mirror of /home/gitosis/repositories/libev.git
1706 lines
76 KiB
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1706 lines
76 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
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<head>
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<title>libev</title>
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<meta name="description" content="Pod documentation for libev" />
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<meta name="inputfile" content="<standard input>" />
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<meta name="outputfile" content="<standard output>" />
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<meta name="created" content="Sat Nov 24 17:33:21 2007" />
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<meta name="generator" content="Pod::Xhtml 1.57" />
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<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
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<body>
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<div class="pod">
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<!-- INDEX START -->
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<h3 id="TOP">Index</h3>
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<ul><li><a href="#NAME">NAME</a></li>
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<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
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<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
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<li><a href="#FEATURES">FEATURES</a></li>
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<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
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<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
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<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
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<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
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<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
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<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
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<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
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</ul>
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</li>
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<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
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<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li>
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<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
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<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
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<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
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<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
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<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
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<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
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<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
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</ul>
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</li>
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<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
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<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
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<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
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<li><a href="#EMBEDDING">EMBEDDING</a>
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<ul><li><a href="#FILESETS">FILESETS</a>
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<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
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<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
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<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
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</ul>
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</li>
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<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
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<li><a href="#EXAMPLES">EXAMPLES</a></li>
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</ul>
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</li>
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<li><a href="#AUTHOR">AUTHOR</a>
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</li>
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</ul><hr />
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<!-- INDEX END -->
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<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p>
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<div id="NAME_CONTENT">
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<p>libev - a high performance full-featured event loop written in C</p>
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</div>
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<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p>
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<div id="SYNOPSIS_CONTENT">
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<pre> #include <ev.h>
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</pre>
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</div>
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<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>
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<div id="DESCRIPTION_CONTENT">
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<p>Libev is an event loop: you register interest in certain events (such as a
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file descriptor being readable or a timeout occuring), and it will manage
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these event sources and provide your program with events.</p>
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<p>To do this, it must take more or less complete control over your process
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(or thread) by executing the <i>event loop</i> handler, and will then
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communicate events via a callback mechanism.</p>
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<p>You register interest in certain events by registering so-called <i>event
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watchers</i>, which are relatively small C structures you initialise with the
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details of the event, and then hand it over to libev by <i>starting</i> the
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watcher.</p>
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</div>
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<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p>
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<div id="FEATURES_CONTENT">
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<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific
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kqueue mechanisms for file descriptor events, relative timers, absolute
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timers with customised rescheduling, signal events, process status change
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events (related to SIGCHLD), and event watchers dealing with the event
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loop mechanism itself (idle, prepare and check watchers). It also is quite
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fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing
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it to libevent for example).</p>
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</div>
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<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
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<div id="CONVENTIONS_CONTENT">
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<p>Libev is very configurable. In this manual the default configuration
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will be described, which supports multiple event loops. For more info
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about various configuration options please have a look at the file
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<cite>README.embed</cite> in the libev distribution. If libev was configured without
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support for multiple event loops, then all functions taking an initial
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argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)
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will not have this argument.</p>
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</div>
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<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
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<div id="TIME_REPRESENTATION_CONTENT">
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<p>Libev represents time as a single floating point number, representing the
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(fractional) number of seconds since the (POSIX) epoch (somewhere near
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the beginning of 1970, details are complicated, don't ask). This type is
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called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
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to the <code>double</code> type in C, and when you need to do any calculations on
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it, you should treat it as such.</p>
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</div>
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<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
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<div id="GLOBAL_FUNCTIONS_CONTENT">
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<p>These functions can be called anytime, even before initialising the
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library in any way.</p>
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<dl>
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<dt>ev_tstamp ev_time ()</dt>
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<dd>
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<p>Returns the current time as libev would use it. Please note that the
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<code>ev_now</code> function is usually faster and also often returns the timestamp
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you actually want to know.</p>
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</dd>
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<dt>int ev_version_major ()</dt>
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<dt>int ev_version_minor ()</dt>
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<dd>
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<p>You can find out the major and minor version numbers of the library
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you linked against by calling the functions <code>ev_version_major</code> and
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<code>ev_version_minor</code>. If you want, you can compare against the global
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symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
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version of the library your program was compiled against.</p>
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<p>Usually, it's a good idea to terminate if the major versions mismatch,
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as this indicates an incompatible change. Minor versions are usually
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compatible to older versions, so a larger minor version alone is usually
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not a problem.</p>
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<p>Example: make sure we haven't accidentally been linked against the wrong
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version:</p>
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<pre> assert (("libev version mismatch",
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ev_version_major () == EV_VERSION_MAJOR
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&& ev_version_minor () >= EV_VERSION_MINOR));
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</pre>
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</dd>
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<dt>unsigned int ev_supported_backends ()</dt>
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<dd>
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<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
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value) compiled into this binary of libev (independent of their
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availability on the system you are running on). See <code>ev_default_loop</code> for
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a description of the set values.</p>
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<p>Example: make sure we have the epoll method, because yeah this is cool and
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a must have and can we have a torrent of it please!!!11</p>
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<pre> assert (("sorry, no epoll, no sex",
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ev_supported_backends () & EVBACKEND_EPOLL));
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</pre>
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</dd>
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<dt>unsigned int ev_recommended_backends ()</dt>
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<dd>
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<p>Return the set of all backends compiled into this binary of libev and also
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recommended for this platform. This set is often smaller than the one
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returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
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most BSDs and will not be autodetected unless you explicitly request it
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(assuming you know what you are doing). This is the set of backends that
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libev will probe for if you specify no backends explicitly.</p>
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</dd>
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<dt>unsigned int ev_embeddable_backends ()</dt>
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<dd>
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<p>Returns the set of backends that are embeddable in other event loops. This
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is the theoretical, all-platform, value. To find which backends
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might be supported on the current system, you would need to look at
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<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
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recommended ones.</p>
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<p>See the description of <code>ev_embed</code> watchers for more info.</p>
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</dd>
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<dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
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<dd>
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<p>Sets the allocation function to use (the prototype is similar to the
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realloc C function, the semantics are identical). It is used to allocate
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and free memory (no surprises here). If it returns zero when memory
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needs to be allocated, the library might abort or take some potentially
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destructive action. The default is your system realloc function.</p>
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<p>You could override this function in high-availability programs to, say,
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free some memory if it cannot allocate memory, to use a special allocator,
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or even to sleep a while and retry until some memory is available.</p>
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<p>Example: replace the libev allocator with one that waits a bit and then
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retries: better than mine).</p>
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<pre> static void *
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persistent_realloc (void *ptr, long size)
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{
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for (;;)
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{
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void *newptr = realloc (ptr, size);
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if (newptr)
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return newptr;
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sleep (60);
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}
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}
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...
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ev_set_allocator (persistent_realloc);
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</pre>
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</dd>
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<dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
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<dd>
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<p>Set the callback function to call on a retryable syscall error (such
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as failed select, poll, epoll_wait). The message is a printable string
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indicating the system call or subsystem causing the problem. If this
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callback is set, then libev will expect it to remedy the sitution, no
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matter what, when it returns. That is, libev will generally retry the
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requested operation, or, if the condition doesn't go away, do bad stuff
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(such as abort).</p>
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<p>Example: do the same thing as libev does internally:</p>
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<pre> static void
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fatal_error (const char *msg)
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{
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perror (msg);
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abort ();
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}
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...
