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Revision 1.110 by root, Thu Jun 20 22:44:59 2019 UTC

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135.IX Title "LIBEV 3" 135.IX Title "LIBEV 3"
136.TH LIBEV 3 "2014-09-05" "libev-4.15" "libev - high performance full featured event loop" 136.TH LIBEV 3 "2019-06-20" "libev-4.25" "libev - high performance full featured event loop"
137.\" For nroff, turn off justification. Always turn off hyphenation; it makes 137.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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139.if n .ad l 139.if n .ad l
140.nh 140.nh
141.SH "NAME" 141.SH "NAME"
… …
392.Sp 392.Sp
393You could override this function in high-availability programs to, say, 393You could override this function in high-availability programs to, say,
394free some memory if it cannot allocate memory, to use a special allocator, 394free some memory if it cannot allocate memory, to use a special allocator,
395or even to sleep a while and retry until some memory is available. 395or even to sleep a while and retry until some memory is available.
396.Sp 396.Sp
397Example: The following is the \f(CW\*(C`realloc\*(C'\fR function that libev itself uses
398which should work with \f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions of all kinds and
399is probably a good basis for your own implementation.
400.Sp
401.Vb 5
402\& static void *
403\& ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
404\& {
405\& if (size)
406\& return realloc (ptr, size);
407\&
408\& free (ptr);
409\& return 0;
410\& }
411.Ve
412.Sp
397Example: Replace the libev allocator with one that waits a bit and then 413Example: Replace the libev allocator with one that waits a bit and then
398retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR). 414retries.
399.Sp 415.Sp
400.Vb 6 416.Vb 8
401\& static void * 417\& static void *
402\& persistent_realloc (void *ptr, size_t size) 418\& persistent_realloc (void *ptr, size_t size)
403\& { 419\& {
420\& if (!size)
421\& {
422\& free (ptr);
423\& return 0;
424\& }
425\&
404\& for (;;) 426\& for (;;)
405\& { 427\& {
406\& void *newptr = realloc (ptr, size); 428\& void *newptr = realloc (ptr, size);
407\& 429\&
408\& if (newptr) 430\& if (newptr)
… …
536make libev check for a fork in each iteration by enabling this flag. 558make libev check for a fork in each iteration by enabling this flag.
537.Sp 559.Sp
538This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop, 560This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
539and thus this might slow down your event loop if you do a lot of loop 561and thus this might slow down your event loop if you do a lot of loop
540iterations and little real work, but is usually not noticeable (on my 562iterations and little real work, but is usually not noticeable (on my
541GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence 563GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn
542without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has 564sequence without a system call and thus \fIvery\fR fast, but my GNU/Linux
543\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). 565system also has \f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). (Update: glibc
566versions 2.25 apparently removed the \f(CW\*(C`getpid\*(C'\fR optimisation again).
544.Sp 567.Sp
545The big advantage of this flag is that you can forget about fork (and 568The big advantage of this flag is that you can forget about fork (and
546forget about forgetting to tell libev about forking) when you use this 569forget about forgetting to tell libev about forking, although you still
547flag. 570have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR) when you use this flag.
548.Sp 571.Sp
549This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR 572This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
550environment variable. 573environment variable.
551.ie n .IP """EVFLAG_NOINOTIFY""" 4 574.ie n .IP """EVFLAG_NOINOTIFY""" 4
552.el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4 575.el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4
… …
584.Sp 607.Sp
585This flag's behaviour will become the default in future versions of libev. 608This flag's behaviour will become the default in future versions of libev.
586.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 609.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
587.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 610.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
588.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 611.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
589This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 612This is your standard \fBselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
590libev tries to roll its own fd_set with no limits on the number of fds, 613libev tries to roll its own fd_set with no limits on the number of fds,
591but if that fails, expect a fairly low limit on the number of fds when 614but if that fails, expect a fairly low limit on the number of fds when
592using this backend. It doesn't scale too well (O(highest_fd)), but its 615using this backend. It doesn't scale too well (O(highest_fd)), but its
593usually the fastest backend for a low number of (low-numbered :) fds. 616usually the fastest backend for a low number of (low-numbered :) fds.
