git.m6w6.name Git - awesomized/libmemcached/blob - libhashkit/one_at_a_time.c

   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 "common.h"
  15
  16 uint32_t hashkit_one_at_a_time(const char *key, size_t key_length, void *context __attribute__((unused)))
  17 {
  18   const char *ptr= key;
  19   uint32_t value= 0;
  20
  21   while (key_length--)
  22   {
  23     uint32_t val= (uint32_t) *ptr++;
  24     value += val;
  25     value += (value << 10);
  26     value ^= (value >> 6);
  27   }
  28   value += (value << 3);
  29   value ^= (value >> 11);
  30   value += (value << 15);
  31
  32   return value;
  33 }