jchuff.c File Reference

#include "jinclude.h"
#include "jpeglib.h"

Include dependency graph for jchuff.c:

Go to the source code of this file.

Classes
struct	c_derived_tbl
struct	savable_state
struct	huff_entropy_encoder
struct	working_state

Macros
#define	JPEG_INTERNALS
#define	ASSIGN_STATE(dest, src)   ((dest) = (src))
#define	MAX_CORR_BITS   1000 /* Max # of correction bits I can buffer */
#define	ISHIFT_TEMPS
#define	IRIGHT_SHIFT(x, shft)   ((x) >> (shft))
#define	emit_byte_s(state, val, action)
#define	emit_byte_e(entropy, val)
#define	MAX_CLEN   32 /* assumed maximum initial code length */

Typedefs
typedef huff_entropy_encoder *	huff_entropy_ptr

Functions
	jpeg_make_c_derived_tbl (j_compress_ptr cinfo, boolean isDC, int tblno, c_derived_tbl **pdtbl)
	dump_buffer_s (working_state *state)
	dump_buffer_e (huff_entropy_ptr entropy)
INLINE	emit_bits_s (working_state *state, unsigned int code, int size)
INLINE	emit_bits_e (huff_entropy_ptr entropy, unsigned int code, int size)
	flush_bits_s (working_state *state)
	flush_bits_e (huff_entropy_ptr entropy)
INLINE	emit_dc_symbol (huff_entropy_ptr entropy, int tbl_no, int symbol)
INLINE	emit_ac_symbol (huff_entropy_ptr entropy, int tbl_no, int symbol)
	emit_buffered_bits (huff_entropy_ptr entropy, char *bufstart, unsigned int nbits)
	emit_eobrun (huff_entropy_ptr entropy)
	emit_restart_s (working_state *state, int restart_num)
	emit_restart_e (huff_entropy_ptr entropy, int restart_num)
	encode_mcu_DC_first (j_compress_ptr cinfo, JBLOCKARRAY MCU_data)
	encode_mcu_AC_first (j_compress_ptr cinfo, JBLOCKARRAY MCU_data)
	encode_mcu_DC_refine (j_compress_ptr cinfo, JBLOCKARRAY MCU_data)
	encode_mcu_AC_refine (j_compress_ptr cinfo, JBLOCKARRAY MCU_data)
	encode_one_block (working_state *state, JCOEFPTR block, int last_dc_val, c_derived_tbl *dctbl, c_derived_tbl *actbl)
	encode_mcu_huff (j_compress_ptr cinfo, JBLOCKARRAY MCU_data)
	finish_pass_huff (j_compress_ptr cinfo)
	htest_one_block (j_compress_ptr cinfo, JCOEFPTR block, int last_dc_val, long dc_counts[], long ac_counts[])
	encode_mcu_gather (j_compress_ptr cinfo, JBLOCKARRAY MCU_data)
	jpeg_gen_optimal_table (j_compress_ptr cinfo, JHUFF_TBL *htbl, long freq[])
	finish_pass_gather (j_compress_ptr cinfo)
	start_pass_huff (j_compress_ptr cinfo, boolean gather_statistics)
	jinit_huff_encoder (j_compress_ptr cinfo)

Macro Definition Documentation

ASSIGN_STATE

#define ASSIGN_STATE	(		dest,
			src
	)		((dest) = (src))

Definition at line 61 of file jchuff.c.

emit_byte_e

#define emit_byte_e	(		entropy,
			val
	)

Value:

    { *(entropy)->next_output_byte++ = (JOCTET) (val);  \
      if (--(entropy)->free_in_buffer == 0)  \
        dump_buffer_e(entropy); }

Definition at line 255 of file jchuff.c.

emit_byte_s

#define emit_byte_s	(		state,
			val,
			action
	)

Value:

    { *(state)->next_output_byte++ = (JOCTET) (val);  \
      if (--(state)->free_in_buffer == 0)  \
        if (! dump_buffer_s(state))  \
          { action; } }

Definition at line 248 of file jchuff.c.

IRIGHT_SHIFT

#define IRIGHT_SHIFT	(		x,
			shft
	)		((x) >> (shft))

Definition at line 145 of file jchuff.c.

ISHIFT_TEMPS

#define ISHIFT_TEMPS

Definition at line 144 of file jchuff.c.

JPEG_INTERNALS

#define JPEG_INTERNALS

Definition at line 23 of file jchuff.c.

MAX_CLEN

#define MAX_CLEN   32 /* assumed maximum initial code length */

MAX_CORR_BITS

#define MAX_CORR_BITS   1000 /* Max # of correction bits I can buffer */

Definition at line 130 of file jchuff.c.

Typedef Documentation

huff_entropy_ptr

typedef huff_entropy_encoder* huff_entropy_ptr

Definition at line 111 of file jchuff.c.

Function Documentation

dump_buffer_e()

dump_buffer_e

(

huff_entropy_ptr

entropy

)

Definition at line 277 of file jchuff.c.

{
  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;
}

dump_buffer_s()

dump_buffer_s

(

working_state *

state

)

Definition at line 262 of file jchuff.c.

{
  struct jpeg_destination_mgr * dest = state->cinfo->dest;
 
  if (! (*dest->empty_output_buffer) (state->cinfo))
    return FALSE;
  /* After a successful buffer dump, must reset buffer pointers */
  state->next_output_byte = dest->next_output_byte;
  state->free_in_buffer = dest->free_in_buffer;
  return TRUE;
}

emit_ac_symbol()

INLINE emit_ac_symbol	(	huff_entropy_ptr	entropy,
		int	tbl_no,
		int	symbol
	)

Definition at line 422 of file jchuff.c.

{
  if (entropy->gather_statistics)
    entropy->ac_count_ptrs[tbl_no][symbol]++;
  else {
    c_derived_tbl * tbl = entropy->ac_derived_tbls[tbl_no];
    emit_bits_e(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]);
  }
}

Referenced by emit_eobrun(), encode_mcu_AC_first(), and encode_mcu_AC_refine().

emit_bits_e()

INLINE emit_bits_e	(	huff_entropy_ptr	entropy,
		unsigned int	code,
		int	size
	)

Definition at line 342 of file jchuff.c.

{
  /* This routine is heavily used, so it's worth coding tightly. */
  register INT32 put_buffer;
  register int 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 */
 
  /* mask off any extra bits in code */
  put_buffer = ((INT32) code) & ((((INT32) 1) << size) - 1);
 
  /* new number of bits in buffer */
  put_bits = size + entropy->saved.put_bits;
 
  put_buffer <<= 24 - put_bits; /* align incoming bits */
 
  /* and merge with old buffer contents */
  put_buffer |= entropy->saved.put_buffer;
 
  while (put_bits >= 8) {
    int c = (int) ((put_buffer >> 16) & 0xFF);
 
    emit_byte_e(entropy, c);
    if (c == 0xFF) {        /* need to stuff a zero byte? */
      emit_byte_e(entropy, 0);
    }
    put_buffer <<= 8;
    put_bits -= 8;
  }
 
  entropy->saved.put_buffer = put_buffer; /* update variables */
  entropy->saved.put_bits = put_bits;
}

Referenced by emit_ac_symbol(), emit_buffered_bits(), emit_dc_symbol(), emit_eobrun(), encode_mcu_AC_first(), encode_mcu_AC_refine(), encode_mcu_DC_first(), encode_mcu_DC_refine(), and flush_bits_e().

emit_bits_s()

INLINE emit_bits_s	(	working_state *	state,
		unsigned int	code,
		int	size
	)

Definition at line 300 of file jchuff.c.

{
  /* This routine is heavily used, so it's worth coding tightly. */
  register INT32 put_buffer;
  register int put_bits;
 
  /* if size is 0, caller used an invalid Huffman table entry */
  if (size == 0)
    ERREXIT(state->cinfo, JERR_HUFF_MISSING_CODE);
 
  /* mask off any extra bits in code */
  put_buffer = ((INT32) code) & ((((INT32) 1) << size) - 1);
 
  /* new number of bits in buffer */
  put_bits = size + state->cur.put_bits;
 
  put_buffer <<= 24 - put_bits; /* align incoming bits */
 
  /* and merge with old buffer contents */
  put_buffer |= state->cur.put_buffer;
 
  while (put_bits >= 8) {
    int c = (int) ((put_buffer >> 16) & 0xFF);
 
    emit_byte_s(state, c, return FALSE);
    if (c == 0xFF) {        /* need to stuff a zero byte? */
      emit_byte_s(state, 0, return FALSE);
    }
    put_buffer <<= 8;
    put_bits -= 8;
  }
 
  state->cur.put_buffer = put_buffer; /* update state variables */
  state->cur.put_bits = put_bits;
 
  return TRUE;
}

Referenced by encode_one_block(), and flush_bits_s().

emit_buffered_bits()

emit_buffered_bits	(	huff_entropy_ptr	entropy,
		char *	bufstart,
		unsigned int	nbits
	)

Definition at line 438 of file jchuff.c.

{
  if (entropy->gather_statistics)
    return;         /* no real work */
 
  while (nbits > 0) {
    emit_bits_e(entropy, (unsigned int) (*bufstart), 1);
    bufstart++;
    nbits--;
  }
}

Referenced by emit_eobrun(), and encode_mcu_AC_refine().

emit_dc_symbol()

INLINE emit_dc_symbol	(	huff_entropy_ptr	entropy,
		int	tbl_no,
		int	symbol
	)

Definition at line 409 of file jchuff.c.

{
  if (entropy->gather_statistics)
    entropy->dc_count_ptrs[tbl_no][symbol]++;
  else {
    c_derived_tbl * tbl = entropy->dc_derived_tbls[tbl_no];
    emit_bits_e(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]);
  }
}

Referenced by encode_mcu_DC_first().

emit_eobrun()

emit_eobrun

(

huff_entropy_ptr

entropy

)

Definition at line 457 of file jchuff.c.

{
  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_ac_symbol(entropy, entropy->ac_tbl_no, nbits << 4);
    if (nbits)
      emit_bits_e(entropy, entropy->EOBRUN, nbits);
 
    entropy->EOBRUN = 0;
 
    /* Emit any buffered correction bits */
    emit_buffered_bits(entropy, entropy->bit_buffer, entropy->BE);
    entropy->BE = 0;
  }
}

Referenced by emit_restart_e(), encode_mcu_AC_first(), encode_mcu_AC_refine(), finish_pass_gather(), and finish_pass_huff().

emit_restart_e()

emit_restart_e	(	huff_entropy_ptr	entropy,
		int	restart_num
	)

Definition at line 509 of file jchuff.c.

{
  int ci;
 
  emit_eobrun(entropy);
 
  if (! entropy->gather_statistics) {
    flush_bits_e(entropy);
    emit_byte_e(entropy, 0xFF);
    emit_byte_e(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->saved.last_dc_val[ci] = 0;
  } else {
    /* Re-initialize all AC-related fields to 0 */
    entropy->EOBRUN = 0;
    entropy->BE = 0;
  }
}

Referenced by encode_mcu_AC_first(), encode_mcu_AC_refine(), encode_mcu_DC_first(), and encode_mcu_DC_refine().

emit_restart_s()

emit_restart_s	(	working_state *	state,
		int	restart_num
	)

Definition at line 488 of file jchuff.c.

{
  int ci;
 
  if (! flush_bits_s(state))
    return FALSE;
 
  emit_byte_s(state, 0xFF, return FALSE);
  emit_byte_s(state, JPEG_RST0 + restart_num, return FALSE);
 
  /* Re-initialize DC predictions to 0 */
  for (ci = 0; ci < state->cinfo->comps_in_scan; ci++)
    state->cur.last_dc_val[ci] = 0;
 
  /* The restart counter is not updated until we successfully write the MCU. */
 
  return TRUE;
}

Referenced by encode_mcu_huff().

encode_mcu_AC_first()

encode_mcu_AC_first	(	j_compress_ptr	cinfo,
		JBLOCKARRAY	MCU_data
	)

Definition at line 626 of file jchuff.c.

{
  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
  const int * natural_order;
  JBLOCKROW block;
  register int temp, temp2;
  register int nbits;
  register int r, k;
  int Se, Al, max_coef_bits;
 
  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_e(entropy, entropy->next_restart_num);
 
  Se = cinfo->Se;
  Al = cinfo->Al;
  natural_order = cinfo->natural_order;
  max_coef_bits = cinfo->data_precision + 2;
 
  /* 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)[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 */
      /* Apply the point transform, and watch out for case */
      /* that nonzero coef is zero after point transform. */
      if ((temp >>= Al) == 0) {
    r++;
    continue;
      }
      /* For a negative coef, want temp2 = bitwise complement of abs(coef) */
      temp2 = ~temp;
    } else {
      /* Apply the point transform, and watch out for case */
      /* that nonzero coef is zero after point transform. */
      if ((temp >>= Al) == 0) {
    r++;
    continue;
      }
      temp2 = temp;
    }
 
    /* 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_ac_symbol(entropy, entropy->ac_tbl_no, 0xF0);
      r -= 16;
    }
 
    /* Find the number of bits needed for the magnitude of the coefficient */
    nbits = 0;
    do nbits++;         /* there must be at least one 1 bit */
    while ((temp >>= 1));
    /* 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_ac_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_e(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;
}

Referenced by start_pass_huff().

encode_mcu_AC_refine()

encode_mcu_AC_refine	(	j_compress_ptr	cinfo,
		JBLOCKARRAY	MCU_data
	)

Definition at line 786 of file jchuff.c.

{
  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
  const int * natural_order;
  JBLOCKROW block;
  register int temp;
  register int r, k;
  int Se, Al;
  int EOB;
  char *BR_buffer;
  unsigned int BR;
  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_e(entropy, entropy->next_restart_num);
 
  Se = cinfo->Se;
  Al = cinfo->Al;
  natural_order = cinfo->natural_order;
 
  /* 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)[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_ac_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_ac_symbol(entropy, entropy->ac_tbl_no, (r << 4) + 1);
 
    /* Emit output bit for newly-nonzero coef */
    temp = ((*block)[natural_order[k]] < 0) ? 0 : 1;
    emit_bits_e(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;
}

Referenced by start_pass_huff().

encode_mcu_DC_first()

encode_mcu_DC_first	(	j_compress_ptr	cinfo,
		JBLOCKARRAY	MCU_data
	)

Definition at line 539 of file jchuff.c.

{
  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
  register int temp, temp2;
  register int nbits;
  int max_coef_bits;
  int blkn, ci, tbl;
  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_e(entropy, entropy->next_restart_num);
 
  /* Since we're encoding a difference, the range limit is twice as much. */
  max_coef_bits = cinfo->data_precision + 3;
 
  /* Encode the MCU data blocks */
  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
    ci = cinfo->MCU_membership[blkn];
    tbl = cinfo->cur_comp_info[ci]->dc_tbl_no;
 
    /* Compute the DC value after the required point transform by Al.
     * This is simply an arithmetic right shift.
     */
    temp = IRIGHT_SHIFT((int) (MCU_data[blkn][0][0]), cinfo->Al);
 
    /* DC differences are figured on the point-transformed values. */
    if ((temp2 = temp - entropy->saved.last_dc_val[ci]) == 0) {
      /* Count/emit the Huffman-coded symbol for the number of bits */
      emit_dc_symbol(entropy, tbl, 0);
 
      continue;
    }
 
    entropy->saved.last_dc_val[ci] = temp;
 
    /* Encode the DC coefficient difference per section G.1.2.1 */
    if ((temp = temp2) < 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;
    do nbits++;         /* there must be at least one 1 bit */
    while ((temp >>= 1));
    /* Check for out-of-range coefficient values */
    if (nbits > max_coef_bits)
      ERREXIT(cinfo, JERR_BAD_DCT_COEF);
 
    /* Count/emit the Huffman-coded symbol for the number of bits */
    emit_dc_symbol(entropy, tbl, nbits);
 
    /* Emit that number of bits of the value, if positive, */
    /* or the complement of its magnitude, if negative. */
    emit_bits_e(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;
}

Referenced by start_pass_huff().

encode_mcu_DC_refine()

encode_mcu_DC_refine	(	j_compress_ptr	cinfo,
		JBLOCKARRAY	MCU_data
	)

Definition at line 743 of file jchuff.c.

{
  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
  int Al, blkn;
 
  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_e(entropy, entropy->next_restart_num);
 
  Al = cinfo->Al;
 
  /* Encode the MCU data blocks */
  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
    /* We simply emit the Al'th bit of the DC coefficient value. */
    emit_bits_e(entropy, (unsigned int) (MCU_data[blkn][0][0] >> 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;
}

Referenced by start_pass_huff().

encode_mcu_gather()

encode_mcu_gather	(	j_compress_ptr	cinfo,
		JBLOCKARRAY	MCU_data
	)

Definition at line 1209 of file jchuff.c.

{
  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
  int blkn, ci;
  jpeg_component_info * compptr;
 
  /* Take care of restart intervals if needed */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0) {
      /* Re-initialize DC predictions to 0 */
      for (ci = 0; ci < cinfo->comps_in_scan; ci++)
    entropy->saved.last_dc_val[ci] = 0;
      /* Update restart state */
      entropy->restarts_to_go = cinfo->restart_interval;
    }
    entropy->restarts_to_go--;
  }
 
  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
    ci = cinfo->MCU_membership[blkn];
    compptr = cinfo->cur_comp_info[ci];
    htest_one_block(cinfo, MCU_data[blkn][0], entropy->saved.last_dc_val[ci],
            entropy->dc_count_ptrs[compptr->dc_tbl_no],
            entropy->ac_count_ptrs[compptr->ac_tbl_no]);
    entropy->saved.last_dc_val[ci] = MCU_data[blkn][0][0];
  }
 
  return TRUE;
}

Referenced by start_pass_huff().

encode_mcu_huff()

encode_mcu_huff	(	j_compress_ptr	cinfo,
		JBLOCKARRAY	MCU_data
	)

Definition at line 1022 of file jchuff.c.

{
  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
  working_state state;
  int blkn, ci;
  jpeg_component_info * compptr;
 
  /* Load up working state */
  state.next_output_byte = cinfo->dest->next_output_byte;
  state.free_in_buffer = cinfo->dest->free_in_buffer;
  ASSIGN_STATE(state.cur, entropy->saved);
  state.cinfo = cinfo;
 
  /* Emit restart marker if needed */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0)
      if (! emit_restart_s(&state, entropy->next_restart_num))
    return FALSE;
  }
 
  /* Encode the MCU data blocks */
  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
    ci = cinfo->MCU_membership[blkn];
    compptr = cinfo->cur_comp_info[ci];
    if (! encode_one_block(&state,
               MCU_data[blkn][0], state.cur.last_dc_val[ci],
               entropy->dc_derived_tbls[compptr->dc_tbl_no],
               entropy->ac_derived_tbls[compptr->ac_tbl_no]))
      return FALSE;
    /* Update last_dc_val */
    state.cur.last_dc_val[ci] = MCU_data[blkn][0][0];
  }
 
  /* Completed MCU, so update state */
  cinfo->dest->next_output_byte = state.next_output_byte;
  cinfo->dest->free_in_buffer = state.free_in_buffer;
  ASSIGN_STATE(entropy->saved, state.cur);
 
  /* 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;
}

Referenced by start_pass_huff().

encode_one_block()

encode_one_block	(	working_state *	state,
		JCOEFPTR	block,
		int	last_dc_val,
		c_derived_tbl *	dctbl,
		c_derived_tbl *	actbl
	)

Definition at line 916 of file jchuff.c.

{
  register int temp, temp2;
  register int nbits;
  register int r, k;
  int Se = state->cinfo->lim_Se;
  int max_coef_bits = state->cinfo->data_precision + 3;
  const int * natural_order = state->cinfo->natural_order;
 
  /* Encode the DC coefficient difference per section F.1.2.1 */
 
  if ((temp = block[0] - last_dc_val) == 0) {
    /* Emit the Huffman-coded symbol for the number of bits */
    if (! emit_bits_s(state, dctbl->ehufco[0], dctbl->ehufsi[0]))
      return FALSE;
  } else {
    if ((temp2 = 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;
    do nbits++;         /* there must be at least one 1 bit */
    while ((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)
      ERREXIT(state->cinfo, JERR_BAD_DCT_COEF);
 
    /* Emit the Huffman-coded symbol for the number of bits */
    if (! emit_bits_s(state, dctbl->ehufco[nbits], dctbl->ehufsi[nbits]))
      return FALSE;
 
    /* Emit that number of bits of the value, if positive, */
    /* or the complement of its magnitude, if negative. */
    if (! emit_bits_s(state, (unsigned int) temp2, nbits))
      return FALSE;
  }
 
  /* Encode the AC coefficients per section F.1.2.2 */
 
  r = 0;            /* r = run length of zeros */
 
  for (k = 1; k <= Se; k++) {
    if ((temp = block[natural_order[k]]) == 0) {
      r++;
      continue;
    }
 
    /* if run length > 15, must emit special run-length-16 codes (0xF0) */
    while (r > 15) {
      if (! emit_bits_s(state, actbl->ehufco[0xF0], actbl->ehufsi[0xF0]))
    return FALSE;
      r -= 16;
    }
 
    if ((temp2 = temp) < 0) {
      temp = -temp;     /* temp is abs value of input */
      /* For a negative coef, want temp2 = bitwise complement of abs(coef) */
      /* 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;
    do nbits++;         /* there must be at least one 1 bit */
    while ((temp >>= 1));
    /* Check for out-of-range coefficient values.
     * Use ">=" instead of ">" so can use the
     * same one larger limit from DC check here.
     */
    if (nbits >= max_coef_bits)
      ERREXIT(state->cinfo, JERR_BAD_DCT_COEF);
 
    /* Emit Huffman symbol for run length / number of bits */
    temp = (r << 4) + nbits;
    if (! emit_bits_s(state, actbl->ehufco[temp], actbl->ehufsi[temp]))
      return FALSE;
 
    /* Emit that number of bits of the value, if positive, */
    /* or the complement of its magnitude, if negative. */
    if (! emit_bits_s(state, (unsigned int) temp2, nbits))
      return FALSE;
 
    r = 0;          /* reset zero run length */
  }
 
  /* If the last coef(s) were zero, emit an end-of-block code */
  if (r > 0)
    if (! emit_bits_s(state, actbl->ehufco[0], actbl->ehufsi[0]))
      return FALSE;
 
  return TRUE;
}

Referenced by encode_mcu_huff().

finish_pass_gather()

finish_pass_gather

(

j_compress_ptr

cinfo

)

Definition at line 1481 of file jchuff.c.

{
  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
  int ci, tbl;
  jpeg_component_info * compptr;
  JHUFF_TBL **htblptr;
  boolean did_dc[NUM_HUFF_TBLS];
  boolean did_ac[NUM_HUFF_TBLS];
 
  if (cinfo->progressive_mode)
    /* Flush out buffered data (all we care about is counting the EOB symbol) */
    emit_eobrun(entropy);
 
  /* It's important not to apply jpeg_gen_optimal_table more than once
   * per table, because it clobbers the input frequency counts!
   */
  MEMZERO(did_dc, SIZEOF(did_dc));
  MEMZERO(did_ac, SIZEOF(did_ac));
 
  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    compptr = cinfo->cur_comp_info[ci];
    /* DC needs no table for refinement scan */
    if (cinfo->Ss == 0 && cinfo->Ah == 0) {
      tbl = compptr->dc_tbl_no;
      if (! did_dc[tbl]) {
    htblptr = & cinfo->dc_huff_tbl_ptrs[tbl];
    if (*htblptr == NULL)
      *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
    jpeg_gen_optimal_table(cinfo, *htblptr, entropy->dc_count_ptrs[tbl]);
    did_dc[tbl] = TRUE;
      }
    }
    /* AC needs no table when not present */
    if (cinfo->Se) {
      tbl = compptr->ac_tbl_no;
      if (! did_ac[tbl]) {
    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->ac_count_ptrs[tbl]);
    did_ac[tbl] = TRUE;
      }
    }
  }
}

Referenced by start_pass_huff().

finish_pass_huff()

finish_pass_huff

(

j_compress_ptr

cinfo

)

Definition at line 1079 of file jchuff.c.

{
  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
  working_state state;
 
  if (cinfo->progressive_mode) {
    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_e(entropy);
 
    cinfo->dest->next_output_byte = entropy->next_output_byte;
    cinfo->dest->free_in_buffer = entropy->free_in_buffer;
  } else {
    /* Load up working state ... flush_bits needs it */
    state.next_output_byte = cinfo->dest->next_output_byte;
    state.free_in_buffer = cinfo->dest->free_in_buffer;
    ASSIGN_STATE(state.cur, entropy->saved);
    state.cinfo = cinfo;
 
    /* Flush out the last data */
    if (! flush_bits_s(&state))
      ERREXIT(cinfo, JERR_CANT_SUSPEND);
 
    /* Update state */
    cinfo->dest->next_output_byte = state.next_output_byte;
    cinfo->dest->free_in_buffer = state.free_in_buffer;
    ASSIGN_STATE(entropy->saved, state.cur);
  }
}

Referenced by start_pass_huff().

flush_bits_e()

flush_bits_e

(

huff_entropy_ptr

entropy

)

Definition at line 395 of file jchuff.c.

{
  emit_bits_e(entropy, 0x7F, 7); /* fill any partial byte with ones */
  entropy->saved.put_buffer = 0; /* and reset bit-buffer to empty */
  entropy->saved.put_bits = 0;
}

Referenced by emit_restart_e(), and finish_pass_huff().

flush_bits_s()

flush_bits_s

(

working_state *

state

)

Definition at line 384 of file jchuff.c.

{
  if (! emit_bits_s(state, 0x7F, 7)) /* fill any partial byte with ones */
    return FALSE;
  state->cur.put_buffer = 0;         /* and reset bit-buffer to empty */
  state->cur.put_bits = 0;
  return TRUE;
}

Referenced by emit_restart_s(), and finish_pass_huff().

htest_one_block()

htest_one_block	(	j_compress_ptr	cinfo,
		JCOEFPTR	block,
		int	last_dc_val,
		long	dc_counts[],
		long	ac_counts[]
	)

Definition at line 1128 of file jchuff.c.

{
  register int temp;
  register int nbits;
  register int r, k;
  int Se = cinfo->lim_Se;
  int max_coef_bits = cinfo->data_precision + 3;
  const int * natural_order = cinfo->natural_order;
 
  /* Encode the DC coefficient difference per section F.1.2.1 */
 
  if ((temp = block[0] - last_dc_val) == 0) {
    /* Count the Huffman symbol for the number of bits */
    dc_counts[0]++;
  } else {
    if (temp < 0)
      temp = -temp;     /* temp is abs value of input */
 
    /* Find the number of bits needed for the magnitude of the coefficient */
    nbits = 0;
    do nbits++;         /* there must be at least one 1 bit */
    while ((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)
      ERREXIT(cinfo, JERR_BAD_DCT_COEF);
 
    /* Count the Huffman symbol for the number of bits */
    dc_counts[nbits]++;
  }
 
  /* Encode the AC coefficients per section F.1.2.2 */
 
  r = 0;            /* r = run length of zeros */
 
  for (k = 1; k <= Se; k++) {
    if ((temp = block[natural_order[k]]) == 0) {
      r++;
      continue;
    }
 
    /* if run length > 15, must emit special run-length-16 codes (0xF0) */
    while (r > 15) {
      ac_counts[0xF0]++;
      r -= 16;
    }
 
    if (temp < 0)
      temp = -temp;     /* temp is abs value of input */
 
    /* Find the number of bits needed for the magnitude of the coefficient */
    nbits = 0;
    do nbits++;         /* there must be at least one 1 bit */
    while ((temp >>= 1));
    /* Check for out-of-range coefficient values.
     * Use ">=" instead of ">" so can use the
     * same one larger limit from DC check here.
     */
    if (nbits >= max_coef_bits)
      ERREXIT(cinfo, JERR_BAD_DCT_COEF);
 
    /* Count Huffman symbol for run length / number of bits */
    ac_counts[(r << 4) + nbits]++;
 
    r = 0;          /* reset zero run length */
  }
 
  /* If the last coef(s) were zero, emit an end-of-block code */
  if (r > 0)
    ac_counts[0]++;
}

Referenced by encode_mcu_gather().

jinit_huff_encoder()

jinit_huff_encoder

(

j_compress_ptr

cinfo

)

Definition at line 1638 of file jchuff.c.

{
  huff_entropy_ptr entropy;
  int i;
 
  entropy = (huff_entropy_ptr) (*cinfo->mem->alloc_small)
    ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(huff_entropy_encoder));
  cinfo->entropy = &entropy->pub;
  entropy->pub.start_pass = start_pass_huff;
 
  /* Mark tables unallocated */
  for (i = 0; i < NUM_HUFF_TBLS; i++) {
    entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
    entropy->dc_count_ptrs[i] = entropy->ac_count_ptrs[i] = NULL;
  }
 
  if (cinfo->progressive_mode)
    entropy->bit_buffer = NULL; /* needed only in AC refinement scan */
}

Referenced by jinit_compress_master(), and transencode_master_selection().

jpeg_gen_optimal_table()

jpeg_gen_optimal_table	(	j_compress_ptr	cinfo,
		JHUFF_TBL *	htbl,
		long	freq[]
	)

Definition at line 1268 of file jchuff.c.

{
#define MAX_CLEN 32     /* assumed maximum initial code length */
  UINT8 bits[MAX_CLEN+1];   /* bits[k] = # of symbols with code length k */
  int codesize[257];        /* codesize[k] = code length of symbol k */
  int others[257];      /* next symbol in current branch of tree */
  int c1, c2, i, j;
  UINT8 *p;
  long v;
 
  freq[256] = 1;        /* make sure 256 has a nonzero count */
  /* Including the pseudo-symbol 256 in the Huffman procedure guarantees
   * that no real symbol is given code-value of all ones, because 256
   * will be placed last in the largest codeword category.
   * In the symbol list build procedure this element serves as sentinel
   * for the zero run loop.
   */
 
#ifndef DONT_USE_FANCY_HUFF_OPT
 
  /* Build list of symbols sorted in order of descending frequency */
  /* This approach has several benefits (thank to John Korejwa for the idea):
   *     1.
   * If a codelength category is split during the length limiting procedure
   * below, the feature that more frequent symbols are assigned shorter
   * codewords remains valid for the adjusted code.
   *     2.
   * To reduce consecutive ones in a Huffman data stream (thus reducing the
   * number of stuff bytes in JPEG) it is preferable to follow 0 branches
   * (and avoid 1 branches) as much as possible.  This is easily done by
   * assigning symbols to leaves of the Huffman tree in order of decreasing
   * frequency, with no secondary sort based on codelengths.
   *     3.
   * The symbol list can be built independently from the assignment of code
   * lengths by the Huffman procedure below.
   * Note: The symbol list build procedure must be performed first, because
   * the Huffman procedure assigning the codelengths clobbers the frequency
   * counts!
   */
 
  /* Here we use the others array as a linked list of nonzero frequencies
   * to be sorted.  Already sorted elements are removed from the list.
   */
 
  /* Building list */
 
  /* This item does not correspond to a valid symbol frequency and is used
   * as starting index.
   */
  j = 256;
 
  for (i = 0;; i++) {
    if (freq[i] == 0)       /* skip zero frequencies */
      continue;
    if (i > 255)
      break;
    others[j] = i;      /* this symbol value */
    j = i;          /* previous symbol value */
  }
  others[j] = -1;       /* mark end of list */
 
  /* Sorting list */
 
  p = htbl->huffval;
  while ((c1 = others[256]) >= 0) {
    v = freq[c1];
    i = c1;         /* first symbol value */
    j = 256;            /* pseudo symbol value for starting index */
    while ((c2 = others[c1]) >= 0) {
      if (freq[c2] > v) {
    v = freq[c2];
    i = c2;         /* this symbol value */
    j = c1;         /* previous symbol value */
      }
      c1 = c2;
    }
    others[j] = others[i];  /* remove this symbol i from list */
    *p++ = (UINT8) i;
  }
 
