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 * Initialize for a Huffman-compressed scan. 88 */ 89 90 METHODDEF(void) 91 start_pass_phuff_decoder (j_decompress_ptr cinfo) 92 { 93 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 94 boolean is_DC_band, bad; 95 int ci, coefi, tbl; 96 int *coef_bit_ptr; 97 jpeg_component_info * compptr; 98 99 is_DC_band = (cinfo->Ss == 0); 100 101 /* Validate scan parameters */ 102 bad = FALSE; 103 if (is_DC_band) { 104 if (cinfo->Se != 0) 105 bad = TRUE; 106 } else { 107 /* need not check Ss/Se < 0 since they came from unsigned bytes */ 108 if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2) 109 bad = TRUE; 110 /* AC scans may have only one component */ 111 if (cinfo->comps_in_scan != 1) 112 bad = TRUE; 113 } 114 if (cinfo->Ah != 0) { 115 /* Successive approximation refinement scan: must have Al = Ah-1. */ 116 if (cinfo->Al != cinfo->Ah-1) 117 bad = TRUE; 118 } 119 if (cinfo->Al > 13) /* need not check for < 0 */ 120 bad = TRUE; 121 /* Arguably the maximum Al value should be less than 13 for 8-bit precision, 122 * but the spec doesn't say so, and we try to be liberal about what we 123 * accept. Note: large Al values could result in out-of-range DC 124 * coefficients during early scans, leading to bizarre displays due to 125 * overflows in the IDCT math. But we won't crash. 126 */ 127 if (bad) 128 ERREXIT4(cinfo, JERR_BAD_PROGRESSION, 129 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al); 130 /* Update progression status, and verify that scan order is legal. 131 * Note that inter-scan inconsistencies are treated as warnings 132 * not fatal errors ... not clear if this is right way to behave. 133 */ 134 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 135 int cindex = cinfo->cur_comp_info[ci]->component_index; 136 coef_bit_ptr = & cinfo->coef_bits[cindex][0]; 137 if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */ 138 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0); 139 for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) { 140 int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi]; 141 if (cinfo->Ah != expected) 142 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi); 143 coef_bit_ptr[coefi] = cinfo->Al; 144 } 145 } 146 147 /* Select MCU decoding routine */ 148 if (cinfo->Ah == 0) { 149 if (is_DC_band) 150 entropy->pub.decode_mcu = decode_mcu_DC_first; 151 else 152 entropy->pub.decode_mcu = decode_mcu_AC_first; 153 } else { 154 if (is_DC_band) 155 entropy->pub.decode_mcu = decode_mcu_DC_refine; 156 else 157 entropy->pub.decode_mcu = decode_mcu_AC_refine; 158 } 159 160 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 161 compptr = cinfo->cur_comp_info[ci]; 162 /* Make sure requested tables are present, and compute derived tables. 163 * We may build same derived table more than once, but it's not expensive. 164 */ 165 if (is_DC_band) { 166 if (cinfo->Ah == 0) { /* DC refinement needs no table */ 167 tbl = compptr->dc_tbl_no; 168 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl, 169 & entropy->derived_tbls[tbl]); 170 } 171 } else { 172 tbl = compptr->ac_tbl_no; 173 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl, 174 & entropy->derived_tbls[tbl]); 175 /* remember the single active table */ 176 entropy->ac_derived_tbl = entropy->derived_tbls[tbl]; 177 } 178 /* Initialize DC predictions to 0 */ 179 entropy->saved.last_dc_val[ci] = 0; 180 } 181 182 /* Initialize bitread state variables */ 183 entropy->bitstate.bits_left = 0; 184 entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */ 185 entropy->pub.insufficient_data = FALSE; 186 187 /* Initialize private state variables */ 188 entropy->saved.EOBRUN = 0; 189 190 /* Initialize restart counter */ 191 entropy->restarts_to_go = cinfo->restart_interval; 192 } 193 194 195 /* 196 * Figure F.12: extend sign bit. 197 * On some machines, a shift and add will be faster than a table lookup. 