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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";
+
+this.EXPORTED_SYMBOLS = ["_SessionFile"];
+
+/**
+ * Implementation of all the disk I/O required by the session store.
+ * This is a private API, meant to be used only by the session store.
+ * It will change. Do not use it for any other purpose.
+ *
+ * Note that this module implicitly depends on one of two things:
+ * 1. either the asynchronous file I/O system enqueues its requests
+ * and never attempts to simultaneously execute two I/O requests on
+ * the files used by this module from two distinct threads; or
+ * 2. the clients of this API are well-behaved and do not place
+ * concurrent requests to the files used by this module.
+ *
+ * Otherwise, we could encounter bugs, especially under Windows,
+ * e.g. if a request attempts to write sessionstore.js while
+ * another attempts to copy that file.
+ *
+ * This implementation uses OS.File, which guarantees property 1.
+ */
+
+const Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/osfile.jsm");
+Cu.import("resource://gre/modules/Promise.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
+ "resource://gre/modules/NetUtil.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
+ "resource://gre/modules/FileUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+ "resource://gre/modules/Task.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "console",
+ "resource://gre/modules/devtools/Console.jsm");
+
+// An encoder to UTF-8.
+XPCOMUtils.defineLazyGetter(this, "gEncoder", function () {
+ return new TextEncoder();
+});
+// A decoder.
+XPCOMUtils.defineLazyGetter(this, "gDecoder", function () {
+ return new TextDecoder();
+});
+
+this._SessionFile = {
+ /**
+ * A promise fulfilled once initialization (either synchronous or
+ * asynchronous) is complete.
+ */
+ promiseInitialized: function SessionFile_initialized() {
+ return SessionFileInternal.promiseInitialized;
+ },
+ /**
+ * Read the contents of the session file, asynchronously.
+ */
+ read: function SessionFile_read() {
+ return SessionFileInternal.read();
+ },
+ /**
+ * Read the contents of the session file, synchronously.
+ */
+ syncRead: function SessionFile_syncRead() {
+ return SessionFileInternal.syncRead();
+ },
+ /**
+ * Write the contents of the session file, asynchronously.
+ */
+ write: function SessionFile_write(aData) {
+ return SessionFileInternal.write(aData);
+ },
+ /**
+ * Create a backup copy, asynchronously.
+ */
+ createBackupCopy: function SessionFile_createBackupCopy() {
+ return SessionFileInternal.createBackupCopy();
+ },
+ /**
+ * Wipe the contents of the session file, asynchronously.
+ */
+ wipe: function SessionFile_wipe() {
+ return SessionFileInternal.wipe();
+ }
+};
+
+Object.freeze(_SessionFile);
+
+/**
+ * Utilities for dealing with promises and Task.jsm
+ */
+const TaskUtils = {
+ /**
+ * Add logging to a promise.
+ *
+ * @param {Promise} promise
+ * @return {Promise} A promise behaving as |promise|, but with additional
+ * logging in case of uncaught error.
+ */
+ captureErrors: function captureErrors(promise) {
+ return promise.then(
+ null,
+ function onError(reason) {
+ console.error("Uncaught asynchronous error:", reason);
+ throw reason;
+ }
+ );
+ },
+ /**
+ * Spawn a new Task from a generator.
+ *
+ * This function behaves as |Task.spawn|, with the exception that it
+ * adds logging in case of uncaught error. For more information, see
+ * the documentation of |Task.jsm|.
+ *
+ * @param {generator} gen Some generator.
+ * @return {Promise} A promise built from |gen|, with the same semantics
+ * as |Task.spawn(gen)|.
+ */
+ spawn: function spawn(gen) {
+ return this.captureErrors(Task.spawn(gen));
+ }
+};
+
+let SessionFileInternal = {
+ /**
+ * A promise fulfilled once initialization is complete
+ */
+ promiseInitialized: Promise.defer(),
+
+ /**
+ * The path to sessionstore.js
+ */
+ path: OS.Path.join(OS.Constants.Path.profileDir, "sessionstore.js"),
+
+ /**
+ * The path to sessionstore.bak
+ */
+ backupPath: OS.Path.join(OS.Constants.Path.profileDir, "sessionstore.bak"),
+
+ /**
+ * Utility function to safely read a file synchronously.
+ * @param aPath
+ * A path to read the file from.
+ * @returns string if successful, undefined otherwise.
+ */
+ readAuxSync: function ssfi_readAuxSync(aPath) {
+ let text;
+ try {
+ let file = new FileUtils.File(aPath);
+ let chan = NetUtil.newChannel(file);
+ let stream = chan.open();
+ text = NetUtil.readInputStreamToString(stream, stream.available(),
+ {charset: "utf-8"});
+ } catch (e if e.result == Components.results.NS_ERROR_FILE_NOT_FOUND) {
+ // Ignore exceptions about non-existent files.
+ } catch (ex) {
+ // Any other error.
