Merge in conversion to C++.

[awesomized/libmemcached] / libhashkit / hsieh.cc

diff --git a/libhashkit/hsieh.cc b/libhashkit/hsieh.cc
new file mode 100644 (file)
index 0000000..35a2e20
--- /dev/null
+++ b/libhashkit/hsieh.cc
@@ -0,0 +1,70 @@
+/* By Paul Hsieh (C) 2004, 2005.  Covered under the Paul Hsieh
+ * derivative license.
+ * See: http://www.azillionmonkeys.com/qed/weblicense.html for license
+ * details.
+ * http://www.azillionmonkeys.com/qed/hash.html
+*/
+
+#include <libhashkit/common.h>
+
+#undef get16bits
+#if (defined(__GNUC__) && defined(__i386__))
+#define get16bits(d) (*((const uint16_t *) (d)))
+#endif
+
+#if !defined (get16bits)
+#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
+                      +(uint32_t)(((const uint8_t *)(d))[0]) )
+#endif
+
+uint32_t hashkit_hsieh(const char *key, size_t key_length, void *context __attribute__((unused)))
+{
+  uint32_t hash = 0, tmp;
+  int rem;
+
+  if (key_length <= 0 || key == NULL)
+    return 0;
+
+  rem = key_length & 3;
+  key_length >>= 2;
+
+  /* Main loop */
+  for (;key_length > 0; key_length--)
+  {
+    hash  += get16bits (key);
+    tmp    = (get16bits (key+2) << 11) ^ hash;
+    hash   = (hash << 16) ^ tmp;
+    key  += 2*sizeof (uint16_t);
+    hash  += hash >> 11;
+  }
+
+  /* Handle end cases */
+  switch (rem)
+  {
+  case 3: hash += get16bits (key);
+          hash ^= hash << 16;
+          hash ^= (uint32_t)key[sizeof (uint16_t)] << 18;
+          hash += hash >> 11;
+          break;
+  case 2: hash += get16bits (key);
+          hash ^= hash << 11;
+          hash += hash >> 17;
+          break;
+  case 1: hash += (unsigned char)(*key);
+          hash ^= hash << 10;
+          hash += hash >> 1;
+  default:
+          break;
+  }
+
+  /* Force "avalanching" of final 127 bits */
+  hash ^= hash << 3;
+  hash += hash >> 5;
+  hash ^= hash << 4;
+  hash += hash >> 17;
+  hash ^= hash << 25;
+  hash += hash >> 6;
+
+  return hash;
+}
+