man/sd_bus_message_append_basic.xml

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  23
  24 <refentry id="sd_bus_message_append_basic">
  25
  26   <refentryinfo>
  27     <title>sd_bus_message_append_basic</title>
  28     <productname>systemd</productname>
  29
  30     <authorgroup>
  31       <author>
  32         <contrib>A monkey with a typewriter</contrib>
  33         <firstname>Zbigniew</firstname>
  34         <surname>Jędrzejewski-Szmek</surname>
  35         <email>zbyszek@in.waw.pl</email>
  36       </author>
  37     </authorgroup>
  38   </refentryinfo>
  39
  40   <refmeta>
  41     <refentrytitle>sd_bus_message_append_basic</refentrytitle>
  42     <manvolnum>3</manvolnum>
  43   </refmeta>
  44
  45   <refnamediv>
  46     <refname>sd_bus_message_append_basic</refname>
  47
  48     <refpurpose>Attach a single field to a message</refpurpose>
  49   </refnamediv>
  50
  51   <refsynopsisdiv>
  52     <funcsynopsis>
  53       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  54
  55       <funcprototype>
  56         <funcdef>int sd_bus_message_append_basic</funcdef>
  57         <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
  58         <paramdef>char <parameter>type</parameter></paramdef>
  59         <paramdef>const void *<parameter>p</parameter></paramdef>
  60       </funcprototype>
  61     </funcsynopsis>
  62   </refsynopsisdiv>
  63
  64   <refsect1>
  65     <title>Description</title>
  66
  67     <para><function>sd_bus_message_append_basic()</function> appends a
  68     single field to the message <parameter>m</parameter>. The
  69     parameter <parameter>type</parameter> determines how the pointer
  70     <parameter>p</parameter> is interpreted.
  71     <parameter>type</parameter> must be one of the basic types as
  72     defined by the <ulink
  73     url="http://dbus.freedesktop.org/doc/dbus-specification.html#basic-types">Basic
  74     Types</ulink> section of the D-Bus specification, and listed in
  75     the table below.
  76     </para>
  77
  78     <table id='format-specifiers'>
  79       <title>Item type specifiers</title>
  80
  81       <tgroup cols='5'>
  82         <colspec colname='specifier' />
  83         <colspec colname='constant' />
  84         <colspec colname='description' />
  85         <colspec colname='size' />
  86         <colspec colname='ctype' />
  87         <thead>
  88           <row>
  89             <entry>Specifier</entry>
  90             <entry>Constant</entry>
  91             <entry>Description</entry>
  92             <entry>Size</entry>
  93             <entry>Expected C Type</entry>
  94           </row>
  95         </thead>
  96         <tbody>
  97           <row>
  98             <entry><literal>y</literal></entry>
  99             <entry><constant>SD_BUS_TYPE_BYTE</constant></entry>
 100             <entry>unsigned integer</entry>
 101             <entry>1 byte</entry>
 102             <entry>uint8_t</entry>
 103           </row>
 104
 105           <row>
 106             <entry><literal>b</literal></entry>
 107             <entry><constant>SD_BUS_TYPE_BOOLEAN</constant></entry>
 108             <entry>boolean</entry>
 109             <entry>4 bytes</entry>
 110             <entry>int</entry>
 111           </row>
 112
 113           <row>
 114             <entry><literal>n</literal></entry>
 115             <entry><constant>SD_BUS_TYPE_INT16</constant></entry>
 116             <entry>signed integer</entry>
 117             <entry>2 bytes</entry>
 118             <entry>int16_t</entry>
 119           </row>
 120
 121           <row>
 122             <entry><literal>q</literal></entry>
 123             <entry><constant>SD_BUS_TYPE_UINT16</constant></entry>
 124             <entry>unsigned integer</entry>
 125             <entry>2 bytes</entry>
 126             <entry>uint16_t</entry>
 127           </row>
 128
 129           <row>
 130             <entry><literal>i</literal></entry>
 131             <entry><constant>SD_BUS_TYPE_INT32</constant></entry>
 132             <entry>signed integer</entry>
 133             <entry>4 bytes</entry>
 134             <entry>int32_t</entry>
 135           </row>
 136
 137           <row>
 138             <entry><literal>u</literal></entry>
 139             <entry><constant>SD_BUS_TYPE_UINT32</constant></entry>
 140             <entry>unsigned integer</entry>
 141             <entry>4 bytes</entry>
 142             <entry>uint32_t</entry>
 143           </row>
 144
 145           <row>
 146             <entry><literal>x</literal></entry>
 147             <entry><constant>SD_BUS_TYPE_INT64</constant></entry>
 148             <entry>signed integer</entry>
 149             <entry>8 bytes</entry>
 150             <entry>int64_t</entry>
 151           </row>
 152
 153           <row>
 154             <entry><literal>t</literal></entry>
 155             <entry><constant>SD_BUS_TYPE_UINT64</constant></entry>
 156             <entry>unsigned integer</entry>
 157             <entry>8 bytes</entry>
