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jdhuff.c
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1 /*
2  * jdhuff.c
3  *
4  * Copyright (C) 1991-1997, 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.
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 jdphuff.c */
21 
22 
23 /*
24  * Expanded entropy decoder object for Huffman decoding.
25  *
26  * The savable_state subrecord contains fields that change within an MCU,
27  * but must not be updated permanently until we complete the MCU.
28  */
29 
30 typedef struct {
31  int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
32 } savable_state;
33 
34 /* This macro is to work around compilers with missing or broken
35  * structure assignment. You'll need to fix this code if you have
36  * such a compiler and you change MAX_COMPS_IN_SCAN.
37  */
38 
39 #ifndef NO_STRUCT_ASSIGN
40 #define ASSIGN_STATE(dest,src) ((dest) = (src))
41 #else
42 #if MAX_COMPS_IN_SCAN == 4
43 #define ASSIGN_STATE(dest,src) \
44  ((dest).last_dc_val[0] = (src).last_dc_val[0], \
45  (dest).last_dc_val[1] = (src).last_dc_val[1], \
46  (dest).last_dc_val[2] = (src).last_dc_val[2], \
47  (dest).last_dc_val[3] = (src).last_dc_val[3])
48 #endif
49 #endif
50 
51 
52 typedef struct {
53  struct jpeg_entropy_decoder pub; /* public fields */
54 
55  /* These fields are loaded into local variables at start of each MCU.
56  * In case of suspension, we exit WITHOUT updating them.
57  */
58  bitread_perm_state bitstate; /* Bit buffer at start of MCU */
59  savable_state saved; /* Other state at start of MCU */
60 
61  /* These fields are NOT loaded into local working state. */
62  unsigned int restarts_to_go; /* MCUs left in this restart interval */
63 
64  /* Pointers to derived tables (these workspaces have image lifespan) */
65  d_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];
66  d_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
67 
68  /* Precalculated info set up by start_pass for use in decode_mcu: */
69 
70  /* Pointers to derived tables to be used for each block within an MCU */
71  d_derived_tbl * dc_cur_tbls[D_MAX_BLOCKS_IN_MCU];
72  d_derived_tbl * ac_cur_tbls[D_MAX_BLOCKS_IN_MCU];
73  /* Whether we care about the DC and AC coefficient values for each block */
74  boolean dc_needed[D_MAX_BLOCKS_IN_MCU];
75  boolean ac_needed[D_MAX_BLOCKS_IN_MCU];
76 } huff_entropy_decoder;
77 
78 typedef huff_entropy_decoder * huff_entropy_ptr;
79 
80 
81 /*
82  * Initialize for a Huffman-compressed scan.
83  */
84 
85 METHODDEF(void)
87 {
88  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
89  int ci, blkn, dctbl, actbl;
91 
92  /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
93  * This ought to be an error condition, but we make it a warning because
94  * there are some baseline files out there with all zeroes in these bytes.
95  */
96  if (cinfo->Ss != 0 || cinfo->Se != DCTSIZE2-1 ||
97  cinfo->Ah != 0 || cinfo->Al != 0)
98  WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
99 
100  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
101  compptr = cinfo->cur_comp_info[ci];
102  dctbl = compptr->dc_tbl_no;
103  actbl = compptr->ac_tbl_no;
104  /* Compute derived values for Huffman tables */
105  /* We may do this more than once for a table, but it's not expensive */
106  jpeg_make_d_derived_tbl(cinfo, TRUE, dctbl,
107  & entropy->dc_derived_tbls[dctbl]);
108  jpeg_make_d_derived_tbl(cinfo, FALSE, actbl,
109  & entropy->ac_derived_tbls[actbl]);
110  /* Initialize DC predictions to 0 */
111  entropy->saved.last_dc_val[ci] = 0;
112  }
113 
114  /* Precalculate decoding info for each block in an MCU of this scan */
115  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
116  ci = cinfo->MCU_membership[blkn];
117  compptr = cinfo->cur_comp_info[ci];
118  /* Precalculate which table to use for each block */
119  entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no];
120  entropy->ac_cur_tbls[blkn] = entropy->ac_derived_tbls[compptr->ac_tbl_no];
121  /* Decide whether we really care about the coefficient values */
122  if (compptr->component_needed) {
123  entropy->dc_needed[blkn] = TRUE;
124  /* we don't need the ACs if producing a 1/8th-size image */
125  entropy->ac_needed[blkn] = (compptr->DCT_scaled_size > 1);
126  } else {
127  entropy->dc_needed[blkn] = entropy->ac_needed[blkn] = FALSE;
128  }
129  }
130 
131  /* Initialize bitread state variables */
132  entropy->bitstate.bits_left = 0;
133  entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
134  entropy->pub.insufficient_data = FALSE;
135 
136  /* Initialize restart counter */
137  entropy->restarts_to_go = cinfo->restart_interval;
138 }
139 
140 
141 /*
142  * Compute the derived values for a Huffman table.
