summaryrefslogtreecommitdiff
path: root/src/libsystemd/sd_bus_message_append.xml
blob: c222d0fd0ef5c2745a25ccb255571ebb468fa45c (plain)
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
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
<?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 2014 Zbigniew Jędrzejewski-Szmek

  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_message_append"
          xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>sd_bus_message_append</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>A monkey with a typewriter</contrib>
        <firstname>Zbigniew</firstname>
        <surname>Jędrzejewski-Szmek</surname>
        <email>zbyszek@in.waw.pl</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_message_append</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_message_append</refname>

    <refpurpose>Attach fields to a D-Bus message based on a type
    string</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>int sd_bus_message_append</funcdef>
        <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
        <paramdef>const char *<parameter>types</parameter></paramdef>
        <paramdef>...</paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>The <function>sd_bus_message_append()</function> function
    appends a sequence of fields to the D-Bus message object
    <parameter>m</parameter>. The type string
    <parameter>types</parameter> describes the types of the field
    arguments that follow. For each type specified in the type string,
    one or more arguments need to be specified, in the same order as
    declared in the type string.</para>

    <para>The type string is composed of the elements shown in the
    table below. It contains zero or more single "complete types".
    Each complete type may be one of the basic types or a fully
    described container type. A container type may be a structure with
    the contained types, a variant, an array with its element type, or
    a dictionary entry with the contained types. The type string is
    <constant>NUL</constant>-terminated.</para>

    <para>In case of a basic type, one argument of the corresponding
    type is expected.</para>

    <para>A structure is denoted by a sequence of complete types
    between <literal>(</literal> and <literal>)</literal>. This
    sequence cannot be empty — it must contain at least one type.
    Arguments corresponding to this nested sequence follow the same
    rules as if they were not nested.</para>

    <para>A variant is denoted by <literal>v</literal>. Corresponding
    arguments must begin with a type string denoting a complete type,
    and following that, arguments corresponding to the specified type.
    </para>

    <para>An array is denoted by <literal>a</literal> followed by a
    complete type. Corresponding arguments must begin with the number of
    entries in the array, followed by the entries themselves,
    matching the element type of the array.</para>

    <para>A dictionary is an array of dictionary entries, denoted by
    <literal>a</literal> followed by a pair of complete types between
    <literal>{</literal> and <literal>}</literal>. The first of those
    types must be a basic type. Corresponding arguments must begin
    with the number of dictionary entries, followed by a pair of
    values for each entry matching the element type of
    the dictionary entries.</para>

    <para>For further details on the D-Bus type system, please consult
    the <ulink
    url="http://dbus.freedesktop.org/doc/dbus-specification.html#type-system">D-Bus
    Specification</ulink>.</para>

    <table>
      <title>Item type specifiers</title>

      <tgroup cols='5'>
        <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers'])//colspec" />
        <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//thead)" />

        <tbody>
          <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//tbody/*)" />

          <row>
            <entry><literal>a</literal></entry>
            <entry><constant>SD_BUS_TYPE_ARRAY</constant></entry>
            <entry>array</entry>
            <entry>determined by array type and size</entry>
            <entry>int, followed by array contents</entry>
          </row>

          <row>
            <entry><literal>v</literal></entry>
            <entry><constant>SD_BUS_TYPE_VARIANT</constant></entry>
            <entry>variant</entry>
            <entry>determined by the type argument</entry>
            <entry>signature string, followed by variant contents</entry>
          </row>

          <row>
            <entry><literal>(</literal></entry>
            <entry><constant>SD_BUS_TYPE_STRUCT_BEGIN</constant></entry>
            <entry>array start</entry>
            <entry morerows="1">determined by the nested types</entry>
            <entry morerows="1">structure contents</entry>
          </row>
          <row>
            <entry><literal>)</literal></entry>
            <entry><constant>SD_BUS_TYPE_STRUCT_END</constant></entry>
            <entry>array end</entry>
          </row>

          <row>
            <entry><literal>{</literal></entry>
            <entry><constant>SD_BUS_TYPE_DICT_ENTRY_BEGIN</constant></entry>
            <entry>dictionary entry start</entry>
            <entry morerows="1">determined by the nested types</entry>
            <entry morerows="1">dictionary contents</entry>
          </row>
          <row>
            <entry><literal>}</literal></entry>
            <entry><constant>SD_BUS_TYPE_DICT_ENTRY_END</constant></entry>
            <entry>dictionary entry end</entry>
          </row>
       </tbody>
      </tgroup>
    </table>

    <para>For types "s" and "g" (unicode string or signature), the pointer may be
    <constant>NULL</constant>, which is equivalent to an empty string. See
    <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    for the precise interpretation of those and other types.</para>

  </refsect1>

  <refsect1>
    <title>Types String Grammar</title>

    <programlisting>types ::= complete_type*
complete_type ::= basic_type | variant | structure | array | dictionary
basic_type ::= "y" | "n" | "q" | "u" | "i" | "x" | "t" | "d" |
               "b" | "h" |
               "s" | "o" | "g"
variant ::= "v"
structure ::= "(" complete_type+ ")"
array ::= "a" complete_type
dictionary ::= "a" "{" basic_type complete_type "}"
</programlisting>
  </refsect1>

  <refsect1>
    <title>Examples</title>

    <para>Append a single basic type (the string <literal>a string</literal>):
    </para>

    <programlisting>sd_bus_message *m;
...
sd_bus_message_append(m, "s", "a string");</programlisting>

    <para>Append all types of integers:</para>

    <programlisting>uint8_t y = 1;
int16_t n = 2;
uint16_t q = 3;
int32_t i = 4;
uint32_t u = 5;
int32_t x = 6;
uint32_t t = 7;
double d = 8.0;
sd_bus_message_append(m, "ynqiuxtd", y, n, q, i, u, x, t, d);</programlisting>

     <para>Append a structure composed of a string and a D-Bus path:</para>

     <programlisting>sd_bus_message_append(m, "(so)", "a string", "/a/path");
</programlisting>

     <para>Append an array of UNIX file descriptors:</para>

     <programlisting>sd_bus_message_append(m, "ah", 3, STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO);
</programlisting>

     <para>Append a variant, with the real type "g" (signature),
     and value "sdbusisgood":</para>

     <programlisting>sd_bus_message_append(m, "v", "g", "sdbusisgood");</programlisting>

     <para>Append a dictionary containing the mapping {1=>"a", 2=>"b", 3=>""}:
     </para>

     <programlisting>sd_bus_message_append(m, "a{is}", 3, 1, "a", 2, "b", 3, NULL);
     </programlisting>
  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>On success, this call returns 0 or a positive
    integer. On failure, this call returns a negative
    errno-style error code.</para>
  </refsect1>

  <xi:include href="sd_bus_message_append_basic.xml" xpointer="errors" />

  <refsect1>
    <title>Notes</title>

    <para><function>sd_bus_open_user()</function> and other functions
    described here are available as a shared library, which can be
    compiled and linked to with the
    <constant>libsystemd-bus</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_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_message_append_array</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>