Hex out stream : ostream « File Stream « C++ Tutorial

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/* 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 <fstream>

void hexMultiplicationTable (std::streambuf* buffer, int num)
{
    std::ostream hexout(buffer);
    hexout << std::hex << std::showbase;

    for (int i=1; i<=num; ++i) {
        for (int j=1; j<=10; ++j) {
            hexout << i*j << ' ';
        }
        hexout << std::endl;
    }

}   // does NOT close buffer

int main()
{
    using namespace std;
    int num = 5;

    cout << "We print " << num
         << " lines hexadecimal" << endl;

    hexMultiplicationTable(cout.rdbuf(),num);

    cout << "That was the output of " << num
         << " hexadecimal lines " << endl;
}

We print 5 lines hexadecimal
0x1 0x2 0x3 0x4 0x5 0x6 0x7 0x8 0x9 0xa
0x2 0x4 0x6 0x8 0xa 0xc 0xe 0x10 0x12 0x14
0x3 0x6 0x9 0xc 0xf 0x12 0x15 0x18 0x1b 0x1e
0x4 0x8 0xc 0x10 0x14 0x18 0x1c 0x20 0x24 0x28
0x5 0xa 0xf 0x14 0x19 0x1e 0x23 0x28 0x2d 0x32
That was the output of 5 hexadecimal lines