src/jpeg/jdphuff.c

   1 /*
   2  * jdphuff.c
   3  *
   4  * Copyright (C) 1995-1997, Thomas G. Lane.
   5  * This file is part of the Independent JPEG Group's software.
   6  * For conditions of distribution and use, see the accompanying README file.
   7  *
   8  * This file contains Huffman entropy decoding routines for progressive JPEG.
   9  *
  10  * Much of the complexity here has to do with supporting input suspension.
  11  * If the data source module demands suspension, we want to be able to back
  12  * up to the start of the current MCU.  To do this, we copy state variables
  13  * into local working storage, and update them back to the permanent
  14  * storage only upon successful completion of an MCU.
  15  */
  16
  17 #define JPEG_INTERNALS
  18 #include "jinclude.h"
  19 #include "jpeglib.h"
  20 #include "jdhuff.h"             /* Declarations shared with jdhuff.c */
  21
  22
  23 #ifdef D_PROGRESSIVE_SUPPORTED
  24
  25 /*
  26  * Expanded entropy decoder object for progressive Huffman decoding.
  27  *
  28  * The savable_state subrecord contains fields that change within an MCU,
  29  * but must not be updated permanently until we complete the MCU.
  30  */
  31
  32 typedef struct {
  33   unsigned int EOBRUN;                  /* remaining EOBs in EOBRUN */
  34   int last_dc_val[MAX_COMPS_IN_SCAN];   /* last DC coef for each component */
  35 } savable_state;
  36
  37 /* This macro is to work around compilers with missing or broken
  38  * structure assignment.  You'll need to fix this code if you have
  39  * such a compiler and you change MAX_COMPS_IN_SCAN.
  40  */
  41
  42 #ifndef NO_STRUCT_ASSIGN
  43 #define ASSIGN_STATE(dest,src)  ((dest) = (src))
  44 #else
  45 #if MAX_COMPS_IN_SCAN == 4
  46 #define ASSIGN_STATE(dest,src)  \
  47         ((dest).EOBRUN = (src).EOBRUN, \
  48          (dest).last_dc_val[0] = (src).last_dc_val[0], \
  49          (dest).last_dc_val[1] = (src).last_dc_val[1], \
  50          (dest).last_dc_val[2] = (src).last_dc_val[2], \
  51          (dest).last_dc_val[3] = (src).last_dc_val[3])
  52 #endif
  53 #endif
  54
  55
  56 typedef struct {
  57   struct jpeg_entropy_decoder pub; /* public fields */
  58
  59   /* These fields are loaded into local variables at start of each MCU.
  60    * In case of suspension, we exit WITHOUT updating them.
  61    */
  62   bitread_perm_state bitstate;  /* Bit buffer at start of MCU */
  63   savable_state saved;          /* Other state at start of MCU */
  64
  65   /* These fields are NOT loaded into local working state. */
  66   unsigned int restarts_to_go;  /* MCUs left in this restart interval */
  67
  68   /* Pointers to derived tables (these workspaces have image lifespan) */
  69   d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
  70
  71   d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
  72 } phuff_entropy_decoder;
  73
  74 typedef phuff_entropy_decoder * phuff_entropy_ptr;
  75
  76 /* Forward declarations */
  77 METHODDEF(boolean) decode_mcu_DC_first JPP((j_decompress_ptr cinfo,
  78                                             JBLOCKROW *MCU_data));
  79 METHODDEF(boolean) decode_mcu_AC_first JPP((j_decompress_ptr cinfo,
  80                                             JBLOCKROW *MCU_data));
  81 METHODDEF(boolean) decode_mcu_DC_refine JPP((j_decompress_ptr cinfo,
  82                                              JBLOCKROW *MCU_data));
  83 METHODDEF(boolean) decode_mcu_AC_refine JPP((j_decompress_ptr cinfo,
  84                                              JBLOCKROW *MCU_data));
  85
  86
  87 /*
  88  * Initialize for a Huffman-compressed scan.
