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Merge string_ref doc changes to release
[SVN r82490]
This commit is contained in:
Marshall Clow
parent
856b01240a
commit
1730c1319b
@ -43,7 +43,7 @@ using quickbook ;
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path-constant boost-images : ../../../doc/src/images ;
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path-constant boost-images : ../../../doc/src/images ;
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xml declval : declval.qbk ;
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xml declval : declval.qbk ;
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boostbook standalone
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boostbook standalone_declval
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:
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:
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declval
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declval
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:
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:
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@ -63,7 +63,7 @@ boostbook standalone
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;
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;
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xml string_ref : string_ref.qbk ;
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xml string_ref : string_ref.qbk ;
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boostbook standalone
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boostbook standalone_string_ref
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:
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:
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string_ref
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string_ref
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:
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:
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@ -79,5 +79,5 @@ boostbook standalone
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<xsl:param>toc.max.depth=1
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<xsl:param>toc.max.depth=1
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# How far down we go with TOC's
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# How far down we go with TOC's
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<xsl:param>generate.section.toc.level=1
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<xsl:param>generate.section.toc.level=1
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;
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;
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280
doc/html/string_ref.html
Normal file
280
doc/html/string_ref.html
Normal file
@ -0,0 +1,280 @@
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
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<title>String_Ref</title>
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<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css">
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<meta name="generator" content="DocBook XSL Stylesheets V1.75.2">
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<link rel="home" href="string_ref.html" title="String_Ref">
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</head>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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<table cellpadding="2" width="100%"><tr>
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<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td>
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<td align="center"><a href="../../../../index.html">Home</a></td>
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<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td>
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<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
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<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
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<td align="center"><a href="../../../../more/index.htm">More</a></td>
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</tr></table>
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<hr>
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<div class="spirit-nav"></div>
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<div class="article">
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<div class="titlepage">
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<div>
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<div><h2 class="title">
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<a name="string_ref"></a>String_Ref</h2></div>
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<div><div class="authorgroup"><div class="author"><h3 class="author">
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<span class="firstname">Marshall</span> <span class="surname">Clow</span>
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</h3></div></div></div>
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<div><p class="copyright">Copyright © 2012 Marshall Clow</p></div>
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<div><div class="legalnotice">
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<a name="string_ref.legal"></a><p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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</p>
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</div></div>
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</div>
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<hr>
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</div>
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<div class="toc">
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<p><b>Table of Contents</b></p>
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<dl>
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<dt><span class="section"><a href="string_ref.html#string_ref.overview">Overview</a></span></dt>
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<dt><span class="section"><a href="string_ref.html#string_ref.examples">Examples</a></span></dt>
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<dt><span class="section"><a href="string_ref.html#string_ref.reference">Reference </a></span></dt>
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<dt><span class="section"><a href="string_ref.html#string_ref.history">History</a></span></dt>
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</dl>
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</div>
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<div class="section string_ref_overview">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="string_ref.overview"></a><a class="link" href="string_ref.html#string_ref.overview" title="Overview">Overview</a>
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</h2></div></div></div>
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<p>
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Boost.StringRef is an implementation of Jeffrey Yaskin's <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3442.html" target="_top">N3442:
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string_ref: a non-owning reference to a string</a>.
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</p>
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<p>
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When you are parsing/processing strings from some external source, frequently
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you want to pass a piece of text to a procedure for specialized processing.
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The canonical way to do this is as a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code>,
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but that has certain drawbacks:
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</p>
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<p>
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1) If you are processing a buffer of text (say a HTTP response or the contents
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of a file), then you have to create the string from the text you want to pass,
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which involves memory allocation and copying of data.
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</p>
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<p>
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2) if a routine receives a constant <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code>
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and wants to pass a portion of that string to another routine, then it must
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create a new string of that substring.
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</p>
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<p>
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3) A routine receives a constant <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code>
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and wants to return a portion of the string, then it must create a new string
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to return.
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</p>
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<p>
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<code class="computeroutput"><span class="identifier">string_ref</span></code> is designed to solve
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these efficiency problems. A <code class="computeroutput"><span class="identifier">string_ref</span></code>
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is a read-only reference to a contiguous sequence of characters, and provides
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much of the functionality of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code>.