594.Sp 617.Sp
… …
603\&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the 626\&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the
604\&\f(CW\*(C`exceptfds\*(C'\fR set on that platform). 627\&\f(CW\*(C`exceptfds\*(C'\fR set on that platform).
605.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 628.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
606.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 629.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
607.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" 630.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
608And this is your standard \fIpoll\fR\|(2) backend. It's more complicated 631And this is your standard \fBpoll\fR\|(2) backend. It's more complicated
609than select, but handles sparse fds better and has no artificial 632than select, but handles sparse fds better and has no artificial
610limit on the number of fds you can use (except it will slow down 633limit on the number of fds you can use (except it will slow down
611considerably with a lot of inactive fds). It scales similarly to select, 634considerably with a lot of inactive fds). It scales similarly to select,
612i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for 635i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for
613performance tips. 636performance tips.
… …
615This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and 638This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and
616\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR. 639\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR.
617.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 640.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
618.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 641.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
619.IX Item "EVBACKEND_EPOLL (value 4, Linux)" 642.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
620Use the linux-specific \fIepoll\fR\|(7) interface (for both pre\- and post\-2.6.9 643Use the linux-specific \fBepoll\fR\|(7) interface (for both pre\- and post\-2.6.9
621kernels). 644kernels).
622.Sp 645.Sp
623For few fds, this backend is a bit little slower than poll and select, but 646For few fds, this backend is a bit little slower than poll and select, but
624it scales phenomenally better. While poll and select usually scale like 647it scales phenomenally better. While poll and select usually scale like
625O(total_fds) where total_fds is the total number of fds (or the highest 648O(total_fds) where total_fds is the total number of fds (or the highest
… …
816to reinitialise the kernel state for backends that have one. Despite 839to reinitialise the kernel state for backends that have one. Despite
817the name, you can call it anytime you are allowed to start or stop 840the name, you can call it anytime you are allowed to start or stop
818watchers (except inside an \f(CW\*(C`ev_prepare\*(C'\fR callback), but it makes most 841watchers (except inside an \f(CW\*(C`ev_prepare\*(C'\fR callback), but it makes most
819sense after forking, in the child process. You \fImust\fR call it (or use 842sense after forking, in the child process. You \fImust\fR call it (or use
820\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR. 843\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR.
844.Sp
845In addition, if you want to reuse a loop (via this function or
846\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR), you \fIalso\fR have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR.
821.Sp 847.Sp
822Again, you \fIhave\fR to call it on \fIany\fR loop that you want to re-use after 848Again, you \fIhave\fR to call it on \fIany\fR loop that you want to re-use after
823a fork, \fIeven if you do not plan to use the loop in the parent\fR. This is 849a fork, \fIeven if you do not plan to use the loop in the parent\fR. This is
824because some kernel interfaces *cough* \fIkqueue\fR *cough* do funny things 850because some kernel interfaces *cough* \fIkqueue\fR *cough* do funny things
825during fork. 851during fork.
… …
1361bug in your program. 1387bug in your program.
1362.Sp 1388.Sp
1363Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for 1389Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for
1364example it might indicate that a fd is readable or writable, and if your 1390example it might indicate that a fd is readable or writable, and if your
1365callbacks is well-written it can just attempt the operation and cope with 1391callbacks is well-written it can just attempt the operation and cope with
1366the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded 1392the error from \fBread()\fR or \fBwrite()\fR. This will not work in multi-threaded
1367programs, though, as the fd could already be closed and reused for another 1393programs, though, as the fd could already be closed and reused for another
1368thing, so beware. 1394thing, so beware.
1369.SS "\s-1GENERIC WATCHER FUNCTIONS\s0" 1395.SS "\s-1GENERIC WATCHER FUNCTIONS\s0"
1370.IX Subsection "GENERIC WATCHER FUNCTIONS" 1396.IX Subsection "GENERIC WATCHER FUNCTIONS"
1371.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 1397.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
… …
1807when writing to a pipe whose other end has been closed, your program gets 1833when writing to a pipe whose other end has been closed, your program gets
1808sent a \s-1SIGPIPE,\s0 which, by default, aborts your program. For most programs 1834sent a \s-1SIGPIPE,\s0 which, by default, aborts your program. For most programs
1809this is sensible behaviour, for daemons, this is usually undesirable. 1835this is sensible behaviour, for daemons, this is usually undesirable.
