text: /*
   * jcphuff.c
   *
   * Copyright (C) 1995-1997, Thomas G. Lane.
   * This file is part of the Independent JPEG Group's software.
   * For conditions of distribution and use, see the accompanying README file.
   *
   * This file contains Huffman entropy encoding routines for progressive JPEG.
   *
   * We do not support output suspension in this module, since the library
   * currently does not allow multiple-scan files to be written with output
   * suspension.
   */
  
  #define JPEG_INTERNALS
  #include "jinclude.h"
  #include "jpeglib.h"
  #include "jchuff.h"             /* Declarations shared with jchuff.c */
  
  #ifdef C_PROGRESSIVE_SUPPORTED
  
  /* Expanded entropy encoder object for progressive Huffman encoding. */
  
  typedef struct {
    struct jpeg_entropy_encoder pub; /* public fields */
  
    /* Mode flag: TRUE for optimization, FALSE for actual data output */
    boolean gather_statistics;
  
    /* Bit-level coding status.
     * next_output_byte/free_in_buffer are local copies of cinfo->dest fields.
     */
    JOCTET * next_output_byte;    /* => next byte to write in buffer */
    size_t free_in_buffer;        /* # of byte spaces remaining in buffer */
    INT32 put_buffer;             /* current bit-accumulation buffer */
    int put_bits;                 /* # of bits now in it */
    j_compress_ptr cinfo;         /* link to cinfo (needed for dump_buffer) */
  
    /* Coding status for DC components */
    int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
  
    /* Coding status for AC components */
    int ac_tbl_no;                /* the table number of the single component */
    unsigned int EOBRUN;          /* run length of EOBs */
    unsigned int BE;              /* # of buffered correction bits before MCU */
    char * bit_buffer;            /* buffer for correction bits (1 per char) */
    /* packing correction bits tightly would save some space but cost time... */
  
    unsigned int restarts_to_go;  /* MCUs left in this restart interval */
    int next_restart_num;         /* next restart number to write (0-7) */
  
    /* Pointers to derived tables (these workspaces have image lifespan).
     * Since any one scan codes only DC or only AC, we only need one set
     * of tables, not one for DC and one for AC.
     */
    c_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
  
    /* Statistics tables for optimization; again, one set is enough */
    long * count_ptrs[NUM_HUFF_TBLS];
  } phuff_entropy_encoder;
  
  typedef phuff_entropy_encoder * phuff_entropy_ptr;
  
  /* MAX_CORR_BITS is the number of bits the AC refinement correction-bit
   * buffer can hold.  Larger sizes may slightly improve compression, but
   * 1000 is already well into the realm of overkill.
   * The minimum safe size is 64 bits.
   */
  
  #define MAX_CORR_BITS  1000     /* Max # of correction bits I can buffer */
  
  /* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than INT32.
   * We assume that int right shift is unsigned if INT32 right shift is,
   * which should be safe.
   */
  
  #ifdef RIGHT_SHIFT_IS_UNSIGNED
  #define ISHIFT_TEMPS    int ishift_temp;
  #define IRIGHT_SHIFT(x,shft)  \
          ((ishift_temp = (x)) < 0 ? \
           (ishift_temp >> (shft)) | ((~0) << (16-(shft))) : \
           (ishift_temp >> (shft)))
  #else
  #define ISHIFT_TEMPS
  #define IRIGHT_SHIFT(x,shft)    ((x) >> (shft))
  #endif
  
  /* Forward declarations */
  METHODDEF(boolean) encode_mcu_DC_first JPP((j_compress_ptr cinfo,
                                              JBLOCKROW *MCU_data));
  METHODDEF(boolean) encode_mcu_AC_first JPP((j_compress_ptr cinfo,
                                              JBLOCKROW *MCU_data));
  METHODDEF(boolean) encode_mcu_DC_refine JPP((j_compress_ptr cinfo,
                                               JBLOCKROW *MCU_data));
  METHODDEF(boolean) encode_mcu_AC_refine JPP((j_compress_ptr cinfo,
                                               JBLOCKROW *MCU_data));
  METHODDEF(void) finish_pass_phuff JPP((j_compress_ptr cinfo));
  METHODDEF(void) finish_pass_gather_phuff JPP((j_compress_ptr cinfo));
  
