300 lines
19 KiB
HTML
300 lines
19 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<head><meta http-equiv="x-ua-compatible" content="ie=edge">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>std::unique_lock</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_thread_unique_lock skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>unique_lock</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-thread.html">thread</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<table class="t-dcl-begin">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-mutex.html"><mutex></a></code></div>
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<td></td>
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<td></td>
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<tr class="t-dcl t-since-cxx11">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Mutex <span class="sy1">></span><br />
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<span class="kw1">class</span> unique_lock<span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<tr class="t-dcl-sep">
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<td></td>
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<p>类 <span class="t-c"><span class="mw-geshi cpp source-cpp">unique_lock</span></span> 是通用互斥包装器，允许延迟锁定、锁定的有时限尝试、递归锁定、所有权转移和与条件变量一同使用。</p>
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<p>类 <span class="t-c"><span class="mw-geshi cpp source-cpp">unique_lock</span></span> 可移动，但不可复制——它满足<a href="cpp-named_req-MoveConstructible.html"><span style="font-style:italic">可移动构造</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(MoveConstructible)</span></a> 和<a href="cpp-named_req-MoveAssignable.html"><span style="font-style:italic">可移动赋值</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(MoveAssignable)</span></a> 但不满足<a href="cpp-named_req-CopyConstructible.html"><span style="font-style:italic">可复制构造</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(CopyConstructible)</span></a> 或<a href="cpp-named_req-CopyAssignable.html"><span style="font-style:italic">可复制赋值</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(CopyAssignable)</span></a> 。</p>
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<p>类 <span class="t-c"><span class="mw-geshi cpp source-cpp">unique_lock</span></span> 满足<a href="cpp-named_req-BasicLockable.html"><span style="font-style:italic">基本可锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(BasicLockable)</span></a> 要求。若 <b>Mutex</b> 满足<a href="cpp-named_req-Lockable.html"><span style="font-style:italic">可锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(Lockable)</span></a> 要求，则 <span class="t-c"><span class="mw-geshi cpp source-cpp">unique_lock</span></span> 亦满足<a href="cpp-named_req-Lockable.html"><span style="font-style:italic">可锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(Lockable)</span></a> 要求（例如：能用于 <span class="t-lc"><a href="cpp-thread-lock.html">std::lock</a></span> ） ；若 <b>Mutex</b> 满足<a href="cpp-named_req-TimedLockable.html"><span style="font-style:italic">可定时锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(TimedLockable)</span></a> 要求，则 <span class="t-c"><span class="mw-geshi cpp source-cpp">unique_lock</span></span> 亦满足<a href="cpp-named_req-TimedLockable.html"><span style="font-style:italic">可定时锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(TimedLockable)</span></a> 要求。</p>
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<h3><span class="mw-headline" id=".E6.A8.A1.E6.9D.BF.E5.BD.A2.E5.8F.82">模板形参</span></h3>
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<table class="t-par-begin">
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<tr class="t-par">
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<td>Mutex</td>
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<td>-</td>
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<td>要锁定的互斥类型。类型必须满足<a href="cpp-named_req-BasicLockable.html"><span style="font-style:italic">基本可锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(BasicLockable)</span></a> 要求</td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E7.B1.BB.E5.9E.8B">成员类型</span></h3>
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<table class="t-dsc-begin">
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<tr class="t-dsc-hitem">
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<td>类型</td>
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<td>定义</td>
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</tr>
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<tr class="t-dsc">
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<td><code>mutex_type</code></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">Mutex</span></span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">成员函数</span></h3>
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<table class="t-dsc-begin">
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<td>
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
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<div><a href="cpp-thread-unique_lock-unique_lock.html"><span class="t-lines"><span>(构造函数)</span></span></a></div>
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</div>
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</td>
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<td>构造 <code>unique_lock</code> ，可选地锁定提供的互斥<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
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<div><a href="cpp-thread-unique_lock-~unique_lock.html"><span class="t-lines"><span>(析构函数)</span></span></a></div>
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</div>
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</td>
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<td>若占有关联互斥，则解锁之<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-unique_lock-operator=.html"><span class="t-lines"><span>operator=</span></span></a></div>
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</div>
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</td>
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<td>若占有则解锁互斥，并取得另一者的所有权<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr>
