1 | /* |
2 | * jdphuff.c |
3 | * |
4 | * This file was part of the Independent JPEG Group's software: |
5 | * Copyright (C) 1995-1997, Thomas G. Lane. |
6 | * libjpeg-turbo Modifications: |
7 | * Copyright (C) 2015-2016, 2018-2021, D. R. Commander. |
8 | * For conditions of distribution and use, see the accompanying README.ijg |
9 | * file. |
10 | * |
11 | * This file contains Huffman entropy decoding routines for progressive JPEG. |
12 | * |
13 | * Much of the complexity here has to do with supporting input suspension. |
14 | * If the data source module demands suspension, we want to be able to back |
15 | * up to the start of the current MCU. To do this, we copy state variables |
16 | * into local working storage, and update them back to the permanent |
17 | * storage only upon successful completion of an MCU. |
18 | * |
19 | * NOTE: All referenced figures are from |
20 | * Recommendation ITU-T T.81 (1992) | ISO/IEC 10918-1:1994. |
21 | */ |
22 | |
23 | #define JPEG_INTERNALS |
24 | #include "jinclude.h" |
25 | #include "jpeglib.h" |
26 | #include "jdhuff.h" /* Declarations shared with jdhuff.c */ |
27 | #include <limits.h> |
28 | |
29 | |
30 | #ifdef D_PROGRESSIVE_SUPPORTED |
31 | |
32 | /* |
33 | * Expanded entropy decoder object for progressive Huffman decoding. |
34 | * |
35 | * The savable_state subrecord contains fields that change within an MCU, |
36 | * but must not be updated permanently until we complete the MCU. |
37 | */ |
38 | |
39 | typedef struct { |
40 | unsigned int EOBRUN; /* remaining EOBs in EOBRUN */ |
41 | int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */ |
42 | } savable_state; |
43 | |
44 | typedef struct { |
45 | struct jpeg_entropy_decoder pub; /* public fields */ |
46 | |
47 | /* These fields are loaded into local variables at start of each MCU. |
48 | * In case of suspension, we exit WITHOUT updating them. |
49 | */ |
50 | bitread_perm_state bitstate; /* Bit buffer at start of MCU */ |
51 | savable_state saved; /* Other state at start of MCU */ |
52 | |
53 | /* These fields are NOT loaded into local working state. */ |
54 | unsigned int restarts_to_go; /* MCUs left in this restart interval */ |
55 | |
56 | /* Pointers to derived tables (these workspaces have image lifespan) */ |
57 | d_derived_tbl *derived_tbls[NUM_HUFF_TBLS]; |
58 | |
59 | d_derived_tbl *ac_derived_tbl; /* active table during an AC scan */ |
60 | } phuff_entropy_decoder; |
61 | |
62 | typedef phuff_entropy_decoder *phuff_entropy_ptr; |
63 | |
64 | /* Forward declarations */ |
65 | METHODDEF(boolean) decode_mcu_DC_first(j_decompress_ptr cinfo, |
66 | JBLOCKROW *MCU_data); |
67 | METHODDEF(boolean) decode_mcu_AC_first(j_decompress_ptr cinfo, |
68 | JBLOCKROW *MCU_data); |
69 | METHODDEF(boolean) decode_mcu_DC_refine(j_decompress_ptr cinfo, |
70 | JBLOCKROW *MCU_data); |
71 | METHODDEF(boolean) decode_mcu_AC_refine(j_decompress_ptr cinfo, |
72 | JBLOCKROW *MCU_data); |
73 | |
74 | |
75 | /* |
76 | * Initialize for a Huffman-compressed scan. |
77 | */ |
78 | |
79 | METHODDEF(void) |
80 | start_pass_phuff_decoder(j_decompress_ptr cinfo) |
81 | { |
82 | phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy; |
83 | boolean is_DC_band, bad; |
84 | int ci, coefi, tbl; |
85 | d_derived_tbl **pdtbl; |
86 | int *coef_bit_ptr, *prev_coef_bit_ptr; |
87 | jpeg_component_info *compptr; |
88 | |
89 | is_DC_band = (cinfo->Ss == 0); |
90 | |
91 | /* Validate scan parameters */ |
92 | bad = FALSE; |
93 | if (is_DC_band) { |
94 | if (cinfo->Se != 0) |
