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e382c49f | 1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | ||
5 | <!-- | |
572eb058 ZJS |
6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
e382c49f | 8 | This file is part of systemd. |
9 | ||
10 | Copyright 2016 Julian Orth | |
11 | ||
12 | systemd is free software; you can redistribute it and/or modify it | |
13 | under the terms of the GNU Lesser General Public License as published by | |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
15 | (at your option) any later version. | |
16 | ||
17 | systemd is distributed in the hope that it will be useful, but | |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | Lesser General Public License for more details. | |
21 | ||
22 | You should have received a copy of the GNU Lesser General Public License | |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
24 | --> | |
25 | ||
26 | <refentry id="sd_bus_add_match"> | |
27 | ||
28 | <refentryinfo> | |
29 | <title>sd_bus_add_match</title> | |
30 | <productname>systemd</productname> | |
31 | ||
32 | <authorgroup> | |
33 | <author> | |
34 | <firstname>Julian</firstname> | |
35 | <surname>Orth</surname> | |
36 | <email>ju.orth@gmail.com</email> | |
37 | </author> | |
38 | </authorgroup> | |
39 | </refentryinfo> | |
40 | ||
41 | <refmeta> | |
42 | <refentrytitle>sd_bus_add_match</refentrytitle> | |
43 | <manvolnum>3</manvolnum> | |
44 | </refmeta> | |
45 | ||
46 | <refnamediv> | |
47 | <refname>sd_bus_add_match</refname> | |
d97eac36 LP |
48 | <refname>sd_bus_add_match_async</refname> |
49 | <refname>sd_bus_match_signal</refname> | |
50 | <refname>sd_bus_match_signal_async</refname> | |
e382c49f | 51 | |
d97eac36 | 52 | <refpurpose>Add a match rule for incoming message dispatching</refpurpose> |
e382c49f | 53 | </refnamediv> |
54 | ||
55 | <refsynopsisdiv> | |
56 | <funcsynopsis> | |
57 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
58 | ||
d97eac36 LP |
59 | <funcprototype> |
60 | <funcdef>typedef int (*<function>sd_bus_message_handler_t</function>)</funcdef> | |
61 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
62 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
63 | <paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef> | |
64 | </funcprototype> | |
65 | ||
e382c49f | 66 | <funcprototype> |
67 | <funcdef>int <function>sd_bus_add_match</function></funcdef> | |
68 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
69 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
70 | <paramdef>const char *<parameter>match</parameter></paramdef> | |
71 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
72 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
73 | </funcprototype> | |
74 | ||
75 | <funcprototype> | |
d97eac36 LP |
76 | <funcdef>int <function>sd_bus_add_match_async</function></funcdef> |
77 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
78 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
79 | <paramdef>const char *<parameter>match</parameter></paramdef> | |
80 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
81 | <paramdef>sd_bus_message_handler_t <parameter>install_callback</parameter></paramdef> | |
82 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
83 | </funcprototype> | |
84 | ||
85 | <funcprototype> | |
86 | <funcdef>int <function>sd_bus_match_signal</function></funcdef> | |
87 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
88 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
89 | <paramdef>const char *<parameter>sender</parameter></paramdef> | |
90 | <paramdef>const char *<parameter>path</parameter></paramdef> | |
91 | <paramdef>const char *<parameter>interface</parameter></paramdef> | |
92 | <paramdef>const char *<parameter>member</parameter></paramdef> | |
93 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
94 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
95 | </funcprototype> | |
96 | ||
97 | <funcprototype> | |
98 | <funcdef>int <function>sd_bus_match_signal_async</function></funcdef> | |
99 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
100 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
101 | <paramdef>const char *<parameter>sender</parameter></paramdef> | |
102 | <paramdef>const char *<parameter>path</parameter></paramdef> | |
103 | <paramdef>const char *<parameter>interface</parameter></paramdef> | |
104 | <paramdef>const char *<parameter>member</parameter></paramdef> | |
105 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
106 | <paramdef>sd_bus_message_handler_t <parameter>install_callback</parameter></paramdef> | |
e382c49f | 107 | <paramdef>void *<parameter>userdata</parameter></paramdef> |
e382c49f | 108 | </funcprototype> |
d97eac36 | 109 | |
e382c49f | 110 | </funcsynopsis> |
111 | </refsynopsisdiv> | |
112 | ||
113 | <refsect1> | |
114 | <title>Description</title> | |
115 | ||
d97eac36 LP |
116 | <para><function>sd_bus_add_match()</function> installs a match rule for messages received on the specified bus |
117 | connection object <parameter>bus</parameter>. The syntax of the match rule expression passed in | |
118 | <parameter>match</parameter> is described in the <ulink | |
119 | url="https://dbus.freedesktop.org/doc/dbus-specification.html">D-Bus Specification</ulink>. The specified handler | |