1810.PP 1836.PP
1811So when you encounter spurious, unexplained daemon exits, make sure you 1837So when you encounter spurious, unexplained daemon exits, make sure you
1812ignore \s-1SIGPIPE \s0(and maybe make sure you log the exit status of your daemon 1838ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon
1813somewhere, as that would have given you a big clue). 1839somewhere, as that would have given you a big clue).
1814.PP 1840.PP
1815\fIThe special problem of \fIaccept()\fIing when you can't\fR 1841\fIThe special problem of \f(BIaccept()\fIing when you can't\fR
1816.IX Subsection "The special problem of accept()ing when you can't" 1842.IX Subsection "The special problem of accept()ing when you can't"
1817.PP 1843.PP
1818Many implementations of the \s-1POSIX \s0\f(CW\*(C`accept\*(C'\fR function (for example, 1844Many implementations of the \s-1POSIX\s0 \f(CW\*(C`accept\*(C'\fR function (for example,
1819found in post\-2004 Linux) have the peculiar behaviour of not removing a 1845found in post\-2004 Linux) have the peculiar behaviour of not removing a
1820connection from the pending queue in all error cases. 1846connection from the pending queue in all error cases.
1821.PP 1847.PP
1822For example, larger servers often run out of file descriptors (because 1848For example, larger servers often run out of file descriptors (because
1823of resource limits), causing \f(CW\*(C`accept\*(C'\fR to fail with \f(CW\*(C`ENFILE\*(C'\fR but not 1849of resource limits), causing \f(CW\*(C`accept\*(C'\fR to fail with \f(CW\*(C`ENFILE\*(C'\fR but not
… …
2247.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 2273.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
2248.PD 0 2274.PD 0
2249.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 2275.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
2250.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 2276.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
2251.PD 2277.PD
2252Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR 2278Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds (fractional and
2253is \f(CW0.\fR, then it will automatically be stopped once the timeout is 2279negative values are supported). If \f(CW\*(C`repeat\*(C'\fR is \f(CW0.\fR, then it will
2254reached. If it is positive, then the timer will automatically be 2280automatically be stopped once the timeout is reached. If it is positive,
2255configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds later, again, and again, 2281then the timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR
2256until stopped manually. 2282seconds later, again, and again, until stopped manually.
2257.Sp 2283.Sp
2258The timer itself will do a best-effort at avoiding drift, that is, if 2284The timer itself will do a best-effort at avoiding drift, that is, if
2259you configure a timer to trigger every 10 seconds, then it will normally 2285you configure a timer to trigger every 10 seconds, then it will normally
2260trigger at exactly 10 second intervals. If, however, your program cannot 2286trigger at exactly 10 second intervals. If, however, your program cannot
2261keep up with the timer (because it takes longer than those 10 seconds to 2287keep up with the timer (because it takes longer than those 10 seconds to
… …
2343Periodic watchers are also timers of a kind, but they are very versatile 2369Periodic watchers are also timers of a kind, but they are very versatile
2344(and unfortunately a bit complex). 2370(and unfortunately a bit complex).
2345.PP 2371.PP
2346Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or 2372Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or
2347relative time, the physical time that passes) but on wall clock time 2373relative time, the physical time that passes) but on wall clock time
2348(absolute time, the thing you can read on your calender or clock). The 2374(absolute time, the thing you can read on your calendar or clock). The
2349difference is that wall clock time can run faster or slower than real 2375difference is that wall clock time can run faster or slower than real
2350time, and time jumps are not uncommon (e.g. when you adjust your 2376time, and time jumps are not uncommon (e.g. when you adjust your
2351wrist-watch). 2377wrist-watch).
2352.PP 2378.PP
2353You can tell a periodic watcher to trigger after some specific point 2379You can tell a periodic watcher to trigger after some specific point
… …
2358\&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting 2384\&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting
2359it, as it uses a relative timeout). 2385it, as it uses a relative timeout).
