added superfasthash

antifork · Sep 22, 2005 · 318d990 · 318d990
1 parent 876a092
commit 318d990
Showing 1 changed file with 60 additions and 0 deletions.
diff --git a/hash/superfasthash.c b/hash/superfasthash.c
@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <stdint.h> /* Replace with <stdint.h> if appropriate */
+
+#undef get16bits
+#if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) \
+  || defined(_MSC_VER) || defined (__BORLANDC__) || defined (__TURBOC__)
+#define get16bits(d) (*((const uint16_t *) (d)))
+#endif
+
+#if !defined (get16bits)
+#define get16bits(d) ((((const uint8_t *)(d))[1] << UINT32_C(8))\
+                      +((const uint8_t *)(d))[0])
+#endif
+
+#define SuperFastHash	hash
+#define uint32_t	unsigned long
+uint32_t SuperFastHash (const char * data, int len) {
+#define hash		__hash
+uint32_t hash = len, tmp;
+int rem;
+
+    if (len <= 0 || data == NULL) return 0;
+
+    rem = len & 3;
+    len >>= 2;
+
+    /* Main loop */
+    for (;len > 0; len--) {
+        hash  += get16bits (data);
+        tmp    = (get16bits (data+2) << 11) ^ hash;
+        hash   = (hash << 16) ^ tmp;
+        data  += 2*sizeof (uint16_t);
+        hash  += hash >> 11;
+    }
+
+    /* Handle end cases */
+    switch (rem) {
+        case 3: hash += get16bits (data);
+                hash ^= hash << 16;
+                hash ^= data[sizeof (uint16_t)] << 18;
+                hash += hash >> 11;
+                break;
+        case 2: hash += get16bits (data);
+                hash ^= hash << 11;
+                hash += hash >> 17;
+                break;
+        case 1: hash += *data;
+                hash ^= hash << 10;
+                hash += hash >> 1;
+    }
+
+    /* Force "avalanching" of final 127 bits */
+    hash ^= hash << 3;
+    hash += hash >> 5;
+    hash ^= hash << 2;
+    hash += hash >> 15;
+    hash ^= hash << 10;
+
+    return hash;
+}