95 | bad = TRUE; |
96 | } else { |
97 | /* need not check Ss/Se < 0 since they came from unsigned bytes */ |
98 | if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2) |
99 | bad = TRUE; |
100 | /* AC scans may have only one component */ |
101 | if (cinfo->comps_in_scan != 1) |
102 | bad = TRUE; |
103 | } |
104 | if (cinfo->Ah != 0) { |
105 | /* Successive approximation refinement scan: must have Al = Ah-1. */ |
106 | if (cinfo->Al != cinfo->Ah - 1) |
107 | bad = TRUE; |
108 | } |
109 | if (cinfo->Al > 13) /* need not check for < 0 */ |
110 | bad = TRUE; |
111 | /* Arguably the maximum Al value should be less than 13 for 8-bit precision, |
112 | * but the spec doesn't say so, and we try to be liberal about what we |
113 | * accept. Note: large Al values could result in out-of-range DC |
114 | * coefficients during early scans, leading to bizarre displays due to |
115 | * overflows in the IDCT math. But we won't crash. |
116 | */ |
117 | if (bad) |
118 | ERREXIT4(cinfo, JERR_BAD_PROGRESSION, |
119 | cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al); |
120 | /* Update progression status, and verify that scan order is legal. |
121 | * Note that inter-scan inconsistencies are treated as warnings |
122 | * not fatal errors ... not clear if this is right way to behave. |
123 | */ |
124 | for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
125 | int cindex = cinfo->cur_comp_info[ci]->component_index; |
126 | coef_bit_ptr = &cinfo->coef_bits[cindex][0]; |
127 | prev_coef_bit_ptr = &cinfo->coef_bits[cindex + cinfo->num_components][0]; |
128 | if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */ |
129 | WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0); |
130 | for (coefi = MIN(cinfo->Ss, 1); coefi <= MAX(cinfo->Se, 9); coefi++) { |
131 | if (cinfo->input_scan_number > 1) |
132 | prev_coef_bit_ptr[coefi] = coef_bit_ptr[coefi]; |
133 | else |
134 | prev_coef_bit_ptr[coefi] = 0; |
135 | } |
136 | for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) { |
137 | int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi]; |
138 | if (cinfo->Ah != expected) |
139 | WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi); |
140 | coef_bit_ptr[coefi] = cinfo->Al; |
141 | } |
142 | } |
143 | |
144 | /* Select MCU decoding routine */ |
145 | if (cinfo->Ah == 0) { |
146 | if (is_DC_band) |
147 | entropy->pub.decode_mcu = decode_mcu_DC_first; |
148 | else |
149 | entropy->pub.decode_mcu = decode_mcu_AC_first; |
150 | } else { |
151 | if (is_DC_band) |
152 | entropy->pub.decode_mcu = decode_mcu_DC_refine; |
153 | else |
154 | entropy->pub.decode_mcu = decode_mcu_AC_refine; |
155 | } |
156 | |
157 | for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
158 | compptr = cinfo->cur_comp_info[ci]; |
159 | /* Make sure requested tables are present, and compute derived tables. |
160 | * We may build same derived table more than once, but it's not expensive. |
161 | */ |
162 | if (is_DC_band) { |
163 | if (cinfo->Ah == 0) { /* DC refinement needs no table */ |
164 | tbl = compptr->dc_tbl_no; |
165 | pdtbl = (d_derived_tbl **)(entropy->derived_tbls) + tbl; |
166 | jpeg_make_d_derived_tbl(cinfo, TRUE, tbl, pdtbl); |
167 | } |
168 | } else { |
169 | tbl = compptr->ac_tbl_no; |
170 | pdtbl = (d_derived_tbl **)(entropy->derived_tbls) + tbl; |
171 | jpeg_make_d_derived_tbl(cinfo, FALSE, tbl, pdtbl); |
172 | /* remember the single active table */ |
173 | entropy->ac_derived_tbl = entropy->derived_tbls[tbl]; |
174 | } |
