source: trunk/libjpeg/jdphuff.c @ 15

Last change on this file since 15 was 15, checked in by Eugene Romanenko, 15 years ago

needed libs update

File size: 20.7 KB
Line 
1/*
2 * jdphuff.c
3 *
4 * Copyright (C) 1995-1997, 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.
7 *
8 * This file contains Huffman entropy decoding routines for progressive JPEG.
9 *
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.
15 */
16
17#define JPEG_INTERNALS
18#include "jinclude.h"
19#include "jpeglib.h"
20#include "jdhuff.h"             /* Declarations shared with jdhuff.c */
21
22
23#ifdef D_PROGRESSIVE_SUPPORTED
24
25/*
26 * Expanded entropy decoder object for progressive Huffman decoding.
27 *
28 * The savable_state subrecord contains fields that change within an MCU,
29 * but must not be updated permanently until we complete the MCU.
30 */
31
32typedef struct {
33  unsigned int EOBRUN;                  /* remaining EOBs in EOBRUN */
34  int last_dc_val[MAX_COMPS_IN_SCAN];   /* last DC coef for each component */
35} savable_state;
36
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.
40 */
41
42#ifndef NO_STRUCT_ASSIGN
43#define ASSIGN_STATE(dest,src)  ((dest) = (src))
44#else
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])
52#endif
53#endif
54
55
56typedef struct {
57  struct jpeg_entropy_decoder pub; /* public fields */
58
59  /* These fields are loaded into local variables at start of each MCU.
60   * In case of suspension, we exit WITHOUT updating them.
61   */
62  bitread_perm_state bitstate;  /* Bit buffer at start of MCU */
63  savable_state saved;          /* Other state at start of MCU */
64
65  /* These fields are NOT loaded into local working state. */
66  unsigned int restarts_to_go;  /* MCUs left in this restart interval */
67
68  /* Pointers to derived tables (these workspaces have image lifespan) */
69  d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
70
71  d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
72} phuff_entropy_decoder;
73
74typedef phuff_entropy_decoder * phuff_entropy_ptr;
75
76/* Forward declarations */
77METHODDEF(boolean) decode_mcu_DC_first JPP((j_decompress_ptr cinfo,
78                                            JBLOCKROW *MCU_data));
79METHODDEF(boolean) decode_mcu_AC_first JPP((j_decompress_ptr cinfo,
80                                            JBLOCKROW *MCU_data));
81METHODDEF(boolean) decode_mcu_DC_refine JPP((j_decompress_ptr cinfo,
82                                             JBLOCKROW *MCU_data));
83METHODDEF(boolean) decode_mcu_AC_refine JPP((j_decompress_ptr cinfo,
84                                             JBLOCKROW *MCU_data));
85
86
87/*
88 * Initialize for a Huffman-compressed scan.
89 */
90
91METHODDEF(void)
92start_pass_phuff_decoder (j_decompress_ptr cinfo)
93{
94  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
95  boolean is_DC_band, bad;
96  int ci, coefi, tbl;
97  int *coef_bit_ptr;
98  jpeg_component_info * compptr;
99
100  is_DC_band = (cinfo->Ss == 0);
101
102  /* Validate scan parameters */
103  bad = FALSE;
104  if (is_DC_band) {
105    if (cinfo->Se != 0)
106      bad = TRUE;
107  } else {
108    /* need not check Ss/Se < 0 since they came from unsigned bytes */
109    if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2)
110      bad = TRUE;
111    /* AC scans may have only one component */
112    if (cinfo->comps_in_scan != 1)
113      bad = TRUE;
114  }
115  if (cinfo->Ah != 0) {
116    /* Successive approximation refinement scan: must have Al = Ah-1. */
117    if (cinfo->Al != cinfo->Ah-1)
118      bad = TRUE;
119  }
120  if (cinfo->Al > 13)           /* need not check for < 0 */
121    bad = TRUE;
122  /* Arguably the maximum Al value should be less than 13 for 8-bit precision,
123   * but the spec doesn't say so, and we try to be liberal about what we
124   * accept.  Note: large Al values could result in out-of-range DC
125   * coefficients during early scans, leading to bizarre displays due to
126   * overflows in the IDCT math.  But we won't crash.
