- sync to 1.6.2GD_1_6_2

1 files changed, 83 insertions, 0 deletions

diff --git a/src/gdcache.h b/src/gdcache.h
new file mode 100644
index 0000000..f2e8509
--- /dev/null
+++ b/src/gdcache.h
@@ -0,0 +1,83 @@
+/* 
+ * 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@lucent.com)  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 <malloc.h>
+#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 );