advstd.h

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/*
 * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program. If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef TRINITY_ADVSTD_H
#define TRINITY_ADVSTD_H
 
#include <version>
 
#ifdef __cpp_lib_bit_cast
#include <bit>
#else
#include <cstring> // for memcpy
#endif
#include <compare>
 
// this namespace holds implementations of upcoming stdlib features that our c++ version doesn't have yet
namespace advstd
{
// libc++ is missing these two
[[nodiscard]] constexpr bool is_eq(std::partial_ordering cmp) noexcept { return cmp == 0; }
[[nodiscard]] constexpr bool is_neq(std::partial_ordering cmp) noexcept { return cmp != 0; }
 
#ifdef __cpp_lib_bit_cast
using std::bit_cast;
#else
// libstdc++ v10 is missing this
template <typename To, typename From,
    std::enable_if_t<std::conjunction_v<
        std::bool_constant<sizeof(To) == sizeof(From)>,
        std::is_trivially_copyable<To>,
        std::is_trivially_copyable<From>>, int> = 0>
[[nodiscard]] constexpr To bit_cast(From const& from) noexcept
{
    To to;
    std::memcpy(&to, &from, sizeof(To));
    return to;
}
#endif
}
 
// std::forward_like
#ifdef __cpp_lib_forward_like
#include <utility>
namespace advstd
{
using std::forward_like;
}
#else
namespace advstd
{
template <class T, class U>
[[nodiscard]] constexpr decltype(auto) forward_like(U&& value) noexcept
{
    using ValueU = std::remove_reference_t<U>;
    using ValueConstU = std::conditional_t<std::is_const_v<std::remove_reference_t<T>>, ValueU const, ValueU>;
    return static_cast<std::conditional_t<std::is_rvalue_reference_v<T&&>, ValueConstU&&, ValueConstU&>>(value);
}
}
#endif
 
// std::ranges::contains
#include <algorithm>
#ifndef __cpp_lib_ranges_contains
#include <functional> // for std::ranges::equal_to, std::identity
#include <iterator> // for std::input_iterator, std::sentinel_for, std::projected
#endif
 
namespace advstd::ranges
{
#ifndef __cpp_lib_ranges_contains
struct Contains
{
    template<std::input_iterator I, std::sentinel_for<I> S, class T, class Proj = std::identity>
    requires std::indirect_binary_predicate<std::ranges::equal_to, std::projected<I, Proj>, T const*>
    [[nodiscard]] inline constexpr bool operator()(I first, S last, T const& value, Proj proj = {}) const
    {
        return std::ranges::find(std::move(first), last, value, proj) != last;
    }
 
    template<std::ranges::input_range R, class T, class Proj = std::identity>
    requires std::indirect_binary_predicate<std::ranges::equal_to, std::projected<std::ranges::iterator_t<R>, Proj>, T const*>
    [[nodiscard]] inline constexpr bool operator()(R&& r, T const& value, Proj proj = {}) const
    {
        auto first = std::ranges::begin(r);
        auto last = std::ranges::end(r);
        return std::ranges::find(std::move(first), last, value, proj) != last;
    }
} inline constexpr contains;
#else
using std::ranges::contains;
#endif
}
 
#endif