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24 | </div> | |
25 | <div class="section"> | |
26 | <div class="titlepage"><div><div><h3 class="title"> | |
27 | <a name="fiber.synchronization.conditions"></a><a class="link" href="conditions.html" title="Condition Variables">Condition Variables</a> | |
28 | </h3></div></div></div> | |
29 | <h5> | |
30 | <a name="fiber.synchronization.conditions.h0"></a> | |
31 | <span><a name="fiber.synchronization.conditions.synopsis"></a></span><a class="link" href="conditions.html#fiber.synchronization.conditions.synopsis">Synopsis</a> | |
32 | </h5> | |
33 | <pre class="programlisting"><span class="keyword">enum</span> <span class="keyword">class</span> <span class="identifier">cv_status</span><span class="special">;</span> <span class="special">{</span> | |
34 | <span class="identifier">no_timeout</span><span class="special">,</span> | |
35 | <span class="identifier">timeout</span> | |
36 | <span class="special">};</span> | |
37 | ||
38 | <span class="keyword">class</span> <span class="identifier">condition_variable</span><span class="special">;</span> | |
39 | <span class="keyword">class</span> <span class="identifier">condition_variable_any</span><span class="special">;</span> | |
40 | </pre> | |
41 | <p> | |
42 | The class <a class="link" href="conditions.html#class_condition_variable"><code class="computeroutput">condition_variable</code></a> provides a mechanism | |
43 | for a fiber to wait for notification from another fiber. When the fiber awakens | |
44 | from the wait, then it checks to see if the appropriate condition is now | |
45 | true, and continues if so. If the condition is not true, then the fiber calls | |
46 | <code class="computeroutput"><span class="identifier">wait</span></code> again to resume waiting. | |
47 | In the simplest case, this condition is just a boolean variable: | |
48 | </p> | |
49 | <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">condition_variable</span> <span class="identifier">cond</span><span class="special">;</span> | |
50 | <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">mutex</span> <span class="identifier">mtx</span><span class="special">;</span> | |
51 | <span class="keyword">bool</span> <span class="identifier">data_ready</span> <span class="special">=</span> <span class="keyword">false</span><span class="special">;</span> | |
52 | ||
53 | <span class="keyword">void</span> <span class="identifier">process_data</span><span class="special">();</span> | |
54 | ||
55 | <span class="keyword">void</span> <span class="identifier">wait_for_data_to_process</span><span class="special">()</span> <span class="special">{</span> | |
56 | <span class="special">{</span> | |
57 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_lock</span><span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">mutex</span> <span class="special">></span> <span class="identifier">lk</span><span class="special">(</span> <span class="identifier">mtx</span><span class="special">);</span> | |
58 | <span class="keyword">while</span> <span class="special">(</span> <span class="special">!</span> <span class="identifier">data_ready</span><span class="special">)</span> <span class="special">{</span> | |
59 | <span class="identifier">cond</span><span class="special">.</span><span class="identifier">wait</span><span class="special">(</span> <span class="identifier">lk</span><span class="special">);</span> | |
60 | <span class="special">}</span> | |
61 | <span class="special">}</span> <span class="comment">// release lk</span> | |
62 | <span class="identifier">process_data</span><span class="special">();</span> | |
63 | <span class="special">}</span> | |
64 | </pre> | |
65 | <p> | |
66 | Notice that the <code class="computeroutput"><span class="identifier">lk</span></code> is passed | |
67 | to <a class="link" href="conditions.html#condition_variable_wait"><code class="computeroutput">condition_variable::wait()</code></a>: <code class="computeroutput"><span class="identifier">wait</span><span class="special">()</span></code> will atomically add the fiber to the set | |
68 | of fibers waiting on the condition variable, and unlock the <a class="link" href="mutex_types.html#class_mutex"><code class="computeroutput">mutex</code></a>. | |
69 | When the fiber is awakened, the <code class="computeroutput"><span class="identifier">mutex</span></code> | |
70 | will be locked again before the call to <code class="computeroutput"><span class="identifier">wait</span><span class="special">()</span></code> returns. This allows other fibers to acquire | |
71 | the <code class="computeroutput"><span class="identifier">mutex</span></code> in order to update | |
72 | the shared data, and ensures that the data associated with the condition | |
73 | is correctly synchronized. | |
74 | </p> | |
75 | <p> | |
76 | <code class="computeroutput"><span class="identifier">wait_for_data_to_process</span><span class="special">()</span></code> could equivalently be written: | |
77 | </p> | |
78 | <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">wait_for_data_to_process</span><span class="special">()</span> <span class="special">{</span> | |
79 | <span class="special">{</span> | |
80 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_lock</span><span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">mutex</span> <span class="special">></span> <span class="identifier">lk</span><span class="special">(</span> <span class="identifier">mtx</span><span class="special">);</span> | |
81 | <span class="comment">// make condition_variable::wait() perform the loop</span> | |
82 | <span class="identifier">cond</span><span class="special">.</span><span class="identifier">wait</span><span class="special">(</span> <span class="identifier">lk</span><span class="special">,</span> <span class="special">[](){</span> <span class="keyword">return</span> <span class="identifier">data_ready</span><span class="special">;</span> <span class="special">});</span> | |
83 | <span class="special">}</span> <span class="comment">// release lk</span> | |
84 | <span class="identifier">process_data</span><span class="special">();</span> | |
85 | <span class="special">}</span> | |
86 | </pre> | |
87 | <p> | |
88 | In the meantime, another fiber sets <code class="computeroutput"><span class="identifier">data_ready</span></code> | |
89 | to <code class="computeroutput"><span class="keyword">true</span></code>, and then calls either | |
90 | <a class="link" href="conditions.html#condition_variable_notify_one"><code class="computeroutput">condition_variable::notify_one()</code></a> or <a class="link" href="conditions.html#condition_variable_notify_all"><code class="computeroutput">condition_variable::notify_all()</code></a> on | |
91 | the <a class="link" href="conditions.html#class_condition_variable"><code class="computeroutput">condition_variable</code></a> <code class="computeroutput"><span class="identifier">cond</span></code> | |
92 | to wake one waiting fiber or all the waiting fibers respectively. | |
93 | </p> | |
94 | <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">retrieve_data</span><span class="special">();</span> | |
95 | <span class="keyword">void</span> <span class="identifier">prepare_data</span><span class="special">();</span> | |
96 | ||
97 | <span class="keyword">void</span> <span class="identifier">prepare_data_for_processing</span><span class="special">()</span> <span class="special">{</span> | |
98 | <span class="identifier">retrieve_data</span><span class="special">();</span> | |
99 | <span class="identifier">prepare_data</span><span class="special">();</span> | |
100 | <span class="special">{</span> | |
101 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_lock</span><span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">mutex</span> <span class="special">></span> <span class="identifier">lk</span><span class="special">(</span> <span class="identifier">mtx</span><span class="special">);</span> | |
102 | <span class="identifier">data_ready</span> <span class="special">=</span> <span class="keyword">true</span><span class="special">;</span> | |
103 | <span class="special">}</span> | |
104 | <span class="identifier">cond</span><span class="special">.</span><span class="identifier">notify_one</span><span class="special">();</span> | |
105 | <span class="special">}</span> | |
106 | </pre> | |
107 | <p> | |
108 | Note that the same <a class="link" href="mutex_types.html#class_mutex"><code class="computeroutput">mutex</code></a> is locked before the shared data is updated, | |
109 | but that the <code class="computeroutput"><span class="identifier">mutex</span></code> does not | |
110 | have to be locked across the call to <a class="link" href="conditions.html#condition_variable_notify_one"><code class="computeroutput">condition_variable::notify_one()</code></a>. | |
111 | </p> | |
112 | <p> | |
113 | Locking is important because the synchronization objects provided by <span class="bold"><strong>Boost.Fiber</strong></span> can be used to synchronize fibers running | |
114 | on different threads. | |
115 | </p> | |
116 | <p> | |
117 | <span class="bold"><strong>Boost.Fiber</strong></span> provides both <a class="link" href="conditions.html#class_condition_variable"><code class="computeroutput">condition_variable</code></a> and | |
118 | <a class="link" href="conditions.html#class_condition_variable_any"><code class="computeroutput">condition_variable_any</code></a>. <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">condition_variable</span></code> | |
119 | can only wait on <a href="http://en.cppreference.com/w/cpp/thread/unique_lock" target="_top"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_lock</span></code></a><code class="computeroutput"><span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span></code><a class="link" href="mutex_types.html#class_mutex"><code class="computeroutput">mutex</code></a><code class="computeroutput"> <span class="special">></span></code> | |
120 | while <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">fibers</span><span class="special">::</span><span class="identifier">condition_variable_any</span></code> can wait on user-defined | |
121 | lock types. | |
122 | </p> | |
123 | <a name="condition_variable_spurious_wakeups"></a><h5> | |
124 | <a name="fiber.synchronization.conditions.h1"></a> | |
125 | <span><a name="fiber.synchronization.conditions.no_spurious_wakeups"></a></span><a class="link" href="conditions.html#fiber.synchronization.conditions.no_spurious_wakeups">No Spurious | |
