Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1674 insertions, 0 deletions

diff --git a/toolkit/components/osfile/modules/osfile_async_front.jsm b/toolkit/components/osfile/modules/osfile_async_front.jsm
new file mode 100644
index 0000000000..fc00e9c3e8
--- /dev/null
+++ b/toolkit/components/osfile/modules/osfile_async_front.jsm
@@ -0,0 +1,1674 @@
+/* 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/. */
+
+/**
+ * Asynchronous front-end for OS.File.
+ *
+ * This front-end is meant to be imported from the main thread. In turn,
+ * it spawns one worker (perhaps more in the future) and delegates all
+ * disk I/O to this worker.
+ *
+ * Documentation note: most of the functions and methods in this module
+ * return promises. For clarity, we denote as follows a promise that may resolve
+ * with type |A| and some value |value| or reject with type |B| and some
+ * reason |reason|
+ * @resolves {A} value
+ * @rejects {B} reason
+ */
+
+"use strict";
+
+var EXPORTED_SYMBOLS = ["OS"];
+
+var SharedAll = {};
+ChromeUtils.import(
+  "resource://gre/modules/osfile/osfile_shared_allthreads.jsm",
+  SharedAll
+);
+ChromeUtils.import("resource://gre/modules/Timer.jsm", this);
+
+// Boilerplate, to simplify the transition to require()
+var LOG = SharedAll.LOG.bind(SharedAll, "Controller");
+var isTypedArray = SharedAll.isTypedArray;
+
+// The constructor for file errors.
+var SysAll = {};
+if (SharedAll.Constants.Win) {
+  ChromeUtils.import(
+    "resource://gre/modules/osfile/osfile_win_allthreads.jsm",
+    SysAll
+  );
+} else if (SharedAll.Constants.libc) {
+  ChromeUtils.import(
+    "resource://gre/modules/osfile/osfile_unix_allthreads.jsm",
+    SysAll
+  );
+} else {
+  throw new Error("I am neither under Windows nor under a Posix system");
+}
+var OSError = SysAll.Error;
+var Type = SysAll.Type;
+
+var Path = {};
+ChromeUtils.import("resource://gre/modules/osfile/ospath.jsm", Path);
+
+// The library of promises.
+ChromeUtils.defineModuleGetter(
+  this,
+  "PromiseUtils",
+  "resource://gre/modules/PromiseUtils.jsm"
+);
+
+// The implementation of communications
+ChromeUtils.import("resource://gre/modules/PromiseWorker.jsm", this);
+ChromeUtils.import("resource://gre/modules/Services.jsm", this);
+ChromeUtils.import("resource://gre/modules/AsyncShutdown.jsm", this);
+var Native = ChromeUtils.import(
+  "resource://gre/modules/osfile/osfile_native.jsm",
+  null
+);
+
+// It's possible for osfile.jsm to get imported before the profile is
+// set up. In this case, some path constants aren't yet available.
+// Here, we make them lazy loaders.
+
+function lazyPathGetter(constProp, dirKey) {
+  return function() {
+    let path;
+    try {
+      path = Services.dirsvc.get(dirKey, Ci.nsIFile).path;
+      delete SharedAll.Constants.Path[constProp];
+      SharedAll.Constants.Path[constProp] = path;
+    } catch (ex) {
+      // Ignore errors if the value still isn't available. Hopefully
+      // the next access will return it.
+    }
+
+    return path;
+  };
+}
+
+for (let [constProp, dirKey] of [
+  ["localProfileDir", "ProfLD"],
+  ["profileDir", "ProfD"],
+  ["userApplicationDataDir", "UAppData"],
+  ["winAppDataDir", "AppData"],
+  ["winLocalAppDataDir", "LocalAppData"],
+  ["winStartMenuProgsDir", "Progs"],
+  ["tmpDir", "TmpD"],
+  ["homeDir", "Home"],
+  ["macUserLibDir", "ULibDir"],
+]) {
+  if (constProp in SharedAll.Constants.Path) {
+    continue;
+  }
+
+  LOG(
+    "Installing lazy getter for OS.Constants.Path." +
+      constProp +
+      " because it isn't defined and profile may not be loaded."
+  );
+  Object.defineProperty(SharedAll.Constants.Path, constProp, {
+    get: lazyPathGetter(constProp, dirKey),
+  });
+}
+
+/**
+ * Return a shallow clone of the enumerable properties of an object.
+ */
+var clone = SharedAll.clone;
+
+/**
+ * Extract a shortened version of an object, fit for logging.
+ *
+ * This function returns a copy of the original object in which all
+ * long strings, Arrays, TypedArrays, ArrayBuffers are removed and
+ * replaced with placeholders. Use this function to sanitize objects
+ * if you wish to log them or to keep them in memory.
+ *
+ * @param {*} obj The obj to shorten.
+ * @return {*} array A shorter object, fit for logging.
+ */
+function summarizeObject(obj) {
+  if (!obj) {
+    return null;
+  }
+  if (typeof obj == "string") {
+    if (obj.length > 1024) {
+      return { "Long string": obj.length };
+    }
+    return obj;
+  }
+  if (typeof obj == "object") {
+    if (Array.isArray(obj)) {
+      if (obj.length > 32) {
+        return { "Long array": obj.length };
+      }
+      return obj.map(summarizeObject);
+    }
+    if ("byteLength" in obj) {
+      // Assume TypedArray or ArrayBuffer
+      return { "Binary Data": obj.byteLength };
+    }
+    let result = {};
+    for (let k of Object.keys(obj)) {
+      result[k] = summarizeObject(obj[k]);
+    }
+    return result;
+  }
+  return obj;
+}
+
+// In order to expose Scheduler to the unfiltered Cu.import return value variant
+// on B2G we need to save it to `this`.  This does not make it public;
+// EXPORTED_SYMBOLS still controls that in all cases.
+var Scheduler = (this.Scheduler = {
+  /**
+   * |true| once we have sent at least one message to the worker.
+   * This field is unaffected by resetting the worker.
+   */
+  launched: false,
+
+  /**
+   * |true| once shutdown has begun i.e. we should reject any
+   * message, including resets.
+   */
+  shutdown: false,
+
+  /**
+   * A promise resolved once all currently pending operations are complete.
+   *
+   * This promise is never rejected and the result is always undefined.
+   */
+  queue: Promise.resolve(),
+
+  /**
+   * A promise resolved once all currently pending `kill` operations
+   * are complete.
+   *
+   * This promise is never rejected and the result is always undefined.
+   */
+  _killQueue: Promise.resolve(),
+
+  /**
+   * Miscellaneous debugging information
+   */
+  Debugging: {
+    /**
+     * The latest message sent and still waiting for a reply.
+     */
+    latestSent: undefined,
+
+    /**
+     * The latest reply received, or null if we are waiting for a reply.
+     */
+    latestReceived: undefined,
+
+    /**
+     * Number of messages sent to the worker. This includes the
+     * initial SET_DEBUG, if applicable.
+     */
+    messagesSent: 0,
+
+    /**
+     * Total number of messages ever queued, including the messages
+     * sent.
