| /* | |
| * 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 */ | |
| /*********************************************************/ | |
| /* 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 ); | |