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 GLOBAL(void) jpeg_configure_huffman_decoder_progressive( 86 j_decompress_ptr cinfo, huffman_offset_data offset); 87 GLOBAL(void) jpeg_get_huffman_decoder_configuration_progressive( 88 j_decompress_ptr cinfo, huffman_offset_data *offset); 89 90 /* 91 * Initialize for a Huffman-compressed scan. 92 */ 93 94 METHODDEF(void) 95 start_pass_phuff_decoder (j_decompress_ptr cinfo) 96 { 97 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 98 boolean is_DC_band, bad; 99 int ci, coefi, tbl; 100 int *coef_bit_ptr; 101 jpeg_component_info * compptr; 102 103 is_DC_band = (cinfo->Ss == 0); 104 105 /* Validate scan parameters */ 106 bad = FALSE; 107 if (is_DC_band) { 108 if (cinfo->Se != 0) 109 bad = TRUE; 110 } else { 111 /* need not check Ss/Se < 0 since they came from unsigned bytes */ 112 if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2) 113 bad = TRUE; 114 /* AC scans may have only one component */ 115 if (cinfo->comps_in_scan != 1) 116 bad = TRUE; 117 } 118 if (cinfo->Ah != 0) { 119 /* Successive approximation refinement scan: must have Al = Ah-1. */ 120 if (cinfo->Al != cinfo->Ah-1) 121 bad = TRUE; 122 } 123 if (cinfo->Al > 13) /* need not check for < 0 */ 124 bad = TRUE; 125 /* Arguably the maximum Al value should be less than 13 for 8-bit precision, 126 * but the spec doesn't say so, and we try to be liberal about what we 127 * accept. Note: large Al values could result in out-of-range DC 128 * coefficients during early scans, leading to bizarre displays due to 129 * overflows in the IDCT math. But we won't crash. 130 */ 131 if (bad) 132 ERREXIT4(cinfo, JERR_BAD_PROGRESSION, 133 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al); 134 /* Update progression status, and verify that scan order is legal. 135 * Note that inter-scan inconsistencies are treated as warnings 136 * not fatal errors ... not clear if this is right way to behave. 137 */ 138 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 139 int cindex = cinfo->cur_comp_info[ci]->component_index; 140 coef_bit_ptr = & cinfo->coef_bits[cindex][0]; 141 if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */ 142 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0); 143 for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) { 144 int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi]; 145 if (cinfo->Ah != expected) 146 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi); 147 coef_bit_ptr[coefi] = cinfo->Al; 148 } 149 } 150 151 /* Select MCU decoding routine */ 152 if (cinfo->Ah == 0) { 153 if (is_DC_band) 154 entropy->pub.decode_mcu = decode_mcu_DC_first; 155 else 156 entropy->pub.decode_mcu = decode_mcu_AC_first; 157 } else { 158 if (is_DC_band) 159 entropy->pub.decode_mcu = decode_mcu_DC_refine; 160 else 161 entropy->pub.decode_mcu = decode_mcu_AC_refine; 162 } 163 164 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 165 compptr = cinfo->cur_comp_info[ci]; 166 /* Make sure requested tables are present, and compute derived tables. 167 * We may build same derived table more than once, but it's not expensive. 168 */ 169 if (is_DC_band) { 170 if (cinfo->Ah == 0) { /* DC refinement needs no table */ 171 tbl = compptr->dc_tbl_no; 172 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl, 173 & entropy->derived_tbls[tbl]); 174 } 175 } else { 176 tbl = compptr->ac_tbl_no; 177 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl, 178 & entropy->derived_tbls[tbl]); 179 /* remember the single active table */ 180 entropy->ac_derived_tbl = entropy->derived_tbls[tbl]; 181 } 182 /* Initialize DC predictions to 0 */ 183 entropy->saved.last_dc_val[ci] = 0; 184 } 185 186 /* Initialize bitread state variables */ 187 entropy->bitstate.bits_left = 0; 188 entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */ 189 entropy->pub.insufficient_data = FALSE; 190 191 /* Initialize private state variables */ 192 entropy->saved.EOBRUN = 0; 193 194 /* Initialize restart counter */ 195 entropy->restarts_to_go = cinfo->restart_interval; 196 } 197 198 199 /* 200 * Figure F.12: extend sign bit. 201 * On some machines, a shift and add will be faster than a table lookup. 