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1 | =encoding utf-8 |
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2 | |
1 | =head1 NAME |
3 | =head1 NAME |
2 | |
4 | |
3 | libev - a high performance full-featured event loop written in C |
5 | libev - a high performance full-featured event loop written in C |
4 | |
6 | |
5 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
6 | |
8 | |
7 | #include <ev.h> |
9 | #include <ev.h> |
8 | |
10 | |
9 | =head2 EXAMPLE PROGRAM |
11 | =head2 EXAMPLE PROGRAM |
10 | |
12 | |
11 | // a single header file is required |
13 | // a single header file is required |
12 | #include <ev.h> |
14 | #include <ev.h> |
13 | |
15 | |
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16 | #include <stdio.h> // for puts |
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17 | |
14 | // every watcher type has its own typedef'd struct |
18 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
19 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
20 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
21 | ev_timer timeout_watcher; |
18 | |
22 | |
19 | // all watcher callbacks have a similar signature |
23 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
24 | // this callback is called when data is readable on stdin |
21 | static void |
25 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
26 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
27 | { |
24 | puts ("stdin ready"); |
28 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
29 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
30 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
31 | ev_io_stop (EV_A_ w); |
28 | |
32 | |
29 | // this causes all nested ev_loop's to stop iterating |
33 | // this causes all nested ev_run's to stop iterating |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
34 | ev_break (EV_A_ EVBREAK_ALL); |
31 | } |
35 | } |
32 | |
36 | |
33 | // another callback, this time for a time-out |
37 | // another callback, this time for a time-out |
34 | static void |
38 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
39 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
40 | { |
37 | puts ("timeout"); |
41 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
42 | // this causes the innermost ev_run to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
43 | ev_break (EV_A_ EVBREAK_ONE); |
40 | } |
44 | } |
41 | |
45 | |
42 | int |
46 | int |
43 | main (void) |
47 | main (void) |
44 | { |
48 | { |
45 | // use the default event loop unless you have special needs |
49 | // use the default event loop unless you have special needs |
46 | struct ev_loop *loop = ev_default_loop (0); |
50 | struct ev_loop *loop = EV_DEFAULT; |
47 | |
51 | |
48 | // initialise an io watcher, then start it |
52 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
53 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
54 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
55 | ev_io_start (loop, &stdin_watcher); |
52 | |
56 | |
53 | // initialise a timer watcher, then start it |
57 | // initialise a timer watcher, then start it |
54 | // simple non-repeating 5.5 second timeout |
58 | // simple non-repeating 5.5 second timeout |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
59 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
56 | ev_timer_start (loop, &timeout_watcher); |
60 | ev_timer_start (loop, &timeout_watcher); |
57 | |
61 | |
58 | // now wait for events to arrive |
62 | // now wait for events to arrive |
59 | ev_loop (loop, 0); |
63 | ev_run (loop, 0); |
60 | |
64 | |
61 | // unloop was called, so exit |
65 | // break was called, so exit |
62 | return 0; |
66 | return 0; |
63 | } |
67 | } |
64 | |
68 | |
65 | =head1 DESCRIPTION |
69 | =head1 ABOUT THIS DOCUMENT |
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70 | |
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71 | This document documents the libev software package. |
66 | |
72 | |
67 | The newest version of this document is also available as an html-formatted |
73 | 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 |
74 | 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>. |
75 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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76 | |
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77 | While this document tries to be as complete as possible in documenting |
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78 | libev, its usage and the rationale behind its design, it is not a tutorial |
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79 | on event-based programming, nor will it introduce event-based programming |
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80 | with libev. |
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81 | |
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82 | Familiarity with event based programming techniques in general is assumed |
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83 | throughout this document. |
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84 | |
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85 | =head1 WHAT TO READ WHEN IN A HURRY |
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86 | |
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87 | This manual tries to be very detailed, but unfortunately, this also makes |
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88 | it very long. If you just want to know the basics of libev, I suggest |
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89 | reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and |
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90 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
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91 | C<ev_timer> sections in L</WATCHER TYPES>. |
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92 | |
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93 | =head1 ABOUT LIBEV |
70 | |
94 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
95 | 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 |
96 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
97 | these event sources and provide your program with events. |
74 | |
98 | |
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81 | details of the event, and then hand it over to libev by I<starting> the |
105 | details of the event, and then hand it over to libev by I<starting> the |
82 | watcher. |
106 | watcher. |
83 | |
107 | |
84 | =head2 FEATURES |
108 | =head2 FEATURES |
85 | |
109 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
110 | Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll> |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
111 | interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
112 | mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify> |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
113 | interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
114 | 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 |
115 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
116 | (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 |
117 | 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 |
118 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
119 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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120 | limited support for fork events (C<ev_fork>). |
96 | |
121 | |
97 | It also is quite fast (see this |
122 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
123 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
124 | for example). |
100 | |
125 | |
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108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
133 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
109 | this argument. |
134 | this argument. |
110 | |
135 | |
111 | =head2 TIME REPRESENTATION |
136 | =head2 TIME REPRESENTATION |
112 | |
137 | |
113 | Libev represents time as a single floating point number, representing the |
138 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
139 | 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 |
140 | 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 |
141 | 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 |
142 | too. It usually aliases to the C<double> type in C. When you need to do |
118 | it, you should treat it as some floatingpoint value. Unlike the name |
143 | any calculations on it, you should treat it as some floating point value. |
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144 | |
119 | component C<stamp> might indicate, it is also used for time differences |
145 | Unlike the name component C<stamp> might indicate, it is also used for |
120 | throughout libev. |
146 | time differences (e.g. delays) throughout libev. |
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147 | |
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148 | =head1 ERROR HANDLING |
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149 | |
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150 | Libev knows three classes of errors: operating system errors, usage errors |
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151 | and internal errors (bugs). |
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152 | |
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153 | When libev catches an operating system error it cannot handle (for example |
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154 | a system call indicating a condition libev cannot fix), it calls the callback |
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155 | set via C<ev_set_syserr_cb>, which is supposed to fix the problem or |
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156 | abort. The default is to print a diagnostic message and to call C<abort |
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157 | ()>. |
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158 | |
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159 | When libev detects a usage error such as a negative timer interval, then |
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160 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
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161 | so C<NDEBUG> will disable this checking): these are programming errors in |
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162 | the libev caller and need to be fixed there. |
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163 | |
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164 | Libev also has a few internal error-checking C<assert>ions, and also has |
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165 | extensive consistency checking code. These do not trigger under normal |
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166 | circumstances, as they indicate either a bug in libev or worse. |
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167 | |
121 | |
168 | |
122 | =head1 GLOBAL FUNCTIONS |
169 | =head1 GLOBAL FUNCTIONS |
123 | |
170 | |
124 | These functions can be called anytime, even before initialising the |
171 | These functions can be called anytime, even before initialising the |
125 | library in any way. |
172 | library in any way. |
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128 | |
175 | |
129 | =item ev_tstamp ev_time () |
176 | =item ev_tstamp ev_time () |
130 | |
177 | |
131 | Returns the current time as libev would use it. Please note that the |
178 | Returns the current time as libev would use it. Please note that the |
132 | C<ev_now> function is usually faster and also often returns the timestamp |
179 | C<ev_now> function is usually faster and also often returns the timestamp |
133 | you actually want to know. |
180 | you actually want to know. Also interesting is the combination of |
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181 | C<ev_now_update> and C<ev_now>. |
134 | |
182 | |
135 | =item ev_sleep (ev_tstamp interval) |
183 | =item ev_sleep (ev_tstamp interval) |
136 | |
184 | |
137 | Sleep for the given interval: The current thread will be blocked until |
185 | Sleep for the given interval: The current thread will be blocked |
138 | either it is interrupted or the given time interval has passed. Basically |
186 | until either it is interrupted or the given time interval has |
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187 | passed (approximately - it might return a bit earlier even if not |
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188 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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189 | |
139 | this is a subsecond-resolution C<sleep ()>. |
190 | Basically this is a sub-second-resolution C<sleep ()>. |
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191 | |
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192 | The range of the C<interval> is limited - libev only guarantees to work |
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193 | with sleep times of up to one day (C<< interval <= 86400 >>). |
140 | |
194 | |
141 | =item int ev_version_major () |
195 | =item int ev_version_major () |
142 | |
196 | |
143 | =item int ev_version_minor () |
197 | =item int ev_version_minor () |
144 | |
198 | |
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155 | as this indicates an incompatible change. Minor versions are usually |
209 | as this indicates an incompatible change. Minor versions are usually |
156 | compatible to older versions, so a larger minor version alone is usually |
210 | compatible to older versions, so a larger minor version alone is usually |
157 | not a problem. |
211 | not a problem. |
158 | |
212 | |
159 | Example: Make sure we haven't accidentally been linked against the wrong |
213 | Example: Make sure we haven't accidentally been linked against the wrong |
160 | version. |
214 | version (note, however, that this will not detect other ABI mismatches, |
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215 | such as LFS or reentrancy). |
161 | |
216 | |
162 | assert (("libev version mismatch", |
217 | assert (("libev version mismatch", |
163 | ev_version_major () == EV_VERSION_MAJOR |
218 | ev_version_major () == EV_VERSION_MAJOR |
164 | && ev_version_minor () >= EV_VERSION_MINOR)); |
219 | && ev_version_minor () >= EV_VERSION_MINOR)); |
165 | |
220 | |
166 | =item unsigned int ev_supported_backends () |
221 | =item unsigned int ev_supported_backends () |
167 | |
222 | |
168 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
223 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
169 | value) compiled into this binary of libev (independent of their |
224 | value) compiled into this binary of libev (independent of their |
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171 | a description of the set values. |
226 | a description of the set values. |
172 | |
227 | |
173 | Example: make sure we have the epoll method, because yeah this is cool and |
228 | Example: make sure we have the epoll method, because yeah this is cool and |
174 | a must have and can we have a torrent of it please!!!11 |
229 | a must have and can we have a torrent of it please!!!11 |
175 | |
230 | |
176 | assert (("sorry, no epoll, no sex", |
231 | assert (("sorry, no epoll, no sex", |
177 | ev_supported_backends () & EVBACKEND_EPOLL)); |
232 | ev_supported_backends () & EVBACKEND_EPOLL)); |
178 | |
233 | |
179 | =item unsigned int ev_recommended_backends () |
234 | =item unsigned int ev_recommended_backends () |
180 | |
235 | |
181 | Return the set of all backends compiled into this binary of libev and also |
236 | Return the set of all backends compiled into this binary of libev and |
182 | recommended for this platform. This set is often smaller than the one |
237 | also recommended for this platform, meaning it will work for most file |
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238 | descriptor types. This set is often smaller than the one returned by |
183 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
239 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
184 | most BSDs and will not be autodetected unless you explicitly request it |
240 | and will not be auto-detected unless you explicitly request it (assuming |
185 | (assuming you know what you are doing). This is the set of backends that |
241 | you know what you are doing). This is the set of backends that libev will |
186 | libev will probe for if you specify no backends explicitly. |
242 | probe for if you specify no backends explicitly. |
187 | |
243 | |
188 | =item unsigned int ev_embeddable_backends () |
244 | =item unsigned int ev_embeddable_backends () |
189 | |
245 | |
190 | Returns the set of backends that are embeddable in other event loops. This |
246 | Returns the set of backends that are embeddable in other event loops. This |
191 | is the theoretical, all-platform, value. To find which backends |
247 | value is platform-specific but can include backends not available on the |
192 | might be supported on the current system, you would need to look at |
248 | current system. To find which embeddable backends might be supported on |
193 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
249 | the current system, you would need to look at C<ev_embeddable_backends () |
194 | recommended ones. |
250 | & ev_supported_backends ()>, likewise for recommended ones. |
195 | |
251 | |
196 | See the description of C<ev_embed> watchers for more info. |
252 | See the description of C<ev_embed> watchers for more info. |
197 | |
253 | |
198 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
254 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
199 | |
255 | |
200 | Sets the allocation function to use (the prototype is similar - the |
256 | Sets the allocation function to use (the prototype is similar - the |
201 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
257 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
202 | used to allocate and free memory (no surprises here). If it returns zero |
258 | used to allocate and free memory (no surprises here). If it returns zero |
203 | when memory needs to be allocated (C<size != 0>), the library might abort |
259 | when memory needs to be allocated (C<size != 0>), the library might abort |
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209 | |
265 | |
210 | You could override this function in high-availability programs to, say, |
266 | You could override this function in high-availability programs to, say, |
211 | free some memory if it cannot allocate memory, to use a special allocator, |
267 | free some memory if it cannot allocate memory, to use a special allocator, |
212 | or even to sleep a while and retry until some memory is available. |
268 | or even to sleep a while and retry until some memory is available. |
213 | |
269 | |
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270 | Example: The following is the C<realloc> function that libev itself uses |
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271 | which should work with C<realloc> and C<free> functions of all kinds and |
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272 | is probably a good basis for your own implementation. |
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273 | |
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274 | static void * |
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275 | ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT |
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276 | { |
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277 | if (size) |
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278 | return realloc (ptr, size); |
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279 | |
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280 | free (ptr); |
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281 | return 0; |
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282 | } |
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283 | |
214 | Example: Replace the libev allocator with one that waits a bit and then |
284 | Example: Replace the libev allocator with one that waits a bit and then |
215 | retries (example requires a standards-compliant C<realloc>). |
285 | retries. |
216 | |
286 | |
217 | static void * |
287 | static void * |
218 | persistent_realloc (void *ptr, size_t size) |
288 | persistent_realloc (void *ptr, size_t size) |
219 | { |
289 | { |
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290 | if (!size) |
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291 | { |
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292 | free (ptr); |
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293 | return 0; |
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294 | } |
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295 | |
220 | for (;;) |
296 | for (;;) |
221 | { |
297 | { |
222 | void *newptr = realloc (ptr, size); |
298 | void *newptr = realloc (ptr, size); |
223 | |
299 | |
224 | if (newptr) |
300 | if (newptr) |
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229 | } |
305 | } |
230 | |
306 | |
231 | ... |
307 | ... |
232 | ev_set_allocator (persistent_realloc); |
308 | ev_set_allocator (persistent_realloc); |
233 | |
309 | |
234 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
310 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
235 | |
311 | |
236 | Set the callback function to call on a retryable syscall error (such |
312 | Set the callback function to call on a retryable system call error (such |
237 | as failed select, poll, epoll_wait). The message is a printable string |
313 | as failed select, poll, epoll_wait). The message is a printable string |
238 | indicating the system call or subsystem causing the problem. If this |
314 | indicating the system call or subsystem causing the problem. If this |
239 | callback is set, then libev will expect it to remedy the sitution, no |
315 | callback is set, then libev will expect it to remedy the situation, no |
240 | matter what, when it returns. That is, libev will generally retry the |
316 | matter what, when it returns. That is, libev will generally retry the |
241 | requested operation, or, if the condition doesn't go away, do bad stuff |
317 | requested operation, or, if the condition doesn't go away, do bad stuff |
242 | (such as abort). |
318 | (such as abort). |
243 | |
319 | |
244 | Example: This is basically the same thing that libev does internally, too. |
320 | Example: This is basically the same thing that libev does internally, too. |
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251 | } |
327 | } |
252 | |
328 | |
253 | ... |
329 | ... |
254 | ev_set_syserr_cb (fatal_error); |
330 | ev_set_syserr_cb (fatal_error); |
255 | |
331 | |
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332 | =item ev_feed_signal (int signum) |
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333 | |
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334 | This function can be used to "simulate" a signal receive. It is completely |
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335 | safe to call this function at any time, from any context, including signal |
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336 | handlers or random threads. |
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337 | |
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338 | Its main use is to customise signal handling in your process, especially |
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339 | in the presence of threads. For example, you could block signals |
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340 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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341 | creating any loops), and in one thread, use C<sigwait> or any other |
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342 | mechanism to wait for signals, then "deliver" them to libev by calling |
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343 | C<ev_feed_signal>. |
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344 | |
256 | =back |
345 | =back |
257 | |
346 | |
258 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
347 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
259 | |
348 | |
260 | An event loop is described by a C<struct ev_loop *>. The library knows two |
349 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
261 | types of such loops, the I<default> loop, which supports signals and child |
350 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
262 | events, and dynamically created loops which do not. |
351 | libev 3 had an C<ev_loop> function colliding with the struct name). |
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352 | |
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353 | The library knows two types of such loops, the I<default> loop, which |
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354 | supports child process events, and dynamically created event loops which |
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355 | do not. |
263 | |
356 | |
264 | =over 4 |
357 | =over 4 |
265 | |
358 | |
266 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
359 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
267 | |
360 | |
268 | This will initialise the default event loop if it hasn't been initialised |
361 | This returns the "default" event loop object, which is what you should |
269 | yet and return it. If the default loop could not be initialised, returns |
362 | normally use when you just need "the event loop". Event loop objects and |
270 | false. If it already was initialised it simply returns it (and ignores the |
363 | the C<flags> parameter are described in more detail in the entry for |
271 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
364 | C<ev_loop_new>. |
|
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365 | |
|
|
366 | If the default loop is already initialised then this function simply |
|
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367 | returns it (and ignores the flags. If that is troubling you, check |
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368 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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369 | flags, which should almost always be C<0>, unless the caller is also the |
|
|
370 | one calling C<ev_run> or otherwise qualifies as "the main program". |
272 | |
371 | |
273 | If you don't know what event loop to use, use the one returned from this |
372 | If you don't know what event loop to use, use the one returned from this |
274 | function. |
373 | function (or via the C<EV_DEFAULT> macro). |
275 | |
374 | |
276 | Note that this function is I<not> thread-safe, so if you want to use it |
375 | Note that this function is I<not> thread-safe, so if you want to use it |
277 | from multiple threads, you have to lock (note also that this is unlikely, |
376 | from multiple threads, you have to employ some kind of mutex (note also |
278 | as loops cannot bes hared easily between threads anyway). |
377 | that this case is unlikely, as loops cannot be shared easily between |
|
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378 | threads anyway). |
279 | |
379 | |
280 | The default loop is the only loop that can handle C<ev_signal> and |
380 | The default loop is the only loop that can handle C<ev_child> watchers, |
281 | C<ev_child> watchers, and to do this, it always registers a handler |
381 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
282 | for C<SIGCHLD>. If this is a problem for your app you can either |
382 | a problem for your application you can either create a dynamic loop with |
283 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
383 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
284 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
384 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
285 | C<ev_default_init>. |
385 | |
|
|
386 | Example: This is the most typical usage. |
|
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387 | |
|
|
388 | if (!ev_default_loop (0)) |
|
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389 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
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390 | |
|
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391 | Example: Restrict libev to the select and poll backends, and do not allow |
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392 | environment settings to be taken into account: |
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393 | |
|
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394 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
395 | |
|
|
396 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
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397 | |
|
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398 | This will create and initialise a new event loop object. If the loop |
|
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399 | could not be initialised, returns false. |
|
|
400 | |
|
|
401 | This function is thread-safe, and one common way to use libev with |
|
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402 | threads is indeed to create one loop per thread, and using the default |
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403 | loop in the "main" or "initial" thread. |
286 | |
404 | |
287 | The flags argument can be used to specify special behaviour or specific |
405 | The flags argument can be used to specify special behaviour or specific |
288 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
406 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
289 | |
407 | |
290 | The following flags are supported: |
408 | The following flags are supported: |
… | |
… | |
296 | The default flags value. Use this if you have no clue (it's the right |
414 | The default flags value. Use this if you have no clue (it's the right |
297 | thing, believe me). |
415 | thing, believe me). |
298 | |
416 | |
299 | =item C<EVFLAG_NOENV> |
417 | =item C<EVFLAG_NOENV> |
300 | |
418 | |