120 | function <parameter>callback</parameter> is called for eaching incoming message matching the specified expression, | |
121 | the <parameter>userdata</parameter> parameter is passed as-is to the callback function. The match is installed | |
122 | synchronously when connected to a bus broker, i.e. the call sends a control message requested the match to be added | |
123 | to the broker and waits until the broker confirms the match has been installed successfully.</para> | |
124 | ||
125 | <para><function>sd_bus_add_match_async()</function> operates very similar to | |
126 | <function>sd_bus_match_signal()</function>, however it installs the match asynchronously, in a non-blocking | |
127 | fashion: a request is sent to the broker, but the call does not wait for a response. The | |
128 | <parameter>install_callback</parameter> function is called when the response is later received, with the response | |
129 | message from the broker as parameter. If this function is specified as <constant>NULL</constant> a default | |
130 | implementation is used that terminates the bus connection should installing the match fail.</para> | |
131 | ||
132 | <para><function>sd_bus_match_signal()</function> is very similar to <function>sd_bus_add_match()</function>, but | |
133 | only matches signals, and instead of a match expression accepts four parameters: <parameter>sender</parameter> (the | |
134 | service name of the sender), <parameter>path</parameter> (the object path of the emitting object), | |
135 | <parameter>interface</parameter> (the interface the signal belongs to), <parameter>member</parameter> (the signal | |
136 | name), from which the match string is internally generated. Optionally, these parameters may be specified as | |
137 | <constant>NULL</constant> in which case the relevant field of incoming signals is not tested.</para> | |
138 | ||
139 | <para><function>sd_bus_match_signal_async()</function> is combines the signal matching logic of | |
140 | <function>sd_bus_match_signal()</function> with the asynchronous behaviour of | |
141 | <function>sd_bus_add_match_async()</function>.</para> | |
142 | ||
143 | <para>On success, and if non-<constant>NULL</constant>, the <parameter>slot</parameter> return parameter will be | |
144 | set to a slot object that may be used as a reference to the installed match, and may be utilized to remove it again | |
145 | at a later time with | |
146 | <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If specified | |
147 | as <constant>NULL</constant> the lifetime of the match is bound to the lifetime of the bus object itself, and the | |
148 | match cannot be removed independently.</para> | |
149 | ||
150 | <para>The message <parameter>m</parameter> passed to the callback is only borrowed, that is, the callback should | |
151 | not call <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
152 | on it. If the callback wants to hold on to the message beyond the lifetime of the callback, it needs to call | |
153 | <citerefentry><refentrytitle>sd_bus_message_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to create a | |
154 | new reference.</para> | |
155 | ||
156 | <para>If an error occurs during the callback invocation, the callback should return a negative error number | |
157 | (optionally, a more precise error may be returned in <parameter>ret_error</parameter>, as well). If it wants other | |
158 | callbacks that match the same rule to be called, it should return 0. Otherwise it should return a positive integer. | |
e382c49f | 159 | </para> |
160 | ||
d97eac36 LP |
161 | <para>If the <parameter>bus</parameter> refers to a direct connection (i.e. not a bus connection, as set with |
162 | <citerefentry><refentrytitle>sd_bus_set_bus_client</refentrytitle><manvolnum>3</manvolnum></citerefentry>) the | |
163 | match is only installed on the client side, and the synchronous and asynchronous functions operate the same.</para> | |
164 | </refsect1> | |
e382c49f | 165 | |
d97eac36 LP |
166 | <refsect1> |
167 | <title>Return Value</title> | |
6b7af821 LP |
168 | |
169 | <para> | |
d97eac36 LP |
170 | On success, <function>sd_bus_add_match()</function> and the other calls return 0 or a positive integer. On |
171 | failure, they return a negative errno-style error code. | |
e382c49f | 172 | </para> |
173 | </refsect1> | |
174 | ||
175 | <refsect1> | |
d97eac36 | 176 | <title>Notes</title> |
e382c49f | 177 | |
d97eac36 LP |
178 | <para><function>sd_bus_add_match()</function> and the other functions described here are available as a shared |
179 | library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry | |
180 | project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para> | |
e382c49f | 181 | </refsect1> |
182 | ||
183 | <refsect1> | |
184 | <title>See Also</title> | |
185 | ||
186 | <para> | |
187 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
d97eac36 LP |
188 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
189 | <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
190 | <citerefentry><refentrytitle>sd_bus_message_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
191 | <citerefentry><refentrytitle>sd_bus_set_bus_client</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
e382c49f | 192 | </para> |
193 | </refsect1> | |
194 | ||
195 | </refentry> |