92 lines
7.2 KiB
HTML
92 lines
7.2 KiB
HTML
<!DOCTYPE html>
|
|
<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
|
|
<head><meta http-equiv="x-ua-compatible" content="ie=edge">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<title>std::basic_istream<CharT,Traits>::basic_istream</title>
|
|
<link rel="stylesheet" href="ext.css" />
|
|
<link rel="stylesheet" href="site_modules.css" />
|
|
</head>
|
|
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_basic_istream_basic_istream skin-cppreference2 action-view cpp-navbar">
|
|
<div id="cpp-content-base">
|
|
<div id="content"><a id="top"></a>
|
|
<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::basic_istream<CharT,Traits>::</span>basic_istream</h1>
|
|
<div id="bodyContent">
|
|
<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-io.html">io</a>‎ | <a href="cpp-io-basic_istream.html">basic istream</a></span></div>
|
|
<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
|
|
<table class="t-dcl-begin">
|
|
<tbody>
|
|
<tr class="t-dcl">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">explicit</span> basic_istream<span class="br0">(</span> <a href="cpp-io-basic_streambuf.html"><span class="kw1666">std::<span class="me2">basic_streambuf</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span><span class="sy2">*</span> sb<span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td>(1)</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
</tr>
|
|
<tr class="t-dcl t-since-cxx11">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">protected</span><span class="sy4">:</span><br />
|
|
basic_istream<span class="br0">(</span> <span class="kw4">const</span> basic_istream<span class="sy3">&</span> rhs <span class="br0">)</span> <span class="sy1">=</span> delete<span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td>(2)</td>
|
|
<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl t-since-cxx11">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">protected</span><span class="sy4">:</span><br />
|
|
basic_istream<span class="br0">(</span> basic_istream<span class="sy3">&&</span> rhs <span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td>(3)</td>
|
|
<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl-sep">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>1) 构造 <code>basic_istream</code> 对象，通过调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">basic_ios<span class="sy4">::</span><span class="me2">init</span><span class="br0">(</span>sb<span class="br0">)</span></span></span> 赋初始值给基类。初始化 <code>gcount()</code> 的值为零。</p>
|
|
<p>2) 复制构造函数为受保护，且被删除。输入流不可复制。</p>
|
|
<p>3) 移动构造函数从 <code>rhs</code> 复制 <code>gcount()</code> 的值，设置 rhs 的 gcount() 值为零，并使用 <code>basic_ios<CharT, Traits>::move(rhs)</code> 从 <code>rhs</code> 移动所有 basic_ios 成员，除了 <code>rdbuf()</code> 到 <code>*this</code> 中。此移动构造函数受保护：它为可移动输入流类 <span class="t-lc"><a href="cpp-io-basic_ifstream.html">std::basic_ifstream</a></span> 和 <span class="t-lc"><a href="cpp-io-basic_istringstream.html">std::basic_istringstream</a></span> 的移动构造函数调用，它们知道如何正确地移动关联流缓冲。</p>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
|
|
<table class="t-par-begin">
|
|
<tr class="t-par">
|
|
<td>sb</td>
|
|
<td>-</td>
|
|
<td>用作底层设备的流缓冲</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
|
<div class="t-example">
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <sstream></span>
|
|
<span class="co2">#include <iostream></span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-io-basic_istringstream.html"><span class="kw1735">std::<span class="me2">istringstream</span></span></a> s1<span class="br0">(</span><span class="st0">"hello"</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-basic_istream.html"><span class="kw1727">std::<span class="me2">istream</span></span></a> s2<span class="br0">(</span>s1.<span class="me1">rdbuf</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// OK ： s2 与 s1 共享缓冲</span>
|
|
|
|
<span class="co1">// std::istream s3(std::istringstream("test")); // 错误：移动构造函数为受保护</span>
|
|
<span class="co1">// std::istream s4(s2); // 错误：复制构造函数被删除</span>
|
|
<a href="cpp-io-basic_istringstream.html"><span class="kw1735">std::<span class="me2">istringstream</span></span></a> s5<span class="br0">(</span><a href="cpp-io-basic_istringstream.html"><span class="kw1735">std::<span class="me2">istringstream</span></span></a><span class="br0">(</span><span class="st0">"world"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// OK ：导出类调用移动构造函数</span>
|
|
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> s2.<span class="me1">rdbuf</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">' '</span> <span class="sy1"><<</span> s5.<span class="me1">rdbuf</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">hello world</pre></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|