55 lines
1 KiB
JavaScript
55 lines
1 KiB
JavaScript
const { setTimeout } = require('timers');
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// A cache that expires.
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module.exports = class Cache extends Map {
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constructor(timeout = 1000) {
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super();
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this.timeout = timeout;
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}
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set(key, value) {
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if (this.has(key)) {
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clearTimeout(super.get(key).tid);
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}
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super.set(key, {
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tid: setTimeout(this.delete.bind(this, key), this.timeout).unref(),
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value,
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});
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}
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get(key) {
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let entry = super.get(key);
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if (entry) {
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return entry.value;
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}
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return null;
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}
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getOrSet(key, fn) {
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if (this.has(key)) {
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return this.get(key);
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} else {
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let value = fn();
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this.set(key, value);
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(async() => {
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try {
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await value;
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} catch (err) {
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this.delete(key);
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}
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})();
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return value;
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}
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}
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delete(key) {
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let entry = super.get(key);
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if (entry) {
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clearTimeout(entry.tid);
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super.delete(key);
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}
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}
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clear() {
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for (let entry of this.values()) {
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clearTimeout(entry.tid);
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}
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super.clear();
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}
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};
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