}

	trailer, err := this.readValue(r, t)
	if err != nil {
		return errors.Wrap(err, "Failed to read value for token: "+t)
	}

	// If /Root is set, then set trailer object so that /Root can be read later
	if _, ok := trailer.Dictionary["/Root"]; ok {
		this.trailer = trailer
	}

	// If a /Prev xref trailer is specified, parse that
	if tr, ok := trailer.Dictionary["/Prev"]; ok {
		// Resolve parent xref table
		this.xrefPos = tr.Int
		return this.readXref()
	}

	return nil
}

// Read root (catalog object)
func (this *PdfReader) readRoot() error {
	var err error

	rootObjSpec := this.trailer.Dictionary["/Root"]

	// Read root (catalog)
	this.catalog, err = this.resolveObject(rootObjSpec)
	if err != nil {
		return errors.Wrap(err, "Failed to resolve root object")
	}

	return nil
}

// Read kids (pages inside a page tree)
func (this *PdfReader) readKids(kids *PdfValue, r int) error {
	// Loop through pages and add to result
	for i := 0; i < len(kids.Array); i++ {
		page, err := this.resolveObject(kids.Array[i])
		if err != nil {
			return errors.Wrap(err, "Failed to resolve page/pages object")
		}

		objType := page.Value.Dictionary["/Type"].Token
		if objType == "/Page" {
			// Set page and increment curPage
			this.pages[this.curPage] = page
			this.curPage++
		} else if objType == "/Pages" {
			// Resolve kids
			subKids, err := this.resolveObject(page.Value.Dictionary["/Kids"])
			if err != nil {
				return errors.Wrap(err, "Failed to resolve kids")
			}

			// Recurse into page tree
			err = this.readKids(subKids, r+1)
			if err != nil {
				return errors.Wrap(err, "Failed to read kids")
			}
		} else {
			return errors.Wrap(err, fmt.Sprintf("Unknown object type '%s'.  Expected: /Pages or /Page", objType))
		}
	}

	return nil
}

// Read all pages in PDF
func (this *PdfReader) readPages() error {
	var err error

	// resolve_pages_dict
	pagesDict, err := this.resolveObject(this.catalog.Value.Dictionary["/Pages"])
	if err != nil {
		return errors.Wrap(err, "Failed to resolve pages object")
	}

	// This will normally return itself
	kids, err := this.resolveObject(pagesDict.Value.Dictionary["/Kids"])
	if err != nil {
		return errors.Wrap(err, "Failed to resolve kids object")
	}

	// Get number of pages
	pageCount, err := this.resolveObject(pagesDict.Value.Dictionary["/Count"])
	if err != nil {
		return errors.Wrap(err, "Failed to get page count")
	}
	this.pageCount = pageCount.Int

	// Allocate pages
	this.pages = make([]*PdfValue, pageCount.Int)

	// Read kids
	err = this.readKids(kids, 0)
	if err != nil {
		return errors.Wrap(err, "Failed to read kids")
	}

	return nil
}

// Get references to page resources for a given page number
func (this *PdfReader) getPageResources(pageno int) (*PdfValue, error) {
	var err error

	// Check to make sure page exists in pages slice
	if len(this.pages) < pageno {
		return nil, errors.New(fmt.Sprintf("Page %d does not exist!!", pageno))
	}

	// Resolve page object
	page, err := this.resolveObject(this.pages[pageno-1])
	if err != nil {
		return nil, errors.Wrap(err, "Failed to resolve page object")
	}

	// Check to see if /Resources exists in Dictionary
	if _, ok := page.Value.Dictionary["/Resources"]; ok {
		// Resolve /Resources object
		res, err := this.resolveObject(page.Value.Dictionary["/Resources"])
		if err != nil {
			return nil, errors.Wrap(err, "Failed to resolve resources object")
		}

		// If type is PDF_TYPE_OBJECT, return its Value
		if res.Type == PDF_TYPE_OBJECT {
			return res.Value, nil
		}

		// Otherwise, returned the resolved object
		return res, nil
	} else {
		// If /Resources does not exist, check to see if /Parent exists and return that
		if _, ok := page.Value.Dictionary["/Parent"]; ok {
			// Resolve parent object
			res, err := this.resolveObject(page.Value.Dictionary["/Parent"])
			if err != nil {
				return nil, errors.Wrap(err, "Failed to resolve parent object")
			}

			// If /Parent object type is PDF_TYPE_OBJECT, return its Value
			if res.Type == PDF_TYPE_OBJECT {
				return res.Value, nil
			}

			// Otherwise, return the resolved parent object
			return res, nil
		}
	}

	// Return an empty PdfValue if we got here
	// TODO:  Improve error handling
	return &PdfValue{}, nil
}

// Get page content and return a slice of PdfValue objects
func (this *PdfReader) getPageContent(objSpec *PdfValue) ([]*PdfValue, error) {
	var err error
	var content *PdfValue

