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9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
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14 | #include <stdio.h> // for puts |
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15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
18 | |
20 | |
19 | // all watcher callbacks have a similar signature |
21 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
22 | // this callback is called when data is readable on stdin |
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24 | puts ("stdin ready"); |
26 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
27 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
28 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
29 | ev_io_stop (EV_A_ w); |
28 | |
30 | |
29 | // this causes all nested ev_loop's to stop iterating |
31 | // this causes all nested ev_run's to stop iterating |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_break (EV_A_ EVBREAK_ALL); |
31 | } |
33 | } |
32 | |
34 | |
33 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
34 | static void |
36 | static void |
35 | timeout_cb (EV_P_ ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
38 | { |
37 | puts ("timeout"); |
39 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_run to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_break (EV_A_ EVBREAK_ONE); |
40 | } |
42 | } |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
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54 | // simple non-repeating 5.5 second timeout |
56 | // simple non-repeating 5.5 second timeout |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
56 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
57 | |
59 | |
58 | // now wait for events to arrive |
60 | // now wait for events to arrive |
59 | ev_loop (loop, 0); |
61 | ev_run (loop, 0); |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // unloop was called, so exit |
62 | return 0; |
64 | return 0; |
63 | } |
65 | } |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
66 | |
70 | |
67 | 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 |
68 | 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 |
69 | 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 |
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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 | Familiarity 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 |
70 | |
84 | |
71 | 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 |
72 | 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 |
73 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
74 | |
88 | |
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84 | =head2 FEATURES |
98 | =head2 FEATURES |
85 | |
99 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
107 | change events (C<ev_child>), and event watchers dealing with the event |
94 | file watchers (C<ev_stat>) and even limited support for fork events |
108 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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110 | limited support for fork events (C<ev_fork>). |
96 | |
111 | |
97 | It also is quite fast (see this |
112 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
113 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
114 | for example). |
100 | |
115 | |
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103 | Libev is very configurable. In this manual the default (and most common) |
118 | Libev is very configurable. In this manual the default (and most common) |
104 | configuration will be described, which supports multiple event loops. For |
119 | configuration will be described, which supports multiple event loops. For |
105 | more info about various configuration options please have a look at |
120 | more info about various configuration options please have a look at |
106 | B<EMBED> section in this manual. If libev was configured without support |
121 | B<EMBED> section in this manual. If libev was configured without support |
107 | for multiple event loops, then all functions taking an initial argument of |
122 | for multiple event loops, then all functions taking an initial argument of |
108 | name C<loop> (which is always of type C<ev_loop *>) will not have |
123 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
109 | this argument. |
124 | this argument. |
110 | |
125 | |
111 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
112 | |
127 | |
113 | Libev represents time as a single floating point number, representing the |
128 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
129 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
130 | somewhere near the beginning of 1970, details are complicated, don't |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
131 | ask). This type is called C<ev_tstamp>, which is what you should use |
117 | to the C<double> type in C, and when you need to do any calculations on |
132 | too. It usually aliases to the C<double> type in C. When you need to do |
118 | it, you should treat it as some floating point value. Unlike the name |
133 | any calculations on it, you should treat it as some floating point value. |
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134 | |
119 | component C<stamp> might indicate, it is also used for time differences |
135 | Unlike the name component C<stamp> might indicate, it is also used for |
120 | throughout libev. |
136 | time differences (e.g. delays) throughout libev. |
121 | |
137 | |
122 | =head1 ERROR HANDLING |
138 | =head1 ERROR HANDLING |
123 | |
139 | |
124 | Libev knows three classes of errors: operating system errors, usage errors |
140 | Libev knows three classes of errors: operating system errors, usage errors |
125 | and internal errors (bugs). |
141 | and internal errors (bugs). |
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149 | |
165 | |
150 | =item ev_tstamp ev_time () |
166 | =item ev_tstamp ev_time () |
151 | |
167 | |
152 | Returns the current time as libev would use it. Please note that the |
168 | Returns the current time as libev would use it. Please note that the |
153 | C<ev_now> function is usually faster and also often returns the timestamp |
169 | C<ev_now> function is usually faster and also often returns the timestamp |
154 | you actually want to know. |
170 | you actually want to know. Also interetsing is the combination of |
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171 | C<ev_update_now> and C<ev_now>. |
155 | |
172 | |
156 | =item ev_sleep (ev_tstamp interval) |
173 | =item ev_sleep (ev_tstamp interval) |
157 | |
174 | |
158 | Sleep for the given interval: The current thread will be blocked until |
175 | Sleep for the given interval: The current thread will be blocked until |
159 | either it is interrupted or the given time interval has passed. Basically |
176 | either it is interrupted or the given time interval has passed. Basically |
… | |
… | |
176 | as this indicates an incompatible change. Minor versions are usually |
193 | as this indicates an incompatible change. Minor versions are usually |
177 | compatible to older versions, so a larger minor version alone is usually |
194 | compatible to older versions, so a larger minor version alone is usually |
178 | not a problem. |
195 | not a problem. |
179 | |
196 | |
180 | Example: Make sure we haven't accidentally been linked against the wrong |
197 | Example: Make sure we haven't accidentally been linked against the wrong |
181 | version. |
198 | version (note, however, that this will not detect ABI mismatches :). |
182 | |
199 | |
183 | assert (("libev version mismatch", |
200 | assert (("libev version mismatch", |
184 | ev_version_major () == EV_VERSION_MAJOR |
201 | ev_version_major () == EV_VERSION_MAJOR |
185 | && ev_version_minor () >= EV_VERSION_MINOR)); |
202 | && ev_version_minor () >= EV_VERSION_MINOR)); |
186 | |
203 | |
… | |
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197 | assert (("sorry, no epoll, no sex", |
214 | assert (("sorry, no epoll, no sex", |
198 | ev_supported_backends () & EVBACKEND_EPOLL)); |
215 | ev_supported_backends () & EVBACKEND_EPOLL)); |
199 | |
216 | |
200 | =item unsigned int ev_recommended_backends () |
217 | =item unsigned int ev_recommended_backends () |
201 | |
218 | |
202 | Return the set of all backends compiled into this binary of libev and also |
219 | Return the set of all backends compiled into this binary of libev and |
203 | recommended for this platform. This set is often smaller than the one |
220 | also recommended for this platform, meaning it will work for most file |
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221 | descriptor types. This set is often smaller than the one returned by |
204 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
222 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
205 | most BSDs and will not be auto-detected unless you explicitly request it |
223 | and will not be auto-detected unless you explicitly request it (assuming |
206 | (assuming you know what you are doing). This is the set of backends that |
224 | you know what you are doing). This is the set of backends that libev will |
207 | libev will probe for if you specify no backends explicitly. |
225 | probe for if you specify no backends explicitly. |
208 | |
226 | |
209 | =item unsigned int ev_embeddable_backends () |
227 | =item unsigned int ev_embeddable_backends () |
210 | |
228 | |
211 | Returns the set of backends that are embeddable in other event loops. This |
229 | Returns the set of backends that are embeddable in other event loops. This |
212 | is the theoretical, all-platform, value. To find which backends |
230 | is the theoretical, all-platform, value. To find which backends |
… | |
… | |
276 | |
294 | |
277 | =back |
295 | =back |
278 | |
296 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
297 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
280 | |
298 | |
281 | An event loop is described by a C<ev_loop *>. The library knows two |
299 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
282 | types of such loops, the I<default> loop, which supports signals and child |
300 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
283 | events, and dynamically created loops which do not. |
301 | libev 3 had an C<ev_loop> function colliding with the struct name). |
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302 | |
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303 | The library knows two types of such loops, the I<default> loop, which |
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304 | supports signals and child events, and dynamically created event loops |
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305 | which do not. |
284 | |
306 | |
285 | =over 4 |
307 | =over 4 |
286 | |
308 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
309 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
310 | |
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294 | If you don't know what event loop to use, use the one returned from this |
316 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
317 | function. |
296 | |
318 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
319 | Note that this function is I<not> thread-safe, so if you want to use it |
298 | from multiple threads, you have to lock (note also that this is unlikely, |
320 | from multiple threads, you have to lock (note also that this is unlikely, |
299 | as loops cannot bes hared easily between threads anyway). |
321 | as loops cannot be shared easily between threads anyway). |
300 | |
322 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
323 | The default loop is the only loop that can handle C<ev_signal> and |
302 | C<ev_child> watchers, and to do this, it always registers a handler |
324 | C<ev_child> watchers, and to do this, it always registers a handler |
303 | for C<SIGCHLD>. If this is a problem for your application you can either |
325 | for C<SIGCHLD>. If this is a problem for your application you can either |
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
326 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
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326 | useful to try out specific backends to test their performance, or to work |
348 | useful to try out specific backends to test their performance, or to work |
327 | around bugs. |
349 | around bugs. |
328 | |
350 | |
329 | =item C<EVFLAG_FORKCHECK> |
351 | =item C<EVFLAG_FORKCHECK> |
330 | |
352 | |
331 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
353 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
332 | a fork, you can also make libev check for a fork in each iteration by |
354 | make libev check for a fork in each iteration by enabling this flag. |
333 | enabling this flag. |
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334 | |
355 | |
335 | This works by calling C<getpid ()> on every iteration of the loop, |
356 | This works by calling C<getpid ()> on every iteration of the loop, |
336 | and thus this might slow down your event loop if you do a lot of loop |
357 | and thus this might slow down your event loop if you do a lot of loop |
337 | iterations and little real work, but is usually not noticeable (on my |
358 | iterations and little real work, but is usually not noticeable (on my |
338 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
359 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
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344 | flag. |
365 | flag. |
345 | |
366 | |
346 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
367 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
347 | environment variable. |
368 | environment variable. |
348 | |
369 | |
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370 | =item C<EVFLAG_NOINOTIFY> |
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371 | |
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372 | When this flag is specified, then libev will not attempt to use the |
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373 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
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374 | testing, this flag can be useful to conserve inotify file descriptors, as |
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375 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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376 | |
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377 | =item C<EVFLAG_SIGNALFD> |
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378 | |
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379 | When this flag is specified, then libev will attempt to use the |
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380 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
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381 | delivers signals synchronously, which makes it both faster and might make |
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382 | it possible to get the queued signal data. It can also simplify signal |
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383 | handling with threads, as long as you properly block signals in your |
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384 | threads that are not interested in handling them. |
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385 | |
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386 | Signalfd will not be used by default as this changes your signal mask, and |
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387 | there are a lot of shoddy libraries and programs (glib's threadpool for |
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388 | example) that can't properly initialise their signal masks. |
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389 | |
349 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
390 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
350 | |
391 | |
351 | This is your standard select(2) backend. Not I<completely> standard, as |
392 | This is your standard select(2) backend. Not I<completely> standard, as |
352 | libev tries to roll its own fd_set with no limits on the number of fds, |
393 | libev tries to roll its own fd_set with no limits on the number of fds, |
353 | but if that fails, expect a fairly low limit on the number of fds when |
394 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
377 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
418 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
378 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
419 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
379 | |
420 | |
380 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
421 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
381 | |
422 | |
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423 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
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424 | kernels). |
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425 | |
382 | For few fds, this backend is a bit little slower than poll and select, |
426 | For few fds, this backend is a bit little slower than poll and select, |
383 | but it scales phenomenally better. While poll and select usually scale |
427 | but it scales phenomenally better. While poll and select usually scale |
384 | like O(total_fds) where n is the total number of fds (or the highest fd), |
428 | like O(total_fds) where n is the total number of fds (or the highest fd), |
385 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
429 | epoll scales either O(1) or O(active_fds). |
386 | of shortcomings, such as silently dropping events in some hard-to-detect |
430 | |
387 | cases and requiring a system call per fd change, no fork support and bad |
431 | The epoll mechanism deserves honorable mention as the most misdesigned |
388 | support for dup. |
432 | of the more advanced event mechanisms: mere annoyances include silently |
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433 | dropping file descriptors, requiring a system call per change per file |
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434 | descriptor (and unnecessary guessing of parameters), problems with dup and |
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435 | so on. The biggest issue is fork races, however - if a program forks then |
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436 | I<both> parent and child process have to recreate the epoll set, which can |
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437 | take considerable time (one syscall per file descriptor) and is of course |
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438 | hard to detect. |
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439 | |
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440 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
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441 | of course I<doesn't>, and epoll just loves to report events for totally |
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442 | I<different> file descriptors (even already closed ones, so one cannot |
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443 | even remove them from the set) than registered in the set (especially |
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444 | on SMP systems). Libev tries to counter these spurious notifications by |
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445 | employing an additional generation counter and comparing that against the |
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446 | events to filter out spurious ones, recreating the set when required. Last |
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447 | not least, it also refuses to work with some file descriptors which work |
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448 | perfectly fine with C<select> (files, many character devices...). |
389 | |
449 | |
390 | While stopping, setting and starting an I/O watcher in the same iteration |
450 | While stopping, setting and starting an I/O watcher in the same iteration |
391 | will result in some caching, there is still a system call per such incident |
451 | will result in some caching, there is still a system call per such |
392 | (because the fd could point to a different file description now), so its |
452 | incident (because the same I<file descriptor> could point to a different |
393 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
453 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
394 | very well if you register events for both fds. |
454 | file descriptors might not work very well if you register events for both |
395 | |
455 | file descriptors. |
396 | Please note that epoll sometimes generates spurious notifications, so you |
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397 | need to use non-blocking I/O or other means to avoid blocking when no data |
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398 | (or space) is available. |
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399 | |
456 | |
400 | Best performance from this backend is achieved by not unregistering all |
457 | Best performance from this backend is achieved by not unregistering all |
401 | watchers for a file descriptor until it has been closed, if possible, |
458 | watchers for a file descriptor until it has been closed, if possible, |
402 | i.e. keep at least one watcher active per fd at all times. Stopping and |
459 | i.e. keep at least one watcher active per fd at all times. Stopping and |
403 | starting a watcher (without re-setting it) also usually doesn't cause |
460 | starting a watcher (without re-setting it) also usually doesn't cause |
404 | extra overhead. |
461 | extra overhead. A fork can both result in spurious notifications as well |
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462 | as in libev having to destroy and recreate the epoll object, which can |
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463 | take considerable time and thus should be avoided. |
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464 | |
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465 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
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466 | faster than epoll for maybe up to a hundred file descriptors, depending on |
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467 | the usage. So sad. |
405 | |
468 | |
406 | While nominally embeddable in other event loops, this feature is broken in |
469 | While nominally embeddable in other event loops, this feature is broken in |
407 | all kernel versions tested so far. |
470 | all kernel versions tested so far. |
408 | |
471 | |
409 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
472 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
410 | C<EVBACKEND_POLL>. |
473 | C<EVBACKEND_POLL>. |
411 | |
474 | |
412 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
475 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
413 | |
476 | |
414 | Kqueue deserves special mention, as at the time of this writing, it was |
477 | Kqueue deserves special mention, as at the time of this writing, it |
415 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
478 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
416 | anything but sockets and pipes, except on Darwin, where of course it's |
479 | with anything but sockets and pipes, except on Darwin, where of course |
417 | completely useless). For this reason it's not being "auto-detected" unless |
480 | it's completely useless). Unlike epoll, however, whose brokenness |
418 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
481 | is by design, these kqueue bugs can (and eventually will) be fixed |
419 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
482 | without API changes to existing programs. For this reason it's not being |
|
|
483 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
|
|
484 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
485 | system like NetBSD. |
420 | |
486 | |
421 | You still can embed kqueue into a normal poll or select backend and use it |
487 | You still can embed kqueue into a normal poll or select backend and use it |
422 | only for sockets (after having made sure that sockets work with kqueue on |
488 | only for sockets (after having made sure that sockets work with kqueue on |
423 | the target platform). See C<ev_embed> watchers for more info. |
489 | the target platform). See C<ev_embed> watchers for more info. |
424 | |
490 | |
425 | It scales in the same way as the epoll backend, but the interface to the |
491 | It scales in the same way as the epoll backend, but the interface to the |
426 | kernel is more efficient (which says nothing about its actual speed, of |
492 | kernel is more efficient (which says nothing about its actual speed, of |
427 | course). While stopping, setting and starting an I/O watcher does never |
493 | course). While stopping, setting and starting an I/O watcher does never |
428 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
494 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
429 | two event changes per incident. Support for C<fork ()> is very bad and it |
495 | two event changes per incident. Support for C<fork ()> is very bad (but |
430 | drops fds silently in similarly hard-to-detect cases. |
496 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
497 | cases |
431 | |
498 | |
432 | This backend usually performs well under most conditions. |
499 | This backend usually performs well under most conditions. |
433 | |
500 | |
434 | While nominally embeddable in other event loops, this doesn't work |
501 | While nominally embeddable in other event loops, this doesn't work |
435 | everywhere, so you might need to test for this. And since it is broken |
502 | everywhere, so you might need to test for this. And since it is broken |
436 | almost everywhere, you should only use it when you have a lot of sockets |
503 | almost everywhere, you should only use it when you have a lot of sockets |
437 | (for which it usually works), by embedding it into another event loop |
504 | (for which it usually works), by embedding it into another event loop |
438 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
505 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
439 | using it only for sockets. |
506 | also broken on OS X)) and, did I mention it, using it only for sockets. |
440 | |
507 | |
441 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
508 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
442 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
509 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
443 | C<NOTE_EOF>. |
510 | C<NOTE_EOF>. |
444 | |
511 | |
… | |
… | |
464 | might perform better. |
531 | might perform better. |
465 | |
532 | |
466 | On the positive side, with the exception of the spurious readiness |
533 | On the positive side, with the exception of the spurious readiness |
467 | notifications, this backend actually performed fully to specification |
534 | notifications, this backend actually performed fully to specification |
468 | in all tests and is fully embeddable, which is a rare feat among the |
