127 lines
10 KiB
HTML
127 lines
10 KiB
HTML
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<title>std::get_temporary_buffer</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_memory_get_temporary_buffer skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>get_temporary_buffer</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-memory.html">memory</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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<div>定义于头文件 <code><a href="cpp-header-memory.html"><memory></a></code></div>
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<td></td>
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<td></td>
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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> T <span class="sy1">></span><br /></span>
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<p><a href="cpp-utility-pair.html"><span class="kw1095">std::<span class="me2">pair</span></span></a><span class="sy1"><</span>T<span class="sy2">*</span>, <a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a><span class="sy1">></span><br /></p>
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get_temporary_buffer<span class="br0">(</span> <a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a> count <span class="br0">)</span><span class="sy4">;</span></div>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx11">(C++11 前)</span></td>
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<tr class="t-dcl t-since-cxx11 t-until-cxx20">
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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> T <span class="sy1">></span><br /></span>
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<p><a href="cpp-utility-pair.html"><span class="kw1095">std::<span class="me2">pair</span></span></a><span class="sy1"><</span>T<span class="sy2">*</span>, <a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a><span class="sy1">></span><br /></p>
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get_temporary_buffer<span class="br0">(</span> <a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a> count <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></div>
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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><br />
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<span class="t-mark">(C++17 中弃用)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></td>
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<p>分配未初始化的相接存储，它应足以存储至多 <code>count</code> 个 <code>T</code> 类型的相邻对象。要求是非绑定的，且实现可以分配少于或多于存储 <code>count</code> 个相邻对象所需的内存。</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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<table class="t-par-begin">
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<tr class="t-par">
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<td>count</td>
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<td>-</td>
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<td>所需的对象数量</td>
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</table>
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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>一个 <span class="t-lc"><a href="cpp-utility-pair.html">std::pair</a></span> ，保有指向被分配存储起始的指针，和适合在实际分配的存储中的对象数。</p>
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<p>若无法分配内存，或若分配的存储不足以存储单个 <code>T</code> 类型元素，则结果的 <code>first</code> 元素为空指针且 <code>second</code> 元素为零。</p>
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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-template-editlink" style=""></div>
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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 <algorithm></span>
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<span class="co2">#include <iostream></span>
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<span class="co2">#include <memory></span>
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<span class="co2">#include <string></span>
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<span class="co2">#include <iterator></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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<span class="kw4">const</span> <a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a> s<span class="br0">[</span><span class="br0">]</span> <span class="sy1">=</span> <span class="br0">{</span><span class="st0">"string"</span>, <span class="st0">"1"</span>, <span class="st0">"test"</span>, <span class="st0">"..."</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">const</span> <span class="kw4">auto</span> p <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">get_temporary_buffer</span><span class="sy1"><</span><a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a><span class="sy1">></span><span class="br0">(</span><span class="nu0">4</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// 要求将 p.first 传递给 return_temporary_buffer</span>
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<span class="co1">// （当心提前退出和异常）</span>
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<a href="cpp-algorithm-copy.html"><span class="kw1581">std::<span class="me2">copy</span></span></a><span class="br0">(</span>s, s <span class="sy2">+</span> p.<span class="me1">second</span>,
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<a href="cpp-memory-raw_storage_iterator.html"><span class="kw730">std::<span class="me2">raw_storage_iterator</span></span></a><span class="sy1"><</span><a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a><span class="sy2">*</span>, <a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a><span class="sy1">></span><span class="br0">(</span>p.<span class="me1">first</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// 要求单独销毁每个 p 中的 string</span>
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<span class="co1">// （当心提前退出和异常）</span>
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<a href="cpp-algorithm-copy.html"><span class="kw1581">std::<span class="me2">copy</span></span></a><span class="br0">(</span>p.<span class="me1">first</span>, p.<span class="me1">first</span> <span class="sy2">+</span> p.<span class="me1">second</span>,
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<a href="cpp-iterator-ostream_iterator.html"><span class="kw670">std::<span class="me2">ostream_iterator</span></span></a><span class="sy1"><</span><a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a><span class="sy1">></span><span class="br0">{</span><a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a>, <span class="st0">"<span class="es1">\n</span>"</span><span class="br0">}</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-algorithm-for_each.html"><span class="kw1567">std::<span class="me2">for_each</span></span></a><span class="br0">(</span>p.<span class="me1">first</span>, p.<span class="me1">first</span> <span class="sy2">+</span> p.<span class="me1">second</span>, <span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a><span class="sy3">&</span> e<span class="br0">)</span> <span class="br0">{</span>
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e.~basic_string<span class="sy1"><</span><span class="kw4">char</span><span class="sy1">></span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-memory-return_temporary_buffer.html"><span class="kw731">std::<span class="me2">return_temporary_buffer</span></span></a><span class="br0">(</span>p.<span class="me1">first</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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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">string
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1
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test
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...</pre></div>
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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-return_temporary_buffer.html"><span class="t-lines"><span>return_temporary_buffer</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-deprecated-cxx17">(C++17 中弃用)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span></span></div>
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</div>
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</td>
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<td>释放未初始化存储<br />
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<span class="t-mark">(函数模板)</span></td>
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