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<header data-kunai-mdinfo="{"meta": {"header": ["condition_variable"], "namespace": ["std"], "class": ["condition_variable_any"], "id-type": ["function template"], "cpp": ["cpp11"]}, "sources": [{"id": "320c8ce95a1c3a4aba634ed1eaa6f35e73340eaa", "source": "#include <iostream>\n#include <condition_variable>\n#include <mutex>\n#include <thread>\n\nstruct ProcessData {\n std::recursive_mutex mtx_;\n std::condition_variable_any cond_;\n\n bool data_ready_ = false;\n\npublic:\n // \u51e6\u7406\u306b\u5fc5\u8981\u306a\u30c7\u30fc\u30bf\u306e\u6e96\u5099\u3092\u3059\u308b\n void prepare_data_for_processing()\n {\n // ...\u6e96\u5099\u51e6\u7406...\n\n {\n std::lock_guard<std::recursive_mutex> lk(mtx_);\n data_ready_ = true;\n }\n\n // \u6e96\u5099\u5b8c\u4e86\u3057\u305f\u306e\u3067\u5f85\u6a5f\u30b9\u30ec\u30c3\u30c9\u3092\u5168\u3066\u8d77\u5e8a\u3055\u305b\u308b\n cond_.notify_all();\n }\n\n void wait_for_data_to_process1()\n {\n std::unique_lock<std::recursive_mutex> lk(mtx_);\n\n // \u30c7\u30fc\u30bf\u306e\u6e96\u5099\u304c\u3067\u304d\u308b\u307e\u3067\u5f85\u6a5f\u3057\u3066\u304b\u3089\u51e6\u7406\u3059\u308b\n while (!data_ready_) {\n // \u8ff0\u8a9e\u3092\u6307\u5b9a\u3057\u306a\u3044\u30d0\u30fc\u30b8\u30e7\u30f3\n cond_.wait(lk);\n }\n process_data();\n }\n\n void wait_for_data_to_process2()\n {\n std::unique_lock<std::recursive_mutex> lk(mtx_);\n\n // \u30c7\u30fc\u30bf\u306e\u6e96\u5099\u304c\u3067\u304d\u308b\u307e\u3067\u5f85\u6a5f\u3057\u3066\u304b\u3089\u51e6\u7406\u3059\u308b\n\n // \u8ff0\u8a9e\u3092\u6307\u5b9a\u3059\u308b\u30d0\u30fc\u30b8\u30e7\u30f3\n cond_.wait(lk, [this] { return data_ready_; });\n process_data();\n }\n\nprivate:\n void process_data()\n {\n // ...\u30c7\u30fc\u30bf\u3092\u51e6\u7406\u3059\u308b...\n std::cout << \"process data\" << std::endl;\n }\n};\n\nint main()\n{\n ProcessData p;\n\n std::thread t1([&] { p.prepare_data_for_processing(); });\n std::thread t2([&] { p.wait_for_data_to_process1(); });\n std::thread t3([&] { p.wait_for_data_to_process2(); });\n\n t1.join();\n t2.join();\n t3.join();\n}\n"}], "page_id": ["reference", "condition_variable", "condition_variable_any", "wait"]}">
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<div class="identifier-type">function template</div><div class="header"><condition_variable></div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="class" title="class condition_variable_any">condition_variable_any::</span><span class="token">wait</span><span class="cpp cpp11" title="C++11で追加">(C++11)</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Lock</span><span class="o">></span>
<span class="kt">void</span><span class="w"> </span><span class="n">wait</span><span class="p">(</span><span class="n">Lock</span><span class="o">&</span><span class="w"> </span><span class="n">lock</span><span class="p">);</span><span class="w"> </span><span class="c1">// (1)</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Lock</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Predicate</span><span class="o">></span>
<span class="kt">void</span><span class="w"> </span><span class="n">wait</span><span class="p">(</span><span class="n">Lock</span><span class="o">&</span><span class="w"> </span><span class="n">lock</span><span class="p">,</span><span class="w"> </span><span class="n">Predicate</span><span class="w"> </span><span class="n">pred</span><span class="p">);</span><span class="w"> </span><span class="c1">// (2)</span>
<span class="k">template</span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Lock</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Predicate</span><span class="o">></span>
<span class="kt">bool</span><span class="w"> </span><span class="n">wait</span><span class="p">(</span><span class="n">Lock</span><span class="o">&</span><span class="w"> </span><span class="n">lock</span><span class="p">,</span>
