From f7c76788f3fceaa3f6ca751dd49b08d4f3164225 Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Sat, 1 Nov 2014 02:05:34 -0700
Subject: [PATCH] Util: Add murmurhash3 hashing

---
 src/util/hash.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/util/hash.h |  8 ++++
 2 files changed, 107 insertions(+)
 create mode 100644 src/util/hash.c
 create mode 100644 src/util/hash.h

diff --git a/src/util/hash.c b/src/util/hash.c
new file mode 100644
index 000000000..96e2ffb7f
--- /dev/null
+++ b/src/util/hash.c
@@ -0,0 +1,99 @@
+// MurmurHash3 was written by Austin Appleby, and is placed in the public
+// domain. The author hereby disclaims copyright to this source code.
+
+#include "hash.h"
+
+#if defined(_MSC_VER)
+
+#define FORCE_INLINE	__forceinline
+
+#include <stdlib.h>
+
+#define ROTL32(x,y)	_rotl(x,y)
+
+#else
+
+#define	FORCE_INLINE inline __attribute__((always_inline))
+
+static inline uint32_t rotl32 ( uint32_t x, int8_t r ) {
+  return (x << r) | (x >> (32 - r));
+}
+
+#define	ROTL32(x,y)	rotl32(x,y)
+
+#endif
+
+//-----------------------------------------------------------------------------
+// Block read - if your platform needs to do endian-swapping or can only
+// handle aligned reads, do the conversion here
+
+static FORCE_INLINE uint32_t getblock32 ( const uint32_t * p, int i ) {
+  return p[i];
+}
+
+//-----------------------------------------------------------------------------
+// Finalization mix - force all bits of a hash block to avalanche
+
+static FORCE_INLINE uint32_t fmix32 (uint32_t h) {
+  h ^= h >> 16;
+  h *= 0x85ebca6b;
+  h ^= h >> 13;
+  h *= 0xc2b2ae35;
+  h ^= h >> 16;
+
+  return h;
+}
+
+//-----------------------------------------------------------------------------
+
+uint32_t hash32(const void* key, int len, uint32_t seed) {
+  const uint8_t * data = (const uint8_t*)key;
+  const int nblocks = len / 4;
+
+  uint32_t h1 = seed;
+
+  const uint32_t c1 = 0xcc9e2d51;
+  const uint32_t c2 = 0x1b873593;
+
+  //----------
+  // body
+
+  const uint32_t * blocks = (const uint32_t *)(data + nblocks*4);
+
+  for(int i = -nblocks; i; i++)
+  {
+    uint32_t k1 = getblock32(blocks,i);
+
+    k1 *= c1;
+    k1 = ROTL32(k1,15);
+    k1 *= c2;
+    
+    h1 ^= k1;
+    h1 = ROTL32(h1,13); 
+    h1 = h1*5+0xe6546b64;
+  }
+
+  //----------
+  // tail
+
+  const uint8_t * tail = (const uint8_t*)(data + nblocks*4);
+
+  uint32_t k1 = 0;
+
+  switch(len & 3)
+  {
+  case 3: k1 ^= tail[2] << 16;
+  case 2: k1 ^= tail[1] << 8;
+  case 1: k1 ^= tail[0];
+          k1 *= c1; k1 = ROTL32(k1,15); k1 *= c2; h1 ^= k1;
+  };
+
+  //----------
+  // finalization
+
+  h1 ^= len;
+
+  h1 = fmix32(h1);
+
+  return h1;
+} 
diff --git a/src/util/hash.h b/src/util/hash.h
new file mode 100644
index 000000000..825d3e152
--- /dev/null
+++ b/src/util/hash.h
@@ -0,0 +1,8 @@
+#ifndef HASH_H
+#define HASH_H
+
+#include "util/common.h"
+
+uint32_t hash32(const void* key, int len, uint32_t seed);
+
+#endif