jdphuff.c (22244B)
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 * Lossless JPEG Modifications: 7 * Copyright (C) 1999, Ken Murchison. 8 * libjpeg-turbo Modifications: 9 * Copyright (C) 2015-2016, 2018-2022, D. R. Commander. 10 * For conditions of distribution and use, see the accompanying README.ijg 11 * file. 12 * 13 * This file contains Huffman entropy decoding routines for progressive JPEG. 14 * 15 * Much of the complexity here has to do with supporting input suspension. 16 * If the data source module demands suspension, we want to be able to back 17 * up to the start of the current MCU. To do this, we copy state variables 18 * into local working storage, and update them back to the permanent 19 * storage only upon successful completion of an MCU. 20 * 21 * NOTE: All referenced figures are from 22 * Recommendation ITU-T T.81 (1992) | ISO/IEC 10918-1:1994. 23 */ 24 25 #define JPEG_INTERNALS 26 #include "jinclude.h" 27 #include "jpeglib.h" 28 #include "jdhuff.h" /* Declarations shared with jd*huff.c */ 29 #include <limits.h> 30 31 32 #ifdef D_PROGRESSIVE_SUPPORTED 33 34 /* 35 * Expanded entropy decoder object for progressive Huffman decoding. 36 * 37 * The savable_state subrecord contains fields that change within an MCU, 38 * but must not be updated permanently until we complete the MCU. 39 */ 40 41 typedef struct { 42 unsigned int EOBRUN; /* remaining EOBs in EOBRUN */ 43 int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */ 44 } savable_state; 45 46 typedef struct { 47 struct jpeg_entropy_decoder pub; /* public fields */ 48 49 /* These fields are loaded into local variables at start of each MCU. 50 * In case of suspension, we exit WITHOUT updating them. 51 */ 52 bitread_perm_state bitstate; /* Bit buffer at start of MCU */ 53 savable_state saved; /* Other state at start of MCU */ 54 55 /* These fields are NOT loaded into local working state. */ 56 unsigned int restarts_to_go; /* MCUs left in this restart interval */ 57 58 /* Pointers to derived tables (these workspaces have image lifespan) */ 59 d_derived_tbl *derived_tbls[NUM_HUFF_TBLS]; 60 61 d_derived_tbl *ac_derived_tbl; /* active table during an AC scan */ 62 } phuff_entropy_decoder; 63 64 typedef phuff_entropy_decoder *phuff_entropy_ptr; 65 66 /* Forward declarations */ 67 METHODDEF(boolean) decode_mcu_DC_first(j_decompress_ptr cinfo, 68 JBLOCKROW *MCU_data); 69 METHODDEF(boolean) decode_mcu_AC_first(j_decompress_ptr cinfo, 70 JBLOCKROW *MCU_data); 71 METHODDEF(boolean) decode_mcu_DC_refine(j_decompress_ptr cinfo, 72 JBLOCKROW *MCU_data); 73 METHODDEF(boolean) decode_mcu_AC_refine(j_decompress_ptr cinfo, 74 JBLOCKROW *MCU_data); 75 76 77 /* 78 * Initialize for a Huffman-compressed scan. 79 */ 80 81 METHODDEF(void) 82 start_pass_phuff_decoder(j_decompress_ptr cinfo) 83 { 84 phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy; 85 boolean is_DC_band, bad; 86 int ci, coefi, tbl; 87 d_derived_tbl **pdtbl; 88 int *coef_bit_ptr, *prev_coef_bit_ptr; 89 jpeg_component_info *compptr; 90 91 is_DC_band = (cinfo->Ss == 0); 92 93 /* Validate scan parameters */ 94 bad = FALSE; 95 if (is_DC_band) { 96 if (cinfo->Se != 0) 97 bad = TRUE; 98 } else { 99 /* need not check Ss/Se < 0 since they came from unsigned bytes */ 100 if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2) 101 bad = TRUE; 102 /* AC scans may have only one component */ 103 if (cinfo->comps_in_scan != 1) 104 bad = TRUE; 105 } 106 if (cinfo->Ah != 0) { 107 /* Successive approximation refinement scan: must have Al = Ah-1. */ 108 if (cinfo->Al != cinfo->Ah - 1) 109 bad = TRUE; 110 } 111 if (cinfo->Al > 13) /* need not check for < 0 */ 112 bad = TRUE; 113 /* Arguably the maximum Al value should be less than 13 for 8-bit precision, 114 * but the spec doesn't say so, and we try to be liberal about what we 115 * accept. Note: large Al values could result in out-of-range DC 116 * coefficients during early scans, leading to bizarre displays due to 117 * overflows in the IDCT math. But we won't crash. 