Convert a string to a vector of bytes in C++

This post will discuss how to convert a string to a vector of bytes in C++.

Starting with C++17, we can use std::byte which represents actual byte data in C++. It is defined in the header <cstddef>. We can convert a single character c to a byte value (collection of bits) with std::byte(c). To convert an entire string to a vector of bytes using any of the following alternatives:

1. Using `std::transform`

The std::transform standard algorithm applies an operation to each of the elements in the specified range and stores the result in another range. It defined in the <algorithm> header. It can be used as follows to convert a std::string to a std::vector<std::byte>:

#include <iostream>

#include <vector>

#include <algorithm>

#include <cstddef>

using namespace std;

std::vector<std::byte> getBytes(std::string const &s)

{

std::vector<std::byte> bytes;

bytes.reserve(s.size());

std::transform(std::begin(s), std::end(s), std::back_inserter(bytes), [](char c){

return std::byte(c);

});

return bytes;

}

int main()

{

std::string s = "C++";

std::vector<std::byte> bytes = getBytes(s);

for (auto &b: bytes) {

std::cout << std::to_integer<int>(b) << ' ';

}

return 0;

}

Download Run Code

Output:

67 43 43

2. Using Loop

The idea is to convert each character of the given string to std::byte, and use the push_back() function to append the resultant byte to the end of a vector. This can be done using a range-based for-loop, as shown below: