ceph/src/boost/libs/thread/example/mutex.cpp

   1 // Copyright (C) 2001-2003
   2 // William E. Kempf
   3 //
   4 //  Distributed under the Boost Software License, Version 1.0. (See accompanying
   5 //  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #include <boost/thread/mutex.hpp>
   8 #include <boost/thread/thread.hpp>
   9 #include <iostream>
  10
  11 boost::mutex io_mutex; // The iostreams are not guaranteed to be thread-safe!
  12
  13 class counter
  14 {
  15 public:
  16     counter() : count(0) { }
  17
  18     int increment() {
  19         boost::unique_lock<boost::mutex> scoped_lock(mutex);
  20         return ++count;
  21     }
  22
  23 private:
  24     boost::mutex mutex;
  25     int count;
  26 };
  27
  28 counter c;
  29
  30 void change_count()
  31 {
  32     int i = c.increment();
  33     boost::unique_lock<boost::mutex> scoped_lock(io_mutex);
  34     std::cout << "count == " << i << std::endl;
  35 }
  36
  37 int main(int, char*[])
  38 {
  39     const int num_threads = 4;
  40     boost::thread_group thrds;
  41     for (int i=0; i < num_threads; ++i)
  42         thrds.create_thread(&change_count);
  43
  44     thrds.join_all();
  45
  46     return 0;
  47 }