#endif /* DONT_USE_FANCY_HUFF_OPT */
 
  /* This algorithm is explained in section K.2 of the JPEG standard */
 
  MEMZERO(bits, SIZEOF(bits));
  MEMZERO(codesize, SIZEOF(codesize));
  for (i = 0; i < 257; i++)
    others[i] = -1;     /* init links to empty */
 
  /* Huffman's basic algorithm to assign optimal code lengths to symbols */
 
  for (;;) {
    /* Find the smallest nonzero frequency, set c1 = its symbol */
    /* In case of ties, take the larger symbol number */
    c1 = -1;
    v = 1000000000L;
    for (i = 0; i <= 256; i++) {
      if (freq[i] && freq[i] <= v) {
    v = freq[i];
    c1 = i;
      }
    }
 
    /* Find the next smallest nonzero frequency, set c2 = its symbol */
    /* In case of ties, take the larger symbol number */
    c2 = -1;
    v = 1000000000L;
    for (i = 0; i <= 256; i++) {
      if (freq[i] && freq[i] <= v && i != c1) {
    v = freq[i];
    c2 = i;
      }
    }
 
    /* Done if we've merged everything into one frequency */
    if (c2 < 0)
      break;
 
    /* Else merge the two counts/trees */
    freq[c1] += freq[c2];
    freq[c2] = 0;
 
    /* Increment the codesize of everything in c1's tree branch */
    codesize[c1]++;
    while (others[c1] >= 0) {
      c1 = others[c1];
      codesize[c1]++;
    }
 
    others[c1] = c2;        /* chain c2 onto c1's tree branch */
 
    /* Increment the codesize of everything in c2's tree branch */
    codesize[c2]++;
    while (others[c2] >= 0) {
      c2 = others[c2];
      codesize[c2]++;
    }
  }
 
  /* Now count the number of symbols of each code length */
  for (i = 0; i <= 256; i++) {
    if (codesize[i]) {
      /* The JPEG standard seems to think that this can't happen, */
      /* but I'm paranoid... */
      if (codesize[i] > MAX_CLEN)
    ERREXIT(cinfo, JERR_HUFF_CLEN_OUTOFBOUNDS);
 
      bits[codesize[i]]++;
    }
  }
 
  /* JPEG doesn't allow symbols with code lengths over 16 bits, so if the pure
   * Huffman procedure assigned any such lengths, we must adjust the coding.
   * Here is what the JPEG spec says about how this next bit works:
   * Since symbols are paired for the longest Huffman code, the symbols are
   * removed from this length category two at a time.  The prefix for the pair
   * (which is one bit shorter) is allocated to one of the pair; then,
   * skipping the BITS entry for that prefix length, a code word from the next
   * shortest nonzero BITS entry is converted into a prefix for two code words
   * one bit longer.
   */
 
  for (i = MAX_CLEN; i > 16; i--) {
    while (bits[i] > 0) {
      j = i - 2;        /* find length of new prefix to be used */
      while (bits[j] == 0) {
    if (j == 0)
      ERREXIT(cinfo, JERR_HUFF_CLEN_OUTOFBOUNDS);
    j--;
      }
 
      bits[i] -= 2;     /* remove two symbols */
      bits[i-1]++;      /* one goes in this length */
      bits[j+1] += 2;       /* two new symbols in this length */
      bits[j]--;        /* symbol of this length is now a prefix */
    }
  }
 
  /* Remove the count for the pseudo-symbol 256 from the largest codelength */
  while (bits[i] == 0)      /* find largest codelength still in use */
    i--;
  bits[i]--;
 
  /* Return final symbol counts (only for lengths 0..16) */
  MEMCOPY(htbl->bits, bits, SIZEOF(htbl->bits));
 
#ifdef DONT_USE_FANCY_HUFF_OPT
 
  /* Return a list of the symbols sorted by code length */
  /* Note: Due to the codelength changes made above, it can happen
   * that more frequent symbols are assigned longer codewords.
   */
  p = htbl->huffval;
  for (i = 1; i <= MAX_CLEN; i++) {
    for (j = 0; j <= 255; j++) {
      if (codesize[j] == i) {
    *p++ = (UINT8) j;
      }
    }
  }
 
#endif /* DONT_USE_FANCY_HUFF_OPT */
 
  /* Set sent_table FALSE so updated table will be written to JPEG file. */
  htbl->sent_table = FALSE;
}

Referenced by finish_pass_gather().

jpeg_make_c_derived_tbl()

jpeg_make_c_derived_tbl	(	j_compress_ptr	cinfo,
		boolean	isDC,
		int	tblno,
		c_derived_tbl **	pdtbl
	)

Definition at line 155 of file jchuff.c.

