PollableEvent.h - mozsearch

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim:set ts=2 sw=2 sts=2 et cindent: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef PollableEvent_h__

#define PollableEvent_h__

#include "mozilla/Mutex.h"

#include "mozilla/TimeStamp.h"

struct PRFileDesc;

namespace mozilla {

namespace net {

// class must be called locked

class PollableEvent {

 public:

  PollableEvent();

  ~PollableEvent();

  // Signal/Clear return false only if they fail

  bool Signal();

  // This is called only when we get non-null out_flags for the socket pair

  bool Clear();

  bool Valid() { return mWriteFD && mReadFD; }

  // We want to detect if writing to one of the socket pair sockets takes

  // too long to be received by the other socket from the pair.

  // Hence, we remember the timestamp of the earliest write by a call to

  // MarkFirstSignalTimestamp() from Signal().  After waking up from poll()

  // we check how long it took get the 'readable' signal on the socket pair.

  void MarkFirstSignalTimestamp();

  // Called right before we enter poll() to exclude any possible delay between

  // the earlist call to Signal() and entering poll() caused by processing

  // of events dispatched to the socket transport thread.

  void AdjustFirstSignalTimestamp();

  // This returns false on following conditions:

  // - PR_Write has failed

  // - no out_flags were signalled on the socket pair for too long after

  //   the earliest Signal()

  bool IsSignallingAlive(TimeDuration const& timeout);

  PRFileDesc* PollableFD() { return mReadFD; }

 private:

  PRFileDesc* mWriteFD{nullptr};

  PRFileDesc* mReadFD{nullptr};

  bool mSignaled{false};

  // true when PR_Write to the socket pair has failed (status < 1)

  bool mWriteFailed{false};

  // Set true after AdjustFirstSignalTimestamp() was called

  // Set false after Clear() was called

  // Ensures shifting the timestamp before entering poll() only once

  // between Clear()'ings.

  bool mSignalTimestampAdjusted{false};

  // Timestamp of the first call to Signal() (or time we enter poll())

  // that happened after the last Clear() call

  TimeStamp mFirstSignalAfterClear;

};

}  // namespace net

}  // namespace mozilla

#endif