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General Caching Facility for Common Lisp

CLACHE

CLACHE is a general caching library for Common Lisp.

Overview

CLACHE provides a general caching facility for Common Lisp. The API is similar with standard hash-table interface. Let me show you an overview of API.

• getcache - Get cache from storage
• setcache - Store cache into storage
• remcache - Remove cache from storage
• clrcache - Clear all cache in storage

As you can see, it is easy to use. Here is an example:

;; Create a store
(defparamater *store* (progn
                         (ensure-directories-exist #p"cache/")
                         (make-instance 'file-store :directory #p"cache/")))

;; Store cache
(setcache 1 "foo" *store*)
;;=> 1

;; Get cache
(getcache 1 *store*)
;;=> 1, T

;; Get non-exited cache
(getcache 42 *store*)
;;=> NIL, NIL

;; Remove cache
(remcache 1 *store*)
;;=> T

;; Clear all cache
(clrcache *store*)

API

Caches

A cache is a triple of a key, a value, and an expiration time.

Cache Keys

Any object can be used as a cache key if the object can be converted into a string properly by using cache-key-to-string.

Cache Values

Same as cache keys, any object can be used as a cache value. However, a type of cache values can be limited by storages. So you have to be careful what storage are you using.

Expiration Time

An expiration time describes how long caches live in seconds. If an expiration time is nil, such caches will never be expired: persistent cache.

Cache Existence

If a cache is stored in a storage and has not yet been expired or a persitent cache, we express the cache exists in the storage.

Storages

Storage is an abstract layer of maintaining caches. You can access storages via API.

Default Storage

Function: getcache

getcache key storage

Retrieve a cache value from storage indicated by key and return values of the cache value and a boolean whether the cache exists in storage. The cache value will be nil if such the cache doesn't exist. For example, (getcache "not-existed-cache") will return nil, nil.

Function: setcache

setcache key value storage &optional expire

Store a cache value into storage with key and expire. expire is an expiration time in seconds. If expire is nil, the cache will never be expired. The return value is value that has been stored.

Function: (setf getcache)

(setf getcache) value key storage &optional expire 

Same as setcache.

Function: remcache

remcache key storage

Remove a cache from storage indicated by key. If the cache has been successfully removed, this function returns t, otherwise returns nil.

Function: clrcache

clrcache storage

Remove all caches from storage. The return value is undefined.

Macro: with-cache

Annotation: cache

Protocol

Supported Implementations

• Allegro CL v8.2
• SBCL v1.0.47
• CMU CL v20b
• Clozure CL v1.6
• ECL v11.1.1
• GNU CLISP v2.48

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Copyright (C) 2011 Tomohiro Matsuyama <[email protected]>