1 files changed, 67 insertions, 0 deletions
diff --git a/netwerk/base/PollableEvent.h b/netwerk/base/PollableEvent.h
new file mode 100644
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+++ b/netwerk/base/PollableEvent.h
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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