535 | in all tests and is fully embeddable, which is a rare feat among the |
469 | OS-specific backends. |
536 | OS-specific backends (I vastly prefer correctness over speed hacks). |
470 | |
537 | |
471 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
538 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
472 | C<EVBACKEND_POLL>. |
539 | C<EVBACKEND_POLL>. |
473 | |
540 | |
474 | =item C<EVBACKEND_ALL> |
541 | =item C<EVBACKEND_ALL> |
… | |
… | |
479 | |
546 | |
480 | It is definitely not recommended to use this flag. |
547 | It is definitely not recommended to use this flag. |
481 | |
548 | |
482 | =back |
549 | =back |
483 | |
550 | |
484 | If one or more of these are or'ed into the flags value, then only these |
551 | If one or more of the backend flags are or'ed into the flags value, |
485 | backends will be tried (in the reverse order as listed here). If none are |
552 | then only these backends will be tried (in the reverse order as listed |
486 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
553 | here). If none are specified, all backends in C<ev_recommended_backends |
|
|
554 | ()> will be tried. |
487 | |
555 | |
488 | Example: This is the most typical usage. |
556 | Example: This is the most typical usage. |
489 | |
557 | |
490 | if (!ev_default_loop (0)) |
558 | if (!ev_default_loop (0)) |
491 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
559 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
… | |
… | |
503 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
571 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
504 | |
572 | |
505 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
573 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
506 | |
574 | |
507 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
575 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
508 | always distinct from the default loop. Unlike the default loop, it cannot |
576 | always distinct from the default loop. |
509 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
510 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
511 | |
577 | |
512 | Note that this function I<is> thread-safe, and the recommended way to use |
578 | Note that this function I<is> thread-safe, and one common way to use |
513 | libev with threads is indeed to create one loop per thread, and using the |
579 | libev with threads is indeed to create one loop per thread, and using the |
514 | default loop in the "main" or "initial" thread. |
580 | default loop in the "main" or "initial" thread. |
515 | |
581 | |
516 | Example: Try to create a event loop that uses epoll and nothing else. |
582 | Example: Try to create a event loop that uses epoll and nothing else. |
517 | |
583 | |
… | |
… | |
519 | if (!epoller) |
585 | if (!epoller) |
520 | fatal ("no epoll found here, maybe it hides under your chair"); |
586 | fatal ("no epoll found here, maybe it hides under your chair"); |
521 | |
587 | |
522 | =item ev_default_destroy () |
588 | =item ev_default_destroy () |
523 | |
589 | |
524 | Destroys the default loop again (frees all memory and kernel state |
590 | Destroys the default loop (frees all memory and kernel state etc.). None |
525 | etc.). None of the active event watchers will be stopped in the normal |
591 | of the active event watchers will be stopped in the normal sense, so |
526 | sense, so e.g. C<ev_is_active> might still return true. It is your |
592 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
527 | responsibility to either stop all watchers cleanly yourself I<before> |
593 | either stop all watchers cleanly yourself I<before> calling this function, |
528 | calling this function, or cope with the fact afterwards (which is usually |
594 | or cope with the fact afterwards (which is usually the easiest thing, you |
529 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
595 | can just ignore the watchers and/or C<free ()> them for example). |
530 | for example). |
|
|
531 | |
596 | |
532 | Note that certain global state, such as signal state, will not be freed by |
597 | Note that certain global state, such as signal state (and installed signal |
533 | this function, and related watchers (such as signal and child watchers) |
598 | handlers), will not be freed by this function, and related watchers (such |
534 | would need to be stopped manually. |
599 | as signal and child watchers) would need to be stopped manually. |
535 | |
600 | |
536 | In general it is not advisable to call this function except in the |
601 | In general it is not advisable to call this function except in the |
537 | rare occasion where you really need to free e.g. the signal handling |
602 | rare occasion where you really need to free e.g. the signal handling |
538 | pipe fds. If you need dynamically allocated loops it is better to use |
603 | pipe fds. If you need dynamically allocated loops it is better to use |
539 | C<ev_loop_new> and C<ev_loop_destroy>). |
604 | C<ev_loop_new> and C<ev_loop_destroy>. |
540 | |
605 | |
541 | =item ev_loop_destroy (loop) |
606 | =item ev_loop_destroy (loop) |
542 | |
607 | |
543 | Like C<ev_default_destroy>, but destroys an event loop created by an |
608 | Like C<ev_default_destroy>, but destroys an event loop created by an |
544 | earlier call to C<ev_loop_new>. |
609 | earlier call to C<ev_loop_new>. |
545 | |
610 | |
546 | =item ev_default_fork () |
611 | =item ev_default_fork () |
547 | |
612 | |
548 | This function sets a flag that causes subsequent C<ev_loop> iterations |
613 | This function sets a flag that causes subsequent C<ev_run> iterations |
549 | to reinitialise the kernel state for backends that have one. Despite the |
614 | to reinitialise the kernel state for backends that have one. Despite the |
550 | name, you can call it anytime, but it makes most sense after forking, in |
615 | name, you can call it anytime, but it makes most sense after forking, in |
551 | the child process (or both child and parent, but that again makes little |
616 | the child process (or both child and parent, but that again makes little |
552 | sense). You I<must> call it in the child before using any of the libev |
617 | sense). You I<must> call it in the child before using any of the libev |
553 | functions, and it will only take effect at the next C<ev_loop> iteration. |
618 | functions, and it will only take effect at the next C<ev_run> iteration. |
|
|
619 | |
|
|
620 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
621 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
622 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
623 | during fork. |
554 | |
624 | |
555 | On the other hand, you only need to call this function in the child |
625 | On the other hand, you only need to call this function in the child |
556 | process if and only if you want to use the event library in the child. If |
626 | process if and only if you want to use the event loop in the child. If |
557 | you just fork+exec, you don't have to call it at all. |
627 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
628 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
629 | difference, but libev will usually detect this case on its own and do a |
|
|
630 | costly reset of the backend). |
558 | |
631 | |
559 | The function itself is quite fast and it's usually not a problem to call |
632 | The function itself is quite fast and it's usually not a problem to call |
560 | it just in case after a fork. To make this easy, the function will fit in |
633 | it just in case after a fork. To make this easy, the function will fit in |
561 | quite nicely into a call to C<pthread_atfork>: |
634 | quite nicely into a call to C<pthread_atfork>: |
562 | |
635 | |
… | |
… | |
564 | |
637 | |
565 | =item ev_loop_fork (loop) |
638 | =item ev_loop_fork (loop) |
566 | |
639 | |
567 | Like C<ev_default_fork>, but acts on an event loop created by |
640 | Like C<ev_default_fork>, but acts on an event loop created by |
568 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
641 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
569 | after fork that you want to re-use in the child, and how you do this is |
642 | after fork that you want to re-use in the child, and how you keep track of |
570 | entirely your own problem. |
643 | them is entirely your own problem. |
571 | |
644 | |
572 | =item int ev_is_default_loop (loop) |
645 | =item int ev_is_default_loop (loop) |
573 | |
646 | |
574 | Returns true when the given loop is, in fact, the default loop, and false |
647 | Returns true when the given loop is, in fact, the default loop, and false |
575 | otherwise. |
648 | otherwise. |
576 | |
649 | |
577 | =item unsigned int ev_loop_count (loop) |
650 | =item unsigned int ev_iteration (loop) |
578 | |
651 | |
579 | Returns the count of loop iterations for the loop, which is identical to |
652 | Returns the current iteration count for the event loop, which is identical |
580 | the number of times libev did poll for new events. It starts at C<0> and |
653 | to the number of times libev did poll for new events. It starts at C<0> |
581 | happily wraps around with enough iterations. |
654 | and happily wraps around with enough iterations. |
582 | |
655 | |
583 | This value can sometimes be useful as a generation counter of sorts (it |
656 | This value can sometimes be useful as a generation counter of sorts (it |
584 | "ticks" the number of loop iterations), as it roughly corresponds with |
657 | "ticks" the number of loop iterations), as it roughly corresponds with |
585 | C<ev_prepare> and C<ev_check> calls. |
658 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
659 | prepare and check phases. |
|
|
660 | |
|
|
661 | =item unsigned int ev_depth (loop) |
|
|
662 | |
|
|
663 | Returns the number of times C<ev_run> was entered minus the number of |
|
|
664 | times C<ev_run> was exited, in other words, the recursion depth. |
|
|
665 | |
|
|
666 | Outside C<ev_run>, this number is zero. In a callback, this number is |
|
|
667 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
|
|
668 | in which case it is higher. |
|
|
669 | |
|
|
670 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
|
|
671 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
|
|
672 | ungentleman-like behaviour unless it's really convenient. |
586 | |
673 | |
587 | =item unsigned int ev_backend (loop) |
674 | =item unsigned int ev_backend (loop) |
588 | |
675 | |
589 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
676 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
590 | use. |
677 | use. |
… | |
… | |
599 | |
686 | |
600 | =item ev_now_update (loop) |
687 | =item ev_now_update (loop) |
601 | |
688 | |
602 | Establishes the current time by querying the kernel, updating the time |
689 | Establishes the current time by querying the kernel, updating the time |
603 | returned by C<ev_now ()> in the progress. This is a costly operation and |
690 | returned by C<ev_now ()> in the progress. This is a costly operation and |
604 | is usually done automatically within C<ev_loop ()>. |
691 | is usually done automatically within C<ev_run ()>. |
605 | |
692 | |
606 | This function is rarely useful, but when some event callback runs for a |
693 | This function is rarely useful, but when some event callback runs for a |
607 | very long time without entering the event loop, updating libev's idea of |
694 | very long time without entering the event loop, updating libev's idea of |
608 | the current time is a good idea. |
695 | the current time is a good idea. |
609 | |
696 | |
610 | See also "The special problem of time updates" in the C<ev_timer> section. |
697 | See also L<The special problem of time updates> in the C<ev_timer> section. |
611 | |
698 | |
|
|
699 | =item ev_suspend (loop) |
|
|
700 | |
|
|
701 | =item ev_resume (loop) |
|
|
702 | |
|
|
703 | These two functions suspend and resume an event loop, for use when the |
|
|
704 | loop is not used for a while and timeouts should not be processed. |
|
|
705 | |
|
|
706 | A typical use case would be an interactive program such as a game: When |
|
|
707 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
708 | would be best to handle timeouts as if no time had actually passed while |
|
|
709 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
710 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
711 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
712 | |
|
|
713 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
714 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
715 | will be rescheduled (that is, they will lose any events that would have |
|
|
716 | occurred while suspended). |
|
|
717 | |
|
|
718 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
719 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
720 | without a previous call to C<ev_suspend>. |
|
|
721 | |
|
|
722 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
723 | event loop time (see C<ev_now_update>). |
|
|
724 | |
612 | =item ev_loop (loop, int flags) |
725 | =item ev_run (loop, int flags) |
613 | |
726 | |
614 | Finally, this is it, the event handler. This function usually is called |
727 | Finally, this is it, the event handler. This function usually is called |
615 | after you initialised all your watchers and you want to start handling |
728 | after you have initialised all your watchers and you want to start |
616 | events. |
729 | handling events. It will ask the operating system for any new events, call |
|
|
730 | the watcher callbacks, an then repeat the whole process indefinitely: This |
|
|
731 | is why event loops are called I<loops>. |
617 | |
732 | |
618 | If the flags argument is specified as C<0>, it will not return until |
733 | If the flags argument is specified as C<0>, it will keep handling events |
619 | either no event watchers are active anymore or C<ev_unloop> was called. |
734 | until either no event watchers are active anymore or C<ev_break> was |
|
|
735 | called. |
620 | |
736 | |
621 | Please note that an explicit C<ev_unloop> is usually better than |
737 | Please note that an explicit C<ev_break> is usually better than |
622 | relying on all watchers to be stopped when deciding when a program has |
738 | relying on all watchers to be stopped when deciding when a program has |
623 | finished (especially in interactive programs), but having a program |
739 | finished (especially in interactive programs), but having a program |
624 | that automatically loops as long as it has to and no longer by virtue |
740 | that automatically loops as long as it has to and no longer by virtue |
625 | of relying on its watchers stopping correctly, that is truly a thing of |
741 | of relying on its watchers stopping correctly, that is truly a thing of |
626 | beauty. |
742 | beauty. |
627 | |
743 | |
628 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
744 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
629 | those events and any already outstanding ones, but will not block your |
745 | those events and any already outstanding ones, but will not wait and |
630 | process in case there are no events and will return after one iteration of |
746 | block your process in case there are no events and will return after one |
631 | the loop. |
747 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
748 | events while doing lengthy calculations, to keep the program responsive. |
632 | |
749 | |
633 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
750 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
634 | necessary) and will handle those and any already outstanding ones. It |
751 | necessary) and will handle those and any already outstanding ones. It |
635 | will block your process until at least one new event arrives (which could |
752 | will block your process until at least one new event arrives (which could |
636 | be an event internal to libev itself, so there is no guarentee that a |
753 | be an event internal to libev itself, so there is no guarantee that a |
637 | user-registered callback will be called), and will return after one |
754 | user-registered callback will be called), and will return after one |
638 | iteration of the loop. |
755 | iteration of the loop. |
639 | |
756 | |
640 | This is useful if you are waiting for some external event in conjunction |
757 | This is useful if you are waiting for some external event in conjunction |
641 | with something not expressible using other libev watchers (i.e. "roll your |
758 | with something not expressible using other libev watchers (i.e. "roll your |
642 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
759 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
643 | usually a better approach for this kind of thing. |
760 | usually a better approach for this kind of thing. |
644 | |
761 | |
645 | Here are the gory details of what C<ev_loop> does: |
762 | Here are the gory details of what C<ev_run> does: |
646 | |
763 | |
|
|
764 | - Increment loop depth. |
|
|
765 | - Reset the ev_break status. |
647 | - Before the first iteration, call any pending watchers. |
766 | - Before the first iteration, call any pending watchers. |
|
|
767 | LOOP: |
648 | * If EVFLAG_FORKCHECK was used, check for a fork. |
768 | - If EVFLAG_FORKCHECK was used, check for a fork. |
649 | - If a fork was detected (by any means), queue and call all fork watchers. |
769 | - If a fork was detected (by any means), queue and call all fork watchers. |
650 | - Queue and call all prepare watchers. |
770 | - Queue and call all prepare watchers. |
|
|
771 | - If ev_break was called, goto FINISH. |
651 | - If we have been forked, detach and recreate the kernel state |
772 | - If we have been forked, detach and recreate the kernel state |
652 | as to not disturb the other process. |
773 | as to not disturb the other process. |
653 | - Update the kernel state with all outstanding changes. |
774 | - Update the kernel state with all outstanding changes. |
654 | - Update the "event loop time" (ev_now ()). |
775 | - Update the "event loop time" (ev_now ()). |
655 | - Calculate for how long to sleep or block, if at all |
776 | - Calculate for how long to sleep or block, if at all |
656 | (active idle watchers, EVLOOP_NONBLOCK or not having |
777 | (active idle watchers, EVRUN_NOWAIT or not having |
657 | any active watchers at all will result in not sleeping). |
778 | any active watchers at all will result in not sleeping). |
658 | - Sleep if the I/O and timer collect interval say so. |
779 | - Sleep if the I/O and timer collect interval say so. |
|
|
780 | - Increment loop iteration counter. |
659 | - Block the process, waiting for any events. |
781 | - Block the process, waiting for any events. |
660 | - Queue all outstanding I/O (fd) events. |
782 | - Queue all outstanding I/O (fd) events. |
661 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
783 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
662 | - Queue all expired timers. |
784 | - Queue all expired timers. |
663 | - Queue all expired periodics. |
785 | - Queue all expired periodics. |
664 | - Unless any events are pending now, queue all idle watchers. |
786 | - Queue all idle watchers with priority higher than that of pending events. |
665 | - Queue all check watchers. |
787 | - Queue all check watchers. |
666 | - Call all queued watchers in reverse order (i.e. check watchers first). |
788 | - Call all queued watchers in reverse order (i.e. check watchers first). |
667 | Signals and child watchers are implemented as I/O watchers, and will |
789 | Signals and child watchers are implemented as I/O watchers, and will |
668 | be handled here by queueing them when their watcher gets executed. |
790 | be handled here by queueing them when their watcher gets executed. |
669 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
791 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
670 | were used, or there are no active watchers, return, otherwise |
792 | were used, or there are no active watchers, goto FINISH, otherwise |
671 | continue with step *. |
793 | continue with step LOOP. |
|
|
794 | FINISH: |
|
|
795 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
796 | - Decrement the loop depth. |
|
|
797 | - Return. |
672 | |
798 | |
673 | Example: Queue some jobs and then loop until no events are outstanding |
799 | Example: Queue some jobs and then loop until no events are outstanding |
674 | anymore. |
800 | anymore. |
675 | |
801 | |
676 | ... queue jobs here, make sure they register event watchers as long |
802 | ... queue jobs here, make sure they register event watchers as long |
677 | ... as they still have work to do (even an idle watcher will do..) |
803 | ... as they still have work to do (even an idle watcher will do..) |
678 | ev_loop (my_loop, 0); |
804 | ev_run (my_loop, 0); |
679 | ... jobs done or somebody called unloop. yeah! |
805 | ... jobs done or somebody called unloop. yeah! |
680 | |
806 | |
681 | =item ev_unloop (loop, how) |
807 | =item ev_break (loop, how) |
682 | |
808 | |
683 | Can be used to make a call to C<ev_loop> return early (but only after it |
809 | Can be used to make a call to C<ev_run> return early (but only after it |
684 | has processed all outstanding events). The C<how> argument must be either |
810 | has processed all outstanding events). The C<how> argument must be either |
685 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
811 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
686 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
812 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
687 | |
813 | |
688 | This "unloop state" will be cleared when entering C<ev_loop> again. |
814 | This "unloop state" will be cleared when entering C<ev_run> again. |
689 | |
815 | |
690 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
816 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
691 | |
817 | |
692 | =item ev_ref (loop) |
818 | =item ev_ref (loop) |
693 | |
819 | |
694 | =item ev_unref (loop) |
820 | =item ev_unref (loop) |
695 | |
821 | |
696 | Ref/unref can be used to add or remove a reference count on the event |
822 | Ref/unref can be used to add or remove a reference count on the event |
697 | loop: Every watcher keeps one reference, and as long as the reference |
823 | loop: Every watcher keeps one reference, and as long as the reference |
698 | count is nonzero, C<ev_loop> will not return on its own. |
824 | count is nonzero, C<ev_run> will not return on its own. |
699 | |
825 | |
700 | If you have a watcher you never unregister that should not keep C<ev_loop> |
826 | This is useful when you have a watcher that you never intend to |
701 | from returning, call ev_unref() after starting, and ev_ref() before |
827 | unregister, but that nevertheless should not keep C<ev_run> from |
|
|
828 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
702 | stopping it. |
829 | before stopping it. |
703 | |
830 | |
704 | As an example, libev itself uses this for its internal signal pipe: It is |
831 | As an example, libev itself uses this for its internal signal pipe: It |
705 | not visible to the libev user and should not keep C<ev_loop> from exiting |
832 | is not visible to the libev user and should not keep C<ev_run> from |
706 | if no event watchers registered by it are active. It is also an excellent |
833 | exiting if no event watchers registered by it are active. It is also an |
707 | way to do this for generic recurring timers or from within third-party |
834 | excellent way to do this for generic recurring timers or from within |
708 | libraries. Just remember to I<unref after start> and I<ref before stop> |
835 | third-party libraries. Just remember to I<unref after start> and I<ref |
709 | (but only if the watcher wasn't active before, or was active before, |
836 | before stop> (but only if the watcher wasn't active before, or was active |
710 | respectively). |
837 | before, respectively. Note also that libev might stop watchers itself |
|
|
838 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
839 | in the callback). |
711 | |
840 | |
712 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
841 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
713 | running when nothing else is active. |
842 | running when nothing else is active. |
714 | |
843 | |
715 | ev_signal exitsig; |
844 | ev_signal exitsig; |
716 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
845 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
717 | ev_signal_start (loop, &exitsig); |
846 | ev_signal_start (loop, &exitsig); |
… | |
… | |
744 | |
873 | |
745 | By setting a higher I<io collect interval> you allow libev to spend more |
874 | By setting a higher I<io collect interval> you allow libev to spend more |
746 | time collecting I/O events, so you can handle more events per iteration, |
875 | time collecting I/O events, so you can handle more events per iteration, |
747 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
876 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
748 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
877 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
749 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
878 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
879 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
880 | once per this interval, on average. |
750 | |
881 | |
751 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
882 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
752 | to spend more time collecting timeouts, at the expense of increased |
883 | to spend more time collecting timeouts, at the expense of increased |
753 | latency/jitter/inexactness (the watcher callback will be called |
884 | latency/jitter/inexactness (the watcher callback will be called |
754 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
885 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
756 | |
887 | |
757 | Many (busy) programs can usually benefit by setting the I/O collect |
888 | Many (busy) programs can usually benefit by setting the I/O collect |
758 | interval to a value near C<0.1> or so, which is often enough for |
889 | interval to a value near C<0.1> or so, which is often enough for |
759 | interactive servers (of course not for games), likewise for timeouts. It |
890 | interactive servers (of course not for games), likewise for timeouts. It |
760 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
891 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
761 | as this approaches the timing granularity of most systems. |
892 | as this approaches the timing granularity of most systems. Note that if |
|
|
893 | you do transactions with the outside world and you can't increase the |
|
|
894 | parallelity, then this setting will limit your transaction rate (if you |
|
|
895 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
896 | then you can't do more than 100 transactions per second). |
762 | |
897 | |
763 | Setting the I<timeout collect interval> can improve the opportunity for |
898 | Setting the I<timeout collect interval> can improve the opportunity for |
764 | saving power, as the program will "bundle" timer callback invocations that |
899 | saving power, as the program will "bundle" timer callback invocations that |
765 | are "near" in time together, by delaying some, thus reducing the number of |
900 | are "near" in time together, by delaying some, thus reducing the number of |
766 | times the process sleeps and wakes up again. Another useful technique to |
901 | times the process sleeps and wakes up again. Another useful technique to |
767 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
902 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
768 | they fire on, say, one-second boundaries only. |
903 | they fire on, say, one-second boundaries only. |
769 | |
904 | |
|
|
905 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
906 | more often than 100 times per second: |
|
|
907 | |
|
|
908 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
909 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
910 | |
|
|
911 | =item ev_invoke_pending (loop) |
|
|
912 | |
|
|
913 | This call will simply invoke all pending watchers while resetting their |
|
|
914 | pending state. Normally, C<ev_run> does this automatically when required, |
|
|
915 | but when overriding the invoke callback this call comes handy. This |
|
|
916 | function can be invoked from a watcher - this can be useful for example |
|
|
917 | when you want to do some lengthy calculation and want to pass further |
|
|
918 | event handling to another thread (you still have to make sure only one |
|
|
919 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
|
|
920 | |
|
|
921 | =item int ev_pending_count (loop) |
|
|
922 | |
|
|
923 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
924 | are pending. |
|
|
925 | |
|
|
926 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
927 | |
|
|
928 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
929 | invoking all pending watchers when there are any, C<ev_run> will call |
|
|
930 | this callback instead. This is useful, for example, when you want to |
|
|
931 | invoke the actual watchers inside another context (another thread etc.). |
|
|
932 | |
|
|
933 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
934 | callback. |
|
|
935 | |
|
|
936 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
937 | |
|
|
938 | Sometimes you want to share the same loop between multiple threads. This |
|
|
939 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
940 | each call to a libev function. |
|
|
941 | |
|
|
942 | However, C<ev_run> can run an indefinite time, so it is not feasible |
|
|
943 | to wait for it to return. One way around this is to wake up the event |
|
|
944 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
|
|
945 | I<release> and I<acquire> callbacks on the loop. |
|
|
946 | |
|
|
947 | When set, then C<release> will be called just before the thread is |
|
|
948 | suspended waiting for new events, and C<acquire> is called just |
|
|
949 | afterwards. |
|
|
950 | |
|
|
951 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
952 | C<acquire> will just call the mutex_lock function again. |
|
|
953 | |
|
|
954 | While event loop modifications are allowed between invocations of |
|
|
955 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
956 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
957 | have no effect on the set of file descriptors being watched, or the time |
|
|
958 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
|
|
959 | to take note of any changes you made. |
|
|
960 | |
|
|
961 | In theory, threads executing C<ev_run> will be async-cancel safe between |
|
|
962 | invocations of C<release> and C<acquire>. |
|
|
963 | |
|
|
964 | See also the locking example in the C<THREADS> section later in this |
|
|
965 | document. |
|
|
966 | |
|
|
967 | =item ev_set_userdata (loop, void *data) |
|
|
968 | |
|
|
969 | =item ev_userdata (loop) |
|
|
970 | |
|
|
971 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
972 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
973 | C<0.> |
|
|
974 | |
|
|
975 | These two functions can be used to associate arbitrary data with a loop, |
|
|
976 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
977 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
978 | any other purpose as well. |
|
|
979 | |
770 | =item ev_loop_verify (loop) |
980 | =item ev_verify (loop) |
771 | |
981 | |
772 | This function only does something when C<EV_VERIFY> support has been |
982 | This function only does something when C<EV_VERIFY> support has been |
773 | compiled in. which is the default for non-minimal builds. It tries to go |
983 | compiled in, which is the default for non-minimal builds. It tries to go |
774 | through all internal structures and checks them for validity. If anything |
984 | through all internal structures and checks them for validity. If anything |
775 | is found to be inconsistent, it will print an error message to standard |
985 | is found to be inconsistent, it will print an error message to standard |
776 | error and call C<abort ()>. |
986 | error and call C<abort ()>. |
777 | |
987 | |
778 | This can be used to catch bugs inside libev itself: under normal |
988 | This can be used to catch bugs inside libev itself: under normal |
… | |
… | |
782 | =back |
992 | =back |
783 | |
993 | |
784 | |
994 | |
785 | =head1 ANATOMY OF A WATCHER |
995 | =head1 ANATOMY OF A WATCHER |
786 | |
996 | |
|
|
997 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
998 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
999 | watchers and C<ev_io_start> for I/O watchers. |
|
|
1000 | |
787 | A watcher is a structure that you create and register to record your |
1001 | A watcher is an opaque structure that you allocate and register to record |
788 | interest in some event. For instance, if you want to wait for STDIN to |
1002 | your interest in some event. To make a concrete example, imagine you want |
789 | become readable, you would create an C<ev_io> watcher for that: |
1003 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1004 | for that: |
790 | |
1005 | |
791 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
1006 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
792 | { |
1007 | { |
793 | ev_io_stop (w); |
1008 | ev_io_stop (w); |
794 | ev_unloop (loop, EVUNLOOP_ALL); |
1009 | ev_break (loop, EVBREAK_ALL); |
795 | } |
1010 | } |
796 | |
1011 | |
797 | struct ev_loop *loop = ev_default_loop (0); |
1012 | struct ev_loop *loop = ev_default_loop (0); |
|
|
1013 | |
798 | ev_io stdin_watcher; |
1014 | ev_io stdin_watcher; |
|
|
1015 | |
799 | ev_init (&stdin_watcher, my_cb); |
1016 | ev_init (&stdin_watcher, my_cb); |
800 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1017 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
801 | ev_io_start (loop, &stdin_watcher); |
1018 | ev_io_start (loop, &stdin_watcher); |
|
|
1019 | |
802 | ev_loop (loop, 0); |
1020 | ev_run (loop, 0); |
803 | |
1021 | |
804 | As you can see, you are responsible for allocating the memory for your |
1022 | As you can see, you are responsible for allocating the memory for your |
805 | watcher structures (and it is usually a bad idea to do this on the stack, |
1023 | watcher structures (and it is I<usually> a bad idea to do this on the |
806 | although this can sometimes be quite valid). |
1024 | stack). |
807 | |
1025 | |
|
|
1026 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
1027 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
|
|
1028 | |
808 | Each watcher structure must be initialised by a call to C<ev_init |
1029 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
809 | (watcher *, callback)>, which expects a callback to be provided. This |
1030 | *, callback)>, which expects a callback to be provided. This callback is |
810 | callback gets invoked each time the event occurs (or, in the case of I/O |
1031 | invoked each time the event occurs (or, in the case of I/O watchers, each |
811 | watchers, each time the event loop detects that the file descriptor given |
1032 | time the event loop detects that the file descriptor given is readable |
812 | is readable and/or writable). |
1033 | and/or writable). |
813 | |
1034 | |
814 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
1035 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
815 | with arguments specific to this watcher type. There is also a macro |
1036 | macro to configure it, with arguments specific to the watcher type. There |
816 | to combine initialisation and setting in one call: C<< ev_<type>_init |
1037 | is also a macro to combine initialisation and setting in one call: C<< |
817 | (watcher *, callback, ...) >>. |
1038 | ev_TYPE_init (watcher *, callback, ...) >>. |
818 | |
1039 | |
819 | To make the watcher actually watch out for events, you have to start it |
1040 | To make the watcher actually watch out for events, you have to start it |
820 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
1041 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
821 | *) >>), and you can stop watching for events at any time by calling the |
1042 | *) >>), and you can stop watching for events at any time by calling the |
822 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
1043 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
823 | |
1044 | |
824 | As long as your watcher is active (has been started but not stopped) you |
1045 | As long as your watcher is active (has been started but not stopped) you |
825 | must not touch the values stored in it. Most specifically you must never |
1046 | must not touch the values stored in it. Most specifically you must never |
826 | reinitialise it or call its C<set> macro. |
1047 | reinitialise it or call its C<ev_TYPE_set> macro. |
827 | |
1048 | |
828 | Each and every callback receives the event loop pointer as first, the |
1049 | Each and every callback receives the event loop pointer as first, the |
829 | registered watcher structure as second, and a bitset of received events as |
1050 | registered watcher structure as second, and a bitset of received events as |
830 | third argument. |
1051 | third argument. |
831 | |
1052 | |
… | |
… | |
840 | =item C<EV_WRITE> |
1061 | =item C<EV_WRITE> |
841 | |
1062 | |
842 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1063 | The file descriptor in the C<ev_io> watcher has become readable and/or |
843 | writable. |
1064 | writable. |
844 | |
1065 | |
845 | =item C<EV_TIMEOUT> |
1066 | =item C<EV_TIMER> |
846 | |
1067 | |
847 | The C<ev_timer> watcher has timed out. |
1068 | The C<ev_timer> watcher has timed out. |
848 | |
1069 | |
849 | =item C<EV_PERIODIC> |
1070 | =item C<EV_PERIODIC> |
850 | |
1071 | |
… | |
… | |
868 | |
1089 | |
869 | =item C<EV_PREPARE> |
1090 | =item C<EV_PREPARE> |
870 | |
1091 | |
871 | =item C<EV_CHECK> |
1092 | =item C<EV_CHECK> |
872 | |
1093 | |
873 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1094 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
874 | to gather new events, and all C<ev_check> watchers are invoked just after |
1095 | to gather new events, and all C<ev_check> watchers are invoked just after |
875 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1096 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
876 | received events. Callbacks of both watcher types can start and stop as |
1097 | received events. Callbacks of both watcher types can start and stop as |
877 | many watchers as they want, and all of them will be taken into account |
1098 | many watchers as they want, and all of them will be taken into account |
878 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1099 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
879 | C<ev_loop> from blocking). |
1100 | C<ev_run> from blocking). |
880 | |
1101 | |
881 | =item C<EV_EMBED> |
1102 | =item C<EV_EMBED> |
882 | |
1103 | |
883 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1104 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
884 | |
1105 | |
… | |
… | |
888 | C<ev_fork>). |
1109 | C<ev_fork>). |
889 | |
1110 | |
890 | =item C<EV_ASYNC> |
1111 | =item C<EV_ASYNC> |
891 | |
1112 | |
892 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1113 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
1114 | |
|
|
1115 | =item C<EV_CUSTOM> |
|
|
1116 | |
|
|
1117 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1118 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
893 | |
1119 | |
894 | =item C<EV_ERROR> |
1120 | =item C<EV_ERROR> |
895 | |
1121 | |
896 | An unspecified error has occurred, the watcher has been stopped. This might |
1122 | An unspecified error has occurred, the watcher has been stopped. This might |
897 | happen because the watcher could not be properly started because libev |
1123 | happen because the watcher could not be properly started because libev |
… | |
… | |
910 | programs, though, as the fd could already be closed and reused for another |
1136 | programs, though, as the fd could already be closed and reused for another |
911 | thing, so beware. |
1137 | thing, so beware. |
912 | |
1138 | |
913 | =back |
1139 | =back |
914 | |
1140 | |
|
|
1141 | =head2 WATCHER STATES |
|
|
1142 | |
|
|
1143 | There are various watcher states mentioned throughout this manual - |
|
|
1144 | active, pending and so on. In this section these states and the rules to |
|
|
1145 | transition between them will be described in more detail - and while these |
|
|
1146 | rules might look complicated, they usually do "the right thing". |
|
|
1147 | |
|
|
1148 | =over 4 |
|
|
1149 | |
|
|
1150 | =item initialiased |
|
|
1151 | |
|
|
1152 | Before a watcher can be registered with the event looop it has to be |
|
|
1153 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1154 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1155 | |
|
|
1156 | In this state it is simply some block of memory that is suitable for use |
|
|
1157 | in an event loop. It can be moved around, freed, reused etc. at will. |
|
|
1158 | |
|
|
1159 | =item started/running/active |
|
|
1160 | |
|
|
1161 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1162 | property of the event loop, and is actively waiting for events. While in |
|
|
1163 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1164 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1165 | and call libev functions on it that are documented to work on active watchers. |
|
|
1166 | |
|
|
1167 | =item pending |
|
|
1168 | |
|
|
1169 | If a watcher is active and libev determines that an event it is interested |
|
|
1170 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1171 | stay in this pending state until either it is stopped or its callback is |
|
|
1172 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1173 | callback. |
|
|
1174 | |
|
|
1175 | The watcher might or might not be active while it is pending (for example, |
|
|
1176 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1177 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1178 | but it is still property of the event loop at this time, so cannot be |
|
|
1179 | moved, freed or reused. And if it is active the rules described in the |
|
|
1180 | previous item still apply. |
|
|
1181 | |
|
|
1182 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1183 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1184 | active. |
|
|
1185 | |
|
|
1186 | =item stopped |
|
|
1187 | |
|
|
1188 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1189 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1190 | latter will clear any pending state the watcher might be in, regardless |
|
|
1191 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1192 | freeing it is often a good idea. |
|
|
1193 | |
|
|
1194 | While stopped (and not pending) the watcher is essentially in the |
|
|
1195 | initialised state, that is it can be reused, moved, modified in any way |
|
|
1196 | you wish. |
|
|
1197 | |
|
|
1198 | =back |
|
|
1199 | |
915 | =head2 GENERIC WATCHER FUNCTIONS |
1200 | =head2 GENERIC WATCHER FUNCTIONS |
916 | |
|
|
917 | In the following description, C<TYPE> stands for the watcher type, |
|
|
918 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
919 | |
1201 | |
920 | =over 4 |
1202 | =over 4 |
921 | |
1203 | |
922 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1204 | =item C<ev_init> (ev_TYPE *watcher, callback) |
923 | |
1205 | |
… | |
… | |
938 | |
1220 | |
939 | ev_io w; |
1221 | ev_io w; |
940 | ev_init (&w, my_cb); |
1222 | ev_init (&w, my_cb); |
941 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1223 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
942 | |
1224 | |
943 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1225 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
944 | |
1226 | |
945 | This macro initialises the type-specific parts of a watcher. You need to |
1227 | This macro initialises the type-specific parts of a watcher. You need to |
946 | call C<ev_init> at least once before you call this macro, but you can |
1228 | call C<ev_init> at least once before you call this macro, but you can |
947 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1229 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
948 | macro on a watcher that is active (it can be pending, however, which is a |
1230 | macro on a watcher that is active (it can be pending, however, which is a |
… | |
… | |
961 | |
1243 | |
962 | Example: Initialise and set an C<ev_io> watcher in one step. |
1244 | Example: Initialise and set an C<ev_io> watcher in one step. |
963 | |
1245 | |
964 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1246 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
965 | |
1247 | |
966 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1248 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
967 | |
1249 | |
968 | Starts (activates) the given watcher. Only active watchers will receive |
1250 | Starts (activates) the given watcher. Only active watchers will receive |
969 | events. If the watcher is already active nothing will happen. |
1251 | events. If the watcher is already active nothing will happen. |
970 | |
1252 | |
971 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1253 | Example: Start the C<ev_io> watcher that is being abused as example in this |
972 | whole section. |
1254 | whole section. |
973 | |
1255 | |
974 | ev_io_start (EV_DEFAULT_UC, &w); |
1256 | ev_io_start (EV_DEFAULT_UC, &w); |
975 | |
1257 | |
976 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1258 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
977 | |
1259 | |
978 | Stops the given watcher if active, and clears the pending status (whether |
1260 | Stops the given watcher if active, and clears the pending status (whether |
979 | the watcher was active or not). |
1261 | the watcher was active or not). |
980 | |
1262 | |
981 | It is possible that stopped watchers are pending - for example, |
1263 | It is possible that stopped watchers are pending - for example, |
… | |
… | |
1006 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1288 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1007 | |
1289 | |
1008 | Change the callback. You can change the callback at virtually any time |
1290 | Change the callback. You can change the callback at virtually any time |
1009 | (modulo threads). |
1291 | (modulo threads). |
1010 | |
1292 | |
1011 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1293 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1012 | |
1294 | |
1013 | =item int ev_priority (ev_TYPE *watcher) |
1295 | =item int ev_priority (ev_TYPE *watcher) |
1014 | |
1296 | |
1015 | Set and query the priority of the watcher. The priority is a small |
1297 | Set and query the priority of the watcher. The priority is a small |
1016 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1298 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1017 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1299 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1018 | before watchers with lower priority, but priority will not keep watchers |
1300 | before watchers with lower priority, but priority will not keep watchers |
1019 | from being executed (except for C<ev_idle> watchers). |
1301 | from being executed (except for C<ev_idle> watchers). |
1020 | |
1302 | |
1021 | This means that priorities are I<only> used for ordering callback |
|
|
1022 | invocation after new events have been received. This is useful, for |
|
|
1023 | example, to reduce latency after idling, or more often, to bind two |
|
|
1024 | watchers on the same event and make sure one is called first. |
|
|
1025 | |
|
|
1026 | If you need to suppress invocation when higher priority events are pending |
1303 | If you need to suppress invocation when higher priority events are pending |
1027 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1304 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1028 | |
1305 | |
1029 | You I<must not> change the priority of a watcher as long as it is active or |
1306 | You I<must not> change the priority of a watcher as long as it is active or |
1030 | pending. |
1307 | pending. |
1031 | |
1308 | |
|
|
1309 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1310 | fine, as long as you do not mind that the priority value you query might |
|
|
1311 | or might not have been clamped to the valid range. |
|
|
1312 | |
1032 | The default priority used by watchers when no priority has been set is |
1313 | The default priority used by watchers when no priority has been set is |
1033 | always C<0>, which is supposed to not be too high and not be too low :). |
1314 | always C<0>, which is supposed to not be too high and not be too low :). |
1034 | |
1315 | |
1035 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1316 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1036 | fine, as long as you do not mind that the priority value you query might |
1317 | priorities. |
1037 | or might not have been adjusted to be within valid range. |
|
|
1038 | |
1318 | |
1039 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1319 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1040 | |
1320 | |
1041 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1321 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1042 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1322 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1049 | returns its C<revents> bitset (as if its callback was invoked). If the |
1329 | returns its C<revents> bitset (as if its callback was invoked). If the |
1050 | watcher isn't pending it does nothing and returns C<0>. |
1330 | watcher isn't pending it does nothing and returns C<0>. |
1051 | |
1331 | |
1052 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1332 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1053 | callback to be invoked, which can be accomplished with this function. |
1333 | callback to be invoked, which can be accomplished with this function. |
|
|
1334 | |
|
|
1335 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1336 | |
|
|
1337 | Feeds the given event set into the event loop, as if the specified event |
|
|
1338 | had happened for the specified watcher (which must be a pointer to an |
|
|
1339 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1340 | not free the watcher as long as it has pending events. |
|
|
1341 | |
|
|
1342 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1343 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1344 | not started in the first place. |
|
|
1345 | |
|
|
1346 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1347 | functions that do not need a watcher. |
1054 | |
1348 | |
1055 | =back |
1349 | =back |
1056 | |
1350 | |
1057 | |
1351 | |
1058 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1352 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
… | |
… | |
1107 | #include <stddef.h> |
1401 | #include <stddef.h> |
1108 | |
1402 | |
1109 | static void |
1403 | static void |
1110 | t1_cb (EV_P_ ev_timer *w, int revents) |
1404 | t1_cb (EV_P_ ev_timer *w, int revents) |
1111 | { |
1405 | { |
1112 | struct my_biggy big = (struct my_biggy * |
1406 | struct my_biggy big = (struct my_biggy *) |
1113 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1407 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1114 | } |
1408 | } |
1115 | |
1409 | |
1116 | static void |
1410 | static void |
1117 | t2_cb (EV_P_ ev_timer *w, int revents) |
1411 | t2_cb (EV_P_ ev_timer *w, int revents) |
1118 | { |
1412 | { |
1119 | struct my_biggy big = (struct my_biggy * |
1413 | struct my_biggy big = (struct my_biggy *) |
1120 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1414 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1121 | } |
1415 | } |
|
|
1416 | |
|
|
1417 | =head2 WATCHER PRIORITY MODELS |
|
|
1418 | |
|
|
1419 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1420 | integers that influence the ordering of event callback invocation |
|
|
1421 | between watchers in some way, all else being equal. |
|
|
1422 | |
|
|
1423 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1424 | description for the more technical details such as the actual priority |
|
|
1425 | range. |
|
|
1426 | |
|
|
1427 | There are two common ways how these these priorities are being interpreted |
|
|
1428 | by event loops: |
|
|
1429 | |
|
|
1430 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1431 | of lower priority watchers, which means as long as higher priority |
|
|
1432 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1433 | |
|
|
1434 | The less common only-for-ordering model uses priorities solely to order |
|
|
1435 | callback invocation within a single event loop iteration: Higher priority |
|
|
1436 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1437 | before polling for new events. |
|
|
1438 | |
|
|
1439 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1440 | except for idle watchers (which use the lock-out model). |
|
|
1441 | |
|
|
1442 | The rationale behind this is that implementing the lock-out model for |
|
|
1443 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1444 | libraries will just poll for the same events again and again as long as |
|
|
1445 | their callbacks have not been executed, which is very inefficient in the |
|
|
1446 | common case of one high-priority watcher locking out a mass of lower |
|
|
1447 | priority ones. |
|
|
1448 | |
|
|
1449 | Static (ordering) priorities are most useful when you have two or more |
|
|
1450 | watchers handling the same resource: a typical usage example is having an |
|
|
1451 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1452 | timeouts. Under load, data might be received while the program handles |
|
|
1453 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1454 | handler will be executed before checking for data. In that case, giving |
|
|
1455 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1456 | handled first even under adverse conditions (which is usually, but not |
|
|
1457 | always, what you want). |
|
|
1458 | |
|
|
1459 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1460 | will only be executed when no same or higher priority watchers have |
|
|
1461 | received events, they can be used to implement the "lock-out" model when |
|
|
1462 | required. |
|
|
1463 | |
|
|
1464 | For example, to emulate how many other event libraries handle priorities, |
|
|