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A <code class="computeroutput"><span class="identifier">string_ref</span></code> is cheap to create,
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copy and pass by value, because it does not actually own the storage that it
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points to.
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</p>
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<p>
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A <code class="computeroutput"><span class="identifier">string_ref</span></code> is implemented
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as a small struct that contains a pointer to the start of the character data
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and a count. A <code class="computeroutput"><span class="identifier">string_ref</span></code> is
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cheap to create and cheap to copy.
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</p>
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<p>
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<code class="computeroutput"><span class="identifier">string_ref</span></code> acts as a container;
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it includes all the methods that you would expect in a container, including
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iteration support, <code class="computeroutput"><span class="keyword">operator</span> <span class="special">[]</span></code>,
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<code class="computeroutput"><span class="identifier">at</span></code> and <code class="computeroutput"><span class="identifier">size</span></code>.
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It can be used with any of the iterator-based algorithms in the STL - as long
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as you don't need to change the underlying data (<code class="computeroutput"><span class="identifier">sort</span></code>
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and <code class="computeroutput"><span class="identifier">remove</span></code>, for example, will
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not work)
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</p>
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<p>
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Besides generic container functionality, <code class="computeroutput"><span class="identifier">string_ref</span></code>
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provides a subset of the interface of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code>.
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This makes it easy to replace parameters of type <code class="computeroutput"><span class="keyword">const</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&</span></code>
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with <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">string_ref</span></code>. Like <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code>,
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<code class="computeroutput"><span class="identifier">string_ref</span></code> has a static member
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variable named <code class="computeroutput"><span class="identifier">npos</span></code> to denote
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the result of failed searches, and to mean "the end".
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</p>
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<p>
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Because a <code class="computeroutput"><span class="identifier">string_ref</span></code> does not
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own the data that it "points to", it introduces lifetime issues into
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code that uses it. The programmer must ensure that the data that a <code class="computeroutput"><span class="identifier">string_ref</span></code> refers to exists as long as the
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<code class="computeroutput"><span class="identifier">string_ref</span></code> does.
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</p>
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</div>
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<div class="section string_ref_examples">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="string_ref.examples"></a><a class="link" href="string_ref.html#string_ref.examples" title="Examples">Examples</a>
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</h2></div></div></div>
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<p>
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Integrating <code class="computeroutput"><span class="identifier">string_ref</span></code> into
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your code is fairly simple. Wherever you pass a <code class="computeroutput"><span class="keyword">const</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&</span></code>
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or <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code> as a parameter, that's a candidate
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for passing a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">string_ref</span></code>.
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</p>
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<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">extract_part</span> <span class="special">(</span> <span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&</span><span class="identifier">bar</span> <span class="special">)</span> <span class="special">{</span>
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<span class="keyword">return</span> <span class="identifier">bar</span><span class="special">.</span><span class="identifier">substr</span> <span class="special">(</span> <span class="number">2</span><span class="special">,</span> <span class="number">3</span> <span class="special">);</span>
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<span class="special">}</span>
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<span class="keyword">if</span> <span class="special">(</span> <span class="identifier">extract_part</span> <span class="special">(</span> <span class="string">"ABCDEFG"</span> <span class="special">).</span><span class="identifier">front</span><span class="special">()</span> <span class="special">==</span> <span class="string">"C"</span> <span class="special">)</span> <span class="special">{</span> <span class="comment">/* do something */</span> <span class="special">}</span>
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</pre>
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<p>
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Let's figure out what happens in this (contrived) example.
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</p>
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<p>
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First, a temporary string is created from the string literal <code class="computeroutput"><span class="string">"ABCDEFG"</span></code>, and it is passed (by reference)
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to the routine <code class="computeroutput"><span class="identifier">extract_part</span></code>.
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Then a second string is created in the call <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">::</span><span class="identifier">substr</span></code>
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and returned to <code class="computeroutput"><span class="identifier">extract_part</span></code>
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(this copy may be elided by RVO). Then <code class="computeroutput"><span class="identifier">extract_part</span></code>
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returns that string back to the caller (again this copy may be elided). The
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first temporary string is deallocated, and <code class="computeroutput"><span class="identifier">front</span></code>
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is called on the second string, and then it is deallocated as well.
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</p>
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<p>
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Two <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code>s are created, and two copy operations.
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That's (potentially) four memory allocations and deallocations, and the associated
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copying of data.
