-
Notifications
You must be signed in to change notification settings - Fork 0
/
jdhuff.c
1559 lines (1331 loc) · 49.1 KB
/
jdhuff.c
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
/*
* jdhuff.c
*
* Copyright (C) 1991-1997, Thomas G. Lane.
* Modified 2006-2020 by Guido Vollbeding.
* This file is part of the Independent JPEG Group's software.
* For conditions of distribution and use, see the accompanying README file.
*
* This file contains Huffman entropy decoding routines.
* Both sequential and progressive modes are supported in this single module.
*
* Much of the complexity here has to do with supporting input suspension.
* If the data source module demands suspension, we want to be able to back
* up to the start of the current MCU. To do this, we copy state variables
* into local working storage, and update them back to the permanent
* storage only upon successful completion of an MCU.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
/* Derived data constructed for each Huffman table */
#define HUFF_LOOKAHEAD 8 /* # of bits of lookahead */
typedef struct {
/* Basic tables: (element [0] of each array is unused) */
INT32 maxcode[18]; /* largest code of length k (-1 if none) */
/* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */
INT32 valoffset[17]; /* huffval[] offset for codes of length k */
/* valoffset[k] = huffval[] index of 1st symbol of code length k, less
* the smallest code of length k; so given a code of length k, the
* corresponding symbol is huffval[code + valoffset[k]]
*/
/* Link to public Huffman table (needed only in jpeg_huff_decode) */
JHUFF_TBL *pub;
/* Lookahead tables: indexed by the next HUFF_LOOKAHEAD bits of
* the input data stream. If the next Huffman code is no more
* than HUFF_LOOKAHEAD bits long, we can obtain its length and
* the corresponding symbol directly from these tables.
*/
int look_nbits[1<<HUFF_LOOKAHEAD]; /* # bits, or 0 if too long */
UINT8 look_sym[1<<HUFF_LOOKAHEAD]; /* symbol, or unused */
} d_derived_tbl;
/*
* Fetching the next N bits from the input stream is a time-critical operation
* for the Huffman decoders. We implement it with a combination of inline
* macros and out-of-line subroutines. Note that N (the number of bits
* demanded at one time) never exceeds 15 for JPEG use.
*
* We read source bytes into get_buffer and dole out bits as needed.
* If get_buffer already contains enough bits, they are fetched in-line
* by the macros CHECK_BIT_BUFFER and GET_BITS. When there aren't enough
* bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer
* as full as possible (not just to the number of bits needed; this
* prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer).
* Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension.
* On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains
* at least the requested number of bits --- dummy zeroes are inserted if
* necessary.
*/
typedef INT32 bit_buf_type; /* type of bit-extraction buffer */
#define BIT_BUF_SIZE 32 /* size of buffer in bits */
/* If long is > 32 bits on your machine, and shifting/masking longs is
* reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE
* appropriately should be a win. Unfortunately we can't define the size
* with something like #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8)
* because not all machines measure sizeof in 8-bit bytes.
*/
typedef struct { /* Bitreading state saved across MCUs */
bit_buf_type get_buffer; /* current bit-extraction buffer */
int bits_left; /* # of unused bits in it */
} bitread_perm_state;
typedef struct { /* Bitreading working state within an MCU */
/* Current data source location */
/* We need a copy, rather than munging the original, in case of suspension */
const JOCTET * next_input_byte; /* => next byte to read from source */
size_t bytes_in_buffer; /* # of bytes remaining in source buffer */
/* Bit input buffer --- note these values are kept in register variables,
* not in this struct, inside the inner loops.
