source: trunk/src/3rdparty/libjpeg/jdarith.c@ 953

Last change on this file since 953 was 846, checked in by Dmitry A. Kuminov, 15 years ago

trunk: Merged in qt 4.7.2 sources from branches/vendor/nokia/qt.
File size: 23.3 KB
Line 
1/*
2 * jdarith.c
3 *
4 * Developed 1997-2009 by Guido Vollbeding.
5 * This file is part of the Independent JPEG Group's software.
6 * For conditions of distribution and use, see the accompanying README file.
7 *
8 * This file contains portable arithmetic entropy decoding routines for JPEG
9 * (implementing the ISO/IEC IS 10918-1 and CCITT Recommendation ITU-T T.81).
10 *
11 * Both sequential and progressive modes are supported in this single module.
12 *
13 * Suspension is not currently supported in this module.
14 */
15
16#define JPEG_INTERNALS
17#include "jinclude.h"
18#include "jpeglib.h"
19
20
21/* Expanded entropy decoder object for arithmetic decoding. */
22
23typedef struct {
24 struct jpeg_entropy_decoder pub; /* public fields */
25
26 INT32 c; /* C register, base of coding interval + input bit buffer */
27 INT32 a; /* A register, normalized size of coding interval */
28 int ct; /* bit shift counter, # of bits left in bit buffer part of C */
29 /* init: ct = -16 */
30 /* run: ct = 0..7 */
31 /* error: ct = -1 */
32 int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
33 int dc_context[MAX_COMPS_IN_SCAN]; /* context index for DC conditioning */
34
35 unsigned int restarts_to_go; /* MCUs left in this restart interval */
36
37 /* Pointers to statistics areas (these workspaces have image lifespan) */
38 unsigned char * dc_stats[NUM_ARITH_TBLS];
39 unsigned char * ac_stats[NUM_ARITH_TBLS];
40
41 /* Statistics bin for coding with fixed probability 0.5 */
42 unsigned char fixed_bin[4];
43} arith_entropy_decoder;
44
45typedef arith_entropy_decoder * arith_entropy_ptr;
46
47/* The following two definitions specify the allocation chunk size
48 * for the statistics area.
49 * According to sections F.1.4.4.1.3 and F.1.4.4.2, we need at least
50 * 49 statistics bins for DC, and 245 statistics bins for AC coding.
51 *
52 * We use a compact representation with 1 byte per statistics bin,
53 * thus the numbers directly represent byte sizes.
54 * This 1 byte per statistics bin contains the meaning of the MPS
55 * (more probable symbol) in the highest bit (mask 0x80), and the
56 * index into the probability estimation state machine table
57 * in the lower bits (mask 0x7F).
58 */
59
60#define DC_STAT_BINS 64
61#define AC_STAT_BINS 256
62
63
64LOCAL(int)
65get_byte (j_decompress_ptr cinfo)
66/* Read next input byte; we do not support suspension in this module. */
67{
68 struct jpeg_source_mgr * src = cinfo->src;
69
70 if (src->bytes_in_buffer == 0)
71 if (! (*src->fill_input_buffer) (cinfo))
72 ERREXIT(cinfo, JERR_CANT_SUSPEND);
73 src->bytes_in_buffer--;
74 return GETJOCTET(*src->next_input_byte++);
75}
76
77
78/*
79 * The core arithmetic decoding routine (common in JPEG and JBIG).
80 * This needs to go as fast as possible.
81 * Machine-dependent optimization facilities
82 * are not utilized in this portable implementation.
83 * However, this code should be fairly efficient and
84 * may be a good base for further optimizations anyway.
85 *
86 * Return value is 0 or 1 (binary decision).
87 *
88 * Note: I've changed the handling of the code base & bit
89 * buffer register C compared to other implementations
90 * based on the standards layout & procedures.
91 * While it also contains both the actual base of the
92 * coding interval (16 bits) and the next-bits buffer,
93 * the cut-point between these two parts is floating
94 * (instead of fixed) with the bit shift counter CT.
95 * Thus, we also need only one (variable instead of
96 * fixed size) shift for the LPS/MPS decision, and
97 * we can get away with any renormalization update
98 * of C (except for new data insertion, of course).
99 *
100 * I've also introduced a new scheme for accessing
101 * the probability estimation state machine table,
102 * derived from Markus Kuhn's JBIG implementation.
103 */
104
105LOCAL(int)
106arith_decode (j_decompress_ptr cinfo, unsigned char *st)
107{
108 register arith_entropy_ptr e = (arith_entropy_ptr) cinfo->entropy;
109 register unsigned char nl, nm;
110 register INT32 qe, temp;
111 register int sv, data;
112
113 /* Renormalization & data input per section D.2.6 */
114 while (e->a < 0x8000L) {
115 if (--e->ct < 0) {
116 /* Need to fetch next data byte */
117 if (cinfo->unread_marker)
118 data = 0; /* stuff zero data */
119 else {
120 data = get_byte(cinfo); /* read next input byte */
121 if (data == 0xFF) { /* zero stuff or marker code */
122 do data = get_byte(cinfo);
123 while (data == 0xFF); /* swallow extra 0xFF bytes */
124 if (data == 0)
125 data = 0xFF; /* discard stuffed zero byte */
126 else {
127 /* Note: Different from the Huffman decoder, hitting
128 * a marker while processing the compressed data
129 * segment is legal in arithmetic coding.
130 * The convention is to supply zero data
131 * then until decoding is complete.
132 */
133 cinfo->unread_marker = data;
134 data = 0;
135 }
136 }
137 }
138 e->c = (e->c << 8) | data; /* insert data into C register */
139 if ((e->ct += 8) < 0) /* update bit shift counter */
140 /* Need more initial bytes */
141 if (++e->ct == 0)
142 /* Got 2 initial bytes -> re-init A and exit loop */
143 e->a = 0x8000L; /* => e->a = 0x10000L after loop exit */
144 }
145 e->a <<= 1;
146 }
147
148 /* Fetch values from our compact representation of Table D.2:
149 * Qe values and probability estimation state machine
150 */
151 sv = *st;
152 qe = jpeg_aritab[sv & 0x7F]; /* => Qe_Value */
153 nl = qe & 0xFF; qe >>= 8; /* Next_Index_LPS + Switch_MPS */
154 nm = qe & 0xFF; qe >>= 8; /* Next_Index_MPS */
155
156 /* Decode & estimation procedures per sections D.2.4 & D.2.5 */
157 temp = e->a - qe;
158 e->a = temp;
159 temp <<= e->ct;
160 if (e->c >= temp) {
161 e->c -= temp;
162 /* Conditional LPS (less probable symbol) exchange */
163 if (e->a < qe) {
164 e->a = qe;
165 *st = (sv & 0x80) ^ nm; /* Estimate_after_MPS */
166 } else {
167 e->a = qe;
168 *st = (sv & 0x80) ^ nl; /* Estimate_after_LPS */
169 sv ^= 0x80; /* Exchange LPS/MPS */
170 }
171 } else if (e->a < 0x8000L) {
172 /* Conditional MPS (more probable symbol) exchange */
173 if (e->a < qe) {
174 *st = (sv & 0x80) ^ nl; /* Estimate_after_LPS */
175 sv ^= 0x80; /* Exchange LPS/MPS */
176 } else {
177 *st = (sv & 0x80) ^ nm; /* Estimate_after_MPS */
178 }
179 }
180
181 return sv >> 7;
182}
183
184
185/*
186 * Check for a restart marker & resynchronize decoder.
