jdphuff.c - third_party/libjpeg-turbo - Git at Google

 /*
  * jdphuff.c
  *
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1995-1997, Thomas G. Lane.
  * libjpeg-turbo Modifications:
  * Copyright (C) 2015, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains Huffman entropy decoding routines for progressive JPEG.
  *
  * Much of the complexity here has to do with supporting input suspension.
  * If the data source module demands suspension, we want to be able to back
  * up to the start of the current MCU.  To do this, we copy state variables
  * into local working storage, and update them back to the permanent
  * storage only upon successful completion of an MCU.
  */

 #define JPEG_INTERNALS
 #include "jinclude.h"
 #include "jpeglib.h"
 #include "jdhuff.h"             /* Declarations shared with jdhuff.c */


 #ifdef D_PROGRESSIVE_SUPPORTED

 /*
  * Expanded entropy decoder object for progressive Huffman decoding.
  *
  * The savable_state subrecord contains fields that change within an MCU,
  * but must not be updated permanently until we complete the MCU.
  */

 typedef struct {
   unsigned int EOBRUN;                  /* remaining EOBs in EOBRUN */
   int last_dc_val[MAX_COMPS_IN_SCAN];   /* last DC coef for each component */
 } savable_state;

 /* This macro is to work around compilers with missing or broken
  * structure assignment.  You'll need to fix this code if you have
  * such a compiler and you change MAX_COMPS_IN_SCAN.
  */

 #ifndef NO_STRUCT_ASSIGN
 #define ASSIGN_STATE(dest,src)  ((dest) = (src))
 #else
 #if MAX_COMPS_IN_SCAN == 4
 #define ASSIGN_STATE(dest,src)  \
         ((dest).EOBRUN = (src).EOBRUN, \
          (dest).last_dc_val[0] = (src).last_dc_val[0], \
          (dest).last_dc_val[1] = (src).last_dc_val[1], \
          (dest).last_dc_val[2] = (src).last_dc_val[2], \
          (dest).last_dc_val[3] = (src).last_dc_val[3])
 #endif
 #endif


 typedef struct {
   struct jpeg_entropy_decoder pub; /* public fields */

   /* These fields are loaded into local variables at start of each MCU.
    * In case of suspension, we exit WITHOUT updating them.
    */
   bitread_perm_state bitstate;  /* Bit buffer at start of MCU */
   savable_state saved;          /* Other state at start of MCU */

   /* These fields are NOT loaded into local working state. */
   unsigned int restarts_to_go;  /* MCUs left in this restart interval */

   /* Pointers to derived tables (these workspaces have image lifespan) */
   d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];

   d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
 } phuff_entropy_decoder;

 typedef phuff_entropy_decoder * phuff_entropy_ptr;

 /* Forward declarations */
 METHODDEF(boolean) decode_mcu_DC_first (j_decompress_ptr cinfo,
                                         JBLOCKROW *MCU_data);
 METHODDEF(boolean) decode_mcu_AC_first (j_decompress_ptr cinfo,
                                         JBLOCKROW *MCU_data);
 METHODDEF(boolean) decode_mcu_DC_refine (j_decompress_ptr cinfo,
                                          JBLOCKROW *MCU_data);
 METHODDEF(boolean) decode_mcu_AC_refine (j_decompress_ptr cinfo,
                                          JBLOCKROW *MCU_data);


 /*
  * Initialize for a Huffman-compressed scan.
  */

 METHODDEF(void)
 start_pass_phuff_decoder (j_decompress_ptr cinfo)
 {
   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
   boolean is_DC_band, bad;
   int ci, coefi, tbl;
   d_derived_tbl **pdtbl;
   int *coef_bit_ptr;
   jpeg_component_info * compptr;

   is_DC_band = (cinfo->Ss == 0);

   /* Validate scan parameters */
   bad = FALSE;
   if (is_DC_band) {
     if (cinfo->Se != 0)
       bad = TRUE;
   } else {
     /* need not check Ss/Se < 0 since they came from unsigned bytes */
     if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2)
       bad = TRUE;
     /* AC scans may have only one component */
     if (cinfo->comps_in_scan != 1)
       bad = TRUE;
   }
   if (cinfo->Ah != 0) {
     /* Successive approximation refinement scan: must have Al = Ah-1. */
     if (cinfo->Al != cinfo->Ah-1)
       bad = TRUE;
   }
   if (cinfo->Al > 13)           /* need not check for < 0 */
     bad = TRUE;
   /* Arguably the maximum Al value should be less than 13 for 8-bit precision,
    * but the spec doesn't say so, and we try to be liberal about what we
    * accept.  Note: large Al values could result in out-of-range DC
    * coefficients during early scans, leading to bizarre displays due to
    * overflows in the IDCT math.  But we won't crash.
    */
   if (bad)
     ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
              cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
   /* Update progression status, and verify that scan order is legal.
    * Note that inter-scan inconsistencies are treated as warnings
    * not fatal errors ... not clear if this is right way to behave.
    */
   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
     int cindex = cinfo->cur_comp_info[ci]->component_index;
     coef_bit_ptr = & cinfo->coef_bits[cindex][0];
     if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
       WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
     for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
       int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
       if (cinfo->Ah != expected)
         WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
       coef_bit_ptr[coefi] = cinfo->Al;
     }
   }

