Convert string to byte array in C++

This post will discuss how to convert string to byte array in C++.

Starting with C++11, we can use std::byte to represent the actual byte data. This post provides an overview of a few plausible options to convert a std::string to a std::byte array.

1. Using `std::memcpy`

A common solution to perform a binary copy of an array using the std::memcpy function. It can be used to convert a string to a byte array along with the std::string::data function, which returns a pointer to an array containing the C-string representation of the string object.

#include <iostream>

#include <cstddef>

#include <cstring>

int main()

{

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

std::byte bytes[s.length()];

std::memcpy(bytes, s.data(), s.length());

for (auto &b: bytes) {

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

}

return 0;

}

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Output:

67 43 43

2. Using `std::transform`

Another alternative is to use the std::transform function, which applies a given operation to each of the given range elements and stores the result in another range. This is demonstrated below, using the std::byte constructor.

#include <iostream>

#include <cstddef>

#include <algorithm>

#include <vector>

int main()

{

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

std::array<std::byte, 3> bytes;

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

return std::byte(c);

});

for (auto &b: bytes) {

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

}

return 0;

}

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Output:

67 43 43

The behavior of this function is effectively equivalent to:

#include <iostream>

#include <cstddef>

#include <cstring>

#include <algorithm>

int main()

{

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

std::byte bytes[s.size()];

for (size_t i = 0; i < s.size(); i++) {

bytes[i] = std::byte(s[i]);

}

for (auto &b: bytes) {

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

}

return 0;

}

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Output:

67 43 43

That’s all about converting string to byte array in C++.

Convert string to byte array in C++

1. Using std::memcpy

2. Using std::transform

Share this:

1. Using `std::memcpy`

2. Using `std::transform`