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ev_set_syserr_cb (fatal_error);
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</pre>
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</dd>
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</dl>
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</div>
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<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
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<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
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<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
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types of such loops, the <i>default</i> loop, which supports signals and child
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events, and dynamically created loops which do not.</p>
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<p>If you use threads, a common model is to run the default event loop
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in your main thread (or in a separate thread) and for each thread you
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create, you also create another event loop. Libev itself does no locking
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whatsoever, so if you mix calls to the same event loop in different
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threads, make sure you lock (this is usually a bad idea, though, even if
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done correctly, because it's hideous and inefficient).</p>
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<dl>
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<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
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<dd>
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<p>This will initialise the default event loop if it hasn't been initialised
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yet and return it. If the default loop could not be initialised, returns
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false. If it already was initialised it simply returns it (and ignores the
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flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
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<p>If you don't know what event loop to use, use the one returned from this
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function.</p>
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<p>The flags argument can be used to specify special behaviour or specific
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backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
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<p>The following flags are supported:</p>
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<p>
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<dl>
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<dt><code>EVFLAG_AUTO</code></dt>
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<dd>
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<p>The default flags value. Use this if you have no clue (it's the right
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thing, believe me).</p>
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</dd>
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<dt><code>EVFLAG_NOENV</code></dt>
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<dd>
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<p>If this flag bit is ored into the flag value (or the program runs setuid
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or setgid) then libev will <i>not</i> look at the environment variable
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<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
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override the flags completely if it is found in the environment. This is
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useful to try out specific backends to test their performance, or to work
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around bugs.</p>
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</dd>
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<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
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<dd>
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<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
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libev tries to roll its own fd_set with no limits on the number of fds,
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but if that fails, expect a fairly low limit on the number of fds when
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using this backend. It doesn't scale too well (O(highest_fd)), but its usually
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the fastest backend for a low number of fds.</p>
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</dd>
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<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
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<dd>
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<p>And this is your standard poll(2) backend. It's more complicated than
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select, but handles sparse fds better and has no artificial limit on the
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number of fds you can use (except it will slow down considerably with a
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lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
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</dd>
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<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
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<dd>
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<p>For few fds, this backend is a bit little slower than poll and select,
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but it scales phenomenally better. While poll and select usually scale like
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O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
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either O(1) or O(active_fds).</p>
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<p>While stopping and starting an I/O watcher in the same iteration will
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result in some caching, there is still a syscall per such incident
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(because the fd could point to a different file description now), so its
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best to avoid that. Also, dup()ed file descriptors might not work very
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well if you register events for both fds.</p>
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<p>Please note that epoll sometimes generates spurious notifications, so you
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need to use non-blocking I/O or other means to avoid blocking when no data
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(or space) is available.</p>
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</dd>
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<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
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<dd>
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<p>Kqueue deserves special mention, as at the time of this writing, it
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was broken on all BSDs except NetBSD (usually it doesn't work with
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anything but sockets and pipes, except on Darwin, where of course its
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completely useless). For this reason its not being "autodetected"
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unless you explicitly specify it explicitly in the flags (i.e. using
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<code>EVBACKEND_KQUEUE</code>).</p>
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<p>It scales in the same way as the epoll backend, but the interface to the
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kernel is more efficient (which says nothing about its actual speed, of
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course). While starting and stopping an I/O watcher does not cause an
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extra syscall as with epoll, it still adds up to four event changes per
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incident, so its best to avoid that.</p>
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</dd>
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<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
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<dd>
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<p>This is not implemented yet (and might never be).</p>
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</dd>
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<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
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<dd>
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<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
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it's really slow, but it still scales very well (O(active_fds)).</p>
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<p>Please note that solaris ports can result in a lot of spurious
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notifications, so you need to use non-blocking I/O or other means to avoid
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blocking when no data (or space) is available.</p>
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</dd>
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<dt><code>EVBACKEND_ALL</code></dt>
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<dd>
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<p>Try all backends (even potentially broken ones that wouldn't be tried
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with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
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<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
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</dd>
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</dl>
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</p>
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<p>If one or more of these are ored into the flags value, then only these
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backends will be tried (in the reverse order as given here). If none are
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specified, most compiled-in backend will be tried, usually in reverse
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order of their flag values :)</p>
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<p>The most typical usage is like this:</p>
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<pre> if (!ev_default_loop (0))
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fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
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</pre>
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<p>Restrict libev to the select and poll backends, and do not allow
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environment settings to be taken into account:</p>
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<pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
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</pre>
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<p>Use whatever libev has to offer, but make sure that kqueue is used if
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available (warning, breaks stuff, best use only with your own private
|
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event loop and only if you know the OS supports your types of fds):</p>
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<pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
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|
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</pre>
|
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</dd>
|
|
<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
|
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<dd>
|
|
<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
|
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always distinct from the default loop. Unlike the default loop, it cannot
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handle signal and child watchers, and attempts to do so will be greeted by
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undefined behaviour (or a failed assertion if assertions are enabled).</p>
|
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<p>Example: try to create a event loop that uses epoll and nothing else.</p>
|
|
<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
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if (!epoller)
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fatal ("no epoll found here, maybe it hides under your chair");
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|
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</pre>
|
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</dd>
|
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<dt>ev_default_destroy ()</dt>
|
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<dd>
|
|
<p>Destroys the default loop again (frees all memory and kernel state
|
|
etc.). None of the active event watchers will be stopped in the normal
|
|
sense, so e.g. <code>ev_is_active</code> might still return true. It is your
|
|
responsibility to either stop all watchers cleanly yoursef <i>before</i>
|
|
calling this function, or cope with the fact afterwards (which is usually
|
|
the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
|
|
for example).</p>
|
|
</dd>
|
|
<dt>ev_loop_destroy (loop)</dt>
|
|
<dd>
|
|
<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
|
|
earlier call to <code>ev_loop_new</code>.</p>
|
|
</dd>
|
|
<dt>ev_default_fork ()</dt>
|
|
<dd>
|
|
<p>This function reinitialises the kernel state for backends that have
|
|
one. Despite the name, you can call it anytime, but it makes most sense
|
|
after forking, in either the parent or child process (or both, but that
|
|
again makes little sense).</p>
|
|
<p>You <i>must</i> call this function in the child process after forking if and
|
|
only if you want to use the event library in both processes. If you just
|
|
fork+exec, you don't have to call it.</p>
|
|
<p>The function itself is quite fast and it's usually not a problem to call
|
|
it just in case after a fork. To make this easy, the function will fit in
|
|
quite nicely into a call to <code>pthread_atfork</code>:</p>
|
|
<pre> pthread_atfork (0, 0, ev_default_fork);
|
|
|
|
</pre>
|
|
<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
|
|
without calling this function, so if you force one of those backends you
|
|
do not need to care.</p>
|
|
</dd>
|
|
<dt>ev_loop_fork (loop)</dt>
|
|
<dd>
|
|
<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
|
|
<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
|
|
after fork, and how you do this is entirely your own problem.</p>
|
|
</dd>
|
|
<dt>unsigned int ev_backend (loop)</dt>
|
|
<dd>
|
|
<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
|
|
use.</p>
|
|
</dd>
|
|
<dt>ev_tstamp ev_now (loop)</dt>
|
|
<dd>
|
|
<p>Returns the current "event loop time", which is the time the event loop
|
|
received events and started processing them. This timestamp does not
|
|
change as long as callbacks are being processed, and this is also the base
|
|
time used for relative timers. You can treat it as the timestamp of the
|
|
event occuring (or more correctly, libev finding out about it).</p>
|
|
</dd>
|
|
<dt>ev_loop (loop, int flags)</dt>
|
|
<dd>
|
|
<p>Finally, this is it, the event handler. This function usually is called
|
|
after you initialised all your watchers and you want to start handling
|
|
events.</p>
|
|
<p>If the flags argument is specified as <code>0</code>, it will not return until
|
|
either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
|
|
<p>Please note that an explicit <code>ev_unloop</code> is usually better than
|
|
relying on all watchers to be stopped when deciding when a program has
|
|
finished (especially in interactive programs), but having a program that
|
|
automatically loops as long as it has to and no longer by virtue of
|
|
relying on its watchers stopping correctly is a thing of beauty.</p>
|
|
<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
|
|
those events and any outstanding ones, but will not block your process in
|
|
case there are no events and will return after one iteration of the loop.</p>
|
|
<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
|
|
neccessary) and will handle those and any outstanding ones. It will block
|
|
your process until at least one new event arrives, and will return after
|
|
one iteration of the loop. This is useful if you are waiting for some
|
|
external event in conjunction with something not expressible using other
|
|
libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
|
|
usually a better approach for this kind of thing.</p>
|
|
<p>Here are the gory details of what <code>ev_loop</code> does:</p>
|
|
<pre> * If there are no active watchers (reference count is zero), return.
|
|
- Queue prepare watchers and then call all outstanding watchers.
|
|
- If we have been forked, recreate the kernel state.
|
|
- Update the kernel state with all outstanding changes.
|
|
- Update the "event loop time".
|
|
- Calculate for how long to block.
|
|
- Block the process, waiting for any events.
|
|
- Queue all outstanding I/O (fd) events.
|
|
- Update the "event loop time" and do time jump handling.
|
|
- Queue all outstanding timers.
|
|
- Queue all outstanding periodics.
|
|
- If no events are pending now, queue all idle watchers.
|
|
- Queue all check watchers.
|
|
- Call all queued watchers in reverse order (i.e. check watchers first).
|
|
Signals and child watchers are implemented as I/O watchers, and will
|
|
be handled here by queueing them when their watcher gets executed.
|
|
- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
|
|
were used, return, otherwise continue with step *.
|
|
|
|
</pre>
|
|
<p>Example: queue some jobs and then loop until no events are outsanding
|
|
anymore.</p>
|
|
<pre> ... queue jobs here, make sure they register event watchers as long
|
|
... as they still have work to do (even an idle watcher will do..)
|
|
ev_loop (my_loop, 0);
|
|
... jobs done. yeah!
|
|
|
|
</pre>
|
|
</dd>
|
|
<dt>ev_unloop (loop, how)</dt>
|
|
<dd>
|
|
<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
|
|
has processed all outstanding events). The <code>how</code> argument must be either
|
|
<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
|
|
<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
|
|
</dd>
|
|
<dt>ev_ref (loop)</dt>
|
|
<dt>ev_unref (loop)</dt>
|
|
<dd>
|
|
<p>Ref/unref can be used to add or remove a reference count on the event
|
|
loop: Every watcher keeps one reference, and as long as the reference
|
|
count is nonzero, <code>ev_loop</code> will not return on its own. If you have
|
|
a watcher you never unregister that should not keep <code>ev_loop</code> from
|
|
returning, ev_unref() after starting, and ev_ref() before stopping it. For
|
|
example, libev itself uses this for its internal signal pipe: It is not
|
|
visible to the libev user and should not keep <code>ev_loop</code> from exiting if
|
|
no event watchers registered by it are active. It is also an excellent
|
|
way to do this for generic recurring timers or from within third-party
|
|
libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
|
|
<p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
|
|
running when nothing else is active.</p>
|
|
<pre> struct dv_signal exitsig;
|
|
ev_signal_init (&exitsig, sig_cb, SIGINT);
|
|
ev_signal_start (myloop, &exitsig);
|
|
evf_unref (myloop);
|
|
|
|
</pre>
|
|
<p>Example: for some weird reason, unregister the above signal handler again.</p>
|
|
<pre> ev_ref (myloop);
|
|
ev_signal_stop (myloop, &exitsig);
|
|
|
|
</pre>
|
|
</dd>
|
|
</dl>
|
|
|
|
|
|
|
|
|
|
|
|
</div>
|
|
<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
|
|
<div id="ANATOMY_OF_A_WATCHER_CONTENT">
|
|
<p>A watcher is a structure that you create and register to record your
|
|
interest in some event. For instance, if you want to wait for STDIN to
|
|
become readable, you would create an <code>ev_io</code> watcher for that:</p>
|
|
<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
|
|
{
|
|
ev_io_stop (w);
|
|
ev_unloop (loop, EVUNLOOP_ALL);
|
|
}
|
|
|
|
struct ev_loop *loop = ev_default_loop (0);
|
|
struct ev_io stdin_watcher;
|
|
ev_init (&stdin_watcher, my_cb);
|
|
ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
|
|
ev_io_start (loop, &stdin_watcher);
|
|
ev_loop (loop, 0);
|
|
|
|
</pre>
|
|
<p>As you can see, you are responsible for allocating the memory for your
|
|
watcher structures (and it is usually a bad idea to do this on the stack,
|
|
although this can sometimes be quite valid).</p>
|
|
<p>Each watcher structure must be initialised by a call to <code>ev_init
|
|
(watcher *, callback)</code>, which expects a callback to be provided. This
|
|
callback gets invoked each time the event occurs (or, in the case of io
|
|
watchers, each time the event loop detects that the file descriptor given
|
|
is readable and/or writable).</p>
|
|
<p>Each watcher type has its own <code>ev_<type>_set (watcher *, ...)</code> macro
|
|
with arguments specific to this watcher type. There is also a macro
|
|
to combine initialisation and setting in one call: <code>ev_<type>_init
|
|
(watcher *, callback, ...)</code>.</p>
|
|
<p>To make the watcher actually watch out for events, you have to start it
|
|
with a watcher-specific start function (<code>ev_<type>_start (loop, watcher
|
|
*)</code>), and you can stop watching for events at any time by calling the
|
|
corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
|
|
<p>As long as your watcher is active (has been started but not stopped) you
|
|
must not touch the values stored in it. Most specifically you must never
|
|
reinitialise it or call its <code>set</code> macro.</p>
|
|
<p>Each and every callback receives the event loop pointer as first, the
|
|
registered watcher structure as second, and a bitset of received events as
|
|
third argument.</p>
|
|
<p>The received events usually include a single bit per event type received
|
|
(you can receive multiple events at the same time). The possible bit masks
|
|
are:</p>
|
|
<dl>
|
|
<dt><code>EV_READ</code></dt>
|
|
<dt><code>EV_WRITE</code></dt>
|
|
<dd>
|
|
<p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
|
|
writable.</p>
|
|
</dd>
|
|
<dt><code>EV_TIMEOUT</code></dt>
|
|
<dd>
|
|
<p>The <code>ev_timer</code> watcher has timed out.</p>
|
|
</dd>
|
|
<dt><code>EV_PERIODIC</code></dt>
|
|
<dd>
|
|
<p>The <code>ev_periodic</code> watcher has timed out.</p>
|
|
</dd>
|
|
<dt><code>EV_SIGNAL</code></dt>
|
|
<dd>
|
|
<p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
|
|
</dd>
|
|
<dt><code>EV_CHILD</code></dt>
|
|
<dd>
|
|
<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
|
|
</dd>
|
|
<dt><code>EV_IDLE</code></dt>
|
|
<dd>
|
|
<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
|
|
</dd>
|
|
<dt><code>EV_PREPARE</code></dt>
|
|
<dt><code>EV_CHECK</code></dt>
|
|
<dd>
|
|
<p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
|
|
to gather new events, and all <code>ev_check</code> watchers are invoked just after
|
|
<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
|
|
received events. Callbacks of both watcher types can start and stop as
|
|
many watchers as they want, and all of them will be taken into account
|
|
(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
|
|
<code>ev_loop</code> from blocking).</p>
|
|
</dd>
|
|
<dt><code>EV_ERROR</code></dt>
|
|
<dd>
|
|
<p>An unspecified error has occured, the watcher has been stopped. This might
|
|
happen because the watcher could not be properly started because libev
|
|
ran out of memory, a file descriptor was found to be closed or any other
|
|
problem. You best act on it by reporting the problem and somehow coping
|
|
with the watcher being stopped.</p>
|
|
<p>Libev will usually signal a few "dummy" events together with an error,
|
|
for example it might indicate that a fd is readable or writable, and if
|
|
your callbacks is well-written it can just attempt the operation and cope
|
|
with the error from read() or write(). This will not work in multithreaded
|
|
programs, though, so beware.</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
</div>
|
|
<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
|
|
<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
|
|
<p>In the following description, <code>TYPE</code> stands for the watcher type,
|
|
e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
|
|
<dl>
|
|
<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
|
|
<dd>
|
|
<p>This macro initialises the generic portion of a watcher. The contents
|
|
of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
|
|
the generic parts of the watcher are initialised, you <i>need</i> to call
|
|
the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
|
|
type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
|
|
which rolls both calls into one.</p>
|
|
<p>You can reinitialise a watcher at any time as long as it has been stopped
|
|
(or never started) and there are no pending events outstanding.</p>
|
|
<p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
|
|
int revents)</code>.</p>
|
|
</dd>
|
|
<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
|
|
<dd>
|
|
<p>This macro initialises the type-specific parts of a watcher. You need to
|
|
call <code>ev_init</code> at least once before you call this macro, but you can
|
|
call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
|
|
macro on a watcher that is active (it can be pending, however, which is a
|
|
difference to the <code>ev_init</code> macro).</p>
|
|
<p>Although some watcher types do not have type-specific arguments
|
|
(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
|
|
</dd>
|
|
<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
|
|
<dd>
|
|
<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
|
|
calls into a single call. This is the most convinient method to initialise
|
|
a watcher. The same limitations apply, of course.</p>
|
|
</dd>
|
|
<dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt>
|
|
<dd>
|
|
<p>Starts (activates) the given watcher. Only active watchers will receive
|
|
events. If the watcher is already active nothing will happen.</p>
|
|
</dd>
|
|
<dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt>
|
|
<dd>
|
|
<p>Stops the given watcher again (if active) and clears the pending
|
|
status. It is possible that stopped watchers are pending (for example,
|
|
non-repeating timers are being stopped when they become pending), but
|
|
<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
|
|
you want to free or reuse the memory used by the watcher it is therefore a
|
|
good idea to always call its <code>ev_TYPE_stop</code> function.</p>
|
|
</dd>
|
|
<dt>bool ev_is_active (ev_TYPE *watcher)</dt>
|
|
<dd>
|
|
<p>Returns a true value iff the watcher is active (i.e. it has been started
|
|
and not yet been stopped). As long as a watcher is active you must not modify
|
|
it.</p>
|
|
</dd>
|
|
<dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
|
|
<dd>
|
|
<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
|
|
events but its callback has not yet been invoked). As long as a watcher
|
|
is pending (but not active) you must not call an init function on it (but
|
|
<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
|
|
libev (e.g. you cnanot <code>free ()</code> it).</p>
|
|
</dd>
|
|
<dt>callback = ev_cb (ev_TYPE *watcher)</dt>
|
|
<dd>
|
|
<p>Returns the callback currently set on the watcher.</p>
|
|
</dd>
|
|
<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
|
|
<dd>
|
|
<p>Change the callback. You can change the callback at virtually any time
|
|
(modulo threads).</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
|
|
|
|
|
|
|
|
</div>
|
|
<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
|
|
<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
|
|
<p>Each watcher has, by default, a member <code>void *data</code> that you can change
|
|
and read at any time, libev will completely ignore it. This can be used
|
|
to associate arbitrary data with your watcher. If you need more data and
|
|
don't want to allocate memory and store a pointer to it in that data
|
|
member, you can also "subclass" the watcher type and provide your own
|
|
data:</p>
|
|
<pre> struct my_io
|
|
{
|
|
struct ev_io io;
|
|
int otherfd;
|
|
void *somedata;
|
|
struct whatever *mostinteresting;
|
|
}
|
|
|
|
</pre>
|
|
<p>And since your callback will be called with a pointer to the watcher, you
|
|
can cast it back to your own type:</p>
|
|
<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
|
|
{
|
|
struct my_io *w = (struct my_io *)w_;
|
|
...
