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Diffstat (limited to 'Build/source/libs/gd/gdcache.c')
-rw-r--r-- | Build/source/libs/gd/gdcache.c | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/Build/source/libs/gd/gdcache.c b/Build/source/libs/gd/gdcache.c new file mode 100644 index 00000000000..b5b8913415a --- /dev/null +++ b/Build/source/libs/gd/gdcache.c @@ -0,0 +1,218 @@ + +#ifdef HAVE_CONFIG_H +#include "config.h" +#endif + +#include "gd.h" +#include "gdhelpers.h" + +#ifdef HAVE_LIBTTF +#define NEED_CACHE 1 +#else +#ifdef HAVE_LIBFREETYPE +#define NEED_CACHE 1 +#endif +#endif + +#ifdef NEED_CACHE + +/* + * gdcache.c + * + * 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. + */ + +#include "gdcache.h" + +/*********************************************************/ +/* implementation */ +/*********************************************************/ + + +/* create a new cache */ +gdCache_head_t * +gdCacheCreate (int size, + gdCacheTestFn_t gdCacheTest, + gdCacheFetchFn_t gdCacheFetch, + gdCacheReleaseFn_t gdCacheRelease) +{ + gdCache_head_t *head; + + head = (gdCache_head_t *) gdMalloc (sizeof (gdCache_head_t)); + head->mru = NULL; + head->size = size; + head->gdCacheTest = gdCacheTest; + head->gdCacheFetch = gdCacheFetch; + head->gdCacheRelease = gdCacheRelease; + return head; +} + +void +gdCacheDelete (gdCache_head_t * head) +{ + gdCache_element_t *elem, *prev; + + elem = head->mru; + while (elem) + { + (*(head->gdCacheRelease)) (elem->userdata); + prev = elem; + elem = elem->next; + gdFree ((char *) prev); + } + gdFree ((char *) head); +} + +void * +gdCacheGet (gdCache_head_t * head, void *keydata) +{ + int i = 0; + gdCache_element_t *elem, *prev = NULL, *prevprev = NULL; + void *userdata; + + elem = head->mru; + while (elem) + { + if ((*(head->gdCacheTest)) (elem->userdata, keydata)) + { + if (i) + { /* if not already most-recently-used */ + /* relink to top of list */ + prev->next = elem->next; + elem->next = head->mru; + head->mru = elem; + } + return elem->userdata; + } + prevprev = prev; + prev = elem; + elem = elem->next; + i++; + } + userdata = (*(head->gdCacheFetch)) (&(head->error), keydata); + if (!userdata) + { + /* if there was an error in the fetch then don't cache */ + return NULL; + } + if (i < head->size) + { /* cache still growing - add new elem */ + elem = (gdCache_element_t *) gdMalloc (sizeof (gdCache_element_t)); + } + else + { /* cache full - replace least-recently-used */ + /* preveprev becomes new end of list */ + prevprev->next = NULL; + elem = prev; + (*(head->gdCacheRelease)) (elem->userdata); + } + /* relink to top of list */ + elem->next = head->mru; + head->mru = elem; + elem->userdata = userdata; + return userdata; +} + + + +/*********************************************************/ +/* test stub */ +/*********************************************************/ + + +#ifdef TEST + +#include <stdio.h> + +typedef struct +{ + int key; + int value; +} +key_value_t; + +static int +cacheTest (void *map, void *key) +{ + return (((key_value_t *) map)->key == *(int *) key); +} + +static void * +cacheFetch (char **error, void *key) +{ + key_value_t *map; + + map = (key_value_t *) gdMalloc (sizeof (key_value_t)); + map->key = *(int *) key; + map->value = 3; + + *error = NULL; + return (void *) map; +} + +static void +cacheRelease (void *map) +{ + gdFree ((char *) map); +} + +int +main (char *argv[], int argc) +{ + gdCache_head_t *cacheTable; + int elem, key; + + cacheTable = gdCacheCreate (3, cacheTest, cacheFetch, cacheRelease); + + key = 20; + elem = *(int *) gdCacheGet (cacheTable, &key); + key = 30; + elem = *(int *) gdCacheGet (cacheTable, &key); + key = 40; + elem = *(int *) gdCacheGet (cacheTable, &key); + key = 50; + elem = *(int *) gdCacheGet (cacheTable, &key); + key = 30; + elem = *(int *) gdCacheGet (cacheTable, &key); + key = 30; + elem = *(int *) gdCacheGet (cacheTable, &key); + + gdCacheDelete (cacheTable); + + return 0; +} + +#endif /* TEST */ +#endif /* HAVE_LIBTTF */ |