xref: /aosp_15_r20/external/deqp/framework/common/tcuMaybe.hpp (revision 35238bce31c2a825756842865a792f8cf7f89930)

#ifndef _TCUMAYBE_HPP
#define _TCUMAYBE_HPP
/*-------------------------------------------------------------------------
 * drawElements Quality Program Tester Core
 * ----------------------------------------
 *
 * Copyright 2015 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 *//*!
 * \file
 * \brief Template for values that may not exist.
 *//*--------------------------------------------------------------------*/

#include "tcuDefs.hpp"

namespace tcu
{

// Empty struct used to initialize Maybe objects without providing the type explicitly.
struct Nothing_T
{
    explicit constexpr Nothing_T(int)
    {
    }
};
constexpr Nothing_T Nothing(0);

// \note Type T is always aligned to same alignment as uint64_t.
// \note This type always uses at least sizeof(T*) + sizeof(uint64_t) of memory.
template <typename T>
class Maybe
{
public:
    Maybe(void);
    Maybe(const Nothing_T &);
    ~Maybe(void);

    Maybe(const T &val);
    Maybe<T> &operator=(const T &val);

    Maybe(const Maybe<T> &other);
    Maybe<T> &operator=(const Maybe<T> &other);

    const T &get(void) const;
    T &get(void);
    const T &operator*(void) const
    {
        return get();
    }
    T &operator*(void)
    {
        return get();
    }

    const T *operator->(void) const;
    T *operator->(void);
    operator bool(void) const
    {
        return !!m_ptr;
    }

private:
    T *m_ptr;

    union
    {
        uint8_t m_data[sizeof(T)];
        uint64_t m_align;
    };
} DE_WARN_UNUSED_TYPE;

template <typename T>
Maybe<T> nothing(void)
{
    return Maybe<T>();
}

template <typename T>
Maybe<T> just(const T &value)
{
    return Maybe<T>(value);
}

template <typename T>
Maybe<T>::Maybe(void) : m_ptr(nullptr)
{
}

template <typename T>
Maybe<T>::Maybe(const Nothing_T &) : m_ptr(nullptr)
{
}

template <typename T>
Maybe<T>::~Maybe(void)
{
    if (m_ptr)
        m_ptr->~T();
}

template <typename T>
Maybe<T>::Maybe(const T &val) : m_ptr(nullptr)
{
    m_ptr = new (m_data) T(val);
}

template <typename T>
Maybe<T> &Maybe<T>::operator=(const T &val)
{
    if (m_ptr)
        m_ptr->~T();

    m_ptr = new (m_data) T(val);

    return *this;
}

template <typename T>
Maybe<T>::Maybe(const Maybe<T> &other) : m_ptr(nullptr)
{
    if (other.m_ptr)
        m_ptr = new (m_data) T(*other.m_ptr);
}

template <typename T>
Maybe<T> &Maybe<T>::operator=(const Maybe<T> &other)
{
    if (this == &other)
        return *this;

    if (m_ptr)
        m_ptr->~T();

    if (other.m_ptr)
        m_ptr = new (m_data) T(*other.m_ptr);
    else
        m_ptr = nullptr;

    return *this;
}

template <typename T>
const T *Maybe<T>::operator->(void) const
{
    DE_ASSERT(m_ptr);
    return m_ptr;
}

template <typename T>
T *Maybe<T>::operator->(void)
{
    DE_ASSERT(m_ptr);
    return m_ptr;
}

template <typename T>
const T &Maybe<T>::get(void) const
{
    DE_ASSERT(m_ptr);
    return *m_ptr;
}

template <typename T>
T &Maybe<T>::get(void)
{
    DE_ASSERT(m_ptr);
    return *m_ptr;
}

} // namespace tcu

#endif // _TCUMAYBE_HPP