4
* Copyright (C) 1991-1997, Thomas G. Lane.
5
* Modified 2006-2009 by Guido Vollbeding.
6
* This file is part of the Independent JPEG Group's software.
7
* For conditions of distribution and use, see the accompanying README file.
9
* This file contains Huffman entropy decoding routines.
10
* Both sequential and progressive modes are supported in this single module.
12
* Much of the complexity here has to do with supporting input suspension.
13
* If the data source module demands suspension, we want to be able to back
14
* up to the start of the current MCU. To do this, we copy state variables
15
* into local working storage, and update them back to the permanent
16
* storage only upon successful completion of an MCU.
19
#define JPEG_INTERNALS
24
/* Derived data constructed for each Huffman table */
26
#define HUFF_LOOKAHEAD 8 /* # of bits of lookahead */
29
/* Basic tables: (element [0] of each array is unused) */
30
INT32 maxcode[18]; /* largest code of length k (-1 if none) */
31
/* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */
32
INT32 valoffset[17]; /* huffval[] offset for codes of length k */
33
/* valoffset[k] = huffval[] index of 1st symbol of code length k, less
34
* the smallest code of length k; so given a code of length k, the
35
* corresponding symbol is huffval[code + valoffset[k]]
38
/* Link to public Huffman table (needed only in jpeg_huff_decode) */
41
/* Lookahead tables: indexed by the next HUFF_LOOKAHEAD bits of
42
* the input data stream. If the next Huffman code is no more
43
* than HUFF_LOOKAHEAD bits long, we can obtain its length and
44
* the corresponding symbol directly from these tables.
46
int look_nbits[1<<HUFF_LOOKAHEAD]; /* # bits, or 0 if too long */
47
UINT8 look_sym[1<<HUFF_LOOKAHEAD]; /* symbol, or unused */
52
* Fetching the next N bits from the input stream is a time-critical operation
53
* for the Huffman decoders. We implement it with a combination of inline
54
* macros and out-of-line subroutines. Note that N (the number of bits
55
* demanded at one time) never exceeds 15 for JPEG use.
57
* We read source bytes into get_buffer and dole out bits as needed.
58
* If get_buffer already contains enough bits, they are fetched in-line
59
* by the macros CHECK_BIT_BUFFER and GET_BITS. When there aren't enough
60
* bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer
61
* as full as possible (not just to the number of bits needed; this
62
* prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer).
63
* Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension.
64
* On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains
65
* at least the requested number of bits --- dummy zeroes are inserted if
69
typedef INT32 bit_buf_type; /* type of bit-extraction buffer */
70
#define BIT_BUF_SIZE 32 /* size of buffer in bits */
72
/* If long is > 32 bits on your machine, and shifting/masking longs is
73
* reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE
74
* appropriately should be a win. Unfortunately we can't define the size
75
* with something like #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8)
76
* because not all machines measure sizeof in 8-bit bytes.
79
typedef struct { /* Bitreading state saved across MCUs */
80
bit_buf_type get_buffer; /* current bit-extraction buffer */
81
int bits_left; /* # of unused bits in it */
84
typedef struct { /* Bitreading working state within an MCU */
85
/* Current data source location */
86
/* We need a copy, rather than munging the original, in case of suspension */
87
const JOCTET * next_input_byte; /* => next byte to read from source */
88
size_t bytes_in_buffer; /* # of bytes remaining in source buffer */
89
/* Bit input buffer --- note these values are kept in register variables,
90
* not in this struct, inside the inner loops.
92
bit_buf_type get_buffer; /* current bit-extraction buffer */
93
int bits_left; /* # of unused bits in it */
94
/* Pointer needed by jpeg_fill_bit_buffer. */
95
j_decompress_ptr cinfo; /* back link to decompress master record */
96
} bitread_working_state;
98
/* Macros to declare and load/save bitread local variables. */
99
#define BITREAD_STATE_VARS \
100
register bit_buf_type get_buffer; \
101
register int bits_left; \
102
bitread_working_state br_state
104
#define BITREAD_LOAD_STATE(cinfop,permstate) \
105
br_state.cinfo = cinfop; \
106
br_state.next_input_byte = cinfop->src->next_input_byte; \
107
br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \
108
get_buffer = permstate.get_buffer; \
109
bits_left = permstate.bits_left;
111
#define BITREAD_SAVE_STATE(cinfop,permstate) \
112
cinfop->src->next_input_byte = br_state.next_input_byte; \
113
cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \
114
permstate.get_buffer = get_buffer; \
115
permstate.bits_left = bits_left
118
* These macros provide the in-line portion of bit fetching.
119
* Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer
120
* before using GET_BITS, PEEK_BITS, or DROP_BITS.
121
* The variables get_buffer and bits_left are assumed to be locals,
122
* but the state struct might not be (jpeg_huff_decode needs this).
123
* CHECK_BIT_BUFFER(state,n,action);
124
* Ensure there are N bits in get_buffer; if suspend, take action.
127
* val = PEEK_BITS(n);
128
* Fetch next N bits without removing them from the buffer.
130
* Discard next N bits.
131
* The value N should be a simple variable, not an expression, because it
132
* is evaluated multiple times.
