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/*
* jchuff.c
*
* Copyright (C) 1991-1997, Thomas G. Lane.
* Modified 2006-2009 by Guido Vollbeding.
* 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.
* Both sequential and progressive modes are supported in this single module.
*
* Much of the complexity here has to do with supporting output suspension.
* If the data destination module demands suspension, we want to be able to
* back up to the start of the current MCU. To do this, we copy state
* variables into local working storage, and update them back to the
* permanent JPEG objects only upon successful completion of an MCU.
*
* We do not support output suspension for the progressive JPEG mode, 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"
/* The legal range of a DCT coefficient is
* -1024 .. +1023 for 8-bit data;
* -16384 .. +16383 for 12-bit data.
* Hence the magnitude should always fit in 10 or 14 bits respectively.
*/
#if BITS_IN_JSAMPLE == 8
#define MAX_COEF_BITS 10
#else
#define MAX_COEF_BITS 14
#endif
/* Derived data constructed for each Huffman table */
typedef struct {
unsigned int ehufco[256]; /* code for each symbol */
char ehufsi[256]; /* length of code for each symbol */
/* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */
} c_derived_tbl;
/* Expanded entropy encoder object for Huffman encoding.
*
* The savable_state subrecord contains fields that change within an MCU,
* but must not be updated permanently until we complete the MCU.
*/
typedef struct {
INT32 put_buffer; /* current bit-accumulation buffer */
int put_bits; /* # of bits now in it */
int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
} savable_state;
/* This macro is to work around compilers with missing or broken
* structure assignment. You'll need to fix this code if you have
* such a compiler and you change MAX_COMPS_IN_SCAN.
*/
#ifndef NO_STRUCT_ASSIGN
#define ASSIGN_STATE(dest,src) ((dest) = (src))
#else
#if MAX_COMPS_IN_SCAN == 4
#define ASSIGN_STATE(dest,src) \
((dest).put_buffer = (src).put_buffer, \
(dest).put_bits = (src).put_bits, \
(dest).last_dc_val[0] = (src).last_dc_val[0], \
(dest).last_dc_val[1] = (src).last_dc_val[1], \
(dest).last_dc_val[2] = (src).last_dc_val[2], \
(dest).last_dc_val[3] = (src).last_dc_val[3])
#endif
#endif
typedef struct {
struct jpeg_entropy_encoder pub; /* public fields */
savable_state saved; /* Bit buffer & DC state at start of MCU */
/* These fields are NOT loaded into local working state. */
unsigned int restarts_to_go; /* MCUs left in this restart interval */
int next_restart_num; /* next restart number to write (0-7) */
/* Pointers to derived tables (these workspaces have image lifespan) */
c_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];
c_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
/* Statistics tables for optimization */
long * dc_count_ptrs[NUM_HUFF_TBLS];
long * ac_count_ptrs[NUM_HUFF_TBLS];
/* Following fields used only in progressive mode */
/* Mode flag: TRUE for optimization, FALSE for actual data output */
boolean gather_statistics;
/* 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 */
j_compress_ptr cinfo; /* link to cinfo (needed for dump_buffer) */
/* 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... */
} huff_entropy_encoder;
typedef huff_entropy_encoder * huff_entropy_ptr;
/* Working state while writing an MCU (sequential mode).
* This struct contains all the fields that are needed by subroutines.
*/
typedef struct {
JOCTET * next_output_byte; /* => next byte to write in buffer */
size_t free_in_buffer; /* # of byte spaces remaining in buffer */
savable_state cur; /* Current bit buffer & DC state */
j_compress_ptr cinfo; /* dump_buffer needs access to this */
} working_state;
/* 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
/*
* Compute the derived values for a Huffman table.
* This routine also performs some validation checks on the table.
*/
LOCAL(void)
jpeg_make_c_derived_tbl (j_compress_ptr cinfo, boolean isDC, int tblno,
c_derived_tbl ** pdtbl)
{
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)
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, 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];
}
}
/* Outputting bytes to the file.
* NB: these must be called only when actually outputting,
* that is, entropy->gather_statistics == FALSE.