202 */ 203 204 #ifdef AVOID_TABLES 205 206 #define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x)) 207 208 #else 209 210 #define HUFF_EXTEND(x,s) ((x) < extend_test[s] ? (x) + extend_offset[s] : (x)) 211 212 static const int extend_test[16] = /* entry n is 2**(n-1) */ 213 { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080, 214 0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 }; 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 #endif /* AVOID_TABLES */ 223 224 225 /* 226 * Check for a restart marker & resynchronize decoder. 227 * Returns FALSE if must suspend. 228 */ 229 230 LOCAL(boolean) 231 process_restart (j_decompress_ptr cinfo) 232 { 233 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 234 int ci; 235 236 /* Throw away any unused bits remaining in bit buffer; */ 237 /* include any full bytes in next_marker's count of discarded bytes */ 238 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8; 239 entropy->bitstate.bits_left = 0; 240 241 /* Advance past the RSTn marker */ 242 if (! (*cinfo->marker->read_restart_marker) (cinfo)) 243 return FALSE; 244 245 /* Re-initialize DC predictions to 0 */ 246 for (ci = 0; ci < cinfo->comps_in_scan; ci++) 247 entropy->saved.last_dc_val[ci] = 0; 248 /* Re-init EOB run count, too */ 249 entropy->saved.EOBRUN = 0; 250 251 /* Reset restart counter */ 252 entropy->restarts_to_go = cinfo->restart_interval; 253 254 /* Reset out-of-data flag, unless read_restart_marker left us smack up 255 * against a marker. In that case we will end up treating the next data 256 * segment as empty, and we can avoid producing bogus output pixels by 257 * leaving the flag set. 258 */ 259 if (cinfo->unread_marker == 0) 260 entropy->pub.insufficient_data = FALSE; 261 262 return TRUE; 263 } 264 265 266 /* 267 * Huffman MCU decoding. 268 * Each of these routines decodes and returns one MCU's worth of 269 * Huffman-compressed coefficients. 270 * The coefficients are reordered from zigzag order into natural array order, 271 * but are not dequantized. 272 * 273 * The i'th block of the MCU is stored into the block pointed to by 274 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER. 275 * 276 * We return FALSE if data source requested suspension. In that case no 277 * changes have been made to permanent state. (Exception: some output 278 * coefficients may already have been assigned. This is harmless for 279 * spectral selection, since we'll just re-assign them on the next call. 280 * Successive approximation AC refinement has to be more careful, however.) 281 */ 282 283 /* 284 * MCU decoding for DC initial scan (either spectral selection, 285 * or first pass of successive approximation). 286 */ 287 288 METHODDEF(boolean) 289 decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 290 { 291 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 292 int Al = cinfo->Al; 293 register int s, r; 294 int blkn, ci; 295 JBLOCKROW block; 296 BITREAD_STATE_VARS; 297 savable_state state; 298 d_derived_tbl * tbl; 299 jpeg_component_info * compptr; 300 301 /* Process restart marker if needed; may have to suspend */ 302 if (cinfo->restart_interval) { 303 if (entropy->restarts_to_go == 0) 304 if (! process_restart(cinfo)) 305 return FALSE; 306 } 307 308 /* If we've run out of data, just leave the MCU set to zeroes. 