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// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MOJO_PUBLIC_CPP_BINDINGS_SYNC_EVENT_WATCHER_H_
#define MOJO_PUBLIC_CPP_BINDINGS_SYNC_EVENT_WATCHER_H_
#include <stddef.h>
#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/sequence_checker.h"
#include "base/synchronization/waitable_event.h"
#include "mojo/public/cpp/bindings/bindings_export.h"
#include "mojo/public/cpp/bindings/sync_handle_registry.h"
namespace mojo {
// SyncEventWatcher supports waiting on a base::WaitableEvent to signal while
// also allowing other SyncEventWatchers and SyncHandleWatchers on the same
// sequence to wake up as needed.
//
// This class is not thread safe.
class MOJO_CPP_BINDINGS_EXPORT SyncEventWatcher {
public:
SyncEventWatcher(base::WaitableEvent* event, const base::Closure& callback);
~SyncEventWatcher();
// Registers |event_| with SyncHandleRegistry, so that when others perform
// sync watching on the same sequence, |event_| will be watched along with
// them.
void AllowWokenUpBySyncWatchOnSameThread();
// Waits on |event_| plus all other events and handles registered with this
// sequence's SyncHandleRegistry, running callbacks synchronously for any
// ready events and handles.
//
// |stop_flags| is treated as an array of |const bool*| with |num_stop_flags|
// entries.
//
// This method:
// - returns true when any flag in |stop_flags| is set to |true|.
// - return false when any error occurs, including this object being
// destroyed during a callback.
bool SyncWatch(const bool** stop_flags, size_t num_stop_flags);
private:
void IncrementRegisterCount();
void DecrementRegisterCount();
base::WaitableEvent* const event_;
const base::Closure callback_;
// Whether |event_| has been registered with SyncHandleRegistry.
bool registered_ = false;
// If non-zero, |event_| should be registered with SyncHandleRegistry.
size_t register_request_count_ = 0;
scoped_refptr<SyncHandleRegistry> registry_;
scoped_refptr<base::RefCountedData<bool>> destroyed_;
SEQUENCE_CHECKER(sequence_checker_);
DISALLOW_COPY_AND_ASSIGN(SyncEventWatcher);
};
} // namespace mojo
#endif // MOJO_PUBLIC_CPP_BINDINGS_SYNC_EVENT_WATCHER_H_
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