/* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ "use strict"; const Cu = Components.utils; const Cc = Components.classes; const Ci = Components.interfaces; Cu.import("resource://gre/modules/osfile.jsm"); /* globals OS*/ Cu.import("resource://gre/modules/Promise.jsm"); // Make it possible to mock out timers for testing var MakeTimer = () => Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer); this.EXPORTED_SYMBOLS = ["DeferredSave"]; // If delay parameter is not provided, default is 50 milliseconds. const DEFAULT_SAVE_DELAY_MS = 50; Cu.import("resource://gre/modules/Log.jsm"); // Configure a logger at the parent 'DeferredSave' level to format // messages for all the modules under DeferredSave.* const DEFERREDSAVE_PARENT_LOGGER_ID = "DeferredSave"; var parentLogger = Log.repository.getLogger(DEFERREDSAVE_PARENT_LOGGER_ID); parentLogger.level = Log.Level.Warn; var formatter = new Log.BasicFormatter(); // Set parent logger (and its children) to append to // the Javascript section of the Browser Console parentLogger.addAppender(new Log.ConsoleAppender(formatter)); // Set parent logger (and its children) to // also append to standard out parentLogger.addAppender(new Log.DumpAppender(formatter)); // Provide the ability to enable/disable logging // messages at runtime. // If the "extensions.logging.enabled" preference is // missing or 'false', messages at the WARNING and higher // severity should be logged to the JS console and standard error. // If "extensions.logging.enabled" is set to 'true', messages // at DEBUG and higher should go to JS console and standard error. Cu.import("resource://gre/modules/Services.jsm"); const PREF_LOGGING_ENABLED = "extensions.logging.enabled"; const NS_PREFBRANCH_PREFCHANGE_TOPIC_ID = "nsPref:changed"; /** * Preference listener which listens for a change in the * "extensions.logging.enabled" preference and changes the logging level of the * parent 'addons' level logger accordingly. */ var PrefObserver = { init: function() { Services.prefs.addObserver(PREF_LOGGING_ENABLED, this, false); Services.obs.addObserver(this, "xpcom-shutdown", false); this.observe(null, NS_PREFBRANCH_PREFCHANGE_TOPIC_ID, PREF_LOGGING_ENABLED); }, observe: function(aSubject, aTopic, aData) { if (aTopic == "xpcom-shutdown") { Services.prefs.removeObserver(PREF_LOGGING_ENABLED, this); Services.obs.removeObserver(this, "xpcom-shutdown"); } else if (aTopic == NS_PREFBRANCH_PREFCHANGE_TOPIC_ID) { let debugLogEnabled = Services.prefs.getBoolPref(PREF_LOGGING_ENABLED, false); if (debugLogEnabled) { parentLogger.level = Log.Level.Debug; } else { parentLogger.level = Log.Level.Warn; } } } }; PrefObserver.init(); /** * A module to manage deferred, asynchronous writing of data files * to disk. Writing is deferred by waiting for a specified delay after * a request to save the data, before beginning to write. If more than * one save request is received during the delay, all requests are * fulfilled by a single write. * * @constructor * @param aPath * String representing the full path of the file where the data * is to be written. * @param aDataProvider * Callback function that takes no argument and returns the data to * be written. If aDataProvider returns an ArrayBufferView, the * bytes it contains are written to the file as is. * If aDataProvider returns a String the data are UTF-8 encoded * and then written to the file. * @param [optional] aDelay * The delay in milliseconds between the first saveChanges() call * that marks the data as needing to be saved, and when the DeferredSave * begins writing the data to disk. Default 50 milliseconds. */ this.DeferredSave = function(aPath, aDataProvider, aDelay) { // Create a new logger (child of 'DeferredSave' logger) // for use by this particular instance of DeferredSave object let leafName = OS.Path.basename(aPath); let logger_id = DEFERREDSAVE_PARENT_LOGGER_ID + "." + leafName; this.logger = Log.repository.getLogger(logger_id); // @type {Deferred|null}, null when no data needs to be written // @resolves with the result of OS.File.writeAtomic when all writes complete // @rejects with the error from OS.File.writeAtomic if the write fails, // or with the error from aDataProvider() if that throws. this._pending = null; // @type {Promise}, completes when the in-progress write (if any) completes, // kept as a resolved promise at other times to simplify logic. // Because _deferredSave() always uses _writing.then() to execute // its next action, we don't need a special case for whether a write // is in progress - if the previous write is complete (and the _writing // promise is already resolved/rejected), _writing.then() starts // the next action immediately. // // @resolves with the result of OS.File.writeAtomic // @rejects with the error from OS.File.writeAtomic this._writing = Promise.resolve(0); // Are we currently waiting for a write to complete this.writeInProgress = false; this._path = aPath; this._dataProvider = aDataProvider; this._timer = null; // Some counters for telemetry // The total number of times the file was written this.totalSaves = 0; // The number of times the data became dirty while // another save was in progress this.overlappedSaves = 0; // Error returned by the most recent write (if any) this._lastError = null; if (aDelay && (aDelay > 0)) this._delay = aDelay; else this._delay = DEFAULT_SAVE_DELAY_MS; } this.DeferredSave.prototype = { get dirty() { return this._pending || this.writeInProgress; }, get lastError() { return this._lastError; }, // Start the pending timer if data is dirty _startTimer: function() { if (!this._pending) { return; } this.logger.debug("Starting timer"); if (!this._timer) this._timer = MakeTimer(); this._timer.initWithCallback(() => this._deferredSave(), this._delay, Ci.nsITimer.TYPE_ONE_SHOT); }, /** * Mark the current stored data dirty, and schedule a flush to disk * @return A Promise that will be resolved after the data is written to disk; * the promise is resolved with the number of bytes written. */ saveChanges: function() { this.logger.debug("Save changes"); if (!this._pending) { if (this.writeInProgress) { this.logger.debug("Data changed while write in progress"); this.overlappedSaves++; } this._pending = Promise.defer(); // Wait until the most recent write completes or fails (if it hasn't already) // and then restart our timer this._writing.then(count => this._startTimer(), error => this._startTimer()); } return this._pending.promise; }, _deferredSave: function() { let pending = this._pending; this._pending = null; let writing = this._writing; this._writing = pending.promise; // In either the success or the exception handling case, we don't need to handle // the error from _writing here; it's already being handled in another then() let toSave = null; try { toSave = this._dataProvider(); } catch (e) { this.logger.error("Deferred save dataProvider failed", e); writing.then(null, error => {}) .then(count => { pending.reject(e); }); return; } writing.then(null, error => { return 0; }) .then(count => { this.logger.debug("Starting write"); this.totalSaves++; this.writeInProgress = true; OS.File.writeAtomic(this._path, toSave, {tmpPath: this._path + ".tmp"}) .then( result => { this._lastError = null; this.writeInProgress = false; this.logger.debug("Write succeeded"); pending.resolve(result); }, error => { this._lastError = error; this.writeInProgress = false; this.logger.warn("Write failed", error); pending.reject(error); }); }); }, /** * Immediately save the dirty data to disk, skipping * the delay of normal operation. Note that the write * still happens asynchronously in the worker * thread from OS.File. * * There are four possible situations: * 1) Nothing to flush * 2) Data is not currently being written, in-memory copy is dirty * 3) Data is currently being written, in-memory copy is clean * 4) Data is being written and in-memory copy is dirty * * @return Promise that will resolve when all in-memory data * has finished being flushed, returning the number of bytes * written. If all in-memory data is clean, completes with the * result of the most recent write. */ flush: function() { // If we have pending changes, cancel our timer and set up the write // immediately (_deferredSave queues the write for after the most // recent write completes, if it hasn't already) if (this._pending) { this.logger.debug("Flush called while data is dirty"); if (this._timer) { this._timer.cancel(); this._timer = null; } this._deferredSave(); } return this._writing; } };