<span class="w"> </span><span class="n"><a href="../../stop_token/stop_token.html">stop_token</a></span><span class="w"> </span><span class="n">stoken</span><span class="p">,</span>
<span class="w"> </span><span class="n">Predicate</span><span class="w"> </span><span class="n">pred</span><span class="p">);</span><span class="w"> </span><span class="c1">// (3) C++20 から</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p>起床されるまで待機する。</p>
<p>この関数は、処理をするための準備ができたことを<code>notify_one()</code>/<code>notify_all()</code>によって通知されるまでスレッドを待機するために使用する。</p>
<p><a class="cpprefjp-defined-word" data-desc="boolを返す関数・関数オブジェクト。predicate">述語</a>を指定しない場合、<code>notify_one()</code>/<code>notify_all()</code>が呼び出された時点でこの関数のブロッキングが解除される。</p>
<p><a class="cpprefjp-defined-word" data-desc="boolを返す関数・関数オブジェクト。predicate">述語</a>を指定する場合、<a class="cpprefjp-defined-word" data-desc="boolを返す関数・関数オブジェクト。predicate">述語</a>呼び出しが<code>true</code>になるまで待機を続行する。</p>
<h2>効果</h2>
<ul>
<li>
<p>(1) :</p>
<ul>
<li>アトミックに<code>lock.<a href="../../mutex/unique_lock/unlock.html">unlock()</a></code>する</li>
<li><code><a href="notify_one.html">notify_one()</a></code>/<code><a href="notify_all.html">notify_all()</a></code>もしくはそれ以外の理由で通知があるまでブロッキングする</li>
<li>この関数を抜ける際に<code>lock.<a href="../../mutex/unique_lock/lock.html">lock()</a></code>する</li>
<li>この関数が<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>送出によって終了する場合、関数を抜ける前に<code>lock.<a href="../../mutex/unique_lock/lock.html">lock()</a></code>する</li>
</ul>
</li>
<li>
<p>(2) : 以下と等価の処理を行う</p>
</li>
</ul>
<p><div class="codehilite"><pre><span></span><code><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">pred</span><span class="p">())</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">wait</span><span class="p">(</span><span class="n">lock</span><span class="p">);</span>
<span class="p">}</span>
</code></pre></div>
</p>
<ul>
<li>(3) : このメンバ関数呼び出しの間だけ<code>stoken</code>に対する停止要求によって<code>*this</code>へ通知が行われるよう登録し、以下と等価の処理を行う</li>
</ul>
<p><div class="codehilite"><pre><span></span><code><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">stoken</span><span class="p">.</span><span class="n"><a href="../../stop_token/stop_token/stop_requested.html">stop_requested()</a></span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pred</span><span class="p">())</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="nb">true</span><span class="p">;</span>
<span class="w"> </span><span class="n">wait</span><span class="p">(</span><span class="n">lock</span><span class="p">);</span>
<span class="p">}</span>
<span class="k">return</span><span class="w"> </span><span class="n">pred</span><span class="p">();</span>
</code></pre></div>
</p>
<h2><a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Postconditions。関数を実行後に満たされている条件。契約属性の`[[ensures]]`に相当">事後条件</a></h2>
<p><code>lock</code>が参照しているミューテックスオブジェクトが、この関数を呼び出したスレッドでロック取得されていること</p>
<h2><a class="cpprefjp-defined-word" data-desc="関数呼び出し式の評価結果となるオブジェクト・値">戻り値</a></h2>
<ul>
<li>(1), (2) : なし</li>
<li>(3) : 停止要求の有無によらず、<code>pred()</code>の結果が返る。</li>
</ul>
<h2><a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a></h2>
<ul>
<li>(1) :<ul>
<li>C++11まで : この関数は、<code>lock.<a href="../../mutex/unique_lock/lock.html">lock()</a></code>および<code>lock.<a href="../../mutex/unique_lock/unlock.html">unlock()</a></code>によって送出されうる、あらゆる<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>が送出される可能性がある。</li>
<li>C++14 : 投げない</li>
</ul>
</li>
<li>(2) : <ul>
<li>C++11まで : この関数は、<code>lock.<a href="../../mutex/unique_lock/lock.html">lock()</a></code>および<code>lock.<a href="../../mutex/unique_lock/unlock.html">unlock()</a></code>によって送出されうる、あらゆる<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>が送出される可能性がある。</li>
<li>C++14 : <code>pred()</code>により送出された<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>。</li>
</ul>
</li>
<li>(3) :<ul>
<li><code>pred()</code>により送出された<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>。</li>
</ul>
</li>
</ul>
<h2>備考</h2>
<ul>
