/* * Copyright (C) 2017 Apple Inc. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF * THE POSSIBILITY OF SUCH DAMAGE. */ #pragma once #include "Function.h" namespace WTF { template<typename> class CompletionHandler; // Wraps a WTF::Function to make sure it is always called once and only once. template <typename Out, typename... In> class CompletionHandler<Out(In...)> { public: CompletionHandler() = default; template<typename CallableType, class = typename std::enable_if<std::is_rvalue_reference<CallableType&&>::value>::type> CompletionHandler(CallableType&& callable) : m_function(WTFMove(callable)) { } CompletionHandler(CompletionHandler&&) = default; CompletionHandler& operator=(CompletionHandler&&) = default; ~CompletionHandler() { ASSERT_WITH_MESSAGE(!m_function, "Completion handler should always be called"); } explicit operator bool() const { return !!m_function; } Out operator()(In... in) const { ASSERT_WITH_MESSAGE(m_function, "Completion handler should not be called more than once"); auto function = WTFMove(m_function); return function(std::forward<In>(in)...); } private: mutable WTF::Function<Out(In...)> m_function; }; } // namespace WTF using WTF::CompletionHandler;