Source/WTF/wtf/SingleThreadIntegralWrapper.h

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 * Copyright (C) 2023-2025 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
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 *    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,
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 */

#pragma once

#include <wtf/Assertions.h>
#if ASSERT_ENABLED && !USE(WEB_THREAD)
#include <wtf/CurrentThread.h>
#endif

namespace WTF {

template <typename IntegralType>
class SingleThreadIntegralWrapper {
public:
    SingleThreadIntegralWrapper(IntegralType);

    operator IntegralType() const;
    explicit operator bool() const;
    SingleThreadIntegralWrapper& operator=(IntegralType);
    SingleThreadIntegralWrapper& operator++();
    SingleThreadIntegralWrapper& operator--();

    IntegralType valueWithoutThreadCheck() const
    {
        // This is called after the destructor in WTF_OVERRIDE_DELETE_FOR_CHECKED_PTR,
        // the compiler can see it as uninitialized.
        IGNORE_GCC_WARNINGS_BEGIN("uninitialized")
        return m_value;
        IGNORE_GCC_WARNINGS_END
    }

private:
#if ASSERT_ENABLED && !USE(WEB_THREAD)
    void assertThread() const { ASSERT(m_creationThread == currentThreadID()); }
#else
    constexpr void assertThread() const { }
#endif

    IntegralType m_value;
#if ASSERT_ENABLED && !USE(WEB_THREAD)
    uint32_t m_creationThread;
#endif
};

template <typename IntegralType>
inline SingleThreadIntegralWrapper<IntegralType>::SingleThreadIntegralWrapper(IntegralType value)
    : m_value { value }
#if ASSERT_ENABLED && !USE(WEB_THREAD)
    , m_creationThread { currentThreadID() }
#endif
{ }

template <typename IntegralType>
inline SingleThreadIntegralWrapper<IntegralType>::operator IntegralType() const
{
    assertThread();
    return m_value;
}

template <typename IntegralType>
inline SingleThreadIntegralWrapper<IntegralType>::operator bool() const
{
    assertThread();
    return m_value;
}

template <typename IntegralType>
inline SingleThreadIntegralWrapper<IntegralType>& SingleThreadIntegralWrapper<IntegralType>::operator=(IntegralType value)
{
    assertThread();
    m_value = value;
    return *this;
}

template <typename IntegralType>
inline SingleThreadIntegralWrapper<IntegralType>& SingleThreadIntegralWrapper<IntegralType>::operator++()
{
    assertThread();
    m_value++;
    return *this;
}

template <typename IntegralType>
inline SingleThreadIntegralWrapper<IntegralType>& SingleThreadIntegralWrapper<IntegralType>::operator--()
{
    assertThread();
    m_value--;
    return *this;
}

} // namespace WTF

using WTF::SingleThreadIntegralWrapper;