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</p>
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<p>
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Now let's look at the same code with <code class="computeroutput"><span class="identifier">string_ref</span></code>:
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</p>
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<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">string_ref</span> <span class="identifier">extract_part</span> <span class="special">(</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">string_ref</span> <span class="identifier">bar</span> <span class="special">)</span> <span class="special">{</span>
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<span class="keyword">return</span> <span class="identifier">bar</span><span class="special">.</span><span class="identifier">substr</span> <span class="special">(</span> <span class="number">2</span><span class="special">,</span> <span class="number">3</span> <span class="special">);</span>
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<span class="special">}</span>
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<span class="keyword">if</span> <span class="special">(</span> <span class="identifier">extract_part</span> <span class="special">(</span> <span class="string">"ABCDEFG"</span> <span class="special">).</span><span class="identifier">front</span><span class="special">()</span> <span class="special">==</span> <span class="string">"C"</span> <span class="special">)</span> <span class="special">{</span> <span class="comment">/* do something */</span> <span class="special">}</span>
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</pre>
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<p>
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No memory allocations. No copying of character data. No changes to the code
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other than the types. There are two <code class="computeroutput"><span class="identifier">string_ref</span></code>s
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created, and two <code class="computeroutput"><span class="identifier">string_ref</span></code>s
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copied, but those are cheap operations.
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</p>
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</div>
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<div class="section string_ref_reference">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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|
<a name="string_ref.reference"></a><a class="link" href="string_ref.html#string_ref.reference" title="Reference">Reference </a>
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</h2></div></div></div>
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<p>
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The header file "string_ref.hpp" defines a template <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">basic_string_ref</span></code>,
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and four specializations - for <code class="computeroutput"><span class="keyword">char</span></code>
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/ <code class="computeroutput"><span class="keyword">wchar_t</span></code> / <code class="computeroutput"><span class="identifier">char16_t</span></code>
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/ <code class="computeroutput"><span class="identifier">char32_t</span></code> .
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</p>
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<p>
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<code class="computeroutput"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">utility</span><span class="special">/</span><span class="identifier">string_ref</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code>
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|
</p>
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<p>
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|
Construction and copying:
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|
</p>
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|
<pre class="programlisting"><span class="identifier">BOOST_CONSTEXPR</span> <span class="identifier">basic_string_ref</span> <span class="special">();</span> <span class="comment">// Constructs an empty string_ref</span>
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|
<span class="identifier">BOOST_CONSTEXPR</span> <span class="identifier">basic_string_ref</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">charT</span><span class="special">*</span> <span class="identifier">str</span><span class="special">);</span> <span class="comment">// Constructs from a NULL-terminated string</span>
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||||||
|
<span class="identifier">BOOST_CONSTEXPR</span> <span class="identifier">basic_string_ref</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">charT</span><span class="special">*</span> <span class="identifier">str</span><span class="special">,</span> <span class="identifier">size_type</span> <span class="identifier">len</span><span class="special">);</span> <span class="comment">// Constructs from a pointer, length pair</span>
|
||||||
|
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Allocator</span><span class="special">></span>
|
||||||
|
<span class="identifier">basic_string_ref</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_string</span><span class="special"><</span><span class="identifier">charT</span><span class="special">,</span> <span class="identifier">traits</span><span class="special">,</span> <span class="identifier">Allocator</span><span class="special">>&</span> <span class="identifier">str</span><span class="special">);</span> <span class="comment">// Constructs from a std::string</span>
|
||||||
|
<span class="identifier">basic_string_ref</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">basic_string_ref</span> <span class="special">&</span><span class="identifier">rhs</span><span class="special">);</span>
|
||||||
|
<span class="identifier">basic_string_ref</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span><span class="keyword">const</span> <span class="identifier">basic_string_ref</span> <span class="special">&</span><span class="identifier">rhs</span><span class="special">);</span>
|
||||||
|
</pre>
|
||||||
|
<p>
|
||||||
|
<code class="computeroutput"><span class="identifier">string_ref</span></code> does not define
|
||||||
|
a move constructor nor a move-assignment operator because copying a <code class="computeroutput"><span class="identifier">string_ref</span></code> is just a cheap as moving one.