  
  /*
   * Initialize for a Huffman-compressed scan using progressive JPEG.
   */
  
  METHODDEF(void)
  start_pass_phuff (j_compress_ptr cinfo, boolean gather_statistics)
  {
    phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
    boolean is_DC_band;
    int ci, tbl;
    jpeg_component_info * compptr;
  
    entropy->cinfo = cinfo;
    entropy->gather_statistics = gather_statistics;
  
    is_DC_band = (cinfo->Ss == 0);
  
    /* We assume jcmaster.c already validated the scan parameters. */
  
    /* Select execution routines */
    if (cinfo->Ah == 0) {
      if (is_DC_band)
        entropy->pub.encode_mcu = encode_mcu_DC_first;
      else
        entropy->pub.encode_mcu = encode_mcu_AC_first;
    } else {
      if (is_DC_band)
        entropy->pub.encode_mcu = encode_mcu_DC_refine;
      else {
        entropy->pub.encode_mcu = encode_mcu_AC_refine;
        /* AC refinement needs a correction bit buffer */
        if (entropy->bit_buffer == NULL)
          entropy->bit_buffer = (char *)
            (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                        MAX_CORR_BITS * SIZEOF(char));
      }
    }
    if (gather_statistics)
      entropy->pub.finish_pass = finish_pass_gather_phuff;
    else
      entropy->pub.finish_pass = finish_pass_phuff;
  
    /* Only DC coefficients may be interleaved, so cinfo->comps_in_scan = 1
     * for AC coefficients.
     */
    for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
      compptr = cinfo->cur_comp_info[ci];
      /* Initialize DC predictions to 0 */
      entropy->last_dc_val[ci] = 0;
      /* Get table index */
      if (is_DC_band) {
        if (cinfo->Ah != 0)       /* DC refinement needs no table */
          continue;
        tbl = compptr->dc_tbl_no;
      } else {
        entropy->ac_tbl_no = tbl = compptr->ac_tbl_no;
      }
      if (gather_statistics) {
        /* Check for invalid table index */
        /* (make_c_derived_tbl does this in the other path) */
        if (tbl < 0 || tbl >= NUM_HUFF_TBLS)
          ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
        /* Allocate and zero the statistics tables */
        /* Note that jpeg_gen_optimal_table expects 257 entries in each table! */
        if (entropy->count_ptrs[tbl] == NULL)
          entropy->count_ptrs[tbl] = (long *)
            (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                        257 * SIZEOF(long));
        MEMZERO(entropy->count_ptrs[tbl], 257 * SIZEOF(long));
      } else {
        /* Compute derived values for Huffman table */
        /* We may do this more than once for a table, but it's not expensive */
        jpeg_make_c_derived_tbl(cinfo, is_DC_band, tbl,
                                & entropy->derived_tbls[tbl]);
      }
    }
  
    /* Initialize AC stuff */
    entropy->EOBRUN = 0;
    entropy->BE = 0;
  
    /* Initialize bit buffer to empty */
    entropy->put_buffer = 0;
    entropy->put_bits = 0;
  
    /* Initialize restart stuff */
    entropy->restarts_to_go = cinfo->restart_interval;
    entropy->next_restart_num = 0;
  }
  
  
  /* Outputting bytes to the file.
   * NB: these must be called only when actually outputting,
   * that is, entropy->gather_statistics == FALSE.
   */
  
  /* Emit a byte */
  #define emit_byte(entropy,val)  \
          { *(entropy)->next_output_byte++ = (JOCTET) (val);  \
            if (--(entropy)->free_in_buffer == 0)  \
              dump_buffer(entropy); }
  
