source: trunk/libjpeg/jcphuff.c @ 15

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

needed libs update

File size: 25.3 KB
Line 
1/*
2 * jcphuff.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 encoding routines for progressive JPEG.
9 *
10 * We do not support output suspension in this module, since the library
11 * currently does not allow multiple-scan files to be written with output
12 * suspension.
13 */
14
15#define JPEG_INTERNALS
16#include "jinclude.h"
17#include "jpeglib.h"
18#include "jchuff.h"             /* Declarations shared with jchuff.c */
19
20#ifdef C_PROGRESSIVE_SUPPORTED
21
22/* Expanded entropy encoder object for progressive Huffman encoding. */
23
24typedef struct {
25  struct jpeg_entropy_encoder pub; /* public fields */
26
27  /* Mode flag: TRUE for optimization, FALSE for actual data output */
28  boolean gather_statistics;
29
30  /* Bit-level coding status.
31   * next_output_byte/free_in_buffer are local copies of cinfo->dest fields.
32   */
33  JOCTET * next_output_byte;    /* => next byte to write in buffer */
34  size_t free_in_buffer;        /* # of byte spaces remaining in buffer */
35  INT32 put_buffer;             /* current bit-accumulation buffer */
36  int put_bits;                 /* # of bits now in it */
37  j_compress_ptr cinfo;         /* link to cinfo (needed for dump_buffer) */
38
39  /* Coding status for DC components */
40  int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
41
42  /* Coding status for AC components */
43  int ac_tbl_no;                /* the table number of the single component */
44  unsigned int EOBRUN;          /* run length of EOBs */
45  unsigned int BE;              /* # of buffered correction bits before MCU */
46  char * bit_buffer;            /* buffer for correction bits (1 per char) */
47  /* packing correction bits tightly would save some space but cost time... */
48
49  unsigned int restarts_to_go;  /* MCUs left in this restart interval */
50  int next_restart_num;         /* next restart number to write (0-7) */
51
52  /* Pointers to derived tables (these workspaces have image lifespan).
53   * Since any one scan codes only DC or only AC, we only need one set
54   * of tables, not one for DC and one for AC.
55   */
56  c_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
57
58  /* Statistics tables for optimization; again, one set is enough */
59  long * count_ptrs[NUM_HUFF_TBLS];
60} phuff_entropy_encoder;
61
62typedef phuff_entropy_encoder * phuff_entropy_ptr;
63
64/* MAX_CORR_BITS is the number of bits the AC refinement correction-bit
65 * buffer can hold.  Larger sizes may slightly improve compression, but
66 * 1000 is already well into the realm of overkill.
67 * The minimum safe size is 64 bits.
68 */
69
70#define MAX_CORR_BITS  1000     /* Max # of correction bits I can buffer */
71
72/* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than INT32.
73 * We assume that int right shift is unsigned if INT32 right shift is,
74 * which should be safe.
75 */
76
77#ifdef RIGHT_SHIFT_IS_UNSIGNED
78#define ISHIFT_TEMPS    int ishift_temp;
79#define IRIGHT_SHIFT(x,shft)  \
80        ((ishift_temp = (x)) < 0 ? \
81         (ishift_temp >> (shft)) | ((~0) << (16-(shft))) : \
82         (ishift_temp >> (shft)))
83#else
84#define ISHIFT_TEMPS
85#define IRIGHT_SHIFT(x,shft)    ((x) >> (shft))
86#endif
87
88/* Forward declarations */
89METHODDEF(boolean) encode_mcu_DC_first JPP((j_compress_ptr cinfo,
90                                            JBLOCKROW *MCU_data));
91METHODDEF(boolean) encode_mcu_AC_first JPP((j_compress_ptr cinfo,
92                                            JBLOCKROW *MCU_data));
93METHODDEF(boolean) encode_mcu_DC_refine JPP((j_compress_ptr cinfo,
94                                             JBLOCKROW *MCU_data));
95METHODDEF(boolean) encode_mcu_AC_refine JPP((j_compress_ptr cinfo,
96                                             JBLOCKROW *MCU_data));
97METHODDEF(void) finish_pass_phuff JPP((j_compress_ptr cinfo));
98METHODDEF(void) finish_pass_gather_phuff JPP((j_compress_ptr cinfo));
99
100
101/*
102 * Initialize for a Huffman-compressed scan using progressive JPEG.
103 */
104
105METHODDEF(void)
106start_pass_phuff (j_compress_ptr cinfo, boolean gather_statistics)
107{ 
108  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
109  boolean is_DC_band;
110  int ci, tbl;
111  jpeg_component_info * compptr;
112
113  entropy->cinfo = cinfo;
114  entropy->gather_statistics = gather_statistics;
115
116  is_DC_band = (cinfo->Ss == 0);
117
118  /* We assume jcmaster.c already validated the scan parameters. */
119
120  /* Select execution routines */
121  if (cinfo->Ah == 0) {
122    if (is_DC_band)
123      entropy->pub.encode_mcu = encode_mcu_DC_first;
124    else
125      entropy->pub.encode_mcu = encode_mcu_AC_first;
126  } else {
127    if (is_DC_band)
128      entropy->pub.encode_mcu = encode_mcu_DC_refine;
129    else {
130      entropy->pub.encode_mcu = encode_mcu_AC_refine;
131      /* AC refinement needs a correction bit buffer */
132      if (entropy->bit_buffer == NULL)
133        entropy->bit_buffer = (char *)
134          (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
135                                      MAX_CORR_BITS * SIZEOF(char));
136    }
137  }
138  if (gather_statistics)
139    entropy->pub.finish_pass = finish_pass_gather_phuff;
140  else
141    entropy->pub.finish_pass = finish_pass_phuff;
142
143  /* Only DC coefficients may be interleaved, so cinfo->comps_in_scan = 1
144   * for AC coefficients.
145   */
146  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
147    compptr = cinfo->cur_comp_info[ci];
148    /* Initialize DC predictions to 0 */
149    entropy->last_dc_val[ci] = 0;
150    /* Get table index */
151    if (is_DC_band) {
152      if (cinfo->Ah != 0)       /* DC refinement needs no table */
153        continue;
154      tbl = compptr->dc_tbl_no;
155    } else {
156      entropy->ac_tbl_no = tbl = compptr->ac_tbl_no;
157    }
158    if (gather_statistics) {
159      /* Check for invalid table index */
160      /* (make_c_derived_tbl does this in the other path) */
161      if (tbl < 0 || tbl >= NUM_HUFF_TBLS)
162        ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
163      /* Allocate and zero the statistics tables */
164      /* Note that jpeg_gen_optimal_table expects 257 entries in each table! */
165      if (entropy->count_ptrs[tbl] == NULL)
166        entropy->count_ptrs[tbl] = (long *)
167          (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
168                                      257 * SIZEOF(long));
169      MEMZERO(entropy->count_ptrs[tbl], 257 * SIZEOF(long));
170    } else {
171      /* Compute derived values for Huffman table */
172      /* We may do this more than once for a table, but it's not expensive */
173      jpeg_make_c_derived_tbl(cinfo, is_DC_band, tbl,
174                              & entropy->derived_tbls[tbl]);
175    }
176  }
177
178  /* Initialize AC stuff */
179  entropy->EOBRUN = 0;
180  entropy->BE = 0;
181
182  /* Initialize bit buffer to empty */
183  entropy->put_buffer = 0;
184  entropy->put_bits = 0;
185
186  /* Initialize restart stuff */
187  entropy->restarts_to_go = cinfo->restart_interval;
188  entropy->next_restart_num = 0;
189}
190
191
192/* Outputting bytes to the file.
193 * NB: these must be called only when actually outputting,
194 * that is, entropy->gather_statistics == FALSE.
195 */
196
197/* Emit a byte */
198#define emit_byte(entropy,val)  \
199        { *(entropy)->next_output_byte++ = (JOCTET) (val);  \
200          if (--(entropy)->free_in_buffer == 0)  \
201            dump_buffer(entropy); }
202
203
204LOCAL(void)
205dump_buffer (phuff_entropy_ptr entropy)
206/* Empty the output buffer; we do not support suspension in this module. */
207{
208  struct jpeg_destination_mgr * dest = entropy->cinfo->dest;
209
210  if (! (*dest->empty_output_buffer) (entropy->cinfo))
211    ERREXIT(entropy->cinfo, JERR_CANT_SUSPEND);
212  /* After a successful buffer dump, must reset buffer pointers */
213  entropy->next_output_byte = dest->next_output_byte;
214  entropy->free_in_buffer = dest->free_in_buffer;
215}
216
217
218/* Outputting bits to the file */
219
220/* Only the right 24 bits of put_buffer are used; the valid bits are
221 * left-justified in this part.  At most 16 bits can be passed to emit_bits
222 * in one call, and we never retain more than 7 bits in put_buffer
223 * between calls, so 24 bits are sufficient.
224 */
225
226INLINE
227LOCAL(void)
228emit_bits (phuff_entropy_ptr entropy, unsigned int code, int size)
229/* Emit some bits, unless we are in gather mode */
230{
231  /* This routine is heavily used, so it's worth coding tightly. */
232  register INT32 put_buffer = (INT32) code;
233  register int put_bits = entropy->put_bits;
234
235  /* if size is 0, caller used an invalid Huffman table entry */
236  if (size == 0)
237    ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
238
239  if (entropy->gather_statistics)
240    return;                     /* do nothing if we're only getting stats */
241
242  put_buffer &= (((INT32) 1)<<size) - 1; /* mask off any extra bits in code */
243 
244  put_bits += size;             /* new number of bits in buffer */
245 
246  put_buffer <<= 24 - put_bits; /* align incoming bits */
247
248  put_buffer |= entropy->put_buffer; /* and merge with old buffer contents */
249
250  while (put_bits >= 8) {
251    int c = (int) ((put_buffer >> 16) & 0xFF);
252   
253    emit_byte(entropy, c);
254    if (c == 0xFF) {            /* need to stuff a zero byte? */
255      emit_byte(entropy, 0);
256    }
257    put_buffer <<= 8;
258    put_bits -= 8;
259  }
260
261  entropy->put_buffer = put_buffer; /* update variables */
262  entropy->put_bits = put_bits;
263}
264
265
266LOCAL(void)
267flush_bits (phuff_entropy_ptr entropy)
268{
269  emit_bits(entropy, 0x7F, 7); /* fill any partial byte with ones */
270  entropy->put_buffer = 0;     /* and reset bit-buffer to empty */
271  entropy->put_bits = 0;
272}
273
274
275/*
276 * Emit (or just count) a Huffman symbol.
277 */
278
279INLINE
280LOCAL(void)
281emit_symbol (phuff_entropy_ptr entropy, int tbl_no, int symbol)
282{
283  if (entropy->gather_statistics)
284    entropy->count_ptrs[tbl_no][symbol]++;
285  else {
286    c_derived_tbl * tbl = entropy->derived_tbls[tbl_no];
287    emit_bits(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]);
288  }
289}
290
291
292/*
293 * Emit bits from a correction bit buffer.
294 */
295
296LOCAL(void)
297emit_buffered_bits (phuff_entropy_ptr entropy, char * bufstart,
298                    unsigned int nbits)
299{
300  if (entropy->gather_statistics)
301    return;                     /* no real work */
302
303  while (nbits > 0) {
304    emit_bits(entropy, (unsigned int) (*bufstart), 1);
305    bufstart++;
306    nbits--;
307  }
308}
309
310
311/*
312 * Emit any pending EOBRUN symbol.
313 */
314
315LOCAL(void)
316emit_eobrun (phuff_entropy_ptr entropy)
317{
318  register int temp, nbits;
319
320  if (entropy->EOBRUN > 0) {    /* if there is any pending EOBRUN */
321    temp = entropy->EOBRUN;
322    nbits = 0;
323    while ((temp >>= 1))
324      nbits++;
325    /* safety check: shouldn't happen given limited correction-bit buffer */
326    if (nbits > 14)
327      ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
328
329    emit_symbol(entropy, entropy->ac_tbl_no, nbits << 4);
330    if (nbits)
331      emit_bits(entropy, entropy->EOBRUN, nbits);
332
333    entropy->EOBRUN = 0;
334
335    /* Emit any buffered correction bits */
336    emit_buffered_bits(entropy, entropy->bit_buffer, entropy->BE);
337    entropy->BE = 0;
338  }
339}
340
341
342/*
343 * Emit a restart marker & resynchronize predictions.