175 | /* Initialize DC predictions to 0 */ |
176 | entropy->saved.last_dc_val[ci] = 0; |
177 | } |
178 | |
179 | /* Initialize bitread state variables */ |
180 | entropy->bitstate.bits_left = 0; |
181 | entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */ |
182 | entropy->pub.insufficient_data = FALSE; |
183 | |
184 | /* Initialize private state variables */ |
185 | entropy->saved.EOBRUN = 0; |
186 | |
187 | /* Initialize restart counter */ |
188 | entropy->restarts_to_go = cinfo->restart_interval; |
189 | } |
190 | |
191 | |
192 | /* |
193 | * Figure F.12: extend sign bit. |
194 | * On some machines, a shift and add will be faster than a table lookup. |
195 | */ |
196 | |
197 | #define AVOID_TABLES |
198 | #ifdef AVOID_TABLES |
199 | |
200 | #define NEG_1 ((unsigned)-1) |
201 | #define HUFF_EXTEND(x, s) \ |
202 | ((x) < (1 << ((s) - 1)) ? (x) + (((NEG_1) << (s)) + 1) : (x)) |
203 | |
204 | #else |
205 | |
206 | #define HUFF_EXTEND(x, s) \ |
207 | ((x) < extend_test[s] ? (x) + extend_offset[s] : (x)) |
208 | |
209 | static const int extend_test[16] = { /* entry n is 2**(n-1) */ |
210 | 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080, |
211 | 0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 |
212 | }; |
213 | |
214 | static const int extend_offset[16] = { /* entry n is (-1 << n) + 1 */ |
215 | 0, ((-1) << 1) + 1, ((-1) << 2) + 1, ((-1) << 3) + 1, ((-1) << 4) + 1, |
216 | ((-1) << 5) + 1, ((-1) << 6) + 1, ((-1) << 7) + 1, ((-1) << 8) + 1, |
217 | ((-1) << 9) + 1, ((-1) << 10) + 1, ((-1) << 11) + 1, ((-1) << 12) + 1, |
218 | ((-1) << 13) + 1, ((-1) << 14) + 1, ((-1) << 15) + 1 |
219 | }; |
220 | |
221 | #endif /* AVOID_TABLES */ |
222 | |
223 | |
224 | /* |
225 | * Check for a restart marker & resynchronize decoder. |
226 | * Returns FALSE if must suspend. |
227 | */ |
228 | |
229 | LOCAL(boolean) |
230 | process_restart(j_decompress_ptr cinfo) |
231 | { |
232 | phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy; |
233 | int ci; |
234 | |
235 | /* Throw away any unused bits remaining in bit buffer; */ |
236 | /* include any full bytes in next_marker's count of discarded bytes */ |
237 | cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8; |
238 | entropy->bitstate.bits_left = 0; |
239 | |
240 | /* Advance past the RSTn marker */ |
241 | if (!(*cinfo->marker->read_restart_marker) (cinfo)) |
242 | return FALSE; |
243 | |
244 | /* Re-initialize DC predictions to 0 */ |
245 | for (ci = 0; ci < cinfo->comps_in_scan; ci++) |
246 | entropy->saved.last_dc_val[ci] = 0; |
247 | /* Re-init EOB run count, too */ |
248 | entropy->saved.EOBRUN = 0; |
249 | |
250 | /* Reset restart counter */ |
251 | entropy->restarts_to_go = cinfo->restart_interval; |
252 | |
253 | /* Reset out-of-data flag, unless read_restart_marker left us smack up |
254 | * against a marker. In that case we will end up treating the next data |
255 | * segment as empty, and we can avoid producing bogus output pixels by |
256 | * leaving the flag set. |
257 | */ |
258 | if (cinfo->unread_marker == 0) |
259 | entropy->pub.insufficient_data = FALSE; |
260 | |
261 | return TRUE; |
262 | } |
263 | |
264 | |
265 | /* |
266 | * Huffman MCU decoding. |
267 | * Each of these routines decodes and returns one MCU's worth of |
268 | * Huffman-compressed coefficients. |
269 | * The coefficients are reordered from zigzag order into natural array order, |
270 | * but are not dequantized. |
271 | * |
272 | * The i'th block of the MCU is stored into the block pointed to by |
