summaryrefslogtreecommitdiffstats
path: root/media/libjpeg/jcphuff.c
blob: 046e2e18d4876502f0bce0e7f064eb8b71f6b122 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
/*
 * jcphuff.c
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1995-1997, Thomas G. Lane.
 * libjpeg-turbo Modifications:
 * Copyright (C) 2015, D. R. Commander.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file contains Huffman entropy encoding routines for progressive JPEG.
 *
 * We do not support output suspension in this module, since the library
 * currently does not allow multiple-scan files to be written with output
 * suspension.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jchuff.h"             /* Declarations shared with jchuff.c */

#ifdef C_PROGRESSIVE_SUPPORTED

/* Expanded entropy encoder object for progressive Huffman encoding. */

typedef struct {
  struct jpeg_entropy_encoder pub; /* public fields */

  /* Mode flag: TRUE for optimization, FALSE for actual data output */
  boolean gather_statistics;

  /* Bit-level coding status.
   * next_output_byte/free_in_buffer are local copies of cinfo->dest fields.
   */
  JOCTET *next_output_byte;     /* => next byte to write in buffer */
  size_t free_in_buffer;        /* # of byte spaces remaining in buffer */
  size_t put_buffer;            /* current bit-accumulation buffer */
  int put_bits;                 /* # of bits now in it */
  j_compress_ptr cinfo;         /* link to cinfo (needed for dump_buffer) */

  /* Coding status for DC components */
  int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */

  /* Coding status for AC components */
  int ac_tbl_no;                /* the table number of the single component */
  unsigned int EOBRUN;          /* run length of EOBs */
  unsigned int BE;              /* # of buffered correction bits before MCU */
  char *bit_buffer;             /* buffer for correction bits (1 per char) */
  /* packing correction bits tightly would save some space but cost time... */

  unsigned int restarts_to_go;  /* MCUs left in this restart interval */
  int next_restart_num;         /* next restart number to write (0-7) */

  /* Pointers to derived tables (these workspaces have image lifespan).
   * Since any one scan codes only DC or only AC, we only need one set
   * of tables, not one for DC and one for AC.
   */
  c_derived_tbl *derived_tbls[NUM_HUFF_TBLS];

  /* Statistics tables for optimization; again, one set is enough */
  long *count_ptrs[NUM_HUFF_TBLS];
} phuff_entropy_encoder;

typedef phuff_entropy_encoder *phuff_entropy_ptr;

/* MAX_CORR_BITS is the number of bits the AC refinement correction-bit
 * buffer can hold.  Larger sizes may slightly improve compression, but
 * 1000 is already well into the realm of overkill.
 * The minimum safe size is 64 bits.
 */

#define MAX_CORR_BITS  1000     /* Max # of correction bits I can buffer */

/* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than JLONG.
 * We assume that int right shift is unsigned if JLONG right shift is,
 * which should be safe.
 */

#ifdef RIGHT_SHIFT_IS_UNSIGNED
#define ISHIFT_TEMPS    int ishift_temp;
#define IRIGHT_SHIFT(x,shft)  \
        ((ishift_temp = (x)) < 0 ? \
         (ishift_temp >> (shft)) | ((~0) << (16-(shft))) : \
         (ishift_temp >> (shft)))
#else
#define ISHIFT_TEMPS
#define IRIGHT_SHIFT(x,shft)    ((x) >> (shft))
#endif

/* Forward declarations */
METHODDEF(boolean) encode_mcu_DC_first (j_compress_ptr cinfo,
                                        JBLOCKROW *MCU_data);
METHODDEF(boolean) encode_mcu_AC_first (j_compress_ptr cinfo,
                                        JBLOCKROW *MCU_data);
METHODDEF(boolean) encode_mcu_DC_refine (j_compress_ptr cinfo,
                                         JBLOCKROW *MCU_data);
METHODDEF(boolean) encode_mcu_AC_refine (j_compress_ptr cinfo,
                                         JBLOCKROW *MCU_data);
METHODDEF(void) finish_pass_phuff (j_compress_ptr cinfo);
METHODDEF(void) finish_pass_gather_phuff (j_compress_ptr cinfo);


