468 lines
10 KiB
JavaScript
468 lines
10 KiB
JavaScript
'use strict'
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module.exports = LRUCache
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// This will be a proper iterable 'Map' in engines that support it,
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// or a fakey-fake PseudoMap in older versions.
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var Map = require('pseudomap')
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var util = require('util')
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// A linked list to keep track of recently-used-ness
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var Yallist = require('yallist')
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// use symbols if possible, otherwise just _props
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var hasSymbol = typeof Symbol === 'function'
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var makeSymbol
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if (hasSymbol) {
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makeSymbol = function (key) {
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return Symbol.for(key)
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}
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} else {
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makeSymbol = function (key) {
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return '_' + key
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}
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}
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var MAX = makeSymbol('max')
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var LENGTH = makeSymbol('length')
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var LENGTH_CALCULATOR = makeSymbol('lengthCalculator')
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var ALLOW_STALE = makeSymbol('allowStale')
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var MAX_AGE = makeSymbol('maxAge')
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var DISPOSE = makeSymbol('dispose')
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var NO_DISPOSE_ON_SET = makeSymbol('noDisposeOnSet')
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var LRU_LIST = makeSymbol('lruList')
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var CACHE = makeSymbol('cache')
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function naiveLength () { return 1 }
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// lruList is a yallist where the head is the youngest
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// item, and the tail is the oldest. the list contains the Hit
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// objects as the entries.
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// Each Hit object has a reference to its Yallist.Node. This
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// never changes.
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//
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// cache is a Map (or PseudoMap) that matches the keys to
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// the Yallist.Node object.
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function LRUCache (options) {
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if (!(this instanceof LRUCache)) {
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return new LRUCache(options)
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}
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if (typeof options === 'number') {
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options = { max: options }
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}
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if (!options) {
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options = {}
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}
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var max = this[MAX] = options.max
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// Kind of weird to have a default max of Infinity, but oh well.
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if (!max ||
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!(typeof max === 'number') ||
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max <= 0) {
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this[MAX] = Infinity
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}
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var lc = options.length || naiveLength
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if (typeof lc !== 'function') {
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lc = naiveLength
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}
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this[LENGTH_CALCULATOR] = lc
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this[ALLOW_STALE] = options.stale || false
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this[MAX_AGE] = options.maxAge || 0
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this[DISPOSE] = options.dispose
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this[NO_DISPOSE_ON_SET] = options.noDisposeOnSet || false
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this.reset()
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}
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// resize the cache when the max changes.
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Object.defineProperty(LRUCache.prototype, 'max', {
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set: function (mL) {
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if (!mL || !(typeof mL === 'number') || mL <= 0) {
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mL = Infinity
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}
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this[MAX] = mL
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trim(this)
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},
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get: function () {
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return this[MAX]
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},
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enumerable: true
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})
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Object.defineProperty(LRUCache.prototype, 'allowStale', {
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set: function (allowStale) {
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this[ALLOW_STALE] = !!allowStale
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},
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get: function () {
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return this[ALLOW_STALE]
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},
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enumerable: true
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})
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Object.defineProperty(LRUCache.prototype, 'maxAge', {
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set: function (mA) {
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if (!mA || !(typeof mA === 'number') || mA < 0) {
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mA = 0
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}
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this[MAX_AGE] = mA
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trim(this)
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},
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get: function () {
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return this[MAX_AGE]
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},
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enumerable: true
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})
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// resize the cache when the lengthCalculator changes.