309 * This way, we return uniform gray for the remainder of the segment. 310 */ 311 if (! entropy->pub.insufficient_data) { 312 313 /* Load up working state */ 314 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 315 ASSIGN_STATE(state, entropy->saved); 316 317 /* Outer loop handles each block in the MCU */ 318 319 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 320 block = MCU_data[blkn]; 321 ci = cinfo->MCU_membership[blkn]; 322 compptr = cinfo->cur_comp_info[ci]; 323 tbl = entropy->derived_tbls[compptr->dc_tbl_no]; 324 325 /* Decode a single block's worth of coefficients */ 326 327 /* Section F.2.2.1: decode the DC coefficient difference */ 328 HUFF_DECODE(s, br_state, tbl, return FALSE, label1); 329 if (s) { 330 CHECK_BIT_BUFFER(br_state, s, return FALSE); 331 r = GET_BITS(s); 332 s = HUFF_EXTEND(r, s); 333 } 334 335 /* Convert DC difference to actual value, update last_dc_val */ 336 s += state.last_dc_val[ci]; 337 state.last_dc_val[ci] = s; 338 /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */ 339 (*block)[0] = (JCOEF) (s << Al); 340 } 341 342 /* Completed MCU, so update state */ 343 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 344 ASSIGN_STATE(entropy->saved, state); 345 } 346 347 /* Account for restart interval (no-op if not using restarts) */ 348 entropy->restarts_to_go--; 349 350 return TRUE; 351 } 352 353 354 /* 355 * MCU decoding for AC initial scan (either spectral selection, 356 * or first pass of successive approximation). 357 */ 358 359 METHODDEF(boolean) 360 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 361 { 362 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 363 int Se = cinfo->Se; 364 int Al = cinfo->Al; 365 register int s, k, r; 366 unsigned int EOBRUN; 367 JBLOCKROW block; 368 BITREAD_STATE_VARS; 369 d_derived_tbl * tbl; 370 371 /* Process restart marker if needed; may have to suspend */ 372 if (cinfo->restart_interval) { 373 if (entropy->restarts_to_go == 0) 374 if (! process_restart(cinfo)) 375 return FALSE; 376 } 377 378 /* If we've run out of data, just leave the MCU set to zeroes. 379 * This way, we return uniform gray for the remainder of the segment. 380 */ 381 if (! entropy->pub.insufficient_data) { 382 383 /* Load up working state. 384 * We can avoid loading/saving bitread state if in an EOB run. 385 */ 386 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ 387 388 /* There is always only one block per MCU */ 389 390 if (EOBRUN > 0) /* if it's a band of zeroes... */ 391 EOBRUN--; /* ...process it now (we do nothing) */ 392 else { 393 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 394 block = MCU_data[0]; 395 tbl = entropy->ac_derived_tbl; 396 397 for (k = cinfo->Ss; k <= Se; k++) { 398 HUFF_DECODE(s, br_state, tbl, return FALSE, label2); 399 r = s >> 4; 400 s &= 15; 401 if (s) { 402 k += r; 403 CHECK_BIT_BUFFER(br_state, s, return FALSE); 404 r = GET_BITS(s); 405 s = HUFF_EXTEND(r, s); 406 /* Scale and output coefficient in natural (dezigzagged) order */ 407 (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al); 408 } else { 409 if (r == 15) { /* ZRL */ 410 k += 15; /* skip 15 zeroes in band */ 411 } else { /* EOBr, run length is 2^r + appended bits */ 412 EOBRUN = 1 << r; 413 if (r) { /* EOBr, r > 0 */ 414 CHECK_BIT_BUFFER(br_state, r, return FALSE); 415 r = GET_BITS(r); 416 EOBRUN += r; 417 } 418 EOBRUN--; /* this band is processed at this moment */ 419 break; /* force end-of-band */ 420 } 421 } 422 } 423 424 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 425 } 426 427 /* Completed MCU, so update state */ 428 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ 429 } 430 431 /* Account for restart interval (no-op if not using restarts) */ 432 entropy->restarts_to_go--; 433 434 return TRUE; 435 } 436 437 438 /* 439 * MCU decoding for DC successive approximation refinement scan. 440 * Note: we assume such scans can be multi-component, although the spec 441 * is not very clear on the point. 