git.m6w6.name Git - awesomized/libmemcached/blob - libmemcached/hash.c

   1 /* LibMemcached
   2  * Copyright (C) 2006-2010 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  * Summary:
   9  *
  10  */
  11
  12 #include "common.h"
  13
  14
  15 uint32_t memcached_generate_hash_value(const char *key, size_t key_length, memcached_hash_t hash_algorithm)
  16 {
  17   return libhashkit_digest(key, key_length, (hashkit_hash_algorithm_t)hash_algorithm);
  18 }
  19
  20 uint32_t generate_hash(memcached_st *ptr, const char *key, size_t key_length)
  21 {
  22   uint32_t hash= 1; /* Just here to remove compile warning */
  23
  24
  25   WATCHPOINT_ASSERT(memcached_server_count(ptr));
  26
  27   if (memcached_server_count(ptr) == 1)
  28     return 0;
  29
  30   hash= hashkit_digest(&ptr->hashkit, key, key_length);
  31
  32   return hash;
  33 }
  34
  35 static uint32_t dispatch_host(memcached_st *ptr, uint32_t hash)
  36 {
  37   switch (ptr->distribution)
  38   {
  39   case MEMCACHED_DISTRIBUTION_CONSISTENT:
  40   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA:
  41   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA_SPY:
  42     {
  43       uint32_t num= ptr->continuum_points_counter;
  44       WATCHPOINT_ASSERT(ptr->continuum);
  45
  46       hash= hash;
  47       memcached_continuum_item_st *begin, *end, *left, *right, *middle;
  48       begin= left= ptr->continuum;
  49       end= right= ptr->continuum + num;
  50
  51       while (left < right)
  52       {
  53         middle= left + (right - left) / 2;
  54         if (middle->value < hash)
  55           left= middle + 1;
  56         else
  57           right= middle;
  58       }
  59       if (right == end)
  60         right= begin;
  61       return right->index;
  62     }
  63   case MEMCACHED_DISTRIBUTION_MODULA:
  64     return hash % memcached_server_count(ptr);
  65   case MEMCACHED_DISTRIBUTION_RANDOM:
  66     return (uint32_t) random() % memcached_server_count(ptr);
  67   case MEMCACHED_DISTRIBUTION_CONSISTENT_MAX:
  68   default:
  69     WATCHPOINT_ASSERT(0); /* We have added a distribution without extending the logic */
  70     return hash % memcached_server_count(ptr);
  71   }
  72   /* NOTREACHED */
  73 }
  74
  75 /*
  76   One day make this public, and have it return the actual memcached_server_st
  77   to the calling application.
  78 */
  79 uint32_t memcached_generate_hash(memcached_st *ptr, const char *key, size_t key_length)
  80 {
  81   uint32_t hash= 1; /* Just here to remove compile warning */
  82
  83   WATCHPOINT_ASSERT(memcached_server_count(ptr));
  84
  85   if (memcached_server_count(ptr) == 1)
  86     return 0;
  87
  88   if (ptr->flags.hash_with_prefix_key)
  89   {
  90     size_t temp_length= ptr->prefix_key_length + key_length;
  91     char temp[temp_length];
  92
  93     if (temp_length > MEMCACHED_MAX_KEY -1)
  94       return 0;
  95
  96     strncpy(temp, ptr->prefix_key, ptr->prefix_key_length);
  97     strncpy(temp + ptr->prefix_key_length, key, key_length);
  98     hash= generate_hash(ptr, temp, temp_length);
  99   }
 100   else
 101   {
 102     hash= generate_hash(ptr, key, key_length);
 103   }
 104
 105   if (memcached_behavior_get(ptr, MEMCACHED_BEHAVIOR_AUTO_EJECT_HOSTS) && ptr->next_distribution_rebuild)
 106   {
 107     struct timeval now;
 108
 109     if (gettimeofday(&now, NULL) == 0 &&
 110         now.tv_sec > ptr->next_distribution_rebuild)
 111     {
 112       run_distribution(ptr);
 113     }
 114   }
 115
 116   return dispatch_host(ptr, hash);
 117 }
 118
 119 hashkit_st *memcached_get_hashkit(memcached_st *ptr)
 120 {
 121   return &ptr->hashkit;
 122 }