bitset.h

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#pragma once
 
#include <cstdint>
 
#include <algorithm>
 
#include "mim/util/types.h"
 
namespace mim {
 
class BitSet {
public:
    class reference {
    private:
        reference(uint64_t* word, uint16_t index)
            : word_(word)
            , index_(index) {}
 
    public:
        reference operator=(bool b) noexcept {
            uint64_t mask = 1_u64 << index();
            if (b)
                word() |= mask;
            else
                word() &= ~mask;
            return *this;
        }
        operator bool() const { return word() & (1_u64 << index()); }
 
    private:
        const uint64_t& word() const { return *word_; }
        uint64_t& word() { return *word_; }
        uint64_t index() const { return index_; }
 
        uint64_t* word_;
        size_t index_;
 
        friend class BitSet;
    };
 
    /// @name constructor, destructor & assignment
    ///@{
    BitSet() noexcept
        : word_(0)
        , num_words_(1) {}
    BitSet(const BitSet& other)
        : BitSet() {
        ensure_capacity(other.num_bits() - 1);
        std::copy_n(other.words(), other.num_words(), words());
        padding = other.padding;
    }
    BitSet(BitSet&& other) noexcept
        : BitSet() {
        swap(*this, other);
    }
    ~BitSet() { dealloc(); }
    BitSet& operator=(BitSet other) noexcept { return swap(*this, other), *this; }
    ///@}
 
    /// @name get, set, clear, toggle, and test bits
    ///@{
    bool test(size_t i) const {
        if ((i / 64_s) >= num_words()) return false;
        return *(words() + i / 64_s) & (1_u64 << i % 64_u64);
    }
 
    // clang-format off
    BitSet& set   (size_t i) { ensure_capacity(i); *(words() + i/64_s) |=  (1_u64 << i%64_u64); return *this; }
    BitSet& toggle(size_t i) { ensure_capacity(i); *(words() + i/64_s) ^=  (1_u64 << i%64_u64); return *this; }
    BitSet& clear (size_t i) { ensure_capacity(i); *(words() + i/64_s) &= ~(1_u64 << i%64_u64); return *this; }
    // clang-format on
    /// clears all bits
    void clear() {
        dealloc();
        num_words_ = 1;
        word_      = 0;
    }
 
    reference operator[](size_t i) {
        ensure_capacity(i);
        return reference(words() + i / 64_s, i % 64_u64);
    }
    bool operator[](size_t i) const { return (*const_cast<BitSet*>(this))[i]; }
    ///@}
 
    /// @name relational operators
    ///@{
    bool operator==(const BitSet&) const;                                    // TODO test
    bool operator!=(const BitSet& other) const { return !(*this == other); } // TODO optimize
    ///@}
 
    /// @name any
    /// Is any bit range set?
    ///@{
    /// Is any bit in `[begin, end[` set?
    bool any_range(const size_t begin, const size_t end) const;
    /// Is any bit in `[0, end[` set?
    bool any_end(const size_t end) const { return any_range(0, end); }
    /// Is any bit in `[begin, ∞[` set?
    bool any_begin(const size_t begin) const { return any_range(begin, num_bits()); }
    bool any() const { return any_range(0, num_bits()); }
    ///@}
 
    /// @name none
    /// Is no bit in range set?
    ///@{
    /// Is no bit in `[begin, end[` set?
    bool none_range(const size_t begin, const size_t end) const { return !any_range(begin, end); }
    /// Is no bit in `[0, end[` set?
    bool none_end(const size_t end) const { return none_range(0, end); }
    /// Is no bit in `[begin, ∞[` set?
    bool none_begin(const size_t begin) const { return none_range(begin, num_bits()); }
    bool none() const { return none_range(0, num_bits()); }
    ///@}
 
    /// @name shift
    ///@{
    BitSet& operator>>=(uint64_t shift);
    BitSet operator>>(uint64_t shift) const {
        BitSet res(*this);
        res >>= shift;
        return res;
    }
    ///@}
 
    /// @name Boolean operators
    ///@{
    // clang-format off
    BitSet& operator&=(const BitSet& other) { return op_assign<std::bit_and<uint64_t>>(other); }
    BitSet& operator|=(const BitSet& other) { return op_assign<std::bit_or <uint64_t>>(other); }
    BitSet& operator^=(const BitSet& other) { return op_assign<std::bit_xor<uint64_t>>(other); }
    BitSet operator&(BitSet b) const { BitSet res(*this); res &= b; return res; }
    BitSet operator|(BitSet b) const { BitSet res(*this); res |= b; return res; }
    BitSet operator^(BitSet b) const { BitSet res(*this); res ^= b; return res; }
    // clang-format on
    ///@}
 
    /// number of bits set
    size_t count() const;
 
    void friend swap(BitSet& b1, BitSet& b2) noexcept {
        using std::swap;
        // clang-format off
        swap(b1.num_words_, b2.num_words_);
        swap(b1.words_,     b2.words_);
        swap(b1.padding,    b2.padding);
        // clang-format on
    }
 
private:
    void ensure_capacity(size_t num_bits) const;
    template<class F> BitSet& op_assign(const BitSet& other) {
        if (this->num_words() < other.num_words()) this->ensure_capacity(other.num_bits() - 1);
        auto this_words  = this->words();
        auto other_words = other.words();
        for (size_t i = 0, e = other.num_words(); i != e; ++i) this_words[i] = F()(this_words[i], other_words[i]);
        return *this;
    }
 
    void dealloc() const;
    const uint64_t* words() const { return num_words_ == 1 ? &word_ : words_; }
    uint64_t* words() { return num_words_ == 1 ? &word_ : words_; }
    size_t num_words() const { return num_words_; }
    size_t num_bits() const { return num_words_ * 64_s; }
 
    union {
        mutable uint64_t* words_;
        uint64_t word_;
    };
    mutable uint32_t num_words_;
 
public:
    uint32_t padding = 0; ///< Unused; do whatever you want with this.
};
 
static_assert(sizeof(BitSet) == 16);
 
} // namespace mim