/* resample a time sequence at the same rate */

#include <math.h>
#include "const.h"

int min2n();
float *farray1();

void originshift(data,n,smplintv,shift)
float *data,smplintv,shift;
int n;
{
int m,i;
float *work,dw,real,imag,cc,ss,fac;
double arg;

	m=min2n(n);
	work=farray1(0,m+2);
	
	for(i=0;i<n;i++) work[i]=data[i];
	for(i=n;i<m;i++) work[i]=0.0;
	  
	cfftr(work,m);
	
	dw=PI/(smplintv*(float)(m/2));
	for(i=0;i<1+m/2;i++)
	{ arg=shift*dw*(float)i;
	  cc=(float)cos(arg);
	  ss=(float)sin(arg);
	  real=work[2*i];
	  imag=work[2*i+1];
	  work[2*i]=real*cc-imag*ss;
	  work[2*i+1]=imag*cc+real*ss;
	}
	
	cfftri(work,m);
	
	fac=2./(float)m;
	for(i=0;i<n;i++) data[i]=fac*work[i];
	
	free_farray1(work,0);

}