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Revision 1.108 by root, Mon Dec 24 10:39:21 2007 UTC vs.
Revision 1.134 by root, Sat Mar 8 07:04:56 2008 UTC

260flags. If that is troubling you, check C<ev_backend ()> afterwards). 260flags. If that is troubling you, check C<ev_backend ()> afterwards).
261 261
262If you don't know what event loop to use, use the one returned from this 262If you don't know what event loop to use, use the one returned from this
263function. 263function.
264 264
265The default loop is the only loop that can handle C<ev_signal> and
266C<ev_child> watchers, and to do this, it always registers a handler
267for C<SIGCHLD>. If this is a problem for your app you can either
268create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
269can simply overwrite the C<SIGCHLD> signal handler I<after> calling
270C<ev_default_init>.
271
265The flags argument can be used to specify special behaviour or specific 272The flags argument can be used to specify special behaviour or specific
266backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). 273backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267 274
268The following flags are supported: 275The following flags are supported:
269 276
403While this backend scales well, it requires one system call per active 410While this backend scales well, it requires one system call per active
404file descriptor per loop iteration. For small and medium numbers of file 411file descriptor per loop iteration. For small and medium numbers of file
405descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend 412descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406might perform better. 413might perform better.
407 414
415On the positive side, ignoring the spurious readyness notifications, this
416backend actually performed to specification in all tests and is fully
417embeddable, which is a rare feat among the OS-specific backends.
418
408=item C<EVBACKEND_ALL> 419=item C<EVBACKEND_ALL>
409 420
410Try all backends (even potentially broken ones that wouldn't be tried 421Try all backends (even potentially broken ones that wouldn't be tried
411with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as 422with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
412C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. 423C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
414It is definitely not recommended to use this flag. 425It is definitely not recommended to use this flag.
415 426
416=back 427=back
417 428
418If one or more of these are ored into the flags value, then only these 429If one or more of these are ored into the flags value, then only these
419backends will be tried (in the reverse order as given here). If none are 430backends will be tried (in the reverse order as listed here). If none are
420specified, most compiled-in backend will be tried, usually in reverse 431specified, all backends in C<ev_recommended_backends ()> will be tried.
421order of their flag values :)
422 432
423The most typical usage is like this: 433The most typical usage is like this:
424 434
425 if (!ev_default_loop (0)) 435 if (!ev_default_loop (0))
426 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); 436 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473Like C<ev_default_destroy>, but destroys an event loop created by an 483Like C<ev_default_destroy>, but destroys an event loop created by an
474earlier call to C<ev_loop_new>. 484earlier call to C<ev_loop_new>.
475 485
476=item ev_default_fork () 486=item ev_default_fork ()
477 487
488This function sets a flag that causes subsequent C<ev_loop> iterations
478This function reinitialises the kernel state for backends that have 489to reinitialise the kernel state for backends that have one. Despite the
479one. Despite the name, you can call it anytime, but it makes most sense 490name, you can call it anytime, but it makes most sense after forking, in
480after forking, in either the parent or child process (or both, but that 491the child process (or both child and parent, but that again makes little
481again makes little sense). 492sense). You I<must> call it in the child before using any of the libev
493functions, and it will only take effect at the next C<ev_loop> iteration.
482 494
483You I<must> call this function in the child process after forking if and 495On the other hand, you only need to call this function in the child
484only if you want to use the event library in both processes. If you just 496process if and only if you want to use the event library in the child. If
485fork+exec, you don't have to call it. 497you just fork+exec, you don't have to call it at all.
486 498
487The function itself is quite fast and it's usually not a problem to call 499The function itself is quite fast and it's usually not a problem to call
488it just in case after a fork. To make this easy, the function will fit in 500it just in case after a fork. To make this easy, the function will fit in
489quite nicely into a call to C<pthread_atfork>: 501quite nicely into a call to C<pthread_atfork>:
490 502
491 pthread_atfork (0, 0, ev_default_fork); 503 pthread_atfork (0, 0, ev_default_fork);
492 504
493At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
494without calling this function, so if you force one of those backends you
495do not need to care.
496
497=item ev_loop_fork (loop) 505=item ev_loop_fork (loop)
498 506
499Like C<ev_default_fork>, but acts on an event loop created by 507Like C<ev_default_fork>, but acts on an event loop created by
500C<ev_loop_new>. Yes, you have to call this on every allocated event loop 508C<ev_loop_new>. Yes, you have to call this on every allocated event loop
501after fork, and how you do this is entirely your own problem. 509after fork, and how you do this is entirely your own problem.
510
511=item int ev_is_default_loop (loop)
512
513Returns true when the given loop actually is the default loop, false otherwise.
502 514
503=item unsigned int ev_loop_count (loop) 515=item unsigned int ev_loop_count (loop)
504 516
505Returns the count of loop iterations for the loop, which is identical to 517Returns the count of loop iterations for the loop, which is identical to
506the number of times libev did poll for new events. It starts at C<0> and 518the number of times libev did poll for new events. It starts at C<0> and
551usually a better approach for this kind of thing. 563usually a better approach for this kind of thing.
