1 //
2 // detail/conditionally_enabled_mutex.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_CONDITIONALLY_ENABLED_MUTEX_HPP
12 #define BOOST_ASIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_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/config.hpp>
19 #include <boost/asio/detail/mutex.hpp>
20 #include <boost/asio/detail/noncopyable.hpp>
21 #include <boost/asio/detail/scoped_lock.hpp>
22
23 #include <boost/asio/detail/push_options.hpp>
24
25 namespace boost {
26 namespace asio {
27 namespace detail {
28
29 // Mutex adapter used to conditionally enable or disable locking.
30 class conditionally_enabled_mutex
31 : private noncopyable
32 {
33 public:
34 // Helper class to lock and unlock a mutex automatically.
35 class scoped_lock
36 : private noncopyable
37 {
38 public:
39 // Tag type used to distinguish constructors.
40 enum adopt_lock_t { adopt_lock };
41
42 // Constructor adopts a lock that is already held.
43 scoped_lock(conditionally_enabled_mutex& m, adopt_lock_t)
44 : mutex_(m),
45 locked_(m.enabled_)
46 {
47 }
48
49 // Constructor acquires the lock.
50 explicit scoped_lock(conditionally_enabled_mutex& m)
51 : mutex_(m)
52 {
53 if (m.enabled_)
54 {
55 mutex_.mutex_.lock();
56 locked_ = true;
57 }
58 else
59 locked_ = false;
60 }
61
62 // Destructor releases the lock.
63 ~scoped_lock()
64 {
65 if (locked_)
66 mutex_.mutex_.unlock();
67 }
68
69 // Explicitly acquire the lock.
70 void lock()
71 {
72 if (mutex_.enabled_ && !locked_)
73 {
|
(3) Event example_lock: |
Example 1: Locking "boost::asio::detail::posix_mutex.mutex_". |
| Also see events: |
[missing_lock][example_access] |
74 mutex_.mutex_.lock();
|
(4) Event example_access: |
Example 1 (cont.): "boost::asio::detail::conditionally_enabled_mutex::scoped_lock.locked_" is accessed with lock "boost::asio::detail::posix_mutex.mutex_" held. |
| Also see events: |
[missing_lock][example_lock] |
75 locked_ = true;
76 }
77 }
78
79 // Explicitly release the lock.
80 void unlock()
81 {
|
(1) Event cond_true: |
Condition "this->locked_", taking true branch. |
82 if (locked_)
83 {
84 mutex_.unlock();
|
(2) Event missing_lock: |
Accessing "this->locked_" without holding lock "boost::asio::detail::posix_mutex.mutex_". Elsewhere, "_ZN5boost4asio6detail27conditionally_enabled_mutex11scoped_lockE.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] |
85 locked_ = false;
86 }
87 }
88
89 // Test whether the lock is held.
90 bool locked() const
91 {
92 return locked_;
93 }
94
95 // Get the underlying mutex.
96 boost::asio::detail::mutex& mutex()
97 {
98 return mutex_.mutex_;
99 }
100
101 private:
102 friend class conditionally_enabled_event;
103 conditionally_enabled_mutex& mutex_;
104 bool locked_;
105 };
106
107 // Constructor.
108 explicit conditionally_enabled_mutex(bool enabled)
109 : enabled_(enabled)
110 {
111 }
112
113 // Destructor.
114 ~conditionally_enabled_mutex()
115 {
116 }
117
118 // Determine whether locking is enabled.
119 bool enabled() const
120 {
121 return enabled_;
122 }
123
124 // Lock the mutex.
125 void lock()
126 {
127 if (enabled_)
128 mutex_.lock();
129 }
130
131 // Unlock the mutex.
132 void unlock()
133 {
134 if (enabled_)
135 mutex_.unlock();
136 }
137
138 private:
139 friend class scoped_lock;
140 friend class conditionally_enabled_event;
141 boost::asio::detail::mutex mutex_;
142 const bool enabled_;
143 };
144
145 } // namespace detail
146 } // namespace asio
147 } // namespace boost
148
149 #include <boost/asio/detail/pop_options.hpp>
150
151 #endif // BOOST_ASIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP
152