  
  LOCAL(void)
  dump_buffer (phuff_entropy_ptr entropy)
  /* Empty the output buffer; we do not support suspension in this module. */
  {
    struct jpeg_destination_mgr * dest = entropy->cinfo->dest;
  
    if (! (*dest->empty_output_buffer) (entropy->cinfo))
      ERREXIT(entropy->cinfo, JERR_CANT_SUSPEND);
    /* After a successful buffer dump, must reset buffer pointers */
    entropy->next_output_byte = dest->next_output_byte;
    entropy->free_in_buffer = dest->free_in_buffer;
  }
  
  
  /* Outputting bits to the file */
  
  /* Only the right 24 bits of put_buffer are used; the valid bits are
   * left-justified in this part.  At most 16 bits can be passed to emit_bits
   * in one call, and we never retain more than 7 bits in put_buffer
   * between calls, so 24 bits are sufficient.
   */
  
  LOCAL(void)
  emit_bits (phuff_entropy_ptr entropy, unsigned int code, int size)
  /* Emit some bits, unless we are in gather mode */
  {
    /* This routine is heavily used, so it's worth coding tightly. */
    register INT32 put_buffer = (INT32) code;
    register int put_bits = entropy->put_bits;
  
    /* if size is 0, caller used an invalid Huffman table entry */
    if (size == 0)
      ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
  
    if (entropy->gather_statistics)
      return;                     /* do nothing if we're only getting stats */
  
    put_buffer &= (((INT32) 1)<<size) - 1; /* mask off any extra bits in code */
  
    put_bits += size;             /* new number of bits in buffer */
  
    put_buffer <<= 24 - put_bits; /* align incoming bits */
  
    put_buffer |= entropy->put_buffer; /* and merge with old buffer contents */
  
    while (put_bits >= 8) {
      int c = (int) ((put_buffer >> 16) & 0xFF);
  
      emit_byte(entropy, c);
      if (c == 0xFF) {            /* need to stuff a zero byte? */
        emit_byte(entropy, 0);
      }
      put_buffer <<= 8;
      put_bits -= 8;
    }
  
    entropy->put_buffer = put_buffer; /* update variables */
    entropy->put_bits = put_bits;
  }
  
  
  LOCAL(void)
  flush_bits (phuff_entropy_ptr entropy)
  {
    emit_bits(entropy, 0x7F, 7); /* fill any partial byte with ones */
    entropy->put_buffer = 0;     /* and reset bit-buffer to empty */
    entropy->put_bits = 0;
  }
  
  
  /*
   * Emit (or just count) a Huffman symbol.
   */
  
  LOCAL(void)
  emit_symbol (phuff_entropy_ptr entropy, int tbl_no, int symbol)
  {
    if (entropy->gather_statistics)
      entropy->count_ptrs[tbl_no][symbol]++;
    else {
      c_derived_tbl * tbl = entropy->derived_tbls[tbl_no];
      emit_bits(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]);
    }
  }
  
  
  /*
   * Emit bits from a correction bit buffer.
   */
  
  LOCAL(void)
  emit_buffered_bits (phuff_entropy_ptr entropy, char * bufstart,
                      unsigned int nbits)
  {
    if (entropy->gather_statistics)
      return;                     /* no real work */
  
    while (nbits > 0) {
      emit_bits(entropy, (unsigned int) (*bufstart), 1);
      bufstart++;
      nbits--;
    }
  }
  
  
  /*
   * Emit any pending EOBRUN symbol.
   */
  
  LOCAL(void)
  emit_eobrun (phuff_entropy_ptr entropy)
  {
    register int temp, nbits;
  
    if (entropy->EOBRUN > 0) {    /* if there is any pending EOBRUN */
      temp = entropy->EOBRUN;
      nbits = 0;
      while ((temp >>= 1))
        nbits++;
      /* safety check: shouldn't happen given limited correction-bit buffer */
      if (nbits > 14)
        ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
  
      emit_symbol(entropy, entropy->ac_tbl_no, nbits << 4);
      if (nbits)
        emit_bits(entropy, entropy->EOBRUN, nbits);
  
      entropy->EOBRUN = 0;
  
      /* Emit any buffered correction bits */
      emit_buffered_bits(entropy, entropy->bit_buffer, entropy->BE);
      entropy->BE = 0;
    }
  }
  
