| // Copyright 2014 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| /** |
| * @fileoverview Queue of pending requests from an origin. |
| * |
| */ |
| 'use strict'; |
| |
| /** |
| * Represents a queued request. Once given a token, call complete() once the |
| * request is processed (or dropped.) |
| * @interface |
| */ |
| function QueuedRequestToken() {} |
| |
| /** Completes (or cancels) this queued request. */ |
| QueuedRequestToken.prototype.complete = function() {}; |
| |
| /** |
| * @param {!RequestQueue} queue The queue for this request. |
| * @param {function(QueuedRequestToken)} beginCb Called when work may begin on |
| * this request. |
| * @param {RequestToken} opt_prev Previous request in the same queue. |
| * @param {RequestToken} opt_next Next request in the same queue. |
| * @constructor |
| * @implements {QueuedRequestToken} |
| */ |
| function RequestToken(queue, beginCb, opt_prev, opt_next) { |
| /** @private {!RequestQueue} */ |
| this.queue_ = queue; |
| /** @type {function(QueuedRequestToken)} */ |
| this.beginCb = beginCb; |
| /** @type {RequestToken} */ |
| this.prev = null; |
| /** @type {RequestToken} */ |
| this.next = null; |
| /** @private {boolean} */ |
| this.completed_ = false; |
| } |
| |
| /** Completes (or cancels) this queued request. */ |
| RequestToken.prototype.complete = function() { |
| if (this.completed_) { |
| // Either the caller called us more than once, or the timer is firing. |
| // Either way, nothing more to do here. |
| return; |
| } |
| this.completed_ = true; |
| this.queue_.complete(this); |
| }; |
| |
| /** @return {boolean} Whether this token has already completed. */ |
| RequestToken.prototype.completed = function() { |
| return this.completed_; |
| }; |
| |
| /** |
| * @constructor |
| */ |
| function RequestQueue() { |
| /** @private {RequestToken} */ |
| this.head_ = null; |
| /** @private {RequestToken} */ |
| this.tail_ = null; |
| } |
| |
| /** |
| * Inserts this token into the queue. |
| * @param {RequestToken} token Queue token |
| * @private |
| */ |
| RequestQueue.prototype.insertToken_ = function(token) { |
| if (this.head_ === null) { |
| this.head_ = token; |
| this.tail_ = token; |
| } else { |
| if (!this.tail_) throw 'Non-empty list missing tail'; |
| this.tail_.next = token; |
| token.prev = this.tail_; |
| this.tail_ = token; |
| } |
| }; |
| |
| /** |
| * Removes this token from the queue. |
| * @param {RequestToken} token Queue token |
| * @private |
| */ |
| RequestQueue.prototype.removeToken_ = function(token) { |
| if (token.next) { |
| token.next.prev = token.prev; |
| } |
| if (token.prev) { |
| token.prev.next = token.next; |
| } |
| if (this.head_ === token && this.tail_ === token) { |
| this.head_ = this.tail_ = null; |
| } else { |
| if (this.head_ === token) { |
| this.head_ = token.next; |
| this.head_.prev = null; |
| } |
| if (this.tail_ === token) { |
| this.tail_ = token.prev; |
| this.tail_.next = null; |
| } |
| } |
| token.prev = token.next = null; |
| }; |
| |
| /** |
| * Completes this token's request, and begins the next queued request, if one |
| * exists. |
| * @param {RequestToken} token Queue token |
| */ |
| RequestQueue.prototype.complete = function(token) { |
| var next = token.next; |
| this.removeToken_(token); |
| if (next) { |
| next.beginCb(next); |
| } |
| }; |
| |
| /** @return {boolean} Whether this queue is empty. */ |
| RequestQueue.prototype.empty = function() { |
| return this.head_ === null; |
| }; |
| |
| /** |
| * Queues this request, and, if it's the first request, begins work on it. |
| * @param {function(QueuedRequestToken)} beginCb Called when work begins on this |
| * request. |
| * @param {Countdown} timer Countdown timer |
| * @return {QueuedRequestToken} A token for the request. |
| */ |
| RequestQueue.prototype.queueRequest = function(beginCb, timer) { |
| var startNow = this.empty(); |
| var token = new RequestToken(this, beginCb); |
| // Clone the timer to set a callback on it, which will ensure complete() is |
| // eventually called, even if the caller never gets around to it. |
| timer.clone(token.complete.bind(token)); |
| this.insertToken_(token); |
| if (startNow) { |
| window.setTimeout(function() { |
| if (!token.completed()) { |
| token.beginCb(token); |
| } |
| }, 0); |
| } |
| return token; |
| }; |
| |
| /** |
| * @constructor |
| */ |
| function OriginKeyedRequestQueue() { |
| /** @private {Object.<string, !RequestQueue>} */ |
| this.requests_ = {}; |
| } |
| |
| /** |
| * Queues this request, and, if it's the first request, begins work on it. |
| * @param {string} appId Application Id |
| * @param {string} origin Request origin |
| * @param {function(QueuedRequestToken)} beginCb Called when work begins on this |
| * request. |
| * @param {Countdown} timer Countdown timer |
| * @return {QueuedRequestToken} A token for the request. |
| */ |
| OriginKeyedRequestQueue.prototype.queueRequest = |
| function(appId, origin, beginCb, timer) { |
| var key = appId + origin; |
| if (!this.requests_.hasOwnProperty(key)) { |
| this.requests_[key] = new RequestQueue(); |
| } |
| var queue = this.requests_[key]; |
| return queue.queueRequest(beginCb, timer); |
| }; |