// Copyright (C) 2001-2003
// William E. Kempf
//
//  Distributed under the Boost Software License, Version 1.0. (See accompanying
//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#include 
#include 
#include 

boost::mutex g_io_mutex; // The iostreams are not guaranteed to be thread-safe!

class counter
{
public:
    counter() : count(0) { }

    int increment() {
        boost::unique_lock scoped_lock(mutex);
        return ++count;
    }

private:
    boost::mutex mutex;
    int count;
};

counter g_counter;

void change_count()
{
    int i = g_counter.increment();
    boost::unique_lock scoped_lock(g_io_mutex);
    std::cout