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diff --git a/src/libsystemd/sd_bus_track_new.xml b/src/libsystemd/sd_bus_track_new.xml new file mode 100644 index 0000000000..60e2e77f75 --- /dev/null +++ b/src/libsystemd/sd_bus_track_new.xml @@ -0,0 +1,263 @@ +<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" +"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> + +<!-- + This file is part of systemd. + + Copyright 2016 Lennart Poettering + + systemd is free software; you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. + + systemd is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with systemd; If not, see <http://www.gnu.org/licenses/>. +--> + +<refentry id="sd_bus_track_new"> + + <refentryinfo> + <title>sd_bus_track_new</title> + <productname>systemd</productname> + + <authorgroup> + <author> + <contrib>Developer</contrib> + <firstname>Lennart</firstname> + <surname>Poettering</surname> + <email>lennart@poettering.net</email> + </author> + </authorgroup> + </refentryinfo> + + <refmeta> + <refentrytitle>sd_bus_track_new</refentrytitle> + <manvolnum>3</manvolnum> + </refmeta> + + <refnamediv> + <refname>sd_bus_track_new</refname> + <refname>sd_bus_track_ref</refname> + <refname>sd_bus_track_unref</refname> + <refname>sd_bus_track_unrefp</refname> + <refname>sd_bus_track_set_recursive</refname> + <refname>sd_bus_track_get_recursive</refname> + <refname>sd_bus_track_get_bus</refname> + <refname>sd_bus_track_get_userdata</refname> + <refname>sd_bus_track_set_userdata</refname> + + <refpurpose>Track bus peers</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <funcsynopsis> + <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> + + <funcprototype> + <funcdef>int <function>sd_bus_track_new</function></funcdef> + <paramdef>sd_bus* <parameter>bus</parameter></paramdef> + <paramdef>sd_bus_track** <parameter>ret</parameter></paramdef> + <paramdef>sd_bus_track_handler_t <parameter>handler</parameter></paramdef> + <paramdef>void* <parameter>userdata</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>sd_bus_track *<function>sd_bus_track_ref</function></funcdef> + <paramdef>sd_bus_track *<parameter>t</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>sd_bus_track *<function>sd_bus_track_unref</function></funcdef> + <paramdef>sd_bus_track *<parameter>t</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>void <function>sd_bus_track_unrefp</function></funcdef> + <paramdef>sd_bus_track **<parameter>t</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_bus_track_get_recursive</function></funcdef> + <paramdef>sd_bus_track *<parameter>t</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_bus_track_set_recursive</function></funcdef> + <paramdef>sd_bus_track *<parameter>t</parameter></paramdef> + <paramdef>int <parameter>b</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>sd_bus* <function>sd_bus_track_get_bus</function></funcdef> + <paramdef>sd_bus_track *<parameter>t</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>void* <function>sd_bus_track_get_userdata</function></funcdef> + <paramdef>sd_bus_track *<parameter>t</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>void* <function>sd_bus_track_set_userdata</function></funcdef> + <paramdef>sd_bus_track *<parameter>t</parameter></paramdef> + <paramdef>void *userdata</paramdef> + </funcprototype> + + </funcsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><function>sd_bus_track_new()</function> creates a new bus peer tracking object. The object is allocated for + the specified bus, and returned in the <parameter>*ret</parameter> parameter. After use, the object should be freed + again by dropping the acquired reference with <function>sd_bus_track_unref()</function> (see below). A bus peer + tracking object may be used to keep track of peers on a specific IPC bus, for cases where peers are making use of + one or more local objects, in order to control the lifecycle of the local objects and ensure they stay around as + long as the peers needing them are around, and unreferenced (and possibly destroyed) as soon as all relevant peers + have vanished. Each bus peer tracking object may be used to track zero, one or more peers add a time. References to + specific bus peers are added via + <citerefentry><refentrytitle>sd_bus_track_add_name</refentrytitle><manvolnum>3</manvolnum></citerefentry> or + <function>sd_bus_track_add_sender()</function>. They may be dropped again via + <function>sd_bus_track_remove_name()</function> and + <function>sd_bus_track_remove_sender()</function>. Alternatively, references on peers are removed automatically + when they disconnect from the bus. If non-NULL the <parameter>handler</parameter> may specify a function that is + invoked whenever the last reference is dropped, regardless whether the reference is dropped explicitly via + <function>sd_bus_track_remove_name()</function> or implicitly because the peer disconnected from the bus. The final + argument <parameter>userdata</parameter> may be used to attach a generic user data pointer to the object. This + pointer is passed to the handler callback when it is invoked.</para> + + <para><function>sd_bus_track_ref()</function> creates a new reference to a bus peer tracking object. This object + will not be destroyed until <function>sd_bus_track_unref()</function> has been called as many times plus once + more. Once the reference count has dropped to zero, the specified object cannot be used anymore, further calls to + <function>sd_bus_track_ref()</function> or <function>sd_bus_track_unref()</function> on the same object are + illegal.</para> + + <para><function>sd_bus_track_unref()</function> destroys a reference to a bus peer tracking object.