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  * @param {!SystemTimer} sysTimer A system timer implementation.
  64  * @constructor
  65  */
  66 function RequestQueue(sysTimer) {
  67   /** @private {!SystemTimer} */
  68   this.sysTimer_ = sysTimer;
  69   /** @private {RequestToken} */
  70   this.head_ = null;
  71   /** @private {RequestToken} */
  72   this.tail_ = null;
  73   /** @private {number} */
  74   this.id_ = 0;
  75 }
  76
  77 /**
  78  * Inserts this token into the queue.
  79  * @param {RequestToken} token Queue token
  80  * @private
  81  */
  82 RequestQueue.prototype.insertToken_ = function(token) {
  83   console.log(UTIL_fmt('token ' + this.id_ + ' inserted'));
  84   if (this.head_ === null) {
  85     this.head_ = token;
  86     this.tail_ = token;
  87   } else {
  88     if (!this.tail_) throw 'Non-empty list missing tail';
  89     this.tail_.next = token;
  90     token.prev = this.tail_;
  91     this.tail_ = token;
  92   }
  93 };
  94
  95 /**
  96  * Removes this token from the queue.
  97  * @param {RequestToken} token Queue token
  98  * @private
  99  */
 100 RequestQueue.prototype.removeToken_ = function(token) {
 101   if (token.next) {
 102     token.next.prev = token.prev;
 103   }
 104   if (token.prev) {
 105     token.prev.next = token.next;
 106   }
 107   if (this.head_ === token && this.tail_ === token) {
 108     this.head_ = this.tail_ = null;
 109   } else {
 110     if (this.head_ === token) {
 111       this.head_ = token.next;
 112       this.head_.prev = null;
 113     }
 114     if (this.tail_ === token) {
 115       this.tail_ = token.prev;
 116       this.tail_.next = null;
 117     }
 118   }
 119   token.prev = token.next = null;
 120 };
 121
 122 /**
 123  * Completes this token's request, and begins the next queued request, if one
 124  * exists.
 125  * @param {RequestToken} token Queue token
 126  */
 127 RequestQueue.prototype.complete = function(token) {
 128   console.log(UTIL_fmt('token ' + this.id_ + ' completed'));
 129   var next = token.next;
 130   this.removeToken_(token);
 131   if (next) {
 132     next.beginCb(next);
 133   }
 134 };
 135
 136 /** @return {boolean} Whether this queue is empty. */
 137 RequestQueue.prototype.empty = function() {
 138   return this.head_ === null;
 139 };
 140
 141 /**
 142  * Queues this request, and, if it's the first request, begins work on it.
 143  * @param {function(QueuedRequestToken)} beginCb Called when work begins on this
 144  *     request.
 145  * @param {Countdown} timer Countdown timer
 146  * @return {QueuedRequestToken} A token for the request.
 147  */
 148 RequestQueue.prototype.queueRequest = function(beginCb, timer) {
 149   var startNow = this.empty();
 150   var token = new RequestToken(this, ++this.id_, beginCb);
 151   // Clone the timer to set a callback on it, which will ensure complete() is
 152   // eventually called, even if the caller never gets around to it.
 153   timer.clone(token.complete.bind(token));
 154   this.insertToken_(token);
 155   if (startNow) {
 156     this.sysTimer_.setTimeout(function() {
 157       if (!token.completed()) {
 158         token.beginCb(token);
 159       }
 160     }, 0);
 161   }
 162   return token;
 163 };
 164
 165 /**
 166  * @param {!SystemTimer} sysTimer A system timer implementation.
 167  * @constructor
 168  */
 169 function OriginKeyedRequestQueue(sysTimer) {
 170   /** @private {!SystemTimer} */
 171   this.sysTimer_ = sysTimer;
 172   /** @private {Object<string, !RequestQueue>} */
 173   this.requests_ = {};
 174 }
 175
 176 /**
 177  * Queues this request, and, if it's the first request, begins work on it.
 178  * @param {string} appId Application Id
 179  * @param {string} origin Request origin
 180  * @param {function(QueuedRequestToken)} beginCb Called when work begins on this
 181  *     request.
 182  * @param {Countdown} timer Countdown timer
 183  * @return {QueuedRequestToken} A token for the request.
 184  */
 185 OriginKeyedRequestQueue.prototype.queueRequest =
 186     function(appId, origin, beginCb, timer) {
 187   var key = appId + ' ' + origin;
 188   if (!this.requests_.hasOwnProperty(key)) {
 189     this.requests_[key] = new RequestQueue(this.sysTimer_);
 190   }
 191   var queue = this.requests_[key];
 192   return queue.queueRequest(beginCb, timer);
 193 };