#include "common.h"
/* Defines */
static uint64_t FNV_64_INIT= UINT64_C(0xcbf29ce484222325);
static uint64_t FNV_64_PRIME= UINT64_C(0x100000001b3);
static uint32_t FNV_32_INIT= 2166136261UL;
static uint32_t FNV_32_PRIME= 16777619;
/* Prototypes */
static uint32_t internal_generate_hash(const char *key, size_t key_length);
static uint32_t internal_generate_md5(const char *key, size_t key_length);
uint32_t memcached_generate_hash_value(const char *key, size_t key_length, memcached_hash hash_algorithm)
{
uint32_t hash= 1; /* Just here to remove compile warning */
uint32_t x= 0;
switch (hash_algorithm)
{
case MEMCACHED_HASH_DEFAULT:
hash= internal_generate_hash(key, key_length);
break;
case MEMCACHED_HASH_MD5:
hash= internal_generate_md5(key, key_length);
break;
case MEMCACHED_HASH_CRC:
hash= ((hash_crc32(key, key_length) >> 16) & 0x7fff);
if (hash == 0)
hash= 1;
break;
/* FNV hash'es lifted from Dustin Sallings work */
case MEMCACHED_HASH_FNV1_64:
{
/* Thanks to pierre@demartines.com for the pointer */
uint64_t temp_hash;
temp_hash= FNV_64_INIT;
for (x= 0; x < key_length; x++)
{
temp_hash *= FNV_64_PRIME;
temp_hash ^= key[x];
}
hash= (uint32_t)temp_hash;
}
break;
case MEMCACHED_HASH_FNV1A_64:
{
hash= FNV_64_INIT;
for (x= 0; x < key_length; x++)
{
hash ^= key[x];
hash *= FNV_64_PRIME;
}
}
break;
case MEMCACHED_HASH_FNV1_32:
{
hash= FNV_32_INIT;
for (x= 0; x < key_length; x++)
{
hash *= FNV_32_PRIME;
hash ^= key[x];
}
}
break;
case MEMCACHED_HASH_FNV1A_32:
{
hash= FNV_32_INIT;
for (x= 0; x < key_length; x++)
{
hash ^= key[x];
hash *= FNV_32_PRIME;
}
}
break;
case MEMCACHED_HASH_HSIEH:
{
#ifdef HAVE_HSIEH_HASH
hash= hsieh_hash(key, key_length);
#endif
break;
}
case MEMCACHED_HASH_MURMUR:
{
hash= murmur_hash(key, key_length);
break;
}
case MEMCACHED_HASH_JENKINS:
{
hash=jenkins_hash(key, key_length, 13);
break;
}
default:
{
WATCHPOINT_ASSERT(hash_algorithm);
break;
}
}
return hash;
}
uint32_t generate_hash(memcached_st *ptr, const char *key, size_t key_length)
{
uint32_t hash= 1; /* Just here to remove compile warning */
WATCHPOINT_ASSERT(ptr->number_of_hosts);
if (ptr->number_of_hosts == 1)
return 0;
hash= memcached_generate_hash_value(key, key_length, ptr->hash);
WATCHPOINT_ASSERT(hash);
return hash;
}
static uint32_t dispatch_host(memcached_st *ptr, uint32_t hash)
{
switch (ptr->distribution)
{
case MEMCACHED_DISTRIBUTION_CONSISTENT:
case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA:
{
uint32_t num= ptr->continuum_points_counter;
WATCHPOINT_ASSERT(ptr->continuum);
hash= hash;
memcached_continuum_item_st *begin, *end, *left, *right, *middle;
begin= left= ptr->continuum;
end= right= ptr->continuum + num;
while (left < right)
{
middle= left + (right - left) / 2;
if (middle->value < hash)
left= middle + 1;
else
right= middle;
}
if (right == end)
right= begin;
return right->index;
}
case MEMCACHED_DISTRIBUTION_MODULA:
return hash % ptr->number_of_hosts;
case MEMCACHED_DISTRIBUTION_RANDOM:
return random() % ptr->number_of_hosts;
default:
WATCHPOINT_ASSERT(0); /* We have added a distribution without extending the logic */
return hash % ptr->number_of_hosts;
}
/* NOTREACHED */
}
/*
One day make this public, and have it return the actual memcached_server_st
to the calling application.
*/
uint32_t memcached_generate_hash(memcached_st *ptr, const char *key, size_t key_length)
{
uint32_t hash= 1; /* Just here to remove compile warning */
WATCHPOINT_ASSERT(ptr->number_of_hosts);
if (ptr->number_of_hosts == 1)
return 0;
if (ptr->flags & MEM_HASH_WITH_PREFIX_KEY)
{
size_t temp_length= ptr->prefix_key_length + key_length;
char temp[temp_length];
if (temp_length > MEMCACHED_MAX_KEY -1)
return 0;
strncpy(temp, ptr->prefix_key, ptr->prefix_key_length);
strncpy(temp + ptr->prefix_key_length, key, key_length);
hash= generate_hash(ptr, temp, temp_length);
}
else
{
hash= generate_hash(ptr, key, key_length);
}
WATCHPOINT_ASSERT(hash);
if (memcached_behavior_get(ptr, MEMCACHED_BEHAVIOR_AUTO_EJECT_HOSTS) && ptr->next_distribution_rebuild) {
struct timeval now;
if (gettimeofday(&now, NULL) == 0 &&
now.tv_sec > ptr->next_distribution_rebuild)
run_distribution(ptr);
}
return dispatch_host(ptr, hash);
}
static uint32_t internal_generate_hash(const char *key, size_t key_length)
{
const char *ptr= key;
uint32_t value= 0;
while (key_length--)
{
value += *ptr++;
value += (value << 10);
value ^= (value >> 6);
}
value += (value << 3);
value ^= (value >> 11);
value += (value << 15);
return value == 0 ? 1 : value;
}
static uint32_t internal_generate_md5(const char *key, size_t key_length)
{
unsigned char results[16];
md5_signature((unsigned char*)key, (unsigned int)key_length, results);
return ((uint32_t) (results[3] & 0xFF) << 24)
| ((uint32_t) (results[2] & 0xFF) << 16)
| ((uint32_t) (results[1] & 0xFF) << 8)
| (results[0] & 0xFF);
}