std::as_bytes, std::as_writable_bytes
Defined in header <span> |
||
|---|---|---|
template< class T, std::size_t N> std::span<const std::byte, S/* see below */> as_bytes(std::span<T, N> s) noexcept; |
(1) | (since C++20) |
template< class T, std::size_t N> std::span<std::byte, S/* see below */> as_writable_bytes(std::span<T, N> s) noexcept; |
(2) | (since C++20) |
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
#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
|
(C++17)
|
the byte type (enum) |
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