mirror of
https://github.com/systemd/systemd.git
synced 2024-11-01 17:51:22 +03:00
1004b2c7bc
Also extend the memory management description of sd-bus highlighting the effect of "floating" slot objects a bit.
186 lines
9.6 KiB
XML
186 lines
9.6 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">
|
||
|
||
<!--
|
||
SPDX-License-Identifier: LGPL-2.1+
|
||
|
||
This file is part of systemd.
|
||
|
||
Copyright 2016 Julian Orth
|
||
-->
|
||
|
||
<refentry id="sd_bus_add_match">
|
||
|
||
<refentryinfo>
|
||
<title>sd_bus_add_match</title>
|
||
<productname>systemd</productname>
|
||
|
||
<authorgroup>
|
||
<author>
|
||
<firstname>Julian</firstname>
|
||
<surname>Orth</surname>
|
||
<email>ju.orth@gmail.com</email>
|
||
</author>
|
||
</authorgroup>
|
||
</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>
|
||
<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 eaching 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 similar to
|
||
<function>sd_bus_match_signal()</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>
|
||
|
||
<refsect1>
|
||
<title>Notes</title>
|
||
|
||
<para><function>sd_bus_add_match()</function> and the other functions 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_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_bus_message_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_bus_set_bus_client</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
</para>
|
||
</refsect1>
|
||
|
||
</refentry>
|