  89  */
  90
  91 METHODDEF(void)
  92 start_pass_phuff_decoder (j_decompress_ptr cinfo)
  93 {
  94   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
  95   boolean is_DC_band, bad;
  96   int ci, coefi, tbl;
  97   int *coef_bit_ptr;
  98   jpeg_component_info * compptr;
  99
 100   is_DC_band = (cinfo->Ss == 0);
 101
 102   /* Validate scan parameters */
 103   bad = FALSE;
 104   if (is_DC_band) {
 105     if (cinfo->Se != 0)
 106       bad = TRUE;
 107   } else {
 108     /* need not check Ss/Se < 0 since they came from unsigned bytes */
 109     if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2)
 110       bad = TRUE;
 111     /* AC scans may have only one component */
 112     if (cinfo->comps_in_scan != 1)
 113       bad = TRUE;
 114   }
 115   if (cinfo->Ah != 0) {
 116     /* Successive approximation refinement scan: must have Al = Ah-1. */
 117     if (cinfo->Al != cinfo->Ah-1)
 118       bad = TRUE;
 119   }
 120   if (cinfo->Al > 13)           /* need not check for < 0 */
 121     bad = TRUE;
 122   /* Arguably the maximum Al value should be less than 13 for 8-bit precision,
 123    * but the spec doesn't say so, and we try to be liberal about what we
 124    * accept.  Note: large Al values could result in out-of-range DC
 125    * coefficients during early scans, leading to bizarre displays due to
 126    * overflows in the IDCT math.  But we won't crash.
 127    */
 128   if (bad)
 129     ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
 130              cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
 131   /* Update progression status, and verify that scan order is legal.
 132    * Note that inter-scan inconsistencies are treated as warnings
 133    * not fatal errors ... not clear if this is right way to behave.
 134    */
 135   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
 136     int cindex = cinfo->cur_comp_info[ci]->component_index;
 137     coef_bit_ptr = & cinfo->coef_bits[cindex][0];
 138     if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
 139       WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
 140     for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
 141       int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
 142       if (cinfo->Ah != expected)
 143         WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
 144       coef_bit_ptr[coefi] = cinfo->Al;
 145     }
 146   }
 147
 148   /* Select MCU decoding routine */
 149   if (cinfo->Ah == 0) {
 150     if (is_DC_band)
 151       entropy->pub.decode_mcu = decode_mcu_DC_first;
 152     else
 153       entropy->pub.decode_mcu = decode_mcu_AC_first;
 154   } else {
 155     if (is_DC_band)
 156       entropy->pub.decode_mcu = decode_mcu_DC_refine;
 157     else
 158       entropy->pub.decode_mcu = decode_mcu_AC_refine;
 159   }
 160
 161   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
 162     compptr = cinfo->cur_comp_info[ci];
 163     /* Make sure requested tables are present, and compute derived tables.
 164      * We may build same derived table more than once, but it's not expensive.
 165      */
 166     if (is_DC_band) {
 167       if (cinfo->Ah == 0) {     /* DC refinement needs no table */
 168         tbl = compptr->dc_tbl_no;
 169         jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
 170                                 & entropy->derived_tbls[tbl]);
 171       }
 172     } else {
 173       tbl = compptr->ac_tbl_no;
 174       jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
 175                               & entropy->derived_tbls[tbl]);
 176       /* remember the single active table */
 177       entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
 178     }
 179     /* Initialize DC predictions to 0 */
 180     entropy->saved.last_dc_val[ci] = 0;
 181   }
 182
 183   /* Initialize bitread state variables */
 184   entropy->bitstate.bits_left = 0;
 185   entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
 186   entropy->pub.insufficient_data = FALSE;
 187
 188   /* Initialize private state variables */
 189   entropy->saved.EOBRUN = 0;
 190
 191   /* Initialize restart counter */
 192   entropy->restarts_to_go = cinfo->restart_interval;
 193 }
 194
 195
 196 /*
 197  * Figure F.12: extend sign bit.
 198  * On some machines, a shift and add will be faster than a table lookup.