/*
 * Initialize for a Huffman-compressed scan using progressive JPEG.
 */

METHODDEF(void)
start_pass_phuff (j_compress_ptr cinfo, boolean gather_statistics)
{
  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
  boolean is_DC_band;
  int ci, tbl;
  jpeg_component_info *compptr;

  entropy->cinfo = cinfo;
  entropy->gather_statistics = gather_statistics;

  is_DC_band = (cinfo->Ss == 0);

  /* We assume jcmaster.c already validated the scan parameters. */

  /* Select execution routines */
  if (cinfo->Ah == 0) {
    if (is_DC_band)
      entropy->pub.encode_mcu = encode_mcu_DC_first;
    else
      entropy->pub.encode_mcu = encode_mcu_AC_first;
  } else {
    if (is_DC_band)
      entropy->pub.encode_mcu = encode_mcu_DC_refine;
    else {
      entropy->pub.encode_mcu = encode_mcu_AC_refine;
      /* AC refinement needs a correction bit buffer */
      if (entropy->bit_buffer == NULL)
        entropy->bit_buffer = (char *)
          (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                      MAX_CORR_BITS * sizeof(char));
    }
  }
  if (gather_statistics)
    entropy->pub.finish_pass = finish_pass_gather_phuff;
  else
    entropy->pub.finish_pass = finish_pass_phuff;

  /* Only DC coefficients may be interleaved, so cinfo->comps_in_scan = 1
   * for AC coefficients.
   */
  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    compptr = cinfo->cur_comp_info[ci];
    /* Initialize DC predictions to 0 */
    entropy->last_dc_val[ci] = 0;
    /* Get table index */
    if (is_DC_band) {
      if (cinfo->Ah != 0)       /* DC refinement needs no table */
        continue;
      tbl = compptr->dc_tbl_no;
    } else {
      entropy->ac_tbl_no = tbl = compptr->ac_tbl_no;
    }
    if (gather_statistics) {
      /* Check for invalid table index */
      /* (make_c_derived_tbl does this in the other path) */
      if (tbl < 0 || tbl >= NUM_HUFF_TBLS)
        ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
      /* Allocate and zero the statistics tables */
      /* Note that jpeg_gen_optimal_table expects 257 entries in each table! */
      if (entropy->count_ptrs[tbl] == NULL)
        entropy->count_ptrs[tbl] = (long *)
          (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                      257 * sizeof(long));
      MEMZERO(entropy->count_ptrs[tbl], 257 * sizeof(long));
    } else {
      /* Compute derived values for Huffman table */
      /* We may do this more than once for a table, but it's not expensive */
      jpeg_make_c_derived_tbl(cinfo, is_DC_band, tbl,
                              & entropy->derived_tbls[tbl]);
    }
  }

  /* Initialize AC stuff */
  entropy->EOBRUN = 0;
  entropy->BE = 0;

  /* Initialize bit buffer to empty */
  entropy->put_buffer = 0;
  entropy->put_bits = 0;

  /* Initialize restart stuff */
  entropy->restarts_to_go = cinfo->restart_interval;
  entropy->next_restart_num = 0;
}


/* Outputting bytes to the file.
 * NB: these must be called only when actually outputting,
 * that is, entropy->gather_statistics == FALSE.
 */

/* Emit a byte */
#define emit_byte(entropy,val)  \
        { *(entropy)->next_output_byte++ = (JOCTET) (val);  \
          if (--(entropy)->free_in_buffer == 0)  \
            dump_buffer(entropy); }


