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// Copyright 2011 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 CC_BASE_COMPLETION_EVENT_H_
#define CC_BASE_COMPLETION_EVENT_H_
#include "base/logging.h"
#include "base/synchronization/waitable_event.h"
#include "base/threading/thread_restrictions.h"
namespace cc {
// Used for making blocking calls from one thread to another. Use only when
// absolutely certain that doing-so will not lead to a deadlock.
//
// It is safe to destroy this object as soon as Wait() returns.
class CompletionEvent {
public:
CompletionEvent()
: event_(false /* manual_reset */, false /* initially_signaled */) {
#if DCHECK_IS_ON()
waited_ = false;
signaled_ = false;
#endif
}
~CompletionEvent() {
#if DCHECK_IS_ON()
DCHECK(waited_);
DCHECK(signaled_);
#endif
}
void Wait() {
#if DCHECK_IS_ON()
DCHECK(!waited_);
waited_ = true;
#endif
base::ThreadRestrictions::ScopedAllowWait allow_wait;
event_.Wait();
}
void Signal() {
#if DCHECK_IS_ON()
DCHECK(!signaled_);
signaled_ = true;
#endif
event_.Signal();
}
private:
base::WaitableEvent event_;
#if DCHECK_IS_ON()
// Used to assert that Wait() and Signal() are each called exactly once.
bool waited_;
bool signaled_;
#endif
};
} // namespace cc
#endif // CC_BASE_COMPLETION_EVENT_H_
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