jvmMain.io.ktor.util.Cache.kt Maven / Gradle / Ivy
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/*
* Copyright 2014-2019 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
*/
package io.ktor.util
import java.util.*
/**
* Initial capacity of [LinkedHashMap] used as [LRUCache].
*/
private const val CACHE_INITIAL_CAPACITY = 10
/**
* Load factory of [LinkedHashMap] used as [LRUCache].
*/
private const val CACHE_LOAD_FACTOR = 0.75f
/**
* Create a new instance of thread safe [LRUCache] and return it.
*/
@InternalAPI
public fun createLRUCache(supplier: (K) -> V, close: (V) -> Unit, maxSize: Int): Map =
Collections.synchronizedMap(LRUCache(supplier, close, maxSize))
/**
* LRU cache based on [LinkedHashMap] with specified [maxSize] and [supplier].
*/
internal class LRUCache internal constructor(
private val supplier: (K) -> V,
private val close: (V) -> Unit,
private val maxSize: Int
) : LinkedHashMap(CACHE_INITIAL_CAPACITY, CACHE_LOAD_FACTOR, true) {
override fun removeEldestEntry(eldest: Map.Entry): Boolean {
return (size > maxSize).also {
if (it) {
close(eldest.value)
}
}
}
override fun get(key: K): V {
return if (maxSize == 0) {
supplier(key)
} else {
synchronized(this) {
super.get(key)?.let { return it }
supplier(key).let {
put(key, it)
it
}
}
}
}
}