126 | Wakeups</a> | |
127 | </h5> | |
128 | <p> | |
129 | Neither <a class="link" href="conditions.html#class_condition_variable"><code class="computeroutput">condition_variable</code></a> nor <a class="link" href="conditions.html#class_condition_variable_any"><code class="computeroutput">condition_variable_any</code></a> are | |
130 | subject to spurious wakeup: <a class="link" href="conditions.html#condition_variable_wait"><code class="computeroutput">condition_variable::wait()</code></a> can | |
131 | only wake up when <a class="link" href="conditions.html#condition_variable_notify_one"><code class="computeroutput">condition_variable::notify_one()</code></a> or | |
132 | <a class="link" href="conditions.html#condition_variable_notify_all"><code class="computeroutput">condition_variable::notify_all()</code></a> is called. Even | |
133 | so, it is prudent to use one of the <code class="computeroutput"><span class="identifier">wait</span><span class="special">(</span> <span class="identifier">lock</span><span class="special">,</span> <span class="identifier">predicate</span> <span class="special">)</span></code> overloads. | |
134 | </p> | |
135 | <p> | |
136 | Consider a set of consumer fibers processing items from a <a href="http://en.cppreference.com/w/cpp/container/queue" target="_top"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">queue</span></code></a>. | |
137 | The queue is continually populated by a set of producer fibers. | |
138 | </p> | |
139 | <p> | |
140 | The consumer fibers might reasonably wait on a <code class="computeroutput"><span class="identifier">condition_variable</span></code> | |
141 | as long as the queue remains <a href="http://en.cppreference.com/w/cpp/container/queue/empty" target="_top"><code class="computeroutput"><span class="identifier">empty</span><span class="special">()</span></code></a>. | |
142 | </p> | |
143 | <p> | |
144 | Because producer fibers might <a href="http://en.cppreference.com/w/cpp/container/queue/push" target="_top"><code class="computeroutput"><span class="identifier">push</span><span class="special">()</span></code></a> | |
145 | items to the queue in bursts, they call <a class="link" href="conditions.html#condition_variable_notify_all"><code class="computeroutput">condition_variable::notify_all()</code></a> rather | |
146 | than <a class="link" href="conditions.html#condition_variable_notify_one"><code class="computeroutput">condition_variable::notify_one()</code></a>. | |
147 | </p> | |
148 | <p> | |
149 | But a given consumer fiber might well wake up from <a class="link" href="conditions.html#condition_variable_wait"><code class="computeroutput">condition_variable::wait()</code></a> and | |
150 | find the queue <code class="computeroutput"><span class="identifier">empty</span><span class="special">()</span></code>, | |
151 | because other consumer fibers might already have processed all pending items. | |
152 | </p> | |
153 | <p> | |
154 | (See also <a class="link" href="../rationale.html#spurious_wakeup">spurious wakeup</a>.) | |
155 | </p> | |
156 | <a name="class_cv_status"></a><h5> | |
157 | <a name="fiber.synchronization.conditions.h2"></a> | |
158 | <span><a name="fiber.synchronization.conditions.enumeration__code__phrase_role__identifier__cv_status__phrase___code_"></a></span><a class="link" href="conditions.html#fiber.synchronization.conditions.enumeration__code__phrase_role__identifier__cv_status__phrase___code_">Enumeration | |
159 | <code class="computeroutput"><span class="identifier">cv_status</span></code></a> | |
160 | </h5> | |
161 | <p> | |
162 | A timed wait operation might return because of timeout or not. | |
163 | </p> | |
164 | <pre class="programlisting"><span class="keyword">enum</span> <span class="keyword">class</span> <span class="identifier">cv_status</span> <span class="special">{</span> | |
165 | <span class="identifier">no_timeout</span><span class="special">,</span> | |
166 | <span class="identifier">timeout</span> | |
167 | <span class="special">};</span> | |
168 | </pre> | |
169 | <h5> | |
170 | <a name="fiber.synchronization.conditions.h3"></a> | |
171 | <span><a name="fiber.synchronization.conditions._code__phrase_role__identifier__no_timeout__phrase___code_"></a></span><a class="link" href="conditions.html#fiber.synchronization.conditions._code__phrase_role__identifier__no_timeout__phrase___code_"><code class="computeroutput"><span class="identifier">no_timeout</span></code></a> | |
172 | </h5> | |
173 | <div class="variablelist"> | |
174 | <p class="title"><b></b></p> | |
175 | <dl> | |
176 | <dt><span class="term">Effects:</span></dt> | |
177 | <dd><p> | |
178 | The condition variable was awakened with <code class="computeroutput"><span class="identifier">notify_one</span></code> | |
179 | or <code class="computeroutput"><span class="identifier">notify_all</span></code>. | |
180 | </p></dd> | |
181 | </dl> | |
182 | </div> | |
183 | <h5> | |
184 | <a name="fiber.synchronization.conditions.h4"></a> | |
185 | <span><a name="fiber.synchronization.conditions._code__phrase_role__identifier__timeout__phrase___code_"></a></span><a class="link" href="conditions.html#fiber.synchronization.conditions._code__phrase_role__identifier__timeout__phrase___code_"><code class="computeroutput"><span class="identifier">timeout</span></code></a> | |
186 | </h5> | |
187 | <div class="variablelist"> | |
188 | <p class="title"><b></b></p> | |
189 | <dl> | |
190 | <dt><span class="term">Effects:</span></dt> | |
191 | <dd><p> | |
192 | The condition variable was awakened by timeout. | |
193 | </p></dd> | |
194 | </dl> | |
195 | </div> | |
196 | <p> | |
197 | </p> | |
198 | <h5> | |
199 | <a name="class_condition_variable_any_bridgehead"></a> | |
200 | <span><a name="class_condition_variable_any"></a></span> | |
201 | <a class="link" href="conditions.html#class_condition_variable_any">Class | |
202 | <code class="computeroutput">condition_variable_any</code></a> | |
203 | </h5> | |
204 | <p> | |
205 | </p> | |
206 | <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fiber</span><span class="special">/</span><span class="identifier">condition_variable</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> | |
207 | ||
208 | <span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> | |
209 | <span class="keyword">namespace</span> <span class="identifier">fibers</span> <span class="special">{</span> | |
210 | ||
211 | <span class="keyword">class</span> condition_variable_any <span class="special">{</span> | |
212 | <span class="keyword">public</span><span class="special">:</span> | |
213 | condition_variable_any<span class="special">();</span> | |
214 | <span class="special">~</span>condition_variable_any<span class="special">();</span> | |
215 | ||
216 | condition_variable_any<span class="special">(</span> condition_variable_any <span class="keyword">const</span><span class="special">&)</span> <span class="special">=</span> <span class="keyword">delete</span><span class="special">;</span> | |
217 | condition_variable_any <span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span> condition_variable_any <span class="keyword">const</span><span class="special">&)</span> <span class="special">=</span> <span class="keyword">delete</span><span class="special">;</span> | |
218 | ||
219 | <span class="keyword">void</span> <span class="identifier">notify_one</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span> | |
220 | <span class="keyword">void</span> <span class="identifier">notify_all</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span> | |
221 | ||
222 | template< typename LockType > | |
223 | void <span class="identifier">wait</span><span class="special">(</span> LockType <span class="special">&);</span> | |
224 | ||
225 | <span class="keyword">template</span><span class="special"><</span> typename LockType, typename <span class="identifier">Pred</span> <span class="special">></span> | |
226 | <span class="keyword">void</span> <span class="identifier">wait</span><span class="special">(</span> LockType <span class="special">&,</span> <span class="identifier">Pred</span><span class="special">);</span> | |
227 | ||
228 | <span class="keyword">template</span><span class="special"><</span> typename LockType, typename <span class="identifier">Clock</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Duration</span> <span class="special">></span> | |
229 | <span class="identifier">cv_status</span> <span class="identifier">wait_until</span><span class="special">(</span> LockType <span class="special">&,</span> | |
230 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">time_point</span><span class="special"><</span> <span class="identifier">Clock</span><span class="special">,</span> <span class="identifier">Duration</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&);</span> | |
231 | ||
232 | <span class="keyword">template</span><span class="special"><</span> typename LockType, typename <span class="identifier">Clock</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Duration</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Pred</span> <span class="special">></span> | |
233 | <span class="keyword">bool</span> <span class="identifier">wait_until</span><span class="special">(</span> LockType <span class="special">&,</span> | |
234 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">time_point</span><span class="special"><</span> <span class="identifier">Clock</span><span class="special">,</span> <span class="identifier">Duration</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&,</span> | |
235 | <span class="identifier">Pred</span><span class="special">);</span> | |
236 | ||
237 | <span class="keyword">template</span><span class="special"><</span> typename LockType, typename <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Period</span> <span class="special">></span> | |
238 | <span class="identifier">cv_status</span> <span class="identifier">wait_for</span><span class="special">(</span> LockType <span class="special">&,</span> | |
239 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&);</span> | |
240 | ||
241 | <span class="keyword">template</span><span class="special"><</span> typename LockType, typename <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Period</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Pred</span> <span class="special">></span> | |
242 | <span class="keyword">bool</span> <span class="identifier">wait_for</span><span class="special">(</span> LockType <span class="special">&,</span> | |
