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- <title>libev</title>
- <meta name="description" content="Pod documentation for libev" />
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- <meta name="created" content="Wed Dec 12 18:55:28 2007" />
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-<body>
-<div class="pod">
-<!-- INDEX START -->
-<h3 id="TOP">Index</h3>
-
-<ul><li><a href="#NAME">NAME</a></li>
-<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
-<li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li>
-<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
-<li><a href="#FEATURES">FEATURES</a></li>
-<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
-<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
-<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
-<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
-<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
-<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
-<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
-</ul>
-</li>
-<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
-<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a>
-<ul><li><a href="#The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</a></li>
-<li><a href="#Watcher_Specific_Functions">Watcher-Specific Functions</a></li>
-</ul>
-</li>
-<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a>
-<ul><li><a href="#Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</a></li>
-</ul>
-</li>
-<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a>
-<ul><li><a href="#Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</a></li>
-</ul>
-</li>
-<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a>
-<ul><li><a href="#Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</a></li>
-</ul>
-</li>
-<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a>
-<ul><li><a href="#Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</a></li>
-</ul>
-</li>
-<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a>
-<ul><li><a href="#Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</a></li>
-</ul>
-</li>
-<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>
-<ul><li><a href="#Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</a></li>
-</ul>
-</li>
-<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>
-<ul><li><a href="#Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</a></li>
-</ul>
-</li>
-<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a>
-<ul><li><a href="#Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</a></li>
-</ul>
-</li>
-<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a>
-<ul><li><a href="#Watcher_Specific_Functions_and_Data_-10">Watcher-Specific Functions and Data Members</a></li>
-</ul>
-</li>
-</ul>
-</li>
-<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
-<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
-<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
-<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
-<li><a href="#EMBEDDING">EMBEDDING</a>
-<ul><li><a href="#FILESETS">FILESETS</a>
-<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
-<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
-<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
-</ul>
-</li>
-<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
-<li><a href="#EXAMPLES">EXAMPLES</a></li>
-</ul>
-</li>
-<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
-<li><a href="#AUTHOR">AUTHOR</a>
-</li>
-</ul><hr />
-<!-- INDEX END -->
-
-<h1 id="NAME">NAME</h1>
-<div id="NAME_CONTENT">
-<p>libev - a high performance full-featured event loop written in C</p>
-
-</div>
-<h1 id="SYNOPSIS">SYNOPSIS</h1>
-<div id="SYNOPSIS_CONTENT">
-<pre> #include <ev.h>
-
-</pre>
-
-</div>
-<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
-<div id="EXAMPLE_PROGRAM_CONTENT">
-<pre> #include <ev.h>
-
- ev_io stdin_watcher;
- ev_timer timeout_watcher;
-
- /* called when data readable on stdin */
- static void
- stdin_cb (EV_P_ struct ev_io *w, int revents)
- {
- /* puts ("stdin ready"); */
- ev_io_stop (EV_A_ w); /* just a syntax example */
- ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
- }
-
- static void
- timeout_cb (EV_P_ struct ev_timer *w, int revents)
- {
- /* puts ("timeout"); */
- ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
- }
-
- int
- main (void)
- {
- struct ev_loop *loop = ev_default_loop (0);
-
- /* initialise an io watcher, then start it */
- ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
- ev_io_start (loop, &stdin_watcher);
-
- /* simple non-repeating 5.5 second timeout */
- ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
- ev_timer_start (loop, &timeout_watcher);
-
- /* loop till timeout or data ready */
- ev_loop (loop, 0);
-
- return 0;
- }
-
-</pre>
-
-</div>
-<h1 id="DESCRIPTION">DESCRIPTION</h1>
-<div id="DESCRIPTION_CONTENT">
-<p>The newest version of this document is also available as a html-formatted
-web page you might find easier to navigate when reading it for the first
-time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p>
-<p>Libev is an event loop: you register interest in certain events (such as a
-file descriptor being readable or a timeout occuring), and it will manage
-these event sources and provide your program with events.</p>
-<p>To do this, it must take more or less complete control over your process
-(or thread) by executing the <i>event loop</i> handler, and will then
-communicate events via a callback mechanism.</p>
-<p>You register interest in certain events by registering so-called <i>event
-watchers</i>, which are relatively small C structures you initialise with the
-details of the event, and then hand it over to libev by <i>starting</i> the
-watcher.</p>
-
-</div>
-<h1 id="FEATURES">FEATURES</h1>
-<div id="FEATURES_CONTENT">
-<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
-BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
-for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
-(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
-with customised rescheduling (<code>ev_periodic</code>), synchronous signals
-(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
-watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
-<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
-file watchers (<code>ev_stat</code>) and even limited support for fork events
-(<code>ev_fork</code>).</p>
-<p>It also is quite fast (see this
-<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
-for example).</p>
-
-</div>
-<h1 id="CONVENTIONS">CONVENTIONS</h1>
-<div id="CONVENTIONS_CONTENT">
-<p>Libev is very configurable. In this manual the default configuration will
-be described, which supports multiple event loops. For more info about
-various configuration options please have a look at <strong>EMBED</strong> section in
-this manual. If libev was configured without support for multiple event
-loops, then all functions taking an initial argument of name <code>loop</code>
-(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
-
-</div>
-<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
-<div id="TIME_REPRESENTATION_CONTENT">
-<p>Libev represents time as a single floating point number, representing the
-(fractional) number of seconds since the (POSIX) epoch (somewhere near
-the beginning of 1970, details are complicated, don't ask). This type is
-called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
-to the <code>double</code> type in C, and when you need to do any calculations on
-it, you should treat it as such.</p>
-
-</div>
-<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
-<div id="GLOBAL_FUNCTIONS_CONTENT">
-<p>These functions can be called anytime, even before initialising the
-library in any way.</p>
-<dl>
- <dt>ev_tstamp ev_time ()</dt>
- <dd>
- <p>Returns the current time as libev would use it. Please note that the
-<code>ev_now</code> function is usually faster and also often returns the timestamp
-you actually want to know.</p>
- </dd>
- <dt>int ev_version_major ()</dt>
- <dt>int ev_version_minor ()</dt>
- <dd>
- <p>You can find out the major and minor ABI version numbers of the library
-you linked against by calling the functions <code>ev_version_major</code> and
-<code>ev_version_minor</code>. If you want, you can compare against the global
-symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
-version of the library your program was compiled against.</p>
- <p>These version numbers refer to the ABI version of the library, not the
-release version.</p>
- <p>Usually, it's a good idea to terminate if the major versions mismatch,
-as this indicates an incompatible change. Minor versions are usually
-compatible to older versions, so a larger minor version alone is usually
-not a problem.</p>
- <p>Example: Make sure we haven't accidentally been linked against the wrong
-version.</p>
-<pre> assert (("libev version mismatch",
- ev_version_major () == EV_VERSION_MAJOR
- && ev_version_minor () >= EV_VERSION_MINOR));
-
-</pre>
- </dd>
- <dt>unsigned int ev_supported_backends ()</dt>
- <dd>
- <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
-value) compiled into this binary of libev (independent of their
-availability on the system you are running on). See <code>ev_default_loop</code> for
-a description of the set values.</p>
- <p>Example: make sure we have the epoll method, because yeah this is cool and
-a must have and can we have a torrent of it please!!!11</p>
-<pre> assert (("sorry, no epoll, no sex",
- ev_supported_backends () & EVBACKEND_EPOLL));
-
-</pre>
- </dd>
- <dt>unsigned int ev_recommended_backends ()</dt>
- <dd>
- <p>Return the set of all backends compiled into this binary of libev and also
-recommended for this platform. This set is often smaller than the one
-returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
-most BSDs and will not be autodetected unless you explicitly request it
-(assuming you know what you are doing). This is the set of backends that
-libev will probe for if you specify no backends explicitly.</p>
- </dd>
- <dt>unsigned int ev_embeddable_backends ()</dt>
- <dd>
- <p>Returns the set of backends that are embeddable in other event loops. This
-is the theoretical, all-platform, value. To find which backends
-might be supported on the current system, you would need to look at
-<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
-recommended ones.</p>
- <p>See the description of <code>ev_embed</code> watchers for more info.</p>
- </dd>
- <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
- <dd>
- <p>Sets the allocation function to use (the prototype is similar - the
-semantics is identical - to the realloc C function). It is used to
-allocate and free memory (no surprises here). If it returns zero when
-memory needs to be allocated, the library might abort or take some
-potentially destructive action. The default is your system realloc
-function.</p>
- <p>You could override this function in high-availability programs to, say,
-free some memory if it cannot allocate memory, to use a special allocator,
-or even to sleep a while and retry until some memory is available.</p>
- <p>Example: Replace the libev allocator with one that waits a bit and then
-retries).</p>
-<pre> static void *
- persistent_realloc (void *ptr, size_t size)
- {
- for (;;)
- {
- void *newptr = realloc (ptr, size);
-
- if (newptr)
- return newptr;
-
- sleep (60);
- }
- }
-
- ...
- ev_set_allocator (persistent_realloc);
-
-</pre>
- </dd>
- <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
- <dd>
- <p>Set the callback function to call on a retryable syscall error (such
-as failed select, poll, epoll_wait). The message is a printable string
-indicating the system call or subsystem causing the problem. If this
-callback is set, then libev will expect it to remedy the sitution, no
-matter what, when it returns. That is, libev will generally retry the
-requested operation, or, if the condition doesn't go away, do bad stuff
-(such as abort).</p>
- <p>Example: This is basically the same thing that libev does internally, too.</p>
-<pre> static void
- fatal_error (const char *msg)
- {
- perror (msg);
- abort ();
- }
-
- ...
- ev_set_syserr_cb (fatal_error);
-
-</pre>
- </dd>
-</dl>
-
-</div>
-<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
-<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
-<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
-types of such loops, the <i>default</i> loop, which supports signals and child
-events, and dynamically created loops which do not.</p>
-<p>If you use threads, a common model is to run the default event loop
-in your main thread (or in a separate thread) and for each thread you
-create, you also create another event loop. Libev itself does no locking
-whatsoever, so if you mix calls to the same event loop in different
-threads, make sure you lock (this is usually a bad idea, though, even if
-done correctly, because it's hideous and inefficient).</p>
-<dl>
- <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
- <dd>
- <p>This will initialise the default event loop if it hasn't been initialised
-yet and return it. If the default loop could not be initialised, returns
-false. If it already was initialised it simply returns it (and ignores the
-flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
- <p>If you don't know what event loop to use, use the one returned from this
-function.</p>
- <p>The flags argument can be used to specify special behaviour or specific
-backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
- <p>The following flags are supported:</p>
- <p>
- <dl>
- <dt><code>EVFLAG_AUTO</code></dt>
- <dd>
- <p>The default flags value. Use this if you have no clue (it's the right
-thing, believe me).</p>
- </dd>
- <dt><code>EVFLAG_NOENV</code></dt>
- <dd>
- <p>If this flag bit is ored into the flag value (or the program runs setuid
-or setgid) then libev will <i>not</i> look at the environment variable
-<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
-override the flags completely if it is found in the environment. This is
-useful to try out specific backends to test their performance, or to work
-around bugs.</p>
- </dd>
- <dt><code>EVFLAG_FORKCHECK</code></dt>
- <dd>
- <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
-a fork, you can also make libev check for a fork in each iteration by
-enabling this flag.</p>
- <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
-and thus this might slow down your event loop if you do a lot of loop
-iterations and little real work, but is usually not noticeable (on my
-Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
-without a syscall and thus <i>very</i> fast, but my Linux system also has
-<code>pthread_atfork</code> which is even faster).</p>
- <p>The big advantage of this flag is that you can forget about fork (and
-forget about forgetting to tell libev about forking) when you use this
-flag.</p>
- <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
-environment variable.</p>
- </dd>
- <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
- <dd>
- <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
-libev tries to roll its own fd_set with no limits on the number of fds,
-but if that fails, expect a fairly low limit on the number of fds when
-using this backend. It doesn't scale too well (O(highest_fd)), but its usually
-the fastest backend for a low number of fds.</p>
- </dd>
- <dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
- <dd>
- <p>And this is your standard poll(2) backend. It's more complicated than
-select, but handles sparse fds better and has no artificial limit on the
-number of fds you can use (except it will slow down considerably with a
-lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
- </dd>
- <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
- <dd>
- <p>For few fds, this backend is a bit little slower than poll and select,
-but it scales phenomenally better. While poll and select usually scale like
-O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
-either O(1) or O(active_fds).</p>
- <p>While stopping and starting an I/O watcher in the same iteration will
-result in some caching, there is still a syscall per such incident
-(because the fd could point to a different file description now), so its
-best to avoid that. Also, dup()ed file descriptors might not work very
-well if you register events for both fds.</p>
- <p>Please note that epoll sometimes generates spurious notifications, so you
-need to use non-blocking I/O or other means to avoid blocking when no data
-(or space) is available.</p>
- </dd>
- <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
- <dd>
- <p>Kqueue deserves special mention, as at the time of this writing, it
-was broken on all BSDs except NetBSD (usually it doesn't work with
-anything but sockets and pipes, except on Darwin, where of course its
-completely useless). For this reason its not being "autodetected"
-unless you explicitly specify it explicitly in the flags (i.e. using
-<code>EVBACKEND_KQUEUE</code>).</p>
- <p>It scales in the same way as the epoll backend, but the interface to the
-kernel is more efficient (which says nothing about its actual speed, of
-course). While starting and stopping an I/O watcher does not cause an
-extra syscall as with epoll, it still adds up to four event changes per
-incident, so its best to avoid that.</p>
- </dd>
- <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
- <dd>
- <p>This is not implemented yet (and might never be).</p>
- </dd>
- <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
- <dd>
- <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
-it's really slow, but it still scales very well (O(active_fds)).</p>
- <p>Please note that solaris ports can result in a lot of spurious
-notifications, so you need to use non-blocking I/O or other means to avoid
-blocking when no data (or space) is available.</p>
- </dd>
- <dt><code>EVBACKEND_ALL</code></dt>
- <dd>
- <p>Try all backends (even potentially broken ones that wouldn't be tried
-with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
-<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
- </dd>
- </dl>
- </p>
- <p>If one or more of these are ored into the flags value, then only these
-backends will be tried (in the reverse order as given here). If none are
-specified, most compiled-in backend will be tried, usually in reverse
-order of their flag values :)</p>
- <p>The most typical usage is like this:</p>
-<pre> if (!ev_default_loop (0))
- fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
-
-</pre>
- <p>Restrict libev to the select and poll backends, and do not allow
-environment settings to be taken into account:</p>
-<pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
-
-</pre>
- <p>Use whatever libev has to offer, but make sure that kqueue is used if
-available (warning, breaks stuff, best use only with your own private
-event loop and only if you know the OS supports your types of fds):</p>
-<pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
-
-</pre>
- </dd>
- <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
- <dd>
- <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
-always distinct from the default loop. Unlike the default loop, it cannot
-handle signal and child watchers, and attempts to do so will be greeted by
-undefined behaviour (or a failed assertion if assertions are enabled).</p>
- <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);
- if (!epoller)
- fatal ("no epoll found here, maybe it hides under your chair");
-
-</pre>
- </dd>
- <dt>ev_default_destroy ()</dt>
- <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_loop_count (loop)</dt>
- <dd>
- <p>Returns the count of loop iterations for the loop, which is identical to
-the number of times libev did poll for new events. It starts at <code>0</code> and
-happily wraps around with enough iterations.</p>
- <p>This value can sometimes be useful as a generation counter of sorts (it
-"ticks" the number of loop iterations), as it roughly corresponds with
-<code>ev_prepare</code> and <code>ev_check</code> calls.</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> - Before the first iteration, call any pending watchers.
- * If there are no active watchers (reference count is zero), return.
