text: /*Copyright (c) 2003-2004, Mark Borgerding
    Lots of modifications by Jean-Marc Valin
    Copyright (c) 2005-2007, Xiph.Org Foundation
    Copyright (c) 2008,      Xiph.Org Foundation, CSIRO
  
    All rights reserved.
  
    Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions are met:
  
      * Redistributions of source code must retain the above copyright notice,
         this list of conditions and the following disclaimer.
      * 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.
  
    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.*/
  
  #ifndef KISS_FFT_H
  #define KISS_FFT_H
  
  #include "arch.h"
  #include <math.h>
  #include <stdlib.h>
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  #ifdef USE_SIMD
  #include <xmmintrin.h>
  #define kiss_fft_scalar __m128
  #define KISS_FFT_MALLOC(nbytes) memalign(16, nbytes)
  #else
  #define KISS_FFT_MALLOC opus_alloc
  #endif
  
  #ifdef FIXED_POINT
  #include "arch.h"
  
  #define kiss_fft_scalar opus_int32
  #define kiss_twiddle_scalar opus_int16
  
  #else
  #ifndef kiss_fft_scalar
  /*  default is float */
  #define kiss_fft_scalar float
  #define kiss_twiddle_scalar float
  #define KF_SUFFIX _celt_single
  #endif
  #endif
  
  typedef struct {
    kiss_fft_scalar r;
    kiss_fft_scalar i;
  } kiss_fft_cpx;
  
  typedef struct {
    kiss_twiddle_scalar r;
    kiss_twiddle_scalar i;
  } kiss_twiddle_cpx;
  
  #define MAXFACTORS 8
  /* e.g. an fft of length 128 has 4 factors
   as far as kissfft is concerned
   4*4*4*2
   */
  
  typedef struct kiss_fft_state {
    int nfft;
  #ifndef FIXED_POINT
    kiss_fft_scalar scale;
  #endif
    int shift;
    opus_int16 factors[2 * MAXFACTORS];
    const opus_int16 *bitrev;
    const kiss_twiddle_cpx *twiddles;
  } kiss_fft_state;
  
  /*typedef struct kiss_fft_state* kiss_fft_cfg;*/
  
  /**
   *  opus_fft_alloc
   *
   *  Initialize a FFT (or IFFT) algorithm's cfg/state buffer.
   *
   *  typical usage:      kiss_fft_cfg mycfg=opus_fft_alloc(1024,0,NULL,NULL);
   *
   *  The return value from fft_alloc is a cfg buffer used internally
   *  by the fft routine or NULL.
   *
   *  If lenmem is NULL, then opus_fft_alloc will allocate a cfg buffer using
   * malloc. The returned value should be free()d when done to avoid memory leaks.
   *
   *  The state can be placed in a user supplied buffer 'mem':
   *  If lenmem is not NULL and mem is not NULL and *lenmem is large enough,
   *      then the function places the cfg in mem and the size used in *lenmem
   *      and returns mem.
   *
   *  If lenmem is not NULL and ( mem is NULL or *lenmem is not large enough),
   *      then the function returns NULL and places the minimum cfg
   *      buffer size in *lenmem.
   * */
  
  kiss_fft_state *opus_fft_alloc_twiddles(int nfft, void *mem, size_t *lenmem,
                                          const kiss_fft_state *base);
  
  kiss_fft_state *opus_fft_alloc(int nfft, void *mem, size_t *lenmem);
  
  /**
   * opus_fft(cfg,in_out_buf)
   *
   * Perform an FFT on a complex input buffer.
   * for a forward FFT,
   * fin should be  f[0] , f[1] , ... ,f[nfft-1]
   * fout will be   F[0] , F[1] , ... ,F[nfft-1]
   * Note that each element is complex and can be accessed like
      f[k].r and f[k].i
   * */
  void opus_fft(const kiss_fft_state *cfg, const kiss_fft_cpx *fin,
                kiss_fft_cpx *fout);
  void opus_ifft(const kiss_fft_state *cfg, const kiss_fft_cpx *fin,
                 kiss_fft_cpx *fout);
  
  void opus_fft_free(const kiss_fft_state *cfg);
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif
  