 199  */
 200
 201 #ifdef AVOID_TABLES
 202
 203 #define HUFF_EXTEND(x,s)  ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x))
 204
 205 #else
 206
 207 #define HUFF_EXTEND(x,s)  ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))
 208
 209 static const int extend_test[16] =   /* entry n is 2**(n-1) */
 210   { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
 211     0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };
 212
 213 static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */
 214   { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1,
 215     ((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1,
 216     ((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1,
 217     ((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 };
 218
 219 #endif /* AVOID_TABLES */
 220
 221
 222 /*
 223  * Check for a restart marker & resynchronize decoder.
 224  * Returns FALSE if must suspend.
 225  */
 226
 227 LOCAL(boolean)
 228 process_restart (j_decompress_ptr cinfo)
 229 {
 230   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
 231   int ci;
 232
 233   /* Throw away any unused bits remaining in bit buffer; */
 234   /* include any full bytes in next_marker's count of discarded bytes */
 235   cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
 236   entropy->bitstate.bits_left = 0;
 237
 238   /* Advance past the RSTn marker */
 239   if (! (*cinfo->marker->read_restart_marker) (cinfo))
 240     return FALSE;
 241
 242   /* Re-initialize DC predictions to 0 */
 243   for (ci = 0; ci < cinfo->comps_in_scan; ci++)
 244     entropy->saved.last_dc_val[ci] = 0;
 245   /* Re-init EOB run count, too */
 246   entropy->saved.EOBRUN = 0;
 247
 248   /* Reset restart counter */
 249   entropy->restarts_to_go = cinfo->restart_interval;
 250
 251   /* Reset out-of-data flag, unless read_restart_marker left us smack up
 252    * against a marker.  In that case we will end up treating the next data
 253    * segment as empty, and we can avoid producing bogus output pixels by
 254    * leaving the flag set.
 255    */
 256   if (cinfo->unread_marker == 0)
 257     entropy->pub.insufficient_data = FALSE;
 258
 259   return TRUE;
 260 }
 261
 262
 263 /*
 264  * Huffman MCU decoding.
 265  * Each of these routines decodes and returns one MCU's worth of
 266  * Huffman-compressed coefficients.
 267  * The coefficients are reordered from zigzag order into natural array order,
 268  * but are not dequantized.
 269  *
 270  * The i'th block of the MCU is stored into the block pointed to by
 271  * MCU_data[i].  WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
 272  *
 273  * We return FALSE if data source requested suspension.  In that case no
 274  * changes have been made to permanent state.  (Exception: some output
 275  * coefficients may already have been assigned.  This is harmless for
 276  * spectral selection, since we'll just re-assign them on the next call.
 277  * Successive approximation AC refinement has to be more careful, however.)
 278  */
 279
 280 /*
 281  * MCU decoding for DC initial scan (either spectral selection,
 282  * or first pass of successive approximation).
 283  */
 284
 285 METHODDEF(boolean)
 286 decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
 287 {
 288   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
 289   int Al = cinfo->Al;
 290   register int s, r;
 291   int blkn, ci;
 292   JBLOCKROW block;
 293   BITREAD_STATE_VARS;
 294   savable_state state;
 295   d_derived_tbl * tbl;
 296   jpeg_component_info * compptr;
 297
 298   /* Process restart marker if needed; may have to suspend */
 299   if (cinfo->restart_interval) {
 300     if (entropy->restarts_to_go == 0)
 301       if (! process_restart(cinfo))
 302         return FALSE;
 303   }
 304
 305   /* If we've run out of data, just leave the MCU set to zeroes.
 306    * This way, we return uniform gray for the remainder of the segment.
 307    */
 308   if (! entropy->pub.insufficient_data) {
 309
 310     /* Load up working state */
 311     BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
 312     ASSIGN_STATE(state, entropy->saved);
 313
 314     /* Outer loop handles each block in the MCU */
 315
 316     for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
 317       block = MCU_data[blkn];
 318       ci = cinfo->MCU_membership[blkn];
 319       compptr = cinfo->cur_comp_info[ci];
 320       tbl = entropy->derived_tbls[compptr->dc_tbl_no];
 321
 322       /* Decode a single block's worth of coefficients */
 323
 324       /* Section F.2.2.1: decode the DC coefficient difference */
 325       HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
 326       if (s) {
 327         CHECK_BIT_BUFFER(br_state, s, return FALSE);
 328         r = GET_BITS(s);
 329         s = HUFF_EXTEND(r, s);
 330       }
 331
 332       /* Convert DC difference to actual value, update last_dc_val */
 333       s += state.last_dc_val[ci];
 334       state.last_dc_val[ci] = s;
 335       /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */
 336       (*block)[0] = (JCOEF) (s << Al);
 337     }
 338
 339     /* Completed MCU, so update state */
 340     BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
 341     ASSIGN_STATE(entropy->saved, state);
 342   }
 343
 344   /* Account for restart interval (no-op if not using restarts) */
 345   entropy->restarts_to_go--;
 346
 347   return TRUE;
 348 }
 349
 350
 351 /*
 352  * MCU decoding for AC initial scan (either spectral selection,
 353  * or first pass of successive approximation).
 354  */
 355
 356 METHODDEF(boolean)
 357 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
 358 {
 359   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
 360   int Se = cinfo->Se;
 361   int Al = cinfo->Al;
 362   register int s, k, r;
 363   unsigned int EOBRUN;
 364   JBLOCKROW block;
 365   BITREAD_STATE_VARS;
 366   d_derived_tbl * tbl;
 367
 368   /* Process restart marker if needed; may have to suspend */
 369   if (cinfo->restart_interval) {
 370     if (entropy->restarts_to_go == 0)
 371       if (! process_restart(cinfo))
 372         return FALSE;
 373   }
 374
 375   /* If we've run out of data, just leave the MCU set to zeroes.
 376    * This way, we return uniform gray for the remainder of the segment.
 377    */
 378   if (! entropy->pub.insufficient_data) {
 379
 380     /* Load up working state.
 381      * We can avoid loading/saving bitread state if in an EOB run.
 382      */
 383     EOBRUN = entropy->saved.EOBRUN;     /* only part of saved state we need */
 384
 385     /* There is always only one block per MCU */
 386
 387     if (EOBRUN > 0)             /* if it's a band of zeroes... */
 388       EOBRUN--;                 /* ...process it now (we do nothing) */
 389     else {
 390       BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
 391       block = MCU_data[0];
 392       tbl = entropy->ac_derived_tbl;
 393
 394       for (k = cinfo->Ss; k <= Se; k++) {
 395         HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
 396         r = s >> 4;
 397         s &= 15;
 398         if (s) {
 399           k += r;
 400           CHECK_BIT_BUFFER(br_state, s, return FALSE);
 401           r = GET_BITS(s);
 402           s = HUFF_EXTEND(r, s);
 403           /* Scale and output coefficient in natural (dezigzagged) order */
 404           (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al);
 405         } else {
 406           if (r == 15) {        /* ZRL */
 407             k += 15;            /* skip 15 zeroes in band */
 408           } else {              /* EOBr, run length is 2^r + appended bits */
 409             EOBRUN = 1 << r;
 410             if (r) {            /* EOBr, r > 0 */
 411               CHECK_BIT_BUFFER(br_state, r, return FALSE);
 412               r = GET_BITS(r);
 413               EOBRUN += r;
 414             }
 415             EOBRUN--;           /* this band is processed at this moment */
 416             break;              /* force end-of-band */
 417           }
 418         }
 419       }
 420
 421       BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
 422     }
 423
 424     /* Completed MCU, so update state */
 425     entropy->saved.EOBRUN = EOBRUN;     /* only part of saved state we need */
 426   }
 427
 428   /* Account for restart interval (no-op if not using restarts) */
 429   entropy->restarts_to_go--;
 430
 431   return TRUE;
 432 }
 433
 434
 435 /*
 436  * MCU decoding for DC successive approximation refinement scan.