LOCAL(void)
dump_buffer (phuff_entropy_ptr entropy)
/* Empty the output buffer; we do not support suspension in this module. */
{
  struct jpeg_destination_mgr *dest = entropy->cinfo->dest;

  if (! (*dest->empty_output_buffer) (entropy->cinfo))
    ERREXIT(entropy->cinfo, JERR_CANT_SUSPEND);
  /* After a successful buffer dump, must reset buffer pointers */
  entropy->next_output_byte = dest->next_output_byte;
  entropy->free_in_buffer = dest->free_in_buffer;
}


/* Outputting bits to the file */

/* Only the right 24 bits of put_buffer are used; the valid bits are
 * left-justified in this part.  At most 16 bits can be passed to emit_bits
 * in one call, and we never retain more than 7 bits in put_buffer
 * between calls, so 24 bits are sufficient.
 */

LOCAL(void)
emit_bits (phuff_entropy_ptr entropy, unsigned int code, int size)
/* Emit some bits, unless we are in gather mode */
{
  /* This routine is heavily used, so it's worth coding tightly. */
  register size_t put_buffer = (size_t) code;
  register int put_bits = entropy->put_bits;

  /* if size is 0, caller used an invalid Huffman table entry */
  if (size == 0)
    ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);

  if (entropy->gather_statistics)
    return;                     /* do nothing if we're only getting stats */

  put_buffer &= (((size_t) 1)<<size) - 1; /* mask off any extra bits in code */

  put_bits += size;             /* new number of bits in buffer */

  put_buffer <<= 24 - put_bits; /* align incoming bits */

  put_buffer |= entropy->put_buffer; /* and merge with old buffer contents */

  while (put_bits >= 8) {
    int c = (int) ((put_buffer >> 16) & 0xFF);

    emit_byte(entropy, c);
    if (c == 0xFF) {            /* need to stuff a zero byte? */
      emit_byte(entropy, 0);
    }
    put_buffer <<= 8;
    put_bits -= 8;
  }

  entropy->put_buffer = put_buffer; /* update variables */
  entropy->put_bits = put_bits;
}


LOCAL(void)
flush_bits (phuff_entropy_ptr entropy)
{
  emit_bits(entropy, 0x7F, 7); /* fill any partial byte with ones */
  entropy->put_buffer = 0;     /* and reset bit-buffer to empty */
  entropy->put_bits = 0;
}


/*
 * Emit (or just count) a Huffman symbol.
 */

LOCAL(void)
emit_symbol (phuff_entropy_ptr entropy, int tbl_no, int symbol)
{
  if (entropy->gather_statistics)
    entropy->count_ptrs[tbl_no][symbol]++;
  else {
    c_derived_tbl *tbl = entropy->derived_tbls[tbl_no];
    emit_bits(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]);
  }
}


/*
 * Emit bits from a correction bit buffer.
 */

LOCAL(void)
emit_buffered_bits (phuff_entropy_ptr entropy, char *bufstart,
                    unsigned int nbits)
{
  if (entropy->gather_statistics)
    return;                     /* no real work */

  while (nbits > 0) {
    emit_bits(entropy, (unsigned int) (*bufstart), 1);
    bufstart++;
    nbits--;
  }
}


/*
 * Emit any pending EOBRUN symbol.
 */

LOCAL(void)
emit_eobrun (phuff_entropy_ptr entropy)
{
  register int temp, nbits;

  if (entropy->EOBRUN > 0) {    /* if there is any pending EOBRUN */
    temp = entropy->EOBRUN;
    nbits = 0;
    while ((temp >>= 1))
      nbits++;
    /* safety check: shouldn't happen given limited correction-bit buffer */
    if (nbits > 14)
      ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);

    emit_symbol(entropy, entropy->ac_tbl_no, nbits << 4);
    if (nbits)
      emit_bits(entropy, entropy->EOBRUN, nbits);

    entropy->EOBRUN = 0;

    /* Emit any buffered correction bits */
    emit_buffered_bits(entropy, entropy->bit_buffer, entropy->BE);
    entropy->BE = 0;
  }
}