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<td colspan="2">
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<h5><span class="mw-headline" id=".E9.94.81.E5.AE.9A">锁定</span></h5>
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</td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-unique_lock-lock.html"><span class="t-lines"><span>lock</span></span></a></div>
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</div>
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</td>
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<td>锁定关联互斥<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-unique_lock-try_lock.html"><span class="t-lines"><span>try_lock</span></span></a></div>
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</div>
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</td>
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<td>尝试锁定关联互斥，若互斥不可用则返回<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-unique_lock-try_lock_for.html"><span class="t-lines"><span>try_lock_for</span></span></a></div>
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</div>
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</td>
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<td>试图锁定关联的<a href="cpp-named_req-TimedLockable.html"><span style="font-style:italic">可定时锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(TimedLockable)</span></a> 互斥，若互斥在给定时长中不可用则返回<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-unique_lock-try_lock_until.html"><span class="t-lines"><span>try_lock_until</span></span></a></div>
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</div>
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</td>
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<td>尝试锁定关联<a href="cpp-named_req-TimedLockable.html"><span style="font-style:italic">可定时锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(TimedLockable)</span></a> 互斥，若抵达指定时间点互斥仍不可用则返回<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-unique_lock-unlock.html"><span class="t-lines"><span>unlock</span></span></a></div>
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</div>
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</td>
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<td>解锁关联互斥<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr>
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<td colspan="2">
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<h5><span class="mw-headline" id=".E4.BF.AE.E6.94.B9.E5.99.A8">修改器</span></h5>
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</td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-unique_lock-swap.html"><span class="t-lines"><span>swap</span></span></a></div>
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</div>
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</td>
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<td>与另一 <span class="t-lc"><strong class="selflink">std::unique_lock</strong></span> 交换状态<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-unique_lock-release.html"><span class="t-lines"><span>release</span></span></a></div>
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</div>
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</td>
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<td>将关联互斥解关联而不解锁它<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr>
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<td colspan="2">
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<h5><span class="mw-headline" id=".E8.A7.82.E5.AF.9F.E5.99.A8">观察器</span></h5>
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</td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-unique_lock-mutex.html"><span class="t-lines"><span>mutex</span></span></a></div>
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</div>
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</td>
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<td>返回指向关联互斥的指针<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-unique_lock-owns_lock.html"><span class="t-lines"><span>owns_lock</span></span></a></div>
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</div>
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</td>
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<td>测试锁是否占有其关联互斥<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-unique_lock-operator_bool.html"><span class="t-lines"><span>operator bool</span></span></a></div>
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</div>
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</td>
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<td>测试锁是否占有其关联互斥<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E9.9D.9E.E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">非成员函数</span></h3>
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<table class="t-dsc-begin">
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-unique_lock-swap2.html"><span class="t-lines"><span>std::swap<span class="t-dsc-small">(std::unique_lock)</span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td><span class="t-lc"><a href="cpp-algorithm-swap.html">std::swap</a></span> 对 <code>unique_lock</code> 的特化<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example">
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <mutex></span>
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<span class="co2">#include <thread></span>
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<span class="co2">#include <chrono></span>
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<span class="kw1">struct</span> Box <span class="br0">{</span>
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<span class="kw1">explicit</span> Box<span class="br0">(</span><span class="kw4">int</span> num<span class="br0">)</span> <span class="sy4">:</span> num_things<span class="br0">{</span>num<span class="br0">}</span> <span class="br0">{</span><span class="br0">}</span>
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<span class="kw4">int</span> num_things<span class="sy4">;</span>
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<a href="cpp-thread-mutex.html"><span class="kw2154">std::<span class="me2">mutex</span></span></a> m<span class="sy4">;</span>
