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gecko-dev/media/libjpeg/jcdctmgr.c

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C
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/*
* jcdctmgr.c
*
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1994-1996, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright (C) 1999-2006, MIYASAKA Masaru.
* Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
* Copyright (C) 2011, 2014-2015, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
*
* This file contains the forward-DCT management logic.
* This code selects a particular DCT implementation to be used,
* and it performs related housekeeping chores including coefficient
* quantization.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h" /* Private declarations for DCT subsystem */
#include "jsimddct.h"
/* Private subobject for this module */
typedef void (*forward_DCT_method_ptr) (DCTELEM *data);
typedef void (*float_DCT_method_ptr) (FAST_FLOAT *data);
typedef void (*convsamp_method_ptr) (JSAMPARRAY sample_data,
JDIMENSION start_col,
DCTELEM *workspace);
typedef void (*float_convsamp_method_ptr) (JSAMPARRAY sample_data,
JDIMENSION start_col,
FAST_FLOAT *workspace);
typedef void (*quantize_method_ptr) (JCOEFPTR coef_block, DCTELEM *divisors,
DCTELEM *workspace);
typedef void (*float_quantize_method_ptr) (JCOEFPTR coef_block,
FAST_FLOAT *divisors,
FAST_FLOAT *workspace);
METHODDEF(void) quantize(JCOEFPTR, DCTELEM *, DCTELEM *);
typedef struct {
struct jpeg_forward_dct pub; /* public fields */
/* Pointer to the DCT routine actually in use */
forward_DCT_method_ptr dct;
convsamp_method_ptr convsamp;
quantize_method_ptr quantize;
/* The actual post-DCT divisors --- not identical to the quant table
* entries, because of scaling (especially for an unnormalized DCT).
* Each table is given in normal array order.
*/
DCTELEM *divisors[NUM_QUANT_TBLS];
/* work area for FDCT subroutine */
DCTELEM *workspace;
#ifdef DCT_FLOAT_SUPPORTED
/* Same as above for the floating-point case. */
float_DCT_method_ptr float_dct;
float_convsamp_method_ptr float_convsamp;
float_quantize_method_ptr float_quantize;
FAST_FLOAT *float_divisors[NUM_QUANT_TBLS];
FAST_FLOAT *float_workspace;
#endif
} my_fdct_controller;
typedef my_fdct_controller *my_fdct_ptr;
#if BITS_IN_JSAMPLE == 8
/*
* Find the highest bit in an integer through binary search.
*/
LOCAL(int)
flss(UINT16 val)
{
int bit;
bit = 16;
if (!val)
return 0;
if (!(val & 0xff00)) {
bit -= 8;
val <<= 8;
}
if (!(val & 0xf000)) {
bit -= 4;
val <<= 4;
}
if (!(val & 0xc000)) {
bit -= 2;
val <<= 2;
}
if (!(val & 0x8000)) {
bit -= 1;
val <<= 1;
}
return bit;
}
/*
* Compute values to do a division using reciprocal.
*
* This implementation is based on an algorithm described in
* "How to optimize for the Pentium family of microprocessors"
* (http://www.agner.org/assem/).
* More information about the basic algorithm can be found in
* the paper "Integer Division Using Reciprocals" by Robert Alverson.
*
* The basic idea is to replace x/d by x * d^-1. In order to store
* d^-1 with enough precision we shift it left a few places. It turns
* out that this algoright gives just enough precision, and also fits
* into DCTELEM:
*
* b = (the number of significant bits in divisor) - 1
* r = (word size) + b
* f = 2^r / divisor
*
* f will not be an integer for most cases, so we need to compensate
* for the rounding error introduced:
*
* no fractional part:
*
* result = input >> r
*
* fractional part of f < 0.5:
*
* round f down to nearest integer
* result = ((input + 1) * f) >> r
*
* fractional part of f > 0.5:
*
* round f up to nearest integer
* result = (input * f) >> r
*
* This is the original algorithm that gives truncated results. But we
* want properly rounded results, so we replace "input" with
* "input + divisor/2".
*
* In order to allow SIMD implementations we also tweak the values to
* allow the same calculation to be made at all times:
*
* dctbl[0] = f rounded to nearest integer
* dctbl[1] = divisor / 2 (+ 1 if fractional part of f < 0.5)
* dctbl[2] = 1 << ((word size) * 2 - r)
* dctbl[3] = r - (word size)
*
* dctbl[2] is for stupid instruction sets where the shift operation
* isn't member wise (e.g. MMX).
*
* The reason dctbl[2] and dctbl[3] reduce the shift with (word size)
* is that most SIMD implementations have a "multiply and store top
* half" operation.
*
* Lastly, we store each of the values in their own table instead
* of in a consecutive manner, yet again in order to allow SIMD
* routines.
*/
LOCAL(int)
compute_reciprocal(UINT16 divisor, DCTELEM *dtbl)
{
UDCTELEM2 fq, fr;
UDCTELEM c;
int b, r;
if (divisor == 1) {
/* divisor == 1 means unquantized, so these reciprocal/correction/shift
* values will cause the C quantization algorithm to act like the
* identity function. Since only the C quantization algorithm is used in
* these cases, the scale value is irrelevant.
*/
dtbl[DCTSIZE2 * 0] = (DCTELEM)1; /* reciprocal */
dtbl[DCTSIZE2 * 1] = (DCTELEM)0; /* correction */
dtbl[DCTSIZE2 * 2] = (DCTELEM)1; /* scale */
dtbl[DCTSIZE2 * 3] = -(DCTELEM)(sizeof(DCTELEM) * 8); /* shift */
return 0;
}
b = flss(divisor) - 1;
r = sizeof(DCTELEM) * 8 + b;
fq = ((UDCTELEM2)1 << r) / divisor;
fr = ((UDCTELEM2)1 << r) % divisor;
c = divisor / 2; /* for rounding */
if (fr == 0) { /* divisor is power of two */
/* fq will be one bit too large to fit in DCTELEM, so adjust */
fq >>= 1;
r--;
} else if (fr <= (divisor / 2U)) { /* fractional part is < 0.5 */
c++;
} else { /* fractional part is > 0.5 */
fq++;
}
dtbl[DCTSIZE2 * 0] = (DCTELEM)fq; /* reciprocal */
dtbl[DCTSIZE2 * 1] = (DCTELEM)c; /* correction + roundfactor */
#ifdef WITH_SIMD
dtbl[DCTSIZE2 * 2] = (DCTELEM)(1 << (sizeof(DCTELEM) * 8 * 2 - r)); /* scale */
#else
dtbl[DCTSIZE2 * 2] = 1;
#endif
dtbl[DCTSIZE2 * 3] = (DCTELEM)r - sizeof(DCTELEM) * 8; /* shift */
if (r <= 16) return 0;
else return 1;
}
#endif
/*
* Initialize for a processing pass.
* Verify that all referenced Q-tables are present, and set up
* the divisor table for each one.
* In the current implementation, DCT of all components is done during
* the first pass, even if only some components will be output in the
* first scan. Hence all components should be examined here.
*/
METHODDEF(void)
start_pass_fdctmgr(j_compress_ptr cinfo)
{
my_fdct_ptr fdct = (my_fdct_ptr)cinfo->fdct;
int ci, qtblno, i;
jpeg_component_info *compptr;
JQUANT_TBL *qtbl;
DCTELEM *dtbl;
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
ci++, compptr++) {
qtblno = compptr->quant_tbl_no;
/* Make sure specified quantization table is present */
if (qtblno < 0 || qtblno >= NUM_QUANT_TBLS ||
cinfo->quant_tbl_ptrs[qtblno] == NULL)
ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno);
qtbl = cinfo->quant_tbl_ptrs[qtblno];
/* Compute divisors for this quant table */
/* We may do this more than once for same table, but it's not a big deal */
switch (cinfo->dct_method) {
#ifdef DCT_ISLOW_SUPPORTED
case JDCT_ISLOW:
/* For LL&M IDCT method, divisors are equal to raw quantization
* coefficients multiplied by 8 (to counteract scaling).
*/
if (fdct->divisors[qtblno] == NULL) {
fdct->divisors[qtblno] = (DCTELEM *)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
(DCTSIZE2 * 4) * sizeof(DCTELEM));
}
dtbl = fdct->divisors[qtblno];
for (i = 0; i < DCTSIZE2; i++) {
#if BITS_IN_JSAMPLE == 8
if (!compute_reciprocal(qtbl->quantval[i] << 3, &dtbl[i]) &&
fdct->quantize == jsimd_quantize)
fdct->quantize = quantize;
#else
dtbl[i] = ((DCTELEM)qtbl->quantval[i]) << 3;
#endif
}
break;
#endif
#ifdef DCT_IFAST_SUPPORTED
case JDCT_IFAST:
{
/* For AA&N IDCT method, divisors are equal to quantization
* coefficients scaled by scalefactor[row]*scalefactor[col], where
* scalefactor[0] = 1
* scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
* We apply a further scale factor of 8.
*/
#define CONST_BITS 14
static const INT16 aanscales[DCTSIZE2] = {
/* precomputed values scaled up by 14 bits */
16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270,
21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906,
19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315,
16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552,
8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446,
4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247
};
SHIFT_TEMPS
if (fdct->divisors[qtblno] == NULL) {
fdct->divisors[qtblno] = (DCTELEM *)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
(DCTSIZE2 * 4) * sizeof(DCTELEM));
}
dtbl = fdct->divisors[qtblno];
for (i = 0; i < DCTSIZE2; i++) {
#if BITS_IN_JSAMPLE == 8
if (!compute_reciprocal(
DESCALE(MULTIPLY16V16((JLONG)qtbl->quantval[i],
(JLONG)aanscales[i]),
CONST_BITS - 3), &dtbl[i]) &&
fdct->quantize == jsimd_quantize)
fdct->quantize = quantize;
#else
dtbl[i] = (DCTELEM)
DESCALE(MULTIPLY16V16((JLONG)qtbl->quantval[i],
(JLONG)aanscales[i]),
CONST_BITS - 3);
#endif
}
}
break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
case JDCT_FLOAT:
{
/* For float AA&N IDCT method, divisors are equal to quantization
* coefficients scaled by scalefactor[row]*scalefactor[col], where
* scalefactor[0] = 1
* scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
* We apply a further scale factor of 8.
* What's actually stored is 1/divisor so that the inner loop can
* use a multiplication rather than a division.
*/
FAST_FLOAT *fdtbl;
int row, col;
static const double aanscalefactor[DCTSIZE] = {
1.0, 1.387039845, 1.306562965, 1.175875602,
1.0, 0.785694958, 0.541196100, 0.275899379
};
if (fdct->float_divisors[qtblno] == NULL) {
fdct->float_divisors[qtblno] = (FAST_FLOAT *)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
DCTSIZE2 * sizeof(FAST_FLOAT));
}
fdtbl = fdct->float_divisors[qtblno];
i = 0;
for (row = 0; row < DCTSIZE; row++) {
for (col = 0; col < DCTSIZE; col++) {
fdtbl[i] = (FAST_FLOAT)
(1.0 / (((double)qtbl->quantval[i] *
aanscalefactor[row] * aanscalefactor[col] * 8.0)));
i++;
}
}
}
break;
#endif
default:
ERREXIT(cinfo, JERR_NOT_COMPILED);
break;
}
}
}
/*
* Load data into workspace, applying unsigned->signed conversion.
*/
METHODDEF(void)
convsamp(JSAMPARRAY sample_data, JDIMENSION start_col, DCTELEM *workspace)
{
register DCTELEM *workspaceptr;
register JSAMPROW elemptr;
register int elemr;
workspaceptr = workspace;
for (elemr = 0; elemr < DCTSIZE; elemr++) {
elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8 /* unroll the inner loop */
*workspaceptr++ = (*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = (*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = (*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = (*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = (*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = (*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = (*elemptr++) - CENTERJSAMPLE;
*workspaceptr++ = (*elemptr++) - CENTERJSAMPLE;
#else
{
register int elemc;
for (elemc = DCTSIZE; elemc > 0; elemc--)
*workspaceptr++ = (*elemptr++) - CENTERJSAMPLE;
}
#endif
}
}
/*
* Quantize/descale the coefficients, and store into coef_blocks[].
*/
METHODDEF(void)
quantize(JCOEFPTR coef_block, DCTELEM *divisors, DCTELEM *workspace)
{
int i;
DCTELEM temp;
JCOEFPTR output_ptr = coef_block;
#if BITS_IN_JSAMPLE == 8
UDCTELEM recip, corr;
int shift;
UDCTELEM2 product;
for (i = 0; i < DCTSIZE2; i++) {
temp = workspace[i];
recip = divisors[i + DCTSIZE2 * 0];
corr = divisors[i + DCTSIZE2 * 1];
shift = divisors[i + DCTSIZE2 * 3];
if (temp < 0) {
temp = -temp;
product = (UDCTELEM2)(temp + corr) * recip;
product >>= shift + sizeof(DCTELEM) * 8;
temp = (DCTELEM)product;
temp = -temp;
} else {
product = (UDCTELEM2)(temp + corr) * recip;
product >>= shift + sizeof(DCTELEM) * 8;
temp = (DCTELEM)product;
}
output_ptr[i] = (JCOEF)temp;
}
#else
register DCTELEM qval;
for (i = 0; i < DCTSIZE2; i++) {
qval = divisors[i];
temp = workspace[i];
/* Divide the coefficient value by qval, ensuring proper rounding.
