flags.h

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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2020, Google Inc.
 *
 * Type-safe enum-based bitfields
 */

#pragma once

#include <type_traits>

namespace libcamera {

template<typename E>
class Flags
{
public:
    static_assert(std::is_enum<E>::value,
              "Flags<> template parameter must be an enum");

    using Type = std::underlying_type_t<E>;

    constexpr Flags()
        : value_(0)
    {
    }

    constexpr Flags(E flag)
        : value_(static_cast<Type>(flag))
    {
    }

    constexpr Flags &operator&=(E flag)
    {
        value_ &= static_cast<Type>(flag);
        return *this;
    }

    constexpr Flags &operator&=(Flags other)
    {
        value_ &= other.value_;
        return *this;
    }

    constexpr Flags &operator|=(E flag)
    {
        value_ |= static_cast<Type>(flag);
        return *this;
    }

    constexpr Flags &operator|=(Flags other)
    {
        value_ |= other.value_;
        return *this;
    }

    constexpr Flags &operator^=(E flag)
    {
        value_ ^= static_cast<Type>(flag);
        return *this;
    }

    constexpr Flags &operator^=(Flags other)
    {
        value_ ^= other.value_;
        return *this;
    }

    constexpr bool operator==(E flag)
    {
        return value_ == static_cast<Type>(flag);
    }

    constexpr bool operator==(Flags other)
    {
        return value_ == static_cast<Type>(other);
    }

    constexpr bool operator!=(E flag)
    {
        return value_ != static_cast<Type>(flag);
    }

    constexpr bool operator!=(Flags other)
    {
        return value_ != static_cast<Type>(other);
    }

    constexpr explicit operator Type() const
    {
        return value_;
    }

    constexpr explicit operator bool() const
    {
        return !!value_;
    }

    constexpr Flags operator&(E flag) const
    {
        return Flags(static_cast<E>(value_ & static_cast<Type>(flag)));
    }

    constexpr Flags operator&(Flags other) const
    {
        return Flags(static_cast<E>(value_ & other.value_));
    }

    constexpr Flags operator|(E flag) const
    {
        return Flags(static_cast<E>(value_ | static_cast<Type>(flag)));
    }

    constexpr Flags operator|(Flags other) const
    {
        return Flags(static_cast<E>(value_ | other.value_));
    }

    constexpr Flags operator^(E flag) const
    {
        return Flags(static_cast<E>(value_ ^ static_cast<Type>(flag)));
    }

    constexpr Flags operator^(Flags other) const
    {
        return Flags(static_cast<E>(value_ ^ other.value_));
    }

    constexpr Flags operator~() const
    {
        return Flags(static_cast<E>(~value_));
    }

    constexpr bool operator!() const
    {
        return !value_;
    }

private:
    Type value_;
};

#ifndef __DOXYGEN__
template<typename E>
struct flags_enable_operators {
    static const bool enable = false;
};

template<typename E>
std::enable_if_t<flags_enable_operators<E>::enable, Flags<E>>
operator|(E lhs, E rhs)
{
    using type = std::underlying_type_t<E>;
    return Flags<E>(static_cast<E>(static_cast<type>(lhs) | static_cast<type>(rhs)));
}

template<typename E>
std::enable_if_t<flags_enable_operators<E>::enable, Flags<E>>
operator&(E lhs, E rhs)
{
    using type = std::underlying_type_t<E>;
    return Flags<E>(static_cast<E>(static_cast<type>(lhs) & static_cast<type>(rhs)));
}

template<typename E>
std::enable_if_t<flags_enable_operators<E>::enable, Flags<E>>
operator^(E lhs, E rhs)
{
    using type = std::underlying_type_t<E>;
    return Flags<E>(static_cast<E>(static_cast<type>(lhs) ^ static_cast<type>(rhs)));
}

template<typename E>
std::enable_if_t<flags_enable_operators<E>::enable, Flags<E>>
operator~(E rhs)
{
    using type = std::underlying_type_t<E>;
    return Flags<E>(static_cast<E>(~static_cast<type>(rhs)));
}

#define LIBCAMERA_FLAGS_ENABLE_OPERATORS(_enum)             \
template<>                              \
struct flags_enable_operators<_enum> {                  \
    static const bool enable = true;                \
};

#else /* __DOXYGEN__ */

#define LIBCAMERA_FLAGS_ENABLE_OPERATORS(_enum)

#endif /* __DOXYGEN__ */

} /* namespace libcamera */