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 | 
<a href="#id3306980" class="shortcut">Description</a></nobr></td></tr>
</table>
<div class="refentry" lang="en">
<a name="glib-Caches"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2>
<a name="id3306665"></a><span class="refentrytitle">Caches</span>
</h2>
<p>Caches — caches allow sharing of complex data structures to save resources.</p>
</td>
<td valign="top" align="right"></td>
</tr></table></div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<pre class="synopsis">
#include <glib.h>
<a href="glib-Caches.html#GCache">GCache</a>;
<a href="glib-Caches.html#GCache">GCache</a>* <a href="glib-Caches.html#g-cache-new">g_cache_new</a> (<a href="glib-Caches.html#GCacheNewFunc">GCacheNewFunc</a> value_new_func,
<a href="glib-Caches.html#GCacheDestroyFunc">GCacheDestroyFunc</a> value_destroy_func,
<a href="glib-Caches.html#GCacheDupFunc">GCacheDupFunc</a> key_dup_func,
<a href="glib-Caches.html#GCacheDestroyFunc">GCacheDestroyFunc</a> key_destroy_func,
<a href="glib-Hash-Tables.html#GHashFunc">GHashFunc</a> hash_key_func,
<a href="glib-Hash-Tables.html#GHashFunc">GHashFunc</a> hash_value_func,
<a href="glib-Hash-Tables.html#GEqualFunc">GEqualFunc</a> key_equal_func);
<a href="glib-Basic-Types.html#gpointer">gpointer</a> <a href="glib-Caches.html#g-cache-insert">g_cache_insert</a> (<a href="glib-Caches.html#GCache">GCache</a> *cache,
<a href="glib-Basic-Types.html#gpointer">gpointer</a> key);
void <a href="glib-Caches.html#g-cache-remove">g_cache_remove</a> (<a href="glib-Caches.html#GCache">GCache</a> *cache,
<a href="glib-Basic-Types.html#gconstpointer">gconstpointer</a> value);
void <a href="glib-Caches.html#g-cache-destroy">g_cache_destroy</a> (<a href="glib-Caches.html#GCache">GCache</a> *cache);
void <a href="glib-Caches.html#g-cache-key-foreach">g_cache_key_foreach</a> (<a href="glib-Caches.html#GCache">GCache</a> *cache,
<a href="glib-Hash-Tables.html#GHFunc">GHFunc</a> func,
<a href="glib-Basic-Types.html#gpointer">gpointer</a> user_data);
void <a href="glib-Caches.html#g-cache-value-foreach">g_cache_value_foreach</a> (<a href="glib-Caches.html#GCache">GCache</a> *cache,
<a href="glib-Hash-Tables.html#GHFunc">GHFunc</a> func,
<a href="glib-Basic-Types.html#gpointer">gpointer</a> user_data);
void (<a href="glib-Caches.html#GCacheDestroyFunc">*GCacheDestroyFunc</a>) (<a href="glib-Basic-Types.html#gpointer">gpointer</a> value);
<a href="glib-Basic-Types.html#gpointer">gpointer</a> (<a href="glib-Caches.html#GCacheDupFunc">*GCacheDupFunc</a>) (<a href="glib-Basic-Types.html#gpointer">gpointer</a> value);
<a href="glib-Basic-Types.html#gpointer">gpointer</a> (<a href="glib-Caches.html#GCacheNewFunc">*GCacheNewFunc</a>) (<a href="glib-Basic-Types.html#gpointer">gpointer</a> key);
</pre>
</div>
<div class="refsect1" lang="en">
<a name="id3306980"></a><h2>Description</h2>
<p>
A <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> allows sharing of complex data structures, in order to save
system resources.
</p>
<p>
GTK+ uses caches for <span class="type">GtkStyles</span> and <span class="type">GdkGCs</span>. These consume a lot of
resources, so a <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> is used to see if a <a
href="../gtk/GtkStyle.html"
><span class="type">GtkStyle</span></a> or <a
href="../gdk/gdk-Graphics-Contexts.html#GdkGC"
><span class="type">GdkGC</span></a> with the
required properties already exists. If it does, then the existing
object is used instead of creating a new one.
</p>
<p>
<a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> uses keys and values.
A <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> key describes the properties of a particular resource.
A <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> value is the actual resource.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id3307083"></a><h2>Details</h2>
<div class="refsect2" lang="en">
<a name="id3307093"></a><h3>
<a name="GCache"></a>GCache</h3>
<a class="indexterm" name="id3307106"></a><pre class="programlisting">typedef struct _GCache GCache;</pre>
<p>
The <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> struct is an opaque data structure containing information about
a <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>. It should only be accessed via the following functions.