+     */
+    messagesQueued: 0,
+
+    /**
+     * Number of messages received from the worker.
+     */
+    messagesReceived: 0,
+  },
+
+  /**
+   * A timer used to automatically shut down the worker after some time.
+   */
+  resetTimer: null,
+
+  /**
+   * A flag indicating whether we had some activities when waiting the
+   * timer and if it's not we can shut down the worker.
+   */
+  hasRecentActivity: false,
+
+  /**
+   * The worker to which to send requests.
+   *
+   * If the worker has never been created or has been reset, this is a
+   * fresh worker, initialized with osfile_async_worker.js.
+   *
+   * @type {PromiseWorker}
+   */
+  get worker() {
+    if (!this._worker) {
+      // Either the worker has never been created or it has been
+      // reset.  In either case, it is time to instantiate the worker.
+      this._worker = new BasePromiseWorker(
+        "resource://gre/modules/osfile/osfile_async_worker.js"
+      );
+      this._worker.log = LOG;
+      this._worker.ExceptionHandlers["OS.File.Error"] = OSError.fromMsg;
+
+      let delay = Services.prefs.getIntPref("osfile.reset_worker_delay", 0);
+      if (delay) {
+        this.resetTimer = setInterval(() => {
+          if (this.hasRecentActivity) {
+            this.hasRecentActivity = false;
+            return;
+          }
+          clearInterval(this.resetTimer);
+          Scheduler.kill({ reset: true, shutdown: false });
+        }, delay);
+      }
+    }
+    return this._worker;
+  },
+
+  _worker: null,
+
+  /**
+   * Restart the OS.File worker killer timer.
+   */
+  restartTimer(arg) {
+    this.hasRecentActivity = true;
+  },
+
+  /**
+   * Shutdown OS.File.
+   *
+   * @param {*} options
+   * - {boolean} shutdown If |true|, reject any further request. Otherwise,
+   *   further requests will resurrect the worker.
+   * - {boolean} reset If |true|, instruct the worker to shutdown if this
+   *   would not cause leaks. Otherwise, assume that the worker will be shutdown
+   *   through some other mean.
+   */
+  kill({ shutdown, reset }) {
+    // Grab the kill queue to make sure that we
+    // cannot be interrupted by another call to `kill`.
+    let killQueue = this._killQueue;
+
+    // Deactivate the queue, to ensure that no message is sent
+    // to an obsolete worker (we reactivate it in the `finally`).
+    // This needs to be done right now so that we maintain relative
+    // ordering with calls to post(), etc.
+    let deferred = PromiseUtils.defer();
+    let savedQueue = this.queue;
+    this.queue = deferred.promise;
+
+    return (this._killQueue = (async () => {
+      await killQueue;
+      // From this point, and until the end of the Task, we are the
+      // only call to `kill`, regardless of any `yield`.
+
+      await savedQueue;
+
+      try {
+        // Enter critical section: no yield in this block
+        // (we want to make sure that we remain the only
+        // request in the queue).
+
+        if (!this.launched || this.shutdown || !this._worker) {
+          // Nothing to kill
+          this.shutdown = this.shutdown || shutdown;
+          this._worker = null;
+          return null;
+        }
+
+        // Exit critical section
+
+        let message = ["Meta_shutdown", [reset]];
+
+        Scheduler.latestReceived = [];
+        let stack = new Error().stack;
+        Scheduler.latestSent = [Date.now(), stack, ...message];
+
+        // Wait for result
+        let resources;
+        try {
+          resources = await this._worker.post(...message);
+
+          Scheduler.latestReceived = [Date.now(), message];
+        } catch (ex) {
+          LOG("Could not dispatch Meta_reset", ex);
+          // It's most likely a programmer error, but we'll assume that
+          // the worker has been shutdown, as it's less risky than the
+          // opposite stance.
+          resources = {
+            openedFiles: [],
+            openedDirectoryIterators: [],
+            killed: true,
+          };
+
+          Scheduler.latestReceived = [Date.now(), message, ex];
+        }
+
+        let { openedFiles, openedDirectoryIterators, killed } = resources;
+        if (
+          !reset &&
+          ((openedFiles && openedFiles.length) ||
+            (openedDirectoryIterators && openedDirectoryIterators.length))
+        ) {
+          // The worker still holds resources. Report them.
+
+          let msg = "";
+          if (openedFiles.length) {
+            msg +=
+              "The following files are still open:\n" + openedFiles.join("\n");
+          }
+          if (openedDirectoryIterators.length) {
+            msg +=
+              "The following directory iterators are still open:\n" +
+              openedDirectoryIterators.join("\n");
+          }
+
+          LOG("WARNING: File descriptors leaks detected.\n" + msg);
+        }
+
+        // Make sure that we do not leave an invalid |worker| around.
+        if (killed || shutdown) {
+          this._worker = null;
+        }
+
+        this.shutdown = shutdown;
+
+        return resources;
+      } finally {
+        // Resume accepting messages. If we have set |shutdown| to |true|,
+        // any pending/future request will be rejected. Otherwise, any
+        // pending/future request will spawn a new worker if necessary.
+        deferred.resolve();
+      }
+    })());
+  },
+
+  /**
+   * Push a task at the end of the queue.
+   *
+   * @param {function} code A function returning a Promise.
+   * This function will be executed once all the previously
+   * pushed tasks have completed.
+   * @return {Promise} A promise with the same behavior as
+   * the promise returned by |code|.
+   */
+  push(code) {
+    let promise = this.queue.then(code);
+    // By definition, |this.queue| can never reject.
+    this.queue = promise.catch(() => undefined);
+    // Fork |promise| to ensure that uncaught errors are reported
+    return promise.then();
+  },
+
+  /**
+   * Post a message to the worker thread.
+   *
+   * @param {string} method The name of the method to call.
+   * @param {...} args The arguments to pass to the method. These arguments
+   * must be clonable.
+   * The last argument by convention may be an object `options`, with some of
+   * the following fields:
+   *   - {number|null} outSerializationDuration A parameter to be filled with
+   *     duration of the `this.worker.post` method.
+   * @return {Promise} A promise conveying the result/error caused by
+   * calling |method| with arguments |args|.
+   */
+  post: function post(method, args = undefined, closure = undefined) {
+    if (this.shutdown) {
+      LOG(
+        "OS.File is not available anymore. The following request has been rejected.",
+        method,
+        args
+      );
+      return Promise.reject(
+        new Error("OS.File has been shut down. Rejecting post to " + method)
+      );
+    }
+    let firstLaunch = !this.launched;
+    this.launched = true;
+
+    if (firstLaunch && SharedAll.Config.DEBUG) {
+      // If we have delayed sending SET_DEBUG, do it now.
