net/quic/quic_alarm.h

   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   // Cancels and sets the alarm if the |deadline| is farther from the current
  46   // deadline than |granularity|, and otherwise does nothing.  If |deadline| is
  47   // not initialized, the alarm is cancelled.
  48   void Update(QuicTime deadline, QuicTime::Delta granularity);
  49
  50   bool IsSet() const;
  51
  52   QuicTime deadline() const { return deadline_; }
  53
  54  protected:
  55   // Subclasses implement this method to perform the platform-specific
  56   // scheduling of the alarm.  Is called from Set() or Fire(), after the
  57   // deadline has been updated.
  58   virtual void SetImpl() = 0;
  59
  60   // Subclasses implement this method to perform the platform-specific
  61   // cancelation of the alarm.
  62   virtual void CancelImpl() = 0;
  63
  64   // Called by subclasses when the alarm fires.  Invokes the
  65   // delegates |OnAlarm| if a delegate is set, and if the deadline
  66   // has been exceeded.  Implementations which do not remove the
  67   // alarm from the underlying scheduler on Cancel() may need to handle
  68   // the situation where the task executes before the deadline has been
  69   // reached, in which case they need to reschedule the task and must not
  70   // call invoke this method.
  71   void Fire();
  72
  73  private:
  74   scoped_ptr<Delegate> delegate_;
  75   QuicTime deadline_;
  76
  77   DISALLOW_COPY_AND_ASSIGN(QuicAlarm);
  78 };
  79
  80 }  // namespace net
  81
  82 #endif  // NET_QUIC_QUIC_ALARM_H_