	// Allocate slice
	contents := make([]*PdfValue, 0)

	if objSpec.Type == PDF_TYPE_OBJREF {
		// If objSpec is an object reference, resolve the object and append it to contents
		content, err = this.resolveObject(objSpec)
		if err != nil {
			return nil, errors.Wrap(err, "Failed to resolve object")
		}
		contents = append(contents, content)
	} else if objSpec.Type == PDF_TYPE_ARRAY {
		// If objSpec is an array, loop through the array and recursively get page content and append to contents
		for i := 0; i < len(objSpec.Array); i++ {
			tmpContents, err := this.getPageContent(objSpec.Array[i])
			if err != nil {
				return nil, errors.Wrap(err, "Failed to get page content")
			}
			for j := 0; j < len(tmpContents); j++ {
				contents = append(contents, tmpContents[j])
			}
		}
	}

	return contents, nil
}

// Get content (i.e. PDF drawing instructions)
func (this *PdfReader) getContent(pageno int) (string, error) {
	var err error
	var contents []*PdfValue

	// Check to make sure page exists in pages slice
	if len(this.pages) < pageno {
		return "", errors.New(fmt.Sprintf("Page %d does not exist.", pageno))
	}

	// Get page
	page := this.pages[pageno-1]

	// FIXME: This could be slow, converting []byte to string and appending many times
	buffer := ""

	// Check to make sure /Contents exists in page dictionary
	if _, ok := page.Value.Dictionary["/Contents"]; ok {
		// Get an array of page content
		contents, err = this.getPageContent(page.Value.Dictionary["/Contents"])
		if err != nil {
			return "", errors.Wrap(err, "Failed to get page content")
		}

		for i := 0; i < len(contents); i++ {
			// Decode content if one or more /Filter is specified.
			// Most common filter is FlateDecode which can be uncompressed with zlib
			tmpBuffer, err := this.rebuildContentStream(contents[i])
			if err != nil {
				return "", errors.Wrap(err, "Failed to rebuild content stream")
			}

			// FIXME:  This is probably slow
			buffer += string(tmpBuffer)
		}
	}

	return buffer, nil
}

// Rebuild content stream
// This will decode content if one or more /Filter (such as FlateDecode) is specified.
// If there are multiple filters, they will be decoded in the order in which they were specified.
func (this *PdfReader) rebuildContentStream(content *PdfValue) ([]byte, error) {
	var err error
	var tmpFilter *PdfValue

	// Allocate slice of PdfValue
	filters := make([]*PdfValue, 0)

	// If content has a /Filter, append it to filters slice
	if _, ok := content.Value.Dictionary["/Filter"]; ok {
		filter := content.Value.Dictionary["/Filter"]

		// If filter type is a reference, resolve it
		if filter.Type == PDF_TYPE_OBJREF {
			tmpFilter, err = this.resolveObject(filter)
			if err != nil {
				return nil, errors.Wrap(err, "Failed to resolve object")
			}
			filter = tmpFilter.Value
		}

		if filter.Type == PDF_TYPE_TOKEN {
			// If filter type is a token (e.g. FlateDecode), appent it to filters slice
			filters = append(filters, filter)
		} else if filter.Type == PDF_TYPE_ARRAY {
			// If filter type is an array, then there are multiple filters.  Set filters variable to array value.
			filters = filter.Array
		}

	}

	// Set stream variable to content bytes
	stream := content.Stream.Bytes

	// Loop through filters and apply each filter to stream
	for i := 0; i < len(filters); i++ {
		switch filters[i].Token {
		case "/FlateDecode":
			// Uncompress zlib compressed data
			var out bytes.Buffer
			zlibReader, _ := zlib.NewReader(bytes.NewBuffer(stream))
			defer zlibReader.Close()
			io.Copy(&out, zlibReader)

			// Set stream to uncompressed data
			stream = out.Bytes()
		default:
			return nil, errors.New("Unspported filter: " + filters[i].Token)
		}
	}

	return stream, nil
}

func (this *PdfReader) getNumPages() (int, error) {
	if this.pageCount == 0 {
		return 0, errors.New("Page count is 0")
	}

	return this.pageCount, nil
}

func (this *PdfReader) getAllPageBoxes(k float64) (map[int]map[string]map[string]float64, error) {
	var err error

	// Allocate result with the number of available boxes
	result := make(map[int]map[string]map[string]float64, len(this.pages))

	for i := 1; i <= len(this.pages); i++ {
		result[i], err = this.getPageBoxes(i, k)
		if result[i] == nil {
			return nil, errors.Wrap(err, "Unable to get page box")
		}
	}

	return result, nil
}

// Get all page box data
func (this *PdfReader) getPageBoxes(pageno int, k float64) (map[string]map[string]float64, error) {
	var err error

	// Allocate result with the number of available boxes
	result := make(map[string]map[string]float64, len(this.availableBoxes))

	// Check to make sure page exists in pages slice
	if len(this.pages) < pageno {
		return nil, errors.New(fmt.Sprintf("Page %d does not exist?", pageno))
	}

	// Resolve page object
	page, err := this.resolveObject(this.pages[pageno-1])
	if err != nil {
		return nil, errors.New("Failed to resolve page object")
	}

	// Loop through available boxes and add to result
	for i := 0; i < len(this.availableBoxes); i++ {
		box, err := this.getPageBox(page, this.availableBoxes[i], k)
		if err != nil {
			return nil, errors.New("Failed to get page box")
		}

		result[this.availableBoxes[i]] = box
	}

	return result, nil
}

// Get a specific page box value (e.g. MediaBox) and return its values
func (this *PdfReader) getPageBox(page *PdfValue, box_index string, k float64) (map[string]float64, error) {
	var err error
	var tmpBox *PdfValue

	// Allocate 8 fields in result
	result := make(map[string]float64, 8)

	// Check to make sure box_index (e.g. MediaBox) exists in page dictionary
	if _, ok := page.Value.Dictionary[box_index]; ok {
		box := page.Value.Dictionary[box_index]

		// If the box type is a reference, resolve it
		if box.Type == PDF_TYPE_OBJREF {
			tmpBox, err = this.resolveObject(box)
			if err != nil {
				return nil, errors.New("Failed to resolve object")
			}
			box = tmpBox.Value
		}

		if box.Type == PDF_TYPE_ARRAY {
			// If the box type is an array, calculate scaled value based on k
			result["x"] = box.Array[0].Real / k
			result["y"] = box.Array[1].Real / k
			result["w"] = math.Abs(box.Array[0].Real-box.Array[2].Real) / k
			result["h"] = math.Abs(box.Array[1].Real-box.Array[3].Real) / k
			result["llx"] = math.Min(box.Array[0].Real, box.Array[2].Real)
			result["lly"] = math.Min(box.Array[1].Real, box.Array[3].Real)
			result["urx"] = math.Max(box.Array[0].Real, box.Array[2].Real)
			result["ury"] = math.Max(box.Array[1].Real, box.Array[3].Real)
		} else {
			// TODO: Improve error handling
			return nil, errors.New("Could not get page box")
		}
	} else if _, ok := page.Value.Dictionary["/Parent"]; ok {
		parentObj, err := this.resolveObject(page.Value.Dictionary["/Parent"])
		if err != nil {
			return nil, errors.Wrap(err, "Could not resolve parent object")
		}

		// If the page box is inherited from /Parent, recursively return page box of parent
		return this.getPageBox(parentObj, box_index, k)
	}

	return result, nil
}

// Get page rotation for a page number
func (this *PdfReader) getPageRotation(pageno int) (*PdfValue, error) {
	// Check to make sure page exists in pages slice
	if len(this.pages) < pageno {
		return nil, errors.New(fmt.Sprintf("Page %d does not exist!!!!", pageno))
	}

	return this._getPageRotation(this.pages[pageno-1])
}

// Get page rotation for a page object spec
func (this *PdfReader) _getPageRotation(page *PdfValue) (*PdfValue, error) {
	var err error

	// Resolve page object
	page, err = this.resolveObject(page)
	if err != nil {
		return nil, errors.New("Failed to resolve page object")
	}

	// Check to make sure /Rotate exists in page dictionary
	if _, ok := page.Value.Dictionary["/Rotate"]; ok {
		res, err := this.resolveObject(page.Value.Dictionary["/Rotate"])
		if err != nil {
			return nil, errors.New("Failed to resolve rotate object")
		}

		// If the type is PDF_TYPE_OBJECT, return its value
		if res.Type == PDF_TYPE_OBJECT {
			return res.Value, nil
		}

		// Otherwise, return the object
		return res, nil
	} else {
		// Check to see if parent has a rotation
		if _, ok := page.Value.Dictionary["/Parent"]; ok {
			// Recursively return /Parent page rotation
			res, err := this._getPageRotation(page.Value.Dictionary["/Parent"])
			if err != nil {
				return nil, errors.Wrap(err, "Failed to get page rotation for parent")
			}

			// If the type is PDF_TYPE_OBJECT, return its value
			if res.Type == PDF_TYPE_OBJECT {
				return res.Value, nil
			}

			// Otherwise, return the object
			return res, nil
		}
	}

	return &PdfValue{Int: 0}, nil
}

func (this *PdfReader) read() error {
	// Only run once
	if !this.alreadyRead {
		var err error

		// Find xref position
		err = this.findXref()
		if err != nil {
			return errors.Wrap(err, "Failed to find xref position")
		}

		// Parse xref table
		err = this.readXref()
		if err != nil {
			return errors.Wrap(err, "Failed to read xref table")
		}

		// Read catalog
		err = this.readRoot()
		if err != nil {
			return errors.Wrap(err, "Failed to read root")
		}

		// Read pages
		err = this.readPages()
		if err != nil {
			return errors.Wrap(err, "Failed to to read pages")
		}

		// Now that this has been read, do not read again
		this.alreadyRead = true
	}

	return nil
}