- - Queue all 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 ev_signal exitsig;
- ev_signal_init (&exitsig, sig_cb, SIGINT);
- ev_signal_start (loop, &exitsig);
- evf_unref (loop);
-
-</pre>
- <p>Example: For some weird reason, unregister the above signal handler again.</p>
-<pre> ev_ref (loop);
- ev_signal_stop (loop, &exitsig);
-
-</pre>
- </dd>
-</dl>
-
-
-
-
-
-</div>
-<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
-<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_STAT</code></dt>
- <dd>
- <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</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_EMBED</code></dt>
- <dd>
- <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
- </dd>
- <dt><code>EV_FORK</code></dt>
- <dd>
- <p>The event loop has been resumed in the child process after fork (see
-<code>ev_fork</code>).</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), you must not change its priority, and you must
-make sure the watcher is available to libev (e.g. you cannot <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>
- <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
- <dt>int ev_priority (ev_TYPE *watcher)</dt>
- <dd>
- <p>Set and query the priority of the watcher. The priority is a small
-integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
-(default: <code>-2</code>). Pending watchers with higher priority will be invoked
-before watchers with lower priority, but priority will not keep watchers
-from being executed (except for <code>ev_idle</code> watchers).</p>
- <p>This means that priorities are <i>only</i> used for ordering callback
-invocation after new events have been received. This is useful, for
-example, to reduce latency after idling, or more often, to bind two
-watchers on the same event and make sure one is called first.</p>
- <p>If you need to suppress invocation when higher priority events are pending
-you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
- <p>You <i>must not</i> change the priority of a watcher as long as it is active or
-pending.</p>
- <p>The default priority used by watchers when no priority has been set is
-always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
- <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
-fine, as long as you do not mind that the priority value you query might
-or might not have been adjusted to be within valid range.</p>
- </dd>
- <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
- <dd>
- <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
-<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
-can deal with that fact.</p>
- </dd>
- <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
- <dd>
- <p>If the watcher is pending, this function returns clears its pending status
-and returns its <code>revents</code> bitset (as if its callback was invoked). If the
-watcher isn't pending it does nothing and returns <code>0</code>.</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 casting your callback type
-instead have been omitted.</p>
-<p>Another common scenario is having some data structure with multiple
-watchers:</p>
-<pre> struct my_biggy
- {
- int some_data;
- ev_timer t1;
- ev_timer t2;
- }
-
-</pre>
-<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
-you need to use <code>offsetof</code>:</p>
-<pre> #include <stddef.h>
-
- static void
- t1_cb (EV_P_ struct ev_timer *w, int revents)
- {
- struct my_biggy big = (struct my_biggy *
- (((char *)w) - offsetof (struct my_biggy, t1));
- }
-
- static void
- t2_cb (EV_P_ struct ev_timer *w, int revents)
- {
- struct my_biggy big = (struct my_biggy *
- (((char *)w) - offsetof (struct my_biggy, t2));
- }
-
-
-
-
-</pre>
-
-</div>
-<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
-<div id="WATCHER_TYPES_CONTENT">
-<p>This section describes each watcher in detail, but will not repeat
-information given in the last section. Any initialisation/set macros,
-functions and members specific to the watcher type are explained.</p>
-<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
-while the watcher is active, you can look at the member and expect some
-sensible content, but you must not modify it (you can modify it while the
-watcher is stopped to your hearts content), or <i>[read-write]</i>, which
-means you can expect it to have some sensible content while the watcher
-is active, but you can also modify it. Modifying it may not do something
-sensible or take immediate effect (or do anything at all), but libev will
-not crash or malfunction in any way.</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
-whether 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>
-
-</div>
-<h3 id="The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</h3>
-<div id="The_special_problem_of_disappearing_-2">
-<p>Some backends (e.g kqueue, epoll) need to be told about closing a file
-descriptor (either by calling <code>close</code> explicitly or by any other means,
-such as <code>dup</code>). The reason is that you register interest in some file
-descriptor, but when it goes away, the operating system will silently drop
-this interest. If another file descriptor with the same number then is
-registered with libev, there is no efficient way to see that this is, in
-fact, a different file descriptor.</p>
-<p>To avoid having to explicitly tell libev about such cases, libev follows
-the following policy: Each time <code>ev_io_set</code> is being called, libev
-will assume that this is potentially a new file descriptor, otherwise
-it is assumed that the file descriptor stays the same. That means that
-you <i>have</i> to call <code>ev_io_set</code> (or <code>ev_io_init</code>) when you change the
-descriptor even if the file descriptor number itself did not change.</p>
-<p>This is how one would do it normally anyway, the important point is that
-the libev application should not optimise around libev but should leave
-optimisations to libev.</p>
-
-
-
-
-
-</div>
-<h3 id="Watcher_Specific_Functions">Watcher-Specific Functions</h3>
-<div id="Watcher_Specific_Functions_CONTENT">
-<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>
- <dt>int fd [read-only]</dt>
- <dd>
- <p>The file descriptor being watched.</p>
- </dd>
- <dt>int events [read-only]</dt>
- <dd>
- <p>The events being watched.</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>
-
-</div>
-<h3 id="Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</h3>
-<div id="Watcher_Specific_Functions_and_Data_-2">
-<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 pending, its pending status is cleared.</p>
- <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
- <p>If the timer is repeating, either start it if necessary (with the
-<code>repeat</code> value), or reset the running timer to the <code>repeat</code> 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 a <code>repeat</code> value of <code>60</code> and then call
-<code>ev_timer_again</code> 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 <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
-automatically restart it if need be.</p>
- <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
-altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
-<pre> ev_timer_init (timer, callback, 0., 5.);
- ev_timer_again (loop, timer);
- ...
- timer->again = 17.;
- ev_timer_again (loop, timer);
- ...
