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<a name="glib-Atomic-Operations"></a><div class="titlepage"></div>
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<td valign="top">
<h2><span class="refentrytitle"><a name="glib-Atomic-Operations.top_of_page"></a>Atomic Operations</span></h2>
<p>Atomic Operations — basic atomic integer and pointer operations</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
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<div class="refsect1">
<a name="glib-Atomic-Operations.functions"></a><h2>Functions</h2>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>
<tbody>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="returnvalue">gint</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-int-get" title="g_atomic_int_get ()">g_atomic_int_get</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-int-set" title="g_atomic_int_set ()">g_atomic_int_set</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-int-inc" title="g_atomic_int_inc ()">g_atomic_int_inc</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#gboolean" title="gboolean"><span class="returnvalue">gboolean</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-int-dec-and-test" title="g_atomic_int_dec_and_test ()">g_atomic_int_dec_and_test</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#gboolean" title="gboolean"><span class="returnvalue">gboolean</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-int-compare-and-exchange" title="g_atomic_int_compare_and_exchange ()">g_atomic_int_compare_and_exchange</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="returnvalue">gint</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-int-add" title="g_atomic_int_add ()">g_atomic_int_add</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="returnvalue">guint</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-int-and" title="g_atomic_int_and ()">g_atomic_int_and</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="returnvalue">guint</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-int-or" title="g_atomic_int_or ()">g_atomic_int_or</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="returnvalue">guint</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-int-xor" title="g_atomic_int_xor ()">g_atomic_int_xor</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#gpointer" title="gpointer"><span class="returnvalue">gpointer</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-pointer-get" title="g_atomic_pointer_get ()">g_atomic_pointer_get</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-pointer-set" title="g_atomic_pointer_set ()">g_atomic_pointer_set</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#gboolean" title="gboolean"><span class="returnvalue">gboolean</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-pointer-compare-and-exchange" title="g_atomic_pointer_compare_and_exchange ()">g_atomic_pointer_compare_and_exchange</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#gssize" title="gssize"><span class="returnvalue">gssize</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-pointer-add" title="g_atomic_pointer_add ()">g_atomic_pointer_add</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="returnvalue">gsize</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-pointer-and" title="g_atomic_pointer_and ()">g_atomic_pointer_and</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="returnvalue">gsize</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-pointer-or" title="g_atomic_pointer_or ()">g_atomic_pointer_or</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="returnvalue">gsize</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-pointer-xor" title="g_atomic_pointer_xor ()">g_atomic_pointer_xor</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="returnvalue">gint</span></a>
</td>
<td class="function_name">
<a class="link" href="glib-Atomic-Operations.html#g-atomic-int-exchange-and-add" title="g_atomic_int_exchange_and_add ()">g_atomic_int_exchange_and_add</a> <span class="c_punctuation">()</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="glib-Atomic-Operations.other"></a><h2>Types and Values</h2>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="name">
<col class="description">
</colgroup>
<tbody><tr>
<td class="define_keyword">#define</td>
<td class="function_name"><a class="link" href="glib-Atomic-Operations.html#G-ATOMIC-LOCK-FREE:CAPS" title="G_ATOMIC_LOCK_FREE">G_ATOMIC_LOCK_FREE</a></td>
</tr></tbody>
</table></div>
</div>
<div class="refsect1">
<a name="glib-Atomic-Operations.includes"></a><h2>Includes</h2>
<pre class="synopsis">#include <glib.h>
</pre>
</div>
<div class="refsect1">
<a name="glib-Atomic-Operations.description"></a><h2>Description</h2>
<p>The following is a collection of compiler macros to provide atomic
access to integer and pointer-sized values.</p>
<p>The macros that have 'int' in the name will operate on pointers to
<a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> and <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a>. The macros with 'pointer' in the name will operate
on pointers to any pointer-sized value, including <a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="type">gsize</span></a>. There is
no support for 64bit operations on platforms with 32bit pointers
because it is not generally possible to perform these operations
atomically.</p>
<p>The get, set and exchange operations for integers and pointers
nominally operate on <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> and <a class="link" href="glib-Basic-Types.html#gpointer" title="gpointer"><span class="type">gpointer</span></a>, respectively. Of the
arithmetic operations, the 'add' operation operates on (and returns)