344 */
345
346LOCAL(void)
347emit_restart (phuff_entropy_ptr entropy, int restart_num)
348{
349  int ci;
350
351  emit_eobrun(entropy);
352
353  if (! entropy->gather_statistics) {
354    flush_bits(entropy);
355    emit_byte(entropy, 0xFF);
356    emit_byte(entropy, JPEG_RST0 + restart_num);
357  }
358
359  if (entropy->cinfo->Ss == 0) {
360    /* Re-initialize DC predictions to 0 */
361    for (ci = 0; ci < entropy->cinfo->comps_in_scan; ci++)
362      entropy->last_dc_val[ci] = 0;
363  } else {
364    /* Re-initialize all AC-related fields to 0 */
365    entropy->EOBRUN = 0;
366    entropy->BE = 0;
367  }
368}
369
370
371/*
372 * MCU encoding for DC initial scan (either spectral selection,
373 * or first pass of successive approximation).
374 */
375
376METHODDEF(boolean)
377encode_mcu_DC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
378{
379  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
380  register int temp, temp2;
381  register int nbits;
382  int blkn, ci;
383  int Al = cinfo->Al;
384  JBLOCKROW block;
385  jpeg_component_info * compptr;
386  ISHIFT_TEMPS
387
388  entropy->next_output_byte = cinfo->dest->next_output_byte;
389  entropy->free_in_buffer = cinfo->dest->free_in_buffer;
390
391  /* Emit restart marker if needed */
392  if (cinfo->restart_interval)
393    if (entropy->restarts_to_go == 0)
394      emit_restart(entropy, entropy->next_restart_num);
395
396  /* Encode the MCU data blocks */
397  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
398    block = MCU_data[blkn];
399    ci = cinfo->MCU_membership[blkn];
400    compptr = cinfo->cur_comp_info[ci];
401
402    /* Compute the DC value after the required point transform by Al.
403     * This is simply an arithmetic right shift.
404     */
405    temp2 = IRIGHT_SHIFT((int) ((*block)[0]), Al);
406
407    /* DC differences are figured on the point-transformed values. */
408    temp = temp2 - entropy->last_dc_val[ci];
409    entropy->last_dc_val[ci] = temp2;
410
411    /* Encode the DC coefficient difference per section G.1.2.1 */
412    temp2 = temp;
413    if (temp < 0) {
414      temp = -temp;             /* temp is abs value of input */
415      /* For a negative input, want temp2 = bitwise complement of abs(input) */
416      /* This code assumes we are on a two's complement machine */
417      temp2--;
418    }
419   
420    /* Find the number of bits needed for the magnitude of the coefficient */
421    nbits = 0;
422    while (temp) {
423      nbits++;
424      temp >>= 1;
425    }
426    /* Check for out-of-range coefficient values.
427     * Since we're encoding a difference, the range limit is twice as much.
428     */
429    if (nbits > MAX_COEF_BITS+1)
430      ERREXIT(cinfo, JERR_BAD_DCT_COEF);
431   
432    /* Count/emit the Huffman-coded symbol for the number of bits */
433    emit_symbol(entropy, compptr->dc_tbl_no, nbits);
434   
435    /* Emit that number of bits of the value, if positive, */
436    /* or the complement of its magnitude, if negative. */
437    if (nbits)                  /* emit_bits rejects calls with size 0 */
438      emit_bits(entropy, (unsigned int) temp2, nbits);
439  }
440
441  cinfo->dest->next_output_byte = entropy->next_output_byte;
442  cinfo->dest->free_in_buffer = entropy->free_in_buffer;
443
444  /* Update restart-interval state too */
445  if (cinfo->restart_interval) {
446    if (entropy->restarts_to_go == 0) {
447      entropy->restarts_to_go = cinfo->restart_interval;
448      entropy->next_restart_num++;
449      entropy->next_restart_num &= 7;
450    }
451    entropy->restarts_to_go--;
452  }
453
454  return TRUE;
455}
456
457
458/*
459 * MCU encoding for AC initial scan (either spectral selection,
460 * or first pass of successive approximation).