198 */ 199 200 #ifdef AVOID_TABLES 201 202 #define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x)) 203 204 #else 205 206 #define HUFF_EXTEND(x,s) ((x) < extend_test[s] ? (x) + extend_offset[s] : (x)) 207 208 static const int extend_test[16] = /* entry n is 2**(n-1) */ 209 { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080, 210 0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 }; 211 212 static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */ 213 { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1, 214 ((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1, 215 ((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1, 216 ((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 }; 217 218 #endif /* AVOID_TABLES */ 219 220 221 /* 222 * Check for a restart marker & resynchronize decoder. 223 * Returns FALSE if must suspend. 224 */ 225 226 LOCAL(boolean) 227 process_restart (j_decompress_ptr cinfo) 228 { 229 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 230 int ci; 231 232 /* Throw away any unused bits remaining in bit buffer; */ 233 /* include any full bytes in next_marker's count of discarded bytes */ 234 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8; 235 entropy->bitstate.bits_left = 0; 236 237 /* Advance past the RSTn marker */ 238 if (! (*cinfo->marker->read_restart_marker) (cinfo)) 239 return FALSE; 240 241 /* Re-initialize DC predictions to 0 */ 242 for (ci = 0; ci < cinfo->comps_in_scan; ci++) 243 entropy->saved.last_dc_val[ci] = 0; 244 /* Re-init EOB run count, too */ 245 entropy->saved.EOBRUN = 0; 246 247 /* Reset restart counter */ 248 entropy->restarts_to_go = cinfo->restart_interval; 249 250 /* Reset out-of-data flag, unless read_restart_marker left us smack up 251 * against a marker. In that case we will end up treating the next data 252 * segment as empty, and we can avoid producing bogus output pixels by 253 * leaving the flag set. 254 */ 255 if (cinfo->unread_marker == 0) 256 entropy->pub.insufficient_data = FALSE; 257 258 return TRUE; 259 } 260 261 262 /* 263 * Huffman MCU decoding. 264 * Each of these routines decodes and returns one MCU's worth of 265 * Huffman-compressed coefficients. 266 * The coefficients are reordered from zigzag order into natural array order, 267 * but are not dequantized. 268 * 269 * The i'th block of the MCU is stored into the block pointed to by 270 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER. 271 * 272 * We return FALSE if data source requested suspension. In that case no 273 * changes have been made to permanent state. (Exception: some output 274 * coefficients may already have been assigned. This is harmless for 275 * spectral selection, since we'll just re-assign them on the next call. 276 * Successive approximation AC refinement has to be more careful, however.) 277 */ 278 279 /* 280 * MCU decoding for DC initial scan (either spectral selection, 281 * or first pass of successive approximation). 282 */ 283 284 METHODDEF(boolean) 285 decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 286 { 287 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 288 int Al = cinfo->Al; 289 register int s, r; 290 int blkn, ci; 291 JBLOCKROW block; 292 BITREAD_STATE_VARS; 293 savable_state state; 294 d_derived_tbl * tbl; 295 jpeg_component_info * compptr; 296 297 /* Process restart marker if needed; may have to suspend */ 298 if (cinfo->restart_interval) { 299 if (entropy->restarts_to_go == 0) 300 if (! process_restart(cinfo)) 301 return FALSE; 302 } 303 304 /* If we've run out of data, just leave the MCU set to zeroes. 