jdphuff.c (20559B)
1 /* 2 * jdphuff.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 decoding routines for progressive JPEG. 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 jdhuff.c */ 21 22 23 #ifdef D_PROGRESSIVE_SUPPORTED 24 25 /* 26 * Expanded entropy decoder object for progressive Huffman decoding. 27 * 28 * The savable_state subrecord contains fields that change within an MCU, 29 * but must not be updated permanently until we complete the MCU. 30 */ 31 32 typedef struct { 33 unsigned int EOBRUN; /* remaining EOBs in EOBRUN */ 34 int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */ 35 } savable_state; 36 37 /* This macro is to work around compilers with missing or broken 38 * structure assignment. You'll need to fix this code if you have 39 * such a compiler and you change MAX_COMPS_IN_SCAN. 40 */ 41 42 #ifndef NO_STRUCT_ASSIGN 43 #define ASSIGN_STATE(dest,src) ((dest) = (src)) 44 #else 45 #if MAX_COMPS_IN_SCAN == 4 46 #define ASSIGN_STATE(dest,src) \ 47 ((dest).EOBRUN = (src).EOBRUN, \ 48 (dest).last_dc_val[0] = (src).last_dc_val[0], \ 49 (dest).last_dc_val[1] = (src).last_dc_val[1], \ 50 (dest).last_dc_val[2] = (src).last_dc_val[2], \ 51 (dest).last_dc_val[3] = (src).last_dc_val[3]) 52 #endif 53 #endif 54 55 56 typedef struct { 57 struct jpeg_entropy_decoder pub; /* public fields */ 58 59 /* These fields are loaded into local variables at start of each MCU. 60 * In case of suspension, we exit WITHOUT updating them. 61 */ 62 bitread_perm_state bitstate; /* Bit buffer at start of MCU */ 63 savable_state saved; /* Other state at start of MCU */ 64 65 /* These fields are NOT loaded into local working state. */ 66 unsigned int restarts_to_go; /* MCUs left in this restart interval */ 67 68 /* Pointers to derived tables (these workspaces have image lifespan) */ 69 d_derived_tbl * derived_tbls[NUM_HUFF_TBLS]; 70 71 d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */ 72 } phuff_entropy_decoder; 73 74 typedef phuff_entropy_decoder * phuff_entropy_ptr; 75 76 /* Forward declarations */ 77 METHODDEF(boolean) decode_mcu_DC_first JPP((j_decompress_ptr cinfo, 78 JBLOCKROW *MCU_data)); 79 METHODDEF(boolean) decode_mcu_AC_first JPP((j_decompress_ptr cinfo, 80 JBLOCKROW *MCU_data)); 81 METHODDEF(boolean) decode_mcu_DC_refine JPP((j_decompress_ptr cinfo, 82 JBLOCKROW *MCU_data)); 83 METHODDEF(boolean) decode_mcu_AC_refine JPP((j_decompress_ptr cinfo, 84 JBLOCKROW *MCU_data)); 85 86 87 /* 88 * Initialize for a Huffman-compressed scan. 89 */ 90 91 METHODDEF(void) 92 start_pass_phuff_decoder (j_decompress_ptr cinfo) 93 { 94 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 95 boolean is_DC_band, bad; 96 int ci, coefi, tbl; 97 int *coef_bit_ptr; 98 jpeg_component_info * compptr; 99 100 is_DC_band = (cinfo->Ss == 0); 101 102 /* Validate scan parameters */ 103 bad = FALSE; 104 if (is_DC_band) { 105 if (cinfo->Se != 0) 106 bad = TRUE; 107 } else { 108 /* need not check Ss/Se < 0 since they came from unsigned bytes */ 109 if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2) 110 bad = TRUE; 111 /* AC scans may have only one component */ 112 if (cinfo->comps_in_scan != 1) 113 bad = TRUE; 114 } 115 if (cinfo->Ah != 0) { 116 /* Successive approximation refinement scan: must have Al = Ah-1. */ 117 if (cinfo->Al != cinfo->Ah-1) 118 bad = TRUE; 119 } 120 if (cinfo->Al > 13) /* need not check for < 0 */ 121 bad = TRUE; 122 /* Arguably the maximum Al value should be less than 13 for 8-bit precision, 123 * but the spec doesn't say so, and we try to be liberal about what we 124 * accept. Note: large Al values could result in out-of-range DC 125 * coefficients during early scans, leading to bizarre displays due to 126 * overflows in the IDCT math. But we won't crash. 127 */ 128 if (bad) 129 ERREXIT4(cinfo, JERR_BAD_PROGRESSION, 130 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al); 131 /* Update progression status, and verify that scan order is legal. 132 * Note that inter-scan inconsistencies are treated as warnings 133 * not fatal errors ... not clear if this is right way to behave. 