document c++ api

[software/libev.git] / ev.3

diff --git a/ev.3 b/ev.3
index 4916dd4a27d7fcb1c8ee4ced0b9fca8623f48642..46ffd2c1e0ffe1a6930830fbc0d49ca65c521da9 100644 (file)
--- a/ev.3
+++ b/ev.3
@@ -129,7 +129,7 @@
 .\" ========================================================================
 .\"
 .IX Title ""<STANDARD INPUT>" 1"
 .\" ========================================================================
 .\"
 .IX Title ""<STANDARD INPUT>" 1"

-.TH "<STANDARD INPUT>" 1 "2007-11-23" "perl v5.8.8" "User Contributed Perl Documentation"
+.TH "<STANDARD INPUT>" 1 "2007-11-24" "perl v5.8.8" "User Contributed Perl Documentation"

 .SH "NAME"
 libev \- a high performance full\-featured event loop written in C
 .SH "SYNOPSIS"
 .SH "NAME"
 libev \- a high performance full\-featured event loop written in C
 .SH "SYNOPSIS"


@@ -233,6 +233,15 @@ returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is br
 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.
 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.

+.IP "unsigned int ev_embeddable_backends ()" 4
+.IX Item "unsigned int ev_embeddable_backends ()"
+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
+\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
+recommended ones.
+.Sp
+See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.

 .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
 .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
 Sets the allocation function to use (the prototype is similar to the
 .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
 .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
 Sets the allocation function to use (the prototype is similar to the


@@ -451,8 +460,12 @@ Example: try to create a event loop that uses epoll and nothing else.
 .IP "ev_default_destroy ()" 4
 .IX Item "ev_default_destroy ()"
 Destroys the default loop again (frees all memory and kernel state
 .IP "ev_default_destroy ()" 4
 .IX Item "ev_default_destroy ()"
 Destroys the default loop again (frees all memory and kernel state

-etc.). This stops all registered event watchers (by not touching them in
-any way whatsoever, although you cannot rely on this :).
+etc.). None of the active event watchers will be stopped in the normal
+sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
+responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
+calling this function, or cope with the fact afterwards (which is usually
+the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
+for example).

 .IP "ev_loop_destroy (loop)" 4
 .IX Item "ev_loop_destroy (loop)"
 Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
 .IP "ev_loop_destroy (loop)" 4
 .IX Item "ev_loop_destroy (loop)"
 Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an


@@ -638,12 +651,7 @@ corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
 .PP
 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
 .PP
 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 set macro.
-.PP
-You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
-(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
-callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
-(watcher *)\*(C'\fR macro.
+reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.

 .PP
 Each and every callback receives the event loop pointer as first, the
 registered watcher structure as second, and a bitset of received events as
 .PP
 Each and every callback receives the event loop pointer as first, the
 registered watcher structure as second, and a bitset of received events as


@@ -711,6 +719,75 @@ 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 \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
 programs, though, so beware.
 your callbacks is well-written it can just attempt the operation and cope
 with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
 programs, though, so beware.

+.Sh "\s-1SUMMARY\s0 \s-1OF\s0 \s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
+.IX Subsection "SUMMARY OF GENERIC WATCHER FUNCTIONS"
+In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
+e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
+.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
+.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
+.IX Item "ev_init (ev_TYPE *watcher, callback)"
+This macro initialises the generic portion of a watcher. The contents
+of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
+the generic parts of the watcher are initialised, you \fIneed\fR to call
+the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
+type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
+which rolls both calls into one.
+.Sp
+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.
+.Sp
+The callbakc is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
+int revents)\*(C'\fR.
+.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
+.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
+.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
+This macro initialises the type-specific parts of a watcher. You need to
+call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
+call \f(CW\*(C`ev_TYPE_set\*(C'\fR 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 \f(CW\*(C`ev_init\*(C'\fR macro).
+.Sp
+Although some watcher types do not have type-specific arguments
+(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
+.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
+.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
+.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
+This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
+calls into a single call. This is the most convinient method to initialise
+a watcher. The same limitations apply, of course.
+.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
+.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
+.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
+Starts (activates) the given watcher. Only active watchers will receive
+events. If the watcher is already active nothing will happen.
+.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
+.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
+.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
+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
+\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR 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 \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
+.IP "bool ev_is_active (ev_TYPE *watcher)" 4
+.IX Item "bool ev_is_active (ev_TYPE *watcher)"
+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.
+.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
+.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
+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).
+.IP "callback = ev_cb (ev_TYPE *watcher)" 4
+.IX Item "callback = ev_cb (ev_TYPE *watcher)"
+Returns the callback currently set on the watcher.
+.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
+.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
+Change the callback. You can change the callback at virtually any time
+(modulo threads).