*/
/* Emit a byte, taking 'action' if must suspend. */
#define emit_byte_s(state,val,action) \
{ *(state)->next_output_byte++ = (JOCTET) (val); \
if (--(state)->free_in_buffer == 0) \
if (! dump_buffer_s(state)) \
{ action; } }
/* Emit a byte */
#define emit_byte_e(entropy,val) \
{ *(entropy)->next_output_byte++ = (JOCTET) (val); \
if (--(entropy)->free_in_buffer == 0) \
dump_buffer_e(entropy); }
LOCAL(boolean)
dump_buffer_s (working_state * state)
/* Empty the output buffer; return TRUE if successful, FALSE if must suspend */
{
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;
}
LOCAL(void)
dump_buffer_e (huff_entropy_ptr entropy)
/* Empty the output buffer; we do not support suspension in this case. */
{
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(boolean)
emit_bits_s (working_state * state, unsigned int code, int size)
/* Emit some bits; return TRUE if successful, FALSE if must suspend */
{
/* This routine is heavily used, so it's worth coding tightly. */
register INT32 put_buffer = (INT32) code;
register int put_bits = state->cur.put_bits;
/* if size is 0, caller used an invalid Huffman table entry */
if (size == 0)
ERREXIT(state->cinfo, JERR_HUFF_MISSING_CODE);
put_buffer &= (((INT32) 1)<<size) - 1; /* mask off any extra bits in code */
put_bits += size; /* new number of bits in buffer */
put_buffer <<= 24 - put_bits; /* align incoming bits */
put_buffer |= state->cur.put_buffer; /* and merge with old buffer contents */
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;
}
INLINE
LOCAL(void)
emit_bits_e (huff_entropy_ptr entropy, unsigned int code, int size)
/* Emit some bits, unless we are in gather mode */
{
/* This routine is heavily used, so it's worth coding tightly. */
register INT32 put_buffer = (INT32) code;
register int put_bits = entropy->saved.put_bits;
/* if size is 0, caller used an invalid Huffman table entry */
if (size == 0)
ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
if (entropy->gather_statistics)
return; /* do nothing if we're only getting stats */
put_buffer &= (((INT32) 1)<<size) - 1; /* mask off any extra bits in code */
put_bits += size; /* new number of bits in buffer */
put_buffer <<= 24 - put_bits; /* align incoming bits */
/* 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;
}
LOCAL(boolean)
flush_bits_s (working_state * state)
{
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;
}
LOCAL(void)
flush_bits_e (huff_entropy_ptr entropy)
{
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;
}
/*
* Emit (or just count) a Huffman symbol.
*/
INLINE
LOCAL(void)
emit_dc_symbol (huff_entropy_ptr entropy, int tbl_no, int symbol)
{
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]);
}
}
INLINE
LOCAL(void)
emit_ac_symbol (huff_entropy_ptr entropy, int tbl_no, int symbol)
{
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]);
}
}
/*
* Emit bits from a correction bit buffer.
*/
LOCAL(void)
emit_buffered_bits (huff_entropy_ptr entropy, char * bufstart,
unsigned int nbits)
{
if (entropy->gather_statistics)
return; /* no real work */
while (nbits > 0) {
emit_bits_e(entropy, (unsigned int) (*bufstart), 1);
bufstart++;
nbits--;
}
}
/*
* Emit any pending EOBRUN symbol.
*/
LOCAL(void)
emit_eobrun (huff_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_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;
}
}
/*
* Emit a restart marker & resynchronize predictions.
*/
LOCAL(boolean)
emit_restart_s (working_state * state, int restart_num)
{
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;
}
LOCAL(void)
emit_restart_e (huff_entropy_ptr entropy, int restart_num)
{
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;
}
}
/*
* 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)
{
huff_entropy_ptr entropy = (huff_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_e(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->saved.last_dc_val[ci];
entropy->saved.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_dc_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_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;
}
/*
* 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)
{
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
register int temp, temp2;
register int nbits;
register int r, k;
int Se, Al;
const int * natural_order;
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_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];
/* 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 */
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_ac_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_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;
}
/*
* 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)
{
huff_entropy_ptr entropy = (huff_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_e(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_e(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)
{
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
register int temp;
register int r, k;
int EOB;
char *BR_buffer;
unsigned int BR;
int Se, Al;
const int * natural_order;
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_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;
}
/* Encode a single block's worth of coefficients */
LOCAL(boolean)
encode_one_block (working_state * state, JCOEFPTR block, int last_dc_val,
c_derived_tbl *dctbl, c_derived_tbl *actbl)
{
register int temp, temp2;
register int nbits;
register int k, r, i;
int Se = state->cinfo->lim_Se;
const int * natural_order = state->cinfo->natural_order;
/* Encode the DC coefficient difference per section F.1.2.1 */
temp = temp2 = block[0] - last_dc_val;
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(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 (nbits) /* emit_bits rejects calls with size 0 */
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++;
} else {
/* 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;
}
temp2 = temp;
if (temp < 0) {
temp = -temp; /* temp is abs value of 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 = 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(state->cinfo, JERR_BAD_DCT_COEF);
/* Emit Huffman symbol for run length / number of bits */
i = (r << 4) + nbits;
if (! emit_bits_s(state, actbl->ehufco[i], actbl->ehufsi[i]))
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;
}
}
/* 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;
}
/*
* Encode and output one MCU's worth of Huffman-compressed coefficients.
*/
METHODDEF(boolean)
encode_mcu_huff (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
{
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;
}
/*
* Finish up at the end of a Huffman-compressed scan.