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Object.defineProperty(LRUCache.prototype, 'lengthCalculator', {
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set: function (lC) {
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if (typeof lC !== 'function') {
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lC = naiveLength
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}
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if (lC !== this[LENGTH_CALCULATOR]) {
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this[LENGTH_CALCULATOR] = lC
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this[LENGTH] = 0
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this[LRU_LIST].forEach(function (hit) {
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hit.length = this[LENGTH_CALCULATOR](hit.value, hit.key)
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this[LENGTH] += hit.length
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}, this)
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}
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trim(this)
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},
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get: function () { return this[LENGTH_CALCULATOR] },
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enumerable: true
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})
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Object.defineProperty(LRUCache.prototype, 'length', {
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get: function () { return this[LENGTH] },
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enumerable: true
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})
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Object.defineProperty(LRUCache.prototype, 'itemCount', {
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get: function () { return this[LRU_LIST].length },
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enumerable: true
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})
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LRUCache.prototype.rforEach = function (fn, thisp) {
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thisp = thisp || this
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for (var walker = this[LRU_LIST].tail; walker !== null;) {
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var prev = walker.prev
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forEachStep(this, fn, walker, thisp)
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walker = prev
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}
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}
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function forEachStep (self, fn, node, thisp) {
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var hit = node.value
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if (isStale(self, hit)) {
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del(self, node)
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if (!self[ALLOW_STALE]) {
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hit = undefined
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}
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}
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if (hit) {
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fn.call(thisp, hit.value, hit.key, self)
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}
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}
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LRUCache.prototype.forEach = function (fn, thisp) {
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thisp = thisp || this
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for (var walker = this[LRU_LIST].head; walker !== null;) {
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var next = walker.next
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forEachStep(this, fn, walker, thisp)
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walker = next
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}
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}
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LRUCache.prototype.keys = function () {
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return this[LRU_LIST].toArray().map(function (k) {
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return k.key
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}, this)
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}
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LRUCache.prototype.values = function () {
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return this[LRU_LIST].toArray().map(function (k) {
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return k.value
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}, this)
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}
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LRUCache.prototype.reset = function () {
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if (this[DISPOSE] &&
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this[LRU_LIST] &&
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this[LRU_LIST].length) {
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this[LRU_LIST].forEach(function (hit) {
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this[DISPOSE](hit.key, hit.value)
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}, this)
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}
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this[CACHE] = new Map() // hash of items by key
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this[LRU_LIST] = new Yallist() // list of items in order of use recency
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this[LENGTH] = 0 // length of items in the list
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}
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LRUCache.prototype.dump = function () {
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return this[LRU_LIST].map(function (hit) {
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if (!isStale(this, hit)) {
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return {
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k: hit.key,
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v: hit.value,
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e: hit.now + (hit.maxAge || 0)
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}
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}
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}, this).toArray().filter(function (h) {
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return h
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})
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}
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LRUCache.prototype.dumpLru = function () {
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return this[LRU_LIST]
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}
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LRUCache.prototype.inspect = function (n, opts) {
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var str = 'LRUCache {'
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var extras = false
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var as = this[ALLOW_STALE]
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if (as) {
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str += '\n allowStale: true'
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extras = true
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}
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var max = this[MAX]
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if (max && max !== Infinity) {
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if (extras) {
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str += ','
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}
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str += '\n max: ' + util.inspect(max, opts)
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extras = true
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}
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var maxAge = this[MAX_AGE]
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if (maxAge) {
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if (extras) {
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str += ','
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}
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str += '\n maxAge: ' + util.inspect(maxAge, opts)
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extras = true
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}
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var lc = this[LENGTH_CALCULATOR]
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if (lc && lc !== naiveLength) {
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if (extras) {
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str += ','
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}
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str += '\n length: ' + util.inspect(this[LENGTH], opts)
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extras = true
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}
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var didFirst = false
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this[LRU_LIST].forEach(function (item) {
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if (didFirst) {
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str += ',\n '
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} else {
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if (extras) {
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str += ',\n'
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}
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didFirst = true
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str += '\n '
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}
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var key = util.inspect(item.key).split('\n').join('\n ')
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var val = { value: item.value }
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if (item.maxAge !== maxAge) {
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val.maxAge = item.maxAge
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}
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if (lc !== naiveLength) {
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val.length = item.length
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}
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if (isStale(this, item)) {
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val.stale = true
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}
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val = util.inspect(val, opts).split('\n').join('\n ')
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str += key + ' => ' + val
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})
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if (didFirst || extras) {
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str += '\n'
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}
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str += '}'
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return str
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}
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LRUCache.prototype.set = function (key, value, maxAge) {
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maxAge = maxAge || this[MAX_AGE]
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var now = maxAge ? Date.now() : 0
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var len = this[LENGTH_CALCULATOR](value, key)
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if (this[CACHE].has(key)) {
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if (len > this[MAX]) {
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del(this, this[CACHE].get(key))
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return false
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}
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var node = this[CACHE].get(key)
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var item = node.value
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// dispose of the old one before overwriting
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// split out into 2 ifs for better coverage tracking
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if (this[DISPOSE]) {
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if (!this[NO_DISPOSE_ON_SET]) {
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this[DISPOSE](key, item.value)
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}
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}
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item.now = now
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item.maxAge = maxAge
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item.value = value
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this[LENGTH] += len - item.length
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item.length = len
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this.get(key)
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trim(this)
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return true
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}
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var hit = new Entry(key, value, len, now, maxAge)
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// oversized objects fall out of cache automatically.
