[PATCH 2/9] Add murmurhash3

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

I use Austin Appleby's Public Domain Murmur3 reference code.
I don't own that code. Murmur hash is available from
http://code.google.com/p/smhasher/wiki/MurmurHash

gcc/:

2013-04-18  Andi Kleen <ak@linux.intel.com>

	* murmurhash3.h: New file.
---
 gcc/murmurhash3.h | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 gcc/murmurhash3.h

diff --git a/gcc/murmurhash3.h b/gcc/murmurhash3.h
new file mode 100644
index 0000000..f4e838e
--- /dev/null
+++ b/gcc/murmurhash3.h
@@ -0,0 +1,80 @@
+#include <stdint.h>
+
+//-----------------------------------------------------------------------------
+// MurmurHash3 was written by Austin Appleby, and is placed in the public
+// domain. The author hereby disclaims copyright to this source code.
+// Minor changes for gcc by AK.
+
+inline uint32_t rotl32(uint32_t x, int8_t r)
+{
+  return (x << r) | (x >> (32 - r));
+}
+
+//-----------------------------------------------------------------------------
+// Finalization mix - force all bits of a hash block to avalanche
+
+inline uint32_t mm3_fmix(uint32_t h)
+{
+  h ^= h >> 16;
+  h *= 0x85ebca6b;
+  h ^= h >> 13;
+  h *= 0xc2b2ae35;
+  h ^= h >> 16;
+
+  return h;
+}
+
+static inline uint32_t murmurhash3_32(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 = 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 = mm3_fmix(h1);
+  return h1;
+} 
-- 
1.8.1.4