  
  /*
   * Emit a restart marker & resynchronize predictions.
   */
  
  LOCAL(void)
  emit_restart (phuff_entropy_ptr entropy, int restart_num)
  {
    int ci;
  
    emit_eobrun(entropy);
  
    if (! entropy->gather_statistics) {
      flush_bits(entropy);
      emit_byte(entropy, 0xFF);
      emit_byte(entropy, JPEG_RST0 + restart_num);
    }
  
    if (entropy->cinfo->Ss == 0) {
      /* Re-initialize DC predictions to 0 */
      for (ci = 0; ci < entropy->cinfo->comps_in_scan; ci++)
        entropy->last_dc_val[ci] = 0;
    } else {
      /* Re-initialize all AC-related fields to 0 */
      entropy->EOBRUN = 0;
      entropy->BE = 0;
    }
  }
  
  
  /*
   * MCU encoding for DC initial scan (either spectral selection,
   * or first pass of successive approximation).
   */
  
  METHODDEF(boolean)
  encode_mcu_DC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
  {
    phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
    register int temp, temp2;
    register int nbits;
    int blkn, ci;
    int Al = cinfo->Al;
    JBLOCKROW block;
    jpeg_component_info * compptr;
    ISHIFT_TEMPS
  
    entropy->next_output_byte = cinfo->dest->next_output_byte;
    entropy->free_in_buffer = cinfo->dest->free_in_buffer;
  
    /* Emit restart marker if needed */
    if (cinfo->restart_interval)
      if (entropy->restarts_to_go == 0)
        emit_restart(entropy, entropy->next_restart_num);
  
    /* Encode the MCU data blocks */
    for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
      block = MCU_data[blkn];
      ci = cinfo->MCU_membership[blkn];
      compptr = cinfo->cur_comp_info[ci];
  
      /* Compute the DC value after the required point transform by Al.
       * This is simply an arithmetic right shift.
       */
      temp2 = IRIGHT_SHIFT((int) ((*block)[0]), Al);
  
      /* DC differences are figured on the point-transformed values. */
      temp = temp2 - entropy->last_dc_val[ci];
      entropy->last_dc_val[ci] = temp2;
  
      /* Encode the DC coefficient difference per section G.1.2.1 */
      temp2 = temp;
      if (temp < 0) {
        temp = -temp;             /* temp is abs value of input */
        /* For a negative input, want temp2 = bitwise complement of abs(input) */
        /* This code assumes we are on a two's complement machine */
        temp2--;
      }
  
      /* Find the number of bits needed for the magnitude of the coefficient */
      nbits = 0;
      while (temp) {
        nbits++;
        temp >>= 1;
      }
      /* Check for out-of-range coefficient values.
       * Since we're encoding a difference, the range limit is twice as much.
       */
      if (nbits > MAX_COEF_BITS+1)
        ERREXIT(cinfo, JERR_BAD_DCT_COEF);
  
      /* Count/emit the Huffman-coded symbol for the number of bits */
      emit_symbol(entropy, compptr->dc_tbl_no, nbits);
  
      /* Emit that number of bits of the value, if positive, */
      /* or the complement of its magnitude, if negative. */
      if (nbits)                  /* emit_bits rejects calls with size 0 */
        emit_bits(entropy, (unsigned int) temp2, nbits);
    }
  
    cinfo->dest->next_output_byte = entropy->next_output_byte;
    cinfo->dest->free_in_buffer = entropy->free_in_buffer;
  
    /* Update restart-interval state too */
    if (cinfo->restart_interval) {
      if (entropy->restarts_to_go == 0) {
        entropy->restarts_to_go = cinfo->restart_interval;
        entropy->next_restart_num++;
        entropy->next_restart_num &= 7;
      }
      entropy->restarts_to_go--;
    }
  
    return TRUE;
  }
  
  
  /*
   * MCU encoding for AC initial scan (either spectral selection,
   * or first pass of successive approximation).
   */
  
