92 lines
5.7 KiB
HTML
92 lines
5.7 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::char_traits<CharT>::length</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_string_char_traits_length 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::char_traits<CharT>::</span>length</h1>
|
|
<div id="bodyContent">
|
|
<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-string.html">string</a>‎ | <a href="cpp-string-char_traits.html">char traits</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></tbody>
|
|
<tbody class="t-dcl-rev">
|
|
<tr class="t-dcl t-until-cxx17">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">static</span> <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> length<span class="br0">(</span> <span class="kw4">const</span> char_type<span class="sy2">*</span> s <span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td><span class="t-mark-rev t-until-cxx17">(C++17 前)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl t-since-cxx17">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">static</span> <span class="kw4">constexpr</span> <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> length<span class="br0">(</span> <span class="kw4">const</span> char_type<span class="sy2">*</span> s <span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
|
|
</tr>
|
|
</tbody>
|
|
<tbody>
|
|
<tr class="t-dcl-sep">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>返回 <code>s</code> 所指的字符序列长度，即空终止字符（ <span class="t-c"><span class="mw-geshi cpp source-cpp">CharT<span class="br0">(</span><span class="br0">)</span></span></span> ）的位置。</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>s</td>
|
|
<td>-</td>
|
|
<td>指向要返回长度的字符序列的指针</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
|
|
<p><code>s</code> 所指向字符序列的长度。</p>
|
|
<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
|
|
<p>不抛出。</p>
|
|
<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">复杂度</span></h3>
|
|
<p>线性。</p>
|
|
<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 <iostream></span>
|
|
|
|
<span class="kw4">void</span> print<span class="br0">(</span><span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> str<span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"string '"</span> <span class="sy1"><<</span> str <span class="sy1"><<</span> <span class="st0">"' "</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"length = "</span> <span class="sy1"><<</span> <a href="cpp-string-char_traits.html"><span class="kw1267">std::<span class="me2">char_traits</span></span></a><span class="sy1"><</span><span class="kw4">char</span><span class="sy1">></span><span class="sy4">::</span><span class="me2">length</span><span class="br0">(</span>str<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>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
print<span class="br0">(</span><span class="st0">"foo"</span><span class="br0">)</span><span class="sy4">;</span>
|
|
|
|
<a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> s<span class="br0">(</span><span class="st0">"booo"</span><span class="br0">)</span><span class="sy4">;</span>
|
|
print<span class="br0">(</span>s.<span class="me1">c_str</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</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">string 'foo' length = 3
|
|
string 'booo' length = 4</pre></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|