1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
|
<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!--
SPDX-License-Identifier: LGPL-2.1-or-later
Copyright © 2016 Julian Orth
-->
<refentry id="sd_bus_add_match" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_bus_add_match</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_add_match</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_add_match</refname>
<refname>sd_bus_add_match_async</refname>
<refname>sd_bus_match_signal</refname>
<refname>sd_bus_match_signal_async</refname>
<refpurpose>Add a match rule for incoming message dispatching</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
<funcprototype id="sd_bus_message_handler_t">
<funcdef>typedef int (*<function>sd_bus_message_handler_t</function>)</funcdef>
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
<paramdef>void *<parameter>userdata</parameter></paramdef>
<paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_add_match</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
<paramdef>const char *<parameter>match</parameter></paramdef>
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
<paramdef>void *<parameter>userdata</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_add_match_async</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
<paramdef>const char *<parameter>match</parameter></paramdef>
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
<paramdef>sd_bus_message_handler_t <parameter>install_callback</parameter></paramdef>
<paramdef>void *<parameter>userdata</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_match_signal</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
<paramdef>const char *<parameter>sender</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
<paramdef>const char *<parameter>interface</parameter></paramdef>
<paramdef>const char *<parameter>member</parameter></paramdef>
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
<paramdef>void *<parameter>userdata</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_match_signal_async</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
<paramdef>const char *<parameter>sender</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
<paramdef>const char *<parameter>interface</parameter></paramdef>
<paramdef>const char *<parameter>member</parameter></paramdef>
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
<paramdef>sd_bus_message_handler_t <parameter>install_callback</parameter></paramdef>
<paramdef>void *<parameter>userdata</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_bus_add_match()</function> installs a match rule for messages received on the specified bus
connection object <parameter>bus</parameter>. The syntax of the match rule expression passed in
<parameter>match</parameter> is described in the <ulink
url="https://dbus.freedesktop.org/doc/dbus-specification.html">D-Bus Specification</ulink>. The specified handler
function <parameter>callback</parameter> is called for each incoming message matching the specified expression,
the <parameter>userdata</parameter> parameter is passed as-is to the callback function. The match is installed
synchronously when connected to a bus broker, i.e. the call sends a control message requested the match to be added
to the broker and waits until the broker confirms the match has been installed successfully.</para>
<para><function>sd_bus_add_match_async()</function> operates very similarly to
<function>sd_bus_add_match()</function>, however it installs the match asynchronously, in a non-blocking
fashion: a request is sent to the broker, but the call does not wait for a response. The
<parameter>install_callback</parameter> function is called when the response is later received, with the response
message from the broker as parameter. If this function is specified as <constant>NULL</constant> a default
implementation is used that terminates the bus connection should installing the match fail.</para>
<para><function>sd_bus_match_signal()</function> is very similar to <function>sd_bus_add_match()</function>, but
only matches signals, and instead of a match expression accepts four parameters: <parameter>sender</parameter> (the
service name of the sender), <parameter>path</parameter> (the object path of the emitting object),
<parameter>interface</parameter> (the interface the signal belongs to), <parameter>member</parameter> (the signal
name), from which the match string is internally generated. Optionally, these parameters may be specified as
<constant>NULL</constant> in which case the relevant field of incoming signals is not tested.</para>
<para><function>sd_bus_match_signal_async()</function> combines the signal matching logic of
<function>sd_bus_match_signal()</function> with the asynchronous behaviour of
<function>sd_bus_add_match_async()</function>.</para>
<para>On success, and if non-<constant>NULL</constant>, the <parameter>slot</parameter> return parameter will be
set to a slot object that may be used as a reference to the installed match, and may be utilized to remove it again
at a later time with
<citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If specified
as <constant>NULL</constant> the lifetime of the match is bound to the lifetime of the bus object itself, and the
match is generally not removed independently. See
<citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
details.</para>
<para>The message <parameter>m</parameter> passed to the callback is only borrowed, that is, the callback should
not call <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
on it. If the callback wants to hold on to the message beyond the lifetime of the callback, it needs to call
<citerefentry><refentrytitle>sd_bus_message_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to create a
new reference.</para>
<para>If an error occurs during the callback invocation, the callback should return a negative error number
(optionally, a more precise error may be returned in <parameter>ret_error</parameter>, as well). If it wants other
callbacks that match the same rule to be called, it should return 0. Otherwise, it should return a positive integer.
</para>
<para>If the <parameter>bus</parameter> refers to a direct connection (i.e. not a bus connection, as set with
<citerefentry><refentrytitle>sd_bus_set_bus_client</refentrytitle><manvolnum>3</manvolnum></citerefentry>) the
match is only installed on the client side, and the synchronous and asynchronous functions operate the same.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>
On success, <function>sd_bus_add_match()</function> and the other calls return 0 or a positive integer. On
failure, they return a negative errno-style error code.
</para>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>History</title>
<para><function>sd_bus_add_match()</function> and
<function>sd_bus_message_handler_t()</function> were added in version 221.</para>
<para><function>sd_bus_add_match_async()</function>,
<function>sd_bus_match_signal()</function>, and
<function>sd_bus_match_signal_async()</function> were added in version 237.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para><simplelist type="inline">
<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_bus_message_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_bus_set_bus_client</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
</simplelist></para>
</refsect1>
</refentry>
|
