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102 lines
4.0 KiB
XML
102 lines
4.0 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="sd_bus_slot_ref" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_bus_slot_ref</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_bus_slot_ref</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_bus_slot_ref</refname>
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<refname>sd_bus_slot_unref</refname>
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<refname>sd_bus_slot_unrefp</refname>
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<refpurpose>Create and destroy references to a bus slot object</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>sd_bus_slot *<function>sd_bus_slot_ref</function></funcdef>
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<paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>sd_bus_slot *<function>sd_bus_slot_unref</function></funcdef>
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<paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>void <function>sd_bus_slot_unrefp</function></funcdef>
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<paramdef>sd_bus_slot **<parameter>slotp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_bus_slot_ref()</function> increases the internal reference counter of
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<parameter>slot</parameter> by one.</para>
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<para><function>sd_bus_slot_unref()</function> decreases the internal reference counter of
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<parameter>slot</parameter> by one. Once the reference count has dropped to zero, slot object is
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destroyed and cannot be used anymore, so further calls to <function>sd_bus_slot_ref()</function>
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or <function>sd_bus_slot_unref()</function> are illegal.</para>
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<para><function>sd_bus_slot_unrefp()</function> is similar to
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<function>sd_bus_slot_unref()</function> but takes a pointer to a pointer to an
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<type>sd_bus_slot</type> object. This call is useful in conjunction with GCC's and LLVM's <ulink
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url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up Variable
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Attribute</ulink>. See
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<citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for an example how to use the cleanup attribute.</para>
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<para><function>sd_bus_slot_ref()</function> and <function>sd_bus_slot_unref()</function>
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execute no operation if the passed in bus object address is
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<constant>NULL</constant>. <function>sd_bus_slot_unrefp()</function> will first dereference
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its argument, which must not be <constant>NULL</constant>, and will execute no operation if
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<emphasis>that</emphasis> is <constant>NULL</constant>.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para><function>sd_bus_slot_ref()</function> always returns the argument.</para>
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<para><function>sd_bus_slot_unref()</function> always returns <constant>NULL</constant>.</para>
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</refsect1>
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<xi:include href="libsystemd-pkgconfig.xml" />
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<refsect1>
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<title>History</title>
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<para><function>sd_bus_slot_ref()</function>,
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<function>sd_bus_slot_unref()</function>, and
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<function>sd_bus_slot_unrefp()</function> were added in version 240.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_call_method_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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