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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
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 * suspension.
13
 */
14

15
#define JPEG_INTERNALS
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#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

24
typedef 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.
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   * 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 */
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  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

62
typedef 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))) : \
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	 (ishift_temp >> (shft)))
83
#else
84
#define ISHIFT_TEMPS
85
#define IRIGHT_SHIFT(x,shft)	((x) >> (shft))
86
#endif
87

88
/* Forward declarations */
89
METHODDEF(boolean) encode_mcu_DC_first JPP((j_compress_ptr cinfo,
90
					    JBLOCKROW *MCU_data));
91
METHODDEF(boolean) encode_mcu_AC_first JPP((j_compress_ptr cinfo,
92
					    JBLOCKROW *MCU_data));
93
METHODDEF(boolean) encode_mcu_DC_refine JPP((j_compress_ptr cinfo,
94
					     JBLOCKROW *MCU_data));
95
METHODDEF(boolean) encode_mcu_AC_refine JPP((j_compress_ptr cinfo,
96
					     JBLOCKROW *MCU_data));
97
METHODDEF(void) finish_pass_phuff JPP((j_compress_ptr cinfo));
98
METHODDEF(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

105
METHODDEF(void)
106
start_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

204
LOCAL(void)
205
dump_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

226
INLINE
227
LOCAL(void)
228
emit_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

266
LOCAL(void)
267
flush_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

279
INLINE
280
LOCAL(void)
281
emit_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

296
LOCAL(void)
297
emit_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

315
LOCAL(void)
316
emit_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

346
LOCAL(void)
347
emit_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

376
METHODDEF(boolean)
377
encode_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

463
METHODDEF(boolean)
464
encode_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

570
METHODDEF(boolean)
571
encode_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

617
METHODDEF(boolean)
618
encode_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

745
METHODDEF(void)
746
finish_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

766
METHODDEF(void)
767
finish_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

813
GLOBAL(void)
814
jinit_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 */
834

835