chrome/browser/resources/cryptotoken/requestqueue.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 /**
   6  * @fileoverview Queue of pending requests from an origin.
   7  *
   8  */
   9 'use strict';
  10
  11 /**
  12  * Represents a queued request. Once given a token, call complete() once the
  13  * request is processed (or dropped.)
  14  * @interface
  15  */
  16 function QueuedRequestToken() {}
  17
  18 /** Completes (or cancels) this queued request. */
  19 QueuedRequestToken.prototype.complete = function() {};
  20
  21 /**
  22  * @param {!RequestQueue} queue The queue for this request.
  23  * @param {number} id An id for this request.
  24  * @param {function(QueuedRequestToken)} beginCb Called when work may begin on
  25  *     this request.
  26  * @param {RequestToken} opt_prev Previous request in the same queue.
  27  * @param {RequestToken} opt_next Next request in the same queue.
  28  * @constructor
  29  * @implements {QueuedRequestToken}
  30  */
  31 function RequestToken(queue, id, beginCb, opt_prev, opt_next) {
  32   /** @private {!RequestQueue} */
  33   this.queue_ = queue;
  34   /** @private {number} */
  35   this.id_ = id;
  36   /** @type {function(QueuedRequestToken)} */
  37   this.beginCb = beginCb;
  38   /** @type {RequestToken} */
  39   this.prev = null;
  40   /** @type {RequestToken} */
  41   this.next = null;
  42   /** @private {boolean} */
  43   this.completed_ = false;
  44 }
  45
  46 /** Completes (or cancels) this queued request. */
  47 RequestToken.prototype.complete = function() {
  48   if (this.completed_) {
  49     // Either the caller called us more than once, or the timer is firing.
  50     // Either way, nothing more to do here.
  51     return;
  52   }
  53   this.completed_ = true;
  54   this.queue_.complete(this);
  55 };
  56
  57 /** @return {boolean} Whether this token has already completed. */
  58 RequestToken.prototype.completed = function() {
  59   return this.completed_;
  60 };
  61
  62 /**
  63  * @constructor
  64  */
  65 function RequestQueue() {
  66   /** @private {RequestToken} */
  67   this.head_ = null;
  68   /** @private {RequestToken} */
  69   this.tail_ = null;
  70   /** @private {number} */
  71   this.id_ = 0;
  72 }
  73
  74 /**
  75  * Inserts this token into the queue.
  76  * @param {RequestToken} token Queue token
  77  * @private
  78  */
  79 RequestQueue.prototype.insertToken_ = function(token) {
  80   console.log(UTIL_fmt('token ' + this.id_ + ' inserted'));
  81   if (this.head_ === null) {
  82     this.head_ = token;
  83     this.tail_ = token;
  84   } else {
  85     if (!this.tail_) throw 'Non-empty list missing tail';
  86     this.tail_.next = token;
  87     token.prev = this.tail_;
  88     this.tail_ = token;
  89   }
  90 };
  91
  92 /**
  93  * Removes this token from the queue.
  94  * @param {RequestToken} token Queue token
  95  * @private
  96  */
  97 RequestQueue.prototype.removeToken_ = function(token) {
  98   if (token.next) {
  99     token.next.prev = token.prev;
 100   }
 101   if (token.prev) {
 102     token.prev.next = token.next;
 103   }
 104   if (this.head_ === token && this.tail_ === token) {
 105     this.head_ = this.tail_ = null;
 106   } else {
 107     if (this.head_ === token) {
 108       this.head_ = token.next;
 109       this.head_.prev = null;
 110     }
 111     if (this.tail_ === token) {
 112       this.tail_ = token.prev;
 113       this.tail_.next = null;
 114     }
 115   }
 116   token.prev = token.next = null;
 117 };
 118
 119 /**
 120  * Completes this token's request, and begins the next queued request, if one
 121  * exists.
 122  * @param {RequestToken} token Queue token
 123  */
 124 RequestQueue.prototype.complete = function(token) {
 125   console.log(UTIL_fmt('token ' + this.id_ + ' completed'));
 126   var next = token.next;
 127   this.removeToken_(token);
 128   if (next) {
 129     next.beginCb(next);
 130   }
 131 };
 132
 133 /** @return {boolean} Whether this queue is empty. */
 134 RequestQueue.prototype.empty = function() {
 135   return this.head_ === null;
 136 };
 137
 138 /**
 139  * Queues this request, and, if it's the first request, begins work on it.
 140  * @param {function(QueuedRequestToken)} beginCb Called when work begins on this
 141  *     request.
 142  * @param {Countdown} timer Countdown timer
 143  * @return {QueuedRequestToken} A token for the request.
 144  */
 145 RequestQueue.prototype.queueRequest = function(beginCb, timer) {
 146   var startNow = this.empty();
 147   var token = new RequestToken(this, ++this.id_, beginCb);
 148   // Clone the timer to set a callback on it, which will ensure complete() is
 149   // eventually called, even if the caller never gets around to it.
 150   timer.clone(token.complete.bind(token));
 151   this.insertToken_(token);
 152   if (startNow) {
 153     window.setTimeout(function() {
 154       if (!token.completed()) {
 155         token.beginCb(token);
 156       }
 157     }, 0);
 158   }
 159   return token;
 160 };
 161
 162 /**
 163  * @constructor
 164  */
 165 function OriginKeyedRequestQueue() {
 166   /** @private {Object<!RequestQueue>} */
 167   this.requests_ = {};
 168 }
 169
 170 /**
 171  * Queues this request, and, if it's the first request, begins work on it.
 172  * @param {string} appId Application Id
 173  * @param {string} origin Request origin
 174  * @param {function(QueuedRequestToken)} beginCb Called when work begins on this
 175  *     request.
 176  * @param {Countdown} timer Countdown timer
 177  * @return {QueuedRequestToken} A token for the request.
 178  */
 179 OriginKeyedRequestQueue.prototype.queueRequest =
 180     function(appId, origin, beginCb, timer) {
 181   var key = appId + ' ' + origin;
 182   if (!this.requests_.hasOwnProperty(key)) {
 183     this.requests_[key] = new RequestQueue();
 184   }
 185   var queue = this.requests_[key];
 186   return queue.queueRequest(beginCb, timer);
 187 };