244 lines
6.9 KiB
C++
244 lines
6.9 KiB
C++
// This file is under the public domain.
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#pragma once
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#include <cstddef>
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#ifdef _WIN32
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#include <intrin.h>
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#endif
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#include <initializer_list>
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#include <new>
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#include <type_traits>
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#include "common/common_types.h"
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// namespace avoids conflict with OS X Carbon; don't use BitSet<T> directly
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namespace Common {
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// Helper functions:
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#ifdef _MSC_VER
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template <typename T>
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static inline int CountSetBits(T v) {
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// from https://graphics.stanford.edu/~seander/bithacks.html
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// GCC has this built in, but MSVC's intrinsic will only emit the actual
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// POPCNT instruction, which we're not depending on
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v = v - ((v >> 1) & (T) ~(T)0 / 3);
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v = (v & (T) ~(T)0 / 15 * 3) + ((v >> 2) & (T) ~(T)0 / 15 * 3);
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v = (v + (v >> 4)) & (T) ~(T)0 / 255 * 15;
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return (T)(v * ((T) ~(T)0 / 255)) >> (sizeof(T) - 1) * 8;
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}
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static inline int LeastSignificantSetBit(u8 val) {
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unsigned long index;
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_BitScanForward(&index, val);
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return (int)index;
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}
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static inline int LeastSignificantSetBit(u16 val) {
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unsigned long index;
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_BitScanForward(&index, val);
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return (int)index;
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}
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static inline int LeastSignificantSetBit(u32 val) {
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unsigned long index;
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_BitScanForward(&index, val);
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return (int)index;
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}
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static inline int LeastSignificantSetBit(u64 val) {
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unsigned long index;
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_BitScanForward64(&index, val);
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return (int)index;
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}
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#else
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static inline int CountSetBits(u8 val) {
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return __builtin_popcount(val);
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}
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static inline int CountSetBits(u16 val) {
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return __builtin_popcount(val);
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}
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static inline int CountSetBits(u32 val) {
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return __builtin_popcount(val);
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}
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static inline int CountSetBits(u64 val) {
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return __builtin_popcountll(val);
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}
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static inline int LeastSignificantSetBit(u8 val) {
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return __builtin_ctz(val);
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}
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static inline int LeastSignificantSetBit(u16 val) {
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return __builtin_ctz(val);
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}
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static inline int LeastSignificantSetBit(u32 val) {
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return __builtin_ctz(val);
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}
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static inline int LeastSignificantSetBit(u64 val) {
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return __builtin_ctzll(val);
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}
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#endif
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// Similar to std::bitset, this is a class which encapsulates a bitset, i.e.
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// using the set bits of an integer to represent a set of integers. Like that
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// class, it acts like an array of bools:
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// BitSet32 bs;
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// bs[1] = true;
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// but also like the underlying integer ([0] = least significant bit):
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// BitSet32 bs2 = ...;
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// bs = (bs ^ bs2) & BitSet32(0xffff);
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// The following additional functionality is provided:
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// - Construction using an initializer list.
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// BitSet bs { 1, 2, 4, 8 };
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// - Efficiently iterating through the set bits:
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// for (int i : bs)
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// [i is the *index* of a set bit]
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// (This uses the appropriate CPU instruction to find the next set bit in one
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// operation.)
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// - Counting set bits using .Count() - see comment on that method.
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// TODO: use constexpr when MSVC gets out of the Dark Ages
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template <typename IntTy>
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class BitSet {
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static_assert(!std::is_signed_v<IntTy>, "BitSet should not be used with signed types");
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public:
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// A reference to a particular bit, returned from operator[].
