Implementation of AutomationEventQueue and associated framework to support generic non-blocking aut…

chrome/browser/automation/automation_event_queue.h

+// Copyright (c) 2012 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.
+
+#ifndef CHROME_BROWSER_AUTOMATION_AUTOMATION_EVENT_QUEUE_H_
+#define CHROME_BROWSER_AUTOMATION_AUTOMATION_EVENT_QUEUE_H_
+
+#include <list>
+#include <map>
+
+#include "base/memory/scoped_ptr.h"
+#include "base/values.h"
+
+class AutomationEventObserver;
+class AutomationJSONReply;
+
+// AutomationEventQueue maintains a queue of unhandled automation events.
+class AutomationEventQueue {
+ public:
+  AutomationEventQueue();
+  virtual ~AutomationEventQueue();
+
+  // AutomationEvent stores return data dictionay for a single event.
+  class AutomationEvent {
+   public:
+    AutomationEvent(int observer_id, DictionaryValue* event_value);
+    virtual ~AutomationEvent() {}
+
+    int GetId() const { return observer_id_; }
+    DictionaryValue* GetValue() { return event_value_.get(); }
+    DictionaryValue* ReleaseValue() { return event_value_.release(); }
+
+   private:
+    scoped_ptr<DictionaryValue> event_value_;
+    int observer_id_;
+  };
+
+  void GetNextEvent(AutomationJSONReply* reply,
+                    int observer_id,
+                    bool blocking);
+  void NotifyEvent(AutomationEvent* event);
+  void Clear();
+  bool IsEmpty();
+  AutomationEvent* PopEvent();
+  AutomationEvent* PopEvent(int observer_id);
+
+  int AddObserver(AutomationEventObserver* observer);
+  bool RemoveObserver(int observer_id);
+
+ private:
+  void ClearEvents();
+  void ClearObservers();
+  bool CheckReturnEvent();
+
+  std::list<AutomationEvent*> event_queue_;
+  std::map<int, AutomationEventObserver*> observers_;
+  int observer_id_count_;

[Nirnimesh, 2012/02/29 03:22:08]

why is this necessary? It's the same as observers_.length()

[craigdh, 2012/02/29 22:53:43]

Not exactly, it's only the same until observers are removed. This is used to
give each new observer a unique id. Using length() could give duplicate ids in
some situations.

+
+  scoped_ptr<AutomationJSONReply> wait_automation_reply_;

[Nirnimesh, 2012/02/29 03:22:08]

What is this for? Add comments

[craigdh, 2012/02/29 22:53:43]

If there is not a matching event already waiting in the queue when
TestingAutomationProvider::GetNextEvent is called, then the automation reply is
stored here until a matching event is raised and the automation call can return.
Comments added.

+  int wait_observer_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(AutomationEventQueue);
+};
+
+#endif  // CHROME_BROWSER_AUTOMATION_AUTOMATION_EVENT_QUEUE_H_