1465 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1466 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1467 | processing is done in the idle watcher callback. This causes libev to |
|
|
1468 | continuously poll and process kernel event data for the watcher, but when |
|
|
1469 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1470 | workable. |
|
|
1471 | |
|
|
1472 | Usually, however, the lock-out model implemented that way will perform |
|
|
1473 | miserably under the type of load it was designed to handle. In that case, |
|
|
1474 | it might be preferable to stop the real watcher before starting the |
|
|
1475 | idle watcher, so the kernel will not have to process the event in case |
|
|
1476 | the actual processing will be delayed for considerable time. |
|
|
1477 | |
|
|
1478 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1479 | priority than the default, and which should only process data when no |
|
|
1480 | other events are pending: |
|
|
1481 | |
|
|
1482 | ev_idle idle; // actual processing watcher |
|
|
1483 | ev_io io; // actual event watcher |
|
|
1484 | |
|
|
1485 | static void |
|
|
1486 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1487 | { |
|
|
1488 | // stop the I/O watcher, we received the event, but |
|
|
1489 | // are not yet ready to handle it. |
|
|
1490 | ev_io_stop (EV_A_ w); |
|
|
1491 | |
|
|
1492 | // start the idle watcher to handle the actual event. |
|
|
1493 | // it will not be executed as long as other watchers |
|
|
1494 | // with the default priority are receiving events. |
|
|
1495 | ev_idle_start (EV_A_ &idle); |
|
|
1496 | } |
|
|
1497 | |
|
|
1498 | static void |
|
|
1499 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1500 | { |
|
|
1501 | // actual processing |
|
|
1502 | read (STDIN_FILENO, ...); |
|
|
1503 | |
|
|
1504 | // have to start the I/O watcher again, as |
|
|
1505 | // we have handled the event |
|
|
1506 | ev_io_start (EV_P_ &io); |
|
|
1507 | } |
|
|
1508 | |
|
|
1509 | // initialisation |
|
|
1510 | ev_idle_init (&idle, idle_cb); |
|
|
1511 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1512 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1513 | |
|
|
1514 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1515 | low-priority connections can not be locked out forever under load. This |
|
|
1516 | enables your program to keep a lower latency for important connections |
|
|
1517 | during short periods of high load, while not completely locking out less |
|
|
1518 | important ones. |
1122 | |
1519 | |
1123 | |
1520 | |
1124 | =head1 WATCHER TYPES |
1521 | =head1 WATCHER TYPES |
1125 | |
1522 | |
1126 | This section describes each watcher in detail, but will not repeat |
1523 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1152 | descriptors to non-blocking mode is also usually a good idea (but not |
1549 | descriptors to non-blocking mode is also usually a good idea (but not |
1153 | required if you know what you are doing). |
1550 | required if you know what you are doing). |
1154 | |
1551 | |
1155 | If you cannot use non-blocking mode, then force the use of a |
1552 | If you cannot use non-blocking mode, then force the use of a |
1156 | known-to-be-good backend (at the time of this writing, this includes only |
1553 | known-to-be-good backend (at the time of this writing, this includes only |
1157 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1554 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1555 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1556 | files) - libev doesn't guarantee any specific behaviour in that case. |
1158 | |
1557 | |
1159 | Another thing you have to watch out for is that it is quite easy to |
1558 | Another thing you have to watch out for is that it is quite easy to |
1160 | receive "spurious" readiness notifications, that is your callback might |
1559 | receive "spurious" readiness notifications, that is your callback might |
1161 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1560 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1162 | because there is no data. Not only are some backends known to create a |
1561 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1227 | |
1626 | |
1228 | So when you encounter spurious, unexplained daemon exits, make sure you |
1627 | So when you encounter spurious, unexplained daemon exits, make sure you |
1229 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1628 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1230 | somewhere, as that would have given you a big clue). |
1629 | somewhere, as that would have given you a big clue). |
1231 | |
1630 | |
|
|
1631 | =head3 The special problem of accept()ing when you can't |
|
|
1632 | |
|
|
1633 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1634 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1635 | connection from the pending queue in all error cases. |
|
|
1636 | |
|
|
1637 | For example, larger servers often run out of file descriptors (because |
|
|
1638 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1639 | rejecting the connection, leading to libev signalling readiness on |
|
|
1640 | the next iteration again (the connection still exists after all), and |
|
|
1641 | typically causing the program to loop at 100% CPU usage. |
|
|
1642 | |
|
|
1643 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1644 | operating systems, there is usually little the app can do to remedy the |
|
|
1645 | situation, and no known thread-safe method of removing the connection to |
|
|
1646 | cope with overload is known (to me). |
|
|
1647 | |
|
|
1648 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1649 | - when the program encounters an overload, it will just loop until the |
|
|
1650 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1651 | event-based way to handle this situation, so it's the best one can do. |
|
|
1652 | |
|
|
1653 | A better way to handle the situation is to log any errors other than |
|
|
1654 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1655 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1656 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1657 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1658 | usage. |
|
|
1659 | |
|
|
1660 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1661 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1662 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1663 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1664 | clients under typical overload conditions. |
|
|
1665 | |
|
|
1666 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1667 | is often done with C<malloc> failures, but this results in an easy |
|
|
1668 | opportunity for a DoS attack. |
1232 | |
1669 | |
1233 | =head3 Watcher-Specific Functions |
1670 | =head3 Watcher-Specific Functions |
1234 | |
1671 | |
1235 | =over 4 |
1672 | =over 4 |
1236 | |
1673 | |
… | |
… | |
1268 | ... |
1705 | ... |
1269 | struct ev_loop *loop = ev_default_init (0); |
1706 | struct ev_loop *loop = ev_default_init (0); |
1270 | ev_io stdin_readable; |
1707 | ev_io stdin_readable; |
1271 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1708 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1272 | ev_io_start (loop, &stdin_readable); |
1709 | ev_io_start (loop, &stdin_readable); |
1273 | ev_loop (loop, 0); |
1710 | ev_run (loop, 0); |
1274 | |
1711 | |
1275 | |
1712 | |
1276 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1713 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1277 | |
1714 | |
1278 | Timer watchers are simple relative timers that generate an event after a |
1715 | Timer watchers are simple relative timers that generate an event after a |
… | |
… | |
1283 | year, it will still time out after (roughly) one hour. "Roughly" because |
1720 | year, it will still time out after (roughly) one hour. "Roughly" because |
1284 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1721 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1285 | monotonic clock option helps a lot here). |
1722 | monotonic clock option helps a lot here). |
1286 | |
1723 | |
1287 | The callback is guaranteed to be invoked only I<after> its timeout has |
1724 | The callback is guaranteed to be invoked only I<after> its timeout has |
1288 | passed, but if multiple timers become ready during the same loop iteration |
1725 | passed (not I<at>, so on systems with very low-resolution clocks this |
1289 | then order of execution is undefined. |
1726 | might introduce a small delay). If multiple timers become ready during the |
|
|
1727 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1728 | before ones of the same priority with later time-out values (but this is |
|
|
1729 | no longer true when a callback calls C<ev_run> recursively). |
1290 | |
1730 | |
1291 | =head3 Be smart about timeouts |
1731 | =head3 Be smart about timeouts |
1292 | |
1732 | |
1293 | Many real-world problems involve some kind of timeout, usually for error |
1733 | Many real-world problems involve some kind of timeout, usually for error |
1294 | recovery. A typical example is an HTTP request - if the other side hangs, |
1734 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1338 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1778 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1339 | member and C<ev_timer_again>. |
1779 | member and C<ev_timer_again>. |
1340 | |
1780 | |
1341 | At start: |
1781 | At start: |
1342 | |
1782 | |
1343 | ev_timer_init (timer, callback); |
1783 | ev_init (timer, callback); |
1344 | timer->repeat = 60.; |
1784 | timer->repeat = 60.; |
1345 | ev_timer_again (loop, timer); |
1785 | ev_timer_again (loop, timer); |
1346 | |
1786 | |
1347 | Each time there is some activity: |
1787 | Each time there is some activity: |
1348 | |
1788 | |
… | |
… | |
1380 | ev_tstamp timeout = last_activity + 60.; |
1820 | ev_tstamp timeout = last_activity + 60.; |
1381 | |
1821 | |
1382 | // if last_activity + 60. is older than now, we did time out |
1822 | // if last_activity + 60. is older than now, we did time out |
1383 | if (timeout < now) |
1823 | if (timeout < now) |
1384 | { |
1824 | { |
1385 | // timeout occured, take action |
1825 | // timeout occurred, take action |
1386 | } |
1826 | } |
1387 | else |
1827 | else |
1388 | { |
1828 | { |
1389 | // callback was invoked, but there was some activity, re-arm |
1829 | // callback was invoked, but there was some activity, re-arm |
1390 | // the watcher to fire in last_activity + 60, which is |
1830 | // the watcher to fire in last_activity + 60, which is |
1391 | // guaranteed to be in the future, so "again" is positive: |
1831 | // guaranteed to be in the future, so "again" is positive: |
1392 | w->again = timeout - now; |
1832 | w->repeat = timeout - now; |
1393 | ev_timer_again (EV_A_ w); |
1833 | ev_timer_again (EV_A_ w); |
1394 | } |
1834 | } |
1395 | } |
1835 | } |
1396 | |
1836 | |
1397 | To summarise the callback: first calculate the real timeout (defined |
1837 | To summarise the callback: first calculate the real timeout (defined |
… | |
… | |
1410 | |
1850 | |
1411 | To start the timer, simply initialise the watcher and set C<last_activity> |
1851 | To start the timer, simply initialise the watcher and set C<last_activity> |
1412 | to the current time (meaning we just have some activity :), then call the |
1852 | to the current time (meaning we just have some activity :), then call the |
1413 | callback, which will "do the right thing" and start the timer: |
1853 | callback, which will "do the right thing" and start the timer: |
1414 | |
1854 | |
1415 | ev_timer_init (timer, callback); |
1855 | ev_init (timer, callback); |
1416 | last_activity = ev_now (loop); |
1856 | last_activity = ev_now (loop); |
1417 | callback (loop, timer, EV_TIMEOUT); |
1857 | callback (loop, timer, EV_TIMER); |
1418 | |
1858 | |
1419 | And when there is some activity, simply store the current time in |
1859 | And when there is some activity, simply store the current time in |
1420 | C<last_activity>, no libev calls at all: |
1860 | C<last_activity>, no libev calls at all: |
1421 | |
1861 | |
1422 | last_actiivty = ev_now (loop); |
1862 | last_activity = ev_now (loop); |
1423 | |
1863 | |
1424 | This technique is slightly more complex, but in most cases where the |
1864 | This technique is slightly more complex, but in most cases where the |
1425 | time-out is unlikely to be triggered, much more efficient. |
1865 | time-out is unlikely to be triggered, much more efficient. |
1426 | |
1866 | |
1427 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1867 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1428 | callback :) - just change the timeout and invoke the callback, which will |
1868 | callback :) - just change the timeout and invoke the callback, which will |
1429 | fix things for you. |
1869 | fix things for you. |
1430 | |
1870 | |
1431 | =item 4. Whee, use a double-linked list for your timeouts. |
1871 | =item 4. Wee, just use a double-linked list for your timeouts. |
1432 | |
1872 | |
1433 | If there is not one request, but many thousands, all employing some kind |
1873 | If there is not one request, but many thousands (millions...), all |
1434 | of timeout with the same timeout value, then one can do even better: |
1874 | employing some kind of timeout with the same timeout value, then one can |
|
|
1875 | do even better: |
1435 | |
1876 | |
1436 | When starting the timeout, calculate the timeout value and put the timeout |
1877 | When starting the timeout, calculate the timeout value and put the timeout |
1437 | at the I<end> of the list. |
1878 | at the I<end> of the list. |
1438 | |
1879 | |
1439 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
1880 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
… | |
… | |
1448 | complication, and having to use a constant timeout. The constant timeout |
1889 | complication, and having to use a constant timeout. The constant timeout |
1449 | ensures that the list stays sorted. |
1890 | ensures that the list stays sorted. |
1450 | |
1891 | |
1451 | =back |
1892 | =back |
1452 | |
1893 | |
1453 | So what method is the best? |
1894 | So which method the best? |
1454 | |
1895 | |
1455 | The method #2 is a simple no-brain-required solution that is adequate in |
1896 | Method #2 is a simple no-brain-required solution that is adequate in most |
1456 | most situations. Method #3 requires a bit more thinking, but handles many |
1897 | situations. Method #3 requires a bit more thinking, but handles many cases |
1457 | cases better, and isn't very complicated either. In most case, choosing |
1898 | better, and isn't very complicated either. In most case, choosing either |
1458 | either one is fine. |
1899 | one is fine, with #3 being better in typical situations. |
1459 | |
1900 | |
1460 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1901 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1461 | rather complicated, but extremely efficient, something that really pays |
1902 | rather complicated, but extremely efficient, something that really pays |
1462 | off after the first or so million of active timers, i.e. it's usually |
1903 | off after the first million or so of active timers, i.e. it's usually |
1463 | overkill :) |
1904 | overkill :) |
1464 | |
1905 | |
1465 | =head3 The special problem of time updates |
1906 | =head3 The special problem of time updates |
1466 | |
1907 | |
1467 | Establishing the current time is a costly operation (it usually takes at |
1908 | Establishing the current time is a costly operation (it usually takes at |
1468 | least two system calls): EV therefore updates its idea of the current |
1909 | least two system calls): EV therefore updates its idea of the current |
1469 | time only before and after C<ev_loop> collects new events, which causes a |
1910 | time only before and after C<ev_run> collects new events, which causes a |
1470 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1911 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1471 | lots of events in one iteration. |
1912 | lots of events in one iteration. |
1472 | |
1913 | |
1473 | The relative timeouts are calculated relative to the C<ev_now ()> |
1914 | The relative timeouts are calculated relative to the C<ev_now ()> |
1474 | time. This is usually the right thing as this timestamp refers to the time |
1915 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
1480 | |
1921 | |
1481 | If the event loop is suspended for a long time, you can also force an |
1922 | If the event loop is suspended for a long time, you can also force an |
1482 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1923 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1483 | ()>. |
1924 | ()>. |
1484 | |
1925 | |
|
|
1926 | =head3 The special problems of suspended animation |
|
|
1927 | |
|
|
1928 | When you leave the server world it is quite customary to hit machines that |
|
|
1929 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1930 | |
|
|
1931 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1932 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1933 | to run until the system is suspended, but they will not advance while the |
|
|
1934 | system is suspended. That means, on resume, it will be as if the program |
|
|
1935 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1936 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1937 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1938 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1939 | be adjusted accordingly. |
|
|
1940 | |
|
|
1941 | I would not be surprised to see different behaviour in different between |
|
|
1942 | operating systems, OS versions or even different hardware. |
|
|
1943 | |
|
|
1944 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1945 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1946 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1947 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1948 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1949 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1950 | |
|
|
1951 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1952 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1953 | deterministic behaviour in this case (you can do nothing against |
|
|
1954 | C<SIGSTOP>). |
|
|
1955 | |
1485 | =head3 Watcher-Specific Functions and Data Members |
1956 | =head3 Watcher-Specific Functions and Data Members |
1486 | |
1957 | |
1487 | =over 4 |
1958 | =over 4 |
1488 | |
1959 | |
1489 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1960 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1512 | If the timer is started but non-repeating, stop it (as if it timed out). |
1983 | If the timer is started but non-repeating, stop it (as if it timed out). |
1513 | |
1984 | |
1514 | If the timer is repeating, either start it if necessary (with the |
1985 | If the timer is repeating, either start it if necessary (with the |
1515 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1986 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1516 | |
1987 | |
1517 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1988 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1518 | usage example. |
1989 | usage example. |
|
|
1990 | |
|
|
1991 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
|
|
1992 | |
|
|
1993 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
1994 | then this time is relative to the current event loop time, otherwise it's |
|
|
1995 | the timeout value currently configured. |
|
|
1996 | |
|
|
1997 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
1998 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
1999 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
2000 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
2001 | too), and so on. |
1519 | |
2002 | |
1520 | =item ev_tstamp repeat [read-write] |
2003 | =item ev_tstamp repeat [read-write] |
1521 | |
2004 | |
1522 | The current C<repeat> value. Will be used each time the watcher times out |
2005 | The current C<repeat> value. Will be used each time the watcher times out |
1523 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
2006 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1549 | } |
2032 | } |
1550 | |
2033 | |
1551 | ev_timer mytimer; |
2034 | ev_timer mytimer; |
1552 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2035 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1553 | ev_timer_again (&mytimer); /* start timer */ |
2036 | ev_timer_again (&mytimer); /* start timer */ |
1554 | ev_loop (loop, 0); |
2037 | ev_run (loop, 0); |
1555 | |
2038 | |
1556 | // and in some piece of code that gets executed on any "activity": |
2039 | // and in some piece of code that gets executed on any "activity": |
1557 | // reset the timeout to start ticking again at 10 seconds |
2040 | // reset the timeout to start ticking again at 10 seconds |
1558 | ev_timer_again (&mytimer); |
2041 | ev_timer_again (&mytimer); |
1559 | |
2042 | |
… | |
… | |
1561 | =head2 C<ev_periodic> - to cron or not to cron? |
2044 | =head2 C<ev_periodic> - to cron or not to cron? |
1562 | |
2045 | |
1563 | Periodic watchers are also timers of a kind, but they are very versatile |
2046 | Periodic watchers are also timers of a kind, but they are very versatile |
1564 | (and unfortunately a bit complex). |
2047 | (and unfortunately a bit complex). |
1565 | |
2048 | |
1566 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
2049 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1567 | but on wall clock time (absolute time). You can tell a periodic watcher |
2050 | relative time, the physical time that passes) but on wall clock time |
1568 | to trigger after some specific point in time. For example, if you tell a |
2051 | (absolute time, the thing you can read on your calender or clock). The |
1569 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
2052 | difference is that wall clock time can run faster or slower than real |
1570 | + 10.>, that is, an absolute time not a delay) and then reset your system |
2053 | time, and time jumps are not uncommon (e.g. when you adjust your |
1571 | clock to January of the previous year, then it will take more than year |
2054 | wrist-watch). |
1572 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1573 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1574 | |
2055 | |
|
|
2056 | You can tell a periodic watcher to trigger after some specific point |
|
|
2057 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
2058 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
2059 | not a delay) and then reset your system clock to January of the previous |
|
|
2060 | year, then it will take a year or more to trigger the event (unlike an |
|
|
2061 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
2062 | it, as it uses a relative timeout). |
|
|
2063 | |
1575 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
2064 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1576 | such as triggering an event on each "midnight, local time", or other |
2065 | timers, such as triggering an event on each "midnight, local time", or |
1577 | complicated rules. |
2066 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
2067 | those cannot react to time jumps. |
1578 | |
2068 | |
1579 | As with timers, the callback is guaranteed to be invoked only when the |
2069 | As with timers, the callback is guaranteed to be invoked only when the |
1580 | time (C<at>) has passed, but if multiple periodic timers become ready |
2070 | point in time where it is supposed to trigger has passed. If multiple |
1581 | during the same loop iteration, then order of execution is undefined. |
2071 | timers become ready during the same loop iteration then the ones with |
|
|
2072 | earlier time-out values are invoked before ones with later time-out values |
|
|
2073 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1582 | |
2074 | |
1583 | =head3 Watcher-Specific Functions and Data Members |
2075 | =head3 Watcher-Specific Functions and Data Members |
1584 | |
2076 | |
1585 | =over 4 |
2077 | =over 4 |
1586 | |
2078 | |
1587 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
2079 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1588 | |
2080 | |
1589 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
2081 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1590 | |
2082 | |
1591 | Lots of arguments, lets sort it out... There are basically three modes of |
2083 | Lots of arguments, let's sort it out... There are basically three modes of |
1592 | operation, and we will explain them from simplest to most complex: |
2084 | operation, and we will explain them from simplest to most complex: |
1593 | |
2085 | |
1594 | =over 4 |
2086 | =over 4 |
1595 | |
2087 | |
1596 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
2088 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1597 | |
2089 | |
1598 | In this configuration the watcher triggers an event after the wall clock |
2090 | In this configuration the watcher triggers an event after the wall clock |
1599 | time C<at> has passed. It will not repeat and will not adjust when a time |
2091 | time C<offset> has passed. It will not repeat and will not adjust when a |
1600 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
2092 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1601 | only run when the system clock reaches or surpasses this time. |
2093 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2094 | this point in time. |
1602 | |
2095 | |
1603 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2096 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1604 | |
2097 | |
1605 | In this mode the watcher will always be scheduled to time out at the next |
2098 | In this mode the watcher will always be scheduled to time out at the next |
1606 | C<at + N * interval> time (for some integer N, which can also be negative) |
2099 | C<offset + N * interval> time (for some integer N, which can also be |
1607 | and then repeat, regardless of any time jumps. |
2100 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
2101 | argument is merely an offset into the C<interval> periods. |
1608 | |
2102 | |
1609 | This can be used to create timers that do not drift with respect to the |
2103 | This can be used to create timers that do not drift with respect to the |
1610 | system clock, for example, here is a C<ev_periodic> that triggers each |
2104 | system clock, for example, here is an C<ev_periodic> that triggers each |
1611 | hour, on the hour: |
2105 | hour, on the hour (with respect to UTC): |
1612 | |
2106 | |
1613 | ev_periodic_set (&periodic, 0., 3600., 0); |
2107 | ev_periodic_set (&periodic, 0., 3600., 0); |
1614 | |
2108 | |
1615 | This doesn't mean there will always be 3600 seconds in between triggers, |
2109 | This doesn't mean there will always be 3600 seconds in between triggers, |
1616 | but only that the callback will be called when the system time shows a |
2110 | but only that the callback will be called when the system time shows a |
1617 | full hour (UTC), or more correctly, when the system time is evenly divisible |
2111 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1618 | by 3600. |
2112 | by 3600. |
1619 | |
2113 | |
1620 | Another way to think about it (for the mathematically inclined) is that |