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class Ref {
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public:
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Ref(Ref&& other) : m_bs(other.m_bs), m_mask(other.m_mask) {}
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Ref(BitSet* bs, IntTy mask) : m_bs(bs), m_mask(mask) {}
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operator bool() const {
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return (m_bs->m_val & m_mask) != 0;
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}
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bool operator=(bool set) {
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m_bs->m_val = (m_bs->m_val & ~m_mask) | (set ? m_mask : 0);
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return set;
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}
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private:
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BitSet* m_bs;
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IntTy m_mask;
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};
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// A STL-like iterator is required to be able to use range-based for loops.
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class Iterator {
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public:
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Iterator(const Iterator& other) : m_val(other.m_val), m_bit(other.m_bit) {}
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Iterator(IntTy val) : m_val(val), m_bit(0) {}
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Iterator& operator=(Iterator other) {
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new (this) Iterator(other);
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return *this;
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}
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int operator*() {
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return m_bit + ComputeLsb();
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}
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Iterator& operator++() {
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int lsb = ComputeLsb();
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m_val >>= lsb + 1;
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m_bit += lsb + 1;
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m_has_lsb = false;
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return *this;
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}
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Iterator operator++(int _) {
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Iterator other(*this);
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++*this;
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return other;
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}
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bool operator==(Iterator other) const {
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return m_val == other.m_val;
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}
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bool operator!=(Iterator other) const {
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return m_val != other.m_val;
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}
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private:
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int ComputeLsb() {
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if (!m_has_lsb) {
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m_lsb = LeastSignificantSetBit(m_val);
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m_has_lsb = true;
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}
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return m_lsb;
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}
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IntTy m_val;
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int m_bit;
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int m_lsb = -1;
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bool m_has_lsb = false;
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};
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BitSet() : m_val(0) {}
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explicit BitSet(IntTy val) : m_val(val) {}
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BitSet(std::initializer_list<int> init) {
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m_val = 0;
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for (int bit : init)
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m_val |= (IntTy)1 << bit;
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}
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static BitSet AllTrue(size_t count) {
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return BitSet(count == sizeof(IntTy) * 8 ? ~(IntTy)0 : (((IntTy)1 << count) - 1));
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}
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Ref operator[](size_t bit) {
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return Ref(this, (IntTy)1 << bit);
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}
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const Ref operator[](size_t bit) const {
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return (*const_cast<BitSet*>(this))[bit];
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}
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bool operator==(BitSet other) const {
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return m_val == other.m_val;
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}
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bool operator!=(BitSet other) const {
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return m_val != other.m_val;
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}
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bool operator<(BitSet other) const {
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return m_val < other.m_val;
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}
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bool operator>(BitSet other) const {
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return m_val > other.m_val;
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}
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BitSet operator|(BitSet other) const {
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return BitSet(m_val | other.m_val);
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}
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BitSet operator&(BitSet other) const {
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return BitSet(m_val & other.m_val);
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}
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BitSet operator^(BitSet other) const {
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return BitSet(m_val ^ other.m_val);
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}
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BitSet operator~() const {
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return BitSet(~m_val);
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}
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BitSet& operator|=(BitSet other) {
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return *this = *this | other;
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}
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BitSet& operator&=(BitSet other) {
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return *this = *this & other;
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}
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BitSet& operator^=(BitSet other) {
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return *this = *this ^ other;
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}
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operator u32() = delete;
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operator bool() {
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return m_val != 0;
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}
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// Warning: Even though on modern CPUs this is a single fast instruction,
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// Dolphin's official builds do not currently assume POPCNT support on x86,
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// so slower explicit bit twiddling is generated. Still should generally
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// be faster than a loop.
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unsigned int Count() const {
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return CountSetBits(m_val);
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}
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Iterator begin() const {
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return Iterator(m_val);
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}
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Iterator end() const {
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return Iterator(0);
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}
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IntTy m_val;
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};
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} // namespace Common
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typedef Common::BitSet<u8> BitSet8;
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typedef Common::BitSet<u16> BitSet16;
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typedef Common::BitSet<u32> BitSet32;
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typedef Common::BitSet<u64> BitSet64;
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