+      this.worker.post("SET_DEBUG", [true]);
+      Scheduler.Debugging.messagesSent++;
+    }
+
+    Scheduler.Debugging.messagesQueued++;
+    return this.push(async () => {
+      if (this.shutdown) {
+        LOG(
+          "OS.File is not available anymore. The following request has been rejected.",
+          method,
+          args
+        );
+        throw new Error(
+          "OS.File has been shut down. Rejecting request to " + method
+        );
+      }
+
+      // Update debugging information. As |args| may be quite
+      // expensive, we only keep a shortened version of it.
+      Scheduler.Debugging.latestReceived = null;
+      Scheduler.Debugging.latestSent = [
+        Date.now(),
+        method,
+        summarizeObject(args),
+      ];
+
+      // Don't kill the worker just yet
+      Scheduler.restartTimer();
+
+      // The last object inside the args may be an options object.
+      let options = null;
+      if (
+        args &&
+        args.length >= 1 &&
+        typeof args[args.length - 1] === "object"
+      ) {
+        options = args[args.length - 1];
+      }
+
+      let reply;
+      try {
+        try {
+          Scheduler.Debugging.messagesSent++;
+          Scheduler.Debugging.latestSent = Scheduler.Debugging.latestSent.slice(
+            0,
+            2
+          );
+          let serializationStartTimeMs = Date.now();
+          reply = await this.worker.post(method, args, closure);
+          let serializationEndTimeMs = Date.now();
+          Scheduler.Debugging.latestReceived = [
+            Date.now(),
+            summarizeObject(reply),
+          ];
+
+          // There were no options for recording the serialization duration.
+          if (options && "outSerializationDuration" in options) {
+            // The difference might be negative for very fast operations, since Date.now() may not be monotonic.
+            let serializationDurationMs = Math.max(
+              0,
+              serializationEndTimeMs - serializationStartTimeMs
+            );
+
+            if (typeof options.outSerializationDuration === "number") {
+              options.outSerializationDuration += serializationDurationMs;
+            } else {
+              options.outSerializationDuration = serializationDurationMs;
+            }
+          }
+          return reply;
+        } finally {
+          Scheduler.Debugging.messagesReceived++;
+        }
+      } catch (error) {
+        Scheduler.Debugging.latestReceived = [
+          Date.now(),
+          error.message,
+          error.fileName,
+          error.lineNumber,
+        ];
+        throw error;
+      } finally {
+        if (firstLaunch) {
+          Scheduler._updateTelemetry();
+        }
+        Scheduler.restartTimer();
+      }
+    });
+  },
+
+  /**
+   * Post Telemetry statistics.
+   *
+   * This is only useful on first launch.
+   */
+  _updateTelemetry() {
+    let worker = this.worker;
+    let workerTimeStamps = worker.workerTimeStamps;
+    if (!workerTimeStamps) {
+      // If the first call to OS.File results in an uncaught errors,
+      // the timestamps are absent. As this case is a developer error,
+      // let's not waste time attempting to extract telemetry from it.
+      return;
+    }
+    let HISTOGRAM_LAUNCH = Services.telemetry.getHistogramById(
+      "OSFILE_WORKER_LAUNCH_MS"
+    );
+    HISTOGRAM_LAUNCH.add(
+      worker.workerTimeStamps.entered - worker.launchTimeStamp
+    );
+
+    let HISTOGRAM_READY = Services.telemetry.getHistogramById(
+      "OSFILE_WORKER_READY_MS"
+    );
+    HISTOGRAM_READY.add(
+      worker.workerTimeStamps.loaded - worker.launchTimeStamp
+    );
+  },
+});
+
+const PREF_OSFILE_LOG = "toolkit.osfile.log";
+const PREF_OSFILE_LOG_REDIRECT = "toolkit.osfile.log.redirect";
+
+/**
+ * Safely read a PREF_OSFILE_LOG preference.
+ * Returns a value read or, in case of an error, oldPref or false.
+ *
+ * @param bool oldPref
+ *        An optional value that the DEBUG flag was set to previously.
+ */
+function readDebugPref(prefName, oldPref = false) {
+  // If neither pref nor oldPref were set, default it to false.
+  return Services.prefs.getBoolPref(prefName, oldPref);
+}
+
+/**
+ * Listen to PREF_OSFILE_LOG changes and update gShouldLog flag
+ * appropriately.
+ */
+Services.prefs.addObserver(PREF_OSFILE_LOG, function prefObserver(
+  aSubject,
+  aTopic,
+  aData
+) {
+  SharedAll.Config.DEBUG = readDebugPref(
+    PREF_OSFILE_LOG,
+    SharedAll.Config.DEBUG
+  );
+  if (Scheduler.launched) {
+    // Don't start the worker just to set this preference.
+    Scheduler.post("SET_DEBUG", [SharedAll.Config.DEBUG]);
+  }
+});
+SharedAll.Config.DEBUG = readDebugPref(PREF_OSFILE_LOG, false);
+
+Services.prefs.addObserver(PREF_OSFILE_LOG_REDIRECT, function prefObserver(
+  aSubject,
+  aTopic,
+  aData
+) {
+  SharedAll.Config.TEST = readDebugPref(
+    PREF_OSFILE_LOG_REDIRECT,
+    OS.Shared.TEST
+  );
+});
+SharedAll.Config.TEST = readDebugPref(PREF_OSFILE_LOG_REDIRECT, false);
+
+/**
+ * If |true|, use the native implementaiton of OS.File methods
+ * whenever possible. Otherwise, force the use of the JS version.
+ */
+var nativeWheneverAvailable = true;
+const PREF_OSFILE_NATIVE = "toolkit.osfile.native";
+Services.prefs.addObserver(PREF_OSFILE_NATIVE, function prefObserver(
+  aSubject,
+  aTopic,
+  aData
+) {
+  nativeWheneverAvailable = readDebugPref(
+    PREF_OSFILE_NATIVE,
+    nativeWheneverAvailable
+  );
+});
+
+// Update worker's DEBUG flag if it's true.
+// Don't start the worker just for this, though.
+if (SharedAll.Config.DEBUG && Scheduler.launched) {
+  Scheduler.post("SET_DEBUG", [true]);
+}
+
+// Preference used to configure test shutdown observer.
+const PREF_OSFILE_TEST_SHUTDOWN_OBSERVER =
+  "toolkit.osfile.test.shutdown.observer";
+
+AsyncShutdown.xpcomWillShutdown.addBlocker(
+  "OS.File: flush pending requests, warn about unclosed files, shut down service.",
+  async function() {
+    // Give clients a last chance to enqueue requests.
+    await Barriers.shutdown.wait({ crashAfterMS: null });
+
+    // Wait until all requests are complete and kill the worker.
+    await Scheduler.kill({ reset: false, shutdown: true });
+  },
+  () => {
+    let details = Barriers.getDetails();
+    details.clients = Barriers.shutdown.state;
+    return details;
+  }
+);
+
+// Attaching an observer for PREF_OSFILE_TEST_SHUTDOWN_OBSERVER to enable or
+// disable the test shutdown event observer.
+// Note: By default the PREF_OSFILE_TEST_SHUTDOWN_OBSERVER is unset.
+// Note: This is meant to be used for testing purposes only.