   /* Select MCU decoding routine */
   if (cinfo->Ah == 0) {
     if (is_DC_band)
       entropy->pub.decode_mcu = decode_mcu_DC_first;
     else
       entropy->pub.decode_mcu = decode_mcu_AC_first;
   } else {
     if (is_DC_band)
       entropy->pub.decode_mcu = decode_mcu_DC_refine;
     else
       entropy->pub.decode_mcu = decode_mcu_AC_refine;
   }

   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
     compptr = cinfo->cur_comp_info[ci];
     /* Make sure requested tables are present, and compute derived tables.
      * We may build same derived table more than once, but it's not expensive.
      */
     if (is_DC_band) {
       if (cinfo->Ah == 0) {     /* DC refinement needs no table */
         tbl = compptr->dc_tbl_no;
         pdtbl = entropy->derived_tbls + tbl;
         jpeg_make_d_derived_tbl(cinfo, TRUE, tbl, pdtbl);
       }
     } else {
       tbl = compptr->ac_tbl_no;
       pdtbl = entropy->derived_tbls + tbl;
       jpeg_make_d_derived_tbl(cinfo, FALSE, tbl, pdtbl);
       /* remember the single active table */
       entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
     }
     /* Initialize DC predictions to 0 */
     entropy->saved.last_dc_val[ci] = 0;
   }

   /* Initialize bitread state variables */
   entropy->bitstate.bits_left = 0;
   entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
   entropy->pub.insufficient_data = FALSE;

   /* Initialize private state variables */
   entropy->saved.EOBRUN = 0;

   /* Initialize restart counter */
   entropy->restarts_to_go = cinfo->restart_interval;
 }


 /*
  * Figure F.12: extend sign bit.
  * On some machines, a shift and add will be faster than a table lookup.
  */

 #define AVOID_TABLES
 #ifdef AVOID_TABLES

 #define NEG_1 ((unsigned)-1)
 #define HUFF_EXTEND(x,s)  ((x) < (1<<((s)-1)) ? (x) + (((NEG_1)<<(s)) + 1) : (x))

 #else

 #define HUFF_EXTEND(x,s)  ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))

 static const int extend_test[16] =   /* entry n is 2**(n-1) */
   { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
     0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };

 static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */
   { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1,
     ((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1,
     ((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1,
     ((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 };

 #endif /* AVOID_TABLES */


 /*
  * Check for a restart marker & resynchronize decoder.
  * Returns FALSE if must suspend.
  */

 LOCAL(boolean)
 process_restart (j_decompress_ptr cinfo)
 {
   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
   int ci;

   /* Throw away any unused bits remaining in bit buffer; */
   /* include any full bytes in next_marker's count of discarded bytes */
   cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
   entropy->bitstate.bits_left = 0;

   /* Advance past the RSTn marker */
   if (! (*cinfo->marker->read_restart_marker) (cinfo))
     return FALSE;

   /* Re-initialize DC predictions to 0 */
   for (ci = 0; ci < cinfo->comps_in_scan; ci++)
     entropy->saved.last_dc_val[ci] = 0;
   /* Re-init EOB run count, too */
   entropy->saved.EOBRUN = 0;

   /* Reset restart counter */
   entropy->restarts_to_go = cinfo->restart_interval;

   /* Reset out-of-data flag, unless read_restart_marker left us smack up
    * against a marker.  In that case we will end up treating the next data
    * segment as empty, and we can avoid producing bogus output pixels by
    * leaving the flag set.
    */
   if (cinfo->unread_marker == 0)
     entropy->pub.insufficient_data = FALSE;

   return TRUE;
 }


 /*
  * Huffman MCU decoding.
  * Each of these routines decodes and returns one MCU's worth of
  * Huffman-compressed coefficients.
  * The coefficients are reordered from zigzag order into natural array order,
  * but are not dequantized.
  *
  * The i'th block of the MCU is stored into the block pointed to by
  * MCU_data[i].  WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
  *
  * We return FALSE if data source requested suspension.  In that case no
  * changes have been made to permanent state.  (Exception: some output
  * coefficients may already have been assigned.  This is harmless for
  * spectral selection, since we'll just re-assign them on the next call.
  * Successive approximation AC refinement has to be more careful, however.)
  */

 /*
  * MCU decoding for DC initial scan (either spectral selection,
  * or first pass of successive approximation).
  */

 METHODDEF(boolean)
 decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
 {
   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
   int Al = cinfo->Al;
   register int s, r;
   int blkn, ci;
   JBLOCKROW block;
   BITREAD_STATE_VARS;
   savable_state state;
   d_derived_tbl * tbl;
   jpeg_component_info * compptr;

   /* Process restart marker if needed; may have to suspend */
   if (cinfo->restart_interval) {
     if (entropy->restarts_to_go == 0)
       if (! process_restart(cinfo))
         return FALSE;
   }

   /* If we've run out of data, just leave the MCU set to zeroes.
    * This way, we return uniform gray for the remainder of the segment.
    */
   if (! entropy->pub.insufficient_data) {

     /* Load up working state */
     BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
     ASSIGN_STATE(state, entropy->saved);

