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<a name="File-Caching"></a>
<div class="header">
<p>
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<hr>
<a name="File-caching"></a>
<h3 class="section">2.16 File caching</h3>
<p>The file caching mechanism is embedded within BFD and allows
the application to open as many BFDs as it wants without
regard to the underlying operating system&rsquo;s file descriptor
limit (often as low as 20 open files).  The module in
<code>cache.c</code> maintains a least recently used list of
<code>bfd_cache_max_open</code> files, and exports the name
<code>bfd_cache_lookup</code>, which runs around and makes sure that
the required BFD is open. If not, then it chooses a file to
close, closes it and opens the one wanted, returning its file
handle.
</p>
<a name="Caching-functions"></a>
<h4 class="subsection">2.16.1 Caching functions</h4>


<a name="index-bfd_005fcache_005finit"></a>
<a name="bfd_005fcache_005finit"></a>
<h4 class="subsubsection">2.16.1.1 <code>bfd_cache_init</code></h4>
<p><strong>Synopsis</strong>
</p><div class="example">
<pre class="example">bfd_boolean bfd_cache_init (bfd *abfd);
</pre></div>
<p><strong>Description</strong><br>
Add a newly opened BFD to the cache.
</p>
<a name="index-bfd_005fcache_005fclose"></a>
<a name="bfd_005fcache_005fclose"></a>
<h4 class="subsubsection">2.16.1.2 <code>bfd_cache_close</code></h4>
<p><strong>Synopsis</strong>
</p><div class="example">
<pre class="example">bfd_boolean bfd_cache_close (bfd *abfd);
</pre></div>
<p><strong>Description</strong><br>
Remove the BFD <var>abfd</var> from the cache. If the attached file is open,
then close it too.
</p>
<p><strong>Returns</strong><br>
<code>FALSE</code> is returned if closing the file fails, <code>TRUE</code> is
returned if all is well.
</p>
<a name="index-bfd_005fcache_005fclose_005fall"></a>
<a name="bfd_005fcache_005fclose_005fall"></a>
<h4 class="subsubsection">2.16.1.3 <code>bfd_cache_close_all</code></h4>
<p><strong>Synopsis</strong>
</p><div class="example">
<pre class="example">bfd_boolean bfd_cache_close_all (void);
</pre></div>
<p><strong>Description</strong><br>
Remove all BFDs from the cache. If the attached file is open,
then close it too.
</p>
<p><strong>Returns</strong><br>
<code>FALSE</code> is returned if closing one of the file fails, <code>TRUE</code> is
returned if all is well.
</p>
<a name="index-bfd_005fopen_005ffile"></a>
<a name="bfd_005fopen_005ffile"></a>
<h4 class="subsubsection">2.16.1.4 <code>bfd_open_file</code></h4>
<p><strong>Synopsis</strong>
</p><div class="example">
<pre class="example">FILE* bfd_open_file (bfd *abfd);
</pre></div>
<p><strong>Description</strong><br>
Call the OS to open a file for <var>abfd</var>.  Return the <code>FILE *</code>
(possibly <code>NULL</code>) that results from this operation.  Set up the
BFD so that future accesses know the file is open. If the <code>FILE *</code>
returned is <code>NULL</code>, then it won&rsquo;t have been put in the
cache, so it won&rsquo;t have to be removed from it.
</p>

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