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Revision 1.6 by root, Fri Nov 23 05:14:58 2007 UTC vs.
Revision 1.8 by root, Fri Nov 23 15:26:08 2007 UTC

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212Return the set of all backends compiled into this binary of libev and also 212Return the set of all backends compiled into this binary of libev and also
213recommended for this platform. This set is often smaller than the one 213recommended for this platform. This set is often smaller than the one
214returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on 214returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
215most BSDs and will not be autodetected unless you explicitly request it 215most BSDs and will not be autodetected unless you explicitly request it
216(assuming you know what you are doing). This is the set of backends that 216(assuming you know what you are doing). This is the set of backends that
217\&\f(CW\*(C`EVFLAG_AUTO\*(C'\fR will probe for. 217libev will probe for if you specify no backends explicitly.
218.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 218.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
219.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 219.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
220Sets the allocation function to use (the prototype is similar to the 220Sets the allocation function to use (the prototype is similar to the
221realloc C function, the semantics are identical). It is used to allocate 221realloc C function, the semantics are identical). It is used to allocate
222and free memory (no surprises here). If it returns zero when memory 222and free memory (no surprises here). If it returns zero when memory
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256.Sp 256.Sp
257If you don't know what event loop to use, use the one returned from this 257If you don't know what event loop to use, use the one returned from this
258function. 258function.
259.Sp 259.Sp
260The flags argument can be used to specify special behaviour or specific 260The flags argument can be used to specify special behaviour or specific
261backends to use, and is usually specified as \f(CW0\fR (or \s-1EVFLAG_AUTO\s0). 261backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
262.Sp 262.Sp
263It supports the following flags: 263The following flags are supported:
264.RS 4 264.RS 4
265.ie n .IP """EVFLAG_AUTO""" 4 265.ie n .IP """EVFLAG_AUTO""" 4
266.el .IP "\f(CWEVFLAG_AUTO\fR" 4 266.el .IP "\f(CWEVFLAG_AUTO\fR" 4
267.IX Item "EVFLAG_AUTO" 267.IX Item "EVFLAG_AUTO"
268The default flags value. Use this if you have no clue (it's the right 268The default flags value. Use this if you have no clue (it's the right
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302While stopping and starting an I/O watcher in the same iteration will 302While stopping and starting an I/O watcher in the same iteration will
303result in some caching, there is still a syscall per such incident 303result in some caching, there is still a syscall per such incident
304(because the fd could point to a different file description now), so its 304(because the fd could point to a different file description now), so its
305best to avoid that. Also, \fIdup()\fRed file descriptors might not work very 305best to avoid that. Also, \fIdup()\fRed file descriptors might not work very
306well if you register events for both fds. 306well if you register events for both fds.
307.Sp
308Please note that epoll sometimes generates spurious notifications, so you
309need to use non-blocking I/O or other means to avoid blocking when no data
310(or space) is available.
307.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 311.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
308.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 312.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
309.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" 313.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
310Kqueue deserves special mention, as at the time of this writing, it 314Kqueue deserves special mention, as at the time of this writing, it
311was broken on all BSDs except NetBSD (usually it doesn't work with 315was broken on all BSDs except NetBSD (usually it doesn't work with
312anything but sockets and pipes, except on Darwin, where of course its 316anything but sockets and pipes, except on Darwin, where of course its
313completely useless). For this reason its not being \*(L"autodetected\*(R" unless 317completely useless). For this reason its not being \*(L"autodetected\*(R"
314you explicitly specify the flags (i.e. you don't use \s-1EVFLAG_AUTO\s0). 318unless you explicitly specify it explicitly in the flags (i.e. using
319\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR).
315.Sp 320.Sp
316It scales in the same way as the epoll backend, but the interface to the 321It scales in the same way as the epoll backend, but the interface to the
317kernel is more efficient (which says nothing about its actual speed, of 322kernel is more efficient (which says nothing about its actual speed, of
318course). While starting and stopping an I/O watcher does not cause an 323course). While starting and stopping an I/O watcher does not cause an
319extra syscall as with epoll, it still adds up to four event changes per 324extra syscall as with epoll, it still adds up to four event changes per
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325.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 330.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
326.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 331.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
327.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" 332.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
328This uses the Solaris 10 port mechanism. As with everything on Solaris, 333This uses the Solaris 10 port mechanism. As with everything on Solaris,
329it's really slow, but it still scales very well (O(active_fds)). 334it's really slow, but it still scales very well (O(active_fds)).
335.Sp
336Please note that solaris ports can result in a lot of spurious
337notifications, so you need to use non-blocking I/O or other means to avoid
338blocking when no data (or space) is available.