243 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&,</span> | |
244 | <span class="identifier">Pred</span><span class="special">);</span> | |
245 | <span class="special">};</span> | |
246 | ||
247 | <span class="special">}}</span> | |
248 | </pre> | |
249 | <h5> | |
250 | <a name="fiber.synchronization.conditions.h5"></a> | |
251 | <span><a name="fiber.synchronization.conditions.constructor"></a></span><a class="link" href="conditions.html#fiber.synchronization.conditions.constructor">Constructor</a> | |
252 | </h5> | |
253 | <pre class="programlisting">condition_variable_any<span class="special">()</span> | |
254 | </pre> | |
255 | <div class="variablelist"> | |
256 | <p class="title"><b></b></p> | |
257 | <dl> | |
258 | <dt><span class="term">Effects:</span></dt> | |
259 | <dd><p> | |
260 | Creates the object. | |
261 | </p></dd> | |
262 | <dt><span class="term">Throws:</span></dt> | |
263 | <dd><p> | |
264 | Nothing. | |
265 | </p></dd> | |
266 | </dl> | |
267 | </div> | |
268 | <h5> | |
269 | <a name="fiber.synchronization.conditions.h6"></a> | |
270 | <span><a name="fiber.synchronization.conditions.destructor"></a></span><a class="link" href="conditions.html#fiber.synchronization.conditions.destructor">Destructor</a> | |
271 | </h5> | |
272 | <pre class="programlisting"><span class="special">~</span>condition_variable_any<span class="special">()</span> | |
273 | </pre> | |
274 | <div class="variablelist"> | |
275 | <p class="title"><b></b></p> | |
276 | <dl> | |
277 | <dt><span class="term">Precondition:</span></dt> | |
278 | <dd><p> | |
279 | All fibers waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> have been notified by a call to | |
280 | <code class="computeroutput"><span class="identifier">notify_one</span></code> or <code class="computeroutput"><span class="identifier">notify_all</span></code> (though the respective | |
281 | calls to <code class="computeroutput"><span class="identifier">wait</span></code>, <code class="computeroutput"><span class="identifier">wait_for</span></code> or <code class="computeroutput"><span class="identifier">wait_until</span></code> | |
282 | need not have returned). | |
283 | </p></dd> | |
284 | <dt><span class="term">Effects:</span></dt> | |
285 | <dd><p> | |
286 | Destroys the object. | |
287 | </p></dd> | |
288 | </dl> | |
289 | </div> | |
290 | <p> | |
291 | </p> | |
292 | <h5> | |
293 | <a name="condition_variable_any_notify_one_bridgehead"></a> | |
294 | <span><a name="condition_variable_any_notify_one"></a></span> | |
295 | <a class="link" href="conditions.html#condition_variable_any_notify_one">Member | |
296 | function <code class="computeroutput">notify_one</code>()</a> | |
297 | </h5> | |
298 | <p> | |
299 | </p> | |
300 | <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">notify_one</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span> | |
301 | </pre> | |
302 | <div class="variablelist"> | |
303 | <p class="title"><b></b></p> | |
304 | <dl> | |
305 | <dt><span class="term">Effects:</span></dt> | |
306 | <dd><p> | |
307 | If any fibers are currently <a class="link" href="../overview.html#blocking"><span class="emphasis"><em>blocked</em></span></a> | |
308 | waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
309 | in a call to <code class="computeroutput"><span class="identifier">wait</span></code>, | |
310 | <code class="computeroutput"><span class="identifier">wait_for</span></code> or <code class="computeroutput"><span class="identifier">wait_until</span></code>, unblocks one of those | |
311 | fibers. | |
312 | </p></dd> | |
313 | <dt><span class="term">Throws:</span></dt> | |
314 | <dd><p> | |
315 | Nothing. | |
316 | </p></dd> | |
317 | <dt><span class="term">Note:</span></dt> | |
318 | <dd><p> | |
319 | It is arbitrary which waiting fiber is resumed. | |
320 | </p></dd> | |
321 | </dl> | |
322 | </div> | |
323 | <p> | |
324 | </p> | |
325 | <h5> | |
326 | <a name="condition_variable_any_notify_all_bridgehead"></a> | |
327 | <span><a name="condition_variable_any_notify_all"></a></span> | |
328 | <a class="link" href="conditions.html#condition_variable_any_notify_all">Member | |
329 | function <code class="computeroutput">notify_all</code>()</a> | |
330 | </h5> | |
331 | <p> | |
332 | </p> | |
333 | <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">notify_all</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span> | |
334 | </pre> | |
335 | <div class="variablelist"> | |
336 | <p class="title"><b></b></p> | |
337 | <dl> | |
338 | <dt><span class="term">Effects:</span></dt> | |
339 | <dd><p> | |
340 | If any fibers are currently <a class="link" href="../overview.html#blocking"><span class="emphasis"><em>blocked</em></span></a> | |
341 | waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
342 | in a call to <code class="computeroutput"><span class="identifier">wait</span></code>, | |
343 | <code class="computeroutput"><span class="identifier">wait_for</span></code> or <code class="computeroutput"><span class="identifier">wait_until</span></code>, unblocks all of those | |
344 | fibers. | |
345 | </p></dd> | |
346 | <dt><span class="term">Throws:</span></dt> | |
347 | <dd><p> | |
348 | Nothing. | |
349 | </p></dd> | |
350 | <dt><span class="term">Note:</span></dt> | |
351 | <dd><p> | |
352 | This is why a waiting fiber must <span class="emphasis"><em>also</em></span> check for | |
353 | the desired program state using a mechanism external to the <code class="computeroutput">condition_variable_any</code>, | |
354 | and retry the wait until that state is reached. A fiber waiting on | |
355 | a <code class="computeroutput">condition_variable_any</code> might well wake up a number of times before | |
356 | the desired state is reached. | |
357 | </p></dd> | |
358 | </dl> | |
359 | </div> | |
360 | <p> | |
361 | </p> | |
362 | <h5> | |
363 | <a name="condition_variable_any_wait_bridgehead"></a> | |
364 | <span><a name="condition_variable_any_wait"></a></span> | |
365 | <a class="link" href="conditions.html#condition_variable_any_wait">Templated | |
366 | member function <code class="computeroutput">wait</code>()</a> | |
367 | </h5> | |
368 | <p> | |
369 | </p> | |
370 | <pre class="programlisting">template< typename LockType > | |
371 | void <span class="identifier">wait</span><span class="special">(</span> LockType <span class="special">&</span> <span class="identifier">lk</span><span class="special">);</span> | |
372 | ||
373 | <span class="keyword">template</span><span class="special"><</span> typename LockType, typename <span class="identifier">Pred</span> <span class="special">></span> | |
374 | <span class="keyword">void</span> <span class="identifier">wait</span><span class="special">(</span> LockType <span class="special">&</span> <span class="identifier">lk</span><span class="special">,</span> <span class="identifier">Pred</span> <span class="identifier">pred</span><span class="special">);</span> | |
375 | </pre> | |
376 | <div class="variablelist"> | |
377 | <p class="title"><b></b></p> | |
378 | <dl> | |
379 | <dt><span class="term">Precondition:</span></dt> | |
380 | <dd><p> | |
381 | <code class="computeroutput"><span class="identifier">lk</span></code> is locked by the | |
382 | current fiber, and either no other fiber is currently waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>, | |
383 | or the execution of the <a href="http://en.cppreference.com/w/cpp/thread/unique_lock/mutex" target="_top"><code class="computeroutput"><span class="identifier">mutex</span><span class="special">()</span></code></a> | |
384 | member function on the <code class="computeroutput"><span class="identifier">lk</span></code> | |
385 | objects supplied in the calls to <code class="computeroutput"><span class="identifier">wait</span></code> | |
386 | in all the fibers currently waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> would return the same value as | |
387 | <code class="computeroutput"><span class="identifier">lk</span><span class="special">-></span><span class="identifier">mutex</span><span class="special">()</span></code> | |
388 | for this call to <code class="computeroutput"><span class="identifier">wait</span></code>. | |
389 | </p></dd> | |
390 | <dt><span class="term">Effects:</span></dt> | |
391 | <dd> | |
392 | <p> | |
393 | Atomically call <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">unlock</span><span class="special">()</span></code> and blocks the current fiber. The | |
394 | fiber will unblock when notified by a call to <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">notify_one</span><span class="special">()</span></code> or <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">notify_all</span><span class="special">()</span></code>. When the fiber is unblocked (for | |
395 | whatever reason), the lock is reacquired by invoking <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">lock</span><span class="special">()</span></code> | |
396 | before the call to <code class="computeroutput"><span class="identifier">wait</span></code> | |
397 | returns. The lock is also reacquired by invoking <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">lock</span><span class="special">()</span></code> if the function exits with an exception. | |
398 | The member function accepting <code class="computeroutput"><span class="identifier">pred</span></code> | |
399 | is shorthand for: | |
400 | </p> | |
401 | <pre class="programlisting"><span class="keyword">while</span> <span class="special">(</span> <span class="special">!</span> <span class="identifier">pred</span><span class="special">()</span> <span class="special">)</span> <span class="special">{</span> | |
402 | <span class="identifier">wait</span><span class="special">(</span> <span class="identifier">lk</span><span class="special">);</span> | |
403 | <span class="special">}</span> | |
404 | </pre> | |
405 | <p> | |
406 | </p> | |
407 | </dd> | |
408 | <dt><span class="term">Postcondition:</span></dt> | |
409 | <dd><p> | |
410 | <code class="computeroutput"><span class="identifier">lk</span></code> is locked by the | |
411 | current fiber. | |
412 | </p></dd> | |
413 | <dt><span class="term">Throws:</span></dt> | |
414 | <dd><p> | |
415 | <code class="computeroutput"><span class="identifier">fiber_error</span></code> if an error | |
416 | occurs. | |
417 | </p></dd> | |
418 | <dt><span class="term">Note:</span></dt> | |
419 | <dd><p> | |
420 | The Precondition is a bit dense. It merely states that all the fibers | |
421 | concurrently calling <code class="computeroutput"><span class="identifier">wait</span></code> | |