*/
bit_buf_type get_buffer; /* current bit-extraction buffer */
int bits_left; /* # of unused bits in it */
/* Pointer needed by jpeg_fill_bit_buffer. */
j_decompress_ptr cinfo; /* back link to decompress master record */
} bitread_working_state;
/* Macros to declare and load/save bitread local variables. */
#define BITREAD_STATE_VARS \
register bit_buf_type get_buffer; \
register int bits_left; \
bitread_working_state br_state
#define BITREAD_LOAD_STATE(cinfop,permstate) \
br_state.cinfo = cinfop; \
br_state.next_input_byte = cinfop->src->next_input_byte; \
br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \
get_buffer = permstate.get_buffer; \
bits_left = permstate.bits_left;
#define BITREAD_SAVE_STATE(cinfop,permstate) \
cinfop->src->next_input_byte = br_state.next_input_byte; \
cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \
permstate.get_buffer = get_buffer; \
permstate.bits_left = bits_left
/*
* These macros provide the in-line portion of bit fetching.
* Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer
* before using GET_BITS, PEEK_BITS, or DROP_BITS.
* The variables get_buffer and bits_left are assumed to be locals,
* but the state struct might not be (jpeg_huff_decode needs this).
* CHECK_BIT_BUFFER(state,n,action);
* Ensure there are N bits in get_buffer; if suspend, take action.
* val = GET_BITS(n);
* Fetch next N bits.
* val = PEEK_BITS(n);
* Fetch next N bits without removing them from the buffer.
* DROP_BITS(n);
* Discard next N bits.
* The value N should be a simple variable, not an expression, because it
* is evaluated multiple times.
*/
#define CHECK_BIT_BUFFER(state,nbits,action) \
{ if (bits_left < (nbits)) { \
if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits)) \
{ action; } \
get_buffer = (state).get_buffer; bits_left = (state).bits_left; } }
#define GET_BITS(nbits) \
(((int) (get_buffer >> (bits_left -= (nbits)))) & BIT_MASK(nbits))
#define PEEK_BITS(nbits) \
(((int) (get_buffer >> (bits_left - (nbits)))) & BIT_MASK(nbits))
#define DROP_BITS(nbits) \
(bits_left -= (nbits))
/*
* Code for extracting next Huffman-coded symbol from input bit stream.
* Again, this is time-critical and we make the main paths be macros.
*
* We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits
* without looping. Usually, more than 95% of the Huffman codes will be 8
* or fewer bits long. The few overlength codes are handled with a loop,
* which need not be inline code.
*
* Notes about the HUFF_DECODE macro:
* 1. Near the end of the data segment, we may fail to get enough bits
* for a lookahead. In that case, we do it the hard way.
* 2. If the lookahead table contains no entry, the next code must be
* more than HUFF_LOOKAHEAD bits long.
* 3. jpeg_huff_decode returns -1 if forced to suspend.
*/
#define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \
{ register int nb, look; \
if (bits_left < HUFF_LOOKAHEAD) { \
if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \
get_buffer = state.get_buffer; bits_left = state.bits_left; \
if (bits_left < HUFF_LOOKAHEAD) { \
nb = 1; goto slowlabel; \
} \
} \
look = PEEK_BITS(HUFF_LOOKAHEAD); \
if ((nb = htbl->look_nbits[look]) != 0) { \
DROP_BITS(nb); \
result = htbl->look_sym[look]; \
} else { \
nb = HUFF_LOOKAHEAD+1; \
slowlabel: \
if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \
{ failaction; } \
get_buffer = state.get_buffer; bits_left = state.bits_left; \
} \
}
/*
* Expanded entropy decoder object for Huffman decoding.
*
* The savable_state subrecord contains fields that change within an MCU,
* but must not be updated permanently until we complete the MCU.
*/
typedef struct {
unsigned int EOBRUN; /* remaining EOBs in EOBRUN */
int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
} savable_state;
/* This macro is to work around compilers with missing or broken
* structure assignment. You'll need to fix this code if you have
* such a compiler and you change MAX_COMPS_IN_SCAN.
*/
#ifndef NO_STRUCT_ASSIGN
#define ASSIGN_STATE(dest,src) ((dest) = (src))
#else
#if MAX_COMPS_IN_SCAN == 4
#define ASSIGN_STATE(dest,src) \
((dest).EOBRUN = (src).EOBRUN, \
(dest).last_dc_val[0] = (src).last_dc_val[0], \
(dest).last_dc_val[1] = (src).last_dc_val[1], \
(dest).last_dc_val[2] = (src).last_dc_val[2], \
(dest).last_dc_val[3] = (src).last_dc_val[3])
#endif
#endif
typedef struct {
struct jpeg_entropy_decoder pub; /* public fields */
/* These fields are loaded into local variables at start of each MCU.
* In case of suspension, we exit WITHOUT updating them.
*/
bitread_perm_state bitstate; /* Bit buffer at start of MCU */
savable_state saved; /* Other state at start of MCU */
/* These fields are NOT loaded into local working state. */
boolean insufficient_data; /* set TRUE after emitting warning */
unsigned int restarts_to_go; /* MCUs left in this restart interval */
/* Following two fields used only in progressive mode */
/* Pointers to derived tables (these workspaces have image lifespan) */
d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
/* Following fields used only in sequential mode */
/* Pointers to derived tables (these workspaces have image lifespan) */
d_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];
d_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
/* Precalculated info set up by start_pass for use in decode_mcu: */
/* Pointers to derived tables to be used for each block within an MCU */
d_derived_tbl * dc_cur_tbls[D_MAX_BLOCKS_IN_MCU];
d_derived_tbl * ac_cur_tbls[D_MAX_BLOCKS_IN_MCU];
/* Whether we care about the DC and AC coefficient values for each block */
int coef_limit[D_MAX_BLOCKS_IN_MCU];
} huff_entropy_decoder;
typedef huff_entropy_decoder * huff_entropy_ptr;
static const int jpeg_zigzag_order[8][8] = {
{ 0, 1, 5, 6, 14, 15, 27, 28 },
{ 2, 4, 7, 13, 16, 26, 29, 42 },
{ 3, 8, 12, 17, 25, 30, 41, 43 },
{ 9, 11, 18, 24, 31, 40, 44, 53 },
{ 10, 19, 23, 32, 39, 45, 52, 54 },
{ 20, 22, 33, 38, 46, 51, 55, 60 },
{ 21, 34, 37, 47, 50, 56, 59, 61 },
{ 35, 36, 48, 49, 57, 58, 62, 63 }
};
static const int jpeg_zigzag_order7[7][7] = {
{ 0, 1, 5, 6, 14, 15, 27 },
{ 2, 4, 7, 13, 16, 26, 28 },
{ 3, 8, 12, 17, 25, 29, 38 },
{ 9, 11, 18, 24, 30, 37, 39 },
{ 10, 19, 23, 31, 36, 40, 45 },
{ 20, 22, 32, 35, 41, 44, 46 },
{ 21, 33, 34, 42, 43, 47, 48 }
};
static const int jpeg_zigzag_order6[6][6] = {
{ 0, 1, 5, 6, 14, 15 },
{ 2, 4, 7, 13, 16, 25 },
{ 3, 8, 12, 17, 24, 26 },
{ 9, 11, 18, 23, 27, 32 },
{ 10, 19, 22, 28, 31, 33 },
{ 20, 21, 29, 30, 34, 35 }
};
static const int jpeg_zigzag_order5[5][5] = {
{ 0, 1, 5, 6, 14 },
{ 2, 4, 7, 13, 15 },
{ 3, 8, 12, 16, 21 },
{ 9, 11, 17, 20, 22 },
{ 10, 18, 19, 23, 24 }
};
static const int jpeg_zigzag_order4[4][4] = {
{ 0, 1, 5, 6 },
{ 2, 4, 7, 12 },
{ 3, 8, 11, 13 },
{ 9, 10, 14, 15 }
};
static const int jpeg_zigzag_order3[3][3] = {
{ 0, 1, 5 },
{ 2, 4, 6 },
{ 3, 7, 8 }
};
static const int jpeg_zigzag_order2[2][2] = {
{ 0, 1 },
{ 2, 3 }
};
/*
* Compute the derived values for a Huffman table.
