mirror of
https://github.com/systemd/systemd.git
synced 2024-12-14 12:43:36 +08:00
b1de39dec8
Logically, this is better, because we're describing a subset of possible return values. Visually this also looks quite good because groff renders refsect2 much less prominently. Also rewrap things, add <constant> in various places, fix some typos.
179 lines
8.4 KiB
XML
179 lines
8.4 KiB
XML
<?xml version='1.0'?>
|
|
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
|
<!-- SPDX-License-Identifier: LGPL-2.1+ -->
|
|
|
|
<refentry id="sd_bus_message_append_array"
|
|
xmlns:xi="http://www.w3.org/2001/XInclude">
|
|
|
|
<refentryinfo>
|
|
<title>sd_bus_message_append_array</title>
|
|
<productname>systemd</productname>
|
|
</refentryinfo>
|
|
|
|
<refmeta>
|
|
<refentrytitle>sd_bus_message_append_array</refentrytitle>
|
|
<manvolnum>3</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>sd_bus_message_append_array</refname>
|
|
<refname>sd_bus_message_append_array_memfd</refname>
|
|
<refname>sd_bus_message_append_array_iovec</refname>
|
|
<refname>sd_bus_message_append_array_space</refname>
|
|
|
|
<refpurpose>Append an array of fields to a D-Bus
|
|
message</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<funcsynopsis>
|
|
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
|
|
|
|
<funcprototype>
|
|
<funcdef>int sd_bus_message_append_array</funcdef>
|
|
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
|
|
<paramdef>char <parameter>type</parameter></paramdef>
|
|
<paramdef>char void *<parameter>ptr</parameter></paramdef>
|
|
<paramdef>size_t <parameter>size</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int sd_bus_message_append_array_memfd</funcdef>
|
|
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
|
|
<paramdef>char <parameter>type</parameter></paramdef>
|
|
<paramdef>int <parameter>memfd</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>offset</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>size</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int sd_bus_message_append_array_iovec</funcdef>
|
|
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
|
|
<paramdef>char <parameter>type</parameter></paramdef>
|
|
<paramdef>const struct iovec *<parameter>iov</parameter></paramdef>
|
|
<paramdef>unsigned <parameter>n</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int sd_bus_message_append_array_space</funcdef>
|
|
<paramdef>char <parameter>type</parameter></paramdef>
|
|
<paramdef>size_t <parameter>size</parameter></paramdef>
|
|
<paramdef>void **<parameter>ptr</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para>The <function>sd_bus_message_append_array()</function>
|
|
function appends an array to a D-Bus message
|
|
<parameter>m</parameter>. A container will be opened, the array
|
|
contents appended, and the container closed. The parameter
|
|
<parameter>type</parameter> determines how the pointer
|
|
<parameter>p</parameter> is interpreted.
|
|
<parameter>type</parameter> must be one of the "trivial" types
|
|
<literal>y</literal>, <literal>n</literal>, <literal>q</literal>,
|
|
<literal>i</literal>, <literal>u</literal>, <literal>x</literal>,
|
|
<literal>t</literal>, <literal>d</literal> (but not
|
|
<literal>b</literal>), as defined by the <ulink
|
|
url="http://dbus.freedesktop.org/doc/dbus-specification.html#basic-types">Basic
|
|
Types</ulink> section of the D-Bus specification, and listed in
|
|
<citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
|
Pointer <parameter>p</parameter> must point to an array of size
|
|
<parameter>size</parameter> bytes containing items of the
|
|
respective type. Size <parameter>size</parameter> must be a
|
|
multiple of the size of the type <parameter>type</parameter>. As a
|
|
special case, <parameter>p</parameter> may be
|
|
<constant>NULL</constant>, if <parameter>size</parameter> is 0.
|
|
The memory pointed to by <parameter>p</parameter> is copied into
|
|
the memory area containing the message and stays in possession of
|
|
the caller. The caller may hence freely change the data after this
|
|
call without affecting the message the array was appended
|
|
to.</para>
|
|
|
|
<para>The <function>sd_bus_message_append_array_memfd()</function>
|
|
function appends an array of a trivial type to message
|
|
<parameter>m</parameter>, similar to
|
|
<function>sd_bus_message_append_array()</function>. The contents
|
|
of the memory file descriptor <parameter>memfd</parameter>
|
|
starting at the specified offset and of the specified size is
|
|
used as the contents of the array. The offset and size must be a
|
|
multiple of the size of the type
|
|
<parameter>type</parameter>. However, as a special exception, if
|
|
the offset is specified as zero and the size specified as
|
|
UINT64_MAX the full memory file descriptor contents is used. The
|
|
memory file descriptor is sealed by this call if it has not been
|
|
sealed yet, and cannot be modified after this call. See
|
|
<citerefentry
|
|
project='man-pages'><refentrytitle>memfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>
|
|
for details about memory file descriptors. Appending arrays with
|
|
memory file descriptors enables efficient zero-copy data transfer,
|
|
as the memory file descriptor may be passed as-is to the
|
|
destination, without copying the memory in it to the destination
|
|
process. Not all protocol transports support passing memory file
|
|
descriptors between participants, in which case this call will
|
|
automatically fall back to copying. Also, as memory file
|
|
descriptor passing is inefficient for smaller amounts of data,
|
|
copying might still be enforced even where memory file descriptor
|
|
passing is supported.</para>
|
|
|
|
<para>The <function>sd_bus_message_append_array_iovec()</function>
|
|
function appends an array of a trivial type to the message
|
|
<parameter>m</parameter>, similar to
|
|
<function>sd_bus_message_append_array()</function>. Contents of
|
|
the I/O vector array <parameter>iov</parameter> are used as the
|
|
contents of the array. The total size of
|
|
<parameter>iov</parameter> payload (the sum of
|
|
<structfield>iov_len</structfield> fields) must be a multiple of
|
|
the size of the type <parameter>type</parameter>. The
|
|
<parameter>iov</parameter> argument must point to
|
|
<parameter>n</parameter> I/O vector structures. Each structure may
|
|
have the <structname>iov_base</structname> field set, in which
|
|
case the memory pointed to will be copied into the message, or
|
|
unset (set to zero), in which case a block of zeros of length
|
|
<structname>iov_len</structname> bytes will be inserted. The
|
|
memory pointed at by <parameter>iov</parameter> may be changed
|
|
after this call.</para>
|
|
|
|
<para>The <function>sd_bus_message_append_array_space()</function>
|
|
function appends space for an array of a trivial type to message
|
|
<parameter>m</parameter>. It behaves the same as
|
|
<function>sd_bus_message_append_array()</function>, but instead of
|
|
copying items to the message, it returns a pointer to the
|
|
destination area to the caller in pointer
|
|
<parameter>p</parameter>. The caller should subsequently write the
|
|
array contents to this memory. Modifications to the memory
|
|
pointed to should only occur until the next operation on the bus
|
|
message is invoked. Most importantly, the memory should not be
|
|
altered anymore when another field has been added to the message
|
|
or the message has been sealed.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Return Value</title>
|
|
|
|
<para>On success, these calls return 0 or a positive integer. On failure, they return a negative
|
|
errno-style error code.</para>
|
|
|
|
<xi:include href="sd_bus_message_append_basic.xml" xpointer="errors" />
|
|
</refsect1>
|
|
|
|
<xi:include href="libsystemd-pkgconfig.xml" />
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
|
|
<para>
|
|
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry project='man-pages'><refentrytitle>memfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
|
|
<ulink url="http://dbus.freedesktop.org/doc/dbus-specification.html">The D-Bus specification</ulink>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|