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cache_callbacks(3) [osx man page]

cache_callbacks(3)					   BSD Library Functions Manual 					cache_callbacks(3)

NAME
cache_callbacks -- Pre-defined cache callbacks used to configure a cache SYNOPSIS
#include <cache.h> #include <cache_callbacks.h> uintptr_t cache_key_hash_cb_cstring(void *key, void *unused); uintptr_t cache_key_hash_cb_integer(void *key, void *unused); bool cache_key_is_equal_cb_cstring(void *key1, void *key2, void *unused); bool cache_key_is_equal_cb_integer(void *key1, void *key2, void *unused); void cache_release_cb_free(void *key_or_value, void *unused); void cache_value_make_purgeable_cb(void *value, void *unused); bool cache_value_make_nonpurgeable_cb(void *value, void *unused); uintptr_t cache_hash_byte_string(const char *data, size_t bytes); DESCRIPTION
These functions are intended to be used as callbacks to configure how a cache functions. They should be set in the cache_attributes_t passed into cache_create. They support common key types and offer support for using purgeable memory to allocate cache values. cache_key_hash_cb_cstring() A key_hash_cb() function for NULL-terminated cstring keys. cache_key_hash_cb_integer() A key_hash_cb() function for integer keys. cache_key_is_equal_cb_cstring() A key_is_equal_cb() function for cstring keys. cache_key_is_equal_cb_integer() A key_is_equal_cb() function for integer keys. cache_release_cb_free() Can be used for key_release_cb() or value_release_cb() for keys/values allocated from malloc and family. cache_value_make_purgeable_cb() Can be used for value_make_purgeable() with values allocated from the purgeable malloc zone (see malloc/mal- loc.h). Calls malloc_make_purgeable() on value when it is unreferenced in order to reduce paging under memory pressure. value_make_purgeable() with values allocated from the purgeable malloc zone (see malloc/malloc.h). Calls malloc_make_purgeable() on value when it is unreferenced in order to reduce paging under memory pressure. cache_hash_byte_string() Calculates a hash from a bytes string data of length bytes. SEE ALSO
libcache(3) cache_create(3) Darwin May 7, 2009 Darwin

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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
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