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      1 /*
      2  * Copyright (C) 2010 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions are
      6  * met:
      7  *
      8  *     * Redistributions of source code must retain the above copyright
      9  * notice, this list of conditions and the following disclaimer.
     10  *     * Redistributions in binary form must reproduce the above
     11  * copyright notice, this list of conditions and the following disclaimer
     12  * in the documentation and/or other materials provided with the
     13  * distribution.
     14  *     * Neither the name of Google Inc. nor the names of its
     15  * contributors may be used to endorse or promote products derived from
     16  * this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #ifndef Task_h
     32 #define Task_h
     33 
     34 #include "webkit/support/webkit_support.h"
     35 #include <wtf/OwnPtr.h>
     36 #include <wtf/Vector.h>
     37 
     38 class TaskList;
     39 
     40 // WebTask represents a task which can run by postTask() or postDelayedTask().
     41 // it is named "WebTask", not "Task", to avoid conflist with base/task.h.
     42 class WebTask : public webkit_support::TaskAdaptor {
     43 public:
     44     WebTask(TaskList*);
     45     // The main code of this task.
     46     // An implementation of run() should return immediately if cancel() was called.
     47     virtual void run() = 0;
     48     virtual void cancel() = 0;
     49     virtual ~WebTask();
     50 
     51 private:
     52     virtual void Run() { run(); }
     53 
     54 protected:
     55     TaskList* m_taskList;
     56 };
     57 
     58 class TaskList {
     59 public:
     60     TaskList() {}
     61     ~TaskList() { revokeAll(); }
     62     void registerTask(WebTask* task) { m_tasks.append(task); }
     63     void unregisterTask(WebTask* task);
     64     void revokeAll();
     65 private:
     66     Vector<WebTask*> m_tasks;
     67 };
     68 
     69 // A task containing an object pointer of class T. Is is supposed that
     70 // runifValid() calls a member function of the object pointer.
     71 // Class T must have "TaskList* taskList()".
     72 template<class T> class MethodTask: public WebTask {
     73 public:
     74     MethodTask(T* object): WebTask(object->taskList()), m_object(object) {}
     75     virtual void run()
     76     {
     77         if (m_object)
     78             runIfValid();
     79     }
     80     virtual void cancel()
     81     {
     82         m_object = 0;
     83         m_taskList->unregisterTask(this);
     84         m_taskList = 0;
     85     }
     86     virtual void runIfValid() = 0;
     87 protected:
     88     T* m_object;
     89 };
     90 
     91 void postTask(WebTask* task);
     92 void postDelayedTask(WebTask* task, int64_t ms);
     93 
     94 #endif // Task_h
     95