A BitSet class for C++03 and older

bitset.h

template <bool defaultState = false>
class BitSet
{
public:
    BitSet(std::size_t size)
        : size_(size), bits_((size_ + 7) / 8, defaultState ? 0xff : 0x0)
    {
        // Masks for each bit. Example,
        //
        //    7 6 5 4 3 2 1 0
        // 0x 0 0 0 1 0 0 0 0 <- masks_[4]
        uint8_t mask = masks_[0] = 0x1;
        for (int i = 1; i < 8; ++i)
        {
            masks_[i] = (mask <<= 1);
        }
    }

    bool Empty() const
    { return size_ == 0; }

    std::size_t Size() const
    { return size_; }

    void Set(std::size_t index, bool value = true)
    {
        if (value)
            bits_[index / 8] |= masks_[index % 8];
        else
            Reset(index);
    }

    void Reset(std::size_t index)
    {
        bits_[index / 8] &= ~masks_[index % 8];
    }

    bool operator [](std::size_t index)
    {
        return (bits_[index / 8] & masks_[index % 8]) != 0x0;
    }

private:
    const std::size_t size_;
    std::vector<uint8_t> bits_;
    uint8_t masks_[8];
};