mirror of
https://github.com/php/php-src.git
synced 2024-09-22 10:27:25 +00:00
87 lines
2.7 KiB
C
87 lines
2.7 KiB
C
/*
|
|
* gdcache.h
|
|
*
|
|
* Caches of pointers to user structs in which the least-recently-used
|
|
* element is replaced in the event of a cache miss after the cache has
|
|
* reached a given size.
|
|
*
|
|
* John Ellson (ellson@graphviz.org) Oct 31, 1997
|
|
*
|
|
* Test this with:
|
|
* gcc -o gdcache -g -Wall -DTEST gdcache.c
|
|
*
|
|
* The cache is implemented by a singly-linked list of elements
|
|
* each containing a pointer to a user struct that is being managed by
|
|
* the cache.
|
|
*
|
|
* The head structure has a pointer to the most-recently-used
|
|
* element, and elements are moved to this position in the list each
|
|
* time they are used. The head also contains pointers to three
|
|
* user defined functions:
|
|
* - a function to test if a cached userdata matches some keydata
|
|
* - a function to provide a new userdata struct to the cache
|
|
* if there has been a cache miss.
|
|
* - a function to release a userdata struct when it is
|
|
* no longer being managed by the cache
|
|
*
|
|
* In the event of a cache miss the cache is allowed to grow up to
|
|
* a specified maximum size. After the maximum size is reached then
|
|
* the least-recently-used element is discarded to make room for the
|
|
* new. The most-recently-returned value is always left at the
|
|
* beginning of the list after retrieval.
|
|
*
|
|
* In the current implementation the cache is traversed by a linear
|
|
* search from most-recent to least-recent. This linear search
|
|
* probably limits the usefulness of this implementation to cache
|
|
* sizes of a few tens of elements.
|
|
*/
|
|
|
|
/*********************************************************/
|
|
/* header */
|
|
/*********************************************************/
|
|
|
|
#include <stdlib.h>
|
|
#ifdef HAVE_MALLOC_H
|
|
#include <malloc.h>
|
|
#endif
|
|
#ifndef NULL
|
|
#define NULL (void *)0
|
|
#endif
|
|
|
|
/* user defined function templates */
|
|
typedef int (*gdCacheTestFn_t)(void *userdata, void *keydata);
|
|
typedef void *(*gdCacheFetchFn_t)(char **error, void *keydata);
|
|
typedef void (*gdCacheReleaseFn_t)(void *userdata);
|
|
|
|
/* element structure */
|
|
typedef struct gdCache_element_s gdCache_element_t;
|
|
struct gdCache_element_s {
|
|
gdCache_element_t *next;
|
|
void *userdata;
|
|
};
|
|
|
|
/* head structure */
|
|
typedef struct gdCache_head_s gdCache_head_t;
|
|
struct gdCache_head_s {
|
|
gdCache_element_t *mru;
|
|
int size;
|
|
char *error;
|
|
gdCacheTestFn_t gdCacheTest;
|
|
gdCacheFetchFn_t gdCacheFetch;
|
|
gdCacheReleaseFn_t gdCacheRelease;
|
|
};
|
|
|
|
/* function templates */
|
|
gdCache_head_t *
|
|
gdCacheCreate(
|
|
int size,
|
|
gdCacheTestFn_t gdCacheTest,
|
|
gdCacheFetchFn_t gdCacheFetch,
|
|
gdCacheReleaseFn_t gdCacheRelease );
|
|
|
|
void
|
|
gdCacheDelete( gdCache_head_t *head );
|
|
|
|
void *
|
|
gdCacheGet( gdCache_head_t *head, void *keydata );
|