From:  <brian@gir-2.local>
Date: Sat, 15 Mar 2008 20:24:40 +0000 (-0700)
Subject: Update on murmur
X-Git-Tag: _20~1^2~54
X-Git-Url: https://git.m6w6.name/?a=commitdiff_plain;h=01de4afa83a6f906eb666ff23a0888fbb5f4005f;p=m6w6%2Flibmemcached

Update on murmur
---

diff --git a/libmemcached/murmur_hash.c b/libmemcached/murmur_hash.c
index abb2deda..ce28ec38 100644
--- a/libmemcached/murmur_hash.c
+++ b/libmemcached/murmur_hash.c
@@ -2,47 +2,42 @@
 
 /* 
   "Murmur"hash provided by Austin, tanjent@gmail.com
-#define MURMUR_POSTMIX
 */
 
+#define MIX(h,k,m) { k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; }
+
 uint32_t murmur_hash(char *key, size_t length)
 {
-  const unsigned int m= 0x7fd652ad;
+  const uint32_t m= 0x5bd1e995;
   const int r= 16;
-
-  uint32_t h= 0xdeadbeef;
+  uint32_t h= length * m;
 
   while(length >= 4)
   {
-    h += *(unsigned int *)key;
-    h *= m;
-    h ^= h >> r;
+    uint32_t k = *(uint32_t*)key;
+    MIX(h,k,m);
 
     key += 4;
     length -= 4;
   }
 
-  switch(length)
+  if (length)
   {
-  case 3:
-    h += key[2] << 16;
-  case 2:
-    h += key[1] << 8;
-  case 1:
-  default:
-    h += key[0];
-    h *= m;
-    h ^= h >> r;
-  };
-
-#ifdef MURMUR_POSTMIX
+    uint32_t k= 0;
+
+    switch(length)
+    {
+    case 3: k += key[2] << 16;
+    case 2: k += key[1] << 8;
+    case 1: k += key[0];
+    };
+    MIX(h,k,m);
+  }
 
   h *= m;
   h ^= h >> 10;
   h *= m;
   h ^= h >> 17;
 
-#endif
-
   return h;
 }