 .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
 .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


@@ -920,8 +997,8 @@ Periodic watchers are also timers of a kind, but they are very versatile
 Unlike \f(CW\*(C`ev_timer\*(C'\fR'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 \*(L"at\*(R" some specific point in time. For example, if you tell a
 Unlike \f(CW\*(C`ev_timer\*(C'\fR'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 \*(L"at\*(R" some specific point in time. For example, if you tell a

-periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()
-+ 10.>) and then reset your system clock to the last year, then it will
+periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
++ 10.\*(C'\fR) and then reset your system clock to the last year, then it will

 take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
 roughly 10 seconds later and of course not if you reset your system time
 again).
 take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
 roughly 10 seconds later and of course not if you reset your system time
 again).


@@ -1161,9 +1238,10 @@ Prepare and check watchers are usually (but not always) used in tandem:
 prepare watchers get invoked before the process blocks and check watchers
 afterwards.
 .PP
 prepare watchers get invoked before the process blocks and check watchers
 afterwards.
 .PP

-Their main purpose is to integrate other event mechanisms into libev. This
-could be used, for example, to track variable changes, implement your own
-watchers, integrate net-snmp or a coroutine library and lots more.
+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.

 .PP
 This is done by examining in each prepare call which file descriptors need
 to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
 .PP
 This is done by examining in each prepare call which file descriptors need
 to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for


@@ -1193,6 +1271,98 @@ parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C
 macros, but using them is utterly, utterly and completely pointless.
 .PP
 Example: *TODO*.
 macros, but using them is utterly, utterly and completely pointless.
 .PP
 Example: *TODO*.

+.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"
+This is a rather advanced watcher type that lets you embed one event loop
+into another (currently only \f(CW\*(C`ev_io\*(C'\fR 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).
+.PP
+There are primarily two reasons you would want that: work around bugs and
+prioritise I/O.
+.PP
+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.
+.PP
+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.
+.PP
+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 \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR 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 \f(CW0\fR, in which case the embed watcher will automatically execute the
+embedded loop sweep.
+.PP
+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 \f(CW0\fR to avoid having to specify one if you are not
+interested in that.
+.PP
+Also, there have not currently been made special provisions for forking:
+when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
+but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
+yourself.
+.PP
+Unfortunately, not all backends are embeddable, only the ones returned by
+\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
+portable one.
+.PP
+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:
+.PP
+.Vb 3
+\&  struct ev_loop *loop_hi = ev_default_init (0);
+\&  struct ev_loop *loop_lo = 0;
+\&  struct ev_embed embed;
+.Ve
+.PP
+.Vb 5
+\&  // 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;
+.Ve
+.PP
+.Vb 8
+\&  // 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;
+.Ve
+.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
+.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
+.PD 0
+.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
+.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
+.PD
+Configures the watcher to embed the given loop, which must be
+embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR 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).
+.IP "ev_embed_sweep (loop, ev_embed *)" 4
+.IX Item "ev_embed_sweep (loop, ev_embed *)"
+Make a single, non-blocking sweep over the embedded loop. This works
+similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
+apropriate way for embedded loops.

