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// SPDX-License-Identifier: CC0-1.0
#pragma once
#include <bit>
#include <cstddef>
#include <initializer_list>
#include <type_traits>
#include "Common/CommonTypes.h"
namespace Common
{
// Similar to std::bitset, this is a class which encapsulates a bitset, i.e.
// using the set bits of an integer to represent a set of integers. Like that
// class, it acts like an array of bools:
// BitSet32 bs;
// bs[1] = true;
// but also like the underlying integer ([0] = least significant bit):
// BitSet32 bs2 = ...;
// bs = (bs ^ bs2) & BitSet32(0xffff);
// The following additional functionality is provided:
// - Construction using an initializer list.
// BitSet bs { 1, 2, 4, 8 };
// - Efficiently iterating through the set bits:
// for (int i : bs)
// [i is the *index* of a set bit]
// (This uses the appropriate CPU instruction to find the next set bit in one
// operation.)
// - Counting set bits using .Count() - see comment on that method.
template <typename IntTy>
class BitSet
{
static_assert(!std::is_signed<IntTy>::value, "BitSet should not be used with signed types");
public:
// A reference to a particular bit, returned from operator[].
class Ref
{
public:
constexpr Ref(Ref&& other) : m_bs(other.m_bs), m_mask(other.m_mask) {}
constexpr Ref(BitSet* bs, IntTy mask) : m_bs(bs), m_mask(mask) {}
constexpr operator bool() const { return (m_bs->m_val & m_mask) != 0; }
bool operator=(bool set)
{
m_bs->m_val = (m_bs->m_val & ~m_mask) | (set ? m_mask : 0);
return set;
}
private:
BitSet* m_bs;
IntTy m_mask;
};
// A STL-like iterator is required to be able to use range-based for loops.
class Iterator
{
public:
constexpr Iterator(const Iterator& other) : m_val(other.m_val), m_bit(other.m_bit) {}
constexpr Iterator(IntTy val, int bit) : m_val(val), m_bit(bit) {}
Iterator& operator=(Iterator other)
{
new (this) Iterator(other);
return *this;
}
Iterator& operator++()
{
if (m_val == 0)
{
m_bit = -1;
}
else
{
int bit = std::countr_zero(m_val);
m_val &= ~(IntTy{1} << bit);
m_bit = bit;
}
return *this;
}
Iterator operator++(int)
{
Iterator other(*this);
++*this;
return other;
}
constexpr int operator*() const { return m_bit; }
constexpr bool operator==(Iterator other) const { return m_bit == other.m_bit; }
constexpr bool operator!=(Iterator other) const { return m_bit != other.m_bit; }
private:
IntTy m_val;
int m_bit;
};
constexpr BitSet() = default;
constexpr explicit BitSet(IntTy val) : m_val(val) {}
constexpr BitSet(std::initializer_list<int> init)
{
for (int bit : init)
m_val |= IntTy{1} << bit;
}
constexpr static BitSet AllTrue(size_t count)
{
return BitSet(count == sizeof(IntTy) * 8 ? ~IntTy{0} : ((IntTy{1} << count) - 1));
}
Ref operator[](size_t bit) { return Ref(this, IntTy{1} << bit); }
constexpr const Ref operator[](size_t bit) const { return (*const_cast<BitSet*>(this))[bit]; }
constexpr bool operator==(BitSet other) const { return m_val == other.m_val; }
constexpr bool operator!=(BitSet other) const { return m_val != other.m_val; }
constexpr bool operator<(BitSet other) const { return m_val < other.m_val; }
constexpr bool operator>(BitSet other) const { return m_val > other.m_val; }
constexpr BitSet operator|(BitSet other) const { return BitSet(m_val | other.m_val); }
constexpr BitSet operator&(BitSet other) const { return BitSet(m_val & other.m_val); }
constexpr BitSet operator^(BitSet other) const { return BitSet(m_val ^ other.m_val); }
constexpr BitSet operator~() const { return BitSet(~m_val); }
constexpr BitSet operator<<(IntTy shift) const { return BitSet(m_val << shift); }
constexpr BitSet operator>>(IntTy shift) const { return BitSet(m_val >> shift); }
constexpr explicit operator bool() const { return m_val != 0; }
BitSet& operator|=(BitSet other) { return *this = *this | other; }
BitSet& operator&=(BitSet other) { return *this = *this & other; }
BitSet& operator^=(BitSet other) { return *this = *this ^ other; }
BitSet& operator<<=(IntTy shift) { return *this = *this << shift; }
BitSet& operator>>=(IntTy shift) { return *this = *this >> shift; }
// Warning: Even though on modern CPUs this is a single fast instruction,
// Dolphin's official builds do not currently assume POPCNT support on x86,
// so slower explicit bit twiddling is generated. Still should generally
// be faster than a loop.
constexpr unsigned int Count() const { return std::popcount(m_val); }
constexpr Iterator begin() const { return ++Iterator(m_val, 0); }
constexpr Iterator end() const { return Iterator(m_val, -1); }
IntTy m_val{};
};
} // namespace Common
using BitSet8 = Common::BitSet<u8>;
using BitSet16 = Common::BitSet<u16>;
using BitSet32 = Common::BitSet<u32>;
using BitSet64 = Common::BitSet<u64>;
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