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6 6
7 #include <ev.h> 7 #include <ev.h>
8 8
9=head2 EXAMPLE PROGRAM 9=head2 EXAMPLE PROGRAM
10 10
11 // a single header file is required
11 #include <ev.h> 12 #include <ev.h>
12 13
14 // every watcher type has its own typedef'd struct
15 // with the name ev_<type>
13 ev_io stdin_watcher; 16 ev_io stdin_watcher;
14 ev_timer timeout_watcher; 17 ev_timer timeout_watcher;
15 18
19 // all watcher callbacks have a similar signature
16 /* called when data readable on stdin */ 20 // this callback is called when data is readable on stdin
17 static void 21 static void
18 stdin_cb (EV_P_ struct ev_io *w, int revents) 22 stdin_cb (EV_P_ struct ev_io *w, int revents)
19 { 23 {
20 /* puts ("stdin ready"); */ 24 puts ("stdin ready");
21 ev_io_stop (EV_A_ w); /* just a syntax example */ 25 // for one-shot events, one must manually stop the watcher
22 ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */ 26 // with its corresponding stop function.
27 ev_io_stop (EV_A_ w);
28
29 // this causes all nested ev_loop's to stop iterating
30 ev_unloop (EV_A_ EVUNLOOP_ALL);
23 } 31 }
24 32
33 // another callback, this time for a time-out
25 static void 34 static void
26 timeout_cb (EV_P_ struct ev_timer *w, int revents) 35 timeout_cb (EV_P_ struct ev_timer *w, int revents)
27 { 36 {
28 /* puts ("timeout"); */ 37 puts ("timeout");
29 ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */ 38 // this causes the innermost ev_loop to stop iterating
39 ev_unloop (EV_A_ EVUNLOOP_ONE);
30 } 40 }
31 41
32 int 42 int
33 main (void) 43 main (void)
34 { 44 {
45 // use the default event loop unless you have special needs
35 struct ev_loop *loop = ev_default_loop (0); 46 struct ev_loop *loop = ev_default_loop (0);
36 47
37 /* initialise an io watcher, then start it */ 48 // initialise an io watcher, then start it
49 // this one will watch for stdin to become readable
38 ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); 50 ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39 ev_io_start (loop, &stdin_watcher); 51 ev_io_start (loop, &stdin_watcher);
40 52
53 // initialise a timer watcher, then start it
41 /* simple non-repeating 5.5 second timeout */ 54 // simple non-repeating 5.5 second timeout
42 ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); 55 ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43 ev_timer_start (loop, &timeout_watcher); 56 ev_timer_start (loop, &timeout_watcher);
44 57
45 /* loop till timeout or data ready */ 58 // now wait for events to arrive
46 ev_loop (loop, 0); 59 ev_loop (loop, 0);
47 60
61 // unloop was called, so exit
48 return 0; 62 return 0;
49 } 63 }
50 64
51=head1 DESCRIPTION 65=head1 DESCRIPTION
52 66
53The newest version of this document is also available as a html-formatted 67The newest version of this document is also available as an html-formatted
54web page you might find easier to navigate when reading it for the first 68web page you might find easier to navigate when reading it for the first
55time: L<http://cvs.schmorp.de/libev/ev.html>. 69time: L<http://cvs.schmorp.de/libev/ev.html>.
56 70
57Libev is an event loop: you register interest in certain events (such as a 71Libev is an event loop: you register interest in certain events (such as a
58file descriptor being readable or a timeout occurring), and it will manage 72file descriptor being readable or a timeout occurring), and it will manage
84L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent 98L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85for example). 99for example).
86 100
87=head2 CONVENTIONS 101=head2 CONVENTIONS
88 102
89Libev is very configurable. In this manual the default configuration will 103Libev is very configurable. In this manual the default (and most common)
90be described, which supports multiple event loops. For more info about 104configuration will be described, which supports multiple event loops. For
91various configuration options please have a look at B<EMBED> section in 105more info about various configuration options please have a look at
92this manual. If libev was configured without support for multiple event 106B<EMBED> section in this manual. If libev was configured without support
93loops, then all functions taking an initial argument of name C<loop> 107for multiple event loops, then all functions taking an initial argument of
94(which is always of type C<struct ev_loop *>) will not have this argument. 108name C<loop> (which is always of type C<struct ev_loop *>) will not have
109this argument.