2360.PP 2386.PP
2361\&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex 2387\&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex
2362timers, such as triggering an event on each \*(L"midnight, local time\*(R", or 2388timers, such as triggering an event on each \*(L"midnight, local time\*(R", or
2363other complicated rules. This cannot be done with \f(CW\*(C`ev_timer\*(C'\fR watchers, as 2389other complicated rules. This cannot easily be done with \f(CW\*(C`ev_timer\*(C'\fR
2364those cannot react to time jumps. 2390watchers, as those cannot react to time jumps.
2365.PP 2391.PP
2366As with timers, the callback is guaranteed to be invoked only when the 2392As with timers, the callback is guaranteed to be invoked only when the
2367point in time where it is supposed to trigger has passed. If multiple 2393point in time where it is supposed to trigger has passed. If multiple
2368timers become ready during the same loop iteration then the ones with 2394timers become ready during the same loop iteration then the ones with
2369earlier time-out values are invoked before ones with later time-out values 2395earlier time-out values are invoked before ones with later time-out values
… …
2430In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being 2456In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being
2431ignored. Instead, each time the periodic watcher gets scheduled, the 2457ignored. Instead, each time the periodic watcher gets scheduled, the
2432reschedule callback will be called with the watcher as first, and the 2458reschedule callback will be called with the watcher as first, and the
2433current time as second argument. 2459current time as second argument.
2434.Sp 2460.Sp
2435\&\s-1NOTE: \s0\fIThis callback \s-1MUST NOT\s0 stop or destroy any periodic watcher, ever, 2461\&\s-1NOTE:\s0 \fIThis callback \s-1MUST NOT\s0 stop or destroy any periodic watcher, ever,
2436or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly 2462or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly
2437allowed by documentation here\fR. 2463allowed by documentation here\fR.
2438.Sp 2464.Sp
2439If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop 2465If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop
2440it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the 2466it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the
… …
2454It must return the next time to trigger, based on the passed time value 2480It must return the next time to trigger, based on the passed time value
2455(that is, the lowest time value larger than to the second argument). It 2481(that is, the lowest time value larger than to the second argument). It
2456will usually be called just before the callback will be triggered, but 2482will usually be called just before the callback will be triggered, but
2457might be called at other times, too. 2483might be called at other times, too.
2458.Sp 2484.Sp
2459\&\s-1NOTE: \s0\fIThis callback must always return a time that is higher than or 2485\&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or
2460equal to the passed \f(CI\*(C`now\*(C'\fI value\fR. 2486equal to the passed \f(CI\*(C`now\*(C'\fI value\fR.
2461.Sp 2487.Sp
2462This can be used to create very complex timers, such as a timer that 2488This can be used to create very complex timers, such as a timer that
2463triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate the 2489triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate
2464next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How 2490the next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for
2465you do this is, again, up to you (but it is not trivial, which is the main 2491this. Here is a (completely untested, no error checking) example on how to
2466reason I omitted it as an example). 2492do this:
2493.Sp
2494.Vb 1
2495\& #include <time.h>
2496\&
2497\& static ev_tstamp
2498\& my_rescheduler (ev_periodic *w, ev_tstamp now)
2499\& {
2500\& time_t tnow = (time_t)now;
2501\& struct tm tm;
2502\& localtime_r (&tnow, &tm);
2503\&
2504\& tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
2505\& ++tm.tm_mday; // midnight next day
2506\&
2507\& return mktime (&tm);
2508\& }
2509.Ve
2510.Sp
2511Note: this code might run into trouble on days that have more then two
2512midnights (beginning and end).
2467.RE 2513.RE
2468.RS 4 2514.RS 4
2469.RE 2515.RE
2470.IP "ev_periodic_again (loop, ev_periodic *)" 4 2516.IP "ev_periodic_again (loop, ev_periodic *)" 4
2471.IX Item "ev_periodic_again (loop, ev_periodic *)" 2517.IX Item "ev_periodic_again (loop, ev_periodic *)"
… …
2589The simplest way to ensure that the signal mask is reset in the child is 2635The simplest way to ensure that the signal mask is reset in the child is
2590to install a fork handler with \f(CW\*(C`pthread_atfork\*(C'\fR that resets it. That will 2636to install a fork handler with \f(CW\*(C`pthread_atfork\*(C'\fR that resets it. That will
2591catch fork calls done by libraries (such as the libc) as well. 2637catch fork calls done by libraries (such as the libc) as well.