305 * This way, we return uniform gray for the remainder of the segment. 306 */ 307 if (! entropy->pub.insufficient_data) { 308 309 /* Load up working state */ 310 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 311 ASSIGN_STATE(state, entropy->saved); 312 313 /* Outer loop handles each block in the MCU */ 314 315 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 316 block = MCU_data[blkn]; 317 ci = cinfo->MCU_membership[blkn]; 318 compptr = cinfo->cur_comp_info[ci]; 319 tbl = entropy->derived_tbls[compptr->dc_tbl_no]; 320 321 /* Decode a single block's worth of coefficients */ 322 323 /* Section F.2.2.1: decode the DC coefficient difference */ 324 HUFF_DECODE(s, br_state, tbl, return FALSE, label1); 325 if (s) { 326 CHECK_BIT_BUFFER(br_state, s, return FALSE); 327 r = GET_BITS(s); 328 s = HUFF_EXTEND(r, s); 329 } 330 331 /* Convert DC difference to actual value, update last_dc_val */ 332 s += state.last_dc_val[ci]; 333 state.last_dc_val[ci] = s; 334 /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */ 335 (*block)[0] = (JCOEF) (s << Al); 336 } 337 338 /* Completed MCU, so update state */ 339 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 340 ASSIGN_STATE(entropy->saved, state); 341 } 342 343 /* Account for restart interval (no-op if not using restarts) */ 344 entropy->restarts_to_go--; 345 346 return TRUE; 347 } 348 349 350 /* 351 * MCU decoding for AC initial scan (either spectral selection, 352 * or first pass of successive approximation). 353 */ 354 355 METHODDEF(boolean) 356 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 357 { 358 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 359 int Se = cinfo->Se; 360 int Al = cinfo->Al; 361 register int s, k, r; 362 unsigned int EOBRUN; 363 JBLOCKROW block; 364 BITREAD_STATE_VARS; 365 d_derived_tbl * tbl; 366 367 /* Process restart marker if needed; may have to suspend */ 368 if (cinfo->restart_interval) { 369 if (entropy->restarts_to_go == 0) 370 if (! process_restart(cinfo)) 371 return FALSE; 372 } 373 374 /* If we've run out of data, just leave the MCU set to zeroes. 375 * This way, we return uniform gray for the remainder of the segment. 376 */ 377 if (! entropy->pub.insufficient_data) { 378 379 /* Load up working state. 380 * We can avoid loading/saving bitread state if in an EOB run. 381 */ 382 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ 383 384 /* There is always only one block per MCU */ 385 386 if (EOBRUN > 0) /* if it's a band of zeroes... */ 387 EOBRUN--; /* ...process it now (we do nothing) */ 388 else { 389 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 390 block = MCU_data[0]; 391 tbl = entropy->ac_derived_tbl; 392 393 for (k = cinfo->Ss; k <= Se; k++) { 394 HUFF_DECODE(s, br_state, tbl, return FALSE, label2); 395 r = s >> 4; 396 s &= 15; 397 if (s) { 398 k += r; 399 CHECK_BIT_BUFFER(br_state, s, return FALSE); 400 r = GET_BITS(s); 401 s = HUFF_EXTEND(r, s); 402 /* Scale and output coefficient in natural (dezigzagged) order */ 403 (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al); 404 } else { 405 if (r == 15) { /* ZRL */ 406 k += 15; /* skip 15 zeroes in band */ 407 } else { /* EOBr, run length is 2^r + appended bits */ 408 EOBRUN = 1 << r; 409 if (r) { /* EOBr, r > 0 */ 410 CHECK_BIT_BUFFER(br_state, r, return FALSE); 411 r = GET_BITS(r); 412 EOBRUN += r; 413 } 414 EOBRUN--; /* this band is processed at this moment */ 415 break; /* force end-of-band */ 416 } 417 } 418 } 419 420 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 421 } 422 423 /* Completed MCU, so update state */ 424 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ 425 } 426 427 /* Account for restart interval (no-op if not using restarts) */ 428 entropy->restarts_to_go--; 429 430 return TRUE; 431 } 432 433 434 /* 435 * MCU decoding for DC successive approximation refinement scan. 436 * Note: we assume such scans can be multi-component, although the spec 437 * is not very clear on the point. 