git.m6w6.name Git - awesomized/libmemcached/blob - libhashkit/fnv_64.cc

   1 /*  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
   2  *
   3  *  HashKit library
   4  *
   5  *  Copyright (C) 2011 Data Differential, http://datadifferential.com/
   6  *  Copyright (C) 2009 Brian Aker All rights reserved.
   7  *
   8  *  Redistribution and use in source and binary forms, with or without
   9  *  modification, are permitted provided that the following conditions are
  10  *  met:
  11  *
  12  *      * Redistributions of source code must retain the above copyright
  13  *  notice, this list of conditions and the following disclaimer.
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  15  *      * Redistributions in binary form must reproduce the above
  16  *  copyright notice, this list of conditions and the following disclaimer
  17  *  in the documentation and/or other materials provided with the
  18  *  distribution.
  19  *
  20  *      * The names of its contributors may not be used to endorse or
  21  *  promote products derived from this software without specific prior
  22  *  written permission.
  23  *
  24  *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  25  *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  26  *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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  34  *  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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  37
  38
  39 #include <libhashkit/common.h>
  40
  41 #if __WORDSIZE == 64 && defined(HAVE_FNV64_HASH)
  42
  43 /* FNV hash'es lifted from Dustin Sallings work */
  44 static uint64_t FNV_64_INIT= 0xcbf29ce484222325;
  45 static uint64_t FNV_64_PRIME= 0x100000001b3;
  46
  47 uint32_t hashkit_fnv1_64(const char *key, size_t key_length, void *)
  48 {
  49   /* Thanks to pierre@demartines.com for the pointer */
  50   uint64_t hash= FNV_64_INIT;
  51
  52   for (size_t x= 0; x < key_length; x++)
  53   {
  54     hash *= FNV_64_PRIME;
  55     hash ^= (uint64_t)key[x];
  56   }
  57
  58   return (uint32_t)hash;
  59 }
  60
  61 uint32_t hashkit_fnv1a_64(const char *key, size_t key_length, void *)
  62 {
  63   uint32_t hash= (uint32_t) FNV_64_INIT;
  64
  65   for (size_t x= 0; x < key_length; x++)
  66   {
  67     uint32_t val= (uint32_t)key[x];
  68     hash ^= val;
  69     hash *= (uint32_t) FNV_64_PRIME;
  70   }
  71
  72   return hash;
  73 }
  74
  75 #else
  76 uint32_t hashkit_fnv1_64(const char *, size_t, void *)
  77 {
  78   return 0;
  79 }
  80
  81 uint32_t hashkit_fnv1a_64(const char *, size_t, void *)
  82 {
  83   return 0;
  84 }
  85 #endif