--- /dev/null
+<?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 elogind.
+
+ Copyright 2015 Lennart Poettering
+
+ elogind 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.
+
+ elogind 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 elogind; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="sd_event_add_io" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_event_add_io</title>
+ <productname>elogind</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Lennart</firstname>
+ <surname>Poettering</surname>
+ <email>lennart@poettering.net</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_event_add_io</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_event_add_io</refname>
+ <refname>sd_event_source_get_io_events</refname>
+ <refname>sd_event_source_set_io_events</refname>
+ <refname>sd_event_source_get_io_revents</refname>
+ <refname>sd_event_source_get_io_fd</refname>
+ <refname>sd_event_source_set_io_fd</refname>
+ <refname>sd_event_source</refname>
+ <refname>sd_event_io_handler_t</refname>
+
+ <refpurpose>Add an I/O event source to an event loop</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <elogind/sd-event.h></funcsynopsisinfo>
+
+ <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>typedef int (*<function>sd_event_io_handler_t</function>)</funcdef>
+ <paramdef>sd_event_source *<parameter>s</parameter></paramdef>
+ <paramdef>int <parameter>fd</parameter></paramdef>
+ <paramdef>uint32_t <parameter>revents</parameter></paramdef>
+ <paramdef>void *<parameter>userdata</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_add_io</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
+ <paramdef>int <parameter>fd</parameter></paramdef>
+ <paramdef>uint32_t <parameter>events</parameter></paramdef>
+ <paramdef>sd_event_io_handler_t <parameter>handler</parameter></paramdef>
+ <paramdef>void *<parameter>userdata</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_get_io_events</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>uint32_t *<parameter>events</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_set_io_events</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>uint32_t <parameter>events</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_get_io_revents</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>uint32_t *<parameter>revents</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_get_io_fd</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_set_io_fd</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>int <parameter>fd</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_event_add_io()</function> adds a new I/O event
+ source to an event loop. The event loop object is specified in the
+ <parameter>event</parameter> parameter, the event source object is
+ returned in the <parameter>source</parameter> parameter. The
+ <parameter>fd</parameter> parameter takes the UNIX file descriptor
+ to watch, which may refer to a socket, a FIFO, a message queue, a
+ serial connection, a character device or any other file descriptor
+ compatible with Linux <citerefentry
+ project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
+ <parameter>events</parameter> parameter takes a bit mask of I/O
+ events to watch the file descriptor for, a combination of the
+ following event flags: <constant>EPOLLIN</constant>,
+ <constant>EPOLLOUT</constant>, <constant>EPOLLRDHUP</constant>,
+ <constant>EPOLLPRI</constant> and <constant>EPOLLET</constant>,
+ see <citerefentry
+ project='man-pages'><refentrytitle>epoll_ctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ for details. The <parameter>handler</parameter> shall reference a
+ function to call when the I/O event source is triggered. The
+ handler function will be passed the
+ <parameter>userdata</parameter> pointer, which may be chosen
+ freely by the caller. The handler will also be passed the file
+ descriptor the event was seen on as well as the actual event flags
+ seen. It's generally a subset of the events watched, however may
+ additionally have <constant>EPOLLERR</constant> and
+ <constant>EPOLLHUP</constant> set.</para>
+
+ <para>By default, the I/O event source will stay enabled
+ continously (<constant>SD_EVENT_ON</constant>), but this may be
+ changed with
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+ If the handler function returns a negative error code, it will be
+ disabled after the invocation, even if the
+ <constant>SD_EVENT_ON</constant> mode was requested before. Note
+ that an I/O event source set to <constant>SD_EVENT_ON</constant> will
+ fire continously unless data is read or written to the file
+ descriptor in order to reset the mask of events seen.
