git.m6w6.name Git - awesomized/libmemcached/blob - lib/memcached_hash.c

   1 #include "common.h"
   2
   3 /* Prototypes */
   4 static unsigned int internal_generate_hash(char *key, size_t key_length);
   5 static uint32_t internal_generate_md5(char *key, size_t key_length);
   6
   7 unsigned int memcached_generate_hash(memcached_st *ptr, char *key, size_t key_length)
   8 {
   9   uint32_t hash;
  10
  11   if (ptr->flags & MEM_USE_MD5)
  12     hash= internal_generate_md5(key, key_length);
  13   else if (ptr->flags & MEM_USE_CRC)
  14     hash= hash_crc32(key, key_length);
  15   else
  16     hash= internal_generate_hash(key, key_length);
  17
  18   if (ptr->flags & MEM_USE_KETAMA)
  19   {
  20     WATCHPOINT_ASSERT(0);
  21     return 0;
  22   }
  23   else
  24     return hash % ptr->number_of_hosts;
  25 }
  26
  27 static uint32_t internal_generate_hash(char *key, size_t key_length)
  28 {
  29   char *ptr= key;
  30   unsigned int value= 0;
  31
  32   while (--key_length)
  33   {
  34     value += *ptr++;
  35     value += (value << 10);
  36     value ^= (value >> 6);
  37   }
  38   value += (value << 3);
  39   value ^= (value >> 11);
  40   value += (value << 15);
  41
  42   return value == 0 ? 1 : value;
  43 }
  44
  45 static uint32_t internal_generate_md5(char *key, size_t key_length)
  46 {
  47   unsigned char results[16];
  48
  49   md5_signature((unsigned char*)key, (unsigned int)key_length, results);
  50
  51   return (uint32_t)(( results[3] << 24 )
  52                     | ( results[2] << 16 )
  53                     | ( results[1] <<  8 )
  54                     |   results[0] );
  55 }