143  * This routine also performs some validation checks on the table.
144  *
145  * Note this is also used by jdphuff.c.
146  */
147 
148 GLOBAL(void)
150  d_derived_tbl ** pdtbl)
151 {
152  JHUFF_TBL *htbl;
153  d_derived_tbl *dtbl;
154  int p, i, l, si, numsymbols;
155  int lookbits, ctr;
156  char huffsize[257];
157  unsigned int huffcode[257];
158  unsigned int code;
159 
160  /* Note that huffsize[] and huffcode[] are filled in code-length order,
161  * paralleling the order of the symbols themselves in htbl->huffval[].
162  */
163 
164  /* Find the input Huffman table */
165  if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
166  ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
167  htbl =
168  isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
169  if (htbl == NULL)
170  ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
171 
172  /* Allocate a workspace if we haven't already done so. */
173  if (*pdtbl == NULL)
174  *pdtbl = (d_derived_tbl *)
175  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
177  dtbl = *pdtbl;
178  dtbl->pub = htbl; /* fill in back link */
179 
180  /* Figure C.1: make table of Huffman code length for each symbol */
181 
182  p = 0;
183  for (l = 1; l <= 16; l++) {
184  i = (int) htbl->bits[l];
185  if (i < 0 || p + i > 256) /* protect against table overrun */
186  ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
187  while (i--)
188  huffsize[p++] = (char) l;
189  }
190  huffsize[p] = 0;
191  numsymbols = p;
192 
193  /* Figure C.2: generate the codes themselves */
194  /* We also validate that the counts represent a legal Huffman code tree. */
195 
196  code = 0;
197  si = huffsize[0];
198  p = 0;
199  while (huffsize[p]) {
200  while (((int) huffsize[p]) == si) {
201  huffcode[p++] = code;
202  code++;
203  }
204  /* code is now 1 more than the last code used for codelength si; but
205  * it must still fit in si bits, since no code is allowed to be all ones.
206  */
207  if (((INT32) code) >= (((INT32) 1) << si))
208  ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
209  code <<= 1;
210  si++;
211  }
212 
213  /* Figure F.15: generate decoding tables for bit-sequential decoding */
214 
215  p = 0;
216  for (l = 1; l <= 16; l++) {
217  if (htbl->bits[l]) {
218  /* valoffset[l] = huffval[] index of 1st symbol of code length l,
219  * minus the minimum code of length l
220  */
221  dtbl->valoffset[l] = (INT32) p - (INT32) huffcode[p];
222  p += htbl->bits[l];
223  dtbl->maxcode[l] = huffcode[p-1]; /* maximum code of length l */
224  } else {
225  dtbl->maxcode[l] = -1; /* -1 if no codes of this length */
226  }
227  }
228  dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */
229 
230  /* Compute lookahead tables to speed up decoding.
231  * First we set all the table entries to 0, indicating "too long";
232  * then we iterate through the Huffman codes that are short enough and
233  * fill in all the entries that correspond to bit sequences starting
234  * with that code.
