initial/alpha version of integer fft

core/lib/ifft.h

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2008, Swedish Institute of Computer Science
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the Institute nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * -----------------------------------------------------------------
+ * ifft - Integer FFT (fast fourier transform) library
+ *
+ *
+ *
+ * Author  : Joakim Eriksson
+ * Created : 2008-03-27
+ * Updated : $Date: 2008/03/27 12:12:24 $
+ *           $Revision: 1.1 $
+ */
+
+#ifndef IFFT_H
+#define IFFT_H
+#include "contiki-conf.h"
+
+/* ifft(xre[], n) - integer (fixpoint) version of Fast Fourier Transform
+   An integer version of FFT that takes in-samples in an int16_t array
+   and does an fft on n samples in the array.
+   The result of the FFT is stored in the same array as the samples
+   was stored.
+
+   Note: This fft is designed to be used with 8 bit values (e.g. not
+   16 bit values). The reason for the int16_t array is for keeping some
+   'room' for the calculations. It is also designed for doing fairly small
+   FFT:s since to large sample arrays might cause it to overflow during
+   calculations.
+*/
+void ifft(int16_t xre[], uint16_t n);
+
+#endif /* IFFT_H */