95 110
96=head2 TIME REPRESENTATION 111=head2 TIME REPRESENTATION
97 112
98Libev represents time as a single floating point number, representing the 113Libev represents time as a single floating point number, representing the
99(fractional) number of seconds since the (POSIX) epoch (somewhere near 114(fractional) number of seconds since the (POSIX) epoch (somewhere near
297enabling this flag. 312enabling this flag.
298 313
299This works by calling C<getpid ()> on every iteration of the loop, 314This works by calling C<getpid ()> on every iteration of the loop,
300and thus this might slow down your event loop if you do a lot of loop 315and thus this might slow down your event loop if you do a lot of loop
301iterations and little real work, but is usually not noticeable (on my 316iterations and little real work, but is usually not noticeable (on my
302Linux system for example, C<getpid> is actually a simple 5-insn sequence 317GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
303without a syscall and thus I<very> fast, but my Linux system also has 318without a syscall and thus I<very> fast, but my GNU/Linux system also has
304C<pthread_atfork> which is even faster). 319C<pthread_atfork> which is even faster).
305 320
306The big advantage of this flag is that you can forget about fork (and 321The big advantage of this flag is that you can forget about fork (and
307forget about forgetting to tell libev about forking) when you use this 322forget about forgetting to tell libev about forking) when you use this
308flag. 323flag.
505=item ev_loop_fork (loop) 520=item ev_loop_fork (loop)
506 521
507Like C<ev_default_fork>, but acts on an event loop created by 522Like C<ev_default_fork>, but acts on an event loop created by
508C<ev_loop_new>. Yes, you have to call this on every allocated event loop 523C<ev_loop_new>. Yes, you have to call this on every allocated event loop
509after fork, and how you do this is entirely your own problem. 524after fork, and how you do this is entirely your own problem.
525
526=item int ev_is_default_loop (loop)
527
528Returns true when the given loop actually is the default loop, false otherwise.
510 529
511=item unsigned int ev_loop_count (loop) 530=item unsigned int ev_loop_count (loop)
512 531
513Returns the count of loop iterations for the loop, which is identical to 532Returns the count of loop iterations for the loop, which is identical to
514the number of times libev did poll for new events. It starts at C<0> and 533the number of times libev did poll for new events. It starts at C<0> and
1152configure a timer to trigger every 10 seconds, then it will trigger at 1171configure a timer to trigger every 10 seconds, then it will trigger at
1153exactly 10 second intervals. If, however, your program cannot keep up with 1172exactly 10 second intervals. If, however, your program cannot keep up with
1154the timer (because it takes longer than those 10 seconds to do stuff) the 1173the timer (because it takes longer than those 10 seconds to do stuff) the
1155timer will not fire more than once per event loop iteration. 1174timer will not fire more than once per event loop iteration.
1156 1175
1157=item ev_timer_again (loop) 1176=item ev_timer_again (loop, ev_timer *)
1158 1177
1159This will act as if the timer timed out and restart it again if it is 1178This will act as if the timer timed out and restart it again if it is
1160repeating. The exact semantics are: 1179repeating. The exact semantics are:
1161 1180
1162If the timer is pending, its pending status is cleared. 1181If the timer is pending, its pending status is cleared.
1271In this configuration the watcher triggers an event at the wallclock time 1290In this configuration the watcher triggers an event at the wallclock time
1272C<at> and doesn't repeat. It will not adjust when a time jump occurs, 1291C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1273that is, if it is to be run at January 1st 2011 then it will run when the 1292that is, if it is to be run at January 1st 2011 then it will run when the
1274system time reaches or surpasses this time. 1293system time reaches or surpasses this time.
1275 1294
1276=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) 1295=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1277 1296
1278In this mode the watcher will always be scheduled to time out at the next 1297In this mode the watcher will always be scheduled to time out at the next
1279C<at + N * interval> time (for some integer N, which can also be negative) 1298C<at + N * interval> time (for some integer N, which can also be negative)
1280and then repeat, regardless of any time jumps. 1299and then repeat, regardless of any time jumps.
1281 1300
1415with the kernel (thus it coexists with your own signal handlers as long 1434with the kernel (thus it coexists with your own signal handlers as long
1416as you don't register any with libev). Similarly, when the last signal 1435as you don't register any with libev). Similarly, when the last signal
1417watcher for a signal is stopped libev will reset the signal handler to 1436watcher for a signal is stopped libev will reset the signal handler to
1418SIG_DFL (regardless of what it was set to before). 1437SIG_DFL (regardless of what it was set to before).
1419 1438
1439If possible and supported, libev will install its handlers with
1440C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
1441interrupted. If you have a problem with syscalls getting interrupted by
1442signals you can block all signals in an C<ev_check> watcher and unblock
1443them in an C<ev_prepare> watcher.
