util/util.hpp

#pragma once

#include <stdint.h>

#include "type.hpp"

namespace util {

// <memory>

// clang-format off

template <typename T>
util::enable_if_t<util::is_object_v<T>, T *> addressof(T &arg) noexcept
{
	return reinterpret_cast<T *>(&const_cast<char &>(reinterpret_cast<const volatile char &>(arg)));
}

template <typename T>
util::enable_if_t<!util::is_object_v<T>, T *> addressof(T &arg) noexcept
{
	return &arg;
}

// <utility>

template <typename T> util::add_rvalue_reference_t<T> declval() noexcept;

template <typename T>
inline constexpr util::remove_reference_t<T> &&move(T &&t) noexcept
{
	return static_cast<util::remove_reference_t<T> &&>(t);
}

template <typename T>
inline constexpr T &&forward(util::remove_reference_t<T> &t) noexcept
{
	return static_cast<T &&>(t);
}

template <typename T>
inline constexpr T &&forward(util::remove_reference_t<T> &&t) noexcept
{
	static_assert(!util::is_lvalue_reference_v<T>, "Can not forward an rvalue as an lvalue.");
	return static_cast<T &&>(t);
}

template <typename T, T... Ints>
struct integer_sequence {
	using __type = integer_sequence;
	using value_type = T;

	static constexpr size_t size() noexcept
	{
		return sizeof...(Ints);
	}
};

template <size_t... Ints> using index_sequence = integer_sequence<size_t, Ints...>;

namespace detail {

template <typename T, typename Seq1, typename Seq2> struct concat;

template <typename T, T... Ints1, T... Ints2>
struct concat<T, integer_sequence<T, Ints1...>, integer_sequence<T, Ints2...>>
    : integer_sequence<T, Ints1..., (sizeof...(Ints1) + Ints2)...>
{};

// uint64_t because this must be able to hold all possible sizes and cannot be T, because then the specialization for 0
// and 1 are not possible
template <typename T, uint64_t N>
struct gen_integer_sequence : detail::concat<T, typename gen_integer_sequence<T, N / 2>::__type,
                                             typename gen_integer_sequence<T, N - N / 2>::__type>
{};

template <typename T> struct gen_integer_sequence<T, 0> : integer_sequence<T> {};
template <typename T> struct gen_integer_sequence<T, 1> : integer_sequence<T, 0> {};

} // namespace detail

template <typename T, T N>
struct make_integer_sequence : detail::gen_integer_sequence<T, N> {
	static_assert(N >= 0, "Integer sequence cannot be negative");
};

template <size_t N> using make_index_sequence = make_integer_sequence<size_t, N>;

template <typename... T> using index_sequence_for = make_index_sequence<sizeof...(T)>;

// Not part of <utility>, but very useful

namespace detail {

template <typename T, T Offset, T... Ints>
inline constexpr integer_sequence<T, (Offset + Ints)...> add_offset(integer_sequence<T, Ints...>) {	return {}; }

} // namespace detail

template <typename T, T Offset, T N>
inline constexpr auto make_offset_integer_sequence()
{
	return detail::add_offset<T, Offset>(make_integer_sequence<T, N>{});
}

template <size_t Offset, size_t N>
inline constexpr auto make_offset_index_sequence()
{
	return make_offset_integer_sequence<size_t, Offset, N>();
}

template <typename Fn, size_t... Ints>
constexpr auto for_constexpr(Fn &&func, index_sequence<Ints...>)
{
	if constexpr (util::is_void_v<util::invoke_result_t<Fn, util::integral_constant<size_t, 0>>>) {
		(func(util::integral_constant<size_t, Ints>{}), ...);
	} else {
		if ((func(util::integral_constant<size_t, Ints>{}) && ...))
			return true;
		return false;
	}
}

// clang-format on

} // namespace util