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||||||
|
</p>
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||||||
|
<p>
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||||||
|
Basic container-like functions:
|
||||||
|
</p>
|
||||||
|
<pre class="programlisting"><span class="identifier">BOOST_CONSTEXPR</span> <span class="identifier">size_type</span> <span class="identifier">size</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">BOOST_CONSTEXPR</span> <span class="identifier">size_type</span> <span class="identifier">length</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">BOOST_CONSTEXPR</span> <span class="identifier">size_type</span> <span class="identifier">max_size</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">BOOST_CONSTEXPR</span> <span class="keyword">bool</span> <span class="identifier">empty</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
|
||||||
|
<span class="comment">// All iterators are const_iterators</span>
|
||||||
|
<span class="identifier">BOOST_CONSTEXPR</span> <span class="identifier">const_iterator</span> <span class="identifier">begin</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">BOOST_CONSTEXPR</span> <span class="identifier">const_iterator</span> <span class="identifier">cbegin</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">BOOST_CONSTEXPR</span> <span class="identifier">const_iterator</span> <span class="identifier">end</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">BOOST_CONSTEXPR</span> <span class="identifier">const_iterator</span> <span class="identifier">cend</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">const_reverse_iterator</span> <span class="identifier">rbegin</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">const_reverse_iterator</span> <span class="identifier">crbegin</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">const_reverse_iterator</span> <span class="identifier">rend</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">const_reverse_iterator</span> <span class="identifier">crend</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
</pre>
|
||||||
|
<p>
|
||||||
|
Access to the individual elements (all of which are const):
|
||||||
|
</p>
|
||||||
|
<pre class="programlisting"><span class="identifier">BOOST_CONSTEXPR</span> <span class="keyword">const</span> <span class="identifier">charT</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">[](</span><span class="identifier">size_type</span> <span class="identifier">pos</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="keyword">const</span> <span class="identifier">charT</span><span class="special">&</span> <span class="identifier">at</span><span class="special">(</span><span class="identifier">size_t</span> <span class="identifier">pos</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">BOOST_CONSTEXPR</span> <span class="keyword">const</span> <span class="identifier">charT</span><span class="special">&</span> <span class="identifier">front</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">BOOST_CONSTEXPR</span> <span class="keyword">const</span> <span class="identifier">charT</span><span class="special">&</span> <span class="identifier">back</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">BOOST_CONSTEXPR</span> <span class="keyword">const</span> <span class="identifier">charT</span><span class="special">*</span> <span class="identifier">data</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
</pre>
|
||||||
|
<p>
|
||||||
|
Modifying the <code class="computeroutput"><span class="identifier">string_ref</span></code> (but
|
||||||
|
not the underlying data):
|
||||||
|
</p>
|
||||||
|
<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">clear</span><span class="special">();</span>
|
||||||
|
<span class="keyword">void</span> <span class="identifier">remove_prefix</span><span class="special">(</span><span class="identifier">size_type</span> <span class="identifier">n</span><span class="special">);</span>
|
||||||
|
<span class="keyword">void</span> <span class="identifier">remove_suffix</span><span class="special">(</span><span class="identifier">size_type</span> <span class="identifier">n</span><span class="special">);</span>
|
||||||
|
</pre>
|
||||||
|
<p>
|
||||||
|
Searching:
|
||||||
|
</p>
|
||||||
|
<pre class="programlisting"><span class="identifier">size_type</span> <span class="identifier">find</span><span class="special">(</span><span class="identifier">basic_string_ref</span> <span class="identifier">s</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">size_type</span> <span class="identifier">find</span><span class="special">(</span><span class="identifier">charT</span> <span class="identifier">c</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">size_type</span> <span class="identifier">rfind</span><span class="special">(</span><span class="identifier">basic_string_ref</span> <span class="identifier">s</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">size_type</span> <span class="identifier">rfind</span><span class="special">(</span><span class="identifier">charT</span> <span class="identifier">c</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">size_type</span> <span class="identifier">find_first_of</span><span class="special">(</span><span class="identifier">charT</span> <span class="identifier">c</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">size_type</span> <span class="identifier">find_last_of</span> <span class="special">(</span><span class="identifier">charT</span> <span class="identifier">c</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
