Display active audio streams on chrome://media-internals.

chrome/browser/resources/media_internals/item_store.js

+// Copyright (c) 2011 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.
+
+cr.define('media', function() {
+
+  /**
+   * This class stores hashes by their id field and provides basic methods for
+   * iterating over the collection.
+   * @constructor
+   */
+  function ItemStore() {
+    this.items_ = {};
+  };
+
+  ItemStore.prototype = {
+    /**
+     * Get a sorted list of item ids.
+     * @return {Array} A sorted array of ids.
+     */
+    ids: function() {
+      var ids = [];
+      for (var i in this.items_)
+        ids.push(i);
+      return ids.sort();
+    },
+
+    /**
+     * Add an item to the store.
+     * @param {Object} item The item to be added.
+     * @param {string} item.id The id of the item.
+     */
+    addItem: function(item) {
+      this.items_[item.id] = item;
+    },
+
+    /**
+     * Add a dictionary of items to the store.
+     * @param {Object} items A dictionary of individual items. The keys are
+     *    irrelevant but each must have an id field.
+     */
+    addItems: function(items) {
+      for (id in items)
+        this.addItem(items[id]);
+    },
+
+    /**
+     * Remove an item from the store.
+     * @param {string} id The id of the item to be removed.
+     */
+    removeItem: function(id) {
+      delete this.items_[id];
+    },
+
+    /**
+     * Map this itemStore to an Array. Items are sorted by id.
+     * @param {function(*)} mapper The mapping function applied to each item.
+     * @return {Array} An array of mapped items.
+     */
+    map: function(mapper) {
+      var items = this.items_;
+      var ids = this.ids();
+      return ids.map(function(id) { return mapper(items[id]); });
+    }
+  };
+
+  return {
+    ItemStore: ItemStore
+  };
+});