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514094f9 | 1 | <?xml version='1.0'?> |
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2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
0307f791 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> |
effbc8e4 | 5 | |
48f69d8f | 6 | <refentry id="sd_bus_message_append_array" |
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7 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
8 | ||
9 | <refentryinfo> | |
10 | <title>sd_bus_message_append_array</title> | |
11 | <productname>systemd</productname> | |
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12 | </refentryinfo> |
13 | ||
14 | <refmeta> | |
15 | <refentrytitle>sd_bus_message_append_array</refentrytitle> | |
16 | <manvolnum>3</manvolnum> | |
17 | </refmeta> | |
18 | ||
19 | <refnamediv> | |
20 | <refname>sd_bus_message_append_array</refname> | |
21 | <refname>sd_bus_message_append_array_memfd</refname> | |
22 | <refname>sd_bus_message_append_array_iovec</refname> | |
23 | <refname>sd_bus_message_append_array_space</refname> | |
24 | ||
dd2b607b | 25 | <refpurpose>Append an array of fields to a D-Bus |
e8216945 | 26 | message</refpurpose> |
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27 | </refnamediv> |
28 | ||
29 | <refsynopsisdiv> | |
30 | <funcsynopsis> | |
31 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
32 | ||
33 | <funcprototype> | |
34 | <funcdef>int sd_bus_message_append_array</funcdef> | |
35 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
36 | <paramdef>char <parameter>type</parameter></paramdef> | |
37 | <paramdef>char void *<parameter>ptr</parameter></paramdef> | |
38 | <paramdef>size_t <parameter>size</parameter></paramdef> | |
39 | </funcprototype> | |
40 | ||
41 | <funcprototype> | |
42 | <funcdef>int sd_bus_message_append_array_memfd</funcdef> | |
43 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
44 | <paramdef>char <parameter>type</parameter></paramdef> | |
fac9c0d5 | 45 | <paramdef>int <parameter>memfd</parameter></paramdef> |
e8216945 LP |
46 | <paramdef>uint64_t <parameter>offset</parameter></paramdef> |
47 | <paramdef>uint64_t <parameter>size</parameter></paramdef> | |
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48 | </funcprototype> |
49 | ||
50 | <funcprototype> | |
51 | <funcdef>int sd_bus_message_append_array_iovec</funcdef> | |
52 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
53 | <paramdef>char <parameter>type</parameter></paramdef> | |
54 | <paramdef>const struct iovec *<parameter>iov</parameter></paramdef> | |
55 | <paramdef>unsigned <parameter>n</parameter></paramdef> | |
56 | </funcprototype> | |
57 | ||
58 | <funcprototype> | |
59 | <funcdef>int sd_bus_message_append_array_space</funcdef> | |
60 | <paramdef>char <parameter>type</parameter></paramdef> | |
61 | <paramdef>size_t <parameter>size</parameter></paramdef> | |
e8216945 | 62 | <paramdef>void **<parameter>ptr</parameter></paramdef> |
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63 | </funcprototype> |
64 | </funcsynopsis> | |
65 | </refsynopsisdiv> | |
66 | ||
67 | <refsect1> | |
68 | <title>Description</title> | |
69 | ||
e8216945 LP |
70 | <para>The <function>sd_bus_message_append_array()</function> |
71 | function appends an array to a D-Bus message | |
72 | <parameter>m</parameter>. A container will be opened, the array | |
73 | contents appended, and the container closed. The parameter | |
74 | <parameter>type</parameter> determines how the pointer | |
75 | <parameter>p</parameter> is interpreted. | |
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76 | <parameter>type</parameter> must be one of the "trivial" types |
77 | <literal>y</literal>, <literal>n</literal>, <literal>q</literal>, | |
78 | <literal>i</literal>, <literal>u</literal>, <literal>x</literal>, | |
79 | <literal>t</literal>, <literal>d</literal> (but not | |
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80 | <literal>b</literal>), as defined by the <ulink |
81 | url="http://dbus.freedesktop.org/doc/dbus-specification.html#basic-types">Basic | |
82 | Types</ulink> section of the D-Bus specification, and listed in | |
effbc8e4 | 83 | <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>. |
cbfaff65 | 84 | Pointer <parameter>p</parameter> must point to an array of size |
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85 | <parameter>size</parameter> bytes containing items of the |
86 | respective type. Size <parameter>size</parameter> must be a | |
87 | multiple of the size of the type <parameter>type</parameter>. As a | |
88 | special case, <parameter>p</parameter> may be | |
89 | <constant>NULL</constant>, if <parameter>size</parameter> is 0. | |
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90 | The memory pointed to by <parameter>p</parameter> is copied into |
91 | the memory area containing the message and stays in possession of | |
92 | the caller. The caller may hence freely change the data after this | |
93 | call without affecting the message the array was appended | |
94 | to.</para> | |
95 | ||
96 | <para>The <function>sd_bus_message_append_array_memfd()</function> | |
97 | function appends an array of a trivial type to message | |
98 | <parameter>m</parameter>, similar to | |
