… | |
… | |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // unloop was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
|
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68 | |
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69 | This document documents the libev software package. |
68 | |
70 | |
69 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
70 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
71 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
|
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
|
|
77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 ABOUT LIBEV |
72 | |
84 | |
73 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
74 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
75 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
76 | |
88 | |
… | |
… | |
110 | name C<loop> (which is always of type C<ev_loop *>) will not have |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
111 | this argument. |
123 | this argument. |
112 | |
124 | |
113 | =head2 TIME REPRESENTATION |
125 | =head2 TIME REPRESENTATION |
114 | |
126 | |
115 | Libev represents time as a single floating point number, representing the |
127 | Libev represents time as a single floating point number, representing |
116 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
117 | the beginning of 1970, details are complicated, don't ask). This type is |
129 | near the beginning of 1970, details are complicated, don't ask). This |
118 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
130 | type is called C<ev_tstamp>, which is what you should use too. It usually |
119 | to the C<double> type in C, and when you need to do any calculations on |
131 | aliases to the C<double> type in C. When you need to do any calculations |
120 | it, you should treat it as some floating point value. Unlike the name |
132 | on it, you should treat it as some floating point value. Unlike the name |
121 | component C<stamp> might indicate, it is also used for time differences |
133 | component C<stamp> might indicate, it is also used for time differences |
122 | throughout libev. |
134 | throughout libev. |
123 | |
135 | |
124 | =head1 ERROR HANDLING |
136 | =head1 ERROR HANDLING |
125 | |
137 | |
… | |
… | |
632 | |
644 | |
633 | This function is rarely useful, but when some event callback runs for a |
645 | This function is rarely useful, but when some event callback runs for a |
634 | very long time without entering the event loop, updating libev's idea of |
646 | very long time without entering the event loop, updating libev's idea of |
635 | the current time is a good idea. |
647 | the current time is a good idea. |
636 | |
648 | |
637 | See also "The special problem of time updates" in the C<ev_timer> section. |
649 | See also L<The special problem of time updates> in the C<ev_timer> section. |
638 | |
650 | |
639 | =item ev_suspend (loop) |
651 | =item ev_suspend (loop) |
640 | |
652 | |
641 | =item ev_resume (loop) |
653 | =item ev_resume (loop) |
642 | |
654 | |
… | |
… | |
1096 | or might not have been clamped to the valid range. |
1108 | or might not have been clamped to the valid range. |
1097 | |
1109 | |
1098 | The default priority used by watchers when no priority has been set is |
1110 | The default priority used by watchers when no priority has been set is |
1099 | always C<0>, which is supposed to not be too high and not be too low :). |
1111 | always C<0>, which is supposed to not be too high and not be too low :). |
1100 | |
1112 | |
1101 | See L<WATCHER PRIORITIES>, below, for a more thorough treatment of |
1113 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1102 | priorities. |
1114 | priorities. |
1103 | |
1115 | |
1104 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1116 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1105 | |
1117 | |
1106 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1118 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1172 | #include <stddef.h> |
1184 | #include <stddef.h> |
1173 | |
1185 | |
1174 | static void |
1186 | static void |
1175 | t1_cb (EV_P_ ev_timer *w, int revents) |
1187 | t1_cb (EV_P_ ev_timer *w, int revents) |
1176 | { |
1188 | { |
1177 | struct my_biggy big = (struct my_biggy * |
1189 | struct my_biggy big = (struct my_biggy *) |
1178 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1190 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1179 | } |
1191 | } |
1180 | |
1192 | |
1181 | static void |
1193 | static void |
1182 | t2_cb (EV_P_ ev_timer *w, int revents) |
1194 | t2_cb (EV_P_ ev_timer *w, int revents) |
1183 | { |
1195 | { |
1184 | struct my_biggy big = (struct my_biggy * |
1196 | struct my_biggy big = (struct my_biggy *) |
1185 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1197 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1186 | } |
1198 | } |
1187 | |
1199 | |
1188 | =head2 WATCHER PRIORITY MODELS |
1200 | =head2 WATCHER PRIORITY MODELS |
1189 | |
1201 | |
… | |
… | |
1265 | // with the default priority are receiving events. |
1277 | // with the default priority are receiving events. |
1266 | ev_idle_start (EV_A_ &idle); |
1278 | ev_idle_start (EV_A_ &idle); |
1267 | } |
1279 | } |
1268 | |
1280 | |
1269 | static void |
1281 | static void |
1270 | idle-cb (EV_P_ ev_idle *w, int revents) |
1282 | idle_cb (EV_P_ ev_idle *w, int revents) |
1271 | { |
1283 | { |
1272 | // actual processing |
1284 | // actual processing |
1273 | read (STDIN_FILENO, ...); |
1285 | read (STDIN_FILENO, ...); |
1274 | |
1286 | |
1275 | // have to start the I/O watcher again, as |
1287 | // have to start the I/O watcher again, as |
… | |
… | |
1320 | descriptors to non-blocking mode is also usually a good idea (but not |
1332 | descriptors to non-blocking mode is also usually a good idea (but not |
1321 | required if you know what you are doing). |
1333 | required if you know what you are doing). |
1322 | |
1334 | |
1323 | If you cannot use non-blocking mode, then force the use of a |
1335 | If you cannot use non-blocking mode, then force the use of a |
1324 | known-to-be-good backend (at the time of this writing, this includes only |
1336 | known-to-be-good backend (at the time of this writing, this includes only |
1325 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1337 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1338 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1339 | files) - libev doesn't guarentee any specific behaviour in that case. |
1326 | |
1340 | |
1327 | Another thing you have to watch out for is that it is quite easy to |
1341 | Another thing you have to watch out for is that it is quite easy to |
1328 | receive "spurious" readiness notifications, that is your callback might |
1342 | receive "spurious" readiness notifications, that is your callback might |
1329 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1343 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1330 | because there is no data. Not only are some backends known to create a |
1344 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1451 | year, it will still time out after (roughly) one hour. "Roughly" because |
1465 | year, it will still time out after (roughly) one hour. "Roughly" because |
1452 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1466 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1453 | monotonic clock option helps a lot here). |
1467 | monotonic clock option helps a lot here). |
1454 | |
1468 | |
1455 | The callback is guaranteed to be invoked only I<after> its timeout has |
1469 | The callback is guaranteed to be invoked only I<after> its timeout has |
1456 | passed. If multiple timers become ready during the same loop iteration |
1470 | passed (not I<at>, so on systems with very low-resolution clocks this |
1457 | then the ones with earlier time-out values are invoked before ones with |
1471 | might introduce a small delay). If multiple timers become ready during the |
|
|
1472 | same loop iteration then the ones with earlier time-out values are invoked |
1458 | later time-out values (but this is no longer true when a callback calls |
1473 | before ones with later time-out values (but this is no longer true when a |
1459 | C<ev_loop> recursively). |
1474 | callback calls C<ev_loop> recursively). |
1460 | |
1475 | |
1461 | =head3 Be smart about timeouts |
1476 | =head3 Be smart about timeouts |
1462 | |
1477 | |
1463 | Many real-world problems involve some kind of timeout, usually for error |
1478 | Many real-world problems involve some kind of timeout, usually for error |
1464 | recovery. A typical example is an HTTP request - if the other side hangs, |
1479 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
2353 | // no longer anything immediate to do. |
2368 | // no longer anything immediate to do. |
2354 | } |
2369 | } |
2355 | |
2370 | |
2356 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2371 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2357 | ev_idle_init (idle_watcher, idle_cb); |
2372 | ev_idle_init (idle_watcher, idle_cb); |
2358 | ev_idle_start (loop, idle_cb); |
2373 | ev_idle_start (loop, idle_watcher); |
2359 | |
2374 | |
2360 | |
2375 | |
2361 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2376 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2362 | |
2377 | |
2363 | Prepare and check watchers are usually (but not always) used in pairs: |
2378 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2696 | event loop blocks next and before C<ev_check> watchers are being called, |
2711 | event loop blocks next and before C<ev_check> watchers are being called, |
2697 | and only in the child after the fork. If whoever good citizen calling |
2712 | and only in the child after the fork. If whoever good citizen calling |
2698 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2713 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2699 | handlers will be invoked, too, of course. |
2714 | handlers will be invoked, too, of course. |
2700 | |
2715 | |
|
|
2716 | =head3 The special problem of life after fork - how is it possible? |
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2717 | |
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|
2718 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
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2719 | up/change the process environment, followed by a call to C<exec()>. This |
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2720 | sequence should be handled by libev without any problems. |
|
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2721 | |
|
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2722 | This changes when the application actually wants to do event handling |
|
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2723 | in the child, or both parent in child, in effect "continuing" after the |
|
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2724 | fork. |
|
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2725 | |
|
|
2726 | The default mode of operation (for libev, with application help to detect |
|
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2727 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2728 | when I<either> the parent I<or> the child process continues. |
|
|
2729 | |
|
|
2730 | When both processes want to continue using libev, then this is usually the |
|
|
2731 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2732 | supposed to continue with all watchers in place as before, while the other |
|
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2733 | process typically wants to start fresh, i.e. without any active watchers. |
|
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2734 | |
|
|
2735 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2736 | simply create a new event loop, which of course will be "empty", and |
|
|
2737 | use that for new watchers. This has the advantage of not touching more |
|
|
2738 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2739 | disadvantage of having to use multiple event loops (which do not support |
|
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2740 | signal watchers). |
|
|
2741 | |
|
|
2742 | When this is not possible, or you want to use the default loop for |
|
|
2743 | other reasons, then in the process that wants to start "fresh", call |
|
|
2744 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2745 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2746 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2747 | also that in that case, you have to re-register any signal watchers. |
|
|
2748 | |
2701 | =head3 Watcher-Specific Functions and Data Members |
2749 | =head3 Watcher-Specific Functions and Data Members |
2702 | |
2750 | |
2703 | =over 4 |
2751 | =over 4 |
2704 | |
2752 | |
2705 | =item ev_fork_init (ev_signal *, callback) |
2753 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
3887 | way (note also that glib is the slowest event library known to man). |
3935 | way (note also that glib is the slowest event library known to man). |
3888 | |
3936 | |
3889 | There is no supported compilation method available on windows except |
3937 | There is no supported compilation method available on windows except |
3890 | embedding it into other applications. |
3938 | embedding it into other applications. |
3891 | |
3939 | |
|
|
3940 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
3941 | tries its best, but under most conditions, signals will simply not work. |
|
|
3942 | |
3892 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3943 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3893 | accept large writes: instead of resulting in a partial write, windows will |
3944 | accept large writes: instead of resulting in a partial write, windows will |
3894 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3945 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3895 | so make sure you only write small amounts into your sockets (less than a |
3946 | so make sure you only write small amounts into your sockets (less than a |
3896 | megabyte seems safe, but this apparently depends on the amount of memory |
3947 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3900 | the abysmal performance of winsockets, using a large number of sockets |
3951 | the abysmal performance of winsockets, using a large number of sockets |
3901 | is not recommended (and not reasonable). If your program needs to use |
3952 | is not recommended (and not reasonable). If your program needs to use |
3902 | more than a hundred or so sockets, then likely it needs to use a totally |
3953 | more than a hundred or so sockets, then likely it needs to use a totally |
3903 | different implementation for windows, as libev offers the POSIX readiness |
3954 | different implementation for windows, as libev offers the POSIX readiness |
3904 | notification model, which cannot be implemented efficiently on windows |
3955 | notification model, which cannot be implemented efficiently on windows |
3905 | (Microsoft monopoly games). |
3956 | (due to Microsoft monopoly games). |
3906 | |
3957 | |
3907 | A typical way to use libev under windows is to embed it (see the embedding |
3958 | A typical way to use libev under windows is to embed it (see the embedding |
3908 | section for details) and use the following F<evwrap.h> header file instead |
3959 | section for details) and use the following F<evwrap.h> header file instead |
3909 | of F<ev.h>: |
3960 | of F<ev.h>: |
3910 | |
3961 | |
… | |
… | |
3946 | |
3997 | |
3947 | Early versions of winsocket's select only supported waiting for a maximum |
3998 | Early versions of winsocket's select only supported waiting for a maximum |
3948 | of C<64> handles (probably owning to the fact that all windows kernels |
3999 | of C<64> handles (probably owning to the fact that all windows kernels |
3949 | can only wait for C<64> things at the same time internally; Microsoft |
4000 | can only wait for C<64> things at the same time internally; Microsoft |
3950 | recommends spawning a chain of threads and wait for 63 handles and the |
4001 | recommends spawning a chain of threads and wait for 63 handles and the |
3951 | previous thread in each. Great). |
4002 | previous thread in each. Sounds great!). |
3952 | |
4003 | |
3953 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4004 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3954 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4005 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3955 | call (which might be in libev or elsewhere, for example, perl does its own |
4006 | call (which might be in libev or elsewhere, for example, perl and many |
3956 | select emulation on windows). |
4007 | other interpreters do their own select emulation on windows). |
3957 | |
4008 | |
3958 | Another limit is the number of file descriptors in the Microsoft runtime |
4009 | Another limit is the number of file descriptors in the Microsoft runtime |
3959 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4010 | libraries, which by default is C<64> (there must be a hidden I<64> |
3960 | or something like this inside Microsoft). You can increase this by calling |
4011 | fetish or something like this inside Microsoft). You can increase this |
3961 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4012 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3962 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4013 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3963 | libraries. |
|
|
3964 | |
|
|
3965 | This might get you to about C<512> or C<2048> sockets (depending on |
4014 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3966 | windows version and/or the phase of the moon). To get more, you need to |
4015 | (depending on windows version and/or the phase of the moon). To get more, |
3967 | wrap all I/O functions and provide your own fd management, but the cost of |
4016 | you need to wrap all I/O functions and provide your own fd management, but |
3968 | calling select (O(n²)) will likely make this unworkable. |
4017 | the cost of calling select (O(n²)) will likely make this unworkable. |
3969 | |
4018 | |
3970 | =back |
4019 | =back |
3971 | |
4020 | |
3972 | =head2 PORTABILITY REQUIREMENTS |
4021 | =head2 PORTABILITY REQUIREMENTS |
3973 | |
4022 | |