     /* Outer loop handles each block in the MCU */

     for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
       block = MCU_data[blkn];
       ci = cinfo->MCU_membership[blkn];
       compptr = cinfo->cur_comp_info[ci];
       tbl = entropy->derived_tbls[compptr->dc_tbl_no];

       /* Decode a single block's worth of coefficients */

       /* Section F.2.2.1: decode the DC coefficient difference */
       HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
       if (s) {
         CHECK_BIT_BUFFER(br_state, s, return FALSE);
         r = GET_BITS(s);
         s = HUFF_EXTEND(r, s);
       }

       /* Convert DC difference to actual value, update last_dc_val */
       s += state.last_dc_val[ci];
       state.last_dc_val[ci] = s;
       /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */
       (*block)[0] = (JCOEF) LEFT_SHIFT(s, Al);
     }

     /* Completed MCU, so update state */
     BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
     ASSIGN_STATE(entropy->saved, state);
   }

   /* Account for restart interval (no-op if not using restarts) */
   entropy->restarts_to_go--;

   return TRUE;
 }


 /*
  * MCU decoding for AC initial scan (either spectral selection,
  * or first pass of successive approximation).
  */

 METHODDEF(boolean)
 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
 {
   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
   int Se = cinfo->Se;
   int Al = cinfo->Al;
   register int s, k, r;
   unsigned int EOBRUN;
   JBLOCKROW block;
   BITREAD_STATE_VARS;
   d_derived_tbl * tbl;

   /* Process restart marker if needed; may have to suspend */
   if (cinfo->restart_interval) {
     if (entropy->restarts_to_go == 0)
       if (! process_restart(cinfo))
         return FALSE;
   }

   /* If we've run out of data, just leave the MCU set to zeroes.
    * This way, we return uniform gray for the remainder of the segment.
    */
   if (! entropy->pub.insufficient_data) {

     /* Load up working state.
      * We can avoid loading/saving bitread state if in an EOB run.
      */
     EOBRUN = entropy->saved.EOBRUN;     /* only part of saved state we need */

     /* There is always only one block per MCU */

     if (EOBRUN > 0)             /* if it's a band of zeroes... */
       EOBRUN--;                 /* ...process it now (we do nothing) */
     else {
       BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
       block = MCU_data[0];
       tbl = entropy->ac_derived_tbl;

       for (k = cinfo->Ss; k <= Se; k++) {
         HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
         r = s >> 4;
         s &= 15;
         if (s) {
           k += r;
           CHECK_BIT_BUFFER(br_state, s, return FALSE);
           r = GET_BITS(s);
           s = HUFF_EXTEND(r, s);
           /* Scale and output coefficient in natural (dezigzagged) order */
           (*block)[jpeg_natural_order[k]] = (JCOEF) LEFT_SHIFT(s, Al);
         } else {
           if (r == 15) {        /* ZRL */
             k += 15;            /* skip 15 zeroes in band */
           } else {              /* EOBr, run length is 2^r + appended bits */
             EOBRUN = 1 << r;
             if (r) {            /* EOBr, r > 0 */
               CHECK_BIT_BUFFER(br_state, r, return FALSE);
               r = GET_BITS(r);
               EOBRUN += r;
             }
             EOBRUN--;           /* this band is processed at this moment */
             break;              /* force end-of-band */
           }
         }
       }

       BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
     }

     /* Completed MCU, so update state */
     entropy->saved.EOBRUN = EOBRUN;     /* only part of saved state we need */
   }

   /* Account for restart interval (no-op if not using restarts) */
   entropy->restarts_to_go--;

   return TRUE;
 }


 /*
  * MCU decoding for DC successive approximation refinement scan.
  * Note: we assume such scans can be multi-component, although the spec
  * is not very clear on the point.
  */

 METHODDEF(boolean)
 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
 {
   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
   int p1 = 1 << cinfo->Al;      /* 1 in the bit position being coded */
   int blkn;
   JBLOCKROW block;
   BITREAD_STATE_VARS;

   /* Process restart marker if needed; may have to suspend */
   if (cinfo->restart_interval) {
     if (entropy->restarts_to_go == 0)
       if (! process_restart(cinfo))
         return FALSE;
   }

   /* Not worth the cycles to check insufficient_data here,
    * since we will not change the data anyway if we read zeroes.
    */

   /* Load up working state */
   BITREAD_LOAD_STATE(cinfo,entropy->bitstate);

   /* Outer loop handles each block in the MCU */

   for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
     block = MCU_data[blkn];

     /* Encoded data is simply the next bit of the two's-complement DC value */
     CHECK_BIT_BUFFER(br_state, 1, return FALSE);
     if (GET_BITS(1))
       (*block)[0] |= p1;
     /* Note: since we use |=, repeating the assignment later is safe */
   }

   /* Completed MCU, so update state */
   BITREAD_SAVE_STATE(cinfo,entropy->bitstate);