2114 | Another way to think about it (for the mathematically inclined) is that |
1621 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2115 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1622 | time where C<time = at (mod interval)>, regardless of any time jumps. |
2116 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1623 | |
2117 | |
1624 | For numerical stability it is preferable that the C<at> value is near |
2118 | For numerical stability it is preferable that the C<offset> value is near |
1625 | C<ev_now ()> (the current time), but there is no range requirement for |
2119 | C<ev_now ()> (the current time), but there is no range requirement for |
1626 | this value, and in fact is often specified as zero. |
2120 | this value, and in fact is often specified as zero. |
1627 | |
2121 | |
1628 | Note also that there is an upper limit to how often a timer can fire (CPU |
2122 | Note also that there is an upper limit to how often a timer can fire (CPU |
1629 | speed for example), so if C<interval> is very small then timing stability |
2123 | speed for example), so if C<interval> is very small then timing stability |
1630 | will of course deteriorate. Libev itself tries to be exact to be about one |
2124 | will of course deteriorate. Libev itself tries to be exact to be about one |
1631 | millisecond (if the OS supports it and the machine is fast enough). |
2125 | millisecond (if the OS supports it and the machine is fast enough). |
1632 | |
2126 | |
1633 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2127 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1634 | |
2128 | |
1635 | In this mode the values for C<interval> and C<at> are both being |
2129 | In this mode the values for C<interval> and C<offset> are both being |
1636 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2130 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1637 | reschedule callback will be called with the watcher as first, and the |
2131 | reschedule callback will be called with the watcher as first, and the |
1638 | current time as second argument. |
2132 | current time as second argument. |
1639 | |
2133 | |
1640 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2134 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1641 | ever, or make ANY event loop modifications whatsoever>. |
2135 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
2136 | allowed by documentation here>. |
1642 | |
2137 | |
1643 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
2138 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1644 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
2139 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1645 | only event loop modification you are allowed to do). |
2140 | only event loop modification you are allowed to do). |
1646 | |
2141 | |
… | |
… | |
1676 | a different time than the last time it was called (e.g. in a crond like |
2171 | a different time than the last time it was called (e.g. in a crond like |
1677 | program when the crontabs have changed). |
2172 | program when the crontabs have changed). |
1678 | |
2173 | |
1679 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2174 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1680 | |
2175 | |
1681 | When active, returns the absolute time that the watcher is supposed to |
2176 | When active, returns the absolute time that the watcher is supposed |
1682 | trigger next. |
2177 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2178 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2179 | rescheduling modes. |
1683 | |
2180 | |
1684 | =item ev_tstamp offset [read-write] |
2181 | =item ev_tstamp offset [read-write] |
1685 | |
2182 | |
1686 | When repeating, this contains the offset value, otherwise this is the |
2183 | When repeating, this contains the offset value, otherwise this is the |
1687 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2184 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2185 | although libev might modify this value for better numerical stability). |
1688 | |
2186 | |
1689 | Can be modified any time, but changes only take effect when the periodic |
2187 | Can be modified any time, but changes only take effect when the periodic |
1690 | timer fires or C<ev_periodic_again> is being called. |
2188 | timer fires or C<ev_periodic_again> is being called. |
1691 | |
2189 | |
1692 | =item ev_tstamp interval [read-write] |
2190 | =item ev_tstamp interval [read-write] |
… | |
… | |
1708 | Example: Call a callback every hour, or, more precisely, whenever the |
2206 | Example: Call a callback every hour, or, more precisely, whenever the |
1709 | system time is divisible by 3600. The callback invocation times have |
2207 | system time is divisible by 3600. The callback invocation times have |
1710 | potentially a lot of jitter, but good long-term stability. |
2208 | potentially a lot of jitter, but good long-term stability. |
1711 | |
2209 | |
1712 | static void |
2210 | static void |
1713 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2211 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1714 | { |
2212 | { |
1715 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2213 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1716 | } |
2214 | } |
1717 | |
2215 | |
1718 | ev_periodic hourly_tick; |
2216 | ev_periodic hourly_tick; |
… | |
… | |
1744 | Signal watchers will trigger an event when the process receives a specific |
2242 | Signal watchers will trigger an event when the process receives a specific |
1745 | signal one or more times. Even though signals are very asynchronous, libev |
2243 | signal one or more times. Even though signals are very asynchronous, libev |
1746 | will try it's best to deliver signals synchronously, i.e. as part of the |
2244 | will try it's best to deliver signals synchronously, i.e. as part of the |
1747 | normal event processing, like any other event. |
2245 | normal event processing, like any other event. |
1748 | |
2246 | |
1749 | If you want signals asynchronously, just use C<sigaction> as you would |
2247 | If you want signals to be delivered truly asynchronously, just use |
1750 | do without libev and forget about sharing the signal. You can even use |
2248 | C<sigaction> as you would do without libev and forget about sharing |
1751 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
2249 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2250 | synchronously wake up an event loop. |
1752 | |
2251 | |
1753 | You can configure as many watchers as you like per signal. Only when the |
2252 | You can configure as many watchers as you like for the same signal, but |
|
|
2253 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2254 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2255 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2256 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2257 | |
1754 | first watcher gets started will libev actually register a signal handler |
2258 | When the first watcher gets started will libev actually register something |
1755 | with the kernel (thus it coexists with your own signal handlers as long as |
2259 | with the kernel (thus it coexists with your own signal handlers as long as |
1756 | you don't register any with libev for the same signal). Similarly, when |
2260 | you don't register any with libev for the same signal). |
1757 | the last signal watcher for a signal is stopped, libev will reset the |
|
|
1758 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1759 | |
2261 | |
1760 | If possible and supported, libev will install its handlers with |
2262 | If possible and supported, libev will install its handlers with |
1761 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2263 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1762 | interrupted. If you have a problem with system calls getting interrupted by |
2264 | not be unduly interrupted. If you have a problem with system calls getting |
1763 | signals you can block all signals in an C<ev_check> watcher and unblock |
2265 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1764 | them in an C<ev_prepare> watcher. |
2266 | and unblock them in an C<ev_prepare> watcher. |
|
|
2267 | |
|
|
2268 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2269 | |
|
|
2270 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2271 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2272 | stopping it again), that is, libev might or might not block the signal, |
|
|
2273 | and might or might not set or restore the installed signal handler. |
|
|
2274 | |
|
|
2275 | While this does not matter for the signal disposition (libev never |
|
|
2276 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2277 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2278 | certain signals to be blocked. |
|
|
2279 | |
|
|
2280 | This means that before calling C<exec> (from the child) you should reset |
|
|
2281 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2282 | choice usually). |
|
|
2283 | |
|
|
2284 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2285 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2286 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2287 | |
|
|
2288 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2289 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2290 | the window of opportunity for problems, it will not go away, as libev |
|
|
2291 | I<has> to modify the signal mask, at least temporarily. |
|
|
2292 | |
|
|
2293 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2294 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2295 | is not a libev-specific thing, this is true for most event libraries. |
1765 | |
2296 | |
1766 | =head3 Watcher-Specific Functions and Data Members |
2297 | =head3 Watcher-Specific Functions and Data Members |
1767 | |
2298 | |
1768 | =over 4 |
2299 | =over 4 |
1769 | |
2300 | |
… | |
… | |
1785 | Example: Try to exit cleanly on SIGINT. |
2316 | Example: Try to exit cleanly on SIGINT. |
1786 | |
2317 | |
1787 | static void |
2318 | static void |
1788 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2319 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1789 | { |
2320 | { |
1790 | ev_unloop (loop, EVUNLOOP_ALL); |
2321 | ev_break (loop, EVBREAK_ALL); |
1791 | } |
2322 | } |
1792 | |
2323 | |
1793 | ev_signal signal_watcher; |
2324 | ev_signal signal_watcher; |
1794 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2325 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1795 | ev_signal_start (loop, &signal_watcher); |
2326 | ev_signal_start (loop, &signal_watcher); |
… | |
… | |
1801 | some child status changes (most typically when a child of yours dies or |
2332 | some child status changes (most typically when a child of yours dies or |
1802 | exits). It is permissible to install a child watcher I<after> the child |
2333 | exits). It is permissible to install a child watcher I<after> the child |
1803 | has been forked (which implies it might have already exited), as long |
2334 | has been forked (which implies it might have already exited), as long |
1804 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2335 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1805 | forking and then immediately registering a watcher for the child is fine, |
2336 | forking and then immediately registering a watcher for the child is fine, |
1806 | but forking and registering a watcher a few event loop iterations later is |
2337 | but forking and registering a watcher a few event loop iterations later or |
1807 | not. |
2338 | in the next callback invocation is not. |
1808 | |
2339 | |
1809 | Only the default event loop is capable of handling signals, and therefore |
2340 | Only the default event loop is capable of handling signals, and therefore |
1810 | you can only register child watchers in the default event loop. |
2341 | you can only register child watchers in the default event loop. |
1811 | |
2342 | |
|
|
2343 | Due to some design glitches inside libev, child watchers will always be |
|
|
2344 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2345 | libev) |
|
|
2346 | |
1812 | =head3 Process Interaction |
2347 | =head3 Process Interaction |
1813 | |
2348 | |
1814 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2349 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1815 | initialised. This is necessary to guarantee proper behaviour even if |
2350 | initialised. This is necessary to guarantee proper behaviour even if the |
1816 | the first child watcher is started after the child exits. The occurrence |
2351 | first child watcher is started after the child exits. The occurrence |
1817 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2352 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1818 | synchronously as part of the event loop processing. Libev always reaps all |
2353 | synchronously as part of the event loop processing. Libev always reaps all |
1819 | children, even ones not watched. |
2354 | children, even ones not watched. |
1820 | |
2355 | |
1821 | =head3 Overriding the Built-In Processing |
2356 | =head3 Overriding the Built-In Processing |
… | |
… | |
1831 | =head3 Stopping the Child Watcher |
2366 | =head3 Stopping the Child Watcher |
1832 | |
2367 | |
1833 | Currently, the child watcher never gets stopped, even when the |
2368 | Currently, the child watcher never gets stopped, even when the |
1834 | child terminates, so normally one needs to stop the watcher in the |
2369 | child terminates, so normally one needs to stop the watcher in the |
1835 | callback. Future versions of libev might stop the watcher automatically |
2370 | callback. Future versions of libev might stop the watcher automatically |
1836 | when a child exit is detected. |
2371 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2372 | problem). |
1837 | |
2373 | |
1838 | =head3 Watcher-Specific Functions and Data Members |
2374 | =head3 Watcher-Specific Functions and Data Members |
1839 | |
2375 | |
1840 | =over 4 |
2376 | =over 4 |
1841 | |
2377 | |
… | |
… | |
1898 | |
2434 | |
1899 | |
2435 | |
1900 | =head2 C<ev_stat> - did the file attributes just change? |
2436 | =head2 C<ev_stat> - did the file attributes just change? |
1901 | |
2437 | |
1902 | This watches a file system path for attribute changes. That is, it calls |
2438 | This watches a file system path for attribute changes. That is, it calls |
1903 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2439 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1904 | compared to the last time, invoking the callback if it did. |
2440 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2441 | it did. |
1905 | |
2442 | |
1906 | The path does not need to exist: changing from "path exists" to "path does |
2443 | The path does not need to exist: changing from "path exists" to "path does |
1907 | not exist" is a status change like any other. The condition "path does |
2444 | not exist" is a status change like any other. The condition "path does not |
1908 | not exist" is signified by the C<st_nlink> field being zero (which is |
2445 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1909 | otherwise always forced to be at least one) and all the other fields of |
2446 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1910 | the stat buffer having unspecified contents. |
2447 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2448 | contents. |
1911 | |
2449 | |
1912 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2450 | The path I<must not> end in a slash or contain special components such as |
|
|
2451 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1913 | relative and your working directory changes, the behaviour is undefined. |
2452 | your working directory changes, then the behaviour is undefined. |
1914 | |
2453 | |
1915 | Since there is no standard kernel interface to do this, the portable |
2454 | Since there is no portable change notification interface available, the |
1916 | implementation simply calls C<stat (2)> regularly on the path to see if |
2455 | portable implementation simply calls C<stat(2)> regularly on the path |
1917 | it changed somehow. You can specify a recommended polling interval for |
2456 | to see if it changed somehow. You can specify a recommended polling |
1918 | this case. If you specify a polling interval of C<0> (highly recommended!) |
2457 | interval for this case. If you specify a polling interval of C<0> (highly |
1919 | then a I<suitable, unspecified default> value will be used (which |
2458 | recommended!) then a I<suitable, unspecified default> value will be used |
1920 | you can expect to be around five seconds, although this might change |
2459 | (which you can expect to be around five seconds, although this might |
1921 | dynamically). Libev will also impose a minimum interval which is currently |
2460 | change dynamically). Libev will also impose a minimum interval which is |
1922 | around C<0.1>, but thats usually overkill. |
2461 | currently around C<0.1>, but that's usually overkill. |
1923 | |
2462 | |
1924 | This watcher type is not meant for massive numbers of stat watchers, |
2463 | This watcher type is not meant for massive numbers of stat watchers, |
1925 | as even with OS-supported change notifications, this can be |
2464 | as even with OS-supported change notifications, this can be |
1926 | resource-intensive. |
2465 | resource-intensive. |
1927 | |
2466 | |
1928 | At the time of this writing, the only OS-specific interface implemented |
2467 | At the time of this writing, the only OS-specific interface implemented |
1929 | is the Linux inotify interface (implementing kqueue support is left as |
2468 | is the Linux inotify interface (implementing kqueue support is left as an |
1930 | an exercise for the reader. Note, however, that the author sees no way |
2469 | exercise for the reader. Note, however, that the author sees no way of |
1931 | of implementing C<ev_stat> semantics with kqueue). |
2470 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1932 | |
2471 | |
1933 | =head3 ABI Issues (Largefile Support) |
2472 | =head3 ABI Issues (Largefile Support) |
1934 | |
2473 | |
1935 | Libev by default (unless the user overrides this) uses the default |
2474 | Libev by default (unless the user overrides this) uses the default |
1936 | compilation environment, which means that on systems with large file |
2475 | compilation environment, which means that on systems with large file |
1937 | support disabled by default, you get the 32 bit version of the stat |
2476 | support disabled by default, you get the 32 bit version of the stat |
1938 | structure. When using the library from programs that change the ABI to |
2477 | structure. When using the library from programs that change the ABI to |
1939 | use 64 bit file offsets the programs will fail. In that case you have to |
2478 | use 64 bit file offsets the programs will fail. In that case you have to |
1940 | compile libev with the same flags to get binary compatibility. This is |
2479 | compile libev with the same flags to get binary compatibility. This is |
1941 | obviously the case with any flags that change the ABI, but the problem is |
2480 | obviously the case with any flags that change the ABI, but the problem is |
1942 | most noticeably disabled with ev_stat and large file support. |
2481 | most noticeably displayed with ev_stat and large file support. |
1943 | |
2482 | |
1944 | The solution for this is to lobby your distribution maker to make large |
2483 | The solution for this is to lobby your distribution maker to make large |
1945 | file interfaces available by default (as e.g. FreeBSD does) and not |
2484 | file interfaces available by default (as e.g. FreeBSD does) and not |
1946 | optional. Libev cannot simply switch on large file support because it has |
2485 | optional. Libev cannot simply switch on large file support because it has |
1947 | to exchange stat structures with application programs compiled using the |
2486 | to exchange stat structures with application programs compiled using the |
1948 | default compilation environment. |
2487 | default compilation environment. |
1949 | |
2488 | |
1950 | =head3 Inotify and Kqueue |
2489 | =head3 Inotify and Kqueue |
1951 | |
2490 | |
1952 | When C<inotify (7)> support has been compiled into libev (generally |
2491 | When C<inotify (7)> support has been compiled into libev and present at |
1953 | only available with Linux 2.6.25 or above due to bugs in earlier |
2492 | runtime, it will be used to speed up change detection where possible. The |
1954 | implementations) and present at runtime, it will be used to speed up |
2493 | inotify descriptor will be created lazily when the first C<ev_stat> |
1955 | change detection where possible. The inotify descriptor will be created |
2494 | watcher is being started. |
1956 | lazily when the first C<ev_stat> watcher is being started. |
|
|
1957 | |
2495 | |
1958 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2496 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1959 | except that changes might be detected earlier, and in some cases, to avoid |
2497 | except that changes might be detected earlier, and in some cases, to avoid |
1960 | making regular C<stat> calls. Even in the presence of inotify support |
2498 | making regular C<stat> calls. Even in the presence of inotify support |
1961 | there are many cases where libev has to resort to regular C<stat> polling, |
2499 | there are many cases where libev has to resort to regular C<stat> polling, |
1962 | but as long as the path exists, libev usually gets away without polling. |
2500 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2501 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2502 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2503 | xfs are fully working) libev usually gets away without polling. |
1963 | |
2504 | |
1964 | There is no support for kqueue, as apparently it cannot be used to |
2505 | There is no support for kqueue, as apparently it cannot be used to |
1965 | implement this functionality, due to the requirement of having a file |
2506 | implement this functionality, due to the requirement of having a file |
1966 | descriptor open on the object at all times, and detecting renames, unlinks |
2507 | descriptor open on the object at all times, and detecting renames, unlinks |
1967 | etc. is difficult. |
2508 | etc. is difficult. |
1968 | |
2509 | |
|
|
2510 | =head3 C<stat ()> is a synchronous operation |
|
|
2511 | |
|
|
2512 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2513 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2514 | ()>, which is a synchronous operation. |
|
|
2515 | |
|
|
2516 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2517 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2518 | as the path data is usually in memory already (except when starting the |
|
|
2519 | watcher). |
|
|
2520 | |
|
|
2521 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2522 | time due to network issues, and even under good conditions, a stat call |
|
|
2523 | often takes multiple milliseconds. |
|
|
2524 | |
|
|
2525 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2526 | paths, although this is fully supported by libev. |
|
|
2527 | |
1969 | =head3 The special problem of stat time resolution |
2528 | =head3 The special problem of stat time resolution |
1970 | |
2529 | |
1971 | The C<stat ()> system call only supports full-second resolution portably, and |
2530 | The C<stat ()> system call only supports full-second resolution portably, |
1972 | even on systems where the resolution is higher, most file systems still |
2531 | and even on systems where the resolution is higher, most file systems |
1973 | only support whole seconds. |
2532 | still only support whole seconds. |
1974 | |
2533 | |
1975 | That means that, if the time is the only thing that changes, you can |
2534 | That means that, if the time is the only thing that changes, you can |
1976 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2535 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1977 | calls your callback, which does something. When there is another update |
2536 | calls your callback, which does something. When there is another update |
1978 | within the same second, C<ev_stat> will be unable to detect unless the |
2537 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
2121 | |
2680 | |
2122 | =head3 Watcher-Specific Functions and Data Members |
2681 | =head3 Watcher-Specific Functions and Data Members |
2123 | |
2682 | |
2124 | =over 4 |
2683 | =over 4 |
2125 | |
2684 | |
2126 | =item ev_idle_init (ev_signal *, callback) |
2685 | =item ev_idle_init (ev_idle *, callback) |
2127 | |
2686 | |
2128 | Initialises and configures the idle watcher - it has no parameters of any |
2687 | Initialises and configures the idle watcher - it has no parameters of any |
2129 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2688 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2130 | believe me. |
2689 | believe me. |
2131 | |
2690 | |
… | |
… | |
2144 | // no longer anything immediate to do. |
2703 | // no longer anything immediate to do. |
2145 | } |
2704 | } |
2146 | |
2705 | |
2147 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2706 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2148 | ev_idle_init (idle_watcher, idle_cb); |
2707 | ev_idle_init (idle_watcher, idle_cb); |
2149 | ev_idle_start (loop, idle_cb); |
2708 | ev_idle_start (loop, idle_watcher); |
2150 | |
2709 | |
2151 | |
2710 | |
2152 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2711 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2153 | |
2712 | |
2154 | Prepare and check watchers are usually (but not always) used in pairs: |
2713 | Prepare and check watchers are usually (but not always) used in pairs: |
2155 | prepare watchers get invoked before the process blocks and check watchers |
2714 | prepare watchers get invoked before the process blocks and check watchers |
2156 | afterwards. |
2715 | afterwards. |
2157 | |
2716 | |
2158 | You I<must not> call C<ev_loop> or similar functions that enter |
2717 | You I<must not> call C<ev_run> or similar functions that enter |
2159 | the current event loop from either C<ev_prepare> or C<ev_check> |
2718 | the current event loop from either C<ev_prepare> or C<ev_check> |
2160 | watchers. Other loops than the current one are fine, however. The |
2719 | watchers. Other loops than the current one are fine, however. The |
2161 | rationale behind this is that you do not need to check for recursion in |
2720 | rationale behind this is that you do not need to check for recursion in |
2162 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2721 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2163 | C<ev_check> so if you have one watcher of each kind they will always be |
2722 | C<ev_check> so if you have one watcher of each kind they will always be |
… | |
… | |
2247 | struct pollfd fds [nfd]; |
2806 | struct pollfd fds [nfd]; |
2248 | // actual code will need to loop here and realloc etc. |
2807 | // actual code will need to loop here and realloc etc. |
2249 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2808 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2250 | |