134 */ 135 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 136 int cindex = cinfo->cur_comp_info[ci]->component_index; 137 coef_bit_ptr = & cinfo->coef_bits[cindex][0]; 138 if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */ 139 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0); 140 for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) { 141 int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi]; 142 if (cinfo->Ah != expected) 143 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi); 144 coef_bit_ptr[coefi] = cinfo->Al; 145 } 146 } 147 148 /* Select MCU decoding routine */ 149 if (cinfo->Ah == 0) { 150 if (is_DC_band) 151 entropy->pub.decode_mcu = decode_mcu_DC_first; 152 else 153 entropy->pub.decode_mcu = decode_mcu_AC_first; 154 } else { 155 if (is_DC_band) 156 entropy->pub.decode_mcu = decode_mcu_DC_refine; 157 else 158 entropy->pub.decode_mcu = decode_mcu_AC_refine; 159 } 160 161 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 162 compptr = cinfo->cur_comp_info[ci]; 163 /* Make sure requested tables are present, and compute derived tables. 164 * We may build same derived table more than once, but it's not expensive. 165 */ 166 if (is_DC_band) { 167 if (cinfo->Ah == 0) { /* DC refinement needs no table */ 168 tbl = compptr->dc_tbl_no; 169 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl, 170 & entropy->derived_tbls[tbl]); 171 } 172 } else { 173 tbl = compptr->ac_tbl_no; 174 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl, 175 & entropy->derived_tbls[tbl]); 176 /* remember the single active table */ 177 entropy->ac_derived_tbl = entropy->derived_tbls[tbl]; 178 } 179 /* Initialize DC predictions to 0 */ 180 entropy->saved.last_dc_val[ci] = 0; 181 } 182 183 /* Initialize bitread state variables */ 184 entropy->bitstate.bits_left = 0; 185 entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */ 186 entropy->pub.insufficient_data = FALSE; 187 188 /* Initialize private state variables */ 189 entropy->saved.EOBRUN = 0; 190 191 /* Initialize restart counter */ 192 entropy->restarts_to_go = cinfo->restart_interval; 193 } 194 195 196 /* 197 * Figure F.12: extend sign bit. 198 * On some machines, a shift and add will be faster than a table lookup. 199 */ 200 201 #ifdef AVOID_TABLES 202 203 #define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x)) 204 205 #else 206 207 #define HUFF_EXTEND(x,s) ((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 static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */ 214 { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1, 215 ((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1, 216 ((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1, 217 ((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 }; 218 219 #endif /* AVOID_TABLES */ 220 221 222 /* 223 * Check for a restart marker & resynchronize decoder. 224 * Returns FALSE if must suspend. 225 */ 226 227 LOCAL(boolean) 228 process_restart (j_decompress_ptr cinfo) 229 { 230 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 231 int ci; 232 233 /* Throw away any unused bits remaining in bit buffer; */ 234 /* include any full bytes in next_marker's count of discarded bytes */ 235 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8; 236 entropy->bitstate.bits_left = 0; 237 238 /* Advance past the RSTn marker */ 239 if (! (*cinfo->marker->read_restart_marker) (cinfo)) 240 return FALSE; 241 242 /* Re-initialize DC predictions to 0 */ 243 for (ci = 0; ci < cinfo->comps_in_scan; ci++) 244 entropy->saved.last_dc_val[ci] = 0; 245 /* Re-init EOB run count, too */ 246 entropy->saved.EOBRUN = 0; 247 248 /* Reset restart counter */ 249 entropy->restarts_to_go = cinfo->restart_interval; 250 251 /* Reset out-of-data flag, unless read_restart_marker left us smack up 252 * against a marker. In that case we will end up treating the next data 253 * segment as empty, and we can avoid producing bogus output pixels by 254 * leaving the flag set. 255 */ 256 if (cinfo->unread_marker == 0) 257 entropy->pub.insufficient_data = FALSE; 258 259 return TRUE; 260 } 261 262 263 /* 264 * Huffman MCU decoding. 265 * Each of these routines decodes and returns one MCU's worth of 266 * Huffman-compressed coefficients. 267 * The coefficients are reordered from zigzag order into natural array order, 268 * but are not dequantized. 269 * 270 * The i'th block of the MCU is stored into the block pointed to by 271 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER. 272 * 273 * We return FALSE if data source requested suspension. In that case no 274 * changes have been made to permanent state. (Exception: some output 275 * coefficients may already have been assigned. This is harmless for 276 * spectral selection, since we'll just re-assign them on the next call. 277 * Successive approximation AC refinement has to be more careful, however.) 278 */ 279 280 /* 281 * MCU decoding for DC initial scan (either spectral selection, 282 * or first pass of successive approximation). 283 */ 284 285 METHODDEF(boolean) 286 decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 287 { 288 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 289 int Al = cinfo->Al; 290 register int s, r; 291 int blkn, ci; 292 JBLOCKROW block; 293 BITREAD_STATE_VARS; 294 savable_state state; 295 d_derived_tbl * tbl; 296 jpeg_component_info * compptr; 297 298 /* Process restart marker if needed; may have to suspend */ 299 if (cinfo->restart_interval) { 300 if (entropy->restarts_to_go == 0) 301 if (! process_restart(cinfo)) 302 return FALSE; 303 } 304 305 /* If we've run out of data, just leave the MCU set to zeroes. 306 * This way, we return uniform gray for the remainder of the segment. 307 */ 308 if (! entropy->pub.insufficient_data) { 309 310 /* Load up working state */ 311 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 312 ASSIGN_STATE(state, entropy->saved); 313 314 /* Outer loop handles each block in the MCU */ 315 316 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 317 block = MCU_data[blkn]; 318 ci = cinfo->MCU_membership[blkn]; 319 compptr = cinfo->cur_comp_info[ci]; 320 tbl = entropy->derived_tbls[compptr->dc_tbl_no]; 321 322 /* Decode a single block's worth of coefficients */ 323 324 /* Section F.2.2.1: decode the DC coefficient difference */ 325 HUFF_DECODE(s, br_state, tbl, return FALSE, label1); 326 if (s) { 327 CHECK_BIT_BUFFER(br_state, s, return FALSE); 328 r = GET_BITS(s); 329 s = HUFF_EXTEND(r, s); 330 } 331 332 /* Convert DC difference to actual value, update last_dc_val */ 333 s += state.last_dc_val[ci]; 334 state.last_dc_val[ci] = s; 335 /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */ 336 (*block)[0] = (JCOEF) (s << Al); 337 } 338 339 /* Completed MCU, so update state */ 340 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 341 ASSIGN_STATE(entropy->saved, state); 342 } 343 344 /* Account for restart interval (no-op if not using restarts) */ 345 entropy->restarts_to_go--; 346 347 return TRUE; 348 } 349 350 351 /* 352 * MCU decoding for AC initial scan (either spectral selection, 353 * or first pass of successive approximation). 354 */ 355 356 METHODDEF(boolean) 357 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 358 { 359 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 360 int Se = cinfo->Se; 361 int Al = cinfo->Al; 362 register int s, k, r; 363 unsigned int EOBRUN; 364 JBLOCKROW block; 365 BITREAD_STATE_VARS; 366 d_derived_tbl * tbl; 367 368 /* Process restart marker if needed; may have to suspend */ 369 if (cinfo->restart_interval) { 370 if (entropy->restarts_to_go == 0) 371 if (! process_restart(cinfo)) 372 return FALSE; 373 } 374 375 /* If we've run out of data, just leave the MCU set to zeroes. 376 * This way, we return uniform gray for the remainder of the segment. 377 */ 378 if (! entropy->pub.insufficient_data) { 379 380 /* Load up working state. 