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/**************************************************************************
*
* Copyright 2008 VMware, Inc.
* All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sub license, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial portions
* of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
* IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
* ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
**************************************************************************/
/**
* @file
* Simple cache implementation.
*
* We simply have fixed size array, and destroy previous values on collision.
*
* @author Jose Fonseca <jfonseca@vmware.com>
*/
#include "pipe/p_compiler.h"
#include "util/u_debug.h"
#include "util/u_math.h"
#include "util/u_memory.h"
#include "util/u_cache.h"
struct util_cache_entry
{
void *key;
void *value;
#ifdef DEBUG
unsigned count;
#endif
};
struct util_cache
{
/** Hash function */
uint32_t (*hash)(const void *key);
/** Compare two keys */
int (*compare)(const void *key1, const void *key2);
/** Destroy a (key, value) pair */
void (*destroy)(void *key, void *value);
uint32_t size;
struct util_cache_entry *entries;
#ifdef DEBUG
unsigned count;
#endif
};
struct util_cache *
util_cache_create(uint32_t (*hash)(const void *key),
int (*compare)(const void *key1, const void *key2),
void (*destroy)(void *key, void *value),
uint32_t size)
{
struct util_cache *cache;
cache = CALLOC_STRUCT(util_cache);
if(!cache)
return NULL;
cache->hash = hash;
cache->compare = compare;
cache->destroy = destroy;
cache->size = size;
cache->entries = CALLOC(size, sizeof(struct util_cache_entry));
if(!cache->entries) {
FREE(cache);
return NULL;
}
return cache;
}
static INLINE struct util_cache_entry *
util_cache_entry_get(struct util_cache *cache,
const void *key)
{
uint32_t hash;
hash = cache->hash(key);
return &cache->entries[hash % cache->size];
}
static INLINE void
util_cache_entry_destroy(struct util_cache *cache,
struct util_cache_entry *entry)
{
void *key = entry->key;
void *value = entry->value;
entry->key = NULL;
entry->value = NULL;
if(key || value)
if(cache->destroy)
cache->destroy(key, value);
}
void
util_cache_set(struct util_cache *cache,
void *key,
void *value)
{
struct util_cache_entry *entry;
assert(cache);
entry = util_cache_entry_get(cache, key);
util_cache_entry_destroy(cache, entry);
#ifdef DEBUG
++entry->count;
++cache->count;
#endif
entry->key = key;
entry->value = value;
}
void *
util_cache_get(struct util_cache *cache,
const void *key)
{
struct util_cache_entry *entry;
assert(cache);
entry = util_cache_entry_get(cache, key);
if(!entry->key && !entry->value)
return NULL;
if(cache->compare(key, entry->key) != 0)
return NULL;
return entry->value;
}
void
util_cache_clear(struct util_cache *cache)
{
uint32_t i;
assert(cache);
for(i = 0; i < cache->size; ++i)
util_cache_entry_destroy(cache, &cache->entries[i]);
}
void
util_cache_destroy(struct util_cache *cache)
{
assert(cache);
#ifdef DEBUG
if(cache->count >= 20*cache->size) {
/* Normal approximation of the Poisson distribution */
double mean = (double)cache->count/(double)cache->size;
double stddev = sqrt(mean);
unsigned i;
for(i = 0; i < cache->size; ++i) {
double z = fabs(cache->count - mean)/stddev;
/* This assert should not fail 99.9999998027% of the times, unless
* the hash function is a poor one */
assert(z <= 6.0);
}
}
#endif
util_cache_clear(cache);
FREE(cache->entries);
FREE(cache);
}
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