|
||||||
|
<span class="identifier">size_type</span> <span class="identifier">find_first_of</span><span class="special">(</span><span class="identifier">basic_string_ref</span> <span class="identifier">s</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">size_type</span> <span class="identifier">find_last_of</span><span class="special">(</span><span class="identifier">basic_string_ref</span> <span class="identifier">s</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">size_type</span> <span class="identifier">find_first_not_of</span><span class="special">(</span><span class="identifier">basic_string_ref</span> <span class="identifier">s</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">size_type</span> <span class="identifier">find_first_not_of</span><span class="special">(</span><span class="identifier">charT</span> <span class="identifier">c</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">size_type</span> <span class="identifier">find_last_not_of</span><span class="special">(</span><span class="identifier">basic_string_ref</span> <span class="identifier">s</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="identifier">size_type</span> <span class="identifier">find_last_not_of</span><span class="special">(</span><span class="identifier">charT</span> <span class="identifier">c</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
</pre>
|
||||||
|
<p>
|
||||||
|
String-like operations:
|
||||||
|
</p>
|
||||||
|
<pre class="programlisting"><span class="identifier">BOOST_CONSTEXPR</span> <span class="identifier">basic_string_ref</span> <span class="identifier">substr</span><span class="special">(</span><span class="identifier">size_type</span> <span class="identifier">pos</span><span class="special">,</span> <span class="identifier">size_type</span> <span class="identifier">n</span><span class="special">=</span><span class="identifier">npos</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span> <span class="comment">// Creates a new string_ref</span>
|
||||||
|
<span class="keyword">bool</span> <span class="identifier">starts_with</span><span class="special">(</span><span class="identifier">charT</span> <span class="identifier">c</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="keyword">bool</span> <span class="identifier">starts_with</span><span class="special">(</span><span class="identifier">basic_string_ref</span> <span class="identifier">x</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="keyword">bool</span> <span class="identifier">ends_with</span><span class="special">(</span><span class="identifier">charT</span> <span class="identifier">c</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
<span class="keyword">bool</span> <span class="identifier">ends_with</span><span class="special">(</span><span class="identifier">basic_string_ref</span> <span class="identifier">x</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
|
||||||
|
</pre>
|
||||||
|
</div>
|
||||||
|
<div class="section string_ref_history">
|
||||||
|
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||||
|
<a name="string_ref.history"></a><a class="link" href="string_ref.html#string_ref.history" title="History">History</a>
|
||||||
|
</h2></div></div></div>
|
||||||
|
<h4>
|
||||||
|
<a name="string_ref.history.h0"></a>
|
||||||
|
<span><a name="string_ref.history.boost_1_53"></a></span><a class="link" href="string_ref.html#string_ref.history.boost_1_53">boost
|
||||||
|
1.53</a>
|
||||||
|
</h4>
|
||||||
|
<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
|
||||||
|
Introduced
|
||||||
|
</li></ul></div>
|
||||||
|
</div>
|
||||||
|
</div>
|
||||||
|
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||||
|
<td align="left"><p><small>Last revised: January 14, 2013 at 16:24:14 GMT</small></p></td>
|
||||||
|
<td align="right"><div class="copyright-footer"></div></td>
|
||||||
|
</tr></table>
|
||||||
|
<hr>
|
||||||
|
<div class="spirit-nav"></div>
|
||||||
|
</body>
|
||||||
|
</html>
|
||||||
@ -37,7 +37,7 @@ A `string_ref` is implemented as a small struct that contains a pointer to the s
|
|||||||
|
|
||||||
`string_ref` acts as a container; it includes all the methods that you would expect in a container, including iteration support, `operator []`, `at` and `size`. It can be used with any of the iterator-based algorithms in the STL - as long as you don't need to change the underlying data (`sort` and `remove`, for example, will not work)
|
`string_ref` acts as a container; it includes all the methods that you would expect in a container, including iteration support, `operator []`, `at` and `size`. It can be used with any of the iterator-based algorithms in the STL - as long as you don't need to change the underlying data (`sort` and `remove`, for example, will not work)
|
||||||
|
|
||||||
Besides generic container functionality, `string_ref` provides a subset of the interface of `std::string`. This makes it easy to replace parameters of type `const std::string &` with `boost::string_ref`.
|
Besides generic container functionality, `string_ref` provides a subset of the interface of `std::string`. This makes it easy to replace parameters of type `const std::string &` with `boost::string_ref`. Like `std::string`, `string_ref` has a static member variable named `npos` to denote the result of failed searches, and to mean "the end".