442 */ 443 444 METHODDEF(boolean) 445 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 446 { 447 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 448 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ 449 int blkn; 450 JBLOCKROW block; 451 BITREAD_STATE_VARS; 452 453 /* Process restart marker if needed; may have to suspend */ 454 if (cinfo->restart_interval) { 455 if (entropy->restarts_to_go == 0) 456 if (! process_restart(cinfo)) 457 return FALSE; 458 } 459 460 /* Not worth the cycles to check insufficient_data here, 461 * since we will not change the data anyway if we read zeroes. 462 */ 463 464 /* Load up working state */ 465 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 466 467 /* Outer loop handles each block in the MCU */ 468 469 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 470 block = MCU_data[blkn]; 471 472 /* Encoded data is simply the next bit of the two's-complement DC value */ 473 CHECK_BIT_BUFFER(br_state, 1, return FALSE); 474 if (GET_BITS(1)) 475 (*block)[0] |= p1; 476 /* Note: since we use |=, repeating the assignment later is safe */ 477 } 478 479 /* Completed MCU, so update state */ 480 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 481 482 /* Account for restart interval (no-op if not using restarts) */ 483 entropy->restarts_to_go--; 484 485 return TRUE; 486 } 487 488 489 /* 490 * MCU decoding for AC successive approximation refinement scan. 491 */ 492 493 METHODDEF(boolean) 494 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) 495 { 496 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 497 int Se = cinfo->Se; 498 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ 499 int m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */ 500 register int s, k, r; 501 unsigned int EOBRUN; 502 JBLOCKROW block; 503 JCOEFPTR thiscoef; 504 BITREAD_STATE_VARS; 505 d_derived_tbl * tbl; 506 int num_newnz; 507 int newnz_pos[DCTSIZE2]; 508 509 /* Process restart marker if needed; may have to suspend */ 510 if (cinfo->restart_interval) { 511 if (entropy->restarts_to_go == 0) 512 if (! process_restart(cinfo)) 513 return FALSE; 514 } 515 516 /* If we've run out of data, don't modify the MCU. 517 */ 518 if (! entropy->pub.insufficient_data) { 519 520 /* Load up working state */ 521 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); 522 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ 523 524 /* There is always only one block per MCU */ 525 block = MCU_data[0]; 526 tbl = entropy->ac_derived_tbl; 527 528 /* If we are forced to suspend, we must undo the assignments to any newly 529 * nonzero coefficients in the block, because otherwise we'd get confused 530 * next time about which coefficients were already nonzero. 