std::basic_streambuf<CharT,Traits>::sgetn, std::basic_streambuf<CharT,Traits>::xsgetn

< cpp‎ | io‎ | basic streambuf
Input/output library
I/O manipulators
C-style I/O
(deprecated in C++98)
File I/O
String I/O
Array I/O
(deprecated in C++98)
(deprecated in C++98)
(deprecated in C++98)
Synchronized Output
Error category interface
std::streamsize sgetn( char_type* s, std::streamsize count );
virtual std::streamsize xsgetn( char_type* s, std::streamsize count );
1) Calls xsgetn(s, count) of the most derived class.
2) Reads count characters from the input sequence and stores them into a character array pointed to by s. The characters are read as if by repeated calls to sbumpc(). That is, if less than count characters are immediately available, the function calls uflow() to provide more until Traits::eof() is returned.
Classes derived from std::basic_streambuf are permitted to provide more efficient implementations of this function.


s - pointer to the beginning of a char_type array
count - maximum number of characters to write

Return value

The number of characters successfully read. If it is less than count the input sequence has reached the end.


The rule about "more efficient implementations" permits bulk I/O without intermediate buffering: that's how std::ifstream::read simply passes the pointer to the POSIX read() system call in some implementations of iostreams


See also

invokes xsputn()
(public member function)