man/sd_bus_get_n_queued_read.xml

   1 <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2018 Lennart Poettering
  11 -->
  12
  13 <refentry id="sd_bus_get_n_queued_read">
  14
  15   <refentryinfo>
  16     <title>sd_bus_get_fd</title>
  17     <productname>systemd</productname>
  18
  19     <authorgroup>
  20       <author>
  21         <contrib>Developer</contrib>
  22         <firstname>Lennart</firstname>
  23         <surname>Poettering</surname>
  24         <email>lennart@poettering.net</email>
  25       </author>
  26     </authorgroup>
  27   </refentryinfo>
  28
  29   <refmeta>
  30     <refentrytitle>sd_bus_get_n_queued_read</refentrytitle>
  31     <manvolnum>3</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>sd_bus_get_n_queued_read</refname>
  36     <refname>sd_bus_get_n_queued_write</refname>
  37
  38     <refpurpose>Get the number of pending bus messages in the read and write queues of a bus connection object</refpurpose>
  39   </refnamediv>
  40
  41   <refsynopsisdiv>
  42     <funcsynopsis>
  43       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  44
  45       <funcprototype>
  46         <funcdef>int <function>sd_bus_get_n_queued_read</function></funcdef>
  47         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  48         <paramdef>uint64_t *<parameter>ret</parameter></paramdef>
  49       </funcprototype>
  50
  51       <funcprototype>
  52         <funcdef>int <function>sd_bus_get_n_queued_write</function></funcdef>
  53         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  54         <paramdef>uint64_t *<parameter>ret</parameter></paramdef>
  55       </funcprototype>
  56     </funcsynopsis>
  57   </refsynopsisdiv>
  58
  59   <refsect1>
  60     <title>Description</title>
  61
  62     <para>
  63       <function>sd_bus_get_n_queued_read()</function> may be used to query the number of bus messages in the read queue
  64       of a bus connection object. The read queue contains all messages read from the transport medium (e.g. network
  65       socket) but not yet processed locally. The function expects two arguments: the bus object to query, and a pointer
  66       to a 64bit counter variable to write the current queue size to. Use <function>sd_bus_process()</function> in
  67       order to process queued messages, i.e. to reduce the size of the read queue (as well as, in fact, the write
  68       queue, see below).
  69     </para>
  70
  71     <para>
  72       Similarly, <function>sd_bus_get_n_queued_write()</function> may be used to query the number of currently pending
  73       bus messages in the write queue of a bus connection object. The write queue contains all messages enqueued into
  74       the connection with a call such as <function>sd_bus_send()</function> but not yet written to the transport
  75       medium. The expected arguments are similar to <function>sd_bus_get_n_queued_read()</function>. Here too, use
  76       <function>sd_bus_process()</function> to reduce the size of the write queue. Alternatively, use
  77       <function>sd_bus_flush()</function> to synchronously write out any pending bus messages until the write queue is
  78       empty.
  79     </para>
  80   </refsect1>
  81
  82   <refsect1>
  83     <title>Return Value</title>
  84
  85     <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
  86     error code.</para>
  87   </refsect1>
  88
  89   <refsect1>
  90     <title>Errors</title>
  91
  92     <para>Returned errors may indicate the following problems:</para>
  93
  94     <variablelist>
  95       <varlistentry>
  96         <term><constant>-ECHILD</constant></term>
  97
  98         <listitem><para>The bus connection was created in a different process.</para></listitem>
  99       </varlistentry>
 100
 101     </variablelist>
 102   </refsect1>
 103
 104   <refsect1>
 105     <title>See Also</title>
 106
 107     <para>
 108       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 109       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 110       <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 111       <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 112       <citerefentry><refentrytitle>sd_bus_flush</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 113     </para>
 114   </refsect1>
 115
 116 </refentry>