mirror of
https://github.com/Atmosphere-NX/Atmosphere
synced 2024-09-20 15:18:59 +00:00
283 lines
10 KiB
C++
283 lines
10 KiB
C++
/*
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* Copyright (c) Atmosphère-NX
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <vapours/common.hpp>
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#include <vapours/assert.hpp>
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namespace ams::util {
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namespace impl {
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template<size_t N>
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constexpr inline size_t Log2 = Log2<N / 2> + 1;
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template<>
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constexpr inline size_t Log2<1> = 0;
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}
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template <typename T> requires std::integral<T>
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class BitsOf {
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private:
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static constexpr ALWAYS_INLINE int GetLsbPos(T v) {
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return __builtin_ctzll(static_cast<u64>(v));
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}
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T m_value;
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public:
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/* Note: GCC has a bug in constant-folding here. Workaround: wrap entire caller with constexpr. */
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constexpr ALWAYS_INLINE BitsOf(T value = T(0u)) : m_value(value) {
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/* ... */
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}
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constexpr ALWAYS_INLINE bool operator==(const BitsOf &other) const {
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return m_value == other.m_value;
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}
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constexpr ALWAYS_INLINE bool operator!=(const BitsOf &other) const {
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return m_value != other.m_value;
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}
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constexpr ALWAYS_INLINE int operator*() const {
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return GetLsbPos(m_value);
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}
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constexpr ALWAYS_INLINE BitsOf &operator++() {
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m_value &= ~(T(1u) << GetLsbPos(m_value));
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return *this;
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}
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constexpr ALWAYS_INLINE BitsOf &operator++(int) {
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BitsOf ret(m_value);
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++(*this);
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return ret;
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}
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constexpr ALWAYS_INLINE BitsOf begin() const {
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return *this;
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}
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constexpr ALWAYS_INLINE BitsOf end() const {
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return BitsOf(T(0u));
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}
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};
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template<typename T = u64, typename ...Args> requires std::integral<T>
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constexpr ALWAYS_INLINE T CombineBits(Args... args) {
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return (... | (T(1u) << args));
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE T ResetLeastSignificantOneBit(T x) {
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return x & (x - 1);
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE T SetLeastSignificantZeroBit(T x) {
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return x | (x + 1);
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE T LeastSignificantOneBit(T x) {
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return x & ~(x - 1);
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE T LeastSignificantZeroBit(T x) {
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return ~x & (x + 1);
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE T ResetTrailingOnes(T x) {
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return x & (x + 1);
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE T SetTrailingZeros(T x) {
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return x | (x - 1);
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE T MaskTrailingZeros(T x) {
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return (~x) & (x - 1);
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE T MaskTrailingOnes(T x) {
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return ~((~x) | (x + 1));
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE T MaskTrailingZerosAndLeastSignificantOneBit(T x) {
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return x ^ (x - 1);
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE T MaskTrailingOnesAndLeastSignificantZeroBit(T x) {
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return x ^ (x + 1);
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE int PopCount(T x) {
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using U = typename std::make_unsigned<T>::type;
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U u = static_cast<U>(x);
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if (std::is_constant_evaluated()) {
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/* https://en.wikipedia.org/wiki/Hamming_weight */
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constexpr U m1 = U(-1) / 0x03;
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constexpr U m2 = U(-1) / 0x05;
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constexpr U m4 = U(-1) / 0x11;
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u = static_cast<U>(u - ((u >> 1) & m1));
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u = static_cast<U>((u & m2) + ((u >> 2) & m2));
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u = static_cast<U>((u + (u >> 4)) & m4);
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for (size_t i = 0; i < impl::Log2<sizeof(T)>; ++i) {
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const size_t shift = (0x1 << i) * BITSIZEOF(u8);
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u += u >> shift;
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}
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return static_cast<int>(u & 0x7Fu);
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} else {
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if constexpr (std::is_same<U, unsigned long long>::value) {
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return __builtin_popcountll(u);
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} else if constexpr (std::is_same<U, unsigned long>::value) {
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return __builtin_popcountl(u);
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} else {
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static_assert(sizeof(U) <= sizeof(unsigned int));
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return __builtin_popcount(static_cast<unsigned int>(u));
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}
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}
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE int CountLeadingZeros(T x) {
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if (std::is_constant_evaluated()) {
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for (size_t i = 0; i < impl::Log2<BITSIZEOF(T)>; ++i) {
