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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 V1.73.2" /><meta name="keywords" content="&#10;      ISO C++&#10;    , &#10;      library&#10;    " /><link rel="start" 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="bk01pt11ch24.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="bk01pt11ch24.html">Prev</a> </td><th width="60%" align="center">Part XI. Input and Output</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt11ch25s02.html">Next</a></td></tr></table><hr /></div><div class="chapter" lang="en" xml:lang="en"><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="bk01pt11ch25.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" lang="en" xml:lang="en"><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>
    </p><p>Creating your own stream buffers for I/O can be remarkably easy.
      If you are interested in doing so, we highly recommend two very
      excellent books:
      <a class="ulink" href="http://www.langer.camelot.de/iostreams.html" target="_top">Standard C++
      IOStreams and Locales</a> by Langer and Kreft, ISBN 0-201-18395-1, and
      <a class="ulink" href="http://www.josuttis.com/libbook/" target="_top">The C++ Standard Library</a>
      by Nicolai Josuttis, ISBN 0-201-37926-0.  Both are published by
      Addison-Wesley, who isn't paying us a cent for saying that, honest.
   </p><p>Here is a simple example, io/outbuf1, from the Josuttis text.  It
      transforms everything sent through it to uppercase.  This version
      assumes many things about the nature of the character type being
      used (for more information, read the books or the newsgroups):
   </p><pre class="programlisting">
    #include &lt;iostream&gt;
    #include &lt;streambuf&gt;
    #include &lt;locale&gt;
    #include &lt;cstdio&gt;

    class outbuf : public std::streambuf
    {
      protected:
	/* central output function
	 * - print characters in uppercase mode
	 */
	virtual int_type overflow (int_type c) {
	    if (c != EOF) {
		// convert lowercase to uppercase
		c = std::toupper(static_cast&lt;char&gt;(c),getloc());

		// and write the character to the standard output
		if (putchar(c) == EOF) {
		    return EOF;
		}
	    }
	    return c;
	}
    };

    int main()
    {
	// create special output buffer
	outbuf ob;
	// initialize output stream with that output buffer
	std::ostream out(&amp;ob);

	out &lt;&lt; "31 hexadecimal: "
	    &lt;&lt; std::hex &lt;&lt; 31 &lt;&lt; std::endl;
	return 0;
    }
   </pre><p>Try it yourself!  More examples can be found in 3.1.x code, in
      <code class="code">include/ext/*_filebuf.h</code>, and on
      <a class="ulink" href="http://www.informatik.uni-konstanz.de/~kuehl/c++/iostream/" target="_top">Dietmar
      Kühl's IOStreams page</a>.
   </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt11ch24.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>