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<title>PTypes: streams: error handling</title>
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<p><a href="../index.html"><img src="title-21.png" width="253" height="39" alt="C++ Portable Types Library (PTypes) Version 2.1" border="0"></a>
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<p class="hpath"><a href="index.html">Top</a>: <a href="streams.html">Streams</a>:
Error handling</p>
<p>When a recoverable error occurs during input/output operations, an exception
of type <span class="lang">(estream*)</span> is thrown. The exception object
contains an error message which can be shown to the user. The message is accessible
through <span class="def">estream::get_message()</span>. </p>
<p>The example below shows how to catch an exception and recover normal execution
of the program:</p>
<blockquote>
<pre>#include <pstreams.h>
USING_PTYPES
infile f("somefile.txt");
try
{
f.open();
while(!f.get_eof())
<span class="comment"> // read the file...</span>
}
catch (estream* e)
{
perr.putline(e->get_message());
delete e;
}
</pre>
</blockquote>
<p>The <span class="lang">estream</span> class provides a system error code in
UNIX errno semantics through <span class="def">estream::get_code()</span>. On
Windows most error codes are translated into corresponding UNIX errno codes. Less
frequently occurring errors are translated to a generic errno code EIO. When an
<span class="lang">estream</span> object returns EIO, the actual message string
is constructed based on the status code of the stream. For example, if the status
code was IO_OPENING, the error code was EIO, the message would be "Couldn't
open <i>[filename]</i>". For explanations on what each errno code means,
see comments in <span class="lang">src/piobase.cxx</span> source file.</p>
<p><span class="lang">Estream</span> also provides a reference to the stream object
that raised the error condition through <span class="lang">estream::get_errstm()</span>.</p>
<p class="seealso">See also: <a href="streams.iobase.html">iobase</a>, <a href="streams.examples.html">Examples</a></p>
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