file to cache fft cfg objects for ease of use.

test/kf1s.c

@@ -0,0 +1,60 @@
+#include "kiss_fft.h"
+
+typedef struct
+{
+    int nfft;
+    int inverse;
+    const void * cfg;
+    void * next;
+} cached_fft;
+
+static cached_fft *cache_root=NULL;
+
+static const void * find_cached_fft(int nfft,int inverse)
+{
+    size_t len;
+    cached_fft * cur=cache_root;
+    cached_fft * prev=NULL;
+    while ( cur ) {
+        if ( cur->nfft == nfft && inverse == cur->inverse )
+            return cur->cfg;
+        prev = cur;
+        cur = (cached_fft*)prev->next;
+    }
+
+    // no cached node found, need to create a new one
+    kiss_fft_alloc(nfft,inverse,0,&len);
+    cur = (cached_fft*)malloc(sizeof(cached_fft) + len );
+    if (cur == NULL)
+        return NULL;
+    cur->cfg = kiss_fft_alloc(nfft,inverse,cur+1,&len);
+    cur->nfft=nfft;
+    cur->inverse=inverse;
+    if ( prev )
+        prev->next = cur;
+    else
+        cache_root = cur;
+    return cur->cfg;
+}
+
+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 );
+}
+
+void kfc_cleanup()
+{
+    cached_fft * cur=cache_root;
+    cached_fft * next=NULL;
+    while (cur){
+        next = (cached_fft*)cur->next;
+        free(cur);
+        cur=(cached_fft*)next;
+    }
+    cache_root = NULL;
+}