- timer->again = 10.;
- ev_timer_again (loop, timer);
-
-</pre>
- <p>This is more slightly efficient then stopping/starting the timer each time
-you want to modify its timeout value.</p>
- </dd>
- <dt>ev_tstamp repeat [read-write]</dt>
- <dd>
- <p>The current <code>repeat</code> value. Will be used each time the watcher times out
-or <code>ev_timer_again</code> is called and determines the next timeout (if any),
-which is also when any modifications are taken into account.</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).</p>
-<p>They can also be used to implement vastly more complex timers, such as
-triggering an event on each midnight, local time or other, complicated,
-rules.</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>
-
-</div>
-<h3 id="Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</h3>
-<div id="Watcher_Specific_Functions_and_Data_-2">
-<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 (at = time, 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 (at = offset, 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, which can also be negative)
-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>
- <p>For numerical stability it is preferable that the <code>at</code> value is near
-<code>ev_now ()</code> (the current time), but there is no range requirement for
-this value.</p>
- </dd>
- <dt>* manual reschedule mode (at and interval ignored, 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 an <code>ev_prepare</code> watcher, which is legal).</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>
- <dt>ev_tstamp offset [read-write]</dt>
- <dd>
- <p>When repeating, this contains the offset value, otherwise this is the
-absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
- <p>Can be modified any time, but changes only take effect when the periodic
-timer fires or <code>ev_periodic_again</code> is being called.</p>
- </dd>
- <dt>ev_tstamp interval [read-write]</dt>
- <dd>
- <p>The current interval value. Can be modified any time, but changes only
-take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
-called.</p>
- </dd>
- <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
- <dd>
- <p>The current reschedule callback, or <code>0</code>, if this functionality is
-switched off. Can be changed any time, but changes only take effect when
-the periodic timer fires or <code>ev_periodic_again</code> is being called.</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>
-
-</div>
-<h3 id="Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</h3>
-<div id="Watcher_Specific_Functions_and_Data_-2-2">
-<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>
- <dt>int signum [read-only]</dt>
- <dd>
- <p>The signal the watcher watches out for.</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>
-
-</div>
-<h3 id="Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</h3>
-<div id="Watcher_Specific_Functions_and_Data_-2-3">
-<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>
- <dt>int pid [read-only]</dt>
- <dd>
- <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
- </dd>
- <dt>int rpid [read-write]</dt>
- <dd>
- <p>The process id that detected a status change.</p>
- </dd>
- <dt>int rstatus [read-write]</dt>
- <dd>
- <p>The process exit/trace status caused by <code>rpid</code> (see your systems
-<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</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_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
-<div id="code_ev_stat_code_did_the_file_attri-2">
-<p>This watches a filesystem path for attribute changes. That is, it calls
-<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
-compared to the last time, invoking the callback if it did.</p>
-<p>The path does not need to exist: changing from "path exists" to "path does
-not exist" is a status change like any other. The condition "path does
-not exist" is signified by the <code>st_nlink</code> field being zero (which is
-otherwise always forced to be at least one) and all the other fields of
-the stat buffer having unspecified contents.</p>
-<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
-relative and your working directory changes, the behaviour is undefined.</p>
-<p>Since there is no standard to do this, the portable implementation simply
-calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
-can specify a recommended polling interval for this case. If you specify
-a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
-unspecified default</i> value will be used (which you can expect to be around
-five seconds, although this might change dynamically). Libev will also
-impose a minimum interval which is currently around <code>0.1</code>, but thats
-usually overkill.</p>
-<p>This watcher type is not meant for massive numbers of stat watchers,
-as even with OS-supported change notifications, this can be
-resource-intensive.</p>
-<p>At the time of this writing, only the Linux inotify interface is
-implemented (implementing kqueue support is left as an exercise for the
-reader). Inotify will be used to give hints only and should not change the
-semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
-to fall back to regular polling again even with inotify, but changes are
-usually detected immediately, and if the file exists there will be no
-polling.</p>
-
-</div>
-<h3 id="Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</h3>
-<div id="Watcher_Specific_Functions_and_Data_-2-4">
-<dl>
- <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
- <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
- <dd>
- <p>Configures the watcher to wait for status changes of the given
-<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
-be detected and should normally be specified as <code>0</code> to let libev choose
-a suitable value. The memory pointed to by <code>path</code> must point to the same
-path for as long as the watcher is active.</p>
- <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
-relative to the attributes at the time the watcher was started (or the
-last change was detected).</p>
- </dd>
- <dt>ev_stat_stat (ev_stat *)</dt>
- <dd>
- <p>Updates the stat buffer immediately with new values. If you change the
-watched path in your callback, you could call this fucntion to avoid
-detecting this change (while introducing a race condition). Can also be
-useful simply to find out the new values.</p>
- </dd>
- <dt>ev_statdata attr [read-only]</dt>
- <dd>
- <p>The most-recently detected attributes of the file. Although the type is of
-<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
-suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
-was some error while <code>stat</code>ing the file.</p>
- </dd>
- <dt>ev_statdata prev [read-only]</dt>
- <dd>
- <p>The previous attributes of the file. The callback gets invoked whenever
-<code>prev</code> != <code>attr</code>.</p>
- </dd>
- <dt>ev_tstamp interval [read-only]</dt>
- <dd>
- <p>The specified interval.</p>
- </dd>
- <dt>const char *path [read-only]</dt>
- <dd>
- <p>The filesystem path that is being watched.</p>
- </dd>
-</dl>
-<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
-<pre> static void
- passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
- {
- /* /etc/passwd changed in some way */
- if (w->attr.st_nlink)
- {
- printf ("passwd current size %ld\n", (long)w->attr.st_size);
- printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
- printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
- }
- else
- /* you shalt not abuse printf for puts */
- puts ("wow, /etc/passwd is not there, expect problems. "
- "if this is windows, they already arrived\n");
- }
-
- ...
