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 #define AVOID_TABLES 202 #ifdef AVOID_TABLES 203 204 #define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x)) 205 206 #else 207 208 #define HUFF_EXTEND(x,s) ((x) < extend_test[s] ? (x) + extend_offset[s] : (x)) 209 210 static const int extend_test[16] = /* entry n is 2**(n-1) */ 211 { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080, 212 0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 }; 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 #endif /* AVOID_TABLES */ 221 222 223 /* 224 * Check for a restart marker & resynchronize decoder. 225 * Returns FALSE if must suspend. 226 */ 227 228 LOCAL(boolean) 229 process_restart (j_decompress_ptr cinfo) 230 { 231 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 232 int ci; 233 234 /* Throw away any unused bits remaining in bit buffer; */ 235 /* include any full bytes in next_marker's count of discarded bytes */ 236 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8; 237 entropy->bitstate.bits_left = 0; 238 239 /* Advance past the RSTn marker */ 240 if (! (*cinfo->marker->read_restart_marker) (cinfo)) 241 return FALSE; 242 243 /* Re-initialize DC predictions to 0 */ 244 for (ci = 0; ci < cinfo->comps_in_scan; ci++) 245 entropy->saved.last_dc_val[ci] = 0; 246 /* Re-init EOB run count, too */ 247 entropy->saved.EOBRUN = 0; 248 249 /* Reset restart counter */ 250 entropy->restarts_to_go = cinfo->restart_interval; 251 252 /* Reset out-of-data flag, unless read_restart_marker left us smack up 253 * against a marker. In that case we will end up treating the next data 254 * segment as empty, and we can avoid producing bogus output pixels by 255 * leaving the flag set. 256 */ 257 if (cinfo->unread_marker == 0) 258 entropy->pub.insufficient_data = FALSE; 259 260 return TRUE; 261 } 262 263 264 /* 265 * Huffman MCU decoding. 266 * Each of these routines decodes and returns one MCU's worth of 267 * Huffman-compressed coefficients. 268 * The coefficients are reordered from zigzag order into natural array order, 269 * but are not dequantized. 270 * 271 * The i'th block of the MCU is stored into the block pointed to by 272 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER. 273 * 274 * We return FALSE if data source requested suspension. In that case no 275 * changes have been made to permanent state. (Exception: some output 276 * coefficients may already have been assigned. This is harmless for 277 * spectral selection, since we'll just re-assign them on the next call. 278 * Successive approximation AC refinement has to be more careful, however.) 279 */ 280 281 /* 282 * MCU decoding for DC initial scan (either spectral selection, 283 * or first pass of successive approximation). 284 */ 285 286 METHODDEF(boolean) 287 decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 288 { 289 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 290 int Al = cinfo->Al; 291 register int s, r; 292 int blkn, ci; 293 JBLOCKROW block; 294 BITREAD_STATE_VARS; 295 savable_state state; 296 d_derived_tbl * tbl; 297 jpeg_component_info * compptr; 298 299 /* Process restart marker if needed; may have to suspend */ 300 if (cinfo->restart_interval) { 301 if (entropy->restarts_to_go == 0) 302 if (! process_restart(cinfo)) 303 return FALSE; 304 } 305 306 /* If we've run out of data, just leave the MCU set to zeroes. 307 * This way, we return uniform gray for the remainder of the segment. 308 */ 309 if (! entropy->pub.insufficient_data) { 310 311 /* Load up working state */ 312 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 313 ASSIGN_STATE(state, entropy->saved); 314 315 /* Outer loop handles each block in the MCU */ 316 317 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 318 block = MCU_data[blkn]; 319 ci = cinfo->MCU_membership[blkn]; 320 compptr = cinfo->cur_comp_info[ci]; 321 tbl = entropy->derived_tbls[compptr->dc_tbl_no]; 322 323 /* Decode a single block's worth of coefficients */ 324 325 /* Section F.2.2.1: decode the DC coefficient difference */ 326 HUFF_DECODE(s, br_state, tbl, return FALSE, label1); 327 if (s) { 328 CHECK_BIT_BUFFER(br_state, s, return FALSE); 329 r = GET_BITS(s); 330 s = HUFF_EXTEND(r, s); 331 } 332 333 /* Convert DC difference to actual value, update last_dc_val */ 334 s += state.last_dc_val[ci]; 335 state.last_dc_val[ci] = s; 336 /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */ 337 (*block)[0] = (JCOEF) (s << Al); 338 } 339 340 /* Completed MCU, so update state */ 341 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 342 ASSIGN_STATE(entropy->saved, state); 343 } 344 345 /* Account for restart interval (no-op if not using restarts) */ 346 entropy->restarts_to_go--; 347 348 return TRUE; 349 } 350 351 352 /* 353 * MCU decoding for AC initial scan (either spectral selection, 354 * or first pass of successive approximation). 355 */ 356 357 METHODDEF(boolean) 358 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 359 { 360 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 361 int Se = cinfo->Se; 362 int Al = cinfo->Al; 363 register int s, k, r; 364 unsigned int EOBRUN; 365 JBLOCKROW block; 366 BITREAD_STATE_VARS; 367 d_derived_tbl * tbl; 368 369 /* Process restart marker if needed; may have to suspend */ 370 if (cinfo->restart_interval) { 371 if (entropy->restarts_to_go == 0) 372 if (! process_restart(cinfo)) 373 return FALSE; 374 } 375 376 /* If we've run out of data, just leave the MCU set to zeroes. 377 * This way, we return uniform gray for the remainder of the segment. 378 */ 379 if (! entropy->pub.insufficient_data) { 380 381 /* Load up working state. 382 * We can avoid loading/saving bitread state if in an EOB run. 383 */ 384 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ 385 386 /* There is always only one block per MCU */ 387 388 if (EOBRUN > 0) /* if it's a band of zeroes... */ 389 EOBRUN--; /* ...process it now (we do nothing) */ 390 else { 391 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 392 block = MCU_data[0]; 393 tbl = entropy->ac_derived_tbl; 394 395 for (k = cinfo->Ss; k <= Se; k++) { 396 HUFF_DECODE(s, br_state, tbl, return FALSE, label2); 397 r = s >> 4; 398 s &= 15; 399 if (s) { 400 k += r; 401 CHECK_BIT_BUFFER(br_state, s, return FALSE); 402 r = GET_BITS(s); 403 s = HUFF_EXTEND(r, s); 404 /* Scale and output coefficient in natural (dezigzagged) order */ 405 (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al); 406 } else { 407 if (r == 15) { /* ZRL */ 408 k += 15; /* skip 15 zeroes in band */ 409 } else { /* EOBr, run length is 2^r + appended bits */ 410 EOBRUN = 1 << r; 411 if (r) { /* EOBr, r > 0 */ 412 CHECK_BIT_BUFFER(br_state, r, return FALSE); 413 r = GET_BITS(r); 414 EOBRUN += r; 415 } 416 EOBRUN--; /* this band is processed at this moment */ 417 break; /* force end-of-band */ 418 } 419 } 420 } 421 422 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 423 } 424 425 /* Completed MCU, so update state */ 426 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ 427 } 428 429 /* Account for restart interval (no-op if not using restarts) */ 430 entropy->restarts_to_go--; 431 432 return TRUE; 433 } 434 435 436 /* 437 * MCU decoding for DC successive approximation refinement scan. 438 * Note: we assume such scans can be multi-component, although the spec 439 * is not very clear on the point. 440 */ 441 442 METHODDEF(boolean) 443 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 444 { 445 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 446 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ 447 int blkn; 448 JBLOCKROW block; 449 BITREAD_STATE_VARS; 450 451 /* Process restart marker if needed; may have to suspend */ 452 if (cinfo->restart_interval) { 453 if (entropy->restarts_to_go == 0) 454 if (! process_restart(cinfo)) 455 return FALSE; 456 } 457 458 /* Not worth the cycles to check insufficient_data here, 459 * since we will not change the data anyway if we read zeroes. 460 */ 461 462 /* Load up working state */ 463 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 464 465 /* Outer loop handles each block in the MCU */ 466 467 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 468 block = MCU_data[blkn]; 469 470 /* Encoded data is simply the next bit of the two's-complement DC value */ 471 CHECK_BIT_BUFFER(br_state, 1, return FALSE); 472 if (GET_BITS(1)) 473 (*block)[0] |= p1; 474 /* Note: since we use |=, repeating the assignment later is safe */ 475 } 476 477 /* Completed MCU, so update state */ 478 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 479 480 /* Account for restart interval (no-op if not using restarts) */ 481 entropy->restarts_to_go--; 482 483 return TRUE; 484 } 485 486 487 /* 488 * MCU decoding for AC successive approximation refinement scan. 489 */ 490 491 METHODDEF(boolean) 492 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 493 { 494 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 495 int Se = cinfo->Se; 496 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ 497 int m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */ 498 register int s, k, r; 499 unsigned int EOBRUN; 500 JBLOCKROW block; 501 JCOEFPTR thiscoef; 502 BITREAD_STATE_VARS; 503 d_derived_tbl * tbl; 504 int num_newnz; 505 int newnz_pos[DCTSIZE2]; 506 507 /* Process restart marker if needed; may have to suspend */ 508 if (cinfo->restart_interval) { 509 if (entropy->restarts_to_go == 0) 510 if (! process_restart(cinfo)) 511 return FALSE; 512 } 513 514 /* If we've run out of data, don't modify the MCU. 515 */ 516 if (! entropy->pub.insufficient_data) { 517 518 /* Load up working state */ 519 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 520 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ 521 522 /* There is always only one block per MCU */ 523 block = MCU_data[0]; 524 tbl = entropy->ac_derived_tbl; 525 526 /* If we are forced to suspend, we must undo the assignments to any newly 527 * nonzero coefficients in the block, because otherwise we'd get confused 528 * next time about which coefficients were already nonzero. 