461 */
462
463METHODDEF(boolean)
464encode_mcu_AC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
465{
466  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
467  register int temp, temp2;
468  register int nbits;
469  register int r, k;
470  int Se = cinfo->Se;
471  int Al = cinfo->Al;
472  JBLOCKROW block;
473
474  entropy->next_output_byte = cinfo->dest->next_output_byte;
475  entropy->free_in_buffer = cinfo->dest->free_in_buffer;
476
477  /* Emit restart marker if needed */
478  if (cinfo->restart_interval)
479    if (entropy->restarts_to_go == 0)
480      emit_restart(entropy, entropy->next_restart_num);
481
482  /* Encode the MCU data block */
483  block = MCU_data[0];
484
485  /* Encode the AC coefficients per section G.1.2.2, fig. G.3 */
486 
487  r = 0;                        /* r = run length of zeros */
488   
489  for (k = cinfo->Ss; k <= Se; k++) {
490    if ((temp = (*block)[jpeg_natural_order[k]]) == 0) {
491      r++;
492      continue;
493    }
494    /* We must apply the point transform by Al.  For AC coefficients this
495     * is an integer division with rounding towards 0.  To do this portably
496     * in C, we shift after obtaining the absolute value; so the code is
497     * interwoven with finding the abs value (temp) and output bits (temp2).
498     */
499    if (temp < 0) {
500      temp = -temp;             /* temp is abs value of input */
501      temp >>= Al;              /* apply the point transform */
502      /* For a negative coef, want temp2 = bitwise complement of abs(coef) */
503      temp2 = ~temp;
504    } else {
505      temp >>= Al;              /* apply the point transform */
506      temp2 = temp;
507    }
508    /* Watch out for case that nonzero coef is zero after point transform */
509    if (temp == 0) {
510      r++;
511      continue;
512    }
513
514    /* Emit any pending EOBRUN */
515    if (entropy->EOBRUN > 0)
516      emit_eobrun(entropy);
517    /* if run length > 15, must emit special run-length-16 codes (0xF0) */
518    while (r > 15) {
519      emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
520      r -= 16;
521    }
522
523    /* Find the number of bits needed for the magnitude of the coefficient */
524    nbits = 1;                  /* there must be at least one 1 bit */
525    while ((temp >>= 1))
526      nbits++;
527    /* Check for out-of-range coefficient values */
528    if (nbits > MAX_COEF_BITS)
529      ERREXIT(cinfo, JERR_BAD_DCT_COEF);
530
531    /* Count/emit Huffman symbol for run length / number of bits */
532    emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + nbits);
533
534    /* Emit that number of bits of the value, if positive, */
535    /* or the complement of its magnitude, if negative. */
536    emit_bits(entropy, (unsigned int) temp2, nbits);
537
538    r = 0;                      /* reset zero run length */
539  }
540
541  if (r > 0) {                  /* If there are trailing zeroes, */
542    entropy->EOBRUN++;          /* count an EOB */
543    if (entropy->EOBRUN == 0x7FFF)
544      emit_eobrun(entropy);     /* force it out to avoid overflow */
545  }
546
547  cinfo->dest->next_output_byte = entropy->next_output_byte;
548  cinfo->dest->free_in_buffer = entropy->free_in_buffer;
549
550  /* Update restart-interval state too */
551  if (cinfo->restart_interval) {
552    if (entropy->restarts_to_go == 0) {
553      entropy->restarts_to_go = cinfo->restart_interval;
554      entropy->next_restart_num++;
555      entropy->next_restart_num &= 7;
556    }
557    entropy->restarts_to_go--;
558  }
559
560  return TRUE;
561}
562
563
564/*
565 * MCU encoding for DC successive approximation refinement scan.
566 * Note: we assume such scans can be multi-component, although the spec
567 * is not very clear on the point.
568 */
569
570METHODDEF(boolean)
571encode_mcu_DC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
572{
573  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
574  register int temp;
575  int blkn;
576  int Al = cinfo->Al;
577  JBLOCKROW block;
578
579  entropy->next_output_byte = cinfo->dest->next_output_byte;
580  entropy->free_in_buffer = cinfo->dest->free_in_buffer;
581
582  /* Emit restart marker if needed */
583  if (cinfo->restart_interval)
584    if (entropy->restarts_to_go == 0)
585      emit_restart(entropy, entropy->next_restart_num);
586
587  /* Encode the MCU data blocks */
588  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
589    block = MCU_data[blkn];
590
591    /* We simply emit the Al'th bit of the DC coefficient value. */
592    temp = (*block)[0];
593    emit_bits(entropy, (unsigned int) (temp >> Al), 1);
594  }
595
596  cinfo->dest->next_output_byte = entropy->next_output_byte;
597  cinfo->dest->free_in_buffer = entropy->free_in_buffer;
598
599  /* Update restart-interval state too */
600  if (cinfo->restart_interval) {
601    if (entropy->restarts_to_go == 0) {
602      entropy->restarts_to_go = cinfo->restart_interval;
603      entropy->next_restart_num++;
604      entropy->next_restart_num &= 7;
605    }
606    entropy->restarts_to_go--;
607  }
608
609  return TRUE;
610}
611
612
613/*
614 * MCU encoding for AC successive approximation refinement scan.