99 | <function>sd_bus_message_append_array()</function>. The contents | |
100 | of the memory file descriptor <parameter>memfd</parameter> | |
dd2b607b | 101 | starting at the specified offset and of the specified size is |
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102 | used as the contents of the array. The offset and size must be a |
103 | multiple of the size of the type | |
104 | <parameter>type</parameter>. However, as a special exception, if | |
105 | the offset is specified as zero and the size specified as | |
106 | UINT64_MAX the full memory file descriptor contents is used. The | |
7ca41557 | 107 | memory file descriptor is sealed by this call if it has not been |
a8eaaee7 | 108 | sealed yet, and cannot be modified after this call. See |
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109 | <citerefentry |
110 | project='man-pages'><refentrytitle>memfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
111 | for details about memory file descriptors. Appending arrays with | |
112 | memory file descriptors enables efficient zero-copy data transfer, | |
113 | as the memory file descriptor may be passed as-is to the | |
114 | destination, without copying the memory in it to the destination | |
115 | process. Not all protocol transports support passing memory file | |
116 | descriptors between participants, in which case this call will | |
117 | automatically fall back to copying. Also, as memory file | |
b938cb90 | 118 | descriptor passing is inefficient for smaller amounts of data, |
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119 | copying might still be enforced even where memory file descriptor |
120 | passing is supported.</para> | |
121 | ||
122 | <para>The <function>sd_bus_message_append_array_iovec()</function> | |
123 | function appends an array of a trivial type to the message | |
124 | <parameter>m</parameter>, similar to | |
125 | <function>sd_bus_message_append_array()</function>. Contents of | |
b938cb90 | 126 | the I/O vector array <parameter>iov</parameter> are used as the |
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127 | contents of the array. The total size of |
128 | <parameter>iov</parameter> payload (the sum of | |
129 | <structfield>iov_len</structfield> fields) must be a multiple of | |
130 | the size of the type <parameter>type</parameter>. The | |
131 | <parameter>iov</parameter> argument must point to | |
b938cb90 | 132 | <parameter>n</parameter> I/O vector structures. Each structure may |
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133 | have the <structname>iov_base</structname> field set, in which |
134 | case the memory pointed to will be copied into the message, or | |
135 | unset (set to zero), in which case a block of zeros of length | |
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136 | <structname>iov_len</structname> bytes will be inserted. The |
137 | memory pointed at by <parameter>iov</parameter> may be changed | |
138 | after this call.</para> | |
139 | ||
e8216945 LP |
140 | <para>The <function>sd_bus_message_append_array_space()</function> |
141 | function appends space for an array of a trivial type to message | |
142 | <parameter>m</parameter>. It behaves the same as | |
143 | <function>sd_bus_message_append_array()</function>, but instead of | |
144 | copying items to the message, it returns a pointer to the | |
145 | destination area to the caller in pointer | |
146 | <parameter>p</parameter>. The caller should subsequently write the | |
a8eaaee7 | 147 | array contents to this memory. Modifications to the memory |
e8216945 | 148 | pointed to should only occur until the next operation on the bus |
b938cb90 | 149 | message is invoked. Most importantly, the memory should not be |
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150 | altered anymore when another field has been added to the message |
151 | or the message has been sealed.</para> | |
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152 | </refsect1> |
153 | ||
154 | <refsect1> | |
155 | <title>Return Value</title> | |
156 | ||
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157 | <para>On success, these calls return 0 or a positive integer. On failure, they return a negative |
158 | errno-style error code.</para> | |
effbc8e4 | 159 | |
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160 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="errors" /> |
161 | </refsect1> | |
effbc8e4 | 162 | |
7d6b2723 | 163 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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164 | |
165 | <refsect1> | |
166 | <title>See Also</title> | |
167 | ||
168 | <para> | |
169 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
170 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
171 | <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
172 | <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
e8216945 | 173 | <citerefentry project='man-pages'><refentrytitle>memfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>, |
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174 | <ulink url="http://dbus.freedesktop.org/doc/dbus-specification.html">The D-Bus specification</ulink> |
175 | </para> | |
176 | </refsect1> | |
177 | ||
178 | </refentry> |