   /* Account for restart interval (no-op if not using restarts) */
   entropy->restarts_to_go--;

   return TRUE;
 }


 /*
  * MCU decoding for AC successive approximation refinement scan.
  */

 METHODDEF(boolean)
 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
 {
   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
   int Se = cinfo->Se;
   int p1 = 1 << cinfo->Al;        /* 1 in the bit position being coded */
   int m1 = (NEG_1) << cinfo->Al;  /* -1 in the bit position being coded */
   register int s, k, r;
   unsigned int EOBRUN;
   JBLOCKROW block;
   JCOEFPTR thiscoef;
   BITREAD_STATE_VARS;
   d_derived_tbl * tbl;
   int num_newnz;
   int newnz_pos[DCTSIZE2];

   /* Process restart marker if needed; may have to suspend */
   if (cinfo->restart_interval) {
     if (entropy->restarts_to_go == 0)
       if (! process_restart(cinfo))
         return FALSE;
   }

   /* If we've run out of data, don't modify the MCU.
    */
   if (! entropy->pub.insufficient_data) {

     /* Load up working state */
     BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
     EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */

     /* There is always only one block per MCU */
     block = MCU_data[0];
     tbl = entropy->ac_derived_tbl;

     /* If we are forced to suspend, we must undo the assignments to any newly
      * nonzero coefficients in the block, because otherwise we'd get confused
      * next time about which coefficients were already nonzero.
      * But we need not undo addition of bits to already-nonzero coefficients;
      * instead, we can test the current bit to see if we already did it.
      */
     num_newnz = 0;

     /* initialize coefficient loop counter to start of band */
     k = cinfo->Ss;

     if (EOBRUN == 0) {
       for (; k <= Se; k++) {
         HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
         r = s >> 4;
         s &= 15;
         if (s) {
           if (s != 1)           /* size of new coef should always be 1 */
             WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
           CHECK_BIT_BUFFER(br_state, 1, goto undoit);
           if (GET_BITS(1))
             s = p1;             /* newly nonzero coef is positive */
           else
             s = m1;             /* newly nonzero coef is negative */
         } else {
           if (r != 15) {
             EOBRUN = 1 << r;    /* EOBr, run length is 2^r + appended bits */
             if (r) {
               CHECK_BIT_BUFFER(br_state, r, goto undoit);
               r = GET_BITS(r);
               EOBRUN += r;
             }
             break;              /* rest of block is handled by EOB logic */
           }
           /* note s = 0 for processing ZRL */
         }
         /* Advance over already-nonzero coefs and r still-zero coefs,
          * appending correction bits to the nonzeroes.  A correction bit is 1
          * if the absolute value of the coefficient must be increased.
          */
         do {
           thiscoef = *block + jpeg_natural_order[k];
           if (*thiscoef != 0) {
             CHECK_BIT_BUFFER(br_state, 1, goto undoit);
             if (GET_BITS(1)) {
               if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
                 if (*thiscoef >= 0)
                   *thiscoef += p1;
                 else
                   *thiscoef += m1;
               }
             }
           } else {
             if (--r < 0)
               break;            /* reached target zero coefficient */
           }
           k++;
         } while (k <= Se);
         if (s) {
           int pos = jpeg_natural_order[k];
           /* Output newly nonzero coefficient */
           (*block)[pos] = (JCOEF) s;
           /* Remember its position in case we have to suspend */
           newnz_pos[num_newnz++] = pos;
         }
       }
     }

     if (EOBRUN > 0) {
       /* Scan any remaining coefficient positions after the end-of-band
        * (the last newly nonzero coefficient, if any).  Append a correction
        * bit to each already-nonzero coefficient.  A correction bit is 1
        * if the absolute value of the coefficient must be increased.
        */
       for (; k <= Se; k++) {
         thiscoef = *block + jpeg_natural_order[k];
         if (*thiscoef != 0) {
           CHECK_BIT_BUFFER(br_state, 1, goto undoit);
           if (GET_BITS(1)) {
             if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
               if (*thiscoef >= 0)
                 *thiscoef += p1;
               else
                 *thiscoef += m1;
             }
           }
         }
       }
       /* Count one block completed in EOB run */
       EOBRUN--;
     }

     /* Completed MCU, so update state */
     BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
     entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
   }

   /* Account for restart interval (no-op if not using restarts) */
   entropy->restarts_to_go--;

   return TRUE;

 undoit:
   /* Re-zero any output coefficients that we made newly nonzero */
   while (num_newnz > 0)
     (*block)[newnz_pos[--num_newnz]] = 0;

   return FALSE;
 }


 /*
  * Module initialization routine for progressive Huffman entropy decoding.
  */

 GLOBAL(void)
 jinit_phuff_decoder (j_decompress_ptr cinfo)
 {
   phuff_entropy_ptr entropy;
   int *coef_bit_ptr;
   int ci, i;

   entropy = (phuff_entropy_ptr)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                 sizeof(phuff_entropy_decoder));
   cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
   entropy->pub.start_pass = start_pass_phuff_decoder;

   /* Mark derived tables unallocated */
   for (i = 0; i < NUM_HUFF_TBLS; i++) {
     entropy->derived_tbls[i] = NULL;
   }

   /* Create progression status table */
   cinfo->coef_bits = (int (*)[DCTSIZE2])
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                 cinfo->num_components*DCTSIZE2*sizeof(int));
   coef_bit_ptr = & cinfo->coef_bits[0][0];
   for (ci = 0; ci < cinfo->num_components; ci++)
     for (i = 0; i < DCTSIZE2; i++)
       *coef_bit_ptr++ = -1;
 }

 #endif /* D_PROGRESSIVE_SUPPORTED */
	/*
	* jdphuff.c
	*
	* This file was part of the Independent JPEG Group's software:
	* Copyright (C) 1995-1997, Thomas G. Lane.
	* libjpeg-turbo Modifications:
	* Copyright (C) 2015, D. R. Commander.
	* For conditions of distribution and use, see the accompanying README file.
	*
	* This file contains Huffman entropy decoding routines for progressive JPEG.
	*
	* Much of the complexity here has to do with supporting input suspension.
	* If the data source module demands suspension, we want to be able to back
	* up to the start of the current MCU. To do this, we copy state variables
	* into local working storage, and update them back to the permanent
	* storage only upon successful completion of an MCU.
	*/

	#define JPEG_INTERNALS
	#include "jinclude.h"
	#include "jpeglib.h"
	#include "jdhuff.h" /* Declarations shared with jdhuff.c */


	#ifdef D_PROGRESSIVE_SUPPORTED

	/*
	* Expanded entropy decoder object for progressive Huffman decoding.
	*
	* The savable_state subrecord contains fields that change within an MCU,
	* but must not be updated permanently until we complete the MCU.
	*/

	typedef struct {
	unsigned int EOBRUN; /* remaining EOBs in EOBRUN */
	int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
	} savable_state;

	/* This macro is to work around compilers with missing or broken
	* structure assignment. You'll need to fix this code if you have
	* such a compiler and you change MAX_COMPS_IN_SCAN.
	*/

	#ifndef NO_STRUCT_ASSIGN
	#define ASSIGN_STATE(dest,src) ((dest) = (src))
	#else
	#if MAX_COMPS_IN_SCAN == 4
	#define ASSIGN_STATE(dest,src) \
	((dest).EOBRUN = (src).EOBRUN, \
	(dest).last_dc_val[0] = (src).last_dc_val[0], \
	(dest).last_dc_val[1] = (src).last_dc_val[1], \
	(dest).last_dc_val[2] = (src).last_dc_val[2], \
	(dest).last_dc_val[3] = (src).last_dc_val[3])
	#endif
	#endif


	typedef struct {
	struct jpeg_entropy_decoder pub; /* public fields */

	/* These fields are loaded into local variables at start of each MCU.
	* In case of suspension, we exit WITHOUT updating them.
	*/
	bitread_perm_state bitstate; /* Bit buffer at start of MCU */
	savable_state saved; /* Other state at start of MCU */

	/* These fields are NOT loaded into local working state. */
	unsigned int restarts_to_go; /* MCUs left in this restart interval */

	/* Pointers to derived tables (these workspaces have image lifespan) */
	d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];

	d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
	} phuff_entropy_decoder;

	typedef phuff_entropy_decoder * phuff_entropy_ptr;

	/* Forward declarations */
	METHODDEF(boolean) decode_mcu_DC_first (j_decompress_ptr cinfo,
	JBLOCKROW *MCU_data);
	METHODDEF(boolean) decode_mcu_AC_first (j_decompress_ptr cinfo,
	JBLOCKROW *MCU_data);
	METHODDEF(boolean) decode_mcu_DC_refine (j_decompress_ptr cinfo,
	JBLOCKROW *MCU_data);
	METHODDEF(boolean) decode_mcu_AC_refine (j_decompress_ptr cinfo,
	JBLOCKROW *MCU_data);


	/*
	* Initialize for a Huffman-compressed scan.
	*/

	METHODDEF(void)
	start_pass_phuff_decoder (j_decompress_ptr cinfo)
	{
	phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
	boolean is_DC_band, bad;
	int ci, coefi, tbl;
	d_derived_tbl **pdtbl;
	int *coef_bit_ptr;
	jpeg_component_info * compptr;

	is_DC_band = (cinfo->Ss == 0);

	/* Validate scan parameters */
	bad = FALSE;
	if (is_DC_band) {
	if (cinfo->Se != 0)
	bad = TRUE;
	} else {
	/* need not check Ss/Se < 0 since they came from unsigned bytes */
	if (cinfo->Ss > cinfo->Se \|\| cinfo->Se >= DCTSIZE2)
	bad = TRUE;
	/* AC scans may have only one component */
	if (cinfo->comps_in_scan != 1)
	bad = TRUE;
	}
	if (cinfo->Ah != 0) {
	/* Successive approximation refinement scan: must have Al = Ah-1. */
	if (cinfo->Al != cinfo->Ah-1)
	bad = TRUE;
	}
	if (cinfo->Al > 13) /* need not check for < 0 */
	bad = TRUE;
	/* Arguably the maximum Al value should be less than 13 for 8-bit precision,
	* but the spec doesn't say so, and we try to be liberal about what we
	* accept. Note: large Al values could result in out-of-range DC
	* coefficients during early scans, leading to bizarre displays due to
	* overflows in the IDCT math. But we won't crash.
	*/
	if (bad)
	ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
	cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
	/* Update progression status, and verify that scan order is legal.
	* Note that inter-scan inconsistencies are treated as warnings
	* not fatal errors ... not clear if this is right way to behave.
	*/
	for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
	int cindex = cinfo->cur_comp_info[ci]->component_index;
	coef_bit_ptr = & cinfo->coef_bits[cindex][0];
	if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
	WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
	for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
	int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
	if (cinfo->Ah != expected)
	WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
	coef_bit_ptr[coefi] = cinfo->Al;
	}
	}