+ </para>
+
+ <para>Setting the I/O event mask to watch for to 0 does not mean
+ that the event source won't be triggered anymore, as
+ <constant>EPOLLHUP</constant> and <constant>EPOLLERR</constant>
+ may be triggered even with a zero event mask. To temporarily
+ disable an I/O event source use
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ with <constant>SD_EVENT_OFF</constant> instead.</para>
+
+ <para>To destroy an event source object use
+ <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ but note that the event source is only removed from the event loop
+ when all references to the event source are dropped. To make sure
+ an event source does not fire anymore, even when there's still a
+ reference to it kept, consider setting the event source to
+ <constant>SD_EVENT_OFF</constant> with
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+
+ <para>If the the second parameter of
+ <function>sd_event_add_io()</function> is passed as NULL no
+ reference to the event source object is returned. In this case the
+ event source is considered "floating", and will be destroyed
+ implicitly when the event loop itself is destroyed.</para>
+
+ <para>It is recommended to use
+ <function>sd_event_add_io()</function> only in conjunction with
+ file descriptors that have <constant>O_NONBLOCK</constant> set, to
+ ensure that all I/O operations from invoked handlers are properly
+ asynchronous and non-blocking. Using file descriptors without
+ <constant>O_NONBLOCK</constant> might result in unexpected
+ starving of other event sources. See <citerefentry
+ project='man-pages'><refentrytitle>fcntl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ for details on enabling <constant>O_NONBLOCK</constant> mode.</para>
+
+ <para><function>sd_event_source_get_io_events()</function> retrieves
+ the configured I/O event mask to watch of an I/O event source created
+ previously with <function>sd_event_add_io()</function>. It takes
+ the event source object and a pointer to a variable to store the
+ event mask in.</para>
+
+ <para><function>sd_event_source_set_io_events()</function> changes the
+ configured I/O event mask to watch of an I/O event source created previously
+ with <function>sd_event_add_io()</function>. It takes the event
+ source object and the new event mask to set.</para>
+
+ <para><function>sd_event_source_get_io_events()</function>
+ retrieves the I/O event mask of currently seen but undispatched
+ events from an I/O event source created previously with
+ <function>sd_event_add_io()</function>. It takes the event source
+ object and a pointer to a variable to store the event mask
+ in. When called from a handler function on the handler's event
+ source object this will return the same mask as passed to the
+ handler's <parameter>revents</parameter> parameter. This call is
+ primarily useful to check for undispatched events of an event
+ source from the handler of an unrelated (possibly higher priority)
+ event source. Note the relation between
+ <function>sd_event_source_get_pending()</function> and
+ <function>sd_event_source_get_io_revents()</function>: both
+ functions will report non-zero results when there's an event
+ pending for the event source, but the former applies to all event
+ source types, the latter only to I/O event sources.</para>
+
+ <para><function>sd_event_source_get_io_fd()</function> retrieves
+ the UNIX file descriptor of an I/O event source created previously
+ with <function>sd_event_add_io()</function>. It takes the event
+ source object and returns the positive file descriptor in the return
+ value, or a negative error number on error (see below).</para>
+
+ <para><function>sd_event_source_set_io_fd()</function>
+ changes the UNIX file descriptor of an I/O event source created
+ previously with <function>sd_event_add_io()</function>. It takes
+ the event source object and the new file descriptor to set.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>On success, these functions return 0 or a positive
+ integer. On failure, they return a negative errno-style error
+ code. </para>
+ </refsect1>
+
+ <refsect1>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>-ENOMEM</constant></term>
+
+ <listitem><para>Not enough memory to allocate an object.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para>An invalid argument has been passed.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ESTALE</constant></term>
+
+ <listitem><para>The event loop is already terminated.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ECHILD</constant></term>
+
+ <listitem><para>The event loop has been created in a different process.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EDOM</constant></term>
+
+ <listitem><para>The passed event source is not an I/O event source.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <xi:include href="libelogind-pkgconfig.xml" />
+
+ <refsect1>
+ <title>See Also</title>
+
+ <para>
+ <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_get_pending</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>epoll_ctl</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>
~ianmdlvl / elogind.git / blobdiff