mirror of
https://github.com/Atmosphere-NX/Atmosphere.git
synced 2024-11-06 12:11:43 +00:00
215 lines
6.6 KiB
C++
215 lines
6.6 KiB
C++
/*
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* Copyright (c) 2018-2020 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>
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class BitsOf {
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private:
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static_assert(std::is_integral<T>::value);
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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 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)) : 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 this->value == other.value;
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}
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constexpr ALWAYS_INLINE bool operator!=(const BitsOf &other) const {
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return this->value != other.value;
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}
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constexpr ALWAYS_INLINE int operator*() const {
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return GetLsbPos(this->value);
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}
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constexpr ALWAYS_INLINE BitsOf &operator++() {
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this->value &= ~(T(1u) << GetLsbPos(this->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(this->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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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constexpr ALWAYS_INLINE int PopCount(T x) {
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/* TODO: C++20 std::bit_cast */
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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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/* TODO: C++20 std::is_constant_evaluated */
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if (false) {
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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>
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constexpr ALWAYS_INLINE int CountLeadingZeros(T x) {
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/* TODO: C++20 std::is_constant_evaluated */
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if (false) {
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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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/* TODO: C++20 std::bit_cast */
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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 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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}
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}
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template<typename 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>
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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>
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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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}
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