Материал из C\C++ эксперт
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data buffer for stream
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#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;
}
};
int main() {
outbuf ob; // create special output buffer
std::ostream out(&ob); // initialize output stream with that output buff
er
out << "31 hexadecimal: " << std::hex << 31 << std::endl;
}31 hexadecimal: 1f
Extends std::streambuf to create output buffer
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <streambuf>
#include <locale>
#include <cstdio>
class outbuf : public std::streambuf
{
protected:
/* central output function
* - print characters in uppercase mode
*/
virtual int_type overflow (int_type c) {
if (c != EOF) {
// convert lowercase to uppercase
c = std::toupper(c,getloc());
// and write the character to the standard output
if (putchar(c) == EOF) {
return EOF;
}
}
return c;
}
};
int main()
{
outbuf ob; // create special output buffer
std::ostream out(&ob); // initialize output stream with that output buffer
out << "31 hexadecimal: " << std::hex << 31 << std::endl;
}
