107 lines
2.3 KiB
JavaScript
107 lines
2.3 KiB
JavaScript
'use strict';
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class LRU {
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constructor(max) {
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this.max = max;
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this.size = 0;
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this.cache = new Map();
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this._cache = new Map();
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}
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get(key, options) {
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let item = this.cache.get(key);
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const maxAge = options && options.maxAge;
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// only call Date.now() when necessary
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let now;
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function getNow() {
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now = now || Date.now();
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return now;
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}
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if (item) {
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// check expired
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if (item.expired && getNow() > item.expired) {
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item.expired = 0;
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item.value = undefined;
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} else {
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// update expired in get
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if (maxAge !== undefined) {
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const expired = maxAge ? getNow() + maxAge : 0;
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item.expired = expired;
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}
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}
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return item.value;
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}
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// try to read from _cache
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item = this._cache.get(key);
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if (item) {
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// check expired
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if (item.expired && getNow() > item.expired) {
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item.expired = 0;
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item.value = undefined;
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} else {
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// not expired, save to cache
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this._update(key, item);
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// update expired in get
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if (maxAge !== undefined) {
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const expired = maxAge ? getNow() + maxAge : 0;
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item.expired = expired;
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}
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}
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return item.value;
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}
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}
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set(key, value, options) {
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const maxAge = options && options.maxAge;
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const expired = maxAge ? Date.now() + maxAge : 0;
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let item = this.cache.get(key);
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if (item) {
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item.expired = expired;
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item.value = value;
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} else {
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item = {
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value,
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expired,
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};
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this._update(key, item);
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}
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}
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keys() {
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const cacheKeys = new Set();
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const now = Date.now();
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for (const entry of this.cache.entries()) {
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checkEntry(entry);
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}
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for (const entry of this._cache.entries()) {
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checkEntry(entry);
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}
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function checkEntry(entry) {
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const key = entry[0];
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const item = entry[1];
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if (entry[1].value && (!entry[1].expired) || item.expired >= now) {
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cacheKeys.add(key);
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}
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}
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return Array.from(cacheKeys.keys());
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}
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_update(key, item) {
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this.cache.set(key, item);
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this.size++;
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if (this.size >= this.max) {
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this.size = 0;
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this._cache = this.cache;
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this.cache = new Map();
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}
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}
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}
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module.exports = LRU;
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