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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 25. Stream Buffers</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="io.html" title="Part XI. Input and Output" /><link rel="prev" href="iostream_objects.html" title="Chapter 24. Iostream Objects" /><link rel="next" href="bk01pt11ch25s02.html" title="Buffering" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 25. Stream Buffers</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="iostream_objects.html">Prev</a> </td><th width="60%" align="center">Part XI.
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Input and Output
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</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt11ch25s02.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 25. Stream Buffers"><div class="titlepage"><div><div><h2 class="title"><a id="manual.io.streambufs"></a>Chapter 25. Stream Buffers</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="streambufs.html#io.streambuf.derived">Derived streambuf Classes</a></span></dt><dt><span class="sect1"><a href="bk01pt11ch25s02.html">Buffering</a></span></dt></dl></div><div class="sect1" title="Derived streambuf Classes"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="io.streambuf.derived"></a>Derived streambuf Classes</h2></div></div></div><p>
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</p><p>Creating your own stream buffers for I/O can be remarkably easy.
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If you are interested in doing so, we highly recommend two very
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excellent books:
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<a class="ulink" href="http://www.angelikalanger.com/iostreams.html" target="_top">Standard C++
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IOStreams and Locales</a> by Langer and Kreft, ISBN 0-201-18395-1, and
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<a class="ulink" href="http://www.josuttis.com/libbook/" target="_top">The C++ Standard Library</a>
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by Nicolai Josuttis, ISBN 0-201-37926-0. Both are published by
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Addison-Wesley, who isn't paying us a cent for saying that, honest.
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</p><p>Here is a simple example, io/outbuf1, from the Josuttis text. It
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transforms everything sent through it to uppercase. This version
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assumes many things about the nature of the character type being
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used (for more information, read the books or the newsgroups):
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</p><pre class="programlisting">
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#include <iostream>
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#include <streambuf>
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#include <locale>
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#include <cstdio>
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class outbuf : public std::streambuf
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{
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protected:
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/* central output function
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* - print characters in uppercase mode
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*/
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virtual int_type overflow (int_type c) {
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if (c != EOF) {
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// convert lowercase to uppercase
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c = std::toupper(static_cast<char>(c),getloc());
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// and write the character to the standard output
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if (putchar(c) == EOF) {
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return EOF;
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}
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}
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return c;
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}
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};
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int main()
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{
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// create special output buffer
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outbuf ob;
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// initialize output stream with that output buffer
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std::ostream out(&ob);
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out << "31 hexadecimal: "
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<< std::hex << 31 << std::endl;
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return 0;
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}
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</pre><p>Try it yourself! More examples can be found in 3.1.x code, in
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<code class="code">include/ext/*_filebuf.h</code>, and in this article by James Kanze:
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<a class="ulink" href="http://kanze.james.neuf.fr/articles/fltrsbf1.html" target="_top">Filtering
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Streambufs</a>.
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</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="iostream_objects.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="io.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt11ch25s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 24. Iostream Objects </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Buffering</td></tr></table></div></body></html>
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