2592.PP 2638.PP
2593In current versions of libev, the signal will not be blocked indefinitely 2639In current versions of libev, the signal will not be blocked indefinitely
2594unless you use the \f(CW\*(C`signalfd\*(C'\fR \s-1API \s0(\f(CW\*(C`EV_SIGNALFD\*(C'\fR). While this reduces 2640unless you use the \f(CW\*(C`signalfd\*(C'\fR \s-1API\s0 (\f(CW\*(C`EV_SIGNALFD\*(C'\fR). While this reduces
2595the window of opportunity for problems, it will not go away, as libev 2641the window of opportunity for problems, it will not go away, as libev
2596\&\fIhas\fR to modify the signal mask, at least temporarily. 2642\&\fIhas\fR to modify the signal mask, at least temporarily.
2597.PP 2643.PP
2598So I can't stress this enough: \fIIf you do not reset your signal mask when 2644So I can't stress this enough: \fIIf you do not reset your signal mask when
2599you expect it to be empty, you have a race condition in your code\fR. This 2645you expect it to be empty, you have a race condition in your code\fR. This
… …
3641is a time window between the event loop checking and resetting the async 3687is a time window between the event loop checking and resetting the async
3642notification, and the callback being invoked. 3688notification, and the callback being invoked.
3643.SH "OTHER FUNCTIONS" 3689.SH "OTHER FUNCTIONS"
3644.IX Header "OTHER FUNCTIONS" 3690.IX Header "OTHER FUNCTIONS"
3645There are some other functions of possible interest. Described. Here. Now. 3691There are some other functions of possible interest. Described. Here. Now.
3646.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 3692.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)" 4
3647.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 3693.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)"
3648This function combines a simple timer and an I/O watcher, calls your 3694This function combines a simple timer and an I/O watcher, calls your
3649callback on whichever event happens first and automatically stops both 3695callback on whichever event happens first and automatically stops both
3650watchers. This is useful if you want to wait for a single event on an fd 3696watchers. This is useful if you want to wait for a single event on an fd
3651or timeout without having to allocate/configure/start/stop/free one or 3697or timeout without having to allocate/configure/start/stop/free one or
3652more watchers yourself. 3698more watchers yourself.
… …
4052files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files: 4098files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files:
4053.PP 4099.PP
4054.Vb 4 4100.Vb 4
4055\& // my_ev.h 4101\& // my_ev.h
4056\& #define EV_CB_DECLARE(type) struct my_coro *cb; 4102\& #define EV_CB_DECLARE(type) struct my_coro *cb;
4057\& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb); 4103\& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb)
4058\& #include "../libev/ev.h" 4104\& #include "../libev/ev.h"
4059\& 4105\&
4060\& // my_ev.c 4106\& // my_ev.c
4061\& #define EV_H "my_ev.h" 4107\& #define EV_H "my_ev.h"
4062\& #include "../libev/ev.c" 4108\& #include "../libev/ev.c"
… …
4102The normal C \s-1API\s0 should work fine when used from \*(C+: both ev.h and the 4148The normal C \s-1API\s0 should work fine when used from \*(C+: both ev.h and the
4103libev sources can be compiled as \*(C+. Therefore, code that uses the C \s-1API\s0 4149libev sources can be compiled as \*(C+. Therefore, code that uses the C \s-1API\s0
4104will work fine. 4150will work fine.
