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std::as_bytes,std::as_writable_bytes(3) | C++ Standard Libary | std::as_bytes,std::as_writable_bytes(3) |
NAME¶
std::as_bytes,std::as_writable_bytes - std::as_bytes,std::as_writable_bytes
Synopsis¶
Defined in header <span>
template< class T, std::size_t N>
std::span<const std::byte, S/* see below */> as_bytes(std::span<T,
(1) (since C++20)
N> s) noexcept;
template< class T, std::size_t N>
std::span<std::byte, S/* see below */> (2) (since C++20)
as_writable_bytes(std::span<T, N> s) noexcept;
Obtains a view to the object representation of the elements of the span
s.
If N is std::dynamic_extent, the extent of the returned span S is also
std::dynamic_extent; otherwise it is sizeof(T) * N.
as_writable_bytes only participates in overload resolution if
std::is_const_v<T> is
false.
Return value¶
1) A span constructed with {reinterpret_cast<const
std::byte*>(s.data()),
s.size_bytes()}.
2) A span constructed with {reinterpret_cast<std::byte*>(s.data()),
s.size_bytes()}.
Example¶
// Run this code
#include <cstddef>
#include <iomanip>
#include <iostream>
#include <span>
void print(float const x, std::span<const std::byte> const bytes)
{
std::cout << std::setprecision(6) << std::setw(8) << x
<< " = { "
<< std::hex << std::uppercase << std::setfill('0');
for (auto const b : bytes) {
std::cout << std::setw(2) << std::to_integer<int>(b)
<< ' ';
}
std::cout << std::dec << "}\n";
}
int main()
{
/* mutable */ float data[1] { 3.141592f };
auto const const_bytes = std::as_bytes(std::span{ data });
print(data[0], const_bytes);
auto const writable_bytes = std::as_writable_bytes(std::span{ data });
// Change the sign bit that is the MSB (IEEE 754 Floating-Point Standard).
writable_bytes[3] |= std::byte{ 0b1000'0000 };
print(data[0], const_bytes);
}
Possible output:¶
3.14159 = { D8 0F 49 40 }
-3.14159 = { D8 0F 49 C0 }
See also¶
byte the byte type
(C++17) (enum)
2022.07.31 | http://cppreference.com |