/*
 * Emit a restart marker & resynchronize predictions.
 */

LOCAL(void)
emit_restart (phuff_entropy_ptr entropy, int restart_num)
{
  int ci;

  emit_eobrun(entropy);

  if (! entropy->gather_statistics) {
    flush_bits(entropy);
    emit_byte(entropy, 0xFF);
    emit_byte(entropy, JPEG_RST0 + restart_num);
  }

  if (entropy->cinfo->Ss == 0) {
    /* Re-initialize DC predictions to 0 */
    for (ci = 0; ci < entropy->cinfo->comps_in_scan; ci++)
      entropy->last_dc_val[ci] = 0;
  } else {
    /* Re-initialize all AC-related fields to 0 */
    entropy->EOBRUN = 0;
    entropy->BE = 0;
  }
}


/*
 * MCU encoding for DC initial scan (either spectral selection,
 * or first pass of successive approximation).
 */

METHODDEF(boolean)
encode_mcu_DC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
{
  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
  register int temp, temp2;
  register int nbits;
  int blkn, ci;
  int Al = cinfo->Al;
  JBLOCKROW block;
  jpeg_component_info *compptr;
  ISHIFT_TEMPS

  entropy->next_output_byte = cinfo->dest->next_output_byte;
  entropy->free_in_buffer = cinfo->dest->free_in_buffer;

  /* Emit restart marker if needed */
  if (cinfo->restart_interval)
    if (entropy->restarts_to_go == 0)
      emit_restart(entropy, entropy->next_restart_num);

  /* Encode the MCU data blocks */
  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
    block = MCU_data[blkn];
    ci = cinfo->MCU_membership[blkn];
    compptr = cinfo->cur_comp_info[ci];

    /* Compute the DC value after the required point transform by Al.
     * This is simply an arithmetic right shift.
     */
    temp2 = IRIGHT_SHIFT((int) ((*block)[0]), Al);

    /* DC differences are figured on the point-transformed values. */
    temp = temp2 - entropy->last_dc_val[ci];
    entropy->last_dc_val[ci] = temp2;

    /* Encode the DC coefficient difference per section G.1.2.1 */
    temp2 = temp;
    if (temp < 0) {
      temp = -temp;             /* temp is abs value of input */
      /* For a negative input, want temp2 = bitwise complement of abs(input) */
      /* This code assumes we are on a two's complement machine */
      temp2--;
    }

    /* Find the number of bits needed for the magnitude of the coefficient */
    nbits = 0;
    while (temp) {
      nbits++;
      temp >>= 1;
    }
    /* Check for out-of-range coefficient values.
     * Since we're encoding a difference, the range limit is twice as much.
     */
    if (nbits > MAX_COEF_BITS+1)
      ERREXIT(cinfo, JERR_BAD_DCT_COEF);

    /* Count/emit the Huffman-coded symbol for the number of bits */
    emit_symbol(entropy, compptr->dc_tbl_no, nbits);

    /* Emit that number of bits of the value, if positive, */
    /* or the complement of its magnitude, if negative. */
    if (nbits)                  /* emit_bits rejects calls with size 0 */
      emit_bits(entropy, (unsigned int) temp2, nbits);
  }

  cinfo->dest->next_output_byte = entropy->next_output_byte;
  cinfo->dest->free_in_buffer = entropy->free_in_buffer;

  /* Update restart-interval state too */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0) {
      entropy->restarts_to_go = cinfo->restart_interval;
      entropy->next_restart_num++;
      entropy->next_restart_num &= 7;
    }
    entropy->restarts_to_go--;
  }

  return TRUE;
}


/*
 * MCU encoding for AC initial scan (either spectral selection,
 * or first pass of successive approximation).
 */

METHODDEF(boolean)
encode_mcu_AC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
{
  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
  register int temp, temp2;
  register int nbits;
  register int r, k;
  int Se = cinfo->Se;
  int Al = cinfo->Al;
  JBLOCKROW block;

  entropy->next_output_byte = cinfo->dest->next_output_byte;
  entropy->free_in_buffer = cinfo->dest->free_in_buffer;

  /* Emit restart marker if needed */
  if (cinfo->restart_interval)
    if (entropy->restarts_to_go == 0)
      emit_restart(entropy, entropy->next_restart_num);

  /* Encode the MCU data block */
  block = MCU_data[0];

  /* Encode the AC coefficients per section G.1.2.2, fig. G.3 */

  r = 0;                        /* r = run length of zeros */

  for (k = cinfo->Ss; k <= Se; k++) {
    if ((temp = (*block)[jpeg_natural_order[k]]) == 0) {
      r++;
      continue;
    }
    /* We must apply the point transform by Al.  For AC coefficients this
     * is an integer division with rounding towards 0.  To do this portably
     * in C, we shift after obtaining the absolute value; so the code is
     * interwoven with finding the abs value (temp) and output bits (temp2).
     */
    if (temp < 0) {
      temp = -temp;             /* temp is abs value of input */
      temp >>= Al;              /* apply the point transform */
      /* For a negative coef, want temp2 = bitwise complement of abs(coef) */
      temp2 = ~temp;
    } else {
      temp >>= Al;              /* apply the point transform */
      temp2 = temp;
    }
    /* Watch out for case that nonzero coef is zero after point transform */
    if (temp == 0) {
      r++;
      continue;
    }

    /* Emit any pending EOBRUN */
    if (entropy->EOBRUN > 0)
      emit_eobrun(entropy);
    /* if run length > 15, must emit special run-length-16 codes (0xF0) */
    while (r > 15) {
      emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
      r -= 16;
    }

    /* Find the number of bits needed for the magnitude of the coefficient */
    nbits = 1;                  /* there must be at least one 1 bit */
    while ((temp >>= 1))
      nbits++;
    /* Check for out-of-range coefficient values */
    if (nbits > MAX_COEF_BITS)
      ERREXIT(cinfo, JERR_BAD_DCT_COEF);

    /* Count/emit Huffman symbol for run length / number of bits */
    emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + nbits);

    /* Emit that number of bits of the value, if positive, */
    /* or the complement of its magnitude, if negative. */
    emit_bits(entropy, (unsigned int) temp2, nbits);

    r = 0;                      /* reset zero run length */
  }

  if (r > 0) {                  /* If there are trailing zeroes, */
    entropy->EOBRUN++;          /* count an EOB */
    if (entropy->EOBRUN == 0x7FFF)
      emit_eobrun(entropy);     /* force it out to avoid overflow */
  }

  cinfo->dest->next_output_byte = entropy->next_output_byte;
  cinfo->dest->free_in_buffer = entropy->free_in_buffer;

  /* Update restart-interval state too */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0) {
      entropy->restarts_to_go = cinfo->restart_interval;
      entropy->next_restart_num++;
      entropy->next_restart_num &= 7;
    }
    entropy->restarts_to_go--;
  }

  return TRUE;
}


/*
 * MCU encoding for DC successive approximation refinement scan.
 * Note: we assume such scans can be multi-component, although the spec
 * is not very clear on the point.
 */

METHODDEF(boolean)
encode_mcu_DC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
{
  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
  register int temp;
  int blkn;
  int Al = cinfo->Al;
  JBLOCKROW block;

  entropy->next_output_byte = cinfo->dest->next_output_byte;
  entropy->free_in_buffer = cinfo->dest->free_in_buffer;

  /* Emit restart marker if needed */
  if (cinfo->restart_interval)
    if (entropy->restarts_to_go == 0)
      emit_restart(entropy, entropy->next_restart_num);

  /* Encode the MCU data blocks */
  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
    block = MCU_data[blkn];

