text: #ifndef KISS_FFT_H
  #define KISS_FFT_H
  
  #include <stdlib.h>
  #include <stdio.h>
  #include <math.h>
  #include <string.h>
  
  #include <pcl/pcl_exports.h>
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /*
   ATTENTION!
   If you would like a :
   -- a utility that will handle the caching of fft objects
   -- real-only (no imaginary time component ) FFT
   -- a multi-dimensional FFT
   -- a command-line utility to perform ffts
   -- a command-line utility to perform fast-convolution filtering
  
   Then see kfc.h kiss_fftr.h kiss_fftnd.h fftutil.c kiss_fastfir.c
    in the tools/ directory.
  */
  
  #ifdef USE_SIMD
  # include <xmmintrin.h>
  # define kiss_fft_scalar __m128
  #define KISS_FFT_MALLOC(nbytes) _mm_malloc(nbytes,16)
  #define KISS_FFT_FREE _mm_free
  #else	
  #define KISS_FFT_MALLOC malloc
  #define KISS_FFT_FREE free
  #endif	
  
  
  #ifdef FIXED_POINT
  #include <sys/types.h>	
  # if (FIXED_POINT == 32)
  #  define kiss_fft_scalar int32_t
  # else	
  #  define kiss_fft_scalar int16_t
  # endif
  #else
  # ifndef kiss_fft_scalar
  /*  default is float */
  #   define kiss_fft_scalar float
  # endif
  #endif
  
  typedef struct {
      kiss_fft_scalar r;
      kiss_fft_scalar i;
  }kiss_fft_cpx;
  
  typedef struct kiss_fft_state* kiss_fft_cfg;
  
  /* 
   *  kiss_fft_alloc
   *  
   *  Initialize a FFT (or IFFT) algorithm's cfg/state buffer.
   *
   *  typical usage:      kiss_fft_cfg mycfg=kiss_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 kiss_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_cfg PCL_EXPORTS 
  kiss_fft_alloc(int nfft,int inverse_fft,void * mem,size_t * lenmem); 
  
  /*
   * kiss_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 PCL_EXPORTS 
  kiss_fft(kiss_fft_cfg cfg,const kiss_fft_cpx *fin,kiss_fft_cpx *fout);
  
  /*
   A more generic version of the above function. It reads its input from every Nth sample.
   * */
  void PCL_EXPORTS 
  kiss_fft_stride(kiss_fft_cfg cfg,const kiss_fft_cpx *fin,kiss_fft_cpx *fout,int fin_stride);
  
  /* If kiss_fft_alloc allocated a buffer, it is one contiguous 
     buffer and can be simply free()d when no longer needed*/
  #define kiss_fft_free free
  
  /*
   Cleans up some memory that gets managed internally. Not necessary to call, but it might clean up 
   your compiler output to call this before you exit.
  */
  void PCL_EXPORTS 
  kiss_fft_cleanup(void);
  
  /*
   * Returns the smallest integer k, such that k>=n and k has only "fast" factors (2,3,5)
   */
  int PCL_EXPORTS 
  kiss_fft_next_fast_size(int n);
  
  /* for real ffts, we need an even size */
  #define kiss_fftr_next_fast_size_real(n) \
          (kiss_fft_next_fast_size( ((n)+1)>>1)<<1)
  
  #ifdef __cplusplus
  } 
  #endif
  
  #endif
  