/*
* =====================================================================================
*
* Filename: cache.c
*
* Description: A simple cache
*
* Version: 1.0
* Created: 04/11/2013 02:31:02 PM
* Revision: none
* Compiler: gcc
*
* Author: Oliver Lorenz (ol), olli@olorenz.org
* Company: https://olorenz.org
* License: This is licensed under the same terms as uthash itself
*
* =====================================================================================
*/
#include <errno.h>
#include <pthread.h>
#include <stdlib.h>
#include "cache.h"
#include "uthash.h"
/**
* A cache entry
*/
struct foo_cache_entry {
char *key; /**<The key */
void *data; /**<Payload */
UT_hash_handle hh; /**<Hash Handle for uthash */
};
#define KEY_MAX_LENGTH 32
/**
* A cache object
*/
struct foo_cache {
size_t max_entries; /**<Amount of entries this cache object can hold */
pthread_rwlock_t cache_lock; /**<A lock for concurrent access */
struct foo_cache_entry *entries; /**<Head pointer for uthash */
void (*free_cb) (void *element);/**<Callback function to free cache entries */
};
/** Creates a new cache object
@param dst
Where the newly allocated cache object will be stored in
@param capacity
The maximum number of elements this cache object can hold
@return EINVAL if dst is NULL, ENOMEM if malloc fails, 0 otherwise
*/
int foo_cache_create(struct foo_cache **dst, const size_t capacity,
void (*free_cb) (void *element))
{
struct foo_cache *new = NULL;
int rv;
if (!dst)
return EINVAL;
if ((new = malloc(sizeof(*new))) == NULL)
return ENOMEM;
if ((rv = pthread_rwlock_init(&(new->cache_lock), NULL)) != 0)
goto err_out;
new->max_entries = capacity;
new->entries = NULL;
new->free_cb = free_cb;
*dst = new;
return 0;
err_out:
if (new)
free(new);
return rv;
}
/** Frees an allocated cache object
@param cache
The cache object to free
@param keep_data
Whether to free contained data or just delete references to it
@return EINVAL if cache is NULL, 0 otherwise
*/
int foo_cache_delete(struct foo_cache *cache, int keep_data)
{
struct foo_cache_entry *entry, *tmp;
int rv;
if (!cache)
return EINVAL;
rv = pthread_rwlock_wrlock(&(cache->cache_lock));
if (rv)
return rv;
if (keep_data) {
HASH_CLEAR(hh, cache->entries);
} else {
HASH_ITER(hh, cache->entries, entry, tmp) {
HASH_DEL(cache->entries, entry);
if (cache->free_cb)
cache->free_cb(entry->data);
free(entry);
}
}
(void)pthread_rwlock_unlock(&(cache->cache_lock));
(void)pthread_rwlock_destroy(&(cache->cache_lock));
free(cache);
cache = NULL;
return 0;
}
/** Checks if a given key is in the cache
@param cache
The cache object
@param key
The key to look-up
@param result
Where to store the result if key is found.
A warning: Even though result is just a pointer,
you have to call this function with a **ptr,
otherwise this will blow up in your face.
@return EINVAL if cache is NULL, 0 otherwise
*/
int foo_cache_lookup(struct foo_cache *cache, char *key, void *result)
{
int rv;
struct foo_cache_entry *tmp = NULL;
char **dirty_hack = result;
if (!cache || !key || !result)
return EINVAL;
rv = pthread_rwlock_wrlock(&(cache->cache_lock));
if (rv)
return rv;
HASH_FIND_STR(cache->entries, key, tmp);
if (tmp) {
size_t key_len = strnlen(tmp->key, KEY_MAX_LENGTH);
HASH_DELETE(hh, cache->entries, tmp);
HASH_ADD_KEYPTR(hh, cache->entries, tmp->key, key_len, tmp);
*dirty_hack = tmp->data;
} else {
*dirty_hack = result = NULL;
}
rv = pthread_rwlock_unlock(&(cache->cache_lock));
return rv;
}
/** Inserts a given <key, value> pair into the cache
@param cache
The cache object
@param key
The key that identifies <value>
@param data
Data associated with <key>
@return EINVAL if cache is NULL, ENOMEM if malloc fails, 0 otherwise
*/
int foo_cache_insert(struct foo_cache *cache, char *key, void *data)
{
struct foo_cache_entry *entry = NULL;
struct foo_cache_entry *tmp_entry = NULL;
size_t key_len = 0;
int rv;
if (!cache || !data)
return EINVAL;
if ((entry = malloc(sizeof(*entry))) == NULL)
return ENOMEM;
if ((rv = pthread_rwlock_wrlock(&(cache->cache_lock))) != 0)
goto err_out;
entry->key = key;
entry->data = data;
key_len = strnlen(entry->key, KEY_MAX_LENGTH);
HASH_ADD_KEYPTR(hh, cache->entries, entry->key, key_len, entry);
if (HASH_COUNT(cache->entries) >= cache->max_entries) {
HASH_ITER(hh, cache->entries, entry, tmp_entry) {
HASH_DELETE(hh, cache->entries, entry);
if (cache->free_cb)
cache->free_cb(entry->data);
else
free(entry->data);
/* free(key->key) if data has been copied */
free(entry);
break;
}
}
rv = pthread_rwlock_unlock(&(cache->cache_lock));
return rv;
err_out:
if (entry)
free(entry);
(void)pthread_rwlock_unlock(&(cache->cache_lock));
return rv;
}