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/*
* Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
* Copyright (C) 2008 - INRIA - Allan SIMON
*
* This file must be used under the terms of the CeCILL.
* This source file is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at
* http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
*
*/
#include "fft_internal.h"
/* get binary log of integer argument; exact if n a power of 2 */
static int fastlog2( int n)
{
int log = -1;
while(n) {
log++;
n >>= 1;
}
return(log);
}
void fft842 (doubleComplex* b, int size , int in)
{
double fn;
doubleComplex temp ;
int L[16],L1,L2,L3,L4,L5,L6,L7,L8,L9,L10,L11,L12,L13,L14,L15;
int j1,j2,j3,j4,j5,j6,j7,j8,j9,j10,j11,j12,j13,j14;
int i = 0, j, ij, ji, ij1, ji1;
int n2pow, n8pow, nthpo, ipass, nxtlt, lengt;
n2pow = fastlog2( size );
nthpo = size ;
fn = 1.0 / (double)nthpo;
if(in==FORWARD)
/* take conjugate */
for(i=0;i< size ;i++)
{
b[i] = DoubleComplex ( zreals( b[i]) , - zimags (b[i]));
}
n8pow = n2pow/3;
if(n8pow)
{
/* if the size if a factor of a power of 8 we call r8tx */
/* radix 8 iterations */
for(ipass=1;ipass<=n8pow;ipass++)
{
nxtlt = 0x1 << (n2pow - 3*ipass);
lengt = 8*nxtlt;
r8tx(nxtlt,nthpo,lengt,
b,b+nxtlt,b+2*nxtlt,
b+3*nxtlt,b+4*nxtlt,b+5*nxtlt,
b+6*nxtlt,b+7*nxtlt);
}
}
/* if the size can be written this way 2^(3*n + 1) , then we call the radix 2 function
if can be written this way 2^(3*n + 1) the we call the radix 4 function */
if(n2pow%3 == 1)
{
/* radix 2 iteration needed */
r2tx(nthpo,b,b+1);
}
if(n2pow%3 == 2)
{
/* radix 4 iteration needed */
r4tx(nthpo,b,b+1,b+2,b+3);
}
for(j=1;j<=15;j++)
{
L[j] = 1;
if(j-n2pow <= 0) L[j] = 0x1 << (n2pow + 1 - j);
}
/* this part can maybe be improved */
L15=L[1];L14=L[2];L13=L[3];L12=L[4];L11=L[5];L10=L[6];L9=L[7];
L8=L[8];L7=L[9];L6=L[10];L5=L[11];L4=L[12];L3=L[13];L2=L[14];L1=L[15];
ij = 1;
/* all the following instruction is to unscramble the output */
for(j1=1;j1<=L1;j1++)
for(j2=j1;j2<=L2;j2+=L1)
for(j3=j2;j3<=L3;j3+=L2)
for(j4=j3;j4<=L4;j4+=L3)
for(j5=j4;j5<=L5;j5+=L4)
for(j6=j5;j6<=L6;j6+=L5)
for(j7=j6;j7<=L7;j7+=L6)
for(j8=j7;j8<=L8;j8+=L7)
for(j9=j8;j9<=L9;j9+=L8)
for(j10=j9;j10<=L10;j10+=L9)
for(j11=j10;j11<=L11;j11+=L10)
for(j12=j11;j12<=L12;j12+=L11)
for(j13=j12;j13<=L13;j13+=L12)
for(j14=j13;j14<=L14;j14+=L13)
for(ji=j14;ji<=L15;ji+=L14)
{
ij1 = ij-1;
ji1 = ji-1;
if(ij-ji<0)
{
temp = b[ij1];
b[ij1] = b[ji1];
b[ji1] = temp;
/*
r = b[ij1].re;
b[ij1].re = b[ji1].re;
b[ji1].re = r;
fi = b[ij1].im;
b[ij1].im = b[ji1].im;
b[ji1].im = fi;
*/
}
ij++;
}
if(in==FORWARD) /* take conjugates & unscramble outputs */
for(i=0,j=size/2;j<size;i++,j++)
{
temp = DoubleComplex ( zreals ( b[j] ) ,- zimags( b[j] ));
b[j] = DoubleComplex ( zreals ( b[i] ) ,- zimags( b[i] ));
b[i] = DoubleComplex ( zreals ( temp ) , zimags( temp ));
/* r = b[j].re; fi = b[j].im;
b[j].re = b[i].re; b[j].im = -b[i].im;
b[i].re = r; b[i].im = -fi;
*/
}
/* this code is two fix a problem of result order which was different from what scilab give */
for ( i = 0 ; i < size /2 ; i++)
{
temp = b[i] ;
b[i] = b[i+(size/2)];
b[i+(size/2)]= temp ;
}
}
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