422 | on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
423 | must wait on <code class="computeroutput"><span class="identifier">lk</span></code> objects | |
424 | governing the <span class="emphasis"><em>same</em></span> <a class="link" href="mutex_types.html#class_mutex"><code class="computeroutput">mutex</code></a>. Three distinct | |
425 | objects are involved in any <code class="computeroutput">condition_variable_any::wait()</code> call: the | |
426 | <code class="computeroutput">condition_variable_any</code> itself, the <code class="computeroutput"><span class="identifier">mutex</span></code> | |
427 | coordinating access between fibers and a local lock object (e.g. <a href="http://en.cppreference.com/w/cpp/thread/unique_lock" target="_top"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_lock</span></code></a>). In general, | |
428 | you can partition the lifespan of a given <code class="computeroutput">condition_variable_any</code> instance | |
429 | into periods with one or more fibers waiting on it, separated by periods | |
430 | when no fibers are waiting on it. When more than one fiber is waiting | |
431 | on that <code class="computeroutput">condition_variable_any</code>, all must pass lock objects referencing | |
432 | the <span class="emphasis"><em>same</em></span> <code class="computeroutput"><span class="identifier">mutex</span></code> | |
433 | instance. | |
434 | </p></dd> | |
435 | </dl> | |
436 | </div> | |
437 | <p> | |
438 | </p> | |
439 | <h5> | |
440 | <a name="condition_variable_any_wait_until_bridgehead"></a> | |
441 | <span><a name="condition_variable_any_wait_until"></a></span> | |
442 | <a class="link" href="conditions.html#condition_variable_any_wait_until">Templated | |
443 | member function <code class="computeroutput">wait_until</code>()</a> | |
444 | </h5> | |
445 | <p> | |
446 | </p> | |
447 | <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> typename LockType, typename <span class="identifier">Clock</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Duration</span> <span class="special">></span> | |
448 | <span class="identifier">cv_status</span> <span class="identifier">wait_until</span><span class="special">(</span> LockType <span class="special">&</span> <span class="identifier">lk</span><span class="special">,</span> | |
449 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">time_point</span><span class="special"><</span> <span class="identifier">Clock</span><span class="special">,</span> <span class="identifier">Duration</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">abs_time</span><span class="special">);</span> | |
450 | ||
451 | <span class="keyword">template</span><span class="special"><</span> typename LockType, typename <span class="identifier">Clock</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Duration</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Pred</span> <span class="special">></span> | |
452 | <span class="keyword">bool</span> <span class="identifier">wait_until</span><span class="special">(</span> LockType <span class="special">&</span> <span class="identifier">lk</span><span class="special">,</span> | |
453 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">time_point</span><span class="special"><</span> <span class="identifier">Clock</span><span class="special">,</span> <span class="identifier">Duration</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">abs_time</span><span class="special">,</span> | |
454 | <span class="identifier">Pred</span> <span class="identifier">pred</span><span class="special">);</span> | |
455 | </pre> | |
456 | <div class="variablelist"> | |
457 | <p class="title"><b></b></p> | |
458 | <dl> | |
459 | <dt><span class="term">Precondition:</span></dt> | |
460 | <dd><p> | |
461 | <code class="computeroutput"><span class="identifier">lk</span></code> is locked by the | |
462 | current fiber, and either no other fiber is currently waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>, | |
463 | or the execution of the <code class="computeroutput"><span class="identifier">mutex</span><span class="special">()</span></code> member function on the <code class="computeroutput"><span class="identifier">lk</span></code> objects supplied in the calls | |
464 | to <code class="computeroutput"><span class="identifier">wait</span></code>, <code class="computeroutput"><span class="identifier">wait_for</span></code> or <code class="computeroutput"><span class="identifier">wait_until</span></code> | |
465 | in all the fibers currently waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> would return the same value as | |
466 | <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">mutex</span><span class="special">()</span></code> | |
467 | for this call to <code class="computeroutput"><span class="identifier">wait_until</span></code>. | |
468 | </p></dd> | |
469 | <dt><span class="term">Effects:</span></dt> | |
470 | <dd> | |
471 | <p> | |
472 | Atomically call <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">unlock</span><span class="special">()</span></code> and blocks the current fiber. The | |
473 | fiber will unblock when notified by a call to <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">notify_one</span><span class="special">()</span></code> or <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">notify_all</span><span class="special">()</span></code>, when the system time would be equal | |
474 | to or later than the specified <code class="computeroutput"><span class="identifier">abs_time</span></code>. | |
475 | When the fiber is unblocked (for whatever reason), the lock is reacquired | |
476 | by invoking <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">lock</span><span class="special">()</span></code> | |
477 | before the call to <code class="computeroutput"><span class="identifier">wait_until</span></code> | |
478 | returns. The lock is also reacquired by invoking <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">lock</span><span class="special">()</span></code> if the function exits with an exception. | |
479 | The member function accepting <code class="computeroutput"><span class="identifier">pred</span></code> | |
480 | is shorthand for: | |
481 | </p> | |
482 | <pre class="programlisting"><span class="keyword">while</span> <span class="special">(</span> <span class="special">!</span> <span class="identifier">pred</span><span class="special">()</span> <span class="special">)</span> <span class="special">{</span> | |
483 | <span class="keyword">if</span> <span class="special">(</span> <span class="identifier">cv_status</span><span class="special">::</span><span class="identifier">timeout</span> <span class="special">==</span> <span class="identifier">wait_until</span><span class="special">(</span> <span class="identifier">lk</span><span class="special">,</span> <span class="identifier">abs_time</span><span class="special">)</span> <span class="special">)</span> | |
484 | <span class="keyword">return</span> <span class="identifier">pred</span><span class="special">();</span> | |
485 | <span class="special">}</span> | |
486 | <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> | |
487 | </pre> | |
488 | <p> | |
489 | That is, even if <code class="computeroutput"><span class="identifier">wait_until</span><span class="special">()</span></code> times out, it can still return <code class="computeroutput"><span class="keyword">true</span></code> if <code class="computeroutput"><span class="identifier">pred</span><span class="special">()</span></code> returns <code class="computeroutput"><span class="keyword">true</span></code> | |
490 | at that time. | |
491 | </p> | |
492 | </dd> | |
493 | <dt><span class="term">Postcondition:</span></dt> | |
494 | <dd><p> | |
495 | <code class="computeroutput"><span class="identifier">lk</span></code> is locked by the | |
496 | current fiber. | |
497 | </p></dd> | |
498 | <dt><span class="term">Throws:</span></dt> | |
499 | <dd><p> | |
500 | <code class="computeroutput"><span class="identifier">fiber_error</span></code> if an error | |
501 | occurs or timeout-related exceptions. | |
502 | </p></dd> | |
503 | <dt><span class="term">Returns:</span></dt> | |
504 | <dd><p> | |
505 | The overload without <code class="computeroutput"><span class="identifier">pred</span></code> | |
506 | returns <code class="computeroutput"><span class="identifier">cv_status</span><span class="special">::</span><span class="identifier">no_timeout</span></code> if awakened by <code class="computeroutput"><span class="identifier">notify_one</span><span class="special">()</span></code> | |
507 | or <code class="computeroutput"><span class="identifier">notify_all</span><span class="special">()</span></code>, | |
508 | or <code class="computeroutput"><span class="identifier">cv_status</span><span class="special">::</span><span class="identifier">timeout</span></code> if awakened because the system | |
509 | time is past <code class="computeroutput"><span class="identifier">abs_time</span></code>. | |
510 | </p></dd> | |
511 | <dt><span class="term">Returns:</span></dt> | |
512 | <dd><p> | |
513 | The overload accepting <code class="computeroutput"><span class="identifier">pred</span></code> | |
514 | returns <code class="computeroutput"><span class="keyword">false</span></code> if the call | |
515 | is returning because the time specified by <code class="computeroutput"><span class="identifier">abs_time</span></code> | |
516 | was reached and the predicate returns <code class="computeroutput"><span class="keyword">false</span></code>, | |
517 | <code class="computeroutput"><span class="keyword">true</span></code> otherwise. | |
518 | </p></dd> | |
519 | <dt><span class="term">Note:</span></dt> | |
520 | <dd><p> | |
521 | See <span class="bold"><strong>Note</strong></span> for <a class="link" href="conditions.html#condition_variable_any_wait"><code class="computeroutput">condition_variable_any::wait()</code></a>. | |
522 | </p></dd> | |
523 | </dl> | |
524 | </div> | |
525 | <p> | |
526 | </p> | |
527 | <h5> | |
528 | <a name="condition_variable_any_wait_for_bridgehead"></a> | |
529 | <span><a name="condition_variable_any_wait_for"></a></span> | |
530 | <a class="link" href="conditions.html#condition_variable_any_wait_for">Templated | |
531 | member function <code class="computeroutput">wait_for</code>()</a> | |
532 | </h5> | |
533 | <p> | |
534 | </p> | |
535 | <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> typename LockType, typename <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Period</span> <span class="special">></span> | |
