The Tor Browser: media/libjpeg/jcdctmgr.c@6474c204b198 (annotated)

media/libjpeg/jcdctmgr.c@6474c204b198 (annotated)

media/libjpeg/jcdctmgr.c

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /*
  * 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 D. R. Commander
  * For conditions of distribution and use, see the accompanying README 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 JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data));
 typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data));
 typedef JMETHOD(void, convsamp_method_ptr,
                 (JSAMPARRAY sample_data, JDIMENSION start_col,
                  DCTELEM * workspace));
 typedef JMETHOD(void, float_convsamp_method_ptr,
                 (JSAMPARRAY sample_data, JDIMENSION start_col,
                  FAST_FLOAT *workspace));
 typedef JMETHOD(void, quantize_method_ptr,
                 (JCOEFPTR coef_block, DCTELEM * divisors,
                  DCTELEM * workspace));
 typedef JMETHOD(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;
 /*
  * 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;
   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 */
   dtbl[DCTSIZE2 * 2] = (DCTELEM) (1 << (sizeof(DCTELEM)*8*2 - r));  /* scale */
   dtbl[DCTSIZE2 * 3] = (DCTELEM) r - sizeof(DCTELEM)*8; /* shift */
   if(r <= 16) return 0;
   else return 1;
 }
 /*
  * 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(!compute_reciprocal(qtbl->quantval[i] << 3, &dtbl[i])
 	  && fdct->quantize == jsimd_quantize)
 	  fdct->quantize = quantize;
       }
       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 */
 , 22725, 21407, 19266, 16384, 12873,  8867,  4520,
 , 31521, 29692, 26722, 22725, 17855, 12299,  6270,
 , 29692, 27969, 25172, 21407, 16819, 11585,  5906,
 , 26722, 25172, 22654, 19266, 15137, 10426,  5315,
 , 22725, 21407, 19266, 16384, 12873,  8867,  4520,
 , 17855, 16819, 15137, 12873, 10114,  6967,  3552,
 , 12299, 11585, 10426,  8867,  6967,  4799,  2446,
 ,  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(!compute_reciprocal(
 	    DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
 				  (INT32) aanscales[i]),
 		    CONST_BITS-3), &dtbl[i])
 	    && fdct->quantize == jsimd_quantize)
 	    fdct->quantize = quantize;
 	}
       }
       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] = {
 .0, 1.387039845, 1.306562965, 1.175875602,
 .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++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
     *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
     *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
     *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
     *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
     *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
     *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
     *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
 #else
     {
       register int elemc;
       for (elemc = DCTSIZE; elemc > 0; elemc--)
         *workspaceptr++ = GETJSAMPLE(*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;
   UDCTELEM recip, corr, shift;
   UDCTELEM2 product;
   JCOEFPTR output_ptr = coef_block;
   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 = product;
       temp = -temp;
     } else {
       product = (UDCTELEM2)(temp + corr) * recip;
       product >>= shift + sizeof(DCTELEM)*8;
       temp = product;
     }
     output_ptr[i] = (JCOEF) temp;
   }
 }
 /*
  * 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)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
     *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
     *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
     *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
     *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
     *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
     *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
     *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
 #else
     {
       register int elemc;
       for (elemc = DCTSIZE; elemc > 0; elemc--)
         *workspaceptr++ = (FAST_FLOAT)
                           (GETJSAMPLE(*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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media/libjpeg/jcdctmgr.c@6474c204b198 (annotated)

media/libjpeg/jcdctmgr.c