381 * We can avoid loading/saving bitread state if in an EOB run. 382 */ 383 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ 384 385 /* There is always only one block per MCU */ 386 387 if (EOBRUN > 0) /* if it's a band of zeroes... */ 388 EOBRUN--; /* ...process it now (we do nothing) */ 389 else { 390 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 391 block = MCU_data[0]; 392 tbl = entropy->ac_derived_tbl; 393 394 for (k = cinfo->Ss; k <= Se; k++) { 395 HUFF_DECODE(s, br_state, tbl, return FALSE, label2); 396 r = s >> 4; 397 s &= 15; 398 if (s) { 399 k += r; 400 CHECK_BIT_BUFFER(br_state, s, return FALSE); 401 r = GET_BITS(s); 402 s = HUFF_EXTEND(r, s); 403 /* Scale and output coefficient in natural (dezigzagged) order */ 404 (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al); 405 } else { 406 if (r == 15) { /* ZRL */ 407 k += 15; /* skip 15 zeroes in band */ 408 } else { /* EOBr, run length is 2^r + appended bits */ 409 EOBRUN = 1 << r; 410 if (r) { /* EOBr, r > 0 */ 411 CHECK_BIT_BUFFER(br_state, r, return FALSE); 412 r = GET_BITS(r); 413 EOBRUN += r; 414 } 415 EOBRUN--; /* this band is processed at this moment */ 416 break; /* force end-of-band */ 417 } 418 } 419 } 420 421 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 422 } 423 424 /* Completed MCU, so update state */ 425 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ 426 } 427 428 /* Account for restart interval (no-op if not using restarts) */ 429 entropy->restarts_to_go--; 430 431 return TRUE; 432 } 433 434 435 /* 436 * MCU decoding for DC successive approximation refinement scan. 437 * Note: we assume such scans can be multi-component, although the spec 438 * is not very clear on the point. 439 */ 440 441 METHODDEF(boolean) 442 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 443 { 444 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 445 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ 446 int blkn; 447 JBLOCKROW block; 448 BITREAD_STATE_VARS; 449 450 /* Process restart marker if needed; may have to suspend */ 451 if (cinfo->restart_interval) { 452 if (entropy->restarts_to_go == 0) 453 if (! process_restart(cinfo)) 454 return FALSE; 455 } 456 457 /* Not worth the cycles to check insufficient_data here, 458 * since we will not change the data anyway if we read zeroes. 459 */ 460 461 /* Load up working state */ 462 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 463 464 /* Outer loop handles each block in the MCU */ 465 466 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 467 block = MCU_data[blkn]; 468 469 /* Encoded data is simply the next bit of the two's-complement DC value */ 470 CHECK_BIT_BUFFER(br_state, 1, return FALSE); 471 if (GET_BITS(1)) 472 (*block)[0] |= p1; 473 /* Note: since we use |=, repeating the assignment later is safe */ 474 } 475 476 /* Completed MCU, so update state */ 477 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 478 479 /* Account for restart interval (no-op if not using restarts) */ 480 entropy->restarts_to_go--; 481 482 return TRUE; 483 } 484 485 486 /* 487 * MCU decoding for AC successive approximation refinement scan. 488 */ 489 490 METHODDEF(boolean) 491 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 492 { 493 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 494 int Se = cinfo->Se; 495 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ 496 int m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */ 497 register int s, k, r; 498 unsigned int EOBRUN; 499 JBLOCKROW block; 500 JCOEFPTR thiscoef; 501 BITREAD_STATE_VARS; 502 d_derived_tbl * tbl; 503 int num_newnz; 504 int newnz_pos[DCTSIZE2]; 505 506 /* Process restart marker if needed; may have to suspend */ 507 if (cinfo->restart_interval) { 508 if (entropy->restarts_to_go == 0) 509 if (! process_restart(cinfo)) 510 return FALSE; 511 } 512 513 /* If we've run out of data, don't modify the MCU. 514 */ 515 if (! entropy->pub.insufficient_data) { 516 517 /* Load up working state */ 518 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 519 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ 520 521 /* There is always only one block per MCU */ 522 block = MCU_data[0]; 523 tbl = entropy->ac_derived_tbl; 524 525 /* If we are forced to suspend, we must undo the assignments to any newly 526 * nonzero coefficients in the block, because otherwise we'd get confused 527 * next time about which coefficients were already nonzero. 