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387 lines
12 KiB
387 lines
12 KiB
/* |
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* jcdctmgr.c |
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* |
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* Copyright (C) 1994-1996, Thomas G. Lane. |
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* This file is part of the Independent JPEG Group's software. |
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* For conditions of distribution and use, see the accompanying README file. |
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* |
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* This file contains the forward-DCT management logic. |
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* This code selects a particular DCT implementation to be used, |
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* and it performs related housekeeping chores including coefficient |
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* quantization. |
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*/ |
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#define JPEG_INTERNALS |
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#include "jinclude.h" |
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#include "jpeglib.h" |
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#include "jdct.h" /* Private declarations for DCT subsystem */ |
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/* Private subobject for this module */ |
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typedef struct { |
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struct jpeg_forward_dct pub; /* public fields */ |
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/* Pointer to the DCT routine actually in use */ |
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forward_DCT_method_ptr do_dct; |
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/* The actual post-DCT divisors --- not identical to the quant table |
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* entries, because of scaling (especially for an unnormalized DCT). |
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* Each table is given in normal array order. |
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*/ |
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DCTELEM * divisors[NUM_QUANT_TBLS]; |
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#ifdef DCT_FLOAT_SUPPORTED |
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/* Same as above for the floating-point case. */ |
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float_DCT_method_ptr do_float_dct; |
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FAST_FLOAT * float_divisors[NUM_QUANT_TBLS]; |
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#endif |
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} my_fdct_controller; |
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typedef my_fdct_controller * my_fdct_ptr; |
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/* |
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* Initialize for a processing pass. |
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* Verify that all referenced Q-tables are present, and set up |
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* the divisor table for each one. |
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* In the current implementation, DCT of all components is done during |
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* the first pass, even if only some components will be output in the |
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* first scan. Hence all components should be examined here. |
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*/ |
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METHODDEF(void) |
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start_pass_fdctmgr (j_compress_ptr cinfo) |
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{ |
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my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct; |
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int ci, qtblno, i; |
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jpeg_component_info *compptr; |
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JQUANT_TBL * qtbl; |
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DCTELEM * dtbl; |
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for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
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ci++, compptr++) { |
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qtblno = compptr->quant_tbl_no; |
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/* Make sure specified quantization table is present */ |
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if (qtblno < 0 || qtblno >= NUM_QUANT_TBLS || |
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cinfo->quant_tbl_ptrs[qtblno] == NULL) |
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ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno); |
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qtbl = cinfo->quant_tbl_ptrs[qtblno]; |
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/* Compute divisors for this quant table */ |
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/* We may do this more than once for same table, but it's not a big deal */ |
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switch (cinfo->dct_method) { |
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#ifdef DCT_ISLOW_SUPPORTED |
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case JDCT_ISLOW: |
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/* For LL&M IDCT method, divisors are equal to raw quantization |
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* coefficients multiplied by 8 (to counteract scaling). |
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*/ |
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if (fdct->divisors[qtblno] == NULL) { |
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fdct->divisors[qtblno] = (DCTELEM *) |
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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DCTSIZE2 * SIZEOF(DCTELEM)); |
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} |
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dtbl = fdct->divisors[qtblno]; |
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for (i = 0; i < DCTSIZE2; i++) { |
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dtbl[i] = ((DCTELEM) qtbl->quantval[i]) << 3; |
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} |
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break; |
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#endif |
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#ifdef DCT_IFAST_SUPPORTED |
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case JDCT_IFAST: |
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{ |
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/* For AA&N IDCT method, divisors are equal to quantization |
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* coefficients scaled by scalefactor[row]*scalefactor[col], where |
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* scalefactor[0] = 1 |
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* scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7 |
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* We apply a further scale factor of 8. |
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*/ |
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#define CONST_BITS 14 |
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static const INT16 aanscales[DCTSIZE2] = { |
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/* precomputed values scaled up by 14 bits */ |
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16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520, |
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22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270, |
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21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906, |
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19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315, |
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16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520, |
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12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552, |
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8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446, |
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4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247 |
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}; |
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SHIFT_TEMPS |
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if (fdct->divisors[qtblno] == NULL) { |
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fdct->divisors[qtblno] = (DCTELEM *) |
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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DCTSIZE2 * SIZEOF(DCTELEM)); |
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} |
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dtbl = fdct->divisors[qtblno]; |
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for (i = 0; i < DCTSIZE2; i++) { |
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dtbl[i] = (DCTELEM) |
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DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i], |
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(INT32) aanscales[i]), |
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CONST_BITS-3); |
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} |
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} |
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break; |
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#endif |
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#ifdef DCT_FLOAT_SUPPORTED |
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case JDCT_FLOAT: |
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{ |
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/* For float AA&N IDCT method, divisors are equal to quantization |
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* coefficients scaled by scalefactor[row]*scalefactor[col], where |
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* scalefactor[0] = 1 |
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* scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7 |
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* We apply a further scale factor of 8. |
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* What's actually stored is 1/divisor so that the inner loop can |
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* use a multiplication rather than a division. |
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*/ |
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FAST_FLOAT * fdtbl; |
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int row, col; |
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static const double aanscalefactor[DCTSIZE] = { |
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1.0, 1.387039845, 1.306562965, 1.175875602, |
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1.0, 0.785694958, 0.541196100, 0.275899379 |
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}; |
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if (fdct->float_divisors[qtblno] == NULL) { |
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fdct->float_divisors[qtblno] = (FAST_FLOAT *) |
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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DCTSIZE2 * SIZEOF(FAST_FLOAT)); |
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} |
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fdtbl = fdct->float_divisors[qtblno]; |
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i = 0; |
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for (row = 0; row < DCTSIZE; row++) { |
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for (col = 0; col < DCTSIZE; col++) { |
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fdtbl[i] = (FAST_FLOAT) |
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(1.0 / (((double) qtbl->quantval[i] * |
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aanscalefactor[row] * aanscalefactor[col] * 8.0))); |
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i++; |
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} |
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} |
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} |
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break; |
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#endif |
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default: |
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ERREXIT(cinfo, JERR_NOT_COMPILED); |
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break; |
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} |
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} |
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} |
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/* |
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* Perform forward DCT on one or more blocks of a component. |
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* |
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* The input samples are taken from the sample_data[] array starting at |
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* position start_row/start_col, and moving to the right for any additional |
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* blocks. The quantized coefficients are returned in coef_blocks[]. |
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*/ |
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METHODDEF(void) |
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forward_DCT (j_compress_ptr cinfo, jpeg_component_info * compptr, |
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JSAMPARRAY sample_data, JBLOCKROW coef_blocks, |
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JDIMENSION start_row, JDIMENSION start_col, |
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JDIMENSION num_blocks) |
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/* This version is used for integer DCT implementations. */ |
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{ |
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/* This routine is heavily used, so it's worth coding it tightly. */ |
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my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct; |
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forward_DCT_method_ptr do_dct = fdct->do_dct; |
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DCTELEM * divisors = fdct->divisors[compptr->quant_tbl_no]; |
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DCTELEM workspace[DCTSIZE2]; /* work area for FDCT subroutine */ |
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JDIMENSION bi; |
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sample_data += start_row; /* fold in the vertical offset once */ |
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for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) { |
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/* Load data into workspace, applying unsigned->signed conversion */ |
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{ register DCTELEM *workspaceptr; |
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register JSAMPROW elemptr; |
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register int elemr; |
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workspaceptr = workspace; |
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for (elemr = 0; elemr < DCTSIZE; elemr++) { |
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elemptr = sample_data[elemr] + start_col; |
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#if DCTSIZE == 8 /* unroll the inner loop */ |
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*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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#else |
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{ register int elemc; |
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for (elemc = DCTSIZE; elemc > 0; elemc--) { |
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*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |
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} |
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} |
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#endif |
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} |
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} |
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/* Perform the DCT */ |
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(*do_dct) (workspace); |
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/* Quantize/descale the coefficients, and store into coef_blocks[] */ |
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{ register DCTELEM temp, qval; |
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register int i; |
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register JCOEFPTR output_ptr = coef_blocks[bi]; |
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for (i = 0; i < DCTSIZE2; i++) { |
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qval = divisors[i]; |
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temp = workspace[i]; |
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/* Divide the coefficient value by qval, ensuring proper rounding. |
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* Since C does not specify the direction of rounding for negative |
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* quotients, we have to force the dividend positive for portability. |
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* |
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* In most files, at least half of the output values will be zero |
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* (at default quantization settings, more like three-quarters...) |
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* so we should ensure that this case is fast. On many machines, |
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* a comparison is enough cheaper than a divide to make a special test |
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* a win. Since both inputs will be nonnegative, we need only test |
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* for a < b to discover whether a/b is 0. |
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* If your machine's division is fast enough, define FAST_DIVIDE. |
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*/ |
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#ifdef FAST_DIVIDE |
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#define DIVIDE_BY(a,b) a /= b |
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#else |