187 */
188
189LOCAL(void)
190process_restart (j_decompress_ptr cinfo)
191{
192 arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
193 int ci;
194 jpeg_component_info * compptr;
195
196 /* Advance past the RSTn marker */
197 if (! (*cinfo->marker->read_restart_marker) (cinfo))
198 ERREXIT(cinfo, JERR_CANT_SUSPEND);
199
200 /* Re-initialize statistics areas */
201 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
202 compptr = cinfo->cur_comp_info[ci];
203 if (! cinfo->progressive_mode || (cinfo->Ss == 0 && cinfo->Ah == 0)) {
204 MEMZERO(entropy->dc_stats[compptr->dc_tbl_no], DC_STAT_BINS);
205 /* Reset DC predictions to 0 */
206 entropy->last_dc_val[ci] = 0;
207 entropy->dc_context[ci] = 0;
208 }
209 if ((! cinfo->progressive_mode && cinfo->lim_Se) ||
210 (cinfo->progressive_mode && cinfo->Ss)) {
211 MEMZERO(entropy->ac_stats[compptr->ac_tbl_no], AC_STAT_BINS);
212 }
213 }
214
215 /* Reset arithmetic decoding variables */
216 entropy->c = 0;
217 entropy->a = 0;
218 entropy->ct = -16; /* force reading 2 initial bytes to fill C */
219
220 /* Reset restart counter */
221 entropy->restarts_to_go = cinfo->restart_interval;
222}
223
224
225/*
226 * Arithmetic MCU decoding.
227 * Each of these routines decodes and returns one MCU's worth of
228 * arithmetic-compressed coefficients.
229 * The coefficients are reordered from zigzag order into natural array order,
230 * but are not dequantized.
231 *
232 * The i'th block of the MCU is stored into the block pointed to by
233 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
234 */
235
236/*
237 * MCU decoding for DC initial scan (either spectral selection,
238 * or first pass of successive approximation).
239 */
240
241METHODDEF(boolean)
242decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
243{
244 arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
245 JBLOCKROW block;
246 unsigned char *st;
247 int blkn, ci, tbl, sign;
248 int v, m;
249
250 /* Process restart marker if needed */
251 if (cinfo->restart_interval) {
252 if (entropy->restarts_to_go == 0)
253 process_restart(cinfo);
254 entropy->restarts_to_go--;
255 }
256
257 if (entropy->ct == -1) return TRUE; /* if error do nothing */
258
259 /* Outer loop handles each block in the MCU */
260
261 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
262 block = MCU_data[blkn];
263 ci = cinfo->MCU_membership[blkn];
264 tbl = cinfo->cur_comp_info[ci]->dc_tbl_no;
265
266 /* Sections F.2.4.1 & F.1.4.4.1: Decoding of DC coefficients */
267
268 /* Table F.4: Point to statistics bin S0 for DC coefficient coding */
269 st = entropy->dc_stats[tbl] + entropy->dc_context[ci];
270
271 /* Figure F.19: Decode_DC_DIFF */
272 if (arith_decode(cinfo, st) == 0)
273 entropy->dc_context[ci] = 0;
274 else {
275 /* Figure F.21: Decoding nonzero value v */
276 /* Figure F.22: Decoding the sign of v */
277 sign = arith_decode(cinfo, st + 1);
278 st += 2; st += sign;
279 /* Figure F.23: Decoding the magnitude category of v */
280 if ((m = arith_decode(cinfo, st)) != 0) {
281 st = entropy->dc_stats[tbl] + 20; /* Table F.4: X1 = 20 */
282 while (arith_decode(cinfo, st)) {
283 if ((m <<= 1) == 0x8000) {
284 WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
285 entropy->ct = -1; /* magnitude overflow */
286 return TRUE;
287 }
288 st += 1;
289 }
290 }
291 /* Section F.1.4.4.1.2: Establish dc_context conditioning category */
292 if (m < (int) ((1L << cinfo->arith_dc_L[tbl]) >> 1))
293 entropy->dc_context[ci] = 0; /* zero diff category */
294 else if (m > (int) ((1L << cinfo->arith_dc_U[tbl]) >> 1))
295 entropy->dc_context[ci] = 12 + (sign * 4); /* large diff category */
296 else
297 entropy->dc_context[ci] = 4 + (sign * 4); /* small diff category */
298 v = m;
299 /* Figure F.24: Decoding the magnitude bit pattern of v */
300 st += 14;
301 while (m >>= 1)
302 if (arith_decode(cinfo, st)) v |= m;
303 v += 1; if (sign) v = -v;
304 entropy->last_dc_val[ci] += v;
305 }
306
307 /* Scale and output the DC coefficient (assumes jpeg_natural_order[0]=0) */
308 (*block)[0] = (JCOEF) (entropy->last_dc_val[ci] << cinfo->Al);
309 }
310
311 return TRUE;
312}
313
314
315/*
316 * MCU decoding for AC initial scan (either spectral selection,
317 * or first pass of successive approximation).