</p>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3307139"></a><h3>
<a name="g-cache-new"></a>g_cache_new ()</h3>
<a class="indexterm" name="id3307151"></a><pre class="programlisting"><a href="glib-Caches.html#GCache">GCache</a>* g_cache_new (<a href="glib-Caches.html#GCacheNewFunc">GCacheNewFunc</a> value_new_func,
<a href="glib-Caches.html#GCacheDestroyFunc">GCacheDestroyFunc</a> value_destroy_func,
<a href="glib-Caches.html#GCacheDupFunc">GCacheDupFunc</a> key_dup_func,
<a href="glib-Caches.html#GCacheDestroyFunc">GCacheDestroyFunc</a> key_destroy_func,
<a href="glib-Hash-Tables.html#GHashFunc">GHashFunc</a> hash_key_func,
<a href="glib-Hash-Tables.html#GHashFunc">GHashFunc</a> hash_value_func,
<a href="glib-Hash-Tables.html#GEqualFunc">GEqualFunc</a> key_equal_func);</pre>
<p>
Creates a new <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>value_new_func</code></em> :</span></td>
<td>a function to create a new object given a key.
This is called by <a href="glib-Caches.html#g-cache-insert"><code class="function">g_cache_insert()</code></a> if an object with the given key
does not already exist.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>value_destroy_func</code></em> :</span></td>
<td>a function to destroy an object. It is
called by <a href="glib-Caches.html#g-cache-remove"><code class="function">g_cache_remove()</code></a> when the object is no longer needed (i.e. its
reference count drops to 0).
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>key_dup_func</code></em> :</span></td>
<td>a function to copy a key. It is called by
<a href="glib-Caches.html#g-cache-insert"><code class="function">g_cache_insert()</code></a> if the key does not already exist in the <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>key_destroy_func</code></em> :</span></td>
<td>a function to destroy a key. It is
called by <a href="glib-Caches.html#g-cache-remove"><code class="function">g_cache_remove()</code></a> when the object is no longer needed (i.e. its
reference count drops to 0).
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>hash_key_func</code></em> :</span></td>
<td>a function to create a hash value from a key.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>hash_value_func</code></em> :</span></td>
<td>a function to create a hash value from a value.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>key_equal_func</code></em> :</span></td>
<td>a function to compare two keys. It should return <a href="glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if
the two keys are equivalent.
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td>a new <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3307426"></a><h3>
<a name="g-cache-insert"></a>g_cache_insert ()</h3>
<a class="indexterm" name="id3307438"></a><pre class="programlisting"><a href="glib-Basic-Types.html#gpointer">gpointer</a> g_cache_insert (<a href="glib-Caches.html#GCache">GCache</a> *cache,
<a href="glib-Basic-Types.html#gpointer">gpointer</a> key);</pre>
<p>
Gets the value corresponding to the given key, creating it if necessary.
It first checks if the value already exists in the <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>, by using
the <em class="parameter"><code>key_equal_func</code></em> function passed to <a href="glib-Caches.html#g-cache-new"><code class="function">g_cache_new()</code></a>.
If it does already exist it is returned, and its reference count is increased
by one.
If the value does not currently exist, if is created by calling the
<em class="parameter"><code>value_new_func</code></em>. The key is duplicated by calling
<em class="parameter"><code>key_dup_func</code></em> and the duplicated key and value are inserted
into the <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cache</code></em> :</span></td>
<td>a <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>key</code></em> :</span></td>
<td>a key describing a <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> object.
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td>a pointer to a <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> value.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3307590"></a><h3>
<a name="g-cache-remove"></a>g_cache_remove ()</h3>
<a class="indexterm" name="id3307603"></a><pre class="programlisting">void g_cache_remove (<a href="glib-Caches.html#GCache">GCache</a> *cache,
<a href="glib-Basic-Types.html#gconstpointer">gconstpointer</a> value);</pre>
<p>
Decreases the reference count of the given value.
