1 /*
   2  * reserved comment block
   3  * DO NOT REMOVE OR ALTER!
   4  */
   5 /*
   6  * jdphuff.c
   7  *
   8  * Copyright (C) 1995-1997, Thomas G. Lane.
   9  * This file is part of the Independent JPEG Group's software.
  10  * For conditions of distribution and use, see the accompanying README file.
  11  *
  12  * This file contains Huffman entropy decoding routines for progressive JPEG.
  13  *
  14  * Much of the complexity here has to do with supporting input suspension.
  15  * If the data source module demands suspension, we want to be able to back
  16  * up to the start of the current MCU.  To do this, we copy state variables
  17  * into local working storage, and update them back to the permanent
  18  * storage only upon successful completion of an MCU.
  19  */
  20 
  21 #define JPEG_INTERNALS
  22 #include "jinclude.h"
  23 #include "jpeglib.h"
  24 #include "jdhuff.h"             /* Declarations shared with jdhuff.c */
  25 
  26 
  27 #ifdef D_PROGRESSIVE_SUPPORTED
  28 
  29 /*
  30  * Expanded entropy decoder object for progressive Huffman decoding.
  31  *
  32  * The savable_state subrecord contains fields that change within an MCU,
  33  * but must not be updated permanently until we complete the MCU.
  34  */
  35 
  36 typedef struct {
  37   unsigned int EOBRUN;                  /* remaining EOBs in EOBRUN */
  38   int last_dc_val[MAX_COMPS_IN_SCAN];   /* last DC coef for each component */
  39 } savable_state;
  40 
  41 /* This macro is to work around compilers with missing or broken
  42  * structure assignment.  You'll need to fix this code if you have
  43  * such a compiler and you change MAX_COMPS_IN_SCAN.
  44  */
  45 
  46 #ifndef NO_STRUCT_ASSIGN
  47 #define ASSIGN_STATE(dest,src)  ((dest) = (src))
  48 #else
  49 #if MAX_COMPS_IN_SCAN == 4
  50 #define ASSIGN_STATE(dest,src)  \
  51         ((dest).EOBRUN = (src).EOBRUN, \
  52          (dest).last_dc_val[0] = (src).last_dc_val[0], \
  53          (dest).last_dc_val[1] = (src).last_dc_val[1], \
  54          (dest).last_dc_val[2] = (src).last_dc_val[2], \
  55          (dest).last_dc_val[3] = (src).last_dc_val[3])
  56 #endif
  57 #endif
  58 
  59 
  60 typedef struct {
  61   struct jpeg_entropy_decoder pub; /* public fields */
  62 
  63   /* These fields are loaded into local variables at start of each MCU.
  64    * In case of suspension, we exit WITHOUT updating them.
  65    */
  66   bitread_perm_state bitstate;  /* Bit buffer at start of MCU */
  67   savable_state saved;          /* Other state at start of MCU */
  68 
  69   /* These fields are NOT loaded into local working state. */
  70   unsigned int restarts_to_go;  /* MCUs left in this restart interval */
  71 
  72   /* Pointers to derived tables (these workspaces have image lifespan) */
  73   d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
  74 
  75   d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
  76 } phuff_entropy_decoder;
  77 
  78 typedef phuff_entropy_decoder * phuff_entropy_ptr;
  79 
  80 /* Forward declarations */
  81 METHODDEF(boolean) decode_mcu_DC_first JPP((j_decompress_ptr cinfo,
  82                                             JBLOCKROW *MCU_data));
  83 METHODDEF(boolean) decode_mcu_AC_first JPP((j_decompress_ptr cinfo,
  84                                             JBLOCKROW *MCU_data));
  85 METHODDEF(boolean) decode_mcu_DC_refine JPP((j_decompress_ptr cinfo,
  86                                              JBLOCKROW *MCU_data));
  87 METHODDEF(boolean) decode_mcu_AC_refine JPP((j_decompress_ptr cinfo,
  88                                              JBLOCKROW *MCU_data));
  89 
  90 
  91 /*
  92  * Initialize for a Huffman-compressed scan.
