now can create win32 portable packages

[chaz/yoink] / src / Moof / HashTools.cc

diff --git a/src/Moof/HashTools.cc b/src/Moof/HashTools.cc
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+
+/*]  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
+