зеркало из https://github.com/mozilla/gecko-dev.git
83 строки
2.4 KiB
JavaScript
83 строки
2.4 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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"use strict";
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ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
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ChromeUtils.defineModuleGetter(this, "OS", "resource://gre/modules/osfile.jsm");
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XPCOMUtils.defineLazyGetter(this, "gTextDecoder", () => new TextDecoder());
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/**
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* A file (disk) based persistent cache of a JSON serializable object.
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*/
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this.PersistentCache = class PersistentCache {
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/**
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* Create a cache object based on a name.
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*
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* @param {string} name Name of the cache. It will be used to create the filename.
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* @param {boolean} preload (optional). Whether the cache should be preloaded from file. Defaults to false.
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*/
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constructor(name, preload = false) {
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this.name = name;
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this._filename = `activity-stream.${name}.json`;
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if (preload) {
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this._load();
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}
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}
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/**
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* Set a value to be cached with the specified key.
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*
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* @param {string} key The cache key.
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* @param {object} value The data to be cached.
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*/
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async set(key, value) {
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const data = await this._load();
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data[key] = value;
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await this._persist(data);
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}
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/**
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* Get a value from the cache.
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*
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* @param {string} key (optional) The cache key. If not provided, we return the full cache.
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* @returns {object} The cached data.
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*/
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async get(key) {
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const data = await this._load();
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return key ? data[key] : data;
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}
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/**
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* Load the cache into memory if it isn't already.
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*/
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_load() {
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return this._cache || (this._cache = new Promise(async resolve => {
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let data = {};
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try {
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const filepath = OS.Path.join(OS.Constants.Path.localProfileDir, this._filename);
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const fileExists = await OS.File.exists(filepath);
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if (fileExists) {
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const binaryData = await OS.File.read(filepath);
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const json = gTextDecoder.decode(binaryData);
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data = JSON.parse(json);
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}
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} catch (error) {
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Cu.reportError(`Failed to load ${this._filename}: ${error.message}`);
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}
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resolve(data);
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}));
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}
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/**
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* Persist the cache to file.
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*/
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_persist(data) {
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const filepath = OS.Path.join(OS.Constants.Path.localProfileDir, this._filename);
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return OS.File.writeAtomic(filepath, JSON.stringify(data), {tmpPath: `${filepath}.tmp`});
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}
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};
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const EXPORTED_SYMBOLS = ["PersistentCache"];
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