118 */ 119 if (bad) 120 ERREXIT4(cinfo, JERR_BAD_PROGRESSION, 121 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al); 122 /* Update progression status, and verify that scan order is legal. 123 * Note that inter-scan inconsistencies are treated as warnings 124 * not fatal errors ... not clear if this is right way to behave. 125 */ 126 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 127 int cindex = cinfo->cur_comp_info[ci]->component_index; 128 coef_bit_ptr = &cinfo->coef_bits[cindex][0]; 129 prev_coef_bit_ptr = &cinfo->coef_bits[cindex + cinfo->num_components][0]; 130 if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */ 131 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0); 132 for (coefi = MIN(cinfo->Ss, 1); coefi <= MAX(cinfo->Se, 9); coefi++) { 133 if (cinfo->input_scan_number > 1) 134 prev_coef_bit_ptr[coefi] = coef_bit_ptr[coefi]; 135 else 136 prev_coef_bit_ptr[coefi] = 0; 137 } 138 for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) { 139 int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi]; 140 if (cinfo->Ah != expected) 141 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi); 142 coef_bit_ptr[coefi] = cinfo->Al; 143 } 144 } 145 146 /* Select MCU decoding routine */ 147 if (cinfo->Ah == 0) { 148 if (is_DC_band) 149 entropy->pub.decode_mcu = decode_mcu_DC_first; 150 else 151 entropy->pub.decode_mcu = decode_mcu_AC_first; 152 } else { 153 if (is_DC_band) 154 entropy->pub.decode_mcu = decode_mcu_DC_refine; 155 else 156 entropy->pub.decode_mcu = decode_mcu_AC_refine; 157 } 158 159 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 160 compptr = cinfo->cur_comp_info[ci]; 161 /* Make sure requested tables are present, and compute derived tables. 162 * We may build same derived table more than once, but it's not expensive. 163 */ 164 if (is_DC_band) { 165 if (cinfo->Ah == 0) { /* DC refinement needs no table */ 166 tbl = compptr->dc_tbl_no; 167 pdtbl = (d_derived_tbl **)(entropy->derived_tbls) + tbl; 168 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl, pdtbl); 169 } 170 } else { 171 tbl = compptr->ac_tbl_no; 172 pdtbl = (d_derived_tbl **)(entropy->derived_tbls) + tbl; 173 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl, pdtbl); 174 /* remember the single active table */ 175 entropy->ac_derived_tbl = entropy->derived_tbls[tbl]; 176 } 177 /* Initialize DC predictions to 0 */ 178 entropy->saved.last_dc_val[ci] = 0; 179 } 180 181 /* Initialize bitread state variables */ 182 entropy->bitstate.bits_left = 0; 183 entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */ 184 entropy->pub.insufficient_data = FALSE; 185 186 /* Initialize private state variables */ 187 entropy->saved.EOBRUN = 0; 188 189 /* Initialize restart counter */ 190 entropy->restarts_to_go = cinfo->restart_interval; 191 } 192 193 194 /* 195 * Figure F.12: extend sign bit. 196 * On some machines, a shift and add will be faster than a table lookup. 