godot/thirdparty/libvorbis/smallft.c

/********************************************************************
 *                                                                  *
 * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE.   *
 * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
 * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
 * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
 *                                                                  *
 * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2009             *
 * by the Xiph.Org Foundation https://xiph.org/                     *
 *                                                                  *
 ********************************************************************

 function: *unnormalized* fft transform

 ********************************************************************/

/* FFT implementation from OggSquish, minus cosine transforms,
 * minus all but radix 2/4 case.  In Vorbis we only need this
 * cut-down version.
 *
 * To do more than just power-of-two sized vectors, see the full
 * version I wrote for NetLib.
 *
 * Note that the packing is a little strange; rather than the FFT r/i
 * packing following R_0, I_n, R_1, I_1, R_2, I_2 ... R_n-1, I_n-1,
 * it follows R_0, R_1, I_1, R_2, I_2 ... R_n-1, I_n-1, I_n like the
 * FORTRAN version
 */

#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "smallft.h"
#include "os.h"
#include "misc.h"

static void drfti1(int n, float *wa, int *ifac){ … }

static void fdrffti(int n, float *wsave, int *ifac){ … }

static void dradf2(int ido,int l1,float *cc,float *ch,float *wa1){ … }

static void dradf4(int ido,int l1,float *cc,float *ch,float *wa1,
            float *wa2,float *wa3){ … }

static void dradfg(int ido,int ip,int l1,int idl1,float *cc,float *c1,
                          float *c2,float *ch,float *ch2,float *wa){ … }

static void drftf1(int n,float *c,float *ch,float *wa,int *ifac){ … }

static void dradb2(int ido,int l1,float *cc,float *ch,float *wa1){ … }

static void dradb3(int ido,int l1,float *cc,float *ch,float *wa1,
                          float *wa2){ … }

static void dradb4(int ido,int l1,float *cc,float *ch,float *wa1,
                          float *wa2,float *wa3){ … }

static void dradbg(int ido,int ip,int l1,int idl1,float *cc,float *c1,
            float *c2,float *ch,float *ch2,float *wa){ … }

static void drftb1(int n, float *c, float *ch, float *wa, int *ifac){ … }

void drft_forward(drft_lookup *l,float *data){ … }

void drft_backward(drft_lookup *l,float *data){ … }

void drft_init(drft_lookup *l,int n){ … }

void drft_clear(drft_lookup *l){ … }