 .SH "OTHER FUNCTIONS"
 .IX Header "OTHER FUNCTIONS"
 There are some other functions of possible interest. Described. Here. Now.
 .SH "OTHER FUNCTIONS"
 .IX Header "OTHER FUNCTIONS"
 There are some other functions of possible interest. Described. Here. Now.


@@ -1231,18 +1401,19 @@ value passed to \f(CW\*(C`ev_once\*(C'\fR:
 .Vb 1
 \&  ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
 .Ve
 .Vb 1
 \&  ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
 .Ve

-.IP "ev_feed_event (loop, watcher, int events)" 4
-.IX Item "ev_feed_event (loop, watcher, int events)"
+.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
+.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"

 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).
 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).

-.IP "ev_feed_fd_event (loop, int fd, int revents)" 4
-.IX Item "ev_feed_fd_event (loop, int fd, int revents)"
+.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
+.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"

 Feed an event on the given fd, as if a file descriptor backend detected
 the given events it.
 Feed an event on the given fd, as if a file descriptor backend detected
 the given events it.

-.IP "ev_feed_signal_event (loop, int signum)" 4
-.IX Item "ev_feed_signal_event (loop, int signum)"
-Feed an event as if the given signal occured (loop must be the default loop!).
+.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
+.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
+Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
+loop!).

 .SH "LIBEVENT EMULATION"
 .IX Header "LIBEVENT EMULATION"
 Libev offers a compatibility emulation layer for libevent. It cannot
 .SH "LIBEVENT EMULATION"
 .IX Header "LIBEVENT EMULATION"
 Libev offers a compatibility emulation layer for libevent. It cannot


@@ -1263,7 +1434,110 @@ emulate the internals of libevent, so here are some usage hints:
 .PD
 .SH "\*(C+ SUPPORT"
 .IX Header " SUPPORT"
 .PD
 .SH "\*(C+ SUPPORT"
 .IX Header " SUPPORT"

-\&\s-1TBD\s0.
+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.
+.PP
+To use it,
+.PP
+.Vb 1
+\&  #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.
+.PP
+It should support all the same embedding options as \fIev.h\fR, most notably
+\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
+.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
+.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
+.IX Item "ev::READ, ev::WRITE etc."
+These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
+macros from \fIev.h\fR.
+.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
+.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
+.IX Item "ev::tstamp, ev::now"
+Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
+.ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4
+.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
+.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
+For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
+the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
+which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
+defines by many implementations.
+.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 *)"
+.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" 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.
+.Sp
+The destructor automatically stops the watcher if it is active.
+.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
+do this when the watcher is inactive (and not pending either).
+.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.
+.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.
+.IP "w\->stop ()" 4
+.IX Item "w->stop ()"
+Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
+.ie n .IP "w\->again ()       ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
+.el .IP "w\->again ()       \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
+.IX Item "w->again ()       ev::timer, ev::periodic only"
+For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
+\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
+.ie n .IP "w\->sweep ()       ""ev::embed"" only" 4
+.el .IP "w\->sweep ()       \f(CWev::embed\fR only" 4
+.IX Item "w->sweep ()       ev::embed only"
+Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
+.RE
+.RS 4
+.RE
+.PP
+Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
+the constructor.
+.PP
+.Vb 4
+\&  class myclass
+\&  {
+\&    ev_io   io;   void io_cb   (ev::io   &w, int revents);
+\&    ev_idle idle  void idle_cb (ev::idle &w, int revents);
+.Ve
+.PP
+.Vb 2
+\&    myclass ();
+\&  }
+.Ve
+.PP
+.Vb 6
+\&  myclass::myclass (int fd)
+\&  : io   (this, &myclass::io_cb),
+\&    idle (this, &myclass::idle_cb)
+\&  {
+\&    io.start (fd, ev::READ);
+\&  }
+.Ve

 .SH "AUTHOR"
 .IX Header "AUTHOR"
 Marc Lehmann <libev@schmorp.de>.
 .SH "AUTHOR"
 .IX Header "AUTHOR"
 Marc Lehmann <libev@schmorp.de>.