552 564
553Here are the gory details of what C<ev_loop> does: 565Here are the gory details of what C<ev_loop> does:
554 566
555 - Before the first iteration, call any pending watchers. 567 - Before the first iteration, call any pending watchers.
556 * If there are no active watchers (reference count is zero), return. 568 * If EVFLAG_FORKCHECK was used, check for a fork.
557 - Queue all prepare watchers and then call all outstanding watchers. 569 - If a fork was detected, queue and call all fork watchers.
570 - Queue and call all prepare watchers.
558 - If we have been forked, recreate the kernel state. 571 - If we have been forked, recreate the kernel state.
559 - Update the kernel state with all outstanding changes. 572 - Update the kernel state with all outstanding changes.
560 - Update the "event loop time". 573 - Update the "event loop time".
561 - Calculate for how long to block. 574 - Calculate for how long to sleep or block, if at all
575 (active idle watchers, EVLOOP_NONBLOCK or not having
576 any active watchers at all will result in not sleeping).
577 - Sleep if the I/O and timer collect interval say so.
562 - Block the process, waiting for any events. 578 - Block the process, waiting for any events.
563 - Queue all outstanding I/O (fd) events. 579 - Queue all outstanding I/O (fd) events.
564 - Update the "event loop time" and do time jump handling. 580 - Update the "event loop time" and do time jump handling.
565 - Queue all outstanding timers. 581 - Queue all outstanding timers.
566 - Queue all outstanding periodics. 582 - Queue all outstanding periodics.
567 - If no events are pending now, queue all idle watchers. 583 - If no events are pending now, queue all idle watchers.
568 - Queue all check watchers. 584 - Queue all check watchers.
569 - Call all queued watchers in reverse order (i.e. check watchers first). 585 - Call all queued watchers in reverse order (i.e. check watchers first).
570 Signals and child watchers are implemented as I/O watchers, and will 586 Signals and child watchers are implemented as I/O watchers, and will
571 be handled here by queueing them when their watcher gets executed. 587 be handled here by queueing them when their watcher gets executed.
572 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 588 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
573 were used, return, otherwise continue with step *. 589 were used, or there are no active watchers, return, otherwise
590 continue with step *.
574 591
575Example: Queue some jobs and then loop until no events are outsanding 592Example: Queue some jobs and then loop until no events are outstanding
576anymore. 593anymore.
577 594
578 ... queue jobs here, make sure they register event watchers as long 595 ... queue jobs here, make sure they register event watchers as long
579 ... as they still have work to do (even an idle watcher will do..) 596 ... as they still have work to do (even an idle watcher will do..)
580 ev_loop (my_loop, 0); 597 ev_loop (my_loop, 0);
584 601
585Can be used to make a call to C<ev_loop> return early (but only after it 602Can be used to make a call to C<ev_loop> return early (but only after it
586has processed all outstanding events). The C<how> argument must be either 603has processed all outstanding events). The C<how> argument must be either
587C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or 604C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
588C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. 605C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
606
607This "unloop state" will be cleared when entering C<ev_loop> again.
589 608
590=item ev_ref (loop) 609=item ev_ref (loop)
591 610
592=item ev_unref (loop) 611=item ev_unref (loop)
593 612
598returning, ev_unref() after starting, and ev_ref() before stopping it. For 617returning, ev_unref() after starting, and ev_ref() before stopping it. For
599example, libev itself uses this for its internal signal pipe: It is not 618example, libev itself uses this for its internal signal pipe: It is not
600visible to the libev user and should not keep C<ev_loop> from exiting if 619visible to the libev user and should not keep C<ev_loop> from exiting if
601no event watchers registered by it are active. It is also an excellent 620no event watchers registered by it are active. It is also an excellent
602way to do this for generic recurring timers or from within third-party 621way to do this for generic recurring timers or from within third-party
603libraries. Just remember to I<unref after start> and I<ref before stop>. 622libraries. Just remember to I<unref after start> and I<ref before stop>
623(but only if the watcher wasn't active before, or was active before,
624respectively).
604 625
605Example: Create a signal watcher, but keep it from keeping C<ev_loop> 626Example: Create a signal watcher, but keep it from keeping C<ev_loop>
606running when nothing else is active. 627running when nothing else is active.
607 628
608 struct ev_signal exitsig; 629 struct ev_signal exitsig;
756 777
757=item C<EV_FORK> 778=item C<EV_FORK>
758 779
759The event loop has been resumed in the child process after fork (see 780The event loop has been resumed in the child process after fork (see
760C<ev_fork>). 781C<ev_fork>).
782
783=item C<EV_ASYNC>
784
785The given async watcher has been asynchronously notified (see C<ev_async>).
761 786
762=item C<EV_ERROR> 787=item C<EV_ERROR>
763 788
764An unspecified error has occured, the watcher has been stopped. This might 789An unspecified error has occured, the watcher has been stopped. This might
765happen because the watcher could not be properly started because libev 790happen because the watcher could not be properly started because libev
983In general you can register as many read and/or write event watchers per 1008In general you can register as many read and/or write event watchers per
984fd as you want (as long as you don't confuse yourself). Setting all file 1009fd as you want (as long as you don't confuse yourself). Setting all file
985descriptors to non-blocking mode is also usually a good idea (but not 1010descriptors to non-blocking mode is also usually a good idea (but not
986required if you know what you are doing). 1011required if you know what you are doing).