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if (hit.length > this[MAX]) {
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if (this[DISPOSE]) {
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this[DISPOSE](key, value)
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}
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return false
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}
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this[LENGTH] += hit.length
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this[LRU_LIST].unshift(hit)
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this[CACHE].set(key, this[LRU_LIST].head)
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trim(this)
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return true
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}
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LRUCache.prototype.has = function (key) {
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if (!this[CACHE].has(key)) return false
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var hit = this[CACHE].get(key).value
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if (isStale(this, hit)) {
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return false
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}
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return true
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}
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LRUCache.prototype.get = function (key) {
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return get(this, key, true)
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}
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LRUCache.prototype.peek = function (key) {
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return get(this, key, false)
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}
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LRUCache.prototype.pop = function () {
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var node = this[LRU_LIST].tail
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if (!node) return null
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del(this, node)
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return node.value
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}
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LRUCache.prototype.del = function (key) {
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del(this, this[CACHE].get(key))
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}
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LRUCache.prototype.load = function (arr) {
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// reset the cache
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this.reset()
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var now = Date.now()
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// A previous serialized cache has the most recent items first
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for (var l = arr.length - 1; l >= 0; l--) {
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var hit = arr[l]
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var expiresAt = hit.e || 0
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if (expiresAt === 0) {
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// the item was created without expiration in a non aged cache
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this.set(hit.k, hit.v)
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} else {
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var maxAge = expiresAt - now
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// dont add already expired items
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if (maxAge > 0) {
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this.set(hit.k, hit.v, maxAge)
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}
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}
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}
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}
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LRUCache.prototype.prune = function () {
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var self = this
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this[CACHE].forEach(function (value, key) {
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get(self, key, false)
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})
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}
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function get (self, key, doUse) {
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var node = self[CACHE].get(key)
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if (node) {
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var hit = node.value
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if (isStale(self, hit)) {
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del(self, node)
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if (!self[ALLOW_STALE]) hit = undefined
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} else {
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if (doUse) {
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self[LRU_LIST].unshiftNode(node)
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}
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}
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if (hit) hit = hit.value
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}
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return hit
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}
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function isStale (self, hit) {
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if (!hit || (!hit.maxAge && !self[MAX_AGE])) {
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return false
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}
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var stale = false
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var diff = Date.now() - hit.now
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if (hit.maxAge) {
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stale = diff > hit.maxAge
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} else {
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stale = self[MAX_AGE] && (diff > self[MAX_AGE])
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}
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return stale
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}
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function trim (self) {
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if (self[LENGTH] > self[MAX]) {
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for (var walker = self[LRU_LIST].tail;
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self[LENGTH] > self[MAX] && walker !== null;) {
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// We know that we're about to delete this one, and also
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// what the next least recently used key will be, so just
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// go ahead and set it now.
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var prev = walker.prev
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del(self, walker)
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walker = prev
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}
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}
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}
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function del (self, node) {
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if (node) {
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var hit = node.value
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if (self[DISPOSE]) {
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self[DISPOSE](hit.key, hit.value)
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}
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self[LENGTH] -= hit.length
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self[CACHE].delete(hit.key)
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self[LRU_LIST].removeNode(node)
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}
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}
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// classy, since V8 prefers predictable objects.
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function Entry (key, value, length, now, maxAge) {
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this.key = key
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this.value = value
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this.length = length
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this.now = now
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this.maxAge = maxAge || 0
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}
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