|
||||||
|
|
||||||
Because a `string_ref` does not own the data that it "points to", it introduces lifetime issues into code that uses it. The programmer must ensure that the data that a `string_ref` refers to exists as long as the `string_ref` does.
|
Because a `string_ref` does not own the data that it "points to", it introduces lifetime issues into code that uses it. The programmer must ensure that the data that a `string_ref` refers to exists as long as the `string_ref` does.
|
||||||
|
|
||||||
@ -50,12 +50,12 @@ Because a `string_ref` does not own the data that it "points to", it introduces
|
|||||||
|
|
||||||
Integrating `string_ref` into your code is fairly simple. Wherever you pass a `const std::string &` or `std::string` as a parameter, that's a candidate for passing a `boost::string_ref`.
|
Integrating `string_ref` into your code is fairly simple. Wherever you pass a `const std::string &` or `std::string` as a parameter, that's a candidate for passing a `boost::string_ref`.
|
||||||
|
|
||||||
std::string extract_part ( const std::string &bar ) {
|
std::string extract_part ( const std::string &bar ) {
|
||||||
return bar.substr ( 2, 3 );
|
return bar.substr ( 2, 3 );
|
||||||
}
|
}
|
||||||
|
|
||||||
if ( extract_part ( "ABCDEFG" ).front() == "C" ) { /* do something */ }
|
if ( extract_part ( "ABCDEFG" ).front() == "C" ) { /* do something */ }
|
||||||
|
|
||||||
Let's figure out what happens in this (contrived) example.
|
Let's figure out what happens in this (contrived) example.
|
||||||
|
|
||||||
First, a temporary string is created from the string literal `"ABCDEFG"`, and it is passed (by reference) to the routine `extract_part`. Then a second string is created in the call `std::string::substr` and returned to `extract_part` (this copy may be elided by RVO). Then `extract_part` returns that string back to the caller (again this copy may be elided). The first temporary string is deallocated, and `front` is called on the second string, and then it is deallocated as well.
|
First, a temporary string is created from the string literal `"ABCDEFG"`, and it is passed (by reference) to the routine `extract_part`. Then a second string is created in the call `std::string::substr` and returned to `extract_part` (this copy may be elided by RVO). Then `extract_part` returns that string back to the caller (again this copy may be elided). The first temporary string is deallocated, and `front` is called on the second string, and then it is deallocated as well.
|
||||||
@ -64,11 +64,11 @@ Two `std::string`s are created, and two copy operations. That's (potentially) fo
|
|||||||
|
|
||||||
Now let's look at the same code with `string_ref`:
|
Now let's look at the same code with `string_ref`:
|
||||||
|
|
||||||
boost::string_ref extract_part ( boost::string_ref bar ) {
|
boost::string_ref extract_part ( boost::string_ref bar ) {
|
||||||
return bar.substr ( 2, 3 );
|
return bar.substr ( 2, 3 );
|
||||||
}
|
}
|
||||||
|
|
||||||
if ( extract_part ( "ABCDEFG" ).front() == "C" ) { /* do something */ }
|
if ( extract_part ( "ABCDEFG" ).front() == "C" ) { /* do something */ }
|
||||||
|
|
||||||
No memory allocations. No copying of character data. No changes to the code other than the types. There are two `string_ref`s created, and two `string_ref`s copied, but those are cheap operations.
|
No memory allocations. No copying of character data. No changes to the code other than the types. There are two `string_ref`s created, and two `string_ref`s copied, but those are cheap operations.
|
||||||
|
|
||||||
@ -83,6 +83,73 @@ The header file "string_ref.hpp" defines a template `boost::basic_string_ref`, a
|
|||||||
|
|
||||||
`#include <boost/utility/string_ref.hpp>`
|
`#include <boost/utility/string_ref.hpp>`
|
||||||
|
|
||||||
|
Construction and copying:
|
||||||
|
|
||||||
|
BOOST_CONSTEXPR basic_string_ref (); // Constructs an empty string_ref
|
||||||
|
BOOST_CONSTEXPR basic_string_ref(const charT* str); // Constructs from a NULL-terminated string
|
||||||
|
BOOST_CONSTEXPR basic_string_ref(const charT* str, size_type len); // Constructs from a pointer, length pair
|
||||||
|
template<typename Allocator>
|
||||||
|
basic_string_ref(const std::basic_string<charT, traits, Allocator>& str); // Constructs from a std::string
|
||||||
|
basic_string_ref (const basic_string_ref &rhs);
|
||||||
|
basic_string_ref& operator=(const basic_string_ref &rhs);
|
||||||
|
|
||||||
|
`string_ref` does not define a move constructor nor a move-assignment operator because copying a `string_ref` is just a cheap as moving one.
