Crawler, second version

lib/bootstrap_xpcom.js

Index: lib/bootstrap_xpcom.js
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+/*
+ * This Source Code is subject to the terms of the Mozilla Public License
+ * version 2.0 (the "License"). You can obtain a copy of the License at
+ * http://mozilla.org/MPL/2.0/.
+ */
+
+
+//Cc["@mozilla.org/observer-service;1"].getService(Ci.nsIObserverService)
+
+var Bootstrap_XPCOM_Base_class = function()
+{
+};
+
+Bootstrap_XPCOM_Base_class.prototype = {
+  registrar: Components.manager.QueryInterface( Ci.nsIComponentRegistrar ),
+  category_manager: Cc["@mozilla.org/categorymanager;1"].getService( Ci.nsICategoryManager ),
+  observer_service: Cc["@mozilla.org/observer-service;1"].getService( Ci.nsIObserverService )
+};
+
+Bootstrap_XPCOM_Base_class.prototype.add_observation_topic = function( topic  )
+{
+  /*
+   * Third argument 'false' means to make a strong reference. This class (right now) supports singletons at
+   * file scope, which have the lifetime of the application.
+   */
+  this.observer_service.addObserver( this, topic, false );
+};
+
+Bootstrap_XPCOM_Base_class.prototype.remove_observation_topic = function( topic  )
+{
+  this.observer_service.removeObserver( this, topic );
+};
+
+//-----------------------------------------------------------------------------------------
+// Singleton_class
+//-----------------------------------------------------------------------------------------
+/**
+ *
+ * @param {string} class_description
+ *    Human-readable description of the class.
+ * @param class_ID
+ *    Class ID for this component.
+ * @param contract_ID
+ *    The contract ID that this component uses. It's only a single ID for this relatively-simple class.
+ * @param {Array} interfaces
+ *    An array of interfaces that this class supports. Used to initialize QueryInterface.
+ * @param {Array} category_entries
+ *    An array of arguments for addCategoryEntry().
+ * @constructor
+ */
+var Singleton_class = function( class_description, class_ID, contract_ID, interfaces, category_entries )
+{
+  this.class_description = class_description;
+  this.class_ID = class_ID;
+  this.contract_ID = contract_ID;
+  this._xpcom_categories = category_entries;
+
+  /**
+   * Standard QI function from the XPCOM utility module.
+   * @type {Function}
+   */
+  this.QueryInterface = XPCOMUtils.generateQI( interfaces );
+};
+Singleton_class.prototype = new Bootstrap_XPCOM_Base_class();
+
+/**
+ * Initialization
+ * @private
+ */
+Singleton_class.prototype.init = function()
+{
+  this.registrar.registerFactory( this.class_ID, this.class_description, this.contract_ID, this );
+  for ( let c of this._xpcom_categories )
+  {
+    //noinspection JSUnusedAssignment
+    this.category_manager.addCategoryEntry( c.category, c.entry, this.contract_ID, false, true );
+  }
+  onShutdown.add( Singleton_class._deinit.bind( this ) );
+};
+
+/**
+ * De-initialization function, run at shutdown time.
+ *
+ * This is a separate function to avoid using a closure for registering the shutdown hook.
+ *
+ * @private
+ */
+Singleton_class._deinit = function()
+{
+  for ( let c of this._xpcom_categories )
+  {
+    //noinspection JSUnusedAssignment
+    this.category_manager.deleteCategoryEntry( c.category, c.entry, false );
+  }
+
+  this.registrar.unregisterFactory( this.class_ID, this );
+};
+
+/**
+ * Standard createInstance implementation for a singleton, returning 'this' rather than a new object.
+ */
+Singleton_class.prototype.createInstance = function( outer, iid )
+{
+  if ( outer )
+    throw Cr.NS_ERROR_NO_AGGREGATION;
+  return this.QueryInterface( iid );
+};
+
+
+//-----------------------------------------------------------------------------------------
+// exports
+//-----------------------------------------------------------------------------------------
+
+var Bootstrap_XPCOM = {
+  Singleton_class: Singleton_class
+};
+exports.Bootstrap_XPCOM = Bootstrap_XPCOM;