235  */
236 
237  MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits));
238 
239  p = 0;
240  for (l = 1; l <= HUFF_LOOKAHEAD; l++) {
241  for (i = 1; i <= (int) htbl->bits[l]; i++, p++) {
242  /* l = current code's length, p = its index in huffcode[] & huffval[]. */
243  /* Generate left-justified code followed by all possible bit sequences */
244  lookbits = huffcode[p] << (HUFF_LOOKAHEAD-l);
245  for (ctr = 1 << (HUFF_LOOKAHEAD-l); ctr > 0; ctr--) {
246  dtbl->look_nbits[lookbits] = l;
247  dtbl->look_sym[lookbits] = htbl->huffval[p];
248  lookbits++;
249  }
250  }
251  }
252 
253  /* Validate symbols as being reasonable.
254  * For AC tables, we make no check, but accept all byte values 0..255.
255  * For DC tables, we require the symbols to be in range 0..15.
256  * (Tighter bounds could be applied depending on the data depth and mode,
257  * but this is sufficient to ensure safe decoding.)
258  */
259  if (isDC) {
260  for (i = 0; i < numsymbols; i++) {
261  int sym = htbl->huffval[i];
262  if (sym < 0 || sym > 15)
263  ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
264  }
265  }
266 }
267 
268 
269 /*
270  * Out-of-line code for bit fetching (shared with jdphuff.c).
271  * See jdhuff.h for info about usage.
272  * Note: current values of get_buffer and bits_left are passed as parameters,
273  * but are returned in the corresponding fields of the state struct.
274  *
275  * On most machines MIN_GET_BITS should be 25 to allow the full 32-bit width
276  * of get_buffer to be used. (On machines with wider words, an even larger
277  * buffer could be used.) However, on some machines 32-bit shifts are
278  * quite slow and take time proportional to the number of places shifted.
279  * (This is true with most PC compilers, for instance.) In this case it may
280  * be a win to set MIN_GET_BITS to the minimum value of 15. This reduces the
281  * average shift distance at the cost of more calls to jpeg_fill_bit_buffer.
282  */
283 
284 #ifdef SLOW_SHIFT_32
285 #define MIN_GET_BITS 15 /* minimum allowable value */
286 #else
287 #define MIN_GET_BITS (BIT_BUF_SIZE-7)
288 #endif
289 
290 
291 GLOBAL(boolean)
293  register bit_buf_type get_buffer, register int bits_left,
294  int nbits)
295 /* Load up the bit buffer to a depth of at least nbits */
296 {
297  /* Copy heavily used state fields into locals (hopefully registers) */
298  register const JOCTET * next_input_byte = state->next_input_byte;
299  register size_t bytes_in_buffer = state->bytes_in_buffer;
300  j_decompress_ptr cinfo = state->cinfo;
301 
302  /* Attempt to load at least MIN_GET_BITS bits into get_buffer. */
303  /* (It is assumed that no request will be for more than that many bits.) */
304  /* We fail to do so only if we hit a marker or are forced to suspend. */
305 
306  if (cinfo->unread_marker == 0) { /* cannot advance past a marker */
307  while (bits_left < MIN_GET_BITS) {
308  register int c;
309 
310  /* Attempt to read a byte */
311  if (bytes_in_buffer == 0) {
312  if (! (*cinfo->src->fill_input_buffer) (cinfo))
313  return FALSE;
314  next_input_byte = cinfo->src->next_input_byte;
315  bytes_in_buffer = cinfo->src->bytes_in_buffer;
316  }
317  bytes_in_buffer--;
318  c = GETJOCTET(*next_input_byte++);
319 
320  /* If it's 0xFF, check and discard stuffed zero byte */
321  if (c == 0xFF) {
322  /* Loop here to discard any padding FF's on terminating marker,
323  * so that we can save a valid unread_marker value. NOTE: we will
324  * accept multiple FF's followed by a 0 as meaning a single FF data
325  * byte. This data pattern is not valid according to the standard.