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<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">void</span> transfer<span class="br0">(</span>Box <span class="sy3">&</span>from, Box <span class="sy3">&</span>to, <span class="kw4">int</span> num<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="co1">// 仍未实际取锁</span>
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std<span class="sy4">::</span><span class="me2">unique_lock</span><span class="sy1"><</span><a href="cpp-thread-mutex.html"><span class="kw2154">std::<span class="me2">mutex</span></span></a><span class="sy1">></span> lock1<span class="br0">(</span>from.<span class="me1">m</span>, <a href="cpp-thread-lock_tag.html"><span class="kw2163">std::<span class="me2">defer_lock</span></span></a><span class="br0">)</span><span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">unique_lock</span><span class="sy1"><</span><a href="cpp-thread-mutex.html"><span class="kw2154">std::<span class="me2">mutex</span></span></a><span class="sy1">></span> lock2<span class="br0">(</span>to.<span class="me1">m</span>, <a href="cpp-thread-lock_tag.html"><span class="kw2163">std::<span class="me2">defer_lock</span></span></a><span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// 锁两个 unique_lock 而不死锁</span>
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<a href="cpp-thread-lock.html"><span class="kw2168">std::<span class="me2">lock</span></span></a><span class="br0">(</span>lock1, lock2<span class="br0">)</span><span class="sy4">;</span>
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from.<span class="me1">num_things</span> <span class="sy2">-</span><span class="sy1">=</span> num<span class="sy4">;</span>
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to.<span class="me1">num_things</span> <span class="sy2">+</span><span class="sy1">=</span> num<span class="sy4">;</span>
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<span class="co1">// 'from.m' 与 'to.m' 互斥解锁于 'unique_lock' 析构函数</span>
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<span class="br0">}</span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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Box acc1<span class="br0">(</span><span class="nu0">100</span><span class="br0">)</span><span class="sy4">;</span>
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Box acc2<span class="br0">(</span><span class="nu0">50</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-thread-thread.html"><span class="kw2146">std::<span class="me2">thread</span></span></a> t1<span class="br0">(</span>transfer, <a href="cpp-utility-functional-ref.html"><span class="kw1069">std::<span class="me2">ref</span></span></a><span class="br0">(</span>acc1<span class="br0">)</span>, <a href="cpp-utility-functional-ref.html"><span class="kw1069">std::<span class="me2">ref</span></span></a><span class="br0">(</span>acc2<span class="br0">)</span>, <span class="nu0">10</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-thread-thread.html"><span class="kw2146">std::<span class="me2">thread</span></span></a> t2<span class="br0">(</span>transfer, <a href="cpp-utility-functional-ref.html"><span class="kw1069">std::<span class="me2">ref</span></span></a><span class="br0">(</span>acc2<span class="br0">)</span>, <a href="cpp-utility-functional-ref.html"><span class="kw1069">std::<span class="me2">ref</span></span></a><span class="br0">(</span>acc1<span class="br0">)</span>, <span class="nu0">5</span><span class="br0">)</span><span class="sy4">;</span>
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t1.<span class="me1">join</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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t2.<span class="me1">join</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">缺陷报告</span></h3>
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<p>下列更改行为的缺陷报告追溯地应用于以前出版的 C++ 标准。</p>
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<table class="dsctable" style="font-size:0.8em">
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<tr>
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<th>DR</th>
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<th>应用于</th>
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<th>出版时的行为</th>
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<th>正确行为</th>
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</tr>
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<tr>
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<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue2981">LWG 2981</a></td>
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<td>C++17</td>
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<td>曾提供来自 <code>unique_lock<Mutex></code> 的冗余推导指引</td>
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<td>已移除</td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-lock_guard.html"><span class="t-lines"><span>lock_guard</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>实现严格基于作用域的互斥体所有权包装器<br />
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<span class="t-mark">(类模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-scoped_lock.html"><span class="t-lines"><span>scoped_lock</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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</div>
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</td>
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<td>用于多个互斥体的免死锁 RAII 封装器<br />
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<span class="t-mark">(类模板)</span></td>
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</tr>
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</table>
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</div>
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<div class="visualClear"></div>
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</div>
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</div>
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</div>
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</body>
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</html>
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