<refentry id="glib-Datasets">
<refmeta>
<refentrytitle>Datasets</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>GLIB Library</refmiscinfo>
</refmeta>
<refnamediv>
<refname>Datasets</refname><refpurpose>associate groups of data elements with particular memory locations.</refpurpose>
</refnamediv>
<refsynopsisdiv><title>Synopsis</title>
<synopsis>
#include <glib.h>
#define <link linkend="g-dataset-id-set-data">g_dataset_id_set_data</link> (l, k, d)
<link linkend="void">void</link> <link linkend="g-dataset-id-set-data-full">g_dataset_id_set_data_full</link> (<link linkend="gconstpointer">gconstpointer</link> dataset_location,
<link linkend="GQuark">GQuark</link> key_id,
<link linkend="gpointer">gpointer</link> data,
<link linkend="GDestroyNotify">GDestroyNotify</link> destroy_func);
<link linkend="void">void</link> (<link linkend="GDestroyNotify">*GDestroyNotify</link>) (<link linkend="gpointer">gpointer</link> data);
<link linkend="gpointer">gpointer</link> <link linkend="g-dataset-id-get-data">g_dataset_id_get_data</link> (<link linkend="gconstpointer">gconstpointer</link> dataset_location,
<link linkend="GQuark">GQuark</link> key_id);
#define <link linkend="g-dataset-id-remove-data">g_dataset_id_remove_data</link> (l, k)
<link linkend="gpointer">gpointer</link> <link linkend="g-dataset-id-remove-no-notify">g_dataset_id_remove_no_notify</link> (<link linkend="gconstpointer">gconstpointer</link> dataset_location,
<link linkend="GQuark">GQuark</link> key_id);
#define <link linkend="g-dataset-set-data">g_dataset_set_data</link> (l, k, d)
#define <link linkend="g-dataset-set-data-full">g_dataset_set_data_full</link> (l, k, d, f)
#define <link linkend="g-dataset-get-data">g_dataset_get_data</link> (l, k)
#define <link linkend="g-dataset-remove-data">g_dataset_remove_data</link> (l, k)
#define <link linkend="g-dataset-remove-no-notify">g_dataset_remove_no_notify</link> (l, k)
<link linkend="void">void</link> <link linkend="g-dataset-foreach">g_dataset_foreach</link> (<link linkend="gconstpointer">gconstpointer</link> dataset_location,
<link linkend="GDataForeachFunc">GDataForeachFunc</link> func,
<link linkend="gpointer">gpointer</link> user_data);
<link linkend="void">void</link> (<link linkend="GDataForeachFunc">*GDataForeachFunc</link>) (<link linkend="GQuark">GQuark</link> key_id,
<link linkend="gpointer">gpointer</link> data,
<link linkend="gpointer">gpointer</link> user_data);
<link linkend="void">void</link> <link linkend="g-dataset-destroy">g_dataset_destroy</link> (<link linkend="gconstpointer">gconstpointer</link> dataset_location);
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
Datasets associate groups of data elements with particular memory locations.
These are useful if you need to associate data with a structure returned
from an external library. Since you cannot modify the structure, you use
its location in memory as the key into a dataset, where you can associate
any number of data elements with it.
</para>
<para>
There are two forms of most of the dataset functions.
The first form uses strings to identify the data elements associated with
a location. The second form uses <link linkend="GQuark"><type>GQuark</type></link> identifiers, which are created
with a call to <link linkend="g-quark-from-string"><function>g_quark_from_string()</function></link> or <link linkend="g-quark-from-static-string"><function>g_quark_from_static_string()</function></link>.
The second form is quicker, since it does not require looking up the string
in the hash table of <link linkend="GQuark"><type>GQuark</type></link> identifiers.
</para>
<para>
There is no function to create a dataset. It is automatically created as
soon as you add elements to it.
</para>
<para>
To add data elements to a dataset use <link linkend="g-dataset-id-set-data"><function>g_dataset_id_set_data()</function></link>,
<link linkend="g-dataset-id-set-data-full"><function>g_dataset_id_set_data_full()</function></link>, <link linkend="g-dataset-set-data"><function>g_dataset_set_data()</function></link>
and <link linkend="g-dataset-set-data-full"><function>g_dataset_set_data_full()</function></link>.
</para>
<para>
To get data elements from a dataset use <link linkend="g-dataset-id-get-data"><function>g_dataset_id_get_data()</function></link> and
<link linkend="g-dataset-get-data"><function>g_dataset_get_data()</function></link>.
</para>
<para>
To iterate over all data elements in a dataset use <link linkend="g-dataset-foreach"><function>g_dataset_foreach()</function></link>.
</para>
<para>
To remove data elements from a dataset use <link linkend="g-dataset-id-remove-data"><function>g_dataset_id_remove_data()</function></link> and
<link linkend="g-dataset-remove-data"><function>g_dataset_remove_data()</function></link>.
</para>
<para>
To destroy a dataset, use <link linkend="g-dataset-destroy"><function>g_dataset_destroy()</function></link>.
</para>
</refsect1>
<refsect1>
<title>Details</title>
<refsect2>
<title><anchor id="g-dataset-id-set-data"/>g_dataset_id_set_data()</title>
<indexterm><primary>g_dataset_id_set_data</primary></indexterm><programlisting>#define g_dataset_id_set_data(l, k, d)</programlisting>
<para>
Sets the data element associated with the given <link linkend="GQuark"><type>GQuark</type></link> id.
Any previous data with the same key is removed, and its destroy function
is called.
</para><variablelist role="params">
<varlistentry><term><parameter>l</parameter> :</term>
<listitem><simpara>the location identifying the dataset.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>k</parameter> :</term>
<listitem><simpara>the <link linkend="GQuark"><type>GQuark</type></link> id to identify the data element.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>d</parameter> :</term>
<listitem><simpara>the data element.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="g-dataset-id-set-data-full"/>g_dataset_id_set_data_full ()</title>
<indexterm><primary>g_dataset_id_set_data_full</primary></indexterm><programlisting><link linkend="void">void</link> g_dataset_id_set_data_full (<link linkend="gconstpointer">gconstpointer</link> dataset_location,
<link linkend="GQuark">GQuark</link> key_id,
<link linkend="gpointer">gpointer</link> data,
<link linkend="GDestroyNotify">GDestroyNotify</link> destroy_func);</programlisting>
<para>
Sets the data element associated with the given <link linkend="GQuark"><type>GQuark</type></link> id, and also the
function to call when the data element is destroyed.
Any previous data with the same key is removed, and its
destroy function is called.
</para><variablelist role="params">
<varlistentry><term><parameter>dataset_location</parameter> :</term>
<listitem><simpara>the location identifying the dataset.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>key_id</parameter> :</term>
<listitem><simpara>the <link linkend="GQuark"><type>GQuark</type></link> id to identify the data element.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>data</parameter> :</term>
<listitem><simpara>the data element.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>destroy_func</parameter> :</term>
<listitem><simpara>the function to call when the data element is removed. This
function will be called with the data element and can be used to free any
memory allocated for it.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="GDestroyNotify"/>GDestroyNotify ()</title>
<indexterm><primary>GDestroyNotify</primary></indexterm><programlisting><link linkend="void">void</link> (*GDestroyNotify) (<link linkend="gpointer">gpointer</link> data);</programlisting>
<para>
Specifies the type of function which is called when a data element is
destroyed. It is passed the pointer to the data element and should free
any memory and resources allocated for it.
</para><variablelist role="params">
<varlistentry><term><parameter>data</parameter> :</term>
<listitem><simpara>the data element.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="g-dataset-id-get-data"/>g_dataset_id_get_data ()</title>
<indexterm><primary>g_dataset_id_get_data</primary></indexterm><programlisting><link linkend="gpointer">gpointer</link> g_dataset_id_get_data (<link linkend="gconstpointer">gconstpointer</link> dataset_location,
<link linkend="GQuark">GQuark</link> key_id);</programlisting>
<para>
Gets the data element corresponding to a <link linkend="GQuark"><type>GQuark</type></link>.