1444
1420=head3 Watcher-Specific Functions and Data Members 1445=head3 Watcher-Specific Functions and Data Members
1421 1446
1422=over 4 1447=over 4
1423 1448
1424=item ev_signal_init (ev_signal *, callback, int signum) 1449=item ev_signal_init (ev_signal *, callback, int signum)
1432 1457
1433The signal the watcher watches out for. 1458The signal the watcher watches out for.
1434 1459
1435=back 1460=back
1436 1461
1462=head3 Examples
1463
1464Example: Try to exit cleanly on SIGINT and SIGTERM.
1465
1466 static void
1467 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1468 {
1469 ev_unloop (loop, EVUNLOOP_ALL);
1470 }
1471
1472 struct ev_signal signal_watcher;
1473 ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1474 ev_signal_start (loop, &sigint_cb);
1475
1437 1476
1438=head2 C<ev_child> - watch out for process status changes 1477=head2 C<ev_child> - watch out for process status changes
1439 1478
1440Child watchers trigger when your process receives a SIGCHLD in response to 1479Child watchers trigger when your process receives a SIGCHLD in response to
1441some child status changes (most typically when a child of yours dies). 1480some child status changes (most typically when a child of yours dies). It
1481is permissible to install a child watcher I<after> the child has been
1482forked (which implies it might have already exited), as long as the event
1483loop isn't entered (or is continued from a watcher).
1484
1485Only the default event loop is capable of handling signals, and therefore
1486you can only rgeister child watchers in the default event loop.
1487
1488=head3 Process Interaction
1489
1490Libev grabs C<SIGCHLD> as soon as the default event loop is
1491initialised. This is necessary to guarantee proper behaviour even if
1492the first child watcher is started after the child exits. The occurance
1493of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1494synchronously as part of the event loop processing. Libev always reaps all
1495children, even ones not watched.
1496
1497=head3 Overriding the Built-In Processing
1498
1499Libev offers no special support for overriding the built-in child
1500processing, but if your application collides with libev's default child
1501handler, you can override it easily by installing your own handler for
1502C<SIGCHLD> after initialising the default loop, and making sure the
1503default loop never gets destroyed. You are encouraged, however, to use an
1504event-based approach to child reaping and thus use libev's support for
1505that, so other libev users can use C<ev_child> watchers freely.
1442 1506
1443=head3 Watcher-Specific Functions and Data Members 1507=head3 Watcher-Specific Functions and Data Members
1444 1508
1445=over 4 1509=over 4
1446 1510
1472 1536
1473=back 1537=back
1474 1538
1475=head3 Examples 1539=head3 Examples
1476 1540
1477Example: Try to exit cleanly on SIGINT and SIGTERM. 1541Example: C<fork()> a new process and install a child handler to wait for
1542its completion.
1543
1544 ev_child cw;
1478 1545
1479 static void 1546 static void
1480 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1547 child_cb (EV_P_ struct ev_child *w, int revents)
1481 { 1548 {
1482 ev_unloop (loop, EVUNLOOP_ALL); 1549 ev_child_stop (EV_A_ w);
1550 printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1483 } 1551 }
1484 1552
1485 struct ev_signal signal_watcher; 1553 pid_t pid = fork ();
1486 ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1554
1487 ev_signal_start (loop, &sigint_cb); 1555 if (pid < 0)
1556 // error
1557 else if (pid == 0)
1558 {
1559 // the forked child executes here
1560 exit (1);
1561 }
1562 else
1563 {
1564 ev_child_init (&cw, child_cb, pid, 0);
1565 ev_child_start (EV_DEFAULT_ &cw);
1566 }
1488 1567
1489 1568
1490=head2 C<ev_stat> - did the file attributes just change? 1569=head2 C<ev_stat> - did the file attributes just change?
1491 1570
1492This watches a filesystem path for attribute changes. That is, it calls 1571This watches a filesystem path for attribute changes. That is, it calls
1572 1651
1573The callback will be receive C<EV_STAT> when a change was detected, 1652The callback will be receive C<EV_STAT> when a change was detected,
1574relative to the attributes at the time the watcher was started (or the 1653relative to the attributes at the time the watcher was started (or the
1575last change was detected). 1654last change was detected).
