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Unified Diff: gcc/libstdc++-v3/doc/html/manual/bk01pt05ch13s04.html

Issue 3050029: [gcc] GCC 4.5.0=>4.5.1 (Closed) Base URL: ssh://git@gitrw.chromium.org:9222/nacl-toolchain.git
Patch Set: Created 10 years, 5 months ago
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Index: gcc/libstdc++-v3/doc/html/manual/bk01pt05ch13s04.html
diff --git a/gcc/libstdc++-v3/doc/html/manual/bk01pt05ch13s04.html b/gcc/libstdc++-v3/doc/html/manual/bk01pt05ch13s04.html
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-<?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
-<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Tokenizing</title><meta name="generator" content="DocBook XSL Stylesheets V1.74.0" /><meta name="keywords" content="&#10; ISO C++&#10; , &#10; library&#10; " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="bk01pt05ch13.html" title="Chapter 13. String Classes" /><link rel="prev" href="bk01pt05ch13s03.html" title="Arbitrary Character Types" /><link rel="next" href="bk01pt05ch13s05.html" title="Shrink to Fit" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Tokenizing</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt05ch13s03.html">Prev</a> </td><th width="60%" align="center">Chapter 13. String Classes</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt05ch13s05.html">Next</a></td></tr></table><hr /></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="strings.string.token"></a>Tokenizing</h2></div></div></div><p>
- </p><p>The Standard C (and C++) function <code class="code">strtok()</code> leaves a lot to
- be desired in terms of user-friendliness. It's unintuitive, it
- destroys the character string on which it operates, and it requires
- you to handle all the memory problems. But it does let the client
- code decide what to use to break the string into pieces; it allows
- you to choose the "whitespace," so to speak.
- </p><p>A C++ implementation lets us keep the good things and fix those
- annoyances. The implementation here is more intuitive (you only
- call it once, not in a loop with varying argument), it does not
- affect the original string at all, and all the memory allocation
- is handled for you.
- </p><p>It's called stringtok, and it's a template function. Sources are
- as below, in a less-portable form than it could be, to keep this
- example simple (for example, see the comments on what kind of
- string it will accept).
- </p><pre class="programlisting">
-#include &lt;string&gt;
-template &lt;typename Container&gt;
-void
-stringtok(Container &amp;container, string const &amp;in,
- const char * const delimiters = " \t\n")
-{
- const string::size_type len = in.length();
- string::size_type i = 0;
-
- while (i &lt; len)
- {
- // Eat leading whitespace
- i = in.find_first_not_of(delimiters, i);
- if (i == string::npos)
- return; // Nothing left but white space
-
- // Find the end of the token
- string::size_type j = in.find_first_of(delimiters, i);
-
- // Push token
- if (j == string::npos)
- {
- container.push_back(in.substr(i));
- return;
- }
- else
- container.push_back(in.substr(i, j-i));
-
- // Set up for next loop
- i = j + 1;
- }
-}
-</pre><p>
- The author uses a more general (but less readable) form of it for
- parsing command strings and the like. If you compiled and ran this
- code using it:
- </p><pre class="programlisting">
- std::list&lt;string&gt; ls;
- stringtok (ls, " this \t is\t\n a test ");
- for (std::list&lt;string&gt;const_iterator i = ls.begin();
- i != ls.end(); ++i)
- {
- std::cerr &lt;&lt; ':' &lt;&lt; (*i) &lt;&lt; ":\n";
- } </pre><p>You would see this as output:
- </p><pre class="programlisting">
- :this:
- :is:
- :a:
- :test: </pre><p>with all the whitespace removed. The original <code class="code">s</code> is still
- available for use, <code class="code">ls</code> will clean up after itself, and
- <code class="code">ls.size()</code> will return how many tokens there were.
- </p><p>As always, there is a price paid here, in that stringtok is not
- as fast as strtok. The other benefits usually outweigh that, however.
- <a class="ulink" href="stringtok_std_h.txt" target="_top">Another version of stringtok is given
- here</a>, suggested by Chris King and tweaked by Petr Prikryl,
- and this one uses the
- transformation functions mentioned below. If you are comfortable
- with reading the new function names, this version is recommended
- as an example.
- </p><p><span class="emphasis"><em>Added February 2001:</em></span> Mark Wilden pointed out that the
- standard <code class="code">std::getline()</code> function can be used with standard
- <a class="ulink" href="../27_io/howto.html" target="_top">istringstreams</a> to perform
- tokenizing as well. Build an istringstream from the input text,
- and then use std::getline with varying delimiters (the three-argument
- signature) to extract tokens into a string.
- </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt05ch13s03.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt05ch13.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt05ch13s05.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Arbitrary Character Types </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Shrink to Fit</td></tr></table></div></body></html>
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