  93  */
  94 
  95 METHODDEF(void)
  96 start_pass_phuff_decoder (j_decompress_ptr cinfo)
  97 {
  98   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
  99   boolean is_DC_band, bad;
 100   int ci, coefi, tbl;
 101   int *coef_bit_ptr;
 102   jpeg_component_info * compptr;
 103 
 104   is_DC_band = (cinfo->Ss == 0);
 105 
 106   /* Validate scan parameters */
 107   bad = FALSE;
 108   if (is_DC_band) {
 109     if (cinfo->Se != 0)
 110       bad = TRUE;
 111   } else {
 112     /* need not check Ss/Se < 0 since they came from unsigned bytes */
 113     if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2)
 114       bad = TRUE;
 115     /* AC scans may have only one component */
 116     if (cinfo->comps_in_scan != 1)
 117       bad = TRUE;
 118   }
 119   if (cinfo->Ah != 0) {
 120     /* Successive approximation refinement scan: must have Al = Ah-1. */
 121     if (cinfo->Al != cinfo->Ah-1)
 122       bad = TRUE;
 123   }
 124   if (cinfo->Al > 13)           /* need not check for < 0 */
 125     bad = TRUE;
 126   /* Arguably the maximum Al value should be less than 13 for 8-bit precision,
 127    * but the spec doesn't say so, and we try to be liberal about what we
 128    * accept.  Note: large Al values could result in out-of-range DC
 129    * coefficients during early scans, leading to bizarre displays due to
 130    * overflows in the IDCT math.  But we won't crash.
 131    */
 132   if (bad)
 133     ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
 134              cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
 135   /* Update progression status, and verify that scan order is legal.
 136    * Note that inter-scan inconsistencies are treated as warnings
 137    * not fatal errors ... not clear if this is right way to behave.
 138    */
 139   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
 140     int cindex = cinfo->cur_comp_info[ci]->component_index;
 141     coef_bit_ptr = & cinfo->coef_bits[cindex][0];
 142     if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
 143       WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
 144     for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
 145       int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
 146       if (cinfo->Ah != expected)
 147         WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
 148       coef_bit_ptr[coefi] = cinfo->Al;
 149     }
 150   }
 151 
 152   /* Select MCU decoding routine */
 153   if (cinfo->Ah == 0) {
 154     if (is_DC_band)
 155       entropy->pub.decode_mcu = decode_mcu_DC_first;
 156     else
 157       entropy->pub.decode_mcu = decode_mcu_AC_first;
 158   } else {
 159     if (is_DC_band)
 160       entropy->pub.decode_mcu = decode_mcu_DC_refine;
 161     else
 162       entropy->pub.decode_mcu = decode_mcu_AC_refine;
 163   }
 164 
 165   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
 166     compptr = cinfo->cur_comp_info[ci];
 167     /* Make sure requested tables are present, and compute derived tables.
 168      * We may build same derived table more than once, but it's not expensive.
 169      */
 170     if (is_DC_band) {
 171       if (cinfo->Ah == 0) {     /* DC refinement needs no table */
 172         tbl = compptr->dc_tbl_no;
 173         jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
 174                                 & entropy->derived_tbls[tbl]);
 175       }
 176     } else {
 177       tbl = compptr->ac_tbl_no;
 178       jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
 179                               & entropy->derived_tbls[tbl]);
 180       /* remember the single active table */
 181       entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
 182     }
 183     /* Initialize DC predictions to 0 */
 184     entropy->saved.last_dc_val[ci] = 0;
 185   }
 186 
 187   /* Initialize bitread state variables */
 188   entropy->bitstate.bits_left = 0;
 189   entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
 190   entropy->pub.insufficient_data = FALSE;
 191 
 192   /* Initialize private state variables */
 193   entropy->saved.EOBRUN = 0;
 194 
 195   /* Initialize restart counter */
 196   entropy->restarts_to_go = cinfo->restart_interval;
 197 }
 198 
 199 
 200 /*
 201  * Figure F.12: extend sign bit.
 202  * On some machines, a shift and add will be faster than a table lookup.
