.\" ========================================================================
.\"
.IX Title ""<STANDARD INPUT>" 1"
-.TH "<STANDARD INPUT>" 1 "2007-12-07" "perl v5.8.8" "User Contributed Perl Documentation"
+.TH "<STANDARD INPUT>" 1 "2007-12-08" "perl v5.8.8" "User Contributed Perl Documentation"
.SH "NAME"
libev \- a high performance full\-featured event loop written in C
.SH "SYNOPSIS"
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
+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: <http://cvs.schmorp.de/libev/ev.html>.
+.PP
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.
.Sp
Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
.Sp
-.Vb 18
+.Vb 19
+\& - Before the first iteration, call any pending watchers.
\& * If there are no active watchers (reference count is zero), return.
-\& - Queue prepare watchers and then call all outstanding watchers.
+\& - 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".
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
-\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
-libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
+\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
+make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
+it).
.IP "callback ev_cb (ev_TYPE *watcher)" 4
.IX Item "callback ev_cb (ev_TYPE *watcher)"
Returns the callback currently set on the watcher.
If you need to suppress invocation when higher priority events are pending
you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
.Sp
+You \fImust not\fR change the priority of a watcher as long as it is active or
+pending.
+.Sp
The default priority used by watchers when no priority has been set is
always \f(CW0\fR, which is supposed to not be too high and not be too low :).
.Sp
Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR 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.
+.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
+.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
+Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
+\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
+can deal with that fact.
+.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
+.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
+If the watcher is pending, this function returns clears its pending status
+and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
+watcher isn't pending it does nothing and returns \f(CW0\fR.
.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
.PP
If you cannot run the fd in non-blocking mode (for example you should not
play around with an Xlib connection), then you have to seperately re-test
-wether a file descriptor is really ready with a known-to-be good interface
+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).
.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
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).
+.PP
+It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
+priority, to ensure that they are being run before any other watchers
+after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
+too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
+supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers did
+their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other event
+loops those other event loops might be in an unusable state until their
+\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
+others).
.IP "ev_prepare_init (ev_prepare *, callback)" 4
.IX Item "ev_prepare_init (ev_prepare *, callback)"
.PD 0
parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
macros, but using them is utterly, utterly and completely pointless.
.PP
-Example: To include a library such as adns, you would add \s-1IO\s0 watchers
-and a timeout watcher in a prepare handler, as required by libadns, and
-in a check watcher, destroy them and call into libadns. What follows is
-pseudo-code only of course:
+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 \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
+use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
+embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
+into the Glib event loop).
+.PP
+Method 1: Add \s-1IO\s0 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 \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
+the callbacks for the IO/timeout watchers might not have been called yet.
.PP
.Vb 2
\& static ev_io iow [nfd];
\& static ev_timer tw;
.Ve
.PP
-.Vb 9
+.Vb 4
\& static void
\& io_cb (ev_loop *loop, ev_io *w, int revents)
\& {
-\& // set the relevant poll flags
-\& // could also call adns_processreadable etc. here
-\& struct pollfd *fd = (struct pollfd *)w->data;
-\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
-\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
\& }
.Ve
.PP
.Ve
.PP
.Vb 6
-\& // create on ev_io per pollfd
+\& // 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 & POLLOUT ? EV_WRITE : 0)));
.Ve
.PP
-.Vb 5
+.Vb 4
\& fds [i].revents = 0;
-\& iow [i].data = fds + i;
\& ev_io_start (loop, iow + i);
\& }
\& }
\& ev_timer_stop (loop, &tw);
.Ve
.PP
-.Vb 2
+.Vb 8
\& for (int i = 0; i < nfd; ++i)
-\& ev_io_stop (loop, iow + 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;
+.Ve
+.PP
+.Vb 3
+\& // now stop the watcher
+\& ev_io_stop (loop, iow + i);
+\& }
.Ve
.PP
.Vb 2
\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
\& }
.Ve
+.PP
+Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
+in the prepare watcher and would dispose of the check watcher.
+.PP
+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.
+.PP
+.Vb 5
+\& static void
+\& timer_cb (EV_P_ ev_timer *w, int revents)
+\& {
+\& adns_state ads = (adns_state)w->data;
+\& update_now (EV_A);
+.Ve
+.PP
+.Vb 2
+\& adns_processtimeouts (ads, &tv_now);
+\& }
+.Ve
+.PP
+.Vb 5
+\& static void
+\& io_cb (EV_P_ ev_io *w, int revents)
+\& {
+\& adns_state ads = (adns_state)w->data;
+\& update_now (EV_A);
+.Ve
+.PP
+.Vb 3
+\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
+\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
+\& }
+.Ve
+.PP
+.Vb 1
+\& // do not ever call adns_afterpoll
+.Ve
+.PP
+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 \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
+this.
+.PP
+.Vb 4
+\& static gint
+\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
+\& {
+\& int got_events = 0;
+.Ve
+.PP
+.Vb 2
+\& for (n = 0; n < nfds; ++n)
+\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
+.Ve
+.PP
+.Vb 2
+\& if (timeout >= 0)
+\& // create/start timer
+.Ve
+.PP
+.Vb 2
+\& // poll
+\& ev_loop (EV_A_ 0);
+.Ve
+.PP
+.Vb 3
+\& // stop timer again
+\& if (timeout >= 0)
+\& ev_timer_stop (EV_A_ &to);
+.Ve
+.PP
+.Vb 3
+\& // stop io watchers again - their callbacks should have set
+\& for (n = 0; n < nfds; ++n)
+\& ev_io_stop (EV_A_ iow [n]);
+.Ve
+.PP
+.Vb 2
+\& return got_events;
+\& }
+.Ve
.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
.IX Subsection "ev_embed - when one backend isn't enough..."
\& #include <ev++.h>
.Ve
.PP
-(it is not installed by default). This automatically includes \fIev.h\fR
-and puts all of its definitions (many of them macros) into the global
-namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.
+This automatically includes \fIev.h\fR and puts all of its definitions (many
+of them macros) into the global namespace. All \*(C+ specific things are
+put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
+options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
+.PP
+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 \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
.PP
-It should support all the same embedding options as \fIev.h\fR, most notably
-\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
+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).
.PP
Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
.Sp
All of those classes have these methods:
.RS 4
-.IP "ev::TYPE::TYPE (object *, object::method *)" 4
-.IX Item "ev::TYPE::TYPE (object *, object::method *)"
+.IP "ev::TYPE::TYPE ()" 4
+.IX Item "ev::TYPE::TYPE ()"
.PD 0
-.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4
-.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"
+.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
+.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
.IP "ev::TYPE::~TYPE" 4
.IX Item "ev::TYPE::~TYPE"
.PD
-The constructor takes a pointer to an object and a method pointer to
-the event handler callback to call in this class. The constructor calls
-\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method
-before starting it. If you do not specify a loop then the constructor
-automatically associates the default loop with this watcher.
+The constructor (optionally) takes an event loop to associate the watcher
+with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
+.Sp
+The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
+\&\f(CW\*(C`set\*(C'\fR method before starting it.
+.Sp
+It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
+method to set a callback before you can start the watcher.
+.Sp
+(The reason why you have to use a method is a limitation in \*(C+ which does
+not allow explicit template arguments for constructors).
.Sp
The destructor automatically stops the watcher if it is active.
+.IP "w\->set<class, &class::method> (object *)" 4
+.IX Item "w->set<class, &class::method> (object *)"
+This method sets the callback method to call. The method has to have a
+signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
+first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
+parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
+.Sp
+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 \f(CW\*(C`set\*(C'\fR 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.
