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514094f9 | 1 | <?xml version='1.0'?> |
effbc8e4 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
48f69d8f | 9 | <refentry id="sd_bus_message_append" |
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10 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
11 | ||
12 | <refentryinfo> | |
13 | <title>sd_bus_message_append</title> | |
14 | <productname>systemd</productname> | |
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15 | </refentryinfo> |
16 | ||
17 | <refmeta> | |
18 | <refentrytitle>sd_bus_message_append</refentrytitle> | |
19 | <manvolnum>3</manvolnum> | |
20 | </refmeta> | |
21 | ||
22 | <refnamediv> | |
23 | <refname>sd_bus_message_append</refname> | |
19fe49f6 | 24 | <refname>sd_bus_message_appendv</refname> |
effbc8e4 | 25 | |
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26 | <refpurpose>Attach fields to a D-Bus message based on a type |
27 | string</refpurpose> | |
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28 | </refnamediv> |
29 | ||
30 | <refsynopsisdiv> | |
31 | <funcsynopsis> | |
32 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
33 | ||
34 | <funcprototype> | |
35 | <funcdef>int sd_bus_message_append</funcdef> | |
36 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
37 | <paramdef>const char *<parameter>types</parameter></paramdef> | |
1eecafb8 | 38 | <paramdef>…</paramdef> |
effbc8e4 | 39 | </funcprototype> |
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40 | |
41 | <funcprototype> | |
42 | <funcdef>int sd_bus_message_appendv</funcdef> | |
43 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
44 | <paramdef>const char *<parameter>types</parameter></paramdef> | |
45 | <paramdef>va_list <parameter>ap</parameter></paramdef> | |
46 | </funcprototype> | |
47 | ||
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48 | </funcsynopsis> |
49 | </refsynopsisdiv> | |
50 | ||
51 | <refsect1> | |
52 | <title>Description</title> | |
53 | ||
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54 | <para>The <function>sd_bus_message_append()</function> function |
55 | appends a sequence of fields to the D-Bus message object | |
56 | <parameter>m</parameter>. The type string | |
57 | <parameter>types</parameter> describes the types of the field | |
b938cb90 | 58 | arguments that follow. For each type specified in the type string, |
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59 | one or more arguments need to be specified, in the same order as |
60 | declared in the type string.</para> | |
effbc8e4 | 61 | |
e8216945 | 62 | <para>The type string is composed of the elements shown in the |
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63 | table below. It contains zero or more single "complete types". |
64 | Each complete type may be one of the basic types or a fully | |
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65 | described container type. A container type may be a structure with |
66 | the contained types, a variant, an array with its element type, or | |
67 | a dictionary entry with the contained types. The type string is | |
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68 | <constant>NUL</constant>-terminated.</para> |
69 | ||
70 | <para>In case of a basic type, one argument of the corresponding | |
71 | type is expected.</para> | |
72 | ||
73 | <para>A structure is denoted by a sequence of complete types | |
74 | between <literal>(</literal> and <literal>)</literal>. This | |
75 | sequence cannot be empty — it must contain at least one type. | |
76 | Arguments corresponding to this nested sequence follow the same | |
77 | rules as if they were not nested.</para> | |
78 | ||
ff9b60f3 | 79 | <para>A variant is denoted by <literal>v</literal>. Corresponding |
e8216945 | 80 | arguments must begin with a type string denoting a complete type, |
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81 | and following that, arguments corresponding to the specified type. |
82 | </para> | |
83 | ||
84 | <para>An array is denoted by <literal>a</literal> followed by a | |
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85 | complete type. Corresponding arguments must begin with the number of |
86 | entries in the array, followed by the entries themselves, | |
87 | matching the element type of the array.</para> | |
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88 | |
89 | <para>A dictionary is an array of dictionary entries, denoted by | |
90 | <literal>a</literal> followed by a pair of complete types between | |
91 | <literal>{</literal> and <literal>}</literal>. The first of those | |
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92 | types must be a basic type. Corresponding arguments must begin |
93 | with the number of dictionary entries, followed by a pair of | |
94 | values for each entry matching the element type of | |
95 | the dictionary entries.</para> | |
96 | ||
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97 | <para>The <function>sd_bus_message_appendv()</function> is equivalent to the |
98 | <function>sd_bus_message_append()</function>, except that it is called with | |
99 | a <literal>va_list</literal> instead of a variable number of arguments. This | |
100 | function does not call the <function>va_end()</function> macro. Because it | |
101 | invokes the <function>va_arg()</function> macro, the value of | |
102 | <parameter>ap</parameter> is undefined after the call.</para> | |
19fe49f6 | 103 | |
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104 | <para>For further details on the D-Bus type system, please consult |
105 | the <ulink | |
106 | url="http://dbus.freedesktop.org/doc/dbus-specification.html#type-system">D-Bus | |
107 | Specification</ulink>.</para> | |
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108 | |
109 | <table> | |
e8216945 | 110 | <title>Item type specifiers</title> |
effbc8e4 | 111 | |
e8216945 | 112 | <tgroup cols='5'> |
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113 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers'])//colspec" /> |
