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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"><title>Caches</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2"><link rel="start" href="index.html" title="GLib Reference Manual"><link rel="up" href="glib-data-types.html" title="GLib Data Types"><link rel="prev" href="glib-Relations-and-Tuples.html" title="Relations and Tuples"><link rel="next" href="glib-Memory-Allocators.html" title="Memory Allocators"><meta name="generator" content="GTK-Doc V1.9 (XML mode)"><link rel="stylesheet" href="style.css" type="text/css"><link rel="chapter" href="glib.html" title="GLib Overview"><link rel="chapter" href="glib-fundamentals.html" title="GLib Fundamentals"><link rel="chapter" href="glib-core.html" title="GLib Core Application Support"><link rel="chapter" href="glib-utilities.html" title="GLib Utilities"><link rel="chapter" href="glib-data-types.html" title="GLib Data 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href="glib-Relations-and-Tuples.html"><img src="left.png" width="24" height="24" border="0" alt="Prev"></a></td><td><a accesskey="u" href="glib-data-types.html"><img src="up.png" width="24" height="24" border="0" alt="Up"></a></td><td><a accesskey="h" href="index.html"><img src="home.png" width="24" height="24" border="0" alt="Home"></a></td><th width="100%" align="center">GLib Reference Manual</th><td><a accesskey="n" href="glib-Memory-Allocators.html"><img src="right.png" width="24" height="24" border="0" alt="Next"></a></td></tr><tr><td colspan="5" class="shortcuts"><nobr><a href="#id3365593" class="shortcut">Top</a>  |  <a href="#id3365914" 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="id3365593"></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 class="link" href="glib-Caches.html#GCache">GCache</a>;<a class="link" href="glib-Caches.html#GCache">GCache</a>* <a class="link" href="glib-Caches.html#g-cache-new">g_cache_new</a> (<a class="link" href="glib-Caches.html#GCacheNewFunc">GCacheNewFunc</a> value_new_func, <a class="link" href="glib-Caches.html#GCacheDestroyFunc">GCacheDestroyFunc</a> value_destroy_func, <a class="link" href="glib-Caches.html#GCacheDupFunc">GCacheDupFunc</a> key_dup_func, <a class="link" href="glib-Caches.html#GCacheDestroyFunc">GCacheDestroyFunc</a> key_destroy_func, <a class="link" href="glib-Hash-Tables.html#GHashFunc">GHashFunc</a> hash_key_func, <a class="link" href="glib-Hash-Tables.html#GHashFunc">GHashFunc</a> hash_value_func, <a class="link" href="glib-Hash-Tables.html#GEqualFunc">GEqualFunc</a> key_equal_func);<a class="link" href="glib-Basic-Types.html#gpointer">gpointer</a> <a class="link" href="glib-Caches.html#g-cache-insert">g_cache_insert</a> (<a class="link" href="glib-Caches.html#GCache">GCache</a> *cache, <a class="link" href="glib-Basic-Types.html#gpointer">gpointer</a> key);void <a class="link" href="glib-Caches.html#g-cache-remove">g_cache_remove</a> (<a class="link" href="glib-Caches.html#GCache">GCache</a> *cache, <a class="link" href="glib-Basic-Types.html#gconstpointer">gconstpointer</a> value);void <a class="link" href="glib-Caches.html#g-cache-destroy">g_cache_destroy</a> (<a class="link" href="glib-Caches.html#GCache">GCache</a> *cache);void <a class="link" href="glib-Caches.html#g-cache-key-foreach">g_cache_key_foreach</a> (<a class="link" href="glib-Caches.html#GCache">GCache</a> *cache, <a class="link" href="glib-Hash-Tables.html#GHFunc">GHFunc</a> func, <a class="link" href="glib-Basic-Types.html#gpointer">gpointer</a> user_data);void <a class="link" href="glib-Caches.html#g-cache-value-foreach">g_cache_value_foreach</a> (<a class="link" href="glib-Caches.html#GCache">GCache</a> *cache, <a class="link" href="glib-Hash-Tables.html#GHFunc">GHFunc</a> func, <a class="link" href="glib-Basic-Types.html#gpointer">gpointer</a> user_data);void (<a class="link" href="glib-Caches.html#GCacheDestroyFunc">*GCacheDestroyFunc</a>) (<a class="link" href="glib-Basic-Types.html#gpointer">gpointer</a> value);<a class="link" href="glib-Basic-Types.html#gpointer">gpointer</a> (<a class="link" href="glib-Caches.html#GCacheDupFunc">*GCacheDupFunc</a>) (<a class="link" href="glib-Basic-Types.html#gpointer">gpointer</a> value);<a class="link" href="glib-Basic-Types.html#gpointer">gpointer</a> (<a class="link" href="glib-Caches.html#GCacheNewFunc">*GCacheNewFunc</a>) (<a class="link" href="glib-Basic-Types.html#gpointer">gpointer</a> key);</pre></div><div class="refsect1" lang="en"><a name="id3365914"></a><h2>Description</h2><p>A <a class="link" href="glib-Caches.html#GCache"><span class="type">GCache</span></a> allows sharing of complex data structures, in order to savesystem resources.</p><p>GTK+ uses caches for <span class="type">GtkStyles</span> and <span class="type">GdkGCs</span>. These consume a lot ofresources, so a <a class="link" href="glib-Caches.html#GCache"><span class="type">GCache</span></a> is used to see if a <ahref="/usr/share/gtk-doc/html/gtk/GtkStyle.html"><span class="type">GtkStyle</span></a> or <ahref="/usr/share/gtk-doc/html/gdk/gdk-Graphics-Contexts.html#GdkGC"><span class="type">GdkGC</span></a> with therequired properties already exists. If it does, then the existingobject is used instead of creating a new one.