15f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)// Copyright 2014 The Chromium Authors. All rights reserved. 25f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)// Use of this source code is governed by a BSD-style license that can be 35f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)// found in the LICENSE file. 45f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 55f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 65f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)/** 75f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) * @fileoverview Utilities for local_ntp.js. 85f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) */ 95f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 105f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 115f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)/** 125f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) * A counter with a callback that gets executed on the 1-to-0 transition. 135f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) * 145f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) * @param {function()} callback The callback to be executed. 155f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) * @constructor 165f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) */ 175f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)function Barrier(callback) { 185f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) /** @private {function()} */ 195f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) this.callback_ = callback; 205f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 215f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) /** @private {number} */ 225f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) this.count_ = 0; 235f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 245f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) /** @private {boolean} */ 255f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) this.isCancelled_ = false; 265f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)} 275f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 285f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 295f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)/** 305f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) * Increments count of the Barrier. 315f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) */ 325f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)Barrier.prototype.add = function() { 335f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) ++this.count_; 345f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)}; 355f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 365f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 375f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)/** 385f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) * Decrements count of the Barrier, and executes callback on 1-to-0 transition. 395f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) */ 405f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)Barrier.prototype.remove = function() { 415f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) if (this.count_ === 0) // Guards against underflow. 425f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) return; 435f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) --this.count_; 445f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) if (!this.isCancelled_ && this.count_ === 0) 455f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) this.callback_(); 465f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)}; 475f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 485f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) 495f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)/** 505f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) * Deactivates the Barrier; the callback will never be executed. 515f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) */ 525f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)Barrier.prototype.cancel = function() { 535f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles) this.isCancelled_ = true; 545f1c94371a64b3196d4be9466099bb892df9b88eTorne (Richard Coles)}; 55