4105.PP 4151.PP
4106Proper exception specifications might have to be added to callbacks passed 4152Proper exception specifications might have to be added to callbacks passed
4107to libev: exceptions may be thrown only from watcher callbacks, all 4153to libev: exceptions may be thrown only from watcher callbacks, all other
4108other callbacks (allocator, syserr, loop acquire/release and periodic 4154callbacks (allocator, syserr, loop acquire/release and periodic reschedule
4109reschedule callbacks) must not throw exceptions, and might need a \f(CW\*(C`throw 4155callbacks) must not throw exceptions, and might need a \f(CW\*(C`noexcept\*(C'\fR
4110()\*(C'\fR specification. If you have code that needs to be compiled as both C 4156specification. If you have code that needs to be compiled as both C and
4111and \*(C+ you can use the \f(CW\*(C`EV_THROW\*(C'\fR macro for this: 4157\&\*(C+ you can use the \f(CW\*(C`EV_NOEXCEPT\*(C'\fR macro for this:
4112.PP 4158.PP
4113.Vb 6 4159.Vb 6
4114\& static void 4160\& static void
4115\& fatal_error (const char *msg) EV_THROW 4161\& fatal_error (const char *msg) EV_NOEXCEPT
4116\& { 4162\& {
4117\& perror (msg); 4163\& perror (msg);
4118\& abort (); 4164\& abort ();
4119\& } 4165\& }
4120\& 4166\&
… …
4494\& #include "ev.c" 4540\& #include "ev.c"
4495.Ve 4541.Ve
4496.PP 4542.PP
4497This will automatically include \fIev.h\fR, too, and should be done in a 4543This will automatically include \fIev.h\fR, too, and should be done in a
4498single C source file only to provide the function implementations. To use 4544single C source file only to provide the function implementations. To use
4499it, do the same for \fIev.h\fR in all files wishing to use this \s-1API \s0(best 4545it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
4500done by writing a wrapper around \fIev.h\fR that you can include instead and 4546done by writing a wrapper around \fIev.h\fR that you can include instead and
4501where you can put other configuration options): 4547where you can put other configuration options):
4502.PP 4548.PP
4503.Vb 2 4549.Vb 2
4504\& #define EV_STANDALONE 1 4550\& #define EV_STANDALONE 1
… …
4518\& ev_vars.h 4564\& ev_vars.h
4519\& ev_wrap.h 4565\& ev_wrap.h
4520\& 4566\&
4521\& ev_win32.c required on win32 platforms only 4567\& ev_win32.c required on win32 platforms only
4522\& 4568\&
4523\& ev_select.c only when select backend is enabled (which is enabled by default) 4569\& ev_select.c only when select backend is enabled
4524\& ev_poll.c only when poll backend is enabled (disabled by default) 4570\& ev_poll.c only when poll backend is enabled
4525\& ev_epoll.c only when the epoll backend is enabled (disabled by default) 4571\& ev_epoll.c only when the epoll backend is enabled
4526\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 4572\& ev_kqueue.c only when the kqueue backend is enabled
4527\& ev_port.c only when the solaris port backend is enabled (disabled by default) 4573\& ev_port.c only when the solaris port backend is enabled
4528.Ve 4574.Ve
4529.PP 4575.PP
4530\&\fIev.c\fR includes the backend files directly when enabled, so you only need 4576\&\fIev.c\fR includes the backend files directly when enabled, so you only need
4531to compile this single file. 4577to compile this single file.
4532.PP 4578.PP
… …
4577values when compiling libev vs. including \fIev.h\fR, so it is permissible 4623values when compiling libev vs. including \fIev.h\fR, so it is permissible
4578to redefine them before including \fIev.h\fR without breaking compatibility 4624to redefine them before including \fIev.h\fR without breaking compatibility
4579to a compiled library. All other symbols change the \s-1ABI,\s0 which means all 4625to a compiled library. All other symbols change the \s-1ABI,\s0 which means all
4580users of libev and the libev code itself must be compiled with compatible 4626users of libev and the libev code itself must be compiled with compatible
4581settings. 4627settings.
4582.IP "\s-1EV_COMPAT3 \s0(h)" 4 4628.IP "\s-1EV_COMPAT3\s0 (h)" 4
4583.IX Item "EV_COMPAT3 (h)" 4629.IX Item "EV_COMPAT3 (h)"
4584Backwards compatibility is a major concern for libev. This is why this 4630Backwards compatibility is a major concern for libev. This is why this
4585release of libev comes with wrappers for the functions and symbols that 4631release of libev comes with wrappers for the functions and symbols that
4586have been renamed between libev version 3 and 4. 4632have been renamed between libev version 3 and 4.
4587.Sp 4633.Sp
… …
4592typedef in that case. 4638typedef in that case.
