🚀 go-pugleaf

(Continued from the previous message)

       }
   }
}

/*         Inverse FFT             */
void
c_ifft( float *buffer, int n )
{
 int step;
 int step2;
 int index;

 bit_reverse( buffer, n );

 for( step = 2, step2 = 2*PI_2; step < 2*n; step *= 2, step2 /= 2 ) {
   for( kk = 0, index = 0; kk < 2*PI_2; kk += step2, index++ ) {
       for(ii = index, jj = index+step/2; ii < n; ii += step, jj += step) {

               buffer[jj*2] = buffer[jj*2]*sines[kk+PI_2]
                                       - buffer[jj*2+1]*sines[kk];
               buffer[jj*2+1] = buffer[jj*2+1]*sines[kk+PI_2]
                                       + buffer[jj*2]*sines[kk];
               buffer[ii*2] = buffer[ii*2] + buffer[jj*2];
               buffer[jj*2] = buffer[ii*2] - 2*buffer[jj*2];
               buffer[ii*2+1] = buffer[ii*2+1] + buffer[jj*2+1];
               buffer[jj*2+1] = buffer[ii*2+1] - 2*buffer[jj*2+1];
               }
       }
   }
}

/*         Bit-reversed indexing */
void
bit_reverse( float *buffer, int n )
{
 for( kk = 0, jj = 1; jj < n; jj++ ) {
   ii = 2;
   while( kk >= n/ii ) {
       kk -= n/ii;
       ii <<= 1;
       }
   kk += n/ii;
   if( kk > jj ) {
       temp = buffer[jj*2];
       buffer[jj*2] = buffer[kk*2];
       buffer[kk*2] = temp;
       temp = buffer[jj*2+1];
       buffer[jj*2+1] = buffer[kk*2+1];
       buffer[kk*2+1] = temp;
       }
   }
}
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 þ DeLuxeý/386 1.25 #9629 þ Best wishes,         Chris Perkins
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