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b1de39dec8
Logically, this is better, because we're describing a subset of possible return values. Visually this also looks quite good because groff renders refsect2 much less prominently. Also rewrap things, add <constant> in various places, fix some typos.
131 lines
5.8 KiB
XML
131 lines
5.8 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+ -->
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<refentry id="sd_bus_slot_set_destroy_callback"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_bus_slot_set_destroy_callback</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_set_destroy_callback</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_set_destroy_callback</refname>
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<refname>sd_bus_slot_get_destroy_callback</refname>
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<refname>sd_bus_track_set_destroy_callback</refname>
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<refname>sd_bus_track_get_destroy_callback</refname>
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<refname>sd_bus_destroy_t</refname>
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<refpurpose>Define the callback function for resource cleanup.</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>typedef int (*<function>sd_bus_destroy_t</function>)</funcdef>
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<paramdef>void *<parameter>userdata</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_slot_set_destroy_callback</function></funcdef>
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<paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
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<paramdef>sd_bus_destroy_t <parameter>callback</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_slot_get_destroy_callback</function></funcdef>
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<paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef>
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<paramdef>sd_bus_destroy_t *<parameter>callback</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_track_set_destroy_callback</function></funcdef>
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<paramdef>sd_bus_track *<parameter>track</parameter></paramdef>
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<paramdef>sd_bus_destroy_t <parameter>callback</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_track_get_destroy_callback</function></funcdef>
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<paramdef>sd_bus_track *<parameter>track</parameter></paramdef>
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<paramdef>sd_bus_destroy_t *<parameter>callback</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_set_destroy_callback()</function> sets <parameter>callback</parameter> as the callback
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function to be called right before the bus slot object <parameter>slot</parameter> is deallocated. The
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<parameter>userdata</parameter> pointer from the slot object will be passed as the <parameter>userdata</parameter>
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parameter. This pointer can be set by an argument to the constructor functions, see
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<citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>, or directly,
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see <citerefentry><refentrytitle>sd_bus_slot_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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This callback function is called even if <parameter>userdata</parameter> is <constant>NULL</constant>. Note that
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this callback is invoked at a time where the bus slot object itself is already invalidated, and executing
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operations or taking new references to the bus slot object is not permissible.</para>
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<para><function>sd_bus_slot_get_destroy_callback()</function> returns the current callback
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for <parameter>slot</parameter> in the <parameter>callback</parameter> parameter.</para>
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<para><function>sd_bus_track_set_destroy_callback()</function> and
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<function>sd_bus_track_get_destroy_callback()</function> provide equivalent functionality for the
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<parameter>userdata</parameter> pointer associated with bus peer tracking objects. For details about bus peer
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tracking objects, see
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<citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success, <function>sd_bus_slot_set_destroy_callback()</function> and
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<function>sd_bus_track_set_destroy_callback()</function> return 0 or a positive integer. On failure, they
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return a negative errno-style error code.</para>
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<para><function>sd_bus_slot_get_destroy_callback()</function> and
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<function>sd_bus_track_get_destroy_callback()</function> return positive if the destroy callback function
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is set, 0 if not. On failure, they return a negative errno-style error code.</para>
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<refsect2>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>The <parameter>slot</parameter> or <parameter>track</parameter> parameter is
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<constant>NULL</constant>.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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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>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_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_slot_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_track_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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