Binary Serialization of std::bitset

Question

std::bitset has a to_string() method for serializing as a char-based string of 1s and 0s. Obviously, this us

Answer 1

This is a possible approach based on explicit creation of an std::vector by reading/writing one bit at a time...

template
std::vector bitset_to_bytes(const std::bitset& bs)
{
    std::vector result((N + 7) >> 3);
    for (int j=0; j>3] |= (bs[j] << (j & 7));
    return result;
}

template
std::bitset bitset_from_bytes(const std::vector& buf)
{
    assert(buf.size() == ((N + 7) >> 3));
    std::bitset result;
    for (int j=0; j>3] >> (j & 7)) & 1);
    return result;
}

Note that to call the de-serialization template function bitset_from_bytes the bitset size N must be specified in the function call, for example

std::bitset bs1;
...
std::vector buffer = bitset_to_bytes(bs1);
...
std::bitset bs2 = bitset_from_bytes(buffer);

If you really care about speed one solution that would gain something would be doing a loop unrolling so that the packing is done for example one byte at a time, but even better is just to write your own bitset implementation that doesn't hide the internal binary representation instead of using std::bitset.