mijin2/source/mijin/container/memory_view.hpp

#pragma once

#if !defined(MIJIN_CONTAINER_MEMORY_VIEW_HPP_INCLUDED)
#define MIJIN_CONTAINER_MEMORY_VIEW_HPP_INCLUDED 1

#include <bit>
#include <span>
#include <string_view>
#include "../debug/assert.hpp"
#include "../internal/common.hpp"

namespace mijin
{

//
// public defines
//

//
// public constants
//

//
// public types
//

template<typename T>
concept MemoryViewable = requires(const T& object)
{
    { object.data() } -> std::convertible_to<const void*>;
    { object.byteSize() } -> std::convertible_to<std::size_t>;
};

template<typename T>
concept RWMemoryViewable = MemoryViewable<T> && requires(T& object)
{
    { object.data() } -> std::convertible_to<void*>;
};

template<typename TConcrete>
class MixinMemoryView
{
public:
    static constexpr bool WRITABLE = requires(TConcrete& object) { { object.data() } -> std::convertible_to<void*>; };

    template<typename T>
    [[nodiscard]]
    auto makeSpan();

    template<typename T>
    [[nodiscard]]
    auto makeSpan() const;

    template<typename TChar = char, typename TTraits = std::char_traits<TChar>>
    [[nodiscard]]
    std::basic_string_view<TChar, TTraits> makeStringView() const ;

    template<typename T>
    [[nodiscard]]
    auto& dataAt(std::size_t offset) MIJIN_NOEXCEPT;

    template<typename T>
    [[nodiscard]]
    auto& dataAt(std::size_t offset) const MIJIN_NOEXCEPT;

    [[nodiscard]]
    auto bytes() MIJIN_NOEXCEPT
    {
        using return_t = mijin::copy_const_t<std::remove_pointer_t<decltype(static_cast<TConcrete*>(this)->data())>, std::byte>;
        return static_cast<return_t*>(static_cast<TConcrete*>(this)->data());
    }

    [[nodiscard]]
    auto bytes() const MIJIN_NOEXCEPT
    {
        using return_t = mijin::copy_const_t<std::remove_pointer_t<decltype(static_cast<const TConcrete*>(this)->data())>, std::byte>;
        return static_cast<return_t*>(static_cast<const TConcrete*>(this)->data());
    }
private:
    std::size_t byteSizeImpl() const MIJIN_NOEXCEPT
    {
        return static_cast<const TConcrete*>(this)->byteSize();
    }
};

class MemoryView : public MixinMemoryView<MemoryView>
{
public:
    using size_type = std::size_t;
private:
    void* data_ = nullptr;
    std::size_t byteSize_ = 0;
public:
    MemoryView() noexcept = default;
    MemoryView(const MemoryView&) = default;
    MemoryView(void* data, std::size_t byteSize) MIJIN_NOEXCEPT : data_(data), byteSize_(byteSize) {}
    template<typename T> requires(!std::is_const_v<T>)
    MemoryView(std::span<T> span) MIJIN_NOEXCEPT : data_(span.data()), byteSize_(span.size_bytes()) {}
    template<RWMemoryViewable T>
    MemoryView(T& memoryViewable) MIJIN_NOEXCEPT : data_(memoryViewable.data()), byteSize_(memoryViewable.byteSize()) {}

    MemoryView& operator=(const MemoryView&) = default;

    [[nodiscard]]
    void* data() const MIJIN_NOEXCEPT { return data_; }

    [[nodiscard]]
    size_type byteSize() const MIJIN_NOEXCEPT { return byteSize_; }
};

class ConstMemoryView : public MixinMemoryView<ConstMemoryView>
{
public:
    using size_type = std::size_t;
private:
    const void* data_;
    std::size_t byteSize_;
public:
    ConstMemoryView() noexcept = default;
    ConstMemoryView(const ConstMemoryView&) = default;
    ConstMemoryView(void* data, std::size_t byteSize) MIJIN_NOEXCEPT : data_(data), byteSize_(byteSize) {}
    template<typename T>
    ConstMemoryView(std::span<T> span) MIJIN_NOEXCEPT : data_(span.data()), byteSize_(span.size_bytes()) {}
    template<MemoryViewable T>
    ConstMemoryView(const T& memoryViewable) MIJIN_NOEXCEPT : data_(memoryViewable.data()), byteSize_(memoryViewable.byteSize()) {}

    ConstMemoryView& operator=(const ConstMemoryView& other) MIJIN_NOEXCEPT = default;

    [[nodiscard]]
    const void* data() const MIJIN_NOEXCEPT { return data_; }

    [[nodiscard]]
    size_type byteSize() const MIJIN_NOEXCEPT { return byteSize_; }
};

//
// public functions
//

template<typename TConcrete>
template<typename T>
auto MixinMemoryView<TConcrete>::makeSpan()
{
    MIJIN_ASSERT(byteSizeImpl() % sizeof(T) == 0, "Buffer cannot be divided into elements of this type.");
    using return_t = mijin::copy_const_t<decltype(*bytes()), T>;
    return std::span<return_t>{
        std::bit_cast<return_t*>(bytes()),
        std::bit_cast<return_t*>(bytes() + byteSizeImpl())
    };
}

template<typename TConcrete>
template<typename T>
auto MixinMemoryView<TConcrete>::makeSpan() const
{
    MIJIN_ASSERT(byteSizeImpl() % sizeof(T) == 0, "Buffer cannot be divided into elements of this type.");
    using return_t = mijin::copy_const_t<decltype(*bytes()), T>;
    return std::span<return_t>{
        std::bit_cast<return_t*>(bytes()),
        std::bit_cast<return_t*>(bytes() + byteSizeImpl())
    };
}

template<typename TConcrete>
template<typename TChar, typename TTraits>
std::basic_string_view<TChar, TTraits> MixinMemoryView<TConcrete>::makeStringView() const
{
    MIJIN_ASSERT(byteSizeImpl() % sizeof(TChar) == 0, "Buffer cannot be divided into elements of this char type.");
    return {std::bit_cast<const TChar*>(bytes()), byteSizeImpl() / sizeof(TChar)};
}

template<typename TConcrete>
template<typename T>
auto& MixinMemoryView<TConcrete>::dataAt(std::size_t offset) MIJIN_NOEXCEPT
{
    MIJIN_ASSERT(offset % alignof(T) == 0, "Offset must be correctly aligned.");
    MIJIN_ASSERT(offset + sizeof(T) < byteSizeImpl(), "Buffer access out-of-range.");

    using return_t = mijin::copy_const_t<decltype(*bytes()), T>;
    return *std::bit_cast<return_t*>(bytes().data() + offset);
}

template<typename TConcrete>
template<typename T>
auto& MixinMemoryView<TConcrete>::dataAt(std::size_t offset) const MIJIN_NOEXCEPT
{
    MIJIN_ASSERT(offset % alignof(T) == 0, "Offset must be correctly aligned.");
    MIJIN_ASSERT(offset + sizeof(T) < byteSizeImpl(), "Buffer access out-of-range.");

    using return_t = mijin::copy_const_t<decltype(*bytes()), T>;
    return *std::bit_cast<return_t*>(bytes().data() + offset);
}
} // namespace mijin

#endif // !defined(MIJIN_CONTAINER_MEMORY_VIEW_HPP_INCLUDED)