1576 1655
1577=item ev_stat_stat (ev_stat *) 1656=item ev_stat_stat (loop, ev_stat *)
1578 1657
1579Updates the stat buffer immediately with new values. If you change the 1658Updates the stat buffer immediately with new values. If you change the
1580watched path in your callback, you could call this fucntion to avoid 1659watched path in your callback, you could call this fucntion to avoid
1581detecting this change (while introducing a race condition). Can also be 1660detecting this change (while introducing a race condition). Can also be
1582useful simply to find out the new values. 1661useful simply to find out the new values.
2070C<ev_async_sent> calls). 2149C<ev_async_sent> calls).
2071 2150
2072Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not 2151Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2073just the default loop. 2152just the default loop.
2074 2153
2154=head3 Queueing
2155
2156C<ev_async> does not support queueing of data in any way. The reason
2157is that the author does not know of a simple (or any) algorithm for a
2158multiple-writer-single-reader queue that works in all cases and doesn't
2159need elaborate support such as pthreads.
2160
2161That means that if you want to queue data, you have to provide your own
2162queue. But at least I can tell you would implement locking around your
2163queue:
2164
2165=over 4
2166
2167=item queueing from a signal handler context
2168
2169To implement race-free queueing, you simply add to the queue in the signal
2170handler but you block the signal handler in the watcher callback. Here is an example that does that for
2171some fictitiuous SIGUSR1 handler:
2172
2173 static ev_async mysig;
2174
2175 static void
2176 sigusr1_handler (void)
2177 {
2178 sometype data;
2179
2180 // no locking etc.
2181 queue_put (data);
2182 ev_async_send (EV_DEFAULT_ &mysig);
2183 }
2184
2185 static void
2186 mysig_cb (EV_P_ ev_async *w, int revents)
2187 {
2188 sometype data;
2189 sigset_t block, prev;
2190
2191 sigemptyset (&block);
2192 sigaddset (&block, SIGUSR1);
2193 sigprocmask (SIG_BLOCK, &block, &prev);
2194
2195 while (queue_get (&data))
2196 process (data);
2197
2198 if (sigismember (&prev, SIGUSR1)
2199 sigprocmask (SIG_UNBLOCK, &block, 0);
2200 }
2201
2202(Note: pthreads in theory requires you to use C<pthread_setmask>
2203instead of C<sigprocmask> when you use threads, but libev doesn't do it
2204either...).
2205
2206=item queueing from a thread context
2207
2208The strategy for threads is different, as you cannot (easily) block
2209threads but you can easily preempt them, so to queue safely you need to
2210employ a traditional mutex lock, such as in this pthread example:
2211
2212 static ev_async mysig;
2213 static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
2214
2215 static void
2216 otherthread (void)
2217 {
2218 // only need to lock the actual queueing operation
2219 pthread_mutex_lock (&mymutex);
2220 queue_put (data);
2221 pthread_mutex_unlock (&mymutex);
2222
2223 ev_async_send (EV_DEFAULT_ &mysig);
2224 }
2225
2226 static void
2227 mysig_cb (EV_P_ ev_async *w, int revents)
2228 {
2229 pthread_mutex_lock (&mymutex);
2230
2231 while (queue_get (&data))
2232 process (data);
2233
2234 pthread_mutex_unlock (&mymutex);
2235 }
2236
2237=back
2238
2239
2075=head3 Watcher-Specific Functions and Data Members 2240=head3 Watcher-Specific Functions and Data Members
2076 2241
2077=over 4 2242=over 4
2078 2243
2079=item ev_async_init (ev_async *, callback) 2244=item ev_async_init (ev_async *, callback)
2342 idle.set <myclass, &myclass::idle_cb> (this); 2507 idle.set <myclass, &myclass::idle_cb> (this);
2343 2508
2344 io.start (fd, ev::READ); 2509 io.start (fd, ev::READ);
2345 } 2510 }
2346 }; 2511 };
2512
2513
2514=head1 OTHER LANGUAGE BINDINGS
2515
2516Libev does not offer other language bindings itself, but bindings for a
2517numbe rof languages exist in the form of third-party packages. If you know
2518any interesting language binding in addition to the ones listed here, drop
2519me a note.
2520
2521=over 4
2522
2523=item Perl
2524
2525The EV module implements the full libev API and is actually used to test
2526libev. EV is developed together with libev. Apart from the EV core module,
2527there are additional modules that implement libev-compatible interfaces
2528to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
2529C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
2530
2531It can be found and installed via CPAN, its homepage is found at
2532L<http://software.schmorp.de/pkg/EV>.
2533
2534=item Ruby
2535
2536Tony Arcieri has written a ruby extension that offers access to a subset
2537of the libev API and adds filehandle abstractions, asynchronous DNS and
2538more on top of it. It can be found via gem servers. Its homepage is at
2539L<http://rev.rubyforge.org/>.
