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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>GObject Reference Manual: Varargs Value Collection</title>
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<a href="#gobject-Varargs-Value-Collection.description" class="shortcut">Description</a>
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<a name="gobject-Varargs-Value-Collection"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="gobject-Varargs-Value-Collection.top_of_page"></a>Varargs Value Collection</span></h2>
<p>Varargs Value Collection — Converting varargs to generic values</p>
</td>
<td valign="top" align="right"></td>
</tr></table></div>
<div class="refsynopsisdiv">
<a name="gobject-Varargs-Value-Collection.synopsis"></a><h2>Synopsis</h2>
<pre class="synopsis">
#include <glib-object.h>
#include <gobject/gvaluecollector.h>
union <a class="link" href="gobject-Varargs-Value-Collection.html#GTypeCValue" title="union GTypeCValue">GTypeCValue</a>;
#define <a class="link" href="gobject-Varargs-Value-Collection.html#G-VALUE-COLLECT-INIT:CAPS" title="G_VALUE_COLLECT_INIT()">G_VALUE_COLLECT_INIT</a> (value,
_value_type,
var_args,
flags,
__error)
#define <a class="link" href="gobject-Varargs-Value-Collection.html#G-VALUE-COLLECT:CAPS" title="G_VALUE_COLLECT()">G_VALUE_COLLECT</a> (value,
var_args,
flags,
__error)
#define <a class="link" href="gobject-Varargs-Value-Collection.html#G-VALUE-COLLECT-SKIP:CAPS" title="G_VALUE_COLLECT_SKIP()">G_VALUE_COLLECT_SKIP</a> (_value_type,
var_args)
#define <a class="link" href="gobject-Varargs-Value-Collection.html#G-VALUE-LCOPY:CAPS" title="G_VALUE_LCOPY()">G_VALUE_LCOPY</a> (value,
var_args,
flags,
__error)
#define <a class="link" href="gobject-Varargs-Value-Collection.html#G-VALUE-COLLECT-FORMAT-MAX-LENGTH:CAPS" title="G_VALUE_COLLECT_FORMAT_MAX_LENGTH">G_VALUE_COLLECT_FORMAT_MAX_LENGTH</a>
</pre>
</div>
<div class="refsect1">
<a name="gobject-Varargs-Value-Collection.description"></a><h2>Description</h2>
<p>
The macros in this section provide the varargs parsing support needed
in variadic GObject functions such as <a class="link" href="gobject-The-Base-Object-Type.html#g-object-new" title="g_object_new ()"><code class="function">g_object_new()</code></a> or <a class="link" href="gobject-The-Base-Object-Type.html#g-object-set" title="g_object_set ()"><code class="function">g_object_set()</code></a>.
They currently support the collection of integral types, floating point
types and pointers.
</p>
</div>
<div class="refsect1">
<a name="gobject-Varargs-Value-Collection.details"></a><h2>Details</h2>
<div class="refsect2">
<a name="GTypeCValue"></a><h3>union GTypeCValue</h3>
<pre class="programlisting">union _GTypeCValue
{
gint v_int;
glong v_long;
gint64 v_int64;
gdouble v_double;
gpointer v_pointer;
};
</pre>
<p>
A union holding one collected value.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gint"><span class="type">gint</span></a> <em class="structfield"><code><a name="GTypeCValue.v-int"></a>v_int</code></em>;</span></p></td>
<td>the field for holding integer values</td>
</tr>
<tr>
<td><p><span class="term"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#glong"><span class="type">glong</span></a> <em class="structfield"><code><a name="GTypeCValue.v-long"></a>v_long</code></em>;</span></p></td>
<td>the field for holding long integer values</td>
</tr>
<tr>
<td><p><span class="term"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gint64"><span class="type">gint64</span></a> <em class="structfield"><code><a name="GTypeCValue.v-int64"></a>v_int64</code></em>;</span></p></td>
<td>the field for holding 64 bit integer values</td>
</tr>
<tr>
<td><p><span class="term"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> <em class="structfield"><code><a name="GTypeCValue.v-double"></a>v_double</code></em>;</span></p></td>
<td>the field for holding floating point values</td>
</tr>
<tr>
<td><p><span class="term"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> <em class="structfield"><code><a name="GTypeCValue.v-pointer"></a>v_pointer</code></em>;</span></p></td>
<td>the field for holding pointers</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="G-VALUE-COLLECT-INIT:CAPS"></a><h3>G_VALUE_COLLECT_INIT()</h3>
<pre class="programlisting">#define G_VALUE_COLLECT_INIT(value, _value_type, var_args, flags, __error)</pre>
<p>
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.