615 */
616
617METHODDEF(boolean)
618encode_mcu_AC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
619{
620  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
621  register int temp;
622  register int r, k;
623  int EOB;
624  char *BR_buffer;
625  unsigned int BR;
626  int Se = cinfo->Se;
627  int Al = cinfo->Al;
628  JBLOCKROW block;
629  int absvalues[DCTSIZE2];
630
631  entropy->next_output_byte = cinfo->dest->next_output_byte;
632  entropy->free_in_buffer = cinfo->dest->free_in_buffer;
633
634  /* Emit restart marker if needed */
635  if (cinfo->restart_interval)
636    if (entropy->restarts_to_go == 0)
637      emit_restart(entropy, entropy->next_restart_num);
638
639  /* Encode the MCU data block */
640  block = MCU_data[0];
641
642  /* It is convenient to make a pre-pass to determine the transformed
643   * coefficients' absolute values and the EOB position.
644   */
645  EOB = 0;
646  for (k = cinfo->Ss; k <= Se; k++) {
647    temp = (*block)[jpeg_natural_order[k]];
648    /* We must apply the point transform by Al.  For AC coefficients this
649     * is an integer division with rounding towards 0.  To do this portably
650     * in C, we shift after obtaining the absolute value.
651     */
652    if (temp < 0)
653      temp = -temp;             /* temp is abs value of input */
654    temp >>= Al;                /* apply the point transform */
655    absvalues[k] = temp;        /* save abs value for main pass */
656    if (temp == 1)
657      EOB = k;                  /* EOB = index of last newly-nonzero coef */
658  }
659
660  /* Encode the AC coefficients per section G.1.2.3, fig. G.7 */
661 
662  r = 0;                        /* r = run length of zeros */
663  BR = 0;                       /* BR = count of buffered bits added now */
664  BR_buffer = entropy->bit_buffer + entropy->BE; /* Append bits to buffer */
665
666  for (k = cinfo->Ss; k <= Se; k++) {
667    if ((temp = absvalues[k]) == 0) {
668      r++;
669      continue;
670    }
671
672    /* Emit any required ZRLs, but not if they can be folded into EOB */
673    while (r > 15 && k <= EOB) {
674      /* emit any pending EOBRUN and the BE correction bits */
675      emit_eobrun(entropy);
676      /* Emit ZRL */
677      emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
678      r -= 16;
679      /* Emit buffered correction bits that must be associated with ZRL */
680      emit_buffered_bits(entropy, BR_buffer, BR);
681      BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
682      BR = 0;
683    }
684
685    /* If the coef was previously nonzero, it only needs a correction bit.
686     * NOTE: a straight translation of the spec's figure G.7 would suggest
687     * that we also need to test r > 15.  But if r > 15, we can only get here
688     * if k > EOB, which implies that this coefficient is not 1.
689     */
690    if (temp > 1) {
691      /* The correction bit is the next bit of the absolute value. */
692      BR_buffer[BR++] = (char) (temp & 1);
693      continue;
694    }
695
696    /* Emit any pending EOBRUN and the BE correction bits */
697    emit_eobrun(entropy);
698
699    /* Count/emit Huffman symbol for run length / number of bits */
700    emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + 1);
701
702    /* Emit output bit for newly-nonzero coef */
703    temp = ((*block)[jpeg_natural_order[k]] < 0) ? 0 : 1;
704    emit_bits(entropy, (unsigned int) temp, 1);
705
706    /* Emit buffered correction bits that must be associated with this code */
707    emit_buffered_bits(entropy, BR_buffer, BR);
708    BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
709    BR = 0;
710    r = 0;                      /* reset zero run length */
711  }
712
713  if (r > 0 || BR > 0) {        /* If there are trailing zeroes, */
714    entropy->EOBRUN++;          /* count an EOB */
715    entropy->BE += BR;          /* concat my correction bits to older ones */
716    /* We force out the EOB if we risk either:
717     * 1. overflow of the EOB counter;
718     * 2. overflow of the correction bit buffer during the next MCU.