273 | * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER. |
274 | * |
275 | * We return FALSE if data source requested suspension. In that case no |
276 | * changes have been made to permanent state. (Exception: some output |
277 | * coefficients may already have been assigned. This is harmless for |
278 | * spectral selection, since we'll just re-assign them on the next call. |
279 | * Successive approximation AC refinement has to be more careful, however.) |
280 | */ |
281 | |
282 | /* |
283 | * MCU decoding for DC initial scan (either spectral selection, |
284 | * or first pass of successive approximation). |
285 | */ |
286 | |
287 | METHODDEF(boolean) |
288 | decode_mcu_DC_first(j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
289 | { |
290 | phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy; |
291 | int Al = cinfo->Al; |
292 | register int s, r; |
293 | int blkn, ci; |
294 | JBLOCKROW block; |
295 | BITREAD_STATE_VARS; |
296 | savable_state state; |
297 | d_derived_tbl *tbl; |
298 | jpeg_component_info *compptr; |
299 | |
300 | /* Process restart marker if needed; may have to suspend */ |
301 | if (cinfo->restart_interval) { |
302 | if (entropy->restarts_to_go == 0) |
303 | if (!process_restart(cinfo)) |
304 | return FALSE; |
305 | } |
306 | |
307 | /* If we've run out of data, just leave the MCU set to zeroes. |
308 | * This way, we return uniform gray for the remainder of the segment. |
309 | */ |
310 | if (!entropy->pub.insufficient_data) { |
311 | |
312 | /* Load up working state */ |
313 | BITREAD_LOAD_STATE(cinfo, entropy->bitstate); |
314 | state = entropy->saved; |
315 | |
316 | /* Outer loop handles each block in the MCU */ |
317 | |
318 | for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { |
319 | block = MCU_data[blkn]; |
320 | ci = cinfo->MCU_membership[blkn]; |
321 | compptr = cinfo->cur_comp_info[ci]; |
322 | tbl = entropy->derived_tbls[compptr->dc_tbl_no]; |
323 | |
324 | /* Decode a single block's worth of coefficients */ |
325 | |
326 | /* Section F.2.2.1: decode the DC coefficient difference */ |
327 | HUFF_DECODE(s, br_state, tbl, return FALSE, label1); |
328 | if (s) { |
329 | CHECK_BIT_BUFFER(br_state, s, return FALSE); |
330 | r = GET_BITS(s); |
331 | s = HUFF_EXTEND(r, s); |
332 | } |
333 | |
334 | /* Convert DC difference to actual value, update last_dc_val */ |
335 | if ((state.last_dc_val[ci] >= 0 && |
336 | s > INT_MAX - state.last_dc_val[ci]) || |
337 | (state.last_dc_val[ci] < 0 && s < INT_MIN - state.last_dc_val[ci])) |
338 | ERREXIT(cinfo, JERR_BAD_DCT_COEF); |
339 | s += state.last_dc_val[ci]; |
340 | state.last_dc_val[ci] = s; |
341 | /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */ |
342 | (*block)[0] = (JCOEF)LEFT_SHIFT(s, Al); |
343 | } |
344 | |
345 | /* Completed MCU, so update state */ |
346 | BITREAD_SAVE_STATE(cinfo, entropy->bitstate); |
347 | entropy->saved = state; |
348 | } |
349 | |
350 | /* Account for restart interval (no-op if not using restarts) */ |
351 | if (cinfo->restart_interval) |
352 | entropy->restarts_to_go--; |
353 | |
354 | return TRUE; |
355 | } |
356 | |
357 | |
358 | /* |
359 | * MCU decoding for AC initial scan (either spectral selection, |
360 | * or first pass of successive approximation). |
361 | */ |
362 | |
363 | METHODDEF(boolean) |
364 | decode_mcu_AC_first(j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
365 | { |
366 | phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy; |
367 | int Se = cinfo->Se; |