528 * But we need not undo addition of bits to already-nonzero coefficients; 529 * instead, we can test the current bit to see if we already did it. 530 */ 531 num_newnz = 0; 532 533 /* initialize coefficient loop counter to start of band */ 534 k = cinfo->Ss; 535 536 if (EOBRUN == 0) { 537 for (; k <= Se; k++) { 538 HUFF_DECODE(s, br_state, tbl, goto undoit, label3); 539 r = s >> 4; 540 s &= 15; 541 if (s) { 542 if (s != 1) /* size of new coef should always be 1 */ 543 WARNMS(cinfo, JWRN_HUFF_BAD_CODE); 544 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 545 if (GET_BITS(1)) 546 s = p1; /* newly nonzero coef is positive */ 547 else 548 s = m1; /* newly nonzero coef is negative */ 549 } else { 550 if (r != 15) { 551 EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */ 552 if (r) { 553 CHECK_BIT_BUFFER(br_state, r, goto undoit); 554 r = GET_BITS(r); 555 EOBRUN += r; 556 } 557 break; /* rest of block is handled by EOB logic */ 558 } 559 /* note s = 0 for processing ZRL */ 560 } 561 /* Advance over already-nonzero coefs and r still-zero coefs, 562 * appending correction bits to the nonzeroes. A correction bit is 1 563 * if the absolute value of the coefficient must be increased. 564 */ 565 do { 566 thiscoef = *block + jpeg_natural_order[k]; 567 if (*thiscoef != 0) { 568 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 569 if (GET_BITS(1)) { 570 if ((*thiscoef & p1) == 0) { /* do nothing if already set it */ 571 if (*thiscoef >= 0) 572 *thiscoef += p1; 573 else 574 *thiscoef += m1; 575 } 576 } 577 } else { 578 if (--r < 0) 579 break; /* reached target zero coefficient */ 580 } 581 k++; 582 } while (k <= Se); 583 if (s) { 584 int pos = jpeg_natural_order[k]; 585 /* Output newly nonzero coefficient */ 586 (*block)[pos] = (JCOEF) s; 587 /* Remember its position in case we have to suspend */ 588 newnz_pos[num_newnz++] = pos; 589 } 590 } 591 } 592 593 if (EOBRUN > 0) { 594 /* Scan any remaining coefficient positions after the end-of-band 595 * (the last newly nonzero coefficient, if any). Append a correction 596 * bit to each already-nonzero coefficient. A correction bit is 1 597 * if the absolute value of the coefficient must be increased. 598 */ 599 for (; k <= Se; k++) { 600 thiscoef = *block + jpeg_natural_order[k]; 601 if (*thiscoef != 0) { 602 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 603 if (GET_BITS(1)) { 604 if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */ 605 if (*thiscoef >= 0) 606 *thiscoef += p1; 607 else 608 *thiscoef += m1; 609 } 610 } 611 } 612 } 613 /* Count one block completed in EOB run */ 614 EOBRUN--; 615 } 616 617 /* Completed MCU, so update state */ 618 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 619 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ 620 } 621 622 /* Account for restart interval (no-op if not using restarts) */ 623 entropy->restarts_to_go--; 624 625 return TRUE; 626 627 undoit: 628 /* Re-zero any output coefficients that we made newly nonzero */ 629 while (num_newnz > 0) 630 (*block)[newnz_pos[--num_newnz]] = 0; 631 632 return FALSE; 633 } 634 635 636 /* 637 * Module initialization routine for progressive Huffman entropy decoding. 638 */ 639 640 GLOBAL(void) 641 jinit_phuff_decoder (j_decompress_ptr cinfo) 642 { 643 phuff_entropy_ptr entropy; 644 int *coef_bit_ptr; 645 int ci, i; 646 647 entropy = (phuff_entropy_ptr) 648 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 649 SIZEOF(phuff_entropy_decoder)); 650 cinfo->entropy = (struct jpeg_entropy_decoder *) entropy; 651 entropy->pub.start_pass = start_pass_phuff_decoder; 652 653 /* Mark derived tables unallocated */ 654 for (i = 0; i < NUM_HUFF_TBLS; i++) { 655 entropy->derived_tbls[i] = NULL; 656 } 657 658 /* Create progression status table */ 659 cinfo->coef_bits = (int (*)[DCTSIZE2]) 660 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 661 cinfo->num_components*DCTSIZE2*SIZEOF(int)); 662 coef_bit_ptr = & cinfo->coef_bits[0][0]; 663 for (ci = 0; ci < cinfo->num_components; ci++) 664 for (i = 0; i < DCTSIZE2; i++) 665 *coef_bit_ptr++ = -1; 666 } 667 668 #endif /* D_PROGRESSIVE_SUPPORTED */