326  */
327  do {
328  if (bytes_in_buffer == 0) {
329  if (! (*cinfo->src->fill_input_buffer) (cinfo))
330  return FALSE;
331  next_input_byte = cinfo->src->next_input_byte;
332  bytes_in_buffer = cinfo->src->bytes_in_buffer;
333  }
334  bytes_in_buffer--;
335  c = GETJOCTET(*next_input_byte++);
336  } while (c == 0xFF);
337 
338  if (c == 0) {
339  /* Found FF/00, which represents an FF data byte */
340  c = 0xFF;
341  } else {
342  /* Oops, it's actually a marker indicating end of compressed data.
343  * Save the marker code for later use.
344  * Fine point: it might appear that we should save the marker into
345  * bitread working state, not straight into permanent state. But
346  * once we have hit a marker, we cannot need to suspend within the
347  * current MCU, because we will read no more bytes from the data
348  * source. So it is OK to update permanent state right away.
349  */
350  cinfo->unread_marker = c;
351  /* See if we need to insert some fake zero bits. */
352  goto no_more_bytes;
353  }
354  }
355 
356  /* OK, load c into get_buffer */
357  get_buffer = (get_buffer << 8) | c;
358  bits_left += 8;
359  } /* end while */
360  } else {
361  no_more_bytes:
362  /* We get here if we've read the marker that terminates the compressed
363  * data segment. There should be enough bits in the buffer register
364  * to satisfy the request; if so, no problem.
365  */
366  if (nbits > bits_left) {
367  /* Uh-oh. Report corrupted data to user and stuff zeroes into
368  * the data stream, so that we can produce some kind of image.
369  * We use a nonvolatile flag to ensure that only one warning message
370  * appears per data segment.
371  */
372  if (! cinfo->entropy->insufficient_data) {
373  WARNMS(cinfo, JWRN_HIT_MARKER);
374  cinfo->entropy->insufficient_data = TRUE;
375  }
376  /* Fill the buffer with zero bits */
377  get_buffer <<= MIN_GET_BITS - bits_left;
378  bits_left = MIN_GET_BITS;
379  }
380  }
381 
382  /* Unload the local registers */
383  state->next_input_byte = next_input_byte;
384  state->bytes_in_buffer = bytes_in_buffer;
385  state->get_buffer = get_buffer;
386  state->bits_left = bits_left;
387 
388  return TRUE;
389 }
390 
391 
392 /*
393  * Out-of-line code for Huffman code decoding.
394  * See jdhuff.h for info about usage.
395  */
396 
397 GLOBAL(int)
399  register bit_buf_type get_buffer, register int bits_left,
400  d_derived_tbl * htbl, int min_bits)
401 {
402  register int l = min_bits;
403  register INT32 code;
404 
405  /* HUFF_DECODE has determined that the code is at least min_bits */
406  /* bits long, so fetch that many bits in one swoop. */
407 
408  CHECK_BIT_BUFFER(*state, l, return -1);
409  code = GET_BITS(l);
410 
411  /* Collect the rest of the Huffman code one bit at a time. */
412  /* This is per Figure F.16 in the JPEG spec. */
413 
414  while (code > htbl->maxcode[l]) {
415  code <<= 1;
416  CHECK_BIT_BUFFER(*state, 1, return -1);
417  code |= GET_BITS(1);
418  l++;
419  }
420 
421  /* Unload the local registers */
422  state->get_buffer = get_buffer;
423  state->bits_left = bits_left;
424 
425  /* With garbage input we may reach the sentinel value l = 17. */
426 
427  if (l > 16) {
428  WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE);
429  return 0; /* fake a zero as the safest result */
430  }
431 
432  return htbl->pub->huffval[ (int) (code + htbl->valoffset[l]) ];
433 }
434 
435 
436 /*
437  * Figure F.12: extend sign bit.
438  * On some machines, a shift and add will be faster than a table lookup.
