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| <!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>Memory Based Streams</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="io.html" title="Chapter 13. Input and Output" /><link rel="prev" href="streambufs.html" title="Stream Buffers" /><link rel="next" href="fstreams.html" title="File Based Streams" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Memory Based Streams</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="streambufs.html">Prev</a> </td><th width="60%" align="center">Chapter 13. |
| Input and Output |
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| </th><td width="20%" align="right"> <a accesskey="n" href="fstreams.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.io.memstreams"></a>Memory Based Streams</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="std.io.memstreams.compat"></a>Compatibility With strstream</h3></div></div></div><p> |
| </p><p>Stringstreams (defined in the header <code class="code"><sstream></code>) |
| are in this author's opinion one of the coolest things since |
| sliced time. An example of their use is in the Received Wisdom |
| section for Sect1 21 (Strings), |
| <a class="link" href="strings.html#strings.string.Cstring" title="CString (MFC)"> describing how to |
| format strings</a>. |
| </p><p>The quick definition is: they are siblings of ifstream and ofstream, |
| and they do for <code class="code">std::string</code> what their siblings do for |
| files. All that work you put into writing <code class="code"><<</code> and |
| <code class="code">>></code> functions for your classes now pays off |
| <span class="emphasis"><em>again!</em></span> Need to format a string before passing the string |
| to a function? Send your stuff via <code class="code"><<</code> to an |
| ostringstream. You've read a string as input and need to parse it? |
| Initialize an istringstream with that string, and then pull pieces |
| out of it with <code class="code">>></code>. Have a stringstream and need to |
| get a copy of the string inside? Just call the <code class="code">str()</code> |
| member function. |
| </p><p>This only works if you've written your |
| <code class="code"><<</code>/<code class="code">>></code> functions correctly, though, |
| and correctly means that they take istreams and ostreams as |
| parameters, not i<span class="emphasis"><em>f</em></span>streams and o<span class="emphasis"><em>f</em></span>streams. If they |
| take the latter, then your I/O operators will work fine with |
| file streams, but with nothing else -- including stringstreams. |
| </p><p>If you are a user of the strstream classes, you need to update |
| your code. You don't have to explicitly append <code class="code">ends</code> to |
| terminate the C-style character array, you don't have to mess with |
| "freezing" functions, and you don't have to manage the |
| memory yourself. The strstreams have been officially deprecated, |
| which means that 1) future revisions of the C++ Standard won't |
| support them, and 2) if you use them, people will laugh at you. |
| </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="streambufs.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="fstreams.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Stream Buffers </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> File Based Streams</td></tr></table></div></body></html> |
