Mirror of roytam1's UXP fork just in case Moonchild and Tobin decide to go after him
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/* 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;
// 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.
//Configure a logger at the parent 'DeferredSave' level to format
//messages for all the modules under 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.
const PREF_LOGGING_ENABLED = "extensions.logging.enabled";
* 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 PrefObserver_init() {
Services.prefs.addObserver(PREF_LOGGING_ENABLED, this, false);
Services.obs.addObserver(this, "xpcom-shutdown", false);
observe: function PrefObserver_observe(aSubject, aTopic, aData) {
if (aTopic == "xpcom-shutdown") {
Services.prefs.removeObserver(PREF_LOGGING_ENABLED, this);
Services.obs.removeObserver(this, "xpcom-shutdown");
let debugLogEnabled = false;
try {
debugLogEnabled = Services.prefs.getBoolPref(PREF_LOGGING_ENABLED);
catch (e) {
if (debugLogEnabled) {
parentLogger.level = Log.Level.Debug;
else {
parentLogger.level = Log.Level.Warn;
* 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;
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) {
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<integer> 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._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 => {
writing.then(null, error => {return 0;})
.then(count => {
this.logger.debug("Starting write");
this.writeInProgress = true;
OS.File.writeAtomic(this._path, toSave, {tmpPath: this._path + ".tmp"})
result => {
this._lastError = null;
this.writeInProgress = false;
this.logger.debug("Write succeeded");
error => {
this._lastError = error;
this.writeInProgress = false;
this.logger.warn("Write failed", 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<integer> 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 = null;
return this._writing;