 203  */
 204 
 205 #ifdef AVOID_TABLES
 206 
 207 #define HUFF_EXTEND(x,s)  ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x))
 208 
 209 #else
 210 
 211 #define HUFF_EXTEND(x,s)  ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))
 212 
 213 static const int extend_test[16] =   /* entry n is 2**(n-1) */
 214   { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
 215     0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };
 216 
 217 static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */
 218   { 0, (0xffffffff<<1) + 1, (0xffffffff<<2) + 1, (0xffffffff<<3) + 1, (0xffffffff<<4) + 1,
 219     (0xffffffff<<5) + 1, (0xffffffff<<6) + 1, (0xffffffff<<7) + 1, (0xffffffff<<8) + 1,
 220     (0xffffffff<<9) + 1, (0xffffffff<<10) + 1, (0xffffffff<<11) + 1, (0xffffffff<<12) + 1,
 221     (0xffffffff<<13) + 1, (0xffffffff<<14) + 1, (0xffffffff<<15) + 1 };
 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     ASSIGN_STATE(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       s += state.last_dc_val[ci];
 338       state.last_dc_val[ci] = s;
 339       /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */
 340       (*block)[0] = (JCOEF) (s << Al);
 341     }
 342 
 343     /* Completed MCU, so update state */
 344     BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
 345     ASSIGN_STATE(entropy->saved, state);
 346   }
 347 
 348   /* Account for restart interval (no-op if not using restarts) */
 349   entropy->restarts_to_go--;
 350 
 351   return TRUE;
 352 }
 353 
 354 
 355 /*
 356  * MCU decoding for AC initial scan (either spectral selection,
 357  * or first pass of successive approximation).
 358  */
 359 
 360 METHODDEF(boolean)
 361 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
 362 {
 363   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
 364   int Se = cinfo->Se;
 365   int Al = cinfo->Al;
 366   register int s, k, r;
 367   unsigned int EOBRUN;
 368   JBLOCKROW block;
 369   BITREAD_STATE_VARS;
 370   d_derived_tbl * tbl;
 371 
 372   /* Process restart marker if needed; may have to suspend */
 373   if (cinfo->restart_interval) {
 374     if (entropy->restarts_to_go == 0)
 375       if (! process_restart(cinfo))
 376         return FALSE;
 377   }
 378 
 379   /* If we've run out of data, just leave the MCU set to zeroes.
 380    * This way, we return uniform gray for the remainder of the segment.
 381    */
 382   if (! entropy->pub.insufficient_data) {
 383 
 384     /* Load up working state.
 385      * We can avoid loading/saving bitread state if in an EOB run.
 386      */
 387     EOBRUN = entropy->saved.EOBRUN;     /* only part of saved state we need */
 388 
 389     /* There is always only one block per MCU */
 390 
 391     if (EOBRUN > 0)             /* if it's a band of zeroes... */
 392       EOBRUN--;                 /* ...process it now (we do nothing) */
 393     else {
 394       BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
 395       block = MCU_data[0];
 396       tbl = entropy->ac_derived_tbl;
 397 
 398       for (k = cinfo->Ss; k <= Se; k++) {
 399         HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
 400         r = s >> 4;
 401         s &= 15;
 402         if (s) {
 403           k += r;
 404           CHECK_BIT_BUFFER(br_state, s, return FALSE);
 405           r = GET_BITS(s);
 406           s = HUFF_EXTEND(r, s);
 407           /* Scale and output coefficient in natural (dezigzagged) order */
 408           (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al);
 409         } else {
 410           if (r == 15) {        /* ZRL */
 411             k += 15;            /* skip 15 zeroes in band */
 412           } else {              /* EOBr, run length is 2^r + appended bits */
 413             EOBRUN = 1 << r;
 414             if (r) {            /* EOBr, r > 0 */
 415               CHECK_BIT_BUFFER(br_state, r, return FALSE);
 416               r = GET_BITS(r);
 417               EOBRUN += r;
 418             }
 419             EOBRUN--;           /* this band is processed at this moment */
 420             break;              /* force end-of-band */
 421           }
 422         }
 423       }
 424 
 425       BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
 426     }
 427 
 428     /* Completed MCU, so update state */
 429     entropy->saved.EOBRUN = EOBRUN;     /* only part of saved state we need */
 430   }
 431 
 432   /* Account for restart interval (no-op if not using restarts) */
 433   entropy->restarts_to_go--;
 434 
 435   return TRUE;
 436 }
 437 
 438 
 439 /*
 440  * MCU decoding for DC successive approximation refinement scan.