signed integer values (<a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> and <a class="link" href="glib-Basic-Types.html#gssize" title="gssize"><span class="type">gssize</span></a>) and the 'and', 'or', and
'xor' operations operate on (and return) unsigned integer values
(<a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a> and <a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="type">gsize</span></a>).</p>
<p>All of the operations act as a full compiler and (where appropriate)
hardware memory barrier. Acquire and release or producer and
consumer barrier semantics are not available through this API.</p>
<p>It is very important that all accesses to a particular integer or
pointer be performed using only this API and that different sizes of
operation are not mixed or used on overlapping memory regions. Never
read or assign directly from or to a value -- always use this API.</p>
<p>For simple reference counting purposes you should use
<a class="link" href="glib-Atomic-Operations.html#g-atomic-int-inc" title="g_atomic_int_inc ()"><code class="function">g_atomic_int_inc()</code></a> and <a class="link" href="glib-Atomic-Operations.html#g-atomic-int-dec-and-test" title="g_atomic_int_dec_and_test ()"><code class="function">g_atomic_int_dec_and_test()</code></a>. Other uses that
fall outside of simple reference counting patterns are prone to
subtle bugs and occasionally undefined behaviour. It is also worth
noting that since all of these operations require global
synchronisation of the entire machine, they can be quite slow. In * the case of performing multiple atomic operations it can often be
faster to simply acquire a mutex lock around the critical area,
perform the operations normally and then release the lock.</p>
</div>
<div class="refsect1">
<a name="glib-Atomic-Operations.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="g-atomic-int-get"></a><h3>g_atomic_int_get ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="returnvalue">gint</span></a>
g_atomic_int_get (<em class="parameter"><code>const volatile <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> *atomic</code></em>);</pre>
<p>Gets the current value of <em class="parameter"><code>atomic</code></em>
.</p>
<p>This call acts as a full compiler and hardware
memory barrier (before the get).</p>
<div class="refsect3">
<a name="id-1.3.9.7.2.6"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> or <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.2.7"></a><h4>Returns</h4>
<p> the value of the integer</p>
<p></p>
</div>
<p class="since">Since 2.4</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-int-set"></a><h3>g_atomic_int_set ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
g_atomic_int_set (<em class="parameter"><code>volatile <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> newval</code></em>);</pre>
<p>Sets the value of <em class="parameter"><code>atomic</code></em>
to <em class="parameter"><code>newval</code></em>
.</p>
<p>This call acts as a full compiler and hardware
memory barrier (after the set).</p>
<div class="refsect3">
<a name="id-1.3.9.7.3.6"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> or <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>newval</p></td>
<td class="parameter_description"><p>a new value to store</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since 2.4</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-int-inc"></a><h3>g_atomic_int_inc ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
g_atomic_int_inc (<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> *atomic</code></em>);</pre>
<p>Increments the value of <em class="parameter"><code>atomic</code></em>
by 1.</p>
<p>Think of this operation as an atomic version of <code class="literal">{ *atomic += 1; }</code>.</p>
<p>This call acts as a full compiler and hardware memory barrier.</p>
<div class="refsect3">
<a name="id-1.3.9.7.4.7"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> or <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<p class="since">Since 2.4</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-int-dec-and-test"></a><h3>g_atomic_int_dec_and_test ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#gboolean" title="gboolean"><span class="returnvalue">gboolean</span></a>
g_atomic_int_dec_and_test (<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> *atomic</code></em>);</pre>
<p>Decrements the value of <em class="parameter"><code>atomic</code></em>
by 1.</p>
<p>Think of this operation as an atomic version of
<code class="literal">{ *atomic -= 1; return (*atomic == 0); }</code>.</p>
<p>This call acts as a full compiler and hardware memory barrier.</p>
<div class="refsect3">
<a name="id-1.3.9.7.5.7"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> or <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.5.8"></a><h4>Returns</h4>
<p> <a class="link" href="glib-Standard-Macros.html#TRUE:CAPS" title="TRUE"><code class="literal">TRUE</code></a> if the resultant value is zero</p>
<p></p>
</div>
<p class="since">Since 2.4</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-int-compare-and-exchange"></a><h3>g_atomic_int_compare_and_exchange ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#gboolean" title="gboolean"><span class="returnvalue">gboolean</span></a>
g_atomic_int_compare_and_exchange (<em class="parameter"><code>volatile <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> oldval</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> newval</code></em>);</pre>
<p>Compares <em class="parameter"><code>atomic</code></em>
to <em class="parameter"><code>oldval</code></em>
and, if equal, sets it to <em class="parameter"><code>newval</code></em>
.
