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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_array" |
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10 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
11 | ||
12 | <refentryinfo> | |
13 | <title>sd_bus_message_append_array</title> | |
14 | <productname>systemd</productname> | |
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15 | </refentryinfo> |
16 | ||
17 | <refmeta> | |
18 | <refentrytitle>sd_bus_message_append_array</refentrytitle> | |
19 | <manvolnum>3</manvolnum> | |
20 | </refmeta> | |
21 | ||
22 | <refnamediv> | |
23 | <refname>sd_bus_message_append_array</refname> | |
24 | <refname>sd_bus_message_append_array_memfd</refname> | |
25 | <refname>sd_bus_message_append_array_iovec</refname> | |
26 | <refname>sd_bus_message_append_array_space</refname> | |
27 | ||
dd2b607b | 28 | <refpurpose>Append an array of fields to a D-Bus |
e8216945 | 29 | message</refpurpose> |
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30 | </refnamediv> |
31 | ||
32 | <refsynopsisdiv> | |
33 | <funcsynopsis> | |
34 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
35 | ||
36 | <funcprototype> | |
37 | <funcdef>int sd_bus_message_append_array</funcdef> | |
38 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
39 | <paramdef>char <parameter>type</parameter></paramdef> | |
40 | <paramdef>char void *<parameter>ptr</parameter></paramdef> | |
41 | <paramdef>size_t <parameter>size</parameter></paramdef> | |
42 | </funcprototype> | |
43 | ||
44 | <funcprototype> | |
45 | <funcdef>int sd_bus_message_append_array_memfd</funcdef> | |
46 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
47 | <paramdef>char <parameter>type</parameter></paramdef> | |
fac9c0d5 | 48 | <paramdef>int <parameter>memfd</parameter></paramdef> |
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49 | <paramdef>uint64_t <parameter>offset</parameter></paramdef> |
50 | <paramdef>uint64_t <parameter>size</parameter></paramdef> | |
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51 | </funcprototype> |
52 | ||
53 | <funcprototype> | |
54 | <funcdef>int sd_bus_message_append_array_iovec</funcdef> | |
55 | <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> | |
56 | <paramdef>char <parameter>type</parameter></paramdef> | |
57 | <paramdef>const struct iovec *<parameter>iov</parameter></paramdef> | |
58 | <paramdef>unsigned <parameter>n</parameter></paramdef> | |
59 | </funcprototype> | |
60 | ||
61 | <funcprototype> | |
62 | <funcdef>int sd_bus_message_append_array_space</funcdef> | |
63 | <paramdef>char <parameter>type</parameter></paramdef> | |
64 | <paramdef>size_t <parameter>size</parameter></paramdef> | |
e8216945 | 65 | <paramdef>void **<parameter>ptr</parameter></paramdef> |
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66 | </funcprototype> |
67 | </funcsynopsis> | |
68 | </refsynopsisdiv> | |
69 | ||
70 | <refsect1> | |
71 | <title>Description</title> | |
72 | ||
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73 | <para>The <function>sd_bus_message_append_array()</function> |
74 | function appends an array to a D-Bus message | |
75 | <parameter>m</parameter>. A container will be opened, the array | |
76 | contents appended, and the container closed. The parameter | |
77 | <parameter>type</parameter> determines how the pointer | |
78 | <parameter>p</parameter> is interpreted. | |
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79 | <parameter>type</parameter> must be one of the "trivial" types |
80 | <literal>y</literal>, <literal>n</literal>, <literal>q</literal>, | |
81 | <literal>i</literal>, <literal>u</literal>, <literal>x</literal>, | |
82 | <literal>t</literal>, <literal>d</literal> (but not | |
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83 | <literal>b</literal>), as defined by the <ulink |
84 | url="http://dbus.freedesktop.org/doc/dbus-specification.html#basic-types">Basic | |
85 | Types</ulink> section of the D-Bus specification, and listed in | |
effbc8e4 | 86 | <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>. |
cbfaff65 | 87 | Pointer <parameter>p</parameter> must point to an array of size |
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88 | <parameter>size</parameter> bytes containing items of the |
89 | respective type. Size <parameter>size</parameter> must be a | |
90 | multiple of the size of the type <parameter>type</parameter>. As a | |
91 | special case, <parameter>p</parameter> may be | |
92 | <constant>NULL</constant>, if <parameter>size</parameter> is 0. | |
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93 | The memory pointed to by <parameter>p</parameter> is copied into |
94 | the memory area containing the message and stays in possession of | |
95 | the caller. The caller may hence freely change the data after this | |
96 | call without affecting the message the array was appended | |
97 | to.</para> | |
98 | ||
99 | <para>The <function>sd_bus_message_append_array_memfd()</function> | |
100 | function appends an array of a trivial type to message | |
101 | <parameter>m</parameter>, similar to | |
102 | <function>sd_bus_message_append_array()</function>. The contents | |
