Annotation of embedaddon/php/ext/gd/libgd/gdcache.h, revision 1.1.1.1
1.1 misho 1: /*
2: * gdcache.h
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@graphviz.org) 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: #include <stdlib.h>
44: #ifdef HAVE_MALLOC_H
45: #include <malloc.h>
46: #endif
47: #ifndef NULL
48: #define NULL (void *)0
49: #endif
50:
51: /* user defined function templates */
52: typedef int (*gdCacheTestFn_t)(void *userdata, void *keydata);
53: typedef void *(*gdCacheFetchFn_t)(char **error, void *keydata);
54: typedef void (*gdCacheReleaseFn_t)(void *userdata);
55:
56: /* element structure */
57: typedef struct gdCache_element_s gdCache_element_t;
58: struct gdCache_element_s {
59: gdCache_element_t *next;
60: void *userdata;
61: };
62:
63: /* head structure */
64: typedef struct gdCache_head_s gdCache_head_t;
65: struct gdCache_head_s {
66: gdCache_element_t *mru;
67: int size;
68: char *error;
69: gdCacheTestFn_t gdCacheTest;
70: gdCacheFetchFn_t gdCacheFetch;
71: gdCacheReleaseFn_t gdCacheRelease;
72: };
73:
74: /* function templates */
75: gdCache_head_t *
76: gdCacheCreate(
77: int size,
78: gdCacheTestFn_t gdCacheTest,
79: gdCacheFetchFn_t gdCacheFetch,
80: gdCacheReleaseFn_t gdCacheRelease );
81:
82: void
83: gdCacheDelete( gdCache_head_t *head );
84:
85: void *
86: gdCacheGet( gdCache_head_t *head, void *keydata );
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