add oversampler

oversampling/WDL/mergesort.h

@@ -0,0 +1,66 @@
+#ifndef _WDL_MERGESORT_H_
+#define _WDL_MERGESORT_H_
+
+#include "wdltypes.h"
+
+static void WDL_STATICFUNC_UNUSED WDL_mergesort(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *), char *tmpspace)
+{
+  char *b1,*b2;
+  size_t n1, n2;
+
+  if (nmemb < 2) return;
+
+  n1 = nmemb / 2;
+  b1 = (char *) base;
+  n2 = nmemb - n1;
+  b2 = b1 + (n1 * size);
+
+  if (nmemb>2)
+  {
+    WDL_mergesort(b1, n1, size, compar, tmpspace);
+    WDL_mergesort(b2, n2, size, compar, tmpspace);
+  }
+
+
+  do
+  {
+    if (compar(b1, b2) > 0) // out of order, go to full merge
+    {
+      size_t sofar = b1-(char*)base;
+      memcpy(tmpspace,base,sofar);
+      memcpy(tmpspace+sofar, b2, size);
+      b2 += size;
+      n2--;
+
+      char *writeptr=tmpspace+sofar+size;
+      while (n1 > 0 && n2 > 0)
+      {
+        if (compar(b1, b2) > 0)
+        {
+          memcpy(writeptr, b2, size);
+          b2 += size;
+          n2--;
+        }
+        else
+        {
+          memcpy(writeptr, b1, size);
+          b1 += size;
+          n1--;
+        }
+        writeptr += size;
+      }
+
+      if (n1 > 0) memcpy(writeptr, b1, n1 * size);
+      memcpy(base, tmpspace, (nmemb - n2) * size);
+
+      break;
+    }
+
+    // in order, just advance
+    b1 += size;
+    n1--;
+  }
+  while (n1 > 0 && n2 > 0);
+}
+
+#endif//_WDL_MERGESORT_H_