<li>C++14 : <a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Postconditions。関数を実行後に満たされている条件。契約属性の`[[ensures]]`に相当">事後条件</a>を満たさない場合、<code><a href="../../exception/terminate.html">std::terminate()</a></code>関数を呼び出して、プログラムを異常終了させる。これは、ミューテックスの再ロック取得が<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を送出した場合に発生する。</li>
</ul>
<h2>例</h2>
<p><div class="yata" id="320c8ce95a1c3a4aba634ed1eaa6f35e73340eaa"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../../condition_variable.html"><condition_variable></a></span>
<span class="cp">#include <a href="../../mutex.html"><mutex></a></span>
<span class="cp">#include <a href="../../thread.html"><thread></a></span>
<span class="k">struct</span><span class="w"> </span><span class="nc">ProcessData</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../../mutex/recursive_mutex.html">std::recursive_mutex</a></span><span class="w"> </span><span class="n">mtx_</span><span class="p">;</span>
<span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">condition_variable_any</span><span class="w"> </span><span class="n">cond_</span><span class="p">;</span>
<span class="w"> </span><span class="kt">bool</span><span class="w"> </span><span class="n">data_ready_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">false</span><span class="p">;</span>
<span class="k">public</span><span class="o">:</span>
<span class="w"> </span><span class="c1">// 処理に必要なデータの準備をする</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">prepare_data_for_processing</span><span class="p">()</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// ...準備処理...</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../../mutex/lock_guard.html">std::lock_guard</a></span><span class="o"><</span><span class="n"><a href="../../mutex/recursive_mutex.html">std::recursive_mutex</a></span><span class="o">></span><span class="w"> </span><span class="n">lk</span><span class="p">(</span><span class="n">mtx_</span><span class="p">);</span>
<span class="w"> </span><span class="n">data_ready_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">true</span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">// 準備完了したので待機スレッドを全て起床させる</span>
<span class="w"> </span><span class="n"><a href="notify_all.html">cond_.notify_all()</a></span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">wait_for_data_to_process1</span><span class="p">()</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../../mutex/unique_lock.html">std::unique_lock</a></span><span class="o"><</span><span class="n"><a href="../../mutex/recursive_mutex.html">std::recursive_mutex</a></span><span class="o">></span><span class="w"> </span><span class="n">lk</span><span class="p">(</span><span class="n">mtx_</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// データの準備ができるまで待機してから処理する</span>
<span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">data_ready_</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// 述語を指定しないバージョン</span>
<span class="w"> </span><span class="n">cond_</span><span class="p">.</span><span class="n"><span style="color:#ff0000">wait</span></span><span class="p">(</span><span class="n">lk</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n">process_data</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">wait_for_data_to_process2</span><span class="p">()</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../../mutex/unique_lock.html">std::unique_lock</a></span><span class="o"><</span><span class="n"><a href="../../mutex/recursive_mutex.html">std::recursive_mutex</a></span><span class="o">></span><span class="w"> </span><span class="n">lk</span><span class="p">(</span><span class="n">mtx_</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// データの準備ができるまで待機してから処理する</span>
<span class="w"> </span><span class="c1">// 述語を指定するバージョン</span>
<span class="w"> </span><span class="n">cond_</span><span class="p">.</span><span class="n"><span style="color:#ff0000">wait</span></span><span class="p">(</span><span class="n">lk</span><span class="p">,</span><span class="w"> </span><span class="p">[</span><span class="k">this</span><span class="p">]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">data_ready_</span><span class="p">;</span><span class="w"> </span><span class="p">});</span>