197 */ 198 199 #define AVOID_TABLES 200 #ifdef AVOID_TABLES 201 202 #define NEG_1 ((unsigned)-1) 203 #define HUFF_EXTEND(x, s) \ 204 ((x) < (1 << ((s) - 1)) ? (x) + (((NEG_1) << (s)) + 1) : (x)) 205 206 #else 207 208 #define HUFF_EXTEND(x, s) \ 209 ((x) < extend_test[s] ? (x) + extend_offset[s] : (x)) 210 211 static const int extend_test[16] = { /* entry n is 2**(n-1) */ 212 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080, 213 0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 214 }; 215 216 static const int extend_offset[16] = { /* entry n is (-1 << n) + 1 */ 217 0, ((-1) << 1) + 1, ((-1) << 2) + 1, ((-1) << 3) + 1, ((-1) << 4) + 1, 218 ((-1) << 5) + 1, ((-1) << 6) + 1, ((-1) << 7) + 1, ((-1) << 8) + 1, 219 ((-1) << 9) + 1, ((-1) << 10) + 1, ((-1) << 11) + 1, ((-1) << 12) + 1, 220 ((-1) << 13) + 1, ((-1) << 14) + 1, ((-1) << 15) + 1 221 }; 222 223 #endif /* AVOID_TABLES */ 224 225 226 /* 227 * Check for a restart marker & resynchronize decoder. 228 * Returns FALSE if must suspend. 229 */ 230 231 LOCAL(boolean) 232 process_restart(j_decompress_ptr cinfo) 233 { 234 phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy; 235 int ci; 236 237 /* Throw away any unused bits remaining in bit buffer; */ 238 /* include any full bytes in next_marker's count of discarded bytes */ 239 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8; 240 entropy->bitstate.bits_left = 0; 241 242 /* Advance past the RSTn marker */ 243 if (!(*cinfo->marker->read_restart_marker) (cinfo)) 244 return FALSE; 245 246 /* Re-initialize DC predictions to 0 */ 247 for (ci = 0; ci < cinfo->comps_in_scan; ci++) 248 entropy->saved.last_dc_val[ci] = 0; 249 /* Re-init EOB run count, too */ 250 entropy->saved.EOBRUN = 0; 251 252 /* Reset restart counter */ 253 entropy->restarts_to_go = cinfo->restart_interval; 254 255 /* Reset out-of-data flag, unless read_restart_marker left us smack up 256 * against a marker. In that case we will end up treating the next data 257 * segment as empty, and we can avoid producing bogus output pixels by 258 * leaving the flag set. 259 */ 260 if (cinfo->unread_marker == 0) 261 entropy->pub.insufficient_data = FALSE; 262 263 return TRUE; 264 } 265 266 267 /* 268 * Huffman MCU decoding. 269 * Each of these routines decodes and returns one MCU's worth of 270 * Huffman-compressed coefficients. 271 * The coefficients are reordered from zigzag order into natural array order, 272 * but are not dequantized. 273 * 274 * The i'th block of the MCU is stored into the block pointed to by 275 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER. 276 * 277 * We return FALSE if data source requested suspension. In that case no 278 * changes have been made to permanent state. (Exception: some output 279 * coefficients may already have been assigned. This is harmless for 280 * spectral selection, since we'll just re-assign them on the next call. 281 * Successive approximation AC refinement has to be more careful, however.) 282 */ 283 284 /* 285 * MCU decoding for DC initial scan (either spectral selection, 286 * or first pass of successive approximation). 287 */ 288 289 METHODDEF(boolean) 290 decode_mcu_DC_first(j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 291 { 292 phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy; 293 int Al = cinfo->Al; 294 register int s, r; 295 int blkn, ci; 296 JBLOCKROW block; 297 BITREAD_STATE_VARS; 298 savable_state state; 299 d_derived_tbl *tbl; 300 jpeg_component_info *compptr; 301 302 /* Process restart marker if needed; may have to suspend */ 303 if (cinfo->restart_interval) { 304 if (entropy->restarts_to_go == 0) 305 if (!process_restart(cinfo)) 306 return FALSE; 307 } 308 309 /* If we've run out of data, just leave the MCU set to zeroes. 310 * This way, we return uniform gray for the remainder of the segment. 