439  */
440 
441 #ifdef AVOID_TABLES
442 
443 #define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x))
444 
445 #else
446 
447 #define HUFF_EXTEND(x,s) ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))
448 
449 static const int extend_test[16] = /* entry n is 2**(n-1) */
450  { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
451  0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };
452 
453 static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */
454  { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1,
455  ((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1,
456  ((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1,
457  ((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 };
458 
459 #endif /* AVOID_TABLES */
460 
461 
462 /*
463  * Check for a restart marker & resynchronize decoder.
464  * Returns FALSE if must suspend.
465  */
466 
467 LOCAL(boolean)
469 {
470  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
471  int ci;
472 
473  /* Throw away any unused bits remaining in bit buffer; */
474  /* include any full bytes in next_marker's count of discarded bytes */
475  cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
476  entropy->bitstate.bits_left = 0;
477 
478  /* Advance past the RSTn marker */
479  if (! (*cinfo->marker->read_restart_marker) (cinfo))
480  return FALSE;
481 
482  /* Re-initialize DC predictions to 0 */
483  for (ci = 0; ci < cinfo->comps_in_scan; ci++)
484  entropy->saved.last_dc_val[ci] = 0;
485 
486  /* Reset restart counter */
487  entropy->restarts_to_go = cinfo->restart_interval;
488 
489  /* Reset out-of-data flag, unless read_restart_marker left us smack up
490  * against a marker. In that case we will end up treating the next data
491  * segment as empty, and we can avoid producing bogus output pixels by
492  * leaving the flag set.
493  */
494  if (cinfo->unread_marker == 0)
495  entropy->pub.insufficient_data = FALSE;
496 
497  return TRUE;
498 }
499 
500 
501 /*
502  * Decode and return one MCU's worth of Huffman-compressed coefficients.
503  * The coefficients are reordered from zigzag order into natural array order,
504  * but are not dequantized.
505  *
506  * The i'th block of the MCU is stored into the block pointed to by
507  * MCU_data[i]. WE ASSUME THIS AREA HAS BEEN ZEROED BY THE CALLER.
508  * (Wholesale zeroing is usually a little faster than retail...)
509  *
510  * Returns FALSE if data source requested suspension. In that case no
511  * changes have been made to permanent state. (Exception: some output
512  * coefficients may already have been assigned. This is harmless for
513  * this module, since we'll just re-assign them on the next call.)
514  */
515 
516 METHODDEF(boolean)
518 {
519  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
520  int blkn;
522  savable_state state;
523 
524  /* Process restart marker if needed; may have to suspend */
525  if (cinfo->restart_interval) {
526  if (entropy->restarts_to_go == 0)
527  if (! process_restart(cinfo))
528  return FALSE;
529  }
530 
531  /* If we've run out of data, just leave the MCU set to zeroes.
532  * This way, we return uniform gray for the remainder of the segment.
533  */
534  if (! entropy->pub.insufficient_data) {
535 
536  /* Load up working state */
537  BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
538  ASSIGN_STATE(state, entropy->saved);
539 
540  /* Outer loop handles each block in the MCU */
541 
542  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
543  JBLOCKROW block = MCU_data[blkn];
544  d_derived_tbl * dctbl = entropy->dc_cur_tbls[blkn];
545  d_derived_tbl * actbl = entropy->ac_cur_tbls[blkn];
546  register int s, k, r;
547 
548  /* Decode a single block's worth of coefficients */
549 
550  /* Section F.2.2.1: decode the DC coefficient difference */
551  HUFF_DECODE(s, br_state, dctbl, return FALSE, label1);
552  if (s) {
553  CHECK_BIT_BUFFER(br_state, s, return FALSE);
554  r = GET_BITS(s);
555  s = HUFF_EXTEND(r, s);
556  }
557 
558  if (entropy->dc_needed[blkn]) {
559  /* Convert DC difference to actual value, update last_dc_val */
560  int ci = cinfo->MCU_membership[blkn];
561  s += state.last_dc_val[ci];
562  state.last_dc_val[ci] = s;
563  /* Output the DC coefficient (assumes jpeg_natural_order[0] = 0) */
564  (*block)[0] = (JCOEF) s;
565  }
566 
567  if (entropy->ac_needed[blkn]) {
568 
569  /* Section F.2.2.2: decode the AC coefficients */
570  /* Since zeroes are skipped, output area must be cleared beforehand */
571  for (k = 1; k < DCTSIZE2; k++) {
572  HUFF_DECODE(s, br_state, actbl, return FALSE, label2);
573 
574  r = s >> 4;
575  s &= 15;
576 
577  if (s) {
578  k += r;
579  CHECK_BIT_BUFFER(br_state, s, return FALSE);
580  r = GET_BITS(s);
581  s = HUFF_EXTEND(r, s);
582  /* Output coefficient in natural (dezigzagged) order.