301 | If this flag bit is ored into the flag value (or the program runs setuid |
419 | If this flag bit is or'ed into the flag value (or the program runs setuid |
302 | or setgid) then libev will I<not> look at the environment variable |
420 | or setgid) then libev will I<not> look at the environment variable |
303 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
421 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
304 | override the flags completely if it is found in the environment. This is |
422 | override the flags completely if it is found in the environment. This is |
305 | useful to try out specific backends to test their performance, or to work |
423 | useful to try out specific backends to test their performance, to work |
306 | around bugs. |
424 | around bugs, or to make libev threadsafe (accessing environment variables |
|
|
425 | cannot be done in a threadsafe way, but usually it works if no other |
|
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426 | thread modifies them). |
307 | |
427 | |
308 | =item C<EVFLAG_FORKCHECK> |
428 | =item C<EVFLAG_FORKCHECK> |
309 | |
429 | |
310 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
430 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
311 | a fork, you can also make libev check for a fork in each iteration by |
431 | make libev check for a fork in each iteration by enabling this flag. |
312 | enabling this flag. |
|
|
313 | |
432 | |
314 | This works by calling C<getpid ()> on every iteration of the loop, |
433 | This works by calling C<getpid ()> on every iteration of the loop, |
315 | and thus this might slow down your event loop if you do a lot of loop |
434 | and thus this might slow down your event loop if you do a lot of loop |
316 | iterations and little real work, but is usually not noticeable (on my |
435 | iterations and little real work, but is usually not noticeable (on my |
317 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
436 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
318 | without a syscall and thus I<very> fast, but my GNU/Linux system also has |
437 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
319 | C<pthread_atfork> which is even faster). |
438 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
|
|
439 | versions 2.25 apparently removed the C<getpid> optimisation again). |
320 | |
440 | |
321 | The big advantage of this flag is that you can forget about fork (and |
441 | The big advantage of this flag is that you can forget about fork (and |
322 | forget about forgetting to tell libev about forking) when you use this |
442 | forget about forgetting to tell libev about forking, although you still |
323 | flag. |
443 | have to ignore C<SIGPIPE>) when you use this flag. |
324 | |
444 | |
325 | This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS> |
445 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
326 | environment variable. |
446 | environment variable. |
|
|
447 | |
|
|
448 | =item C<EVFLAG_NOINOTIFY> |
|
|
449 | |
|
|
450 | When this flag is specified, then libev will not attempt to use the |
|
|
451 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
|
|
452 | testing, this flag can be useful to conserve inotify file descriptors, as |
|
|
453 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
|
|
454 | |
|
|
455 | =item C<EVFLAG_SIGNALFD> |
|
|
456 | |
|
|
457 | When this flag is specified, then libev will attempt to use the |
|
|
458 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
|
|
459 | delivers signals synchronously, which makes it both faster and might make |
|
|
460 | it possible to get the queued signal data. It can also simplify signal |
|
|
461 | handling with threads, as long as you properly block signals in your |
|
|
462 | threads that are not interested in handling them. |
|
|
463 | |
|
|
464 | Signalfd will not be used by default as this changes your signal mask, and |
|
|
465 | there are a lot of shoddy libraries and programs (glib's threadpool for |
|
|
466 | example) that can't properly initialise their signal masks. |
|
|
467 | |
|
|
468 | =item C<EVFLAG_NOSIGMASK> |
|
|
469 | |
|
|
470 | When this flag is specified, then libev will avoid to modify the signal |
|
|
471 | mask. Specifically, this means you have to make sure signals are unblocked |
|
|
472 | when you want to receive them. |
|
|
473 | |
|
|
474 | This behaviour is useful when you want to do your own signal handling, or |
|
|
475 | want to handle signals only in specific threads and want to avoid libev |
|
|
476 | unblocking the signals. |
|
|
477 | |
|
|
478 | It's also required by POSIX in a threaded program, as libev calls |
|
|
479 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
|
480 | |
|
|
481 | This flag's behaviour will become the default in future versions of libev. |
327 | |
482 | |
328 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
483 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
329 | |
484 | |
330 | This is your standard select(2) backend. Not I<completely> standard, as |
485 | This is your standard select(2) backend. Not I<completely> standard, as |
331 | libev tries to roll its own fd_set with no limits on the number of fds, |
486 | libev tries to roll its own fd_set with no limits on the number of fds, |
332 | but if that fails, expect a fairly low limit on the number of fds when |
487 | but if that fails, expect a fairly low limit on the number of fds when |
333 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
488 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
334 | usually the fastest backend for a low number of (low-numbered :) fds. |
489 | usually the fastest backend for a low number of (low-numbered :) fds. |
335 | |
490 | |
336 | To get good performance out of this backend you need a high amount of |
491 | To get good performance out of this backend you need a high amount of |
337 | parallelity (most of the file descriptors should be busy). If you are |
492 | parallelism (most of the file descriptors should be busy). If you are |
338 | writing a server, you should C<accept ()> in a loop to accept as many |
493 | writing a server, you should C<accept ()> in a loop to accept as many |
339 | connections as possible during one iteration. You might also want to have |
494 | connections as possible during one iteration. You might also want to have |
340 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
495 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
341 | readiness notifications you get per iteration. |
496 | readiness notifications you get per iteration. |
|
|
497 | |
|
|
498 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
|
|
499 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
|
|
500 | C<exceptfds> set on that platform). |
342 | |
501 | |
343 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
502 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
344 | |
503 | |
345 | And this is your standard poll(2) backend. It's more complicated |
504 | And this is your standard poll(2) backend. It's more complicated |
346 | than select, but handles sparse fds better and has no artificial |
505 | than select, but handles sparse fds better and has no artificial |
347 | limit on the number of fds you can use (except it will slow down |
506 | limit on the number of fds you can use (except it will slow down |
348 | considerably with a lot of inactive fds). It scales similarly to select, |
507 | considerably with a lot of inactive fds). It scales similarly to select, |
349 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
508 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
350 | performance tips. |
509 | performance tips. |
351 | |
510 | |
|
|
511 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
|
|
512 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
|
|
513 | |
352 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
514 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
353 | |
515 | |
|
|
516 | Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
|
|
517 | kernels). |
|
|
518 | |
354 | For few fds, this backend is a bit little slower than poll and select, |
519 | For few fds, this backend is a bit little slower than poll and select, but |
355 | but it scales phenomenally better. While poll and select usually scale |
520 | it scales phenomenally better. While poll and select usually scale like |
356 | like O(total_fds) where n is the total number of fds (or the highest fd), |
521 | O(total_fds) where total_fds is the total number of fds (or the highest |
357 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
522 | fd), epoll scales either O(1) or O(active_fds). |
358 | of shortcomings, such as silently dropping events in some hard-to-detect |
523 | |
359 | cases and requiring a syscall per fd change, no fork support and bad |
524 | The epoll mechanism deserves honorable mention as the most misdesigned |
360 | support for dup. |
525 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
526 | dropping file descriptors, requiring a system call per change per file |
|
|
527 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
528 | returning before the timeout value, resulting in additional iterations |
|
|
529 | (and only giving 5ms accuracy while select on the same platform gives |
|
|
530 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
|
|
531 | forks then I<both> parent and child process have to recreate the epoll |
|
|
532 | set, which can take considerable time (one syscall per file descriptor) |
|
|
533 | and is of course hard to detect. |
|
|
534 | |
|
|
535 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
|
|
536 | but of course I<doesn't>, and epoll just loves to report events for |
|
|
537 | totally I<different> file descriptors (even already closed ones, so |
|
|
538 | one cannot even remove them from the set) than registered in the set |
|
|
539 | (especially on SMP systems). Libev tries to counter these spurious |
|
|
540 | notifications by employing an additional generation counter and comparing |
|
|
541 | that against the events to filter out spurious ones, recreating the set |
|
|
542 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
543 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
544 | because epoll returns immediately despite a nonzero timeout. And last |
|
|
545 | not least, it also refuses to work with some file descriptors which work |
|
|
546 | perfectly fine with C<select> (files, many character devices...). |
|
|
547 | |
|
|
548 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
549 | cobbled together in a hurry, no thought to design or interaction with |
|
|
550 | others. Oh, the pain, will it ever stop... |
361 | |
551 | |
362 | While stopping, setting and starting an I/O watcher in the same iteration |
552 | While stopping, setting and starting an I/O watcher in the same iteration |
363 | will result in some caching, there is still a syscall per such incident |
553 | will result in some caching, there is still a system call per such |
364 | (because the fd could point to a different file description now), so its |
554 | incident (because the same I<file descriptor> could point to a different |
365 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
555 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
366 | very well if you register events for both fds. |
556 | file descriptors might not work very well if you register events for both |
367 | |
557 | file descriptors. |
368 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
369 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
370 | (or space) is available. |
|
|
371 | |
558 | |
372 | Best performance from this backend is achieved by not unregistering all |
559 | Best performance from this backend is achieved by not unregistering all |
373 | watchers for a file descriptor until it has been closed, if possible, i.e. |
560 | watchers for a file descriptor until it has been closed, if possible, |
374 | keep at least one watcher active per fd at all times. |
561 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
562 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
563 | extra overhead. A fork can both result in spurious notifications as well |
|
|
564 | as in libev having to destroy and recreate the epoll object, which can |
|
|
565 | take considerable time and thus should be avoided. |
375 | |
566 | |
|
|
567 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
568 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
569 | the usage. So sad. |
|
|
570 | |
376 | While nominally embeddeble in other event loops, this feature is broken in |
571 | While nominally embeddable in other event loops, this feature is broken in |
377 | all kernel versions tested so far. |
572 | a lot of kernel revisions, but probably(!) works in current versions. |
|
|
573 | |
|
|
574 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
575 | C<EVBACKEND_POLL>. |
|
|
576 | |
|
|
577 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
|
|
578 | |
|
|
579 | Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<< |
|
|
580 | io_submit(2) >>) event interface available in post-4.18 kernels (but libev |
|
|
581 | only tries to use it in 4.19+). |
|
|
582 | |
|
|
583 | This is another Linux train wreck of an event interface. |
|
|
584 | |
|
|
585 | If this backend works for you (as of this writing, it was very |
|
|
586 | experimental), it is the best event interface available on Linux and might |
|
|
587 | be well worth enabling it - if it isn't available in your kernel this will |
|
|
588 | be detected and this backend will be skipped. |
|
|
589 | |
|
|
590 | This backend can batch oneshot requests and supports a user-space ring |
|
|
591 | buffer to receive events. It also doesn't suffer from most of the design |
|
|
592 | problems of epoll (such as not being able to remove event sources from |
|
|
593 | the epoll set), and generally sounds too good to be true. Because, this |
|
|
594 | being the Linux kernel, of course it suffers from a whole new set of |
|
|
595 | limitations, forcing you to fall back to epoll, inheriting all its design |
|
|
596 | issues. |
|
|
597 | |
|
|
598 | For one, it is not easily embeddable (but probably could be done using |
|
|
599 | an event fd at some extra overhead). It also is subject to a system wide |
|
|
600 | limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO |
|
|
601 | requests are left, this backend will be skipped during initialisation, and |
|
|
602 | will switch to epoll when the loop is active. |
|
|
603 | |
|
|
604 | Most problematic in practice, however, is that not all file descriptors |
|
|
605 | work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds, |
|
|
606 | files, F</dev/null> and many others are supported, but ttys do not work |
|
|
607 | properly (a known bug that the kernel developers don't care about, see |
|
|
608 | L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
|
|
609 | (yet?) a generic event polling interface. |
|
|
610 | |
|
|
611 | Overall, it seems the Linux developers just don't want it to have a |
|
|
612 | generic event handling mechanism other than C<select> or C<poll>. |
|
|
613 | |
|
|
614 | To work around all these problem, the current version of libev uses its |
|
|
615 | epoll backend as a fallback for file descriptor types that do not work. Or |
|
|
616 | falls back completely to epoll if the kernel acts up. |
|
|
617 | |
|
|
618 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
619 | C<EVBACKEND_POLL>. |
378 | |
620 | |
379 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
621 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
380 | |
622 | |
381 | Kqueue deserves special mention, as at the time of this writing, it |
623 | Kqueue deserves special mention, as at the time this backend was |
382 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
624 | implemented, it was broken on all BSDs except NetBSD (usually it doesn't |
383 | with anything but sockets and pipes, except on Darwin, where of course |
625 | work reliably with anything but sockets and pipes, except on Darwin, |
384 | it's completely useless). For this reason it's not being "autodetected" |
626 | where of course it's completely useless). Unlike epoll, however, whose |
385 | unless you explicitly specify it explicitly in the flags (i.e. using |
627 | brokenness is by design, these kqueue bugs can be (and mostly have been) |
386 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
628 | fixed without API changes to existing programs. For this reason it's not |
387 | system like NetBSD. |
629 | being "auto-detected" on all platforms unless you explicitly specify it |
|
|
630 | in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a |
|
|
631 | known-to-be-good (-enough) system like NetBSD. |
388 | |
632 | |
389 | You still can embed kqueue into a normal poll or select backend and use it |
633 | You still can embed kqueue into a normal poll or select backend and use it |
390 | only for sockets (after having made sure that sockets work with kqueue on |
634 | only for sockets (after having made sure that sockets work with kqueue on |
391 | the target platform). See C<ev_embed> watchers for more info. |
635 | the target platform). See C<ev_embed> watchers for more info. |
392 | |
636 | |
393 | It scales in the same way as the epoll backend, but the interface to the |
637 | It scales in the same way as the epoll backend, but the interface to the |
394 | kernel is more efficient (which says nothing about its actual speed, of |
638 | kernel is more efficient (which says nothing about its actual speed, of |
395 | course). While stopping, setting and starting an I/O watcher does never |
639 | course). While stopping, setting and starting an I/O watcher does never |
396 | cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to |
640 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
397 | two event changes per incident, support for C<fork ()> is very bad and it |
641 | two event changes per incident. Support for C<fork ()> is very bad (you |
|
|
642 | might have to leak fds on fork, but it's more sane than epoll) and it |
398 | drops fds silently in similarly hard-to-detect cases. |
643 | drops fds silently in similarly hard-to-detect cases. |
399 | |
644 | |
400 | This backend usually performs well under most conditions. |
645 | This backend usually performs well under most conditions. |
401 | |
646 | |
402 | While nominally embeddable in other event loops, this doesn't work |
647 | While nominally embeddable in other event loops, this doesn't work |
403 | everywhere, so you might need to test for this. And since it is broken |
648 | everywhere, so you might need to test for this. And since it is broken |
404 | almost everywhere, you should only use it when you have a lot of sockets |
649 | almost everywhere, you should only use it when you have a lot of sockets |
405 | (for which it usually works), by embedding it into another event loop |
650 | (for which it usually works), by embedding it into another event loop |
406 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
651 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
407 | sockets. |
652 | also broken on OS X)) and, did I mention it, using it only for sockets. |
|
|
653 | |
|
|
654 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
655 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
656 | C<NOTE_EOF>. |
408 | |
657 | |
409 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
658 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
410 | |
659 | |
411 | This is not implemented yet (and might never be, unless you send me an |
660 | This is not implemented yet (and might never be, unless you send me an |
412 | implementation). According to reports, C</dev/poll> only supports sockets |
661 | implementation). According to reports, C</dev/poll> only supports sockets |
… | |
… | |
416 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
665 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
417 | |
666 | |
418 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
667 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
419 | it's really slow, but it still scales very well (O(active_fds)). |
668 | it's really slow, but it still scales very well (O(active_fds)). |
420 | |
669 | |
421 | Please note that solaris event ports can deliver a lot of spurious |
|
|
422 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
423 | blocking when no data (or space) is available. |
|
|
424 | |
|
|
425 | While this backend scales well, it requires one system call per active |
670 | While this backend scales well, it requires one system call per active |
426 | file descriptor per loop iteration. For small and medium numbers of file |
671 | file descriptor per loop iteration. For small and medium numbers of file |
427 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
672 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
428 | might perform better. |
673 | might perform better. |
429 | |
674 | |
430 | On the positive side, ignoring the spurious readiness notifications, this |
675 | On the positive side, this backend actually performed fully to |
431 | backend actually performed to specification in all tests and is fully |
676 | specification in all tests and is fully embeddable, which is a rare feat |
432 | embeddable, which is a rare feat among the OS-specific backends. |
677 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
678 | hacks). |
|
|
679 | |
|
|
680 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
681 | even sun itself gets it wrong in their code examples: The event polling |
|
|
682 | function sometimes returns events to the caller even though an error |
|
|
683 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
684 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
685 | absolutely have to know whether an event occurred or not because you have |
|
|
686 | to re-arm the watcher. |
|
|
687 | |
|
|
688 | Fortunately libev seems to be able to work around these idiocies. |
|
|
689 | |
|
|
690 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
691 | C<EVBACKEND_POLL>. |
433 | |
692 | |
434 | =item C<EVBACKEND_ALL> |
693 | =item C<EVBACKEND_ALL> |
435 | |
694 | |
436 | Try all backends (even potentially broken ones that wouldn't be tried |
695 | Try all backends (even potentially broken ones that wouldn't be tried |
437 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
696 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
438 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
697 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
439 | |
698 | |
440 | It is definitely not recommended to use this flag. |
699 | It is definitely not recommended to use this flag, use whatever |
|
|
700 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
701 | at all. |
|
|
702 | |
|
|
703 | =item C<EVBACKEND_MASK> |
|
|
704 | |
|
|
705 | Not a backend at all, but a mask to select all backend bits from a |
|
|
706 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
707 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
441 | |
708 | |
442 | =back |
709 | =back |
443 | |
710 | |
444 | If one or more of these are ored into the flags value, then only these |
711 | If one or more of the backend flags are or'ed into the flags value, |
445 | backends will be tried (in the reverse order as listed here). If none are |
712 | then only these backends will be tried (in the reverse order as listed |
446 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
713 | here). If none are specified, all backends in C<ev_recommended_backends |
447 | |
714 | ()> will be tried. |
448 | The most typical usage is like this: |
|
|
449 | |
|
|
450 | if (!ev_default_loop (0)) |
|
|
451 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
452 | |
|
|
453 | Restrict libev to the select and poll backends, and do not allow |
|
|
454 | environment settings to be taken into account: |
|
|
455 | |
|
|
456 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
457 | |
|
|
458 | Use whatever libev has to offer, but make sure that kqueue is used if |
|
|
459 | available (warning, breaks stuff, best use only with your own private |
|
|
460 | event loop and only if you know the OS supports your types of fds): |
|
|
461 | |
|
|
462 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
463 | |
|
|
464 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
465 | |
|
|
466 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
467 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
468 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
469 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
470 | |
|
|
471 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
472 | libev with threads is indeed to create one loop per thread, and using the |
|
|
473 | default loop in the "main" or "initial" thread. |
|
|
474 | |
715 | |
475 | Example: Try to create a event loop that uses epoll and nothing else. |
716 | Example: Try to create a event loop that uses epoll and nothing else. |
476 | |
717 | |
477 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
718 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
478 | if (!epoller) |
719 | if (!epoller) |
479 | fatal ("no epoll found here, maybe it hides under your chair"); |
720 | fatal ("no epoll found here, maybe it hides under your chair"); |
480 | |
721 | |
|
|
722 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
723 | used if available. |
|
|
724 | |
|
|
725 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
726 | |
|
|
727 | Example: Similarly, on linux, you mgiht want to take advantage of the |
|
|
728 | linux aio backend if possible, but fall back to something else if that |
|
|
729 | isn't available. |
|
|
730 | |
|
|
731 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO); |
|
|
732 | |
481 | =item ev_default_destroy () |
733 | =item ev_loop_destroy (loop) |
482 | |
734 | |
483 | Destroys the default loop again (frees all memory and kernel state |
735 | Destroys an event loop object (frees all memory and kernel state |
484 | etc.). None of the active event watchers will be stopped in the normal |
736 | etc.). None of the active event watchers will be stopped in the normal |
485 | sense, so e.g. C<ev_is_active> might still return true. It is your |
737 | sense, so e.g. C<ev_is_active> might still return true. It is your |
486 | responsibility to either stop all watchers cleanly yoursef I<before> |
738 | responsibility to either stop all watchers cleanly yourself I<before> |
487 | calling this function, or cope with the fact afterwards (which is usually |
739 | calling this function, or cope with the fact afterwards (which is usually |
488 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
740 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
489 | for example). |
741 | for example). |
490 | |
742 | |
491 | Note that certain global state, such as signal state, will not be freed by |
743 | Note that certain global state, such as signal state (and installed signal |
492 | this function, and related watchers (such as signal and child watchers) |
744 | handlers), will not be freed by this function, and related watchers (such |
493 | would need to be stopped manually. |
745 | as signal and child watchers) would need to be stopped manually. |
494 | |
746 | |
495 | In general it is not advisable to call this function except in the |
747 | This function is normally used on loop objects allocated by |
496 | rare occasion where you really need to free e.g. the signal handling |
748 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
749 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
750 | |
|
|
751 | Note that it is not advisable to call this function on the default loop |
|
|
752 | except in the rare occasion where you really need to free its resources. |
497 | pipe fds. If you need dynamically allocated loops it is better to use |
753 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
498 | C<ev_loop_new> and C<ev_loop_destroy>). |
754 | and C<ev_loop_destroy>. |
499 | |
755 | |
500 | =item ev_loop_destroy (loop) |
756 | =item ev_loop_fork (loop) |
501 | |
757 | |
502 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
503 | earlier call to C<ev_loop_new>. |
|
|
504 | |
|
|
505 | =item ev_default_fork () |
|
|
506 | |
|
|
507 | This function sets a flag that causes subsequent C<ev_loop> iterations |
758 | This function sets a flag that causes subsequent C<ev_run> iterations |
508 | to reinitialise the kernel state for backends that have one. Despite the |
759 | to reinitialise the kernel state for backends that have one. Despite |
509 | name, you can call it anytime, but it makes most sense after forking, in |
760 | the name, you can call it anytime you are allowed to start or stop |
510 | the child process (or both child and parent, but that again makes little |
761 | watchers (except inside an C<ev_prepare> callback), but it makes most |
511 | sense). You I<must> call it in the child before using any of the libev |
762 | sense after forking, in the child process. You I<must> call it (or use |
512 | functions, and it will only take effect at the next C<ev_loop> iteration. |
763 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
|
|
764 | |
|
|
765 | In addition, if you want to reuse a loop (via this function or |
|
|
766 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
|
|
767 | |
|
|
768 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
769 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
770 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
771 | during fork. |
513 | |
772 | |
514 | On the other hand, you only need to call this function in the child |
773 | On the other hand, you only need to call this function in the child |
515 | process if and only if you want to use the event library in the child. If |
774 | process if and only if you want to use the event loop in the child. If |
516 | you just fork+exec, you don't have to call it at all. |
775 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
776 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
777 | difference, but libev will usually detect this case on its own and do a |
|
|
778 | costly reset of the backend). |
517 | |
779 | |
518 | The function itself is quite fast and it's usually not a problem to call |
780 | The function itself is quite fast and it's usually not a problem to call |
519 | it just in case after a fork. To make this easy, the function will fit in |
781 | it just in case after a fork. |
520 | quite nicely into a call to C<pthread_atfork>: |
|
|
521 | |
782 | |
|
|
783 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
784 | using pthreads. |
|
|
785 | |
|
|
786 | static void |
|
|
787 | post_fork_child (void) |
|
|
788 | { |
|
|
789 | ev_loop_fork (EV_DEFAULT); |
|
|
790 | } |
|
|
791 | |
|
|
792 | ... |
522 | pthread_atfork (0, 0, ev_default_fork); |
793 | pthread_atfork (0, 0, post_fork_child); |
523 | |
|
|
524 | =item ev_loop_fork (loop) |
|
|
525 | |
|
|
526 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
527 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
528 | after fork, and how you do this is entirely your own problem. |
|
|
529 | |
794 | |
530 | =item int ev_is_default_loop (loop) |
795 | =item int ev_is_default_loop (loop) |
531 | |
796 | |
532 | Returns true when the given loop actually is the default loop, false otherwise. |
797 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
798 | otherwise. |
533 | |
799 | |
534 | =item unsigned int ev_loop_count (loop) |
800 | =item unsigned int ev_iteration (loop) |
535 | |
801 | |
536 | Returns the count of loop iterations for the loop, which is identical to |
802 | Returns the current iteration count for the event loop, which is identical |
537 | the number of times libev did poll for new events. It starts at C<0> and |
803 | to the number of times libev did poll for new events. It starts at C<0> |
538 | happily wraps around with enough iterations. |
804 | and happily wraps around with enough iterations. |
539 | |
805 | |
540 | This value can sometimes be useful as a generation counter of sorts (it |
806 | This value can sometimes be useful as a generation counter of sorts (it |
541 | "ticks" the number of loop iterations), as it roughly corresponds with |
807 | "ticks" the number of loop iterations), as it roughly corresponds with |
542 | C<ev_prepare> and C<ev_check> calls. |
808 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
809 | prepare and check phases. |
|
|
810 | |
|
|
811 | =item unsigned int ev_depth (loop) |
|
|
812 | |
|
|
813 | Returns the number of times C<ev_run> was entered minus the number of |
|
|
814 | times C<ev_run> was exited normally, in other words, the recursion depth. |
|
|
815 | |
|
|
816 | Outside C<ev_run>, this number is zero. In a callback, this number is |
|
|
817 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
|
|
818 | in which case it is higher. |
|
|
819 | |
|
|
820 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
|
|
821 | throwing an exception etc.), doesn't count as "exit" - consider this |
|
|
822 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
823 | convenient, in which case it is fully supported. |
543 | |
824 | |
544 | =item unsigned int ev_backend (loop) |
825 | =item unsigned int ev_backend (loop) |
545 | |
826 | |
546 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
827 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
547 | use. |
828 | use. |
… | |
… | |
552 | received events and started processing them. This timestamp does not |
833 | received events and started processing them. This timestamp does not |
553 | change as long as callbacks are being processed, and this is also the base |
834 | change as long as callbacks are being processed, and this is also the base |
554 | time used for relative timers. You can treat it as the timestamp of the |
835 | time used for relative timers. You can treat it as the timestamp of the |
555 | event occurring (or more correctly, libev finding out about it). |
836 | event occurring (or more correctly, libev finding out about it). |
556 | |
837 | |
|
|
838 | =item ev_now_update (loop) |
|
|
839 | |
|
|
840 | Establishes the current time by querying the kernel, updating the time |
|
|
841 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
842 | is usually done automatically within C<ev_run ()>. |
|
|
843 | |
|
|
844 | This function is rarely useful, but when some event callback runs for a |
|
|
845 | very long time without entering the event loop, updating libev's idea of |
|
|
846 | the current time is a good idea. |
|
|
847 | |
|
|
848 | See also L</The special problem of time updates> in the C<ev_timer> section. |
|
|
849 | |
|
|
850 | =item ev_suspend (loop) |
|
|
851 | |
|
|
852 | =item ev_resume (loop) |
|
|
853 | |
|
|
854 | These two functions suspend and resume an event loop, for use when the |
|
|
855 | loop is not used for a while and timeouts should not be processed. |
|
|
856 | |
|
|
857 | A typical use case would be an interactive program such as a game: When |
|
|
858 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
859 | would be best to handle timeouts as if no time had actually passed while |
|
|
860 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
861 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
862 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
863 | |
|
|
864 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
865 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
866 | will be rescheduled (that is, they will lose any events that would have |
|
|
867 | occurred while suspended). |
|
|
868 | |
|
|
869 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
870 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
871 | without a previous call to C<ev_suspend>. |
|
|
872 | |
|
|
873 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
874 | event loop time (see C<ev_now_update>). |
|
|
875 | |
557 | =item ev_loop (loop, int flags) |
876 | =item bool ev_run (loop, int flags) |
558 | |
877 | |
559 | Finally, this is it, the event handler. This function usually is called |
878 | Finally, this is it, the event handler. This function usually is called |
560 | after you initialised all your watchers and you want to start handling |
879 | after you have initialised all your watchers and you want to start |
561 | events. |
880 | handling events. It will ask the operating system for any new events, call |
|
|
881 | the watcher callbacks, and then repeat the whole process indefinitely: This |
|
|
882 | is why event loops are called I<loops>. |
562 | |
883 | |
563 | If the flags argument is specified as C<0>, it will not return until |
884 | If the flags argument is specified as C<0>, it will keep handling events |
564 | either no event watchers are active anymore or C<ev_unloop> was called. |
885 | until either no event watchers are active anymore or C<ev_break> was |
|
|
886 | called. |
565 | |
887 | |
|
|
888 | The return value is false if there are no more active watchers (which |
|
|
889 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
890 | (which usually means " you should call C<ev_run> again"). |
|
|
891 | |
566 | Please note that an explicit C<ev_unloop> is usually better than |
892 | Please note that an explicit C<ev_break> is usually better than |
567 | relying on all watchers to be stopped when deciding when a program has |
893 | relying on all watchers to be stopped when deciding when a program has |
568 | finished (especially in interactive programs), but having a program that |
894 | finished (especially in interactive programs), but having a program |
569 | automatically loops as long as it has to and no longer by virtue of |
895 | that automatically loops as long as it has to and no longer by virtue |
570 | relying on its watchers stopping correctly is a thing of beauty. |
896 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
897 | beauty. |
571 | |
898 | |
|
|
899 | This function is I<mostly> exception-safe - you can break out of a |
|
|
900 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
901 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
902 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
903 | |
572 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
904 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
573 | those events and any outstanding ones, but will not block your process in |
905 | those events and any already outstanding ones, but will not wait and |
574 | case there are no events and will return after one iteration of the loop. |
906 | block your process in case there are no events and will return after one |
|
|
907 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
908 | events while doing lengthy calculations, to keep the program responsive. |
575 | |
909 | |
576 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
910 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
577 | neccessary) and will handle those and any outstanding ones. It will block |
911 | necessary) and will handle those and any already outstanding ones. It |
578 | your process until at least one new event arrives, and will return after |
912 | will block your process until at least one new event arrives (which could |
579 | one iteration of the loop. This is useful if you are waiting for some |
913 | be an event internal to libev itself, so there is no guarantee that a |
580 | external event in conjunction with something not expressible using other |
914 | user-registered callback will be called), and will return after one |
|
|
915 | iteration of the loop. |
|
|
916 | |
|
|
917 | This is useful if you are waiting for some external event in conjunction |
|
|
918 | with something not expressible using other libev watchers (i.e. "roll your |
581 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
919 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
582 | usually a better approach for this kind of thing. |
920 | usually a better approach for this kind of thing. |
583 | |
921 | |
584 | Here are the gory details of what C<ev_loop> does: |
922 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
923 | understanding, not a guarantee that things will work exactly like this in |
|
|
924 | future versions): |
585 | |
925 | |
|
|
926 | - Increment loop depth. |
|
|
927 | - Reset the ev_break status. |
586 | - Before the first iteration, call any pending watchers. |
928 | - Before the first iteration, call any pending watchers. |
|
|
929 | LOOP: |
587 | * If EVFLAG_FORKCHECK was used, check for a fork. |
930 | - If EVFLAG_FORKCHECK was used, check for a fork. |
588 | - If a fork was detected, queue and call all fork watchers. |
931 | - If a fork was detected (by any means), queue and call all fork watchers. |
589 | - Queue and call all prepare watchers. |
932 | - Queue and call all prepare watchers. |
|
|
933 | - If ev_break was called, goto FINISH. |
590 | - If we have been forked, recreate the kernel state. |
934 | - If we have been forked, detach and recreate the kernel state |
|
|
935 | as to not disturb the other process. |
591 | - Update the kernel state with all outstanding changes. |
936 | - Update the kernel state with all outstanding changes. |
592 | - Update the "event loop time". |
937 | - Update the "event loop time" (ev_now ()). |
593 | - Calculate for how long to sleep or block, if at all |
938 | - Calculate for how long to sleep or block, if at all |
594 | (active idle watchers, EVLOOP_NONBLOCK or not having |
939 | (active idle watchers, EVRUN_NOWAIT or not having |
595 | any active watchers at all will result in not sleeping). |
940 | any active watchers at all will result in not sleeping). |
596 | - Sleep if the I/O and timer collect interval say so. |
941 | - Sleep if the I/O and timer collect interval say so. |
|
|
942 | - Increment loop iteration counter. |
597 | - Block the process, waiting for any events. |
943 | - Block the process, waiting for any events. |
598 | - Queue all outstanding I/O (fd) events. |
944 | - Queue all outstanding I/O (fd) events. |
599 | - Update the "event loop time" and do time jump handling. |
945 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
600 | - Queue all outstanding timers. |
946 | - Queue all expired timers. |
601 | - Queue all outstanding periodics. |
947 | - Queue all expired periodics. |
602 | - If no events are pending now, queue all idle watchers. |
948 | - Queue all idle watchers with priority higher than that of pending events. |
603 | - Queue all check watchers. |
949 | - Queue all check watchers. |
604 | - Call all queued watchers in reverse order (i.e. check watchers first). |
950 | - Call all queued watchers in reverse order (i.e. check watchers first). |
605 | Signals and child watchers are implemented as I/O watchers, and will |
951 | Signals and child watchers are implemented as I/O watchers, and will |
606 | be handled here by queueing them when their watcher gets executed. |
952 | be handled here by queueing them when their watcher gets executed. |
607 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
953 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
608 | were used, or there are no active watchers, return, otherwise |
954 | were used, or there are no active watchers, goto FINISH, otherwise |
609 | continue with step *. |
955 | continue with step LOOP. |
|
|
956 | FINISH: |
|
|
957 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
958 | - Decrement the loop depth. |
|
|
959 | - Return. |
610 | |
960 | |
611 | Example: Queue some jobs and then loop until no events are outstanding |
961 | Example: Queue some jobs and then loop until no events are outstanding |
612 | anymore. |
962 | anymore. |
613 | |
963 | |
614 | ... queue jobs here, make sure they register event watchers as long |
964 | ... queue jobs here, make sure they register event watchers as long |
615 | ... as they still have work to do (even an idle watcher will do..) |
965 | ... as they still have work to do (even an idle watcher will do..) |
616 | ev_loop (my_loop, 0); |
966 | ev_run (my_loop, 0); |
617 | ... jobs done. yeah! |
967 | ... jobs done or somebody called break. yeah! |
618 | |
968 | |
619 | =item ev_unloop (loop, how) |
969 | =item ev_break (loop, how) |
620 | |
970 | |
621 | Can be used to make a call to C<ev_loop> return early (but only after it |
971 | Can be used to make a call to C<ev_run> return early (but only after it |
622 | has processed all outstanding events). The C<how> argument must be either |
972 | has processed all outstanding events). The C<how> argument must be either |
623 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
973 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
624 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
974 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
625 | |
975 | |
626 | This "unloop state" will be cleared when entering C<ev_loop> again. |
976 | This "break state" will be cleared on the next call to C<ev_run>. |
|
|
977 | |
|
|
978 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
979 | which case it will have no effect. |
627 | |
980 | |
628 | =item ev_ref (loop) |
981 | =item ev_ref (loop) |
629 | |
982 | |
630 | =item ev_unref (loop) |
983 | =item ev_unref (loop) |
631 | |
984 | |
632 | Ref/unref can be used to add or remove a reference count on the event |
985 | Ref/unref can be used to add or remove a reference count on the event |
633 | loop: Every watcher keeps one reference, and as long as the reference |
986 | loop: Every watcher keeps one reference, and as long as the reference |
634 | count is nonzero, C<ev_loop> will not return on its own. If you have |
987 | count is nonzero, C<ev_run> will not return on its own. |
635 | a watcher you never unregister that should not keep C<ev_loop> from |
988 | |
636 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
989 | This is useful when you have a watcher that you never intend to |
|
|
990 | unregister, but that nevertheless should not keep C<ev_run> from |
|
|
991 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
|
|
992 | before stopping it. |
|
|
993 | |
637 | example, libev itself uses this for its internal signal pipe: It is not |
994 | As an example, libev itself uses this for its internal signal pipe: It |
638 | visible to the libev user and should not keep C<ev_loop> from exiting if |
995 | is not visible to the libev user and should not keep C<ev_run> from |
639 | no event watchers registered by it are active. It is also an excellent |
996 | exiting if no event watchers registered by it are active. It is also an |
640 | way to do this for generic recurring timers or from within third-party |
997 | excellent way to do this for generic recurring timers or from within |
641 | libraries. Just remember to I<unref after start> and I<ref before stop> |
998 | third-party libraries. Just remember to I<unref after start> and I<ref |
642 | (but only if the watcher wasn't active before, or was active before, |
999 | before stop> (but only if the watcher wasn't active before, or was active |
643 | respectively). |
1000 | before, respectively. Note also that libev might stop watchers itself |
|
|
1001 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
1002 | in the callback). |
644 | |
1003 | |
645 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
1004 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
646 | running when nothing else is active. |
1005 | running when nothing else is active. |
647 | |
1006 | |
648 | struct ev_signal exitsig; |
1007 | ev_signal exitsig; |
649 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
1008 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
650 | ev_signal_start (loop, &exitsig); |
1009 | ev_signal_start (loop, &exitsig); |
651 | evf_unref (loop); |
1010 | ev_unref (loop); |
652 | |
1011 | |
653 | Example: For some weird reason, unregister the above signal handler again. |
1012 | Example: For some weird reason, unregister the above signal handler again. |
654 | |
1013 | |
655 | ev_ref (loop); |
1014 | ev_ref (loop); |
656 | ev_signal_stop (loop, &exitsig); |
1015 | ev_signal_stop (loop, &exitsig); |
657 | |
1016 | |
658 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
1017 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
659 | |
1018 | |
660 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
1019 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
661 | |
1020 | |
662 | These advanced functions influence the time that libev will spend waiting |
1021 | These advanced functions influence the time that libev will spend waiting |
663 | for events. Both are by default C<0>, meaning that libev will try to |
1022 | for events. Both time intervals are by default C<0>, meaning that libev |
664 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
1023 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
1024 | latency. |
665 | |
1025 | |
666 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
1026 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
667 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
1027 | allows libev to delay invocation of I/O and timer/periodic callbacks |
668 | increase efficiency of loop iterations. |
1028 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
1029 | opportunities). |
669 | |
1030 | |
670 | The background is that sometimes your program runs just fast enough to |
1031 | The idea is that sometimes your program runs just fast enough to handle |
671 | handle one (or very few) event(s) per loop iteration. While this makes |
1032 | one (or very few) event(s) per loop iteration. While this makes the |
672 | the program responsive, it also wastes a lot of CPU time to poll for new |
1033 | program responsive, it also wastes a lot of CPU time to poll for new |
673 | events, especially with backends like C<select ()> which have a high |
1034 | events, especially with backends like C<select ()> which have a high |
674 | overhead for the actual polling but can deliver many events at once. |
1035 | overhead for the actual polling but can deliver many events at once. |
675 | |
1036 | |
676 | By setting a higher I<io collect interval> you allow libev to spend more |
1037 | By setting a higher I<io collect interval> you allow libev to spend more |
677 | time collecting I/O events, so you can handle more events per iteration, |
1038 | time collecting I/O events, so you can handle more events per iteration, |
678 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
1039 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
679 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
1040 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
680 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
1041 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
1042 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
1043 | once per this interval, on average (as long as the host time resolution is |
|
|
1044 | good enough). |
681 | |
1045 | |
682 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
1046 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
683 | to spend more time collecting timeouts, at the expense of increased |
1047 | to spend more time collecting timeouts, at the expense of increased |
684 | latency (the watcher callback will be called later). C<ev_io> watchers |
1048 | latency/jitter/inexactness (the watcher callback will be called |
685 | will not be affected. Setting this to a non-null value will not introduce |
1049 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
686 | any overhead in libev. |
1050 | value will not introduce any overhead in libev. |
687 | |
1051 | |
688 | Many (busy) programs can usually benefit by setting the io collect |
1052 | Many (busy) programs can usually benefit by setting the I/O collect |
689 | interval to a value near C<0.1> or so, which is often enough for |
1053 | interval to a value near C<0.1> or so, which is often enough for |
690 | interactive servers (of course not for games), likewise for timeouts. It |
1054 | interactive servers (of course not for games), likewise for timeouts. It |
691 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
1055 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
692 | as this approsaches the timing granularity of most systems. |
1056 | as this approaches the timing granularity of most systems. Note that if |
|
|
1057 | you do transactions with the outside world and you can't increase the |
|
|
1058 | parallelity, then this setting will limit your transaction rate (if you |
|
|
1059 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
1060 | then you can't do more than 100 transactions per second). |
|
|
1061 | |
|
|
1062 | Setting the I<timeout collect interval> can improve the opportunity for |
|
|
1063 | saving power, as the program will "bundle" timer callback invocations that |
|
|
1064 | are "near" in time together, by delaying some, thus reducing the number of |
|
|
1065 | times the process sleeps and wakes up again. Another useful technique to |
|
|
1066 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
|
|
1067 | they fire on, say, one-second boundaries only. |
|
|
1068 | |
|
|
1069 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
1070 | more often than 100 times per second: |
|
|
1071 | |
|
|
1072 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
1073 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
1074 | |
|
|
1075 | =item ev_invoke_pending (loop) |
|
|
1076 | |
|
|
1077 | This call will simply invoke all pending watchers while resetting their |
|
|
1078 | pending state. Normally, C<ev_run> does this automatically when required, |
|
|
1079 | but when overriding the invoke callback this call comes handy. This |
|
|
1080 | function can be invoked from a watcher - this can be useful for example |
|
|
1081 | when you want to do some lengthy calculation and want to pass further |
|
|
1082 | event handling to another thread (you still have to make sure only one |
|
|
1083 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
|
|
1084 | |
|
|
1085 | =item int ev_pending_count (loop) |
|
|
1086 | |
|
|
1087 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
1088 | are pending. |
|
|
1089 | |
|
|
1090 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
1091 | |
|
|
1092 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
1093 | invoking all pending watchers when there are any, C<ev_run> will call |
|
|
1094 | this callback instead. This is useful, for example, when you want to |
|
|
1095 | invoke the actual watchers inside another context (another thread etc.). |
|
|
1096 | |
|
|
1097 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
1098 | callback. |
|
|
1099 | |
|
|
1100 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
|
|
1101 | |
|
|
1102 | Sometimes you want to share the same loop between multiple threads. This |
|
|
1103 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
1104 | each call to a libev function. |
|
|
1105 | |
|
|
1106 | However, C<ev_run> can run an indefinite time, so it is not feasible |
|
|
1107 | to wait for it to return. One way around this is to wake up the event |
|
|
1108 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
|
|
1109 | I<release> and I<acquire> callbacks on the loop. |
|
|
1110 | |
|
|
1111 | When set, then C<release> will be called just before the thread is |
|
|
1112 | suspended waiting for new events, and C<acquire> is called just |
|
|
1113 | afterwards. |
|
|
1114 | |
|
|
1115 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
1116 | C<acquire> will just call the mutex_lock function again. |
|
|
1117 | |
|
|
1118 | While event loop modifications are allowed between invocations of |
|
|
1119 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
1120 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
1121 | have no effect on the set of file descriptors being watched, or the time |
|
|
1122 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
|
|
1123 | to take note of any changes you made. |
|
|
1124 | |
|
|
1125 | In theory, threads executing C<ev_run> will be async-cancel safe between |
|
|
1126 | invocations of C<release> and C<acquire>. |
|
|
1127 | |
|
|
1128 | See also the locking example in the C<THREADS> section later in this |
|
|
1129 | document. |
|
|
1130 | |
|
|
1131 | =item ev_set_userdata (loop, void *data) |
|
|
1132 | |
|
|
1133 | =item void *ev_userdata (loop) |
|
|
1134 | |
|
|
1135 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
1136 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
1137 | C<0>. |
|
|
1138 | |
|
|
1139 | These two functions can be used to associate arbitrary data with a loop, |
|
|
1140 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
1141 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
1142 | any other purpose as well. |
|
|
1143 | |
|
|
1144 | =item ev_verify (loop) |
|
|
1145 | |
|
|
1146 | This function only does something when C<EV_VERIFY> support has been |
|
|
1147 | compiled in, which is the default for non-minimal builds. It tries to go |
|
|
1148 | through all internal structures and checks them for validity. If anything |
|
|
1149 | is found to be inconsistent, it will print an error message to standard |
|
|
1150 | error and call C<abort ()>. |
|
|
1151 | |
|
|
1152 | This can be used to catch bugs inside libev itself: under normal |
|
|
1153 | circumstances, this function will never abort as of course libev keeps its |
|
|
1154 | data structures consistent. |
693 | |
1155 | |
694 | =back |
1156 | =back |
695 | |
1157 | |
696 | |
1158 | |
697 | =head1 ANATOMY OF A WATCHER |
1159 | =head1 ANATOMY OF A WATCHER |
698 | |
1160 | |
|
|
1161 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
1162 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
1163 | watchers and C<ev_io_start> for I/O watchers. |
|
|
1164 | |
699 | A watcher is a structure that you create and register to record your |
1165 | A watcher is an opaque structure that you allocate and register to record |
700 | interest in some event. For instance, if you want to wait for STDIN to |
1166 | your interest in some event. To make a concrete example, imagine you want |
701 | become readable, you would create an C<ev_io> watcher for that: |
1167 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1168 | for that: |
702 | |
1169 | |
703 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1170 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
704 | { |
1171 | { |
705 | ev_io_stop (w); |
1172 | ev_io_stop (w); |
706 | ev_unloop (loop, EVUNLOOP_ALL); |
1173 | ev_break (loop, EVBREAK_ALL); |
707 | } |
1174 | } |
708 | |
1175 | |
709 | struct ev_loop *loop = ev_default_loop (0); |
1176 | struct ev_loop *loop = ev_default_loop (0); |
|
|
1177 | |
710 | struct ev_io stdin_watcher; |
1178 | ev_io stdin_watcher; |
|
|
1179 | |
711 | ev_init (&stdin_watcher, my_cb); |
1180 | ev_init (&stdin_watcher, my_cb); |
712 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1181 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
713 | ev_io_start (loop, &stdin_watcher); |
1182 | ev_io_start (loop, &stdin_watcher); |
|
|
1183 | |
714 | ev_loop (loop, 0); |
1184 | ev_run (loop, 0); |
715 | |
1185 | |
716 | As you can see, you are responsible for allocating the memory for your |
1186 | As you can see, you are responsible for allocating the memory for your |
717 | watcher structures (and it is usually a bad idea to do this on the stack, |
1187 | watcher structures (and it is I<usually> a bad idea to do this on the |
718 | although this can sometimes be quite valid). |
1188 | stack). |
719 | |
1189 | |
|
|
1190 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
1191 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
|
|
1192 | |
720 | Each watcher structure must be initialised by a call to C<ev_init |
1193 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
721 | (watcher *, callback)>, which expects a callback to be provided. This |
1194 | *, callback)>, which expects a callback to be provided. This callback is |
722 | callback gets invoked each time the event occurs (or, in the case of io |
1195 | invoked each time the event occurs (or, in the case of I/O watchers, each |
723 | watchers, each time the event loop detects that the file descriptor given |
1196 | time the event loop detects that the file descriptor given is readable |
724 | is readable and/or writable). |
1197 | and/or writable). |
725 | |
1198 | |
726 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
