X-Git-Url: https://git.dogcows.com/gitweb?a=blobdiff_plain;f=src%2FMoof%2FHashTools.cc;fp=src%2FMoof%2FHashTools.cc;h=9bcefe3c071489303ba5df4d8c6cbf3fa4d6b01d;hb=0b8dbc2d02c7f78d273ad9cfdf05c927c648ffd1;hp=0000000000000000000000000000000000000000;hpb=6c47a7028f7c72fabc40f417aa41111c28de8a84;p=chaz%2Fyoink

diff --git a/src/Moof/HashTools.cc b/src/Moof/HashTools.cc
new file mode 100644
index 0000000..9bcefe3
--- /dev/null
+++ b/src/Moof/HashTools.cc
@@ -0,0 +1,88 @@
+
+/*]  Copyright (c) 2009-2010, Charles McGarvey  [**************************
+**]  All rights reserved.
+*
+* vi:ts=4 sw=4 tw=75
+*
+* Distributable under the terms and conditions of the 2-clause BSD license;
+* see the file COPYING for a complete text of the license.
+*
+**************************************************************************/
+
+#include "HashTools.hh"
+
+
+namespace Mf {
+
+
+// MurmurHash2, by Austin Appleby
+// http://murmurhash.googlepages.com/
+
+// This function is in the public domain.
+
+// Note - This code makes a few assumptions about how your machine behaves -
+
+// 1. We can read a 4-byte value from any address without crashing
+// 2. sizeof(int) == 4
+
+// And it has a few limitations -
+
+// 1. It will not work incrementally.
+// 2. It will not produce the same results on little-endian and big-endian
+//    machines.
+
+unsigned HashFunction::operator()(const void* key, int len,
+							 unsigned int seed) const
+{
+	// 'm' and 'r' are mixing constants generated offline.
+	// They're not really 'magic', they just happen to work well.
+
+	const unsigned int m = 0x5bd1e995;
+	const int r = 24;
+
+	// Initialize the hash to a 'random' value
+
+	unsigned int h = seed ^ len;
+
+	// Mix 4 bytes at a time into the hash
+
+	const unsigned char* data = (const unsigned char*)key;
+
+	while (len >= 4)
+	{
+		unsigned int k = *(unsigned int*)data;
+
+		k *= m; 
+		k ^= k >> r; 
+		k *= m; 
+		
+		h *= m; 
+		h ^= k;
+
+		data += 4;
+		len -= 4;
+	}
+	
+	// Handle the last few bytes of the input array
+
+	switch (len)
+	{
+	case 3: h ^= data[2] << 16;
+	case 2: h ^= data[1] << 8;
+	case 1: h ^= data[0];
+	        h *= m;
+	};
+
+	// Do a few final mixes of the hash to ensure the last few
+	// bytes are well-incorporated.
+
+	h ^= h >> 13;
+	h *= m;
+	h ^= h >> 15;
+
+	return h;
+} 
+
+
+} // namespace Mf
+