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files >> //lib/node_modules/npm/node_modules/lru-cache/index.js
'use strict' // A linked list to keep track of recently-used-ness const Yallist = require('yallist') const MAX = Symbol('max') const LENGTH = Symbol('length') const LENGTH_CALCULATOR = Symbol('lengthCalculator') const ALLOW_STALE = Symbol('allowStale') const MAX_AGE = Symbol('maxAge') const DISPOSE = Symbol('dispose') const NO_DISPOSE_ON_SET = Symbol('noDisposeOnSet') const LRU_LIST = Symbol('lruList') const CACHE = Symbol('cache') const UPDATE_AGE_ON_GET = Symbol('updateAgeOnGet') const naiveLength = () => 1 // lruList is a yallist where the head is the youngest // item, and the tail is the oldest. the list contains the Hit // objects as the entries. // Each Hit object has a reference to its Yallist.Node. This // never changes. // // cache is a Map (or PseudoMap) that matches the keys to // the Yallist.Node object. class LRUCache { constructor (options) { if (typeof options === 'number') options = { max: options } if (!options) options = {} if (options.max && (typeof options.max !== 'number' || options.max < 0)) throw new TypeError('max must be a non-negative number') // Kind of weird to have a default max of Infinity, but oh well. const max = this[MAX] = options.max || Infinity const lc = options.length || naiveLength this[LENGTH_CALCULATOR] = (typeof lc !== 'function') ? naiveLength : lc this[ALLOW_STALE] = options.stale || false if (options.maxAge && typeof options.maxAge !== 'number') throw new TypeError('maxAge must be a number') this[MAX_AGE] = options.maxAge || 0 this[DISPOSE] = options.dispose this[NO_DISPOSE_ON_SET] = options.noDisposeOnSet || false this[UPDATE_AGE_ON_GET] = options.updateAgeOnGet || false this.reset() } // resize the cache when the max changes. set max (mL) { if (typeof mL !== 'number' || mL < 0) throw new TypeError('max must be a non-negative number') this[MAX] = mL || Infinity trim(this) } get max () { return this[MAX] } set allowStale (allowStale) { this[ALLOW_STALE] = !!allowStale } get allowStale () { return this[ALLOW_STALE] } set maxAge (mA) { if (typeof mA !== 'number') throw new TypeError('maxAge must be a non-negative number') this[MAX_AGE] = mA trim(this) } get maxAge () { return this[MAX_AGE] } // resize the cache when the lengthCalculator changes. set lengthCalculator (lC) { if (typeof lC !== 'function') lC = naiveLength if (lC !== this[LENGTH_CALCULATOR]) { this[LENGTH_CALCULATOR] = lC this[LENGTH] = 0 this[LRU_LIST].forEach(hit => { hit.length = this[LENGTH_CALCULATOR](hit.value, hit.key) this[LENGTH] += hit.length }) } trim(this) } get lengthCalculator () { return this[LENGTH_CALCULATOR] } get length () { return this[LENGTH] } get itemCount () { return this[LRU_LIST].length } rforEach (fn, thisp) { thisp = thisp || this for (let walker = this[LRU_LIST].tail; walker !== null;) { const prev = walker.prev forEachStep(this, fn, walker, thisp) walker = prev } } forEach (fn, thisp) { thisp = thisp || this for (let walker = this[LRU_LIST].head; walker !== null;) { const next = walker.next forEachStep(this, fn, walker, thisp) walker = next } } keys () { return this[LRU_LIST].toArray().map(k => k.key) } values () { return this[LRU_LIST].toArray().map(k => k.value) } reset () { if (this[DISPOSE] && this[LRU_LIST] && this[LRU_LIST].length) { this[LRU_LIST].forEach(hit => this[DISPOSE](hit.key, hit.value)) } this[CACHE] = new Map() // hash of items by key this[LRU_LIST] = new Yallist() // list of items in order of use recency this[LENGTH] = 0 // length of items in the list } dump () { return this[LRU_LIST].map(hit => isStale(this, hit) ? false : { k: hit.key, v: hit.value, e: hit.now + (hit.maxAge || 0) }).toArray().filter(h => h) } dumpLru () { return this[LRU_LIST] } set (key, value, maxAge) { maxAge = maxAge || this[MAX_AGE] if (maxAge && typeof maxAge !