  METHODDEF(boolean)
  encode_mcu_AC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
  {
    phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
    register int temp, temp2;
    register int nbits;
    register int r, k;
    int Se = cinfo->Se;
    int Al = cinfo->Al;
    JBLOCKROW block;
  
    entropy->next_output_byte = cinfo->dest->next_output_byte;
    entropy->free_in_buffer = cinfo->dest->free_in_buffer;
  
    /* Emit restart marker if needed */
    if (cinfo->restart_interval)
      if (entropy->restarts_to_go == 0)
        emit_restart(entropy, entropy->next_restart_num);
  
    /* Encode the MCU data block */
    block = MCU_data[0];
  
    /* Encode the AC coefficients per section G.1.2.2, fig. G.3 */
  
    r = 0;                        /* r = run length of zeros */
  
    for (k = cinfo->Ss; k <= Se; k++) {
      if ((temp = (*block)[jpeg_natural_order[k]]) == 0) {
        r++;
        continue;
      }
      /* We must apply the point transform by Al.  For AC coefficients this
       * is an integer division with rounding towards 0.  To do this portably
       * in C, we shift after obtaining the absolute value; so the code is
       * interwoven with finding the abs value (temp) and output bits (temp2).
       */
      if (temp < 0) {
        temp = -temp;             /* temp is abs value of input */
        temp >>= Al;              /* apply the point transform */
        /* For a negative coef, want temp2 = bitwise complement of abs(coef) */
        temp2 = ~temp;
      } else {
        temp >>= Al;              /* apply the point transform */
        temp2 = temp;
      }
      /* Watch out for case that nonzero coef is zero after point transform */
      if (temp == 0) {
        r++;
        continue;
      }
  
      /* Emit any pending EOBRUN */
      if (entropy->EOBRUN > 0)
        emit_eobrun(entropy);
      /* if run length > 15, must emit special run-length-16 codes (0xF0) */
      while (r > 15) {
        emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
        r -= 16;
      }
  
      /* Find the number of bits needed for the magnitude of the coefficient */
      nbits = 1;                  /* there must be at least one 1 bit */
      while ((temp >>= 1))
        nbits++;
      /* Check for out-of-range coefficient values */
      if (nbits > MAX_COEF_BITS)
        ERREXIT(cinfo, JERR_BAD_DCT_COEF);
  
      /* Count/emit Huffman symbol for run length / number of bits */
      emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + nbits);
  
      /* Emit that number of bits of the value, if positive, */
      /* or the complement of its magnitude, if negative. */
      emit_bits(entropy, (unsigned int) temp2, nbits);
  
      r = 0;                      /* reset zero run length */
    }
  
    if (r > 0) {                  /* If there are trailing zeroes, */
      entropy->EOBRUN++;          /* count an EOB */
      if (entropy->EOBRUN == 0x7FFF)
        emit_eobrun(entropy);     /* force it out to avoid overflow */
    }
  
    cinfo->dest->next_output_byte = entropy->next_output_byte;
    cinfo->dest->free_in_buffer = entropy->free_in_buffer;
  
    /* Update restart-interval state too */
    if (cinfo->restart_interval) {
      if (entropy->restarts_to_go == 0) {
        entropy->restarts_to_go = cinfo->restart_interval;
        entropy->next_restart_num++;
        entropy->next_restart_num &= 7;
      }
      entropy->restarts_to_go--;
    }
  
    return TRUE;
  }
  
  
  /*
   * MCU encoding 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)
  encode_mcu_DC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
  {
    phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
    register int temp;
    int blkn;
    int Al = cinfo->Al;
    JBLOCKROW block;
  
    entropy->next_output_byte = cinfo->dest->next_output_byte;
    entropy->free_in_buffer = cinfo->dest->free_in_buffer;
  
    /* Emit restart marker if needed */
    if (cinfo->restart_interval)
      if (entropy->restarts_to_go == 0)
        emit_restart(entropy, entropy->next_restart_num);
  
    /* Encode the MCU data blocks */
    for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
      block = MCU_data[blkn];
  
      /* We simply emit the Al'th bit of the DC coefficient value. */
      temp = (*block)[0];
      emit_bits(entropy, (unsigned int) (temp >> Al), 1);
    }
  
    cinfo->dest->next_output_byte = entropy->next_output_byte;
    cinfo->dest->free_in_buffer = entropy->free_in_buffer;
  
    /* Update restart-interval state too */
    if (cinfo->restart_interval) {
      if (entropy->restarts_to_go == 0) {
        entropy->restarts_to_go = cinfo->restart_interval;
        entropy->next_restart_num++;
        entropy->next_restart_num &= 7;
      }
      entropy->restarts_to_go--;
    }
  
    return TRUE;
  }
  
  
  /*
   * MCU encoding for AC successive approximation refinement scan.
   */
  
  METHODDEF(boolean)
  encode_mcu_AC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
  {
    phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
    register int temp;
    register int r, k;
    int EOB;
    char *BR_buffer;
    unsigned int BR;
    int Se = cinfo->Se;
    int Al = cinfo->Al;
    JBLOCKROW block;
    int absvalues[DCTSIZE2];
  
    entropy->next_output_byte = cinfo->dest->next_output_byte;
    entropy->free_in_buffer = cinfo->dest->free_in_buffer;
  
    /* Emit restart marker if needed */
    if (cinfo->restart_interval)
      if (entropy->restarts_to_go == 0)
        emit_restart(entropy, entropy->next_restart_num);
  
    /* Encode the MCU data block */
    block = MCU_data[0];
  
    /* It is convenient to make a pre-pass to determine the transformed
     * coefficients' absolute values and the EOB position.
     */
    EOB = 0;
    for (k = cinfo->Ss; k <= Se; k++) {
      temp = (*block)[jpeg_natural_order[k]];
      /* We must apply the point transform by Al.  For AC coefficients this
       * is an integer division with rounding towards 0.  To do this portably
       * in C, we shift after obtaining the absolute value.
       */
      if (temp < 0)
        temp = -temp;             /* temp is abs value of input */
      temp >>= Al;                /* apply the point transform */
      absvalues[k] = temp;        /* save abs value for main pass */
      if (temp == 1)
        EOB = k;                  /* EOB = index of last newly-nonzero coef */
    }
  
    /* Encode the AC coefficients per section G.1.2.3, fig. G.7 */
  
    r = 0;                        /* r = run length of zeros */
    BR = 0;                       /* BR = count of buffered bits added now */
    BR_buffer = entropy->bit_buffer + entropy->BE; /* Append bits to buffer */
  
    for (k = cinfo->Ss; k <= Se; k++) {
      if ((temp = absvalues[k]) == 0) {
        r++;
        continue;
      }
  
      /* Emit any required ZRLs, but not if they can be folded into EOB */
      while (r > 15 && k <= EOB) {
        /* emit any pending EOBRUN and the BE correction bits */
        emit_eobrun(entropy);
        /* Emit ZRL */
        emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
        r -= 16;
        /* Emit buffered correction bits that must be associated with ZRL */
        emit_buffered_bits(entropy, BR_buffer, BR);
        BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
        BR = 0;
      }
  
      /* If the coef was previously nonzero, it only needs a correction bit.
       * NOTE: a straight translation of the spec's figure G.7 would suggest
       * that we also need to test r > 15.  But if r > 15, we can only get here
       * if k > EOB, which implies that this coefficient is not 1.
       */
      if (temp > 1) {
        /* The correction bit is the next bit of the absolute value. */
        BR_buffer[BR++] = (char) (temp & 1);
        continue;
      }
  
      /* Emit any pending EOBRUN and the BE correction bits */
      emit_eobrun(entropy);
  
      /* Count/emit Huffman symbol for run length / number of bits */
      emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + 1);
  
      /* Emit output bit for newly-nonzero coef */
      temp = ((*block)[jpeg_natural_order[k]] < 0) ? 0 : 1;
      emit_bits(entropy, (unsigned int) temp, 1);
  