If <em class="parameter"><code>atomic</code></em>
was not equal to <em class="parameter"><code>oldval</code></em>
then no change occurs.</p>
<p>This compare and exchange is done atomically.</p>
<p>Think of this operation as an atomic version of
<code class="literal">{ if (*atomic == oldval) { *atomic = newval; return TRUE; } else return FALSE; }</code>.</p>
<p>This call acts as a full compiler and hardware memory barrier.</p>
<div class="refsect3">
<a name="id-1.3.9.7.6.8"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> or <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>oldval</p></td>
<td class="parameter_description"><p>the value to compare with</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>newval</p></td>
<td class="parameter_description"><p>the value to conditionally replace with</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.6.9"></a><h4>Returns</h4>
<p> <a class="link" href="glib-Standard-Macros.html#TRUE:CAPS" title="TRUE"><code class="literal">TRUE</code></a> if the exchange took place</p>
<p></p>
</div>
<p class="since">Since 2.4</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-int-add"></a><h3>g_atomic_int_add ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="returnvalue">gint</span></a>
g_atomic_int_add (<em class="parameter"><code>volatile <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> val</code></em>);</pre>
<p>Atomically adds <em class="parameter"><code>val</code></em>
to the value of <em class="parameter"><code>atomic</code></em>
.</p>
<p>Think of this operation as an atomic version of
<code class="literal">{ tmp = *atomic; *atomic += val; return tmp; }</code>.</p>
<p>This call acts as a full compiler and hardware memory barrier.</p>
<p>Before version 2.30, this function did not return a value
(but <a class="link" href="glib-Atomic-Operations.html#g-atomic-int-exchange-and-add" title="g_atomic_int_exchange_and_add ()"><code class="function">g_atomic_int_exchange_and_add()</code></a> did, and had the same meaning).</p>
<div class="refsect3">
<a name="id-1.3.9.7.7.8"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> or <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>val</p></td>
<td class="parameter_description"><p>the value to add</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.7.9"></a><h4>Returns</h4>
<p> the value of <em class="parameter"><code>atomic</code></em>
before the add, signed</p>
<p></p>
</div>
<p class="since">Since 2.4</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-int-and"></a><h3>g_atomic_int_and ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="returnvalue">guint</span></a>
g_atomic_int_and (<em class="parameter"><code>volatile <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a> val</code></em>);</pre>
<p>Performs an atomic bitwise 'and' of the value of <em class="parameter"><code>atomic</code></em>
and <em class="parameter"><code>val</code></em>
,
storing the result back in <em class="parameter"><code>atomic</code></em>
.</p>
<p>This call acts as a full compiler and hardware memory barrier.</p>
<p>Think of this operation as an atomic version of
<code class="literal">{ tmp = *atomic; *atomic &= val; return tmp; }</code>.</p>
<div class="refsect3">
<a name="id-1.3.9.7.8.7"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> or <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>val</p></td>
<td class="parameter_description"><p>the value to 'and'</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.8.8"></a><h4>Returns</h4>
<p> the value of <em class="parameter"><code>atomic</code></em>
before the operation, unsigned</p>
<p></p>
</div>
<p class="since">Since 2.30</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-int-or"></a><h3>g_atomic_int_or ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="returnvalue">guint</span></a>
g_atomic_int_or (<em class="parameter"><code>volatile <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a> val</code></em>);</pre>
<p>Performs an atomic bitwise 'or' of the value of <em class="parameter"><code>atomic</code></em>
and <em class="parameter"><code>val</code></em>
,
storing the result back in <em class="parameter"><code>atomic</code></em>
.</p>
<p>Think of this operation as an atomic version of
<code class="literal">{ tmp = *atomic; *atomic |= val; return tmp; }</code>.</p>