</para> + + <para><function>sd_bus_track_unrefp()</function> is similar to <function>sd_bus_track_unref()</function> but takes + a pointer to a pointer to an <type>sd_bus_track</type> object. This call is useful in conjunction with GCC's and + LLVM's <ulink url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up Variable + Attribute</ulink>. Note that this function is defined as inline function.</para> + + <para><function>sd_bus_track_ref()</function>, <function>sd_bus_track_unref()</function> and + <function>sd_bus_track_unrefp()</function> execute no operation if the passed in bus peer tracking object is + <constant>NULL</constant>.</para> + + <para>Bus peer tracking objects may exist in two modes: by default they operate in non-recursive mode, but may + optionally be switched into recursive mode. If operating in the default non-recursive mode a peer is either tracked + or not tracked. In this mode invoking <function>sd_bus_track_add_name()</function> multiple times in a row for the + same peer is fully equivalent to calling it just once, as the call adds the peer to the set of tracked peers if + necessary, and executes no operation if the peer is already being tracked. A single invocation of + <function>sd_bus_track_remove_name()</function> removes the reference on the peer again, regardless how many times + <function>sd_bus_track_add_name()</function> was called before. If operating in recursive mode, the number of times + <function>sd_bus_track_add_name()</function> is invoked for the same peer name is counted and + <function>sd_bus_track_remove_name()</function> must be called the same number of times before the peer is not + tracked anymore, with the exception when the tracked peer vanishes from the bus, in which case the count is + irrelevant and the tracking of the specific peer is immediately + removed. <function>sd_bus_track_get_recursive()</function> may be used to determine whether the bus peer tracking + object is operating in recursive mode. <function>sd_bus_track_set_recursive()</function> may be used to enable or + disable recursive mode. By default a bus peer tracking object operates in non-recursive mode, and + <function>sd_bus_track_get_recursive()</function> for a newly allocated object hence returns a value equal to + zero. Use <function>sd_bus_track_set_recursive()</function> to enable recursive mode, right after allocation. It + takes a boolean argument to enable or disable recursive mode. Note that tracking objects for which + <function>sd_bus_track_add_name()</function> was already invoked at least once (and which hence track already one + or more peers) may not be switched from recursive to non-recursive mode anymore.</para> + + <para><function>sd_bus_track_get_bus()</function> returns the bus object the bus peer tracking object belongs + to. It returns the bus object initially passed to <function>sd_bus_track_new()</function> when the object was + allocated.</para> + + <para><function>sd_bus_track_get_userdata()</function> returns the generic user data pointer set on the bus peer + tracking object at the time of creation using <function>sd_bus_track_new()</function> or at a later time, using + <function>sd_bus_track_set_userdata()</function>.</para> + </refsect1> + + <refsect1> + <title>Return Value</title> + + <para>On success, <function>sd_bus_track_new()</function> and <function>sd_bus_track_set_recursive()</function> + return 0 or a positive integer. On failure, they return a negative errno-style error code.</para> + + <para><function>sd_bus_track_ref()</function> always returns the argument.</para> + + <para><function>sd_bus_track_unref()</function> always returns <constant>NULL</constant>.</para> + + <para><function>sd_bus_track_get_recursive()</function> returns 0 if non-recursive mode is selected (default), and + greater than 0 if recursive mode is selected. On failure a negative errno-style error code is returned.</para> + + <para><function>sd_bus_track_get_bus()</function> returns the bus object associated to the bus peer tracking + object.</para> + + <para><function>sd_bus_track_get_userdata()</function> returns the generic user data pointer associated with the + bus peer tracking object. <function>sd_bus_track_set_userdata()</function> returns the previous user data pointer + set.</para> + + </refsect1> + + <refsect1> + <title>Reference ownership</title> + + <para>The <function>sd_bus_track_new()</function> function creates a new object and the caller owns the sole + reference. When not needed anymore, this reference should be destroyed with + <function>sd_bus_track_unref()</function>. + </para> + </refsect1> + + <refsect1> + <title>Errors</title> + + <para>Returned errors may indicate the following problems:</para> + + <variablelist> + + <varlistentry> + <term><constant>-EBUSY</constant></term> + + <listitem><para>Bus peers have already been added to the bus peer tracking object and + <function>sd_bus_track_set_recursive()</function> was called to change tracking mode.</para></listitem> + </varlistentry> + + <varlistentry> + <term><constant>-EINVAL</constant></term> + + <listitem><para>Specified parameter is invalid + (<constant>NULL</constant> in case of output + parameters).</para></listitem> + </varlistentry> + + <varlistentry> + <term><constant>-ENOMEM</constant></term> + + <listitem><para>Memory allocation failed.</para></listitem> + </varlistentry> + + </variablelist> + </refsect1> + + <refsect1> + <title>Notes</title> + + <para><function>sd_bus_track_new()</function> and the other calls described here are available as a shared library, + which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry + project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para> + </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_track_add_name</refentrytitle><manvolnum>3</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |