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229 lines
6.1 KiB
C
229 lines
6.1 KiB
C
/*____________________________________________________________________________
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FreeAmp - The Free MP3 Player
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MP3 Decoder originally Copyright (C) 1995-1997 Xing Technology
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Corp. http://www.xingtech.com
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Portions Copyright (C) 1998-1999 EMusic.com
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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$Id: mdct.c,v 1.4 1999/10/19 07:13:09 elrod Exp $
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____________________________________________________________________________*/
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/**** mdct.c ***************************************************
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Layer III
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cos transform for n=18, n=6
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computes c[k] = Sum( cos((pi/4*n)*(2*k+1)*(2*p+1))*f[p] )
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k = 0, ...n-1, p = 0...n-1
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inplace ok.
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******************************************************************/
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#include <stdlib.h>
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#include <stdio.h>
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#include <float.h>
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#include <math.h>
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/*------ 18 point xform -------*/
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float mdct18w[18]; // effectively constant
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float mdct18w2[9]; // " "
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float coef[9][4]; // " "
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float mdct6_3v[6]; // " "
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float mdct6_3v2[3]; // " "
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float coef87; // " "
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typedef struct
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{
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float *w;
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float *w2;
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void *coef;
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}
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IMDCT_INIT_BLOCK;
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static const IMDCT_INIT_BLOCK imdct_info_18 =
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{mdct18w, mdct18w2, coef};
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static const IMDCT_INIT_BLOCK imdct_info_6 =
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{mdct6_3v, mdct6_3v2, &coef87};
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/*====================================================================*/
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const IMDCT_INIT_BLOCK *imdct_init_addr_18()
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{
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return &imdct_info_18;
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}
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const IMDCT_INIT_BLOCK *imdct_init_addr_6()
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{
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return &imdct_info_6;
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}
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/*--------------------------------------------------------------------*/
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void imdct18(float f[18]) /* 18 point */
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{
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int p;
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float a[9], b[9];
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float ap, bp, a8p, b8p;
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float g1, g2;
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for (p = 0; p < 4; p++)
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{
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g1 = mdct18w[p] * f[p];
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g2 = mdct18w[17 - p] * f[17 - p];
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ap = g1 + g2; // a[p]
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bp = mdct18w2[p] * (g1 - g2); // b[p]
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g1 = mdct18w[8 - p] * f[8 - p];
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g2 = mdct18w[9 + p] * f[9 + p];
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a8p = g1 + g2; // a[8-p]
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b8p = mdct18w2[8 - p] * (g1 - g2); // b[8-p]
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a[p] = ap + a8p;
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a[5 + p] = ap - a8p;
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b[p] = bp + b8p;
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b[5 + p] = bp - b8p;
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}
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g1 = mdct18w[p] * f[p];
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g2 = mdct18w[17 - p] * f[17 - p];
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a[p] = g1 + g2;
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b[p] = mdct18w2[p] * (g1 - g2);
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f[0] = 0.5f * (a[0] + a[1] + a[2] + a[3] + a[4]);
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f[1] = 0.5f * (b[0] + b[1] + b[2] + b[3] + b[4]);
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f[2] = coef[1][0] * a[5] + coef[1][1] * a[6] + coef[1][2] * a[7]
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+ coef[1][3] * a[8];
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f[3] = coef[1][0] * b[5] + coef[1][1] * b[6] + coef[1][2] * b[7]
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+ coef[1][3] * b[8] - f[1];
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f[1] = f[1] - f[0];
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f[2] = f[2] - f[1];
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f[4] = coef[2][0] * a[0] + coef[2][1] * a[1] + coef[2][2] * a[2]
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+ coef[2][3] * a[3] - a[4];
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f[5] = coef[2][0] * b[0] + coef[2][1] * b[1] + coef[2][2] * b[2]
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+ coef[2][3] * b[3] - b[4] - f[3];
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f[3] = f[3] - f[2];
