extensions/renderer/resources/async_waiter.js

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 define('async_waiter', [
   6     'mojo/public/js/bindings/support',
   7 ], function(supportModule) {
   8   /**
   9    * @module async_waiter
  10    */
  11
  12   /**
  13    * @callback module:async_waiter.AsyncWaiter.Callback
  14    * @param {number} result The result of waiting.
  15    */
  16
  17   /**
  18    * A waiter that waits for a handle to be ready for either reading or writing.
  19    * @param {MojoHandle} handle The handle to wait on.
  20    * @param {int} signals The signals to wait for handle to be ready for.
  21    * @param {module:async_waiter.AsyncWaiter.Callback} callback The callback to
  22    *     call when handle is ready.
  23    * @constructor
  24    * @alias module:async_waiter.AsyncWaiter
  25    */
  26   function AsyncWaiter(handle, signals, callback) {
  27     /**
  28      * The handle to wait on.
  29      * @type {MojoHandle}
  30      * @private
  31      */
  32     this.handle_ = handle;
  33
  34     /**
  35      * The signals to wait for.
  36      * @type {number}
  37      * @private
  38      */
  39     this.signals_ = signals;
  40
  41     /**
  42      * The callback to invoke when
  43      * |[handle_]{@link module:async_waiter.AsyncWaiter#handle_}| is ready.
  44      * @type {module:async_waiter.AsyncWaiter.Callback}
  45      * @private
  46      */
  47     this.callback_ = callback;
  48     this.id_ = null;
  49   }
  50
  51   /**
  52    * Start waiting for the handle to be ready.
  53    * @throws Will throw if this is already waiting.
  54    */
  55   AsyncWaiter.prototype.start = function() {
  56     if (this.id_)
  57       throw new Error('Already started');
  58     this.id_ = supportModule.asyncWait(
  59         this.handle_, this.signals_, this.onHandleReady_.bind(this));
  60   };
  61
  62   /**
  63    * Stop waiting for the handle to be ready.
  64    */
  65   AsyncWaiter.prototype.stop = function() {
  66     if (!this.id_)
  67       return;
  68
  69     supportModule.cancelWait(this.id_);
  70     this.id_ = null;
  71   };
  72
  73   /**
  74    * Returns whether this {@ linke AsyncWaiter} is waiting.
  75    * @return {boolean} Whether this AsyncWaiter is waiting.
  76    */
  77   AsyncWaiter.prototype.isWaiting = function() {
  78     return !!this.id_;
  79   };
  80
  81   /**
  82    * Invoked when |[handle_]{@link module:async_waiter.AsyncWaiter#handle_}| is
  83    * ready.
  84    * @param {number} result The result of the wait.
  85    * @private
  86    */
  87   AsyncWaiter.prototype.onHandleReady_ = function(result) {
  88     this.id_ = null;
  89     this.callback_(result);
  90   };
  91
  92   return {AsyncWaiter: AsyncWaiter};
  93 });