kfc.c

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/*
 *  Copyright (c) 2003-2004, Mark Borgerding. All rights reserved.
 *  This file is part of KISS FFT - https://github.com/mborgerding/kissfft
 *
 *  SPDX-License-Identifier: BSD-3-Clause
 *  See COPYING file for more information.
 */
 
#include "kfc.h"
 
typedef struct cached_fft *kfc_cfg;
 
struct cached_fft
{
    int nfft;
    int inverse;
    kiss_fft_cfg cfg;
    kfc_cfg next;
};
 
static kfc_cfg cache_root=NULL;
static int ncached=0;
 
static kiss_fft_cfg find_cached_fft(int nfft,int inverse)
{
    size_t len;
    kfc_cfg  cur=cache_root;
    kfc_cfg  prev=NULL;
    while ( cur ) {
        if ( cur->nfft == nfft && inverse == cur->inverse )
            break;/*found the right node*/
        prev = cur;
        cur = prev->next;
    }
    if (cur== NULL) {
        /* no cached node found, need to create a new one*/
        kiss_fft_alloc(nfft,inverse,0,&len);
#ifdef USE_SIMD
        int padding = (16-sizeof(struct cached_fft)) & 15;
        // make sure the cfg aligns on a 16 byte boundary
        len += padding;
#endif
        cur = (kfc_cfg)KISS_FFT_MALLOC((sizeof(struct cached_fft) + len ));
        if (cur == NULL)
            return NULL;
        cur->cfg = (kiss_fft_cfg)(cur+1);
#ifdef USE_SIMD
        cur->cfg = (kiss_fft_cfg) ((char*)(cur+1)+padding);
#endif
        kiss_fft_alloc(nfft,inverse,cur->cfg,&len);
        cur->nfft=nfft;
        cur->inverse=inverse;
        cur->next = NULL;
        if ( prev )
            prev->next = cur;
        else
            cache_root = cur;
        ++ncached;
    }
    return cur->cfg;
}
 
void kfc_cleanup(void)
{
    kfc_cfg  cur=cache_root;
    kfc_cfg  next=NULL;
    while (cur){
        next = cur->next;
        free(cur);
        cur=next;
    }
    ncached=0;
    cache_root = NULL;
}
void kfc_fft(int nfft, const kiss_fft_cpx * fin,kiss_fft_cpx * fout)
{
    kiss_fft( find_cached_fft(nfft,0),fin,fout );
}
 
void kfc_ifft(int nfft, const kiss_fft_cpx * fin,kiss_fft_cpx * fout)
{
    kiss_fft( find_cached_fft(nfft,1),fin,fout );
}
 
#ifdef KFC_TEST
static void check(int nc)
{
    if (ncached != nc) {
        fprintf(stderr,"ncached should be %d,but it is %d\n",nc,ncached);
        exit(1);
    }
}
 
int main(void)
{
    kiss_fft_cpx buf1[1024],buf2[1024];
    memset(buf1,0,sizeof(buf1));
    check(0);
    kfc_fft(512,buf1,buf2);
    check(1);
    kfc_fft(512,buf1,buf2);
    check(1);
    kfc_ifft(512,buf1,buf2);
    check(2);
    kfc_cleanup();
    check(0);
    return 0;
}
#endif