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3802a3d3 | 1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
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> | |
15 | ||
16 | <authorgroup> | |
17 | <author> | |
18 | <contrib>A monkey with a typewriter</contrib> | |
19 | <firstname>Zbigniew</firstname> | |
20 | <surname>Jędrzejewski-Szmek</surname> | |
21 | <email>zbyszek@in.waw.pl</email> | |
22 | </author> | |
23 | </authorgroup> | |
24 | </refentryinfo> | |
25 | ||
26 | <refmeta> | |
27 | <refentrytitle>sd_bus_message_append</refentrytitle> | |
28 | <manvolnum>3</manvolnum> | |
29 | </refmeta> | |
30 | ||
31 | <refnamediv> | |
32 | <refname>sd_bus_message_append</refname> | |
19fe49f6 | 33 | <refname>sd_bus_message_appendv</refname> |
effbc8e4 | 34 | |
e8216945 LP |
35 | <refpurpose>Attach fields to a D-Bus message based on a type |
36 | string</refpurpose> | |
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37 | </refnamediv> |
38 | ||
39 | <refsynopsisdiv> | |
40 | <funcsynopsis> | |
41 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
42 | ||
43 | <funcprototype> | |
44 | <funcdef>int sd_bus_message_append</funcdef> | |
45 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
46 | <paramdef>const char *<parameter>types</parameter></paramdef> | |
1eecafb8 | 47 | <paramdef>…</paramdef> |
effbc8e4 | 48 | </funcprototype> |
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49 | |
50 | <funcprototype> | |
51 | <funcdef>int sd_bus_message_appendv</funcdef> | |
52 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
53 | <paramdef>const char *<parameter>types</parameter></paramdef> | |
54 | <paramdef>va_list <parameter>ap</parameter></paramdef> | |
55 | </funcprototype> | |
56 | ||
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57 | </funcsynopsis> |
58 | </refsynopsisdiv> | |
59 | ||
60 | <refsect1> | |
61 | <title>Description</title> | |
62 | ||
e8216945 LP |
63 | <para>The <function>sd_bus_message_append()</function> function |
64 | appends a sequence of fields to the D-Bus message object | |
65 | <parameter>m</parameter>. The type string | |
66 | <parameter>types</parameter> describes the types of the field | |
b938cb90 | 67 | arguments that follow. For each type specified in the type string, |
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68 | one or more arguments need to be specified, in the same order as |
69 | declared in the type string.</para> | |
effbc8e4 | 70 | |
e8216945 | 71 | <para>The type string is composed of the elements shown in the |
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72 | table below. It contains zero or more single "complete types". |
73 | Each complete type may be one of the basic types or a fully | |
e8216945 LP |
74 | described container type. A container type may be a structure with |
75 | the contained types, a variant, an array with its element type, or | |
76 | a dictionary entry with the contained types. The type string is | |
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77 | <constant>NUL</constant>-terminated.</para> |
78 | ||
79 | <para>In case of a basic type, one argument of the corresponding | |
80 | type is expected.</para> | |
81 | ||
82 | <para>A structure is denoted by a sequence of complete types | |
83 | between <literal>(</literal> and <literal>)</literal>. This | |
84 | sequence cannot be empty — it must contain at least one type. | |
85 | Arguments corresponding to this nested sequence follow the same | |
86 | rules as if they were not nested.</para> | |
87 | ||
ff9b60f3 | 88 | <para>A variant is denoted by <literal>v</literal>. Corresponding |
e8216945 | 89 | arguments must begin with a type string denoting a complete type, |
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90 | and following that, arguments corresponding to the specified type. |
91 | </para> | |
92 | ||
93 | <para>An array is denoted by <literal>a</literal> followed by a | |
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94 | complete type. Corresponding arguments must begin with the number of |
95 | entries in the array, followed by the entries themselves, | |
96 | matching the element type of the array.</para> | |
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97 | |
98 | <para>A dictionary is an array of dictionary entries, denoted by | |
99 | <literal>a</literal> followed by a pair of complete types between | |
100 | <literal>{</literal> and <literal>}</literal>. The first of those | |
e8216945 LP |
101 | types must be a basic type. Corresponding arguments must begin |
102 | with the number of dictionary entries, followed by a pair of | |
103 | values for each entry matching the element type of | |
104 | the dictionary entries.</para> | |
105 | ||
19fe49f6 FDP |
106 | <para>The <function>sd_bus_message_appendv()</function> is equivalent to |
107 | the function <function>sd_bus_message_append()</function>, | |
108 | except that it is called with a <literal>va_list</literal> instead of | |
109 | a variable number of arguments. This function does not call the | |
110 | <function>va_end()</function> macro. Because it invokes the | |
111 | <function>va_arg()</function> macro, the value of ap | |
112 | is undefined after the call.</para> | |
113 | ||
e8216945 LP |
114 | <para>For further details on the D-Bus type system, please consult |
115 | the <ulink | |
116 | url="http://dbus.freedesktop.org/doc/dbus-specification.html#type-system">D-Bus | |
117 | Specification</ulink>.</para> | |
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118 | |
119 | <table> | |
e8216945 | 120 | <title>Item type specifiers</title> |
effbc8e4 | 121 | |
e8216945 | 122 | <tgroup cols='5'> |
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123 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers'])//colspec" /> |
124 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//thead)" /> | |
125 | ||
126 | <tbody> | |