318 */
319
320METHODDEF(boolean)
321decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
322{
323 arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
324 JBLOCKROW block;
325 unsigned char *st;
326 int tbl, sign, k;
327 int v, m;
328 const int * natural_order;
329
330 /* Process restart marker if needed */
331 if (cinfo->restart_interval) {
332 if (entropy->restarts_to_go == 0)
333 process_restart(cinfo);
334 entropy->restarts_to_go--;
335 }
336
337 if (entropy->ct == -1) return TRUE; /* if error do nothing */
338
339 natural_order = cinfo->natural_order;
340
341 /* There is always only one block per MCU */
342 block = MCU_data[0];
343 tbl = cinfo->cur_comp_info[0]->ac_tbl_no;
344
345 /* Sections F.2.4.2 & F.1.4.4.2: Decoding of AC coefficients */
346
347 /* Figure F.20: Decode_AC_coefficients */
348 for (k = cinfo->Ss; k <= cinfo->Se; k++) {
349 st = entropy->ac_stats[tbl] + 3 * (k - 1);
350 if (arith_decode(cinfo, st)) break; /* EOB flag */
351 while (arith_decode(cinfo, st + 1) == 0) {
352 st += 3; k++;
353 if (k > cinfo->Se) {
354 WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
355 entropy->ct = -1; /* spectral overflow */
356 return TRUE;
357 }
358 }
359 /* Figure F.21: Decoding nonzero value v */
360 /* Figure F.22: Decoding the sign of v */
361 sign = arith_decode(cinfo, entropy->fixed_bin);
362 st += 2;
363 /* Figure F.23: Decoding the magnitude category of v */
364 if ((m = arith_decode(cinfo, st)) != 0) {
365 if (arith_decode(cinfo, st)) {
366 m <<= 1;
367 st = entropy->ac_stats[tbl] +
368 (k <= cinfo->arith_ac_K[tbl] ? 189 : 217);
369 while (arith_decode(cinfo, st)) {
370 if ((m <<= 1) == 0x8000) {
371 WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
372 entropy->ct = -1; /* magnitude overflow */
373 return TRUE;
374 }
375 st += 1;
376 }
377 }
378 }
379 v = m;
380 /* Figure F.24: Decoding the magnitude bit pattern of v */
381 st += 14;
382 while (m >>= 1)
383 if (arith_decode(cinfo, st)) v |= m;
384 v += 1; if (sign) v = -v;
385 /* Scale and output coefficient in natural (dezigzagged) order */
386 (*block)[natural_order[k]] = (JCOEF) (v << cinfo->Al);
387 }
388
389 return TRUE;
390}
391
392
393/*
394 * MCU decoding for DC successive approximation refinement scan.
395 */
396
397METHODDEF(boolean)
398decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
399{
400 arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
401 unsigned char *st;
402 int p1, blkn;
403
404 /* Process restart marker if needed */
405 if (cinfo->restart_interval) {
406 if (entropy->restarts_to_go == 0)
407 process_restart(cinfo);
408 entropy->restarts_to_go--;
409 }
410
411 st = entropy->fixed_bin; /* use fixed probability estimation */
412 p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
413
414 /* Outer loop handles each block in the MCU */
415
416 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
417 /* Encoded data is simply the next bit of the two's-complement DC value */
418 if (arith_decode(cinfo, st))
419 MCU_data[blkn][0][0] |= p1;
420 }
421
422 return TRUE;
423}
424
425
426/*
427 * MCU decoding for AC successive approximation refinement scan.