	/* Select MCU decoding routine */
	if (cinfo->Ah == 0) {
	if (is_DC_band)
	entropy->pub.decode_mcu = decode_mcu_DC_first;
	else
	entropy->pub.decode_mcu = decode_mcu_AC_first;
	} else {
	if (is_DC_band)
	entropy->pub.decode_mcu = decode_mcu_DC_refine;
	else
	entropy->pub.decode_mcu = decode_mcu_AC_refine;
	}

	for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
	compptr = cinfo->cur_comp_info[ci];
	/* Make sure requested tables are present, and compute derived tables.
	* We may build same derived table more than once, but it's not expensive.
	*/
	if (is_DC_band) {
	if (cinfo->Ah == 0) { /* DC refinement needs no table */
	tbl = compptr->dc_tbl_no;
	pdtbl = entropy->derived_tbls + tbl;
	jpeg_make_d_derived_tbl(cinfo, TRUE, tbl, pdtbl);
	}
	} else {
	tbl = compptr->ac_tbl_no;
	pdtbl = entropy->derived_tbls + tbl;
	jpeg_make_d_derived_tbl(cinfo, FALSE, tbl, pdtbl);
	/* remember the single active table */
	entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
	}
	/* Initialize DC predictions to 0 */
	entropy->saved.last_dc_val[ci] = 0;
	}

	/* Initialize bitread state variables */
	entropy->bitstate.bits_left = 0;
	entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
	entropy->pub.insufficient_data = FALSE;

	/* Initialize private state variables */
	entropy->saved.EOBRUN = 0;

	/* Initialize restart counter */
	entropy->restarts_to_go = cinfo->restart_interval;
	}


	/*
	* Figure F.12: extend sign bit.
	* On some machines, a shift and add will be faster than a table lookup.
	*/

	#define AVOID_TABLES
	#ifdef AVOID_TABLES

	#define NEG_1 ((unsigned)-1)
	#define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((NEG_1)<<(s)) + 1) : (x))

	#else

	#define HUFF_EXTEND(x,s) ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))

	static const int extend_test[16] = /* entry n is 2*(n-1) /
	{ 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
	0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };

	static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */
	{ 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1,
	((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1,
	((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1,
	((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 };

	#endif /* AVOID_TABLES */


	/*
	* Check for a restart marker & resynchronize decoder.
	* Returns FALSE if must suspend.
	*/

	LOCAL(boolean)
	process_restart (j_decompress_ptr cinfo)
	{
	phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
	int ci;

	/* Throw away any unused bits remaining in bit buffer; */
	/* include any full bytes in next_marker's count of discarded bytes */
	cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
	entropy->bitstate.bits_left = 0;

	/* Advance past the RSTn marker */
	if (! (*cinfo->marker->read_restart_marker) (cinfo))
	return FALSE;

	/* Re-initialize DC predictions to 0 */
	for (ci = 0; ci < cinfo->comps_in_scan; ci++)
	entropy->saved.last_dc_val[ci] = 0;
	/* Re-init EOB run count, too */
	entropy->saved.EOBRUN = 0;

	/* Reset restart counter */
	entropy->restarts_to_go = cinfo->restart_interval;

	/* Reset out-of-data flag, unless read_restart_marker left us smack up
	* against a marker. In that case we will end up treating the next data
	* segment as empty, and we can avoid producing bogus output pixels by
	* leaving the flag set.
	*/
	if (cinfo->unread_marker == 0)
	entropy->pub.insufficient_data = FALSE;

	return TRUE;
	}


	/*
	* Huffman MCU decoding.
	* Each of these routines decodes and returns one MCU's worth of
	* Huffman-compressed coefficients.
	* The coefficients are reordered from zigzag order into natural array order,
	* but are not dequantized.
	*
	* The i'th block of the MCU is stored into the block pointed to by
	* MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
	*
	* We return FALSE if data source requested suspension. In that case no
	* changes have been made to permanent state. (Exception: some output
	* coefficients may already have been assigned. This is harmless for
	* spectral selection, since we'll just re-assign them on the next call.
	* Successive approximation AC refinement has to be more careful, however.)
	*/

	/*
	* MCU decoding for DC initial scan (either spectral selection,
	* or first pass of successive approximation).
	*/

	METHODDEF(boolean)
	decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
	{
	phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
	int Al = cinfo->Al;
	register int s, r;
	int blkn, ci;
	JBLOCKROW block;
	BITREAD_STATE_VARS;
	savable_state state;
	d_derived_tbl * tbl;
	jpeg_component_info * compptr;

	/* Process restart marker if needed; may have to suspend */
	if (cinfo->restart_interval) {
	if (entropy->restarts_to_go == 0)
	if (! process_restart(cinfo))
	return FALSE;
	}

	/* If we've run out of data, just leave the MCU set to zeroes.
	* This way, we return uniform gray for the remainder of the segment.
	*/
	if (! entropy->pub.insufficient_data) {