529 * But we need not undo addition of bits to already-nonzero coefficients; 530 * instead, we can test the current bit to see if we already did it. 531 */ 532 num_newnz = 0; 533 534 /* initialize coefficient loop counter to start of band */ 535 k = cinfo->Ss; 536 537 if (EOBRUN == 0) { 538 for (; k <= Se; k++) { 539 HUFF_DECODE(s, br_state, tbl, goto undoit, label3); 540 r = s >> 4; 541 s &= 15; 542 if (s) { 543 if (s != 1) /* size of new coef should always be 1 */ 544 WARNMS(cinfo, JWRN_HUFF_BAD_CODE); 545 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 546 if (GET_BITS(1)) 547 s = p1; /* newly nonzero coef is positive */ 548 else 549 s = m1; /* newly nonzero coef is negative */ 550 } else { 551 if (r != 15) { 552 EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */ 553 if (r) { 554 CHECK_BIT_BUFFER(br_state, r, goto undoit); 555 r = GET_BITS(r); 556 EOBRUN += r; 557 } 558 break; /* rest of block is handled by EOB logic */ 559 } 560 /* note s = 0 for processing ZRL */ 561 } 562 /* Advance over already-nonzero coefs and r still-zero coefs, 563 * appending correction bits to the nonzeroes. A correction bit is 1 564 * if the absolute value of the coefficient must be increased. 565 */ 566 do { 567 thiscoef = *block + jpeg_natural_order[k]; 568 if (*thiscoef != 0) { 569 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 570 if (GET_BITS(1)) { 571 if ((*thiscoef & p1) == 0) { /* do nothing if already set it */ 572 if (*thiscoef >= 0) 573 *thiscoef += p1; 574 else 575 *thiscoef += m1; 576 } 577 } 578 } else { 579 if (--r < 0) 580 break; /* reached target zero coefficient */ 581 } 582 k++; 583 } while (k <= Se); 584 if (s) { 585 int pos = jpeg_natural_order[k]; 586 /* Output newly nonzero coefficient */ 587 (*block)[pos] = (JCOEF) s; 588 /* Remember its position in case we have to suspend */ 589 newnz_pos[num_newnz++] = pos; 590 } 591 } 592 } 593 594 if (EOBRUN > 0) { 595 /* Scan any remaining coefficient positions after the end-of-band 596 * (the last newly nonzero coefficient, if any). Append a correction 597 * bit to each already-nonzero coefficient. A correction bit is 1 598 * if the absolute value of the coefficient must be increased. 599 */ 600 for (; k <= Se; k++) { 601 thiscoef = *block + jpeg_natural_order[k]; 602 if (*thiscoef != 0) { 603 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 604 if (GET_BITS(1)) { 605 if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */ 606 if (*thiscoef >= 0) 607 *thiscoef += p1; 608 else 609 *thiscoef += m1; 610 } 611 } 612 } 613 } 614 /* Count one block completed in EOB run */ 615 EOBRUN--; 616 } 617 618 /* Completed MCU, so update state */ 619 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 620 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ 621 } 622 623 /* Account for restart interval (no-op if not using restarts) */ 624 entropy->restarts_to_go--; 625 626 return TRUE; 627 628 undoit: 629 /* Re-zero any output coefficients that we made newly nonzero */ 630 while (num_newnz > 0) 631 (*block)[newnz_pos[--num_newnz]] = 0; 632 633 return FALSE; 634 } 635 636 637 /* 638 * Module initialization routine for progressive Huffman entropy decoding. 639 */ 640 641 GLOBAL(void) 642 jinit_phuff_decoder (j_decompress_ptr cinfo) 643 { 644 phuff_entropy_ptr entropy; 645 int *coef_bit_ptr; 646 int ci, i; 647 648 entropy = (phuff_entropy_ptr) 649 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 650 SIZEOF(phuff_entropy_decoder)); 651 cinfo->entropy = (struct jpeg_entropy_decoder *) entropy; 652 entropy->pub.start_pass = start_pass_phuff_decoder; 653 654 /* Mark derived tables unallocated */ 655 for (i = 0; i < NUM_HUFF_TBLS; i++) { 656 entropy->derived_tbls[i] = NULL; 657 } 658 659 /* Create progression status table */ 660 cinfo->coef_bits = (int (*)[DCTSIZE2]) 661 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 662 cinfo->num_components*DCTSIZE2*SIZEOF(int)); 663 coef_bit_ptr = & cinfo->coef_bits[0][0]; 664 for (ci = 0; ci < cinfo->num_components; ci++) 665 for (i = 0; i < DCTSIZE2; i++) 666 *coef_bit_ptr++ = -1; 667 } 668 669 #endif /* D_PROGRESSIVE_SUPPORTED */ 670