135
#define CHECK_BIT_BUFFER(state,nbits,action) \
136
{ if (bits_left < (nbits)) { \
137
if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits)) \
139
get_buffer = (state).get_buffer; bits_left = (state).bits_left; } }
141
#define GET_BITS(nbits) \
142
(((int) (get_buffer >> (bits_left -= (nbits)))) & BIT_MASK(nbits))
144
#define PEEK_BITS(nbits) \
145
(((int) (get_buffer >> (bits_left - (nbits)))) & BIT_MASK(nbits))
147
#define DROP_BITS(nbits) \
148
(bits_left -= (nbits))
152
* Code for extracting next Huffman-coded symbol from input bit stream.
153
* Again, this is time-critical and we make the main paths be macros.
155
* We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits
156
* without looping. Usually, more than 95% of the Huffman codes will be 8
157
* or fewer bits long. The few overlength codes are handled with a loop,
158
* which need not be inline code.
160
* Notes about the HUFF_DECODE macro:
161
* 1. Near the end of the data segment, we may fail to get enough bits
162
* for a lookahead. In that case, we do it the hard way.
163
* 2. If the lookahead table contains no entry, the next code must be
164
* more than HUFF_LOOKAHEAD bits long.
165
* 3. jpeg_huff_decode returns -1 if forced to suspend.
168
#define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \
169
{ register int nb, look; \
170
if (bits_left < HUFF_LOOKAHEAD) { \
171
if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \
172
get_buffer = state.get_buffer; bits_left = state.bits_left; \
173
if (bits_left < HUFF_LOOKAHEAD) { \
174
nb = 1; goto slowlabel; \
177
look = PEEK_BITS(HUFF_LOOKAHEAD); \
178
if ((nb = htbl->look_nbits[look]) != 0) { \
180
result = htbl->look_sym[look]; \
182
nb = HUFF_LOOKAHEAD+1; \
184
if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \
186
get_buffer = state.get_buffer; bits_left = state.bits_left; \
192
* Expanded entropy decoder object for Huffman decoding.
194
* The savable_state subrecord contains fields that change within an MCU,
195
* but must not be updated permanently until we complete the MCU.
199
unsigned int EOBRUN; /* remaining EOBs in EOBRUN */
200
int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
203
/* This macro is to work around compilers with missing or broken
204
* structure assignment. You'll need to fix this code if you have
205
* such a compiler and you change MAX_COMPS_IN_SCAN.
208
#ifndef NO_STRUCT_ASSIGN
209
#define ASSIGN_STATE(dest,src) ((dest) = (src))
211
#if MAX_COMPS_IN_SCAN == 4
212
#define ASSIGN_STATE(dest,src) \
213
((dest).EOBRUN = (src).EOBRUN, \
214
(dest).last_dc_val[0] = (src).last_dc_val[0], \
215
(dest).last_dc_val[1] = (src).last_dc_val[1], \
216
(dest).last_dc_val[2] = (src).last_dc_val[2], \
217
(dest).last_dc_val[3] = (src).last_dc_val[3])
223
struct jpeg_entropy_decoder pub; /* public fields */
225
/* These fields are loaded into local variables at start of each MCU.
226
* In case of suspension, we exit WITHOUT updating them.
228
bitread_perm_state bitstate; /* Bit buffer at start of MCU */
229
savable_state saved; /* Other state at start of MCU */
231
/* These fields are NOT loaded into local working state. */
232
boolean insufficient_data; /* set TRUE after emitting warning */
233
unsigned int restarts_to_go; /* MCUs left in this restart interval */
235
/* Following two fields used only in progressive mode */
237
/* Pointers to derived tables (these workspaces have image lifespan) */
238
d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
240
d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
242
/* Following fields used only in sequential mode */
244
/* Pointers to derived tables (these workspaces have image lifespan) */
245
d_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];
246
d_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
248
/* Precalculated info set up by start_pass for use in decode_mcu: */
250
/* Pointers to derived tables to be used for each block within an MCU */
251
d_derived_tbl * dc_cur_tbls[D_MAX_BLOCKS_IN_MCU];
252
d_derived_tbl * ac_cur_tbls[D_MAX_BLOCKS_IN_MCU];
253
/* Whether we care about the DC and AC coefficient values for each block */
254
int coef_limit[D_MAX_BLOCKS_IN_MCU];
255
} huff_entropy_decoder;
257
typedef huff_entropy_decoder * huff_entropy_ptr;
260
static const int jpeg_zigzag_order[8][8] = {
261
{ 0, 1, 5, 6, 14, 15, 27, 28 },
262
{ 2, 4, 7, 13, 16, 26, 29, 42 },
263
{ 3, 8, 12, 17, 25, 30, 41, 43 },
264
{ 9, 11, 18, 24, 31, 40, 44, 53 },
265
{ 10, 19, 23, 32, 39, 45, 52, 54 },
266
{ 20, 22, 33, 38, 46, 51, 55, 60 },
267
{ 21, 34, 37, 47, 50, 56, 59, 61 },
268
{ 35, 36, 48, 49, 57, 58, 62, 63 }
271
static const int jpeg_zigzag_order7[7][7] = {
272
{ 0, 1, 5, 6, 14, 15, 27 },
273
{ 2, 4, 7, 13, 16, 26, 28 },
274
{ 3, 8, 12, 17, 25, 29, 38 },
275
{ 9, 11, 18, 24, 30, 37, 39 },
276
{ 10, 19, 23, 31, 36, 40, 45 },
277
{ 20, 22, 32, 35, 41, 44, 46 },
278
{ 21, 33, 34, 42, 43, 47, 48 }
281
static const int jpeg_zigzag_order6[6][6] = {
282
{ 0, 1, 5, 6, 14, 15 },
283
{ 2, 4, 7, 13, 16, 25 },
284
{ 3, 8, 12, 17, 24, 26 },
285
{ 9, 11, 18, 23, 27, 32 },
286
{ 10, 19, 22, 28, 31, 33 },
287
{ 20, 21, 29, 30, 34, 35 }
290
static const int jpeg_zigzag_order5[5][5] = {
293
{ 3, 8, 12, 16, 21 },
294
{ 9, 11, 17, 20, 22 },
295
{ 10, 18, 19, 23, 24 }
298
static const int jpeg_zigzag_order4[4][4] = {
305
static const int jpeg_zigzag_order3[3][3] = {
311
static const int jpeg_zigzag_order2[2][2] = {
318
* Compute the derived values for a Huffman table.
319
* This routine also performs some validation checks on the table.
323
jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno,
324
d_derived_tbl ** pdtbl)
328
int p, i, l, si, numsymbols;
331
unsigned int huffcode[257];
334
/* Note that huffsize[] and huffcode[] are filled in code-length order,
335
* paralleling the order of the symbols themselves in htbl->huffval[].
338
/* Find the input Huffman table */
339
if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
340
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
342
isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
344
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
346
/* Allocate a workspace if we haven't already done so. */
348
*pdtbl = (d_derived_tbl *)
349
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
350
SIZEOF(d_derived_tbl));
352
dtbl->pub = htbl; /* fill in back link */
354
/* Figure C.1: make table of Huffman code length for each symbol */
357
for (l = 1; l <= 16; l++) {
358
i = (int) htbl->bits[l];
359
if (i < 0 || p + i > 256) /* protect against table overrun */
360
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
362
huffsize[p++] = (char) l;
367
/* Figure C.2: generate the codes themselves */
368
/* We also validate that the counts represent a legal Huffman code tree. */
373
while (huffsize[p]) {
374
while (((int) huffsize[p]) == si) {
375
huffcode[p++] = code;
378
/* code is now 1 more than the last code used for codelength si; but
379
* it must still fit in si bits, since no code is allowed to be all ones.
381
if (((INT32) code) >= (((INT32) 1) << si))
382
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
387
/* Figure F.15: generate decoding tables for bit-sequential decoding */
390
for (l = 1; l <= 16; l++) {
392
/* valoffset[l] = huffval[] index of 1st symbol of code length l,
393
* minus the minimum code of length l
395
dtbl->valoffset[l] = (INT32) p - (INT32) huffcode[p];
397
dtbl->maxcode[l] = huffcode[p-1]; /* maximum code of length l */
399
dtbl->maxcode[l] = -1; /* -1 if no codes of this length */
402
dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */
404
/* Compute lookahead tables to speed up decoding.
405
* First we set all the table entries to 0, indicating "too long";
406
* then we iterate through the Huffman codes that are short enough and
407
* fill in all the entries that correspond to bit sequences starting
411
MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits));
414
for (l = 1; l <= HUFF_LOOKAHEAD; l++) {
415
for (i = 1; i <= (int) htbl->bits[l]; i++, p++) {
416
/* l = current code's length, p = its index in huffcode[] & huffval[]. */
417
/* Generate left-justified code followed by all possible bit sequences */
418
lookbits = huffcode[p] << (HUFF_LOOKAHEAD-l);
419
for (ctr = 1 << (HUFF_LOOKAHEAD-l); ctr > 0; ctr--) {
420
dtbl->look_nbits[lookbits] = l;
421
dtbl->look_sym[lookbits] = htbl->huffval[p];
427
/* Validate symbols as being reasonable.
428
* For AC tables, we make no check, but accept all byte values 0..255.
429
* For DC tables, we require the symbols to be in range 0..15.
430
* (Tighter bounds could be applied depending on the data depth and mode,
431
* but this is sufficient to ensure safe decoding.)
434
for (i = 0; i < numsymbols; i++) {
435
int sym = htbl->huffval[i];
436
if (sym < 0 || sym > 15)
437
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
444
* Out-of-line code for bit fetching.
445
* Note: current values of get_buffer and bits_left are passed as parameters,
446
* but are returned in the corresponding fields of the state struct.
448
* On most machines MIN_GET_BITS should be 25 to allow the full 32-bit width
449
* of get_buffer to be used. (On machines with wider words, an even larger
450
* buffer could be used.) However, on some machines 32-bit shifts are
451
* quite slow and take time proportional to the number of places shifted.
452
* (This is true with most PC compilers, for instance.) In this case it may
453
* be a win to set MIN_GET_BITS to the minimum value of 15. This reduces the
454
* average shift distance at the cost of more calls to jpeg_fill_bit_buffer.
458
#define MIN_GET_BITS 15 /* minimum allowable value */
460
#define MIN_GET_BITS (BIT_BUF_SIZE-7)
465
jpeg_fill_bit_buffer (bitread_working_state * state,
466
register bit_buf_type get_buffer, register int bits_left,
468
/* Load up the bit buffer to a depth of at least nbits */
470
/* Copy heavily used state fields into locals (hopefully registers) */
471
register const JOCTET * next_input_byte = state->next_input_byte;
472
register size_t bytes_in_buffer = state->bytes_in_buffer;
473
j_decompress_ptr cinfo = state->cinfo;
475
/* Attempt to load at least MIN_GET_BITS bits into get_buffer. */
476
/* (It is assumed that no request will be for more than that many bits.) */
477
/* We fail to do so only if we hit a marker or are forced to suspend. */
479
if (cinfo->unread_marker == 0) { /* cannot advance past a marker */
480
while (bits_left < MIN_GET_BITS) {
483
/* Attempt to read a byte */
484
if (bytes_in_buffer == 0) {
485
if (! (*cinfo->src->fill_input_buffer) (cinfo))
487
next_input_byte = cinfo->src->next_input_byte;
488
bytes_in_buffer = cinfo->src->bytes_in_buffer;
491
c = GETJOCTET(*next_input_byte++);
493
/* If it's 0xFF, check and discard stuffed zero byte */
495
/* Loop here to discard any padding FF's on terminating marker,
496
* so that we can save a valid unread_marker value. NOTE: we will
497
* accept multiple FF's followed by a 0 as meaning a single FF data
498
* byte. This data pattern is not valid according to the standard.