127   */
128  if (bad)
129    ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
130             cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
131  /* Update progression status, and verify that scan order is legal.
132   * Note that inter-scan inconsistencies are treated as warnings
133   * not fatal errors ... not clear if this is right way to behave.
134   */
135  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
136    int cindex = cinfo->cur_comp_info[ci]->component_index;
137    coef_bit_ptr = & cinfo->coef_bits[cindex][0];
138    if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
139      WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
140    for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
141      int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
142      if (cinfo->Ah != expected)
143        WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
144      coef_bit_ptr[coefi] = cinfo->Al;
145    }
146  }
147
148  /* Select MCU decoding routine */
149  if (cinfo->Ah == 0) {
150    if (is_DC_band)
151      entropy->pub.decode_mcu = decode_mcu_DC_first;
152    else
153      entropy->pub.decode_mcu = decode_mcu_AC_first;
154  } else {
155    if (is_DC_band)
156      entropy->pub.decode_mcu = decode_mcu_DC_refine;
157    else
158      entropy->pub.decode_mcu = decode_mcu_AC_refine;
159  }
160
161  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
162    compptr = cinfo->cur_comp_info[ci];
163    /* Make sure requested tables are present, and compute derived tables.
164     * We may build same derived table more than once, but it's not expensive.
165     */
166    if (is_DC_band) {
167      if (cinfo->Ah == 0) {     /* DC refinement needs no table */
168        tbl = compptr->dc_tbl_no;
169        jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
170                                & entropy->derived_tbls[tbl]);
171      }
172    } else {
173      tbl = compptr->ac_tbl_no;
174      jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
175                              & entropy->derived_tbls[tbl]);
176      /* remember the single active table */
177      entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
178    }
179    /* Initialize DC predictions to 0 */
180    entropy->saved.last_dc_val[ci] = 0;
181  }
182
183  /* Initialize bitread state variables */
184  entropy->bitstate.bits_left = 0;
185  entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
186  entropy->pub.insufficient_data = FALSE;
187
188  /* Initialize private state variables */
189  entropy->saved.EOBRUN = 0;
190
191  /* Initialize restart counter */
192  entropy->restarts_to_go = cinfo->restart_interval;
193}
194
195
196/*
197 * Figure F.12: extend sign bit.
198 * On some machines, a shift and add will be faster than a table lookup.
199 */
200
201#ifdef AVOID_TABLES
202
203#define HUFF_EXTEND(x,s)  ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x))
204
205#else
206
207#define HUFF_EXTEND(x,s)  ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))
208
209static 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 };
212
213static 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 };
218
219#endif /* AVOID_TABLES */
220
221
222/*
223 * Check for a restart marker & resynchronize decoder.
224 * Returns FALSE if must suspend.
225 */
226
227LOCAL(boolean)
228process_restart (j_decompress_ptr cinfo)
229{
230  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
231  int ci;
232
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;
237
238  /* Advance past the RSTn marker */
239  if (! (*cinfo->marker->read_restart_marker) (cinfo))
240    return FALSE;
241
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;
247
248  /* Reset restart counter */
249  entropy->restarts_to_go = cinfo->restart_interval;
250
251  /* Reset out-of-data flag, unless read_restart_marker left us smack up
252   * against a marker.  In that case we will end up treating the next data
253   * segment as empty, and we can avoid producing bogus output pixels by
254   * leaving the flag set.
255   */
256  if (cinfo->unread_marker == 0)
257    entropy->pub.insufficient_data = FALSE;
258
259  return TRUE;
260}
261
262
263/*
264 * Huffman MCU decoding.
265 * Each of these routines decodes and returns one MCU's worth of
266 * Huffman-compressed coefficients.
267 * The coefficients are reordered from zigzag order into natural array order,
268 * but are not dequantized.
269 *
270 * The i'th block of the MCU is stored into the block pointed to by
271 * MCU_data[i].  WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
272 *
273 * We return FALSE if data source requested suspension.  In that case no
274 * changes have been made to permanent state.  (Exception: some output
275 * coefficients may already have been assigned.  This is harmless for
276 * spectral selection, since we'll just re-assign them on the next call.