    /* We simply emit the Al'th bit of the DC coefficient value. */
    temp = (*block)[0];
    emit_bits(entropy, (unsigned int) (temp >> Al), 1);
  }

  cinfo->dest->next_output_byte = entropy->next_output_byte;
  cinfo->dest->free_in_buffer = entropy->free_in_buffer;

  /* Update restart-interval state too */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0) {
      entropy->restarts_to_go = cinfo->restart_interval;
      entropy->next_restart_num++;
      entropy->next_restart_num &= 7;
    }
    entropy->restarts_to_go--;
  }

  return TRUE;
}


/*
 * MCU encoding for AC successive approximation refinement scan.
 */

METHODDEF(boolean)
encode_mcu_AC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
{
  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
  register int temp;
  register int r, k;
  int EOB;
  char *BR_buffer;
  unsigned int BR;
  int Se = cinfo->Se;
  int Al = cinfo->Al;
  JBLOCKROW block;
  int absvalues[DCTSIZE2];

  entropy->next_output_byte = cinfo->dest->next_output_byte;
  entropy->free_in_buffer = cinfo->dest->free_in_buffer;

  /* Emit restart marker if needed */
  if (cinfo->restart_interval)
    if (entropy->restarts_to_go == 0)
      emit_restart(entropy, entropy->next_restart_num);

  /* Encode the MCU data block */
  block = MCU_data[0];

  /* It is convenient to make a pre-pass to determine the transformed
   * coefficients' absolute values and the EOB position.
   */
  EOB = 0;
  for (k = cinfo->Ss; k <= Se; k++) {
    temp = (*block)[jpeg_natural_order[k]];
    /* We must apply the point transform by Al.  For AC coefficients this
     * is an integer division with rounding towards 0.  To do this portably
     * in C, we shift after obtaining the absolute value.
     */
    if (temp < 0)
      temp = -temp;             /* temp is abs value of input */
    temp >>= Al;                /* apply the point transform */
    absvalues[k] = temp;        /* save abs value for main pass */
    if (temp == 1)
      EOB = k;                  /* EOB = index of last newly-nonzero coef */
  }

  /* Encode the AC coefficients per section G.1.2.3, fig. G.7 */

  r = 0;                        /* r = run length of zeros */
  BR = 0;                       /* BR = count of buffered bits added now */
  BR_buffer = entropy->bit_buffer + entropy->BE; /* Append bits to buffer */

  for (k = cinfo->Ss; k <= Se; k++) {
    if ((temp = absvalues[k]) == 0) {
      r++;
      continue;
    }

    /* Emit any required ZRLs, but not if they can be folded into EOB */
    while (r > 15 && k <= EOB) {
      /* emit any pending EOBRUN and the BE correction bits */
      emit_eobrun(entropy);
      /* Emit ZRL */
      emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
      r -= 16;
      /* Emit buffered correction bits that must be associated with ZRL */
      emit_buffered_bits(entropy, BR_buffer, BR);
      BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
      BR = 0;
    }

    /* If the coef was previously nonzero, it only needs a correction bit.
     * NOTE: a straight translation of the spec's figure G.7 would suggest
     * that we also need to test r > 15.  But if r > 15, we can only get here
     * if k > EOB, which implies that this coefficient is not 1.
     */
    if (temp > 1) {
      /* The correction bit is the next bit of the absolute value. */
      BR_buffer[BR++] = (char) (temp & 1);
      continue;
    }

    /* Emit any pending EOBRUN and the BE correction bits */
    emit_eobrun(entropy);

    /* Count/emit Huffman symbol for run length / number of bits */
    emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + 1);

    /* Emit output bit for newly-nonzero coef */
    temp = ((*block)[jpeg_natural_order[k]] < 0) ? 0 : 1;
    emit_bits(entropy, (unsigned int) temp, 1);

    /* Emit buffered correction bits that must be associated with this code */
    emit_buffered_bits(entropy, BR_buffer, BR);
    BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
    BR = 0;
    r = 0;                      /* reset zero run length */
  }

  if (r > 0 || BR > 0) {        /* If there are trailing zeroes, */
    entropy->EOBRUN++;          /* count an EOB */
    entropy->BE += BR;          /* concat my correction bits to older ones */
    /* We force out the EOB if we risk either:
     * 1. overflow of the EOB counter;
     * 2. overflow of the correction bit buffer during the next MCU.
     */
    if (entropy->EOBRUN == 0x7FFF || entropy->BE > (MAX_CORR_BITS-DCTSIZE2+1))
      emit_eobrun(entropy);
  }

  cinfo->dest->next_output_byte = entropy->next_output_byte;
  cinfo->dest->free_in_buffer = entropy->free_in_buffer;

  /* Update restart-interval state too */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0) {
      entropy->restarts_to_go = cinfo->restart_interval;
      entropy->next_restart_num++;
      entropy->next_restart_num &= 7;
    }
    entropy->restarts_to_go--;
  }

  return TRUE;
}


/*
 * Finish up at the end of a Huffman-compressed progressive scan.
 */

METHODDEF(void)
finish_pass_phuff (j_compress_ptr cinfo)
{
  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  entropy->next_output_byte = cinfo->dest->next_output_byte;
  entropy->free_in_buffer = cinfo->dest->free_in_buffer;

  /* Flush out any buffered data */
  emit_eobrun(entropy);
  flush_bits(entropy);

  cinfo->dest->next_output_byte = entropy->next_output_byte;
  cinfo->dest->free_in_buffer = entropy->free_in_buffer;
}


/*
 * Finish up a statistics-gathering pass and create the new Huffman tables.
 */

METHODDEF(void)
finish_pass_gather_phuff (j_compress_ptr cinfo)
{
  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
  boolean is_DC_band;
  int ci, tbl;
  jpeg_component_info *compptr;
  JHUFF_TBL **htblptr;
  boolean did[NUM_HUFF_TBLS];

  /* Flush out buffered data (all we care about is counting the EOB symbol) */
  emit_eobrun(entropy);

  is_DC_band = (cinfo->Ss == 0);

  /* It's important not to apply jpeg_gen_optimal_table more than once
   * per table, because it clobbers the input frequency counts!
   */
  MEMZERO(did, sizeof(did));

  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    compptr = cinfo->cur_comp_info[ci];
    if (is_DC_band) {
      if (cinfo->Ah != 0)       /* DC refinement needs no table */
        continue;
      tbl = compptr->dc_tbl_no;
    } else {
      tbl = compptr->ac_tbl_no;
    }
    if (! did[tbl]) {
      if (is_DC_band)
        htblptr = & cinfo->dc_huff_tbl_ptrs[tbl];
      else
        htblptr = & cinfo->ac_huff_tbl_ptrs[tbl];
      if (*htblptr == NULL)
        *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
      jpeg_gen_optimal_table(cinfo, *htblptr, entropy->count_ptrs[tbl]);
      did[tbl] = TRUE;
    }
  }
}


/*
 * Module initialization routine for progressive Huffman entropy encoding.
 */

GLOBAL(void)
jinit_phuff_encoder (j_compress_ptr cinfo)
{
  phuff_entropy_ptr entropy;
  int i;

  entropy = (phuff_entropy_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                sizeof(phuff_entropy_encoder));
  cinfo->entropy = (struct jpeg_entropy_encoder *) entropy;
  entropy->pub.start_pass = start_pass_phuff;

  /* Mark tables unallocated */
  for (i = 0; i < NUM_HUFF_TBLS; i++) {
    entropy->derived_tbls[i] = NULL;
    entropy->count_ptrs[i] = NULL;
  }
  entropy->bit_buffer = NULL;   /* needed only in AC refinement scan */
}

#endif /* C_PROGRESSIVE_SUPPORTED */