    /*
     * 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 */
      int 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 */
      long 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 long.
     * We assume that int right shift is unsigned if long 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(int) encode_mcu_DC_first JPP((j_compress_ptr cinfo,
    					    JBLOCKROW *MCU_data));
    METHODDEF(int) encode_mcu_AC_first JPP((j_compress_ptr cinfo,
    					    JBLOCKROW *MCU_data));
    METHODDEF(int) encode_mcu_DC_refine JPP((j_compress_ptr cinfo,
    					     JBLOCKROW *MCU_data));
    METHODDEF(int) 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, int gather_statistics)
    {
      phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
      int 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.
     */

    inline
    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 long put_buffer = (long) 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 &= (((long) 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.
     */

    inline
    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(int)
    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(int)
    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(int)
    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(int)
    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;
      int is_DC_band;
      int ci, tbl;
      jpeg_component_info * compptr;
      JHUFF_TBL **htblptr;
      int 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 */