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