* This routine also performs some validation checks on the table.
*/
LOCAL(void)
jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno,
d_derived_tbl ** pdtbl)
{
JHUFF_TBL *htbl;
d_derived_tbl *dtbl;
int p, i, l, si, numsymbols;
int lookbits, ctr;
char huffsize[257];
unsigned int huffcode[257];
unsigned int code;
/* Note that huffsize[] and huffcode[] are filled in code-length order,
* paralleling the order of the symbols themselves in htbl->huffval[].
*/
/* Find the input Huffman table */
if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
htbl =
isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
if (htbl == NULL)
htbl = jpeg_std_huff_table((j_common_ptr) cinfo, isDC, tblno);
/* Allocate a workspace if we haven't already done so. */
if (*pdtbl == NULL)
*pdtbl = (d_derived_tbl *) (*cinfo->mem->alloc_small)
((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(d_derived_tbl));
dtbl = *pdtbl;
dtbl->pub = htbl; /* fill in back link */
/* Figure C.1: make table of Huffman code length for each symbol */
p = 0;
for (l = 1; l <= 16; l++) {
i = (int) htbl->bits[l];
if (i < 0 || p + i > 256) /* protect against table overrun */
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
while (i--)
huffsize[p++] = (char) l;
}
huffsize[p] = 0;
numsymbols = p;
/* Figure C.2: generate the codes themselves */
/* We also validate that the counts represent a legal Huffman code tree. */
code = 0;
si = huffsize[0];
p = 0;
while (huffsize[p]) {
while (((int) huffsize[p]) == si) {
huffcode[p++] = code;
code++;
}
/* code is now 1 more than the last code used for codelength si; but
* it must still fit in si bits, since no code is allowed to be all ones.
*/
if (((INT32) code) >= (((INT32) 1) << si))
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
code <<= 1;
si++;
}
/* Figure F.15: generate decoding tables for bit-sequential decoding */
p = 0;
for (l = 1; l <= 16; l++) {
if (htbl->bits[l]) {
/* valoffset[l] = huffval[] index of 1st symbol of code length l,
* minus the minimum code of length l
*/
dtbl->valoffset[l] = (INT32) p - (INT32) huffcode[p];
p += htbl->bits[l];
dtbl->maxcode[l] = huffcode[p-1]; /* maximum code of length l */
} else {
dtbl->maxcode[l] = -1; /* -1 if no codes of this length */
}
}
dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */
/* Compute lookahead tables to speed up decoding.
* First we set all the table entries to 0, indicating "too long";
* then we iterate through the Huffman codes that are short enough and
* fill in all the entries that correspond to bit sequences starting
* with that code.
*/
MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits));
p = 0;
for (l = 1; l <= HUFF_LOOKAHEAD; l++) {
for (i = 1; i <= (int) htbl->bits[l]; i++, p++) {
/* l = current code's length, p = its index in huffcode[] & huffval[]. */
/* Generate left-justified code followed by all possible bit sequences */
lookbits = huffcode[p] << (HUFF_LOOKAHEAD-l);
for (ctr = 1 << (HUFF_LOOKAHEAD-l); ctr > 0; ctr--) {
dtbl->look_nbits[lookbits] = l;
dtbl->look_sym[lookbits] = htbl->huffval[p];
lookbits++;
}
}
}
/* Validate symbols as being reasonable.
* For AC tables, we make no check, but accept all byte values 0..255.
* For DC tables, we require the symbols to be in range 0..15.
* (Tighter bounds could be applied depending on the data depth and mode,
* but this is sufficient to ensure safe decoding.)
*/
if (isDC) {
for (i = 0; i < numsymbols; i++) {
int sym = htbl->huffval[i];
if (sym < 0 || sym > 15)
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
}
}
}
/*
* Out-of-line code for bit fetching.
* Note: current values of get_buffer and bits_left are passed as parameters,
* but are returned in the corresponding fields of the state struct.