311 */ 312 if (!entropy->pub.insufficient_data) { 313 314 /* Load up working state */ 315 BITREAD_LOAD_STATE(cinfo, entropy->bitstate); 316 state = entropy->saved; 317 318 /* Outer loop handles each block in the MCU */ 319 320 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 321 block = MCU_data[blkn]; 322 ci = cinfo->MCU_membership[blkn]; 323 compptr = cinfo->cur_comp_info[ci]; 324 tbl = entropy->derived_tbls[compptr->dc_tbl_no]; 325 326 /* Decode a single block's worth of coefficients */ 327 328 /* Section F.2.2.1: decode the DC coefficient difference */ 329 HUFF_DECODE(s, br_state, tbl, return FALSE, label1); 330 if (s) { 331 CHECK_BIT_BUFFER(br_state, s, return FALSE); 332 r = GET_BITS(s); 333 s = HUFF_EXTEND(r, s); 334 } 335 336 /* Convert DC difference to actual value, update last_dc_val */ 337 if ((state.last_dc_val[ci] >= 0 && 338 s > INT_MAX - state.last_dc_val[ci]) || 339 (state.last_dc_val[ci] < 0 && s < INT_MIN - state.last_dc_val[ci])) 340 ERREXIT(cinfo, JERR_BAD_DCT_COEF); 341 s += state.last_dc_val[ci]; 342 state.last_dc_val[ci] = s; 343 /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */ 344 (*block)[0] = (JCOEF)LEFT_SHIFT(s, Al); 345 } 346 347 /* Completed MCU, so update state */ 348 BITREAD_SAVE_STATE(cinfo, entropy->bitstate); 349 entropy->saved = state; 350 } 351 352 /* Account for restart interval (no-op if not using restarts) */ 353 if (cinfo->restart_interval) 354 entropy->restarts_to_go--; 355 356 return TRUE; 357 } 358 359 360 /* 361 * MCU decoding for AC initial scan (either spectral selection, 362 * or first pass of successive approximation). 363 */ 364 365 METHODDEF(boolean) 366 decode_mcu_AC_first(j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 367 { 368 phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy; 369 int Se = cinfo->Se; 370 int Al = cinfo->Al; 371 register int s, k, r; 372 unsigned int EOBRUN; 373 JBLOCKROW block; 374 BITREAD_STATE_VARS; 375 d_derived_tbl *tbl; 376 377 /* Process restart marker if needed; may have to suspend */ 378 if (cinfo->restart_interval) { 379 if (entropy->restarts_to_go == 0) 380 if (!process_restart(cinfo)) 381 return FALSE; 382 } 383 384 /* If we've run out of data, just leave the MCU set to zeroes. 385 * This way, we return uniform gray for the remainder of the segment. 386 */ 387 if (!entropy->pub.insufficient_data) { 388 389 /* Load up working state. 390 * We can avoid loading/saving bitread state if in an EOB run. 391 */ 392 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ 393 394 /* There is always only one block per MCU */ 395 396 if (EOBRUN > 0) /* if it's a band of zeroes... */ 397 EOBRUN--; /* ...process it now (we do nothing) */ 398 else { 399 BITREAD_LOAD_STATE(cinfo, entropy->bitstate); 400 block = MCU_data[0]; 401 tbl = entropy->ac_derived_tbl; 402 403 for (k = cinfo->Ss; k <= Se; k++) { 404 HUFF_DECODE(s, br_state, tbl, return FALSE, label2); 405 r = s >> 4; 406 s &= 15; 407 if (s) { 408 k += r; 409 CHECK_BIT_BUFFER(br_state, s, return FALSE); 410 r = GET_BITS(s); 411 s = HUFF_EXTEND(r, s); 412 /* Scale and output coefficient in natural (dezigzagged) order */ 413 (*block)[jpeg_natural_order[k]] = (JCOEF)LEFT_SHIFT(s, Al); 414 } else { 415 if (r == 15) { /* ZRL */ 416 k += 15; /* skip 15 zeroes in band */ 417 } else { /* EOBr, run length is 2^r + appended bits */ 418 EOBRUN = 1 << r; 419 if (r) { /* EOBr, r > 0 */ 420 CHECK_BIT_BUFFER(br_state, r, return FALSE); 421 r = GET_BITS(r); 422 EOBRUN += r; 423 } 424 EOBRUN--; /* this band is processed at this moment */ 425 break; /* force end-of-band */ 426 } 427 } 428 } 429 430 BITREAD_SAVE_STATE(cinfo, entropy->bitstate); 431 } 432 433 /* Completed MCU, so update state */ 434 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ 435 } 436 437 /* Account for restart interval (no-op if not using restarts) */ 438 if (cinfo->restart_interval) 439 entropy->restarts_to_go--; 440 441 return TRUE; 442 } 443 444 445 /* 446 * MCU decoding for DC successive approximation refinement scan. 447 * Note: we assume such scans can be multi-component, although the spec 448 * is not very clear on the point. 449 */ 450 451 METHODDEF(boolean) 452 decode_mcu_DC_refine(j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 453 { 454 phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy; 455 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ 456 int blkn; 457 JBLOCKROW block; 458 BITREAD_STATE_VARS; 459 460 /* Process restart marker if needed; may have to suspend */ 461 if (cinfo->restart_interval) { 462 if (entropy->restarts_to_go == 0) 463 if (!process_restart(cinfo)) 464 return FALSE; 465 } 466 467 /* Not worth the cycles to check insufficient_data here, 468 * since we will not change the data anyway if we read zeroes. 469 */ 470 471 /* Load up working state */ 472 BITREAD_LOAD_STATE(cinfo, entropy->bitstate); 473 474 /* Outer loop handles each block in the MCU */ 475 476 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 477 block = MCU_data[blkn]; 478 479 /* Encoded data is simply the next bit of the two's-complement DC value */ 480 CHECK_BIT_BUFFER(br_state, 1, return FALSE); 481 if (GET_BITS(1)) 482 (*block)[0] |= p1; 483 /* Note: since we use |=, repeating the assignment later is safe */ 484 } 485 486 /* Completed MCU, so update state */ 487 BITREAD_SAVE_STATE(cinfo, entropy->bitstate); 488 489 /* Account for restart interval (no-op if not using restarts) */ 490 if (cinfo->restart_interval) 491 entropy->restarts_to_go--; 492 493 return TRUE; 494 } 495 496 497 /* 498 * MCU decoding for AC successive approximation refinement scan. 499 */ 500 501 METHODDEF(boolean) 502 decode_mcu_AC_refine(j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 503 { 504 phuff_entropy_ptr entropy = (phuff_entropy_ptr)cinfo->entropy; 505 int Se = cinfo->Se; 506 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ 507 int m1 = (NEG_1) << cinfo->Al; /* -1 in the bit position being coded */ 508 register int s, k, r; 509 unsigned int EOBRUN; 510 JBLOCKROW block; 511 JCOEFPTR thiscoef; 512 BITREAD_STATE_VARS; 513 d_derived_tbl *tbl; 514 int num_newnz; 515 int newnz_pos[DCTSIZE2]; 516 517 /* Process restart marker if needed; may have to suspend */ 518 if (cinfo->restart_interval) { 519 if (entropy->restarts_to_go == 0) 520 if (!process_restart(cinfo)) 521 return FALSE; 522 } 523 524 /* If we've run out of data, don't modify the MCU. 525 */ 526 if (!entropy->pub.insufficient_data) { 527 528 /* Load up working state */ 529 BITREAD_LOAD_STATE(cinfo, entropy->bitstate); 530 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ 531 532 /* There is always only one block per MCU */ 533 block = MCU_data[0]; 534 tbl = entropy->ac_derived_tbl; 535 536 /* If we are forced to suspend, we must undo the assignments to any newly 537 * nonzero coefficients in the block, because otherwise we'd get confused 538 * next time about which coefficients were already nonzero. 