501
if (bytes_in_buffer == 0) {
502
if (! (*cinfo->src->fill_input_buffer) (cinfo))
504
next_input_byte = cinfo->src->next_input_byte;
505
bytes_in_buffer = cinfo->src->bytes_in_buffer;
508
c = GETJOCTET(*next_input_byte++);
512
/* Found FF/00, which represents an FF data byte */
515
/* Oops, it's actually a marker indicating end of compressed data.
516
* Save the marker code for later use.
517
* Fine point: it might appear that we should save the marker into
518
* bitread working state, not straight into permanent state. But
519
* once we have hit a marker, we cannot need to suspend within the
520
* current MCU, because we will read no more bytes from the data
521
* source. So it is OK to update permanent state right away.
523
cinfo->unread_marker = c;
524
/* See if we need to insert some fake zero bits. */
529
/* OK, load c into get_buffer */
530
get_buffer = (get_buffer << 8) | c;
535
/* We get here if we've read the marker that terminates the compressed
536
* data segment. There should be enough bits in the buffer register
537
* to satisfy the request; if so, no problem.
539
if (nbits > bits_left) {
540
/* Uh-oh. Report corrupted data to user and stuff zeroes into
541
* the data stream, so that we can produce some kind of image.
542
* We use a nonvolatile flag to ensure that only one warning message
543
* appears per data segment.
545
if (! ((huff_entropy_ptr) cinfo->entropy)->insufficient_data) {
546
WARNMS(cinfo, JWRN_HIT_MARKER);
547
((huff_entropy_ptr) cinfo->entropy)->insufficient_data = TRUE;
549
/* Fill the buffer with zero bits */
550
get_buffer <<= MIN_GET_BITS - bits_left;
551
bits_left = MIN_GET_BITS;
555
/* Unload the local registers */
556
state->next_input_byte = next_input_byte;
557
state->bytes_in_buffer = bytes_in_buffer;
558
state->get_buffer = get_buffer;
559
state->bits_left = bits_left;
566
* Figure F.12: extend sign bit.
567
* On some machines, a shift and sub will be faster than a table lookup.
572
#define BIT_MASK(nbits) ((1<<(nbits))-1)
573
#define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) - ((1<<(s))-1) : (x))
577
#define BIT_MASK(nbits) bmask[nbits]
578
#define HUFF_EXTEND(x,s) ((x) <= bmask[(s) - 1] ? (x) - bmask[s] : (x))
580
static const int bmask[16] = /* bmask[n] is mask for n rightmost bits */
581
{ 0, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF,
582
0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF };
584
#endif /* AVOID_TABLES */
588
* Out-of-line code for Huffman code decoding.
592
jpeg_huff_decode (bitread_working_state * state,
593
register bit_buf_type get_buffer, register int bits_left,
594
d_derived_tbl * htbl, int min_bits)
596
register int l = min_bits;
599
/* HUFF_DECODE has determined that the code is at least min_bits */
600
/* bits long, so fetch that many bits in one swoop. */
602
CHECK_BIT_BUFFER(*state, l, return -1);
605
/* Collect the rest of the Huffman code one bit at a time. */
606
/* This is per Figure F.16 in the JPEG spec. */
608
while (code > htbl->maxcode[l]) {
610
CHECK_BIT_BUFFER(*state, 1, return -1);
615
/* Unload the local registers */
616
state->get_buffer = get_buffer;
617
state->bits_left = bits_left;
619
/* With garbage input we may reach the sentinel value l = 17. */
622
WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE);
623
return 0; /* fake a zero as the safest result */
626
return htbl->pub->huffval[ (int) (code + htbl->valoffset[l]) ];
631
* Check for a restart marker & resynchronize decoder.
632
* Returns FALSE if must suspend.
636
process_restart (j_decompress_ptr cinfo)
638
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
641
/* Throw away any unused bits remaining in bit buffer; */
642
/* include any full bytes in next_marker's count of discarded bytes */
643
cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
644
entropy->bitstate.bits_left = 0;
646
/* Advance past the RSTn marker */
647
if (! (*cinfo->marker->read_restart_marker) (cinfo))
650
/* Re-initialize DC predictions to 0 */
651
for (ci = 0; ci < cinfo->comps_in_scan; ci++)
652
entropy->saved.last_dc_val[ci] = 0;
653
/* Re-init EOB run count, too */
654
entropy->saved.EOBRUN = 0;
656
/* Reset restart counter */
657
entropy->restarts_to_go = cinfo->restart_interval;
659
/* Reset out-of-data flag, unless read_restart_marker left us smack up
660
* against a marker. In that case we will end up treating the next data
661
* segment as empty, and we can avoid producing bogus output pixels by
662
* leaving the flag set.
664
if (cinfo->unread_marker == 0)
665
entropy->insufficient_data = FALSE;
672
* Huffman MCU decoding.
