chromium/components/sync/engine/cancelation_signal.h

// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_SYNC_ENGINE_CANCELATION_SIGNAL_H_
#define COMPONENTS_SYNC_ENGINE_CANCELATION_SIGNAL_H_

#include "base/memory/raw_ptr.h"
#include "base/synchronization/lock.h"

namespace syncer {

// This class is used to allow one thread to request that another abort and
// return early.
//
// The signalling thread owns this class and my call Signal() at any time.
// After that call, this class' IsSignalled() will always return true.  The
// intended use case is that the task intending to support early exit will
// periodically check the value of IsSignalled() to see if it should return
// early.
//
// The receiving task may also choose to register an observer whose
// OnCancelationSignalReceived() method will be executed on the signaller's
// thread when Signal() is called.  This may be used for sending an early
// Signal() to a WaitableEvent.  The registration of the handler is necessarily
// racy.  If Signal() is executes before TryRegisterHandler(),
// TryRegisterHandler() will not perform any registration and return false. That
// function's caller must handle this case.
//
// This class supports only one handler, though it could easily support multiple
// observers if we found a use case for such a feature.
class CancelationSignal { … };

}  // namespace syncer

#endif  // COMPONENTS_SYNC_ENGINE_CANCELATION_SIGNAL_H_