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const size_t shift = (0x1 << i);
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x |= x >> shift;
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}
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return PopCount(static_cast<T>(~x));
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} else {
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using U = typename std::make_unsigned<T>::type;
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const U u = static_cast<U>(x);
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if (u != 0) {
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if constexpr (std::is_same<U, unsigned long long>::value) {
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return __builtin_clzll(u);
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} else if constexpr (std::is_same<U, unsigned long>::value) {
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return __builtin_clzl(u);
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} else if constexpr(std::is_same<U, unsigned int>::value) {
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return __builtin_clz(u);
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} else {
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static_assert(sizeof(U) < sizeof(unsigned int));
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constexpr size_t BitDiff = BITSIZEOF(unsigned int) - BITSIZEOF(U);
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return __builtin_clz(static_cast<unsigned int>(u)) - BitDiff;
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}
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} else {
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return BITSIZEOF(U);
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}
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}
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}
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static_assert(CountLeadingZeros(~static_cast<u64>(0)) == 0);
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static_assert(CountLeadingZeros(static_cast<u64>(1) << 5) == BITSIZEOF(u64) - 1 - 5);
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static_assert(CountLeadingZeros(static_cast<u64>(0)) == BITSIZEOF(u64));
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE int CountTrailingZeros(T x) {
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if (std::is_constant_evaluated()) {
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auto count = 0;
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for (size_t i = 0; i < BITSIZEOF(T) && (x & 1) == 0; ++i) {
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x >>= 1;
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++count;
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}
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return count;
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} else {
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using U = typename std::make_unsigned<T>::type;
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const U u = static_cast<U>(x);
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if (u != 0) {
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if constexpr (std::is_same<U, unsigned long long>::value) {
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return __builtin_ctzll(u);
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} else if constexpr (std::is_same<U, unsigned long>::value) {
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return __builtin_ctzl(u);
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} else if constexpr(std::is_same<U, unsigned int>::value) {
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return __builtin_ctz(u);
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} else {
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static_assert(sizeof(U) < sizeof(unsigned int));
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return __builtin_ctz(static_cast<unsigned int>(u));
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}
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} else {
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return BITSIZEOF(U);
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}
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}
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}
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static_assert(CountTrailingZeros(~static_cast<u64>(0)) == 0);
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static_assert(CountTrailingZeros(static_cast<u64>(1) << 5) == 5);
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static_assert(CountTrailingZeros(static_cast<u64>(0)) == BITSIZEOF(u64));
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE bool IsPowerOfTwo(T x) {
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return x > 0 && ResetLeastSignificantOneBit(x) == 0;
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE T CeilingPowerOfTwo(T x) {
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AMS_ASSERT(x > 0);
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return T(1) << (BITSIZEOF(T) - CountLeadingZeros(T(x - 1)));
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}
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template<typename T> requires std::integral<T>
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constexpr ALWAYS_INLINE T FloorPowerOfTwo(T x) {
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AMS_ASSERT(x > 0);
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return T(1) << (BITSIZEOF(T) - CountLeadingZeros(x) - 1);
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}
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template<typename T, typename U>
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constexpr ALWAYS_INLINE T DivideUp(T v, U d) {
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using Unsigned = typename std::make_unsigned<U>::type;
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const Unsigned add = static_cast<Unsigned>(d) - 1;
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return static_cast<T>((v + add) / d);
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}
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template<typename T, T N, T D>
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constexpr ALWAYS_INLINE T ScaleByConstantFactor(const T V) {
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/* Multiplying and dividing by large numerator/denominator can cause error to be introduced. */
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/* This algorithm multiples/divides in stages, so as to mitigate this (particularly with large denominator). */
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/* Justification for the algorithm. */
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/* Calculate: (V * N) / D */
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/* = (Quot_V * D + Rem_V) * (Quot_N * D + Rem_N) / D */
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/* = (D^2 * (Quot_V * Quot_N) + D * (Quot_V * Rem_N + Rem_V * Quot_N) + Rem_V * Rem_N) / D */
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/* = (D * Quot_V * Quot_N) + (Quot_V * Rem_N) + (Rem_V * Quot_N) + ((Rem_V * Rem_N) / D) */
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/* Calculate quotients/remainders. */
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const T Quot_V = V / D;
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const T Rem_V = V % D;
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constexpr T Quot_N = N / D;
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constexpr T Rem_N = N % D;
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/* Calculate the remainder multiplication, rounding up. */
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const T rem_mult = ((Rem_V * Rem_N) + (D - 1)) / D;
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/* Calculate results. */
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return (D * Quot_N * Quot_V) + (Quot_V * Rem_N) + (Rem_V * Quot_N) + rem_mult;
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}
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}
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