*/
METHODDEF(void)
finish_pass_huff (j_compress_ptr cinfo)
{
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);
}
}
/*
* Huffman coding optimization.
*
* We first scan the supplied data and count the number of uses of each symbol
* that is to be Huffman-coded. (This process MUST agree with the code above.)
* Then we build a Huffman coding tree for the observed counts.
* Symbols which are not needed at all for the particular image are not
* assigned any code, which saves space in the DHT marker as well as in
* the compressed data.
*/
/* Process a single block's worth of coefficients */
LOCAL(void)
htest_one_block (j_compress_ptr cinfo, JCOEFPTR block, int last_dc_val,
long dc_counts[], long ac_counts[])
{
register int temp;
register int nbits;
register int k, r;
int Se = cinfo->lim_Se;
const int * natural_order = cinfo->natural_order;
/* Encode the DC coefficient difference per section F.1.2.1 */
temp = block[0] - last_dc_val;
if (temp < 0)
temp = -temp;
/* 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 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++;
} else {
/* if run length > 15, must emit special run-length-16 codes (0xF0) */
while (r > 15) {
ac_counts[0xF0]++;
r -= 16;
}
/* Find the number of bits needed for the magnitude of the coefficient */
if (temp < 0)
temp = -temp;
/* 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 Huffman symbol for run length / number of bits */
ac_counts[(r << 4) + nbits]++;
r = 0;
}
}
/* If the last coef(s) were zero, emit an end-of-block code */
if (r > 0)
ac_counts[0]++;
}
/*
* Trial-encode one MCU's worth of Huffman-compressed coefficients.
* No data is actually output, so no suspension return is possible.
*/
METHODDEF(boolean)
encode_mcu_gather (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
{
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;
}
/*
* Generate the best Huffman code table for the given counts, fill htbl.
*
* The JPEG standard requires that no symbol be assigned a codeword of all
* one bits (so that padding bits added at the end of a compressed segment
* can't look like a valid code). Because of the canonical ordering of
* codewords, this just means that there must be an unused slot in the
* longest codeword length category. Section K.2 of the JPEG spec suggests
* reserving such a slot by pretending that symbol 256 is a valid symbol
* with count 1. In theory that's not optimal; giving it count zero but
* including it in the symbol set anyway should give a better Huffman code.
* But the theoretically better code actually seems to come out worse in
* practice, because it produces more all-ones bytes (which incur stuffed
* zero bytes in the final file). In any case the difference is tiny.
*
* The JPEG standard requires Huffman codes to be no more than 16 bits long.
* If some symbols have a very small but nonzero probability, the Huffman tree
* must be adjusted to meet the code length restriction. We currently use
* the adjustment method suggested in JPEG section K.2. This method is *not*
* optimal; it may not choose the best possible limited-length code. But
* typically only very-low-frequency symbols will be given less-than-optimal
* lengths, so the code is almost optimal. Experimental comparisons against
* an optimal limited-length-code algorithm indicate that the difference is
* microscopic --- usually less than a hundredth of a percent of total size.
* So the extra complexity of an optimal algorithm doesn't seem worthwhile.
*/
LOCAL(void)
jpeg_gen_optimal_table (j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[])
{
#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;
int p, i, j;
long v;
/* 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 */
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.
*/
/* 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_OVERFLOW);
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)
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));
/* Return a list of the symbols sorted by code length */
/* It's not real clear to me why we don't need to consider the codelength
* changes made above, but the JPEG spec seems to think this works.
*/
p = 0;
for (i = 1; i <= MAX_CLEN; i++) {
for (j = 0; j <= 255; j++) {
if (codesize[j] == i) {
htbl->huffval[p] = (UINT8) j;
p++;
}
}
}
/* Set sent_table FALSE so updated table will be written to JPEG file. */
htbl->sent_table = FALSE;
}
/*
* Finish up a statistics-gathering pass and create the new Huffman tables.
*/
METHODDEF(void)
finish_pass_gather (j_compress_ptr cinfo)
{
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];
/* It's important not to apply jpeg_gen_optimal_table more than once
* per table, because it clobbers the input frequency counts!
*/
if (cinfo->progressive_mode)
/* Flush out buffered data (all we care about is counting the EOB symbol) */
emit_eobrun(entropy);
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;
}
}
}
}
/*
* Initialize for a Huffman-compressed scan.
* If gather_statistics is TRUE, we do not output anything during the scan,
* just count the Huffman symbols used and generate Huffman code tables.
*/
METHODDEF(void)
start_pass_huff (j_compress_ptr cinfo, boolean gather_statistics)
{
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;
}
/*
* Module initialization routine for Huffman entropy encoding.
*/
GLOBAL(void)
jinit_huff_encoder (j_compress_ptr cinfo)
{
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 = (struct jpeg_entropy_encoder *) entropy;
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 */
}
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