1 /*
2  * Copyright (C) 2008 Tommi Maekitalo
3  *
4  * This library is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * As a special exception, you may use this file as part of a free
10  * software library without restriction. Specifically, if other files
11  * instantiate templates or use macros or inline functions from this
12  * file, or you compile this file and link it with other files to
13  * produce an executable, this file does not by itself cause the
14  * resulting executable to be covered by the GNU General Public
15  * License. This exception does not however invalidate any other
16  * reasons why the executable file might be covered by the GNU Library
17  * General Public License.
18  *
19  * This library is distributed in the hope that it will be useful,
20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
22  * Lesser General Public License for more details.
23  *
24  * You should have received a copy of the GNU Lesser General Public
25  * License along with this library; if not, write to the Free Software
26  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
27  */
28 
29 #include <cxxtools/mutex.h>
30 #include <cxxtools/condition.h>
31 #include <cxxtools/clock.h>
32 #include <stdint.h>
33 
34 template <typename T>
35 class ModificationTracker
36 {
37     T _value;
38     unsigned _serial;
39     mutable cxxtools::Mutex _mutex;
40     mutable cxxtools::Condition _condition;
41 
42   public:
43     typedef std::pair<T, unsigned> ValueSerial;
44 
ModificationTracker()45     ModificationTracker()
46       : _serial(0)
47     { }
48 
49     /// set value
set(const T & value)50     void set(const T& value)
51     {
52       cxxtools::MutexLock lock(_mutex);
53       _value = value;
54       ++_serial;
55       _condition.broadcast();
56     }
57 
58     /// get value and serial number of value
get()59     ValueSerial get() const
60     {
61       cxxtools::MutexLock lock(_mutex);
62       return ValueSerial(_value, _serial);
63     }
64 
65     /// wait value change up to specified timeout
get(unsigned serial,unsigned timeoutMsec)66     ValueSerial get(unsigned serial, unsigned timeoutMsec) const
67     {
68       cxxtools::MutexLock lock(_mutex);
69       cxxtools::Clock clock;
70       clock.start();
71       while (_serial <= serial)
72       {
73         int64_t timeoutLeft = static_cast<int64_t>(timeoutMsec) - clock.stop().totalMSecs();
74         if (timeoutLeft <= 0)
75           break;
76 
77         _condition.wait(lock, timeoutLeft);
78       }
79 
80       return ValueSerial(_value, _serial);
81     }
82 
83 };
84