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1 | // |
2 | // detail/std_event.hpp | |
3 | // ~~~~~~~~~~~~~~~~~~~~ | |
4 | // | |
5 | // Copyright (c) 2003-2016 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_STD_EVENT_HPP | |
12 | #define BOOST_ASIO_DETAIL_STD_EVENT_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 | ||
20 | #if defined(BOOST_ASIO_HAS_STD_MUTEX_AND_CONDVAR) | |
21 | ||
22 | #include <chrono> | |
23 | #include <condition_variable> | |
24 | #include <boost/asio/detail/assert.hpp> | |
25 | #include <boost/asio/detail/noncopyable.hpp> | |
26 | ||
27 | #include <boost/asio/detail/push_options.hpp> | |
28 | ||
29 | namespace boost { | |
30 | namespace asio { | |
31 | namespace detail { | |
32 | ||
33 | class std_event | |
34 | : private noncopyable | |
35 | { | |
36 | public: | |
37 | // Constructor. | |
38 | std_event() | |
39 | : state_(0) | |
40 | { | |
41 | } | |
42 | ||
43 | // Destructor. | |
44 | ~std_event() | |
45 | { | |
46 | } | |
47 | ||
48 | // Signal the event. (Retained for backward compatibility.) | |
49 | template <typename Lock> | |
50 | void signal(Lock& lock) | |
51 | { | |
52 | this->signal_all(lock); | |
53 | } | |
54 | ||
55 | // Signal all waiters. | |
56 | template <typename Lock> | |
57 | void signal_all(Lock& lock) | |
58 | { | |
59 | BOOST_ASIO_ASSERT(lock.locked()); | |
60 | (void)lock; | |
61 | state_ |= 1; | |
62 | cond_.notify_all(); | |
63 | } | |
64 | ||
65 | // Unlock the mutex and signal one waiter. | |
66 | template <typename Lock> | |
67 | void unlock_and_signal_one(Lock& lock) | |
68 | { | |
69 | BOOST_ASIO_ASSERT(lock.locked()); | |
70 | state_ |= 1; | |
71 | bool have_waiters = (state_ > 1); | |
72 | lock.unlock(); | |
73 | if (have_waiters) | |
74 | cond_.notify_one(); | |
75 | } | |
76 | ||
77 | // If there's a waiter, unlock the mutex and signal it. | |
78 | template <typename Lock> | |
79 | bool maybe_unlock_and_signal_one(Lock& lock) | |
80 | { | |
81 | BOOST_ASIO_ASSERT(lock.locked()); | |
82 | state_ |= 1; | |
83 | if (state_ > 1) | |
84 | { | |
85 | lock.unlock(); | |
86 | cond_.notify_one(); | |
87 | return true; | |
88 | } | |
89 | return false; | |
90 | } | |
91 | ||
92 | // Reset the event. | |
93 | template <typename Lock> | |
94 | void clear(Lock& lock) | |
95 | { | |
96 | BOOST_ASIO_ASSERT(lock.locked()); | |
97 | (void)lock; | |
98 | state_ &= ~std::size_t(1); | |
99 | } | |
100 | ||
101 | // Wait for the event to become signalled. | |
102 | template <typename Lock> | |
103 | void wait(Lock& lock) | |
104 | { | |
105 | BOOST_ASIO_ASSERT(lock.locked()); | |
106 | unique_lock_adapter u_lock(lock); | |
107 | while ((state_ & 1) == 0) | |
108 | { | |
109 | waiter w(state_); | |
110 | cond_.wait(u_lock.unique_lock_); | |
111 | } | |
112 | } | |
113 | ||
114 | // Timed wait for the event to become signalled. | |
115 | template <typename Lock> | |
116 | bool wait_for_usec(Lock& lock, long usec) | |
117 | { | |
118 | BOOST_ASIO_ASSERT(lock.locked()); | |
119 | unique_lock_adapter u_lock(lock); | |
120 | if ((state_ & 1) == 0) | |
121 | { | |
122 | waiter w(state_); | |
123 | cond_.wait_for(u_lock.unique_lock_, std::chrono::microseconds(usec)); | |
124 | } | |
125 | return (state_ & 1) != 0; | |
126 | } | |
127 | ||
128 | private: | |
129 | // Helper class to temporarily adapt a scoped_lock into a unique_lock so that | |
130 | // it can be passed to std::condition_variable::wait(). | |
131 | struct unique_lock_adapter | |
132 | { | |
133 | template <typename Lock> | |
134 | explicit unique_lock_adapter(Lock& lock) | |
135 | : unique_lock_(lock.mutex().mutex_, std::adopt_lock) | |
136 | { | |
137 | } | |
138 | ||
139 | ~unique_lock_adapter() | |
140 | { | |
141 | unique_lock_.release(); | |
142 | } | |
143 | ||
144 | std::unique_lock<std::mutex> unique_lock_; | |
145 | }; | |
146 | ||
147 | // Helper to increment and decrement the state to track outstanding waiters. | |
148 | class waiter | |
149 | { | |
150 | public: | |
151 | explicit waiter(std::size_t& state) | |
152 | : state_(state) | |
153 | { | |
154 | state_ += 2; | |
155 | } | |
156 | ||
157 | ~waiter() | |
158 | { | |
159 | state_ -= 2; | |
160 | } | |
161 | ||
162 | private: | |
163 | std::size_t& state_; | |
164 | }; | |
165 | ||
166 | std::condition_variable cond_; | |
167 | std::size_t state_; | |
168 | }; | |
169 | ||
170 | } // namespace detail | |
171 | } // namespace asio | |
172 | } // namespace boost | |
173 | ||
174 | #include <boost/asio/detail/pop_options.hpp> | |
175 | ||
176 | #endif // defined(BOOST_ASIO_HAS_STD_MUTEX_AND_CONDVAR) | |
177 | ||
178 | #endif // BOOST_ASIO_DETAIL_STD_EVENT_HPP |