- ev_stat passwd;
-
- ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
- ev_stat_start (loop, &passwd);
-
-
-
-
-</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 no other events of the same or higher
-priority are pending (prepare, check and other idle watchers do not
-count).</p>
-<p>That is, as long as your process is busy handling sockets or timeouts
-(or even signals, imagine) of the same or higher priority it will not be
-triggered. But when your process is idle (or only lower-priority watchers
-are pending), the idle watchers are being called once per event loop
-iteration - until stopped, that is, or your process receives more events
-and becomes busy again with higher priority stuff.</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>
-
-</div>
-<h3 id="Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</h3>
-<div id="Watcher_Specific_Functions_and_Data_-2-5">
-<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> watcher, start it, and in the
-callback, free it. Also, 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>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
-the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
-watchers. Other loops than the current one are fine, however. The
-rationale behind this is that you do not need to check for recursion in
-those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
-<code>ev_check</code> so if you have one watcher of each kind they will always be
-called in pairs bracketing the blocking call.</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. They are also occasionally useful if
-you cache some data and want to flush it before blocking (for example,
-in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
-watcher).</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>
-<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
-priority, to ensure that they are being run before any other watchers
-after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
-too) should not activate ("feed") events into libev. While libev fully
-supports this, they will be called before other <code>ev_check</code> watchers did
-their job. As <code>ev_check</code> watchers are often used to embed other event
-loops those other event loops might be in an unusable state until their
-<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
-others).</p>
-
-</div>
-<h3 id="Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</h3>
-<div id="Watcher_Specific_Functions_and_Data_-2-6">
-<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>There are a number of principal ways to embed other event loops or modules
-into libev. Here are some ideas on how to include libadns into libev
-(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
-use for an actually working example. Another Perl module named <code>EV::Glib</code>
-embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
-into the Glib event loop).</p>
-<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
-and in a check watcher, destroy them and call into libadns. What follows
-is pseudo-code only of course. This requires you to either use a low
-priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
-the callbacks for the IO/timeout watchers might not have been called yet.</p>
-<pre> static ev_io iow [nfd];
- static ev_timer tw;
-
- static void
- io_cb (ev_loop *loop, ev_io *w, int revents)
- {
- }
-
- // create io watchers for each fd and a timer before blocking
- static void
- adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
- {
- int timeout = 3600000;
- struct pollfd fds [nfd];
- // actual code will need to loop here and realloc etc.
- adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
-
- /* the callback is illegal, but won't be called as we stop during check */
- ev_timer_init (&tw, 0, timeout * 1e-3);
- ev_timer_start (loop, &tw);
-
- // create one ev_io per pollfd
- for (int i = 0; i < nfd; ++i)
- {
- ev_io_init (iow + i, io_cb, fds [i].fd,
- ((fds [i].events & POLLIN ? EV_READ : 0)
- | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
-
- fds [i].revents = 0;
- ev_io_start (loop, iow + i);
- }
- }
-
- // stop all watchers after blocking
- static void
- adns_check_cb (ev_loop *loop, ev_check *w, int revents)
- {
- ev_timer_stop (loop, &tw);
-
- for (int i = 0; i < nfd; ++i)
- {
- // set the relevant poll flags
- // could also call adns_processreadable etc. here
- struct pollfd *fd = fds + i;
- int revents = ev_clear_pending (iow + i);
- if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
- if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
-
- // now stop the watcher
- ev_io_stop (loop, iow + i);
- }
-
- adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
- }
-
-</pre>
-<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
-in the prepare watcher and would dispose of the check watcher.</p>
-<p>Method 3: If the module to be embedded supports explicit event
-notification (adns does), you can also make use of the actual watcher
-callbacks, and only destroy/create the watchers in the prepare watcher.</p>
-<pre> static void
- timer_cb (EV_P_ ev_timer *w, int revents)
- {
- adns_state ads = (adns_state)w->data;
- update_now (EV_A);
-
- adns_processtimeouts (ads, &tv_now);
- }
-
- static void
- io_cb (EV_P_ ev_io *w, int revents)
- {
- adns_state ads = (adns_state)w->data;
- update_now (EV_A);
-
- if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
- if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
- }
-
- // do not ever call adns_afterpoll
-
-</pre>
-<p>Method 4: Do not use a prepare or check watcher because the module you
-want to embed is too inflexible to support it. Instead, youc na override
-their poll function. The drawback with this solution is that the main
-loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
-this.</p>
-<pre> static gint
- event_poll_func (GPollFD *fds, guint nfds, gint timeout)
- {
- int got_events = 0;
-
- for (n = 0; n < nfds; ++n)
- // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
-
- if (timeout >= 0)
- // create/start timer
-
- // poll
- ev_loop (EV_A_ 0);
-
- // stop timer again
- if (timeout >= 0)
- ev_timer_stop (EV_A_ &to);
-
- // stop io watchers again - their callbacks should have set
- for (n = 0; n < nfds; ++n)
- ev_io_stop (EV_A_ iow [n]);
-
- return got_events;
- }
-
-
-
-
-</pre>
-
-</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>
-
-</div>
