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Revision 1.414 by root, Fri May 4 20:50:57 2012 UTC vs.
Revision 1.422 by root, Thu Nov 15 01:39:45 2012 UTC

569kernel is more efficient (which says nothing about its actual speed, of 569kernel is more efficient (which says nothing about its actual speed, of
570course). While stopping, setting and starting an I/O watcher does never 570course). While stopping, setting and starting an I/O watcher does never
571cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to 571cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
572two event changes per incident. Support for C<fork ()> is very bad (you 572two event changes per incident. Support for C<fork ()> is very bad (you
573might have to leak fd's on fork, but it's more sane than epoll) and it 573might have to leak fd's on fork, but it's more sane than epoll) and it
574drops fds silently in similarly hard-to-detect cases 574drops fds silently in similarly hard-to-detect cases.
575 575
576This backend usually performs well under most conditions. 576This backend usually performs well under most conditions.
577 577
578While nominally embeddable in other event loops, this doesn't work 578While nominally embeddable in other event loops, this doesn't work
579everywhere, so you might need to test for this. And since it is broken 579everywhere, so you might need to test for this. And since it is broken
1393transition between them will be described in more detail - and while these 1393transition between them will be described in more detail - and while these
1394rules might look complicated, they usually do "the right thing". 1394rules might look complicated, they usually do "the right thing".
1395 1395
1396=over 4 1396=over 4
1397 1397
1398=item initialiased 1398=item initialised
1399 1399
1400Before a watcher can be registered with the event loop it has to be 1400Before a watcher can be registered with the event loop it has to be
1401initialised. This can be done with a call to C<ev_TYPE_init>, or calls to 1401initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1402C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. 1402C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1403 1403
2858 2858
2859This mode of operation can be useful together with an C<ev_check> watcher, 2859This mode of operation can be useful together with an C<ev_check> watcher,
2860to do something on each event loop iteration - for example to balance load 2860to do something on each event loop iteration - for example to balance load
2861between different connections. 2861between different connections.
2862 2862
2863See L</Abusing an C<ev_check> watcher for its side-effect> for a longer 2863See L</Abusing an ev_check watcher for its side-effect> for a longer
2864example. 2864example.
2865 2865
2866=head3 Watcher-Specific Functions and Data Members 2866=head3 Watcher-Specific Functions and Data Members
2867 2867
2868=over 4 2868=over 4
2961connections have a chance of making progress. 2961connections have a chance of making progress.
2962 2962
2963Using an C<ev_check> watcher is almost enough: it will be called on the 2963Using an C<ev_check> watcher is almost enough: it will be called on the
2964next event loop iteration. However, that isn't as soon as possible - 2964next event loop iteration. However, that isn't as soon as possible -
2965without external events, your C<ev_check> watcher will not be invoked. 2965without external events, your C<ev_check> watcher will not be invoked.
2966
2967 2966
2968This is where C<ev_idle> watchers come in handy - all you need is a 2967This is where C<ev_idle> watchers come in handy - all you need is a
2969single global idle watcher that is active as long as you have one active 2968single global idle watcher that is active as long as you have one active
2970C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop 2969C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
2971will not sleep, and the C<ev_check> watcher makes sure a callback gets 2970will not sleep, and the C<ev_check> watcher makes sure a callback gets
3251 3250
3252=head2 C<ev_fork> - the audacity to resume the event loop after a fork 3251=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3253 3252
3254Fork watchers are called when a C<fork ()> was detected (usually because 3253Fork watchers are called when a C<fork ()> was detected (usually because
3255whoever is a good citizen cared to tell libev about it by calling 3254whoever is a good citizen cared to tell libev about it by calling
3256C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the 3255C<ev_loop_fork>). The invocation is done before the event loop blocks next
3257event loop blocks next and before C<ev_check> watchers are being called, 3256and before C<ev_check> watchers are being called, and only in the child
3258and only in the child after the fork. If whoever good citizen calling 3257after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3259C<ev_default_fork> cheats and calls it in the wrong process, the fork 3258and calls it in the wrong process, the fork handlers will be invoked, too,
3260handlers will be invoked, too, of course. 3259of course.
3261 3260
3262=head3 The special problem of life after fork - how is it possible? 3261=head3 The special problem of life after fork - how is it possible?
3263 3262
3264Most uses of C<fork()> consist of forking, then some simple calls to set 3263Most uses of C<fork()> consist of forking, then some simple calls to set
3265up/change the process environment, followed by a call to C<exec()>. This 3264up/change the process environment, followed by a call to C<exec()>. This
3950libev sources can be compiled as C++. Therefore, code that uses the C API 3949libev sources can be compiled as C++. Therefore, code that uses the C API
3951will work fine. 3950will work fine.
3952 3951
3953Proper exception specifications might have to be added to callbacks passed 3952Proper exception specifications might have to be added to callbacks passed
3954to libev: exceptions may be thrown only from watcher callbacks, all 3953to libev: exceptions may be thrown only from watcher callbacks, all
3955other callbacks (allocator, syserr, loop acquire/release and periodioc 3954other callbacks (allocator, syserr, loop acquire/release and periodic
3956reschedule callbacks) must not throw exceptions, and might need a C<throw 3955reschedule callbacks) must not throw exceptions, and might need a C<throw
3957()> specification. If you have code that needs to be compiled as both C 3956()> specification. If you have code that needs to be compiled as both C
3958and C++ you can use the C<EV_THROW> macro for this: 3957and C++ you can use the C<EV_THROW> macro for this:
3959 3958
3960 static void 3959 static void
4121Associates a different C<struct ev_loop> with this watcher. You can only 4120Associates a different C<struct ev_loop> with this watcher. You can only
4122do this when the watcher is inactive (and not pending either). 4121do this when the watcher is inactive (and not pending either).