583  * Note: the extra entries in jpeg_natural_order[] will save us
584  * if k >= DCTSIZE2, which could happen if the data is corrupted.
585  */
586  (*block)[jpeg_natural_order[k]] = (JCOEF) s;
587  } else {
588  if (r != 15)
589  break;
590  k += 15;
591  }
592  }
593 
594  } else {
595 
596  /* Section F.2.2.2: decode the AC coefficients */
597  /* In this path we just discard the values */
598  for (k = 1; k < DCTSIZE2; k++) {
599  HUFF_DECODE(s, br_state, actbl, return FALSE, label3);
600 
601  r = s >> 4;
602  s &= 15;
603 
604  if (s) {
605  k += r;
606  CHECK_BIT_BUFFER(br_state, s, return FALSE);
607  DROP_BITS(s);
608  } else {
609  if (r != 15)
610  break;
611  k += 15;
612  }
613  }
614 
615  }
616  }
617 
618  /* Completed MCU, so update state */
619  BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
620  ASSIGN_STATE(entropy->saved, state);
621  }
622 
623  /* Account for restart interval (no-op if not using restarts) */
624  entropy->restarts_to_go--;
625 
626  return TRUE;
627 }
628 
629 
630 /*
631  * Module initialization routine for Huffman entropy decoding.
632  */
633 
634 GLOBAL(void)
636 {
637  huff_entropy_ptr entropy;
638  int i;
639 
640  entropy = (huff_entropy_ptr)
641  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
642  SIZEOF(huff_entropy_decoder));
643  cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
644  entropy->pub.start_pass = start_pass_huff_decoder;
645  entropy->pub.decode_mcu = decode_mcu;
646 
647  /* Mark tables unallocated */
648  for (i = 0; i < NUM_HUFF_TBLS; i++) {
649  entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
650  }
651 }
#define BITREAD_STATE_VARS
Definition: jdhuff.h:102
#define HUFF_EXTEND(x, s)
Definition: jdhuff.c:447
UINT8 look_sym[1<< HUFF_LOOKAHEAD]
Definition: jdhuff.h:45
jpeg_huff_decode(bitread_working_state *state, register bit_buf_type get_buffer, register int bits_left, d_derived_tbl *htbl, int min_bits)
Definition: jdhuff.c:398
boolean int c_derived_tbl ** pdtbl
Definition: jchuff.h:42
#define DROP_BITS(nbits)
Definition: jdhuff.h:150
GLfloat GLfloat p
#define MIN_GET_BITS
Definition: jdhuff.c:287
INT32 valoffset[17]
Definition: jdhuff.h:30
huff_entropy_encoder * huff_entropy_ptr
Definition: jchuff.c:74
#define GETJOCTET(value)
Definition: jmorecfg.h:119
#define NULL
Definition: ftobjs.h:61
int look_nbits[1<< HUFF_LOOKAHEAD]
Definition: jdhuff.h:44
const int jpeg_natural_order[]
Definition: jutils.c:53
struct jpeg_common_struct * j_common_ptr
Definition: jpeglib.h:261
#define NUM_HUFF_TBLS
Definition: jpeglib.h:44
huff_entropy_decoder * huff_entropy_ptr
Definition: jdhuff.c:78
#define ERREXIT(cinfo, code)
Definition: jerror.h:205
#define SIZEOF(object)
Definition: jinclude.h:80
boolean component_needed
Definition: jpeglib.h:160
short JCOEF
Definition: jmorecfg.h:99
long INT32
Definition: jmorecfg.h:164