-<h3 id="Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</h3>
-<div id="Watcher_Specific_Functions_and_Data_-2-7">
-<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>
- <dt>struct ev_loop *loop [read-only]</dt>
- <dd>
- <p>The embedded event loop.</p>
- </dd>
-</dl>
-
-
-
-
-
-</div>
-<h2 id="code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</h2>
-<div id="code_ev_fork_code_the_audacity_to_re-2">
-<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
-whoever is a good citizen cared to tell libev about it by calling
-<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
-event loop blocks next and before <code>ev_check</code> watchers are being called,
-and only in the child after the fork. If whoever good citizen calling
-<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
-handlers will be invoked, too, of course.</p>
-
-</div>
-<h3 id="Watcher_Specific_Functions_and_Data_-10">Watcher-Specific Functions and Data Members</h3>
-<div id="Watcher_Specific_Functions_and_Data_-2-8">
-<dl>
- <dt>ev_fork_init (ev_signal *, callback)</dt>
- <dd>
- <p>Initialises and configures the fork watcher - it has no parameters of any
-kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
-believe me.</p>
- </dd>
-</dl>
-
-
-
-
-
-</div>
-<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
-<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>
-<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>
-<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>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. It should support all the same embedding
-options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
-<p>Care has been taken to keep the overhead low. The only data member the C++
-classes add (compared to plain C-style watchers) is the event loop pointer
-that the watcher is associated with (or no additional members at all if
-you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
-<p>Currently, functions, and static and non-static member functions can be
-used as callbacks. Other types should be easy to add as long as they only
-need one additional pointer for context. If you need support for other
-types of functors please contact the author (preferably after implementing
-it).</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 ()</dt>
- <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
- <dt>ev::TYPE::~TYPE</dt>
- <dd>
- <p>The constructor (optionally) takes an event loop to associate the watcher
-with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
- <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
-<code>set</code> method before starting it.</p>
- <p>It will not set a callback, however: You have to call the templated <code>set</code>
-method to set a callback before you can start the watcher.</p>
- <p>(The reason why you have to use a method is a limitation in C++ which does
-not allow explicit template arguments for constructors).</p>
- <p>The destructor automatically stops the watcher if it is active.</p>
- </dd>
- <dt>w->set<class, &class::method> (object *)</dt>
- <dd>
- <p>This method sets the callback method to call. The method has to have a
-signature of <code>void (*)(ev_TYPE &, int)</code>, it receives the watcher as
-first argument and the <code>revents</code> as second. The object must be given as
-parameter and is stored in the <code>data</code> member of the watcher.</p>
- <p>This method synthesizes efficient thunking code to call your method from
-the C callback that libev requires. If your compiler can inline your
-callback (i.e. it is visible to it at the place of the <code>set</code> call and
-your compiler is good :), then the method will be fully inlined into the
-thunking function, making it as fast as a direct C callback.</p>
- <p>Example: simple class declaration and watcher initialisation</p>
-<pre> struct myclass
- {
- void io_cb (ev::io &w, int revents) { }
- }
-
- myclass obj;
- ev::io iow;
- iow.set <myclass, &myclass::io_cb> (&obj);
-
-</pre>
- </dd>
- <dt>w->set<function> (void *data = 0)</dt>
- <dd>
- <p>Also sets a callback, but uses a static method or plain function as
-callback. The optional <code>data</code> argument will be stored in the watcher's
-<code>data</code> member and is free for you to use.</p>
- <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &w, int)</code>.</p>
- <p>See the method-<code>set</code> above for more details.</p>
- <p>Example:</p>
-<pre> static void io_cb (ev::io &w, int revents) { }
- iow.set <io_cb> ();
-
-</pre>
- </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 when reconfiguring it with this
-method.</p>
- </dd>
- <dt>w->start ()</dt>
- <dd>
- <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
-constructor already stores the event 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>
- <dt>w->update () <code>ev::stat</code> only</dt>
- <dd>
- <p>Invokes <code>ev_stat_stat</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 .set <myclass, &myclass::io_cb > (this);
- idle.set <myclass, &myclass::idle_cb> (this);
-
- io.start (fd, ev::READ);
- }
-
-
-
-
-</pre>
-
-</div>
-<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
-<div id="MACRO_MAGIC_CONTENT">
-<p>Libev can be compiled with a variety of options, the most fundemantal is
-<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
-callbacks have an initial <code>struct ev_loop *</code> argument.</p>
-<p>To make it easier to write programs that cope with either variant, the
-following macros are defined:</p>
-<dl>
- <dt><code>EV_A</code>, <code>EV_A_</code></dt>
- <dd>
- <p>This provides the loop <i>argument</i> for functions, if one is required ("ev
-loop argument"). The <code>EV_A</code> form is used when this is the sole argument,
-<code>EV_A_</code> is used when other arguments are following. Example:</p>
-<pre> ev_unref (EV_A);
- ev_timer_add (EV_A_ watcher);
- ev_loop (EV_A_ 0);
-
-</pre>
- <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
-which is often provided by the following macro.</p>
- </dd>
- <dt><code>EV_P</code>, <code>EV_P_</code></dt>
- <dd>
- <p>This provides the loop <i>parameter</i> for functions, if one is required ("ev
-loop parameter"). The <code>EV_P</code> form is used when this is the sole parameter,
-<code>EV_P_</code> is used when other parameters are following. Example:</p>
-<pre> // this is how ev_unref is being declared
- static void ev_unref (EV_P);
-
- // this is how you can declare your typical callback