4593.Sp 4639.Sp
4594In some future version, the default for \f(CW\*(C`EV_COMPAT3\*(C'\fR will become \f(CW0\fR, 4640In some future version, the default for \f(CW\*(C`EV_COMPAT3\*(C'\fR will become \f(CW0\fR,
4595and in some even more future version the compatibility code will be 4641and in some even more future version the compatibility code will be
4596removed completely. 4642removed completely.
4597.IP "\s-1EV_STANDALONE \s0(h)" 4 4643.IP "\s-1EV_STANDALONE\s0 (h)" 4
4598.IX Item "EV_STANDALONE (h)" 4644.IX Item "EV_STANDALONE (h)"
4599Must always be \f(CW1\fR if you do not use autoconf configuration, which 4645Must always be \f(CW1\fR if you do not use autoconf configuration, which
4600keeps libev from including \fIconfig.h\fR, and it also defines dummy 4646keeps libev from including \fIconfig.h\fR, and it also defines dummy
4601implementations for some libevent functions (such as logging, which is not 4647implementations for some libevent functions (such as logging, which is not
4602supported). It will also not define any of the structs usually found in 4648supported). It will also not define any of the structs usually found in
… …
4760handler \*(L"locking\*(R" as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR 4806handler \*(L"locking\*(R" as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR
4761watchers. 4807watchers.
4762.Sp 4808.Sp
4763In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR 4809In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR
4764(from \fIsignal.h\fR), which is usually good enough on most platforms. 4810(from \fIsignal.h\fR), which is usually good enough on most platforms.
4765.IP "\s-1EV_H \s0(h)" 4 4811.IP "\s-1EV_H\s0 (h)" 4
4766.IX Item "EV_H (h)" 4812.IX Item "EV_H (h)"
4767The name of the \fIev.h\fR header file used to include it. The default if 4813The name of the \fIev.h\fR header file used to include it. The default if
4768undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be 4814undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be
4769used to virtually rename the \fIev.h\fR header file in case of conflicts. 4815used to virtually rename the \fIev.h\fR header file in case of conflicts.
4770.IP "\s-1EV_CONFIG_H \s0(h)" 4 4816.IP "\s-1EV_CONFIG_H\s0 (h)" 4
4771.IX Item "EV_CONFIG_H (h)" 4817.IX Item "EV_CONFIG_H (h)"
4772If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override 4818If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
4773\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to 4819\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
4774\&\f(CW\*(C`EV_H\*(C'\fR, above. 4820\&\f(CW\*(C`EV_H\*(C'\fR, above.
4775.IP "\s-1EV_EVENT_H \s0(h)" 4 4821.IP "\s-1EV_EVENT_H\s0 (h)" 4
4776.IX Item "EV_EVENT_H (h)" 4822.IX Item "EV_EVENT_H (h)"
4777Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea 4823Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
4778of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR. 4824of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR.
4779.IP "\s-1EV_PROTOTYPES \s0(h)" 4 4825.IP "\s-1EV_PROTOTYPES\s0 (h)" 4
4780.IX Item "EV_PROTOTYPES (h)" 4826.IX Item "EV_PROTOTYPES (h)"
4781If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function 4827If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
4782prototypes, but still define all the structs and other symbols. This is 4828prototypes, but still define all the structs and other symbols. This is
4783occasionally useful if you want to provide your own wrapper functions 4829occasionally useful if you want to provide your own wrapper functions
4784around libev functions. 4830around libev functions.
… …
4993.Vb 3 5039.Vb 3
4994\& #define EV_COMMON \e 5040\& #define EV_COMMON \e
4995\& SV *self; /* contains this struct */ \e 5041\& SV *self; /* contains this struct */ \e
4996\& SV *cb_sv, *fh /* note no trailing ";" */ 5042\& SV *cb_sv, *fh /* note no trailing ";" */
4997.Ve 5043.Ve
4998.IP "\s-1EV_CB_DECLARE \s0(type)" 4 5044.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
4999.IX Item "EV_CB_DECLARE (type)" 5045.IX Item "EV_CB_DECLARE (type)"
5000.PD 0 5046.PD 0
5001.IP "\s-1EV_CB_INVOKE \s0(watcher, revents)" 4 5047.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
5002.IX Item "EV_CB_INVOKE (watcher, revents)" 5048.IX Item "EV_CB_INVOKE (watcher, revents)"
5003.IP "ev_set_cb (ev, cb)" 4 5049.IP "ev_set_cb (ev, cb)" 4
5004.IX Item "ev_set_cb (ev, cb)" 5050.IX Item "ev_set_cb (ev, cb)"
5005.PD 5051.PD
5006Can be used to change the callback member declaration in each watcher, 5052Can be used to change the callback member declaration in each watcher,
… …
5009their default definitions. One possible use for overriding these is to 5055their default definitions. One possible use for overriding these is to
5010avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use 5056avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
5011method calls instead of plain function calls in \*(C+. 5057method calls instead of plain function calls in \*(C+.