103 | of the memory file descriptor <parameter>memfd</parameter> | |
dd2b607b | 104 | starting at the specified offset and of the specified size is |
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105 | used as the contents of the array. The offset and size must be a |
106 | multiple of the size of the type | |
107 | <parameter>type</parameter>. However, as a special exception, if | |
108 | the offset is specified as zero and the size specified as | |
109 | UINT64_MAX the full memory file descriptor contents is used. The | |
7ca41557 | 110 | memory file descriptor is sealed by this call if it has not been |
a8eaaee7 | 111 | sealed yet, and cannot be modified after this call. See |
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112 | <citerefentry |
113 | project='man-pages'><refentrytitle>memfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
114 | for details about memory file descriptors. Appending arrays with | |
115 | memory file descriptors enables efficient zero-copy data transfer, | |
116 | as the memory file descriptor may be passed as-is to the | |
117 | destination, without copying the memory in it to the destination | |
118 | process. Not all protocol transports support passing memory file | |
119 | descriptors between participants, in which case this call will | |
120 | automatically fall back to copying. Also, as memory file | |
b938cb90 | 121 | descriptor passing is inefficient for smaller amounts of data, |
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122 | copying might still be enforced even where memory file descriptor |
123 | passing is supported.</para> | |
124 | ||
125 | <para>The <function>sd_bus_message_append_array_iovec()</function> | |
126 | function appends an array of a trivial type to the message | |
127 | <parameter>m</parameter>, similar to | |
128 | <function>sd_bus_message_append_array()</function>. Contents of | |
b938cb90 | 129 | the I/O vector array <parameter>iov</parameter> are used as the |
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130 | contents of the array. The total size of |
131 | <parameter>iov</parameter> payload (the sum of | |
132 | <structfield>iov_len</structfield> fields) must be a multiple of | |
133 | the size of the type <parameter>type</parameter>. The | |
134 | <parameter>iov</parameter> argument must point to | |
b938cb90 | 135 | <parameter>n</parameter> I/O vector structures. Each structure may |
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136 | have the <structname>iov_base</structname> field set, in which |
137 | case the memory pointed to will be copied into the message, or | |
138 | unset (set to zero), in which case a block of zeros of length | |
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139 | <structname>iov_len</structname> bytes will be inserted. The |
140 | memory pointed at by <parameter>iov</parameter> may be changed | |
141 | after this call.</para> | |
142 | ||
e8216945 LP |
143 | <para>The <function>sd_bus_message_append_array_space()</function> |
144 | function appends space for an array of a trivial type to message | |
145 | <parameter>m</parameter>. It behaves the same as | |
146 | <function>sd_bus_message_append_array()</function>, but instead of | |
147 | copying items to the message, it returns a pointer to the | |
148 | destination area to the caller in pointer | |
149 | <parameter>p</parameter>. The caller should subsequently write the | |
a8eaaee7 | 150 | array contents to this memory. Modifications to the memory |
e8216945 | 151 | pointed to should only occur until the next operation on the bus |
b938cb90 | 152 | message is invoked. Most importantly, the memory should not be |
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153 | altered anymore when another field has been added to the message |
154 | or the message has been sealed.</para> | |
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155 | </refsect1> |
156 | ||
157 | <refsect1> | |
158 | <title>Return Value</title> | |
159 | ||
b8bde116 | 160 | <para>On success, these calls return 0 or a positive integer. On |
dd2b607b | 161 | failure, they return a negative errno-style error code.</para> |
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162 | </refsect1> |
163 | ||
164 | <xi:include href="sd_bus_message_append_basic.xml" xpointer="errors" /> | |
165 | ||
7d6b2723 | 166 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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167 | |
168 | <refsect1> | |
169 | <title>See Also</title> | |
170 | ||
171 | <para> | |
172 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
173 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
174 | <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
175 | <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
e8216945 | 176 | <citerefentry project='man-pages'><refentrytitle>memfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>, |
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177 | <ulink url="http://dbus.freedesktop.org/doc/dbus-specification.html">The D-Bus specification</ulink> |
178 | </para> | |
179 | </refsect1> | |
180 | ||
181 | </refentry> |