673
* Each of these routines decodes and returns one MCU's worth of
674
* Huffman-compressed coefficients.
675
* The coefficients are reordered from zigzag order into natural array order,
676
* but are not dequantized.
678
* The i'th block of the MCU is stored into the block pointed to by
679
* MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
680
* (Wholesale zeroing is usually a little faster than retail...)
682
* We return FALSE if data source requested suspension. In that case no
683
* changes have been made to permanent state. (Exception: some output
684
* coefficients may already have been assigned. This is harmless for
685
* spectral selection, since we'll just re-assign them on the next call.
686
* Successive approximation AC refinement has to be more careful, however.)
690
* MCU decoding for DC initial scan (either spectral selection,
691
* or first pass of successive approximation).
695
decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
697
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
705
jpeg_component_info * compptr;
707
/* Process restart marker if needed; may have to suspend */
708
if (cinfo->restart_interval) {
709
if (entropy->restarts_to_go == 0)
710
if (! process_restart(cinfo))
714
/* If we've run out of data, just leave the MCU set to zeroes.
715
* This way, we return uniform gray for the remainder of the segment.
717
if (! entropy->insufficient_data) {
719
/* Load up working state */
720
BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
721
ASSIGN_STATE(state, entropy->saved);
723
/* Outer loop handles each block in the MCU */
725
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
726
block = MCU_data[blkn];
727
ci = cinfo->MCU_membership[blkn];
728
compptr = cinfo->cur_comp_info[ci];
729
tbl = entropy->derived_tbls[compptr->dc_tbl_no];
731
/* Decode a single block's worth of coefficients */
733
/* Section F.2.2.1: decode the DC coefficient difference */
734
HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
736
CHECK_BIT_BUFFER(br_state, s, return FALSE);
738
s = HUFF_EXTEND(r, s);
741
/* Convert DC difference to actual value, update last_dc_val */
742
s += state.last_dc_val[ci];
743
state.last_dc_val[ci] = s;
744
/* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */
745
(*block)[0] = (JCOEF) (s << Al);
748
/* Completed MCU, so update state */
749
BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
750
ASSIGN_STATE(entropy->saved, state);
753
/* Account for restart interval (no-op if not using restarts) */
754
entropy->restarts_to_go--;
761
* MCU decoding for AC initial scan (either spectral selection,
762
* or first pass of successive approximation).
766
decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
768
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
769
register int s, k, r;
772
const int * natural_order;
777
/* Process restart marker if needed; may have to suspend */
778
if (cinfo->restart_interval) {
779
if (entropy->restarts_to_go == 0)
780
if (! process_restart(cinfo))
784
/* If we've run out of data, just leave the MCU set to zeroes.
785
* This way, we return uniform gray for the remainder of the segment.
787
if (! entropy->insufficient_data) {
791
natural_order = cinfo->natural_order;
793
/* Load up working state.
794
* We can avoid loading/saving bitread state if in an EOB run.
796
EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
798
/* There is always only one block per MCU */
800
if (EOBRUN > 0) /* if it's a band of zeroes... */
801
EOBRUN--; /* ...process it now (we do nothing) */
803
BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
805
tbl = entropy->ac_derived_tbl;
807
for (k = cinfo->Ss; k <= Se; k++) {
808
HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
813
CHECK_BIT_BUFFER(br_state, s, return FALSE);
815
s = HUFF_EXTEND(r, s);
816
/* Scale and output coefficient in natural (dezigzagged) order */
817
(*block)[natural_order[k]] = (JCOEF) (s << Al);
819
if (r == 15) { /* ZRL */
820
k += 15; /* skip 15 zeroes in band */
821
} else { /* EOBr, run length is 2^r + appended bits */
823
if (r) { /* EOBr, r > 0 */
824
CHECK_BIT_BUFFER(br_state, r, return FALSE);
828
EOBRUN--; /* this band is processed at this moment */
829
break; /* force end-of-band */
834
BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
837
/* Completed MCU, so update state */
838
entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
841
/* Account for restart interval (no-op if not using restarts) */
842
entropy->restarts_to_go--;
849
* MCU decoding for DC successive approximation refinement scan.
850
* Note: we assume such scans can be multi-component, although the spec
851
* is not very clear on the point.
855
decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
857
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
858
int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
863
/* Process restart marker if needed; may have to suspend */
864
if (cinfo->restart_interval) {
865
if (entropy->restarts_to_go == 0)
866
if (! process_restart(cinfo))
870
/* Not worth the cycles to check insufficient_data here,
871
* since we will not change the data anyway if we read zeroes.
874
/* Load up working state */
875
BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
877
/* Outer loop handles each block in the MCU */
879
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
880
block = MCU_data[blkn];
882
/* Encoded data is simply the next bit of the two's-complement DC value */
883
CHECK_BIT_BUFFER(br_state, 1, return FALSE);
886
/* Note: since we use |=, repeating the assignment later is safe */
889
/* Completed MCU, so update state */
890
BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
892
/* Account for restart interval (no-op if not using restarts) */
893
entropy->restarts_to_go--;
900
* MCU decoding for AC successive approximation refinement scan.
904
decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
906
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
907
register int s, k, r;
910
const int * natural_order;
916
int newnz_pos[DCTSIZE2];
918
/* Process restart marker if needed; may have to suspend */
919
if (cinfo->restart_interval) {
920
if (entropy->restarts_to_go == 0)
921
if (! process_restart(cinfo))
925
/* If we've run out of data, don't modify the MCU.
