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onoff_switch.hpp
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1 /***************************************************************************
2  * foxxll/common/onoff_switch.hpp
3  *
4  * Kind of binary semaphore: initially OFF, then multiple waiters can attach
5  * to the switch, which get notified one-by-one when switched ON.
6  *
7  * Part of FOXXLL. See http://foxxll.org
8  *
9  * Copyright (C) 2002 Roman Dementiev <[email protected]>
10  * Copyright (C) 2013 Timo Bingmann <[email protected]>
11  *
12  * Distributed under the Boost Software License, Version 1.0.
13  * (See accompanying file LICENSE_1_0.txt or copy at
14  * http://www.boost.org/LICENSE_1_0.txt)
15  **************************************************************************/
16 
17 #ifndef FOXXLL_COMMON_ONOFF_SWITCH_HEADER
18 #define FOXXLL_COMMON_ONOFF_SWITCH_HEADER
19 
20 #include <condition_variable>
21 #include <mutex>
22 
23 namespace foxxll {
24 
26 {
27  //! mutex for condition variable
28  std::mutex mutex_;
29 
30  //! condition variable
31  std::condition_variable cond_;
32 
33  //! the switch's state
34  bool on_;
35 
36 public:
37  //! construct switch
38  explicit onoff_switch(bool flag = false)
39  : on_(flag)
40  { }
41 
42  //! non-copyable: delete copy-constructor
43  onoff_switch(const onoff_switch&) = delete;
44  //! non-copyable: delete assignment operator
45  onoff_switch& operator = (const onoff_switch&) = delete;
46 
47  //! turn switch ON and notify one waiter
48  void on()
49  {
50  std::unique_lock<std::mutex> lock(mutex_);
51  on_ = true;
52  cond_.notify_one();
53  }
54 
55  //! turn switch OFF and notify one waiter
56  void off()
57  {
58  std::unique_lock<std::mutex> lock(mutex_);
59  on_ = false;
60  cond_.notify_one();
61  }
62 
63  //! wait for switch to turn ON
64  void wait_for_on()
65  {
66  std::unique_lock<std::mutex> lock(mutex_);
67  if (!on_)
68  cond_.wait(lock);
69  }
70 
71  //! wait for switch to turn OFF
72  void wait_for_off()
73  {
74  std::unique_lock<std::mutex> lock(mutex_);
75  if (on_)
76  cond_.wait(lock);
77  }
78 
79  //! return true if switch is ON
80  bool is_on()
81  {
82  std::unique_lock<std::mutex> lock(mutex_);
83  return on_;
84  }
85 };
86 
87 } // namespace foxxll
88 
89 #endif // !FOXXLL_COMMON_ONOFF_SWITCH_HEADER
90 
91 /**************************************************************************/
void wait_for_on()
wait for switch to turn ON
bool on_
the switch's state
std::condition_variable cond_
condition variable
void wait_for_off()
wait for switch to turn OFF
onoff_switch & operator=(const onoff_switch &)=delete
non-copyable: delete assignment operator
void off()
turn switch OFF and notify one waiter
void on()
turn switch ON and notify one waiter
onoff_switch(bool flag=false)
construct switch
bool is_on()
return true if switch is ON
std::mutex mutex_
mutex for condition variable