<p>This call acts as a full compiler and hardware memory barrier.</p>
<div class="refsect3">
<a name="id-1.3.9.7.9.7"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> or <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>val</p></td>
<td class="parameter_description"><p>the value to 'or'</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.9.8"></a><h4>Returns</h4>
<p> the value of <em class="parameter"><code>atomic</code></em>
before the operation, unsigned</p>
<p></p>
</div>
<p class="since">Since 2.30</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-int-xor"></a><h3>g_atomic_int_xor ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="returnvalue">guint</span></a>
g_atomic_int_xor (<em class="parameter"><code>volatile <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a> val</code></em>);</pre>
<p>Performs an atomic bitwise 'xor' of the value of <em class="parameter"><code>atomic</code></em>
and <em class="parameter"><code>val</code></em>
,
storing the result back in <em class="parameter"><code>atomic</code></em>
.</p>
<p>Think of this operation as an atomic version of
<code class="literal">{ tmp = *atomic; *atomic ^= val; return tmp; }</code>.</p>
<p>This call acts as a full compiler and hardware memory barrier.</p>
<div class="refsect3">
<a name="id-1.3.9.7.10.7"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> or <a class="link" href="glib-Basic-Types.html#guint" title="guint"><span class="type">guint</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>val</p></td>
<td class="parameter_description"><p>the value to 'xor'</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.10.8"></a><h4>Returns</h4>
<p> the value of <em class="parameter"><code>atomic</code></em>
before the operation, unsigned</p>
<p></p>
</div>
<p class="since">Since 2.30</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-pointer-get"></a><h3>g_atomic_pointer_get ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#gpointer" title="gpointer"><span class="returnvalue">gpointer</span></a>
g_atomic_pointer_get (<em class="parameter"><code>const volatile <span class="type">void</span> *atomic</code></em>);</pre>
<p>Gets the current value of <em class="parameter"><code>atomic</code></em>
.</p>
<p>This call acts as a full compiler and hardware
memory barrier (before the get).</p>
<div class="refsect3">
<a name="id-1.3.9.7.11.6"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <span class="type">gpointer-sized</span> value</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.11.7"></a><h4>Returns</h4>
<p> the value of the pointer</p>
<p></p>
</div>
<p class="since">Since 2.4</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-pointer-set"></a><h3>g_atomic_pointer_set ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
g_atomic_pointer_set (<em class="parameter"><code>volatile <span class="type">void</span> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gpointer" title="gpointer"><span class="type">gpointer</span></a> newval</code></em>);</pre>
<p>Sets the value of <em class="parameter"><code>atomic</code></em>
to <em class="parameter"><code>newval</code></em>
.</p>
<p>This call acts as a full compiler and hardware
memory barrier (after the set).</p>
<div class="refsect3">
<a name="id-1.3.9.7.12.6"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <span class="type">gpointer-sized</span> value</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>newval</p></td>
<td class="parameter_description"><p>a new value to store</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since 2.4</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-pointer-compare-and-exchange"></a><h3>g_atomic_pointer_compare_and_exchange ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#gboolean" title="gboolean"><span class="returnvalue">gboolean</span></a>
g_atomic_pointer_compare_and_exchange (<em class="parameter"><code>volatile <span class="type">void</span> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gpointer" title="gpointer"><span class="type">gpointer</span></a> oldval</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gpointer" title="gpointer"><span class="type">gpointer</span></a> newval</code></em>);</pre>
<p>Compares <em class="parameter"><code>atomic</code></em>
to <em class="parameter"><code>oldval</code></em>
and, if equal, sets it to <em class="parameter"><code>newval</code></em>
.
