git.m6w6.name Git - m6w6/libmemcached/blob - libhashkit/one_at_a_time.cc

   1 /* HashKit
   2  * Copyright (C) 2009 Brian Aker
   3  * All rights reserved.
   4  *
   5  * Use and distribution licensed under the BSD license.  See
   6  * the COPYING file in the parent directory for full text.
   7  */
   8
   9 /*
  10   This has is Jenkin's "One at A time Hash".
  11 http://en.wikipedia.org/wiki/Jenkins_hash_function
  12 */
  13
  14 #include <libhashkit/common.h>
  15
  16 uint32_t hashkit_one_at_a_time(const char *key, size_t key_length, void *context)
  17 {
  18   const char *ptr= key;
  19   uint32_t value= 0;
  20   (void)context;
  21
  22   while (key_length--)
  23   {
  24     uint32_t val= (uint32_t) *ptr++;
  25     value += val;
  26     value += (value << 10);
  27     value ^= (value >> 6);
  28   }
  29   value += (value << 3);
  30   value ^= (value >> 11);
  31   value += (value << 15);
  32
  33   return value;
  34 }