277 * Successive approximation AC refinement has to be more careful, however.)
278 */
279
280/*
281 * MCU decoding for DC initial scan (either spectral selection,
282 * or first pass of successive approximation).
283 */
284
285METHODDEF(boolean)
286decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
287{   
288  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
289  int Al = cinfo->Al;
290  register int s, r;
291  int blkn, ci;
292  JBLOCKROW block;
293  BITREAD_STATE_VARS;
294  savable_state state;
295  d_derived_tbl * tbl;
296  jpeg_component_info * compptr;
297
298  /* Process restart marker if needed; may have to suspend */
299  if (cinfo->restart_interval) {
300    if (entropy->restarts_to_go == 0)
301      if (! process_restart(cinfo))
302        return FALSE;
303  }
304
305  /* If we've run out of data, just leave the MCU set to zeroes.
306   * This way, we return uniform gray for the remainder of the segment.
307   */
308  if (! entropy->pub.insufficient_data) {
309
310    /* Load up working state */
311    BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
312    ASSIGN_STATE(state, entropy->saved);
313
314    /* Outer loop handles each block in the MCU */
315
316    for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
317      block = MCU_data[blkn];
318      ci = cinfo->MCU_membership[blkn];
319      compptr = cinfo->cur_comp_info[ci];
320      tbl = entropy->derived_tbls[compptr->dc_tbl_no];
321
322      /* Decode a single block's worth of coefficients */
323
324      /* Section F.2.2.1: decode the DC coefficient difference */
325      HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
326      if (s) {
327        CHECK_BIT_BUFFER(br_state, s, return FALSE);
328        r = GET_BITS(s);
329        s = HUFF_EXTEND(r, s);
330      }
331
332      /* Convert DC difference to actual value, update last_dc_val */
333      s += state.last_dc_val[ci];
334      state.last_dc_val[ci] = s;
335      /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */
336      (*block)[0] = (JCOEF) (s << Al);
337    }
338
339    /* Completed MCU, so update state */
340    BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
341    ASSIGN_STATE(entropy->saved, state);
342  }
343
344  /* Account for restart interval (no-op if not using restarts) */
345  entropy->restarts_to_go--;
346
347  return TRUE;
348}
349
350
351/*
352 * MCU decoding for AC initial scan (either spectral selection,
353 * or first pass of successive approximation).
354 */
355
356METHODDEF(boolean)
357decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
358{   
359  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
360  int Se = cinfo->Se;
361  int Al = cinfo->Al;
362  register int s, k, r;
363  unsigned int EOBRUN;
364  JBLOCKROW block;
365  BITREAD_STATE_VARS;
366  d_derived_tbl * tbl;
367
368  /* Process restart marker if needed; may have to suspend */
369  if (cinfo->restart_interval) {
370    if (entropy->restarts_to_go == 0)
371      if (! process_restart(cinfo))
372        return FALSE;
373  }
374
375  /* If we've run out of data, just leave the MCU set to zeroes.
376   * This way, we return uniform gray for the remainder of the segment.
377   */
378  if (! entropy->pub.insufficient_data) {
379
380    /* Load up working state.
381     * We can avoid loading/saving bitread state if in an EOB run.
382     */
383    EOBRUN = entropy->saved.EOBRUN;     /* only part of saved state we need */
384
385    /* There is always only one block per MCU */
386
387    if (EOBRUN > 0)             /* if it's a band of zeroes... */
388      EOBRUN--;                 /* ...process it now (we do nothing) */
389    else {
390      BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
391      block = MCU_data[0];
392      tbl = entropy->ac_derived_tbl;
393
394      for (k = cinfo->Ss; k <= Se; k++) {
395        HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
396        r = s >> 4;
397        s &= 15;
398        if (s) {
399          k += r;
400          CHECK_BIT_BUFFER(br_state, s, return FALSE);
401          r = GET_BITS(s);
402          s = HUFF_EXTEND(r, s);
403          /* Scale and output coefficient in natural (dezigzagged) order */
404          (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al);
405        } else {
406          if (r == 15) {        /* ZRL */
407            k += 15;            /* skip 15 zeroes in band */
408          } else {              /* EOBr, run length is 2^r + appended bits */
409            EOBRUN = 1 << r;
410            if (r) {            /* EOBr, r > 0 */
411              CHECK_BIT_BUFFER(br_state, r, return FALSE);
412              r = GET_BITS(r);
413              EOBRUN += r;
414            }
415            EOBRUN--;           /* this band is processed at this moment */
416            break;              /* force end-of-band */
417          }
418        }
419      }
420
421      BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
422    }
423
424    /* Completed MCU, so update state */
425    entropy->saved.EOBRUN = EOBRUN;     /* only part of saved state we need */
426  }
427
428  /* Account for restart interval (no-op if not using restarts) */
429  entropy->restarts_to_go--;
430
431  return TRUE;
432}
433
434
435/*
436 * MCU decoding for DC successive approximation refinement scan.
