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/*
* multiply current input I by window W (both of length Nw);
* using modulus arithmetic, fold and rotate windowed input
* into output array O of (FFT) length N according to current
* input time n
*/
void fold( float *I, float *W, int Nw, float *O, int N, int n )
{
int i;
for ( i = 0; i < N; i++ )
O[i] = 0.;
while ( n < 0 )
n += N;
n %= N;
for ( i = 0; i < Nw; i++ ) {
O[n] += I[i]*W[i];
if ( ++n == N )
n = 0;
}
}
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