|
|
}
|
|
|
|
</pre>
|
|
<p>More interesting and less C-conformant ways of catsing your callback type
|
|
have been omitted....</p>
|
|
|
|
|
|
|
|
|
|
|
|
</div>
|
|
<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
|
|
<div id="WATCHER_TYPES_CONTENT">
|
|
<p>This section describes each watcher in detail, but will not repeat
|
|
information given in the last section.</p>
|
|
|
|
|
|
|
|
|
|
|
|
</div>
|
|
<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
|
|
<div id="code_ev_io_code_is_this_file_descrip-2">
|
|
<p>I/O watchers check whether a file descriptor is readable or writable
|
|
in each iteration of the event loop, or, more precisely, when reading
|
|
would not block the process and writing would at least be able to write
|
|
some data. This behaviour is called level-triggering because you keep
|
|
receiving events as long as the condition persists. Remember you can stop
|
|
the watcher if you don't want to act on the event and neither want to
|
|
receive future events.</p>
|
|
<p>In general you can register as many read and/or write event watchers per
|
|
fd as you want (as long as you don't confuse yourself). Setting all file
|
|
descriptors to non-blocking mode is also usually a good idea (but not
|
|
required if you know what you are doing).</p>
|
|
<p>You have to be careful with dup'ed file descriptors, though. Some backends
|
|
(the linux epoll backend is a notable example) cannot handle dup'ed file
|
|
descriptors correctly if you register interest in two or more fds pointing
|
|
to the same underlying file/socket/etc. description (that is, they share
|
|
the same underlying "file open").</p>
|
|
<p>If you must do this, then force the use of a known-to-be-good backend
|
|
(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
|
|
<code>EVBACKEND_POLL</code>).</p>
|
|
<p>Another thing you have to watch out for is that it is quite easy to
|
|
receive "spurious" readyness notifications, that is your callback might
|
|
be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
|
|
because there is no data. Not only are some backends known to create a
|
|
lot of those (for example solaris ports), it is very easy to get into
|
|
this situation even with a relatively standard program structure. Thus
|
|
it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
|
|
<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
|
|
<p>If you cannot run the fd in non-blocking mode (for example you should not
|
|
play around with an Xlib connection), then you have to seperately re-test
|
|
wether a file descriptor is really ready with a known-to-be good interface
|
|
such as poll (fortunately in our Xlib example, Xlib already does this on
|
|
its own, so its quite safe to use).</p>
|
|
<dl>
|
|
<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
|
|
<dt>ev_io_set (ev_io *, int fd, int events)</dt>
|
|
<dd>
|
|
<p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
|
|
rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
|
|
<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
|
|
</dd>
|
|
</dl>
|
|
<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
|
|
readable, but only once. Since it is likely line-buffered, you could
|
|
attempt to read a whole line in the callback:</p>
|
|
<pre> static void
|
|
stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
|
|
{
|
|
ev_io_stop (loop, w);
|
|
.. read from stdin here (or from w->fd) and haqndle any I/O errors
|
|
}
|
|
|
|
...
|
|
struct ev_loop *loop = ev_default_init (0);
|
|
struct ev_io stdin_readable;
|
|
ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
|
|
ev_io_start (loop, &stdin_readable);
|
|
ev_loop (loop, 0);
|
|
|
|
|
|
|
|
|
|
</pre>
|
|
|
|
</div>
|
|
<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
|
|
<div id="code_ev_timer_code_relative_and_opti-2">
|
|
<p>Timer watchers are simple relative timers that generate an event after a
|
|
given time, and optionally repeating in regular intervals after that.</p>
|
|
<p>The timers are based on real time, that is, if you register an event that
|
|
times out after an hour and you reset your system clock to last years
|
|
time, it will still time out after (roughly) and hour. "Roughly" because
|
|
detecting time jumps is hard, and some inaccuracies are unavoidable (the
|
|
monotonic clock option helps a lot here).</p>
|
|
<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
|
|
time. This is usually the right thing as this timestamp refers to the time
|
|
of the event triggering whatever timeout you are modifying/starting. If
|
|
you suspect event processing to be delayed and you <i>need</i> to base the timeout
|
|
on the current time, use something like this to adjust for this:</p>
|
|
<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
|
|
|
|
</pre>
|
|
<p>The callback is guarenteed to be invoked only when its timeout has passed,
|
|
but if multiple timers become ready during the same loop iteration then
|
|
order of execution is undefined.</p>
|
|
<dl>
|
|
<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
|
|
<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
|
|
<dd>
|
|
<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
|
|
<code>0.</code>, then it will automatically be stopped. If it is positive, then the
|
|
timer will automatically be configured to trigger again <code>repeat</code> seconds
|
|
later, again, and again, until stopped manually.</p>
|
|
<p>The timer itself will do a best-effort at avoiding drift, that is, if you
|
|
configure a timer to trigger every 10 seconds, then it will trigger at
|
|
exactly 10 second intervals. If, however, your program cannot keep up with
|
|
the timer (because it takes longer than those 10 seconds to do stuff) the
|
|
timer will not fire more than once per event loop iteration.</p>
|
|
</dd>
|
|
<dt>ev_timer_again (loop)</dt>
|
|
<dd>
|
|
<p>This will act as if the timer timed out and restart it again if it is
|
|
repeating. The exact semantics are:</p>
|
|
<p>If the timer is started but nonrepeating, stop it.</p>
|
|
<p>If the timer is repeating, either start it if necessary (with the repeat
|
|
value), or reset the running timer to the repeat value.</p>
|
|
<p>This sounds a bit complicated, but here is a useful and typical
|
|
example: Imagine you have a tcp connection and you want a so-called idle
|
|
timeout, that is, you want to be called when there have been, say, 60
|
|
seconds of inactivity on the socket. The easiest way to do this is to
|
|
configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each
|
|
time you successfully read or write some data. If you go into an idle
|
|
state where you do not expect data to travel on the socket, you can stop
|
|
the timer, and again will automatically restart it if need be.</p>
|
|
</dd>
|
|
</dl>
|
|
<p>Example: create a timer that fires after 60 seconds.</p>
|
|
<pre> static void
|
|
one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
|
|
{
|
|
.. one minute over, w is actually stopped right here
|
|
}
|
|
|
|
struct ev_timer mytimer;
|
|
ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
|
|
ev_timer_start (loop, &mytimer);
|
|
|
|
</pre>
|
|
<p>Example: create a timeout timer that times out after 10 seconds of
|
|
inactivity.</p>
|
|
<pre> static void
|
|
timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
|
|
{
|
|
.. ten seconds without any activity
|
|
}
|
|
|
|
struct ev_timer mytimer;
|
|
ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
|
|
ev_timer_again (&mytimer); /* start timer */
|
|
ev_loop (loop, 0);
|
|
|
|
// and in some piece of code that gets executed on any "activity":
|
|
// reset the timeout to start ticking again at 10 seconds
|
|
ev_timer_again (&mytimer);
|
|
|
|
|
|
|
|
|
|
</pre>
|
|
|
|
</div>
|
|
<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
|
|
<div id="code_ev_periodic_code_to_cron_or_not-2">
|
|
<p>Periodic watchers are also timers of a kind, but they are very versatile
|
|
(and unfortunately a bit complex).</p>
|
|
<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
|
|
but on wallclock time (absolute time). You can tell a periodic watcher
|
|
to trigger "at" some specific point in time. For example, if you tell a
|
|
periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
|
|
+ 10.</code>) and then reset your system clock to the last year, then it will
|
|
take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
|
|
roughly 10 seconds later and of course not if you reset your system time
|
|
again).</p>
|
|
<p>They can also be used to implement vastly more complex timers, such as
|
|
triggering an event on eahc midnight, local time.</p>
|
|
<p>As with timers, the callback is guarenteed to be invoked only when the
|
|
time (<code>at</code>) has been passed, but if multiple periodic timers become ready
|
|
during the same loop iteration then order of execution is undefined.</p>
|
|
<dl>
|
|
<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
|
|
<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
|
|
<dd>
|
|
<p>Lots of arguments, lets sort it out... There are basically three modes of
|
|
operation, and we will explain them from simplest to complex:</p>
|
|
<p>
|
|
<dl>
|
|
<dt>* absolute timer (interval = reschedule_cb = 0)</dt>
|
|
<dd>
|
|
<p>In this configuration the watcher triggers an event at the wallclock time
|
|
<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
|
|
that is, if it is to be run at January 1st 2011 then it will run when the
|
|
system time reaches or surpasses this time.</p>
|
|
</dd>
|
|
<dt>* non-repeating interval timer (interval > 0, reschedule_cb = 0)</dt>
|
|
<dd>
|
|
<p>In this mode the watcher will always be scheduled to time out at the next
|
|
<code>at + N * interval</code> time (for some integer N) and then repeat, regardless
|
|
of any time jumps.</p>
|
|
<p>This can be used to create timers that do not drift with respect to system
|
|
time:</p>
|
|
<pre> ev_periodic_set (&periodic, 0., 3600., 0);
|
|
|
|
</pre>
|
|
<p>This doesn't mean there will always be 3600 seconds in between triggers,
|
|
but only that the the callback will be called when the system time shows a
|
|
full hour (UTC), or more correctly, when the system time is evenly divisible
|
|
by 3600.</p>
|
|
<p>Another way to think about it (for the mathematically inclined) is that
|
|
<code>ev_periodic</code> will try to run the callback in this mode at the next possible
|
|
time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
|
|
</dd>
|
|
<dt>* manual reschedule mode (reschedule_cb = callback)</dt>
|
|
<dd>
|
|
<p>In this mode the values for <code>interval</code> and <code>at</code> are both being
|
|
ignored. Instead, each time the periodic watcher gets scheduled, the
|
|
reschedule callback will be called with the watcher as first, and the
|
|
current time as second argument.</p>
|
|
<p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
|
|
ever, or make any event loop modifications</i>. If you need to stop it,
|
|
return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
|
|
starting a prepare watcher).</p>
|
|
<p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
|
|
ev_tstamp now)</code>, e.g.:</p>
|
|
<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
|
|
{
|
|
return now + 60.;
|
|
}
|
|
|
|
</pre>
|
|
<p>It must return the next time to trigger, based on the passed time value
|
|
(that is, the lowest time value larger than to the second argument). It
|
|
will usually be called just before the callback will be triggered, but
|
|
might be called at other times, too.</p>
|
|
<p>NOTE: <i>This callback must always return a time that is later than the
|
|
passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
|
|
<p>This can be used to create very complex timers, such as a timer that
|
|
triggers on each midnight, local time. To do this, you would calculate the
|
|
next midnight after <code>now</code> and return the timestamp value for this. How
|
|
you do this is, again, up to you (but it is not trivial, which is the main
|
|
reason I omitted it as an example).</p>
|
|
</dd>
|
|
</dl>
|
|
</p>
|
|
</dd>
|
|
<dt>ev_periodic_again (loop, ev_periodic *)</dt>
|
|
<dd>
|
|
<p>Simply stops and restarts the periodic watcher again. This is only useful
|
|
when you changed some parameters or the reschedule callback would return
|
|
a different time than the last time it was called (e.g. in a crond like
|
|
program when the crontabs have changed).</p>
|
|
</dd>
|
|
</dl>
|
|
<p>Example: call a callback every hour, or, more precisely, whenever the
|
|
system clock is divisible by 3600. The callback invocation times have
|
|
potentially a lot of jittering, but good long-term stability.</p>
|
|
<pre> static void
|
|
clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
|
|
{
|
|
... its now a full hour (UTC, or TAI or whatever your clock follows)
|
|
}
|
|
|
|
struct ev_periodic hourly_tick;
|
|
ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
|
|
ev_periodic_start (loop, &hourly_tick);
|
|
|
|
</pre>
|
|
<p>Example: the same as above, but use a reschedule callback to do it:</p>
|
|
<pre> #include <math.h>
|
|
|
|
static ev_tstamp
|
|
my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
|
|
{
|
|
return fmod (now, 3600.) + 3600.;
|
|
}
|
|
|
|
ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
|
|
|
|
</pre>
|
|
<p>Example: call a callback every hour, starting now:</p>
|
|
<pre> struct ev_periodic hourly_tick;
|
|
ev_periodic_init (&hourly_tick, clock_cb,
|
|
fmod (ev_now (loop), 3600.), 3600., 0);
|
|
ev_periodic_start (loop, &hourly_tick);
|
|
|
|
|
|
|
|
|
|
</pre>
|
|
|
|
</div>
|
|
<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
|
|
<div id="code_ev_signal_code_signal_me_when_a-2">
|
|
<p>Signal watchers will trigger an event when the process receives a specific
|
|
signal one or more times. Even though signals are very asynchronous, libev
|
|
will try it's best to deliver signals synchronously, i.e. as part of the
|
|
normal event processing, like any other event.</p>
|
|
<p>You can configure as many watchers as you like per signal. Only when the
|
|
first watcher gets started will libev actually register a signal watcher
|
|
with the kernel (thus it coexists with your own signal handlers as long
|
|
as you don't register any with libev). Similarly, when the last signal
|
|
watcher for a signal is stopped libev will reset the signal handler to
|
|
SIG_DFL (regardless of what it was set to before).</p>
|
|
<dl>
|
|
<dt>ev_signal_init (ev_signal *, callback, int signum)</dt>
|
|
<dt>ev_signal_set (ev_signal *, int signum)</dt>
|
|
<dd>
|
|
<p>Configures the watcher to trigger on the given signal number (usually one
|
|
of the <code>SIGxxx</code> constants).</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
|
|
|
|
|
|
|
|
</div>
|
|
<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
|
|
<div id="code_ev_child_code_watch_out_for_pro-2">
|
|
<p>Child watchers trigger when your process receives a SIGCHLD in response to
|
|
some child status changes (most typically when a child of yours dies).</p>
|
|
<dl>
|
|
<dt>ev_child_init (ev_child *, callback, int pid)</dt>
|
|
<dt>ev_child_set (ev_child *, int pid)</dt>
|
|
<dd>
|
|
<p>Configures the watcher to wait for status changes of process <code>pid</code> (or
|
|
<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
|
|
at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
|
|
the status word (use the macros from <code>sys/wait.h</code> and see your systems
|
|
<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
|
|
process causing the status change.</p>
|
|
</dd>
|
|
</dl>
|
|
<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
|
|
<pre> static void
|
|
sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
|
|
{
|
|
ev_unloop (loop, EVUNLOOP_ALL);
|
|
}
|
|
|
|
struct ev_signal signal_watcher;
|
|
ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
|
|
ev_signal_start (loop, &sigint_cb);
|
|
|
|
|
|
|
|
|
|
</pre>
|
|
|
|
</div>
|
|
<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
|
|
<div id="code_ev_idle_code_when_you_ve_got_no-2">
|
|
<p>Idle watchers trigger events when there are no other events are pending
|
|
(prepare, check and other idle watchers do not count). That is, as long
|
|
as your process is busy handling sockets or timeouts (or even signals,
|
|
imagine) it will not be triggered. But when your process is idle all idle
|
|
watchers are being called again and again, once per event loop iteration -
|
|
until stopped, that is, or your process receives more events and becomes
|
|
busy.</p>
|
|
<p>The most noteworthy effect is that as long as any idle watchers are
|
|
active, the process will not block when waiting for new events.</p>
|
|
<p>Apart from keeping your process non-blocking (which is a useful
|
|
effect on its own sometimes), idle watchers are a good place to do
|
|
"pseudo-background processing", or delay processing stuff to after the
|
|
event loop has handled all outstanding events.</p>
|
|
<dl>
|
|
<dt>ev_idle_init (ev_signal *, callback)</dt>
|
|
<dd>
|
|
<p>Initialises and configures the idle watcher - it has no parameters of any
|
|
kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
|
|
believe me.</p>
|
|
</dd>
|
|
</dl>
|
|
<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
|
|
callback, free it. Alos, use no error checking, as usual.</p>
|
|
<pre> static void
|
|
idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
|
|
{
|
|
free (w);
|
|
// now do something you wanted to do when the program has
|
|
// no longer asnything immediate to do.