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f[4] = f[4] - f[3];
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f[6] = coef[3][0] * (a[5] - a[7] - a[8]);
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f[7] = coef[3][0] * (b[5] - b[7] - b[8]) - f[5];
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f[5] = f[5] - f[4];
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f[6] = f[6] - f[5];
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f[8] = coef[4][0] * a[0] + coef[4][1] * a[1] + coef[4][2] * a[2]
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+ coef[4][3] * a[3] + a[4];
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f[9] = coef[4][0] * b[0] + coef[4][1] * b[1] + coef[4][2] * b[2]
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+ coef[4][3] * b[3] + b[4] - f[7];
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f[7] = f[7] - f[6];
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f[8] = f[8] - f[7];
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f[10] = coef[5][0] * a[5] + coef[5][1] * a[6] + coef[5][2] * a[7]
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+ coef[5][3] * a[8];
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f[11] = coef[5][0] * b[5] + coef[5][1] * b[6] + coef[5][2] * b[7]
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+ coef[5][3] * b[8] - f[9];
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f[9] = f[9] - f[8];
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f[10] = f[10] - f[9];
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f[12] = 0.5f * (a[0] + a[2] + a[3]) - a[1] - a[4];
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f[13] = 0.5f * (b[0] + b[2] + b[3]) - b[1] - b[4] - f[11];
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f[11] = f[11] - f[10];
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f[12] = f[12] - f[11];
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f[14] = coef[7][0] * a[5] + coef[7][1] * a[6] + coef[7][2] * a[7]
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+ coef[7][3] * a[8];
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f[15] = coef[7][0] * b[5] + coef[7][1] * b[6] + coef[7][2] * b[7]
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+ coef[7][3] * b[8] - f[13];
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f[13] = f[13] - f[12];
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f[14] = f[14] - f[13];
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f[16] = coef[8][0] * a[0] + coef[8][1] * a[1] + coef[8][2] * a[2]
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+ coef[8][3] * a[3] + a[4];
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f[17] = coef[8][0] * b[0] + coef[8][1] * b[1] + coef[8][2] * b[2]
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+ coef[8][3] * b[3] + b[4] - f[15];
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f[15] = f[15] - f[14];
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f[16] = f[16] - f[15];
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f[17] = f[17] - f[16];
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return;
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}
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/*--------------------------------------------------------------------*/
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/* does 3, 6 pt dct. changes order from f[i][window] c[window][i] */
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void imdct6_3(float f[]) /* 6 point */
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{
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int w;
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float buf[18];
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float *a, *c; // b[i] = a[3+i]
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float g1, g2;
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float a02, b02;
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c = f;
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a = buf;
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for (w = 0; w < 3; w++)
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{
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g1 = mdct6_3v[0] * f[3 * 0];
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g2 = mdct6_3v[5] * f[3 * 5];
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a[0] = g1 + g2;
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a[3 + 0] = mdct6_3v2[0] * (g1 - g2);
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g1 = mdct6_3v[1] * f[3 * 1];
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g2 = mdct6_3v[4] * f[3 * 4];
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a[1] = g1 + g2;
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a[3 + 1] = mdct6_3v2[1] * (g1 - g2);
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g1 = mdct6_3v[2] * f[3 * 2];
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g2 = mdct6_3v[3] * f[3 * 3];
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a[2] = g1 + g2;
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a[3 + 2] = mdct6_3v2[2] * (g1 - g2);
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a += 6;
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f++;
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}
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a = buf;
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for (w = 0; w < 3; w++)
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{
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a02 = (a[0] + a[2]);
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b02 = (a[3 + 0] + a[3 + 2]);
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c[0] = a02 + a[1];
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c[1] = b02 + a[3 + 1];
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c[2] = coef87 * (a[0] - a[2]);
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c[3] = coef87 * (a[3 + 0] - a[3 + 2]) - c[1];
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c[1] = c[1] - c[0];
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c[2] = c[2] - c[1];
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c[4] = a02 - a[1] - a[1];
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c[5] = b02 - a[3 + 1] - a[3 + 1] - c[3];
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c[3] = c[3] - c[2];
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c[4] = c[4] - c[3];
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c[5] = c[5] - c[4];
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a += 6;
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c += 6;
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}
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return;
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}
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/*--------------------------------------------------------------------*/
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