NAME¶

std::basic_ospanstream::span - std::basic_ospanstream::span

Synopsis¶

std::span<CharT> span() const noexcept; (1) (since C++23)
void span( std::span<CharT> s ) noexcept; (2) (since C++23)

1) Gets a span referencing the written area if std::ios_base::out is set in the open
mode of the wrapped std::basic_spanbuf, or a span referencing the underlying buffer
otherwise.
2) Makes the wrapped std::basic_spanbuf perform I/O on the buffer referenced by s.

Parameters¶

s - std::span referencing the storage to be use as the new underlying buffer of
stream

Return value¶

1) A std::span referencing the underlying buffer or written area, depending on the
open mode of the wrapped std::basic_spanbuf.
2) (none)

Example¶

// Run this code

#include <cassert>
#include <iostream>
#include <span>
#include <spanstream>

int main()
{
char out_buf[16];
std::ospanstream ost{std::span<char>{out_buf}};
ost << "C++" << ' ' << 23 << '\0'; // note explicit null-termination
auto sp = ost.span();
assert(
sp[0] == 'C' && sp[1] == '+' && sp[2] == '+' &&
sp[3] == ' ' && sp[4] == '2' && sp[5] == '3' &&
sp[6] == '\0'
);
std::cout << "sp.data(): [" << sp.data() << "]\n";
std::cout << "out_buf: [" << out_buf << "]\n";
// spanstream uses out_buf as internal storage, no allocations
assert(static_cast<char*>(out_buf) == sp.data());

const char in_buf[] = "X Y 42";
std::ispanstream ist{std::span<const char>{in_buf}};
assert(static_cast<const char*>(in_buf) == ist.span().data());
char c;
ist >> c;
assert(c == 'X');
ist >> c;
assert(c == 'Y');
int i;
ist >> i;
assert(i == 42);
ist >> i; // buffer is exhausted
assert(!ist);
}

Output:¶

sp.data(): [C++ 23]
out_buf: [C++ 23]

See also¶

span obtains or initializes an underlying buffer according to mode
(C++23) (public member function of std::basic_spanbuf<CharT,Traits>)