www.pudn.com > imgport.rar > jcphuff.c, change:2008-11-05,size:25968b


/* 
 * 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 */ 
  JPEG_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. 
 */ 
 
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 JPEG_INT32 put_buffer = (JPEG_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 &= (((JPEG_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. 
 */ 
 
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(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 */