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#define DIVIDE_BY(a,b) if (a >= b) a /= b; else a = 0 |
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#endif |
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if (temp < 0) { |
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temp = -temp; |
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temp += qval>>1; /* for rounding */ |
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DIVIDE_BY(temp, qval); |
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temp = -temp; |
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} else { |
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temp += qval>>1; /* for rounding */ |
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DIVIDE_BY(temp, qval); |
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} |
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output_ptr[i] = (JCOEF) temp; |
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} |
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} |
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} |
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} |
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#ifdef DCT_FLOAT_SUPPORTED |
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METHODDEF(void) |
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forward_DCT_float (j_compress_ptr cinfo, jpeg_component_info * compptr, |
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JSAMPARRAY sample_data, JBLOCKROW coef_blocks, |
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JDIMENSION start_row, JDIMENSION start_col, |
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JDIMENSION num_blocks) |
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/* This version is used for floating-point DCT implementations. */ |
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{ |
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/* This routine is heavily used, so it's worth coding it tightly. */ |
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my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct; |
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float_DCT_method_ptr do_dct = fdct->do_float_dct; |
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FAST_FLOAT * divisors = fdct->float_divisors[compptr->quant_tbl_no]; |
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FAST_FLOAT workspace[DCTSIZE2]; /* work area for FDCT subroutine */ |
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JDIMENSION bi; |
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sample_data += start_row; /* fold in the vertical offset once */ |
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for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) { |
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/* Load data into workspace, applying unsigned->signed conversion */ |
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{ register FAST_FLOAT *workspaceptr; |
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register JSAMPROW elemptr; |
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register int elemr; |
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workspaceptr = workspace; |
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for (elemr = 0; elemr < DCTSIZE; elemr++) { |
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elemptr = sample_data[elemr] + start_col; |
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#if DCTSIZE == 8 /* unroll the inner loop */ |
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*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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*workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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#else |
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{ register int elemc; |
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for (elemc = DCTSIZE; elemc > 0; elemc--) { |
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*workspaceptr++ = (FAST_FLOAT) |
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(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |
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} |
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} |
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#endif |
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} |
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} |
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/* Perform the DCT */ |
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(*do_dct) (workspace); |
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/* Quantize/descale the coefficients, and store into coef_blocks[] */ |
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{ register FAST_FLOAT temp; |
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register int i; |
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register JCOEFPTR output_ptr = coef_blocks[bi]; |
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for (i = 0; i < DCTSIZE2; i++) { |
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/* Apply the quantization and scaling factor */ |
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temp = workspace[i] * divisors[i]; |
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/* Round to nearest integer. |
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* Since C does not specify the direction of rounding for negative |
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* quotients, we have to force the dividend positive for portability. |
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* The maximum coefficient size is +-16K (for 12-bit data), so this |
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* code should work for either 16-bit or 32-bit ints. |
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*/ |
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output_ptr[i] = (JCOEF) ((int) (temp + (FAST_FLOAT) 16384.5) - 16384); |
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} |
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} |
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} |
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} |
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#endif /* DCT_FLOAT_SUPPORTED */ |
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/* |
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* Initialize FDCT manager. |
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*/ |
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GLOBAL(void) |
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jinit_forward_dct (j_compress_ptr cinfo) |
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{ |
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my_fdct_ptr fdct; |
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int i; |
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fdct = (my_fdct_ptr) |
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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SIZEOF(my_fdct_controller)); |
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cinfo->fdct = (struct jpeg_forward_dct *) fdct; |
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fdct->pub.start_pass = start_pass_fdctmgr; |
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switch (cinfo->dct_method) { |
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#ifdef DCT_ISLOW_SUPPORTED |
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case JDCT_ISLOW: |
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fdct->pub.forward_DCT = forward_DCT; |
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fdct->do_dct = jpeg_fdct_islow; |
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break; |
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#endif |
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#ifdef DCT_IFAST_SUPPORTED |
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case JDCT_IFAST: |
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fdct->pub.forward_DCT = forward_DCT; |
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fdct->do_dct = jpeg_fdct_ifast; |
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break; |
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#endif |
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#ifdef DCT_FLOAT_SUPPORTED |
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case JDCT_FLOAT: |
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fdct->pub.forward_DCT = forward_DCT_float; |
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fdct->do_float_dct = jpeg_fdct_float; |
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break; |
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#endif |
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default: |
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ERREXIT(cinfo, JERR_NOT_COMPILED); |
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break; |
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} |
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/* Mark divisor tables unallocated */ |
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for (i = 0; i < NUM_QUANT_TBLS; i++) { |
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fdct->divisors[i] = NULL; |
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#ifdef DCT_FLOAT_SUPPORTED |
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fdct->float_divisors[i] = NULL; |
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#endif |
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} |
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}
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