438 */ 439 440 METHODDEF(boolean) 441 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 442 { 443 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 444 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ 445 int blkn; 446 JBLOCKROW block; 447 BITREAD_STATE_VARS; 448 449 /* Process restart marker if needed; may have to suspend */ 450 if (cinfo->restart_interval) { 451 if (entropy->restarts_to_go == 0) 452 if (! process_restart(cinfo)) 453 return FALSE; 454 } 455 456 /* Not worth the cycles to check insufficient_data here, 457 * since we will not change the data anyway if we read zeroes. 458 */ 459 460 /* Load up working state */ 461 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 462 463 /* Outer loop handles each block in the MCU */ 464 465 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 466 block = MCU_data[blkn]; 467 468 /* Encoded data is simply the next bit of the two's-complement DC value */ 469 CHECK_BIT_BUFFER(br_state, 1, return FALSE); 470 if (GET_BITS(1)) 471 (*block)[0] |= p1; 472 /* Note: since we use |=, repeating the assignment later is safe */ 473 } 474 475 /* Completed MCU, so update state */ 476 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 477 478 /* Account for restart interval (no-op if not using restarts) */ 479 entropy->restarts_to_go--; 480 481 return TRUE; 482 } 483 484 485 /* 486 * MCU decoding for AC successive approximation refinement scan. 487 */ 488 489 METHODDEF(boolean) 490 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 491 { 492 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 493 int Se = cinfo->Se; 494 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ 495 int m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */ 496 register int s, k, r; 497 unsigned int EOBRUN; 498 JBLOCKROW block; 499 JCOEFPTR thiscoef; 500 BITREAD_STATE_VARS; 501 d_derived_tbl * tbl; 502 int num_newnz; 503 int newnz_pos[DCTSIZE2]; 504 505 /* Process restart marker if needed; may have to suspend */ 506 if (cinfo->restart_interval) { 507 if (entropy->restarts_to_go == 0) 508 if (! process_restart(cinfo)) 509 return FALSE; 510 } 511 512 /* If we've run out of data, don't modify the MCU. 513 */ 514 if (! entropy->pub.insufficient_data) { 515 516 /* Load up working state */ 517 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 518 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ 519 520 /* There is always only one block per MCU */ 521 block = MCU_data[0]; 522 tbl = entropy->ac_derived_tbl; 523 524 /* If we are forced to suspend, we must undo the assignments to any newly 525 * nonzero coefficients in the block, because otherwise we'd get confused 526 * next time about which coefficients were already nonzero. 527 * But we need not undo addition of bits to already-nonzero coefficients; 528 * instead, we can test the current bit to see if we already did it. 529 */ 530 num_newnz = 0; 531 532 /* initialize coefficient loop counter to start of band */ 533 k = cinfo->Ss; 534 535 if (EOBRUN == 0) { 536 for (; k <= Se; k++) { 537 HUFF_DECODE(s, br_state, tbl, goto undoit, label3); 538 r = s >> 4; 539 s &= 15; 540 if (s) { 541 if (s != 1) /* size of new coef should always be 1 */ 542 WARNMS(cinfo, JWRN_HUFF_BAD_CODE); 543 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 544 if (GET_BITS(1)) 545 s = p1; /* newly nonzero coef is positive */ 546 else 547 s = m1; /* newly nonzero coef is negative */ 548 } else { 549 if (r != 15) { 550 EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */ 551 if (r) { 552 CHECK_BIT_BUFFER(br_state, r, goto undoit); 553 r = GET_BITS(r); 554 EOBRUN += r; 555 } 556 break; /* rest of block is handled by EOB logic */ 557 } 558 /* note s = 0 for processing ZRL */ 559 } 560 /* Advance over already-nonzero coefs and r still-zero coefs, 561 * appending correction bits to the nonzeroes. A correction bit is 1 562 * if the absolute value of the coefficient must be increased. 563 */ 564 do { 565 thiscoef = *block + jpeg_natural_order[k]; 566 if (*thiscoef != 0) { 567 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 568 if (GET_BITS(1)) { 569 if ((*thiscoef & p1) == 0) { /* do nothing if already set it */ 570 if (*thiscoef >= 0) 571 *thiscoef += p1; 572 else 573 *thiscoef += m1; 574 } 575 } 576 } else { 577 if (--r < 0) 578 break; /* reached target zero coefficient */ 579 } 580 k++; 581 } while (k <= Se); 582 if (s) { 583 int pos = jpeg_natural_order[k]; 584 /* Output newly nonzero coefficient */ 585 (*block)[pos] = (JCOEF) s; 586 /* Remember its position in case we have to suspend */ 587 newnz_pos[num_newnz++] = pos; 588 } 589 } 590 } 591 592 if (EOBRUN > 0) { 593 /* Scan any remaining coefficient positions after the end-of-band 594 * (the last newly nonzero coefficient, if any). Append a correction 595 * bit to each already-nonzero coefficient. A correction bit is 1 596 * if the absolute value of the coefficient must be increased. 597 */ 598 for (; k <= Se; k++) { 599 thiscoef = *block + jpeg_natural_order[k]; 600 if (*thiscoef != 0) { 601 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 602 if (GET_BITS(1)) { 603 if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */ 604 if (*thiscoef >= 0) 605 *thiscoef += p1; 606 else 607 *thiscoef += m1; 608 } 609 } 610 } 611 } 612 /* Count one block completed in EOB run */ 613 EOBRUN--; 614 } 615 616 /* Completed MCU, so update state */ 617 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 618 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ 619 } 620 621 /* Account for restart interval (no-op if not using restarts) */ 622 entropy->restarts_to_go--; 623 624 return TRUE; 625 626 undoit: 627 /* Re-zero any output coefficients that we made newly nonzero */ 628 while (num_newnz > 0) 629 (*block)[newnz_pos[--num_newnz]] = 0; 630 631 return FALSE; 632 } 633 634 /* 635 * Save the current Huffman deocde position and the DC coefficients 636 * for each component into bitstream_offset and dc_info[], respectively. 637 */ 638 METHODDEF(void) 639 get_huffman_decoder_configuration(j_decompress_ptr cinfo, 640 huffman_offset_data *offset) 641 { 642 int i; 643 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 644 jpeg_get_huffman_decoder_configuration_progressive(cinfo, offset); 645 offset->EOBRUN = entropy->saved.EOBRUN; 646 for (i = 0; i < cinfo->comps_in_scan; i++) 647 offset->prev_dc[i] = entropy->saved.last_dc_val[i]; 648 } 649 650 651 /* 652 * Save the current Huffman decoder position and the bit buffer 653 * into bitstream_offset and get_buffer, respectively. 