If <em class="parameter"><code>atomic</code></em>
was not equal to <em class="parameter"><code>oldval</code></em>
then no change occurs.</p>
<p>This compare and exchange is done atomically.</p>
<p>Think of this operation as an atomic version of
<code class="literal">{ if (*atomic == oldval) { *atomic = newval; return TRUE; } else return FALSE; }</code>.</p>
<p>This call acts as a full compiler and hardware memory barrier.</p>
<div class="refsect3">
<a name="id-1.3.9.7.13.8"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <span class="type">gpointer-sized</span> value</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>oldval</p></td>
<td class="parameter_description"><p>the value to compare with</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>newval</p></td>
<td class="parameter_description"><p>the value to conditionally replace with</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.13.9"></a><h4>Returns</h4>
<p> <a class="link" href="glib-Standard-Macros.html#TRUE:CAPS" title="TRUE"><code class="literal">TRUE</code></a> if the exchange took place</p>
<p></p>
</div>
<p class="since">Since 2.4</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-pointer-add"></a><h3>g_atomic_pointer_add ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#gssize" title="gssize"><span class="returnvalue">gssize</span></a>
g_atomic_pointer_add (<em class="parameter"><code>volatile <span class="type">void</span> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gssize" title="gssize"><span class="type">gssize</span></a> val</code></em>);</pre>
<p>Atomically adds <em class="parameter"><code>val</code></em>
to the value of <em class="parameter"><code>atomic</code></em>
.</p>
<p>Think of this operation as an atomic version of
<code class="literal">{ tmp = *atomic; *atomic += val; return tmp; }</code>.</p>
<p>This call acts as a full compiler and hardware memory barrier.</p>
<div class="refsect3">
<a name="id-1.3.9.7.14.7"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <span class="type">gpointer-sized</span> value</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>val</p></td>
<td class="parameter_description"><p>the value to add</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.14.8"></a><h4>Returns</h4>
<p> the value of <em class="parameter"><code>atomic</code></em>
before the add, signed</p>
<p></p>
</div>
<p class="since">Since 2.30</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-pointer-and"></a><h3>g_atomic_pointer_and ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="returnvalue">gsize</span></a>
g_atomic_pointer_and (<em class="parameter"><code>volatile <span class="type">void</span> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="type">gsize</span></a> val</code></em>);</pre>
<p>Performs an atomic bitwise 'and' of the value of <em class="parameter"><code>atomic</code></em>
and <em class="parameter"><code>val</code></em>
,
storing the result back in <em class="parameter"><code>atomic</code></em>
.</p>
<p>Think of this operation as an atomic version of
<code class="literal">{ tmp = *atomic; *atomic &= val; return tmp; }</code>.</p>
<p>This call acts as a full compiler and hardware memory barrier.</p>
<div class="refsect3">
<a name="id-1.3.9.7.15.7"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <span class="type">gpointer-sized</span> value</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>val</p></td>
<td class="parameter_description"><p>the value to 'and'</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.15.8"></a><h4>Returns</h4>
<p> the value of <em class="parameter"><code>atomic</code></em>
before the operation, unsigned</p>
<p></p>
</div>
<p class="since">Since 2.30</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-pointer-or"></a><h3>g_atomic_pointer_or ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="returnvalue">gsize</span></a>
g_atomic_pointer_or (<em class="parameter"><code>volatile <span class="type">void</span> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="type">gsize</span></a> val</code></em>);</pre>
<p>Performs an atomic bitwise 'or' of the value of <em class="parameter"><code>atomic</code></em>
and <em class="parameter"><code>val</code></em>
,
storing the result back in <em class="parameter"><code>atomic</code></em>
.</p>
<p>Think of this operation as an atomic version of
<code class="literal">{ tmp = *atomic; *atomic |= val; return tmp; }</code>.</p>
<p>This call acts as a full compiler and hardware memory barrier.</p>
<div class="refsect3">