|
|
}
|
|
|
|
struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
|
|
ev_idle_init (idle_watcher, idle_cb);
|
|
ev_idle_start (loop, idle_cb);
|
|
|
|
|
|
|
|
|
|
</pre>
|
|
|
|
</div>
|
|
<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
|
|
<div id="code_ev_prepare_code_and_code_ev_che-2">
|
|
<p>Prepare and check watchers are usually (but not always) used in tandem:
|
|
prepare watchers get invoked before the process blocks and check watchers
|
|
afterwards.</p>
|
|
<p>Their main purpose is to integrate other event mechanisms into libev and
|
|
their use is somewhat advanced. This could be used, for example, to track
|
|
variable changes, implement your own watchers, integrate net-snmp or a
|
|
coroutine library and lots more.</p>
|
|
<p>This is done by examining in each prepare call which file descriptors need
|
|
to be watched by the other library, registering <code>ev_io</code> watchers for
|
|
them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
|
|
provide just this functionality). Then, in the check watcher you check for
|
|
any events that occured (by checking the pending status of all watchers
|
|
and stopping them) and call back into the library. The I/O and timer
|
|
callbacks will never actually be called (but must be valid nevertheless,
|
|
because you never know, you know?).</p>
|
|
<p>As another example, the Perl Coro module uses these hooks to integrate
|
|
coroutines into libev programs, by yielding to other active coroutines
|
|
during each prepare and only letting the process block if no coroutines
|
|
are ready to run (it's actually more complicated: it only runs coroutines
|
|
with priority higher than or equal to the event loop and one coroutine
|
|
of lower priority, but only once, using idle watchers to keep the event
|
|
loop from blocking if lower-priority coroutines are active, thus mapping
|
|
low-priority coroutines to idle/background tasks).</p>
|
|
<dl>
|
|
<dt>ev_prepare_init (ev_prepare *, callback)</dt>
|
|
<dt>ev_check_init (ev_check *, callback)</dt>
|
|
<dd>
|
|
<p>Initialises and configures the prepare or check watcher - they have no
|
|
parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
|
|
macros, but using them is utterly, utterly and completely pointless.</p>
|
|
</dd>
|
|
</dl>
|
|
<p>Example: *TODO*.</p>
|
|
|
|
|
|
|
|
|
|
|
|
</div>
|
|
<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
|
|
<div id="code_ev_embed_code_when_one_backend_-2">
|
|
<p>This is a rather advanced watcher type that lets you embed one event loop
|
|
into another (currently only <code>ev_io</code> events are supported in the embedded
|
|
loop, other types of watchers might be handled in a delayed or incorrect
|
|
fashion and must not be used).</p>
|
|
<p>There are primarily two reasons you would want that: work around bugs and
|
|
prioritise I/O.</p>
|
|
<p>As an example for a bug workaround, the kqueue backend might only support
|
|
sockets on some platform, so it is unusable as generic backend, but you
|
|
still want to make use of it because you have many sockets and it scales
|
|
so nicely. In this case, you would create a kqueue-based loop and embed it
|
|
into your default loop (which might use e.g. poll). Overall operation will
|
|
be a bit slower because first libev has to poll and then call kevent, but
|
|
at least you can use both at what they are best.</p>
|
|
<p>As for prioritising I/O: rarely you have the case where some fds have
|
|
to be watched and handled very quickly (with low latency), and even
|
|
priorities and idle watchers might have too much overhead. In this case
|
|
you would put all the high priority stuff in one loop and all the rest in
|
|
a second one, and embed the second one in the first.</p>
|
|
<p>As long as the watcher is active, the callback will be invoked every time
|
|
there might be events pending in the embedded loop. The callback must then
|
|
call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
|
|
their callbacks (you could also start an idle watcher to give the embedded
|
|
loop strictly lower priority for example). You can also set the callback
|
|
to <code>0</code>, in which case the embed watcher will automatically execute the
|
|
embedded loop sweep.</p>
|
|
<p>As long as the watcher is started it will automatically handle events. The
|
|
callback will be invoked whenever some events have been handled. You can
|
|
set the callback to <code>0</code> to avoid having to specify one if you are not
|
|
interested in that.</p>
|
|
<p>Also, there have not currently been made special provisions for forking:
|
|
when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
|
|
but you will also have to stop and restart any <code>ev_embed</code> watchers
|
|
yourself.</p>
|
|
<p>Unfortunately, not all backends are embeddable, only the ones returned by
|
|
<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
|
|
portable one.</p>
|
|
<p>So when you want to use this feature you will always have to be prepared
|
|
that you cannot get an embeddable loop. The recommended way to get around
|
|
this is to have a separate variables for your embeddable loop, try to
|
|
create it, and if that fails, use the normal loop for everything:</p>
|
|
<pre> struct ev_loop *loop_hi = ev_default_init (0);
|
|
struct ev_loop *loop_lo = 0;
|
|
struct ev_embed embed;
|
|
|
|
// see if there is a chance of getting one that works
|
|
// (remember that a flags value of 0 means autodetection)
|
|
loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
|
|
? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
|
|
: 0;
|
|
|
|
// if we got one, then embed it, otherwise default to loop_hi
|
|
if (loop_lo)
|
|
{
|
|
ev_embed_init (&embed, 0, loop_lo);
|
|
ev_embed_start (loop_hi, &embed);
|
|
}
|
|
else
|
|
loop_lo = loop_hi;
|
|
|
|
</pre>
|
|
<dl>
|
|
<dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
|
|
<dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
|
|
<dd>
|
|
<p>Configures the watcher to embed the given loop, which must be
|
|
embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
|
|
invoked automatically, otherwise it is the responsibility of the callback
|
|
to invoke it (it will continue to be called until the sweep has been done,
|
|
if you do not want thta, you need to temporarily stop the embed watcher).</p>
|
|
</dd>
|
|
<dt>ev_embed_sweep (loop, ev_embed *)</dt>
|
|
<dd>
|
|
<p>Make a single, non-blocking sweep over the embedded loop. This works
|
|
similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
|
|
apropriate way for embedded loops.</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
|
|
|
|
|
|
|
|
</div>
|
|
<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
|
|
<div id="OTHER_FUNCTIONS_CONTENT">
|
|
<p>There are some other functions of possible interest. Described. Here. Now.</p>
|
|
<dl>
|
|
<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
|
|
<dd>
|
|
<p>This function combines a simple timer and an I/O watcher, calls your
|
|
callback on whichever event happens first and automatically stop both
|
|
watchers. This is useful if you want to wait for a single event on an fd
|
|
or timeout without having to allocate/configure/start/stop/free one or
|
|
more watchers yourself.</p>
|
|
<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
|
|
is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
|
|
<code>events</code> set will be craeted and started.</p>
|
|
<p>If <code>timeout</code> is less than 0, then no timeout watcher will be
|
|
started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
|
|
repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
|
|
dubious value.</p>
|
|
<p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
|
|
passed an <code>revents</code> set like normal event callbacks (a combination of
|
|
<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
|
|
value passed to <code>ev_once</code>:</p>
|
|
<pre> static void stdin_ready (int revents, void *arg)
|
|
{
|
|
if (revents & EV_TIMEOUT)
|
|
/* doh, nothing entered */;
|
|
else if (revents & EV_READ)
|
|
/* stdin might have data for us, joy! */;
|
|
}
|
|
|
|
ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
|
|
|
|
</pre>
|
|
</dd>
|
|
<dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt>
|
|
<dd>
|
|
<p>Feeds the given event set into the event loop, as if the specified event
|
|
had happened for the specified watcher (which must be a pointer to an
|
|
initialised but not necessarily started event watcher).</p>
|
|
</dd>
|
|
<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
|
|
<dd>
|
|
<p>Feed an event on the given fd, as if a file descriptor backend detected
|
|
the given events it.</p>
|
|
</dd>
|
|
<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
|
|
<dd>
|
|
<p>Feed an event as if the given signal occured (<code>loop</code> must be the default
|
|
loop!).</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
|
|
|
|
|
|
|
|
</div>
|
|
<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
|
|
<div id="LIBEVENT_EMULATION_CONTENT">
|
|
<p>Libev offers a compatibility emulation layer for libevent. It cannot
|
|
emulate the internals of libevent, so here are some usage hints:</p>
|
|
<dl>
|
|
<dt>* Use it by including <event.h>, as usual.</dt>
|
|
<dt>* The following members are fully supported: ev_base, ev_callback,
|
|
ev_arg, ev_fd, ev_res, ev_events.</dt>
|
|
<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
|
|
maintained by libev, it does not work exactly the same way as in libevent (consider
|
|
it a private API).</dt>
|
|
<dt>* Priorities are not currently supported. Initialising priorities
|
|
will fail and all watchers will have the same priority, even though there
|
|
is an ev_pri field.</dt>
|
|
<dt>* Other members are not supported.</dt>
|
|
<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
|
|
to use the libev header file and library.</dt>
|
|
</dl>
|
|
|
|
</div>
|
|
<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
|
|
<div id="C_SUPPORT_CONTENT">
|
|
<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
|
|
you to use some convinience methods to start/stop watchers and also change
|
|
the callback model to a model using method callbacks on objects.</p>
|
|
<p>To use it,</p>
|
|
<pre> #include <ev++.h>
|
|
|
|
</pre>
|
|
<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
|
|
and puts all of its definitions (many of them macros) into the global
|
|
namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
|
|
<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
|
|
<code>EV_MULTIPLICITY</code>.</p>
|
|
<p>Here is a list of things available in the <code>ev</code> namespace:</p>
|
|
<dl>
|
|
<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
|
|
<dd>
|
|
<p>These are just enum values with the same values as the <code>EV_READ</code> etc.