+Services.prefs.addObserver(
+  PREF_OSFILE_TEST_SHUTDOWN_OBSERVER,
+  function prefObserver() {
+    // The temporary phase topic used to trigger the unclosed
+    // phase warning.
+    let TOPIC = Services.prefs.getCharPref(
+      PREF_OSFILE_TEST_SHUTDOWN_OBSERVER,
+      ""
+    );
+    if (TOPIC) {
+      // Generate a phase, add a blocker.
+      // Note that this can work only if AsyncShutdown itself has been
+      // configured for testing by the testsuite.
+      let phase = AsyncShutdown._getPhase(TOPIC);
+      phase.addBlocker(
+        "(for testing purposes) OS.File: warn about unclosed files",
+        () => Scheduler.kill({ shutdown: false, reset: false })
+      );
+    }
+  }
+);
+
+/**
+ * Representation of a file, with asynchronous methods.
+ *
+ * @param {*} fdmsg The _message_ representing the platform-specific file
+ * handle.
+ *
+ * @constructor
+ */
+var File = function File(fdmsg) {
+  // FIXME: At the moment, |File| does not close on finalize
+  // (see bug 777715)
+  this._fdmsg = fdmsg;
+  this._closeResult = null;
+  this._closed = null;
+};
+
+File.prototype = {
+  /**
+   * Close a file asynchronously.
+   *
+   * This method is idempotent.
+   *
+   * @return {promise}
+   * @resolves {null}
+   * @rejects {OS.File.Error}
+   */
+  close: function close() {
+    if (this._fdmsg != null) {
+      let msg = this._fdmsg;
+      this._fdmsg = null;
+      return (this._closeResult = Scheduler.post(
+        "File_prototype_close",
+        [msg],
+        this
+      ));
+    }
+    return this._closeResult;
+  },
+
+  /**
+   * Fetch information about the file.
+   *
+   * @return {promise}
+   * @resolves {OS.File.Info} The latest information about the file.
+   * @rejects {OS.File.Error}
+   */
+  stat: function stat() {
+    return Scheduler.post("File_prototype_stat", [this._fdmsg], this).then(
+      File.Info.fromMsg
+    );
+  },
+
+  /**
+   * Write bytes from a buffer to this file.
+   *
+   * Note that, by default, this function may perform several I/O
+   * operations to ensure that the buffer is fully written.
+   *
+   * @param {Typed array | C pointer} buffer The buffer in which the
+   * the bytes are stored. The buffer must be large enough to
+   * accomodate |bytes| bytes. Using the buffer before the operation
+   * is complete is a BAD IDEA.
+   * @param {*=} options Optionally, an object that may contain the
+   * following fields:
+   * - {number} bytes The number of |bytes| to write from the buffer. If
+   * unspecified, this is |buffer.byteLength|. Note that |bytes| is required
+   * if |buffer| is a C pointer.
+   *
+   * @return {number} The number of bytes actually written.
+   */
+  write: function write(buffer, options = {}) {
+    // If |buffer| is a typed array and there is no |bytes| options,
+    // we need to extract the |byteLength| now, as it will be lost
+    // by communication.
+    // Options might be a nullish value, so better check for that before using
+    // the |in| operator.
+    if (isTypedArray(buffer) && !(options && "bytes" in options)) {
+      // Preserve reference to option |outExecutionDuration|, |outSerializationDuration|, if it is passed.
+      options = clone(options, [
+        "outExecutionDuration",
+        "outSerializationDuration",
+      ]);
+      options.bytes = buffer.byteLength;
+    }
+    return Scheduler.post(
+      "File_prototype_write",
+      [this._fdmsg, Type.void_t.in_ptr.toMsg(buffer), options],
+      buffer /* Ensure that |buffer| is not gc-ed*/
+    );
+  },
+
+  /**
+   * Read bytes from this file to a new buffer.
+   *
+   * @param {number=} bytes If unspecified, read all the remaining bytes from
+   * this file. If specified, read |bytes| bytes, or less if the file does not
+   * contain that many bytes.
+   * @param {JSON} options
+   * @return {promise}
+   * @resolves {Uint8Array} An array containing the bytes read.
+   */
+  read: function read(nbytes, options = {}) {
+    let promise = Scheduler.post("File_prototype_read", [
+      this._fdmsg,
+      nbytes,
+      options,
+    ]);
+    return promise.then(function onSuccess(data) {
+      return new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
+    });
+  },
+
+  /**
+   * Return the current position in the file, as bytes.
+   *
+   * @return {promise}
+   * @resolves {number} The current position in the file,
+   * as a number of bytes since the start of the file.
+   */
+  getPosition: function getPosition() {
+    return Scheduler.post("File_prototype_getPosition", [this._fdmsg]);
+  },
+
+  /**
+   * Set the current position in the file, as bytes.
+   *
+   * @param {number} pos A number of bytes.
+   * @param {number} whence The reference position in the file,
+   * which may be either POS_START (from the start of the file),
+   * POS_END (from the end of the file) or POS_CUR (from the
+   * current position in the file).
+   *
+   * @return {promise}
+   */
+  setPosition: function setPosition(pos, whence) {
+    return Scheduler.post("File_prototype_setPosition", [
+      this._fdmsg,
+      pos,
+      whence,
+    ]);
+  },
+
+  /**
+   * Flushes the file's buffers and causes all buffered data
+   * to be written.
+   * Disk flushes are very expensive and therefore should be used carefully,
+   * sparingly and only in scenarios where it is vital that data survives
+   * system crashes. Even though the function will be executed off the
+   * main-thread, it might still affect the overall performance of any running
+   * application.
+   *
+   * @return {promise}
+   */
+  flush: function flush() {
+    return Scheduler.post("File_prototype_flush", [this._fdmsg]);
+  },
+
+  /**
+   * Set the file's access permissions.  This does nothing on Windows.
+   *
+   * This operation is likely to fail if applied to a file that was
+   * not created by the currently running program (more precisely,
+   * if it was created by a program running under a different OS-level
+   * user account).  It may also fail, or silently do nothing, if the
+   * filesystem containing the file does not support access permissions.
+   *
+   * @param {*=} options Object specifying the requested permissions:
+   *
+   * - {number} unixMode The POSIX file mode to set on the file.  If omitted,
+   *  the POSIX file mode is reset to the default used by |OS.file.open|.  If
+   *  specified, the permissions will respect the process umask as if they
+   *  had been specified as arguments of |OS.File.open|, unless the
+   *  |unixHonorUmask| parameter tells otherwise.
+   * - {bool} unixHonorUmask If omitted or true, any |unixMode| value is
+   *  modified by the process umask, as |OS.File.open| would have done.  If
+   *  false, the exact value of |unixMode| will be applied.
+   */
+  setPermissions: function setPermissions(options = {}) {
+    return Scheduler.post("File_prototype_setPermissions", [
+      this._fdmsg,
+      options,
+    ]);
+  },
+};
+
+if (SharedAll.Constants.Sys.Name != "Android") {
+  /**
+   * Set the last access and modification date of the file.
