<li><a href="#8">Pathetic performance? Ditch C.</a></li>
<li><a href="#9">Threads and I/O</a></li>
<li><a href="#10">Which header?</a></li>
+ <li><a href="#11">Using FILE*s and file descriptors with IOStreams</a></li>
</ul>
<hr />
</p>
+<hr />
+<h2><a name="11">Using FILE*s and file descriptors with IOStreams</a></h2>
+ <p>The v2 library included non-standard extensions to construct
+ <code>std::filebuf</code>s from C stdio types such as
+ <code>FILE*</code>s and POSIX file descriptors.
+ Today the recommended way to use stdio types with libstdc++-v3
+ IOStreams is via the <code>stdio_filebuf</code> class (see below),
+ but earlier releases provided slightly different mechanisms.
+ </p>
+ <ul>
+ <li>3.0.x <code>filebuf</code>s have another ctor with this signature:
+ <br />
+ <code>basic_filebuf(__c_file_type*, ios_base::openmode, int_type);</code>
+ <br />This comes in very handy in a number of places, such as
+ attaching Unix sockets, pipes, and anything else which uses file
+ descriptors, into the IOStream buffering classes. The three
+ arguments are as follows:
+ <ul>
+ <li><code>__c_file_type* F </code>
+ // the __c_file_type typedef usually boils down to stdio's FILE
+ </li>
+ <li><code>ios_base::openmode M </code>
+ // same as all the other uses of openmode
+ </li>
+ <li><code>int_type B </code>
+ // buffer size, defaults to BUFSIZ if not specified
+ </li>
+ </ul>
+ For those wanting to use file descriptors instead of FILE*'s, I
+ invite you to contemplate the mysteries of C's <code>fdopen()</code>.
+ </li>
+ <li>In library snapshot 3.0.95 and later, <code>filebuf</code>s bring
+ back an old extension: the <code>fd()</code> member function. The
+ integer returned from this function can be used for whatever file
+ descriptors can be used for on your platform. Naturally, the
+ library cannot track what you do on your own with a file descriptor,
+ so if you perform any I/O directly, don't expect the library to be
+ aware of it.
+ </li>
+ <li>Beginning with 3.1, the extra <code>filebuf</code> constructor and
+ the <code>fd()</code> function were removed from the standard
+ filebuf. Instead, <code><ext/stdio_filebuf.h></code> contains
+ a derived class called <code>__gnu_cxx::stdio_filebuf</code>. This
+ class can be constructed from a C <code>FILE*</code> or a file
+ descriptor, and provides the <code>fd()</code> function.
+ </li>
+ </ul>
+ <p>If you want to access a <code>filebuf</code>s file descriptor to
+ implement file locking (e.g. using the <code>fcntl()</code> system
+ call) then you might be interested in Henry Suter's
+ <a href="http://suter.home.cern.ch/suter/RWLock.html">RWLock</a>
+ class.
+ </p>
+
<!-- ####################################################### -->
<hr />
<a href="sgiexts.html">their own page</a>. Since the SGI STL is no
longer actively maintained, we will try and keep this code working
ourselves.</li>
- <li>3.0.x <code>filebuf</code>s have another ctor with this signature:
- <br />
- <code>basic_filebuf(__c_file_type*, ios_base::openmode, int_type);</code>
- <br />This comes in very handy in a number of places, such as
- attaching Unix sockets, pipes, and anything else which uses file
- descriptors, into the IOStream buffering classes. The three
- arguments are as follows:
- <ul>
- <li><code>__c_file_type* F </code>
- // the __c_file_type typedef usually boils down to stdio's FILE
- </li>
- <li><code>ios_base::openmode M </code>
- // same as all the other uses of openmode
- </li>
- <li><code>int_type B </code>
- // buffer size, defaults to BUFSIZ if not specified
- </li>
- </ul>
- For those wanting to use file descriptors instead of FILE*'s, I
- invite you to contemplate the mysteries of C's <code>fdopen()</code>.
- </li>
- <li>In library snapshot 3.0.95 and later, <code>filebuf</code>s bring
- back an old extension: the <code>fd()</code> member function. The
- integer returned from this function can be used for whatever file
- descriptors can be used for on your platform. Naturally, the
- library cannot track what you do on your own with a file descriptor,
- so if you perform any I/O directly, don't expect the library to be
- aware of it.
- </li>
- <li>Beginning with 3.1, the extra <code>filebuf</code> constructor and
- the <code>fd()</code> function were removed from the standard
- filebuf. Instead, <code><ext/stdio_filebuf.h></code> contains
- a derived class called <code>__gnu_cxx::stdio_filebuf</code>.
- </li>
+ <li>Extensions allowing <code>filebuf</code>s to be constructed from
+ stdio types are described in the
+ <a href="../27_io/howto.html#11">chapter 27 notes</a>.</li>
</ul>
<p>Return <a href="#top">to top of page</a> or
<a href="../faq/index.html">to the FAQ</a>.
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