4123 4122
4124=item w->set ([arguments]) 4123=item w->set ([arguments])
4125 4124
4126Basically the same as C<ev_TYPE_set>, with the same arguments. Either this 4125Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
4127method or a suitable start method must be called at least once. Unlike the 4126with the same arguments. Either this method or a suitable start method
4128C counterpart, an active watcher gets automatically stopped and restarted 4127must be called at least once. Unlike the C counterpart, an active watcher
4129when reconfiguring it with this method. 4128gets automatically stopped and restarted when reconfiguring it with this
4129method.
4130
4131For C<ev::embed> watchers this method is called C<set_embed>, to avoid
4132clashing with the C<set (loop)> method.
4130 4133
4131=item w->start () 4134=item w->start ()
4132 4135
4133Starts the watcher. Note that there is no C<loop> argument, as the 4136Starts the watcher. Note that there is no C<loop> argument, as the
4134constructor already stores the event loop. 4137constructor already stores the event loop.
4237=item Lua 4240=item Lua
4238 4241
4239Brian Maher has written a partial interface to libev for lua (at the 4242Brian Maher has written a partial interface to libev for lua (at the
4240time of this writing, only C<ev_io> and C<ev_timer>), to be found at 4243time of this writing, only C<ev_io> and C<ev_timer>), to be found at
4241L<http://github.com/brimworks/lua-ev>. 4244L<http://github.com/brimworks/lua-ev>.
4245
4246=item Javascript
4247
4248Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
4249
4250=item Others
4251
4252There are others, and I stopped counting.
4242 4253
4243=back 4254=back
4244 4255
4245 4256
4246=head1 MACRO MAGIC 4257=head1 MACRO MAGIC
4545 4556
4546If programs implement their own fd to handle mapping on win32, then this 4557If programs implement their own fd to handle mapping on win32, then this
4547macro can be used to override the C<close> function, useful to unregister 4558macro can be used to override the C<close> function, useful to unregister
4548file descriptors again. Note that the replacement function has to close 4559file descriptors again. Note that the replacement function has to close
4549the underlying OS handle. 4560the underlying OS handle.
4561
4562=item EV_USE_WSASOCKET
4563
4564If defined to be C<1>, libev will use C<WSASocket> to create its internal
4565communication socket, which works better in some environments. Otherwise,
4566the normal C<socket> function will be used, which works better in other
4567environments.
4550 4568
4551=item EV_USE_POLL 4569=item EV_USE_POLL
4552 4570
4553If defined to be C<1>, libev will compile in support for the C<poll>(2) 4571If defined to be C<1>, libev will compile in support for the C<poll>(2)
4554backend. Otherwise it will be enabled on non-win32 platforms. It 4572backend. Otherwise it will be enabled on non-win32 platforms. It
4606above. This reduces dependencies and makes libev faster. 4624above. This reduces dependencies and makes libev faster.
4607 4625
4608=item EV_ATOMIC_T 4626=item EV_ATOMIC_T
4609 4627
4610Libev requires an integer type (suitable for storing C<0> or C<1>) whose 4628Libev requires an integer type (suitable for storing C<0> or C<1>) whose
4611access is atomic and serialised with respect to other threads or signal 4629access is atomic with respect to other threads or signal contexts. No
4612contexts. No such type is easily found in the C language, so you can 4630such type is easily found in the C language, so you can provide your own
4613provide your own type that you know is safe for your purposes. It is used 4631type that you know is safe for your purposes. It is used both for signal
4614both for signal handler "locking" as well as for signal and thread safety 4632handler "locking" as well as for signal and thread safety in C<ev_async>
4615in C<ev_async> watchers. 4633watchers.
4616 4634
4617In the absence of this define, libev will use C<sig_atomic_t volatile> 4635In the absence of this define, libev will use C<sig_atomic_t volatile>
4618(from F<signal.h>), which is usually good enough on most platforms, 4636(from F<signal.h>), which is usually good enough on most platforms.
4619although strictly speaking using a type that also implies a memory fence
4620is required.
4621 4637
4622=item EV_H (h) 4638=item EV_H (h)
4623 4639
4624The name of the F<ev.h> header file used to include it. The default if 4640The name of the F<ev.h> header file used to include it. The default if
4625undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be 4641undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
5294thread" or will block signals process-wide, both behaviours would 5310thread" or will block signals process-wide, both behaviours would
5295be compatible with libev. Interaction between C<sigprocmask> and 5311be compatible with libev. Interaction between C<sigprocmask> and
5296C<pthread_sigmask> could complicate things, however. 5312C<pthread_sigmask> could complicate things, however.
5297 5313
5298The most portable way to handle signals is to block signals in all threads 5314The most portable way to handle signals is to block signals in all threads
5299except the initial one, and run the default loop in the initial thread as 5315except the initial one, and run the signal handling loop in the initial
5300well. 5316thread as well.
5301 5317
5302=item C<long> must be large enough for common memory allocation sizes 5318=item C<long> must be large enough for common memory allocation sizes
5303 5319
5304To improve portability and simplify its API, libev uses C<long> internally 5320To improve portability and simplify its API, libev uses C<long> internally
5305instead of C<size_t> when allocating its data structures. On non-POSIX 5321instead of C<size_t> when allocating its data structures. On non-POSIX

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