2809 | |
2251 | /* the callback is illegal, but won't be called as we stop during check */ |
2810 | /* the callback is illegal, but won't be called as we stop during check */ |
2252 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2811 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2253 | ev_timer_start (loop, &tw); |
2812 | ev_timer_start (loop, &tw); |
2254 | |
2813 | |
2255 | // create one ev_io per pollfd |
2814 | // create one ev_io per pollfd |
2256 | for (int i = 0; i < nfd; ++i) |
2815 | for (int i = 0; i < nfd; ++i) |
2257 | { |
2816 | { |
… | |
… | |
2331 | |
2890 | |
2332 | if (timeout >= 0) |
2891 | if (timeout >= 0) |
2333 | // create/start timer |
2892 | // create/start timer |
2334 | |
2893 | |
2335 | // poll |
2894 | // poll |
2336 | ev_loop (EV_A_ 0); |
2895 | ev_run (EV_A_ 0); |
2337 | |
2896 | |
2338 | // stop timer again |
2897 | // stop timer again |
2339 | if (timeout >= 0) |
2898 | if (timeout >= 0) |
2340 | ev_timer_stop (EV_A_ &to); |
2899 | ev_timer_stop (EV_A_ &to); |
2341 | |
2900 | |
… | |
… | |
2370 | some fds have to be watched and handled very quickly (with low latency), |
2929 | some fds have to be watched and handled very quickly (with low latency), |
2371 | and even priorities and idle watchers might have too much overhead. In |
2930 | and even priorities and idle watchers might have too much overhead. In |
2372 | this case you would put all the high priority stuff in one loop and all |
2931 | this case you would put all the high priority stuff in one loop and all |
2373 | the rest in a second one, and embed the second one in the first. |
2932 | the rest in a second one, and embed the second one in the first. |
2374 | |
2933 | |
2375 | As long as the watcher is active, the callback will be invoked every time |
2934 | As long as the watcher is active, the callback will be invoked every |
2376 | there might be events pending in the embedded loop. The callback must then |
2935 | time there might be events pending in the embedded loop. The callback |
2377 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2936 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2378 | their callbacks (you could also start an idle watcher to give the embedded |
2937 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2379 | loop strictly lower priority for example). You can also set the callback |
2938 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2380 | to C<0>, in which case the embed watcher will automatically execute the |
2939 | to give the embedded loop strictly lower priority for example). |
2381 | embedded loop sweep. |
|
|
2382 | |
2940 | |
2383 | As long as the watcher is started it will automatically handle events. The |
2941 | You can also set the callback to C<0>, in which case the embed watcher |
2384 | callback will be invoked whenever some events have been handled. You can |
2942 | will automatically execute the embedded loop sweep whenever necessary. |
2385 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2386 | interested in that. |
|
|
2387 | |
2943 | |
2388 | Also, there have not currently been made special provisions for forking: |
2944 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2389 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2945 | is active, i.e., the embedded loop will automatically be forked when the |
2390 | but you will also have to stop and restart any C<ev_embed> watchers |
2946 | embedding loop forks. In other cases, the user is responsible for calling |
2391 | yourself - but you can use a fork watcher to handle this automatically, |
2947 | C<ev_loop_fork> on the embedded loop. |
2392 | and future versions of libev might do just that. |
|
|
2393 | |
2948 | |
2394 | Unfortunately, not all backends are embeddable: only the ones returned by |
2949 | Unfortunately, not all backends are embeddable: only the ones returned by |
2395 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2950 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2396 | portable one. |
2951 | portable one. |
2397 | |
2952 | |
… | |
… | |
2423 | if you do not want that, you need to temporarily stop the embed watcher). |
2978 | if you do not want that, you need to temporarily stop the embed watcher). |
2424 | |
2979 | |
2425 | =item ev_embed_sweep (loop, ev_embed *) |
2980 | =item ev_embed_sweep (loop, ev_embed *) |
2426 | |
2981 | |
2427 | Make a single, non-blocking sweep over the embedded loop. This works |
2982 | Make a single, non-blocking sweep over the embedded loop. This works |
2428 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
2983 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2429 | appropriate way for embedded loops. |
2984 | appropriate way for embedded loops. |
2430 | |
2985 | |
2431 | =item struct ev_loop *other [read-only] |
2986 | =item struct ev_loop *other [read-only] |
2432 | |
2987 | |
2433 | The embedded event loop. |
2988 | The embedded event loop. |
… | |
… | |
2491 | event loop blocks next and before C<ev_check> watchers are being called, |
3046 | event loop blocks next and before C<ev_check> watchers are being called, |
2492 | and only in the child after the fork. If whoever good citizen calling |
3047 | and only in the child after the fork. If whoever good citizen calling |
2493 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3048 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2494 | handlers will be invoked, too, of course. |
3049 | handlers will be invoked, too, of course. |
2495 | |
3050 | |
|
|
3051 | =head3 The special problem of life after fork - how is it possible? |
|
|
3052 | |
|
|
3053 | Most uses of C<fork()> consist of forking, then some simple calls to set |
|
|
3054 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
3055 | sequence should be handled by libev without any problems. |
|
|
3056 | |
|
|
3057 | This changes when the application actually wants to do event handling |
|
|
3058 | in the child, or both parent in child, in effect "continuing" after the |
|
|
3059 | fork. |
|
|
3060 | |
|
|
3061 | The default mode of operation (for libev, with application help to detect |
|
|
3062 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3063 | when I<either> the parent I<or> the child process continues. |
|
|
3064 | |
|
|
3065 | When both processes want to continue using libev, then this is usually the |
|
|
3066 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3067 | supposed to continue with all watchers in place as before, while the other |
|
|
3068 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3069 | |
|
|
3070 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3071 | simply create a new event loop, which of course will be "empty", and |
|
|
3072 | use that for new watchers. This has the advantage of not touching more |
|
|
3073 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3074 | disadvantage of having to use multiple event loops (which do not support |
|
|
3075 | signal watchers). |
|
|
3076 | |
|
|
3077 | When this is not possible, or you want to use the default loop for |
|
|
3078 | other reasons, then in the process that wants to start "fresh", call |
|
|
3079 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
3080 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
3081 | have to be careful not to execute code that modifies those watchers. Note |
|
|
3082 | also that in that case, you have to re-register any signal watchers. |
|
|
3083 | |
2496 | =head3 Watcher-Specific Functions and Data Members |
3084 | =head3 Watcher-Specific Functions and Data Members |
2497 | |
3085 | |
2498 | =over 4 |
3086 | =over 4 |
2499 | |
3087 | |
2500 | =item ev_fork_init (ev_signal *, callback) |
3088 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2504 | believe me. |
3092 | believe me. |
2505 | |
3093 | |
2506 | =back |
3094 | =back |
2507 | |
3095 | |
2508 | |
3096 | |
2509 | =head2 C<ev_async> - how to wake up another event loop |
3097 | =head2 C<ev_async> - how to wake up an event loop |
2510 | |
3098 | |
2511 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3099 | In general, you cannot use an C<ev_run> from multiple threads or other |
2512 | asynchronous sources such as signal handlers (as opposed to multiple event |
3100 | asynchronous sources such as signal handlers (as opposed to multiple event |
2513 | loops - those are of course safe to use in different threads). |
3101 | loops - those are of course safe to use in different threads). |
2514 | |
3102 | |
2515 | Sometimes, however, you need to wake up another event loop you do not |
3103 | Sometimes, however, you need to wake up an event loop you do not control, |
2516 | control, for example because it belongs to another thread. This is what |
3104 | for example because it belongs to another thread. This is what C<ev_async> |
2517 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3105 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2518 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3106 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2519 | safe. |
|
|
2520 | |
3107 | |
2521 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3108 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2522 | too, are asynchronous in nature, and signals, too, will be compressed |
3109 | too, are asynchronous in nature, and signals, too, will be compressed |
2523 | (i.e. the number of callback invocations may be less than the number of |
3110 | (i.e. the number of callback invocations may be less than the number of |
2524 | C<ev_async_sent> calls). |
3111 | C<ev_async_sent> calls). |
… | |
… | |
2529 | =head3 Queueing |
3116 | =head3 Queueing |
2530 | |
3117 | |
2531 | C<ev_async> does not support queueing of data in any way. The reason |
3118 | C<ev_async> does not support queueing of data in any way. The reason |
2532 | is that the author does not know of a simple (or any) algorithm for a |
3119 | is that the author does not know of a simple (or any) algorithm for a |
2533 | multiple-writer-single-reader queue that works in all cases and doesn't |
3120 | multiple-writer-single-reader queue that works in all cases and doesn't |
2534 | need elaborate support such as pthreads. |
3121 | need elaborate support such as pthreads or unportable memory access |
|
|
3122 | semantics. |
2535 | |
3123 | |
2536 | That means that if you want to queue data, you have to provide your own |
3124 | That means that if you want to queue data, you have to provide your own |
2537 | queue. But at least I can tell you how to implement locking around your |
3125 | queue. But at least I can tell you how to implement locking around your |
2538 | queue: |
3126 | queue: |
2539 | |
3127 | |
… | |
… | |
2617 | =over 4 |
3205 | =over 4 |
2618 | |
3206 | |
2619 | =item ev_async_init (ev_async *, callback) |
3207 | =item ev_async_init (ev_async *, callback) |
2620 | |
3208 | |
2621 | Initialises and configures the async watcher - it has no parameters of any |
3209 | Initialises and configures the async watcher - it has no parameters of any |
2622 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3210 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2623 | trust me. |
3211 | trust me. |
2624 | |
3212 | |
2625 | =item ev_async_send (loop, ev_async *) |
3213 | =item ev_async_send (loop, ev_async *) |
2626 | |
3214 | |
2627 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3215 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2628 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3216 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2629 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3217 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2630 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3218 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2631 | section below on what exactly this means). |
3219 | section below on what exactly this means). |
2632 | |
3220 | |
|
|
3221 | Note that, as with other watchers in libev, multiple events might get |
|
|
3222 | compressed into a single callback invocation (another way to look at this |
|
|
3223 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3224 | reset when the event loop detects that). |
|
|
3225 | |
2633 | This call incurs the overhead of a system call only once per loop iteration, |
3226 | This call incurs the overhead of a system call only once per event loop |
2634 | so while the overhead might be noticeable, it doesn't apply to repeated |
3227 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2635 | calls to C<ev_async_send>. |
3228 | repeated calls to C<ev_async_send> for the same event loop. |
2636 | |
3229 | |
2637 | =item bool = ev_async_pending (ev_async *) |
3230 | =item bool = ev_async_pending (ev_async *) |
2638 | |
3231 | |
2639 | Returns a non-zero value when C<ev_async_send> has been called on the |
3232 | Returns a non-zero value when C<ev_async_send> has been called on the |
2640 | watcher but the event has not yet been processed (or even noted) by the |
3233 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2643 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3236 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2644 | the loop iterates next and checks for the watcher to have become active, |
3237 | the loop iterates next and checks for the watcher to have become active, |
2645 | it will reset the flag again. C<ev_async_pending> can be used to very |
3238 | it will reset the flag again. C<ev_async_pending> can be used to very |
2646 | quickly check whether invoking the loop might be a good idea. |
3239 | quickly check whether invoking the loop might be a good idea. |
2647 | |
3240 | |
2648 | Not that this does I<not> check whether the watcher itself is pending, only |
3241 | Not that this does I<not> check whether the watcher itself is pending, |
2649 | whether it has been requested to make this watcher pending. |
3242 | only whether it has been requested to make this watcher pending: there |
|
|
3243 | is a time window between the event loop checking and resetting the async |
|
|
3244 | notification, and the callback being invoked. |
2650 | |
3245 | |
2651 | =back |
3246 | =back |
2652 | |
3247 | |
2653 | |
3248 | |
2654 | =head1 OTHER FUNCTIONS |
3249 | =head1 OTHER FUNCTIONS |
… | |
… | |
2671 | |
3266 | |
2672 | If C<timeout> is less than 0, then no timeout watcher will be |
3267 | If C<timeout> is less than 0, then no timeout watcher will be |
2673 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3268 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2674 | repeat = 0) will be started. C<0> is a valid timeout. |
3269 | repeat = 0) will be started. C<0> is a valid timeout. |
2675 | |
3270 | |
2676 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3271 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2677 | passed an C<revents> set like normal event callbacks (a combination of |
3272 | passed an C<revents> set like normal event callbacks (a combination of |
2678 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3273 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2679 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3274 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
2680 | a timeout and an io event at the same time - you probably should give io |
3275 | a timeout and an io event at the same time - you probably should give io |
2681 | events precedence. |
3276 | events precedence. |
2682 | |
3277 | |
2683 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3278 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2684 | |
3279 | |
2685 | static void stdin_ready (int revents, void *arg) |
3280 | static void stdin_ready (int revents, void *arg) |
2686 | { |
3281 | { |
2687 | if (revents & EV_READ) |
3282 | if (revents & EV_READ) |
2688 | /* stdin might have data for us, joy! */; |
3283 | /* stdin might have data for us, joy! */; |
2689 | else if (revents & EV_TIMEOUT) |
3284 | else if (revents & EV_TIMER) |
2690 | /* doh, nothing entered */; |
3285 | /* doh, nothing entered */; |
2691 | } |
3286 | } |
2692 | |
3287 | |
2693 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3288 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2694 | |
3289 | |
2695 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
|
|
2696 | |
|
|
2697 | Feeds the given event set into the event loop, as if the specified event |
|
|
2698 | had happened for the specified watcher (which must be a pointer to an |
|
|
2699 | initialised but not necessarily started event watcher). |
|
|
2700 | |
|
|
2701 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
3290 | =item ev_feed_fd_event (loop, int fd, int revents) |
2702 | |
3291 | |
2703 | Feed an event on the given fd, as if a file descriptor backend detected |
3292 | Feed an event on the given fd, as if a file descriptor backend detected |
2704 | the given events it. |
3293 | the given events it. |
2705 | |
3294 | |
2706 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
3295 | =item ev_feed_signal_event (loop, int signum) |
2707 | |
3296 | |
2708 | Feed an event as if the given signal occurred (C<loop> must be the default |
3297 | Feed an event as if the given signal occurred (C<loop> must be the default |
2709 | loop!). |
3298 | loop!). |
2710 | |
3299 | |
2711 | =back |
3300 | =back |
… | |
… | |
2791 | |
3380 | |
2792 | =over 4 |
3381 | =over 4 |
2793 | |
3382 | |
2794 | =item ev::TYPE::TYPE () |
3383 | =item ev::TYPE::TYPE () |
2795 | |
3384 | |
2796 | =item ev::TYPE::TYPE (struct ev_loop *) |
3385 | =item ev::TYPE::TYPE (loop) |
2797 | |
3386 | |
2798 | =item ev::TYPE::~TYPE |
3387 | =item ev::TYPE::~TYPE |
2799 | |
3388 | |
2800 | The constructor (optionally) takes an event loop to associate the watcher |
3389 | The constructor (optionally) takes an event loop to associate the watcher |
2801 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3390 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2833 | |
3422 | |
2834 | myclass obj; |
3423 | myclass obj; |
2835 | ev::io iow; |
3424 | ev::io iow; |
2836 | iow.set <myclass, &myclass::io_cb> (&obj); |
3425 | iow.set <myclass, &myclass::io_cb> (&obj); |
2837 | |
3426 | |
|
|
3427 | =item w->set (object *) |
|
|
3428 | |
|
|
3429 | This is a variation of a method callback - leaving out the method to call |
|
|
3430 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3431 | functor objects without having to manually specify the C<operator ()> all |
|
|
3432 | the time. Incidentally, you can then also leave out the template argument |
|
|
3433 | list. |
|
|
3434 | |
|
|
3435 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3436 | int revents)>. |
|
|
3437 | |
|
|
3438 | See the method-C<set> above for more details. |
|
|
3439 | |
|
|
3440 | Example: use a functor object as callback. |
|
|
3441 | |
|
|
3442 | struct myfunctor |
|
|
3443 | { |
|
|
3444 | void operator() (ev::io &w, int revents) |
|
|
3445 | { |
|
|
3446 | ... |
|
|
3447 | } |
|
|
3448 | } |
|
|
3449 | |
|
|
3450 | myfunctor f; |
|
|
3451 | |
|
|
3452 | ev::io w; |
|
|
3453 | w.set (&f); |
|
|
3454 | |
2838 | =item w->set<function> (void *data = 0) |
3455 | =item w->set<function> (void *data = 0) |
2839 | |
3456 | |
2840 | Also sets a callback, but uses a static method or plain function as |
3457 | Also sets a callback, but uses a static method or plain function as |
2841 | callback. The optional C<data> argument will be stored in the watcher's |
3458 | callback. The optional C<data> argument will be stored in the watcher's |
2842 | C<data> member and is free for you to use. |
3459 | C<data> member and is free for you to use. |
… | |
… | |
2848 | Example: Use a plain function as callback. |
3465 | Example: Use a plain function as callback. |
2849 | |
3466 | |
2850 | static void io_cb (ev::io &w, int revents) { } |
3467 | static void io_cb (ev::io &w, int revents) { } |
2851 | iow.set <io_cb> (); |
3468 | iow.set <io_cb> (); |
2852 | |
3469 | |
2853 | =item w->set (struct ev_loop *) |
3470 | =item w->set (loop) |
2854 | |
3471 | |
2855 | Associates a different C<struct ev_loop> with this watcher. You can only |
3472 | Associates a different C<struct ev_loop> with this watcher. You can only |
2856 | do this when the watcher is inactive (and not pending either). |
3473 | do this when the watcher is inactive (and not pending either). |
2857 | |
3474 | |
2858 | =item w->set ([arguments]) |
3475 | =item w->set ([arguments]) |
2859 | |
3476 | |
2860 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
3477 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
2861 | called at least once. Unlike the C counterpart, an active watcher gets |
3478 | method or a suitable start method must be called at least once. Unlike the |
2862 | automatically stopped and restarted when reconfiguring it with this |
3479 | C counterpart, an active watcher gets automatically stopped and restarted |
2863 | method. |
3480 | when reconfiguring it with this method. |
2864 | |
3481 | |
2865 | =item w->start () |
3482 | =item w->start () |
2866 | |
3483 | |
2867 | Starts the watcher. Note that there is no C<loop> argument, as the |
3484 | Starts the watcher. Note that there is no C<loop> argument, as the |
2868 | constructor already stores the event loop. |
3485 | constructor already stores the event loop. |
2869 | |
3486 | |
|
|
3487 | =item w->start ([arguments]) |
|
|
3488 | |
|
|
3489 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
3490 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
3491 | the configure C<set> method of the watcher. |
|
|
3492 | |
2870 | =item w->stop () |
3493 | =item w->stop () |
2871 | |
3494 | |
2872 | Stops the watcher if it is active. Again, no C<loop> argument. |
3495 | Stops the watcher if it is active. Again, no C<loop> argument. |
2873 | |
3496 | |
2874 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
3497 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
2886 | |
3509 | |
2887 | =back |
3510 | =back |
2888 | |
3511 | |
2889 | =back |
3512 | =back |
2890 | |
3513 | |
2891 | Example: Define a class with an IO and idle watcher, start one of them in |
3514 | Example: Define a class with two I/O and idle watchers, start the I/O |
2892 | the constructor. |
3515 | watchers in the constructor. |
2893 | |
3516 | |
2894 | class myclass |
3517 | class myclass |
2895 | { |
3518 | { |
2896 | ev::io io ; void io_cb (ev::io &w, int revents); |
3519 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
3520 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
2897 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3521 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2898 | |
3522 | |
2899 | myclass (int fd) |
3523 | myclass (int fd) |
2900 | { |
3524 | { |
2901 | io .set <myclass, &myclass::io_cb > (this); |
3525 | io .set <myclass, &myclass::io_cb > (this); |
|
|
3526 | io2 .set <myclass, &myclass::io2_cb > (this); |
2902 | idle.set <myclass, &myclass::idle_cb> (this); |
3527 | idle.set <myclass, &myclass::idle_cb> (this); |
2903 | |
3528 | |
2904 | io.start (fd, ev::READ); |
3529 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
3530 | io.start (); // start it whenever convenient |
|
|
3531 | |
|
|
3532 | io2.start (fd, ev::READ); // set + start in one call |
2905 | } |
3533 | } |
2906 | }; |
3534 | }; |
2907 | |
3535 | |
2908 | |
3536 | |
2909 | =head1 OTHER LANGUAGE BINDINGS |
3537 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
2928 | L<http://software.schmorp.de/pkg/EV>. |
3556 | L<http://software.schmorp.de/pkg/EV>. |
2929 | |
3557 | |
2930 | =item Python |
3558 | =item Python |
2931 | |
3559 | |
2932 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3560 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2933 | seems to be quite complete and well-documented. Note, however, that the |
3561 | seems to be quite complete and well-documented. |
2934 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2935 | for everybody else, and therefore, should never be applied in an installed |
|
|
2936 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2937 | libev). |
|
|
2938 | |
3562 | |
2939 | =item Ruby |
3563 | =item Ruby |
2940 | |
3564 | |
2941 | Tony Arcieri has written a ruby extension that offers access to a subset |
3565 | Tony Arcieri has written a ruby extension that offers access to a subset |
2942 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3566 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2943 | more on top of it. It can be found via gem servers. Its homepage is at |
3567 | more on top of it. It can be found via gem servers. Its homepage is at |
2944 | L<http://rev.rubyforge.org/>. |
3568 | L<http://rev.rubyforge.org/>. |
2945 | |
3569 | |
|
|
3570 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3571 | makes rev work even on mingw. |
|
|
3572 | |
|
|
3573 | =item Haskell |
|
|
3574 | |
|
|
3575 | A haskell binding to libev is available at |
|
|
3576 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3577 | |
2946 | =item D |
3578 | =item D |
2947 | |
3579 | |
2948 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3580 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2949 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3581 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3582 | |
|
|
3583 | =item Ocaml |
|
|
3584 | |
|
|
3585 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3586 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3587 | |
|
|
3588 | =item Lua |
|
|
3589 | |
|
|
3590 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
3591 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
3592 | L<http://github.com/brimworks/lua-ev>. |
2950 | |
3593 | |
2951 | =back |
3594 | =back |
2952 | |
3595 | |
2953 | |
3596 | |
2954 | =head1 MACRO MAGIC |
3597 | =head1 MACRO MAGIC |
… | |
… | |
2968 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3611 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
2969 | C<EV_A_> is used when other arguments are following. Example: |
3612 | C<EV_A_> is used when other arguments are following. Example: |
2970 | |
3613 | |
2971 | ev_unref (EV_A); |
3614 | ev_unref (EV_A); |
2972 | ev_timer_add (EV_A_ watcher); |
3615 | ev_timer_add (EV_A_ watcher); |
2973 | ev_loop (EV_A_ 0); |
3616 | ev_run (EV_A_ 0); |
2974 | |
3617 | |
2975 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3618 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
2976 | which is often provided by the following macro. |
3619 | which is often provided by the following macro. |
2977 | |
3620 | |
2978 | =item C<EV_P>, C<EV_P_> |
3621 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
3018 | } |
3661 | } |
3019 | |
3662 | |
3020 | ev_check check; |
3663 | ev_check check; |
3021 | ev_check_init (&check, check_cb); |
3664 | ev_check_init (&check, check_cb); |
3022 | ev_check_start (EV_DEFAULT_ &check); |
3665 | ev_check_start (EV_DEFAULT_ &check); |
3023 | ev_loop (EV_DEFAULT_ 0); |
3666 | ev_run (EV_DEFAULT_ 0); |
3024 | |
3667 | |
3025 | =head1 EMBEDDING |
3668 | =head1 EMBEDDING |
3026 | |
3669 | |
3027 | Libev can (and often is) directly embedded into host |
3670 | Libev can (and often is) directly embedded into host |
3028 | applications. Examples of applications that embed it include the Deliantra |
3671 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
3055 | |
3698 | |
3056 | #define EV_STANDALONE 1 |
3699 | #define EV_STANDALONE 1 |
3057 | #include "ev.h" |
3700 | #include "ev.h" |
3058 | |
3701 | |
3059 | Both header files and implementation files can be compiled with a C++ |
3702 | Both header files and implementation files can be compiled with a C++ |
3060 | compiler (at least, thats a stated goal, and breakage will be treated |
3703 | compiler (at least, that's a stated goal, and breakage will be treated |
3061 | as a bug). |
3704 | as a bug). |
3062 | |
3705 | |
3063 | You need the following files in your source tree, or in a directory |
3706 | You need the following files in your source tree, or in a directory |
3064 | in your include path (e.g. in libev/ when using -Ilibev): |
3707 | in your include path (e.g. in libev/ when using -Ilibev): |
3065 | |
3708 | |
… | |
… | |
3108 | libev.m4 |
3751 | libev.m4 |
3109 | |
3752 | |
3110 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3753 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3111 | |
3754 | |
3112 | Libev can be configured via a variety of preprocessor symbols you have to |
3755 | Libev can be configured via a variety of preprocessor symbols you have to |
3113 | define before including any of its files. The default in the absence of |
3756 | define before including (or compiling) any of its files. The default in |
3114 | autoconf is documented for every option. |
3757 | the absence of autoconf is documented for every option. |
|
|
3758 | |
|
|
3759 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3760 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3761 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
3762 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3763 | users of libev and the libev code itself must be compiled with compatible |
|
|
3764 | settings. |
3115 | |
3765 | |
3116 | =over 4 |
3766 | =over 4 |
3117 | |
3767 | |
|
|
3768 | =item EV_COMPAT3 (h) |
|
|
3769 | |
|
|
3770 | Backwards compatibility is a major concern for libev. This is why this |
|
|
3771 | release of libev comes with wrappers for the functions and symbols that |
|
|
3772 | have been renamed between libev version 3 and 4. |
|
|
3773 | |
|
|
3774 | You can disable these wrappers (to test compatibility with future |
|
|
3775 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
3776 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
3777 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
3778 | typedef in that case. |
|
|
3779 | |
|
|
3780 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
3781 | and in some even more future version the compatibility code will be |
|
|
3782 | removed completely. |
|
|
3783 | |
3118 | =item EV_STANDALONE |
3784 | =item EV_STANDALONE (h) |
3119 | |
3785 | |
3120 | Must always be C<1> if you do not use autoconf configuration, which |
3786 | Must always be C<1> if you do not use autoconf configuration, which |
3121 | keeps libev from including F<config.h>, and it also defines dummy |
3787 | keeps libev from including F<config.h>, and it also defines dummy |
3122 | implementations for some libevent functions (such as logging, which is not |
3788 | implementations for some libevent functions (such as logging, which is not |
3123 | supported). It will also not define any of the structs usually found in |
3789 | supported). It will also not define any of the structs usually found in |
3124 | F<event.h> that are not directly supported by the libev core alone. |
3790 | F<event.h> that are not directly supported by the libev core alone. |
3125 | |
3791 | |
|
|
3792 | In standalone mode, libev will still try to automatically deduce the |
|
|
3793 | configuration, but has to be more conservative. |
|
|
3794 | |
3126 | =item EV_USE_MONOTONIC |
3795 | =item EV_USE_MONOTONIC |
3127 | |
3796 | |
3128 | If defined to be C<1>, libev will try to detect the availability of the |
3797 | If defined to be C<1>, libev will try to detect the availability of the |
3129 | monotonic clock option at both compile time and runtime. Otherwise no use |
3798 | monotonic clock option at both compile time and runtime. Otherwise no |
3130 | of the monotonic clock option will be attempted. If you enable this, you |
3799 | use of the monotonic clock option will be attempted. If you enable this, |
3131 | usually have to link against librt or something similar. Enabling it when |
3800 | you usually have to link against librt or something similar. Enabling it |
3132 | the functionality isn't available is safe, though, although you have |
3801 | when the functionality isn't available is safe, though, although you have |
3133 | to make sure you link against any libraries where the C<clock_gettime> |
3802 | to make sure you link against any libraries where the C<clock_gettime> |
3134 | function is hiding in (often F<-lrt>). |
3803 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3135 | |
3804 | |
3136 | =item EV_USE_REALTIME |
3805 | =item EV_USE_REALTIME |
3137 | |
3806 | |
3138 | If defined to be C<1>, libev will try to detect the availability of the |
3807 | If defined to be C<1>, libev will try to detect the availability of the |
3139 | real-time clock option at compile time (and assume its availability at |
3808 | real-time clock option at compile time (and assume its availability |
3140 | runtime if successful). Otherwise no use of the real-time clock option will |
3809 | at runtime if successful). Otherwise no use of the real-time clock |
3141 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3810 | option will be attempted. This effectively replaces C<gettimeofday> |
3142 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3811 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3143 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3812 | correctness. See the note about libraries in the description of |
|
|
3813 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3814 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3815 | |
|
|
3816 | =item EV_USE_CLOCK_SYSCALL |
|
|
3817 | |
|
|
3818 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3819 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3820 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3821 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3822 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3823 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3824 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3825 | higher, as it simplifies linking (no need for C<-lrt>). |
3144 | |
3826 | |
3145 | =item EV_USE_NANOSLEEP |
3827 | =item EV_USE_NANOSLEEP |
3146 | |
3828 | |
3147 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3829 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3148 | and will use it for delays. Otherwise it will use C<select ()>. |
3830 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3164 | |
3846 | |
3165 | =item EV_SELECT_USE_FD_SET |
3847 | =item EV_SELECT_USE_FD_SET |
3166 | |
3848 | |
3167 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3849 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3168 | structure. This is useful if libev doesn't compile due to a missing |
3850 | structure. This is useful if libev doesn't compile due to a missing |
3169 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3851 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3170 | exotic systems. This usually limits the range of file descriptors to some |
3852 | on exotic systems. This usually limits the range of file descriptors to |
3171 | low limit such as 1024 or might have other limitations (winsocket only |
3853 | some low limit such as 1024 or might have other limitations (winsocket |
3172 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3854 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3173 | influence the size of the C<fd_set> used. |
3855 | configures the maximum size of the C<fd_set>. |
3174 | |
3856 | |
3175 | =item EV_SELECT_IS_WINSOCKET |
3857 | =item EV_SELECT_IS_WINSOCKET |
3176 | |
3858 | |
3177 | When defined to C<1>, the select backend will assume that |
3859 | When defined to C<1>, the select backend will assume that |
3178 | select/socket/connect etc. don't understand file descriptors but |
3860 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3180 | be used is the winsock select). This means that it will call |
3862 | be used is the winsock select). This means that it will call |
3181 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3863 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3182 | it is assumed that all these functions actually work on fds, even |
3864 | it is assumed that all these functions actually work on fds, even |
3183 | on win32. Should not be defined on non-win32 platforms. |
3865 | on win32. Should not be defined on non-win32 platforms. |
3184 | |
3866 | |
3185 | =item EV_FD_TO_WIN32_HANDLE |
3867 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3186 | |
3868 | |
3187 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3869 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3188 | file descriptors to socket handles. When not defining this symbol (the |
3870 | file descriptors to socket handles. When not defining this symbol (the |
3189 | default), then libev will call C<_get_osfhandle>, which is usually |
3871 | default), then libev will call C<_get_osfhandle>, which is usually |
3190 | correct. In some cases, programs use their own file descriptor management, |
3872 | correct. In some cases, programs use their own file descriptor management, |
3191 | in which case they can provide this function to map fds to socket handles. |
3873 | in which case they can provide this function to map fds to socket handles. |
|
|
3874 | |
|
|
3875 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3876 | |
|
|
3877 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3878 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3879 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3880 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3881 | |
|
|
3882 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3883 | |
|
|
3884 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3885 | macro can be used to override the C<close> function, useful to unregister |
|
|
3886 | file descriptors again. Note that the replacement function has to close |
|
|
3887 | the underlying OS handle. |
3192 | |
3888 | |
3193 | =item EV_USE_POLL |
3889 | =item EV_USE_POLL |
3194 | |
3890 | |
3195 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3891 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3196 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3892 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3243 | as well as for signal and thread safety in C<ev_async> watchers. |
3939 | as well as for signal and thread safety in C<ev_async> watchers. |
3244 | |
3940 | |
3245 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3941 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3246 | (from F<signal.h>), which is usually good enough on most platforms. |
3942 | (from F<signal.h>), which is usually good enough on most platforms. |
3247 | |
3943 | |
3248 | =item EV_H |
3944 | =item EV_H (h) |
3249 | |
3945 | |
3250 | The name of the F<ev.h> header file used to include it. The default if |
3946 | The name of the F<ev.h> header file used to include it. The default if |
3251 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3947 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3252 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3948 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3253 | |
3949 | |
3254 | =item EV_CONFIG_H |
3950 | =item EV_CONFIG_H (h) |
3255 | |
3951 | |
3256 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3952 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3257 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3953 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3258 | C<EV_H>, above. |
3954 | C<EV_H>, above. |
3259 | |
3955 | |
3260 | =item EV_EVENT_H |
3956 | =item EV_EVENT_H (h) |
3261 | |
3957 | |
3262 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3958 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3263 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3959 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3264 | |
3960 | |
3265 | =item EV_PROTOTYPES |
3961 | =item EV_PROTOTYPES (h) |
3266 | |
3962 | |
3267 | If defined to be C<0>, then F<ev.h> will not define any function |
3963 | If defined to be C<0>, then F<ev.h> will not define any function |
3268 | prototypes, but still define all the structs and other symbols. This is |
3964 | prototypes, but still define all the structs and other symbols. This is |
3269 | occasionally useful if you want to provide your own wrapper functions |
3965 | occasionally useful if you want to provide your own wrapper functions |
3270 | around libev functions. |
3966 | around libev functions. |
… | |
… | |
3292 | fine. |
3988 | fine. |
3293 | |
3989 | |
3294 | If your embedding application does not need any priorities, defining these |
3990 | If your embedding application does not need any priorities, defining these |
3295 | both to C<0> will save some memory and CPU. |
3991 | both to C<0> will save some memory and CPU. |
3296 | |
3992 | |
3297 | =item EV_PERIODIC_ENABLE |
3993 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
3994 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
3995 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3298 | |
3996 | |
3299 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3997 | If undefined or defined to be C<1> (and the platform supports it), then |
3300 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3998 | the respective watcher type is supported. If defined to be C<0>, then it |
3301 | code. |
3999 | is not. Disabling watcher types mainly saves code size. |
3302 | |
4000 | |
3303 | =item EV_IDLE_ENABLE |
4001 | =item EV_FEATURES |
3304 | |
|
|
3305 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3306 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3307 | code. |
|
|
3308 | |
|
|
3309 | =item EV_EMBED_ENABLE |
|
|
3310 | |
|
|
3311 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3312 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3313 | watcher types, which therefore must not be disabled. |
|
|
3314 | |
|
|
3315 | =item EV_STAT_ENABLE |
|
|
3316 | |
|
|
3317 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3318 | defined to be C<0>, then they are not. |
|
|
3319 | |
|
|
3320 | =item EV_FORK_ENABLE |
|
|
3321 | |
|
|
3322 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3323 | defined to be C<0>, then they are not. |
|
|
3324 | |
|
|
3325 | =item EV_ASYNC_ENABLE |
|
|
3326 | |
|
|
3327 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3328 | defined to be C<0>, then they are not. |
|
|
3329 | |
|
|
3330 | =item EV_MINIMAL |
|
|
3331 | |
4002 | |
3332 | If you need to shave off some kilobytes of code at the expense of some |
4003 | If you need to shave off some kilobytes of code at the expense of some |
3333 | speed, define this symbol to C<1>. Currently this is used to override some |
4004 | speed (but with the full API), you can define this symbol to request |
3334 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
4005 | certain subsets of functionality. The default is to enable all features |
3335 | much smaller 2-heap for timer management over the default 4-heap. |
4006 | that can be enabled on the platform. |
|
|
4007 | |
|
|
4008 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
4009 | with some broad features you want) and then selectively re-enable |
|
|
4010 | additional parts you want, for example if you want everything minimal, |
|
|
4011 | but multiple event loop support, async and child watchers and the poll |
|
|
4012 | backend, use this: |
|
|
4013 | |
|
|
4014 | #define EV_FEATURES 0 |
|
|
4015 | #define EV_MULTIPLICITY 1 |
|
|
4016 | #define EV_USE_POLL 1 |
|
|
4017 | #define EV_CHILD_ENABLE 1 |
|
|
4018 | #define EV_ASYNC_ENABLE 1 |
|
|
4019 | |
|
|
4020 | The actual value is a bitset, it can be a combination of the following |
|
|
4021 | values: |
|
|
4022 | |
|
|
4023 | =over 4 |
|
|
4024 | |
|
|
4025 | =item C<1> - faster/larger code |
|
|
4026 | |
|
|
4027 | Use larger code to speed up some operations. |
|
|
4028 | |
|
|
4029 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4030 | code size by roughly 30% on amd64). |
|
|
4031 | |
|
|
4032 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
4033 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
4034 | assertions. |
|
|
4035 | |
|
|
4036 | =item C<2> - faster/larger data structures |
|
|
4037 | |
|
|
4038 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
4039 | hash table sizes and so on. This will usually further increase code size |
|
|
4040 | and can additionally have an effect on the size of data structures at |
|
|
4041 | runtime. |
|
|
4042 | |
|
|
4043 | =item C<4> - full API configuration |
|
|
4044 | |
|
|
4045 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
4046 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
4047 | |
|
|
4048 | =item C<8> - full API |
|
|
4049 | |
|
|
4050 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
4051 | details on which parts of the API are still available without this |
|
|
4052 | feature, and do not complain if this subset changes over time. |
|
|
4053 | |
|
|
4054 | =item C<16> - enable all optional watcher types |
|
|
4055 | |
|
|
4056 | Enables all optional watcher types. If you want to selectively enable |
|
|
4057 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4058 | embed, async, child...) you can enable them manually by defining |
|
|
4059 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
4060 | |
|
|
4061 | =item C<32> - enable all backends |
|
|
4062 | |
|
|
4063 | This enables all backends - without this feature, you need to enable at |
|
|
4064 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
4065 | |
|
|
4066 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4067 | |
|
|
4068 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4069 | default. |
|
|
4070 | |
|
|
4071 | =back |
|
|
4072 | |
|
|
4073 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4074 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4075 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4076 | watchers, timers and monotonic clock support. |
|
|
4077 | |
|
|
4078 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4079 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4080 | your program might be left out as well - a binary starting a timer and an |
|
|
4081 | I/O watcher then might come out at only 5Kb. |
|
|
4082 | |
|
|
4083 | =item EV_AVOID_STDIO |
|
|
4084 | |
|
|
4085 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4086 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4087 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4088 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4089 | big. |
|
|
4090 | |
|
|
4091 | Note that error messages might become less precise when this option is |
|
|
4092 | enabled. |
|
|
4093 | |
|
|
4094 | =item EV_NSIG |
|
|
4095 | |
|
|
4096 | The highest supported signal number, +1 (or, the number of |
|
|
4097 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4098 | automatically, but sometimes this fails, in which case it can be |
|
|
4099 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4100 | good for about any system in existence) can save some memory, as libev |
|
|
4101 | statically allocates some 12-24 bytes per signal number. |
3336 | |
4102 | |
3337 | =item EV_PID_HASHSIZE |
4103 | =item EV_PID_HASHSIZE |
3338 | |
4104 | |
3339 | C<ev_child> watchers use a small hash table to distribute workload by |
4105 | C<ev_child> watchers use a small hash table to distribute workload by |
3340 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4106 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3341 | than enough. If you need to manage thousands of children you might want to |
4107 | usually more than enough. If you need to manage thousands of children you |
3342 | increase this value (I<must> be a power of two). |
4108 | might want to increase this value (I<must> be a power of two). |
3343 | |
4109 | |
3344 | =item EV_INOTIFY_HASHSIZE |
4110 | =item EV_INOTIFY_HASHSIZE |
3345 | |
4111 | |
3346 | C<ev_stat> watchers use a small hash table to distribute workload by |
4112 | C<ev_stat> watchers use a small hash table to distribute workload by |
3347 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4113 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3348 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4114 | disabled), usually more than enough. If you need to manage thousands of |
3349 | watchers you might want to increase this value (I<must> be a power of |
4115 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3350 | two). |
4116 | power of two). |
3351 | |
4117 | |
3352 | =item EV_USE_4HEAP |
4118 | =item EV_USE_4HEAP |
3353 | |
4119 | |
3354 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4120 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3355 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4121 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3356 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4122 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3357 | faster performance with many (thousands) of watchers. |
4123 | faster performance with many (thousands) of watchers. |
3358 | |
4124 | |
3359 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4125 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3360 | (disabled). |
4126 | will be C<0>. |
3361 | |
4127 | |
3362 | =item EV_HEAP_CACHE_AT |
4128 | =item EV_HEAP_CACHE_AT |
3363 | |
4129 | |
3364 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4130 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3365 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4131 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3366 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4132 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3367 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4133 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3368 | but avoids random read accesses on heap changes. This improves performance |
4134 | but avoids random read accesses on heap changes. This improves performance |
3369 | noticeably with many (hundreds) of watchers. |
4135 | noticeably with many (hundreds) of watchers. |
3370 | |
4136 | |
3371 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4137 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3372 | (disabled). |
4138 | will be C<0>. |
3373 | |
4139 | |
3374 | =item EV_VERIFY |
4140 | =item EV_VERIFY |
3375 | |
4141 | |
3376 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4142 | Controls how much internal verification (see C<ev_verify ()>) will |
3377 | be done: If set to C<0>, no internal verification code will be compiled |
4143 | be done: If set to C<0>, no internal verification code will be compiled |
3378 | in. If set to C<1>, then verification code will be compiled in, but not |
4144 | in. If set to C<1>, then verification code will be compiled in, but not |
3379 | called. If set to C<2>, then the internal verification code will be |
4145 | called. If set to C<2>, then the internal verification code will be |
3380 | called once per loop, which can slow down libev. If set to C<3>, then the |
4146 | called once per loop, which can slow down libev. If set to C<3>, then the |
3381 | verification code will be called very frequently, which will slow down |
4147 | verification code will be called very frequently, which will slow down |
3382 | libev considerably. |
4148 | libev considerably. |
3383 | |
4149 | |
3384 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4150 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3385 | C<0>. |
4151 | will be C<0>. |
3386 | |
4152 | |
3387 | =item EV_COMMON |
4153 | =item EV_COMMON |
3388 | |
4154 | |
3389 | By default, all watchers have a C<void *data> member. By redefining |
4155 | By default, all watchers have a C<void *data> member. By redefining |
3390 | this macro to a something else you can include more and other types of |
4156 | this macro to something else you can include more and other types of |
3391 | members. You have to define it each time you include one of the files, |
4157 | members. You have to define it each time you include one of the files, |
3392 | though, and it must be identical each time. |
4158 | though, and it must be identical each time. |
3393 | |
4159 | |
3394 | For example, the perl EV module uses something like this: |
4160 | For example, the perl EV module uses something like this: |
3395 | |
4161 | |
… | |
… | |
3448 | file. |
4214 | file. |
3449 | |
4215 | |
3450 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4216 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3451 | that everybody includes and which overrides some configure choices: |
4217 | that everybody includes and which overrides some configure choices: |
3452 | |
4218 | |
3453 | #define EV_MINIMAL 1 |
4219 | #define EV_FEATURES 8 |
3454 | #define EV_USE_POLL 0 |
4220 | #define EV_USE_SELECT 1 |
3455 | #define EV_MULTIPLICITY 0 |
|
|
3456 | #define EV_PERIODIC_ENABLE 0 |
4221 | #define EV_PREPARE_ENABLE 1 |
|
|
4222 | #define EV_IDLE_ENABLE 1 |
3457 | #define EV_STAT_ENABLE 0 |
4223 | #define EV_SIGNAL_ENABLE 1 |
3458 | #define EV_FORK_ENABLE 0 |
4224 | #define EV_CHILD_ENABLE 1 |
|
|
4225 | #define EV_USE_STDEXCEPT 0 |
3459 | #define EV_CONFIG_H <config.h> |
4226 | #define EV_CONFIG_H <config.h> |
3460 | #define EV_MINPRI 0 |
|
|
3461 | #define EV_MAXPRI 0 |
|
|
3462 | |
4227 | |
3463 | #include "ev++.h" |
4228 | #include "ev++.h" |
3464 | |
4229 | |
3465 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4230 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3466 | |
4231 | |
… | |
… | |
3526 | default loop and triggering an C<ev_async> watcher from the default loop |
4291 | default loop and triggering an C<ev_async> watcher from the default loop |
3527 | watcher callback into the event loop interested in the signal. |
4292 | watcher callback into the event loop interested in the signal. |
3528 | |
4293 | |
3529 | =back |
4294 | =back |
3530 | |
4295 | |
|
|
4296 | =head4 THREAD LOCKING EXAMPLE |
|
|
4297 | |
|
|
4298 | Here is a fictitious example of how to run an event loop in a different |
|
|
4299 | thread than where callbacks are being invoked and watchers are |
|
|
4300 | created/added/removed. |
|
|
4301 | |
|
|
4302 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4303 | which uses exactly this technique (which is suited for many high-level |
|
|
4304 | languages). |
|
|
4305 | |
|
|
4306 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4307 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4308 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4309 | |
|
|
4310 | First, you need to associate some data with the event loop: |
|
|
4311 | |
|
|
4312 | typedef struct { |
|
|
4313 | mutex_t lock; /* global loop lock */ |
|
|
4314 | ev_async async_w; |
|
|
4315 | thread_t tid; |
|
|
4316 | cond_t invoke_cv; |
|
|
4317 | } userdata; |
|
|
4318 | |
|
|
4319 | void prepare_loop (EV_P) |
|
|
4320 | { |
|
|
4321 | // for simplicity, we use a static userdata struct. |
|
|
4322 | static userdata u; |
|
|
4323 | |
|
|
4324 | ev_async_init (&u->async_w, async_cb); |
|
|
4325 | ev_async_start (EV_A_ &u->async_w); |
|
|
4326 | |
|
|
4327 | pthread_mutex_init (&u->lock, 0); |
|
|
4328 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4329 | |
|
|
4330 | // now associate this with the loop |
|
|
4331 | ev_set_userdata (EV_A_ u); |
|
|
4332 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4333 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4334 | |
|
|
4335 | // then create the thread running ev_loop |
|
|
4336 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4337 | } |
|
|
4338 | |
|
|
4339 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4340 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4341 | that might have been added: |
|
|
4342 | |
|
|
4343 | static void |
|
|
4344 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4345 | { |
|
|
4346 | // just used for the side effects |
|
|
4347 | } |
|
|
4348 | |
|
|
4349 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4350 | protecting the loop data, respectively. |
|
|
4351 | |
|
|
4352 | static void |
|
|
4353 | l_release (EV_P) |
|
|
4354 | { |
|
|
4355 | userdata *u = ev_userdata (EV_A); |
|
|
4356 | pthread_mutex_unlock (&u->lock); |
|
|
4357 | } |
|
|
4358 | |
|
|
4359 | static void |
|
|
4360 | l_acquire (EV_P) |
|
|
4361 | { |
|
|
4362 | userdata *u = ev_userdata (EV_A); |
|
|
4363 | pthread_mutex_lock (&u->lock); |
|
|
4364 | } |
|
|
4365 | |
|
|
4366 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4367 | into C<ev_run>: |
|
|
4368 | |
|
|
4369 | void * |
|
|
4370 | l_run (void *thr_arg) |
|
|
4371 | { |
|
|
4372 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4373 | |
|
|
4374 | l_acquire (EV_A); |
|
|
4375 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4376 | ev_run (EV_A_ 0); |
|
|
4377 | l_release (EV_A); |
|
|
4378 | |
|
|
4379 | return 0; |
|
|
4380 | } |
|
|
4381 | |
|
|
4382 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4383 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4384 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4385 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4386 | and b) skipping inter-thread-communication when there are no pending |
|
|
4387 | watchers is very beneficial): |
|
|
4388 | |
|
|
4389 | static void |
|
|
4390 | l_invoke (EV_P) |
|
|
4391 | { |
|
|
4392 | userdata *u = ev_userdata (EV_A); |
|
|
4393 | |
|
|
4394 | while (ev_pending_count (EV_A)) |
|
|
4395 | { |
|
|
4396 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4397 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4398 | } |
|
|
4399 | } |
|
|
4400 | |
|
|
4401 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4402 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4403 | thread to continue: |
|
|
4404 | |
|
|
4405 | static void |
|
|
4406 | real_invoke_pending (EV_P) |
|
|
4407 | { |
|
|
4408 | userdata *u = ev_userdata (EV_A); |
|
|
4409 | |
|
|
4410 | pthread_mutex_lock (&u->lock); |
|
|
4411 | ev_invoke_pending (EV_A); |
|
|
4412 | pthread_cond_signal (&u->invoke_cv); |
|
|
4413 | pthread_mutex_unlock (&u->lock); |
|
|
4414 | } |
|
|
4415 | |
|
|
4416 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4417 | event loop, you will now have to lock: |
|
|
4418 | |
|
|
4419 | ev_timer timeout_watcher; |
|
|
4420 | userdata *u = ev_userdata (EV_A); |
|
|
4421 | |
|
|
4422 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4423 | |
|
|
4424 | pthread_mutex_lock (&u->lock); |
|
|
4425 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4426 | ev_async_send (EV_A_ &u->async_w); |
|
|
4427 | pthread_mutex_unlock (&u->lock); |
|
|
4428 | |
|
|
4429 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4430 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4431 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4432 | watchers in the next event loop iteration. |
|
|
4433 | |
3531 | =head3 COROUTINES |
4434 | =head3 COROUTINES |
3532 | |
4435 | |
3533 | Libev is very accommodating to coroutines ("cooperative threads"): |
4436 | Libev is very accommodating to coroutines ("cooperative threads"): |
3534 | libev fully supports nesting calls to its functions from different |
4437 | libev fully supports nesting calls to its functions from different |
3535 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4438 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
3536 | different coroutines, and switch freely between both coroutines running the |
4439 | different coroutines, and switch freely between both coroutines running |
3537 | loop, as long as you don't confuse yourself). The only exception is that |
4440 | the loop, as long as you don't confuse yourself). The only exception is |
3538 | you must not do this from C<ev_periodic> reschedule callbacks. |
4441 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3539 | |
4442 | |
3540 | Care has been taken to ensure that libev does not keep local state inside |
4443 | Care has been taken to ensure that libev does not keep local state inside |
3541 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4444 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
3542 | they do not clal any callbacks. |
4445 | they do not call any callbacks. |
3543 | |
4446 | |
3544 | =head2 COMPILER WARNINGS |
4447 | =head2 COMPILER WARNINGS |
3545 | |
4448 | |
3546 | Depending on your compiler and compiler settings, you might get no or a |
4449 | Depending on your compiler and compiler settings, you might get no or a |
3547 | lot of warnings when compiling libev code. Some people are apparently |
4450 | lot of warnings when compiling libev code. Some people are apparently |
… | |
… | |
3557 | maintainable. |
4460 | maintainable. |
3558 | |
4461 | |
3559 | And of course, some compiler warnings are just plain stupid, or simply |
4462 | And of course, some compiler warnings are just plain stupid, or simply |
3560 | wrong (because they don't actually warn about the condition their message |
4463 | wrong (because they don't actually warn about the condition their message |
3561 | seems to warn about). For example, certain older gcc versions had some |
4464 | seems to warn about). For example, certain older gcc versions had some |
3562 | warnings that resulted an extreme number of false positives. These have |
4465 | warnings that resulted in an extreme number of false positives. These have |
3563 | been fixed, but some people still insist on making code warn-free with |
4466 | been fixed, but some people still insist on making code warn-free with |
3564 | such buggy versions. |
4467 | such buggy versions. |
3565 | |
4468 | |
3566 | While libev is written to generate as few warnings as possible, |
4469 | While libev is written to generate as few warnings as possible, |
3567 | "warn-free" code is not a goal, and it is recommended not to build libev |
4470 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
3581 | ==2274== definitely lost: 0 bytes in 0 blocks. |
4484 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3582 | ==2274== possibly lost: 0 bytes in 0 blocks. |
4485 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3583 | ==2274== still reachable: 256 bytes in 1 blocks. |
4486 | ==2274== still reachable: 256 bytes in 1 blocks. |
3584 | |
4487 | |
3585 | Then there is no memory leak, just as memory accounted to global variables |
4488 | Then there is no memory leak, just as memory accounted to global variables |
3586 | is not a memleak - the memory is still being refernced, and didn't leak. |
4489 | is not a memleak - the memory is still being referenced, and didn't leak. |
3587 | |
4490 | |
3588 | Similarly, under some circumstances, valgrind might report kernel bugs |
4491 | Similarly, under some circumstances, valgrind might report kernel bugs |
3589 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
4492 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3590 | although an acceptable workaround has been found here), or it might be |
4493 | although an acceptable workaround has been found here), or it might be |
3591 | confused. |
4494 | confused. |
… | |
… | |
3603 | I suggest using suppression lists. |
4506 | I suggest using suppression lists. |
3604 | |
4507 | |
3605 | |
4508 | |
3606 | =head1 PORTABILITY NOTES |
4509 | =head1 PORTABILITY NOTES |
3607 | |
4510 | |
|
|
4511 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
4512 | |
|
|
4513 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4514 | interfaces but I<disables> them by default. |
|
|
4515 | |
|
|
4516 | That means that libev compiled in the default environment doesn't support |
|
|
4517 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
4518 | |
|
|
4519 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4520 | by enabling the large file API, which makes them incompatible with the |
|
|
4521 | standard libev compiled for their system. |
|
|
4522 | |
|
|
4523 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4524 | suddenly make it incompatible to the default compile time environment, |
|
|
4525 | i.e. all programs not using special compile switches. |
|
|
4526 | |
|
|
4527 | =head2 OS/X AND DARWIN BUGS |
|
|
4528 | |
|
|
4529 | The whole thing is a bug if you ask me - basically any system interface |
|
|
4530 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
4531 | OpenGL drivers. |
|
|
4532 | |
|
|
4533 | =head3 C<kqueue> is buggy |
|
|
4534 | |
|
|
4535 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4536 | only sockets, many support pipes. |
|
|
4537 | |
|
|
4538 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
4539 | rotten platform, but of course you can still ask for it when creating a |
|
|
4540 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
4541 | probably going to work well. |
|
|
4542 | |
|
|
4543 | =head3 C<poll> is buggy |
|
|
4544 | |
|
|
4545 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4546 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4547 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4548 | |
|
|
4549 | Libev tries to work around this by not using C<poll> by default on |
|
|
4550 | this rotten platform, but of course you can still ask for it when creating |
|
|
4551 | a loop. |
|
|
4552 | |
|
|
4553 | =head3 C<select> is buggy |
|
|
4554 | |
|
|
4555 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4556 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4557 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
4558 | you use more. |
|
|
4559 | |
|
|
4560 | There is an undocumented "workaround" for this - defining |
|
|
4561 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4562 | work on OS/X. |
|
|
4563 | |
|
|
4564 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4565 | |
|
|
4566 | =head3 C<errno> reentrancy |
|
|
4567 | |
|
|
4568 | The default compile environment on Solaris is unfortunately so |
|
|
4569 | thread-unsafe that you can't even use components/libraries compiled |
|
|
4570 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
4571 | defined by default. A valid, if stupid, implementation choice. |
|
|
4572 | |
|
|
4573 | If you want to use libev in threaded environments you have to make sure |
|
|
4574 | it's compiled with C<_REENTRANT> defined. |
|
|
4575 | |
|
|
4576 | =head3 Event port backend |
|
|
4577 | |
|
|
4578 | The scalable event interface for Solaris is called "event |
|
|
4579 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
4580 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
4581 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
4582 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
4583 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
4584 | great. |
|
|
4585 | |
|
|
4586 | If you can't get it to work, you can try running the program by setting |
|
|
4587 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
4588 | C<select> backends. |
|
|
4589 | |
|
|
4590 | =head2 AIX POLL BUG |
|
|
4591 | |
|
|
4592 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4593 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4594 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4595 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
4596 | |
3608 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4597 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4598 | |
|
|
4599 | =head3 General issues |
3609 | |
4600 | |
3610 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4601 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3611 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4602 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3612 | model. Libev still offers limited functionality on this platform in |
4603 | model. Libev still offers limited functionality on this platform in |
3613 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4604 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3614 | descriptors. This only applies when using Win32 natively, not when using |
4605 | descriptors. This only applies when using Win32 natively, not when using |
3615 | e.g. cygwin. |
4606 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4607 | as every compielr comes with a slightly differently broken/incompatible |
|
|
4608 | environment. |
3616 | |
4609 | |
3617 | Lifting these limitations would basically require the full |
4610 | Lifting these limitations would basically require the full |
3618 | re-implementation of the I/O system. If you are into these kinds of |
4611 | re-implementation of the I/O system. If you are into this kind of thing, |
3619 | things, then note that glib does exactly that for you in a very portable |
4612 | then note that glib does exactly that for you in a very portable way (note |
3620 | way (note also that glib is the slowest event library known to man). |
4613 | also that glib is the slowest event library known to man). |
3621 | |
4614 | |
3622 | There is no supported compilation method available on windows except |
4615 | There is no supported compilation method available on windows except |
3623 | embedding it into other applications. |
4616 | embedding it into other applications. |
|
|
4617 | |
|
|
4618 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4619 | tries its best, but under most conditions, signals will simply not work. |
3624 | |
4620 | |
3625 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4621 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3626 | accept large writes: instead of resulting in a partial write, windows will |
4622 | accept large writes: instead of resulting in a partial write, windows will |
3627 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4623 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3628 | so make sure you only write small amounts into your sockets (less than a |
4624 | so make sure you only write small amounts into your sockets (less than a |
… | |
… | |
3633 | the abysmal performance of winsockets, using a large number of sockets |
4629 | the abysmal performance of winsockets, using a large number of sockets |
3634 | is not recommended (and not reasonable). If your program needs to use |
4630 | is not recommended (and not reasonable). If your program needs to use |
3635 | more than a hundred or so sockets, then likely it needs to use a totally |
4631 | more than a hundred or so sockets, then likely it needs to use a totally |
3636 | different implementation for windows, as libev offers the POSIX readiness |
4632 | different implementation for windows, as libev offers the POSIX readiness |
3637 | notification model, which cannot be implemented efficiently on windows |
4633 | notification model, which cannot be implemented efficiently on windows |
3638 | (Microsoft monopoly games). |
4634 | (due to Microsoft monopoly games). |
3639 | |
4635 | |
3640 | A typical way to use libev under windows is to embed it (see the embedding |
4636 | A typical way to use libev under windows is to embed it (see the embedding |
3641 | section for details) and use the following F<evwrap.h> header file instead |
4637 | section for details) and use the following F<evwrap.h> header file instead |
3642 | of F<ev.h>: |
4638 | of F<ev.h>: |
3643 | |
4639 | |
… | |
… | |
3650 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4646 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3651 | |
4647 | |
3652 | #include "evwrap.h" |
4648 | #include "evwrap.h" |
3653 | #include "ev.c" |
4649 | #include "ev.c" |
3654 | |
4650 | |
3655 | =over 4 |
|
|
3656 | |
|
|
3657 | =item The winsocket select function |
4651 | =head3 The winsocket C<select> function |
3658 | |
4652 | |
3659 | The winsocket C<select> function doesn't follow POSIX in that it |
4653 | The winsocket C<select> function doesn't follow POSIX in that it |
3660 | requires socket I<handles> and not socket I<file descriptors> (it is |
4654 | requires socket I<handles> and not socket I<file descriptors> (it is |
3661 | also extremely buggy). This makes select very inefficient, and also |
4655 | also extremely buggy). This makes select very inefficient, and also |
3662 | requires a mapping from file descriptors to socket handles (the Microsoft |
4656 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
3671 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4665 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3672 | |
4666 | |
3673 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4667 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3674 | complexity in the O(n²) range when using win32. |
4668 | complexity in the O(n²) range when using win32. |
3675 | |
4669 | |
3676 | =item Limited number of file descriptors |
4670 | =head3 Limited number of file descriptors |
3677 | |
4671 | |
3678 | Windows has numerous arbitrary (and low) limits on things. |
4672 | Windows has numerous arbitrary (and low) limits on things. |
3679 | |
4673 | |
3680 | Early versions of winsocket's select only supported waiting for a maximum |
4674 | Early versions of winsocket's select only supported waiting for a maximum |
3681 | of C<64> handles (probably owning to the fact that all windows kernels |
4675 | of C<64> handles (probably owning to the fact that all windows kernels |
3682 | can only wait for C<64> things at the same time internally; Microsoft |
4676 | can only wait for C<64> things at the same time internally; Microsoft |
3683 | recommends spawning a chain of threads and wait for 63 handles and the |
4677 | recommends spawning a chain of threads and wait for 63 handles and the |
3684 | previous thread in each. Great). |
4678 | previous thread in each. Sounds great!). |
3685 | |
4679 | |
3686 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4680 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3687 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4681 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3688 | call (which might be in libev or elsewhere, for example, perl does its own |
4682 | call (which might be in libev or elsewhere, for example, perl and many |
3689 | select emulation on windows). |
4683 | other interpreters do their own select emulation on windows). |
3690 | |
4684 | |
3691 | Another limit is the number of file descriptors in the Microsoft runtime |
4685 | Another limit is the number of file descriptors in the Microsoft runtime |
3692 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4686 | libraries, which by default is C<64> (there must be a hidden I<64> |
3693 | or something like this inside Microsoft). You can increase this by calling |
4687 | fetish or something like this inside Microsoft). You can increase this |
3694 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4688 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3695 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4689 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3696 | libraries. |
|
|
3697 | |
|
|
3698 | This might get you to about C<512> or C<2048> sockets (depending on |
4690 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3699 | windows version and/or the phase of the moon). To get more, you need to |
4691 | (depending on windows version and/or the phase of the moon). To get more, |
3700 | wrap all I/O functions and provide your own fd management, but the cost of |
4692 | you need to wrap all I/O functions and provide your own fd management, but |
3701 | calling select (O(n²)) will likely make this unworkable. |
4693 | the cost of calling select (O(n²)) will likely make this unworkable. |
3702 | |
|
|
3703 | =back |
|
|
3704 | |
4694 | |
3705 | =head2 PORTABILITY REQUIREMENTS |
4695 | =head2 PORTABILITY REQUIREMENTS |
3706 | |
4696 | |
3707 | In addition to a working ISO-C implementation and of course the |
4697 | In addition to a working ISO-C implementation and of course the |
3708 | backend-specific APIs, libev relies on a few additional extensions: |
4698 | backend-specific APIs, libev relies on a few additional extensions: |
… | |
… | |
3747 | watchers. |
4737 | watchers. |
3748 | |
4738 | |
3749 | =item C<double> must hold a time value in seconds with enough accuracy |
4739 | =item C<double> must hold a time value in seconds with enough accuracy |
3750 | |
4740 | |
3751 | The type C<double> is used to represent timestamps. It is required to |
4741 | The type C<double> is used to represent timestamps. It is required to |
3752 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4742 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
3753 | enough for at least into the year 4000. This requirement is fulfilled by |
4743 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
4744 | (the design goal for libev). This requirement is overfulfilled by |
3754 | implementations implementing IEEE 754 (basically all existing ones). |
4745 | implementations using IEEE 754, which is basically all existing ones. With |
|
|
4746 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
3755 | |
4747 | |
3756 | =back |
4748 | =back |
3757 | |
4749 | |
3758 | If you know of other additional requirements drop me a note. |
4750 | If you know of other additional requirements drop me a note. |
3759 | |
4751 | |
… | |
… | |
3827 | involves iterating over all running async watchers or all signal numbers. |
4819 | involves iterating over all running async watchers or all signal numbers. |
3828 | |
4820 | |
3829 | =back |
4821 | =back |
3830 | |
4822 | |
3831 | |
4823 | |
|
|
4824 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
4825 | |
|
|
4826 | The major version 4 introduced some minor incompatible changes to the API. |
|
|
4827 | |
|
|
4828 | At the moment, the C<ev.h> header file tries to implement superficial |
|
|
4829 | compatibility, so most programs should still compile. Those might be |
|
|
4830 | removed in later versions of libev, so better update early than late. |
|
|
4831 | |
|
|
4832 | =over 4 |
|
|
4833 | |
|
|
4834 | =item function/symbol renames |
|
|
4835 | |
|
|
4836 | A number of functions and symbols have been renamed: |
|
|
4837 | |
|
|
4838 | ev_loop => ev_run |
|
|
4839 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
4840 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
4841 | |
|
|
4842 | ev_unloop => ev_break |
|
|
4843 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
4844 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
4845 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
4846 | |
|
|
4847 | EV_TIMEOUT => EV_TIMER |
|
|
4848 | |
|
|
4849 | ev_loop_count => ev_iteration |
|
|
4850 | ev_loop_depth => ev_depth |
|
|
4851 | ev_loop_verify => ev_verify |
|
|
4852 | |
|
|
4853 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
4854 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
4855 | associated constants have been renamed to not collide with the C<struct |
|
|
4856 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
4857 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
4858 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
4859 | typedef. |
|
|
4860 | |
|
|
4861 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4862 | |
|
|
4863 | The backward compatibility mechanism can be controlled by |
|
|
4864 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4865 | section. |
|
|
4866 | |
|
|
4867 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
4868 | |
|
|
4869 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
4870 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
4871 | and work, but the library code will of course be larger. |
|
|
4872 | |
|
|
4873 | =back |
|
|
4874 | |
|
|
4875 | |
|
|
4876 | =head1 GLOSSARY |
|
|
4877 | |
|
|
4878 | =over 4 |
|
|
4879 | |
|
|
4880 | =item active |
|
|
4881 | |
|
|
4882 | A watcher is active as long as it has been started and not yet stopped. |
|
|
4883 | See L<WATCHER STATES> for details. |
|
|
4884 | |
|
|
4885 | =item application |
|
|
4886 | |
|
|
4887 | In this document, an application is whatever is using libev. |
|
|
4888 | |
|
|
4889 | =item backend |
|
|
4890 | |
|
|
4891 | The part of the code dealing with the operating system interfaces. |
|
|
4892 | |
|
|
4893 | =item callback |
|
|
4894 | |
|
|
4895 | The address of a function that is called when some event has been |
|
|
4896 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4897 | received the event, and the actual event bitset. |
|
|
4898 | |
|
|
4899 | =item callback/watcher invocation |
|
|
4900 | |
|
|
4901 | The act of calling the callback associated with a watcher. |
|
|
4902 | |
|
|
4903 | =item event |
|
|
4904 | |
|
|
4905 | A change of state of some external event, such as data now being available |
|
|
4906 | for reading on a file descriptor, time having passed or simply not having |
|
|
4907 | any other events happening anymore. |
|
|
4908 | |
|
|
4909 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4910 | C<EV_TIMER>). |
|
|
4911 | |
|
|
4912 | =item event library |
|
|
4913 | |
|
|
4914 | A software package implementing an event model and loop. |
|
|
4915 | |
|
|
4916 | =item event loop |
|
|
4917 | |
|
|
4918 | An entity that handles and processes external events and converts them |
|
|
4919 | into callback invocations. |
|
|
4920 | |
|
|
4921 | =item event model |
|
|
4922 | |
|
|
4923 | The model used to describe how an event loop handles and processes |
|
|
4924 | watchers and events. |
|
|
4925 | |
|
|
4926 | =item pending |
|
|
4927 | |
|
|
4928 | A watcher is pending as soon as the corresponding event has been |
|
|
4929 | detected. See L<WATCHER STATES> for details. |
|
|
4930 | |
|
|
4931 | =item real time |
|
|
4932 | |
|
|
4933 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4934 | |
|
|
4935 | =item wall-clock time |
|
|
4936 | |
|
|
4937 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4938 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4939 | clock. |
|
|
4940 | |
|
|
4941 | =item watcher |
|
|
4942 | |
|
|
4943 | A data structure that describes interest in certain events. Watchers need |
|
|
4944 | to be started (attached to an event loop) before they can receive events. |
|
|
4945 | |
|
|
4946 | =back |
|
|
4947 | |
3832 | =head1 AUTHOR |
4948 | =head1 AUTHOR |
3833 | |
4949 | |
3834 | Marc Lehmann <libev@schmorp.de>. |
4950 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3835 | |
4951 | |