|
|
macros from <cite>ev.h</cite>.</p>
|
|
</dd>
|
|
<dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
|
|
<dd>
|
|
<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
|
|
</dd>
|
|
<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
|
|
<dd>
|
|
<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
|
|
the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
|
|
which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
|
|
defines by many implementations.</p>
|
|
<p>All of those classes have these methods:</p>
|
|
<p>
|
|
<dl>
|
|
<dt>ev::TYPE::TYPE (object *, object::method *)</dt>
|
|
<dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
|
|
<dt>ev::TYPE::~TYPE</dt>
|
|
<dd>
|
|
<p>The constructor takes a pointer to an object and a method pointer to
|
|
the event handler callback to call in this class. The constructor calls
|
|
<code>ev_init</code> for you, which means you have to call the <code>set</code> method
|
|
before starting it. If you do not specify a loop then the constructor
|
|
automatically associates the default loop with this watcher.</p>
|
|
<p>The destructor automatically stops the watcher if it is active.</p>
|
|
</dd>
|
|
<dt>w->set (struct ev_loop *)</dt>
|
|
<dd>
|
|
<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
|
|
do this when the watcher is inactive (and not pending either).</p>
|
|
</dd>
|
|
<dt>w->set ([args])</dt>
|
|
<dd>
|
|
<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
|
|
called at least once. Unlike the C counterpart, an active watcher gets
|
|
automatically stopped and restarted.</p>
|
|
</dd>
|
|
<dt>w->start ()</dt>
|
|
<dd>
|
|
<p>Starts the watcher. Note that there is no <code>loop</code> argument as the
|
|
constructor already takes the loop.</p>
|
|
</dd>
|
|
<dt>w->stop ()</dt>
|
|
<dd>
|
|
<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
|
|
</dd>
|
|
<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
|
|
<dd>
|
|
<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
|
|
<code>ev_TYPE_again</code> function.</p>
|
|
</dd>
|
|
<dt>w->sweep () <code>ev::embed</code> only</dt>
|
|
<dd>
|
|
<p>Invokes <code>ev_embed_sweep</code>.</p>
|
|
</dd>
|
|
</dl>
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
<p>Example: Define a class with an IO and idle watcher, start one of them in
|
|
the constructor.</p>
|
|
<pre> class myclass
|
|
{
|
|
ev_io io; void io_cb (ev::io &w, int revents);
|
|
ev_idle idle void idle_cb (ev::idle &w, int revents);
|
|
|
|
myclass ();
|
|
}
|
|
|
|
myclass::myclass (int fd)
|
|
: io (this, &myclass::io_cb),
|
|
idle (this, &myclass::idle_cb)
|
|
{
|
|
io.start (fd, ev::READ);
|
|
}
|
|
|
|
</pre>
|
|
|
|
</div>
|
|
<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
|
|
<div id="EMBEDDING_CONTENT">
|
|
<p>Libev can (and often is) directly embedded into host
|
|
applications. Examples of applications that embed it include the Deliantra
|
|
Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
|
|
and rxvt-unicode.</p>
|
|
<p>The goal is to enable you to just copy the neecssary files into your
|
|
source directory without having to change even a single line in them, so
|
|
you can easily upgrade by simply copying (or having a checked-out copy of
|
|
libev somewhere in your source tree).</p>
|
|
|
|
</div>
|
|
<h2 id="FILESETS">FILESETS</h2>
|
|
<div id="FILESETS_CONTENT">
|
|
<p>Depending on what features you need you need to include one or more sets of files
|
|
in your app.</p>
|
|
|
|
</div>
|
|
<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
|
|
<div id="CORE_EVENT_LOOP_CONTENT">
|
|
<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
|
|
configuration (no autoconf):</p>
|
|
<pre> #define EV_STANDALONE 1
|
|
#include "ev.c"
|
|
|
|
</pre>
|
|
<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
|
|
single C source file only to provide the function implementations. To use
|
|
it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
|
|
done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
|
|
where you can put other configuration options):</p>
|
|
<pre> #define EV_STANDALONE 1
|
|
#include "ev.h"
|
|
|
|
</pre>
|
|
<p>Both header files and implementation files can be compiled with a C++
|
|
compiler (at least, thats a stated goal, and breakage will be treated
|
|
as a bug).</p>
|
|
<p>You need the following files in your source tree, or in a directory
|
|
in your include path (e.g. in libev/ when using -Ilibev):</p>
|
|
<pre> ev.h
|
|
ev.c
|
|
ev_vars.h
|
|
ev_wrap.h
|
|
|
|
ev_win32.c required on win32 platforms only
|
|
|
|
ev_select.c only when select backend is enabled (which is by default)
|
|
ev_poll.c only when poll backend is enabled (disabled by default)
|
|
ev_epoll.c only when the epoll backend is enabled (disabled by default)
|
|
ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
|
|
ev_port.c only when the solaris port backend is enabled (disabled by default)
|
|
|
|
</pre>
|
|
<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
|
|
to compile this single file.</p>
|
|
|
|
</div>
|
|
<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
|
|
<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
|
|
<p>To include the libevent compatibility API, also include:</p>
|
|
<pre> #include "event.c"
|
|
|
|
</pre>
|
|
<p>in the file including <cite>ev.c</cite>, and:</p>
|
|
<pre> #include "event.h"
|
|
|
|
</pre>
|
|
<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
|
|
<p>You need the following additional files for this:</p>
|
|
<pre> event.h
|
|
event.c
|
|
|
|
</pre>
|
|
|
|
</div>
|
|
<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
|
|
<div id="AUTOCONF_SUPPORT_CONTENT">
|
|
<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
|
|
whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
|
|
<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
|
|
include <cite>config.h</cite> and configure itself accordingly.</p>
|
|
<p>For this of course you need the m4 file:</p>
|
|
<pre> libev.m4
|
|
|
|
</pre>
|
|
|
|
</div>
|
|
<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
|
|
<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
|
|
<p>Libev can be configured via a variety of preprocessor symbols you have to define
|
|
before including any of its files. The default is not to build for multiplicity
|
|
and only include the select backend.</p>
|
|
<dl>
|
|
<dt>EV_STANDALONE</dt>
|
|
<dd>
|
|
<p>Must always be <code>1</code> if you do not use autoconf configuration, which
|
|
keeps libev from including <cite>config.h</cite>, and it also defines dummy
|
|
implementations for some libevent functions (such as logging, which is not
|
|
supported). It will also not define any of the structs usually found in
|
|
<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
|
|
</dd>
|
|
<dt>EV_USE_MONOTONIC</dt>
|
|
<dd>
|
|
<p>If defined to be <code>1</code>, libev will try to detect the availability of the
|
|
monotonic clock option at both compiletime and runtime. Otherwise no use
|
|
of the monotonic clock option will be attempted. If you enable this, you
|
|
usually have to link against librt or something similar. Enabling it when
|
|
the functionality isn't available is safe, though, althoguh you have
|
|
to make sure you link against any libraries where the <code>clock_gettime</code>