</p><p><a class="link" href="glib-Caches.html#GCache"><span class="type">GCache</span></a> uses keys and values.A <a class="link" href="glib-Caches.html#GCache"><span class="type">GCache</span></a> key describes the properties of a particular resource.A <a class="link" 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="id3366016"></a><h2>Details</h2><div class="refsect2" lang="en"><a name="id3366026"></a><h3><a name="GCache"></a>GCache</h3><a class="indexterm" name="id3366039"></a><pre class="programlisting">typedef struct _GCache GCache;</pre><p>The <a class="link" href="glib-Caches.html#GCache"><span class="type">GCache</span></a> struct is an opaque data structure containing information abouta <a class="link" 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="id3366072"></a><h3><a name="g-cache-new"></a>g_cache_new ()</h3><a class="indexterm" name="id3366084"></a><pre class="programlisting"><a class="link" href="glib-Caches.html#GCache">GCache</a>* g_cache_new (<a class="link" href="glib-Caches.html#GCacheNewFunc">GCacheNewFunc</a> value_new_func, <a class="link" href="glib-Caches.html#GCacheDestroyFunc">GCacheDestroyFunc</a> value_destroy_func, <a class="link" href="glib-Caches.html#GCacheDupFunc">GCacheDupFunc</a> key_dup_func, <a class="link" href="glib-Caches.html#GCacheDestroyFunc">GCacheDestroyFunc</a> key_destroy_func, <a class="link" href="glib-Hash-Tables.html#GHashFunc">GHashFunc</a> hash_key_func, <a class="link" href="glib-Hash-Tables.html#GHashFunc">GHashFunc</a> hash_value_func, <a class="link" href="glib-Hash-Tables.html#GEqualFunc">GEqualFunc</a> key_equal_func);</pre><p>Creates a new <a class="link" 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><p><span class="term"><em class="parameter"><code>value_new_func</code></em> :</span></p></td><td>a function to create a new object given a key.This is called by <a class="link" href="glib-Caches.html#g-cache-insert"><code class="function">g_cache_insert()</code></a> if an object with the given keydoes not already exist.</td></tr><tr><td><p><span class="term"><em class="parameter"><code>value_destroy_func</code></em> :</span></p></td><td>a function to destroy an object. It iscalled by <a class="link" href="glib-Caches.html#g-cache-remove"><code class="function">g_cache_remove()</code></a> when the object is no longer needed (i.e. itsreference count drops to 0).</td></tr><tr><td><p><span class="term"><em class="parameter"><code>key_dup_func</code></em> :</span></p></td><td>a function to copy a key. It is called by<a class="link" 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 class="link" href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.</td></tr><tr><td><p><span class="term"><em class="parameter"><code>key_destroy_func</code></em> :</span></p></td><td>a function to destroy a key. It iscalled by <a class="link" href="glib-Caches.html#g-cache-remove"><code class="function">g_cache_remove()</code></a> when the object is no longer needed (i.e. itsreference count drops to 0).</td></tr><tr><td><p><span class="term"><em class="parameter"><code>hash_key_func</code></em> :</span></p></td><td>a function to create a hash value from a key.</td></tr><tr><td><p><span class="term"><em class="parameter"><code>hash_value_func</code></em> :</span></p></td><td>a function to create a hash value from a value.</td></tr><tr><td><p><span class="term"><em class="parameter"><code>key_equal_func</code></em> :</span></p></td><td>a function to compare two keys. It should return <a class="link" href="glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> ifthe two keys are equivalent.</td></tr><tr><td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td><td>a new <a class="link" 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="id3366360"></a><h3><a name="g-cache-insert"></a>g_cache_insert ()</h3><a class="indexterm" name="id3366373"></a><pre class="programlisting"><a class="link" href="glib-Basic-Types.html#gpointer">gpointer</a> g_cache_insert (<a class="link" href="glib-Caches.html#GCache">GCache</a> *cache, <a class="link" 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 class="link" href="glib-Caches.html#GCache"><span class="type">GCache</span></a>, by usingthe <em class="parameter"><code>key_equal_func</code></em> function passed to <a class="link" 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 increasedby 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 insertedinto the <a class="link" 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><p><span class="term"><em class="parameter"><code>cache</code></em> :</span></p></td><td>a <a class="link" href="glib-Caches.html#GCache"><span class="type">GCache</span></a>.</td></tr><tr><td><p><span class="term"><em class="parameter"><code>key</code></em> :</span></p></td><td>a key describing a <a class="link" href="glib-Caches.html#GCache"><span class="type">GCache</span></a> object.</td></tr><tr><td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td><td>a pointer to a <a class="link" href="glib-Caches.html#GCache"><span class="type">GCache</span></a> value.⌨️ 快捷键说明
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