5012.SS "\s-1EXPORTED API SYMBOLS\s0" 5058.SS "\s-1EXPORTED API SYMBOLS\s0"
5013.IX Subsection "EXPORTED API SYMBOLS" 5059.IX Subsection "EXPORTED API SYMBOLS"
5014If you need to re-export the \s-1API \s0(e.g. via a \s-1DLL\s0) and you need a list of 5060If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of
5015exported symbols, you can use the provided \fISymbol.*\fR files which list 5061exported symbols, you can use the provided \fISymbol.*\fR files which list
5016all public symbols, one per line: 5062all public symbols, one per line:
5017.PP 5063.PP
5018.Vb 2 5064.Vb 2
5019\& Symbols.ev for libev proper 5065\& Symbols.ev for libev proper
… …
5251.PP 5297.PP
5252\fI\f(CI\*(C`select\*(C'\fI is buggy\fR 5298\fI\f(CI\*(C`select\*(C'\fI is buggy\fR
5253.IX Subsection "select is buggy" 5299.IX Subsection "select is buggy"
5254.PP 5300.PP
5255All that's left is \f(CW\*(C`select\*(C'\fR, and of course Apple found a way to fuck this 5301All that's left is \f(CW\*(C`select\*(C'\fR, and of course Apple found a way to fuck this
5256one up as well: On \s-1OS/X, \s0\f(CW\*(C`select\*(C'\fR actively limits the number of file 5302one up as well: On \s-1OS/X,\s0 \f(CW\*(C`select\*(C'\fR actively limits the number of file
5257descriptors you can pass in to 1024 \- your program suddenly crashes when 5303descriptors you can pass in to 1024 \- your program suddenly crashes when
5258you use more. 5304you use more.
5259.PP 5305.PP
5260There is an undocumented \*(L"workaround\*(R" for this \- defining 5306There is an undocumented \*(L"workaround\*(R" for this \- defining
5261\&\f(CW\*(C`_DARWIN_UNLIMITED_SELECT\*(C'\fR, which libev tries to use, so select \fIshould\fR 5307\&\f(CW\*(C`_DARWIN_UNLIMITED_SELECT\*(C'\fR, which libev tries to use, so select \fIshould\fR
… …
5409Libev assumes not only that all watcher pointers have the same internal 5455Libev assumes not only that all watcher pointers have the same internal
5410structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO C\s0 for example), but it also 5456structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO C\s0 for example), but it also
5411assumes that the same (machine) code can be used to call any watcher 5457assumes that the same (machine) code can be used to call any watcher
5412callback: The watcher callbacks have different type signatures, but libev 5458callback: The watcher callbacks have different type signatures, but libev
5413calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally. 5459calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally.
5460.IP "null pointers and integer zero are represented by 0 bytes" 4
5461.IX Item "null pointers and integer zero are represented by 0 bytes"
5462Libev uses \f(CW\*(C`memset\*(C'\fR to initialise structs and arrays to \f(CW0\fR bytes, and
5463relies on this setting pointers and integers to null.
5414.IP "pointer accesses must be thread-atomic" 4 5464.IP "pointer accesses must be thread-atomic" 4
5415.IX Item "pointer accesses must be thread-atomic" 5465.IX Item "pointer accesses must be thread-atomic"
5416Accessing a pointer value must be atomic, it must both be readable and 5466Accessing a pointer value must be atomic, it must both be readable and
5417writable in one piece \- this is the case on all current architectures. 5467writable in one piece \- this is the case on all current architectures.
5418.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4 5468.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4

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