114 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//thead)" /> | |
115 | ||
116 | <tbody> | |
117 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//tbody/*)" /> | |
118 | ||
119 | <row> | |
120 | <entry><literal>a</literal></entry> | |
121 | <entry><constant>SD_BUS_TYPE_ARRAY</constant></entry> | |
122 | <entry>array</entry> | |
123 | <entry>determined by array type and size</entry> | |
e8216945 | 124 | <entry>int, followed by array contents</entry> |
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125 | </row> |
126 | ||
127 | <row> | |
128 | <entry><literal>v</literal></entry> | |
129 | <entry><constant>SD_BUS_TYPE_VARIANT</constant></entry> | |
130 | <entry>variant</entry> | |
131 | <entry>determined by the type argument</entry> | |
e8216945 | 132 | <entry>signature string, followed by variant contents</entry> |
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133 | </row> |
134 | ||
135 | <row> | |
136 | <entry><literal>(</literal></entry> | |
137 | <entry><constant>SD_BUS_TYPE_STRUCT_BEGIN</constant></entry> | |
138 | <entry>array start</entry> | |
139 | <entry morerows="1">determined by the nested types</entry> | |
e8216945 | 140 | <entry morerows="1">structure contents</entry> |
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141 | </row> |
142 | <row> | |
143 | <entry><literal>)</literal></entry> | |
144 | <entry><constant>SD_BUS_TYPE_STRUCT_END</constant></entry> | |
145 | <entry>array end</entry> | |
146 | </row> | |
147 | ||
148 | <row> | |
149 | <entry><literal>{</literal></entry> | |
150 | <entry><constant>SD_BUS_TYPE_DICT_ENTRY_BEGIN</constant></entry> | |
151 | <entry>dictionary entry start</entry> | |
152 | <entry morerows="1">determined by the nested types</entry> | |
e8216945 | 153 | <entry morerows="1">dictionary contents</entry> |
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154 | </row> |
155 | <row> | |
156 | <entry><literal>}</literal></entry> | |
157 | <entry><constant>SD_BUS_TYPE_DICT_ENTRY_END</constant></entry> | |
158 | <entry>dictionary entry end</entry> | |
159 | </row> | |
160 | </tbody> | |
161 | </tgroup> | |
162 | </table> | |
e8216945 | 163 | |
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164 | <para>For types "s" and "g" (unicode string or signature), the pointer may be |
165 | <constant>NULL</constant>, which is equivalent to an empty string. See | |
166 | <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
167 | for the precise interpretation of those and other types.</para> | |
168 | ||
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169 | </refsect1> |
170 | ||
171 | <refsect1> | |
e8216945 | 172 | <title>Types String Grammar</title> |
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173 | |
174 | <programlisting>types ::= complete_type* | |
175 | complete_type ::= basic_type | variant | structure | array | dictionary | |
176 | basic_type ::= "y" | "n" | "q" | "u" | "i" | "x" | "t" | "d" | | |
177 | "b" | "h" | | |
178 | "s" | "o" | "g" | |
179 | variant ::= "v" | |
180 | structure ::= "(" complete_type+ ")" | |
181 | array ::= "a" complete_type | |
182 | dictionary ::= "a" "{" basic_type complete_type "}" | |
183 | </programlisting> | |
184 | </refsect1> | |
185 | ||
186 | <refsect1> | |
187 | <title>Examples</title> | |
188 | ||
189 | <para>Append a single basic type (the string <literal>a string</literal>): | |
190 | </para> | |
191 | ||
192 | <programlisting>sd_bus_message *m; | |
1eecafb8 | 193 | … |
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194 | sd_bus_message_append(m, "s", "a string");</programlisting> |
195 | ||
196 | <para>Append all types of integers:</para> | |
197 | ||
198 | <programlisting>uint8_t y = 1; | |
199 | int16_t n = 2; | |
200 | uint16_t q = 3; | |
201 | int32_t i = 4; | |
202 | uint32_t u = 5; | |
203 | int32_t x = 6; | |
204 | uint32_t t = 7; | |
205 | double d = 8.0; | |
206 | sd_bus_message_append(m, "ynqiuxtd", y, n, q, i, u, x, t, d);</programlisting> | |
207 | ||
e8216945 | 208 | <para>Append a structure composed of a string and a D-Bus path:</para> |
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209 | |
210 | <programlisting>sd_bus_message_append(m, "(so)", "a string", "/a/path"); | |
211 | </programlisting> | |
212 | ||
213 | <para>Append an array of UNIX file descriptors:</para> | |
214 | ||
215 | <programlisting>sd_bus_message_append(m, "ah", 3, STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO); | |
216 | </programlisting> | |
217 | ||
218 | <para>Append a variant, with the real type "g" (signature), | |
219 | and value "sdbusisgood":</para> | |
220 | ||
221 | <programlisting>sd_bus_message_append(m, "v", "g", "sdbusisgood");</programlisting> | |
222 | ||
223 | <para>Append a dictionary containing the mapping {1=>"a", 2=>"b", 3=>""}: | |
224 | </para> | |
225 | ||
226 | <programlisting>sd_bus_message_append(m, "a{is}", 3, 1, "a", 2, "b", 3, NULL); | |
227 | </programlisting> | |
228 | </refsect1> | |
229 | ||
230 | <refsect1> | |
231 | <title>Return Value</title> | |
232 | ||
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233 | <para>On success, these functions return 0 or a positive |
234 | integer. On failure, these functions return a negative | |
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235 | errno-style error code.</para> |
236 | </refsect1> | |
237 | ||
238 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="errors" /> | |
239 | ||
7d6b2723 | 240 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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241 | |
242 | <refsect1> | |
243 | <title>See Also</title> | |
244 | ||
245 | <para> | |
246 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
247 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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248 | <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
249 | <citerefentry><refentrytitle>sd_bus_message_append_array</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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250 | </para> |
251 | </refsect1> | |
252 | ||
253 | </refentry> |