std::basic_streambuf<CharT,Traits>::sputn,std::basic_streambuf<CharT,Traits>::xsputn (3) - Linux Manuals

std::basic_streambuf<CharT,Traits>::sputn,std::basic_streambuf<CharT,Traits>::xsputn: std::basic_streambuf<CharT,Traits>::sputn,std::basic_streambuf<CharT,Traits>::xsputn

NAME

std::basic_streambuf<CharT,Traits>::sputn,std::basic_streambuf<CharT,Traits>::xsputn - std::basic_streambuf<CharT,Traits>::sputn,std::basic_streambuf<CharT,Traits>::xsputn

Synopsis

std::streamsize sputn( const char_type* s, std::streamsize count ); (1)
protected: (2)
virtual std::streamsize xsputn( const char_type* s, std::streamsize count );

1) Calls xsputn(s, count) of the most derived class.
2) Writes count characters to the output sequence from the character array whose first element is pointed to by s. The characters are written as if by repeated calls to sputc(). Writing stops when either count characters are written or a call to sputc() would have returned Traits::eof().
If the put area becomes full (pptr() == epptr()), this function may call overflow(), or achieve the effect of calling overflow() by some other, unspecified, means.

Parameters

(none)

Return value

The number of characters successfully written.

Notes

"achieving effects of overflow() by unspecified means" permits bulk I/O without intermediate buffering: that's how std::ofstream::write simply passes the pointer to the POSIX write() system call in some implementations of iostreams

Example

// Run this code

  #include <iostream>
  #include <sstream>

  int main()
  {
      std::ostringstream s1;
      std::streamsize sz = s1.rdbuf()->sputn("This is a test", 14);
      s1 << '\n';
      std::cout << "The call to sputn() returned " << sz << '\n'
                << "The output sequence contains " << s1.str();

      std::istringstream s2;
      sz = s2.rdbuf()->sputn("This is a test", 14);
      std::cout << "The call to sputn() on an input stream returned " << sz << '\n';
  }

Output:

  The call to sputn() returned 14
  The output sequence contains This is a test
  The call to sputn() on an input stream returned 0