1199 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
727 | with arguments specific to this watcher type. There is also a macro |
1200 | macro to configure it, with arguments specific to the watcher type. There |
728 | to combine initialisation and setting in one call: C<< ev_<type>_init |
1201 | is also a macro to combine initialisation and setting in one call: C<< |
729 | (watcher *, callback, ...) >>. |
1202 | ev_TYPE_init (watcher *, callback, ...) >>. |
730 | |
1203 | |
731 | To make the watcher actually watch out for events, you have to start it |
1204 | To make the watcher actually watch out for events, you have to start it |
732 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
1205 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
733 | *) >>), and you can stop watching for events at any time by calling the |
1206 | *) >>), and you can stop watching for events at any time by calling the |
734 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
1207 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
735 | |
1208 | |
736 | As long as your watcher is active (has been started but not stopped) you |
1209 | As long as your watcher is active (has been started but not stopped) you |
737 | must not touch the values stored in it. Most specifically you must never |
1210 | must not touch the values stored in it. Most specifically you must never |
738 | reinitialise it or call its C<set> macro. |
1211 | reinitialise it or call its C<ev_TYPE_set> macro. |
739 | |
1212 | |
740 | Each and every callback receives the event loop pointer as first, the |
1213 | Each and every callback receives the event loop pointer as first, the |
741 | registered watcher structure as second, and a bitset of received events as |
1214 | registered watcher structure as second, and a bitset of received events as |
742 | third argument. |
1215 | third argument. |
743 | |
1216 | |
… | |
… | |
752 | =item C<EV_WRITE> |
1225 | =item C<EV_WRITE> |
753 | |
1226 | |
754 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1227 | The file descriptor in the C<ev_io> watcher has become readable and/or |
755 | writable. |
1228 | writable. |
756 | |
1229 | |
757 | =item C<EV_TIMEOUT> |
1230 | =item C<EV_TIMER> |
758 | |
1231 | |
759 | The C<ev_timer> watcher has timed out. |
1232 | The C<ev_timer> watcher has timed out. |
760 | |
1233 | |
761 | =item C<EV_PERIODIC> |
1234 | =item C<EV_PERIODIC> |
762 | |
1235 | |
… | |
… | |
780 | |
1253 | |
781 | =item C<EV_PREPARE> |
1254 | =item C<EV_PREPARE> |
782 | |
1255 | |
783 | =item C<EV_CHECK> |
1256 | =item C<EV_CHECK> |
784 | |
1257 | |
785 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1258 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
786 | to gather new events, and all C<ev_check> watchers are invoked just after |
1259 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
787 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1260 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1261 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1262 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1263 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1264 | or lower priority within an event loop iteration. |
|
|
1265 | |
788 | received events. Callbacks of both watcher types can start and stop as |
1266 | Callbacks of both watcher types can start and stop as many watchers as |
789 | many watchers as they want, and all of them will be taken into account |
1267 | they want, and all of them will be taken into account (for example, a |
790 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1268 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
791 | C<ev_loop> from blocking). |
1269 | blocking). |
792 | |
1270 | |
793 | =item C<EV_EMBED> |
1271 | =item C<EV_EMBED> |
794 | |
1272 | |
795 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1273 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
796 | |
1274 | |
797 | =item C<EV_FORK> |
1275 | =item C<EV_FORK> |
798 | |
1276 | |
799 | The event loop has been resumed in the child process after fork (see |
1277 | The event loop has been resumed in the child process after fork (see |
800 | C<ev_fork>). |
1278 | C<ev_fork>). |
801 | |
1279 | |
|
|
1280 | =item C<EV_CLEANUP> |
|
|
1281 | |
|
|
1282 | The event loop is about to be destroyed (see C<ev_cleanup>). |
|
|
1283 | |
802 | =item C<EV_ASYNC> |
1284 | =item C<EV_ASYNC> |
803 | |
1285 | |
804 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1286 | The given async watcher has been asynchronously notified (see C<ev_async>). |
805 | |
1287 | |
|
|
1288 | =item C<EV_CUSTOM> |
|
|
1289 | |
|
|
1290 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1291 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
1292 | |
806 | =item C<EV_ERROR> |
1293 | =item C<EV_ERROR> |
807 | |
1294 | |
808 | An unspecified error has occured, the watcher has been stopped. This might |
1295 | An unspecified error has occurred, the watcher has been stopped. This might |
809 | happen because the watcher could not be properly started because libev |
1296 | happen because the watcher could not be properly started because libev |
810 | ran out of memory, a file descriptor was found to be closed or any other |
1297 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1298 | problem. Libev considers these application bugs. |
|
|
1299 | |
811 | problem. You best act on it by reporting the problem and somehow coping |
1300 | You best act on it by reporting the problem and somehow coping with the |
812 | with the watcher being stopped. |
1301 | watcher being stopped. Note that well-written programs should not receive |
|
|
1302 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1303 | bug in your program. |
813 | |
1304 | |
814 | Libev will usually signal a few "dummy" events together with an error, |
1305 | Libev will usually signal a few "dummy" events together with an error, for |
815 | for example it might indicate that a fd is readable or writable, and if |
1306 | example it might indicate that a fd is readable or writable, and if your |
816 | your callbacks is well-written it can just attempt the operation and cope |
1307 | callbacks is well-written it can just attempt the operation and cope with |
817 | with the error from read() or write(). This will not work in multithreaded |
1308 | the error from read() or write(). This will not work in multi-threaded |
818 | programs, though, so beware. |
1309 | programs, though, as the fd could already be closed and reused for another |
|
|
1310 | thing, so beware. |
819 | |
1311 | |
820 | =back |
1312 | =back |
821 | |
1313 | |
822 | =head2 GENERIC WATCHER FUNCTIONS |
1314 | =head2 GENERIC WATCHER FUNCTIONS |
823 | |
|
|
824 | In the following description, C<TYPE> stands for the watcher type, |
|
|
825 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
826 | |
1315 | |
827 | =over 4 |
1316 | =over 4 |
828 | |
1317 | |
829 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1318 | =item C<ev_init> (ev_TYPE *watcher, callback) |
830 | |
1319 | |
… | |
… | |
836 | which rolls both calls into one. |
1325 | which rolls both calls into one. |
837 | |
1326 | |
838 | You can reinitialise a watcher at any time as long as it has been stopped |
1327 | You can reinitialise a watcher at any time as long as it has been stopped |
839 | (or never started) and there are no pending events outstanding. |
1328 | (or never started) and there are no pending events outstanding. |
840 | |
1329 | |
841 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1330 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
842 | int revents)>. |
1331 | int revents)>. |
843 | |
1332 | |
|
|
1333 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1334 | |
|
|
1335 | ev_io w; |
|
|
1336 | ev_init (&w, my_cb); |
|
|
1337 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1338 | |
844 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1339 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
845 | |
1340 | |
846 | This macro initialises the type-specific parts of a watcher. You need to |
1341 | This macro initialises the type-specific parts of a watcher. You need to |
847 | call C<ev_init> at least once before you call this macro, but you can |
1342 | call C<ev_init> at least once before you call this macro, but you can |
848 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1343 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
849 | macro on a watcher that is active (it can be pending, however, which is a |
1344 | macro on a watcher that is active (it can be pending, however, which is a |
850 | difference to the C<ev_init> macro). |
1345 | difference to the C<ev_init> macro). |
851 | |
1346 | |
852 | Although some watcher types do not have type-specific arguments |
1347 | Although some watcher types do not have type-specific arguments |
853 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
1348 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
854 | |
1349 | |
|
|
1350 | See C<ev_init>, above, for an example. |
|
|
1351 | |
855 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
1352 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
856 | |
1353 | |
857 | This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
1354 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
858 | calls into a single call. This is the most convinient method to initialise |
1355 | calls into a single call. This is the most convenient method to initialise |
859 | a watcher. The same limitations apply, of course. |
1356 | a watcher. The same limitations apply, of course. |
860 | |
1357 | |
|
|
1358 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1359 | |
|
|
1360 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1361 | |
861 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1362 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
862 | |
1363 | |
863 | Starts (activates) the given watcher. Only active watchers will receive |
1364 | Starts (activates) the given watcher. Only active watchers will receive |
864 | events. If the watcher is already active nothing will happen. |
1365 | events. If the watcher is already active nothing will happen. |
865 | |
1366 | |
|
|
1367 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1368 | whole section. |
|
|
1369 | |
|
|
1370 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1371 | |
866 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1372 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
867 | |
1373 | |
868 | Stops the given watcher again (if active) and clears the pending |
1374 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1375 | the watcher was active or not). |
|
|
1376 | |
869 | status. It is possible that stopped watchers are pending (for example, |
1377 | It is possible that stopped watchers are pending - for example, |
870 | non-repeating timers are being stopped when they become pending), but |
1378 | non-repeating timers are being stopped when they become pending - but |
871 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1379 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
872 | you want to free or reuse the memory used by the watcher it is therefore a |
1380 | pending. If you want to free or reuse the memory used by the watcher it is |
873 | good idea to always call its C<ev_TYPE_stop> function. |
1381 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
874 | |
1382 | |
875 | =item bool ev_is_active (ev_TYPE *watcher) |
1383 | =item bool ev_is_active (ev_TYPE *watcher) |
876 | |
1384 | |
877 | Returns a true value iff the watcher is active (i.e. it has been started |
1385 | Returns a true value iff the watcher is active (i.e. it has been started |
878 | and not yet been stopped). As long as a watcher is active you must not modify |
1386 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
889 | |
1397 | |
890 | =item callback ev_cb (ev_TYPE *watcher) |
1398 | =item callback ev_cb (ev_TYPE *watcher) |
891 | |
1399 | |
892 | Returns the callback currently set on the watcher. |
1400 | Returns the callback currently set on the watcher. |
893 | |
1401 | |
894 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1402 | =item ev_set_cb (ev_TYPE *watcher, callback) |
895 | |
1403 | |
896 | Change the callback. You can change the callback at virtually any time |
1404 | Change the callback. You can change the callback at virtually any time |
897 | (modulo threads). |
1405 | (modulo threads). |
898 | |
1406 | |
899 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1407 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
900 | |
1408 | |
901 | =item int ev_priority (ev_TYPE *watcher) |
1409 | =item int ev_priority (ev_TYPE *watcher) |
902 | |
1410 | |
903 | Set and query the priority of the watcher. The priority is a small |
1411 | Set and query the priority of the watcher. The priority is a small |
904 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1412 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
905 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1413 | (default: C<-2>). Pending watchers with higher priority will be invoked |
906 | before watchers with lower priority, but priority will not keep watchers |
1414 | before watchers with lower priority, but priority will not keep watchers |
907 | from being executed (except for C<ev_idle> watchers). |
1415 | from being executed (except for C<ev_idle> watchers). |
908 | |
1416 | |
909 | This means that priorities are I<only> used for ordering callback |
|
|
910 | invocation after new events have been received. This is useful, for |
|
|
911 | example, to reduce latency after idling, or more often, to bind two |
|
|
912 | watchers on the same event and make sure one is called first. |
|
|
913 | |
|
|
914 | If you need to suppress invocation when higher priority events are pending |
1417 | If you need to suppress invocation when higher priority events are pending |
915 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1418 | you need to look at C<ev_idle> watchers, which provide this functionality. |
916 | |
1419 | |
917 | You I<must not> change the priority of a watcher as long as it is active or |
1420 | You I<must not> change the priority of a watcher as long as it is active or |
918 | pending. |
1421 | pending. |
919 | |
1422 | |
|
|
1423 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1424 | fine, as long as you do not mind that the priority value you query might |
|
|
1425 | or might not have been clamped to the valid range. |
|
|
1426 | |
920 | The default priority used by watchers when no priority has been set is |
1427 | The default priority used by watchers when no priority has been set is |
921 | always C<0>, which is supposed to not be too high and not be too low :). |
1428 | always C<0>, which is supposed to not be too high and not be too low :). |
922 | |
1429 | |
923 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1430 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
924 | fine, as long as you do not mind that the priority value you query might |
1431 | priorities. |
925 | or might not have been adjusted to be within valid range. |
|
|
926 | |
1432 | |
927 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1433 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
928 | |
1434 | |
929 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1435 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
930 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1436 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
931 | can deal with that fact. |
1437 | can deal with that fact, as both are simply passed through to the |
|
|
1438 | callback. |
932 | |
1439 | |
933 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1440 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
934 | |
1441 | |
935 | If the watcher is pending, this function returns clears its pending status |
1442 | If the watcher is pending, this function clears its pending status and |
936 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1443 | returns its C<revents> bitset (as if its callback was invoked). If the |
937 | watcher isn't pending it does nothing and returns C<0>. |
1444 | watcher isn't pending it does nothing and returns C<0>. |
938 | |
1445 | |
|
|
1446 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1447 | callback to be invoked, which can be accomplished with this function. |
|
|
1448 | |
|
|
1449 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1450 | |
|
|
1451 | Feeds the given event set into the event loop, as if the specified event |
|
|
1452 | had happened for the specified watcher (which must be a pointer to an |
|
|
1453 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1454 | not free the watcher as long as it has pending events. |
|
|
1455 | |
|
|
1456 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1457 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1458 | not started in the first place. |
|
|
1459 | |
|
|
1460 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1461 | functions that do not need a watcher. |
|
|
1462 | |
939 | =back |
1463 | =back |
940 | |
1464 | |
|
|
1465 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
|
|
1466 | OWN COMPOSITE WATCHERS> idioms. |
941 | |
1467 | |
942 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1468 | =head2 WATCHER STATES |
943 | |
1469 | |
944 | Each watcher has, by default, a member C<void *data> that you can change |
1470 | There are various watcher states mentioned throughout this manual - |
945 | and read at any time, libev will completely ignore it. This can be used |
1471 | active, pending and so on. In this section these states and the rules to |
946 | to associate arbitrary data with your watcher. If you need more data and |
1472 | transition between them will be described in more detail - and while these |
947 | don't want to allocate memory and store a pointer to it in that data |
1473 | rules might look complicated, they usually do "the right thing". |
948 | member, you can also "subclass" the watcher type and provide your own |
|
|
949 | data: |
|
|
950 | |
1474 | |
951 | struct my_io |
1475 | =over 4 |
952 | { |
|
|
953 | struct ev_io io; |
|
|
954 | int otherfd; |
|
|
955 | void *somedata; |
|
|
956 | struct whatever *mostinteresting; |
|
|
957 | } |
|
|
958 | |
1476 | |
959 | And since your callback will be called with a pointer to the watcher, you |
1477 | =item initialised |
960 | can cast it back to your own type: |
|
|
961 | |
1478 | |
962 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1479 | Before a watcher can be registered with the event loop it has to be |
963 | { |
1480 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
964 | struct my_io *w = (struct my_io *)w_; |
1481 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
965 | ... |
|
|
966 | } |
|
|
967 | |
1482 | |
968 | More interesting and less C-conformant ways of casting your callback type |
1483 | In this state it is simply some block of memory that is suitable for |
969 | instead have been omitted. |
1484 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1485 | will - as long as you either keep the memory contents intact, or call |
|
|
1486 | C<ev_TYPE_init> again. |
970 | |
1487 | |
971 | Another common scenario is having some data structure with multiple |
1488 | =item started/running/active |
972 | watchers: |
|
|
973 | |
1489 | |
974 | struct my_biggy |
1490 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
975 | { |
1491 | property of the event loop, and is actively waiting for events. While in |
976 | int some_data; |
1492 | this state it cannot be accessed (except in a few documented ways), moved, |
977 | ev_timer t1; |
1493 | freed or anything else - the only legal thing is to keep a pointer to it, |
978 | ev_timer t2; |
1494 | and call libev functions on it that are documented to work on active watchers. |
979 | } |
|
|
980 | |
1495 | |
981 | In this case getting the pointer to C<my_biggy> is a bit more complicated, |
1496 | =item pending |
982 | you need to use C<offsetof>: |
|
|
983 | |
1497 | |
984 | #include <stddef.h> |
1498 | If a watcher is active and libev determines that an event it is interested |
|
|
1499 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1500 | stay in this pending state until either it is stopped or its callback is |
|
|
1501 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1502 | callback. |
985 | |
1503 | |
|
|
1504 | The watcher might or might not be active while it is pending (for example, |
|
|
1505 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1506 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1507 | but it is still property of the event loop at this time, so cannot be |
|
|
1508 | moved, freed or reused. And if it is active the rules described in the |
|
|
1509 | previous item still apply. |
|
|
1510 | |
|
|
1511 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1512 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1513 | active. |
|
|
1514 | |
|
|
1515 | =item stopped |
|
|
1516 | |
|
|
1517 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1518 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1519 | latter will clear any pending state the watcher might be in, regardless |
|
|
1520 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1521 | freeing it is often a good idea. |
|
|
1522 | |
|
|
1523 | While stopped (and not pending) the watcher is essentially in the |
|
|
1524 | initialised state, that is, it can be reused, moved, modified in any way |
|
|
1525 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1526 | it again). |
|
|
1527 | |
|
|
1528 | =back |
|
|
1529 | |
|
|
1530 | =head2 WATCHER PRIORITY MODELS |
|
|
1531 | |
|
|
1532 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1533 | integers that influence the ordering of event callback invocation |
|
|
1534 | between watchers in some way, all else being equal. |
|
|
1535 | |
|
|
1536 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1537 | description for the more technical details such as the actual priority |
|
|
1538 | range. |
|
|
1539 | |
|
|
1540 | There are two common ways how these these priorities are being interpreted |
|
|
1541 | by event loops: |
|
|
1542 | |
|
|
1543 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1544 | of lower priority watchers, which means as long as higher priority |
|
|
1545 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1546 | |
|
|
1547 | The less common only-for-ordering model uses priorities solely to order |
|
|
1548 | callback invocation within a single event loop iteration: Higher priority |
|
|
1549 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1550 | before polling for new events. |
|
|
1551 | |
|
|
1552 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1553 | except for idle watchers (which use the lock-out model). |
|
|
1554 | |
|
|
1555 | The rationale behind this is that implementing the lock-out model for |
|
|
1556 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1557 | libraries will just poll for the same events again and again as long as |
|
|
1558 | their callbacks have not been executed, which is very inefficient in the |
|
|
1559 | common case of one high-priority watcher locking out a mass of lower |
|
|
1560 | priority ones. |
|
|
1561 | |
|
|
1562 | Static (ordering) priorities are most useful when you have two or more |
|
|
1563 | watchers handling the same resource: a typical usage example is having an |
|
|
1564 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1565 | timeouts. Under load, data might be received while the program handles |
|
|
1566 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1567 | handler will be executed before checking for data. In that case, giving |
|
|
1568 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1569 | handled first even under adverse conditions (which is usually, but not |
|
|
1570 | always, what you want). |
|
|
1571 | |
|
|
1572 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1573 | will only be executed when no same or higher priority watchers have |
|
|
1574 | received events, they can be used to implement the "lock-out" model when |
|
|
1575 | required. |
|
|
1576 | |
|
|
1577 | For example, to emulate how many other event libraries handle priorities, |
|
|
1578 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1579 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1580 | processing is done in the idle watcher callback. This causes libev to |
|
|
1581 | continuously poll and process kernel event data for the watcher, but when |
|
|
1582 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1583 | workable. |
|
|
1584 | |
|
|
1585 | Usually, however, the lock-out model implemented that way will perform |
|
|
1586 | miserably under the type of load it was designed to handle. In that case, |
|
|
1587 | it might be preferable to stop the real watcher before starting the |
|
|
1588 | idle watcher, so the kernel will not have to process the event in case |
|
|
1589 | the actual processing will be delayed for considerable time. |
|
|
1590 | |
|
|
1591 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1592 | priority than the default, and which should only process data when no |
|
|
1593 | other events are pending: |
|
|
1594 | |
|
|
1595 | ev_idle idle; // actual processing watcher |
|
|
1596 | ev_io io; // actual event watcher |
|
|
1597 | |
986 | static void |
1598 | static void |
987 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1599 | io_cb (EV_P_ ev_io *w, int revents) |
988 | { |
1600 | { |
989 | struct my_biggy big = (struct my_biggy * |
1601 | // stop the I/O watcher, we received the event, but |
990 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1602 | // are not yet ready to handle it. |
|
|
1603 | ev_io_stop (EV_A_ w); |
|
|
1604 | |
|
|
1605 | // start the idle watcher to handle the actual event. |
|
|
1606 | // it will not be executed as long as other watchers |
|
|
1607 | // with the default priority are receiving events. |
|
|
1608 | ev_idle_start (EV_A_ &idle); |
991 | } |
1609 | } |
992 | |
1610 | |
993 | static void |
1611 | static void |
994 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1612 | idle_cb (EV_P_ ev_idle *w, int revents) |
995 | { |
1613 | { |
996 | struct my_biggy big = (struct my_biggy * |
1614 | // actual processing |
997 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1615 | read (STDIN_FILENO, ...); |
|
|
1616 | |
|
|
1617 | // have to start the I/O watcher again, as |
|
|
1618 | // we have handled the event |
|
|
1619 | ev_io_start (EV_P_ &io); |
998 | } |
1620 | } |
|
|
1621 | |
|
|
1622 | // initialisation |
|
|
1623 | ev_idle_init (&idle, idle_cb); |
|
|
1624 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1625 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1626 | |
|
|
1627 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1628 | low-priority connections can not be locked out forever under load. This |
|
|
1629 | enables your program to keep a lower latency for important connections |
|
|
1630 | during short periods of high load, while not completely locking out less |
|
|
1631 | important ones. |
999 | |
1632 | |
1000 | |
1633 | |
1001 | =head1 WATCHER TYPES |
1634 | =head1 WATCHER TYPES |
1002 | |
1635 | |
1003 | This section describes each watcher in detail, but will not repeat |
1636 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1027 | In general you can register as many read and/or write event watchers per |
1660 | In general you can register as many read and/or write event watchers per |
1028 | fd as you want (as long as you don't confuse yourself). Setting all file |
1661 | fd as you want (as long as you don't confuse yourself). Setting all file |
1029 | descriptors to non-blocking mode is also usually a good idea (but not |
1662 | descriptors to non-blocking mode is also usually a good idea (but not |
1030 | required if you know what you are doing). |
1663 | required if you know what you are doing). |
1031 | |
1664 | |
1032 | If you must do this, then force the use of a known-to-be-good backend |
|
|
1033 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
|
|
1034 | C<EVBACKEND_POLL>). |
|
|
1035 | |
|
|
1036 | Another thing you have to watch out for is that it is quite easy to |
1665 | Another thing you have to watch out for is that it is quite easy to |
1037 | receive "spurious" readiness notifications, that is your callback might |
1666 | receive "spurious" readiness notifications, that is, your callback might |
1038 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1667 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1039 | because there is no data. Not only are some backends known to create a |
1668 | because there is no data. It is very easy to get into this situation even |
1040 | lot of those (for example solaris ports), it is very easy to get into |
1669 | with a relatively standard program structure. Thus it is best to always |
1041 | this situation even with a relatively standard program structure. Thus |
1670 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1042 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1043 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1671 | preferable to a program hanging until some data arrives. |
1044 | |
1672 | |
1045 | If you cannot run the fd in non-blocking mode (for example you should not |
1673 | If you cannot run the fd in non-blocking mode (for example you should |
1046 | play around with an Xlib connection), then you have to seperately re-test |
1674 | not play around with an Xlib connection), then you have to separately |
1047 | whether a file descriptor is really ready with a known-to-be good interface |
1675 | re-test whether a file descriptor is really ready with a known-to-be good |
1048 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1676 | interface such as poll (fortunately in the case of Xlib, it already does |
1049 | its own, so its quite safe to use). |
1677 | this on its own, so its quite safe to use). Some people additionally |
|
|
1678 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1679 | indefinitely. |
|
|
1680 | |
|
|
1681 | But really, best use non-blocking mode. |
1050 | |
1682 | |
1051 | =head3 The special problem of disappearing file descriptors |