	/* Load up working state */
	BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
	ASSIGN_STATE(state, entropy->saved);

	/* Outer loop handles each block in the MCU */

	for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
	block = MCU_data[blkn];
	ci = cinfo->MCU_membership[blkn];
	compptr = cinfo->cur_comp_info[ci];
	tbl = entropy->derived_tbls[compptr->dc_tbl_no];

	/* Decode a single block's worth of coefficients */

	/* Section F.2.2.1: decode the DC coefficient difference */
	HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
	if (s) {
	CHECK_BIT_BUFFER(br_state, s, return FALSE);
	r = GET_BITS(s);
	s = HUFF_EXTEND(r, s);
	}

	/* Convert DC difference to actual value, update last_dc_val */
	s += state.last_dc_val[ci];
	state.last_dc_val[ci] = s;
	/* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */
	(*block)[0] = (JCOEF) LEFT_SHIFT(s, Al);
	}

	/* Completed MCU, so update state */
	BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
	ASSIGN_STATE(entropy->saved, state);
	}

	/* Account for restart interval (no-op if not using restarts) */
	entropy->restarts_to_go--;

	return TRUE;
	}


	/*
	* MCU decoding for AC initial scan (either spectral selection,
	* or first pass of successive approximation).
	*/

	METHODDEF(boolean)
	decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
	{
	phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
	int Se = cinfo->Se;
	int Al = cinfo->Al;
	register int s, k, r;
	unsigned int EOBRUN;
	JBLOCKROW block;
	BITREAD_STATE_VARS;
	d_derived_tbl * tbl;

	/* Process restart marker if needed; may have to suspend */
	if (cinfo->restart_interval) {
	if (entropy->restarts_to_go == 0)
	if (! process_restart(cinfo))
	return FALSE;
	}

	/* If we've run out of data, just leave the MCU set to zeroes.
	* This way, we return uniform gray for the remainder of the segment.
	*/
	if (! entropy->pub.insufficient_data) {

	/* Load up working state.
	* We can avoid loading/saving bitread state if in an EOB run.
	*/
	EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */

	/* There is always only one block per MCU */

	if (EOBRUN > 0) /* if it's a band of zeroes... */
	EOBRUN--; /* ...process it now (we do nothing) */
	else {
	BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
	block = MCU_data[0];
	tbl = entropy->ac_derived_tbl;

	for (k = cinfo->Ss; k <= Se; k++) {
	HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
	r = s >> 4;
	s &= 15;
	if (s) {
	k += r;
	CHECK_BIT_BUFFER(br_state, s, return FALSE);
	r = GET_BITS(s);
	s = HUFF_EXTEND(r, s);
	/* Scale and output coefficient in natural (dezigzagged) order */
	(*block)[jpeg_natural_order[k]] = (JCOEF) LEFT_SHIFT(s, Al);
	} else {
	if (r == 15) { /* ZRL */
	k += 15; /* skip 15 zeroes in band */
	} else { /* EOBr, run length is 2^r + appended bits */
	EOBRUN = 1 << r;
	if (r) { /* EOBr, r > 0 */
	CHECK_BIT_BUFFER(br_state, r, return FALSE);
	r = GET_BITS(r);
	EOBRUN += r;
	}
	EOBRUN--; /* this band is processed at this moment */
	break; /* force end-of-band */
	}
	}
	}

	BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
	}

	/* Completed MCU, so update state */
	entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
	}

	/* Account for restart interval (no-op if not using restarts) */
	entropy->restarts_to_go--;

	return TRUE;
	}


	/*
	* MCU decoding for DC successive approximation refinement scan.
	* Note: we assume such scans can be multi-component, although the spec
	* is not very clear on the point.
	*/

	METHODDEF(boolean)
	decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
	{
	phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
	int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
	int blkn;
	JBLOCKROW block;
	BITREAD_STATE_VARS;

	/* Process restart marker if needed; may have to suspend */
	if (cinfo->restart_interval) {
	if (entropy->restarts_to_go == 0)
	if (! process_restart(cinfo))
	return FALSE;
	}

	/* Not worth the cycles to check insufficient_data here,
	* since we will not change the data anyway if we read zeroes.
	*/

	/* Load up working state */
	BITREAD_LOAD_STATE(cinfo,entropy->bitstate);

	/* Outer loop handles each block in the MCU */

	for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
	block = MCU_data[blkn];

	/* Encoded data is simply the next bit of the two's-complement DC value */
	CHECK_BIT_BUFFER(br_state, 1, return FALSE);
	if (GET_BITS(1))
	(*block)[0] \|= p1;
	/* Note: since we use \|=, repeating the assignment later is safe */
	}

	/* Completed MCU, so update state */
	BITREAD_SAVE_STATE(cinfo,entropy->bitstate);

	/* Account for restart interval (no-op if not using restarts) */
	entropy->restarts_to_go--;

	return TRUE;
	}


	/*
	* MCU decoding for AC successive approximation refinement scan.
	*/

	METHODDEF(boolean)
	decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
	{
	phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
	int Se = cinfo->Se;
	int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
	int m1 = (NEG_1) << cinfo->Al; /* -1 in the bit position being coded */
	register int s, k, r;
	unsigned int EOBRUN;
	JBLOCKROW block;
	JCOEFPTR thiscoef;
	BITREAD_STATE_VARS;
	d_derived_tbl * tbl;
	int num_newnz;
	int newnz_pos[DCTSIZE2];

