144 lines
2.5 KiB
JavaScript
144 lines
2.5 KiB
JavaScript
'use strict';
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const Assert = require('@hapi/hoek/lib/assert');
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const Clone = require('@hapi/hoek/lib/clone');
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const Common = require('./common');
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const internals = {
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max: 1000,
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supported: new Set(['undefined', 'boolean', 'number', 'string'])
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};
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exports.provider = {
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provision(options) {
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return new internals.Cache(options);
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}
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};
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// Least Recently Used (LRU) Cache
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internals.Cache = class {
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constructor(options = {}) {
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Common.assertOptions(options, ['max']);
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Assert(options.max === undefined || options.max && options.max > 0 && isFinite(options.max), 'Invalid max cache size');
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this._max = options.max || internals.max;
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this._map = new Map(); // Map of nodes by key
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this._list = new internals.List(); // List of nodes (most recently used in head)
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}
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get length() {
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return this._map.size;
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}
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set(key, value) {
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if (key !== null &&
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!internals.supported.has(typeof key)) {
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return;
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}
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let node = this._map.get(key);
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if (node) {
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node.value = value;
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this._list.first(node);
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return;
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}
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node = this._list.unshift({ key, value });
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this._map.set(key, node);
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this._compact();
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}
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get(key) {
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const node = this._map.get(key);
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if (node) {
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this._list.first(node);
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return Clone(node.value);
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}
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}
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_compact() {
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if (this._map.size > this._max) {
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const node = this._list.pop();
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this._map.delete(node.key);
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}
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}
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};
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internals.List = class {
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constructor() {
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this.tail = null;
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this.head = null;
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}
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unshift(node) {
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node.next = null;
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node.prev = this.head;
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if (this.head) {
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this.head.next = node;
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}
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this.head = node;
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if (!this.tail) {
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this.tail = node;
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}
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return node;
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}
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first(node) {
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if (node === this.head) {
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return;
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}
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this._remove(node);
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this.unshift(node);
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}
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pop() {
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return this._remove(this.tail);
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}
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_remove(node) {
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const { next, prev } = node;
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next.prev = prev;
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if (prev) {
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prev.next = next;
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}
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if (node === this.tail) {
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this.tail = next;
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}
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node.prev = null;
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node.next = null;
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return node;
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}
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};
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