== 'number') throw new TypeError('maxAge must be a number') const now = maxAge ? Date.now() : 0 const len = this[LENGTH_CALCULATOR](value, key) if (this[CACHE].has(key)) { if (len > this[MAX]) { del(this, this[CACHE].get(key)) return false } const node = this[CACHE].get(key) const item = node.value // dispose of the old one before overwriting // split out into 2 ifs for better coverage tracking if (this[DISPOSE]) { if (!this[NO_DISPOSE_ON_SET]) this[DISPOSE](key, item.value) } item.now = now item.maxAge = maxAge item.value = value this[LENGTH] += len - item.length item.length = len this.get(key) trim(this) return true } const hit = new Entry(key, value, len, now, maxAge) // oversized objects fall out of cache automatically. if (hit.length > this[MAX]) { if (this[DISPOSE]) this[DISPOSE](key, value) return false } this[LENGTH] += hit.length this[LRU_LIST].unshift(hit) this[CACHE].set(key, this[LRU_LIST].head) trim(this) return true } has (key) { if (!this[CACHE].has(key)) return false const hit = this[CACHE].get(key).value return !isStale(this, hit) } get (key) { return get(this, key, true) } peek (key) { return get(this, key, false) } pop () { const node = this[LRU_LIST].tail if (!node) return null del(this, node) return node.value } del (key) { del(this, this[CACHE].get(key)) } load (arr) { // reset the cache this.reset() const now = Date.now() // A previous serialized cache has the most recent items first for (let l = arr.length - 1; l >= 0; l--) { const hit = arr[l] const expiresAt = hit.e || 0 if (expiresAt === 0) // the item was created without expiration in a non aged cache this.set(hit.k, hit.v) else { const maxAge = expiresAt - now // dont add already expired items if (maxAge > 0) { this.set(hit.k, hit.v, maxAge) } } } } prune () { this[CACHE].forEach((value, key) => get(this, key, false)) } } const get = (self, key, doUse) => { const node = self[CACHE].get(key) if (node) { const hit = node.value if (isStale(self, hit)) { del(self, node) if (!self[ALLOW_STALE]) return undefined } else { if (doUse) { if (self[UPDATE_AGE_ON_GET]) node.value.now = Date.now() self[LRU_LIST].unshiftNode(node) } } return hit.value } } const isStale = (self, hit) => { if (!hit || (!hit.maxAge && !self[MAX_AGE])) return false const diff = Date.now() - hit.now return hit.maxAge ? diff > hit.maxAge : self[MAX_AGE] && (diff > self[MAX_AGE]) } const trim = self => { if (self[LENGTH] > self[MAX]) { for (let walker = self[LRU_LIST].tail; self[LENGTH] > self[MAX] && walker !== null;) { // We know that we're about to delete this one, and also // what the next least recently used key will be, so just // go ahead and set it now. const prev = walker.prev del(self, walker) walker = prev } } } const del = (self, node) => { if (node) { const hit = node.value if (self[DISPOSE]) self[DISPOSE](hit.key, hit.value) self[LENGTH] -= hit.length self[CACHE].delete(hit.key) self[LRU_LIST].removeNode(node) } } class Entry { constructor (key, value, length, now, maxAge) { this.key = key this.value = value this.length = length this.now = now this.maxAge = maxAge || 0 } } const forEachStep = (self, fn, node, thisp) => { let hit = node.value if (isStale(self, hit)) { del(self, node) if (!self[ALLOW_STALE]) hit = undefined } if (hit) fn.call(thisp, hit.value, hit.key, self) } module.exports = LRUCache
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