std::basic_ispanstream<CharT,Traits>::span - cppreference.com (original) (raw)

std::span<const CharT> span() const noexcept; (1) (since C++23)
void span( std::span<CharT> s ) noexcept; (2) (since C++23)
template< class SpanLike > void span( SpanLike&& r ) noexcept; (3) (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.

[edit] Parameters

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

[edit] Return value

  1. A std::span referencing the underlying buffer or written area, depending on the open mode of the wrapped std::basic_spanbuf.

2,3) (none)

[edit] Example

#include #include #include #include   int main() { char out_buf[16]; std::ospanstream ost{std::span{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{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]

[edit] See also

| | obtains or initializes an underlying buffer according to mode (public member function of std::basic_spanbuf<CharT,Traits>) [edit] | | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |