mirror of
https://github.com/systemd/systemd.git
synced 2024-11-24 10:43:35 +08:00
ecddb2b586
And while ware at it, also drop some references to kdbus, and stop claiming sd-bus wasn't stable yet. Also order man page references in the main sd-bus man page alphabetically.
264 lines
13 KiB
XML
264 lines
13 KiB
XML
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
|
||
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
||
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
||
|
||
<!--
|
||
This file is part of systemd.
|
||
|
||
Copyright 2016 Lennart Poettering
|
||
|
||
systemd is free software; you can redistribute it and/or modify it
|
||
under the terms of the GNU Lesser General Public License as published by
|
||
the Free Software Foundation; either version 2.1 of the License, or
|
||
(at your option) any later version.
|
||
|
||
systemd is distributed in the hope that it will be useful, but
|
||
WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
||
Lesser General Public License for more details.
|
||
|
||
You should have received a copy of the GNU Lesser General Public License
|
||
along with systemd; If not, see <http://www.gnu.org/licenses/>.
|
||
-->
|
||
|
||
<refentry id="sd_bus_track_new">
|
||
|
||
<refentryinfo>
|
||
<title>sd_bus_track_new</title>
|
||
<productname>systemd</productname>
|
||
|
||
<authorgroup>
|
||
<author>
|
||
<contrib>Developer</contrib>
|
||
<firstname>Lennart</firstname>
|
||
<surname>Poettering</surname>
|
||
<email>lennart@poettering.net</email>
|
||
</author>
|
||
</authorgroup>
|
||
</refentryinfo>
|
||
|
||
<refmeta>
|
||
<refentrytitle>sd_bus_track_new</refentrytitle>
|
||
<manvolnum>3</manvolnum>
|
||
</refmeta>
|
||
|
||
<refnamediv>
|
||
<refname>sd_bus_track_new</refname>
|
||
<refname>sd_bus_track_ref</refname>
|
||
<refname>sd_bus_track_unref</refname>
|
||
<refname>sd_bus_track_unrefp</refname>
|
||
<refname>sd_bus_track_set_recursive</refname>
|
||
<refname>sd_bus_track_get_recursive</refname>
|
||
<refname>sd_bus_track_get_bus</refname>
|
||
<refname>sd_bus_track_get_userdata</refname>
|
||
<refname>sd_bus_track_set_userdata</refname>
|
||
|
||
<refpurpose>Track bus peers</refpurpose>
|
||
</refnamediv>
|
||
|
||
<refsynopsisdiv>
|
||
<funcsynopsis>
|
||
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_track_new</function></funcdef>
|
||
<paramdef>sd_bus* <parameter>bus</parameter></paramdef>
|
||
<paramdef>sd_bus_track** <parameter>ret</parameter></paramdef>
|
||
<paramdef>sd_bus_track_handler_t <parameter>handler</parameter></paramdef>
|
||
<paramdef>void* <parameter>userdata</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>sd_bus_track *<function>sd_bus_track_ref</function></funcdef>
|
||
<paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>sd_bus_track *<function>sd_bus_track_unref</function></funcdef>
|
||
<paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>void <function>sd_bus_track_unrefp</function></funcdef>
|
||
<paramdef>sd_bus_track **<parameter>t</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_track_get_recursive</function></funcdef>
|
||
<paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_track_set_recursive</function></funcdef>
|
||
<paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
|
||
<paramdef>int <parameter>b</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>sd_bus* <function>sd_bus_track_get_bus</function></funcdef>
|
||
<paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>void* <function>sd_bus_track_get_userdata</function></funcdef>
|
||
<paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>void* <function>sd_bus_track_set_userdata</function></funcdef>
|
||
<paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
|
||
<paramdef>void *userdata</paramdef>
|
||
</funcprototype>
|
||
|
||
</funcsynopsis>
|
||
</refsynopsisdiv>
|
||
|
||
<refsect1>
|
||
<title>Description</title>
|
||
|
||
<para><function>sd_bus_track_new()</function> creates a new bus peer tracking object. The object is allocated for
|
||
the specified bus, and returned in the <parameter>*ret</parameter> parameter. After use, the object should be freed
|
||
again by dropping the acquired reference with <function>sd_bus_track_unref()</function> (see below). A bus peer
|
||
tracking object may be used to keep track of peers on a specific IPC bus, for cases where peers are making use of
|
||
one or more local objects, in order to control the lifecycle of the local objects and ensure they stay around as
|
||
long as the peers needing them are around, and unreferenced (and possibly destroyed) as soon as all relevant peers
|
||
have vanished. Each bus peer tracking object may be used to track zero, one or more peers add a time. References to
|
||
specific bus peers are added via
|
||
<citerefentry><refentrytitle>sd_bus_track_add_name</refentrytitle><manvolnum>3</manvolnum></citerefentry> or
|
||
<function>sd_bus_track_add_sender()</function>. They may be dropped again via
|
||
<function>sd_bus_track_remove_name()</function> and
|
||
<function>sd_bus_track_remove_sender()</function>. Alternatively, references on peers are removed automatically
|
||
when they disconnect from the bus. If non-NULL the <parameter>handler</parameter> may specify a function that is
|
||
invoked whenever the last reference is dropped, regardless whether the reference is dropped explicitly via
|
||
<function>sd_bus_track_remove_name()</function> or implicitly because the peer disconnected from the bus. The final
|
||
argument <parameter>userdata</parameter> may be used to attach a generic user data pointer to the object. This
|
||
pointer is passed to the handler callback when it is invoked.</para>
|
||
|
||
<para><function>sd_bus_track_ref()</function> creates a new reference to a bus peer tracking object. This object
|
||
will not be destroyed until <function>sd_bus_track_unref()</function> has been called as many times plus once
|
||
more. Once the reference count has dropped to zero, the specified object cannot be used anymore, further calls to
|
||
<function>sd_bus_track_ref()</function> or <function>sd_bus_track_unref()</function> on the same object are
|
||
illegal.</para>
|
||
|
||
<para><function>sd_bus_track_unref()</function> destroys a reference to a bus peer tracking object.</para>
|
||
|
||
<para><function>sd_bus_track_unrefp()</function> is similar to <function>sd_bus_track_unref()</function> but takes
|
||
a pointer to a pointer to an <type>sd_bus_track</type> object. This call is useful in conjunction with GCC's and
|
||
LLVM's <ulink url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up Variable
|
||
Attribute</ulink>. Note that this function is defined as inline function.</para>
|
||
|
||
<para><function>sd_bus_track_ref()</function>, <function>sd_bus_track_unref()</function> and
|
||
<function>sd_bus_track_unrefp()</function> execute no operation if the passed in bus peer tracking object is
|
||
<constant>NULL</constant>.</para>
|
||
|
||
<para>Bus peer tracking objects may exist in two modes: by default they operate in non-recursive mode, but may
|
||
optionally be switched into recursive mode. If operating in the default non-recursive mode a peer is either tracked
|
||
or not tracked. In this mode invoking <function>sd_bus_track_add_name()</function> multiple times in a row for the
|
||
same peer is fully equivalent to calling it just once, as the call adds the peer to the set of tracked peers if
|
||
necessary, and executes no operation if the peer is already being tracked. A single invocation of
|
||
<function>sd_bus_track_remove_name()</function> removes the reference on the peer again, regardless how many times
|
||
<function>sd_bus_track_add_name()</function> was called before. If operating in recursive mode, the number of times
|
||
<function>sd_bus_track_add_name()</function> is invoked for the same peer name is counted and
|
||
<function>sd_bus_track_remove_name()</function> must be called the same number of times before the peer is not
|
||
tracked anymore, with the exception when the tracked peer vanishes from the bus, in which case the count is
|
||
irrelevant and the tracking of the specific peer is immediately
|
||
removed. <function>sd_bus_track_get_recursive()</function> may be used to determine whether the bus peer tracking
|
||
object is operating in recursive mode. <function>sd_bus_track_set_recursive()</function> may be used to enable or
|
||
disable recursive mode. By default a bus peer tracking object operates in non-recursive mode, and
|
||
<function>sd_bus_track_get_recursive()</function> for a newly allocated object hence returns a value equal to
|
||
zero. Use <function>sd_bus_track_set_recursive()</function> to enable recursive mode, right after allocation. It
|
||
takes a boolean argument to enable or disable recursive mode. Note that tracking objects for which
|
||
<function>sd_bus_track_add_name()</function> was already invoked at least once (and which hence track already one
|
||
or more peers) may not be switched from recursive to non-recursive mode anymore.</para>
|
||
|
||
<para><function>sd_bus_track_get_bus()</function> returns the bus object the bus peer tracking object belongs
|
||
to. It returns the bus object initially passed to <function>sd_bus_track_new()</function> when the object was
|
||
allocated.</para>
|
||
|
||
<para><function>sd_bus_track_get_userdata()</function> returns the generic user data pointer set on the bus peer
|
||
tracking object at the time of creation using <function>sd_bus_track_new()</function> or at a later time, using
|
||
<function>sd_bus_track_set_userdata()</function>.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Return Value</title>
|
||
|
||
<para>On success, <function>sd_bus_track_new()</function> and <function>sd_bus_track_set_recursive()</function>
|
||
return 0 or a positive integer. On failure, they return a negative errno-style error code.</para>
|
||
|
||
<para><function>sd_bus_track_ref()</function> always returns the argument.</para>
|
||
|
||
<para><function>sd_bus_track_unref()</function> always returns <constant>NULL</constant>.</para>
|
||
|
||
<para><function>sd_bus_track_get_recursive()</function> returns 0 if non-recursive mode is selected (default), and
|
||
greater than 0 if recursive mode is selected. On failure a negative errno-style error code is returned.</para>
|
||
|
||
<para><function>sd_bus_track_get_bus()</function> returns the bus object associated to the bus peer tracking
|
||
object.</para>
|
||
|
||
<para><function>sd_bus_track_get_userdata()</function> returns the generic user data pointer associated with the
|
||
bus peer tracking object. <function>sd_bus_track_set_userdata()</function> returns the previous user data pointer
|
||
set.</para>
|
||
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Reference ownership</title>
|
||
|
||
<para>The <function>sd_bus_track_new()</function> function creates a new object and the caller owns the sole
|
||
reference. When not needed anymore, this reference should be destroyed with
|
||
<function>sd_bus_track_unref()</function>.
|
||
</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Errors</title>
|
||
|
||
<para>Returned errors may indicate the following problems:</para>
|
||
|
||
<variablelist>
|
||
|
||
<varlistentry>
|
||
<term><constant>-EBUSY</constant></term>
|
||
|
||
<listitem><para>Bus peers have already been added to the bus peer tracking object and
|
||
<function>sd_bus_track_set_recursive()</function> was called to change tracking mode.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><constant>-EINVAL</constant></term>
|
||
|
||
<listitem><para>Specified parameter is invalid
|
||
(<constant>NULL</constant> in case of output
|
||
parameters).</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><constant>-ENOMEM</constant></term>
|
||
|
||
<listitem><para>Memory allocation failed.</para></listitem>
|
||
</varlistentry>
|
||
|
||
</variablelist>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Notes</title>
|
||
|
||
<para><function>sd_bus_track_new()</function> and the other calls described here are available as a shared library,
|
||
which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry
|
||
project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>See Also</title>
|
||
|
||
<para>
|
||
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
<citerefentry><refentrytitle>sd_bus_track_add_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
</para>
|
||
</refsect1>
|
||
|
||
</refentry>
|