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">
6 This file is part of elogind.
8 Copyright 2014 Zbigniew Jędrzejewski-Szmek
10 elogind is free software; you can redistribute it and/or modify it
11 under the terms of the GNU Lesser General Public License as published by
12 the Free Software Foundation; either version 2.1 of the License, or
13 (at your option) any later version.
15 elogind is distributed in the hope that it will be useful, but
16 WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 Lesser General Public License for more details.
20 You should have received a copy of the GNU Lesser General Public License
21 along with elogind; If not, see <http://www.gnu.org/licenses/>.
24 <refentry id="sd_bus_message_append"
25 xmlns:xi="http://www.w3.org/2001/XInclude">
28 <title>sd_bus_message_append</title>
29 <productname>elogind</productname>
33 <contrib>A monkey with a typewriter</contrib>
34 <firstname>Zbigniew</firstname>
35 <surname>Jędrzejewski-Szmek</surname>
36 <email>zbyszek@in.waw.pl</email>
42 <refentrytitle>sd_bus_message_append</refentrytitle>
43 <manvolnum>3</manvolnum>
47 <refname>sd_bus_message_append</refname>
49 <refpurpose>Attach fields to a D-Bus message based on a type
55 <funcsynopsisinfo>#include <elogind/sd-bus.h></funcsynopsisinfo>
58 <funcdef>int sd_bus_message_append</funcdef>
59 <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
60 <paramdef>const char *<parameter>types</parameter></paramdef>
61 <paramdef>...</paramdef>
67 <title>Description</title>
69 <para>The <function>sd_bus_message_append()</function> function
70 appends a sequence of fields to the D-Bus message object
71 <parameter>m</parameter>. The type string
72 <parameter>types</parameter> describes the types of the field
73 arguments that follow. For each type specified in the type string,
74 one or more arguments need to be specified, in the same order as
75 declared in the type string.</para>
77 <para>The type string is composed of the elements shown in the
78 table below. It contains zero or more single "complete types".
79 Each complete type may be one of the basic types or a fully
80 described container type. A container type may be a structure with
81 the contained types, a variant, an array with its element type, or
82 a dictionary entry with the contained types. The type string is
83 <constant>NUL</constant>-terminated.</para>
85 <para>In case of a basic type, one argument of the corresponding
86 type is expected.</para>
88 <para>A structure is denoted by a sequence of complete types
89 between <literal>(</literal> and <literal>)</literal>. This
90 sequence cannot be empty — it must contain at least one type.
91 Arguments corresponding to this nested sequence follow the same
92 rules as if they were not nested.</para>
94 <para>A variant is denoted by <literal>v</literal>. Corresponding
95 arguments must begin with a type string denoting a complete type,
96 and following that, arguments corresponding to the specified type.
99 <para>An array is denoted by <literal>a</literal> followed by a
100 complete type. Corresponding arguments must begin with the number of
101 entries in the array, followed by the entries themselves,
102 matching the element type of the array.</para>
104 <para>A dictionary is an array of dictionary entries, denoted by
105 <literal>a</literal> followed by a pair of complete types between
106 <literal>{</literal> and <literal>}</literal>. The first of those
107 types must be a basic type. Corresponding arguments must begin
108 with the number of dictionary entries, followed by a pair of
109 values for each entry matching the element type of
110 the dictionary entries.</para>
112 <para>For further details on the D-Bus type system, please consult
114 url="http://dbus.freedesktop.org/doc/dbus-specification.html#type-system">D-Bus
115 Specification</ulink>.</para>
118 <title>Item type specifiers</title>
121 <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers'])//colspec" />
122 <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//thead)" />
125 <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//tbody/*)" />
128 <entry><literal>a</literal></entry>
129 <entry><constant>SD_BUS_TYPE_ARRAY</constant></entry>
131 <entry>determined by array type and size</entry>
132 <entry>int, followed by array contents</entry>
136 <entry><literal>v</literal></entry>
137 <entry><constant>SD_BUS_TYPE_VARIANT</constant></entry>
138 <entry>variant</entry>
139 <entry>determined by the type argument</entry>
140 <entry>signature string, followed by variant contents</entry>
144 <entry><literal>(</literal></entry>
145 <entry><constant>SD_BUS_TYPE_STRUCT_BEGIN</constant></entry>
146 <entry>array start</entry>
147 <entry morerows="1">determined by the nested types</entry>
148 <entry morerows="1">structure contents</entry>
151 <entry><literal>)</literal></entry>
152 <entry><constant>SD_BUS_TYPE_STRUCT_END</constant></entry>
153 <entry>array end</entry>
157 <entry><literal>{</literal></entry>
158 <entry><constant>SD_BUS_TYPE_DICT_ENTRY_BEGIN</constant></entry>
159 <entry>dictionary entry start</entry>
160 <entry morerows="1">determined by the nested types</entry>
161 <entry morerows="1">dictionary contents</entry>
164 <entry><literal>}</literal></entry>
165 <entry><constant>SD_BUS_TYPE_DICT_ENTRY_END</constant></entry>
166 <entry>dictionary entry end</entry>
175 <title>Types String Grammar</title>
177 <programlisting>types ::= complete_type*
178 complete_type ::= basic_type | variant | structure | array | dictionary
179 basic_type ::= "y" | "n" | "q" | "u" | "i" | "x" | "t" | "d" |
183 structure ::= "(" complete_type+ ")"
184 array ::= "a" complete_type
185 dictionary ::= "a" "{" basic_type complete_type "}"
190 <title>Examples</title>
192 <para>Append a single basic type (the string <literal>a string</literal>):
195 <programlisting>sd_bus_message *m;
197 sd_bus_message_append(m, "s", "a string");</programlisting>
199 <para>Append all types of integers:</para>
201 <programlisting>uint8_t y = 1;
209 sd_bus_message_append(m, "ynqiuxtd", y, n, q, i, u, x, t, d);</programlisting>
211 <para>Append a structure composed of a string and a D-Bus path:</para>
213 <programlisting>sd_bus_message_append(m, "(so)", "a string", "/a/path");
216 <para>Append an array of UNIX file descriptors:</para>
218 <programlisting>sd_bus_message_append(m, "ah", 3, STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO);
221 <para>Append a variant, with the real type "g" (signature),
222 and value "sdbusisgood":</para>
224 <programlisting>sd_bus_message_append(m, "v", "g", "sdbusisgood");</programlisting>
226 <para>Append a dictionary containing the mapping {1=>"a", 2=>"b", 3=>""}:
229 <programlisting>sd_bus_message_append(m, "a{is}", 3, 1, "a", 2, "b", 3, NULL);
234 <title>Return Value</title>
236 <para>On success, this call returns 0 or a positive
237 integer. On failure, this call returns a negative
238 errno-style error code.</para>
241 <xi:include href="sd_bus_message_append_basic.xml" xpointer="errors" />
246 <para><function>sd_bus_open_user()</function> and other functions
247 described here are available as a shared library, which can be
248 compiled and linked to with the
249 <constant>libelogind-bus</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
254 <title>See Also</title>
257 <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
258 <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
259 <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
260 <citerefentry><refentrytitle>sd_bus_message_append_array</refentrytitle><manvolnum>3</manvolnum></citerefentry>