* Since C does not specify the direction of rounding for negative
* quotients, we have to force the dividend positive for portability.
*
* In most files, at least half of the output values will be zero
* (at default quantization settings, more like three-quarters...)
* so we should ensure that this case is fast. On many machines,
* a comparison is enough cheaper than a divide to make a special test
* a win. Since both inputs will be nonnegative, we need only test
* for a < b to discover whether a/b is 0.
* If your machine's division is fast enough, define FAST_DIVIDE.
*/
#ifdef FAST_DIVIDE
#define DIVIDE_BY(a, b) a /= b
#else
#define DIVIDE_BY(a, b) if (a >= b) a /= b; else a = 0
#endif
if (temp < 0) {
temp = -temp;
temp += qval >> 1; /* for rounding */
DIVIDE_BY(temp, qval);
temp = -temp;
} else {
temp += qval >> 1; /* for rounding */
DIVIDE_BY(temp, qval);
}
output_ptr[i] = (JCOEF)temp;
}
#endif
}
/*
* Perform forward DCT on one or more blocks of a component.
*
* The input samples are taken from the sample_data[] array starting at
* position start_row/start_col, and moving to the right for any additional
* blocks. The quantized coefficients are returned in coef_blocks[].
*/
METHODDEF(void)
forward_DCT(j_compress_ptr cinfo, jpeg_component_info *compptr,
JSAMPARRAY sample_data, JBLOCKROW coef_blocks,
JDIMENSION start_row, JDIMENSION start_col, JDIMENSION num_blocks)
/* This version is used for integer DCT implementations. */
{
/* This routine is heavily used, so it's worth coding it tightly. */
my_fdct_ptr fdct = (my_fdct_ptr)cinfo->fdct;
DCTELEM *divisors = fdct->divisors[compptr->quant_tbl_no];
DCTELEM *workspace;
JDIMENSION bi;
/* Make sure the compiler doesn't look up these every pass */
forward_DCT_method_ptr do_dct = fdct->dct;
convsamp_method_ptr do_convsamp = fdct->convsamp;
quantize_method_ptr do_quantize = fdct->quantize;
workspace = fdct->workspace;
sample_data += start_row; /* fold in the vertical offset once */
for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) {
/* Load data into workspace, applying unsigned->signed conversion */
(*do_convsamp) (sample_data, start_col, workspace);
/* Perform the DCT */
(*do_dct) (workspace);
/* Quantize/descale the coefficients, and store into coef_blocks[] */
(*do_quantize) (coef_blocks[bi], divisors, workspace);
}
}
#ifdef DCT_FLOAT_SUPPORTED
METHODDEF(void)
convsamp_float(JSAMPARRAY sample_data, JDIMENSION start_col,
FAST_FLOAT *workspace)
{
register FAST_FLOAT *workspaceptr;
register JSAMPROW elemptr;
register int elemr;
workspaceptr = workspace;
for (elemr = 0; elemr < DCTSIZE; elemr++) {
elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8 /* unroll the inner loop */
*workspaceptr++ = (FAST_FLOAT)((*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)((*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)((*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)((*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)((*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)((*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)((*elemptr++) - CENTERJSAMPLE);
*workspaceptr++ = (FAST_FLOAT)((*elemptr++) - CENTERJSAMPLE);
#else
{
register int elemc;
for (elemc = DCTSIZE; elemc > 0; elemc--)
*workspaceptr++ = (FAST_FLOAT)((*elemptr++) - CENTERJSAMPLE);
}
#endif
}
}
METHODDEF(void)
quantize_float(JCOEFPTR coef_block, FAST_FLOAT *divisors,
FAST_FLOAT *workspace)
{
register FAST_FLOAT temp;
register int i;
register JCOEFPTR output_ptr = coef_block;
for (i = 0; i < DCTSIZE2; i++) {
/* Apply the quantization and scaling factor */
temp = workspace[i] * divisors[i];
/* Round to nearest integer.
* Since C does not specify the direction of rounding for negative
* quotients, we have to force the dividend positive for portability.
* The maximum coefficient size is +-16K (for 12-bit data), so this
* code should work for either 16-bit or 32-bit ints.
