netwerk/base/PollableEvent.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim:set ts=2 sw=2 sts=2 et cindent: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef PollableEvent_h__
   8 #define PollableEvent_h__
   9
  10 #include "mozilla/Mutex.h"
  11 #include "mozilla/TimeStamp.h"
  12
  13 struct PRFileDesc;
  14
  15 namespace mozilla {
  16 namespace net {
  17
  18 // class must be called locked
  19 class PollableEvent {
  20  public:
  21   PollableEvent();
  22   ~PollableEvent();
  23
  24   // Signal/Clear return false only if they fail
  25   bool Signal();
  26   // This is called only when we get non-null out_flags for the socket pair
  27   bool Clear();
  28   bool Valid() { return mWriteFD && mReadFD; }
  29
  30   // We want to detect if writing to one of the socket pair sockets takes
  31   // too long to be received by the other socket from the pair.
  32   // Hence, we remember the timestamp of the earliest write by a call to
  33   // MarkFirstSignalTimestamp() from Signal().  After waking up from poll()
  34   // we check how long it took get the 'readable' signal on the socket pair.
  35   void MarkFirstSignalTimestamp();
  36   // Called right before we enter poll() to exclude any possible delay between
  37   // the earlist call to Signal() and entering poll() caused by processing
  38   // of events dispatched to the socket transport thread.
  39   void AdjustFirstSignalTimestamp();
  40   // This returns false on following conditions:
  41   // - PR_Write has failed
  42   // - no out_flags were signalled on the socket pair for too long after
  43   //   the earliest Signal()
  44   bool IsSignallingAlive(TimeDuration const& timeout);
  45
  46   PRFileDesc* PollableFD() { return mReadFD; }
  47
  48  private:
  49   PRFileDesc* mWriteFD{nullptr};
  50   PRFileDesc* mReadFD{nullptr};
  51   bool mSignaled{false};
  52   // true when PR_Write to the socket pair has failed (status < 1)
  53   bool mWriteFailed{false};
  54   // Set true after AdjustFirstSignalTimestamp() was called
  55   // Set false after Clear() was called
  56   // Ensures shifting the timestamp before entering poll() only once
  57   // between Clear()'ings.
  58   bool mSignalTimestampAdjusted{false};
  59   // Timestamp of the first call to Signal() (or time we enter poll())
  60   // that happened after the last Clear() call
  61   TimeStamp mFirstSignalAfterClear;
  62 };
  63
  64 }  // namespace net
  65 }  // namespace mozilla
  66
  67 #endif