 437  * Note: we assume such scans can be multi-component, although the spec
 438  * is not very clear on the point.
 439  */
 440
 441 METHODDEF(boolean)
 442 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
 443 {
 444   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
 445   int p1 = 1 << cinfo->Al;      /* 1 in the bit position being coded */
 446   int blkn;
 447   JBLOCKROW block;
 448   BITREAD_STATE_VARS;
 449
 450   /* Process restart marker if needed; may have to suspend */
 451   if (cinfo->restart_interval) {
 452     if (entropy->restarts_to_go == 0)
 453       if (! process_restart(cinfo))
 454         return FALSE;
 455   }
 456
 457   /* Not worth the cycles to check insufficient_data here,
 458    * since we will not change the data anyway if we read zeroes.
 459    */
 460
 461   /* Load up working state */
 462   BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
 463
 464   /* Outer loop handles each block in the MCU */
 465
 466   for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
 467     block = MCU_data[blkn];
 468
 469     /* Encoded data is simply the next bit of the two's-complement DC value */
 470     CHECK_BIT_BUFFER(br_state, 1, return FALSE);
 471     if (GET_BITS(1))
 472       (*block)[0] |= p1;
 473     /* Note: since we use |=, repeating the assignment later is safe */
 474   }
 475
 476   /* Completed MCU, so update state */
 477   BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
 478
 479   /* Account for restart interval (no-op if not using restarts) */
 480   entropy->restarts_to_go--;
 481
 482   return TRUE;
 483 }
 484
 485
 486 /*
 487  * MCU decoding for AC successive approximation refinement scan.
 488  */
 489
 490 METHODDEF(boolean)
 491 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
 492 {
 493   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
 494   int Se = cinfo->Se;
 495   int p1 = 1 << cinfo->Al;      /* 1 in the bit position being coded */
 496   int m1 = (-1) << cinfo->Al;   /* -1 in the bit position being coded */
 497   register int s, k, r;
 498   unsigned int EOBRUN;
 499   JBLOCKROW block;
 500   JCOEFPTR thiscoef;
 501   BITREAD_STATE_VARS;
 502   d_derived_tbl * tbl;
 503   int num_newnz;
 504   int newnz_pos[DCTSIZE2];
 505
 506   /* Process restart marker if needed; may have to suspend */
 507   if (cinfo->restart_interval) {
 508     if (entropy->restarts_to_go == 0)
 509       if (! process_restart(cinfo))
 510         return FALSE;
 511   }
 512
 513   /* If we've run out of data, don't modify the MCU.
 514    */
 515   if (! entropy->pub.insufficient_data) {
 516
 517     /* Load up working state */
 518     BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
 519     EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
 520
 521     /* There is always only one block per MCU */
 522     block = MCU_data[0];
 523     tbl = entropy->ac_derived_tbl;
 524
 525     /* If we are forced to suspend, we must undo the assignments to any newly
 526      * nonzero coefficients in the block, because otherwise we'd get confused
 527      * next time about which coefficients were already nonzero.
 528      * But we need not undo addition of bits to already-nonzero coefficients;
 529      * instead, we can test the current bit to see if we already did it.
 530      */
 531     num_newnz = 0;
 532
 533     /* initialize coefficient loop counter to start of band */
 534     k = cinfo->Ss;
 535
 536     if (EOBRUN == 0) {
 537       for (; k <= Se; k++) {
 538         HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
 539         r = s >> 4;
 540         s &= 15;
 541         if (s) {
 542           if (s != 1)           /* size of new coef should always be 1 */
 543             WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
 544           CHECK_BIT_BUFFER(br_state, 1, goto undoit);
 545           if (GET_BITS(1))
 546             s = p1;             /* newly nonzero coef is positive */
 547           else
 548             s = m1;             /* newly nonzero coef is negative */
 549         } else {
 550           if (r != 15) {
 551             EOBRUN = 1 << r;    /* EOBr, run length is 2^r + appended bits */
 552             if (r) {
 553               CHECK_BIT_BUFFER(br_state, r, goto undoit);
 554               r = GET_BITS(r);
 555               EOBRUN += r;
 556             }
 557             break;              /* rest of block is handled by EOB logic */
 558           }
 559           /* note s = 0 for processing ZRL */
 560         }
 561         /* Advance over already-nonzero coefs and r still-zero coefs,
 562          * appending correction bits to the nonzeroes.  A correction bit is 1
 563          * if the absolute value of the coefficient must be increased.
