man/sd_bus_get_n_queued_read.xml

   1 <?xml version='1.0'?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="sd_bus_get_n_queued_read">
   7
   8   <refentryinfo>
   9     <title>sd_bus_get_fd</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>sd_bus_get_n_queued_read</refentrytitle>
  15     <manvolnum>3</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>sd_bus_get_n_queued_read</refname>
  20     <refname>sd_bus_get_n_queued_write</refname>
  21
  22     <refpurpose>Get the number of pending bus messages in the read and write queues of a bus connection object</refpurpose>
  23   </refnamediv>
  24
  25   <refsynopsisdiv>
  26     <funcsynopsis>
  27       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  28
  29       <funcprototype>
  30         <funcdef>int <function>sd_bus_get_n_queued_read</function></funcdef>
  31         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  32         <paramdef>uint64_t *<parameter>ret</parameter></paramdef>
  33       </funcprototype>
  34
  35       <funcprototype>
  36         <funcdef>int <function>sd_bus_get_n_queued_write</function></funcdef>
  37         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  38         <paramdef>uint64_t *<parameter>ret</parameter></paramdef>
  39       </funcprototype>
  40     </funcsynopsis>
  41   </refsynopsisdiv>
  42
  43   <refsect1>
  44     <title>Description</title>
  45
  46     <para>
  47       <function>sd_bus_get_n_queued_read()</function> may be used to query the number of bus messages in the read queue
  48       of a bus connection object. The read queue contains all messages read from the transport medium (e.g. network
  49       socket) but not yet processed locally. The function expects two arguments: the bus object to query, and a pointer
  50       to a 64bit counter variable to write the current queue size to. Use <function>sd_bus_process()</function> in
  51       order to process queued messages, i.e. to reduce the size of the read queue (as well as, in fact, the write
  52       queue, see below).
  53     </para>
  54
  55     <para>
  56       Similarly, <function>sd_bus_get_n_queued_write()</function> may be used to query the number of currently pending
  57       bus messages in the write queue of a bus connection object. The write queue contains all messages enqueued into
  58       the connection with a call such as <function>sd_bus_send()</function> but not yet written to the transport
  59       medium. The expected arguments are similar to <function>sd_bus_get_n_queued_read()</function>. Here too, use
  60       <function>sd_bus_process()</function> to reduce the size of the write queue. Alternatively, use
  61       <function>sd_bus_flush()</function> to synchronously write out any pending bus messages until the write queue is
  62       empty.
  63     </para>
  64   </refsect1>
  65
  66   <refsect1>
  67     <title>Return Value</title>
  68
  69     <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
  70     error code.</para>
  71
  72     <refsect2>
  73       <title>Errors</title>
  74
  75       <para>Returned errors may indicate the following problems:</para>
  76
  77       <variablelist>
  78         <varlistentry>
  79           <term><constant>-ECHILD</constant></term>
  80
  81           <listitem><para>The bus connection was created in a different process.</para></listitem>
  82         </varlistentry>
  83
  84       </variablelist>
  85     </refsect2>
  86   </refsect1>
  87
  88   <refsect1>
  89     <title>See Also</title>
  90
  91     <para>
  92       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  93       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  94       <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  95       <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  96       <citerefentry><refentrytitle>sd_bus_flush</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  97     </para>
  98   </refsect1>
  99
 100 </refentry>