2540
2541=item D
2542
2543Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2544be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
2545
2546=back
2347 2547
2348 2548
2349=head1 MACRO MAGIC 2549=head1 MACRO MAGIC
2350 2550
2351Libev can be compiled with a variety of options, the most fundamantal 2551Libev can be compiled with a variety of options, the most fundamantal
2607 2807
2608If defined to be C<1>, libev will compile in support for the Linux inotify 2808If defined to be C<1>, libev will compile in support for the Linux inotify
2609interface to speed up C<ev_stat> watchers. Its actual availability will 2809interface to speed up C<ev_stat> watchers. Its actual availability will
2610be detected at runtime. 2810be detected at runtime.
2611 2811
2812=item EV_ATOMIC_T
2813
2814Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2815access is atomic with respect to other threads or signal contexts. No such
2816type is easily found in the C language, so you can provide your own type
2817that you know is safe for your purposes. It is used both for signal handler "locking"
2818as well as for signal and thread safety in C<ev_async> watchers.
2819
2820In the absense of this define, libev will use C<sig_atomic_t volatile>
2821(from F<signal.h>), which is usually good enough on most platforms.
2822
2612=item EV_H 2823=item EV_H
2613 2824
2614The name of the F<ev.h> header file used to include it. The default if 2825The name of the F<ev.h> header file used to include it. The default if
2615undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be 2826undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2616used to virtually rename the F<ev.h> header file in case of conflicts. 2827used to virtually rename the F<ev.h> header file in case of conflicts.
2681defined to be C<0>, then they are not. 2892defined to be C<0>, then they are not.
2682 2893
2683=item EV_FORK_ENABLE 2894=item EV_FORK_ENABLE
2684 2895
2685If undefined or defined to be C<1>, then fork watchers are supported. If 2896If undefined or defined to be C<1>, then fork watchers are supported. If
2897defined to be C<0>, then they are not.
2898
2899=item EV_ASYNC_ENABLE
2900
2901If undefined or defined to be C<1>, then async watchers are supported. If
2686defined to be C<0>, then they are not. 2902defined to be C<0>, then they are not.
2687 2903
2688=item EV_MINIMAL 2904=item EV_MINIMAL
2689 2905
2690If you need to shave off some kilobytes of code at the expense of some 2906If you need to shave off some kilobytes of code at the expense of some
2811=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) 3027=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2812 3028
2813That means that changing a timer costs less than removing/adding them 3029That means that changing a timer costs less than removing/adding them
2814as only the relative motion in the event queue has to be paid for. 3030as only the relative motion in the event queue has to be paid for.
2815 3031
2816=item Starting io/check/prepare/idle/signal/child watchers: O(1) 3032=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2817 3033
2818These just add the watcher into an array or at the head of a list. 3034These just add the watcher into an array or at the head of a list.
2819 3035
2820=item Stopping check/prepare/idle watchers: O(1) 3036=item Stopping check/prepare/idle/fork/async watchers: O(1)
2821 3037
2822=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 3038=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2823 3039
2824These watchers are stored in lists then need to be walked to find the 3040These watchers are stored in lists then need to be walked to find the
2825correct watcher to remove. The lists are usually short (you don't usually 3041correct watcher to remove. The lists are usually short (you don't usually
2841=item Priority handling: O(number_of_priorities) 3057=item Priority handling: O(number_of_priorities)
2842 3058
2843Priorities are implemented by allocating some space for each 3059Priorities are implemented by allocating some space for each
2844priority. When doing priority-based operations, libev usually has to 3060priority. When doing priority-based operations, libev usually has to
2845linearly search all the priorities, but starting/stopping and activating 3061linearly search all the priorities, but starting/stopping and activating
2846watchers becomes O(1) w.r.t. prioritiy handling. 3062watchers becomes O(1) w.r.t. priority handling.
3063
3064=item Sending an ev_async: O(1)
3065
3066=item Processing ev_async_send: O(number_of_async_watchers)
3067
3068=item Processing signals: O(max_signal_number)
3069
3070Sending involves a syscall I<iff> there were no other C<ev_async_send>
3071calls in the current loop iteration. Checking for async and signal events
3072involves iterating over all running async watchers or all signal numbers.
2847 3073
2848=back 3074=back
2849 3075
2850 3076
2851=head1 Win32 platform limitations and workarounds 3077=head1 Win32 platform limitations and workarounds

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