- static void cb (EV_P_ ev_timer *w, int revents)
-
-</pre>
- <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
-suitable for use with <code>EV_A</code>.</p>
- </dd>
- <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
- <dd>
- <p>Similar to the other two macros, this gives you the value of the default
-loop, if multiple loops are supported ("ev loop default").</p>
- </dd>
-</dl>
-<p>Example: Declare and initialise a check watcher, utilising the above
-macros so it will work regardless of whether multiple loops are supported
-or not.</p>
-<pre> static void
- check_cb (EV_P_ ev_timer *w, int revents)
- {
- ev_check_stop (EV_A_ w);
- }
-
- ev_check check;
- ev_check_init (&check, check_cb);
- ev_check_start (EV_DEFAULT_ &check);
- ev_loop (EV_DEFAULT_ 0);
-
-</pre>
-
-</div>
-<h1 id="EMBEDDING">EMBEDDING</h1>
-<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 enabled 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_USE_INOTIFY</dt>
- <dd>
- <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
-interface to speed up <code>ev_stat</code> watchers. Its actual availability will
-be detected at runtime.</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_MINPRI</dt>
- <dt>EV_MAXPRI</dt>
- <dd>
- <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
-<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
-provide for more priorities by overriding those symbols (usually defined
-to be <code>-2</code> and <code>2</code>, respectively).</p>
- <p>When doing priority-based operations, libev usually has to linearly search
-all the priorities, so having many of them (hundreds) uses a lot of space
-and time, so using the defaults of five priorities (-2 .. +2) is usually
-fine.</p>
- <p>If your embedding app does not need any priorities, defining these both to
-<code>0</code> will save some memory and cpu.</p>
- </dd>
- <dt>EV_PERIODIC_ENABLE</dt>
- <dd>
- <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
-defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
-code.</p>
- </dd>
- <dt>EV_IDLE_ENABLE</dt>
- <dd>
- <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
-defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
-code.</p>
- </dd>
- <dt>EV_EMBED_ENABLE</dt>
- <dd>
- <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
-defined to be <code>0</code>, then they are not.</p>
- </dd>
- <dt>EV_STAT_ENABLE</dt>
- <dd>
- <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
-defined to be <code>0</code>, then they are not.</p>
- </dd>
- <dt>EV_FORK_ENABLE</dt>
- <dd>
- <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
-defined to be <code>0</code>, then they are not.</p>
- </dd>
- <dt>EV_MINIMAL</dt>
- <dd>
- <p>If you need to shave off some kilobytes of code at the expense of some
-speed, define this symbol to <code>1</code>. Currently only used for gcc to override
-some inlining decisions, saves roughly 30% codesize of amd64.</p>
- </dd>
- <dt>EV_PID_HASHSIZE</dt>
- <dd>
- <p><code>ev_child</code> watchers use a small hash table to distribute workload by
-pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
-than enough. If you need to manage thousands of children you might want to
-increase this value (<i>must</i> be a power of two).</p>
- </dd>
- <dt>EV_INOTIFY_HASHSIZE</dt>
- <dd>
- <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
-inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
-usually more than enough. If you need to manage thousands of <code>ev_stat</code>
-watchers you might want to increase this value (<i>must</i> be a power of
-two).</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 <code>struct ev_loop *</code> 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 configure choices:</p>
-<pre> #define EV_MINIMAL 1
- #define EV_USE_POLL 0
- #define EV_MULTIPLICITY 0
- #define EV_PERIODIC_ENABLE 0
- #define EV_STAT_ENABLE 0
- #define EV_FORK_ENABLE 0
- #define EV_CONFIG_H <config.h>
- #define EV_MINPRI 0
- #define EV_MAXPRI 0
-
- #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="COMPLEXITIES">COMPLEXITIES</h1>
-<div id="COMPLEXITIES_CONTENT">
- <p>In this section the complexities of (many of) the algorithms used inside
-libev will be explained. For complexity discussions about backends see the
-documentation for <code>ev_default_init</code>.</p>
- <p>All of the following are about amortised time: If an array needs to be
-extended, libev needs to realloc and move the whole array, but this
-happens asymptotically never with higher number of elements, so O(1) might
-mean it might do a lengthy realloc operation in rare cases, but on average
-it is much faster and asymptotically approaches constant time.</p>
- <p>
- <dl>
- <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
- <dd>
- <p>This means that, when you have a watcher that triggers in one hour and
-there are 100 watchers that would trigger before that then inserting will
-have to skip those 100 watchers.</p>
- </dd>
- <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
- <dd>
- <p>That means that for changing a timer costs less than removing/adding them
-as only the relative motion in the event queue has to be paid for.</p>
- </dd>
- <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
- <dd>
- <p>These just add the watcher into an array or at the head of a list.
-=item Stopping check/prepare/idle watchers: O(1)</p>
- </dd>
- <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
- <dd>
- <p>These watchers are stored in lists then need to be walked to find the
-correct watcher to remove. The lists are usually short (you don't usually
-have many watchers waiting for the same fd or signal).</p>
- </dd>
- <dt>Finding the next timer per loop iteration: O(1)</dt>
- <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
- <dd>
- <p>A change means an I/O watcher gets started or stopped, which requires
-libev to recalculate its status (and possibly tell the kernel).</p>
- </dd>
- <dt>Activating one watcher: O(1)</dt>
- <dt>Priority handling: O(number_of_priorities)</dt>
- <dd>
- <p>Priorities are implemented by allocating some space for each
-priority. When doing priority-based operations, libev usually has to
-linearly search all the priorities.</p>
- </dd>
- </dl>
- </p>
-
-
-
-
-
-</div>
-<h1 id="AUTHOR">AUTHOR</h1>
-<div id="AUTHOR_CONTENT">
- <p>Marc Lehmann <libev@schmorp.de>.</p>
-
-</div>
-</div></body>
-</html>
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