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3<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="&#10;      ISO C++&#10;    , &#10;      library&#10;    " /><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.��
4  Input and Output
5  
6</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>
7    </p><p>Creating your own stream buffers for I/O can be remarkably easy.
8      If you are interested in doing so, we highly recommend two very
9      excellent books:
10      <a class="ulink" href="http://www.angelikalanger.com/iostreams.html" target="_top">Standard C++
11      IOStreams and Locales</a> by Langer and Kreft, ISBN 0-201-18395-1, and
12      <a class="ulink" href="http://www.josuttis.com/libbook/" target="_top">The C++ Standard Library</a>
13      by Nicolai Josuttis, ISBN 0-201-37926-0.  Both are published by
14      Addison-Wesley, who isn't paying us a cent for saying that, honest.
15   </p><p>Here is a simple example, io/outbuf1, from the Josuttis text.  It
16      transforms everything sent through it to uppercase.  This version
17      assumes many things about the nature of the character type being
18      used (for more information, read the books or the newsgroups):
19   </p><pre class="programlisting">
20    #include &lt;iostream&gt;
21    #include &lt;streambuf&gt;
22    #include &lt;locale&gt;
23    #include &lt;cstdio&gt;
24
25    class outbuf : public std::streambuf
26    {
27      protected:
28	/* central output function
29	 * - print characters in uppercase mode
30	 */
31	virtual int_type overflow (int_type c) {
32	    if (c != EOF) {
33		// convert lowercase to uppercase
34		c = std::toupper(static_cast&lt;char&gt;(c),getloc());
35
36		// and write the character to the standard output
37		if (putchar(c) == EOF) {
38		    return EOF;
39		}
40	    }
41	    return c;
42	}
43    };
44
45    int main()
46    {
47	// create special output buffer
48	outbuf ob;
49	// initialize output stream with that output buffer
50	std::ostream out(&amp;ob);
51
52	out &lt;&lt; "31 hexadecimal: "
53	    &lt;&lt; std::hex &lt;&lt; 31 &lt;&lt; std::endl;
54	return 0;
55    }
56   </pre><p>Try it yourself!  More examples can be found in 3.1.x code, in
57      <code class="code">include/ext/*_filebuf.h</code>, and in this article by James Kanze:
58      <a class="ulink" href="http://kanze.james.neuf.fr/articles/fltrsbf1.html" target="_top">Filtering
59      Streambufs</a>.
60   </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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