+.Sp
+Example: simple class declaration and watcher initialisation
+.Sp
+.Vb 4
+\& struct myclass
+\& {
+\& void io_cb (ev::io &w, int revents) { }
+\& }
+.Ve
+.Sp
+.Vb 3
+\& myclass obj;
+\& ev::io iow;
+\& iow.set <myclass, &myclass::io_cb> (&obj);
+.Ve
+.IP "w\->set<function> (void *data = 0)" 4
+.IX Item "w->set<function> (void *data = 0)"
+Also sets a callback, but uses a static method or plain function as
+callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
+\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
+.Sp
+The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
+.Sp
+See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
+.Sp
+Example:
+.Sp
+.Vb 2
+\& static void io_cb (ev::io &w, int revents) { }
+\& iow.set <io_cb> ();
+.Ve
.IP "w\->set (struct ev_loop *)" 4
.IX Item "w->set (struct ev_loop *)"
Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
.IP "w\->set ([args])" 4
.IX Item "w->set ([args])"
Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
-called at least once. Unlike the C counterpart, an active watcher gets
-automatically stopped and restarted.
+called at least once. Unlike the C counterpart, an active watcher gets
+automatically stopped and restarted when reconfiguring it with this
+method.
.IP "w\->start ()" 4
.IX Item "w->start ()"
-Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the
-constructor already takes the loop.
+Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
+constructor already stores the event loop.
.IP "w\->stop ()" 4
.IX Item "w->stop ()"
Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
\& }
.Ve
.PP
-.Vb 6
+.Vb 4
\& myclass::myclass (int fd)
-\& : io (this, &myclass::io_cb),
-\& idle (this, &myclass::idle_cb)
\& {
+\& io .set <myclass, &myclass::io_cb > (this);
+\& idle.set <myclass, &myclass::idle_cb> (this);
+.Ve
+.PP
+.Vb 2
\& io.start (fd, ev::READ);
\& }
.Ve
.SH "MACRO MAGIC"
.IX Header "MACRO MAGIC"
Libev can be compiled with a variety of options, the most fundemantal is
-\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines wether (most) functions and
+\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) functions and
callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
.PP
To make it easier to write programs that cope with either variant, the
loop, if multiple loops are supported (\*(L"ev loop default\*(R").
.PP
Example: Declare and initialise a check watcher, utilising the above
-macros so it will work regardless of wether multiple loops are supported
+macros so it will work regardless of whether multiple loops are supported
or not.
.PP
.Vb 5
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.
+.IP "\s-1EV_MINPRI\s0" 4
+.IX Item "EV_MINPRI"
+.PD 0
+.IP "\s-1EV_MAXPRI\s0" 4
+.IX Item "EV_MAXPRI"
+.PD
+The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
+\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
+provide for more priorities by overriding those symbols (usually defined
+to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
+.Sp
+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.
+.Sp
+If your embedding app does not need any priorities, defining these both to
+\&\f(CW0\fR will save some memory and cpu.
.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
.IX Item "EV_PERIODIC_ENABLE"
If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
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 \f(CW\*(C`ev_default_init\*(C'\fR.
+.Sp
+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.
.RS 4
.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
-.PD 0
+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.
.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
+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.
.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
-.IP "Stopping check/prepare/idle watchers: O(1)" 4
-.IX Item "Stopping check/prepare/idle watchers: O(1)"
+These just add the watcher into an array or at the head of a list.
+=item Stopping check/prepare/idle watchers: O(1)
.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
+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).
.IP "Finding the next timer per loop iteration: O(1)" 4
.IX Item "Finding the next timer per loop iteration: O(1)"
+.PD 0
.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
+.PD
+A change means an I/O watcher gets started or stopped, which requires
+libev to recalculate its status (and possibly tell the kernel).
.IP "Activating one watcher: O(1)" 4
.IX Item "Activating one watcher: O(1)"
+.PD 0
+.IP "Priority handling: O(number_of_priorities)" 4
+.IX Item "Priority handling: O(number_of_priorities)"
+.PD
+Priorities are implemented by allocating some space for each
+priority. When doing priority-based operations, libev usually has to
+linearly search all the priorities.
.RE
.RS 4
-.PD
.SH "AUTHOR"
.IX Header "AUTHOR"
Marc Lehmann <libev@schmorp.de>.
projects / software / libev.git / blobdiff