1 //
2 // detail/scoped_lock.hpp
3 // ~~~~~~~~~~~~~~~~~~~~~~
4 //
5 // Copyright (c) 2003-2018 Christopher M. Kohlhoff (chris at kohlhoff dot com)
6 //
7 // Distributed under the Boost Software License, Version 1.0. (See accompanying
8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
9 //
10
11 #ifndef BOOST_ASIO_DETAIL_SCOPED_LOCK_HPP
12 #define BOOST_ASIO_DETAIL_SCOPED_LOCK_HPP
13
14 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
15 # pragma once
16 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
17
18 #include <boost/asio/detail/noncopyable.hpp>
19
20 #include <boost/asio/detail/push_options.hpp>
21
22 namespace boost {
23 namespace asio {
24 namespace detail {
25
26 // Helper class to lock and unlock a mutex automatically.
27 template <typename Mutex>
28 class scoped_lock
29 : private noncopyable
30 {
31 public:
32 // Tag type used to distinguish constructors.
33 enum adopt_lock_t { adopt_lock };
34
35 // Constructor adopts a lock that is already held.
36 scoped_lock(Mutex& m, adopt_lock_t)
37 : mutex_(m),
38 locked_(true)
39 {
40 }
41
42 // Constructor acquires the lock.
43 explicit scoped_lock(Mutex& m)
44 : mutex_(m)
45 {
46 mutex_.lock();
47 locked_ = true;
48 }
49
50 // Destructor releases the lock.
51 ~scoped_lock()
52 {
53 if (locked_)
54 mutex_.unlock();
55 }
56
57 // Explicitly acquire the lock.
58 void lock()
59 {
60 if (!locked_)
61 {
|
(3) Event example_lock: |
Example 1: Locking "boost::asio::detail::posix_mutex.mutex_". |
| Also see events: |
[missing_lock][example_access] |
62 mutex_.lock();
|
(4) Event example_access: |
Example 1 (cont.): "boost::asio::detail::scoped_lock<boost::asio::detail::posix_mutex>.locked_" is accessed with lock "boost::asio::detail::posix_mutex.mutex_" held. |
| Also see events: |
[missing_lock][example_lock] |
63 locked_ = true;
64 }
65 }
66
67 // Explicitly release the lock.
68 void unlock()
69 {
|
(1) Event cond_true: |
Condition "this->locked_", taking true branch. |
70 if (locked_)
71 {
72 mutex_.unlock();
|
(2) Event missing_lock: |
Accessing "this->locked_" without holding lock "boost::asio::detail::posix_mutex.mutex_". Elsewhere, "_ZN5boost4asio6detail11scoped_lockINS1_11posix_mutexEEE.locked_" is accessed with "boost::asio::detail::posix_mutex.mutex_" held 1 out of 2 times (1 of these accesses strongly imply that it is necessary). |
| Also see events: |
[example_lock][example_access] |
73 locked_ = false;
74 }
75 }
76
77 // Test whether the lock is held.
78 bool locked() const
79 {
80 return locked_;
81 }
82
83 // Get the underlying mutex.
84 Mutex& mutex()
85 {
86 return mutex_;
87 }
88
89 private:
90 // The underlying mutex.
91 Mutex& mutex_;
92
93 // Whether the mutex is currently locked or unlocked.
94 bool locked_;
95 };
96
97 } // namespace detail
98 } // namespace asio
99 } // namespace boost
100
101 #include <boost/asio/detail/pop_options.hpp>
102
103 #endif // BOOST_ASIO_DETAIL_SCOPED_LOCK_HPP
104