531 * But we need not undo addition of bits to already-nonzero coefficients; 532 * instead, we can test the current bit to see if we already did it. 533 */ 534 num_newnz = 0; 535 536 /* initialize coefficient loop counter to start of band */ 537 k = cinfo->Ss; 538 539 if (EOBRUN == 0) { 540 for (; k <= Se; k++) { 541 HUFF_DECODE(s, br_state, tbl, goto undoit, label3); 542 r = s >> 4; 543 s &= 15; 544 if (s) { 545 if (s != 1) /* size of new coef should always be 1 */ 546 WARNMS(cinfo, JWRN_HUFF_BAD_CODE); 547 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 548 if (GET_BITS(1)) 549 s = p1; /* newly nonzero coef is positive */ 550 else 551 s = m1; /* newly nonzero coef is negative */ 552 } else { 553 if (r != 15) { 554 EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */ 555 if (r) { 556 CHECK_BIT_BUFFER(br_state, r, goto undoit); 557 r = GET_BITS(r); 558 EOBRUN += r; 559 } 560 break; /* rest of block is handled by EOB logic */ 561 } 562 /* note s = 0 for processing ZRL */ 563 } 564 /* Advance over already-nonzero coefs and r still-zero coefs, 565 * appending correction bits to the nonzeroes. A correction bit is 1 566 * if the absolute value of the coefficient must be increased. 567 */ 568 do { 569 thiscoef = *block + jpeg_natural_order[k]; 570 if (*thiscoef != 0) { 571 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 572 if (GET_BITS(1)) { 573 if ((*thiscoef & p1) == 0) { /* do nothing if already set it */ 574 if (*thiscoef >= 0) 575 *thiscoef += p1; 576 else 577 *thiscoef += m1; 578 } 579 } 580 } else { 581 if (--r < 0) 582 break; /* reached target zero coefficient */ 583 } 584 k++; 585 } while (k <= Se); 586 if (s) { 587 int pos = jpeg_natural_order[k]; 588 /* Output newly nonzero coefficient */ 589 (*block)[pos] = (JCOEF) s; 590 /* Remember its position in case we have to suspend */ 591 newnz_pos[num_newnz++] = pos; 592 } 593 } 594 } 595 596 if (EOBRUN > 0) { 597 /* Scan any remaining coefficient positions after the end-of-band 598 * (the last newly nonzero coefficient, if any). Append a correction 599 * bit to each already-nonzero coefficient. A correction bit is 1 600 * if the absolute value of the coefficient must be increased. 601 */ 602 for (; k <= Se; k++) { 603 thiscoef = *block + jpeg_natural_order[k]; 604 if (*thiscoef != 0) { 605 CHECK_BIT_BUFFER(br_state, 1, goto undoit); 606 if (GET_BITS(1)) { 607 if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */ 608 if (*thiscoef >= 0) 609 *thiscoef += p1; 610 else 611 *thiscoef += m1; 612 } 613 } 614 } 615 } 616 /* Count one block completed in EOB run */ 617 EOBRUN--; 618 } 619 620 /* Completed MCU, so update state */ 621 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); 622 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ 623 } 624 625 /* Account for restart interval (no-op if not using restarts) */ 626 entropy->restarts_to_go--; 627 628 return TRUE; 629 630 undoit: 631 /* Re-zero any output coefficients that we made newly nonzero */ 632 while (num_newnz > 0) 633 (*block)[newnz_pos[--num_newnz]] = 0; 634 635 return FALSE; 636 } 637 638 /* 639 * Save the current Huffman deocde position and the DC coefficients 640 * for each component into bitstream_offset and dc_info[], respectively. 641 */ 642 METHODDEF(void) 643 get_huffman_decoder_configuration(j_decompress_ptr cinfo, 644 huffman_offset_data *offset) 645 { 646 int i; 647 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 648 jpeg_get_huffman_decoder_configuration_progressive(cinfo, offset); 649 offset->EOBRUN = entropy->saved.EOBRUN; 650 for (i = 0; i < cinfo->comps_in_scan; i++) 651 offset->prev_dc[i] = entropy->saved.last_dc_val[i]; 652 } 653 654 655 /* 656 * Save the current Huffman decoder position and the bit buffer 657 * into bitstream_offset and get_buffer, respectively. 