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