927
if (! entropy->insufficient_data) {
930
p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
931
m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */
932
natural_order = cinfo->natural_order;
934
/* Load up working state */
935
BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
936
EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
938
/* There is always only one block per MCU */
940
tbl = entropy->ac_derived_tbl;
942
/* If we are forced to suspend, we must undo the assignments to any newly
943
* nonzero coefficients in the block, because otherwise we'd get confused
944
* next time about which coefficients were already nonzero.
945
* But we need not undo addition of bits to already-nonzero coefficients;
946
* instead, we can test the current bit to see if we already did it.
950
/* initialize coefficient loop counter to start of band */
954
for (; k <= Se; k++) {
955
HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
959
if (s != 1) /* size of new coef should always be 1 */
960
WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
961
CHECK_BIT_BUFFER(br_state, 1, goto undoit);
963
s = p1; /* newly nonzero coef is positive */
965
s = m1; /* newly nonzero coef is negative */
968
EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */
970
CHECK_BIT_BUFFER(br_state, r, goto undoit);
974
break; /* rest of block is handled by EOB logic */
976
/* note s = 0 for processing ZRL */
978
/* Advance over already-nonzero coefs and r still-zero coefs,
979
* appending correction bits to the nonzeroes. A correction bit is 1
980
* if the absolute value of the coefficient must be increased.
983
thiscoef = *block + natural_order[k];
984
if (*thiscoef != 0) {
985
CHECK_BIT_BUFFER(br_state, 1, goto undoit);
987
if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
996
break; /* reached target zero coefficient */
1001
int pos = natural_order[k];
1002
/* Output newly nonzero coefficient */
1003
(*block)[pos] = (JCOEF) s;
1004
/* Remember its position in case we have to suspend */
1005
newnz_pos[num_newnz++] = pos;
1011
/* Scan any remaining coefficient positions after the end-of-band
1012
* (the last newly nonzero coefficient, if any). Append a correction
1013
* bit to each already-nonzero coefficient. A correction bit is 1
1014
* if the absolute value of the coefficient must be increased.
1016
for (; k <= Se; k++) {
1017
thiscoef = *block + natural_order[k];
1018
if (*thiscoef != 0) {
1019
CHECK_BIT_BUFFER(br_state, 1, goto undoit);
1021
if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
1030
/* Count one block completed in EOB run */
1034
/* Completed MCU, so update state */
1035
BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1036
entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
1039
/* Account for restart interval (no-op if not using restarts) */
1040
entropy->restarts_to_go--;
1045
/* Re-zero any output coefficients that we made newly nonzero */
1046
while (num_newnz > 0)
1047
(*block)[newnz_pos[--num_newnz]] = 0;
1054
* Decode one MCU's worth of Huffman-compressed coefficients,
1059
decode_mcu_sub (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
1061
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1062
const int * natural_order;
1065
savable_state state;
1067
/* Process restart marker if needed; may have to suspend */
1068
if (cinfo->restart_interval) {
1069
if (entropy->restarts_to_go == 0)
1070
if (! process_restart(cinfo))
1074
/* If we've run out of data, just leave the MCU set to zeroes.
1075
* This way, we return uniform gray for the remainder of the segment.
1077
if (! entropy->insufficient_data) {
1079
natural_order = cinfo->natural_order;
1082
/* Load up working state */
1083
BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
1084
ASSIGN_STATE(state, entropy->saved);
1086
/* Outer loop handles each block in the MCU */
1088
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1089
JBLOCKROW block = MCU_data[blkn];
1090
d_derived_tbl * htbl;
1091
register int s, k, r;
1094
/* Decode a single block's worth of coefficients */
1096
/* Section F.2.2.1: decode the DC coefficient difference */
1097
htbl = entropy->dc_cur_tbls[blkn];
1098
HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
1100
htbl = entropy->ac_cur_tbls[blkn];
1102
coef_limit = entropy->coef_limit[blkn];
1104
/* Convert DC difference to actual value, update last_dc_val */
1106
CHECK_BIT_BUFFER(br_state, s, return FALSE);
1108
s = HUFF_EXTEND(r, s);
1110
ci = cinfo->MCU_membership[blkn];
1111
s += state.last_dc_val[ci];
1112
state.last_dc_val[ci] = s;
1113
/* Output the DC coefficient */
1114
(*block)[0] = (JCOEF) s;
1116
/* Section F.2.2.2: decode the AC coefficients */
1117
/* Since zeroes are skipped, output area must be cleared beforehand */
1118
for (; k < coef_limit; k++) {
1119
HUFF_DECODE(s, br_state, htbl, return FALSE, label2);
1126
CHECK_BIT_BUFFER(br_state, s, return FALSE);
1128
s = HUFF_EXTEND(r, s);
1129
/* Output coefficient in natural (dezigzagged) order.
1130
* Note: the extra entries in natural_order[] will save us
1131
* if k > Se, which could happen if the data is corrupted.
1133
(*block)[natural_order[k]] = (JCOEF) s;
1142
CHECK_BIT_BUFFER(br_state, s, return FALSE);
1147
/* Section F.2.2.2: decode the AC coefficients */
1148
/* In this path we just discard the values */
1149
for (; k <= Se; k++) {
1150
HUFF_DECODE(s, br_state, htbl, return FALSE, label3);
1157
CHECK_BIT_BUFFER(br_state, s, return FALSE);
1169
/* Completed MCU, so update state */
1170
BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1171
ASSIGN_STATE(entropy->saved, state);
1174
/* Account for restart interval (no-op if not using restarts) */
1175
entropy->restarts_to_go--;
1182
* Decode one MCU's worth of Huffman-compressed coefficients,
1187
decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
1189
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1192
savable_state state;
1194
/* Process restart marker if needed; may have to suspend */
1195
if (cinfo->restart_interval) {
1196
if (entropy->restarts_to_go == 0)
1197
if (! process_restart(cinfo))
1201
/* If we've run out of data, just leave the MCU set to zeroes.