 564          */
 565         do {
 566           thiscoef = *block + jpeg_natural_order[k];
 567           if (*thiscoef != 0) {
 568             CHECK_BIT_BUFFER(br_state, 1, goto undoit);
 569             if (GET_BITS(1)) {
 570               if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
 571                 if (*thiscoef >= 0)
 572                   *thiscoef += p1;
 573                 else
 574                   *thiscoef += m1;
 575               }
 576             }
 577           } else {
 578             if (--r < 0)
 579               break;            /* reached target zero coefficient */
 580           }
 581           k++;
 582         } while (k <= Se);
 583         if (s) {
 584           int pos = jpeg_natural_order[k];
 585           /* Output newly nonzero coefficient */
 586           (*block)[pos] = (JCOEF) s;
 587           /* Remember its position in case we have to suspend */
 588           newnz_pos[num_newnz++] = pos;
 589         }
 590       }
 591     }
 592
 593     if (EOBRUN > 0) {
 594       /* Scan any remaining coefficient positions after the end-of-band
 595        * (the last newly nonzero coefficient, if any).  Append a correction
 596        * bit to each already-nonzero coefficient.  A correction bit is 1
 597        * if the absolute value of the coefficient must be increased.
 598        */
 599       for (; k <= Se; k++) {
 600         thiscoef = *block + jpeg_natural_order[k];
 601         if (*thiscoef != 0) {
 602           CHECK_BIT_BUFFER(br_state, 1, goto undoit);
 603           if (GET_BITS(1)) {
 604             if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
 605               if (*thiscoef >= 0)
 606                 *thiscoef += p1;
 607               else
 608                 *thiscoef += m1;
 609             }
 610           }
 611         }
 612       }
 613       /* Count one block completed in EOB run */
 614       EOBRUN--;
 615     }
 616
 617     /* Completed MCU, so update state */
 618     BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
 619     entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
 620   }
 621
 622   /* Account for restart interval (no-op if not using restarts) */
 623   entropy->restarts_to_go--;
 624
 625   return TRUE;
 626
 627 undoit:
 628   /* Re-zero any output coefficients that we made newly nonzero */
 629   while (num_newnz > 0)
 630     (*block)[newnz_pos[--num_newnz]] = 0;
 631
 632   return FALSE;
 633 }
 634
 635
 636 /*
 637  * Module initialization routine for progressive Huffman entropy decoding.
 638  */
 639
 640 GLOBAL(void)
 641 jinit_phuff_decoder (j_decompress_ptr cinfo)
 642 {
 643   phuff_entropy_ptr entropy;
 644   int *coef_bit_ptr;
 645   int ci, i;
 646
 647   entropy = (phuff_entropy_ptr)
 648     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 649                                 SIZEOF(phuff_entropy_decoder));
 650   cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
 651   entropy->pub.start_pass = start_pass_phuff_decoder;
 652
 653   /* Mark derived tables unallocated */
 654   for (i = 0; i < NUM_HUFF_TBLS; i++) {
 655     entropy->derived_tbls[i] = NULL;
 656   }
 657
 658   /* Create progression status table */
 659   cinfo->coef_bits = (int (*)[DCTSIZE2])
 660     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 661                                 cinfo->num_components*DCTSIZE2*SIZEOF(int));
 662   coef_bit_ptr = & cinfo->coef_bits[0][0];
 663   for (ci = 0; ci < cinfo->num_components; ci++)
 664     for (i = 0; i < DCTSIZE2; i++)
 665       *coef_bit_ptr++ = -1;
 666 }
 667
 668 #endif /* D_PROGRESSIVE_SUPPORTED */