value_collection.xml   [plain text]

<refentry id="gobject-Varargs-Value-Collection">
<refmeta>
<refentrytitle>Varargs Value Collection</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>GOBJECT Library</refmiscinfo>
</refmeta>

<refnamediv>
<refname>Varargs Value Collection</refname><refpurpose>Converting varargs to generic values</refpurpose>
</refnamediv>

<refsynopsisdiv><title>Synopsis</title>

<synopsis>

#include &lt;glib-object.h&gt;
#include &lt;gobject/gvaluecollector.h&gt;


union       <link linkend="GTypeCValue">GTypeCValue</link>;
#define     <link linkend="G-VALUE-COLLECT-CAPS">G_VALUE_COLLECT</link>                 (value, var_args, flags, __error)
#define     <link linkend="G-VALUE-LCOPY-CAPS">G_VALUE_LCOPY</link>                   (value, var_args, flags, __error)
#define     <link linkend="G-VALUE-COLLECT-FORMAT-MAX-LENGTH-CAPS">G_VALUE_COLLECT_FORMAT_MAX_LENGTH</link>
</synopsis>
</refsynopsisdiv>









<refsect1>
<title>Description</title>
<para>

</para>
</refsect1>

<refsect1>
<title>Details</title>
<refsect2>
<title><anchor id="GTypeCValue"/>union GTypeCValue</title>
<indexterm><primary>GTypeCValue</primary></indexterm><programlisting>union GTypeCValue
{
  gint     v_int;
  glong    v_long;
  gint64   v_int64;
  gdouble  v_double;
  gpointer v_pointer;
};
</programlisting>
<para>
A union holding one collected value.
</para></refsect2>
<refsect2>
<title><anchor id="G-VALUE-COLLECT-CAPS"/>G_VALUE_COLLECT()</title>
<indexterm><primary>G_VALUE_COLLECT</primary></indexterm><programlisting>#define     G_VALUE_COLLECT(value, var_args, flags, __error)</programlisting>
<para>
Collects a variable argument value from a va_list. We have to
implement the varargs collection as a macro, because on some systems
va_list variables cannot be passed by reference.
</para><variablelist role="params">
<varlistentry><term><parameter>value</parameter>&nbsp;:</term>
<listitem><simpara>a <link linkend="GValue"><type>GValue</type></link> return location. <parameter>value</parameter> is supposed to be initialized 
  according to the value type to be collected
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>var_args</parameter>&nbsp;:</term>
<listitem><simpara>the va_list variable; it may be evaluated multiple times
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>flags</parameter>&nbsp;:</term>
<listitem><simpara>flags which are passed on to the <link linkend="collect-value"><function>collect_value()</function></link> function of
  the <link linkend="GTypeValueTable"><type>GTypeValueTable</type></link> of <parameter>value</parameter>.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>__error</parameter>&nbsp;:</term>
<listitem><simpara>a <link linkend="gchar"><type>gchar</type></link>** variable that will be modified to hold a <link linkend="g-new"><function>g_new()</function></link>
  allocated error messages if something fails


</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="G-VALUE-LCOPY-CAPS"/>G_VALUE_LCOPY()</title>
<indexterm><primary>G_VALUE_LCOPY</primary></indexterm><programlisting>#define     G_VALUE_LCOPY(value, var_args, flags, __error)</programlisting>
<para>
Collects a value's variable argument locations from a va_list. 
</para><variablelist role="params">
<varlistentry><term><parameter>value</parameter>&nbsp;:</term>
<listitem><simpara>a <link linkend="GValue"><type>GValue</type></link> return location. <parameter>value</parameter> is supposed to be initialized 
  according to the value type to be collected
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>var_args</parameter>&nbsp;:</term>
<listitem><simpara>the va_list variable; it may be evaluated multiple times
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>flags</parameter>&nbsp;:</term>
<listitem><simpara>flags which are passed on to the <link linkend="lcopy-value"><function>lcopy_value()</function></link> function of
  the <link linkend="GTypeValueTable"><type>GTypeValueTable</type></link> of <parameter>value</parameter>.
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>__error</parameter>&nbsp;:</term>
<listitem><simpara>a <link linkend="gchar"><type>gchar</type></link>** variable that will be modified to hold a <link linkend="g-new"><function>g_new()</function></link>
  allocated error messages if something fails


</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="G-VALUE-COLLECT-FORMAT-MAX-LENGTH-CAPS"/>G_VALUE_COLLECT_FORMAT_MAX_LENGTH</title>
<indexterm><primary>G_VALUE_COLLECT_FORMAT_MAX_LENGTH</primary></indexterm><programlisting>#define	G_VALUE_COLLECT_FORMAT_MAX_LENGTH	(8)
</programlisting>
<para>
The maximal number of <link linkend="GTypeCValue"><type>GTypeCValue</type></link><!-- -->s which can be collected for a 
single <link linkend="GValue"><type>GValue</type></link>.
</para></refsect2>

</refsect1>




</refentry>