1202
* This way, we return uniform gray for the remainder of the segment.
1204
if (! entropy->insufficient_data) {
1206
/* Load up working state */
1207
BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
1208
ASSIGN_STATE(state, entropy->saved);
1210
/* Outer loop handles each block in the MCU */
1212
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1213
JBLOCKROW block = MCU_data[blkn];
1214
d_derived_tbl * htbl;
1215
register int s, k, r;
1218
/* Decode a single block's worth of coefficients */
1220
/* Section F.2.2.1: decode the DC coefficient difference */
1221
htbl = entropy->dc_cur_tbls[blkn];
1222
HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
1224
htbl = entropy->ac_cur_tbls[blkn];
1226
coef_limit = entropy->coef_limit[blkn];
1228
/* Convert DC difference to actual value, update last_dc_val */
1230
CHECK_BIT_BUFFER(br_state, s, return FALSE);
1232
s = HUFF_EXTEND(r, s);
1234
ci = cinfo->MCU_membership[blkn];
1235
s += state.last_dc_val[ci];
1236
state.last_dc_val[ci] = s;
1237
/* Output the DC coefficient */
1238
(*block)[0] = (JCOEF) s;
1240
/* Section F.2.2.2: decode the AC coefficients */
1241
/* Since zeroes are skipped, output area must be cleared beforehand */
1242
for (; k < coef_limit; k++) {
1243
HUFF_DECODE(s, br_state, htbl, return FALSE, label2);
1250
CHECK_BIT_BUFFER(br_state, s, return FALSE);
1252
s = HUFF_EXTEND(r, s);
1253
/* Output coefficient in natural (dezigzagged) order.
1254
* Note: the extra entries in jpeg_natural_order[] will save us
1255
* if k >= DCTSIZE2, which could happen if the data is corrupted.
1257
(*block)[jpeg_natural_order[k]] = (JCOEF) s;
1266
CHECK_BIT_BUFFER(br_state, s, return FALSE);
1271
/* Section F.2.2.2: decode the AC coefficients */
1272
/* In this path we just discard the values */
1273
for (; k < DCTSIZE2; k++) {
1274
HUFF_DECODE(s, br_state, htbl, return FALSE, label3);
1281
CHECK_BIT_BUFFER(br_state, s, return FALSE);
1293
/* Completed MCU, so update state */
1294
BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
1295
ASSIGN_STATE(entropy->saved, state);
1298
/* Account for restart interval (no-op if not using restarts) */
1299
entropy->restarts_to_go--;
1306
* Initialize for a Huffman-compressed scan.
1310
start_pass_huff_decoder (j_decompress_ptr cinfo)
1312
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1313
int ci, blkn, tbl, i;
1314
jpeg_component_info * compptr;
1316
if (cinfo->progressive_mode) {
1317
/* Validate progressive scan parameters */
1318
if (cinfo->Ss == 0) {
1322
/* need not check Ss/Se < 0 since they came from unsigned bytes */
1323
if (cinfo->Se < cinfo->Ss || cinfo->Se > cinfo->lim_Se)
1325
/* AC scans may have only one component */
1326
if (cinfo->comps_in_scan != 1)
1329
if (cinfo->Ah != 0) {
1330
/* Successive approximation refinement scan: must have Al = Ah-1. */
1331
if (cinfo->Ah-1 != cinfo->Al)
1334
if (cinfo->Al > 13) { /* need not check for < 0 */
1335
/* Arguably the maximum Al value should be less than 13 for 8-bit precision,
1336
* but the spec doesn't say so, and we try to be liberal about what we
1337
* accept. Note: large Al values could result in out-of-range DC
1338
* coefficients during early scans, leading to bizarre displays due to
1339
* overflows in the IDCT math. But we won't crash.
1342
ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
1343
cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
1345
/* Update progression status, and verify that scan order is legal.
1346
* Note that inter-scan inconsistencies are treated as warnings
1347
* not fatal errors ... not clear if this is right way to behave.
1349
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1350
int coefi, cindex = cinfo->cur_comp_info[ci]->component_index;
1351
int *coef_bit_ptr = & cinfo->coef_bits[cindex][0];
1352
if (cinfo->Ss && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
1353
WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
1354
for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
1355
int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
1356
if (cinfo->Ah != expected)
1357
WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
1358
coef_bit_ptr[coefi] = cinfo->Al;
1362
/* Select MCU decoding routine */
1363
if (cinfo->Ah == 0) {
1365
entropy->pub.decode_mcu = decode_mcu_DC_first;
1367
entropy->pub.decode_mcu = decode_mcu_AC_first;
1370
entropy->pub.decode_mcu = decode_mcu_DC_refine;
1372
entropy->pub.decode_mcu = decode_mcu_AC_refine;
1375
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1376
compptr = cinfo->cur_comp_info[ci];
1377
/* Make sure requested tables are present, and compute derived tables.
1378
* We may build same derived table more than once, but it's not expensive.