 441  * Note: we assume such scans can be multi-component, although the spec
 442  * is not very clear on the point.
 443  */
 444 
 445 METHODDEF(boolean)
 446 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
 447 {
 448   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
 449   int p1 = 1 << cinfo->Al;      /* 1 in the bit position being coded */
 450   int blkn;
 451   JBLOCKROW block;
 452   BITREAD_STATE_VARS;
 453 
 454   /* Process restart marker if needed; may have to suspend */
 455   if (cinfo->restart_interval) {
 456     if (entropy->restarts_to_go == 0)
 457       if (! process_restart(cinfo))
 458         return FALSE;
 459   }
 460 
 461   /* Not worth the cycles to check insufficient_data here,
 462    * since we will not change the data anyway if we read zeroes.
 463    */
 464 
 465   /* Load up working state */
 466   BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
 467 
 468   /* Outer loop handles each block in the MCU */
 469 
 470   for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
 471     block = MCU_data[blkn];
 472 
 473     /* Encoded data is simply the next bit of the two's-complement DC value */
 474     CHECK_BIT_BUFFER(br_state, 1, return FALSE);
 475     if (GET_BITS(1))
 476       (*block)[0] |= p1;
 477     /* Note: since we use |=, repeating the assignment later is safe */
 478   }
 479 
 480   /* Completed MCU, so update state */
 481   BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
 482 
 483   /* Account for restart interval (no-op if not using restarts) */
 484   entropy->restarts_to_go--;
 485 
 486   return TRUE;
 487 }
 488 
 489 
 490 /*
 491  * MCU decoding for AC successive approximation refinement scan.
 492  */
 493 
 494 METHODDEF(boolean)
 495 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
 496 {
 497   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
 498   int Se = cinfo->Se;
 499   int p1 = 1 << cinfo->Al;          /* 1 in the bit position being coded */
 500   int m1 = 0xffffffff << cinfo->Al; /* -1 in the bit position being coded */
 501   register int s, k, r;
 502   unsigned int EOBRUN;
 503   JBLOCKROW block;
 504   JCOEFPTR thiscoef;
 505   BITREAD_STATE_VARS;
 506   d_derived_tbl * tbl;
 507   int num_newnz;
 508   int newnz_pos[DCTSIZE2];
 509 
 510   /* Process restart marker if needed; may have to suspend */
 511   if (cinfo->restart_interval) {
 512     if (entropy->restarts_to_go == 0)
 513       if (! process_restart(cinfo))
 514         return FALSE;
 515   }
 516 
 517   /* If we've run out of data, don't modify the MCU.
 518    */
 519   if (! entropy->pub.insufficient_data) {
 520 
 521     /* Load up working state */
 522     BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
 523     EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
 524 
 525     /* There is always only one block per MCU */
 526     block = MCU_data[0];
 527     tbl = entropy->ac_derived_tbl;
 528 
 529     /* If we are forced to suspend, we must undo the assignments to any newly
 530      * nonzero coefficients in the block, because otherwise we'd get confused
 531      * next time about which coefficients were already nonzero.
 532      * But we need not undo addition of bits to already-nonzero coefficients;
 533      * instead, we can test the current bit to see if we already did it.
 534      */
 535     num_newnz = 0;
 536 
 537     /* initialize coefficient loop counter to start of band */
 538     k = cinfo->Ss;
 539 
 540     if (EOBRUN == 0) {
 541       for (; k <= Se; k++) {
 542         HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
 543         r = s >> 4;
 544         s &= 15;
 545         if (s) {
 546           if (s != 1)           /* size of new coef should always be 1 */
 547             WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
 548           CHECK_BIT_BUFFER(br_state, 1, goto undoit);
 549           if (GET_BITS(1))
 550             s = p1;             /* newly nonzero coef is positive */
 551           else
 552             s = m1;             /* newly nonzero coef is negative */
 553         } else {
 554           if (r != 15) {
 555             EOBRUN = 1 << r;    /* EOBr, run length is 2^r + appended bits */
 556             if (r) {
 557               CHECK_BIT_BUFFER(br_state, r, goto undoit);
 558               r = GET_BITS(r);
 559               EOBRUN += r;
 560             }
 561             break;              /* rest of block is handled by EOB logic */
 562           }
 563           /* note s = 0 for processing ZRL */
 564         }
 565         /* Advance over already-nonzero coefs and r still-zero coefs,
 566          * appending correction bits to the nonzeroes.  A correction bit is 1
 567          * if the absolute value of the coefficient must be increased.
