std::byte
Defined in header <cstddef>
|
||
enum class byte : unsigned char {}; |
(since C++17) | |
std::byte
is a distinct type that implements the concept of byte as specified in the C++ language definition.
Like unsigned char, it can be used to access raw memory occupied by other objects (object representation), but unlike unsigned char, it is not a character type and is not an arithmetic type. std::byte
models a mere collection of bits, supporting only bitshift operations with an integer, and bitwise and comparison operations with another std::byte
.
Contents |
[edit] Non-member functions
std::to_integer
template< class IntegerType > constexpr IntegerType to_integer( std::byte b ) noexcept; |
(since C++17) | |
Equivalent to: return IntegerType(b); This overload participates in overload resolution only if std::is_integral_v<IntegerType> is true.
std::operator<<=,operator>>=
template< class IntegerType > constexpr std::byte& operator<<=( std::byte& b, IntegerType shift ) noexcept; |
(1) | (since C++17) |
template< class IntegerType > constexpr std::byte& operator>>=( std::byte& b, IntegerType shift ) noexcept; |
(2) | (since C++17) |
This overload participates in overload resolution only if std::is_integral_v<IntegerType> is true.
std::operator<<,operator>>
template< class IntegerType > constexpr std::byte operator<<( std::byte b, IntegerType shift ) noexcept; |
(1) | (since C++17) |
template< class IntegerType > constexpr std::byte operator>>( std::byte b, IntegerType shift ) noexcept; |
(2) | (since C++17) |
This overload participates in overload resolution only if std::is_integral_v<IntegerType> is true.
std::operator|=,operator&=,operator^=
constexpr std::byte& operator|=( std::byte& l, std::byte r ) noexcept; |
(1) | (since C++17) |
constexpr std::byte& operator&=( std::byte& l, std::byte r ) noexcept; |
(2) | (since C++17) |
constexpr std::byte& operator^=( std::byte& l, std::byte r ) noexcept; |
(3) | (since C++17) |
std::operator|,operator&,operator^,operator~
constexpr std::byte operator|( std::byte l, std::byte r ) noexcept; |
(1) | (since C++17) |
constexpr std::byte operator&( std::byte l, std::byte r ) noexcept; |
(2) | (since C++17) |
constexpr std::byte operator^( std::byte l, std::byte r ) noexcept; |
(3) | (since C++17) |
constexpr std::byte operator~( std::byte b ) noexcept; |
(4) | (since C++17) |
[edit] Notes
A numeric value n can be converted to a byte value using std::byte{n}, due to C++17 relaxed enum class initialization rules.
A byte can be converted to a numeric value (such as to produce an integer hash of an object) the usual way with an explicit conversion or alternatively with std::to_integer
.
Feature-test macro | Value | Std | Feature |
---|---|---|---|
__cpp_lib_byte |
201603L |
(C++17) | std::byte
|
[edit] Example
#include <bitset> #include <cassert> #include <cstddef> #include <iostream> #include <utility> std::ostream& operator<<(std::ostream& os, std::byte b) { return os << std::bitset<8>(std::to_integer<int>(b)); } int main() { // std::byte y = 1; // Error: cannot convert int to byte. std::byte y{1}; // OK // if (y == 13) {} // Error: cannot be compared. if (y == std::byte{13}) {} // OK, bytes are comparable int arr[]{1, 2, 3}; // int c = a[y]; // Error: array subscript is not an integer [[maybe_unused]] int i = arr[std::to_integer<int>(y)]; // OK [[maybe_unused]] int j = arr[std::to_underlying(y)]; // OK auto to_int = [](std::byte b) { return std::to_integer<int>(b); }; std::byte b{42}; assert(to_int(b) == 0b00101010); std::cout << b << '\n'; // b *= 2; // Error: b is not of arithmetic type b <<= 1; assert(to_int(b) == 0b01010100); b >>= 1; assert(to_int(b) == 0b00101010); assert(to_int(b << 1) == 0b01010100); assert(to_int(b >> 1) == 0b00010101); b |= std::byte{0b11110000}; assert(to_int(b) == 0b11111010); b &= std::byte{0b11110000}; assert(to_int(b) == 0b11110000); b ^= std::byte{0b11111111}; assert(to_int(b) == 0b00001111); }
Output:
00101010