add oversampler

oversampling/WDL/rng.cpp

@@ -0,0 +1,92 @@
+/*
+    WDL - rng.cpp
+    Copyright (C) 2005 and later, Cockos Incorporated
+   
+    This software is provided 'as-is', without any express or implied
+    warranty.  In no event will the authors be held liable for any damages
+    arising from the use of this software.
+
+    Permission is granted to anyone to use this software for any purpose,
+    including commercial applications, and to alter it and redistribute it
+    freely, subject to the following restrictions:
+
+    1. The origin of this software must not be misrepresented; you must not
+       claim that you wrote the original software. If you use this software
+       in a product, an acknowledgment in the product documentation would be
+       appreciated but is not required.
+    2. Altered source versions must be plainly marked as such, and must not be
+       misrepresented as being the original software.
+    3. This notice may not be removed or altered from any source distribution.
+      
+*/
+
+/*
+
+  This file provides the implementation of a decent random number generator, 
+  that internally uses a 256-bit state, and SHA-1 to iterate.
+
+*/
+
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <stdlib.h>
+#include <memory.h>
+#include <string.h>
+#endif
+
+
+#include "rng.h"
+#include "sha.h"
+
+static unsigned char state[32];
+
+void WDL_RNG_addentropy(void *buf, int buflen)
+{
+  WDL_SHA1 tmp;
+  tmp.add(state,sizeof(state));
+  tmp.result(state);
+  tmp.reset();
+  tmp.add((unsigned char *)buf,buflen);
+  tmp.result(state+sizeof(state) - WDL_SHA1SIZE);
+}
+
+static void rngcycle()
+{
+  int i;
+  for (i = 0; i < (int)sizeof(state) && state[i]++; i++);
+}
+
+int WDL_RNG_int32()
+{
+  WDL_SHA1 tmp;
+  tmp.add(state,sizeof(state));
+  rngcycle();
+  union { 
+    char buf[WDL_SHA1SIZE];
+    int a;
+  } b;
+  tmp.result(b.buf);
+  return b.a;
+
+}
+
+
+void WDL_RNG_bytes(void *buf, int buflen)
+{
+  char *b=(char *)buf;
+  while (buflen > 0)
+  {
+    char tb[WDL_SHA1SIZE];
+    WDL_SHA1 tmp;
+    tmp.add(state,sizeof(state));
+    rngcycle();
+
+    tmp.result(tb);
+    const int l=buflen < WDL_SHA1SIZE ? buflen : WDL_SHA1SIZE;
+    memcpy(b,tb,l);
+    buflen-=l;
+    b+=l;
+  }
+}
+