 568          */
 569         do {
 570           thiscoef = *block + jpeg_natural_order[k];
 571           if (*thiscoef != 0) {
 572             CHECK_BIT_BUFFER(br_state, 1, goto undoit);
 573             if (GET_BITS(1)) {
 574               if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
 575                 if (*thiscoef >= 0)
 576                   *thiscoef += p1;
 577                 else
 578                   *thiscoef += m1;
 579               }
 580             }
 581           } else {
 582             if (--r < 0)
 583               break;            /* reached target zero coefficient */
 584           }
 585           k++;
 586         } while (k <= Se);
 587         if (s) {
 588           int pos = jpeg_natural_order[k];
 589           /* Output newly nonzero coefficient */
 590           (*block)[pos] = (JCOEF) s;
 591           /* Remember its position in case we have to suspend */
 592           newnz_pos[num_newnz++] = pos;
 593         }
 594       }
 595     }
 596 
 597     if (EOBRUN > 0) {
 598       /* Scan any remaining coefficient positions after the end-of-band
 599        * (the last newly nonzero coefficient, if any).  Append a correction
 600        * bit to each already-nonzero coefficient.  A correction bit is 1
 601        * if the absolute value of the coefficient must be increased.
 602        */
 603       for (; k <= Se; k++) {
 604         thiscoef = *block + jpeg_natural_order[k];
 605         if (*thiscoef != 0) {
 606           CHECK_BIT_BUFFER(br_state, 1, goto undoit);
 607           if (GET_BITS(1)) {
 608             if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
 609               if (*thiscoef >= 0)
 610                 *thiscoef += p1;
 611               else
 612                 *thiscoef += m1;
 613             }
 614           }
 615         }
 616       }
 617       /* Count one block completed in EOB run */
 618       EOBRUN--;
 619     }
 620 
 621     /* Completed MCU, so update state */
 622     BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
 623     entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
 624   }
 625 
 626   /* Account for restart interval (no-op if not using restarts) */
 627   entropy->restarts_to_go--;
 628 
 629   return TRUE;
 630 
 631 undoit:
 632   /* Re-zero any output coefficients that we made newly nonzero */
 633   while (num_newnz > 0)
 634     (*block)[newnz_pos[--num_newnz]] = 0;
 635 
 636   return FALSE;
 637 }
 638 
 639 
 640 /*
 641  * Module initialization routine for progressive Huffman entropy decoding.
 642  */
 643 
 644 GLOBAL(void)
 645 jinit_phuff_decoder (j_decompress_ptr cinfo)
 646 {
 647   phuff_entropy_ptr entropy;
 648   int *coef_bit_ptr;
 649   int ci, i;
 650 
 651   entropy = (phuff_entropy_ptr)
 652     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 653                                 SIZEOF(phuff_entropy_decoder));
 654   cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
 655   entropy->pub.start_pass = start_pass_phuff_decoder;
 656 
 657   /* Mark derived tables unallocated */
 658   for (i = 0; i < NUM_HUFF_TBLS; i++) {
 659     entropy->derived_tbls[i] = NULL;
 660   }
 661 
 662   /* Create progression status table */
 663   cinfo->coef_bits = (int (*)[DCTSIZE2])
 664     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 665                                 cinfo->num_components*DCTSIZE2*SIZEOF(int));
 666   coef_bit_ptr = & cinfo->coef_bits[0][0];
 667   for (ci = 0; ci < cinfo->num_components; ci++)
 668     for (i = 0; i < DCTSIZE2; i++)
 669       *coef_bit_ptr++ = -1;
 670 }
 671 
 672 #endif /* D_PROGRESSIVE_SUPPORTED */
--- EOF ---