net.liftweb.util.KeyedCache.scala Maven / Gradle / Ivy
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/*
* Copyright 2006-2011 WorldWide Conferencing, LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package net.liftweb
package util
import common._
/**
* A simple Read-through cache.
*
* An example of using it with a ProtoUser subclass:
*
* object UserCache extends KeyedCache[Long, User](100, Full(0.75f),
* (id: Long) => User.find(By(User.id, id)))
*
* @param size the size of the cache
* @param loadFactor the optional Load Factor
* @param cons A function that will take a value of type K and return a Box[T]
* populated into the cache if the return value is Full.
*
* @author Steve Jenson ([email protected])
*/
class KeyedCache[K, T](size: Int, loadFactor: Box[Float], cons: K => Box[T]) {
val cache = new LRU[K, T](size, loadFactor)
/**
* Evict a value from the cache.
*/
def remove(key: K) = cache.remove(key)
/**
* Update the cache yourself with KeyedCache(1) = "hello"
*/
def update(key: K, value: T) = cache.update(key, value)
/**
* If the cache contains a value mapped to {@code key} then return it,
* otherwise run cons and add that value to the cache and return it.
*/
def apply(key: K): Box[T] = if (cache.contains(key)) {
Full(cache(key))
} else {
cons(key) match {
case f@Full(v) => cache.update(key, v); f
case _ => Empty
}
}
}