536 | <span class="identifier">cv_status</span> <span class="identifier">wait_for</span><span class="special">(</span> LockType <span class="special">&</span> <span class="identifier">lk</span><span class="special">,</span> | |
537 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rel_time</span><span class="special">);</span> | |
538 | ||
539 | <span class="keyword">template</span><span class="special"><</span> typename LockType, typename <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Period</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Pred</span> <span class="special">></span> | |
540 | <span class="keyword">bool</span> <span class="identifier">wait_for</span><span class="special">(</span> LockType <span class="special">&</span> <span class="identifier">lk</span><span class="special">,</span> | |
541 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rel_time</span><span class="special">,</span> | |
542 | <span class="identifier">Pred</span> <span class="identifier">pred</span><span class="special">);</span> | |
543 | </pre> | |
544 | <div class="variablelist"> | |
545 | <p class="title"><b></b></p> | |
546 | <dl> | |
547 | <dt><span class="term">Precondition:</span></dt> | |
548 | <dd><p> | |
549 | <code class="computeroutput"><span class="identifier">lk</span></code> is locked by the | |
550 | current fiber, and either no other fiber is currently waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>, | |
551 | or the execution of the <code class="computeroutput"><span class="identifier">mutex</span><span class="special">()</span></code> member function on the <code class="computeroutput"><span class="identifier">lk</span></code> objects supplied in the calls | |
552 | to <code class="computeroutput"><span class="identifier">wait</span></code>, <code class="computeroutput"><span class="identifier">wait_for</span></code> or <code class="computeroutput"><span class="identifier">wait_until</span></code> | |
553 | in all the fibers currently waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> would return the same value as | |
554 | <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">mutex</span><span class="special">()</span></code> | |
555 | for this call to <code class="computeroutput"><span class="identifier">wait_for</span></code>. | |
556 | </p></dd> | |
557 | <dt><span class="term">Effects:</span></dt> | |
558 | <dd> | |
559 | <p> | |
560 | Atomically call <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">unlock</span><span class="special">()</span></code> and blocks the current fiber. The | |
561 | fiber will unblock when notified by a call to <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">notify_one</span><span class="special">()</span></code> or <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">notify_all</span><span class="special">()</span></code>, when a time interval equal to or | |
562 | greater than the specified <code class="computeroutput"><span class="identifier">rel_time</span></code> | |
563 | has elapsed. When the fiber is unblocked (for whatever reason), the | |
564 | lock is reacquired by invoking <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">lock</span><span class="special">()</span></code> before the call to <code class="computeroutput"><span class="identifier">wait</span></code> returns. The lock is also reacquired | |
565 | by invoking <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">lock</span><span class="special">()</span></code> | |
566 | if the function exits with an exception. The <code class="computeroutput"><span class="identifier">wait_for</span><span class="special">()</span></code> member function accepting <code class="computeroutput"><span class="identifier">pred</span></code> is shorthand for: | |
567 | </p> | |
568 | <pre class="programlisting"><span class="keyword">while</span> <span class="special">(</span> <span class="special">!</span> <span class="identifier">pred</span><span class="special">()</span> <span class="special">)</span> <span class="special">{</span> | |
569 | <span class="keyword">if</span> <span class="special">(</span> <span class="identifier">cv_status</span><span class="special">::</span><span class="identifier">timeout</span> <span class="special">==</span> <span class="identifier">wait_for</span><span class="special">(</span> <span class="identifier">lk</span><span class="special">,</span> <span class="identifier">rel_time</span><span class="special">)</span> <span class="special">)</span> <span class="special">{</span> | |
570 | <span class="keyword">return</span> <span class="identifier">pred</span><span class="special">();</span> | |
571 | <span class="special">}</span> | |
572 | <span class="special">}</span> | |
573 | <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> | |
574 | </pre> | |
575 | <p> | |
576 | (except of course that <code class="computeroutput"><span class="identifier">rel_time</span></code> | |
577 | is adjusted for each iteration). The point is that, even if <code class="computeroutput"><span class="identifier">wait_for</span><span class="special">()</span></code> | |
578 | times out, it can still return <code class="computeroutput"><span class="keyword">true</span></code> | |
579 | if <code class="computeroutput"><span class="identifier">pred</span><span class="special">()</span></code> | |
580 | returns <code class="computeroutput"><span class="keyword">true</span></code> at that time. | |
581 | </p> | |
582 | </dd> | |
583 | <dt><span class="term">Postcondition:</span></dt> | |
584 | <dd><p> | |
585 | <code class="computeroutput"><span class="identifier">lk</span></code> is locked by the | |
586 | current fiber. | |
587 | </p></dd> | |
588 | <dt><span class="term">Throws:</span></dt> | |
589 | <dd><p> | |
590 | <code class="computeroutput"><span class="identifier">fiber_error</span></code> if an error | |
591 | occurs or timeout-related exceptions. | |
592 | </p></dd> | |
593 | <dt><span class="term">Returns:</span></dt> | |
594 | <dd><p> | |
595 | The overload without <code class="computeroutput"><span class="identifier">pred</span></code> | |
596 | returns <code class="computeroutput"><span class="identifier">cv_status</span><span class="special">::</span><span class="identifier">no_timeout</span></code> if awakened by <code class="computeroutput"><span class="identifier">notify_one</span><span class="special">()</span></code> | |
597 | or <code class="computeroutput"><span class="identifier">notify_all</span><span class="special">()</span></code>, | |
598 | or <code class="computeroutput"><span class="identifier">cv_status</span><span class="special">::</span><span class="identifier">timeout</span></code> if awakened because at least | |
599 | <code class="computeroutput"><span class="identifier">rel_time</span></code> has elapsed. | |
600 | </p></dd> | |
601 | <dt><span class="term">Returns:</span></dt> | |
602 | <dd><p> | |
603 | The overload accepting <code class="computeroutput"><span class="identifier">pred</span></code> | |
604 | returns <code class="computeroutput"><span class="keyword">false</span></code> if the call | |
605 | is returning because at least <code class="computeroutput"><span class="identifier">rel_time</span></code> | |
606 | has elapsed and the predicate returns <code class="computeroutput"><span class="keyword">false</span></code>, | |
607 | <code class="computeroutput"><span class="keyword">true</span></code> otherwise. | |
608 | </p></dd> | |
609 | <dt><span class="term">Note:</span></dt> | |
610 | <dd><p> | |
611 | See <span class="bold"><strong>Note</strong></span> for <a class="link" href="conditions.html#condition_variable_any_wait"><code class="computeroutput">condition_variable_any::wait()</code></a>. | |
612 | </p></dd> | |
613 | </dl> | |
614 | </div> | |
615 | <p> | |
616 | </p> | |
617 | <h5> | |
618 | <a name="class_condition_variable_bridgehead"></a> | |
619 | <span><a name="class_condition_variable"></a></span> | |
620 | <a class="link" href="conditions.html#class_condition_variable">Class | |
621 | <code class="computeroutput">condition_variable</code></a> | |
622 | </h5> | |
623 | <p> | |
624 | </p> | |
625 | <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fiber</span><span class="special">/</span><span class="identifier">condition_variable</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> | |
626 | ||
627 | <span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> | |
628 | <span class="keyword">namespace</span> <span class="identifier">fibers</span> <span class="special">{</span> | |
629 | ||
630 | <span class="keyword">class</span> condition_variable <span class="special">{</span> | |
631 | <span class="keyword">public</span><span class="special">:</span> | |
632 | condition_variable<span class="special">();</span> | |
633 | <span class="special">~</span>condition_variable<span class="special">();</span> | |
634 | ||
635 | condition_variable<span class="special">(</span> condition_variable <span class="keyword">const</span><span class="special">&)</span> <span class="special">=</span> <span class="keyword">delete</span><span class="special">;</span> | |
636 | condition_variable <span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span> condition_variable <span class="keyword">const</span><span class="special">&)</span> <span class="special">=</span> <span class="keyword">delete</span><span class="special">;</span> | |
637 | ||
638 | <span class="keyword">void</span> <span class="identifier">notify_one</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span> | |
639 | <span class="keyword">void</span> <span class="identifier">notify_all</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span> | |
640 | ||
641 | void <span class="identifier">wait</span><span class="special">(</span> std::unique_lock< mutex > <span class="special">&);</span> | |
642 | ||
643 | <span class="keyword">template</span><span class="special"><</span> typename <span class="identifier">Pred</span> <span class="special">></span> | |
644 | <span class="keyword">void</span> <span class="identifier">wait</span><span class="special">(</span> std::unique_lock< mutex > <span class="special">&,</span> <span class="identifier">Pred</span><span class="special">);</span> | |
645 | ||
646 | <span class="keyword">template</span><span class="special"><</span> typename <span class="identifier">Clock</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Duration</span> <span class="special">></span> | |