#define HUFF_DECODE(result, state, htbl, failaction, slowlabel)
Definition: jdhuff.h:176
png_uint_32 i
Definition: png.h:2640
jpeg_component_info * compptr
Definition: jdct.h:102
#define GET_BITS(nbits)
Definition: jdhuff.h:144
#define JPOOL_IMAGE
Definition: jpeglib.h:749
register bit_buf_type register int d_derived_tbl int min_bits
Definition: jdhuff.h:200
jpeg_make_d_derived_tbl(j_decompress_ptr cinfo, boolean isDC, int tblno, d_derived_tbl **pdtbl)
Definition: jdhuff.c:149
#define DCTSIZE2
Definition: jpeglib.h:42
#define LOCAL(type)
Definition: jmorecfg.h:189
GLdouble GLdouble GLdouble r
#define CHECK_BIT_BUFFER(state, nbits, action)
Definition: jdhuff.h:138
decode_mcu(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
Definition: jdhuff.c:517
start_pass_huff_decoder(j_decompress_ptr cinfo)
Definition: jdhuff.c:86
size_t bytes_in_buffer
Definition: jpeglib.h:727
JBLOCK FAR * JBLOCKROW
Definition: jpeglib.h:71
register bit_buf_type register int int nbits
Definition: jdhuff.h:155
const GLubyte * c
#define WARNMS(cinfo, code)
Definition: jerror.h:238
INT32 maxcode[18]
Definition: jdhuff.h:28
INT32 bit_buf_type
Definition: jdhuff.h:72
#define HUFF_LOOKAHEAD
Definition: jdhuff.h:24
#define FALSE
Definition: ftobjs.h:57
#define ERREXIT1(cinfo, code, p1)
Definition: jerror.h:208
UINT8 bits[17]
Definition: jpeglib.h:102
#define BITREAD_SAVE_STATE(cinfop, permstate)
Definition: jdhuff.h:114
jpeg_fill_bit_buffer(bitread_working_state *state, register bit_buf_type get_buffer, register int bits_left, int nbits)
Definition: jdhuff.c:292
#define ASSIGN_STATE(dest, src)
Definition: jdhuff.c:40
Definition: inftree9.h:24
struct jpeg_source_mgr * src
Definition: jpeglib.h:415
if(!abbox) return FT_THROW(Invalid_Argument)
typedef int
Definition: png.h:978
#define GLOBAL(type)
Definition: jmorecfg.h:191
#define D_MAX_BLOCKS_IN_MCU
Definition: jpeglib.h:57
#define METHODDEF(type)
Definition: jmorecfg.h:187
process_restart(j_decompress_ptr cinfo)
Definition: jdhuff.c:468
UINT8 huffval[256]
Definition: jpeglib.h:104
GLdouble s
#define BITREAD_LOAD_STATE(cinfop, permstate)
Definition: jdhuff.h:107
JHUFF_TBL * htbl
Definition: jchuff.h:47
char JOCTET
Definition: jmorecfg.h:115
boolean insufficient_data
Definition: jpegint.h:216
register bit_buf_type get_buffer
Definition: jdhuff.h:155
local int * code
Definition: enough.c:174
const JOCTET * next_input_byte
Definition: jpeglib.h:726
boolean int tblno
Definition: jchuff.h:42
boolean isDC
Definition: jchuff.h:42
JHUFF_TBL * pub
Definition: jdhuff.h:37
register bit_buf_type register int bits_left
Definition: jdhuff.h:155
struct jpeg_entropy_decoder * entropy
Definition: jpeglib.h:625
#define TRUE
Definition: ftobjs.h:53
#define MAX_COMPS_IN_SCAN
Definition: jpeglib.h:46
#define MEMZERO(target, size)
Definition: jinclude.h:67
jinit_huff_decoder(j_decompress_ptr cinfo)
Definition: jdhuff.c:635