+   * The time stamp resolution is 1 second at best, but might be worse
+   * depending on the platform.
+   *
+   * WARNING: This method is not implemented on Android/B2G. On Android/B2G,
+   * you should use File.setDates instead.
+   *
+   * @return {promise}
+   * @rejects {TypeError}
+   * @rejects {OS.File.Error}
+   */
+  File.prototype.setDates = function(accessDate, modificationDate) {
+    return Scheduler.post(
+      "File_prototype_setDates",
+      [this._fdmsg, accessDate, modificationDate],
+      this
+    );
+  };
+}
+
+/**
+ * Open a file asynchronously.
+ *
+ * @return {promise}
+ * @resolves {OS.File}
+ * @rejects {OS.Error}
+ */
+File.open = function open(path, mode, options) {
+  return Scheduler.post(
+    "open",
+    [Type.path.toMsg(path), mode, options],
+    path
+  ).then(function onSuccess(msg) {
+    return new File(msg);
+  });
+};
+
+/**
+ * Creates and opens a file with a unique name. By default, generate a random HEX number and use it to create a unique new file name.
+ *
+ * @param {string} path The path to the file.
+ * @param {*=} options Additional options for file opening. This
+ * implementation interprets the following fields:
+ *
+ * - {number} humanReadable If |true|, create a new filename appending a decimal number. ie: filename-1.ext, filename-2.ext.
+ *  If |false| use HEX numbers ie: filename-A65BC0.ext
+ * - {number} maxReadableNumber Used to limit the amount of tries after a failed
+ *  file creation. Default is 20.
+ *
+ * @return {Object} contains A file object{file} and the path{path}.
+ * @throws {OS.File.Error} If the file could not be opened.
+ */
+File.openUnique = function openUnique(path, options) {
+  return Scheduler.post(
+    "openUnique",
+    [Type.path.toMsg(path), options],
+    path
+  ).then(function onSuccess(msg) {
+    return {
+      path: msg.path,
+      file: new File(msg.file),
+    };
+  });
+};
+
+/**
+ * Get the information on the file.
+ *
+ * @return {promise}
+ * @resolves {OS.File.Info}
+ * @rejects {OS.Error}
+ */
+File.stat = function stat(path, options) {
+  return Scheduler.post("stat", [Type.path.toMsg(path), options], path).then(
+    File.Info.fromMsg
+  );
+};
+
+/**
+ * Set the last access and modification date of the file.
+ * The time stamp resolution is 1 second at best, but might be worse
+ * depending on the platform.
+ *
+ * @return {promise}
+ * @rejects {TypeError}
+ * @rejects {OS.File.Error}
+ */
+File.setDates = function setDates(path, accessDate, modificationDate) {
+  return Scheduler.post(
+    "setDates",
+    [Type.path.toMsg(path), accessDate, modificationDate],
+    this
+  );
+};
+
+/**
+ * Set the file's access permissions.  This does nothing on Windows.
+ *
+ * This operation is likely to fail if applied to a file that was
+ * not created by the currently running program (more precisely,
+ * if it was created by a program running under a different OS-level
+ * user account).  It may also fail, or silently do nothing, if the
+ * filesystem containing the file does not support access permissions.
+ *
+ * @param {string} path The path to the file.
+ * @param {*=} options Object specifying the requested permissions:
+ *
+ * - {number} unixMode The POSIX file mode to set on the file.  If omitted,
+ *  the POSIX file mode is reset to the default used by |OS.file.open|.  If
+ *  specified, the permissions will respect the process umask as if they
+ *  had been specified as arguments of |OS.File.open|, unless the
+ *  |unixHonorUmask| parameter tells otherwise.
+ * - {bool} unixHonorUmask If omitted or true, any |unixMode| value is
+ *  modified by the process umask, as |OS.File.open| would have done.  If
+ *  false, the exact value of |unixMode| will be applied.
+ */
+File.setPermissions = function setPermissions(path, options = {}) {
+  return Scheduler.post("setPermissions", [Type.path.toMsg(path), options]);
+};
+
+/**
+ * Fetch the current directory
+ *
+ * @return {promise}
+ * @resolves {string} The current directory, as a path usable with OS.Path
+ * @rejects {OS.Error}
+ */
+File.getCurrentDirectory = function getCurrentDirectory() {
+  return Scheduler.post("getCurrentDirectory").then(Type.path.fromMsg);
+};
+
+/**
+ * Change the current directory
+ *
+ * @param {string} path The OS-specific path to the current directory.
+ * You should use the methods of OS.Path and the constants of OS.Constants.Path
+ * to build OS-specific paths in a portable manner.
+ *
+ * @return {promise}
+ * @resolves {null}
+ * @rejects {OS.Error}
+ */
+File.setCurrentDirectory = function setCurrentDirectory(path) {
+  return Scheduler.post("setCurrentDirectory", [Type.path.toMsg(path)], path);
+};
+
+/**
+ * Copy a file to a destination.
+ *
+ * @param {string} sourcePath The platform-specific path at which
+ * the file may currently be found.
+ * @param {string} destPath The platform-specific path at which the
+ * file should be copied.
+ * @param {*=} options An object which may contain the following fields:
+ *
+ * @option {bool} noOverwrite - If true, this function will fail if
+ * a file already exists at |destPath|. Otherwise, if this file exists,
+ * it will be erased silently.
+ *
+ * @rejects {OS.File.Error} In case of any error.
+ *
+ * General note: The behavior of this function is defined only when
+ * it is called on a single file. If it is called on a directory, the
+ * behavior is undefined and may not be the same across all platforms.
+ *
+ * General note: The behavior of this function with respect to metadata
+ * is unspecified. Metadata may or may not be copied with the file. The
+ * behavior may not be the same across all platforms.
+ */
+File.copy = function copy(sourcePath, destPath, options) {
+  return Scheduler.post(
+    "copy",
+    [Type.path.toMsg(sourcePath), Type.path.toMsg(destPath), options],
+    [sourcePath, destPath]
+  );
+};
+
+/**
+ * Move a file to a destination.
+ *
+ * @param {string} sourcePath The platform-specific path at which
+ * the file may currently be found.
+ * @param {string} destPath The platform-specific path at which the
+ * file should be moved.
+ * @param {*=} options An object which may contain the following fields:
+ *
+ * @option {bool} noOverwrite - If set, this function will fail if
+ * a file already exists at |destPath|. Otherwise, if this file exists,
+ * it will be erased silently.
+ *
+ * @returns {Promise}
+ * @rejects {OS.File.Error} In case of any error.
+ *
+ * General note: The behavior of this function is defined only when
+ * it is called on a single file. If it is called on a directory, the
+ * behavior is undefined and may not be the same across all platforms.
+ *
+ * General note: The behavior of this function with respect to metadata
+ * is unspecified. Metadata may or may not be moved with the file. The
+ * behavior may not be the same across all platforms.
+ */
+File.move = function move(sourcePath, destPath, options) {
+  return Scheduler.post(
+    "move",
+    [Type.path.toMsg(sourcePath), Type.path.toMsg(destPath), options],
+    [sourcePath, destPath]
+  );
+};
+
+/**
+ * Create a symbolic link to a source.
