1 files changed, 186 insertions, 0 deletions
diff --git a/utils/murmur_hash.h b/utils/murmur_hash.h
new file mode 100755
index 00000000..8dbd7807
--- /dev/null
+++ b/utils/murmur_hash.h
@@ -0,0 +1,186 @@
+#ifndef _MURMUR_HASH_H_
+#define _MURMUR_HASH_H_
+
+//NOTE: quite fast, nice collision properties, but endian dependent hash values
+
+#include "have_64_bits.h"
+typedef uintptr_t MurmurInt;
+
+// MurmurHash2, by Austin Appleby
+
+static const uint32_t DEFAULT_SEED=2654435769U;
+
+#if HAVE_64_BITS
+//MurmurInt MurmurHash(void const *key, int len, uint32_t seed=DEFAULT_SEED);
+
+inline uint64_t MurmurHash64( const void * key, int len, unsigned int seed=DEFAULT_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;
+}
+
+inline uint32_t MurmurHash32(void const *key, int len, uint32_t seed=DEFAULT_SEED)
+{
+  return (uint32_t) MurmurHash64(key,len,seed);
+}
+
+inline MurmurInt MurmurHash(void const *key, int len, uint32_t seed=DEFAULT_SEED)
+{
+  return MurmurHash64(key,len,seed);
+}
+
+#else
+// 32-bit
+
+// 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
+inline uint32_t MurmurHash32 ( const void * key, int len, uint32_t seed=DEFAULT_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;
+}
+
+inline MurmurInt MurmurHash ( const void * key, int len, uint32_t seed=DEFAULT_SEED) {
+  return MurmurHash32(key,len,seed);
+}
+
+// 64-bit hash for 32-bit platforms
+
+inline uint64_t MurmurHash64 ( const void * key, int len, uint32_t seed=DEFAULT_SEED)
+{
+  const uint32_t m = 0x5bd1e995;
+  const int r = 24;
+
+  uint32_t h1 = seed ^ len;
+  uint32_t h2 = 0;
+
+  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;
+}
+
+#endif
+//32bit
+
+#endif