      /* Emit buffered correction bits that must be associated with this code */
      emit_buffered_bits(entropy, BR_buffer, BR);
      BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
      BR = 0;
      r = 0;                      /* reset zero run length */
    }
  
    if (r > 0 || BR > 0) {        /* If there are trailing zeroes, */
      entropy->EOBRUN++;          /* count an EOB */
      entropy->BE += BR;          /* concat my correction bits to older ones */
      /* We force out the EOB if we risk either:
       * 1. overflow of the EOB counter;
       * 2. overflow of the correction bit buffer during the next MCU.
       */
      if (entropy->EOBRUN == 0x7FFF || entropy->BE > (MAX_CORR_BITS-DCTSIZE2+1))
        emit_eobrun(entropy);
    }
  
    cinfo->dest->next_output_byte = entropy->next_output_byte;
    cinfo->dest->free_in_buffer = entropy->free_in_buffer;
  
    /* Update restart-interval state too */
    if (cinfo->restart_interval) {
      if (entropy->restarts_to_go == 0) {
        entropy->restarts_to_go = cinfo->restart_interval;
        entropy->next_restart_num++;
        entropy->next_restart_num &= 7;
      }
      entropy->restarts_to_go--;
    }
  
    return TRUE;
  }
  
  
  /*
   * Finish up at the end of a Huffman-compressed progressive scan.
   */
  
  METHODDEF(void)
  finish_pass_phuff (j_compress_ptr cinfo)
  {
    phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
  
    entropy->next_output_byte = cinfo->dest->next_output_byte;
    entropy->free_in_buffer = cinfo->dest->free_in_buffer;
  
    /* Flush out any buffered data */
    emit_eobrun(entropy);
    flush_bits(entropy);
  
    cinfo->dest->next_output_byte = entropy->next_output_byte;
    cinfo->dest->free_in_buffer = entropy->free_in_buffer;
  }
  
  
  /*
   * Finish up a statistics-gathering pass and create the new Huffman tables.
   */
  
  METHODDEF(void)
  finish_pass_gather_phuff (j_compress_ptr cinfo)
  {
    phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
    boolean is_DC_band;
    int ci, tbl;
    jpeg_component_info * compptr;
    JHUFF_TBL **htblptr;
    boolean did[NUM_HUFF_TBLS];
  
    /* Flush out buffered data (all we care about is counting the EOB symbol) */
    emit_eobrun(entropy);
  
    is_DC_band = (cinfo->Ss == 0);
  
    /* It's important not to apply jpeg_gen_optimal_table more than once
     * per table, because it clobbers the input frequency counts!
     */
    MEMZERO(did, SIZEOF(did));
  
    for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
      compptr = cinfo->cur_comp_info[ci];
      if (is_DC_band) {
        if (cinfo->Ah != 0)       /* DC refinement needs no table */
          continue;
        tbl = compptr->dc_tbl_no;
      } else {
        tbl = compptr->ac_tbl_no;
      }
      if (! did[tbl]) {
        if (is_DC_band)
          htblptr = & cinfo->dc_huff_tbl_ptrs[tbl];
        else
          htblptr = & cinfo->ac_huff_tbl_ptrs[tbl];
        if (*htblptr == NULL)
          *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
        jpeg_gen_optimal_table(cinfo, *htblptr, entropy->count_ptrs[tbl]);
        did[tbl] = TRUE;
      }
    }
  }
  
  
  /*
   * Module initialization routine for progressive Huffman entropy encoding.
   */
  
  GLOBAL(void)
  jinit_phuff_encoder (j_compress_ptr cinfo)
  {
    phuff_entropy_ptr entropy;
    int i;
  
    entropy = (phuff_entropy_ptr)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                  SIZEOF(phuff_entropy_encoder));
    cinfo->entropy = (struct jpeg_entropy_encoder *) entropy;
    entropy->pub.start_pass = start_pass_phuff;
  
    /* Mark tables unallocated */
    for (i = 0; i < NUM_HUFF_TBLS; i++) {
      entropy->derived_tbls[i] = NULL;
      entropy->count_ptrs[i] = NULL;
    }
    entropy->bit_buffer = NULL;   /* needed only in AC refinement scan */
  }
  
  #endif /* C_PROGRESSIVE_SUPPORTED */
  