*
* On most machines MIN_GET_BITS should be 25 to allow the full 32-bit width
* of get_buffer to be used. (On machines with wider words, an even larger
* buffer could be used.) However, on some machines 32-bit shifts are
* quite slow and take time proportional to the number of places shifted.
* (This is true with most PC compilers, for instance.) In this case it may
* be a win to set MIN_GET_BITS to the minimum value of 15. This reduces the
* average shift distance at the cost of more calls to jpeg_fill_bit_buffer.
*/
#ifdef SLOW_SHIFT_32
#define MIN_GET_BITS 15 /* minimum allowable value */
#else
#define MIN_GET_BITS (BIT_BUF_SIZE-7)
#endif
LOCAL(boolean)
jpeg_fill_bit_buffer (bitread_working_state * state,
register bit_buf_type get_buffer, register int bits_left,
int nbits)
/* Load up the bit buffer to a depth of at least nbits */
{
/* Copy heavily used state fields into locals (hopefully registers) */
register const JOCTET * next_input_byte = state->next_input_byte;
register size_t bytes_in_buffer = state->bytes_in_buffer;
j_decompress_ptr cinfo = state->cinfo;
/* Attempt to load at least MIN_GET_BITS bits into get_buffer. */
/* (It is assumed that no request will be for more than that many bits.) */
/* We fail to do so only if we hit a marker or are forced to suspend. */
if (cinfo->unread_marker == 0) { /* cannot advance past a marker */
while (bits_left < MIN_GET_BITS) {
register int c;
/* Attempt to read a byte */
if (bytes_in_buffer == 0) {
if (! (*cinfo->src->fill_input_buffer) (cinfo))
return FALSE;
next_input_byte = cinfo->src->next_input_byte;
bytes_in_buffer = cinfo->src->bytes_in_buffer;
}
bytes_in_buffer--;
c = GETJOCTET(*next_input_byte++);
/* If it's 0xFF, check and discard stuffed zero byte */
if (c == 0xFF) {
/* Loop here to discard any padding FF's on terminating marker,
* so that we can save a valid unread_marker value. NOTE: we will
* accept multiple FF's followed by a 0 as meaning a single FF data
* byte. This data pattern is not valid according to the standard.
*/
do {
if (bytes_in_buffer == 0) {
if (! (*cinfo->src->fill_input_buffer) (cinfo))
return FALSE;
next_input_byte = cinfo->src->next_input_byte;
bytes_in_buffer = cinfo->src->bytes_in_buffer;
}
bytes_in_buffer--;
c = GETJOCTET(*next_input_byte++);
} while (c == 0xFF);
if (c == 0) {
/* Found FF/00, which represents an FF data byte */
c = 0xFF;
} else {
/* Oops, it's actually a marker indicating end of compressed data.
* Save the marker code for later use.
* Fine point: it might appear that we should save the marker into
* bitread working state, not straight into permanent state. But
* once we have hit a marker, we cannot need to suspend within the
* current MCU, because we will read no more bytes from the data
* source. So it is OK to update permanent state right away.
*/
cinfo->unread_marker = c;
/* See if we need to insert some fake zero bits. */
goto no_more_bytes;
}
}
/* OK, load c into get_buffer */
get_buffer = (get_buffer << 8) | c;
bits_left += 8;
} /* end while */
} else {
no_more_bytes:
/* We get here if we've read the marker that terminates the compressed
* data segment. There should be enough bits in the buffer register
* to satisfy the request; if so, no problem.
*/
if (nbits > bits_left) {
/* Uh-oh. Report corrupted data to user and stuff zeroes into
* the data stream, so that we can produce some kind of image.
* We use a nonvolatile flag to ensure that only one warning message
* appears per data segment.
