CODEWITHSUNDEEP
c++
Lars Kakavandi-Nielsen
Lars Kakavandi-Nielsen

Reputation: 2198

How to convert std::vector<uint8_t> to std::basic_string<std:::byte> for usage with pqxx

I am upgrading an application from using libpqxx 7.1.2 to 7.3.1 and one of the things that have changed in the meantime is that pqxx::binarystring has been deprecated in favour of std::basic_string<std::byte>. My issue is that I use std::vector<uint8_t> in C++ to represent a SHA-1 hash, which I then need to store in Postgress as BYTEA. So now I need to find a way to convert std::vector<uint8_t> to std::basic_string<std::byte> and back. But I have been unable to find a way to get from vector -> string.

I have been looking at the constructor for std::basic_string<T> and simply cannot figure out how to do it. Amongst other ways to construct std::basic_strig<T> I have tried this, but all give compiler errors error: no matching constructor for initialization of 'std::basic_string<std::byte>'. But when I look at the documentation, I thought the different options I have tried should be legal. So how do I achieve this?

#include <string>
#include <vector>
#include <cstdint>
#include <cstddef>

int main(void)
{
    std::vector<uint8_t> data = {1, 2, 3, 4};
    std::basic_string<std::byte> a(std::begin(data), std::end(data));
    std::basic_string<std::byte> b((char*)data.data(), data.size()); 
}

Upvotes: 1

Views: 1326

Answers (1)

Acorn
Acorn

Reputation: 26196

It is strange that they have chosen a basic_string instead of a vector for this, but this works:

std::basic_string<std::byte> a(
    static_cast<const std::byte *>(static_cast<const void *>(data.data())),
    data.size()
);

It should be fine because uint8_t is trivially copyable and std::byte pointers can alias others.

Upvotes: 2

Related Questions