mirror of
https://github.com/systemd/systemd.git
synced 2024-10-30 23:21:22 +03:00
238 lines
8.4 KiB
XML
238 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-or-later
|
|
|
|
Copyright © 2016 Julian Orth
|
|
-->
|
|
|
|
<refentry id="sd_bus_message_read_basic">
|
|
|
|
<refentryinfo>
|
|
<title>sd_bus_message_read_basic</title>
|
|
<productname>systemd</productname>
|
|
</refentryinfo>
|
|
|
|
<refmeta>
|
|
<refentrytitle>sd_bus_message_read_basic</refentrytitle>
|
|
<manvolnum>3</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>sd_bus_message_read_basic</refname>
|
|
|
|
<refpurpose>Read a basic type from a message</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<funcsynopsis>
|
|
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_bus_message_read_basic</function></funcdef>
|
|
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
|
|
<paramdef>char <parameter>type</parameter></paramdef>
|
|
<paramdef>void *<parameter>p</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para>
|
|
<function>sd_bus_message_read_basic()</function> reads a basic type from a
|
|
message and advances the read position in the message. The set of basic
|
|
types and their ascii codes passed in <parameter>type</parameter> are
|
|
described in the <ulink
|
|
url="https://dbus.freedesktop.org/doc/dbus-specification.html">D-Bus
|
|
Specification</ulink>.
|
|
</para>
|
|
|
|
<para>
|
|
If <parameter>p</parameter> is not <constant>NULL</constant>, it should contain a pointer to an
|
|
appropriate object. For example, if <parameter>type</parameter> is <constant>'y'</constant>, the object
|
|
passed in <parameter>p</parameter> should have type <type>uint8_t *</type>. If
|
|
<parameter>type</parameter> is <constant>'s'</constant>, the object passed in <parameter>p</parameter>
|
|
should have type <type>const char **</type>. Note that, if the basic type is a pointer (e.g.,
|
|
<type>const char *</type> in the case of a string), the pointer is only borrowed and the contents must
|
|
be copied if they are to be used after the end of the messages lifetime. Similarly, during the lifetime
|
|
of such a pointer, the message must not be modified. If <parameter>type</parameter> is
|
|
<constant>'h'</constant> (UNIX file descriptor), the descriptor is not duplicated by this call and the
|
|
returned descriptor remains in possession of the message object, and needs to be duplicated by the caller
|
|
in order to keep an open reference to it after the message object is freed (for example by calling
|
|
<literal>fcntl(fd, FD_DUPFD_CLOEXEC, 3)</literal>). See the table below for a complete list of
|
|
allowed types.
|
|
</para>
|
|
|
|
<table id='format-specifiers'>
|
|
<title>Item type specifiers</title>
|
|
|
|
<tgroup cols='4'>
|
|
<colspec colname='specifier' />
|
|
<colspec colname='constant' />
|
|
<colspec colname='description' />
|
|
<colspec colname='ctype' />
|
|
<thead>
|
|
<row>
|
|
<entry>Specifier</entry>
|
|
<entry>Constant</entry>
|
|
<entry>Description</entry>
|
|
<entry>Expected C Type</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>y</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_BYTE</constant></entry>
|
|
<entry>8bit unsigned integer</entry>
|
|
<entry><type>uint8_t *</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>b</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_BOOLEAN</constant></entry>
|
|
<entry>boolean</entry>
|
|
<entry><type>int *</type> (NB: not <type>bool *</type>)</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>n</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_INT16</constant></entry>
|
|
<entry>16bit signed integer</entry>
|
|
<entry><type>int16_t *</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>q</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_UINT16</constant></entry>
|
|
<entry>16bit unsigned integer</entry>
|
|
<entry><type>uint16_t *</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>i</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_INT32</constant></entry>
|
|
<entry>32bit signed integer</entry>
|
|
<entry><type>int32_t *</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>u</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_UINT32</constant></entry>
|
|
<entry>32bit unsigned integer</entry>
|
|
<entry><type>uint32_t *</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>x</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_INT64</constant></entry>
|
|
<entry>64bit signed integer</entry>
|
|
<entry><type>int64_t *</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>t</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_UINT64</constant></entry>
|
|
<entry>64bit unsigned integer</entry>
|
|
<entry><type>uint64_t *</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>d</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_DOUBLE</constant></entry>
|
|
<entry>IEEE 754 double precision floating-point</entry>
|
|
<entry><type>double *</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>s</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_STRING</constant></entry>
|
|
<entry>UTF-8 string</entry>
|
|
<entry><type>const char **</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>o</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_OBJECT_PATH</constant></entry>
|
|
<entry>D-Bus object path string</entry>
|
|
<entry><type>const char **</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>g</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_SIGNATURE</constant></entry>
|
|
<entry>D-Bus signature string</entry>
|
|
<entry><type>const char **</type></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>h</literal></entry>
|
|
<entry><constant>SD_BUS_TYPE_UNIX_FD</constant></entry>
|
|
<entry>UNIX file descriptor</entry>
|
|
<entry><type>int *</type></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
If there is no object of the specified type at the current position in the
|
|
message, an error is returned.
|
|
</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Return Value</title>
|
|
|
|
<para>
|
|
On success, <function>sd_bus_message_read_basic()</function> returns a positive integer.
|
|
If the end of the currently opened array has been reached, it returns 0.
|
|
On failure, it returns a negative errno-style error code.
|
|
</para>
|
|
|
|
<refsect2 id='errors'>
|
|
<title>Errors</title>
|
|
|
|
<para>Returned errors may indicate the following problems:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><constant>-EINVAL</constant></term>
|
|
|
|
<listitem><para>Specified type string is invalid or the message parameter is
|
|
<constant>NULL</constant>.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-ENXIO</constant></term>
|
|
|
|
<listitem><para>The message does not contain the specified type at current position.
|
|
</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-EBADMSG</constant></term>
|
|
|
|
<listitem><para>The message cannot be parsed.</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect2>
|
|
</refsect1>
|
|
|
|
<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_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_bus_message_skip</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_bus_message_read</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|