1683 | =head3 The special problem of disappearing file descriptors |
1052 | |
1684 | |
1053 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1685 | Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing |
1054 | descriptor (either by calling C<close> explicitly or by any other means, |
1686 | a file descriptor (either due to calling C<close> explicitly or any other |
1055 | such as C<dup>). The reason is that you register interest in some file |
1687 | means, such as C<dup2>). The reason is that you register interest in some |
1056 | descriptor, but when it goes away, the operating system will silently drop |
1688 | file descriptor, but when it goes away, the operating system will silently |
1057 | this interest. If another file descriptor with the same number then is |
1689 | drop this interest. If another file descriptor with the same number then |
1058 | registered with libev, there is no efficient way to see that this is, in |
1690 | is registered with libev, there is no efficient way to see that this is, |
1059 | fact, a different file descriptor. |
1691 | in fact, a different file descriptor. |
1060 | |
1692 | |
1061 | To avoid having to explicitly tell libev about such cases, libev follows |
1693 | To avoid having to explicitly tell libev about such cases, libev follows |
1062 | the following policy: Each time C<ev_io_set> is being called, libev |
1694 | the following policy: Each time C<ev_io_set> is being called, libev |
1063 | will assume that this is potentially a new file descriptor, otherwise |
1695 | will assume that this is potentially a new file descriptor, otherwise |
1064 | it is assumed that the file descriptor stays the same. That means that |
1696 | it is assumed that the file descriptor stays the same. That means that |
… | |
… | |
1078 | |
1710 | |
1079 | There is no workaround possible except not registering events |
1711 | There is no workaround possible except not registering events |
1080 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1712 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1081 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1713 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1082 | |
1714 | |
|
|
1715 | =head3 The special problem of files |
|
|
1716 | |
|
|
1717 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1718 | representing files, and expect it to become ready when their program |
|
|
1719 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1720 | |
|
|
1721 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1722 | notification as soon as the kernel knows whether and how much data is |
|
|
1723 | there, and in the case of open files, that's always the case, so you |
|
|
1724 | always get a readiness notification instantly, and your read (or possibly |
|
|
1725 | write) will still block on the disk I/O. |
|
|
1726 | |
|
|
1727 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1728 | devices and so on, there is another party (the sender) that delivers data |
|
|
1729 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1730 | will not send data on its own, simply because it doesn't know what you |
|
|
1731 | wish to read - you would first have to request some data. |
|
|
1732 | |
|
|
1733 | Since files are typically not-so-well supported by advanced notification |
|
|
1734 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1735 | to files, even though you should not use it. The reason for this is |
|
|
1736 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1737 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1738 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1739 | F</dev/urandom>), and even though the file might better be served with |
|
|
1740 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1741 | it "just works" instead of freezing. |
|
|
1742 | |
|
|
1743 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1744 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1745 | when you rarely read from a file instead of from a socket, and want to |
|
|
1746 | reuse the same code path. |
|
|
1747 | |
1083 | =head3 The special problem of fork |
1748 | =head3 The special problem of fork |
1084 | |
1749 | |
1085 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1750 | Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()> |
1086 | useless behaviour. Libev fully supports fork, but needs to be told about |
1751 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1087 | it in the child. |
1752 | to be told about it in the child if you want to continue to use it in the |
|
|
1753 | child. |
1088 | |
1754 | |
1089 | To support fork in your programs, you either have to call |
1755 | To support fork in your child processes, you have to call C<ev_loop_fork |
1090 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1756 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1091 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1757 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1092 | C<EVBACKEND_POLL>. |
|
|
1093 | |
1758 | |
1094 | =head3 The special problem of SIGPIPE |
1759 | =head3 The special problem of SIGPIPE |
1095 | |
1760 | |
1096 | While not really specific to libev, it is easy to forget about SIGPIPE: |
1761 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1097 | when reading from a pipe whose other end has been closed, your program |
1762 | when writing to a pipe whose other end has been closed, your program gets |
1098 | gets send a SIGPIPE, which, by default, aborts your program. For most |
1763 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
1099 | programs this is sensible behaviour, for daemons, this is usually |
1764 | this is sensible behaviour, for daemons, this is usually undesirable. |
1100 | undesirable. |
|
|
1101 | |
1765 | |
1102 | So when you encounter spurious, unexplained daemon exits, make sure you |
1766 | So when you encounter spurious, unexplained daemon exits, make sure you |
1103 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1767 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1104 | somewhere, as that would have given you a big clue). |
1768 | somewhere, as that would have given you a big clue). |
1105 | |
1769 | |
|
|
1770 | =head3 The special problem of accept()ing when you can't |
|
|
1771 | |
|
|
1772 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1773 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1774 | connection from the pending queue in all error cases. |
|
|
1775 | |
|
|
1776 | For example, larger servers often run out of file descriptors (because |
|
|
1777 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1778 | rejecting the connection, leading to libev signalling readiness on |
|
|
1779 | the next iteration again (the connection still exists after all), and |
|
|
1780 | typically causing the program to loop at 100% CPU usage. |
|
|
1781 | |
|
|
1782 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1783 | operating systems, there is usually little the app can do to remedy the |
|
|
1784 | situation, and no known thread-safe method of removing the connection to |
|
|
1785 | cope with overload is known (to me). |
|
|
1786 | |
|
|
1787 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1788 | - when the program encounters an overload, it will just loop until the |
|
|
1789 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1790 | event-based way to handle this situation, so it's the best one can do. |
|
|
1791 | |
|
|
1792 | A better way to handle the situation is to log any errors other than |
|
|
1793 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1794 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1795 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1796 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1797 | usage. |
|
|
1798 | |
|
|
1799 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1800 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1801 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1802 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1803 | clients under typical overload conditions. |
|
|
1804 | |
|
|
1805 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1806 | is often done with C<malloc> failures, but this results in an easy |
|
|
1807 | opportunity for a DoS attack. |
1106 | |
1808 | |
1107 | =head3 Watcher-Specific Functions |
1809 | =head3 Watcher-Specific Functions |
1108 | |
1810 | |
1109 | =over 4 |
1811 | =over 4 |
1110 | |
1812 | |
1111 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1813 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1112 | |
1814 | |
1113 | =item ev_io_set (ev_io *, int fd, int events) |
1815 | =item ev_io_set (ev_io *, int fd, int events) |
1114 | |
1816 | |
1115 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1817 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1116 | rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1818 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1117 | C<EV_READ | EV_WRITE> to receive the given events. |
1819 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1118 | |
1820 | |
1119 | =item int fd [read-only] |
1821 | =item int fd [read-only] |
1120 | |
1822 | |
1121 | The file descriptor being watched. |
1823 | The file descriptor being watched. |
1122 | |
1824 | |
… | |
… | |
1130 | |
1832 | |
1131 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1833 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1132 | readable, but only once. Since it is likely line-buffered, you could |
1834 | readable, but only once. Since it is likely line-buffered, you could |
1133 | attempt to read a whole line in the callback. |
1835 | attempt to read a whole line in the callback. |
1134 | |
1836 | |
1135 | static void |
1837 | static void |
1136 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1838 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1137 | { |
1839 | { |
1138 | ev_io_stop (loop, w); |
1840 | ev_io_stop (loop, w); |
1139 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1841 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1140 | } |
1842 | } |
1141 | |
1843 | |
1142 | ... |
1844 | ... |
1143 | struct ev_loop *loop = ev_default_init (0); |
1845 | struct ev_loop *loop = ev_default_init (0); |
1144 | struct ev_io stdin_readable; |
1846 | ev_io stdin_readable; |
1145 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1847 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1146 | ev_io_start (loop, &stdin_readable); |
1848 | ev_io_start (loop, &stdin_readable); |
1147 | ev_loop (loop, 0); |
1849 | ev_run (loop, 0); |
1148 | |
1850 | |
1149 | |
1851 | |
1150 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1852 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1151 | |
1853 | |
1152 | Timer watchers are simple relative timers that generate an event after a |
1854 | Timer watchers are simple relative timers that generate an event after a |
1153 | given time, and optionally repeating in regular intervals after that. |
1855 | given time, and optionally repeating in regular intervals after that. |
1154 | |
1856 | |
1155 | The timers are based on real time, that is, if you register an event that |
1857 | The timers are based on real time, that is, if you register an event that |
1156 | times out after an hour and you reset your system clock to january last |
1858 | times out after an hour and you reset your system clock to January last |
1157 | year, it will still time out after (roughly) and hour. "Roughly" because |
1859 | year, it will still time out after (roughly) one hour. "Roughly" because |
1158 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1860 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1159 | monotonic clock option helps a lot here). |
1861 | monotonic clock option helps a lot here). |
|
|
1862 | |
|
|
1863 | The callback is guaranteed to be invoked only I<after> its timeout has |
|
|
1864 | passed (not I<at>, so on systems with very low-resolution clocks this |
|
|
1865 | might introduce a small delay, see "the special problem of being too |
|
|
1866 | early", below). If multiple timers become ready during the same loop |
|
|
1867 | iteration then the ones with earlier time-out values are invoked before |
|
|
1868 | ones of the same priority with later time-out values (but this is no |
|
|
1869 | longer true when a callback calls C<ev_run> recursively). |
|
|
1870 | |
|
|
1871 | =head3 Be smart about timeouts |
|
|
1872 | |
|
|
1873 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1874 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1875 | you want to raise some error after a while. |
|
|
1876 | |
|
|
1877 | What follows are some ways to handle this problem, from obvious and |
|
|
1878 | inefficient to smart and efficient. |
|
|
1879 | |
|
|
1880 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1881 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1882 | data or other life sign was received). |
|
|
1883 | |
|
|
1884 | =over 4 |
|
|
1885 | |
|
|
1886 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1887 | |
|
|
1888 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1889 | start the watcher: |
|
|
1890 | |
|
|
1891 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1892 | ev_timer_start (loop, timer); |
|
|
1893 | |
|
|
1894 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1895 | and start it again: |
|
|
1896 | |
|
|
1897 | ev_timer_stop (loop, timer); |
|
|
1898 | ev_timer_set (timer, 60., 0.); |
|
|
1899 | ev_timer_start (loop, timer); |
|
|
1900 | |
|
|
1901 | This is relatively simple to implement, but means that each time there is |
|
|
1902 | some activity, libev will first have to remove the timer from its internal |
|
|
1903 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1904 | still not a constant-time operation. |
|
|
1905 | |
|
|
1906 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1907 | |
|
|
1908 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1909 | C<ev_timer_start>. |
|
|
1910 | |
|
|
1911 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1912 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1913 | successfully read or write some data. If you go into an idle state where |
|
|
1914 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1915 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1916 | |
|
|
1917 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1918 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1919 | member and C<ev_timer_again>. |
|
|
1920 | |
|
|
1921 | At start: |
|
|
1922 | |
|
|
1923 | ev_init (timer, callback); |
|
|
1924 | timer->repeat = 60.; |
|
|
1925 | ev_timer_again (loop, timer); |
|
|
1926 | |
|
|
1927 | Each time there is some activity: |
|
|
1928 | |
|
|
1929 | ev_timer_again (loop, timer); |
|
|
1930 | |
|
|
1931 | It is even possible to change the time-out on the fly, regardless of |
|
|
1932 | whether the watcher is active or not: |
|
|
1933 | |
|
|
1934 | timer->repeat = 30.; |
|
|
1935 | ev_timer_again (loop, timer); |
|
|
1936 | |
|
|
1937 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1938 | you want to modify its timeout value, as libev does not have to completely |
|
|
1939 | remove and re-insert the timer from/into its internal data structure. |
|
|
1940 | |
|
|
1941 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1942 | |
|
|
1943 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1944 | |
|
|
1945 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1946 | relatively long compared to the intervals between other activity - in |
|
|
1947 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1948 | associated activity resets. |
|
|
1949 | |
|
|
1950 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1951 | but remember the time of last activity, and check for a real timeout only |
|
|
1952 | within the callback: |
|
|
1953 | |
|
|
1954 | ev_tstamp timeout = 60.; |
|
|
1955 | ev_tstamp last_activity; // time of last activity |
|
|
1956 | ev_timer timer; |
|
|
1957 | |
|
|
1958 | static void |
|
|
1959 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1960 | { |
|
|
1961 | // calculate when the timeout would happen |
|
|
1962 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
|
|
1963 | |
|
|
1964 | // if negative, it means we the timeout already occurred |
|
|
1965 | if (after < 0.) |
|
|
1966 | { |
|
|
1967 | // timeout occurred, take action |
|
|
1968 | } |
|
|
1969 | else |
|
|
1970 | { |
|
|
1971 | // callback was invoked, but there was some recent |
|
|
1972 | // activity. simply restart the timer to time out |
|
|
1973 | // after "after" seconds, which is the earliest time |
|
|
1974 | // the timeout can occur. |
|
|
1975 | ev_timer_set (w, after, 0.); |
|
|
1976 | ev_timer_start (EV_A_ w); |
|
|
1977 | } |
|
|
1978 | } |
|
|
1979 | |
|
|
1980 | To summarise the callback: first calculate in how many seconds the |
|
|
1981 | timeout will occur (by calculating the absolute time when it would occur, |
|
|
1982 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
|
|
1983 | (EV_A)> from that). |
|
|
1984 | |
|
|
1985 | If this value is negative, then we are already past the timeout, i.e. we |
|
|
1986 | timed out, and need to do whatever is needed in this case. |
|
|
1987 | |
|
|
1988 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1989 | and simply start the timer with this timeout value. |
|
|
1990 | |
|
|
1991 | In other words, each time the callback is invoked it will check whether |
|
|
1992 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1993 | again at the earliest time it could time out. Rinse. Repeat. |
|
|
1994 | |
|
|
1995 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1996 | minus half the average time between activity), but virtually no calls to |
|
|
1997 | libev to change the timeout. |
|
|
1998 | |
|
|
1999 | To start the machinery, simply initialise the watcher and set |
|
|
2000 | C<last_activity> to the current time (meaning there was some activity just |
|
|
2001 | now), then call the callback, which will "do the right thing" and start |
|
|
2002 | the timer: |
|
|
2003 | |
|
|
2004 | last_activity = ev_now (EV_A); |
|
|
2005 | ev_init (&timer, callback); |
|
|
2006 | callback (EV_A_ &timer, 0); |
|
|
2007 | |
|
|
2008 | When there is some activity, simply store the current time in |
|
|
2009 | C<last_activity>, no libev calls at all: |
|
|
2010 | |
|
|
2011 | if (activity detected) |
|
|
2012 | last_activity = ev_now (EV_A); |
|
|
2013 | |
|
|
2014 | When your timeout value changes, then the timeout can be changed by simply |
|
|
2015 | providing a new value, stopping the timer and calling the callback, which |
|
|
2016 | will again do the right thing (for example, time out immediately :). |
|
|
2017 | |
|
|
2018 | timeout = new_value; |
|
|
2019 | ev_timer_stop (EV_A_ &timer); |
|
|
2020 | callback (EV_A_ &timer, 0); |
|
|
2021 | |
|
|
2022 | This technique is slightly more complex, but in most cases where the |
|
|
2023 | time-out is unlikely to be triggered, much more efficient. |
|
|
2024 | |
|
|
2025 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
2026 | |
|
|
2027 | If there is not one request, but many thousands (millions...), all |
|
|
2028 | employing some kind of timeout with the same timeout value, then one can |
|
|
2029 | do even better: |
|
|
2030 | |
|
|
2031 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
2032 | at the I<end> of the list. |
|
|
2033 | |
|
|
2034 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
2035 | the list is expected to fire (for example, using the technique #3). |
|
|
2036 | |
|
|
2037 | When there is some activity, remove the timer from the list, recalculate |
|
|
2038 | the timeout, append it to the end of the list again, and make sure to |
|
|
2039 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
2040 | |
|
|
2041 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
2042 | starting, stopping and updating the timers, at the expense of a major |
|
|
2043 | complication, and having to use a constant timeout. The constant timeout |
|
|
2044 | ensures that the list stays sorted. |
|
|
2045 | |
|
|
2046 | =back |
|
|
2047 | |
|
|
2048 | So which method the best? |
|
|
2049 | |
|
|
2050 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
2051 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
2052 | better, and isn't very complicated either. In most case, choosing either |
|
|
2053 | one is fine, with #3 being better in typical situations. |
|
|
2054 | |
|
|
2055 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
2056 | rather complicated, but extremely efficient, something that really pays |
|
|
2057 | off after the first million or so of active timers, i.e. it's usually |
|
|
2058 | overkill :) |
|
|
2059 | |
|
|
2060 | =head3 The special problem of being too early |
|
|
2061 | |
|
|
2062 | If you ask a timer to call your callback after three seconds, then |
|
|
2063 | you expect it to be invoked after three seconds - but of course, this |
|
|
2064 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
2065 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
2066 | process with a STOP signal for a few hours for example. |
|
|
2067 | |
|
|
2068 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
2069 | delay has occurred, but cannot guarantee this. |
|
|
2070 | |
|
|
2071 | A less obvious failure mode is calling your callback too early: many event |
|
|
2072 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
2073 | this can cause your callback to be invoked much earlier than you would |
|
|
2074 | expect. |
|
|
2075 | |
|
|
2076 | To see why, imagine a system with a clock that only offers full second |
|
|
2077 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2078 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2079 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2080 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2081 | |
|
|
2082 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2083 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2084 | one-second delay was requested - this is being "too early", despite best |
|
|
2085 | intentions. |
|
|
2086 | |
|
|
2087 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2088 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2089 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2090 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2091 | |
|
|
2092 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2093 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2094 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2095 | late" side of things. |
|
|
2096 | |
|
|
2097 | =head3 The special problem of time updates |
|
|
2098 | |
|
|
2099 | Establishing the current time is a costly operation (it usually takes |
|
|
2100 | at least one system call): EV therefore updates its idea of the current |
|
|
2101 | time only before and after C<ev_run> collects new events, which causes a |
|
|
2102 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
2103 | lots of events in one iteration. |
1160 | |
2104 | |
1161 | The relative timeouts are calculated relative to the C<ev_now ()> |
2105 | The relative timeouts are calculated relative to the C<ev_now ()> |
1162 | time. This is usually the right thing as this timestamp refers to the time |
2106 | time. This is usually the right thing as this timestamp refers to the time |
1163 | of the event triggering whatever timeout you are modifying/starting. If |
2107 | of the event triggering whatever timeout you are modifying/starting. If |
1164 | you suspect event processing to be delayed and you I<need> to base the timeout |
2108 | you suspect event processing to be delayed and you I<need> to base the |
1165 | on the current time, use something like this to adjust for this: |
2109 | timeout on the current time, use something like the following to adjust |
|
|
2110 | for it: |
1166 | |
2111 | |
1167 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2112 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
1168 | |
2113 | |
1169 | The callback is guarenteed to be invoked only after its timeout has passed, |
2114 | If the event loop is suspended for a long time, you can also force an |
1170 | but if multiple timers become ready during the same loop iteration then |
2115 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1171 | order of execution is undefined. |
2116 | ()>, although that will push the event time of all outstanding events |
|
|
2117 | further into the future. |
|
|
2118 | |
|
|
2119 | =head3 The special problem of unsynchronised clocks |
|
|
2120 | |
|
|
2121 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2122 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2123 | jumps). |
|
|
2124 | |
|
|
2125 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2126 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2127 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2128 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2129 | than a directly following call to C<time>. |
|
|
2130 | |
|
|
2131 | The moral of this is to only compare libev-related timestamps with |
|
|
2132 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2133 | a second or so. |
|
|
2134 | |
|
|
2135 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2136 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2137 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2138 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2139 | |
|
|
2140 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2141 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2142 | I<measured according to the real time>, not the system clock. |
|
|
2143 | |
|
|
2144 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2145 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2146 | exactly the right behaviour. |
|
|
2147 | |
|
|
2148 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2149 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2150 | time, where your comparisons will always generate correct results. |
|
|
2151 | |
|
|
2152 | =head3 The special problems of suspended animation |
|
|
2153 | |
|
|
2154 | When you leave the server world it is quite customary to hit machines that |
|
|
2155 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
2156 | |
|
|
2157 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
2158 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
2159 | to run until the system is suspended, but they will not advance while the |
|
|
2160 | system is suspended. That means, on resume, it will be as if the program |
|
|
2161 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
2162 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
2163 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
2164 | long suspend would be detected as a time jump by libev, and timers would |
|
|
2165 | be adjusted accordingly. |
|
|
2166 | |
|
|
2167 | I would not be surprised to see different behaviour in different between |
|
|
2168 | operating systems, OS versions or even different hardware. |
|
|
2169 | |
|
|
2170 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
2171 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
2172 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
2173 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
2174 | will be counted towards the timers. When no monotonic clock source is in |
|
|
2175 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
2176 | |
|
|
2177 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
2178 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
2179 | deterministic behaviour in this case (you can do nothing against |
|
|
2180 | C<SIGSTOP>). |
1172 | |
2181 | |
1173 | =head3 Watcher-Specific Functions and Data Members |
2182 | =head3 Watcher-Specific Functions and Data Members |
1174 | |
2183 | |
1175 | =over 4 |
2184 | =over 4 |
1176 | |
2185 | |
1177 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2186 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1178 | |
2187 | |
1179 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2188 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1180 | |
2189 | |
1181 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2190 | Configure the timer to trigger after C<after> seconds (fractional and |
1182 | is C<0.>, then it will automatically be stopped once the timeout is |
2191 | negative values are supported). If C<repeat> is C<0.>, then it will |
1183 | reached. If it is positive, then the timer will automatically be |
2192 | automatically be stopped once the timeout is reached. If it is positive, |
1184 | configured to trigger again C<repeat> seconds later, again, and again, |
2193 | then the timer will automatically be configured to trigger again C<repeat> |
1185 | until stopped manually. |
2194 | seconds later, again, and again, until stopped manually. |
1186 | |
2195 | |
1187 | The timer itself will do a best-effort at avoiding drift, that is, if |
2196 | The timer itself will do a best-effort at avoiding drift, that is, if |
1188 | you configure a timer to trigger every 10 seconds, then it will normally |
2197 | you configure a timer to trigger every 10 seconds, then it will normally |
1189 | trigger at exactly 10 second intervals. If, however, your program cannot |
2198 | trigger at exactly 10 second intervals. If, however, your program cannot |
1190 | keep up with the timer (because it takes longer than those 10 seconds to |
2199 | keep up with the timer (because it takes longer than those 10 seconds to |
1191 | do stuff) the timer will not fire more than once per event loop iteration. |
2200 | do stuff) the timer will not fire more than once per event loop iteration. |
1192 | |
2201 | |
1193 | =item ev_timer_again (loop, ev_timer *) |
2202 | =item ev_timer_again (loop, ev_timer *) |
1194 | |
2203 | |
1195 | This will act as if the timer timed out and restart it again if it is |
2204 | This will act as if the timer timed out, and restarts it again if it is |
1196 | repeating. The exact semantics are: |
2205 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2206 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1197 | |
2207 | |
|
|
2208 | The exact semantics are as in the following rules, all of which will be |
|
|
2209 | applied to the watcher: |
|
|
2210 | |
|
|
2211 | =over 4 |
|
|
2212 | |
1198 | If the timer is pending, its pending status is cleared. |
2213 | =item If the timer is pending, the pending status is always cleared. |
1199 | |
2214 | |
1200 | If the timer is started but nonrepeating, stop it (as if it timed out). |
2215 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2216 | out, without invoking it). |
1201 | |
2217 | |
1202 | If the timer is repeating, either start it if necessary (with the |
2218 | =item If the timer is repeating, make the C<repeat> value the new timeout |
1203 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2219 | and start the timer, if necessary. |
1204 | |
2220 | |
1205 | This sounds a bit complicated, but here is a useful and typical |
2221 | =back |
1206 | example: Imagine you have a tcp connection and you want a so-called idle |
|
|
1207 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1208 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1209 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1210 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1211 | you go into an idle state where you do not expect data to travel on the |
|
|
1212 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1213 | automatically restart it if need be. |
|
|
1214 | |
2222 | |
1215 | That means you can ignore the C<after> value and C<ev_timer_start> |
2223 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
1216 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
2224 | usage example. |
1217 | |
2225 | |
1218 | ev_timer_init (timer, callback, 0., 5.); |
2226 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1219 | ev_timer_again (loop, timer); |
|
|
1220 | ... |
|
|
1221 | timer->again = 17.; |
|
|
1222 | ev_timer_again (loop, timer); |
|
|
1223 | ... |
|
|
1224 | timer->again = 10.; |
|
|
1225 | ev_timer_again (loop, timer); |
|
|
1226 | |
2227 | |
1227 | This is more slightly efficient then stopping/starting the timer each time |
2228 | Returns the remaining time until a timer fires. If the timer is active, |
1228 | you want to modify its timeout value. |
2229 | then this time is relative to the current event loop time, otherwise it's |
|
|
2230 | the timeout value currently configured. |
|
|
2231 | |
|
|
2232 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
2233 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
2234 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
2235 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
2236 | too), and so on. |
1229 | |
2237 | |
1230 | =item ev_tstamp repeat [read-write] |
2238 | =item ev_tstamp repeat [read-write] |
1231 | |
2239 | |
1232 | The current C<repeat> value. Will be used each time the watcher times out |
2240 | The current C<repeat> value. Will be used each time the watcher times out |
1233 | or C<ev_timer_again> is called and determines the next timeout (if any), |
2241 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1234 | which is also when any modifications are taken into account. |
2242 | which is also when any modifications are taken into account. |
1235 | |
2243 | |
1236 | =back |
2244 | =back |
1237 | |
2245 | |
1238 | =head3 Examples |
2246 | =head3 Examples |
1239 | |
2247 | |
1240 | Example: Create a timer that fires after 60 seconds. |
2248 | Example: Create a timer that fires after 60 seconds. |
1241 | |
2249 | |
1242 | static void |
2250 | static void |
1243 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2251 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1244 | { |
2252 | { |
1245 | .. one minute over, w is actually stopped right here |
2253 | .. one minute over, w is actually stopped right here |
1246 | } |
2254 | } |
1247 | |
2255 | |
1248 | struct ev_timer mytimer; |
2256 | ev_timer mytimer; |
1249 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
2257 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1250 | ev_timer_start (loop, &mytimer); |
2258 | ev_timer_start (loop, &mytimer); |
1251 | |
2259 | |
1252 | Example: Create a timeout timer that times out after 10 seconds of |
2260 | Example: Create a timeout timer that times out after 10 seconds of |
1253 | inactivity. |
2261 | inactivity. |
1254 | |
2262 | |
1255 | static void |
2263 | static void |
1256 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2264 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1257 | { |
2265 | { |
1258 | .. ten seconds without any activity |
2266 | .. ten seconds without any activity |
1259 | } |
2267 | } |
1260 | |
2268 | |
1261 | struct ev_timer mytimer; |
2269 | ev_timer mytimer; |
1262 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2270 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1263 | ev_timer_again (&mytimer); /* start timer */ |
2271 | ev_timer_again (&mytimer); /* start timer */ |
1264 | ev_loop (loop, 0); |
2272 | ev_run (loop, 0); |
1265 | |
2273 | |
1266 | // and in some piece of code that gets executed on any "activity": |
2274 | // and in some piece of code that gets executed on any "activity": |
1267 | // reset the timeout to start ticking again at 10 seconds |
2275 | // reset the timeout to start ticking again at 10 seconds |
1268 | ev_timer_again (&mytimer); |
2276 | ev_timer_again (&mytimer); |
1269 | |
2277 | |
1270 | |
2278 | |
1271 | =head2 C<ev_periodic> - to cron or not to cron? |
2279 | =head2 C<ev_periodic> - to cron or not to cron? |
1272 | |
2280 | |
1273 | Periodic watchers are also timers of a kind, but they are very versatile |
2281 | Periodic watchers are also timers of a kind, but they are very versatile |
1274 | (and unfortunately a bit complex). |
2282 | (and unfortunately a bit complex). |
1275 | |
2283 | |
1276 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
2284 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1277 | but on wallclock time (absolute time). You can tell a periodic watcher |
2285 | relative time, the physical time that passes) but on wall clock time |
1278 | to trigger after some specific point in time. For example, if you tell a |
2286 | (absolute time, the thing you can read on your calendar or clock). The |
1279 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
2287 | difference is that wall clock time can run faster or slower than real |
1280 | + 10.>, that is, an absolute time not a delay) and then reset your system |
2288 | time, and time jumps are not uncommon (e.g. when you adjust your |
1281 | clock to january of the previous year, then it will take more than year |
2289 | wrist-watch). |
1282 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1283 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1284 | |
2290 | |
|
|
2291 | You can tell a periodic watcher to trigger after some specific point |
|
|
2292 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
2293 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
2294 | not a delay) and then reset your system clock to January of the previous |
|
|
2295 | year, then it will take a year or more to trigger the event (unlike an |
|
|
2296 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
2297 | it, as it uses a relative timeout). |
|
|
2298 | |
1285 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
2299 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1286 | such as triggering an event on each "midnight, local time", or other |
2300 | timers, such as triggering an event on each "midnight, local time", or |
1287 | complicated, rules. |
2301 | other complicated rules. This cannot easily be done with C<ev_timer> |
|
|
2302 | watchers, as those cannot react to time jumps. |
1288 | |
2303 | |
1289 | As with timers, the callback is guarenteed to be invoked only when the |
2304 | As with timers, the callback is guaranteed to be invoked only when the |
1290 | time (C<at>) has passed, but if multiple periodic timers become ready |
2305 | point in time where it is supposed to trigger has passed. If multiple |
1291 | during the same loop iteration then order of execution is undefined. |
2306 | timers become ready during the same loop iteration then the ones with |
|
|
2307 | earlier time-out values are invoked before ones with later time-out values |
|
|
2308 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1292 | |
2309 | |
1293 | =head3 Watcher-Specific Functions and Data Members |
2310 | =head3 Watcher-Specific Functions and Data Members |
1294 | |
2311 | |
1295 | =over 4 |
2312 | =over 4 |
1296 | |
2313 | |
1297 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
2314 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1298 | |
2315 | |
1299 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
2316 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1300 | |
2317 | |
1301 | Lots of arguments, lets sort it out... There are basically three modes of |
2318 | Lots of arguments, let's sort it out... There are basically three modes of |
1302 | operation, and we will explain them from simplest to complex: |
2319 | operation, and we will explain them from simplest to most complex: |
1303 | |
2320 | |
1304 | =over 4 |
2321 | =over 4 |
1305 | |
2322 | |
1306 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
2323 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1307 | |
2324 | |
1308 | In this configuration the watcher triggers an event after the wallclock |
2325 | In this configuration the watcher triggers an event after the wall clock |
1309 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
2326 | time C<offset> has passed. It will not repeat and will not adjust when a |
1310 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
2327 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1311 | run when the system time reaches or surpasses this time. |
2328 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2329 | this point in time. |
1312 | |
2330 | |
1313 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2331 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1314 | |
2332 | |
1315 | In this mode the watcher will always be scheduled to time out at the next |
2333 | In this mode the watcher will always be scheduled to time out at the next |
1316 | C<at + N * interval> time (for some integer N, which can also be negative) |
2334 | C<offset + N * interval> time (for some integer N, which can also be |
1317 | and then repeat, regardless of any time jumps. |
2335 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
2336 | argument is merely an offset into the C<interval> periods. |
1318 | |
2337 | |
1319 | This can be used to create timers that do not drift with respect to system |
2338 | This can be used to create timers that do not drift with respect to the |
1320 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
2339 | system clock, for example, here is an C<ev_periodic> that triggers each |
1321 | the hour: |
2340 | hour, on the hour (with respect to UTC): |
1322 | |
2341 | |
1323 | ev_periodic_set (&periodic, 0., 3600., 0); |
2342 | ev_periodic_set (&periodic, 0., 3600., 0); |
1324 | |
2343 | |
1325 | This doesn't mean there will always be 3600 seconds in between triggers, |
2344 | This doesn't mean there will always be 3600 seconds in between triggers, |
1326 | but only that the the callback will be called when the system time shows a |
2345 | but only that the callback will be called when the system time shows a |
1327 | full hour (UTC), or more correctly, when the system time is evenly divisible |
2346 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1328 | by 3600. |
2347 | by 3600. |
1329 | |
2348 | |
1330 | Another way to think about it (for the mathematically inclined) is that |
2349 | Another way to think about it (for the mathematically inclined) is that |
1331 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2350 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1332 | time where C<time = at (mod interval)>, regardless of any time jumps. |
2351 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1333 | |
2352 | |
1334 | For numerical stability it is preferable that the C<at> value is near |
2353 | The C<interval> I<MUST> be positive, and for numerical stability, the |
1335 | C<ev_now ()> (the current time), but there is no range requirement for |
2354 | interval value should be higher than C<1/8192> (which is around 100 |
1336 | this value, and in fact is often specified as zero. |
2355 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2356 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2357 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2358 | C<0> and C<interval>, which is also the recommended range. |
1337 | |
2359 | |
1338 | Note also that there is an upper limit to how often a timer can fire (cpu |
2360 | Note also that there is an upper limit to how often a timer can fire (CPU |
1339 | speed for example), so if C<interval> is very small then timing stability |
2361 | speed for example), so if C<interval> is very small then timing stability |
1340 | will of course detoriate. Libev itself tries to be exact to be about one |
2362 | will of course deteriorate. Libev itself tries to be exact to be about one |
1341 | millisecond (if the OS supports it and the machine is fast enough). |
2363 | millisecond (if the OS supports it and the machine is fast enough). |
1342 | |
2364 | |
1343 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2365 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1344 | |
2366 | |
1345 | In this mode the values for C<interval> and C<at> are both being |
2367 | In this mode the values for C<interval> and C<offset> are both being |
1346 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2368 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1347 | reschedule callback will be called with the watcher as first, and the |
2369 | reschedule callback will be called with the watcher as first, and the |
1348 | current time as second argument. |
2370 | current time as second argument. |
1349 | |
2371 | |
1350 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2372 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1351 | ever, or make ANY event loop modifications whatsoever>. |
2373 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
2374 | allowed by documentation here>. |
1352 | |
2375 | |
1353 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
2376 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1354 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
2377 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1355 | only event loop modification you are allowed to do). |
2378 | only event loop modification you are allowed to do). |
1356 | |
2379 | |
1357 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
2380 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1358 | *w, ev_tstamp now)>, e.g.: |
2381 | *w, ev_tstamp now)>, e.g.: |
1359 | |
2382 | |
|
|
2383 | static ev_tstamp |
1360 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2384 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1361 | { |
2385 | { |
1362 | return now + 60.; |
2386 | return now + 60.; |
1363 | } |
2387 | } |
1364 | |
2388 | |
1365 | It must return the next time to trigger, based on the passed time value |
2389 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1369 | |
2393 | |
1370 | NOTE: I<< This callback must always return a time that is higher than or |
2394 | NOTE: I<< This callback must always return a time that is higher than or |
1371 | equal to the passed C<now> value >>. |
2395 | equal to the passed C<now> value >>. |
1372 | |
2396 | |
1373 | This can be used to create very complex timers, such as a timer that |
2397 | This can be used to create very complex timers, such as a timer that |
1374 | triggers on "next midnight, local time". To do this, you would calculate the |
2398 | triggers on "next midnight, local time". To do this, you would calculate |
1375 | next midnight after C<now> and return the timestamp value for this. How |
2399 | the next midnight after C<now> and return the timestamp value for |
1376 | you do this is, again, up to you (but it is not trivial, which is the main |
2400 | this. Here is a (completely untested, no error checking) example on how to |
1377 | reason I omitted it as an example). |
2401 | do this: |
|
|
2402 | |
|
|
2403 | #include <time.h> |
|
|
2404 | |
|
|
2405 | static ev_tstamp |
|
|
2406 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2407 | { |
|
|
2408 | time_t tnow = (time_t)now; |
|
|
2409 | struct tm tm; |
|
|
2410 | localtime_r (&tnow, &tm); |
|
|
2411 | |
|
|
2412 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2413 | ++tm.tm_mday; // midnight next day |
|
|
2414 | |
|
|
2415 | return mktime (&tm); |
|
|
2416 | } |
|
|
2417 | |
|
|
2418 | Note: this code might run into trouble on days that have more then two |
|
|
2419 | midnights (beginning and end). |
1378 | |
2420 | |
1379 | =back |
2421 | =back |
1380 | |
2422 | |
1381 | =item ev_periodic_again (loop, ev_periodic *) |
2423 | =item ev_periodic_again (loop, ev_periodic *) |
1382 | |
2424 | |
… | |
… | |
1385 | a different time than the last time it was called (e.g. in a crond like |
2427 | a different time than the last time it was called (e.g. in a crond like |
1386 | program when the crontabs have changed). |
2428 | program when the crontabs have changed). |
1387 | |
2429 | |
1388 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2430 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1389 | |
2431 | |
1390 | When active, returns the absolute time that the watcher is supposed to |
2432 | When active, returns the absolute time that the watcher is supposed |
1391 | trigger next. |
2433 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2434 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2435 | rescheduling modes. |
1392 | |
2436 | |
1393 | =item ev_tstamp offset [read-write] |
2437 | =item ev_tstamp offset [read-write] |
1394 | |
2438 | |
1395 | When repeating, this contains the offset value, otherwise this is the |
2439 | When repeating, this contains the offset value, otherwise this is the |
1396 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2440 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2441 | although libev might modify this value for better numerical stability). |
1397 | |
2442 | |
1398 | Can be modified any time, but changes only take effect when the periodic |
2443 | Can be modified any time, but changes only take effect when the periodic |
1399 | timer fires or C<ev_periodic_again> is being called. |
2444 | timer fires or C<ev_periodic_again> is being called. |
1400 | |
2445 | |
1401 | =item ev_tstamp interval [read-write] |
2446 | =item ev_tstamp interval [read-write] |
1402 | |
2447 | |
1403 | The current interval value. Can be modified any time, but changes only |
2448 | The current interval value. Can be modified any time, but changes only |
1404 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
2449 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1405 | called. |
2450 | called. |
1406 | |
2451 | |
1407 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
2452 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1408 | |
2453 | |
1409 | The current reschedule callback, or C<0>, if this functionality is |
2454 | The current reschedule callback, or C<0>, if this functionality is |
1410 | switched off. Can be changed any time, but changes only take effect when |
2455 | switched off. Can be changed any time, but changes only take effect when |
1411 | the periodic timer fires or C<ev_periodic_again> is being called. |
2456 | the periodic timer fires or C<ev_periodic_again> is being called. |
1412 | |
2457 | |
1413 | =back |
2458 | =back |
1414 | |
2459 | |
1415 | =head3 Examples |
2460 | =head3 Examples |
1416 | |
2461 | |
1417 | Example: Call a callback every hour, or, more precisely, whenever the |
2462 | Example: Call a callback every hour, or, more precisely, whenever the |
1418 | system clock is divisible by 3600. The callback invocation times have |
2463 | system time is divisible by 3600. The callback invocation times have |
1419 | potentially a lot of jittering, but good long-term stability. |
2464 | potentially a lot of jitter, but good long-term stability. |
1420 | |
2465 | |
1421 | static void |
2466 | static void |
1422 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2467 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1423 | { |
2468 | { |
1424 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2469 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1425 | } |
2470 | } |
1426 | |
2471 | |
1427 | struct ev_periodic hourly_tick; |
2472 | ev_periodic hourly_tick; |
1428 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2473 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1429 | ev_periodic_start (loop, &hourly_tick); |
2474 | ev_periodic_start (loop, &hourly_tick); |
1430 | |
2475 | |
1431 | Example: The same as above, but use a reschedule callback to do it: |
2476 | Example: The same as above, but use a reschedule callback to do it: |
1432 | |
2477 | |
1433 | #include <math.h> |
2478 | #include <math.h> |
1434 | |
2479 | |
1435 | static ev_tstamp |
2480 | static ev_tstamp |
1436 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2481 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1437 | { |
2482 | { |
1438 | return fmod (now, 3600.) + 3600.; |
2483 | return now + (3600. - fmod (now, 3600.)); |
1439 | } |
2484 | } |
1440 | |
2485 | |
1441 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2486 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1442 | |
2487 | |
1443 | Example: Call a callback every hour, starting now: |
2488 | Example: Call a callback every hour, starting now: |
1444 | |
2489 | |
1445 | struct ev_periodic hourly_tick; |
2490 | ev_periodic hourly_tick; |
1446 | ev_periodic_init (&hourly_tick, clock_cb, |
2491 | ev_periodic_init (&hourly_tick, clock_cb, |
1447 | fmod (ev_now (loop), 3600.), 3600., 0); |
2492 | fmod (ev_now (loop), 3600.), 3600., 0); |
1448 | ev_periodic_start (loop, &hourly_tick); |
2493 | ev_periodic_start (loop, &hourly_tick); |
1449 | |
2494 | |
1450 | |
2495 | |
1451 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2496 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1452 | |
2497 | |
1453 | Signal watchers will trigger an event when the process receives a specific |
2498 | Signal watchers will trigger an event when the process receives a specific |
1454 | signal one or more times. Even though signals are very asynchronous, libev |
2499 | signal one or more times. Even though signals are very asynchronous, libev |
1455 | will try it's best to deliver signals synchronously, i.e. as part of the |
2500 | will try its best to deliver signals synchronously, i.e. as part of the |
1456 | normal event processing, like any other event. |
2501 | normal event processing, like any other event. |
1457 | |
2502 | |
|
|
2503 | If you want signals to be delivered truly asynchronously, just use |
|
|
2504 | C<sigaction> as you would do without libev and forget about sharing |
|
|
2505 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2506 | synchronously wake up an event loop. |
|
|
2507 | |
1458 | You can configure as many watchers as you like per signal. Only when the |
2508 | You can configure as many watchers as you like for the same signal, but |
1459 | first watcher gets started will libev actually register a signal watcher |
2509 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
1460 | with the kernel (thus it coexists with your own signal handlers as long |
2510 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
1461 | as you don't register any with libev). Similarly, when the last signal |
2511 | C<SIGINT> in both the default loop and another loop at the same time. At |
1462 | watcher for a signal is stopped libev will reset the signal handler to |
2512 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
1463 | SIG_DFL (regardless of what it was set to before). |
2513 | |
|
|
2514 | Only after the first watcher for a signal is started will libev actually |
|
|
2515 | register something with the kernel. It thus coexists with your own signal |
|
|
2516 | handlers as long as you don't register any with libev for the same signal. |
1464 | |
2517 | |
1465 | If possible and supported, libev will install its handlers with |
2518 | If possible and supported, libev will install its handlers with |
1466 | C<SA_RESTART> behaviour enabled, so syscalls should not be unduly |
2519 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1467 | interrupted. If you have a problem with syscalls getting interrupted by |
2520 | not be unduly interrupted. If you have a problem with system calls getting |
1468 | signals you can block all signals in an C<ev_check> watcher and unblock |
2521 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1469 | them in an C<ev_prepare> watcher. |
2522 | and unblock them in an C<ev_prepare> watcher. |
|
|
2523 | |
|
|
2524 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2525 | |
|
|
2526 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2527 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2528 | stopping it again), that is, libev might or might not block the signal, |
|
|
2529 | and might or might not set or restore the installed signal handler (but |
|
|
2530 | see C<EVFLAG_NOSIGMASK>). |
|
|
2531 | |
|
|
2532 | While this does not matter for the signal disposition (libev never |
|
|
2533 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2534 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2535 | certain signals to be blocked. |
|
|
2536 | |
|
|
2537 | This means that before calling C<exec> (from the child) you should reset |
|
|
2538 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2539 | choice usually). |
|
|
2540 | |
|
|
2541 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2542 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2543 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2544 | |
|
|
2545 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2546 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2547 | the window of opportunity for problems, it will not go away, as libev |
|
|
2548 | I<has> to modify the signal mask, at least temporarily. |
|
|
2549 | |
|
|
2550 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2551 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2552 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2553 | |
|
|
2554 | =head3 The special problem of threads signal handling |
|
|
2555 | |
|
|
2556 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2557 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2558 | threads in a process block signals, which is hard to achieve. |
|
|
2559 | |
|
|
2560 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2561 | for the same signals), you can tackle this problem by globally blocking |
|
|
2562 | all signals before creating any threads (or creating them with a fully set |
|
|
2563 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2564 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2565 | these signals. You can pass on any signals that libev might be interested |
|
|
2566 | in by calling C<ev_feed_signal>. |
1470 | |
2567 | |
1471 | =head3 Watcher-Specific Functions and Data Members |
2568 | =head3 Watcher-Specific Functions and Data Members |
1472 | |
2569 | |
1473 | =over 4 |
2570 | =over 4 |
1474 | |
2571 | |
… | |
… | |
1485 | |
2582 | |
1486 | =back |
2583 | =back |
1487 | |
2584 | |
1488 | =head3 Examples |
2585 | =head3 Examples |
1489 | |
2586 | |
1490 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2587 | Example: Try to exit cleanly on SIGINT. |
1491 | |
2588 | |
1492 | static void |
2589 | static void |
1493 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2590 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1494 | { |
2591 | { |
1495 | ev_unloop (loop, EVUNLOOP_ALL); |
2592 | ev_break (loop, EVBREAK_ALL); |
1496 | } |
2593 | } |
1497 | |
2594 | |
1498 | struct ev_signal signal_watcher; |
2595 | ev_signal signal_watcher; |
1499 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2596 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1500 | ev_signal_start (loop, &sigint_cb); |
2597 | ev_signal_start (loop, &signal_watcher); |
1501 | |
2598 | |
1502 | |
2599 | |
1503 | =head2 C<ev_child> - watch out for process status changes |
2600 | =head2 C<ev_child> - watch out for process status changes |
1504 | |
2601 | |
1505 | Child watchers trigger when your process receives a SIGCHLD in response to |
2602 | Child watchers trigger when your process receives a SIGCHLD in response to |
1506 | some child status changes (most typically when a child of yours dies). It |
2603 | some child status changes (most typically when a child of yours dies or |
1507 | is permissible to install a child watcher I<after> the child has been |
2604 | exits). It is permissible to install a child watcher I<after> the child |
1508 | forked (which implies it might have already exited), as long as the event |
2605 | has been forked (which implies it might have already exited), as long |
1509 | loop isn't entered (or is continued from a watcher). |
2606 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2607 | forking and then immediately registering a watcher for the child is fine, |
|
|
2608 | but forking and registering a watcher a few event loop iterations later or |
|
|
2609 | in the next callback invocation is not. |
1510 | |
2610 | |
1511 | Only the default event loop is capable of handling signals, and therefore |
2611 | Only the default event loop is capable of handling signals, and therefore |
1512 | you can only rgeister child watchers in the default event loop. |
2612 | you can only register child watchers in the default event loop. |
|
|
2613 | |
|
|
2614 | Due to some design glitches inside libev, child watchers will always be |
|
|
2615 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2616 | libev) |
1513 | |
2617 | |
1514 | =head3 Process Interaction |
2618 | =head3 Process Interaction |
1515 | |
2619 | |
1516 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2620 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1517 | initialised. This is necessary to guarantee proper behaviour even if |
2621 | initialised. This is necessary to guarantee proper behaviour even if the |
1518 | the first child watcher is started after the child exits. The occurance |
2622 | first child watcher is started after the child exits. The occurrence |
1519 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2623 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1520 | synchronously as part of the event loop processing. Libev always reaps all |
2624 | synchronously as part of the event loop processing. Libev always reaps all |
1521 | children, even ones not watched. |
2625 | children, even ones not watched. |
1522 | |
2626 | |
1523 | =head3 Overriding the Built-In Processing |
2627 | =head3 Overriding the Built-In Processing |
… | |
… | |
1527 | handler, you can override it easily by installing your own handler for |
2631 | handler, you can override it easily by installing your own handler for |
1528 | C<SIGCHLD> after initialising the default loop, and making sure the |
2632 | C<SIGCHLD> after initialising the default loop, and making sure the |
1529 | default loop never gets destroyed. You are encouraged, however, to use an |
2633 | default loop never gets destroyed. You are encouraged, however, to use an |
1530 | event-based approach to child reaping and thus use libev's support for |
2634 | event-based approach to child reaping and thus use libev's support for |
1531 | that, so other libev users can use C<ev_child> watchers freely. |
2635 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
2636 | |
|
|
2637 | =head3 Stopping the Child Watcher |
|
|
2638 | |
|
|
2639 | Currently, the child watcher never gets stopped, even when the |
|
|
2640 | child terminates, so normally one needs to stop the watcher in the |
|
|
2641 | callback. Future versions of libev might stop the watcher automatically |
|
|
2642 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2643 | problem). |
1532 | |
2644 | |
1533 | =head3 Watcher-Specific Functions and Data Members |
2645 | =head3 Watcher-Specific Functions and Data Members |
1534 | |
2646 | |
1535 | =over 4 |
2647 | =over 4 |
1536 | |
2648 | |
… | |
… | |
1565 | =head3 Examples |
2677 | =head3 Examples |
1566 | |
2678 | |
1567 | Example: C<fork()> a new process and install a child handler to wait for |
2679 | Example: C<fork()> a new process and install a child handler to wait for |
1568 | its completion. |
2680 | its completion. |
1569 | |
2681 | |
1570 | ev_child cw; |
2682 | ev_child cw; |
1571 | |
2683 | |
1572 | static void |
2684 | static void |
1573 | child_cb (EV_P_ struct ev_child *w, int revents) |
2685 | child_cb (EV_P_ ev_child *w, int revents) |
1574 | { |
2686 | { |
1575 | ev_child_stop (EV_A_ w); |
2687 | ev_child_stop (EV_A_ w); |
1576 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2688 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1577 | } |
2689 | } |
1578 | |
2690 | |
1579 | pid_t pid = fork (); |
2691 | pid_t pid = fork (); |
1580 | |
2692 | |
1581 | if (pid < 0) |
2693 | if (pid < 0) |
1582 | // error |
2694 | // error |
1583 | else if (pid == 0) |
2695 | else if (pid == 0) |
1584 | { |
2696 | { |
1585 | // the forked child executes here |
2697 | // the forked child executes here |
1586 | exit (1); |
2698 | exit (1); |
1587 | } |
2699 | } |
1588 | else |
2700 | else |
1589 | { |
2701 | { |
1590 | ev_child_init (&cw, child_cb, pid, 0); |
2702 | ev_child_init (&cw, child_cb, pid, 0); |
1591 | ev_child_start (EV_DEFAULT_ &cw); |
2703 | ev_child_start (EV_DEFAULT_ &cw); |
1592 | } |
2704 | } |
1593 | |
2705 | |
1594 | |
2706 | |
1595 | =head2 C<ev_stat> - did the file attributes just change? |
2707 | =head2 C<ev_stat> - did the file attributes just change? |
1596 | |
2708 | |
1597 | This watches a filesystem path for attribute changes. That is, it calls |
2709 | This watches a file system path for attribute changes. That is, it calls |
1598 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2710 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1599 | compared to the last time, invoking the callback if it did. |
2711 | and sees if it changed compared to the last time, invoking the callback |
|
|
2712 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2713 | happen after the watcher has been started will be reported. |
1600 | |
2714 | |
1601 | The path does not need to exist: changing from "path exists" to "path does |
2715 | The path does not need to exist: changing from "path exists" to "path does |
1602 | not exist" is a status change like any other. The condition "path does |
2716 | not exist" is a status change like any other. The condition "path does not |
1603 | not exist" is signified by the C<st_nlink> field being zero (which is |
2717 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1604 | otherwise always forced to be at least one) and all the other fields of |
2718 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1605 | the stat buffer having unspecified contents. |
2719 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2720 | contents. |
1606 | |
2721 | |
1607 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2722 | The path I<must not> end in a slash or contain special components such as |
|
|
2723 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1608 | relative and your working directory changes, the behaviour is undefined. |
2724 | your working directory changes, then the behaviour is undefined. |
1609 | |
2725 | |
1610 | Since there is no standard to do this, the portable implementation simply |
2726 | Since there is no portable change notification interface available, the |
1611 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
2727 | portable implementation simply calls C<stat(2)> regularly on the path |
1612 | can specify a recommended polling interval for this case. If you specify |
2728 | to see if it changed somehow. You can specify a recommended polling |
1613 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
2729 | interval for this case. If you specify a polling interval of C<0> (highly |
1614 | unspecified default> value will be used (which you can expect to be around |
2730 | recommended!) then a I<suitable, unspecified default> value will be used |
1615 | five seconds, although this might change dynamically). Libev will also |
2731 | (which you can expect to be around five seconds, although this might |
1616 | impose a minimum interval which is currently around C<0.1>, but thats |
2732 | change dynamically). Libev will also impose a minimum interval which is |
1617 | usually overkill. |
2733 | currently around C<0.1>, but that's usually overkill. |
1618 | |
2734 | |
1619 | This watcher type is not meant for massive numbers of stat watchers, |
2735 | This watcher type is not meant for massive numbers of stat watchers, |
1620 | as even with OS-supported change notifications, this can be |
2736 | as even with OS-supported change notifications, this can be |
1621 | resource-intensive. |
2737 | resource-intensive. |
1622 | |
2738 | |
1623 | At the time of this writing, only the Linux inotify interface is |
2739 | At the time of this writing, the only OS-specific interface implemented |
1624 | implemented (implementing kqueue support is left as an exercise for the |
2740 | is the Linux inotify interface (implementing kqueue support is left as an |
1625 | reader, note, however, that the author sees no way of implementing ev_stat |
2741 | exercise for the reader. Note, however, that the author sees no way of |
1626 | semantics with kqueue). Inotify will be used to give hints only and should |
2742 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1627 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1628 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1629 | but changes are usually detected immediately, and if the file exists there |
|
|
1630 | will be no polling. |
|
|
1631 | |
2743 | |
1632 | =head3 ABI Issues (Largefile Support) |
2744 | =head3 ABI Issues (Largefile Support) |
1633 | |
2745 | |
1634 | Libev by default (unless the user overrides this) uses the default |
2746 | Libev by default (unless the user overrides this) uses the default |
1635 | compilation environment, which means that on systems with optionally |
2747 | compilation environment, which means that on systems with large file |
1636 | disabled large file support, you get the 32 bit version of the stat |
2748 | support disabled by default, you get the 32 bit version of the stat |
1637 | structure. When using the library from programs that change the ABI to |
2749 | structure. When using the library from programs that change the ABI to |
1638 | use 64 bit file offsets the programs will fail. In that case you have to |
2750 | use 64 bit file offsets the programs will fail. In that case you have to |
1639 | compile libev with the same flags to get binary compatibility. This is |
2751 | compile libev with the same flags to get binary compatibility. This is |
1640 | obviously the case with any flags that change the ABI, but the problem is |
2752 | obviously the case with any flags that change the ABI, but the problem is |
1641 | most noticably with ev_stat and largefile support. |
2753 | most noticeably displayed with ev_stat and large file support. |
1642 | |
2754 | |
1643 | =head3 Inotify |
2755 | The solution for this is to lobby your distribution maker to make large |
|
|
2756 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
2757 | optional. Libev cannot simply switch on large file support because it has |
|
|
2758 | to exchange stat structures with application programs compiled using the |
|
|
2759 | default compilation environment. |
1644 | |
2760 | |
|
|
2761 | =head3 Inotify and Kqueue |
|
|
2762 | |
1645 | When C<inotify (7)> support has been compiled into libev (generally only |
2763 | When C<inotify (7)> support has been compiled into libev and present at |
1646 | available on Linux) and present at runtime, it will be used to speed up |
2764 | runtime, it will be used to speed up change detection where possible. The |
1647 | change detection where possible. The inotify descriptor will be created lazily |
2765 | inotify descriptor will be created lazily when the first C<ev_stat> |
1648 | when the first C<ev_stat> watcher is being started. |
2766 | watcher is being started. |
1649 | |
2767 | |
1650 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2768 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1651 | except that changes might be detected earlier, and in some cases, to avoid |
2769 | except that changes might be detected earlier, and in some cases, to avoid |
1652 | making regular C<stat> calls. Even in the presence of inotify support |
2770 | making regular C<stat> calls. Even in the presence of inotify support |
1653 | there are many cases where libev has to resort to regular C<stat> polling. |
2771 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2772 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2773 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2774 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2775 | xfs are fully working) libev usually gets away without polling. |
1654 | |
2776 | |
1655 | (There is no support for kqueue, as apparently it cannot be used to |
2777 | There is no support for kqueue, as apparently it cannot be used to |
1656 | implement this functionality, due to the requirement of having a file |
2778 | implement this functionality, due to the requirement of having a file |
1657 | descriptor open on the object at all times). |
2779 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2780 | etc. is difficult. |
|
|
2781 | |
|
|
2782 | =head3 C<stat ()> is a synchronous operation |
|
|
2783 | |
|
|
2784 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2785 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2786 | ()>, which is a synchronous operation. |
|
|
2787 | |
|
|
2788 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2789 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2790 | as the path data is usually in memory already (except when starting the |
|
|
2791 | watcher). |
|
|
2792 | |
|
|
2793 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2794 | time due to network issues, and even under good conditions, a stat call |
|
|
2795 | often takes multiple milliseconds. |
|
|
2796 | |
|
|
2797 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2798 | paths, although this is fully supported by libev. |
1658 | |
2799 | |
1659 | =head3 The special problem of stat time resolution |
2800 | =head3 The special problem of stat time resolution |
1660 | |
2801 | |
1661 | The C<stat ()> syscall only supports full-second resolution portably, and |
2802 | The C<stat ()> system call only supports full-second resolution portably, |
1662 | even on systems where the resolution is higher, many filesystems still |
2803 | and even on systems where the resolution is higher, most file systems |
1663 | only support whole seconds. |
2804 | still only support whole seconds. |
1664 | |
2805 | |
1665 | That means that, if the time is the only thing that changes, you can |
2806 | That means that, if the time is the only thing that changes, you can |
1666 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2807 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1667 | calls your callback, which does something. When there is another update |
2808 | calls your callback, which does something. When there is another update |
1668 | within the same second, C<ev_stat> will be unable to detect it as the stat |
2809 | within the same second, C<ev_stat> will be unable to detect unless the |
1669 | data does not change. |
2810 | stat data does change in other ways (e.g. file size). |
1670 | |
2811 | |
1671 | The solution to this is to delay acting on a change for slightly more |
2812 | The solution to this is to delay acting on a change for slightly more |
1672 | than a second (or till slightly after the next full second boundary), using |
2813 | than a second (or till slightly after the next full second boundary), using |
1673 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
2814 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1674 | ev_timer_again (loop, w)>). |
2815 | ev_timer_again (loop, w)>). |
… | |
… | |
1694 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2835 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1695 | be detected and should normally be specified as C<0> to let libev choose |
2836 | be detected and should normally be specified as C<0> to let libev choose |
1696 | a suitable value. The memory pointed to by C<path> must point to the same |
2837 | a suitable value. The memory pointed to by C<path> must point to the same |
1697 | path for as long as the watcher is active. |
2838 | path for as long as the watcher is active. |
1698 | |
2839 | |
1699 | The callback will receive C<EV_STAT> when a change was detected, relative |
2840 | The callback will receive an C<EV_STAT> event when a change was detected, |
1700 | to the attributes at the time the watcher was started (or the last change |
2841 | relative to the attributes at the time the watcher was started (or the |
1701 | was detected). |
2842 | last change was detected). |
1702 | |
2843 | |
1703 | =item ev_stat_stat (loop, ev_stat *) |
2844 | =item ev_stat_stat (loop, ev_stat *) |
1704 | |
2845 | |
1705 | Updates the stat buffer immediately with new values. If you change the |
2846 | Updates the stat buffer immediately with new values. If you change the |
1706 | watched path in your callback, you could call this function to avoid |
2847 | watched path in your callback, you could call this function to avoid |
… | |
… | |
1727 | |
2868 | |
1728 | The specified interval. |
2869 | The specified interval. |
1729 | |
2870 | |
1730 | =item const char *path [read-only] |
2871 | =item const char *path [read-only] |
1731 | |
2872 | |
1732 | The filesystem path that is being watched. |
2873 | The file system path that is being watched. |
1733 | |
2874 | |
1734 | =back |
2875 | =back |
1735 | |
2876 | |
1736 | =head3 Examples |
2877 | =head3 Examples |
1737 | |
2878 | |
1738 | Example: Watch C</etc/passwd> for attribute changes. |
2879 | Example: Watch C</etc/passwd> for attribute changes. |
1739 | |
2880 | |
1740 | static void |
2881 | static void |
1741 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
2882 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
1742 | { |
2883 | { |
1743 | /* /etc/passwd changed in some way */ |
2884 | /* /etc/passwd changed in some way */ |
1744 | if (w->attr.st_nlink) |
2885 | if (w->attr.st_nlink) |
1745 | { |
2886 | { |
1746 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
2887 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
1747 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
2888 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
1748 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
2889 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
1749 | } |
2890 | } |
1750 | else |
2891 | else |
1751 | /* you shalt not abuse printf for puts */ |
2892 | /* you shalt not abuse printf for puts */ |
1752 | puts ("wow, /etc/passwd is not there, expect problems. " |
2893 | puts ("wow, /etc/passwd is not there, expect problems. " |
1753 | "if this is windows, they already arrived\n"); |
2894 | "if this is windows, they already arrived\n"); |
1754 | } |
2895 | } |
1755 | |
2896 | |
1756 | ... |
2897 | ... |
1757 | ev_stat passwd; |
2898 | ev_stat passwd; |
1758 | |
2899 | |
1759 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
2900 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
1760 | ev_stat_start (loop, &passwd); |
2901 | ev_stat_start (loop, &passwd); |
1761 | |
2902 | |
1762 | Example: Like above, but additionally use a one-second delay so we do not |
2903 | Example: Like above, but additionally use a one-second delay so we do not |
1763 | miss updates (however, frequent updates will delay processing, too, so |
2904 | miss updates (however, frequent updates will delay processing, too, so |
1764 | one might do the work both on C<ev_stat> callback invocation I<and> on |
2905 | one might do the work both on C<ev_stat> callback invocation I<and> on |
1765 | C<ev_timer> callback invocation). |
2906 | C<ev_timer> callback invocation). |
1766 | |
2907 | |
1767 | static ev_stat passwd; |
2908 | static ev_stat passwd; |
1768 | static ev_timer timer; |
2909 | static ev_timer timer; |
1769 | |
2910 | |
1770 | static void |
2911 | static void |
1771 | timer_cb (EV_P_ ev_timer *w, int revents) |
2912 | timer_cb (EV_P_ ev_timer *w, int revents) |
1772 | { |
2913 | { |
1773 | ev_timer_stop (EV_A_ w); |
2914 | ev_timer_stop (EV_A_ w); |
1774 | |
2915 | |
1775 | /* now it's one second after the most recent passwd change */ |
2916 | /* now it's one second after the most recent passwd change */ |
1776 | } |
2917 | } |
1777 | |
2918 | |
1778 | static void |
2919 | static void |
1779 | stat_cb (EV_P_ ev_stat *w, int revents) |
2920 | stat_cb (EV_P_ ev_stat *w, int revents) |
1780 | { |
2921 | { |
1781 | /* reset the one-second timer */ |
2922 | /* reset the one-second timer */ |
1782 | ev_timer_again (EV_A_ &timer); |
2923 | ev_timer_again (EV_A_ &timer); |
1783 | } |
2924 | } |
1784 | |
2925 | |
1785 | ... |
2926 | ... |
1786 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
2927 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1787 | ev_stat_start (loop, &passwd); |
2928 | ev_stat_start (loop, &passwd); |
1788 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
2929 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1789 | |
2930 | |
1790 | |
2931 | |
1791 | =head2 C<ev_idle> - when you've got nothing better to do... |
2932 | =head2 C<ev_idle> - when you've got nothing better to do... |
1792 | |
2933 | |
1793 | Idle watchers trigger events when no other events of the same or higher |
2934 | Idle watchers trigger events when no other events of the same or higher |
1794 | priority are pending (prepare, check and other idle watchers do not |
2935 | priority are pending (prepare, check and other idle watchers do not count |
1795 | count). |
2936 | as receiving "events"). |
1796 | |
2937 | |
1797 | That is, as long as your process is busy handling sockets or timeouts |
2938 | That is, as long as your process is busy handling sockets or timeouts |
1798 | (or even signals, imagine) of the same or higher priority it will not be |
2939 | (or even signals, imagine) of the same or higher priority it will not be |
1799 | triggered. But when your process is idle (or only lower-priority watchers |
2940 | triggered. But when your process is idle (or only lower-priority watchers |
1800 | are pending), the idle watchers are being called once per event loop |
2941 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1807 | Apart from keeping your process non-blocking (which is a useful |
2948 | Apart from keeping your process non-blocking (which is a useful |
1808 | effect on its own sometimes), idle watchers are a good place to do |
2949 | effect on its own sometimes), idle watchers are a good place to do |
1809 | "pseudo-background processing", or delay processing stuff to after the |
2950 | "pseudo-background processing", or delay processing stuff to after the |
1810 | event loop has handled all outstanding events. |
2951 | event loop has handled all outstanding events. |
1811 | |
2952 | |
|
|
2953 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2954 | |
|
|
2955 | As long as there is at least one active idle watcher, libev will never |
|
|
2956 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2957 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2958 | lowest priority will do. |
|
|
2959 | |
|
|
2960 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2961 | to do something on each event loop iteration - for example to balance load |
|
|
2962 | between different connections. |
|
|
2963 | |
|
|
2964 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2965 | example. |
|
|
2966 | |
1812 | =head3 Watcher-Specific Functions and Data Members |
2967 | =head3 Watcher-Specific Functions and Data Members |
1813 | |
2968 | |
1814 | =over 4 |
2969 | =over 4 |
1815 | |
2970 | |
1816 | =item ev_idle_init (ev_signal *, callback) |
2971 | =item ev_idle_init (ev_idle *, callback) |
1817 | |
2972 | |
1818 | Initialises and configures the idle watcher - it has no parameters of any |
2973 | Initialises and configures the idle watcher - it has no parameters of any |
1819 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2974 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1820 | believe me. |
2975 | believe me. |
1821 | |
2976 | |
… | |
… | |
1824 | =head3 Examples |
2979 | =head3 Examples |
1825 | |
2980 | |
1826 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2981 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1827 | callback, free it. Also, use no error checking, as usual. |
2982 | callback, free it. Also, use no error checking, as usual. |
1828 | |
2983 | |
1829 | static void |
2984 | static void |
1830 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2985 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1831 | { |
2986 | { |
|
|
2987 | // stop the watcher |
|
|
2988 | ev_idle_stop (loop, w); |
|
|
2989 | |
|
|
2990 | // now we can free it |
1832 | free (w); |
2991 | free (w); |
|
|
2992 | |
1833 | // now do something you wanted to do when the program has |
2993 | // now do something you wanted to do when the program has |
1834 | // no longer anything immediate to do. |
2994 | // no longer anything immediate to do. |
1835 | } |
2995 | } |
1836 | |
2996 | |
1837 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2997 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1838 | ev_idle_init (idle_watcher, idle_cb); |
2998 | ev_idle_init (idle_watcher, idle_cb); |
1839 | ev_idle_start (loop, idle_cb); |
2999 | ev_idle_start (loop, idle_watcher); |
1840 | |
3000 | |
1841 | |
3001 | |
1842 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
3002 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1843 | |
3003 | |
1844 | Prepare and check watchers are usually (but not always) used in tandem: |
3004 | Prepare and check watchers are often (but not always) used in pairs: |
1845 | prepare watchers get invoked before the process blocks and check watchers |
3005 | prepare watchers get invoked before the process blocks and check watchers |
1846 | afterwards. |
3006 | afterwards. |
1847 | |
3007 | |
1848 | You I<must not> call C<ev_loop> or similar functions that enter |
3008 | You I<must not> call C<ev_run> (or similar functions that enter the |
1849 | the current event loop from either C<ev_prepare> or C<ev_check> |
3009 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
1850 | watchers. Other loops than the current one are fine, however. The |
3010 | C<ev_check> watchers. Other loops than the current one are fine, |
1851 | rationale behind this is that you do not need to check for recursion in |
3011 | however. The rationale behind this is that you do not need to check |
1852 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
3012 | for recursion in those watchers, i.e. the sequence will always be |
1853 | C<ev_check> so if you have one watcher of each kind they will always be |
3013 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
1854 | called in pairs bracketing the blocking call. |
3014 | kind they will always be called in pairs bracketing the blocking call. |
1855 | |
3015 | |
1856 | Their main purpose is to integrate other event mechanisms into libev and |
3016 | Their main purpose is to integrate other event mechanisms into libev and |
1857 | their use is somewhat advanced. This could be used, for example, to track |
3017 | their use is somewhat advanced. They could be used, for example, to track |
1858 | variable changes, implement your own watchers, integrate net-snmp or a |
3018 | variable changes, implement your own watchers, integrate net-snmp or a |
1859 | coroutine library and lots more. They are also occasionally useful if |
3019 | coroutine library and lots more. They are also occasionally useful if |
1860 | you cache some data and want to flush it before blocking (for example, |
3020 | you cache some data and want to flush it before blocking (for example, |
1861 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
3021 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1862 | watcher). |
3022 | watcher). |
1863 | |
3023 | |
1864 | This is done by examining in each prepare call which file descriptors need |
3024 | This is done by examining in each prepare call which file descriptors |
1865 | to be watched by the other library, registering C<ev_io> watchers for |
3025 | need to be watched by the other library, registering C<ev_io> watchers |
1866 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
3026 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1867 | provide just this functionality). Then, in the check watcher you check for |
3027 | libraries provide exactly this functionality). Then, in the check watcher, |
1868 | any events that occured (by checking the pending status of all watchers |
3028 | you check for any events that occurred (by checking the pending status |
1869 | and stopping them) and call back into the library. The I/O and timer |
3029 | of all watchers and stopping them) and call back into the library. The |
1870 | callbacks will never actually be called (but must be valid nevertheless, |
3030 | I/O and timer callbacks will never actually be called (but must be valid |
1871 | because you never know, you know?). |
3031 | nevertheless, because you never know, you know?). |
1872 | |
3032 | |
1873 | As another example, the Perl Coro module uses these hooks to integrate |
3033 | As another example, the Perl Coro module uses these hooks to integrate |
1874 | coroutines into libev programs, by yielding to other active coroutines |
3034 | coroutines into libev programs, by yielding to other active coroutines |
1875 | during each prepare and only letting the process block if no coroutines |
3035 | during each prepare and only letting the process block if no coroutines |
1876 | are ready to run (it's actually more complicated: it only runs coroutines |
3036 | are ready to run (it's actually more complicated: it only runs coroutines |
1877 | with priority higher than or equal to the event loop and one coroutine |
3037 | with priority higher than or equal to the event loop and one coroutine |
1878 | of lower priority, but only once, using idle watchers to keep the event |
3038 | of lower priority, but only once, using idle watchers to keep the event |
1879 | loop from blocking if lower-priority coroutines are active, thus mapping |
3039 | loop from blocking if lower-priority coroutines are active, thus mapping |
1880 | low-priority coroutines to idle/background tasks). |
3040 | low-priority coroutines to idle/background tasks). |
1881 | |
3041 | |
1882 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
3042 | When used for this purpose, it is recommended to give C<ev_check> watchers |
1883 | priority, to ensure that they are being run before any other watchers |
3043 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
|
|
3044 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
3045 | watchers). |
|
|
3046 | |
1884 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
3047 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1885 | too) should not activate ("feed") events into libev. While libev fully |
3048 | activate ("feed") events into libev. While libev fully supports this, they |
1886 | supports this, they might get executed before other C<ev_check> watchers |
3049 | might get executed before other C<ev_check> watchers did their job. As |
1887 | did their job. As C<ev_check> watchers are often used to embed other |
3050 | C<ev_check> watchers are often used to embed other (non-libev) event |
1888 | (non-libev) event loops those other event loops might be in an unusable |
3051 | loops those other event loops might be in an unusable state until their |
1889 | state until their C<ev_check> watcher ran (always remind yourself to |
3052 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1890 | coexist peacefully with others). |
3053 | others). |
|
|
3054 | |
|
|
3055 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
3056 | |
|
|
3057 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
