4
* Copyright (C) 1995, Thomas G. Lane.
5
* This file is part of the Independent JPEG Group's software.
6
* For conditions of distribution and use, see the accompanying README file.
8
* This file contains Huffman entropy decoding routines for progressive JPEG.
10
* Much of the complexity here has to do with supporting input suspension.
11
* If the data source module demands suspension, we want to be able to back
12
* up to the start of the current MCU. To do this, we copy state variables
13
* into local working storage, and update them back to the permanent
14
* storage only upon successful completion of an MCU.
17
#define JPEG_INTERNALS
20
#include "jdhuff.h" /* Declarations shared with jdhuff.c */
23
#ifdef D_PROGRESSIVE_SUPPORTED
26
* Expanded entropy decoder object for progressive Huffman decoding.
28
* The savable_state subrecord contains fields that change within an MCU,
29
* but must not be updated permanently until we complete the MCU.
33
unsigned int EOBRUN; /* remaining EOBs in EOBRUN */
34
int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
37
/* This macro is to work around compilers with missing or broken
38
* structure assignment. You'll need to fix this code if you have
39
* such a compiler and you change MAX_COMPS_IN_SCAN.
42
#ifndef NO_STRUCT_ASSIGN
43
#define ASSIGN_STATE(dest,src) ((dest) = (src))
45
#if MAX_COMPS_IN_SCAN == 4
46
#define ASSIGN_STATE(dest,src) \
47
((dest).EOBRUN = (src).EOBRUN, \
48
(dest).last_dc_val[0] = (src).last_dc_val[0], \
49
(dest).last_dc_val[1] = (src).last_dc_val[1], \
50
(dest).last_dc_val[2] = (src).last_dc_val[2], \
51
(dest).last_dc_val[3] = (src).last_dc_val[3])
57
struct jpeg_entropy_decoder pub; /* public fields */
59
/* These fields are loaded into local variables at start of each MCU.
60
* In case of suspension, we exit WITHOUT updating them.
62
bitread_perm_state bitstate; /* Bit buffer at start of MCU */
63
savable_state saved; /* Other state at start of MCU */
65
/* These fields are NOT loaded into local working state. */
66
unsigned int restarts_to_go; /* MCUs left in this restart interval */
68
/* Pointers to derived tables (these workspaces have image lifespan) */
69
d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
71
d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
72
} phuff_entropy_decoder;
74
typedef phuff_entropy_decoder * phuff_entropy_ptr;
76
/* Forward declarations */
77
METHODDEF boolean decode_mcu_DC_first JPP((j_decompress_ptr cinfo,
78
JBLOCKROW *MCU_data));
79
METHODDEF boolean decode_mcu_AC_first JPP((j_decompress_ptr cinfo,
80
JBLOCKROW *MCU_data));
81
METHODDEF boolean decode_mcu_DC_refine JPP((j_decompress_ptr cinfo,
82
JBLOCKROW *MCU_data));
83
METHODDEF boolean decode_mcu_AC_refine JPP((j_decompress_ptr cinfo,
84
JBLOCKROW *MCU_data));
88
* Initialize for a Huffman-compressed scan.
92
start_pass_phuff_decoder (j_decompress_ptr cinfo)
94
phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
95
boolean is_DC_band, bad;
98
jpeg_component_info * compptr;
100
is_DC_band = (cinfo->Ss == 0);
102
/* Validate scan parameters */
108
/* need not check Ss/Se < 0 since they came from unsigned bytes */
109
if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2)
111
/* AC scans may have only one component */
112
if (cinfo->comps_in_scan != 1)
115
if (cinfo->Ah != 0) {
116
/* Successive approximation refinement scan: must have Al = Ah-1. */
117
if (cinfo->Al != cinfo->Ah-1)
120
if (cinfo->Al > 13) /* need not check for < 0 */
123
ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
124
cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
125
/* Update progression status, and verify that scan order is legal.
126
* Note that inter-scan inconsistencies are treated as warnings
127
* not fatal errors ... not clear if this is right way to behave.
129
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
130
int cindex = cinfo->cur_comp_info[ci]->component_index;
131
coef_bit_ptr = & cinfo->coef_bits[cindex][0];
132
if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
133
WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
134
for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
135
int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
136
if (cinfo->Ah != expected)
137
WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
138
coef_bit_ptr[coefi] = cinfo->Al;
142
/* Select MCU decoding routine */
143
if (cinfo->Ah == 0) {
145
entropy->pub.decode_mcu = decode_mcu_DC_first;
147
entropy->pub.decode_mcu = decode_mcu_AC_first;
150
entropy->pub.decode_mcu = decode_mcu_DC_refine;
152
entropy->pub.decode_mcu = decode_mcu_AC_refine;
155
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
156
compptr = cinfo->cur_comp_info[ci];
157
/* Make sure requested tables are present, and compute derived tables.
158
* We may build same derived table more than once, but it's not expensive.
161
if (cinfo->Ah == 0) { /* DC refinement needs no table */
162
tbl = compptr->dc_tbl_no;
163
if (tbl < 0 || tbl >= NUM_HUFF_TBLS ||
164
cinfo->dc_huff_tbl_ptrs[tbl] == NULL)
165
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
166
jpeg_make_d_derived_tbl(cinfo, cinfo->dc_huff_tbl_ptrs[tbl],
167
& entropy->derived_tbls[tbl]);
170
tbl = compptr->ac_tbl_no;
171
if (tbl < 0 || tbl >= NUM_HUFF_TBLS ||
172
cinfo->ac_huff_tbl_ptrs[tbl] == NULL)
173
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
174
jpeg_make_d_derived_tbl(cinfo, cinfo->ac_huff_tbl_ptrs[tbl],
175
& entropy->derived_tbls[tbl]);
176
/* remember the single active table */
177
entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
179
/* Initialize DC predictions to 0 */
180
entropy->saved.last_dc_val[ci] = 0;
183
/* Initialize bitread state variables */
184
entropy->bitstate.bits_left = 0;
185
entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
186
entropy->bitstate.printed_eod = FALSE;
188
/* Initialize private state variables */
189
entropy->saved.EOBRUN = 0;
191
/* Initialize restart counter */
192
entropy->restarts_to_go = cinfo->restart_interval;
197
* Figure F.12: extend sign bit.
198
* On some machines, a shift and add will be faster than a table lookup.
203
#define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x))
207
#define HUFF_EXTEND(x,s) ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))
209
static const int extend_test[16] = /* entry n is 2**(n-1) */
210
{ 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
211
0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };
213
static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */
214
{ 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1,
215
((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1,
216
((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1,
217
((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 };
219
#endif /* AVOID_TABLES */
223
* Check for a restart marker & resynchronize decoder.
224
* Returns FALSE if must suspend.
228
process_restart (j_decompress_ptr cinfo)
230
phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
233
/* Throw away any unused bits remaining in bit buffer; */
234
/* include any full bytes in next_marker's count of discarded bytes */
235
cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
236
entropy->bitstate.bits_left = 0;
238
/* Advance past the RSTn marker */
239
if (! (*cinfo->marker->read_restart_marker) (cinfo))
242
/* Re-initialize DC predictions to 0 */
243
for (ci = 0; ci < cinfo->comps_in_scan; ci++)
244
entropy->saved.last_dc_val[ci] = 0;
245
/* Re-init EOB run count, too */
246
entropy->saved.EOBRUN = 0;
248
/* Reset restart counter */
249
entropy->restarts_to_go = cinfo->restart_interval;
251
/* Next segment can get another out-of-data warning */
252
entropy->bitstate.printed_eod = FALSE;
259
* Huffman MCU decoding.
260
* Each of these routines decodes and returns one MCU's worth of
261
* Huffman-compressed coefficients.
262
* The coefficients are reordered from zigzag order into natural array order,
263
* but are not dequantized.
265
* The i'th block of the MCU is stored into the block pointed to by
266
* MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
268
* We return FALSE if data source requested suspension. In that case no
269
* changes have been made to permanent state. (Exception: some output
270
* coefficients may already have been assigned. This is harmless for
271
* spectral selection, since we'll just re-assign them on the next call.