368 | int Al = cinfo->Al; |
369 | register int s, k, r; |
370 | unsigned int EOBRUN; |
371 | JBLOCKROW block; |
372 | BITREAD_STATE_VARS; |
373 | d_derived_tbl *tbl; |
374 | |
375 | /* Process restart marker if needed; may have to suspend */ |
376 | if (cinfo->restart_interval) { |
377 | if (entropy->restarts_to_go == 0) |
378 | if (!process_restart(cinfo)) |
379 | return FALSE; |
380 | } |
381 | |
382 | /* If we've run out of data, just leave the MCU set to zeroes. |
383 | * This way, we return uniform gray for the remainder of the segment. |
384 | */ |
385 | if (!entropy->pub.insufficient_data) { |
386 | |
387 | /* Load up working state. |
388 | * We can avoid loading/saving bitread state if in an EOB run. |
389 | */ |
390 | EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ |
391 | |
392 | /* There is always only one block per MCU */ |
393 | |
394 | if (EOBRUN > 0) /* if it's a band of zeroes... */ |
395 | EOBRUN--; /* ...process it now (we do nothing) */ |
396 | else { |
397 | BITREAD_LOAD_STATE(cinfo, entropy->bitstate); |
398 | block = MCU_data[0]; |
399 | tbl = entropy->ac_derived_tbl; |
400 | |
401 | for (k = cinfo->Ss; k <= Se; k++) { |
402 | HUFF_DECODE(s, br_state, tbl, return FALSE, label2); |
403 | r = s >> 4; |
404 | s &= 15; |
405 | if (s) { |
406 | k += r; |
407 | CHECK_BIT_BUFFER(br_state, s, return FALSE); |
408 | r = GET_BITS(s); |
409 | s = HUFF_EXTEND(r, s); |
410 | /* Scale and output coefficient in natural (dezigzagged) order */ |
411 | (*block)[jpeg_natural_order[k]] = (JCOEF)LEFT_SHIFT(s, Al); |
412 | } else { |
413 | if (r == 15) { /* ZRL */ |
414 | k += 15; /* skip 15 zeroes in band */ |
415 | } else { /* EOBr, run length is 2^r + appended bits */ |
416 | EOBRUN = 1 << r; |
417 | if (r) { /* EOBr, r > 0 */ |
418 | CHECK_BIT_BUFFER(br_state, r, return FALSE); |
419 | r = GET_BITS(r); |
420 | EOBRUN += r; |
421 | } |
422 | EOBRUN--; /* this band is processed at this moment */ |
423 | break; /* force end-of-band */ |
424 | } |
425 | } |
426 | } |
427 | |
428 | BITREAD_SAVE_STATE(cinfo, entropy->bitstate); |
429 | } |
430 | |
431 | /* Completed MCU, so update state */ |
432 | entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ |
433 | } |
434 | |
435 | /* Account for restart interval (no-op if not using restarts) */ |
436 | if (cinfo->restart_interval) |
437 | entropy->restarts_to_go--; |
438 | |
439 | return TRUE; |
440 | } |
441 | |
442 | |
443 | /* |
444 | * MCU decoding for DC successive approximation refinement scan. |
445 | * Note: we assume such scans can be multi-component, although the spec |
446 | * is not very clear on the point. |
447 | */ |
448 | |
449 | METHODDEF(boolean) |
450 | decode_mcu_DC_refine(j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
451 | { |
452 | phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy; |
453 | int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ |
454 | int blkn; |
455 | JBLOCKROW block; |
456 | BITREAD_STATE_VARS; |
457 | |
458 | /* Process restart marker if needed; may have to suspend */ |
459 | if (cinfo->restart_interval) { |
460 | if (entropy->restarts_to_go == 0) |
461 | if (!process_restart(cinfo)) |
462 | return FALSE; |
463 | } |
464 | |
465 | /* Not worth the cycles to check insufficient_data here, |
466 | * since we will not change the data anyway if we read zeroes. |
467 | */ |
468 | |
469 | /* Load up working state */ |
470 | BITREAD_LOAD_STATE(cinfo, entropy->bitstate); |
471 | |
472 | /* Outer loop handles each block in the MCU */ |