	/* Process restart marker if needed; may have to suspend */
	if (cinfo->restart_interval) {
	if (entropy->restarts_to_go == 0)
	if (! process_restart(cinfo))
	return FALSE;
	}

	/* If we've run out of data, don't modify the MCU.
	*/
	if (! entropy->pub.insufficient_data) {

	/* Load up working state */
	BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
	EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */

	/* There is always only one block per MCU */
	block = MCU_data[0];
	tbl = entropy->ac_derived_tbl;

	/* If we are forced to suspend, we must undo the assignments to any newly
	* nonzero coefficients in the block, because otherwise we'd get confused
	* next time about which coefficients were already nonzero.
	* But we need not undo addition of bits to already-nonzero coefficients;
	* instead, we can test the current bit to see if we already did it.
	*/
	num_newnz = 0;

	/* initialize coefficient loop counter to start of band */
	k = cinfo->Ss;

	if (EOBRUN == 0) {
	for (; k <= Se; k++) {
	HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
	r = s >> 4;
	s &= 15;
	if (s) {
	if (s != 1) /* size of new coef should always be 1 */
	WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
	CHECK_BIT_BUFFER(br_state, 1, goto undoit);
	if (GET_BITS(1))
	s = p1; /* newly nonzero coef is positive */
	else
	s = m1; /* newly nonzero coef is negative */
	} else {
	if (r != 15) {
	EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */
	if (r) {
	CHECK_BIT_BUFFER(br_state, r, goto undoit);
	r = GET_BITS(r);
	EOBRUN += r;
	}
	break; /* rest of block is handled by EOB logic */
	}
	/* note s = 0 for processing ZRL */
	}
	/* Advance over already-nonzero coefs and r still-zero coefs,
	* appending correction bits to the nonzeroes. A correction bit is 1
	* if the absolute value of the coefficient must be increased.
	*/
	do {
	thiscoef = *block + jpeg_natural_order[k];
	if (*thiscoef != 0) {
	CHECK_BIT_BUFFER(br_state, 1, goto undoit);
	if (GET_BITS(1)) {
	if ((thiscoef & p1) == 0) { / do nothing if already set it */
	if (*thiscoef >= 0)
	*thiscoef += p1;
	else
	*thiscoef += m1;
	}
	}
	} else {
	if (--r < 0)
	break; /* reached target zero coefficient */
	}
	k++;
	} while (k <= Se);
	if (s) {
	int pos = jpeg_natural_order[k];
	/* Output newly nonzero coefficient */
	(*block)[pos] = (JCOEF) s;
	/* Remember its position in case we have to suspend */
	newnz_pos[num_newnz++] = pos;
	}
	}
	}

	if (EOBRUN > 0) {
	/* Scan any remaining coefficient positions after the end-of-band
	* (the last newly nonzero coefficient, if any). Append a correction
	* bit to each already-nonzero coefficient. A correction bit is 1
	* if the absolute value of the coefficient must be increased.
	*/
	for (; k <= Se; k++) {
	thiscoef = *block + jpeg_natural_order[k];
	if (*thiscoef != 0) {
	CHECK_BIT_BUFFER(br_state, 1, goto undoit);
	if (GET_BITS(1)) {
	if ((thiscoef & p1) == 0) { / do nothing if already changed it */
	if (*thiscoef >= 0)
	*thiscoef += p1;
	else
	*thiscoef += m1;
	}
	}
	}
	}
	/* Count one block completed in EOB run */
	EOBRUN--;
	}

	/* Completed MCU, so update state */
	BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
	entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
	}

	/* Account for restart interval (no-op if not using restarts) */
	entropy->restarts_to_go--;

	return TRUE;

	undoit:
	/* Re-zero any output coefficients that we made newly nonzero */
	while (num_newnz > 0)
	(*block)[newnz_pos[--num_newnz]] = 0;

	return FALSE;
	}


	/*
	* Module initialization routine for progressive Huffman entropy decoding.
	*/

	GLOBAL(void)
	jinit_phuff_decoder (j_decompress_ptr cinfo)
	{
	phuff_entropy_ptr entropy;
	int *coef_bit_ptr;
	int ci, i;

	entropy = (phuff_entropy_ptr)
	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	sizeof(phuff_entropy_decoder));
	cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
	entropy->pub.start_pass = start_pass_phuff_decoder;

	/* Mark derived tables unallocated */
	for (i = 0; i < NUM_HUFF_TBLS; i++) {
	entropy->derived_tbls[i] = NULL;
	}

	/* Create progression status table */
	cinfo->coef_bits = (int (*)[DCTSIZE2])
	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	cinfo->num_componentsDCTSIZE2sizeof(int));
	coef_bit_ptr = & cinfo->coef_bits[0][0];
	for (ci = 0; ci < cinfo->num_components; ci++)
	for (i = 0; i < DCTSIZE2; i++)
	*coef_bit_ptr++ = -1;
	}

	#endif /* D_PROGRESSIVE_SUPPORTED */