987 1012
988You have to be careful with dup'ed file descriptors, though. Some backends
989(the linux epoll backend is a notable example) cannot handle dup'ed file
990descriptors correctly if you register interest in two or more fds pointing
991to the same underlying file/socket/etc. description (that is, they share
992the same underlying "file open").
993
994If you must do this, then force the use of a known-to-be-good backend 1013If you must do this, then force the use of a known-to-be-good backend
995(at the time of this writing, this includes only C<EVBACKEND_SELECT> and 1014(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
996C<EVBACKEND_POLL>). 1015C<EVBACKEND_POLL>).
997 1016
998Another thing you have to watch out for is that it is quite easy to 1017Another thing you have to watch out for is that it is quite easy to
1033 1052
1034=head3 The special problem of dup'ed file descriptors 1053=head3 The special problem of dup'ed file descriptors
1035 1054
1036Some backends (e.g. epoll), cannot register events for file descriptors, 1055Some backends (e.g. epoll), cannot register events for file descriptors,
1037but only events for the underlying file descriptions. That means when you 1056but only events for the underlying file descriptions. That means when you
1038have C<dup ()>'ed file descriptors and register events for them, only one 1057have C<dup ()>'ed file descriptors or weirder constellations, and register
1039file descriptor might actually receive events. 1058events for them, only one file descriptor might actually receive events.
1040 1059
1041There is no workaround possible except not registering events 1060There is no workaround possible except not registering events
1042for potentially C<dup ()>'ed file descriptors, or to resort to 1061for potentially C<dup ()>'ed file descriptors, or to resort to
1043C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. 1062C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1044 1063
1073=item int events [read-only] 1092=item int events [read-only]
1074 1093
1075The events being watched. 1094The events being watched.
1076 1095
1077=back 1096=back
1097
1098=head3 Examples
1078 1099
1079Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1100Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1080readable, but only once. Since it is likely line-buffered, you could 1101readable, but only once. Since it is likely line-buffered, you could
1081attempt to read a whole line in the callback. 1102attempt to read a whole line in the callback.
1082 1103
1135configure a timer to trigger every 10 seconds, then it will trigger at 1156configure a timer to trigger every 10 seconds, then it will trigger at
1136exactly 10 second intervals. If, however, your program cannot keep up with 1157exactly 10 second intervals. If, however, your program cannot keep up with
1137the timer (because it takes longer than those 10 seconds to do stuff) the 1158the timer (because it takes longer than those 10 seconds to do stuff) the
1138timer will not fire more than once per event loop iteration. 1159timer will not fire more than once per event loop iteration.
1139 1160
1140=item ev_timer_again (loop) 1161=item ev_timer_again (loop, ev_timer *)
1141 1162
1142This will act as if the timer timed out and restart it again if it is 1163This will act as if the timer timed out and restart it again if it is
1143repeating. The exact semantics are: 1164repeating. The exact semantics are:
1144 1165
1145If the timer is pending, its pending status is cleared. 1166If the timer is pending, its pending status is cleared.
1180or C<ev_timer_again> is called and determines the next timeout (if any), 1201or C<ev_timer_again> is called and determines the next timeout (if any),
1181which is also when any modifications are taken into account. 1202which is also when any modifications are taken into account.
1182 1203
1183=back 1204=back
1184 1205
1206=head3 Examples
1207
1185Example: Create a timer that fires after 60 seconds. 1208Example: Create a timer that fires after 60 seconds.
1186 1209
1187 static void 1210 static void
1188 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1211 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1189 { 1212 {
1252In this configuration the watcher triggers an event at the wallclock time 1275In this configuration the watcher triggers an event at the wallclock time
1253C<at> and doesn't repeat. It will not adjust when a time jump occurs, 1276C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1254that is, if it is to be run at January 1st 2011 then it will run when the 1277that is, if it is to be run at January 1st 2011 then it will run when the
1255system time reaches or surpasses this time. 1278system time reaches or surpasses this time.
1256 1279
1257=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) 1280=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1258 1281
1259In this mode the watcher will always be scheduled to time out at the next 1282In this mode the watcher will always be scheduled to time out at the next
1260C<at + N * interval> time (for some integer N, which can also be negative) 1283C<at + N * interval> time (for some integer N, which can also be negative)
1261and then repeat, regardless of any time jumps. 1284and then repeat, regardless of any time jumps.
1262 1285
1345 1368
1346When active, contains the absolute time that the watcher is supposed to 1369When active, contains the absolute time that the watcher is supposed to
1347trigger next. 1370trigger next.
1348 1371
1349=back 1372=back
1373
1374=head3 Examples
1350 1375
1351Example: Call a callback every hour, or, more precisely, whenever the 1376Example: Call a callback every hour, or, more precisely, whenever the
1352system clock is divisible by 3600. The callback invocation times have 1377system clock is divisible by 3600. The callback invocation times have
1353potentially a lot of jittering, but good long-term stability. 1378potentially a lot of jittering, but good long-term stability.
1354 1379
1411 1436
1412The signal the watcher watches out for. 1437The signal the watcher watches out for.
