first commit

.gitignore

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+*~
+.eunit
+c_src/*.o
+doc
+ebin
+priv

README.md

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+## Description
+
+The **erlang-murmurhash** library provides [MurmurHash](http://code.google.com/p/smhasher/) hash functions implemented in Erlang NIFs.
+
+## Building and Installing
+
+The **erlang-murmurhash** library is built with [rebar](https://github.com/basho/rebar), which must be in the command `PATH`.
+
+## Erlang Version
+
+The **erlang-murmurhash** library requires Erlang R14B or later.

c_src/MurmurHash2.cpp

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+#include "MurmurHash2.h"
+
+//-----------------------------------------------------------------------------
+// MurmurHash2, by Austin Appleby
+
+// 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.
+
+uint32_t MurmurHash2 ( const void * key, int len, uint32_t seed )
+{
+	// 'm' and 'r' are mixing constants generated offline.
+	// They're not really 'magic', they just happen to work well.
+
+	const uint32_t m = 0x5bd1e995;
+	const int r = 24;
+
+	// Initialize the hash to a 'random' value
+
+	uint32_t h = seed ^ len;
+
+	// Mix 4 bytes at a time into the hash
+
+	const unsigned char * data = (const unsigned char *)key;
+
+	while(len >= 4)
+	{
+		uint32_t k = *(uint32_t*)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;
+} 
+
+//-----------------------------------------------------------------------------
+// MurmurHash2, 64-bit versions, by Austin Appleby
+
+// The same caveats as 32-bit MurmurHash2 apply here - beware of alignment 
+// and endian-ness issues if used across multiple platforms.
+
+// 64-bit hash for 64-bit platforms
+
+uint64_t MurmurHash64A ( const void * key, int len, uint64_t seed )
+{
+	const uint64_t m = 0xc6a4a7935bd1e995;
+	const int r = 47;
+
+	uint64_t h = seed ^ (len * m);
+
+	const uint64_t * data = (const uint64_t *)key;
+	const uint64_t * end = data + (len/8);
+
+	while(data != end)
+	{
+		uint64_t k = *data++;
+
+		k *= m; 
+		k ^= k >> r; 
+		k *= m; 
+
+		h ^= k;
+		h *= m; 
+	}
+
+	const unsigned char * data2 = (const unsigned char*)data;
+
+	switch(len & 7)
+	{
+	case 7: h ^= uint64_t(data2[6]) << 48;
+	case 6: h ^= uint64_t(data2[5]) << 40;
+	case 5: h ^= uint64_t(data2[4]) << 32;
+	case 4: h ^= uint64_t(data2[3]) << 24;
+	case 3: h ^= uint64_t(data2[2]) << 16;
+	case 2: h ^= uint64_t(data2[1]) << 8;
+	case 1: h ^= uint64_t(data2[0]);
+	        h *= m;
+	};
+
+	h ^= h >> r;
+	h *= m;
+	h ^= h >> r;
+
+	return h;
+} 
+
+
+// 64-bit hash for 32-bit platforms
+
+uint64_t MurmurHash64B ( const void * key, int len, uint64_t seed )
+{
+	const uint32_t m = 0x5bd1e995;
+	const int r = 24;
+
+	uint32_t h1 = uint32_t(seed) ^ len;
+	uint32_t h2 = uint32_t(seed >> 32);
+
+	const uint32_t * data = (const uint32_t *)key;
+
+	while(len >= 8)
+	{
+		uint32_t k1 = *data++;
+		k1 *= m; k1 ^= k1 >> r; k1 *= m;
+		h1 *= m; h1 ^= k1;
+		len -= 4;
+
+		uint32_t k2 = *data++;
+		k2 *= m; k2 ^= k2 >> r; k2 *= m;
+		h2 *= m; h2 ^= k2;
+		len -= 4;