<a name="id-1.3.9.7.16.7"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <span class="type">gpointer-sized</span> value</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>val</p></td>
<td class="parameter_description"><p>the value to 'or'</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.16.8"></a><h4>Returns</h4>
<p> the value of <em class="parameter"><code>atomic</code></em>
before the operation, unsigned</p>
<p></p>
</div>
<p class="since">Since 2.30</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-pointer-xor"></a><h3>g_atomic_pointer_xor ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="returnvalue">gsize</span></a>
g_atomic_pointer_xor (<em class="parameter"><code>volatile <span class="type">void</span> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="type">gsize</span></a> val</code></em>);</pre>
<p>Performs an atomic bitwise 'xor' of the value of <em class="parameter"><code>atomic</code></em>
and <em class="parameter"><code>val</code></em>
,
storing the result back in <em class="parameter"><code>atomic</code></em>
.</p>
<p>Think of this operation as an atomic version of
<code class="literal">{ tmp = *atomic; *atomic ^= val; return tmp; }</code>.</p>
<p>This call acts as a full compiler and hardware memory barrier.</p>
<div class="refsect3">
<a name="id-1.3.9.7.17.7"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <span class="type">gpointer-sized</span> value</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>val</p></td>
<td class="parameter_description"><p>the value to 'xor'</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.17.8"></a><h4>Returns</h4>
<p> the value of <em class="parameter"><code>atomic</code></em>
before the operation, unsigned</p>
<p></p>
</div>
<p class="since">Since 2.30</p>
</div>
<hr>
<div class="refsect2">
<a name="g-atomic-int-exchange-and-add"></a><h3>g_atomic_int_exchange_and_add ()</h3>
<pre class="programlisting"><a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="returnvalue">gint</span></a>
g_atomic_int_exchange_and_add (<em class="parameter"><code>volatile <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> *atomic</code></em>,
<em class="parameter"><code><a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a> val</code></em>);</pre>
<div class="warning">
<p><code class="literal">g_atomic_int_exchange_and_add</code> has been deprecated since version 2.30 and should not be used in newly-written code.</p>
<p>Use <a class="link" href="glib-Atomic-Operations.html#g-atomic-int-add" title="g_atomic_int_add ()"><code class="function">g_atomic_int_add()</code></a> instead.</p>
</div>
<p>This function existed before <a class="link" href="glib-Atomic-Operations.html#g-atomic-int-add" title="g_atomic_int_add ()"><code class="function">g_atomic_int_add()</code></a> returned the prior
value of the integer (which it now does). It is retained only for
compatibility reasons. Don't use this function in new code.</p>
<div class="refsect3">
<a name="id-1.3.9.7.18.7"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>atomic</p></td>
<td class="parameter_description"><p>a pointer to a <a class="link" href="glib-Basic-Types.html#gint" title="gint"><span class="type">gint</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>val</p></td>
<td class="parameter_description"><p>the value to add</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.3.9.7.18.8"></a><h4>Returns</h4>
<p> the value of <em class="parameter"><code>atomic</code></em>
before the add, signed</p>
<p></p>
</div>
<p class="since">Since 2.4</p>
</div>
</div>
<div class="refsect1">
<a name="glib-Atomic-Operations.other_details"></a><h2>Types and Values</h2>
<div class="refsect2">
<a name="G-ATOMIC-LOCK-FREE:CAPS"></a><h3>G_ATOMIC_LOCK_FREE</h3>
<pre class="programlisting">#define G_ATOMIC_LOCK_FREE
</pre>
<p>This macro is defined if the atomic operations of GLib are
implemented using real hardware atomic operations. This means that
the GLib atomic API can be used between processes and safely mixed
with other (hardware) atomic APIs.</p>
<p>If this macro is not defined, the atomic operations may be
emulated using a mutex. In that case, the GLib atomic operations are
only atomic relative to themselves and within a single process.</p>
</div>
</div>
<div class="refsect1">
<a name="glib-Atomic-Operations.see-also"></a><h2>See Also</h2>
<p><a class="link" href="glib-Threads.html#GMutex" title="union GMutex"><span class="type">GMutex</span></a></p>
</div>
</div>
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