1413 1438
1414=back 1439=back
1415 1440
1441=head3 Examples
1442
1443Example: Try to exit cleanly on SIGINT and SIGTERM.
1444
1445 static void
1446 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1447 {
1448 ev_unloop (loop, EVUNLOOP_ALL);
1449 }
1450
1451 struct ev_signal signal_watcher;
1452 ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1453 ev_signal_start (loop, &sigint_cb);
1454
1416 1455
1417=head2 C<ev_child> - watch out for process status changes 1456=head2 C<ev_child> - watch out for process status changes
1418 1457
1419Child watchers trigger when your process receives a SIGCHLD in response to 1458Child watchers trigger when your process receives a SIGCHLD in response to
1420some child status changes (most typically when a child of yours dies). 1459some child status changes (most typically when a child of yours dies). It
1460is permissible to install a child watcher I<after> the child has been
1461forked (which implies it might have already exited), as long as the event
1462loop isn't entered (or is continued from a watcher).
1463
1464Only the default event loop is capable of handling signals, and therefore
1465you can only rgeister child watchers in the default event loop.
1466
1467=head3 Process Interaction
1468
1469Libev grabs C<SIGCHLD> as soon as the default event loop is
1470initialised. This is necessary to guarantee proper behaviour even if
1471the first child watcher is started after the child exits. The occurance
1472of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1473synchronously as part of the event loop processing. Libev always reaps all
1474children, even ones not watched.
1475
1476=head3 Overriding the Built-In Processing
1477
1478Libev offers no special support for overriding the built-in child
1479processing, but if your application collides with libev's default child
1480handler, you can override it easily by installing your own handler for
1481C<SIGCHLD> after initialising the default loop, and making sure the
1482default loop never gets destroyed. You are encouraged, however, to use an
1483event-based approach to child reaping and thus use libev's support for
1484that, so other libev users can use C<ev_child> watchers freely.
1421 1485
1422=head3 Watcher-Specific Functions and Data Members 1486=head3 Watcher-Specific Functions and Data Members
1423 1487
1424=over 4 1488=over 4
1425 1489
1426=item ev_child_init (ev_child *, callback, int pid) 1490=item ev_child_init (ev_child *, callback, int pid, int trace)
1427 1491
1428=item ev_child_set (ev_child *, int pid) 1492=item ev_child_set (ev_child *, int pid, int trace)
1429 1493
1430Configures the watcher to wait for status changes of process C<pid> (or 1494Configures the watcher to wait for status changes of process C<pid> (or
1431I<any> process if C<pid> is specified as C<0>). The callback can look 1495I<any> process if C<pid> is specified as C<0>). The callback can look
1432at the C<rstatus> member of the C<ev_child> watcher structure to see 1496at the C<rstatus> member of the C<ev_child> watcher structure to see
1433the status word (use the macros from C<sys/wait.h> and see your systems 1497the status word (use the macros from C<sys/wait.h> and see your systems
1434C<waitpid> documentation). The C<rpid> member contains the pid of the 1498C<waitpid> documentation). The C<rpid> member contains the pid of the
1435process causing the status change. 1499process causing the status change. C<trace> must be either C<0> (only
1500activate the watcher when the process terminates) or C<1> (additionally
1501activate the watcher when the process is stopped or continued).
1436 1502
1437=item int pid [read-only] 1503=item int pid [read-only]
1438 1504
1439The process id this watcher watches out for, or C<0>, meaning any process id. 1505The process id this watcher watches out for, or C<0>, meaning any process id.
1440 1506
1447The process exit/trace status caused by C<rpid> (see your systems 1513The process exit/trace status caused by C<rpid> (see your systems
1448C<waitpid> and C<sys/wait.h> documentation for details). 1514C<waitpid> and C<sys/wait.h> documentation for details).
1449 1515
1450=back 1516=back
1451 1517
1452Example: Try to exit cleanly on SIGINT and SIGTERM. 1518=head3 Examples
1519
1520Example: C<fork()> a new process and install a child handler to wait for
1521its completion.
1522
1523 ev_child cw;
1453 1524
1454 static void 1525 static void
1455 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1526 child_cb (EV_P_ struct ev_child *w, int revents)
1456 { 1527 {
1457 ev_unloop (loop, EVUNLOOP_ALL); 1528 ev_child_stop (EV_A_ w);
1529 printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1458 } 1530 }
1459 1531
1460 struct ev_signal signal_watcher; 1532 pid_t pid = fork ();
1461 ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1533
1462 ev_signal_start (loop, &sigint_cb); 1534 if (pid < 0)
1535 // error
1536 else if (pid == 0)
1537 {
1538 // the forked child executes here
1539 exit (1);
1540 }
1541 else
1542 {
1543 ev_child_init (&cw, child_cb, pid, 0);
1544 ev_child_start (EV_DEFAULT_ &cw);
1545 }
1463 1546
1464 1547
1465=head2 C<ev_stat> - did the file attributes just change? 1548=head2 C<ev_stat> - did the file attributes just change?