473 | |
474 | for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { |
475 | block = MCU_data[blkn]; |
476 | |
477 | /* Encoded data is simply the next bit of the two's-complement DC value */ |
478 | CHECK_BIT_BUFFER(br_state, 1, return FALSE); |
479 | if (GET_BITS(1)) |
480 | (*block)[0] |= p1; |
481 | /* Note: since we use |=, repeating the assignment later is safe */ |
482 | } |
483 | |
484 | /* Completed MCU, so update state */ |
485 | BITREAD_SAVE_STATE(cinfo, entropy->bitstate); |
486 | |
487 | /* Account for restart interval (no-op if not using restarts) */ |
488 | if (cinfo->restart_interval) |
489 | entropy->restarts_to_go--; |
490 | |
491 | return TRUE; |
492 | } |
493 | |
494 | |
495 | /* |
496 | * MCU decoding for AC successive approximation refinement scan. |
497 | */ |
498 | |
499 | METHODDEF(boolean) |
500 | decode_mcu_AC_refine(j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
501 | { |
502 | phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy; |
503 | int Se = cinfo->Se; |
504 | int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ |
505 | int m1 = (NEG_1) << cinfo->Al; /* -1 in the bit position being coded */ |
506 | register int s, k, r; |
507 | unsigned int EOBRUN; |
508 | JBLOCKROW block; |
509 | JCOEFPTR thiscoef; |
510 | BITREAD_STATE_VARS; |
511 | d_derived_tbl *tbl; |
512 | int num_newnz; |
513 | int newnz_pos[DCTSIZE2]; |
514 | |
515 | /* Process restart marker if needed; may have to suspend */ |
516 | if (cinfo->restart_interval) { |
517 | if (entropy->restarts_to_go == 0) |
518 | if (!process_restart(cinfo)) |
519 | return FALSE; |
520 | } |
521 | |
522 | /* If we've run out of data, don't modify the MCU. |
523 | */ |
524 | if (!entropy->pub.insufficient_data) { |
525 | |
526 | /* Load up working state */ |
527 | BITREAD_LOAD_STATE(cinfo, entropy->bitstate); |
528 | EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ |
529 | |
530 | /* There is always only one block per MCU */ |
531 | block = MCU_data[0]; |
532 | tbl = entropy->ac_derived_tbl; |
533 | |
534 | /* If we are forced to suspend, we must undo the assignments to any newly |
535 | * nonzero coefficients in the block, because otherwise we'd get confused |
536 | * next time about which coefficients were already nonzero. |
537 | * But we need not undo addition of bits to already-nonzero coefficients; |
538 | * instead, we can test the current bit to see if we already did it. |
539 | */ |
540 | num_newnz = 0; |
541 | |
542 | /* initialize coefficient loop counter to start of band */ |
543 | k = cinfo->Ss; |
544 | |
545 | if (EOBRUN == 0) { |
546 | for (; k <= Se; k++) { |
547 | HUFF_DECODE(s, br_state, tbl, goto undoit, label3); |
548 | r = s >> 4; |
549 | s &= 15; |
550 | if (s) { |
551 | if (s != 1) /* size of new coef should always be 1 */ |
552 | WARNMS(cinfo, JWRN_HUFF_BAD_CODE); |
553 | CHECK_BIT_BUFFER(br_state, 1, goto undoit); |
554 | if (GET_BITS(1)) |
555 | s = p1; /* newly nonzero coef is positive */ |
556 | else |
557 | s = m1; /* newly nonzero coef is negative */ |
558 | } else { |
559 | if (r != 15) { |
560 | EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */ |
561 | if (r) { |
562 | CHECK_BIT_BUFFER(br_state, r, goto undoit); |
563 | r = GET_BITS(r); |
564 | EOBRUN += r; |
565 | } |
566 | break; /* rest of block is handled by EOB logic */ |
567 | } |
568 | /* note s = 0 for processing ZRL */ |
569 | } |
570 | /* Advance over already-nonzero coefs and r still-zero coefs, |