*/
if (! ((huff_entropy_ptr) cinfo->entropy)->insufficient_data) {
WARNMS(cinfo, JWRN_HIT_MARKER);
((huff_entropy_ptr) cinfo->entropy)->insufficient_data = TRUE;
}
/* Fill the buffer with zero bits */
get_buffer <<= MIN_GET_BITS - bits_left;
bits_left = MIN_GET_BITS;
}
}
/* Unload the local registers */
state->next_input_byte = next_input_byte;
state->bytes_in_buffer = bytes_in_buffer;
state->get_buffer = get_buffer;
state->bits_left = bits_left;
return TRUE;
}
/*
* Figure F.12: extend sign bit.
* On some machines, a shift and sub will be faster than a table lookup.
*/
#ifdef AVOID_TABLES
#define BIT_MASK(nbits) ((1<<(nbits))-1)
#define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) - ((1<<(s))-1) : (x))
#else
#define BIT_MASK(nbits) bmask[nbits]
#define HUFF_EXTEND(x,s) ((x) <= bmask[(s) - 1] ? (x) - bmask[s] : (x))
static const int bmask[16] = /* bmask[n] is mask for n rightmost bits */
{ 0, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF,
0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF };
#endif /* AVOID_TABLES */
/*
* Out-of-line code for Huffman code decoding.
*/
LOCAL(int)
jpeg_huff_decode (bitread_working_state * state,
register bit_buf_type get_buffer, register int bits_left,
d_derived_tbl * htbl, int min_bits)
{
register int l = min_bits;
register INT32 code;
/* HUFF_DECODE has determined that the code is at least min_bits */
/* bits long, so fetch that many bits in one swoop. */
CHECK_BIT_BUFFER(*state, l, return -1);
code = GET_BITS(l);
/* Collect the rest of the Huffman code one bit at a time. */
/* This is per Figure F.16 in the JPEG spec. */
while (code > htbl->maxcode[l]) {
code <<= 1;
CHECK_BIT_BUFFER(*state, 1, return -1);
code |= GET_BITS(1);
l++;
}
/* Unload the local registers */
state->get_buffer = get_buffer;
state->bits_left = bits_left;
/* With garbage input we may reach the sentinel value l = 17. */
if (l > 16) {
WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE);
return 0; /* fake a zero as the safest result */
}
return htbl->pub->huffval[ (int) (code + htbl->valoffset[l]) ];
}
/*
* Finish up at the end of a Huffman-compressed scan.
*/
METHODDEF(void)
finish_pass_huff (j_decompress_ptr cinfo)
{
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
/* Throw away any unused bits remaining in bit buffer; */
/* include any full bytes in next_marker's count of discarded bytes */
cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
entropy->bitstate.bits_left = 0;
}
/*
* Check for a restart marker & resynchronize decoder.
* Returns FALSE if must suspend.
*/
LOCAL(boolean)
process_restart (j_decompress_ptr cinfo)
{
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
int ci;
finish_pass_huff(cinfo);
/* Advance past the RSTn marker */
if (! (*cinfo->marker->read_restart_marker) (cinfo))
return FALSE;
/* Re-initialize DC predictions to 0 */
for (ci = 0; ci < cinfo->comps_in_scan; ci++)
entropy->saved.last_dc_val[ci] = 0;
/* Re-init EOB run count, too */
entropy->saved.EOBRUN = 0;
/* Reset restart counter */
entropy->restarts_to_go = cinfo->restart_interval;
/* Reset out-of-data flag, unless read_restart_marker left us smack up
* against a marker. In that case we will end up treating the next data
* segment as empty, and we can avoid producing bogus output pixels by
* leaving the flag set.
*/
if (cinfo->unread_marker == 0)
entropy->insufficient_data = FALSE;
return TRUE;
}
/*
* Huffman MCU decoding.
* Each of these routines decodes and returns one MCU's worth of
* Huffman-compressed coefficients.
* The coefficients are reordered from zigzag order into natural array order,
* but are not dequantized.
*
* The i'th block of the MCU is stored into the block pointed to by
* MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
* (Wholesale zeroing is usually a little faster than retail...)
*
* We return FALSE if data source requested suspension. In that case no
* changes have been made to permanent state. (Exception: some output
* coefficients may already have been assigned. This is harmless for
* spectral selection, since we'll just re-assign them on the next call.
* Successive approximation AC refinement has to be more careful, however.)
*/
/*
* MCU decoding for DC initial scan (either spectral selection,
* or first pass of successive approximation).
*/
METHODDEF(boolean)
decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKARRAY MCU_data)
{
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
int Al = cinfo->Al;
register int s, r;
int blkn, ci;
JBLOCKROW block;
BITREAD_STATE_VARS;
savable_state state;
d_derived_tbl * tbl;
jpeg_component_info * compptr;
/* Process restart marker if needed; may have to suspend */
if (cinfo->restart_interval) {
if (entropy->restarts_to_go == 0)
if (! process_restart(cinfo))
return FALSE;
}
/* If we've run out of data, just leave the MCU set to zeroes.
* This way, we return uniform gray for the remainder of the segment.
*/
if (! entropy->insufficient_data) {
/* Load up working state */
BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
ASSIGN_STATE(state, entropy->saved);
/* Outer loop handles each block in the MCU */
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
block = MCU_data[blkn];
ci = cinfo->MCU_membership[blkn];
compptr = cinfo->cur_comp_info[ci];
tbl = entropy->derived_tbls[compptr->dc_tbl_no];
/* Decode a single block's worth of coefficients */
/* Section F.2.2.1: decode the DC coefficient difference */
HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
if (s) {
CHECK_BIT_BUFFER(br_state, s, return FALSE);
r = GET_BITS(s);
s = HUFF_EXTEND(r, s);
}
/* Convert DC difference to actual value, update last_dc_val */
s += state.last_dc_val[ci];
state.last_dc_val[ci] = s;
/* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */
(*block)[0] = (JCOEF) (s << Al);
}
/* Completed MCU, so update state */
BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
ASSIGN_STATE(entropy->saved, state);
}
/* Account for restart interval if using restarts */
if (cinfo->restart_interval)
entropy->restarts_to_go--;
return TRUE;
}
/*
* MCU decoding for AC initial scan (either spectral selection,
* or first pass of successive approximation).
*/
METHODDEF(boolean)
decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKARRAY MCU_data)
{
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
register int s, k, r;
unsigned int EOBRUN;
int Se, Al;
const int * natural_order;
JBLOCKROW block;
BITREAD_STATE_VARS;
d_derived_tbl * tbl;
/* Process restart marker if needed; may have to suspend */
if (cinfo->restart_interval) {
if (entropy->restarts_to_go == 0)
if (! process_restart(cinfo))
return FALSE;
}
/* If we've run out of data, just leave the MCU set to zeroes.
* This way, we return uniform gray for the remainder of the segment.
*/
if (! entropy->insufficient_data) {
/* Load up working state.
* We can avoid loading/saving bitread state if in an EOB run.
*/
EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
/* There is always only one block per MCU */
if (EOBRUN) /* if it's a band of zeroes... */
EOBRUN--; /* ...process it now (we do nothing) */
else {
BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
Se = cinfo->Se;
Al = cinfo->Al;
natural_order = cinfo->natural_order;
block = MCU_data[0];
tbl = entropy->ac_derived_tbl;
for (k = cinfo->Ss; k <= Se; k++) {
HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
r = s >> 4;
s &= 15;
if (s) {
k += r;
CHECK_BIT_BUFFER(br_state, s, return FALSE);
r = GET_BITS(s);
s = HUFF_EXTEND(r, s);
/* Scale and output coefficient in natural (dezigzagged) order */
(*block)[natural_order[k]] = (JCOEF) (s << Al);
} else {
if (r != 15) { /* EOBr, run length is 2^r + appended bits */
if (r) { /* EOBr, r > 0 */
EOBRUN = 1 << r;
CHECK_BIT_BUFFER(br_state, r, return FALSE);
r = GET_BITS(r);
EOBRUN += r;
EOBRUN--; /* this band is processed at this moment */
}
break; /* force end-of-band */
}
k += 15; /* ZRL: skip 15 zeroes in band */
}
}
BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
}
/* Completed MCU, so update state */
entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
}
/* Account for restart interval if using restarts */
if (cinfo->restart_interval)
entropy->restarts_to_go--;
return TRUE;
}
/*
* MCU decoding for DC successive approximation refinement scan.
* Note: we assume such scans can be multi-component,
* although the spec is not very clear on the point.
*/
METHODDEF(boolean)
decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKARRAY MCU_data)
{
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
JCOEF p1;
int blkn;
BITREAD_STATE_VARS;
/* Process restart marker if needed; may have to suspend */
if (cinfo->restart_interval) {
if (entropy->restarts_to_go == 0)
if (! process_restart(cinfo))
return FALSE;
}
/* Not worth the cycles to check insufficient_data here,
* since we will not change the data anyway if we read zeroes.
*/
/* Load up working state */
BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
/* Outer loop handles each block in the MCU */
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
/* Encoded data is simply the next bit of the two's-complement DC value */
CHECK_BIT_BUFFER(br_state, 1, return FALSE);
if (GET_BITS(1))
MCU_data[blkn][0][0] |= p1;
/* Note: since we use |=, repeating the assignment later is safe */
}
/* Completed MCU, so update state */
BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
/* Account for restart interval if using restarts */
if (cinfo->restart_interval)
entropy->restarts_to_go--;
return TRUE;
}
/*
* MCU decoding for AC successive approximation refinement scan.
*/
METHODDEF(boolean)
decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKARRAY MCU_data)
{
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
register int s, k, r;
unsigned int EOBRUN;
int Se;
JCOEF p1, m1;
const int * natural_order;
JBLOCKROW block;
JCOEFPTR thiscoef;
BITREAD_STATE_VARS;
d_derived_tbl * tbl;
int num_newnz;
int newnz_pos[DCTSIZE2];
/* Process restart marker if needed; may have to suspend */
if (cinfo->restart_interval) {
if (entropy->restarts_to_go == 0)
if (! process_restart(cinfo))
return FALSE;
}
/* If we've run out of data, don't modify the MCU.
*/
if (! entropy->insufficient_data) {
Se = cinfo->Se;
p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
m1 = -p1; /* -1 in the bit position being coded */
natural_order = cinfo->natural_order;
/* Load up working state */
BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
/* There is always only one block per MCU */
block = MCU_data[0];
tbl = entropy->ac_derived_tbl;
/* If we are forced to suspend, we must undo the assignments to any newly
* nonzero coefficients in the block, because otherwise we'd get confused
* next time about which coefficients were already nonzero.
* But we need not undo addition of bits to already-nonzero coefficients;
* instead, we can test the current bit to see if we already did it.
*/
num_newnz = 0;
/* initialize coefficient loop counter to start of band */
k = cinfo->Ss;
if (EOBRUN == 0) {
do {
HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
r = s >> 4;
s &= 15;
if (s) {
if (s != 1) /* size of new coef should always be 1 */
WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
CHECK_BIT_BUFFER(br_state, 1, goto undoit);
if (GET_BITS(1))
s = p1; /* newly nonzero coef is positive */
else
s = m1; /* newly nonzero coef is negative */
} else {
if (r != 15) {
EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */
if (r) {
CHECK_BIT_BUFFER(br_state, r, goto undoit);
r = GET_BITS(r);
EOBRUN += r;
}
break; /* rest of block is handled by EOB logic */
}
/* note s = 0 for processing ZRL */
}
/* Advance over already-nonzero coefs and r still-zero coefs,
* appending correction bits to the nonzeroes. A correction bit is 1
* if the absolute value of the coefficient must be increased.
*/
do {
thiscoef = *block + natural_order[k];
if (*thiscoef) {
CHECK_BIT_BUFFER(br_state, 1, goto undoit);
if (GET_BITS(1)) {
if ((*thiscoef & p1) == 0) { /* do nothing if already set it */