1466 1549
1467This watches a filesystem path for attribute changes. That is, it calls 1550This watches a filesystem path for attribute changes. That is, it calls
1547 1630
1548The callback will be receive C<EV_STAT> when a change was detected, 1631The callback will be receive C<EV_STAT> when a change was detected,
1549relative to the attributes at the time the watcher was started (or the 1632relative to the attributes at the time the watcher was started (or the
1550last change was detected). 1633last change was detected).
1551 1634
1552=item ev_stat_stat (ev_stat *) 1635=item ev_stat_stat (loop, ev_stat *)
1553 1636
1554Updates the stat buffer immediately with new values. If you change the 1637Updates the stat buffer immediately with new values. If you change the
1555watched path in your callback, you could call this fucntion to avoid 1638watched path in your callback, you could call this fucntion to avoid
1556detecting this change (while introducing a race condition). Can also be 1639detecting this change (while introducing a race condition). Can also be
1557useful simply to find out the new values. 1640useful simply to find out the new values.
1664kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1747kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1665believe me. 1748believe me.
1666 1749
1667=back 1750=back
1668 1751
1752=head3 Examples
1753
1669Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1754Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1670callback, free it. Also, use no error checking, as usual. 1755callback, free it. Also, use no error checking, as usual.
1671 1756
1672 static void 1757 static void
1673 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1758 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1674 { 1759 {
1675 free (w); 1760 free (w);
1676 // now do something you wanted to do when the program has 1761 // now do something you wanted to do when the program has
1677 // no longer asnything immediate to do. 1762 // no longer anything immediate to do.
1678 } 1763 }
1679 1764
1680 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1765 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1681 ev_idle_init (idle_watcher, idle_cb); 1766 ev_idle_init (idle_watcher, idle_cb);
1682 ev_idle_start (loop, idle_cb); 1767 ev_idle_start (loop, idle_cb);
1744parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1829parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1745macros, but using them is utterly, utterly and completely pointless. 1830macros, but using them is utterly, utterly and completely pointless.
1746 1831
1747=back 1832=back
1748 1833
1834=head3 Examples
1835
1749There are a number of principal ways to embed other event loops or modules 1836There are a number of principal ways to embed other event loops or modules
1750into libev. Here are some ideas on how to include libadns into libev 1837into libev. Here are some ideas on how to include libadns into libev
1751(there is a Perl module named C<EV::ADNS> that does this, which you could 1838(there is a Perl module named C<EV::ADNS> that does this, which you could
1752use for an actually working example. Another Perl module named C<EV::Glib> 1839use for an actually working example. Another Perl module named C<EV::Glib>
1753embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV 1840embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
1921portable one. 2008portable one.
1922 2009
1923So when you want to use this feature you will always have to be prepared 2010So when you want to use this feature you will always have to be prepared
1924that you cannot get an embeddable loop. The recommended way to get around 2011that you cannot get an embeddable loop. The recommended way to get around
1925this is to have a separate variables for your embeddable loop, try to 2012this is to have a separate variables for your embeddable loop, try to
1926create it, and if that fails, use the normal loop for everything: 2013create it, and if that fails, use the normal loop for everything.
2014
2015=head3 Watcher-Specific Functions and Data Members
2016
2017=over 4
2018
2019=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2020
2021=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
2022
2023Configures the watcher to embed the given loop, which must be
2024embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2025invoked automatically, otherwise it is the responsibility of the callback
2026to invoke it (it will continue to be called until the sweep has been done,
2027if you do not want thta, you need to temporarily stop the embed watcher).
2028
2029=item ev_embed_sweep (loop, ev_embed *)
2030
2031Make a single, non-blocking sweep over the embedded loop. This works
2032similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2033apropriate way for embedded loops.
2034
2035=item struct ev_loop *other [read-only]
2036
2037The embedded event loop.
2038
2039=back
2040
2041=head3 Examples
2042
2043Example: Try to get an embeddable event loop and embed it into the default
2044event loop. If that is not possible, use the default loop. The default
2045loop is stored in C<loop_hi>, while the mebeddable loop is stored in
2046C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
2047used).
1927 2048
1928 struct ev_loop *loop_hi = ev_default_init (0); 2049 struct ev_loop *loop_hi = ev_default_init (0);
1929 struct ev_loop *loop_lo = 0; 2050 struct ev_loop *loop_lo = 0;
1930 struct ev_embed embed; 2051 struct ev_embed embed;
1931 2052
1942 ev_embed_start (loop_hi, &embed); 2063 ev_embed_start (loop_hi, &embed);
1943 } 2064 }
1944 else 2065 else
1945 loop_lo = loop_hi; 2066 loop_lo = loop_hi;
1946 2067
1947=head3 Watcher-Specific Functions and Data Members 2068Example: Check if kqueue is available but not recommended and create
2069a kqueue backend for use with sockets (which usually work with any
2070kqueue implementation). Store the kqueue/socket-only event loop in
2071C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1948 2072
1949=over 4 2073 struct ev_loop *loop = ev_default_init (0);
2074 struct ev_loop *loop_socket = 0;
2075 struct ev_embed embed;
2076
2077 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2078 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2079 {
2080 ev_embed_init (&embed, 0, loop_socket);
2081 ev_embed_start (loop, &embed);
2082 }
1950 2083
1951=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 2084 if (!loop_socket)
2085 loop_socket = loop;
1952 2086
1953=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 2087 // now use loop_socket for all sockets, and loop for everything else
1954
1955Configures the watcher to embed the given loop, which must be
1956embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1957invoked automatically, otherwise it is the responsibility of the callback
1958to invoke it (it will continue to be called until the sweep has been done,
1959if you do not want thta, you need to temporarily stop the embed watcher).
