How do I serialise/deserialise a std::vector<bool> most efficiently?

Question

I'm trying to write the contents of a std::vector<bool> to disk into a binary file. As the write() method of many of the STL output streams takes in a pointer to the array itself, as well as the number of bytes to write, for a 'normal' vector I'd end up doing something like this:

std::vector<unsigned int> dataVector = {0, 1, 2, 3, 4};
std::fstream outStream = std::fstream("vectordump.bin", std::ios::out | std::ios::binary);
outStream.write((char*) dataVector.data(), dataVector.size() * sizeof(unsigned int));
outStream.close();

However, the std::vector<bool> is a special case, as the STL implementation is allowed to pack the bools into single bits. The above approach will therefore technically not consistently work, because it's unspecified how the data is precisely laid out in memory.

Is there any way of serialising/deserialising my bool vector without having to pack/unpack the data?

Answer 1

I think you're better off to just translate that vector into std::vector<std::byte>/std::vector<unsigned char>.

std::vector<bool> isn't even required to have contiguous memory so writing starting from data() is implementation defined too.

Answer 2

No, there isn't.

Sorry.

A good reason to avoid this container!