 158             <entry>uint64_t</entry>
 159           </row>
 160
 161           <row>
 162             <entry><literal>d</literal></entry>
 163             <entry><constant>SD_BUS_TYPE_DOUBLE</constant></entry>
 164             <entry>floating-point</entry>
 165             <entry>8 bytes</entry>
 166             <entry>double</entry>
 167           </row>
 168
 169           <row>
 170             <entry><literal>s</literal></entry>
 171             <entry><constant>SD_BUS_TYPE_STRING</constant></entry>
 172             <entry>Unicode string</entry>
 173             <entry>variable</entry>
 174             <entry>char[]</entry>
 175           </row>
 176
 177           <row>
 178             <entry><literal>o</literal></entry>
 179             <entry><constant>SD_BUS_TYPE_OBJECT_PATH</constant></entry>
 180             <entry>object path</entry>
 181             <entry>variable</entry>
 182             <entry>char[]</entry>
 183           </row>
 184
 185           <row>
 186             <entry><literal>g</literal></entry>
 187             <entry><constant>SD_BUS_TYPE_SIGNATURE</constant></entry>
 188             <entry>signature</entry>
 189             <entry>variable</entry>
 190             <entry>char[]</entry>
 191           </row>
 192
 193           <row>
 194             <entry><literal>h</literal></entry>
 195             <entry><constant>SD_BUS_TYPE_UNIX_FD</constant></entry>
 196             <entry>UNIX file descriptor</entry>
 197             <entry>4 bytes</entry>
 198             <entry>int</entry>
 199           </row>
 200        </tbody>
 201       </tgroup>
 202     </table>
 203
 204     <para>The value of the parameter is copied into a memory area held
 205     by the message object, stays in the possession of the caller and
 206     may hence be freely changed after this call without affecting the
 207     bus message it has been added to. If <parameter>type</parameter>
 208     is <literal>h</literal> (UNIX file descriptor), the descriptor is
 209     duplicated by this call and the passed descriptor stays in
 210     possession of the caller.</para>
 211
 212     <para>For types <literal>s</literal>, <literal>o</literal>, and
 213     <literal>g</literal>, the parameter <parameter>p</parameter> is
 214     interpreted as a pointer to a <constant>NUL</constant>-terminated
 215     character sequence. As a special case, a <constant>NULL</constant>
 216     pointer is interpreted as an empty string. The string should be
 217     valid Unicode string encoded as UTF-8. In case of the two latter
 218     types, the additional requirements for a D-Bus object path or
 219     type signature should be satisfied. Those requirements should be
 220     verified by the recipient of the message.
 221     </para>
 222   </refsect1>
 223
 224   <refsect1>
 225     <title>Return Value</title>
 226
 227     <para>On success, this call returns 0 or a positive integer. On
 228     failure, it returns a negative errno-style error code.</para>
 229   </refsect1>
 230
 231   <refsect1 id='errors'>
 232     <title>Errors</title>
 233
 234     <para>Returned errors may indicate the following problems:</para>
 235
 236     <variablelist>
 237
 238       <varlistentry>
 239         <term><constant>-EINVAL</constant></term>
 240
 241         <listitem><para>Specified parameter is invalid.
 242         </para></listitem>
 243       </varlistentry>
 244
 245       <varlistentry>
 246         <term><constant>-EPERM</constant></term>
 247
 248         <listitem><para>Message has been sealed.
 249         </para></listitem>
 250       </varlistentry>
 251
 252       <varlistentry>
 253         <term><constant>-ESTALE</constant></term>
 254
 255         <listitem><para>Message is in invalid state.
 256         </para></listitem>
 257       </varlistentry>
 258
 259       <varlistentry>
 260         <term><constant>-ENXIO</constant></term>
 261
 262         <listitem><para>Message cannot be appended to.
 263         </para></listitem>
 264       </varlistentry>
 265
 266       <varlistentry>
 267         <term><constant>-ENOMEM</constant></term>
 268
 269         <listitem><para>Memory allocation failed.</para></listitem>
 270       </varlistentry>
 271     </variablelist>
 272   </refsect1>
 273
 274   <refsect1>
 275     <title>Notes</title>
 276
 277     <para>The <function>sd_bus_append_basic()</function> function
 278     described here is available as a shared library, which can be
 279     compiled and linked to with the
 280     <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 281     file.</para>
 282   </refsect1>
 283
 284   <refsect1>
 285     <title>See Also</title>
 286
 287     <para>
 288       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 289       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 290       <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 291       <ulink url="http://dbus.freedesktop.org/doc/dbus-specification.html">The D-Bus specification</ulink>
 292     </para>
 293   </refsect1>
 294
 295 </refentry>