1960
1961=item ev_embed_sweep (loop, ev_embed *)
1962
1963Make a single, non-blocking sweep over the embedded loop. This works
1964similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1965apropriate way for embedded loops.
1966
1967=item struct ev_loop *other [read-only]
1968
1969The embedded event loop.
1970
1971=back
1972 2088
1973 2089
1974=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2090=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1975 2091
1976Fork watchers are called when a C<fork ()> was detected (usually because 2092Fork watchers are called when a C<fork ()> was detected (usually because
1992believe me. 2108believe me.
1993 2109
1994=back 2110=back
1995 2111
1996 2112
2113=head2 C<ev_async> - how to wake up another event loop
2114
2115In general, you cannot use an C<ev_loop> from multiple threads or other
2116asynchronous sources such as signal handlers (as opposed to multiple event
2117loops - those are of course safe to use in different threads).
2118
2119Sometimes, however, you need to wake up another event loop you do not
2120control, for example because it belongs to another thread. This is what
2121C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
2122can signal it by calling C<ev_async_send>, which is thread- and signal
2123safe.
2124
2125This functionality is very similar to C<ev_signal> watchers, as signals,
2126too, are asynchronous in nature, and signals, too, will be compressed
2127(i.e. the number of callback invocations may be less than the number of
2128C<ev_async_sent> calls).
2129
2130Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2131just the default loop.
2132
2133=head3 Queueing
2134
2135C<ev_async> does not support queueing of data in any way. The reason
2136is that the author does not know of a simple (or any) algorithm for a
2137multiple-writer-single-reader queue that works in all cases and doesn't
2138need elaborate support such as pthreads.
2139
2140That means that if you want to queue data, you have to provide your own
2141queue. But at least I can tell you would implement locking around your
2142queue:
2143
2144=over 4
2145
2146=item queueing from a signal handler context
2147
2148To implement race-free queueing, you simply add to the queue in the signal
2149handler but you block the signal handler in the watcher callback. Here is an example that does that for
2150some fictitiuous SIGUSR1 handler:
2151
2152 static ev_async mysig;
2153
2154 static void
2155 sigusr1_handler (void)
2156 {
2157 sometype data;
2158
2159 // no locking etc.
2160 queue_put (data);
2161 ev_async_send (EV_DEFAULT_ &mysig);
2162 }
2163
2164 static void
2165 mysig_cb (EV_P_ ev_async *w, int revents)
2166 {
2167 sometype data;
2168 sigset_t block, prev;
2169
2170 sigemptyset (&block);
2171 sigaddset (&block, SIGUSR1);
2172 sigprocmask (SIG_BLOCK, &block, &prev);
2173
2174 while (queue_get (&data))
2175 process (data);
2176
2177 if (sigismember (&prev, SIGUSR1)
2178 sigprocmask (SIG_UNBLOCK, &block, 0);
2179 }
2180
2181(Note: pthreads in theory requires you to use C<pthread_setmask>
2182instead of C<sigprocmask> when you use threads, but libev doesn't do it
2183either...).
2184
2185=item queueing from a thread context
2186
2187The strategy for threads is different, as you cannot (easily) block
2188threads but you can easily preempt them, so to queue safely you need to
2189employ a traditional mutex lock, such as in this pthread example:
2190
2191 static ev_async mysig;
2192 static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
2193
2194 static void
2195 otherthread (void)
2196 {
2197 // only need to lock the actual queueing operation
2198 pthread_mutex_lock (&mymutex);
2199 queue_put (data);
2200 pthread_mutex_unlock (&mymutex);
2201
2202 ev_async_send (EV_DEFAULT_ &mysig);
2203 }
2204
2205 static void
2206 mysig_cb (EV_P_ ev_async *w, int revents)
2207 {
2208 pthread_mutex_lock (&mymutex);
2209
2210 while (queue_get (&data))
2211 process (data);
2212
2213 pthread_mutex_unlock (&mymutex);
2214 }
2215
2216=back
2217
2218
2219=head3 Watcher-Specific Functions and Data Members
2220
2221=over 4
2222
2223=item ev_async_init (ev_async *, callback)
2224
2225Initialises and configures the async watcher - it has no parameters of any
2226kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2227believe me.
2228
2229=item ev_async_send (loop, ev_async *)
2230
2231Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2232an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2233C<ev_feed_event>, this call is safe to do in other threads, signal or
2234similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
2235section below on what exactly this means).
2236
2237This call incurs the overhead of a syscall only once per loop iteration,
2238so while the overhead might be noticable, it doesn't apply to repeated
2239calls to C<ev_async_send>.
2240
2241=back
2242
2243
1997=head1 OTHER FUNCTIONS 2244=head1 OTHER FUNCTIONS
1998 2245
1999There are some other functions of possible interest. Described. Here. Now. 2246There are some other functions of possible interest. Described. Here. Now.
2000 2247
2001=over 4 2248=over 4
2228Example: Define a class with an IO and idle watcher, start one of them in 2475Example: Define a class with an IO and idle watcher, start one of them in
2229the constructor. 2476the constructor.
2230 2477
2231 class myclass 2478 class myclass
2232 { 2479 {
2233 ev_io io; void io_cb (ev::io &w, int revents); 2480 ev::io io; void io_cb (ev::io &w, int revents);
2234 ev_idle idle void idle_cb (ev::idle &w, int revents); 2481 ev:idle idle void idle_cb (ev::idle &w, int revents);
2235 2482
2236 myclass (); 2483 myclass (int fd)
2237 }
2238
2239 myclass::myclass (int fd)
2240 { 2484 {
2241 io .set <myclass, &myclass::io_cb > (this); 2485 io .set <myclass, &myclass::io_cb > (this);
2242 idle.set <myclass, &myclass::idle_cb> (this); 2486 idle.set <myclass, &myclass::idle_cb> (this);
2243 2487
2244 io.start (fd, ev::READ); 2488 io.start (fd, ev::READ);
2489 }
2245 } 2490 };
2246 2491
2247 2492
2248=head1 MACRO MAGIC 2493=head1 MACRO MAGIC
2249 2494
2250Libev can be compiled with a variety of options, the most fundamantal 2495Libev can be compiled with a variety of options, the most fundamantal
2455wants osf handles on win32 (this is the case when the select to 2700wants osf handles on win32 (this is the case when the select to
2456be used is the winsock select). This means that it will call 2701be used is the winsock select). This means that it will call
2457C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, 2702C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2458it is assumed that all these functions actually work on fds, even 2703it is assumed that all these functions actually work on fds, even
2459on win32. Should not be defined on non-win32 platforms. 2704on win32. Should not be defined on non-win32 platforms.
2705
2706=item EV_FD_TO_WIN32_HANDLE
2707
2708If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2709file descriptors to socket handles. When not defining this symbol (the
2710default), then libev will call C<_get_osfhandle>, which is usually
2711correct. In some cases, programs use their own file descriptor management,
2712in which case they can provide this function to map fds to socket handles.
2460 2713
2461=item EV_USE_POLL 2714=item EV_USE_POLL
2462 2715
2463If defined to be C<1>, libev will compile in support for the C<poll>(2) 2716If defined to be C<1>, libev will compile in support for the C<poll>(2)
2464backend. Otherwise it will be enabled on non-win32 platforms. It 2717backend. Otherwise it will be enabled on non-win32 platforms. It
2498 2751
2499If defined to be C<1>, libev will compile in support for the Linux inotify 2752If defined to be C<1>, libev will compile in support for the Linux inotify
2500interface to speed up C<ev_stat> watchers. Its actual availability will 2753interface to speed up C<ev_stat> watchers. Its actual availability will
2501be detected at runtime. 2754be detected at runtime.
2502 2755
2756=item EV_ATOMIC_T
2757
2758Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2759access is atomic with respect to other threads or signal contexts. No such
2760type is easily found in the C language, so you can provide your own type
2761that you know is safe for your purposes. It is used both for signal handler "locking"
2762as well as for signal and thread safety in C<ev_async> watchers.
2763
2764In the absense of this define, libev will use C<sig_atomic_t volatile>
2765(from F<signal.h>), which is usually good enough on most platforms.
2766
2503=item EV_H 2767=item EV_H
2504 2768
2505The name of the F<ev.h> header file used to include it. The default if 2769The name of the F<ev.h> header file used to include it. The default if
2506undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2770undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2507can be used to virtually rename the F<ev.h> header file in case of conflicts. 2771used to virtually rename the F<ev.h> header file in case of conflicts.
2508 2772
2509=item EV_CONFIG_H 2773=item EV_CONFIG_H
2510 2774
2511If C<EV_STANDALONE> isn't C<1>, this variable can be used to override 2775If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2512F<ev.c>'s idea of where to find the F<config.h> file, similarly to 2776F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2513C<EV_H>, above. 2777C<EV_H>, above.
2514 2778
2515=item EV_EVENT_H 2779=item EV_EVENT_H
2516 2780
2517Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea 2781Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2518of how the F<event.h> header can be found. 2782of how the F<event.h> header can be found, the default is C<"event.h">.
2519 2783
2520=item EV_PROTOTYPES 2784=item EV_PROTOTYPES
2521 2785
2522If defined to be C<0>, then F<ev.h> will not define any function 2786If defined to be C<0>, then F<ev.h> will not define any function
2523prototypes, but still define all the structs and other symbols. This is 2787prototypes, but still define all the structs and other symbols. This is
2572defined to be C<0>, then they are not. 2836defined to be C<0>, then they are not.
2573 2837
2574=item EV_FORK_ENABLE 2838=item EV_FORK_ENABLE
2575 2839
2576If undefined or defined to be C<1>, then fork watchers are supported. If 2840If undefined or defined to be C<1>, then fork watchers are supported. If
2841defined to be C<0>, then they are not.