647 | <span class="identifier">cv_status</span> <span class="identifier">wait_until</span><span class="special">(</span> std::unique_lock< mutex > <span class="special">&,</span> | |
648 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">time_point</span><span class="special"><</span> <span class="identifier">Clock</span><span class="special">,</span> <span class="identifier">Duration</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&);</span> | |
649 | ||
650 | <span class="keyword">template</span><span class="special"><</span> typename <span class="identifier">Clock</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Duration</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Pred</span> <span class="special">></span> | |
651 | <span class="keyword">bool</span> <span class="identifier">wait_until</span><span class="special">(</span> std::unique_lock< mutex > <span class="special">&,</span> | |
652 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">time_point</span><span class="special"><</span> <span class="identifier">Clock</span><span class="special">,</span> <span class="identifier">Duration</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&,</span> | |
653 | <span class="identifier">Pred</span><span class="special">);</span> | |
654 | ||
655 | <span class="keyword">template</span><span class="special"><</span> typename <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Period</span> <span class="special">></span> | |
656 | <span class="identifier">cv_status</span> <span class="identifier">wait_for</span><span class="special">(</span> std::unique_lock< mutex > <span class="special">&,</span> | |
657 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&);</span> | |
658 | ||
659 | <span class="keyword">template</span><span class="special"><</span> typename <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Period</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Pred</span> <span class="special">></span> | |
660 | <span class="keyword">bool</span> <span class="identifier">wait_for</span><span class="special">(</span> std::unique_lock< mutex > <span class="special">&,</span> | |
661 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&,</span> | |
662 | <span class="identifier">Pred</span><span class="special">);</span> | |
663 | <span class="special">};</span> | |
664 | ||
665 | <span class="special">}}</span> | |
666 | </pre> | |
667 | <h5> | |
668 | <a name="fiber.synchronization.conditions.h7"></a> | |
669 | <span><a name="fiber.synchronization.conditions.constructor0"></a></span><a class="link" href="conditions.html#fiber.synchronization.conditions.constructor0">Constructor</a> | |
670 | </h5> | |
671 | <pre class="programlisting">condition_variable<span class="special">()</span> | |
672 | </pre> | |
673 | <div class="variablelist"> | |
674 | <p class="title"><b></b></p> | |
675 | <dl> | |
676 | <dt><span class="term">Effects:</span></dt> | |
677 | <dd><p> | |
678 | Creates the object. | |
679 | </p></dd> | |
680 | <dt><span class="term">Throws:</span></dt> | |
681 | <dd><p> | |
682 | Nothing. | |
683 | </p></dd> | |
684 | </dl> | |
685 | </div> | |
686 | <h5> | |
687 | <a name="fiber.synchronization.conditions.h8"></a> | |
688 | <span><a name="fiber.synchronization.conditions.destructor0"></a></span><a class="link" href="conditions.html#fiber.synchronization.conditions.destructor0">Destructor</a> | |
689 | </h5> | |
690 | <pre class="programlisting"><span class="special">~</span>condition_variable<span class="special">()</span> | |
691 | </pre> | |
692 | <div class="variablelist"> | |
693 | <p class="title"><b></b></p> | |
694 | <dl> | |
695 | <dt><span class="term">Precondition:</span></dt> | |
696 | <dd><p> | |
697 | All fibers waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> have been notified by a call to | |
698 | <code class="computeroutput"><span class="identifier">notify_one</span></code> or <code class="computeroutput"><span class="identifier">notify_all</span></code> (though the respective | |
699 | calls to <code class="computeroutput"><span class="identifier">wait</span></code>, <code class="computeroutput"><span class="identifier">wait_for</span></code> or <code class="computeroutput"><span class="identifier">wait_until</span></code> | |
700 | need not have returned). | |
701 | </p></dd> | |
702 | <dt><span class="term">Effects:</span></dt> | |
703 | <dd><p> | |
704 | Destroys the object. | |
705 | </p></dd> | |
706 | </dl> | |
707 | </div> | |
708 | <p> | |
709 | </p> | |
710 | <h5> | |
711 | <a name="condition_variable_notify_one_bridgehead"></a> | |
712 | <span><a name="condition_variable_notify_one"></a></span> | |
713 | <a class="link" href="conditions.html#condition_variable_notify_one">Member | |
714 | function <code class="computeroutput">notify_one</code>()</a> | |
715 | </h5> | |
716 | <p> | |
717 | </p> | |
718 | <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">notify_one</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span> | |
719 | </pre> | |
720 | <div class="variablelist"> | |
721 | <p class="title"><b></b></p> | |
722 | <dl> | |
723 | <dt><span class="term">Effects:</span></dt> | |
724 | <dd><p> | |
725 | If any fibers are currently <a class="link" href="../overview.html#blocking"><span class="emphasis"><em>blocked</em></span></a> | |
726 | waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
727 | in a call to <code class="computeroutput"><span class="identifier">wait</span></code>, | |
728 | <code class="computeroutput"><span class="identifier">wait_for</span></code> or <code class="computeroutput"><span class="identifier">wait_until</span></code>, unblocks one of those | |
729 | fibers. | |
730 | </p></dd> | |
731 | <dt><span class="term">Throws:</span></dt> | |
732 | <dd><p> | |
733 | Nothing. | |
734 | </p></dd> | |
735 | <dt><span class="term">Note:</span></dt> | |
736 | <dd><p> | |
737 | It is arbitrary which waiting fiber is resumed. | |
738 | </p></dd> | |
739 | </dl> | |
740 | </div> | |
741 | <p> | |
742 | </p> | |
743 | <h5> | |
744 | <a name="condition_variable_notify_all_bridgehead"></a> | |
745 | <span><a name="condition_variable_notify_all"></a></span> | |
746 | <a class="link" href="conditions.html#condition_variable_notify_all">Member | |
747 | function <code class="computeroutput">notify_all</code>()</a> | |
748 | </h5> | |
749 | <p> | |
750 | </p> | |
751 | <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">notify_all</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span> | |
752 | </pre> | |
753 | <div class="variablelist"> | |
754 | <p class="title"><b></b></p> | |
755 | <dl> | |
756 | <dt><span class="term">Effects:</span></dt> | |
757 | <dd><p> | |
758 | If any fibers are currently <a class="link" href="../overview.html#blocking"><span class="emphasis"><em>blocked</em></span></a> | |
759 | waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
760 | in a call to <code class="computeroutput"><span class="identifier">wait</span></code>, | |
761 | <code class="computeroutput"><span class="identifier">wait_for</span></code> or <code class="computeroutput"><span class="identifier">wait_until</span></code>, unblocks all of those | |
762 | fibers. | |
763 | </p></dd> | |
764 | <dt><span class="term">Throws:</span></dt> | |
765 | <dd><p> | |
766 | Nothing. | |
767 | </p></dd> | |
768 | <dt><span class="term">Note:</span></dt> | |
769 | <dd><p> | |
770 | This is why a waiting fiber must <span class="emphasis"><em>also</em></span> check for | |
771 | the desired program state using a mechanism external to the <code class="computeroutput">condition_variable</code>, | |
772 | and retry the wait until that state is reached. A fiber waiting on | |
773 | a <code class="computeroutput">condition_variable</code> might well wake up a number of times before the | |
774 | desired state is reached. | |
775 | </p></dd> | |
776 | </dl> | |
777 | </div> | |
778 | <p> | |
779 | </p> | |
780 | <h5> | |
781 | <a name="condition_variable_wait_bridgehead"></a> | |
782 | <span><a name="condition_variable_wait"></a></span> | |
783 | <a class="link" href="conditions.html#condition_variable_wait">Templated | |
784 | member function <code class="computeroutput">wait</code>()</a> | |
785 | </h5> | |
786 | <p> | |
787 | </p> | |
788 | <pre class="programlisting">void <span class="identifier">wait</span><span class="special">(</span> std::unique_lock< mutex > <span class="special">&</span> <span class="identifier">lk</span><span class="special">);</span> | |
789 | ||
790 | <span class="keyword">template</span><span class="special"><</span> typename <span class="identifier">Pred</span> <span class="special">></span> | |
791 | <span class="keyword">void</span> <span class="identifier">wait</span><span class="special">(</span> std::unique_lock< mutex > <span class="special">&</span> <span class="identifier">lk</span><span class="special">,</span> <span class="identifier">Pred</span> <span class="identifier">pred</span><span class="special">);</span> | |
792 | </pre> | |
793 | <div class="variablelist"> | |
794 | <p class="title"><b></b></p> | |
795 | <dl> | |
796 | <dt><span class="term">Precondition:</span></dt> | |
797 | <dd><p> | |
798 | <code class="computeroutput"><span class="identifier">lk</span></code> is locked by the | |
799 | current fiber, and either no other fiber is currently waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>, | |
800 | or the execution of the <a href="http://en.cppreference.com/w/cpp/thread/unique_lock/mutex" target="_top"><code class="computeroutput"><span class="identifier">mutex</span><span class="special">()</span></code></a> | |
801 | member function on the <code class="computeroutput"><span class="identifier">lk</span></code> | |
802 | objects supplied in the calls to <code class="computeroutput"><span class="identifier">wait</span></code> | |
803 | in all the fibers currently waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> would return the same value as | |
804 | <code class="computeroutput"><span class="identifier">lk</span><span class="special">-></span><span class="identifier">mutex</span><span class="special">()</span></code> | |
805 | for this call to <code class="computeroutput"><span class="identifier">wait</span></code>. | |
806 | </p></dd> | |
807 | <dt><span class="term">Effects:</span></dt> | |
808 | <dd> | |
809 | <p> | |
810 | Atomically call <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">unlock</span><span class="special">()</span></code> and blocks the current fiber. The | |
