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      1 // Copyright 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef NET_QUIC_QUIC_ALARM_H_
      6 #define NET_QUIC_QUIC_ALARM_H_
      7 
      8 #include "base/memory/scoped_ptr.h"
      9 #include "net/base/net_export.h"
     10 #include "net/quic/quic_time.h"
     11 
     12 namespace net {
     13 
     14 // Abstract class which represents an alarm which will go off at a
     15 // scheduled time, and execute the |OnAlarm| method of the delegate.
     16 // An alarm may be cancelled, in which case it may or may not be
     17 // removed from the underlying scheduling system, but in either case
     18 // the task will not be executed.
     19 class NET_EXPORT_PRIVATE QuicAlarm {
     20  public:
     21   class NET_EXPORT_PRIVATE Delegate {
     22    public:
     23     virtual ~Delegate() {}
     24 
     25     // Invoked when the alarm fires.  If the return value is not
     26     // infinite, then the alarm will be rescheduled at the
     27     // specified time.
     28     virtual QuicTime OnAlarm() = 0;
     29   };
     30 
     31   explicit QuicAlarm(Delegate* delegate);
     32   virtual ~QuicAlarm();
     33 
     34   // Sets the alarm to fire at |deadline|.  Must not be called while
     35   // the alarm is set.  To reschedule an alarm, call Cancel() first,
     36   // then Set().
     37   void Set(QuicTime deadline);
     38 
     39   // Cancels the alarm.  May be called repeatedly.  Does not
     40   // guarantee that the underlying scheduling system will remove
     41   // the alarm's associated task, but guarantees that the
     42   // delegates OnAlarm method will not be called.
     43   void Cancel();
     44 
     45   bool IsSet() const;
     46 
     47   QuicTime deadline() const { return deadline_; }
     48 
     49  protected:
     50   // Subclasses implement this method to perform the platform-specific
     51   // scheduling of the alarm.  Is called from Set() or Fire(), after the
     52   // deadline has been updated.
     53   virtual void SetImpl() = 0;
     54 
     55   // Subclasses implement this method to perform the platform-specific
     56   // cancelation of the alarm.
     57   virtual void CancelImpl() = 0;
     58 
     59   // Called by subclasses when the alarm fires.  Invokes the
     60   // delegates |OnAlarm| if a delegate is set, and if the deadline
     61   // has been exceeded.  Implementations which do not remove the
     62   // alarm from the underlying scheduler on Cancel() may need to handle
     63   // the situation where the task executes before the deadline has been
     64   // reached, in which case they need to reschedule the task and must not
     65   // call invoke this method.
     66   void Fire();
     67 
     68  private:
     69   scoped_ptr<Delegate> delegate_;
     70   QuicTime deadline_;
     71 
     72   DISALLOW_COPY_AND_ASSIGN(QuicAlarm);
     73 };
     74 
     75 }  // namespace net
     76 
     77 #endif  // NET_QUIC_QUIC_ALARM_H_
     78