437 * Note: we assume such scans can be multi-component, although the spec
438 * is not very clear on the point.
439 */
440
441METHODDEF(boolean)
442decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
443{   
444  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
445  int p1 = 1 << cinfo->Al;      /* 1 in the bit position being coded */
446  int blkn;
447  JBLOCKROW block;
448  BITREAD_STATE_VARS;
449
450  /* Process restart marker if needed; may have to suspend */
451  if (cinfo->restart_interval) {
452    if (entropy->restarts_to_go == 0)
453      if (! process_restart(cinfo))
454        return FALSE;
455  }
456
457  /* Not worth the cycles to check insufficient_data here,
458   * since we will not change the data anyway if we read zeroes.
459   */
460
461  /* Load up working state */
462  BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
463
464  /* Outer loop handles each block in the MCU */
465
466  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
467    block = MCU_data[blkn];
468
469    /* Encoded data is simply the next bit of the two's-complement DC value */
470    CHECK_BIT_BUFFER(br_state, 1, return FALSE);
471    if (GET_BITS(1))
472      (*block)[0] |= p1;
473    /* Note: since we use |=, repeating the assignment later is safe */
474  }
475
476  /* Completed MCU, so update state */
477  BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
478
479  /* Account for restart interval (no-op if not using restarts) */
480  entropy->restarts_to_go--;
481
482  return TRUE;
483}
484
485
486/*
487 * MCU decoding for AC successive approximation refinement scan.
488 */
489
490METHODDEF(boolean)
491decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
492{   
493  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
494  int Se = cinfo->Se;
495  int p1 = 1 << cinfo->Al;      /* 1 in the bit position being coded */
496  int m1 = (-1) << cinfo->Al;   /* -1 in the bit position being coded */
497  register int s, k, r;
498  unsigned int EOBRUN;
499  JBLOCKROW block;
500  JCOEFPTR thiscoef;
501  BITREAD_STATE_VARS;
502  d_derived_tbl * tbl;
503  int num_newnz;
504  int newnz_pos[DCTSIZE2];
505
506  /* Process restart marker if needed; may have to suspend */
507  if (cinfo->restart_interval) {
508    if (entropy->restarts_to_go == 0)
509      if (! process_restart(cinfo))
510        return FALSE;
511  }
512
513  /* If we've run out of data, don't modify the MCU.
514   */
515  if (! entropy->pub.insufficient_data) {
516
517    /* Load up working state */
518    BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
519    EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
520
521    /* There is always only one block per MCU */
522    block = MCU_data[0];
523    tbl = entropy->ac_derived_tbl;
524
525    /* If we are forced to suspend, we must undo the assignments to any newly
526     * nonzero coefficients in the block, because otherwise we'd get confused
527     * next time about which coefficients were already nonzero.
528     * But we need not undo addition of bits to already-nonzero coefficients;
529     * instead, we can test the current bit to see if we already did it.
530     */
531    num_newnz = 0;
532
533    /* initialize coefficient loop counter to start of band */
534    k = cinfo->Ss;
535
536    if (EOBRUN == 0) {
537      for (; k <= Se; k++) {
538        HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
539        r = s >> 4;
540        s &= 15;
541        if (s) {
542          if (s != 1)           /* size of new coef should always be 1 */
543            WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
544          CHECK_BIT_BUFFER(br_state, 1, goto undoit);
545          if (GET_BITS(1))
546            s = p1;             /* newly nonzero coef is positive */
547          else
548            s = m1;             /* newly nonzero coef is negative */
549        } else {
550          if (r != 15) {
551            EOBRUN = 1 << r;    /* EOBr, run length is 2^r + appended bits */
552            if (r) {
553              CHECK_BIT_BUFFER(br_state, r, goto undoit);
554              r = GET_BITS(r);
555              EOBRUN += r;
556            }
557            break;              /* rest of block is handled by EOB logic */
558          }
559          /* note s = 0 for processing ZRL */
560        }
561        /* Advance over already-nonzero coefs and r still-zero coefs,
562         * appending correction bits to the nonzeroes.  A correction bit is 1
563         * if the absolute value of the coefficient must be increased.
564         */
565        do {
566          thiscoef = *block + jpeg_natural_order[k];
567          if (*thiscoef != 0) {
568            CHECK_BIT_BUFFER(br_state, 1, goto undoit);
569            if (GET_BITS(1)) {
570              if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
571                if (*thiscoef >= 0)
572                  *thiscoef += p1;
573                else
574                  *thiscoef += m1;
575              }
576            }
577          } else {
578            if (--r < 0)
579              break;            /* reached target zero coefficient */
580          }
581          k++;
582        } while (k <= Se);
583        if (s) {
584          int pos = jpeg_natural_order[k];
585          /* Output newly nonzero coefficient */
586          (*block)[pos] = (JCOEF) s;
587          /* Remember its position in case we have to suspend */
588          newnz_pos[num_newnz++] = pos;
589        }
590      }
591    }
592
593    if (EOBRUN > 0) {
594      /* Scan any remaining coefficient positions after the end-of-band
595       * (the last newly nonzero coefficient, if any).  Append a correction
596       * bit to each already-nonzero coefficient.  A correction bit is 1
597       * if the absolute value of the coefficient must be increased.
598       */
599      for (; k <= Se; k++) {
600        thiscoef = *block + jpeg_natural_order[k];
601        if (*thiscoef != 0) {
602          CHECK_BIT_BUFFER(br_state, 1, goto undoit);
603          if (GET_BITS(1)) {
604            if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
605              if (*thiscoef >= 0)
606                *thiscoef += p1;
607              else
608                *thiscoef += m1;
609            }
610          }
611        }
612      }
613      /* Count one block completed in EOB run */
614      EOBRUN--;
615    }
616
617    /* Completed MCU, so update state */
618    BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
619    entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
620  }
621
622  /* Account for restart interval (no-op if not using restarts) */
623  entropy->restarts_to_go--;
624
625  return TRUE;
626
627undoit:
628  /* Re-zero any output coefficients that we made newly nonzero */
629  while (num_newnz > 0)
630    (*block)[newnz_pos[--num_newnz]] = 0;
631
632  return FALSE;
633}
634
635
636/*
637 * Module initialization routine for progressive Huffman entropy decoding.
638 */
639
640GLOBAL(void)
641jinit_phuff_decoder (j_decompress_ptr cinfo)
642{
643  phuff_entropy_ptr entropy;
644  int *coef_bit_ptr;
645  int ci, i;
646
647  entropy = (phuff_entropy_ptr)
648    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
649                                SIZEOF(phuff_entropy_decoder));
650  cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
651  entropy->pub.start_pass = start_pass_phuff_decoder;
652
653  /* Mark derived tables unallocated */
654  for (i = 0; i < NUM_HUFF_TBLS; i++) {
655    entropy->derived_tbls[i] = NULL;
656  }
657
658  /* Create progression status table */
659  cinfo->coef_bits = (int (*)[DCTSIZE2])
660    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
661                                cinfo->num_components*DCTSIZE2*SIZEOF(int));
662  coef_bit_ptr = & cinfo->coef_bits[0][0];
663  for (ci = 0; ci < cinfo->num_components; ci++) 
664    for (i = 0; i < DCTSIZE2; i++)
665      *coef_bit_ptr++ = -1;
666}
667
668#endif /* D_PROGRESSIVE_SUPPORTED */
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