cache_create(3) 					   BSD Library Functions Manual 					   cache_create(3)

NAME

     cache_create -- Creates an in memory cache

SYNOPSIS

     #include <cache.h>

     int
     cache_create(const char *name, cache_attributes_t *attrs, cache_t **cache_out);

     int
     cache_destroy(cache_t *cache);

DESCRIPTION

     cache_create() Creates a cache using attributes attrs (see below) and name name and if successful stores it in cache_out.	name is a NULL-
     terminated cstring in reverse-DNS form (e.g. "com.mycompany.imagecache") and is used for debugging and performance tools.	It must not be
     NULL.

     cache_destroy() Removes all unreferenced values in cache and deallocates it.

CACHE ATTRIBUTES

     Cache attributes are callbacks passed to cache_create() to support different types of keys and values and to configure cache behavior.  The
     cache framework provides preexisting cache_callbacks(3) functions that can be used for these callbacks to support common key and value types

     typedef struct cache_attributes_s {
	 uint32_t version;
	 cache_key_hash_cb_t key_hash_cb;
	 cache_key_is_equal_cb_t key_is_equal_cb;

	 cache_key_retain_cb_t	key_retain_cb;
	 cache_release_cb_t key_release_cb;
	 cache_release_cb_t value_release_cb;

	 cache_value_make_nonpurgeable_cb_t value_make_nonpurgeable_cb;
	 cache_value_make_purgeable_cb_t value_make_purgeable_cb;

	 void *user_data;
	 cache_value_retain_cb_t value_retain_cb;
     } cache_attributes_t;
     #define CACHE_ATTRIBUTES_VERSION_2 2

     key_hash_cb		    Calculates a hash value using key

     key_is_equal_cb		    Determines if two keys are equal

     key_retain_cb		    Called when a key is added to a cache using cache_set_and_retain() to allow key to be copied, or retained if
				    it is a reference-counted object.

     key_release_cb		    Called when a key is removed or evicted from a cache to allow the key to be deallocated, or released if it is
				    a reference-counted object.

     value_retain_cb		    Called when a value is added to a cache using cache_set_and_retain() to allow value to be retained if it is a
				    reference-counted object.

     value_release_cb		    Called when a value is removed or evicted from a cache to allow the key to be deallocated, or released if it
				    is a reference-counted object.

     value_make_nonpurgeable_cb     Called when a value is referenced using cache_get_and_retain() to allow it to be made nonpurgeable or uncom-
				    pressed.

     value_make_purgeable_cb	    Called when a value is unreferenced to allow it to be made purgeable or compressed.

     version			    Attributes version number used for binary compatibility.

     user_data			    This value will be passed to all other callbacks for this cache.  May be NULL.

RETURN VALUES

     All functions return 0 for success and non-zero for failure.

EXAMPLE

     The following example uses pre-existing cache_callbacks(3) to create a cache with cstring keys and malloc(3) allocated values.  The

     #include <cache.h>
     #include <cache_callbcaks.h>

     cache_t *im_cache;
     cache_attributes_t attrs = {
	 .version = CACHE_ATTRIBUTES_VERSION_2,
	 .key_hash_cb = cache_key_hash_cb_cstring,
	 .key_is_equal_cb = cache_key_is_equal_cb_cstring,
	 .key_retain_cb = my_copy_string,
	 .key_release_cb = cache_release_cb_free,
	 .value_release_cb = cache_release_cb_free,
     };
     cache_create("com.acme.im_cache", &attrs, &im_cache);

SEE ALSO

     cache(3) cache_set_and_retain(3) cache_callbacks(3)

Darwin								    May 7, 2009 							    Darwin