{
  JHUFF_TBL *htbl;
  c_derived_tbl *dtbl;
  int p, i, l, lastp, si, maxsymbol;
  char huffsize[257];
  unsigned int huffcode[257];
  unsigned int code;
 
  /* Note that huffsize[] and huffcode[] are filled in code-length order,
   * paralleling the order of the symbols themselves in htbl->huffval[].
   */
 
  /* Find the input Huffman table */
  if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
    ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
  htbl =
    isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
  if (htbl == NULL)
    htbl = jpeg_std_huff_table((j_common_ptr) cinfo, isDC, tblno);
 
  /* Allocate a workspace if we haven't already done so. */
  if (*pdtbl == NULL)
    *pdtbl = (c_derived_tbl *) (*cinfo->mem->alloc_small)
      ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(c_derived_tbl));
  dtbl = *pdtbl;
  
  /* Figure C.1: make table of Huffman code length for each symbol */
 
  p = 0;
  for (l = 1; l <= 16; l++) {
    i = (int) htbl->bits[l];
    if (i < 0 || p + i > 256)   /* protect against table overrun */
      ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
    while (i--)
      huffsize[p++] = (char) l;
  }
  huffsize[p] = 0;
  lastp = p;
  
  /* Figure C.2: generate the codes themselves */
  /* We also validate that the counts represent a legal Huffman code tree. */
 
  code = 0;
  si = huffsize[0];
  p = 0;
  while (huffsize[p]) {
    while (((int) huffsize[p]) == si) {
      huffcode[p++] = code;
      code++;
    }
    /* code is now 1 more than the last code used for codelength si; but
     * it must still fit in si bits, since no code is allowed to be all ones.
     */
    if (((INT32) code) >= (((INT32) 1) << si))
      ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
    code <<= 1;
    si++;
  }
  
  /* Figure C.3: generate encoding tables */
  /* These are code and size indexed by symbol value */
 
  /* Set all codeless symbols to have code length 0;
   * this lets us detect duplicate VAL entries here, and later
   * allows emit_bits to detect any attempt to emit such symbols.
   */
  MEMZERO(dtbl->ehufsi, SIZEOF(dtbl->ehufsi));
 
  /* This is also a convenient place to check for out-of-range
   * and duplicated VAL entries.  We allow 0..255 for AC symbols
   * but only 0..15 for DC.  (We could constrain them further
   * based on data depth and mode, but this seems enough.)
   */
  maxsymbol = isDC ? 15 : 255;
 
  for (p = 0; p < lastp; p++) {
    i = htbl->huffval[p];
    if (i < 0 || i > maxsymbol || dtbl->ehufsi[i])
      ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
    dtbl->ehufco[i] = huffcode[p];
    dtbl->ehufsi[i] = huffsize[p];
  }
}

Referenced by start_pass_huff().

start_pass_huff()

start_pass_huff	(	j_compress_ptr	cinfo,
		boolean	gather_statistics
	)

Definition at line 1535 of file jchuff.c.

{
  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
  int ci, tbl;
  jpeg_component_info * compptr;
 
  if (gather_statistics)
    entropy->pub.finish_pass = finish_pass_gather;
  else
    entropy->pub.finish_pass = finish_pass_huff;
 
  if (cinfo->progressive_mode) {
    entropy->cinfo = cinfo;
    entropy->gather_statistics = gather_statistics;
 
    /* We assume jcmaster.c already validated the scan parameters. */
 
    /* Select execution routine */
    if (cinfo->Ah == 0) {
      if (cinfo->Ss == 0)
    entropy->pub.encode_mcu = encode_mcu_DC_first;
      else
    entropy->pub.encode_mcu = encode_mcu_AC_first;
    } else {
      if (cinfo->Ss == 0)
    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));
      }
    }
 
    /* Initialize AC stuff */
    entropy->ac_tbl_no = cinfo->cur_comp_info[0]->ac_tbl_no;
    entropy->EOBRUN = 0;
    entropy->BE = 0;
  } else {
    if (gather_statistics)
      entropy->pub.encode_mcu = encode_mcu_gather;
    else
      entropy->pub.encode_mcu = encode_mcu_huff;
  }
 
  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    compptr = cinfo->cur_comp_info[ci];
    /* DC needs no table for refinement scan */
    if (cinfo->Ss == 0 && cinfo->Ah == 0) {
      tbl = compptr->dc_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->dc_count_ptrs[tbl] == NULL)
      entropy->dc_count_ptrs[tbl] = (long *) (*cinfo->mem->alloc_small)
        ((j_common_ptr) cinfo, JPOOL_IMAGE, 257 * SIZEOF(long));
    MEMZERO(entropy->dc_count_ptrs[tbl], 257 * SIZEOF(long));
      } else {
    /* Compute derived values for Huffman tables */
    /* We may do this more than once for a table, but it's not expensive */
    jpeg_make_c_derived_tbl(cinfo, TRUE, tbl,
                & entropy->dc_derived_tbls[tbl]);
      }
      /* Initialize DC predictions to 0 */
      entropy->saved.last_dc_val[ci] = 0;
    }
    /* AC needs no table when not present */
    if (cinfo->Se) {
      tbl = compptr->ac_tbl_no;
      if (gather_statistics) {
    if (tbl < 0 || tbl >= NUM_HUFF_TBLS)
      ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
    if (entropy->ac_count_ptrs[tbl] == NULL)
      entropy->ac_count_ptrs[tbl] = (long *) (*cinfo->mem->alloc_small)
        ((j_common_ptr) cinfo, JPOOL_IMAGE, 257 * SIZEOF(long));
    MEMZERO(entropy->ac_count_ptrs[tbl], 257 * SIZEOF(long));
      } else {
    jpeg_make_c_derived_tbl(cinfo, FALSE, tbl,
                & entropy->ac_derived_tbls[tbl]);
      }
    }
  }
 
  /* Initialize bit buffer to empty */
  entropy->saved.put_buffer = 0;
  entropy->saved.put_bits = 0;
 
  /* Initialize restart stuff */
  entropy->restarts_to_go = cinfo->restart_interval;
  entropy->next_restart_num = 0;
}

Referenced by jinit_huff_encoder().