1 files changed, 1 insertions, 0 deletions
diff --git a/lib/leanunconvert.c b/lib/leanunconvert.c
new file mode 100644
index 0000000..4880729
--- /dev/null
+++ b/lib/leanunconvert.c
@@ -0,0 +1 @@
+#include "fftease.h"
+/* unconvert essentially undoes what convert does, i.e., it
+  turns N2+1 PAIRS of amplitude and frequency values in
+  C into N2 PAIR of complex spectrum data (in rfft format)
+  in output array S; sampling rate R and interpolation factor
+  I are used to recompute phase values from frequencies */
+void leanunconvert( float *C, float *S, int N2 )
+{
+double cos(), sin();
+  int		real, imag,
+		amp, phase;
+  register int		i;
+  
+  for ( i = 0; i <= N2; i++ ) {
+    imag = phase = ( real = amp = i<<1 ) + 1;
+    S[real] = *(C+amp) * cos( *(C+phase) );
+    if ( i != N2 )
+      S[imag] = -*(C+amp) * sin( *(C+phase) );
+  }
+}
+\ No newline at end of file