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std::byte(3)		       C++ Standard Libary		    std::byte(3)

NAME
     std::byte - std::byte

Synopsis
	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, sup-
     porting only
	bitshift  operations  with an integer, and bitwise and comparison opera-
     tions with
	another std::byte.

Non-member functions
     std::to_integer

	template   <class   IntegerType>				  (since
     C++17)
	 constexpr IntegerType to_integer( std::byte b ) noexcept;

	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  (1)
     (since C++17)
	) noexcept;
	template <class IntegerType>
	 constexpr  std::byte&	operator>>=( std::byte& b, IntegerType shift (2)
     (since C++17)
	) noexcept;

	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>>

	template <class IntegerType>
	 constexpr  std::byte  operator<<( std::byte b, IntegerType shift )  (1)
     (since C++17)
	noexcept;
	template <class IntegerType>
	 constexpr std::byte operator>>( std::byte b, IntegerType shift  )   (2)
     (since C++17)
	noexcept;

	1)  Equivalent	to:  return  std::byte(static_cast<unsigned  int>(b)  <<
     shift); This
	overload participates  in  overload  resolution  only  if  std::is_inte-
     gral_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^=

	constexpr std::byte& operator|=( std::byte& l, std::byte r  )	     (1)
     (since C++17)
	noexcept;
	constexpr  std::byte&  operator&=( std::byte& l, std::byte r )	     (2)
     (since C++17)
	noexcept;
	constexpr std::byte& operator^=( std::byte& l, std::byte r  )	     (3)
     (since C++17)
	noexcept;

	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~

	constexpr  std::byte  operator|( std::byte l, std::byte r )	     (1)
     (since C++17)
	noexcept;
	constexpr std::byte operator&( std::byte l, std::byte r  )	     (2)
     (since C++17)
	noexcept;
	constexpr  std::byte  operator^( std::byte l, std::byte r )	     (3)
     (since C++17)
	noexcept;
	constexpr std::byte operator~( std::byte b )  noexcept; 	     (4)
     (since C++17)

	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));

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  inte-
     ger 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

Example
     // Run this code

      #include <bitset>
      #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

	  std::byte b{42};
	  std::cout << "1. " << b << '\n';

	  // b *= 2; // Error: b is not of arithmetic type
	  b <<= 1;
	  std::cout << "2. " << b << '\n';

	  b >>= 1;
	  std::cout << "3. " << b << '\n';

	  std::cout << "4. " << (b << 1) << '\n';
	  std::cout << "5. " << (b >> 1) << '\n';

	  b |= std::byte{0b11110000};
	  std::cout << "6. " << b << '\n';

	  b &= std::byte{0b11110000};
	  std::cout << "7. " << b << '\n';

	  b ^= std::byte{0b11111111};
	  std::cout << "8. " << b << '\n';
      }

Output:
      1. 00101010
      2. 01010100
      3. 00101010
      4. 01010100
      5. 00010101
      6. 11111010
      7. 11110000
      8. 00001111

http://cppreference.com 	   2024.06.10			    std::byte(3)
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