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122 lines
4.8 KiB
XML
122 lines
4.8 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="sd_bus_message_read_array">
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<refentryinfo>
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<title>sd_bus_message_read_array</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_bus_message_read_array</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_bus_message_read_array</refname>
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<refpurpose>Access an array of elements in a message</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_bus_message_read_array</function></funcdef>
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<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
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<paramdef>char <parameter>type</parameter></paramdef>
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<paramdef>const void **<parameter>ptr</parameter></paramdef>
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<paramdef>size_t *<parameter>size</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_bus_message_read_array()</function> provides access to an array elements in the
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bus message <parameter>m</parameter>. The "read pointer" in the message must be right before an array of type
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<parameter>type</parameter>. As a special case, <parameter>type</parameter> may be
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<constant>NUL</constant>, in which case any trivial type is acceptable. A pointer to the array data is returned
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in the parameter <parameter>ptr</parameter> and the size of array data (in bytes) is returned in the
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parameter <parameter>size</parameter>. If the returned <parameter>size</parameter> parameter is 0, a
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valid non-null pointer will be returned as <parameter>ptr</parameter>, but it may not be
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dereferenced. The data is aligned as appropriate for the data type. The data is part of the message — it
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may not be modified and is valid only as long as the message is referenced. After this function returns,
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the "read pointer" points at the next element after the array.</para>
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<para>Note that this function only supports arrays of trivial types, i.e. arrays of booleans, the various
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integer types, as well as floating point numbers. In particular it may not be used for arrays of strings,
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structures or similar.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>
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On success and when an array was read, <function>sd_bus_message_read_array()</function> returns an
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integer greater than zero. If invoked while inside a container element (such as an array, e.g. when
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operating on an array of arrays) and the final element of the outer container has been read already and
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the read pointer is thus behind the last element of the outer container this call returns 0 (and the
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returned pointer will be <constant>NULL</constant> and the size will be 0). On failure, it returns a
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negative errno-style error code.
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</para>
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<refsect2>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>Specified type is invalid or not a trivial type (see above), or the message
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parameter or one of the output parameters are <constant>NULL</constant>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EOPNOTSUPP</constant></term>
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<listitem><para>The byte order in the message is different than native byte
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order.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EPERM</constant></term>
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<listitem><para>The message is not sealed.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EBADMSG</constant></term>
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<listitem><para>The message cannot be parsed.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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</refsect1>
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<refsect1>
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<title>History</title>
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<para><function>sd_bus_message_read_array()</function> was added in version 240.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_read</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_read_strv</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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