|
|
function is hiding in (often <cite>-lrt</cite>).</p>
|
|
</dd>
|
|
<dt>EV_USE_REALTIME</dt>
|
|
<dd>
|
|
<p>If defined to be <code>1</code>, libev will try to detect the availability of the
|
|
realtime clock option at compiletime (and assume its availability at
|
|
runtime if successful). Otherwise no use of the realtime clock option will
|
|
be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
|
|
(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
|
|
in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
|
|
</dd>
|
|
<dt>EV_USE_SELECT</dt>
|
|
<dd>
|
|
<p>If undefined or defined to be <code>1</code>, libev will compile in support for the
|
|
<code>select</code>(2) backend. No attempt at autodetection will be done: if no
|
|
other method takes over, select will be it. Otherwise the select backend
|
|
will not be compiled in.</p>
|
|
</dd>
|
|
<dt>EV_SELECT_USE_FD_SET</dt>
|
|
<dd>
|
|
<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
|
|
structure. This is useful if libev doesn't compile due to a missing
|
|
<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
|
|
exotic systems. This usually limits the range of file descriptors to some
|
|
low limit such as 1024 or might have other limitations (winsocket only
|
|
allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
|
|
influence the size of the <code>fd_set</code> used.</p>
|
|
</dd>
|
|
<dt>EV_SELECT_IS_WINSOCKET</dt>
|
|
<dd>
|
|
<p>When defined to <code>1</code>, the select backend will assume that
|
|
select/socket/connect etc. don't understand file descriptors but
|
|
wants osf handles on win32 (this is the case when the select to
|
|
be used is the winsock select). This means that it will call
|
|
<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
|
|
it is assumed that all these functions actually work on fds, even
|
|
on win32. Should not be defined on non-win32 platforms.</p>
|
|
</dd>
|
|
<dt>EV_USE_POLL</dt>
|
|
<dd>
|
|
<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
|
|
backend. Otherwise it will be enabled on non-win32 platforms. It
|
|
takes precedence over select.</p>
|
|
</dd>
|
|
<dt>EV_USE_EPOLL</dt>
|
|
<dd>
|
|
<p>If defined to be <code>1</code>, libev will compile in support for the Linux
|
|
<code>epoll</code>(7) backend. Its availability will be detected at runtime,
|
|
otherwise another method will be used as fallback. This is the
|
|
preferred backend for GNU/Linux systems.</p>
|
|
</dd>
|
|
<dt>EV_USE_KQUEUE</dt>
|
|
<dd>
|
|
<p>If defined to be <code>1</code>, libev will compile in support for the BSD style
|
|
<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
|
|
otherwise another method will be used as fallback. This is the preferred
|
|
backend for BSD and BSD-like systems, although on most BSDs kqueue only
|
|
supports some types of fds correctly (the only platform we found that
|
|
supports ptys for example was NetBSD), so kqueue might be compiled in, but
|
|
not be used unless explicitly requested. The best way to use it is to find
|
|
out whether kqueue supports your type of fd properly and use an embedded
|
|
kqueue loop.</p>
|
|
</dd>
|
|
<dt>EV_USE_PORT</dt>
|
|
<dd>
|
|
<p>If defined to be <code>1</code>, libev will compile in support for the Solaris
|
|
10 port style backend. Its availability will be detected at runtime,
|
|
otherwise another method will be used as fallback. This is the preferred
|
|
backend for Solaris 10 systems.</p>
|
|
</dd>
|
|
<dt>EV_USE_DEVPOLL</dt>
|
|
<dd>
|
|
<p>reserved for future expansion, works like the USE symbols above.</p>
|
|
</dd>
|
|
<dt>EV_H</dt>
|
|
<dd>
|
|
<p>The name of the <cite>ev.h</cite> header file used to include it. The default if
|
|
undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
|
|
can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
|
|
</dd>
|
|
<dt>EV_CONFIG_H</dt>
|
|
<dd>
|
|
<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
|
|
<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
|
|
<code>EV_H</code>, above.</p>
|
|
</dd>
|
|
<dt>EV_EVENT_H</dt>
|
|
<dd>
|
|
<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
|
|
of how the <cite>event.h</cite> header can be found.</p>
|
|
</dd>
|
|
<dt>EV_PROTOTYPES</dt>
|
|
<dd>
|
|
<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
|
|
prototypes, but still define all the structs and other symbols. This is
|
|
occasionally useful if you want to provide your own wrapper functions
|
|
around libev functions.</p>
|
|
</dd>
|
|
<dt>EV_MULTIPLICITY</dt>
|
|
<dd>
|
|
<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
|
|
will have the <code>struct ev_loop *</code> as first argument, and you can create
|
|
additional independent event loops. Otherwise there will be no support
|
|
for multiple event loops and there is no first event loop pointer
|
|
argument. Instead, all functions act on the single default loop.</p>
|
|
</dd>
|
|
<dt>EV_PERIODICS</dt>
|
|
<dd>
|
|
<p>If undefined or defined to be <code>1</code>, then periodic timers are supported,
|
|
otherwise not. This saves a few kb of code.</p>
|
|
</dd>
|
|
<dt>EV_COMMON</dt>
|
|
<dd>
|
|
<p>By default, all watchers have a <code>void *data</code> member. By redefining
|
|
this macro to a something else you can include more and other types of
|
|
members. You have to define it each time you include one of the files,
|
|
though, and it must be identical each time.</p>
|
|
<p>For example, the perl EV module uses something like this:</p>
|
|
<pre> #define EV_COMMON \
|
|
SV *self; /* contains this struct */ \
|
|
SV *cb_sv, *fh /* note no trailing ";" */
|
|
|
|
</pre>
|
|
</dd>
|
|
<dt>EV_CB_DECLARE(type)</dt>
|
|
<dt>EV_CB_INVOKE(watcher,revents)</dt>
|
|
<dt>ev_set_cb(ev,cb)</dt>
|
|
<dd>
|
|
<p>Can be used to change the callback member declaration in each watcher,
|
|
and the way callbacks are invoked and set. Must expand to a struct member
|
|
definition and a statement, respectively. See the <cite>ev.v</cite> header file for
|
|
their default definitions. One possible use for overriding these is to
|
|
avoid the ev_loop pointer as first argument in all cases, or to use method
|
|
calls instead of plain function calls in C++.</p>
|
|
|
|
</div>
|
|
<h2 id="EXAMPLES">EXAMPLES</h2>
|
|
<div id="EXAMPLES_CONTENT">
|
|
<p>For a real-world example of a program the includes libev
|
|
verbatim, you can have a look at the EV perl module
|
|
(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
|
|
the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
|
|
interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
|
|
will be compiled. It is pretty complex because it provides its own header
|
|
file.</p>
|
|
<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
|
|
that everybody includes and which overrides some autoconf choices:</p>
|
|
<pre> #define EV_USE_POLL 0
|
|
#define EV_MULTIPLICITY 0
|
|
#define EV_PERIODICS 0
|
|
#define EV_CONFIG_H <config.h>
|
|
|
|
#include "ev++.h"
|
|
|
|
</pre>
|
|
<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
|
|
<pre> #include "ev_cpp.h"
|
|
#include "ev.c"
|
|
|
|
</pre>
|
|
|
|
</div>
|
|
<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
|
|
<div id="AUTHOR_CONTENT">
|
|
<p>Marc Lehmann <libev@schmorp.de>.</p>
|
|
|
|
</div>
|
|
</div></body>
|
|
</html>
|