127 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="xpointer(//table[@id='format-specifiers']//tbody/*)" /> | |
128 | ||
129 | <row> | |
130 | <entry><literal>a</literal></entry> | |
131 | <entry><constant>SD_BUS_TYPE_ARRAY</constant></entry> | |
132 | <entry>array</entry> | |
133 | <entry>determined by array type and size</entry> | |
e8216945 | 134 | <entry>int, followed by array contents</entry> |
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135 | </row> |
136 | ||
137 | <row> | |
138 | <entry><literal>v</literal></entry> | |
139 | <entry><constant>SD_BUS_TYPE_VARIANT</constant></entry> | |
140 | <entry>variant</entry> | |
141 | <entry>determined by the type argument</entry> | |
e8216945 | 142 | <entry>signature string, followed by variant contents</entry> |
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143 | </row> |
144 | ||
145 | <row> | |
146 | <entry><literal>(</literal></entry> | |
147 | <entry><constant>SD_BUS_TYPE_STRUCT_BEGIN</constant></entry> | |
148 | <entry>array start</entry> | |
149 | <entry morerows="1">determined by the nested types</entry> | |
e8216945 | 150 | <entry morerows="1">structure contents</entry> |
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151 | </row> |
152 | <row> | |
153 | <entry><literal>)</literal></entry> | |
154 | <entry><constant>SD_BUS_TYPE_STRUCT_END</constant></entry> | |
155 | <entry>array end</entry> | |
156 | </row> | |
157 | ||
158 | <row> | |
159 | <entry><literal>{</literal></entry> | |
160 | <entry><constant>SD_BUS_TYPE_DICT_ENTRY_BEGIN</constant></entry> | |
161 | <entry>dictionary entry start</entry> | |
162 | <entry morerows="1">determined by the nested types</entry> | |
e8216945 | 163 | <entry morerows="1">dictionary contents</entry> |
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164 | </row> |
165 | <row> | |
166 | <entry><literal>}</literal></entry> | |
167 | <entry><constant>SD_BUS_TYPE_DICT_ENTRY_END</constant></entry> | |
168 | <entry>dictionary entry end</entry> | |
169 | </row> | |
170 | </tbody> | |
171 | </tgroup> | |
172 | </table> | |
e8216945 | 173 | |
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174 | <para>For types "s" and "g" (unicode string or signature), the pointer may be |
175 | <constant>NULL</constant>, which is equivalent to an empty string. See | |
176 | <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
177 | for the precise interpretation of those and other types.</para> | |
178 | ||
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179 | </refsect1> |
180 | ||
181 | <refsect1> | |
e8216945 | 182 | <title>Types String Grammar</title> |
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183 | |
184 | <programlisting>types ::= complete_type* | |
185 | complete_type ::= basic_type | variant | structure | array | dictionary | |
186 | basic_type ::= "y" | "n" | "q" | "u" | "i" | "x" | "t" | "d" | | |
187 | "b" | "h" | | |
188 | "s" | "o" | "g" | |
189 | variant ::= "v" | |
190 | structure ::= "(" complete_type+ ")" | |
191 | array ::= "a" complete_type | |
192 | dictionary ::= "a" "{" basic_type complete_type "}" | |
193 | </programlisting> | |
194 | </refsect1> | |
195 | ||
196 | <refsect1> | |
197 | <title>Examples</title> | |
198 | ||
199 | <para>Append a single basic type (the string <literal>a string</literal>): | |
200 | </para> | |
201 | ||
202 | <programlisting>sd_bus_message *m; | |
1eecafb8 | 203 | … |
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204 | sd_bus_message_append(m, "s", "a string");</programlisting> |
205 | ||
206 | <para>Append all types of integers:</para> | |
207 | ||
208 | <programlisting>uint8_t y = 1; | |
209 | int16_t n = 2; | |
210 | uint16_t q = 3; | |
211 | int32_t i = 4; | |
212 | uint32_t u = 5; | |
213 | int32_t x = 6; | |
214 | uint32_t t = 7; | |
215 | double d = 8.0; | |
216 | sd_bus_message_append(m, "ynqiuxtd", y, n, q, i, u, x, t, d);</programlisting> | |
217 | ||
e8216945 | 218 | <para>Append a structure composed of a string and a D-Bus path:</para> |
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219 | |
220 | <programlisting>sd_bus_message_append(m, "(so)", "a string", "/a/path"); | |
221 | </programlisting> | |
222 | ||
223 | <para>Append an array of UNIX file descriptors:</para> | |
224 | ||
225 | <programlisting>sd_bus_message_append(m, "ah", 3, STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO); | |
226 | </programlisting> | |
227 | ||
228 | <para>Append a variant, with the real type "g" (signature), | |
229 | and value "sdbusisgood":</para> | |
230 | ||
231 | <programlisting>sd_bus_message_append(m, "v", "g", "sdbusisgood");</programlisting> | |
232 | ||
233 | <para>Append a dictionary containing the mapping {1=>"a", 2=>"b", 3=>""}: | |
234 | </para> | |
235 | ||
236 | <programlisting>sd_bus_message_append(m, "a{is}", 3, 1, "a", 2, "b", 3, NULL); | |
237 | </programlisting> | |
238 | </refsect1> | |
239 | ||
240 | <refsect1> | |
241 | <title>Return Value</title> | |
242 | ||
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243 | <para>On success, these functions return 0 or a positive |
244 | integer. On failure, these functions return a negative | |
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245 | errno-style error code.</para> |
246 | </refsect1> | |
247 | ||
248 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="errors" /> | |
249 | ||
7d6b2723 | 250 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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251 | |
252 | <refsect1> | |
253 | <title>See Also</title> | |
254 | ||
255 | <para> | |
256 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
257 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
e8216945 LP |
258 | <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
259 | <citerefentry><refentrytitle>sd_bus_message_append_array</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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260 | </para> |
261 | </refsect1> | |
262 | ||
263 | </refentry> |