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diff --git a/gcc-4.4.3/libstdc++-v3/doc/html/manual/bk01pt05ch13s04.html b/gcc-4.4.3/libstdc++-v3/doc/html/manual/bk01pt05ch13s04.html new file mode 100644 index 000000000..0ae02e162 --- /dev/null +++ b/gcc-4.4.3/libstdc++-v3/doc/html/manual/bk01pt05ch13s04.html @@ -0,0 +1,85 @@ +<?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=" ISO C++ , library " /><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 <string> +template <typename Container> +void +stringtok(Container &container, string const &in, + const char * const delimiters = " \t\n") +{ + const string::size_type len = in.length(); + string::size_type i = 0; + + while (i < 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<string> ls; + stringtok (ls, " this \t is\t\n a test "); + for (std::list<string>const_iterator i = ls.begin(); + i != ls.end(); ++i) + { + std::cerr << ':' << (*i) << ":\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> |