*/
output_ptr[i] = (JCOEF)((int)(temp + (FAST_FLOAT)16384.5) - 16384);
}
}
METHODDEF(void)
forward_DCT_float(j_compress_ptr cinfo, jpeg_component_info *compptr,
JSAMPARRAY sample_data, JBLOCKROW coef_blocks,
JDIMENSION start_row, JDIMENSION start_col,
JDIMENSION num_blocks)
/* This version is used for floating-point DCT implementations. */
{
/* This routine is heavily used, so it's worth coding it tightly. */
my_fdct_ptr fdct = (my_fdct_ptr)cinfo->fdct;
FAST_FLOAT *divisors = fdct->float_divisors[compptr->quant_tbl_no];
FAST_FLOAT *workspace;
JDIMENSION bi;
/* Make sure the compiler doesn't look up these every pass */
float_DCT_method_ptr do_dct = fdct->float_dct;
float_convsamp_method_ptr do_convsamp = fdct->float_convsamp;
float_quantize_method_ptr do_quantize = fdct->float_quantize;
workspace = fdct->float_workspace;
sample_data += start_row; /* fold in the vertical offset once */
for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) {
/* Load data into workspace, applying unsigned->signed conversion */
(*do_convsamp) (sample_data, start_col, workspace);
/* Perform the DCT */
(*do_dct) (workspace);
/* Quantize/descale the coefficients, and store into coef_blocks[] */
(*do_quantize) (coef_blocks[bi], divisors, workspace);
}
}
#endif /* DCT_FLOAT_SUPPORTED */
/*
* Initialize FDCT manager.
*/
GLOBAL(void)
jinit_forward_dct(j_compress_ptr cinfo)
{
my_fdct_ptr fdct;
int i;
fdct = (my_fdct_ptr)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
sizeof(my_fdct_controller));
cinfo->fdct = (struct jpeg_forward_dct *)fdct;
fdct->pub.start_pass = start_pass_fdctmgr;
/* First determine the DCT... */
switch (cinfo->dct_method) {
#ifdef DCT_ISLOW_SUPPORTED
case JDCT_ISLOW:
fdct->pub.forward_DCT = forward_DCT;
if (jsimd_can_fdct_islow())
fdct->dct = jsimd_fdct_islow;
else
fdct->dct = jpeg_fdct_islow;
break;
#endif
#ifdef DCT_IFAST_SUPPORTED
case JDCT_IFAST:
fdct->pub.forward_DCT = forward_DCT;
if (jsimd_can_fdct_ifast())
fdct->dct = jsimd_fdct_ifast;
else
fdct->dct = jpeg_fdct_ifast;
break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
case JDCT_FLOAT:
fdct->pub.forward_DCT = forward_DCT_float;
if (jsimd_can_fdct_float())
fdct->float_dct = jsimd_fdct_float;
else
fdct->float_dct = jpeg_fdct_float;
break;
#endif
default:
ERREXIT(cinfo, JERR_NOT_COMPILED);
break;
}
/* ...then the supporting stages. */
switch (cinfo->dct_method) {
#ifdef DCT_ISLOW_SUPPORTED
case JDCT_ISLOW:
#endif
#ifdef DCT_IFAST_SUPPORTED
case JDCT_IFAST:
#endif
#if defined(DCT_ISLOW_SUPPORTED) || defined(DCT_IFAST_SUPPORTED)
if (jsimd_can_convsamp())
fdct->convsamp = jsimd_convsamp;
else
fdct->convsamp = convsamp;
if (jsimd_can_quantize())
fdct->quantize = jsimd_quantize;
else
fdct->quantize = quantize;
break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
case JDCT_FLOAT:
if (jsimd_can_convsamp_float())
fdct->float_convsamp = jsimd_convsamp_float;
else
fdct->float_convsamp = convsamp_float;
if (jsimd_can_quantize_float())
fdct->float_quantize = jsimd_quantize_float;
else
fdct->float_quantize = quantize_float;
break;
#endif
default:
ERREXIT(cinfo, JERR_NOT_COMPILED);
break;
}
/* Allocate workspace memory */
#ifdef DCT_FLOAT_SUPPORTED
if (cinfo->dct_method == JDCT_FLOAT)
fdct->float_workspace = (FAST_FLOAT *)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
sizeof(FAST_FLOAT) * DCTSIZE2);
else
#endif
fdct->workspace = (DCTELEM *)
(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
sizeof(DCTELEM) * DCTSIZE2);
/* Mark divisor tables unallocated */
for (i = 0; i < NUM_QUANT_TBLS; i++) {
fdct->divisors[i] = NULL;
#ifdef DCT_FLOAT_SUPPORTED
fdct->float_divisors[i] = NULL;
#endif
}
}
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