If it drops to 0 then the value and its corresponding key are destroyed,
using the <em class="parameter"><code>value_destroy_func</code></em> and <em class="parameter"><code>key_destroy_func</code></em> passed to <a href="glib-Caches.html#g-cache-new"><code class="function">g_cache_new()</code></a>.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cache</code></em> :</span></td>
<td>a <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>value</code></em> :</span></td>
<td>the value to remove.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3307704"></a><h3>
<a name="g-cache-destroy"></a>g_cache_destroy ()</h3>
<a class="indexterm" name="id3307717"></a><pre class="programlisting">void g_cache_destroy (<a href="glib-Caches.html#GCache">GCache</a> *cache);</pre>
<p>
Frees the memory allocated for the <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</p>
<p>
Note that it does not destroy the keys and values which were contained in the
<a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td>
<span class="term"><em class="parameter"><code>cache</code></em> :</span></td>
<td>a <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3307792"></a><h3>
<a name="g-cache-key-foreach"></a>g_cache_key_foreach ()</h3>
<a class="indexterm" name="id3307805"></a><pre class="programlisting">void g_cache_key_foreach (<a href="glib-Caches.html#GCache">GCache</a> *cache,
<a href="glib-Hash-Tables.html#GHFunc">GHFunc</a> func,
<a href="glib-Basic-Types.html#gpointer">gpointer</a> user_data);</pre>
<p>
Calls the given function for each of the keys in the <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p><em class="parameter"><code>func</code></em> is passed three parameters, the value and key of a
cache entry and the <em class="parameter"><code>user_data</code></em>. The order of value and key is different
from the order in which <a href="glib-Hash-Tables.html#g-hash-table-foreach"><code class="function">g_hash_table_foreach()</code></a> passes key-value pairs
to its callback function !
</p>
</div>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cache</code></em> :</span></td>
<td>a <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>func</code></em> :</span></td>
<td>the function to call with each <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> key.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>user_data</code></em> :</span></td>
<td>user data to pass to the function.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3307948"></a><h3>
<a name="g-cache-value-foreach"></a>g_cache_value_foreach ()</h3>
<a class="indexterm" name="id3307963"></a><pre class="programlisting">void g_cache_value_foreach (<a href="glib-Caches.html#GCache">GCache</a> *cache,
<a href="glib-Hash-Tables.html#GHFunc">GHFunc</a> func,
<a href="glib-Basic-Types.html#gpointer">gpointer</a> user_data);</pre>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p><code class="literal">g_cache_value_foreach</code> has been deprecated since version 2.10 and should not be used in newly-written code. The reason is that it passes pointers to internal data
structures to <em class="parameter"><code>func</code></em>; use <a href="glib-Caches.html#g-cache-key-foreach"><code class="function">g_cache_key_foreach()</code></a> instead</p>
</div>
<p>
Calls the given function for each of the values in the <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cache</code></em> :</span></td>
<td>a <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>func</code></em> :</span></td>
<td>the function to call with each <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> value.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>user_data</code></em> :</span></td>
<td>user data to pass to the function.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3308109"></a><h3>
<a name="GCacheDestroyFunc"></a>GCacheDestroyFunc ()</h3>
<a class="indexterm" name="id3308122"></a><pre class="programlisting">void (*GCacheDestroyFunc) (<a href="glib-Basic-Types.html#gpointer">gpointer</a> value);</pre>
<p>
Specifies the type of the <em class="parameter"><code>value_destroy_func</code></em> and <em class="parameter"><code>key_destroy_func</code></em> functions
passed to <a href="glib-Caches.html#g-cache-new"><code class="function">g_cache_new()</code></a>.
The functions are passed a pointer to the <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> key or <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> value and
should free any memory and other resources associated with it.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td>
<span class="term"><em class="parameter"><code>value</code></em> :</span></td>
<td>the <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> value to destroy.
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3308217"></a><h3>
<a name="GCacheDupFunc"></a>GCacheDupFunc ()</h3>
<a class="indexterm" name="id3308229"></a><pre class="programlisting"><a href="glib-Basic-Types.html#gpointer">gpointer</a> (*GCacheDupFunc) (<a href="glib-Basic-Types.html#gpointer">gpointer</a> value);</pre>
<p>
Specifies the type of the <em class="parameter"><code>key_dup_func</code></em> function passed to <a href="glib-Caches.html#g-cache-new"><code class="function">g_cache_new()</code></a>.
The function is passed a key (<span class="emphasis"><em>not</em></span> a value as the prototype implies) and
should return a duplicate of the key.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>value</code></em> :</span></td>
<td>the <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> key to destroy (<span class="emphasis"><em>not</em></span> a <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> value as it seems).
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td>a copy of the <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> key.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3308336"></a><h3>
<a name="GCacheNewFunc"></a>GCacheNewFunc ()</h3>
<a class="indexterm" name="id3308348"></a><pre class="programlisting"><a href="glib-Basic-Types.html#gpointer">gpointer</a> (*GCacheNewFunc) (<a href="glib-Basic-Types.html#gpointer">gpointer</a> key);</pre>
<p>
Specifies the type of the <em class="parameter"><code>value_new_func</code></em> function passed to <a href="glib-Caches.html#g-cache-new"><code class="function">g_cache_new()</code></a>.
It is passed a <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> key and should create the value corresponding to the
key.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>key</code></em> :</span></td>
<td>a <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> key.
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td>a new <a href="glib-Caches.html#GCache"><span class="type">GCache</span></a> value corresponding to the key.
</td>
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