68 lines
5.0 KiB
HTML
68 lines
5.0 KiB
HTML
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<title>std::pmr::monotonic_buffer_resource::do_allocate</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::pmr::monotonic_buffer_resource::</span>do_allocate</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-monotonic_buffer_resource.html">monotonic buffer resource</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">virtual</span> <span class="kw4">void</span><span class="sy2">*</span> do_allocate<span class="br0">(</span><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> bytes, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> alignment<span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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<p>分配存储</p>
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<p>若<i>当前缓冲区</i>足以不使用空间以适合一个拥有指定大小和对齐的块，则从当前缓冲区分配返回的块。</p>
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<p>否则，此函数通过调用 <code>upstream_resource()->allocate(n, m)</code> 分配新缓冲区，其中 <code>n</code> 不小于<code>bytes</code> 与<i>下个缓冲区大小</i>的较大者，且 <code>m</code> 不小于 <code>alignment</code> 。它设置新缓冲区为<i>当前缓冲区</i>，以实现定义的增长因子（不必是整数）增加<i>下个缓冲区大小</i>，然后从新分配的缓冲区分配返回块。</p>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p>指向至少 <code>bytes</code> 字节大小的指针，若支持该对齐则对齐到指定的 <code>alignment</code> ，否则对齐到 <span class="t-c"><span class="mw-geshi cpp source-cpp">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></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>不抛出任何异常，除非上游 memory_resource 的 <code>allocate()</code> 抛出。</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-memory_resource-allocate.html"><span class="t-lines"><span>allocate</span></span></a></div>
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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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<div><a href="cpp-memory-memory_resource-do_allocate.html"><span class="t-lines"><span>do_allocate</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-cmark">[虚]</span></span></span></div>
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<td>分配内存<br />
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<span class="t-mark">(<code>std::pmr::memory_resource</code> 的虚私有成员函数)</span></td>
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