std::byteswap
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Coroutine support (C++20)
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General utilities
(C++20)(C++20)(C++20)
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Bit manipulation
(C++20)
byteswap
(C++23)
(C++20)
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(C++20)
Defined in header
<bit>
template< class T >
constexpr T byteswap( T n ) noexcept;
(since C++23)
constexpr T byteswap( T n ) noexcept;
Reverses the bytes in the given integer value n.
std::byteswap participates in overload resolution only if T satisfies integral, i.e., T is an integer type. The program is ill-formed if T has padding bits.
[edit] Parameters
n
-
integer value
[edit] Return value
An integer value of type T whose object representation comprises the bytes of that of n in reversed order.
[edit] Notes
This function is useful for processing data of different endianness.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_byteswap |
202110L |
(C++23) | std::byteswap
|
[edit] Possible implementation
template<std::integral T> constexpr T byteswap(T value) noexcept { static_assert(std::has_unique_object_representations_v <T>, "T may not have padding bits"); auto value_representation = std::bit_cast <std::array <std::byte, sizeof(T)>>(value); std::ranges::reverse (value_representation); return std::bit_cast <T>(value_representation); }
[edit] Example
Run this code
#include <bit> #include <concepts> #include <cstdint> #include <iomanip> #include <iostream> template<std::integral T> void dump(T v, char term = '\n') { std::cout << std::hex << std::uppercase << std::setfill ('0') << std::setw (sizeof(T) * 2) << v << " : "; for (std::size_t i{}; i != sizeof(T); ++i, v >>= 8) std::cout << std::setw (2) << static_cast<unsigned>(T(0xFF) & v) << ' '; std::cout << std::dec << term; } int main() { static_assert(std::byteswap('a') == 'a'); std::cout << "byteswap for U16:\n"; constexpr auto x = std::uint16_t (0xCAFE); dump(x); dump(std::byteswap(x)); std::cout << "\nbyteswap for U32:\n"; constexpr auto y = std::uint32_t (0xDEADBEEFu); dump(y); dump(std::byteswap(y)); std::cout << "\nbyteswap for U64:\n"; constexpr auto z = std::uint64_t {0x0123456789ABCDEFull}; dump(z); dump(std::byteswap(z)); }
Possible output:
byteswap for U16: CAFE : FE CA FECA : CA FE byteswap for U32: DEADBEEF : EF BE AD DE EFBEADDE : DE AD BE EF byteswap for U64: 0123456789ABCDEF : EF CD AB 89 67 45 23 01 EFCDAB8967452301 : 01 23 45 67 89 AB CD EF