+ *
+ * @param {string} sourcePath The platform-specific path to which
+ * the symbolic link should point.
+ * @param {string} destPath The platform-specific path at which the
+ * symbolic link should be created.
+ *
+ * @returns {Promise}
+ * @rejects {OS.File.Error} In case of any error.
+ */
+if (!SharedAll.Constants.Win) {
+  File.unixSymLink = function unixSymLink(sourcePath, destPath) {
+    return Scheduler.post(
+      "unixSymLink",
+      [Type.path.toMsg(sourcePath), Type.path.toMsg(destPath)],
+      [sourcePath, destPath]
+    );
+  };
+}
+
+/**
+ * Remove an empty directory.
+ *
+ * @param {string} path The name of the directory to remove.
+ * @param {*=} options Additional options.
+ *   - {bool} ignoreAbsent If |true|, do not fail if the
+ *     directory does not exist yet.
+ */
+File.removeEmptyDir = function removeEmptyDir(path, options) {
+  return Scheduler.post(
+    "removeEmptyDir",
+    [Type.path.toMsg(path), options],
+    path
+  );
+};
+
+/**
+ * Remove an existing file.
+ *
+ * @param {string} path The name of the file.
+ * @param {*=} options Additional options.
+ *   - {bool} ignoreAbsent If |false|, throw an error if the file does
+ *     not exist. |true| by default.
+ *
+ * @throws {OS.File.Error} In case of I/O error.
+ */
+File.remove = function remove(path, options) {
+  return Scheduler.post("remove", [Type.path.toMsg(path), options], path);
+};
+
+// Extended attribute functions are MacOS only at this point.
+if (SharedAll.Constants.Sys.Name == "Darwin") {
+  /**
+   * Get an extended attribute (xattr) from a file.
+   *
+   * @param {string} path The name of the file.
+   * @param {string} name The name of the extended attribute.
+   *
+   * @returns {promise}
+   * @resolves {Uint8Array} An array containing the value of the attribute.
+   * @rejects {OS.File.Error} In case of an I/O error or invalid options.
+   */
+  File.macGetXAttr = function macGetXAttr(path, name) {
+    let promise = Scheduler.post(
+      "macGetXAttr",
+      [Type.path.toMsg(path), Type.cstring.toMsg(name)],
+      [path, name]
+    );
+    return promise.then(data => {
+      return new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
+    });
+  };
+
+  /**
+   * Remove an extended attribute (xattr) from a file.
+   *
+   * @param {string} path The name of the file.
+   * @param {string} name The name of the extended attribute.
+   *
+   * @returns {promise}
+   * @resolves {null}
+   * @rejects {OS.File.Error} In case of an I/O error.
+   */
+  File.macRemoveXAttr = function macRemoveXAttr(path, name) {
+    return Scheduler.post(
+      "macRemoveXAttr",
+      [Type.path.toMsg(path), Type.cstring.toMsg(name)],
+      [path, name]
+    );
+  };
+
+  /**
+   * Set an extended attribute (xattr) on a file.
+   *
+   * @param {string} path The name of the file.
+   * @param {string} name The name of the extended attribute.
+   * @param {Uint8Array} value A byte array containing the value to set the
+   * xattr to.
+   *
+   * @returns {promise}
+   * @resolves {null}
+   * @rejects {OS.File.Error} In case of an I/O error.
+   */
+  File.macSetXAttr = function macSetXAttr(path, name, value, number) {
+    return Scheduler.post(
+      "macSetXAttr",
+      [
+        Type.path.toMsg(path),
+        Type.cstring.toMsg(name),
+        Type.void_t.in_ptr.toMsg(value),
+        value.length,
+      ],
+      [path, name, value]
+    );
+  };
+}
+
+/**
+ * Create a directory and, optionally, its parent directories.
+ *
+ * @param {string} path The name of the directory.
+ * @param {*=} options Additional options.
+ *
+ * - {string} from If specified, the call to |makeDir| creates all the
+ * ancestors of |path| that are descendants of |from|. Note that |path|
+ * must be a descendant of |from|, and that |from| and its existing
+ * subdirectories present in |path|  must be user-writeable.
+ * Example:
+ *   makeDir(Path.join(profileDir, "foo", "bar"), { from: profileDir });
+ *  creates directories profileDir/foo, profileDir/foo/bar
+ * - {bool} ignoreExisting If |false|, throw an error if the directory
+ * already exists. |true| by default. Ignored if |from| is specified.
+ * - {number} unixMode Under Unix, if specified, a file creation mode,
+ * as per libc function |mkdir|. If unspecified, dirs are
+ * created with a default mode of 0700 (dir is private to
+ * the user, the user can read, write and execute). Ignored under Windows
+ * or if the file system does not support file creation modes.
+ * - {C pointer} winSecurity Under Windows, if specified, security
+ * attributes as per winapi function |CreateDirectory|. If
+ * unspecified, use the default security descriptor, inherited from
+ * the parent directory. Ignored under Unix or if the file system
+ * does not support security descriptors.
+ */
+File.makeDir = function makeDir(path, options) {
+  return Scheduler.post("makeDir", [Type.path.toMsg(path), options], path);
+};
+
+/**
+ * Return the contents of a file
+ *
+ * @param {string} path The path to the file.
+ * @param {number=} bytes Optionally, an upper bound to the number of bytes
+ * to read. DEPRECATED - please use options.bytes instead.
+ * @param {JSON} options Additional options.
+ * - {boolean} sequential A flag that triggers a population of the page cache
+ * with data from a file so that subsequent reads from that file would not
+ * block on disk I/O. If |true| or unspecified, inform the system that the
+ * contents of the file will be read in order. Otherwise, make no such
+ * assumption. |true| by default.
+ * - {number} bytes An upper bound to the number of bytes to read.
+ * - {string} compression If "lz4" and if the file is compressed using the lz4
+ * compression algorithm, decompress the file contents on the fly.
+ *
+ * @resolves {Uint8Array} A buffer holding the bytes
+ * read from the file.
+ */
+File.read = function read(path, bytes, options = {}) {
+  if (typeof bytes == "object") {
+    // Passing |bytes| as an argument is deprecated.
+    // We should now be passing it as a field of |options|.
+    options = bytes || {};
+  } else {
+    options = clone(options, [
+      "outExecutionDuration",
+      "outSerializationDuration",
+    ]);
+    if (typeof bytes != "undefined") {
+      options.bytes = bytes;
+    }
+  }
+
+  if (options.compression || !nativeWheneverAvailable) {
+    // We need to use the JS implementation.
+    let promise = Scheduler.post(
+      "read",
+      [Type.path.toMsg(path), bytes, options],
+      path
+    );
+    return promise.then(function onSuccess(data) {
+      if (typeof data == "string") {
+        return data;
+      }
+      return new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
+    });
+  }
+
+  // Otherwise, use the native implementation.
+  return Scheduler.push(() => Native.read(path, options));
+};
+
+/**
+ * Find outs if a file exists.
+ *
+ * @param {string} path The path to the file.
+ *
+ * @return {bool} true if the file exists, false otherwise.
+ */
+File.exists = function exists(path) {
+  return Scheduler.post("exists", [Type.path.toMsg(path)], path);
+};
+
+/**
+ * Write a file, atomically.
+ *
+ * By opposition to a regular |write|, this operation ensures that,
+ * until the contents are fully written, the destination file is
+ * not modified.
+ *
+ * Limitation: In a few extreme cases (hardware failure during the
+ * write, user unplugging disk during the write, etc.), data may be
+ * corrupted. If your data is user-critical (e.g. preferences,
+ * application data, etc.), you may wish to consider adding options
+ * |tmpPath| and/or |flush| to reduce the likelihood of corruption, as
+ * detailed below. Note that no combination of options can be
+ * guaranteed to totally eliminate the risk of corruption.
+ *
+ * @param {string} path The path of the file to modify.
+ * @param {Typed Array | C pointer} buffer A buffer containing the bytes to write.
+ * @param {*=} options Optionally, an object determining the behavior
+ * of this function. This object may contain the following fields:
+ * - {number} bytes The number of bytes to write. If unspecified,
+ * |buffer.byteLength|. Required if |buffer| is a C pointer.
+ * - {string} tmpPath If |null| or unspecified, write all data directly
+ * to |path|. If specified, write all data to a temporary file called
+ * |tmpPath| and, once this write is complete, rename the file to
+ * replace |path|. Performing this additional operation is a little
+ * slower but also a little safer.
+ * - {bool} noOverwrite - If set, this function will fail if a file already
+ * exists at |path|.
+ * - {bool} flush - If |false| or unspecified, return immediately once the
+ * write is complete. If |true|, before writing, force the operating system
+ * to write its internal disk buffers to the disk. This is considerably slower
+ * (not just for the application but for the whole system) but also safer:
+ * if the system shuts down improperly (typically due to a kernel freeze
+ * or a power failure) or if the device is disconnected before the buffer
+ * is flushed, the file has more chances of not being corrupted.
+ * - {string} backupTo - If specified, backup the destination file as |backupTo|.
+ * Note that this function renames the destination file before overwriting it.
+ * If the process or the operating system freezes or crashes
+ * during the short window between these operations,
+ * the destination file will have been moved to its backup.
+ *
+ * @return {promise}
+ * @resolves {number} The number of bytes actually written.
+ */
+File.writeAtomic = function writeAtomic(path, buffer, options = {}) {
+  const useNativeImplementation =
+    nativeWheneverAvailable &&
+    !options.compression &&
+    !(isTypedArray(buffer) && "byteOffset" in buffer && buffer.byteOffset > 0);
+  // Copy |options| to avoid modifying the original object but preserve the
+  // reference to |outExecutionDuration|, |outSerializationDuration| option if it is passed.
+  options = clone(options, [
+    "outExecutionDuration",
+    "outSerializationDuration",
+  ]);
+  // As options.tmpPath is a path, we need to encode it as |Type.path| message, but only
+  // if we are not using the native implementation.
+  if ("tmpPath" in options && !useNativeImplementation) {
+    options.tmpPath = Type.path.toMsg(options.tmpPath);
+  }
+  if (isTypedArray(buffer) && !("bytes" in options)) {
+    options.bytes = buffer.byteLength;
+  }
+  let refObj = {};
+  let promise;
+  TelemetryStopwatch.start("OSFILE_WRITEATOMIC_JANK_MS", refObj);
+  if (useNativeImplementation) {
+    promise = Scheduler.push(() => Native.writeAtomic(path, buffer, options));
+  } else {
+    promise = Scheduler.post(
+      "writeAtomic",
+      [Type.path.toMsg(path), Type.void_t.in_ptr.toMsg(buffer), options],
+      [options, buffer, path]
+    );
+  }
+  TelemetryStopwatch.finish("OSFILE_WRITEATOMIC_JANK_MS", refObj);
+  return promise;
+};
+
+File.removeDir = function(path, options = {}) {
+  return Scheduler.post("removeDir", [Type.path.toMsg(path), options], path);
+};
+
+/**
+ * Information on a file, as returned by OS.File.stat or
+ * OS.File.prototype.stat
+ *
+ * @constructor
+ */
+File.Info = function Info(value) {
+  // Note that we can't just do this[k] = value[k] because our
+  // prototype defines getters for all of these fields.
+  for (let k in value) {
+    if (k != "creationDate") {
+      Object.defineProperty(this, k, { value: value[k] });
+    }
+  }
+  Object.defineProperty(this, "_deprecatedCreationDate", {
+    value: value.creationDate,
+  });
+};
+File.Info.prototype = SysAll.AbstractInfo.prototype;
+
+// Deprecated
+Object.defineProperty(File.Info.prototype, "creationDate", {
+  get: function creationDate() {
+    let { Deprecated } = ChromeUtils.import(
+      "resource://gre/modules/Deprecated.jsm"
+    );
+    Deprecated.warning(
+      "Field 'creationDate' is deprecated.",
+      "https://developer.mozilla.org/en-US/docs/JavaScript_OS.File/OS.File.Info#Cross-platform_Attributes"
+    );
+    return this._deprecatedCreationDate;
+  },
+});
+
+File.Info.fromMsg = function fromMsg(value) {
+  return new File.Info(value);
+};
+
+/**
+ * Get worker's current DEBUG flag.
+ * Note: This is used for testing purposes.
+ */
+File.GET_DEBUG = function GET_DEBUG() {
+  return Scheduler.post("GET_DEBUG");
+};
+
+/**
+ * Iterate asynchronously through a directory
+ *
+ * @constructor
+ */
+var DirectoryIterator = function DirectoryIterator(path, options) {
+  /**
+   * Open the iterator on the worker thread
+   *
+   * @type {Promise}
+   * @resolves {*} A message accepted by the methods of DirectoryIterator
+   * in the worker thread
+   */
+  this._itmsg = Scheduler.post(
+    "new_DirectoryIterator",
+    [Type.path.toMsg(path), options],
+    path
+  );
+  this._isClosed = false;
+};
+DirectoryIterator.prototype = {
+  [Symbol.asyncIterator]() {
+    return this;
+  },
+
+  _itmsg: null,
+
+  /**
+   * Determine whether the directory exists.
+   *
+   * @resolves {boolean}
+   */
+  async exists() {
+    if (this._isClosed) {
+      return Promise.resolve(false);
+    }
+    let iterator = await this._itmsg;
+    return Scheduler.post("DirectoryIterator_prototype_exists", [iterator]);
+  },
+  /**
+   * Get the next entry in the directory.
+   *
+   * @return {Promise}
+   * @resolves By definition of the async iterator protocol, either
+   * `{value: {File.Entry}, done: false}` if there is an unvisited entry
+   * in the directory, or `{value: undefined, done: true}`, otherwise.