272
* Successive approximation AC refinement has to be more careful, however.)
276
* MCU decoding for DC initial scan (either spectral selection,
277
* or first pass of successive approximation).
281
decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
283
phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
291
jpeg_component_info * compptr;
293
/* Process restart marker if needed; may have to suspend */
294
if (cinfo->restart_interval) {
295
if (entropy->restarts_to_go == 0)
296
if (! process_restart(cinfo))
300
/* Load up working state */
301
BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
302
ASSIGN_STATE(state, entropy->saved);
304
/* Outer loop handles each block in the MCU */
306
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
307
block = MCU_data[blkn];
308
ci = cinfo->MCU_membership[blkn];
309
compptr = cinfo->cur_comp_info[ci];
310
tbl = entropy->derived_tbls[compptr->dc_tbl_no];
312
/* Decode a single block's worth of coefficients */
314
/* Section F.2.2.1: decode the DC coefficient difference */
315
HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
317
CHECK_BIT_BUFFER(br_state, s, return FALSE);
319
s = HUFF_EXTEND(r, s);
322
/* Convert DC difference to actual value, update last_dc_val */
323
s += state.last_dc_val[ci];
324
state.last_dc_val[ci] = s;
325
/* Scale and output the DC coefficient (assumes jpeg_natural_order[0]=0) */
326
(*block)[0] = (JCOEF) (s << Al);
329
/* Completed MCU, so update state */
330
BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
331
ASSIGN_STATE(entropy->saved, state);
333
/* Account for restart interval (no-op if not using restarts) */
334
entropy->restarts_to_go--;
341
* MCU decoding for AC initial scan (either spectral selection,
342
* or first pass of successive approximation).
346
decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
348
phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
351
register int s, k, r;
357
/* Process restart marker if needed; may have to suspend */
358
if (cinfo->restart_interval) {
359
if (entropy->restarts_to_go == 0)
360
if (! process_restart(cinfo))
364
/* Load up working state.
365
* We can avoid loading/saving bitread state if in an EOB run.
367
EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we care about */
369
/* There is always only one block per MCU */
371
if (EOBRUN > 0) /* if it's a band of zeroes... */
372
EOBRUN--; /* ...process it now (we do nothing) */
374
BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
376
tbl = entropy->ac_derived_tbl;
378
for (k = cinfo->Ss; k <= Se; k++) {
379
HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
384
CHECK_BIT_BUFFER(br_state, s, return FALSE);
386
s = HUFF_EXTEND(r, s);
387
/* Scale and output coefficient in natural (dezigzagged) order */
388
(*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al);
390
if (r == 15) { /* ZRL */
391
k += 15; /* skip 15 zeroes in band */
392
} else { /* EOBr, run length is 2^r + appended bits */
394
if (r) { /* EOBr, r > 0 */
395
CHECK_BIT_BUFFER(br_state, r, return FALSE);
399
EOBRUN--; /* this band is processed at this moment */
400
break; /* force end-of-band */
405
BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
408
/* Completed MCU, so update state */
409
entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we care about */
411
/* Account for restart interval (no-op if not using restarts) */
412
entropy->restarts_to_go--;
419
* MCU decoding for DC successive approximation refinement scan.
420
* Note: we assume such scans can be multi-component, although the spec
421
* is not very clear on the point.
425
decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
427
phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
428
int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
433
/* Process restart marker if needed; may have to suspend */
434
if (cinfo->restart_interval) {
435
if (entropy->restarts_to_go == 0)
436
if (! process_restart(cinfo))
440
/* Load up working state */
441
BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
443
/* Outer loop handles each block in the MCU */
445
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
446
block = MCU_data[blkn];
448
/* Encoded data is simply the next bit of the two's-complement DC value */
449
CHECK_BIT_BUFFER(br_state, 1, return FALSE);
452
/* Note: since we use |=, repeating the assignment later is safe */
455
/* Completed MCU, so update state */
456
BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
458
/* Account for restart interval (no-op if not using restarts) */
459
entropy->restarts_to_go--;
466
* MCU decoding for AC successive approximation refinement scan.