330.ie n .IP """EVBACKEND_ALL""" 4 339.ie n .IP """EVBACKEND_ALL""" 4
331.el .IP "\f(CWEVBACKEND_ALL\fR" 4 340.el .IP "\f(CWEVBACKEND_ALL\fR" 4
332.IX Item "EVBACKEND_ALL" 341.IX Item "EVBACKEND_ALL"
333Try all backends (even potentially broken ones that wouldn't be tried 342Try all backends (even potentially broken ones that wouldn't be tried
334with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as 343with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
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338.Sp 347.Sp
339If one or more of these are ored into the flags value, then only these 348If one or more of these are ored into the flags value, then only these
340backends will be tried (in the reverse order as given here). If none are 349backends will be tried (in the reverse order as given here). If none are
341specified, most compiled-in backend will be tried, usually in reverse 350specified, most compiled-in backend will be tried, usually in reverse
342order of their flag values :) 351order of their flag values :)
352.Sp
353The most typical usage is like this:
354.Sp
355.Vb 2
356\& if (!ev_default_loop (0))
357\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
358.Ve
359.Sp
360Restrict libev to the select and poll backends, and do not allow
361environment settings to be taken into account:
362.Sp
363.Vb 1
364\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
365.Ve
366.Sp
367Use whatever libev has to offer, but make sure that kqueue is used if
368available (warning, breaks stuff, best use only with your own private
369event loop and only if you know the \s-1OS\s0 supports your types of fds):
370.Sp
371.Vb 1
372\& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
373.Ve
343.RE 374.RE
344.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 375.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
345.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" 376.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
346Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 377Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
347always distinct from the default loop. Unlike the default loop, it cannot 378always distinct from the default loop. Unlike the default loop, it cannot
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398.IX Item "ev_loop (loop, int flags)" 429.IX Item "ev_loop (loop, int flags)"
399Finally, this is it, the event handler. This function usually is called 430Finally, this is it, the event handler. This function usually is called
400after you initialised all your watchers and you want to start handling 431after you initialised all your watchers and you want to start handling
401events. 432events.
402.Sp 433.Sp
403If the flags argument is specified as 0, it will not return until either 434If the flags argument is specified as \f(CW0\fR, it will not return until
404no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. 435either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
405.Sp 436.Sp
406A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle 437A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
407those events and any outstanding ones, but will not block your process in 438those events and any outstanding ones, but will not block your process in
408case there are no events and will return after one iteration of the loop. 439case there are no events and will return after one iteration of the loop.
409.Sp 440.Sp
410A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if 441A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if
411neccessary) and will handle those and any outstanding ones. It will block 442neccessary) and will handle those and any outstanding ones. It will block
412your process until at least one new event arrives, and will return after 443your process until at least one new event arrives, and will return after
413one iteration of the loop. 444one iteration of the loop. This is useful if you are waiting for some
445external event in conjunction with something not expressible using other
446libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
447usually a better approach for this kind of thing.
414.Sp 448.Sp
415This flags value could be used to implement alternative looping
416constructs, but the \f(CW\*(C`prepare\*(C'\fR and \f(CW\*(C`check\*(C'\fR watchers provide a better and
417more generic mechanism.
418.Sp
419Here are the gory details of what ev_loop does: 449Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
420.Sp 450.Sp
421.Vb 15 451.Vb 18
422\& 1. If there are no active watchers (reference count is zero), return. 452\& * If there are no active watchers (reference count is zero), return.
423\& 2. Queue and immediately call all prepare watchers. 453\& - Queue prepare watchers and then call all outstanding watchers.
424\& 3. If we have been forked, recreate the kernel state. 454\& - If we have been forked, recreate the kernel state.
425\& 4. Update the kernel state with all outstanding changes. 455\& - Update the kernel state with all outstanding changes.
426\& 5. Update the "event loop time". 456\& - Update the "event loop time".
427\& 6. Calculate for how long to block. 457\& - Calculate for how long to block.
428\& 7. Block the process, waiting for events. 458\& - Block the process, waiting for any events.
459\& - Queue all outstanding I/O (fd) events.
429\& 8. Update the "event loop time" and do time jump handling. 460\& - Update the "event loop time" and do time jump handling.
430\& 9. Queue all outstanding timers. 461\& - Queue all outstanding timers.
431\& 10. Queue all outstanding periodics. 462\& - Queue all outstanding periodics.
432\& 11. If no events are pending now, queue all idle watchers. 463\& - If no events are pending now, queue all idle watchers.
433\& 12. Queue all check watchers. 464\& - Queue all check watchers.
434\& 13. Call all queued watchers in reverse order (i.e. check watchers first). 465\& - Call all queued watchers in reverse order (i.e. check watchers first).
466\& Signals and child watchers are implemented as I/O watchers, and will
467\& be handled here by queueing them when their watcher gets executed.
435\& 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 468\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
436\& was used, return, otherwise continue with step #1. 469\& were used, return, otherwise continue with step *.
437.Ve 470.Ve
438.IP "ev_unloop (loop, how)" 4 471.IP "ev_unloop (loop, how)" 4
439.IX Item "ev_unloop (loop, how)" 472.IX Item "ev_unloop (loop, how)"
440Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it 473Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
441has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either 474has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
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641.IX Item "ev_io_set (ev_io *, int fd, int events)" 674.IX Item "ev_io_set (ev_io *, int fd, int events)"
642.PD 675.PD
643Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 676Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive
644events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ | 677events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ |
645EV_WRITE\*(C'\fR to receive the given events. 678EV_WRITE\*(C'\fR to receive the given events.
679.Sp
680Please note that most of the more scalable backend mechanisms (for example
681epoll and solaris ports) can result in spurious readyness notifications
682for file descriptors, so you practically need to use non-blocking I/O (and
683treat callback invocation as hint only), or retest separately with a safe
684interface before doing I/O (XLib can do this), or force the use of either
685\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this
686problem. Also note that it is quite easy to have your callback invoked
687when the readyness condition is no longer valid even when employing
688typical ways of handling events, so its a good idea to use non-blocking
689I/O unconditionally.
646.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 690.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts"
647.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 691.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts"
648.IX Subsection "ev_timer - relative and optionally recurring timeouts" 692.IX Subsection "ev_timer - relative and optionally recurring timeouts"
649Timer watchers are simple relative timers that generate an event after a 693Timer watchers are simple relative timers that generate an event after a
650given time, and optionally repeating in regular intervals after that. 694given time, and optionally repeating in regular intervals after that.

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