539 * But we need not undo addition of bits to already-nonzero coefficients; 540 * instead, we can test the current bit to see if we already did it. 541 */ 542 num_newnz = 0; 543 544 /* initialize coefficient loop counter to start of band */ 545 k = cinfo->Ss; 546 547 if (EOBRUN == 0) { 548 for (; k <= Se; k++) { 549 HUFF_DECODE(s, br_state, tbl, goto undoit, label3); 550 r = s >> 4; 551 s &= 15; 552 if (s) { 553 if (s != 1) /* size of new coef should always be 1 */ 554 WARNMS(cinfo, JWRN_HUFF_BAD_CODE); 555 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 556 if (GET_BITS(1)) 557 s = p1; /* newly nonzero coef is positive */ 558 else 559 s = m1; /* newly nonzero coef is negative */ 560 } else { 561 if (r != 15) { 562 EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */ 563 if (r) { 564 CHECK_BIT_BUFFER(br_state, r, goto undoit); 565 r = GET_BITS(r); 566 EOBRUN += r; 567 } 568 break; /* rest of block is handled by EOB logic */ 569 } 570 /* note s = 0 for processing ZRL */ 571 } 572 /* Advance over already-nonzero coefs and r still-zero coefs, 573 * appending correction bits to the nonzeroes. A correction bit is 1 574 * if the absolute value of the coefficient must be increased. 575 */ 576 do { 577 thiscoef = *block + jpeg_natural_order[k]; 578 if (*thiscoef != 0) { 579 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 580 if (GET_BITS(1)) { 581 if ((*thiscoef & p1) == 0) { /* do nothing if already set it */ 582 if (*thiscoef >= 0) 583 *thiscoef += (JCOEF)p1; 584 else 585 *thiscoef += (JCOEF)m1; 586 } 587 } 588 } else { 589 if (--r < 0) 590 break; /* reached target zero coefficient */ 591 } 592 k++; 593 } while (k <= Se); 594 if (s) { 595 int pos = jpeg_natural_order[k]; 596 /* Output newly nonzero coefficient */ 597 (*block)[pos] = (JCOEF)s; 598 /* Remember its position in case we have to suspend */ 599 newnz_pos[num_newnz++] = pos; 600 } 601 } 602 } 603 604 if (EOBRUN > 0) { 605 /* Scan any remaining coefficient positions after the end-of-band 606 * (the last newly nonzero coefficient, if any). Append a correction 607 * bit to each already-nonzero coefficient. A correction bit is 1 608 * if the absolute value of the coefficient must be increased. 609 */ 610 for (; k <= Se; k++) { 611 thiscoef = *block + jpeg_natural_order[k]; 612 if (*thiscoef != 0) { 613 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 614 if (GET_BITS(1)) { 615 if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */ 616 if (*thiscoef >= 0) 617 *thiscoef += (JCOEF)p1; 618 else 619 *thiscoef += (JCOEF)m1; 620 } 621 } 622 } 623 } 624 /* Count one block completed in EOB run */ 625 EOBRUN--; 626 } 627 628 /* Completed MCU, so update state */ 629 BITREAD_SAVE_STATE(cinfo, entropy->bitstate); 630 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ 631 } 632 633 /* Account for restart interval (no-op if not using restarts) */ 634 if (cinfo->restart_interval) 635 entropy->restarts_to_go--; 636 637 return TRUE; 638 639 undoit: 640 /* Re-zero any output coefficients that we made newly nonzero */ 641 while (num_newnz > 0) 642 (*block)[newnz_pos[--num_newnz]] = 0; 643 644 return FALSE; 645 } 646 647 648 /* 649 * Module initialization routine for progressive Huffman entropy decoding. 650 */ 651 652 GLOBAL(void) 653 jinit_phuff_decoder(j_decompress_ptr cinfo) 654 { 655 phuff_entropy_ptr entropy; 656 int *coef_bit_ptr; 657 int ci, i; 658 659 entropy = (phuff_entropy_ptr) 660 (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE, 661 sizeof(phuff_entropy_decoder)); 662 cinfo->entropy = (struct jpeg_entropy_decoder *)entropy; 663 entropy->pub.start_pass = start_pass_phuff_decoder; 664 665 /* Mark derived tables unallocated */ 666 for (i = 0; i < NUM_HUFF_TBLS; i++) { 667 entropy->derived_tbls[i] = NULL; 668 } 669 670 /* Create progression status table */ 671 cinfo->coef_bits = (int (*)[DCTSIZE2]) 672 (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE, 673 cinfo->num_components * 2 * DCTSIZE2 * 674 sizeof(int)); 675 coef_bit_ptr = &cinfo->coef_bits[0][0]; 676 for (ci = 0; ci < cinfo->num_components; ci++) 677 for (i = 0; i < DCTSIZE2; i++) 678 *coef_bit_ptr++ = -1; 679 } 680 681 #endif /* D_PROGRESSIVE_SUPPORTED */