658 */ 659 GLOBAL(void) 660 jpeg_get_huffman_decoder_configuration_progressive(j_decompress_ptr cinfo, 661 huffman_offset_data *offset) 662 { 663 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 664 665 if (cinfo->restart_interval) { 666 // We are at the end of a data segment 667 if (entropy->restarts_to_go == 0) 668 if (! process_restart(cinfo)) 669 return; 670 } 671 672 // Save restarts_to_go and next_restart_num. 673 offset->restarts_to_go = (unsigned short) entropy->restarts_to_go; 674 offset->next_restart_num = cinfo->marker->next_restart_num; 675 676 offset->bitstream_offset = 677 (jget_input_stream_position(cinfo) << LOG_TWO_BIT_BUF_SIZE) 678 + entropy->bitstate.bits_left; 679 680 offset->get_buffer = entropy->bitstate.get_buffer; 681 } 682 683 684 /* 685 * Configure the Huffman decoder to decode the image 686 * starting from (iMCU_row_offset, iMCU_col_offset). 687 */ 688 METHODDEF(void) 689 configure_huffman_decoder(j_decompress_ptr cinfo, huffman_offset_data offset) 690 { 691 int i; 692 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 693 jpeg_configure_huffman_decoder_progressive(cinfo, offset); 694 entropy->saved.EOBRUN = offset.EOBRUN; 695 for (i = 0; i < cinfo->comps_in_scan; i++) 696 entropy->saved.last_dc_val[i] = offset.prev_dc[i]; 697 } 698 699 /* 700 * Configure the Huffman decoder reader position and bit buffer. 701 */ 702 GLOBAL(void) 703 jpeg_configure_huffman_decoder_progressive(j_decompress_ptr cinfo, 704 huffman_offset_data offset) 705 { 706 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 707 708 // Restore restarts_to_go and next_restart_num 709 cinfo->unread_marker = 0; 710 entropy->restarts_to_go = offset.restarts_to_go; 711 cinfo->marker->next_restart_num = offset.next_restart_num; 712 713 unsigned int bitstream_offset = offset.bitstream_offset; 714 int blkn, i; 715 716 unsigned int byte_offset = bitstream_offset >> LOG_TWO_BIT_BUF_SIZE; 717 unsigned int bit_in_bit_buffer = 718 bitstream_offset & ((1 << LOG_TWO_BIT_BUF_SIZE) - 1); 719 720 jset_input_stream_position_bit(cinfo, byte_offset, 721 bit_in_bit_buffer, offset.get_buffer); 722 } 723 724 GLOBAL(void) 725 jpeg_configure_huffman_index_scan(j_decompress_ptr cinfo, 726 huffman_index *index, int scan_no, int offset) 727 { 728 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 729 if (scan_no >= index->scan_count) { 730 index->scan = realloc(index->scan, 731 (scan_no + 1) * sizeof(huffman_scan_header)); 732 index->mem_used += (scan_no - index->scan_count + 1) 733 * (sizeof(huffman_scan_header) + cinfo->total_iMCU_rows 734 * sizeof(huffman_offset_data*)); 735 index->scan_count = scan_no + 1; 736 } 737 index->scan[scan_no].offset = (huffman_offset_data**)malloc( 738 cinfo->total_iMCU_rows * sizeof(huffman_offset_data*)); 739 index->scan[scan_no].bitstream_offset = offset; 740 } 741 742 /* 743 * Module initialization routine for progressive Huffman entropy decoding. 744 */ 745 GLOBAL(void) 746 jinit_phuff_decoder (j_decompress_ptr cinfo) 747 { 748 phuff_entropy_ptr entropy; 749 int *coef_bit_ptr; 750 int ci, i; 751 752 entropy = (phuff_entropy_ptr) 753 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 754 SIZEOF(phuff_entropy_decoder)); 755 cinfo->entropy = (struct jpeg_entropy_decoder *) entropy; 756 entropy->pub.start_pass = start_pass_phuff_decoder; 757 entropy->pub.configure_huffman_decoder = configure_huffman_decoder; 758 entropy->pub.get_huffman_decoder_configuration = 759 get_huffman_decoder_configuration; 760 761 /* Mark derived tables unallocated */ 762 for (i = 0; i < NUM_HUFF_TBLS; i++) { 763 entropy->derived_tbls[i] = NULL; 764 } 765 766 /* Create progression status table */ 767 cinfo->coef_bits = (int (*)[DCTSIZE2]) 768 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 769 cinfo->num_components*DCTSIZE2*SIZEOF(int)); 770 coef_bit_ptr = & cinfo->coef_bits[0][0]; 771 for (ci = 0; ci < cinfo->num_components; ci++) 772 for (i = 0; i < DCTSIZE2; i++) 773 *coef_bit_ptr++ = -1; 774 } 775 776 #endif /* D_PROGRESSIVE_SUPPORTED */ 777