<span class="w"> </span><span class="n">process_data</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="k">private</span><span class="o">:</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">process_data</span><span class="p">()</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// ...データを処理する...</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"process data"</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">};</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w"> </span><span class="n">ProcessData</span><span class="w"> </span><span class="n">p</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../thread/thread.html">std::thread</a></span><span class="w"> </span><span class="n">t1</span><span class="p">([</span><span class="o">&</span><span class="p">]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">p</span><span class="p">.</span><span class="n">prepare_data_for_processing</span><span class="p">();</span><span class="w"> </span><span class="p">});</span>
<span class="w"> </span><span class="n"><a href="../../thread/thread.html">std::thread</a></span><span class="w"> </span><span class="n">t2</span><span class="p">([</span><span class="o">&</span><span class="p">]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">p</span><span class="p">.</span><span class="n">wait_for_data_to_process1</span><span class="p">();</span><span class="w"> </span><span class="p">});</span>
<span class="w"> </span><span class="n"><a href="../../thread/thread.html">std::thread</a></span><span class="w"> </span><span class="n">t3</span><span class="p">([</span><span class="o">&</span><span class="p">]</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">p</span><span class="p">.</span><span class="n">wait_for_data_to_process2</span><span class="p">();</span><span class="w"> </span><span class="p">});</span>
<span class="w"> </span><span class="n"><a href="../../thread/thread/join.html">t1.join()</a></span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../thread/thread/join.html">t2.join()</a></span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../thread/thread/join.html">t3.join()</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h3>出力</h3>
<p><pre><code>process data
process data
</code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++11</li>
</ul>
<h3>処理系</h3>
<ul>
<li><a href="../../../implementation.html#clang">Clang</a>: 9.0.1 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../../implementation.html#gcc">GCC</a>: 4.7.0 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../../implementation.html#visual_cpp">Visual C++</a>: 2012 <span aria-label="検証済" role="img" title="検証済">✅</span>, 2013 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
</ul>
<h2>参照</h2>
<ul>
<li><a href="https://cplusplus.github.io/LWG/issue1222" target="_blank">LWG Issue 1222. <code>condition_variable</code> incorrect effects for exception safety</a><ul>
<li>C++11で、<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>送出によってこの関数を抜ける場合に呼び出されるのが<code>lock.unlock()</code>ではなく<code>lock.<a href="../../mutex/unique_lock/lock.html">lock()</a></code>であると修正された</li>
</ul>
</li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2093" target="_blank">LWG Issue 2093. Throws clause of <code>condition_variable::wait</code> with predicate</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p0660r10.pdf" target="_blank">P0660R10 Stop Token and Joining Thread, Rev 10</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1869r1.html" target="_blank">P1869R1 Rename <code>condition_variable_any</code> interruptible wait methods</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2135" target="_blank">LWG Issue 2135. Unclear requirement for exceptions thrown in <code>condition_variable::wait()</code></a></li>
</ul></div>
</div>
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