std::byte - cppreference.com (original) (raw)

| | | | | ----------------------------------- | | ------------- | | 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

• 1 Non-member functions
• 2 std::to_integer
• 3 std::operator<<=,operator>>=
• 4 std::operator<<,operator>>
• 5 std::operator|=,operator&=,operator^=
• 6 std::operator|,operator&,operator^,operator~
  • 6.1 Notes
  • 6.2 Example

[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>>=

1. Equivalent to: return b = b << shift;This overload participates in overload resolution only if std::is_integral_v<IntegerType> is true.

2. Equivalent to: return b = b >> shift;

This overload participates in overload resolution only if std::is_integral_v<IntegerType> is true.

std::operator<<,operator>>

1. Equivalent to: return std::byte(static_cast<unsigned int>(b) << shift);This overload participates in overload resolution only if std::is_integral_v<IntegerType> is true.

2. Equivalent to: return std::byte(static_cast<unsigned int>(b) >> shift);

This overload participates in overload resolution only if std::is_integral_v<IntegerType> is true.

std::operator|=,operator&=,operator^=

1. Equivalent to: return l = l | r;.

2. Equivalent to: return l = l & r;.

3. Equivalent to: return l = l ^ r;.

std::operator|,operator&,operator^,operator~

1. Equivalent to: return std::byte(static_cast<unsigned int>(l) | static_cast<unsigned int>(r));.

2. Equivalent to: return std::byte(static_cast<unsigned int>(l) & static_cast<unsigned int>(r));.

3. Equivalent to: return std::byte(static_cast<unsigned int>(l) ^ static_cast<unsigned int>(r));.

4. Equivalent to: return std::byte(~static_cast<unsigned int>(b));

[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.

[edit] Example

#include #include #include #include #include   std::ostream& operator<<(std::ostream& os, std::byte b) { return os << std::bitset<8>(std::to_integer(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(y)]; // OK [[maybe_unused]] int j = arr[std::to_underlying(y)]; // OK   auto to_int = [](std::byte b) { return std::to_integer(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); }

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