2842
2843=item EV_ASYNC_ENABLE
2844
2845If undefined or defined to be C<1>, then async watchers are supported. If
2577defined to be C<0>, then they are not. 2846defined to be C<0>, then they are not.
2578 2847
2579=item EV_MINIMAL 2848=item EV_MINIMAL
2580 2849
2581If you need to shave off some kilobytes of code at the expense of some 2850If you need to shave off some kilobytes of code at the expense of some
2702=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) 2971=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2703 2972
2704That means that changing a timer costs less than removing/adding them 2973That means that changing a timer costs less than removing/adding them
2705as only the relative motion in the event queue has to be paid for. 2974as only the relative motion in the event queue has to be paid for.
2706 2975
2707=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2976=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2708 2977
2709These just add the watcher into an array or at the head of a list. 2978These just add the watcher into an array or at the head of a list.
2710 2979
2711=item Stopping check/prepare/idle watchers: O(1) 2980=item Stopping check/prepare/idle/fork/async watchers: O(1)
2712 2981
2713=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 2982=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2714 2983
2715These watchers are stored in lists then need to be walked to find the 2984These watchers are stored in lists then need to be walked to find the
2716correct watcher to remove. The lists are usually short (you don't usually 2985correct watcher to remove. The lists are usually short (you don't usually
2732=item Priority handling: O(number_of_priorities) 3001=item Priority handling: O(number_of_priorities)
2733 3002
2734Priorities are implemented by allocating some space for each 3003Priorities are implemented by allocating some space for each
2735priority. When doing priority-based operations, libev usually has to 3004priority. When doing priority-based operations, libev usually has to
2736linearly search all the priorities, but starting/stopping and activating 3005linearly search all the priorities, but starting/stopping and activating
2737watchers becomes O(1) w.r.t. prioritiy handling. 3006watchers becomes O(1) w.r.t. priority handling.
3007
3008=item Sending an ev_async: O(1)
3009
3010=item Processing ev_async_send: O(number_of_async_watchers)
3011
3012=item Processing signals: O(max_signal_number)
3013
3014Sending involves a syscall I<iff> there were no other C<ev_async_send>
3015calls in the current loop iteration. Checking for async and signal events
3016involves iterating over all running async watchers or all signal numbers.
2738 3017
2739=back 3018=back
2740 3019
2741 3020
3021=head1 Win32 platform limitations and workarounds
3022
3023Win32 doesn't support any of the standards (e.g. POSIX) that libev
3024requires, and its I/O model is fundamentally incompatible with the POSIX
3025model. Libev still offers limited functionality on this platform in
3026the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3027descriptors. This only applies when using Win32 natively, not when using
3028e.g. cygwin.
3029
3030There is no supported compilation method available on windows except
3031embedding it into other applications.
3032
3033Due to the many, low, and arbitrary limits on the win32 platform and the
3034abysmal performance of winsockets, using a large number of sockets is not
3035recommended (and not reasonable). If your program needs to use more than
3036a hundred or so sockets, then likely it needs to use a totally different
3037implementation for windows, as libev offers the POSIX model, which cannot
3038be implemented efficiently on windows (microsoft monopoly games).
3039
3040=over 4
3041
3042=item The winsocket select function
3043
3044The winsocket C<select> function doesn't follow POSIX in that it requires
3045socket I<handles> and not socket I<file descriptors>. This makes select
3046very inefficient, and also requires a mapping from file descriptors
3047to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
3048C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
3049symbols for more info.
3050
3051The configuration for a "naked" win32 using the microsoft runtime
3052libraries and raw winsocket select is:
3053
3054 #define EV_USE_SELECT 1
3055 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3056
3057Note that winsockets handling of fd sets is O(n), so you can easily get a
3058complexity in the O(n²) range when using win32.
3059
3060=item Limited number of file descriptors
3061
3062Windows has numerous arbitrary (and low) limits on things. Early versions
3063of winsocket's select only supported waiting for a max. of C<64> handles
3064(probably owning to the fact that all windows kernels can only wait for
3065C<64> things at the same time internally; microsoft recommends spawning a
3066chain of threads and wait for 63 handles and the previous thread in each).
3067
3068Newer versions support more handles, but you need to define C<FD_SETSIZE>
3069to some high number (e.g. C<2048>) before compiling the winsocket select
3070call (which might be in libev or elsewhere, for example, perl does its own
3071select emulation on windows).
3072
3073Another limit is the number of file descriptors in the microsoft runtime
3074libraries, which by default is C<64> (there must be a hidden I<64> fetish
3075or something like this inside microsoft). You can increase this by calling
3076C<_setmaxstdio>, which can increase this limit to C<2048> (another
3077arbitrary limit), but is broken in many versions of the microsoft runtime
3078libraries.
3079
3080This might get you to about C<512> or C<2048> sockets (depending on
3081windows version and/or the phase of the moon). To get more, you need to
3082wrap all I/O functions and provide your own fd management, but the cost of
3083calling select (O(n²)) will likely make this unworkable.
3084
3085=back
3086
3087
2742=head1 AUTHOR 3088=head1 AUTHOR
2743 3089
2744Marc Lehmann <libev@schmorp.de>. 3090Marc Lehmann <libev@schmorp.de>.
2745 3091

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