Annotation of embedaddon/php/ext/gd/gdcache.h, revision 1.1
1.1 ! misho 1: /*
! 2: * $Id: gdcache.h 242949 2007-09-26 15:44:16Z cvs2svn $
! 3: *
! 4: * Caches of pointers to user structs in which the least-recently-used
! 5: * element is replaced in the event of a cache miss after the cache has
! 6: * reached a given size.
! 7: *
! 8: * John Ellson (ellson@lucent.com) Oct 31, 1997
! 9: *
! 10: * Test this with:
! 11: * gcc -o gdcache -g -Wall -DTEST gdcache.c
! 12: *
! 13: * The cache is implemented by a singly-linked list of elements
! 14: * each containing a pointer to a user struct that is being managed by
! 15: * the cache.
! 16: *
! 17: * The head structure has a pointer to the most-recently-used
! 18: * element, and elements are moved to this position in the list each
! 19: * time they are used. The head also contains pointers to three
! 20: * user defined functions:
! 21: * - a function to test if a cached userdata matches some keydata
! 22: * - a function to provide a new userdata struct to the cache
! 23: * if there has been a cache miss.
! 24: * - a function to release a userdata struct when it is
! 25: * no longer being managed by the cache
! 26: *
! 27: * In the event of a cache miss the cache is allowed to grow up to
! 28: * a specified maximum size. After the maximum size is reached then
! 29: * the least-recently-used element is discarded to make room for the
! 30: * new. The most-recently-returned value is always left at the
! 31: * beginning of the list after retrieval.
! 32: *
! 33: * In the current implementation the cache is traversed by a linear
! 34: * search from most-recent to least-recent. This linear search
! 35: * probably limits the usefulness of this implementation to cache
! 36: * sizes of a few tens of elements.
! 37: */
! 38:
! 39: /*********************************************************/
! 40: /* header */
! 41: /*********************************************************/
! 42:
! 43: #if (!defined(_OSD_POSIX) && !defined(__FreeBSD__)) && HAVE_MALLOC_H
! 44: #include <malloc.h>
! 45: #else
! 46: #include <stdlib.h> /* BS2000/OSD defines malloc() & friends in stdlib.h */
! 47: #endif
! 48: #ifndef NULL
! 49: #define NULL (void *)0
! 50: #endif
! 51:
! 52: /* user defined function templates */
! 53: typedef int (*gdCacheTestFn_t)(void *userdata, void *keydata);
! 54: typedef void *(*gdCacheFetchFn_t)(char **error, void *keydata);
! 55: typedef void (*gdCacheReleaseFn_t)(void *userdata);
! 56:
! 57: /* element structure */
! 58: typedef struct gdCache_element_s gdCache_element_t;
! 59: struct gdCache_element_s {
! 60: gdCache_element_t *next;
! 61: void *userdata;
! 62: };
! 63:
! 64: /* head structure */
! 65: typedef struct gdCache_head_s gdCache_head_t;
! 66: struct gdCache_head_s {
! 67: gdCache_element_t *mru;
! 68: int size;
! 69: char *error;
! 70: gdCacheTestFn_t gdCacheTest;
! 71: gdCacheFetchFn_t gdCacheFetch;
! 72: gdCacheReleaseFn_t gdCacheRelease;
! 73: };
! 74:
! 75: /* function templates */
! 76: gdCache_head_t *
! 77: gdCacheCreate(
! 78: int size,
! 79: gdCacheTestFn_t gdCacheTest,
! 80: gdCacheFetchFn_t gdCacheFetch,
! 81: gdCacheReleaseFn_t gdCacheRelease );
! 82:
! 83: void
! 84: gdCacheDelete( gdCache_head_t *head );
! 85:
! 86: void *
! 87: gdCacheGet( gdCache_head_t *head, void *keydata );
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