The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference, 2nd Edition
by Nicolai M. Josuttis, Addison Wesley Longman, 2012
Copyright © 2012 by Pearson Education, Inc. and Nicolai M. Josuttis
#include <streambuf>
#include <locale>
#include <cstdio>
template <typename charT,
typename traits = std::char_traits<charT> >
class basic_outbuf : public std::basic_streambuf<charT,traits>
{
protected:
// central output function
// - print characters in uppercase mode
virtual typename traits::int_type
overflow (typename traits::int_type c) {
if (!traits::eq_int_type(c,traits::eof())) {
// convert lowercase to uppercase
c = std::toupper(c,this->getloc());
// convert the character into a char (default: '?')
char cc = std::use_facet<std::ctype<charT>>
(this->getloc()).narrow(c,'?');
// and write the character to the standard output
if (std::putchar(cc) == EOF) {
return traits::eof();
}
}
return traits::not_eof(c);
}
};
typedef basic_outbuf<char> outbuf;
typedef basic_outbuf<wchar_t> woutbuf;