428 */
429
430METHODDEF(boolean)
431decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
432{
433 arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
434 JBLOCKROW block;
435 JCOEFPTR thiscoef;
436 unsigned char *st;
437 int tbl, k, kex;
438 int p1, m1;
439 const int * natural_order;
440
441 /* Process restart marker if needed */
442 if (cinfo->restart_interval) {
443 if (entropy->restarts_to_go == 0)
444 process_restart(cinfo);
445 entropy->restarts_to_go--;
446 }
447
448 if (entropy->ct == -1) return TRUE; /* if error do nothing */
449
450 natural_order = cinfo->natural_order;
451
452 /* There is always only one block per MCU */
453 block = MCU_data[0];
454 tbl = cinfo->cur_comp_info[0]->ac_tbl_no;
455
456 p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
457 m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */
458
459 /* Establish EOBx (previous stage end-of-block) index */
460 for (kex = cinfo->Se; kex > 0; kex--)
461 if ((*block)[natural_order[kex]]) break;
462
463 for (k = cinfo->Ss; k <= cinfo->Se; k++) {
464 st = entropy->ac_stats[tbl] + 3 * (k - 1);
465 if (k > kex)
466 if (arith_decode(cinfo, st)) break; /* EOB flag */
467 for (;;) {
468 thiscoef = *block + natural_order[k];
469 if (*thiscoef) { /* previously nonzero coef */
470 if (arith_decode(cinfo, st + 2)) {
471 if (*thiscoef < 0)
472 *thiscoef += m1;
473 else
474 *thiscoef += p1;
475 }
476 break;
477 }
478 if (arith_decode(cinfo, st + 1)) { /* newly nonzero coef */
479 if (arith_decode(cinfo, entropy->fixed_bin))
480 *thiscoef = m1;
481 else
482 *thiscoef = p1;
483 break;
484 }
485 st += 3; k++;
486 if (k > cinfo->Se) {
487 WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
488 entropy->ct = -1; /* spectral overflow */
489 return TRUE;
490 }
491 }
492 }
493
494 return TRUE;
495}
496
497
498/*
499 * Decode one MCU's worth of arithmetic-compressed coefficients.
500 */
501
502METHODDEF(boolean)
503decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
504{
505 arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
506 jpeg_component_info * compptr;
507 JBLOCKROW block;
508 unsigned char *st;
509 int blkn, ci, tbl, sign, k;
510 int v, m;
511 const int * natural_order;
512
513 /* Process restart marker if needed */
514 if (cinfo->restart_interval) {
515 if (entropy->restarts_to_go == 0)
516 process_restart(cinfo);
517 entropy->restarts_to_go--;
518 }
519
520 if (entropy->ct == -1) return TRUE; /* if error do nothing */
521
522 natural_order = cinfo->natural_order;
523
524 /* Outer loop handles each block in the MCU */
525
526 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
527 block = MCU_data[blkn];
528 ci = cinfo->MCU_membership[blkn];
529 compptr = cinfo->cur_comp_info[ci];
530
531 /* Sections F.2.4.1 & F.1.4.4.1: Decoding of DC coefficients */
532
533 tbl = compptr->dc_tbl_no;
534
535 /* Table F.4: Point to statistics bin S0 for DC coefficient coding */
536 st = entropy->dc_stats[tbl] + entropy->dc_context[ci];
537
538 /* Figure F.19: Decode_DC_DIFF */
539 if (arith_decode(cinfo, st) == 0)
540 entropy->dc_context[ci] = 0;
541 else {
542 /* Figure F.21: Decoding nonzero value v */
543 /* Figure F.22: Decoding the sign of v */
544 sign = arith_decode(cinfo, st + 1);
545 st += 2; st += sign;
546 /* Figure F.23: Decoding the magnitude category of v */
547 if ((m = arith_decode(cinfo, st)) != 0) {
548 st = entropy->dc_stats[tbl] + 20; /* Table F.4: X1 = 20 */
549 while (arith_decode(cinfo, st)) {
550 if ((m <<= 1) == 0x8000) {
551 WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
552 entropy->ct = -1; /* magnitude overflow */
553 return TRUE;
554 }
555 st += 1;
556 }
557 }
558 /* Section F.1.4.4.1.2: Establish dc_context conditioning category */
559 if (m < (int) ((1L << cinfo->arith_dc_L[tbl]) >> 1))
560 entropy->dc_context[ci] = 0; /* zero diff category */
561 else if (m > (int) ((1L << cinfo->arith_dc_U[tbl]) >> 1))
562 entropy->dc_context[ci] = 12 + (sign * 4); /* large diff category */
563 else
564 entropy->dc_context[ci] = 4 + (sign * 4); /* small diff category */
565 v = m;
566 /* Figure F.24: Decoding the magnitude bit pattern of v */
567 st += 14;
568 while (m >>= 1)
569 if (arith_decode(cinfo, st)) v |= m;
570 v += 1; if (sign) v = -v;
571 entropy->last_dc_val[ci] += v;
572 }
573
574 (*block)[0] = (JCOEF) entropy->last_dc_val[ci];
575
576 /* Sections F.2.4.2 & F.1.4.4.2: Decoding of AC coefficients */
577
578 tbl = compptr->ac_tbl_no;
579
580 /* Figure F.20: Decode_AC_coefficients */
581 for (k = 1; k <= cinfo->lim_Se; k++) {
582 st = entropy->ac_stats[tbl] + 3 * (k - 1);
583 if (arith_decode(cinfo, st)) break; /* EOB flag */
584 while (arith_decode(cinfo, st + 1) == 0) {
585 st += 3; k++;
586 if (k > cinfo->lim_Se) {
587 WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
588 entropy->ct = -1; /* spectral overflow */
589 return TRUE;
590 }
591 }
592 /* Figure F.21: Decoding nonzero value v */
593 /* Figure F.22: Decoding the sign of v */
594 sign = arith_decode(cinfo, entropy->fixed_bin);
595 st += 2;
596 /* Figure F.23: Decoding the magnitude category of v */
597 if ((m = arith_decode(cinfo, st)) != 0) {
598 if (arith_decode(cinfo, st)) {
599 m <<= 1;
600 st = entropy->ac_stats[tbl] +
601 (k <= cinfo->arith_ac_K[tbl] ? 189 : 217);
602 while (arith_decode(cinfo, st)) {
603 if ((m <<= 1) == 0x8000) {
604 WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
605 entropy->ct = -1; /* magnitude overflow */
606 return TRUE;
607 }
608 st += 1;
609 }
610 }
611 }
612 v = m;
613 /* Figure F.24: Decoding the magnitude bit pattern of v */
614 st += 14;
615 while (m >>= 1)
616 if (arith_decode(cinfo, st)) v |= m;
617 v += 1; if (sign) v = -v;
618 (*block)[natural_order[k]] = (JCOEF) v;
619 }
620 }
621
622 return TRUE;
623}
624
625
626/*
627 * Initialize for an arithmetic-compressed scan.
628 */
629
630METHODDEF(void)
631start_pass (j_decompress_ptr cinfo)
632{
633 arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
634 int ci, tbl;
635 jpeg_component_info * compptr;
636
637 if (cinfo->progressive_mode) {
638 /* Validate progressive scan parameters */
639 if (cinfo->Ss == 0) {
640 if (cinfo->Se != 0)
641 goto bad;
642 } else {
643 /* need not check Ss/Se < 0 since they came from unsigned bytes */
644 if (cinfo->Se < cinfo->Ss || cinfo->Se > cinfo->lim_Se)
645 goto bad;
646 /* AC scans may have only one component */
647 if (cinfo->comps_in_scan != 1)
648 goto bad;
649 }
650 if (cinfo->Ah != 0) {
651 /* Successive approximation refinement scan: must have Al = Ah-1. */
652 if (cinfo->Ah-1 != cinfo->Al)
653 goto bad;
654 }
655 if (cinfo->Al > 13) { /* need not check for < 0 */
656 bad:
657 ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
658 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
659 }
660 /* Update progression status, and verify that scan order is legal.
661 * Note that inter-scan inconsistencies are treated as warnings
662 * not fatal errors ... not clear if this is right way to behave.