811 | fiber will unblock when notified by a call to <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">notify_one</span><span class="special">()</span></code> or <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">notify_all</span><span class="special">()</span></code>. When the fiber is unblocked (for | |
812 | whatever reason), the lock is reacquired by invoking <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">lock</span><span class="special">()</span></code> | |
813 | before the call to <code class="computeroutput"><span class="identifier">wait</span></code> | |
814 | returns. The lock is also reacquired by invoking <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">lock</span><span class="special">()</span></code> if the function exits with an exception. | |
815 | The member function accepting <code class="computeroutput"><span class="identifier">pred</span></code> | |
816 | is shorthand for: | |
817 | </p> | |
818 | <pre class="programlisting"><span class="keyword">while</span> <span class="special">(</span> <span class="special">!</span> <span class="identifier">pred</span><span class="special">()</span> <span class="special">)</span> <span class="special">{</span> | |
819 | <span class="identifier">wait</span><span class="special">(</span> <span class="identifier">lk</span><span class="special">);</span> | |
820 | <span class="special">}</span> | |
821 | </pre> | |
822 | <p> | |
823 | </p> | |
824 | </dd> | |
825 | <dt><span class="term">Postcondition:</span></dt> | |
826 | <dd><p> | |
827 | <code class="computeroutput"><span class="identifier">lk</span></code> is locked by the | |
828 | current fiber. | |
829 | </p></dd> | |
830 | <dt><span class="term">Throws:</span></dt> | |
831 | <dd><p> | |
832 | <code class="computeroutput"><span class="identifier">fiber_error</span></code> if an error | |
833 | occurs. | |
834 | </p></dd> | |
835 | <dt><span class="term">Note:</span></dt> | |
836 | <dd><p> | |
837 | The Precondition is a bit dense. It merely states that all the fibers | |
838 | concurrently calling <code class="computeroutput"><span class="identifier">wait</span></code> | |
839 | on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
840 | must wait on <code class="computeroutput"><span class="identifier">lk</span></code> objects | |
841 | governing the <span class="emphasis"><em>same</em></span> <a class="link" href="mutex_types.html#class_mutex"><code class="computeroutput">mutex</code></a>. Three distinct | |
842 | objects are involved in any <code class="computeroutput">condition_variable::wait()</code> call: the <code class="computeroutput">condition_variable</code> itself, | |
843 | the <code class="computeroutput"><span class="identifier">mutex</span></code> coordinating | |
844 | access between fibers and a local lock object (e.g. <a href="http://en.cppreference.com/w/cpp/thread/unique_lock" target="_top"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_lock</span></code></a>). In general, | |
845 | you can partition the lifespan of a given <code class="computeroutput">condition_variable</code> instance | |
846 | into periods with one or more fibers waiting on it, separated by periods | |
847 | when no fibers are waiting on it. When more than one fiber is waiting | |
848 | on that <code class="computeroutput">condition_variable</code>, all must pass lock objects referencing | |
849 | the <span class="emphasis"><em>same</em></span> <code class="computeroutput"><span class="identifier">mutex</span></code> | |
850 | instance. | |
851 | </p></dd> | |
852 | </dl> | |
853 | </div> | |
854 | <p> | |
855 | </p> | |
856 | <h5> | |
857 | <a name="condition_variable_wait_until_bridgehead"></a> | |
858 | <span><a name="condition_variable_wait_until"></a></span> | |
859 | <a class="link" href="conditions.html#condition_variable_wait_until">Templated | |
860 | member function <code class="computeroutput">wait_until</code>()</a> | |
861 | </h5> | |
862 | <p> | |
863 | </p> | |
864 | <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> typename <span class="identifier">Clock</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Duration</span> <span class="special">></span> | |
865 | <span class="identifier">cv_status</span> <span class="identifier">wait_until</span><span class="special">(</span> std::unique_lock< mutex > <span class="special">&</span> <span class="identifier">lk</span><span class="special">,</span> | |
866 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">time_point</span><span class="special"><</span> <span class="identifier">Clock</span><span class="special">,</span> <span class="identifier">Duration</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">abs_time</span><span class="special">);</span> | |
867 | ||
868 | <span class="keyword">template</span><span class="special"><</span> typename <span class="identifier">Clock</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Duration</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Pred</span> <span class="special">></span> | |
869 | <span class="keyword">bool</span> <span class="identifier">wait_until</span><span class="special">(</span> std::unique_lock< mutex > <span class="special">&</span> <span class="identifier">lk</span><span class="special">,</span> | |
870 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">time_point</span><span class="special"><</span> <span class="identifier">Clock</span><span class="special">,</span> <span class="identifier">Duration</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">abs_time</span><span class="special">,</span> | |
871 | <span class="identifier">Pred</span> <span class="identifier">pred</span><span class="special">);</span> | |
872 | </pre> | |
873 | <div class="variablelist"> | |
874 | <p class="title"><b></b></p> | |
875 | <dl> | |
876 | <dt><span class="term">Precondition:</span></dt> | |
877 | <dd><p> | |
878 | <code class="computeroutput"><span class="identifier">lk</span></code> is locked by the | |
879 | current fiber, and either no other fiber is currently waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>, | |
880 | or the execution of the <code class="computeroutput"><span class="identifier">mutex</span><span class="special">()</span></code> member function on the <code class="computeroutput"><span class="identifier">lk</span></code> objects supplied in the calls | |
881 | to <code class="computeroutput"><span class="identifier">wait</span></code>, <code class="computeroutput"><span class="identifier">wait_for</span></code> or <code class="computeroutput"><span class="identifier">wait_until</span></code> | |
882 | in all the fibers currently waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> would return the same value as | |
883 | <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">mutex</span><span class="special">()</span></code> | |
884 | for this call to <code class="computeroutput"><span class="identifier">wait_until</span></code>. | |
885 | </p></dd> | |
886 | <dt><span class="term">Effects:</span></dt> | |
887 | <dd> | |
888 | <p> | |
889 | Atomically call <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">unlock</span><span class="special">()</span></code> and blocks the current fiber. The | |
890 | fiber will unblock when notified by a call to <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">notify_one</span><span class="special">()</span></code> or <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">notify_all</span><span class="special">()</span></code>, when the system time would be equal | |
891 | to or later than the specified <code class="computeroutput"><span class="identifier">abs_time</span></code>. | |
892 | When the fiber is unblocked (for whatever reason), the lock is reacquired | |
893 | by invoking <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">lock</span><span class="special">()</span></code> | |
894 | before the call to <code class="computeroutput"><span class="identifier">wait_until</span></code> | |
895 | returns. The lock is also reacquired by invoking <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">lock</span><span class="special">()</span></code> if the function exits with an exception. | |
896 | The member function accepting <code class="computeroutput"><span class="identifier">pred</span></code> | |
897 | is shorthand for: | |
898 | </p> | |
899 | <pre class="programlisting"><span class="keyword">while</span> <span class="special">(</span> <span class="special">!</span> <span class="identifier">pred</span><span class="special">()</span> <span class="special">)</span> <span class="special">{</span> | |
900 | <span class="keyword">if</span> <span class="special">(</span> <span class="identifier">cv_status</span><span class="special">::</span><span class="identifier">timeout</span> <span class="special">==</span> <span class="identifier">wait_until</span><span class="special">(</span> <span class="identifier">lk</span><span class="special">,</span> <span class="identifier">abs_time</span><span class="special">)</span> <span class="special">)</span> | |
901 | <span class="keyword">return</span> <span class="identifier">pred</span><span class="special">();</span> | |
902 | <span class="special">}</span> | |
903 | <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> | |
904 | </pre> | |
905 | <p> | |
906 | That is, even if <code class="computeroutput"><span class="identifier">wait_until</span><span class="special">()</span></code> times out, it can still return <code class="computeroutput"><span class="keyword">true</span></code> if <code class="computeroutput"><span class="identifier">pred</span><span class="special">()</span></code> returns <code class="computeroutput"><span class="keyword">true</span></code> | |
907 | at that time. | |
908 | </p> | |
909 | </dd> | |
910 | <dt><span class="term">Postcondition:</span></dt> | |
911 | <dd><p> | |
912 | <code class="computeroutput"><span class="identifier">lk</span></code> is locked by the | |
913 | current fiber. | |
914 | </p></dd> | |
915 | <dt><span class="term">Throws:</span></dt> | |
916 | <dd><p> | |
917 | <code class="computeroutput"><span class="identifier">fiber_error</span></code> if an error | |
918 | occurs or timeout-related exceptions. | |
919 | </p></dd> | |
920 | <dt><span class="term">Returns:</span></dt> | |
921 | <dd><p> | |
922 | The overload without <code class="computeroutput"><span class="identifier">pred</span></code> | |
923 | returns <code class="computeroutput"><span class="identifier">cv_status</span><span class="special">::</span><span class="identifier">no_timeout</span></code> if awakened by <code class="computeroutput"><span class="identifier">notify_one</span><span class="special">()</span></code> | |
924 | or <code class="computeroutput"><span class="identifier">notify_all</span><span class="special">()</span></code>, | |
925 | or <code class="computeroutput"><span class="identifier">cv_status</span><span class="special">::</span><span class="identifier">timeout</span></code> if awakened because the system | |
926 | time is past <code class="computeroutput"><span class="identifier">abs_time</span></code>. | |
927 | </p></dd> | |
928 | <dt><span class="term">Returns:</span></dt> | |
929 | <dd><p> | |
930 | The overload accepting <code class="computeroutput"><span class="identifier">pred</span></code> | |
931 | returns <code class="computeroutput"><span class="keyword">false</span></code> if the call | |
932 | is returning because the time specified by <code class="computeroutput"><span class="identifier">abs_time</span></code> | |
933 | was reached and the predicate returns <code class="computeroutput"><span class="keyword">false</span></code>, | |
934 | <code class="computeroutput"><span class="keyword">true</span></code> otherwise. | |
935 | </p></dd> | |
936 | <dt><span class="term">Note:</span></dt> | |
937 | <dd><p> | |
938 | See <span class="bold"><strong>Note</strong></span> for <a class="link" href="conditions.html#condition_variable_wait"><code class="computeroutput">condition_variable::wait()</code></a>. | |
939 | </p></dd> | |
940 | </dl> | |
941 | </div> | |
942 | <p> | |
943 | </p> | |
944 | <h5> | |
945 | <a name="condition_variable_wait_for_bridgehead"></a> | |
946 | <span><a name="condition_variable_wait_for"></a></span> | |
947 | <a class="link" href="conditions.html#condition_variable_wait_for">Templated | |
948 | member function <code class="computeroutput">wait_for</code>()</a> | |
949 | </h5> | |
950 | <p> | |
951 | </p> | |
952 | <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> typename <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Period</span> <span class="special">></span> | |
953 | <span class="identifier">cv_status</span> <span class="identifier">wait_for</span><span class="special">(</span> std::unique_lock< mutex > <span class="special">&</span> <span class="identifier">lk</span><span class="special">,</span> | |
954 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rel_time</span><span class="special">);</span> | |
955 | ||
956 | <span class="keyword">template</span><span class="special"><</span> typename <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Period</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Pred</span> <span class="special">></span> | |
957 | <span class="keyword">bool</span> <span class="identifier">wait_for</span><span class="special">(</span> std::unique_lock< mutex > <span class="special">&</span> <span class="identifier">lk</span><span class="special">,</span> | |
958 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span> <span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rel_time</span><span class="special">,</span> | |
959 | <span class="identifier">Pred</span> <span class="identifier">pred</span><span class="special">);</span> | |
960 | </pre> | |
961 | <div class="variablelist"> | |
962 | <p class="title"><b></b></p> | |
963 | <dl> | |
964 | <dt><span class="term">Precondition:</span></dt> | |
965 | <dd><p> | |
966 | <code class="computeroutput"><span class="identifier">lk</span></code> is locked by the | |
967 | current fiber, and either no other fiber is currently waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>, | |
968 | or the execution of the <code class="computeroutput"><span class="identifier">mutex</span><span class="special">()</span></code> member function on the <code class="computeroutput"><span class="identifier">lk</span></code> objects supplied in the calls | |
969 | to <code class="computeroutput"><span class="identifier">wait</span></code>, <code class="computeroutput"><span class="identifier">wait_for</span></code> or <code class="computeroutput"><span class="identifier">wait_until</span></code> | |
970 | in all the fibers currently waiting on <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> would return the same value as | |
971 | <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">mutex</span><span class="special">()</span></code> | |
972 | for this call to <code class="computeroutput"><span class="identifier">wait_for</span></code>. | |
973 | </p></dd> | |
974 | <dt><span class="term">Effects:</span></dt> | |
975 | <dd> | |
976 | <p> | |
977 | Atomically call <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">unlock</span><span class="special">()</span></code> and blocks the current fiber. The | |
978 | fiber will unblock when notified by a call to <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">notify_one</span><span class="special">()</span></code> or <code class="computeroutput"><span class="keyword">this</span><span class="special">-></span><span class="identifier">notify_all</span><span class="special">()</span></code>, when a time interval equal to or | |
979 | greater than the specified <code class="computeroutput"><span class="identifier">rel_time</span></code> | |
980 | has elapsed. When the fiber is unblocked (for whatever reason), the | |
981 | lock is reacquired by invoking <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">lock</span><span class="special">()</span></code> before the call to <code class="computeroutput"><span class="identifier">wait</span></code> returns. The lock is also reacquired | |
982 | by invoking <code class="computeroutput"><span class="identifier">lk</span><span class="special">.</span><span class="identifier">lock</span><span class="special">()</span></code> | |
983 | if the function exits with an exception. The <code class="computeroutput"><span class="identifier">wait_for</span><span class="special">()</span></code> member function accepting <code class="computeroutput"><span class="identifier">pred</span></code> is shorthand for: | |
984 | </p> | |
985 | <pre class="programlisting"><span class="keyword">while</span> <span class="special">(</span> <span class="special">!</span> <span class="identifier">pred</span><span class="special">()</span> <span class="special">)</span> <span class="special">{</span> | |
986 | <span class="keyword">if</span> <span class="special">(</span> <span class="identifier">cv_status</span><span class="special">::</span><span class="identifier">timeout</span> <span class="special">==</span> <span class="identifier">wait_for</span><span class="special">(</span> <span class="identifier">lk</span><span class="special">,</span> <span class="identifier">rel_time</span><span class="special">)</span> <span class="special">)</span> <span class="special">{</span> | |
987 | <span class="keyword">return</span> <span class="identifier">pred</span><span class="special">();</span> | |
988 | <span class="special">}</span> | |
989 | <span class="special">}</span> | |
990 | <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> | |
991 | </pre> | |
992 | <p> | |
993 | (except of course that <code class="computeroutput"><span class="identifier">rel_time</span></code> | |
994 | is adjusted for each iteration). The point is that, even if <code class="computeroutput"><span class="identifier">wait_for</span><span class="special">()</span></code> | |
995 | times out, it can still return <code class="computeroutput"><span class="keyword">true</span></code> | |
996 | if <code class="computeroutput"><span class="identifier">pred</span><span class="special">()</span></code> | |
997 | returns <code class="computeroutput"><span class="keyword">true</span></code> at that time. | |
998 | </p> | |
999 | </dd> | |
1000 | <dt><span class="term">Postcondition:</span></dt> | |
1001 | <dd><p> | |
1002 | <code class="computeroutput"><span class="identifier">lk</span></code> is locked by the | |
1003 | current fiber. | |
1004 | </p></dd> | |
1005 | <dt><span class="term">Throws:</span></dt> | |
1006 | <dd><p> | |
1007 | <code class="computeroutput"><span class="identifier">fiber_error</span></code> if an error | |
1008 | occurs or timeout-related exceptions. | |
1009 | </p></dd> | |
1010 | <dt><span class="term">Returns:</span></dt> | |
1011 | <dd><p> | |
1012 | The overload without <code class="computeroutput"><span class="identifier">pred</span></code> | |
1013 | returns <code class="computeroutput"><span class="identifier">cv_status</span><span class="special">::</span><span class="identifier">no_timeout</span></code> if awakened by <code class="computeroutput"><span class="identifier">notify_one</span><span class="special">()</span></code> | |
1014 | or <code class="computeroutput"><span class="identifier">notify_all</span><span class="special">()</span></code>, | |
1015 | or <code class="computeroutput"><span class="identifier">cv_status</span><span class="special">::</span><span class="identifier">timeout</span></code> if awakened because at least | |
1016 | <code class="computeroutput"><span class="identifier">rel_time</span></code> has elapsed. | |
1017 | </p></dd> | |
1018 | <dt><span class="term">Returns:</span></dt> | |
1019 | <dd><p> | |
1020 | The overload accepting <code class="computeroutput"><span class="identifier">pred</span></code> | |
1021 | returns <code class="computeroutput"><span class="keyword">false</span></code> if the call | |
1022 | is returning because at least <code class="computeroutput"><span class="identifier">rel_time</span></code> | |
1023 | has elapsed and the predicate returns <code class="computeroutput"><span class="keyword">false</span></code>, | |
1024 | <code class="computeroutput"><span class="keyword">true</span></code> otherwise. | |
1025 | </p></dd> | |
1026 | <dt><span class="term">Note:</span></dt> | |
1027 | <dd><p> | |
1028 | See <span class="bold"><strong>Note</strong></span> for <a class="link" href="conditions.html#condition_variable_wait"><code class="computeroutput">condition_variable::wait()</code></a>. | |
1029 | </p></dd> | |
1030 | </dl> | |
1031 | </div> | |
1032 | </div> | |
1033 | <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> | |
1034 | <td align="left"></td> | |
1035 | <td align="right"><div class="copyright-footer">Copyright © 2013 Oliver Kowalke<p> | |
1036 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
1037 | file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) | |
1038 | </p> | |
1039 | </div></td> | |
1040 | </tr></table> | |
1041 | <hr> | |
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