719     */
720    if (entropy->EOBRUN == 0x7FFF || entropy->BE > (MAX_CORR_BITS-DCTSIZE2+1))
721      emit_eobrun(entropy);
722  }
723
724  cinfo->dest->next_output_byte = entropy->next_output_byte;
725  cinfo->dest->free_in_buffer = entropy->free_in_buffer;
726
727  /* Update restart-interval state too */
728  if (cinfo->restart_interval) {
729    if (entropy->restarts_to_go == 0) {
730      entropy->restarts_to_go = cinfo->restart_interval;
731      entropy->next_restart_num++;
732      entropy->next_restart_num &= 7;
733    }
734    entropy->restarts_to_go--;
735  }
736
737  return TRUE;
738}
739
740
741/*
742 * Finish up at the end of a Huffman-compressed progressive scan.
743 */
744
745METHODDEF(void)
746finish_pass_phuff (j_compress_ptr cinfo)
747{   
748  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
749
750  entropy->next_output_byte = cinfo->dest->next_output_byte;
751  entropy->free_in_buffer = cinfo->dest->free_in_buffer;
752
753  /* Flush out any buffered data */
754  emit_eobrun(entropy);
755  flush_bits(entropy);
756
757  cinfo->dest->next_output_byte = entropy->next_output_byte;
758  cinfo->dest->free_in_buffer = entropy->free_in_buffer;
759}
760
761
762/*
763 * Finish up a statistics-gathering pass and create the new Huffman tables.
764 */
765
766METHODDEF(void)
767finish_pass_gather_phuff (j_compress_ptr cinfo)
768{
769  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
770  boolean is_DC_band;
771  int ci, tbl;
772  jpeg_component_info * compptr;
773  JHUFF_TBL **htblptr;
774  boolean did[NUM_HUFF_TBLS];
775
776  /* Flush out buffered data (all we care about is counting the EOB symbol) */
777  emit_eobrun(entropy);
778
779  is_DC_band = (cinfo->Ss == 0);
780
781  /* It's important not to apply jpeg_gen_optimal_table more than once
782   * per table, because it clobbers the input frequency counts!
783   */
784  MEMZERO(did, SIZEOF(did));
785
786  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
787    compptr = cinfo->cur_comp_info[ci];
788    if (is_DC_band) {
789      if (cinfo->Ah != 0)       /* DC refinement needs no table */
790        continue;
791      tbl = compptr->dc_tbl_no;
792    } else {
793      tbl = compptr->ac_tbl_no;
794    }
795    if (! did[tbl]) {
796      if (is_DC_band)
797        htblptr = & cinfo->dc_huff_tbl_ptrs[tbl];
798      else
799        htblptr = & cinfo->ac_huff_tbl_ptrs[tbl];
800      if (*htblptr == NULL)
801        *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
802      jpeg_gen_optimal_table(cinfo, *htblptr, entropy->count_ptrs[tbl]);
803      did[tbl] = TRUE;
804    }
805  }
806}
807
808
809/*
810 * Module initialization routine for progressive Huffman entropy encoding.
811 */
812
813GLOBAL(void)
814jinit_phuff_encoder (j_compress_ptr cinfo)
815{
816  phuff_entropy_ptr entropy;
817  int i;
818
819  entropy = (phuff_entropy_ptr)
820    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
821                                SIZEOF(phuff_entropy_encoder));
822  cinfo->entropy = (struct jpeg_entropy_encoder *) entropy;
823  entropy->pub.start_pass = start_pass_phuff;
824
825  /* Mark tables unallocated */
826  for (i = 0; i < NUM_HUFF_TBLS; i++) {
827    entropy->derived_tbls[i] = NULL;
828    entropy->count_ptrs[i] = NULL;
829  }
830  entropy->bit_buffer = NULL;   /* needed only in AC refinement scan */
831}
832
833#endif /* C_PROGRESSIVE_SUPPORTED */
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