97 lines
1.9 KiB
JavaScript
97 lines
1.9 KiB
JavaScript
module.exports = function(size) {
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return new LruCache(size)
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}
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function LruCache(size) {
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this.capacity = size | 0
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this.map = Object.create(null)
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this.list = new DoublyLinkedList()
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}
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LruCache.prototype.get = function(key) {
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var node = this.map[key]
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if (node == null) return undefined
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this.used(node)
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return node.val
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}
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LruCache.prototype.set = function(key, val) {
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var node = this.map[key]
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if (node != null) {
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node.val = val
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} else {
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if (!this.capacity) this.prune()
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if (!this.capacity) return false
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node = new DoublyLinkedNode(key, val)
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this.map[key] = node
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this.capacity--
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}
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this.used(node)
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return true
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}
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LruCache.prototype.used = function(node) {
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this.list.moveToFront(node)
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}
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LruCache.prototype.prune = function() {
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var node = this.list.pop()
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if (node != null) {
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delete this.map[node.key]
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this.capacity++
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}
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}
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function DoublyLinkedList() {
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this.firstNode = null
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this.lastNode = null
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}
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DoublyLinkedList.prototype.moveToFront = function(node) {
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if (this.firstNode == node) return
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this.remove(node)
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if (this.firstNode == null) {
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this.firstNode = node
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this.lastNode = node
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node.prev = null
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node.next = null
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} else {
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node.prev = null
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node.next = this.firstNode
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node.next.prev = node
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this.firstNode = node
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}
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}
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DoublyLinkedList.prototype.pop = function() {
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var lastNode = this.lastNode
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if (lastNode != null) {
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this.remove(lastNode)
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}
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return lastNode
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}
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DoublyLinkedList.prototype.remove = function(node) {
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if (this.firstNode == node) {
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this.firstNode = node.next
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} else if (node.prev != null) {
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node.prev.next = node.next
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}
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if (this.lastNode == node) {
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this.lastNode = node.prev
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} else if (node.next != null) {
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node.next.prev = node.prev
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}
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}
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function DoublyLinkedNode(key, val) {
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this.key = key
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this.val = val
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this.prev = null
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this.next = null
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}
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