FIDO U2F component extension

chrome/browser/resources/cryptotoken/requestqueue.js

+// Copyright (c) 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.
+ *
+ * @author juanlang@google.com (Juan Lang)
+ */
+'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
+ * @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
+ * @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
+ */
+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
+ * @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
+ * @param {string} origin
+ * @param {function(QueuedRequestToken)} beginCb Called when work begins on this
+ *     request.
+ * @param {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);
+};