The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference
by Nicolai M. Josuttis, Addison-Wesley, 1999
© Copyright Nicolai M. Josuttis 1999
#include <cstdio>
#include <streambuf>
// for write():
#ifdef _MSC_VER
# include <io.h>
#else
# include <unistd.h>
#endif
class outbuf : public std::streambuf {
protected:
static const int bufferSize = 10; // size of data buffer
char buffer[bufferSize]; // data buffer
public:
/* constructor
* - initialize data buffer
* - one character less to let the bufferSizeth character
* cause a call of overflow()
*/
outbuf() {
setp (buffer, buffer+(bufferSize-1));
}
/* destructor
* - flush data buffer
*/
virtual ~outbuf() {
sync();
}
protected:
// flush the characters in the buffer
int flushBuffer () {
int num = pptr()-pbase();
if (write (1, buffer, num) != num) {
return EOF;
}
pbump (-num); // reset put pointer accordingly
return num;
}
/* buffer full
* - write c and all previous characters
*/
virtual int_type overflow (int_type c) {
if (c != EOF) {
// insert character into the buffer
*pptr() = c;
pbump(1);
}
// flush the buffer
if (flushBuffer() == EOF) {
// ERROR
return EOF;
}
return c;
}
/* synchronize data with file/destination
* - flush the data in the buffer
*/
virtual int sync () {
if (flushBuffer() == EOF) {
// ERROR
return -1;
}
return 0;
}
};