1380
if (cinfo->Ss == 0) {
1381
if (cinfo->Ah == 0) { /* DC refinement needs no table */
1382
tbl = compptr->dc_tbl_no;
1383
jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
1384
& entropy->derived_tbls[tbl]);
1387
tbl = compptr->ac_tbl_no;
1388
jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
1389
& entropy->derived_tbls[tbl]);
1390
/* remember the single active table */
1391
entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
1393
/* Initialize DC predictions to 0 */
1394
entropy->saved.last_dc_val[ci] = 0;
1397
/* Initialize private state variables */
1398
entropy->saved.EOBRUN = 0;
1400
/* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
1401
* This ought to be an error condition, but we make it a warning because
1402
* there are some baseline files out there with all zeroes in these bytes.
1404
if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 ||
1405
((cinfo->is_baseline || cinfo->Se < DCTSIZE2) &&
1406
cinfo->Se != cinfo->lim_Se))
1407
WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
1409
/* Select MCU decoding routine */
1410
/* We retain the hard-coded case for full-size blocks.
1411
* This is not necessary, but it appears that this version is slightly
1412
* more performant in the given implementation.
1413
* With an improved implementation we would prefer a single optimized
1416
if (cinfo->lim_Se != DCTSIZE2-1)
1417
entropy->pub.decode_mcu = decode_mcu_sub;
1419
entropy->pub.decode_mcu = decode_mcu;
1421
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1422
compptr = cinfo->cur_comp_info[ci];
1423
/* Compute derived values for Huffman tables */
1424
/* We may do this more than once for a table, but it's not expensive */
1425
tbl = compptr->dc_tbl_no;
1426
jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
1427
& entropy->dc_derived_tbls[tbl]);
1428
if (cinfo->lim_Se) { /* AC needs no table when not present */
1429
tbl = compptr->ac_tbl_no;
1430
jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
1431
& entropy->ac_derived_tbls[tbl]);
1433
/* Initialize DC predictions to 0 */
1434
entropy->saved.last_dc_val[ci] = 0;
1437
/* Precalculate decoding info for each block in an MCU of this scan */
1438
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1439
ci = cinfo->MCU_membership[blkn];
1440
compptr = cinfo->cur_comp_info[ci];
1441
/* Precalculate which table to use for each block */
1442
entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no];
1443
entropy->ac_cur_tbls[blkn] = entropy->ac_derived_tbls[compptr->ac_tbl_no];
1444
/* Decide whether we really care about the coefficient values */
1445
if (compptr->component_needed) {
1446
ci = compptr->DCT_v_scaled_size;
1447
i = compptr->DCT_h_scaled_size;
1448
switch (cinfo->lim_Se) {
1450
entropy->coef_limit[blkn] = 1;
1453
if (ci <= 0 || ci > 2) ci = 2;
1454
if (i <= 0 || i > 2) i = 2;
1455
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order2[ci - 1][i - 1];
1458
if (ci <= 0 || ci > 3) ci = 3;
1459
if (i <= 0 || i > 3) i = 3;
1460
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order3[ci - 1][i - 1];
1463
if (ci <= 0 || ci > 4) ci = 4;
1464
if (i <= 0 || i > 4) i = 4;
1465
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order4[ci - 1][i - 1];
1468
if (ci <= 0 || ci > 5) ci = 5;
1469
if (i <= 0 || i > 5) i = 5;
1470
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order5[ci - 1][i - 1];
1473
if (ci <= 0 || ci > 6) ci = 6;
1474
if (i <= 0 || i > 6) i = 6;
1475
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order6[ci - 1][i - 1];
1478
if (ci <= 0 || ci > 7) ci = 7;
1479
if (i <= 0 || i > 7) i = 7;
1480
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order7[ci - 1][i - 1];
1483
if (ci <= 0 || ci > 8) ci = 8;
1484
if (i <= 0 || i > 8) i = 8;
1485
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[ci - 1][i - 1];
1489
entropy->coef_limit[blkn] = 0;
1494
/* Initialize bitread state variables */
1495
entropy->bitstate.bits_left = 0;
1496
entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
1497
entropy->insufficient_data = FALSE;
1499
/* Initialize restart counter */
1500
entropy->restarts_to_go = cinfo->restart_interval;
1505
* Module initialization routine for Huffman entropy decoding.
1509
jinit_huff_decoder (j_decompress_ptr cinfo)
1511
huff_entropy_ptr entropy;
1514
entropy = (huff_entropy_ptr)
1515
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1516
SIZEOF(huff_entropy_decoder));
1517
cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
1518
entropy->pub.start_pass = start_pass_huff_decoder;
1520
if (cinfo->progressive_mode) {
1521
/* Create progression status table */
1522
int *coef_bit_ptr, ci;
1523
cinfo->coef_bits = (int (*)[DCTSIZE2])
1524
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1525
cinfo->num_components*DCTSIZE2*SIZEOF(int));
1526
coef_bit_ptr = & cinfo->coef_bits[0][0];
1527
for (ci = 0; ci < cinfo->num_components; ci++)
1528
for (i = 0; i < DCTSIZE2; i++)
1529
*coef_bit_ptr++ = -1;
1531
/* Mark derived tables unallocated */
1532
for (i = 0; i < NUM_HUFF_TBLS; i++) {
1533
entropy->derived_tbls[i] = NULL;
1536
/* Mark tables unallocated */
1537
for (i = 0; i < NUM_HUFF_TBLS; i++) {
1538
entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
added
removed
source/Irrlicht/jpeglib/jdhuff.c