+ console.error("Uncaught error:", ex);
+ } finally {
+ return text;
+ }
+ },
+
+ /**
+ * Read the sessionstore file synchronously.
+ *
+ * This function is meant to serve as a fallback in case of race
+ * between a synchronous usage of the API and asynchronous
+ * initialization.
+ *
+ * In case if sessionstore.js file does not exist or is corrupted (something
+ * happened between backup and write), attempt to read the sessionstore.bak
+ * instead.
+ */
+ syncRead: function ssfi_syncRead() {
+ // First read the sessionstore.js.
+ let text = this.readAuxSync(this.path);
+ if (typeof text === "undefined") {
+ // If sessionstore.js does not exist or is corrupted, read sessionstore.bak.
+ text = this.readAuxSync(this.backupPath);
+ }
+ return text || "";
+ },
+
+ /**
+ * Utility function to safely read a file asynchronously.
+ * @param aPath
+ * A path to read the file from.
+ * @param aReadOptions
+ * Read operation options.
+ * |outExecutionDuration| option will be reused and can be
+ * incrementally updated by the worker process.
+ * @returns string if successful, undefined otherwise.
+ */
+ readAux: function ssfi_readAux(aPath, aReadOptions) {
+ let self = this;
+ return TaskUtils.spawn(function () {
+ let text;
+ try {
+ let bytes = yield OS.File.read(aPath, undefined, aReadOptions);
+ text = gDecoder.decode(bytes);
+ } catch (ex if self._isNoSuchFile(ex)) {
+ // Ignore exceptions about non-existent files.
+ } catch (ex) {
+ // Any other error.
+ console.error("Uncaught error - with the file: " + self.path, ex);
+ }
+ throw new Task.Result(text);
+ });
+ },
+
+ /**
+ * Read the sessionstore file asynchronously.
+ *
+ * In case sessionstore.js file does not exist or is corrupted (something
+ * happened between backup and write), attempt to read the sessionstore.bak
+ * instead.
+ */
+ read: function ssfi_read() {
+ let self = this;
+ return TaskUtils.spawn(function task() {
+ // Specify |outExecutionDuration| option to hold the combined duration of
+ // the asynchronous reads off the main thread (of both sessionstore.js and
+ // sessionstore.bak, if necessary). If sessionstore.js does not exist or
+ // is corrupted, |outExecutionDuration| will register the time it took to
+ // attempt to read the file. It will then be subsequently incremented by
+ // the read time of sessionsore.bak.
+ let readOptions = {
+ outExecutionDuration: null
+ };
+ // First read the sessionstore.js.
+ let text = yield self.readAux(self.path, readOptions);
+ if (typeof text === "undefined") {
+ // If sessionstore.js does not exist or is corrupted, read the
+ // sessionstore.bak.
+ text = yield self.readAux(self.backupPath, readOptions);
+ }
+ // Return either the content of the sessionstore.bak if it was read
+ // successfully or an empty string otherwise.
+ throw new Task.Result(text || "");
+ });
+ },
+
+ write: function ssfi_write(aData) {
+ let refObj = {};
+ let self = this;
+ return TaskUtils.spawn(function task() {
+ let bytes = gEncoder.encode(aData);
+
+ try {
+ let promise = OS.File.writeAtomic(self.path, bytes, {tmpPath: self.path + ".tmp"});
+ yield promise;
+ } catch (ex) {
+ console.error("Could not write session state file: " + self.path, ex);
+ }
+ });
+ },
+
+ createBackupCopy: function ssfi_createBackupCopy() {
+ let backupCopyOptions = {
+ outExecutionDuration: null
+ };
+ let self = this;
+ return TaskUtils.spawn(function task() {
+ try {
+ yield OS.File.move(self.path, self.backupPath, backupCopyOptions);
+ } catch (ex if self._isNoSuchFile(ex)) {
+ // Ignore exceptions about non-existent files.
+ } catch (ex) {
+ console.error("Could not backup session state file: " + self.path, ex);
+ throw ex;
+ }
+ });
+ },
+
+ wipe: function ssfi_wipe() {
+ let self = this;
+ return TaskUtils.spawn(function task() {
+ try {
+ yield OS.File.remove(self.path);
+ } catch (ex if self._isNoSuchFile(ex)) {
+ // Ignore exceptions about non-existent files.
+ } catch (ex) {
+ console.error("Could not remove session state file: " + self.path, ex);
+ throw ex;
+ }
+
+ try {
+ yield OS.File.remove(self.backupPath);
+ } catch (ex if self._isNoSuchFile(ex)) {
+ // Ignore exceptions about non-existent files.
+ } catch (ex) {
+ console.error("Could not remove session state backup file: " + self.path, ex);
+ throw ex;
+ }
+ });
+ },
+
+ _isNoSuchFile: function ssfi_isNoSuchFile(aReason) {
+ return aReason instanceof OS.File.Error && aReason.becauseNoSuchFile;
+ }
+};