</para><variablelist role="params">
<varlistentry><term><parameter>dataset_location</parameter> :</term>
<listitem><simpara>the location identifying the dataset.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>key_id</parameter> :</term>
<listitem><simpara>the <link linkend="GQuark"><type>GQuark</type></link> id to identify the data element.
</simpara></listitem></varlistentry>
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara>the data element corresponding to the <link linkend="GQuark"><type>GQuark</type></link>, or <literal>NULL</literal> if it is
not found.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="g-dataset-id-remove-data"/>g_dataset_id_remove_data()</title>
<indexterm><primary>g_dataset_id_remove_data</primary></indexterm><programlisting>#define g_dataset_id_remove_data(l, k)</programlisting>
<para>
Removes a data element from a dataset.
The data element's destroy function is called if it has been set.
</para><variablelist role="params">
<varlistentry><term><parameter>l</parameter> :</term>
<listitem><simpara>the location identifying the dataset.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>k</parameter> :</term>
<listitem><simpara>the <link linkend="GQuark"><type>GQuark</type></link> id identifying the data element.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="g-dataset-id-remove-no-notify"/>g_dataset_id_remove_no_notify ()</title>
<indexterm><primary>g_dataset_id_remove_no_notify</primary></indexterm><programlisting><link linkend="gpointer">gpointer</link> g_dataset_id_remove_no_notify (<link linkend="gconstpointer">gconstpointer</link> dataset_location,
<link linkend="GQuark">GQuark</link> key_id);</programlisting>
<para>
Removes an element, without calling its destroy notification function.
</para><variablelist role="params">
<varlistentry><term><parameter>dataset_location</parameter> :</term>
<listitem><simpara>the location identifying the dataset.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>key_id</parameter> :</term>
<listitem><simpara>the <link linkend="GQuark"><type>GQuark</type></link> ID identifying the data element.
</simpara></listitem></varlistentry>
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara>the data previously stored at <parameter>key_id</parameter>, or <literal>NULL</literal> if none.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="g-dataset-set-data"/>g_dataset_set_data()</title>
<indexterm><primary>g_dataset_set_data</primary></indexterm><programlisting>#define g_dataset_set_data(l, k, d)</programlisting>
<para>
Sets the data corresponding to the given string identifier.
</para><variablelist role="params">
<varlistentry><term><parameter>l</parameter> :</term>
<listitem><simpara>the location identifying the dataset.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>k</parameter> :</term>
<listitem><simpara>the string to identify the data element.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>d</parameter> :</term>
<listitem><simpara>the data element.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="g-dataset-set-data-full"/>g_dataset_set_data_full()</title>
<indexterm><primary>g_dataset_set_data_full</primary></indexterm><programlisting>#define g_dataset_set_data_full(l, k, d, f)</programlisting>
<para>
Sets the data corresponding to the given string identifier, and the function
to call when the data element is destroyed.
</para><variablelist role="params">
<varlistentry><term><parameter>l</parameter> :</term>
<listitem><simpara>the location identifying the dataset.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>k</parameter> :</term>
<listitem><simpara>the string to identify the data element.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>d</parameter> :</term>
<listitem><simpara>the data element.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>f</parameter> :</term>
<listitem><simpara>the function to call when the data element is removed. This
function will be called with the data element and can be used to free any
memory allocated for it.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="g-dataset-get-data"/>g_dataset_get_data()</title>
<indexterm><primary>g_dataset_get_data</primary></indexterm><programlisting>#define g_dataset_get_data(l, k)</programlisting>
<para>
Gets the data element corresponding to a string.
</para><variablelist role="params">
<varlistentry><term><parameter>l</parameter> :</term>
<listitem><simpara>the location identifying the dataset.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>k</parameter> :</term>
<listitem><simpara>the string identifying the data element.
</simpara></listitem></varlistentry>
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara>the data element corresponding to the string, or <literal>NULL</literal> if it is not
found.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="g-dataset-remove-data"/>g_dataset_remove_data()</title>
<indexterm><primary>g_dataset_remove_data</primary></indexterm><programlisting>#define g_dataset_remove_data(l, k)</programlisting>
<para>
Removes a data element corresponding to a string.
Its destroy function is called if it has been set.
</para><variablelist role="params">
<varlistentry><term><parameter>l</parameter> :</term>
<listitem><simpara>the location identifying the dataset.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>k</parameter> :</term>
<listitem><simpara>the string identifying the data element.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="g-dataset-remove-no-notify"/>g_dataset_remove_no_notify()</title>
<indexterm><primary>g_dataset_remove_no_notify</primary></indexterm><programlisting>#define g_dataset_remove_no_notify(l, k)</programlisting>
<para>
Removes an element, without calling its destroy notifier.
</para><variablelist role="params">
<varlistentry><term><parameter>l</parameter> :</term>
<listitem><simpara>the location identifying the dataset.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>k</parameter> :</term>
<listitem><simpara>the string identifying the data element.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="g-dataset-foreach"/>g_dataset_foreach ()</title>
<indexterm><primary>g_dataset_foreach</primary></indexterm><programlisting><link linkend="void">void</link> g_dataset_foreach (<link linkend="gconstpointer">gconstpointer</link> dataset_location,
<link linkend="GDataForeachFunc">GDataForeachFunc</link> func,
<link linkend="gpointer">gpointer</link> user_data);</programlisting>
<para>
Calls the given function for each data element which is associated with the
given location.
</para><variablelist role="params">
<varlistentry><term><parameter>dataset_location</parameter> :</term>
<listitem><simpara>the location identifying the dataset.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>func</parameter> :</term>
<listitem><simpara>the function to call for each data element.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>user_data</parameter> :</term>
<listitem><simpara>user data to pass to the function.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="GDataForeachFunc"/>GDataForeachFunc ()</title>
<indexterm><primary>GDataForeachFunc</primary></indexterm><programlisting><link linkend="void">void</link> (*GDataForeachFunc) (<link linkend="GQuark">GQuark</link> key_id,
<link linkend="gpointer">gpointer</link> data,
<link linkend="gpointer">gpointer</link> user_data);</programlisting>
<para>
Specifies the type of function passed to <link linkend="g-dataset-foreach"><function>g_dataset_foreach()</function></link>.
It is called with each <link linkend="GQuark"><type>GQuark</type></link> id and associated data element,
together with the <parameter>user_data</parameter> parameter supplied to <link linkend="g-dataset-foreach"><function>g_dataset_foreach()</function></link>.
</para><variablelist role="params">
<varlistentry><term><parameter>key_id</parameter> :</term>
<listitem><simpara>the <link linkend="GQuark"><type>GQuark</type></link> id to identifying the data element.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>data</parameter> :</term>
<listitem><simpara>the data element.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>user_data</parameter> :</term>
<listitem><simpara>user data passed to <link linkend="g-dataset-foreach"><function>g_dataset_foreach()</function></link>.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="g-dataset-destroy"/>g_dataset_destroy ()</title>
<indexterm><primary>g_dataset_destroy</primary></indexterm><programlisting><link linkend="void">void</link> g_dataset_destroy (<link linkend="gconstpointer">gconstpointer</link> dataset_location);</programlisting>
<para>
Destroys the dataset, freeing all memory allocated, and calling any
destroy functions set for data elements.
</para><variablelist role="params">
<varlistentry><term><parameter>dataset_location</parameter> :</term>
<listitem><simpara>the location identifying the dataset.
</simpara></listitem></varlistentry>
</variablelist></refsect2>
</refsect1>
</refentry>