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// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MOJO_PUBLIC_CPP_SYSTEM_HANDLE_SIGNAL_TRACKER_H_
#define MOJO_PUBLIC_CPP_SYSTEM_HANDLE_SIGNAL_TRACKER_H_
#include "base/functional/callback.h"
#include "base/task/sequenced_task_runner.h"
#include "mojo/public/c/system/types.h"
#include "mojo/public/cpp/system/handle.h"
#include "mojo/public/cpp/system/simple_watcher.h"
#include "mojo/public/cpp/system/system_export.h"
namespace base {
class SequencedTaskRunner;
}
namespace mojo {
// This class helps track the state of specific signal on a handle so that
// the user doesn't have to manually query the signal state every time they
// want to know the handle's state.
//
// Usage of this class is specifically targeting cases where the signal state
// changes infrequently but must be queried frequently. If either condition does
// not hold, consider using Handle::QuerySignalsState (or
// MojoQueryHandleSignalsState) directly instead.
class MOJO_CPP_SYSTEM_EXPORT HandleSignalTracker {
public:
using NotificationCallback =
base::RepeatingCallback<void(const HandleSignalsState& signals_state)>;
// Constructs a tracker which tracks |signals| on |handle|. |signals| may
// be any single signal flag or any combination of signal flags.
HandleSignalTracker(Handle handle,
MojoHandleSignals signals,
scoped_refptr<base::SequencedTaskRunner> task_runner =
base::SequencedTaskRunner::GetCurrentDefault());
HandleSignalTracker(const HandleSignalTracker&) = delete;
HandleSignalTracker& operator=(const HandleSignalTracker&) = delete;
~HandleSignalTracker();
const HandleSignalsState& last_known_state() const {
return last_known_state_;
}
// Sets an optional callback to be invoked any time the tracker is notified of
// a relevant state change.
void set_notification_callback(NotificationCallback callback) {
notification_callback_ = std::move(callback);
}
private:
class State;
void Arm();
void OnNotify(MojoResult result, const HandleSignalsState& state);
NotificationCallback notification_callback_;
// The last known signaliing state of the handle.
HandleSignalsState last_known_state_ = {0, 0};
// Watches for the signal(s) to be signaled. May only be armed when
// |low_watcher_| is not.
SimpleWatcher high_watcher_;
// Watches for the signal(s) to be cleared. May only be armed when
// |high_watcher_| is not.
SimpleWatcher low_watcher_;
};
} // namespace mojo
#endif // MOJO_PUBLIC_CPP_SYSTEM_HANDLE_SIGNAL_TRACKER_H_
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