</p>
<div class="variablelist"><table border="0" class="variablelist">
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<col align="left" valign="top">
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</colgroup>
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<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>a <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> return location. <em class="parameter"><code>value</code></em> must contain only 0 bytes.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>_value_type</code></em> :</span></p></td>
<td>the <a class="link" href="gobject-Type-Information.html#GType" title="GType"><span class="type">GType</span></a> to use for <em class="parameter"><code>value</code></em>.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>var_args</code></em> :</span></p></td>
<td>the va_list variable; it may be evaluated multiple times</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>flags</code></em> :</span></p></td>
<td>flags which are passed on to the <code class="function">collect_value()</code> function of
the <a class="link" href="gobject-Type-Information.html#GTypeValueTable" title="struct GTypeValueTable"><span class="type">GTypeValueTable</span></a> of <em class="parameter"><code>value</code></em>.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>__error</code></em> :</span></p></td>
<td>a <a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a>** variable that will be modified to hold a <a href="http://library.gnome.org/devel/glib/unstable/glib-Memory-Allocation.html#g-new"><code class="function">g_new()</code></a>
allocated error messages if something fails</td>
</tr>
</tbody>
</table></div>
<p class="since">Since 2.24</p>
</div>
<hr>
<div class="refsect2">
<a name="G-VALUE-COLLECT:CAPS"></a><h3>G_VALUE_COLLECT()</h3>
<pre class="programlisting">#define G_VALUE_COLLECT(value, var_args, flags, __error)</pre>
<p>
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.
</p>
<p>
Note: If you are creating the <em class="parameter"><code>value</code></em> argument just before calling this macro,
you should use the <a class="link" href="gobject-Varargs-Value-Collection.html#G-VALUE-COLLECT-INIT:CAPS" title="G_VALUE_COLLECT_INIT()"><span class="type">G_VALUE_COLLECT_INIT</span></a> variant and pass the unitialized
<a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a>. That variant is faster than <a class="link" href="gobject-Varargs-Value-Collection.html#G-VALUE-COLLECT:CAPS" title="G_VALUE_COLLECT()"><span class="type">G_VALUE_COLLECT</span></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
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<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>a <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> return location. <em class="parameter"><code>value</code></em> is supposed to be initialized
according to the value type to be collected</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>var_args</code></em> :</span></p></td>
<td>the va_list variable; it may be evaluated multiple times</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>flags</code></em> :</span></p></td>
<td>flags which are passed on to the <code class="function">collect_value()</code> function of
the <a class="link" href="gobject-Type-Information.html#GTypeValueTable" title="struct GTypeValueTable"><span class="type">GTypeValueTable</span></a> of <em class="parameter"><code>value</code></em>.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>__error</code></em> :</span></p></td>
<td>a <a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a>** variable that will be modified to hold a <a href="http://library.gnome.org/devel/glib/unstable/glib-Memory-Allocation.html#g-new"><code class="function">g_new()</code></a>
allocated error messages if something fails</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="G-VALUE-COLLECT-SKIP:CAPS"></a><h3>G_VALUE_COLLECT_SKIP()</h3>
<pre class="programlisting">#define G_VALUE_COLLECT_SKIP(_value_type, var_args)</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="G-VALUE-LCOPY:CAPS"></a><h3>G_VALUE_LCOPY()</h3>
<pre class="programlisting">#define G_VALUE_LCOPY(value, var_args, flags, __error)</pre>
<p>
Collects a value's variable argument locations from a va_list. Usage is
analogous to <a class="link" href="gobject-Varargs-Value-Collection.html#G-VALUE-COLLECT:CAPS" title="G_VALUE_COLLECT()"><code class="function">G_VALUE_COLLECT()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>a <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a> return location. <em class="parameter"><code>value</code></em> is supposed to be initialized
according to the value type to be collected</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>var_args</code></em> :</span></p></td>
<td>the va_list variable; it may be evaluated multiple times</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>flags</code></em> :</span></p></td>
<td>flags which are passed on to the <code class="function">lcopy_value()</code> function of
the <a class="link" href="gobject-Type-Information.html#GTypeValueTable" title="struct GTypeValueTable"><span class="type">GTypeValueTable</span></a> of <em class="parameter"><code>value</code></em>.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>__error</code></em> :</span></p></td>
<td>a <a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a>** variable that will be modified to hold a <a href="http://library.gnome.org/devel/glib/unstable/glib-Memory-Allocation.html#g-new"><code class="function">g_new()</code></a>
allocated error messages if something fails</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="G-VALUE-COLLECT-FORMAT-MAX-LENGTH:CAPS"></a><h3>G_VALUE_COLLECT_FORMAT_MAX_LENGTH</h3>
<pre class="programlisting">#define G_VALUE_COLLECT_FORMAT_MAX_LENGTH (8)
</pre>
<p>
The maximal number of <a class="link" href="gobject-Varargs-Value-Collection.html#GTypeCValue" title="union GTypeCValue"><span class="type">GTypeCValue</span></a>s which can be collected for a
single <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a>.
</p>
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