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Cross-platform base for C++ UI apps
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bit.h
    1/*
    2 * AUI Framework - Declarative UI toolkit for modern C++20
    3 * Copyright (C) 2020-2025 Alex2772 and Contributors
    4 *
    5 * SPDX-License-Identifier: MPL-2.0
    6 *
    7 * This Source Code Form is subject to the terms of the Mozilla Public
    8 * License, v. 2.0. If a copy of the MPL was not distributed with this
    9 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   10 */
   11
   12#pragma once
   13
   14// android again lacks C++20 features.
   15// this header implements #include <bit> (notably, std::bit_ceil)
   16
   17#include <concepts>
   18#include <bit>
   19#include "concepts.h"
   20
   21namespace aui {
   22
   23template <aui::unsigned_integral T>
   24    requires(!aui::same_as<T, bool>) && (!aui::same_as<T, char>) && (!aui::same_as<T, char8_t>) &&
   25            (!aui::same_as<T, char16_t>) && (!aui::same_as<T, char32_t>) && (!aui::same_as<T, wchar_t>)
   26constexpr T bit_width(T x) noexcept {
   27    return std::numeric_limits<T>::digits - std::countl_zero(x);
   28}
   29
   30template <aui::unsigned_integral T>
   31    requires(!aui::same_as<T, bool>) && (!aui::same_as<T, char>) && (!aui::same_as<T, char8_t>) &&
   32            (!aui::same_as<T, char16_t>) && (!aui::same_as<T, char32_t>) && (!aui::same_as<T, wchar_t>)
   33constexpr T bit_ceil(T x) noexcept {
   34    if (x <= 1u)
   35        return T(1);
   36    if constexpr (aui::same_as<T, decltype(+x)>)
   37        return T(1) << aui::bit_width(T(x - 1));
   38    else {   // for types subject to integral promotion
   39        constexpr int offset_for_ub = std::numeric_limits<unsigned>::digits - std::numeric_limits<T>::digits;
   40        return T(1u << (aui::bit_width(T(x - 1)) + offset_for_ub) >> offset_for_ub);
   41    }
   42}
   43
   44template <aui::unsigned_integral T>
   45    requires(!std::same_as<T, bool>) && (!std::same_as<T, char>) && (!std::same_as<T, char8_t>) &&
   46            (!std::same_as<T, char16_t>) && (!std::same_as<T, char32_t>) && (!std::same_as<T, wchar_t>)
   47constexpr T bit_floor(T x) noexcept {
   48    if (x != 0)
   49        return T { 1 } << (aui::bit_width(x) - 1);
   50    return 0;
   51}
   52
   53}   // namespace aui

© 2025 AUI Framework Contributors. Documentation contributions included herein are the copyrights of their respective owners. The documentation provided herein is licensed under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation. All trademarks are property of their respective owners.