<?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>Memory Based Streams</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.77.1" /><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
  
</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">&lt;sstream&gt;</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">&lt;&lt;</code> and
      <code class="code">&gt;&gt;</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">&lt;&lt;</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">&gt;&gt;</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">&lt;&lt;</code>/<code class="code">&gt;&gt;</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>