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      1 /*
      2  * Copyright (C) 2013 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 AsyncMethodRunner_h
     32 #define AsyncMethodRunner_h
     33 
     34 #include "platform/Timer.h"
     35 #include "wtf/FastAllocBase.h"
     36 #include "wtf/Noncopyable.h"
     37 
     38 namespace WebCore {
     39 
     40 template <typename TargetClass>
     41 class AsyncMethodRunner FINAL {
     42     WTF_MAKE_NONCOPYABLE(AsyncMethodRunner);
     43     WTF_MAKE_FAST_ALLOCATED;
     44 public:
     45     typedef void (TargetClass::*TargetMethod)();
     46 
     47     AsyncMethodRunner(TargetClass* object, TargetMethod method)
     48         : m_timer(this, &AsyncMethodRunner<TargetClass>::fired)
     49         , m_object(object)
     50         , m_method(method)
     51         , m_suspended(false)
     52         , m_runWhenResumed(false)
     53     {
     54     }
     55 
     56     // Schedules to run the method asynchronously. Do nothing if it's already
     57     // scheduled. If it's suspended, remember to schedule to run the method when
     58     // resume() is called.
     59     void runAsync()
     60     {
     61         if (m_suspended) {
     62             ASSERT(!m_timer.isActive());
     63             m_runWhenResumed = true;
     64             return;
     65         }
     66 
     67         if (!m_timer.isActive())
     68             m_timer.startOneShot(0);
     69     }
     70 
     71     // If it's scheduled to run the method, cancel it and remember to schedule
     72     // it again when resume() is called. Mainly for implementing
     73     // ActiveDOMObject::suspend().
     74     void suspend()
     75     {
     76         ASSERT(!m_suspended);
     77         m_suspended = true;
     78 
     79         if (!m_timer.isActive())
     80             return;
     81 
     82         m_timer.stop();
     83         m_runWhenResumed = true;
     84     }
     85 
     86     // Resumes pending method run.
     87     void resume()
     88     {
     89         ASSERT(m_suspended);
     90         m_suspended = false;
     91 
     92         if (!m_runWhenResumed)
     93             return;
     94 
     95         m_runWhenResumed = false;
     96         m_timer.startOneShot(0);
     97     }
     98 
     99     void stop()
    100     {
    101         if (m_suspended) {
    102             ASSERT(!m_timer.isActive());
    103             m_runWhenResumed = false;
    104             m_suspended = false;
    105             return;
    106         }
    107 
    108         ASSERT(!m_runWhenResumed);
    109         if (m_timer.isActive())
    110             m_timer.stop();
    111     }
    112 
    113     bool isActive() const
    114     {
    115         return m_timer.isActive();
    116     }
    117 
    118 private:
    119     void fired(Timer<AsyncMethodRunner<TargetClass> >*) { (m_object->*m_method)(); }
    120 
    121     Timer<AsyncMethodRunner<TargetClass> > m_timer;
    122 
    123     TargetClass* m_object;
    124     TargetMethod m_method;
    125 
    126     bool m_suspended;
    127     bool m_runWhenResumed;
    128 };
    129 
    130 }
    131 
    132 #endif
    133