用C实现FFT算法

用C语言编写FFT算法 

转http://blog.sina.com.cn/s/blog_65d639d50101buo1.html

#include "math.h"
#define PI 3.1415926
#define SAMPLENUMBER 512

void InitForFFT();
void MakeWave();
void FFT();

int INPUT[SAMPLENUMBER],DATA[SAMPLENUMBER];
float fWaveR[SAMPLENUMBER],fWaveI[SAMPLENUMBER],w[SAMPLENUMBER];
float sin_tab[SAMPLENUMBER],cos_tab[SAMPLENUMBER];

main()
{
int i;
InitForFFT();
MakeWave();
for ( i=;i
{
fWaveR[i]=INPUT[i];
fWaveI[i]=0.0f;
w[i]=0.0f;
}
FFT(fWaveR,fWaveI);
for ( i=;i
{
DATA[i]=w[i];
}
while (  ); // break point
}

void FFT(float dataR[SAMPLENUMBER],float dataI[SAMPLENUMBER])
{
int x0,x1,x2,x3,x4,x5,x6,x7,x8,xx;
int i,j,k,b,p,L;
float TR,TI,temp;
for ( i=;i
{
x0=x1=x2=x3=x4=x5=x6=x7=x8=;
x0=i&0x01; x1=(i/)&0x01; x2=(i/)&0x01; x3=(i/)&0x01;x4=(i/)&0x01; x5=(i/)&0x01; x6=(i/)&0x01;x7=(i/)&0x01;x8=(i/)&0x01;
xx=x0*+x1*+x2*+x3*+x4*+x5*+x6*+x7*+x8;
dataI[xx]=dataR[i];
}
for ( i=;i
{
dataR[i]=dataI[i]; dataI[i]=;
}

for ( L=;L<=;L++ )
{
b=; i=L-;
while ( i> )
{
b=b*; i--;
}
for ( j=;j<=b-;j++ )
{
p=; i=-L;
while ( i> )
{
p=p*; i--;
}
p=p*j;
for ( k=j;k<;k=k+*b )
{
TR=dataR[k]; TI=dataI[k]; temp=dataR[k+b];
dataR[k]=dataR[k]+dataR[k+b]*cos_tab[p]+dataI[k+b]*sin_tab[p];
dataI[k]=dataI[k]-dataR[k+b]*sin_tab[p]+dataI[k+b]*cos_tab[p];
dataR[k+b]=TR-dataR[k+b]*cos_tab[p]-dataI[k+b]*sin_tab[p];
dataI[k+b]=TI+temp*sin_tab[p]-dataI[k+b]*cos_tab[p];
}
}
}
for ( i=;i
{
w[i]=sqrt(dataR[i]*dataR[i]+dataI[i]*dataI[i]);
}
}

void InitForFFT()
{
int i;
for ( i=;i
{
sin_tab[i]=sin(PI**i/SAMPLENUMBER);
cos_tab[i]=cos(PI**i/SAMPLENUMBER);
}
}

void MakeWave()
{
int i;
for ( i=;i
{
INPUT[i]=sin(PI**i/SAMPLENUMBER*)*;
}
}