|
||||||
|
|
||||||
|
Basic container-like functions:
|
||||||
|
|
||||||
|
BOOST_CONSTEXPR size_type size() const ;
|
||||||
|
BOOST_CONSTEXPR size_type length() const ;
|
||||||
|
BOOST_CONSTEXPR size_type max_size() const ;
|
||||||
|
BOOST_CONSTEXPR bool empty() const ;
|
||||||
|
|
||||||
|
// All iterators are const_iterators
|
||||||
|
BOOST_CONSTEXPR const_iterator begin() const ;
|
||||||
|
BOOST_CONSTEXPR const_iterator cbegin() const ;
|
||||||
|
BOOST_CONSTEXPR const_iterator end() const ;
|
||||||
|
BOOST_CONSTEXPR const_iterator cend() const ;
|
||||||
|
const_reverse_iterator rbegin() const ;
|
||||||
|
const_reverse_iterator crbegin() const ;
|
||||||
|
const_reverse_iterator rend() const ;
|
||||||
|
const_reverse_iterator crend() const ;
|
||||||
|
|
||||||
|
Access to the individual elements (all of which are const):
|
||||||
|
|
||||||
|
BOOST_CONSTEXPR const charT& operator[](size_type pos) const ;
|
||||||
|
const charT& at(size_t pos) const ;
|
||||||
|
BOOST_CONSTEXPR const charT& front() const ;
|
||||||
|
BOOST_CONSTEXPR const charT& back() const ;
|
||||||
|
BOOST_CONSTEXPR const charT* data() const ;
|
||||||
|
|
||||||
|
Modifying the `string_ref` (but not the underlying data):
|
||||||
|
|
||||||
|
void clear();
|
||||||
|
void remove_prefix(size_type n);
|
||||||
|
void remove_suffix(size_type n);
|
||||||
|
|
||||||
|
Searching:
|
||||||
|
|
||||||
|
size_type find(basic_string_ref s) const ;
|
||||||
|
size_type find(charT c) const ;
|
||||||
|
size_type rfind(basic_string_ref s) const ;
|
||||||
|
size_type rfind(charT c) const ;
|
||||||
|
size_type find_first_of(charT c) const ;
|
||||||
|
size_type find_last_of (charT c) const ;
|
||||||
|
|
||||||
|
size_type find_first_of(basic_string_ref s) const ;
|
||||||
|
size_type find_last_of(basic_string_ref s) const ;
|
||||||
|
size_type find_first_not_of(basic_string_ref s) const ;
|
||||||
|
size_type find_first_not_of(charT c) const ;
|
||||||
|
size_type find_last_not_of(basic_string_ref s) const ;
|
||||||
|
size_type find_last_not_of(charT c) const ;
|
||||||
|
|
||||||
|
String-like operations:
|
||||||
|
|
||||||
|
BOOST_CONSTEXPR basic_string_ref substr(size_type pos, size_type n=npos) const ; // Creates a new string_ref
|
||||||
|
bool starts_with(charT c) const ;
|
||||||
|
bool starts_with(basic_string_ref x) const ;
|
||||||
|
bool ends_with(charT c) const ;
|
||||||
|
bool ends_with(basic_string_ref x) const ;
|
||||||
|
|
||||||
[endsect]
|
[endsect]
|
||||||
|
|
||||||
[/===============]
|
[/===============]
|
||||||
@ -91,7 +158,7 @@ The header file "string_ref.hpp" defines a template `boost::basic_string_ref`, a
|
|||||||
|
|
||||||
[heading boost 1.53]
|
[heading boost 1.53]
|
||||||
* Introduced
|
* Introduced
|
||||||
|
|
||||||
|
|
||||||
[endsect]
|
[endsect]
|
||||||
|
|
||||||
|
|||||||
Loading…
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Reference in New Issue
Block a user