weex_core/Source/include/wtf/DeprecatedOptional.h

/*
 * Copyright (C) 2014, 2016 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.
 *
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 * 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
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// This file contains a deprecated version of WTF::Optional which a released
// version of Safari uses. Once Safari stops using this, we can remove this.
// New code should use std::optional.

#pragma once

#include <type_traits>

namespace WTF {

template<typename T>
class Optional {
public:
    explicit operator bool() const { return m_isEngaged; }
    T& value() { return *asPtr(); }

private:
    T* asPtr() { return reinterpret_cast<T*>(&m_value); }

    bool m_isEngaged;
    typename std::aligned_storage<sizeof(T), std::alignment_of<T>::value>::type m_value;
};

template<typename T> using DeprecatedOptional = WTF::Optional<T>;

} // namespace WTF