470
decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
472
phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
474
int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
475
int m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */
476
register int s, k, r;
483
int newnz_pos[DCTSIZE2];
485
/* Process restart marker if needed; may have to suspend */
486
if (cinfo->restart_interval) {
487
if (entropy->restarts_to_go == 0)
488
if (! process_restart(cinfo))
492
/* Load up working state */
493
BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
494
EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we care about */
496
/* There is always only one block per MCU */
498
tbl = entropy->ac_derived_tbl;
500
/* If we are forced to suspend, we must undo the assignments to any newly
501
* nonzero coefficients in the block, because otherwise we'd get confused
502
* next time about which coefficients were already nonzero.
503
* But we need not undo addition of bits to already-nonzero coefficients;
504
* instead, we can test the current bit position to see if we already did it.
508
/* initialize coefficient loop counter to start of band */
512
for (; k <= Se; k++) {
513
HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
517
if (s != 1) /* size of new coef should always be 1 */
518
WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
519
CHECK_BIT_BUFFER(br_state, 1, goto undoit);
521
s = p1; /* newly nonzero coef is positive */
523
s = m1; /* newly nonzero coef is negative */
526
EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */
528
CHECK_BIT_BUFFER(br_state, r, goto undoit);
532
break; /* rest of block is handled by EOB logic */
534
/* note s = 0 for processing ZRL */
536
/* Advance over already-nonzero coefs and r still-zero coefs,
537
* appending correction bits to the nonzeroes. A correction bit is 1
538
* if the absolute value of the coefficient must be increased.
541
thiscoef = *block + jpeg_natural_order[k];
542
if (*thiscoef != 0) {
543
CHECK_BIT_BUFFER(br_state, 1, goto undoit);
545
if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
554
break; /* reached target zero coefficient */
559
int pos = jpeg_natural_order[k];
560
/* Output newly nonzero coefficient */
561
(*block)[pos] = (JCOEF) s;
562
/* Remember its position in case we have to suspend */
563
newnz_pos[num_newnz++] = pos;
569
/* Scan any remaining coefficient positions after the end-of-band
570
* (the last newly nonzero coefficient, if any). Append a correction
571
* bit to each already-nonzero coefficient. A correction bit is 1
572
* if the absolute value of the coefficient must be increased.
574
for (; k <= Se; k++) {
575
thiscoef = *block + jpeg_natural_order[k];
576
if (*thiscoef != 0) {
577
CHECK_BIT_BUFFER(br_state, 1, goto undoit);
579
if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
588
/* Count one block completed in EOB run */
592
/* Completed MCU, so update state */
593
BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
594
entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we care about */
596
/* Account for restart interval (no-op if not using restarts) */
597
entropy->restarts_to_go--;
602
/* Re-zero any output coefficients that we made newly nonzero */
603
while (num_newnz > 0)
604
(*block)[newnz_pos[--num_newnz]] = 0;
611
* Module initialization routine for progressive Huffman entropy decoding.
615
jinit_phuff_decoder (j_decompress_ptr cinfo)
617
phuff_entropy_ptr entropy;
621
entropy = (phuff_entropy_ptr)
622
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
623
SIZEOF(phuff_entropy_decoder));
624
cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
625
entropy->pub.start_pass = start_pass_phuff_decoder;
627
/* Mark derived tables unallocated */
628
for (i = 0; i < NUM_HUFF_TBLS; i++) {
629
entropy->derived_tbls[i] = NULL;
632
/* Create progression status table */
633
cinfo->coef_bits = (int (*)[DCTSIZE2])
634
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
635
cinfo->num_components*DCTSIZE2*SIZEOF(int));
636
coef_bit_ptr = & cinfo->coef_bits[0][0];
637
for (ci = 0; ci < cinfo->num_components; ci++)
638
for (i = 0; i < DCTSIZE2; i++)
639
*coef_bit_ptr++ = -1;
642
#endif /* D_PROGRESSIVE_SUPPORTED */
added
removed
code/jpeg-6/jdphuff.c
