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1 | <?xml version='1.0'?> | |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> | |
5 | ||
6 | <refentry id="sd_bus_message_append" | |
7 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
8 | ||
9 | <refentryinfo> | |
10 | <title>sd_bus_message_append</title> | |
11 | <productname>systemd</productname> | |
12 | </refentryinfo> | |
13 | ||
14 | <refmeta> | |
15 | <refentrytitle>sd_bus_message_append</refentrytitle> | |
16 | <manvolnum>3</manvolnum> | |
17 | </refmeta> | |
18 | ||
19 | <refnamediv> | |
20 | <refname>sd_bus_message_append</refname> | |
21 | <refname>sd_bus_message_appendv</refname> | |
22 | ||
23 | <refpurpose>Attach fields to a D-Bus message based on a type | |
24 | string</refpurpose> | |
25 | </refnamediv> | |
26 | ||
27 | <refsynopsisdiv> | |
28 | <funcsynopsis> | |
29 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
30 | ||
31 | <funcprototype> | |
32 | <funcdef>int sd_bus_message_append</funcdef> | |
33 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
34 | <paramdef>const char *<parameter>types</parameter></paramdef> | |
35 | <paramdef>…</paramdef> | |
36 | </funcprototype> | |
37 | ||
38 | <funcprototype> | |
39 | <funcdef>int sd_bus_message_appendv</funcdef> | |
40 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
41 | <paramdef>const char *<parameter>types</parameter></paramdef> | |
42 | <paramdef>va_list <parameter>ap</parameter></paramdef> | |
43 | </funcprototype> | |
44 | ||
45 | </funcsynopsis> | |
46 | </refsynopsisdiv> | |
47 | ||
48 | <refsect1> | |
49 | <title>Description</title> | |
50 | ||
51 | <para>The <function>sd_bus_message_append()</function> function | |
52 | appends a sequence of fields to the D-Bus message object | |
53 | <parameter>m</parameter>. The type string | |
54 | <parameter>types</parameter> describes the types of the field | |
55 | arguments that follow. For each type specified in the type string, | |
56 | one or more arguments need to be specified, in the same order as | |
57 | declared in the type string.</para> | |
58 | ||
59 | <para>The type string is composed of the elements shown in the | |
60 | table below. It contains zero or more single "complete types". | |
61 | Each complete type may be one of the basic types or a fully | |
62 | described container type. A container type may be a structure with | |
63 | the contained types, a variant, an array with its element type, or | |
64 | a dictionary entry with the contained types. The type string is | |
65 | <constant>NUL</constant>-terminated.</para> | |
66 | ||
67 | <para>In case of a basic type, one argument of the corresponding | |
68 | type is expected.</para> | |
69 | ||
70 | <para>A structure is denoted by a sequence of complete types | |
71 | between <literal>(</literal> and <literal>)</literal>. This | |
72 | sequence cannot be empty — it must contain at least one type. | |
73 | Arguments corresponding to this nested sequence follow the same | |
74 | rules as if they were not nested.</para> | |
75 | ||
76 | <para>A variant is denoted by <literal>v</literal>. Corresponding | |
77 | arguments must begin with a type string denoting a complete type, | |
78 | and following that, arguments corresponding to the specified type. | |
79 | </para> | |
80 | ||
81 | <para>An array is denoted by <literal>a</literal> followed by a | |
82 | complete type. Corresponding arguments must begin with the number of | |
83 | entries in the array, followed by the entries themselves, | |
84 | matching the element type of the array.</para> | |
85 | ||
86 | <para>A dictionary is an array of dictionary entries, denoted by | |
87 | <literal>a</literal> followed by a pair of complete types between | |
88 | <literal>{</literal> and <literal>}</literal>. The first of those | |
89 | types must be a basic type. Corresponding arguments must begin | |
90 | with the number of dictionary entries, followed by a pair of | |
91 | values for each entry matching the element type of | |
92 | the dictionary entries.</para> | |
93 | ||
94 | <para>The <function>sd_bus_message_appendv()</function> is equivalent to the | |
95 | <function>sd_bus_message_append()</function>, except that it is called with | |
96 | a <literal>va_list</literal> instead of a variable number of arguments. This | |
97 | function does not call the <function>va_end()</function> macro. Because it | |
98 | invokes the <function>va_arg()</function> macro, the value of | |
99 | <parameter>ap</parameter> is undefined after the call.</para> | |
100 | ||
101 | <para>For further details on the D-Bus type system, please consult | |
102 | the <ulink | |
103 | url="http://dbus.freedesktop.org/doc/dbus-specification.html#type-system">D-Bus | |
104 | Specification</ulink>.</para> | |
105 | ||
106 | <table> | |
107 | <title>Item type specifiers</title> | |
108 | ||
109 | <tgroup cols='5'> | |
110 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers'])//colspec" /> | |
111 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//thead)" /> | |
112 | ||
113 | <tbody> | |
114 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//tbody/*)" /> | |
115 | ||
116 | <row> | |
117 | <entry><literal>a</literal></entry> | |
118 | <entry><constant>SD_BUS_TYPE_ARRAY</constant></entry> | |
119 | <entry>array</entry> | |
120 | <entry>determined by array type and size</entry> | |
121 | <entry>int, followed by array contents</entry> | |
122 | </row> | |
123 | ||
124 | <row> | |
125 | <entry><literal>v</literal></entry> | |
126 | <entry><constant>SD_BUS_TYPE_VARIANT</constant></entry> | |
127 | <entry>variant</entry> | |
128 | <entry>determined by the type argument</entry> | |
129 | <entry>signature string, followed by variant contents</entry> | |
130 | </row> | |
131 | ||
132 | <row> | |
133 | <entry><literal>(</literal></entry> | |
134 | <entry><constant>SD_BUS_TYPE_STRUCT_BEGIN</constant></entry> | |
135 | <entry>array start</entry> | |
136 | <entry morerows="1">determined by the nested types</entry> | |
137 | <entry morerows="1">structure contents</entry> | |
138 | </row> | |
139 | <row> | |
140 | <entry><literal>)</literal></entry> | |
141 | <entry><constant>SD_BUS_TYPE_STRUCT_END</constant></entry> | |
142 | <entry>array end</entry> | |
143 | </row> | |
144 | ||
145 | <row> | |
146 | <entry><literal>{</literal></entry> | |
147 | <entry><constant>SD_BUS_TYPE_DICT_ENTRY_BEGIN</constant></entry> | |
148 | <entry>dictionary entry start</entry> | |
149 | <entry morerows="1">determined by the nested types</entry> | |
150 | <entry morerows="1">dictionary contents</entry> | |
151 | </row> | |
152 | <row> | |
153 | <entry><literal>}</literal></entry> | |
154 | <entry><constant>SD_BUS_TYPE_DICT_ENTRY_END</constant></entry> | |
155 | <entry>dictionary entry end</entry> | |
156 | </row> | |
157 | </tbody> | |
158 | </tgroup> | |
159 | </table> | |
160 | ||
161 | <para>For types "s" and "g" (unicode string or signature), the pointer may be | |
162 | <constant>NULL</constant>, which is equivalent to an empty string. See | |
163 | <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
164 | for the precise interpretation of those and other types.</para> | |
165 | ||
166 | </refsect1> | |
167 | ||
168 | <refsect1> | |
169 | <title>Types String Grammar</title> | |
170 | ||
171 | <programlisting>types ::= complete_type* | |
172 | complete_type ::= basic_type | variant | structure | array | dictionary | |
173 | basic_type ::= "y" | "n" | "q" | "u" | "i" | "x" | "t" | "d" | | |
174 | "b" | "h" | | |
175 | "s" | "o" | "g" | |
176 | variant ::= "v" | |
177 | structure ::= "(" complete_type+ ")" | |
178 | array ::= "a" complete_type | |
179 | dictionary ::= "a" "{" basic_type complete_type "}" | |
180 | </programlisting> | |
181 | </refsect1> | |
182 | ||
183 | <refsect1> | |
184 | <title>Examples</title> | |
185 | ||
186 | <para>Append a single basic type (the string <literal>a string</literal>): | |
187 | </para> | |
188 | ||
189 | <programlisting>sd_bus_message *m; | |
190 | … | |
191 | sd_bus_message_append(m, "s", "a string");</programlisting> | |
192 | ||
193 | <para>Append all types of integers:</para> | |
194 | ||
195 | <programlisting>uint8_t y = 1; | |
196 | int16_t n = 2; | |
197 | uint16_t q = 3; | |
198 | int32_t i = 4; | |
199 | uint32_t u = 5; | |
200 | int32_t x = 6; | |
201 | uint32_t t = 7; | |
202 | double d = 8.0; | |
203 | sd_bus_message_append(m, "ynqiuxtd", y, n, q, i, u, x, t, d);</programlisting> | |
204 | ||
205 | <para>Append a structure composed of a string and a D-Bus path:</para> | |
206 | ||
207 | <programlisting>sd_bus_message_append(m, "(so)", "a string", "/a/path"); | |
208 | </programlisting> | |
209 | ||
210 | <para>Append an array of UNIX file descriptors:</para> | |
211 | ||
212 | <programlisting>sd_bus_message_append(m, "ah", 3, STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO); | |
213 | </programlisting> | |
214 | ||
215 | <para>Append a variant, with the real type "g" (signature), | |
216 | and value "sdbusisgood":</para> | |
217 | ||
218 | <programlisting>sd_bus_message_append(m, "v", "g", "sdbusisgood");</programlisting> | |
219 | ||
220 | <para>Append a dictionary containing the mapping {1=>"a", 2=>"b", 3=>""}: | |
221 | </para> | |
222 | ||
223 | <programlisting>sd_bus_message_append(m, "a{is}", 3, 1, "a", 2, "b", 3, NULL); | |
224 | </programlisting> | |
225 | </refsect1> | |
226 | ||
227 | <refsect1> | |
228 | <title>Return Value</title> | |
229 | ||
230 | <para>On success, these functions return 0 or a positive integer. On failure, they return a negative | |
231 | errno-style error code.</para> | |
232 | ||
233 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="errors" /> | |
234 | </refsect1> | |
235 | ||
236 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
237 | ||
238 | <refsect1> | |
239 | <title>See Also</title> | |
240 | ||
241 | <para> | |
242 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
243 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
244 | <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
245 | <citerefentry><refentrytitle>sd_bus_message_append_array</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
246 | </para> | |
247 | </refsect1> | |
248 | ||
249 | </refentry> |