571 | * appending correction bits to the nonzeroes. A correction bit is 1 |
572 | * if the absolute value of the coefficient must be increased. |
573 | */ |
574 | do { |
575 | thiscoef = *block + jpeg_natural_order[k]; |
576 | if (*thiscoef != 0) { |
577 | CHECK_BIT_BUFFER(br_state, 1, goto undoit); |
578 | if (GET_BITS(1)) { |
579 | if ((*thiscoef & p1) == 0) { /* do nothing if already set it */ |
580 | if (*thiscoef >= 0) |
581 | *thiscoef += p1; |
582 | else |
583 | *thiscoef += m1; |
584 | } |
585 | } |
586 | } else { |
587 | if (--r < 0) |
588 | break; /* reached target zero coefficient */ |
589 | } |
590 | k++; |
591 | } while (k <= Se); |
592 | if (s) { |
593 | int pos = jpeg_natural_order[k]; |
594 | /* Output newly nonzero coefficient */ |
595 | (*block)[pos] = (JCOEF)s; |
596 | /* Remember its position in case we have to suspend */ |
597 | newnz_pos[num_newnz++] = pos; |
598 | } |
599 | } |
600 | } |
601 | |
602 | if (EOBRUN > 0) { |
603 | /* Scan any remaining coefficient positions after the end-of-band |
604 | * (the last newly nonzero coefficient, if any). Append a correction |
605 | * bit to each already-nonzero coefficient. A correction bit is 1 |
606 | * if the absolute value of the coefficient must be increased. |
607 | */ |
608 | for (; k <= Se; k++) { |
609 | thiscoef = *block + jpeg_natural_order[k]; |
610 | if (*thiscoef != 0) { |
611 | CHECK_BIT_BUFFER(br_state, 1, goto undoit); |
612 | if (GET_BITS(1)) { |
613 | if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */ |
614 | if (*thiscoef >= 0) |
615 | *thiscoef += p1; |
616 | else |
617 | *thiscoef += m1; |
618 | } |
619 | } |
620 | } |
621 | } |
622 | /* Count one block completed in EOB run */ |
623 | EOBRUN--; |
624 | } |
625 | |
626 | /* Completed MCU, so update state */ |
627 | BITREAD_SAVE_STATE(cinfo, entropy->bitstate); |
628 | entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ |
629 | } |
630 | |
631 | /* Account for restart interval (no-op if not using restarts) */ |
632 | if (cinfo->restart_interval) |
633 | entropy->restarts_to_go--; |
634 | |
635 | return TRUE; |
636 | |
637 | undoit: |
638 | /* Re-zero any output coefficients that we made newly nonzero */ |
639 | while (num_newnz > 0) |
640 | (*block)[newnz_pos[--num_newnz]] = 0; |
641 | |
642 | return FALSE; |
643 | } |
644 | |
645 | |
646 | /* |
647 | * Module initialization routine for progressive Huffman entropy decoding. |
648 | */ |
649 | |
650 | GLOBAL(void) |
651 | jinit_phuff_decoder(j_decompress_ptr cinfo) |
652 | { |
653 | phuff_entropy_ptr entropy; |
654 | int *coef_bit_ptr; |
655 | int ci, i; |
656 | |
657 | entropy = (phuff_entropy_ptr) |
658 | (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE, |
659 | sizeof(phuff_entropy_decoder)); |
660 | cinfo->entropy = (struct jpeg_entropy_decoder *)entropy; |
661 | entropy->pub.start_pass = start_pass_phuff_decoder; |
662 | |
663 | /* Mark derived tables unallocated */ |
664 | for (i = 0; i < NUM_HUFF_TBLS; i++) { |
665 | entropy->derived_tbls[i] = NULL; |
666 | } |
667 | |
668 | /* Create progression status table */ |
669 | cinfo->coef_bits = (int (*)[DCTSIZE2]) |
670 | (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE, |
671 | cinfo->num_components * 2 * DCTSIZE2 * |
672 | sizeof(int)); |
673 | coef_bit_ptr = &cinfo->coef_bits[0][0]; |
674 | for (ci = 0; ci < cinfo->num_components; ci++) |
675 | for (i = 0; i < DCTSIZE2; i++) |
676 | *coef_bit_ptr++ = -1; |
677 | } |
678 | |
679 | #endif /* D_PROGRESSIVE_SUPPORTED */ |
680 | |