+	}
+
+	if(len >= 4)
+	{
+		uint32_t k1 = *data++;
+		k1 *= m; k1 ^= k1 >> r; k1 *= m;
+		h1 *= m; h1 ^= k1;
+		len -= 4;
+	}
+
+	switch(len)
+	{
+	case 3: h2 ^= ((unsigned char*)data)[2] << 16;
+	case 2: h2 ^= ((unsigned char*)data)[1] << 8;
+	case 1: h2 ^= ((unsigned char*)data)[0];
+			h2 *= m;
+	};
+
+	h1 ^= h2 >> 18; h1 *= m;
+	h2 ^= h1 >> 22; h2 *= m;
+	h1 ^= h2 >> 17; h1 *= m;
+	h2 ^= h1 >> 19; h2 *= m;
+
+	uint64_t h = h1;
+
+	h = (h << 32) | h2;
+
+	return h;
+} 
+
+//-----------------------------------------------------------------------------
+// MurmurHash2A, by Austin Appleby
+
+// This is a variant of MurmurHash2 modified to use the Merkle-Damgard 
+// construction. Bulk speed should be identical to Murmur2, small-key speed 
+// will be 10%-20% slower due to the added overhead at the end of the hash.
+
+// This variant fixes a minor issue where null keys were more likely to
+// collide with each other than expected, and also makes the function
+// more amenable to incremental implementations.
+
+#define mmix(h,k) { k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; }
+
+uint32_t MurmurHash2A ( const void * key, int len, uint32_t seed )
+{
+	const uint32_t m = 0x5bd1e995;
+	const int r = 24;
+	uint32_t l = len;
+
+	const unsigned char * data = (const unsigned char *)key;
+
+	uint32_t h = seed;
+
+	while(len >= 4)
+	{
+		uint32_t k = *(uint32_t*)data;
+
+		mmix(h,k);
+
+		data += 4;
+		len -= 4;
+	}
+
+	uint32_t t = 0;
+
+	switch(len)
+	{
+	case 3: t ^= data[2] << 16;
+	case 2: t ^= data[1] << 8;
+	case 1: t ^= data[0];
+	};
+
+	mmix(h,t);
+	mmix(h,l);
+
+	h ^= h >> 13;
+	h *= m;
+	h ^= h >> 15;
+
+	return h;
+}
+
+//-----------------------------------------------------------------------------
+// MurmurHashNeutral2, by Austin Appleby
+
+// Same as MurmurHash2, but endian- and alignment-neutral.
+// Half the speed though, alas.
+
+uint32_t MurmurHashNeutral2 ( const void * key, int len, uint32_t seed )
+{
+	const uint32_t m = 0x5bd1e995;
+	const int r = 24;
+
+	uint32_t h = seed ^ len;
+
+	const unsigned char * data = (const unsigned char *)key;
+
+	while(len >= 4)
+	{
+		uint32_t k;
+
+		k  = data[0];
+		k |= data[1] << 8;
+		k |= data[2] << 16;
+		k |= data[3] << 24;
+
+		k *= m; 
+		k ^= k >> r; 
+		k *= m;
+
+		h *= m;
+		h ^= k;
+
+		data += 4;
+		len -= 4;
+	}
+
+	switch(len)
+	{
+	case 3: h ^= data[2] << 16;
+	case 2: h ^= data[1] << 8;
+	case 1: h ^= data[0];
+	        h *= m;
+	};
+
+	h ^= h >> 13;
+	h *= m;
+	h ^= h >> 15;
+
+	return h;
+} 
+
+//-----------------------------------------------------------------------------
+

c_src/MurmurHash2.h

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+#include <inttypes.h>
+
+uint32_t MurmurHash2        ( const void * key, int len, uint32_t seed );
+uint64_t MurmurHash64A      ( const void * key, int len, uint64_t seed );
+uint64_t MurmurHash64B      ( const void * key, int len, uint64_t seed );
+uint32_t MurmurHash2A       ( const void * key, int len, uint32_t seed );
+uint32_t MurmurHashNeutral2 ( const void * key, int len, uint32_t seed );