663 */
664 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
665 int coefi, cindex = cinfo->cur_comp_info[ci]->component_index;
666 int *coef_bit_ptr = & cinfo->coef_bits[cindex][0];
667 if (cinfo->Ss && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
668 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
669 for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
670 int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
671 if (cinfo->Ah != expected)
672 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
673 coef_bit_ptr[coefi] = cinfo->Al;
674 }
675 }
676 /* Select MCU decoding routine */
677 if (cinfo->Ah == 0) {
678 if (cinfo->Ss == 0)
679 entropy->pub.decode_mcu = decode_mcu_DC_first;
680 else
681 entropy->pub.decode_mcu = decode_mcu_AC_first;
682 } else {
683 if (cinfo->Ss == 0)
684 entropy->pub.decode_mcu = decode_mcu_DC_refine;
685 else
686 entropy->pub.decode_mcu = decode_mcu_AC_refine;
687 }
688 } else {
689 /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
690 * This ought to be an error condition, but we make it a warning.
691 */
692 if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 ||
693 (cinfo->Se < DCTSIZE2 && cinfo->Se != cinfo->lim_Se))
694 WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
695 /* Select MCU decoding routine */
696 entropy->pub.decode_mcu = decode_mcu;
697 }
698
699 /* Allocate & initialize requested statistics areas */
700 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
701 compptr = cinfo->cur_comp_info[ci];
702 if (! cinfo->progressive_mode || (cinfo->Ss == 0 && cinfo->Ah == 0)) {
703 tbl = compptr->dc_tbl_no;
704 if (tbl < 0 || tbl >= NUM_ARITH_TBLS)
705 ERREXIT1(cinfo, JERR_NO_ARITH_TABLE, tbl);
706 if (entropy->dc_stats[tbl] == NULL)
707 entropy->dc_stats[tbl] = (unsigned char *) (*cinfo->mem->alloc_small)
708 ((j_common_ptr) cinfo, JPOOL_IMAGE, DC_STAT_BINS);
709 MEMZERO(entropy->dc_stats[tbl], DC_STAT_BINS);
710 /* Initialize DC predictions to 0 */
711 entropy->last_dc_val[ci] = 0;
712 entropy->dc_context[ci] = 0;
713 }
714 if ((! cinfo->progressive_mode && cinfo->lim_Se) ||
715 (cinfo->progressive_mode && cinfo->Ss)) {
716 tbl = compptr->ac_tbl_no;
717 if (tbl < 0 || tbl >= NUM_ARITH_TBLS)
718 ERREXIT1(cinfo, JERR_NO_ARITH_TABLE, tbl);
719 if (entropy->ac_stats[tbl] == NULL)
720 entropy->ac_stats[tbl] = (unsigned char *) (*cinfo->mem->alloc_small)
721 ((j_common_ptr) cinfo, JPOOL_IMAGE, AC_STAT_BINS);
722 MEMZERO(entropy->ac_stats[tbl], AC_STAT_BINS);
723 }
724 }
725
726 /* Initialize arithmetic decoding variables */
727 entropy->c = 0;
728 entropy->a = 0;
729 entropy->ct = -16; /* force reading 2 initial bytes to fill C */
730
731 /* Initialize restart counter */
732 entropy->restarts_to_go = cinfo->restart_interval;
733}
734
735
736/*
737 * Module initialization routine for arithmetic entropy decoding.
738 */
739
740GLOBAL(void)
741jinit_arith_decoder (j_decompress_ptr cinfo)
742{
743 arith_entropy_ptr entropy;
744 int i;
745
746 entropy = (arith_entropy_ptr)
747 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
748 SIZEOF(arith_entropy_decoder));
749 cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
750 entropy->pub.start_pass = start_pass;
751
752 /* Mark tables unallocated */
753 for (i = 0; i < NUM_ARITH_TBLS; i++) {
754 entropy->dc_stats[i] = NULL;
755 entropy->ac_stats[i] = NULL;
756 }
757
758 /* Initialize index for fixed probability estimation */
759 entropy->fixed_bin[0] = 113;
760
761 if (cinfo->progressive_mode) {
762 /* Create progression status table */
763 int *coef_bit_ptr, ci;
764 cinfo->coef_bits = (int (*)[DCTSIZE2])
765 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
766 cinfo->num_components*DCTSIZE2*SIZEOF(int));
767 coef_bit_ptr = & cinfo->coef_bits[0][0];
768 for (ci = 0; ci < cinfo->num_components; ci++)
769 for (i = 0; i < DCTSIZE2; i++)
770 *coef_bit_ptr++ = -1;
771 }
772}
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