654 */ 655 GLOBAL(void) 656 jpeg_get_huffman_decoder_configuration_progressive(j_decompress_ptr cinfo, 657 huffman_offset_data *offset) 658 { 659 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 660 661 if (cinfo->restart_interval) { 662 // We are at the end of a data segment 663 if (entropy->restarts_to_go == 0) 664 if (! process_restart(cinfo)) 665 return; 666 } 667 668 // Save restarts_to_go and next_restart_num. 669 offset->restarts_to_go = (unsigned short) entropy->restarts_to_go; 670 offset->next_restart_num = cinfo->marker->next_restart_num; 671 672 offset->bitstream_offset = 673 (jget_input_stream_position(cinfo) << LOG_TWO_BIT_BUF_SIZE) 674 + entropy->bitstate.bits_left; 675 676 offset->get_buffer = entropy->bitstate.get_buffer; 677 } 678 679 680 /* 681 * Configure the Huffman decoder to decode the image 682 * starting from (iMCU_row_offset, iMCU_col_offset). 683 */ 684 METHODDEF(void) 685 configure_huffman_decoder(j_decompress_ptr cinfo, huffman_offset_data offset) 686 { 687 int i; 688 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 689 jpeg_configure_huffman_decoder_progressive(cinfo, offset); 690 entropy->saved.EOBRUN = offset.EOBRUN; 691 for (i = 0; i < cinfo->comps_in_scan; i++) 692 entropy->saved.last_dc_val[i] = offset.prev_dc[i]; 693 } 694 695 /* 696 * Configure the Huffman decoder reader position and bit buffer. 697 */ 698 GLOBAL(void) 699 jpeg_configure_huffman_decoder_progressive(j_decompress_ptr cinfo, 700 huffman_offset_data offset) 701 { 702 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 703 704 // Restore restarts_to_go and next_restart_num 705 cinfo->unread_marker = 0; 706 entropy->restarts_to_go = offset.restarts_to_go; 707 cinfo->marker->next_restart_num = offset.next_restart_num; 708 709 unsigned int bitstream_offset = offset.bitstream_offset; 710 int blkn, i; 711 712 unsigned int byte_offset = bitstream_offset >> LOG_TWO_BIT_BUF_SIZE; 713 unsigned int bit_in_bit_buffer = 714 bitstream_offset & ((1 << LOG_TWO_BIT_BUF_SIZE) - 1); 715 716 jset_input_stream_position_bit(cinfo, byte_offset, 717 bit_in_bit_buffer, offset.get_buffer); 718 } 719 720 GLOBAL(void) 721 jpeg_configure_huffman_index_scan(j_decompress_ptr cinfo, 722 huffman_index *index, int scan_no, int offset) 723 { 724 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 725 if (scan_no >= index->scan_count) { 726 index->scan = realloc(index->scan, 727 (scan_no + 1) * sizeof(huffman_scan_header)); 728 index->mem_used += (scan_no - index->scan_count + 1) 729 * (sizeof(huffman_scan_header) + cinfo->total_iMCU_rows 730 * sizeof(huffman_offset_data*)); 731 index->scan_count = scan_no + 1; 732 } 733 index->scan[scan_no].offset = (huffman_offset_data**)malloc( 734 cinfo->total_iMCU_rows * sizeof(huffman_offset_data*)); 735 index->scan[scan_no].bitstream_offset = offset; 736 } 737 738 /* 739 * Module initialization routine for progressive Huffman entropy decoding. 740 */ 741 GLOBAL(void) 742 jinit_phuff_decoder (j_decompress_ptr cinfo) 743 { 744 phuff_entropy_ptr entropy; 745 int *coef_bit_ptr; 746 int ci, i; 747 748 entropy = (phuff_entropy_ptr) 749 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 750 SIZEOF(phuff_entropy_decoder)); 751 cinfo->entropy = (struct jpeg_entropy_decoder *) entropy; 752 entropy->pub.start_pass = start_pass_phuff_decoder; 753 entropy->pub.configure_huffman_decoder = configure_huffman_decoder; 754 entropy->pub.get_huffman_decoder_configuration = 755 get_huffman_decoder_configuration; 756 757 /* Mark derived tables unallocated */ 758 for (i = 0; i < NUM_HUFF_TBLS; i++) { 759 entropy->derived_tbls[i] = NULL; 760 } 761 762 /* Create progression status table */ 763 cinfo->coef_bits = (int (*)[DCTSIZE2]) 764 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 765 cinfo->num_components*DCTSIZE2*SIZEOF(int)); 766 coef_bit_ptr = & cinfo->coef_bits[0][0]; 767 for (ci = 0; ci < cinfo->num_components; ci++) 768 for (i = 0; i < DCTSIZE2; i++) 769 *coef_bit_ptr++ = -1; 770 } 771 772 #endif /* D_PROGRESSIVE_SUPPORTED */ 773
