std::as_bytes, std::as_writable_bytes
From cppreference.com
| Defined in header <span>
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| 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
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
| (C++17) |
the byte type (enum) |