<meta name="description" content="Pod documentation for libev" />
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- <meta name="created" content="Tue Nov 27 21:14:27 2007" />
+ <meta name="created" content="Wed Nov 28 19:29:25 2007" />
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<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>
</ul><hr />
<!-- INDEX END -->
-<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<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><p><a href="#TOP" class="toplink">Top</a></p>
+<h1 id="SYNOPSIS">SYNOPSIS</h1>
<div id="SYNOPSIS_CONTENT">
-<pre> /* this is the only header you need */
- #include <ev.h>
+<pre> #include <ev.h>
+
+</pre>
+
+</div>
+<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
+<div id="EXAMPLE_PROGRAM_CONTENT">
+<pre> #include <ev.h>
- /* what follows is a fully working example program */
ev_io stdin_watcher;
ev_timer timeout_watcher;
</pre>
</div>
-<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<h1 id="DESCRIPTION">DESCRIPTION</h1>
<div id="DESCRIPTION_CONTENT">
<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
watcher.</p>
</div>
-<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<h1 id="FEATURES">FEATURES</h1>
<div id="FEATURES_CONTENT">
-<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific
-kqueue mechanisms for file descriptor events, relative timers, absolute
-timers with customised rescheduling, signal events, process status change
-events (related to SIGCHLD), and event watchers dealing with the event
-loop mechanism itself (idle, prepare and check watchers). It also is quite
-fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing
-it to libevent for example).</p>
+<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><p><a href="#TOP" class="toplink">Top</a></p>
+<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 the file
-<cite>README.embed</cite> in the libev distribution. 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>
+<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><p><a href="#TOP" class="toplink">Top</a></p>
+<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
it, you should treat it as such.</p>
</div>
-<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<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>
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>
+ <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));
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, size_t size))</dt>
+ <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
<dd>
- <p>Sets the allocation function to use (the prototype and semantics are
-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>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: better than mine).</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)
{
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: do the same thing as libev does internally:</p>
+ <p>Example: This is basically the same thing that libev does internally, too.</p>
<pre> static void
fatal_error (const char *msg)
{
</dl>
</div>
-<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<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
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>
+ <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");
were used, return, otherwise continue with step *.
</pre>
- <p>Example: queue some jobs and then loop until no events are outsanding
+ <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..)
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>
+ <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
running when nothing else is active.</p>
-<pre> struct dv_signal exitsig;
+<pre> struct ev_signal exitsig;
ev_signal_init (&exitsig, sig_cb, SIGINT);
- ev_signal_start (myloop, &exitsig);
- evf_unref (myloop);
+ 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 (myloop);
- ev_signal_stop (myloop, &exitsig);
+ <p>Example: For some weird reason, unregister the above signal handler again.</p>
+<pre> ev_ref (loop);
+ ev_signal_stop (loop, &exitsig);
</pre>
</dd>
</div>
-<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<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
<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
libev (e.g. you cnanot <code>free ()</code> it).</p>
</dd>
- <dt>callback = ev_cb (ev_TYPE *watcher)</dt>
+ <dt>callback ev_cb (ev_TYPE *watcher)</dt>
<dd>
<p>Returns the callback currently set on the watcher.</p>
</dd>
}
</pre>
-<p>More interesting and less C-conformant ways of catsing your callback type
-have been omitted....</p>
+<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><p><a href="#TOP" class="toplink">Top</a></p>
+<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,
<p>The events being watched.</p>
</dd>
</dl>
-<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
+<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>
+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)
{
which is also when any modifications are taken into account.</p>
</dd>
</dl>
-<p>Example: create a timer that fires after 60 seconds.</p>
+<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)
{
ev_timer_start (loop, &mytimer);
</pre>
-<p>Example: create a timeout timer that times out after 10 seconds of
+<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)
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
+<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
ev_periodic_start (loop, &hourly_tick);
</pre>
-<p>Example: the same as above, but use a reschedule callback to do it:</p>
+<p>Example: The same as above, but use a reschedule callback to do it:</p>
<pre> #include <math.h>
static ev_tstamp
ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
</pre>
-<p>Example: call a callback every hour, starting now:</p>
+<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);
<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>
+<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)
{
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> regulalry on the path to see if it changed somehow. You
+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
<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, no specific OS backends are implemented, but
-if demand increases, at least a kqueue and inotify backend will be added.</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>
<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>
believe me.</p>
</dd>
</dl>
-<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
-callback, free it. Alos, use no error checking, as usual.</p>
+<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)
{
</div>
-<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<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>
</div>
-<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<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>
</div>
-<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<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
</pre>
</div>
-<h1 id="MACRO_MAGIC">MACRO MAGIC</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<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 wether (most) functions and
</pre>
</div>
-<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<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
<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
<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.</p>
+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>
</pre>
</div>
-<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<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
<dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
<dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
<dt>Stopping check/prepare/idle watchers: O(1)</dt>
- <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
+ <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
<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>
<dt>Activating one watcher: O(1)</dt>
</div>
-<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<h1 id="AUTHOR">AUTHOR</h1>
<div id="AUTHOR_CONTENT">
<p>Marc Lehmann <libev@schmorp.de>.</p>
projects / software / libev.git / blobdiff