112 lines
7.0 KiB
HTML
112 lines
7.0 KiB
HTML
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<title>std::pmr::polymorphic_allocator<T>::allocate_bytes</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::pmr::polymorphic_allocator<T>::</span>allocate_bytes</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-memory.html">memory</a>‎ | <a href="cpp-memory-polymorphic_allocator.html">polymorphic allocator</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="br0">[</span><span class="br0">[</span>nodiscard<span class="br0">]</span><span class="br0">]</span> <span class="kw4">void</span><span class="sy2">*</span> allocate_bytes<span class="br0">(</span> <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> nbytes,<br />
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<a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> alignment <span class="sy1">=</span> alignof<span class="br0">(</span><a href="cpp-types-max_align_t.html"><span class="kw104">std::<span class="me2">max_align_t</span></span></a><span class="br0">)</span> <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<p>分配按指定 <code>alignment</code> 对齐的 <code>nbytes</code> 字节存储。等价于 <code>return resource()->allocate(nbytes, alignment);</code> 。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<td>nbytes</td>
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<td>-</td>
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<td>要分配的字节数</td>
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<td>alignment</td>
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<td>-</td>
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<td>使用的对齐</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E">返回</span></h3>
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<p>指向分配的存储的指针。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p>引入此函数是为了用于全特化分配器 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">polymorphic_allocator</span><span class="sy1"><></span></span></span> ，但它可能在任何特化中都有用。</p>
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<p>返回类型为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span><span class="sy2">*</span></span></span> （而非 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">byte</span><span class="sy2">*</span></span></span> 之类），以支持通过 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">static_cast</span><span class="sy1"><</span>U<span class="sy2">*</span><span class="sy1">></span></span></span> 转换到任意指针类型 <span class="t-c"><span class="mw-geshi cpp source-cpp">U<span class="sy2">*</span></span></span> 。</p>
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<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
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<p>可能抛出任何调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">resource<span class="br0">(</span><span class="br0">)</span><span class="sy2">-</span><span class="sy1">></span>allocate</span></span> 所抛的异常。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<div class="t-dsc-member-div">
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<div><a href="cpp-memory-polymorphic_allocator-allocate_object.html"><span class="t-lines"><span>allocate_object</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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</div>
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</td>
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<td>分配适合单个对象或数组的未处理内存<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-memory-polymorphic_allocator-new_object.html"><span class="t-lines"><span>new_object</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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</div>
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</td>
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<td>分配并创建对象<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-memory-polymorphic_allocator-allocate.html"><span class="t-lines"><span>allocate</span></span></a></div>
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</td>
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<td>分配内存<br />
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<span class="t-mark">(公开成员函数)</span></td>
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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-memory-allocator_traits-allocate.html"><span class="t-lines"><span>allocate</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-cmark">[静态]</span></span></span></div>
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</div>
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</td>
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<td>用分配器分配未初始化的存储<br />
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<span class="t-mark">(<code>std::allocator_traits<Alloc></code> 的公开静态成员函数)</span></td>
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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-memory-memory_resource-allocate.html"><span class="t-lines"><span>allocate</span></span></a></div>
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</td>
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<td>分配内存<br />
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<span class="t-mark">(<code>std::pmr::memory_resource</code> 的公开成员函数)</span></td>
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