Unsigned Ints vs std::byte

Unsigned integer types like uint8_t, uint16_t, and uint32_t have traditionally been used to represent raw binary data in C++. This is largely due to historical reasons.

Before the introduction of std::byte in C++17, there wasn't a dedicated type specifically designed to represent a byte of data. Developers used unsigned integers because they provide a way to work directly with sequences of bits without the negative values associated with signed integers.

std::byte is Relatively New

Another reason for the continued prevalence of unsigned integers is that std::byte is a relatively recent addition to the language. Many existing codebases and libraries predate C++17 and therefore rely on unsigned integers for binary data manipulation.

Even in newer codebases, programmers familiar with using unsigned types may continue to use them out of habit.

std::byte is Restrictive

std::byte was designed with the explicit goal of representing raw data and not numeric values. It intentionally omits arithmetic operators to prevent accidental numerical operations on binary data.

While this can be beneficial for clarity, it also means that performing bitwise operations like AND (&), OR (|), or XOR (^) requires casting between std::byte and an unsigned integer type.

1#include <cstddef>  // std::byte
2#include <iostream>
3
4int main() {
5  std::byte MyByte{0b10101010};
6
7  // Error: no matching operator found
8  MyByte |= std::byte{0b00000001}; 
9
10  // To make this work, we need to cast to an
11  // integer type like uint8_t
12  uint8_t Temp{static_cast<uint8_t>(MyByte)};
13  Temp |= 0b00000001;
14  MyByte = std::byte{Temp};
15
16  std::cout << std::to_integer<int>(MyByte);
17}

1error: no match for 'operator|=' (operand types are 'std::byte' and 'std::byte')

The need for explicit casting can make code more verbose and potentially less efficient compared to directly using unsigned integers.

Familiarity and Ecosystem

Finally, unsigned integers are deeply ingrained in the C++ ecosystem. Many low-level APIs, hardware interfaces, and system libraries expect data to be represented using unsigned types.

Changing to std::byte might introduce compatibility issues or require significant code modifications.

Despite the existence of std::byte, unsigned integer types remain a popular choice for representing binary data in C++ due to their historical use, direct bit manipulation capabilities, and widespread adoption in existing codebases and APIs.