+   */
+  async next() {
+    if (this._isClosed) {
+      return { value: undefined, done: true };
+    }
+    return this._next(await this._itmsg);
+  },
+  /**
+   * Get several entries at once.
+   *
+   * @param {number=} length If specified, the number of entries
+   * to return. If unspecified, return all remaining entries.
+   * @return {Promise}
+   * @resolves {Array} An array containing the |length| next entries.
+   */
+  async nextBatch(size) {
+    if (this._isClosed) {
+      return [];
+    }
+    let iterator = await this._itmsg;
+    let array = await Scheduler.post("DirectoryIterator_prototype_nextBatch", [
+      iterator,
+      size,
+    ]);
+    return array.map(DirectoryIterator.Entry.fromMsg);
+  },
+  /**
+   * Apply a function to all elements of the directory sequentially.
+   *
+   * @param {Function} cb This function will be applied to all entries
+   * of the directory. It receives as arguments
+   *  - the OS.File.Entry corresponding to the entry;
+   *  - the index of the entry in the enumeration;
+   *  - the iterator itself - return |iterator.close()| to stop the loop.
+   *
+   * If the callback returns a promise, iteration waits until the
+   * promise is resolved before proceeding.
+   *
+   * @return {Promise} A promise resolved once the loop has reached
+   * its end.
+   */
+  async forEach(cb, options) {
+    if (this._isClosed) {
+      return undefined;
+    }
+    let position = 0;
+    let iterator = await this._itmsg;
+    while (true) {
+      if (this._isClosed) {
+        return undefined;
+      }
+      let { value, done } = await this._next(iterator);
+      if (done) {
+        return undefined;
+      }
+      await cb(value, position++, this);
+    }
+  },
+  /**
+   * Auxiliary method: fetch the next item
+   *
+   * @resolves `{value: undefined, done: true}` If all entries have already
+   * been visited or the iterator has been closed.
+   */
+  async _next(iterator) {
+    if (this._isClosed) {
+      return { value: undefined, done: true };
+    }
+    let {
+      value,
+      done,
+    } = await Scheduler.post("DirectoryIterator_prototype_next", [iterator]);
+    if (done) {
+      this.close();
+      return { value: undefined, done: true };
+    }
+    return { value: DirectoryIterator.Entry.fromMsg(value), done: false };
+  },
+  /**
+   * Close the iterator
+   */
+  async close() {
+    if (this._isClosed) {
+      return undefined;
+    }
+    this._isClosed = true;
+    let iterator = this._itmsg;
+    this._itmsg = null;
+    return Scheduler.post("DirectoryIterator_prototype_close", [iterator]);
+  },
+};
+
+DirectoryIterator.Entry = function Entry(value) {
+  return value;
+};
+DirectoryIterator.Entry.prototype = Object.create(
+  SysAll.AbstractEntry.prototype
+);
+
+DirectoryIterator.Entry.fromMsg = function fromMsg(value) {
+  return new DirectoryIterator.Entry(value);
+};
+
+File.resetWorker = function() {
+  return (async function() {
+    let resources = await Scheduler.kill({ shutdown: false, reset: true });
+    if (resources && !resources.killed) {
+      throw new Error(
+        "Could not reset worker, this would leak file descriptors: " +
+          JSON.stringify(resources)
+      );
+    }
+  })();
+};
+
+// Constants
+File.POS_START = SysAll.POS_START;
+File.POS_CURRENT = SysAll.POS_CURRENT;
+File.POS_END = SysAll.POS_END;
+
+// Exports
+File.Error = OSError;
+File.DirectoryIterator = DirectoryIterator;
+
+var OS = {};
+OS.File = File;
+OS.Constants = SharedAll.Constants;
+OS.Shared = {
+  LOG: SharedAll.LOG,
+  Type: SysAll.Type,
+  get DEBUG() {
+    return SharedAll.Config.DEBUG;
+  },
+  set DEBUG(x) {
+    return (SharedAll.Config.DEBUG = x);
+  },
+};
+Object.freeze(OS.Shared);
+OS.Path = Path;
+
+// Returns a resolved promise when all the queued operation have been completed.
+Object.defineProperty(OS.File, "queue", {
+  get() {
+    return Scheduler.queue;
+  },
+});
+
+// `true` if this is a content process, `false` otherwise.
+// It would be nicer to go through `Services.appinfo`, but some tests need to be
+// able to replace that field with a custom implementation before it is first
+// called.
+const isContent =
+  // eslint-disable-next-line mozilla/use-services
+  Cc["@mozilla.org/xre/app-info;1"].getService(Ci.nsIXULRuntime).processType ==
+  Ci.nsIXULRuntime.PROCESS_TYPE_CONTENT;
+
+/**
+ * Shutdown barriers, to let clients register to be informed during shutdown.
+ */
+var Barriers = {
+  shutdown: new AsyncShutdown.Barrier(
+    "OS.File: Waiting for clients before full shutdown"
+  ),
+  /**
+   * Return the shutdown state of OS.File
+   */
+  getDetails() {
+    let result = {
+      launched: Scheduler.launched,
+      shutdown: Scheduler.shutdown,
+      worker: !!Scheduler._worker,
+      pendingReset: !!Scheduler.resetTimer,
+      latestSent: Scheduler.Debugging.latestSent,
+      latestReceived: Scheduler.Debugging.latestReceived,
+      messagesSent: Scheduler.Debugging.messagesSent,
+      messagesReceived: Scheduler.Debugging.messagesReceived,
+      messagesQueued: Scheduler.Debugging.messagesQueued,
+      DEBUG: SharedAll.Config.DEBUG,
+    };
+    // Convert dates to strings for better readability
+    for (let key of ["latestSent", "latestReceived"]) {
+      if (result[key] && typeof result[key][0] == "number") {
+        result[key][0] = Date(result[key][0]);
+      }
+    }
+    return result;
+  },
+};
+
+function setupShutdown(phaseName) {
+  Barriers[phaseName] = new AsyncShutdown.Barrier(
+    `OS.File: Waiting for clients before ${phaseName}`
+  );
+  File[phaseName] = Barriers[phaseName].client;
+
+  // Auto-flush OS.File during `phaseName`. This ensures that any I/O
+  // that has been queued *before* `phaseName` is properly completed.
+  // To ensure that I/O queued *during* `phaseName` change is completed,
+  // clients should register using AsyncShutdown.addBlocker.
+  AsyncShutdown[phaseName].addBlocker(
+    `OS.File: flush I/O queued before ${phaseName}`,
+    async function() {
+      // Give clients a last chance to enqueue requests.
+      await Barriers[phaseName].wait({ crashAfterMS: null });
+
+      // Wait until all currently enqueued requests are completed.
+      await Scheduler.queue;
+    },
+    () => {
+      let details = Barriers.getDetails();
+      details.clients = Barriers[phaseName].state;
+      return details;
+    }
+  );
+}
+
+// profile-before-change only exists in the parent, and OS.File should
+// not be used in the child process anyways.
+if (!isContent) {
+  setupShutdown("profileBeforeChange");
+}
+File.shutdown = Barriers.shutdown.client;