3058 | useful because they are called once per event loop iteration. For |
|
|
3059 | example, if you want to handle a large number of connections fairly, you |
|
|
3060 | normally only do a bit of work for each active connection, and if there |
|
|
3061 | is more work to do, you wait for the next event loop iteration, so other |
|
|
3062 | connections have a chance of making progress. |
|
|
3063 | |
|
|
3064 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
3065 | next event loop iteration. However, that isn't as soon as possible - |
|
|
3066 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
3067 | |
|
|
3068 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
3069 | single global idle watcher that is active as long as you have one active |
|
|
3070 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
3071 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
3072 | invoked. Neither watcher alone can do that. |
1891 | |
3073 | |
1892 | =head3 Watcher-Specific Functions and Data Members |
3074 | =head3 Watcher-Specific Functions and Data Members |
1893 | |
3075 | |
1894 | =over 4 |
3076 | =over 4 |
1895 | |
3077 | |
… | |
… | |
1897 | |
3079 | |
1898 | =item ev_check_init (ev_check *, callback) |
3080 | =item ev_check_init (ev_check *, callback) |
1899 | |
3081 | |
1900 | Initialises and configures the prepare or check watcher - they have no |
3082 | Initialises and configures the prepare or check watcher - they have no |
1901 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
3083 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1902 | macros, but using them is utterly, utterly and completely pointless. |
3084 | macros, but using them is utterly, utterly, utterly and completely |
|
|
3085 | pointless. |
1903 | |
3086 | |
1904 | =back |
3087 | =back |
1905 | |
3088 | |
1906 | =head3 Examples |
3089 | =head3 Examples |
1907 | |
3090 | |
… | |
… | |
1916 | and in a check watcher, destroy them and call into libadns. What follows |
3099 | and in a check watcher, destroy them and call into libadns. What follows |
1917 | is pseudo-code only of course. This requires you to either use a low |
3100 | is pseudo-code only of course. This requires you to either use a low |
1918 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
3101 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
1919 | the callbacks for the IO/timeout watchers might not have been called yet. |
3102 | the callbacks for the IO/timeout watchers might not have been called yet. |
1920 | |
3103 | |
1921 | static ev_io iow [nfd]; |
3104 | static ev_io iow [nfd]; |
1922 | static ev_timer tw; |
3105 | static ev_timer tw; |
1923 | |
3106 | |
1924 | static void |
3107 | static void |
1925 | io_cb (ev_loop *loop, ev_io *w, int revents) |
3108 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
1926 | { |
3109 | { |
1927 | } |
3110 | } |
1928 | |
3111 | |
1929 | // create io watchers for each fd and a timer before blocking |
3112 | // create io watchers for each fd and a timer before blocking |
1930 | static void |
3113 | static void |
1931 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
3114 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
1932 | { |
3115 | { |
1933 | int timeout = 3600000; |
3116 | int timeout = 3600000; |
1934 | struct pollfd fds [nfd]; |
3117 | struct pollfd fds [nfd]; |
1935 | // actual code will need to loop here and realloc etc. |
3118 | // actual code will need to loop here and realloc etc. |
1936 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
3119 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1937 | |
3120 | |
1938 | /* the callback is illegal, but won't be called as we stop during check */ |
3121 | /* the callback is illegal, but won't be called as we stop during check */ |
1939 | ev_timer_init (&tw, 0, timeout * 1e-3); |
3122 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
1940 | ev_timer_start (loop, &tw); |
3123 | ev_timer_start (loop, &tw); |
1941 | |
3124 | |
1942 | // create one ev_io per pollfd |
3125 | // create one ev_io per pollfd |
1943 | for (int i = 0; i < nfd; ++i) |
3126 | for (int i = 0; i < nfd; ++i) |
1944 | { |
3127 | { |
1945 | ev_io_init (iow + i, io_cb, fds [i].fd, |
3128 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1946 | ((fds [i].events & POLLIN ? EV_READ : 0) |
3129 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1947 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
3130 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1948 | |
3131 | |
1949 | fds [i].revents = 0; |
3132 | fds [i].revents = 0; |
1950 | ev_io_start (loop, iow + i); |
3133 | ev_io_start (loop, iow + i); |
1951 | } |
3134 | } |
1952 | } |
3135 | } |
1953 | |
3136 | |
1954 | // stop all watchers after blocking |
3137 | // stop all watchers after blocking |
1955 | static void |
3138 | static void |
1956 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
3139 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
1957 | { |
3140 | { |
1958 | ev_timer_stop (loop, &tw); |
3141 | ev_timer_stop (loop, &tw); |
1959 | |
3142 | |
1960 | for (int i = 0; i < nfd; ++i) |
3143 | for (int i = 0; i < nfd; ++i) |
1961 | { |
3144 | { |
1962 | // set the relevant poll flags |
3145 | // set the relevant poll flags |
1963 | // could also call adns_processreadable etc. here |
3146 | // could also call adns_processreadable etc. here |
1964 | struct pollfd *fd = fds + i; |
3147 | struct pollfd *fd = fds + i; |
1965 | int revents = ev_clear_pending (iow + i); |
3148 | int revents = ev_clear_pending (iow + i); |
1966 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
3149 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
1967 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
3150 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
1968 | |
3151 | |
1969 | // now stop the watcher |
3152 | // now stop the watcher |
1970 | ev_io_stop (loop, iow + i); |
3153 | ev_io_stop (loop, iow + i); |
1971 | } |
3154 | } |
1972 | |
3155 | |
1973 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
3156 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1974 | } |
3157 | } |
1975 | |
3158 | |
1976 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
3159 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
1977 | in the prepare watcher and would dispose of the check watcher. |
3160 | in the prepare watcher and would dispose of the check watcher. |
1978 | |
3161 | |
1979 | Method 3: If the module to be embedded supports explicit event |
3162 | Method 3: If the module to be embedded supports explicit event |
1980 | notification (adns does), you can also make use of the actual watcher |
3163 | notification (libadns does), you can also make use of the actual watcher |
1981 | callbacks, and only destroy/create the watchers in the prepare watcher. |
3164 | callbacks, and only destroy/create the watchers in the prepare watcher. |
1982 | |
3165 | |
1983 | static void |
3166 | static void |
1984 | timer_cb (EV_P_ ev_timer *w, int revents) |
3167 | timer_cb (EV_P_ ev_timer *w, int revents) |
1985 | { |
3168 | { |
1986 | adns_state ads = (adns_state)w->data; |
3169 | adns_state ads = (adns_state)w->data; |
1987 | update_now (EV_A); |
3170 | update_now (EV_A); |
1988 | |
3171 | |
1989 | adns_processtimeouts (ads, &tv_now); |
3172 | adns_processtimeouts (ads, &tv_now); |
1990 | } |
3173 | } |
1991 | |
3174 | |
1992 | static void |
3175 | static void |
1993 | io_cb (EV_P_ ev_io *w, int revents) |
3176 | io_cb (EV_P_ ev_io *w, int revents) |
1994 | { |
3177 | { |
1995 | adns_state ads = (adns_state)w->data; |
3178 | adns_state ads = (adns_state)w->data; |
1996 | update_now (EV_A); |
3179 | update_now (EV_A); |
1997 | |
3180 | |
1998 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
3181 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
1999 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
3182 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
2000 | } |
3183 | } |
2001 | |
3184 | |
2002 | // do not ever call adns_afterpoll |
3185 | // do not ever call adns_afterpoll |
2003 | |
3186 | |
2004 | Method 4: Do not use a prepare or check watcher because the module you |
3187 | Method 4: Do not use a prepare or check watcher because the module you |
2005 | want to embed is too inflexible to support it. Instead, youc na override |
3188 | want to embed is not flexible enough to support it. Instead, you can |
2006 | their poll function. The drawback with this solution is that the main |
3189 | override their poll function. The drawback with this solution is that the |
2007 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
3190 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
2008 | this. |
3191 | this approach, effectively embedding EV as a client into the horrible |
|
|
3192 | libglib event loop. |
2009 | |
3193 | |
2010 | static gint |
3194 | static gint |
2011 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
3195 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2012 | { |
3196 | { |
2013 | int got_events = 0; |
3197 | int got_events = 0; |
2014 | |
3198 | |
2015 | for (n = 0; n < nfds; ++n) |
3199 | for (n = 0; n < nfds; ++n) |
2016 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
3200 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
2017 | |
3201 | |
2018 | if (timeout >= 0) |
3202 | if (timeout >= 0) |
2019 | // create/start timer |
3203 | // create/start timer |
2020 | |
3204 | |
2021 | // poll |
3205 | // poll |
2022 | ev_loop (EV_A_ 0); |
3206 | ev_run (EV_A_ 0); |
2023 | |
3207 | |
2024 | // stop timer again |
3208 | // stop timer again |
2025 | if (timeout >= 0) |
3209 | if (timeout >= 0) |
2026 | ev_timer_stop (EV_A_ &to); |
3210 | ev_timer_stop (EV_A_ &to); |
2027 | |
3211 | |
2028 | // stop io watchers again - their callbacks should have set |
3212 | // stop io watchers again - their callbacks should have set |
2029 | for (n = 0; n < nfds; ++n) |
3213 | for (n = 0; n < nfds; ++n) |
2030 | ev_io_stop (EV_A_ iow [n]); |
3214 | ev_io_stop (EV_A_ iow [n]); |
2031 | |
3215 | |
2032 | return got_events; |
3216 | return got_events; |
2033 | } |
3217 | } |
2034 | |
3218 | |
2035 | |
3219 | |
2036 | =head2 C<ev_embed> - when one backend isn't enough... |
3220 | =head2 C<ev_embed> - when one backend isn't enough... |
2037 | |
3221 | |
2038 | This is a rather advanced watcher type that lets you embed one event loop |
3222 | This is a rather advanced watcher type that lets you embed one event loop |
… | |
… | |
2044 | prioritise I/O. |
3228 | prioritise I/O. |
2045 | |
3229 | |
2046 | As an example for a bug workaround, the kqueue backend might only support |
3230 | As an example for a bug workaround, the kqueue backend might only support |
2047 | sockets on some platform, so it is unusable as generic backend, but you |
3231 | sockets on some platform, so it is unusable as generic backend, but you |
2048 | still want to make use of it because you have many sockets and it scales |
3232 | still want to make use of it because you have many sockets and it scales |
2049 | so nicely. In this case, you would create a kqueue-based loop and embed it |
3233 | so nicely. In this case, you would create a kqueue-based loop and embed |
2050 | into your default loop (which might use e.g. poll). Overall operation will |
3234 | it into your default loop (which might use e.g. poll). Overall operation |
2051 | be a bit slower because first libev has to poll and then call kevent, but |
3235 | will be a bit slower because first libev has to call C<poll> and then |
2052 | at least you can use both at what they are best. |
3236 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
3237 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2053 | |
3238 | |
2054 | As for prioritising I/O: rarely you have the case where some fds have |
3239 | As for prioritising I/O: under rare circumstances you have the case where |
2055 | to be watched and handled very quickly (with low latency), and even |
3240 | some fds have to be watched and handled very quickly (with low latency), |
2056 | priorities and idle watchers might have too much overhead. In this case |
3241 | and even priorities and idle watchers might have too much overhead. In |
2057 | you would put all the high priority stuff in one loop and all the rest in |
3242 | this case you would put all the high priority stuff in one loop and all |
2058 | a second one, and embed the second one in the first. |
3243 | the rest in a second one, and embed the second one in the first. |
2059 | |
3244 | |
2060 | As long as the watcher is active, the callback will be invoked every time |
3245 | As long as the watcher is active, the callback will be invoked every |
2061 | there might be events pending in the embedded loop. The callback must then |
3246 | time there might be events pending in the embedded loop. The callback |
2062 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
3247 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2063 | their callbacks (you could also start an idle watcher to give the embedded |
3248 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2064 | loop strictly lower priority for example). You can also set the callback |
3249 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2065 | to C<0>, in which case the embed watcher will automatically execute the |
3250 | to give the embedded loop strictly lower priority for example). |
2066 | embedded loop sweep. |
|
|
2067 | |
3251 | |
2068 | As long as the watcher is started it will automatically handle events. The |
3252 | You can also set the callback to C<0>, in which case the embed watcher |
2069 | callback will be invoked whenever some events have been handled. You can |
3253 | will automatically execute the embedded loop sweep whenever necessary. |
2070 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2071 | interested in that. |
|
|
2072 | |
3254 | |
2073 | Also, there have not currently been made special provisions for forking: |
3255 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2074 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
3256 | is active, i.e., the embedded loop will automatically be forked when the |
2075 | but you will also have to stop and restart any C<ev_embed> watchers |
3257 | embedding loop forks. In other cases, the user is responsible for calling |
2076 | yourself. |
3258 | C<ev_loop_fork> on the embedded loop. |
2077 | |
3259 | |
2078 | Unfortunately, not all backends are embeddable, only the ones returned by |
3260 | Unfortunately, not all backends are embeddable: only the ones returned by |
2079 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
3261 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2080 | portable one. |
3262 | portable one. |
2081 | |
3263 | |
2082 | So when you want to use this feature you will always have to be prepared |
3264 | So when you want to use this feature you will always have to be prepared |
2083 | that you cannot get an embeddable loop. The recommended way to get around |
3265 | that you cannot get an embeddable loop. The recommended way to get around |
2084 | this is to have a separate variables for your embeddable loop, try to |
3266 | this is to have a separate variables for your embeddable loop, try to |
2085 | create it, and if that fails, use the normal loop for everything. |
3267 | create it, and if that fails, use the normal loop for everything. |
2086 | |
3268 | |
|
|
3269 | =head3 C<ev_embed> and fork |
|
|
3270 | |
|
|
3271 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
3272 | automatically be applied to the embedded loop as well, so no special |
|
|
3273 | fork handling is required in that case. When the watcher is not running, |
|
|
3274 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
3275 | as applicable. |
|
|
3276 | |
2087 | =head3 Watcher-Specific Functions and Data Members |
3277 | =head3 Watcher-Specific Functions and Data Members |
2088 | |
3278 | |
2089 | =over 4 |
3279 | =over 4 |
2090 | |
3280 | |
2091 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3281 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2092 | |
3282 | |
2093 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3283 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
2094 | |
3284 | |
2095 | Configures the watcher to embed the given loop, which must be |
3285 | Configures the watcher to embed the given loop, which must be |
2096 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3286 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2097 | invoked automatically, otherwise it is the responsibility of the callback |
3287 | invoked automatically, otherwise it is the responsibility of the callback |
2098 | to invoke it (it will continue to be called until the sweep has been done, |
3288 | to invoke it (it will continue to be called until the sweep has been done, |
2099 | if you do not want thta, you need to temporarily stop the embed watcher). |
3289 | if you do not want that, you need to temporarily stop the embed watcher). |
2100 | |
3290 | |
2101 | =item ev_embed_sweep (loop, ev_embed *) |
3291 | =item ev_embed_sweep (loop, ev_embed *) |
2102 | |
3292 | |
2103 | Make a single, non-blocking sweep over the embedded loop. This works |
3293 | Make a single, non-blocking sweep over the embedded loop. This works |
2104 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
3294 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2105 | apropriate way for embedded loops. |
3295 | appropriate way for embedded loops. |
2106 | |
3296 | |
2107 | =item struct ev_loop *other [read-only] |
3297 | =item struct ev_loop *other [read-only] |
2108 | |
3298 | |
2109 | The embedded event loop. |
3299 | The embedded event loop. |
2110 | |
3300 | |
… | |
… | |
2112 | |
3302 | |
2113 | =head3 Examples |
3303 | =head3 Examples |
2114 | |
3304 | |
2115 | Example: Try to get an embeddable event loop and embed it into the default |
3305 | Example: Try to get an embeddable event loop and embed it into the default |
2116 | event loop. If that is not possible, use the default loop. The default |
3306 | event loop. If that is not possible, use the default loop. The default |
2117 | loop is stored in C<loop_hi>, while the mebeddable loop is stored in |
3307 | loop is stored in C<loop_hi>, while the embeddable loop is stored in |
2118 | C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be |
3308 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2119 | used). |
3309 | used). |
2120 | |
3310 | |
2121 | struct ev_loop *loop_hi = ev_default_init (0); |
3311 | struct ev_loop *loop_hi = ev_default_init (0); |
2122 | struct ev_loop *loop_lo = 0; |
3312 | struct ev_loop *loop_lo = 0; |
2123 | struct ev_embed embed; |
3313 | ev_embed embed; |
2124 | |
3314 | |
2125 | // see if there is a chance of getting one that works |
3315 | // see if there is a chance of getting one that works |
2126 | // (remember that a flags value of 0 means autodetection) |
3316 | // (remember that a flags value of 0 means autodetection) |
2127 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3317 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2128 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3318 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2129 | : 0; |
3319 | : 0; |
2130 | |
3320 | |
2131 | // if we got one, then embed it, otherwise default to loop_hi |
3321 | // if we got one, then embed it, otherwise default to loop_hi |
2132 | if (loop_lo) |
3322 | if (loop_lo) |
2133 | { |
3323 | { |
2134 | ev_embed_init (&embed, 0, loop_lo); |
3324 | ev_embed_init (&embed, 0, loop_lo); |
2135 | ev_embed_start (loop_hi, &embed); |
3325 | ev_embed_start (loop_hi, &embed); |
2136 | } |
3326 | } |
2137 | else |
3327 | else |
2138 | loop_lo = loop_hi; |
3328 | loop_lo = loop_hi; |
2139 | |
3329 | |
2140 | Example: Check if kqueue is available but not recommended and create |
3330 | Example: Check if kqueue is available but not recommended and create |
2141 | a kqueue backend for use with sockets (which usually work with any |
3331 | a kqueue backend for use with sockets (which usually work with any |
2142 | kqueue implementation). Store the kqueue/socket-only event loop in |
3332 | kqueue implementation). Store the kqueue/socket-only event loop in |
2143 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3333 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2144 | |
3334 | |
2145 | struct ev_loop *loop = ev_default_init (0); |
3335 | struct ev_loop *loop = ev_default_init (0); |
2146 | struct ev_loop *loop_socket = 0; |
3336 | struct ev_loop *loop_socket = 0; |
2147 | struct ev_embed embed; |
3337 | ev_embed embed; |
2148 | |
3338 | |
2149 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3339 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2150 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3340 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2151 | { |
3341 | { |
2152 | ev_embed_init (&embed, 0, loop_socket); |
3342 | ev_embed_init (&embed, 0, loop_socket); |
2153 | ev_embed_start (loop, &embed); |
3343 | ev_embed_start (loop, &embed); |
2154 | } |
3344 | } |
2155 | |
3345 | |
2156 | if (!loop_socket) |
3346 | if (!loop_socket) |
2157 | loop_socket = loop; |
3347 | loop_socket = loop; |
2158 | |
3348 | |
2159 | // now use loop_socket for all sockets, and loop for everything else |
3349 | // now use loop_socket for all sockets, and loop for everything else |
2160 | |
3350 | |
2161 | |
3351 | |
2162 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3352 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
2163 | |
3353 | |
2164 | Fork watchers are called when a C<fork ()> was detected (usually because |
3354 | Fork watchers are called when a C<fork ()> was detected (usually because |
2165 | whoever is a good citizen cared to tell libev about it by calling |
3355 | whoever is a good citizen cared to tell libev about it by calling |
2166 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3356 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
2167 | event loop blocks next and before C<ev_check> watchers are being called, |
3357 | and before C<ev_check> watchers are being called, and only in the child |
2168 | and only in the child after the fork. If whoever good citizen calling |
3358 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
2169 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3359 | and calls it in the wrong process, the fork handlers will be invoked, too, |
2170 | handlers will be invoked, too, of course. |
3360 | of course. |
|
|
3361 | |
|
|
3362 | =head3 The special problem of life after fork - how is it possible? |
|
|
3363 | |
|
|
3364 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
|
|
3365 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
3366 | sequence should be handled by libev without any problems. |
|
|
3367 | |
|
|
3368 | This changes when the application actually wants to do event handling |
|
|
3369 | in the child, or both parent in child, in effect "continuing" after the |
|
|
3370 | fork. |
|
|
3371 | |
|
|
3372 | The default mode of operation (for libev, with application help to detect |
|
|
3373 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3374 | when I<either> the parent I<or> the child process continues. |
|
|
3375 | |
|
|
3376 | When both processes want to continue using libev, then this is usually the |
|
|
3377 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3378 | supposed to continue with all watchers in place as before, while the other |
|
|
3379 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3380 | |
|
|
3381 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3382 | simply create a new event loop, which of course will be "empty", and |
|
|
3383 | use that for new watchers. This has the advantage of not touching more |
|
|
3384 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3385 | disadvantage of having to use multiple event loops (which do not support |
|
|
3386 | signal watchers). |
|
|
3387 | |
|
|
3388 | When this is not possible, or you want to use the default loop for |
|
|
3389 | other reasons, then in the process that wants to start "fresh", call |
|
|
3390 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
|
|
3391 | Destroying the default loop will "orphan" (not stop) all registered |
|
|
3392 | watchers, so you have to be careful not to execute code that modifies |
|
|
3393 | those watchers. Note also that in that case, you have to re-register any |
|
|
3394 | signal watchers. |
2171 | |
3395 | |
2172 | =head3 Watcher-Specific Functions and Data Members |
3396 | =head3 Watcher-Specific Functions and Data Members |
2173 | |
3397 | |
2174 | =over 4 |
3398 | =over 4 |
2175 | |
3399 | |
2176 | =item ev_fork_init (ev_signal *, callback) |
3400 | =item ev_fork_init (ev_fork *, callback) |
2177 | |
3401 | |
2178 | Initialises and configures the fork watcher - it has no parameters of any |
3402 | Initialises and configures the fork watcher - it has no parameters of any |
2179 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3403 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
2180 | believe me. |
3404 | really. |
2181 | |
3405 | |
2182 | =back |
3406 | =back |
2183 | |
3407 | |
2184 | |
3408 | |
|
|
3409 | =head2 C<ev_cleanup> - even the best things end |
|
|
3410 | |
|
|
3411 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3412 | by a call to C<ev_loop_destroy>. |
|
|
3413 | |
|
|
3414 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3415 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3416 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3417 | loop when you want them to be invoked. |
|
|
3418 | |
|
|
3419 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3420 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3421 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3422 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3423 | |
|
|
3424 | =head3 Watcher-Specific Functions and Data Members |
|
|
3425 | |
|
|
3426 | =over 4 |
|
|
3427 | |
|
|
3428 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3429 | |
|
|
3430 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3431 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3432 | pointless, I assure you. |
|
|
3433 | |
|
|
3434 | =back |
|
|
3435 | |
|
|
3436 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3437 | cleanup functions are called. |
|
|
3438 | |
|
|
3439 | static void |
|
|
3440 | program_exits (void) |
|
|
3441 | { |
|
|
3442 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3443 | } |
|
|
3444 | |
|
|
3445 | ... |
|
|
3446 | atexit (program_exits); |
|
|
3447 | |
|
|
3448 | |
2185 | =head2 C<ev_async> - how to wake up another event loop |
3449 | =head2 C<ev_async> - how to wake up an event loop |
2186 | |
3450 | |
2187 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3451 | In general, you cannot use an C<ev_loop> from multiple threads or other |
2188 | asynchronous sources such as signal handlers (as opposed to multiple event |
3452 | asynchronous sources such as signal handlers (as opposed to multiple event |
2189 | loops - those are of course safe to use in different threads). |
3453 | loops - those are of course safe to use in different threads). |
2190 | |
3454 | |
2191 | Sometimes, however, you need to wake up another event loop you do not |
3455 | Sometimes, however, you need to wake up an event loop you do not control, |
2192 | control, for example because it belongs to another thread. This is what |
3456 | for example because it belongs to another thread. This is what C<ev_async> |
2193 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3457 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2194 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3458 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2195 | safe. |
|
|
2196 | |
3459 | |
2197 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3460 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2198 | too, are asynchronous in nature, and signals, too, will be compressed |
3461 | too, are asynchronous in nature, and signals, too, will be compressed |
2199 | (i.e. the number of callback invocations may be less than the number of |
3462 | (i.e. the number of callback invocations may be less than the number of |
2200 | C<ev_async_sent> calls). |
3463 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
2201 | |
3464 | of "global async watchers" by using a watcher on an otherwise unused |
2202 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3465 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
2203 | just the default loop. |
3466 | even without knowing which loop owns the signal. |
2204 | |
3467 | |
2205 | =head3 Queueing |
3468 | =head3 Queueing |
2206 | |
3469 | |
2207 | C<ev_async> does not support queueing of data in any way. The reason |
3470 | C<ev_async> does not support queueing of data in any way. The reason |
2208 | is that the author does not know of a simple (or any) algorithm for a |
3471 | is that the author does not know of a simple (or any) algorithm for a |
2209 | multiple-writer-single-reader queue that works in all cases and doesn't |
3472 | multiple-writer-single-reader queue that works in all cases and doesn't |
2210 | need elaborate support such as pthreads. |
3473 | need elaborate support such as pthreads or unportable memory access |
|
|
3474 | semantics. |
2211 | |
3475 | |
2212 | That means that if you want to queue data, you have to provide your own |
3476 | That means that if you want to queue data, you have to provide your own |
2213 | queue. But at least I can tell you would implement locking around your |
3477 | queue. But at least I can tell you how to implement locking around your |
2214 | queue: |
3478 | queue: |
2215 | |
3479 | |
2216 | =over 4 |
3480 | =over 4 |
2217 | |
3481 | |
2218 | =item queueing from a signal handler context |
3482 | =item queueing from a signal handler context |
2219 | |
3483 | |
2220 | To implement race-free queueing, you simply add to the queue in the signal |
3484 | To implement race-free queueing, you simply add to the queue in the signal |
2221 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
3485 | handler but you block the signal handler in the watcher callback. Here is |
2222 | some fictitiuous SIGUSR1 handler: |
3486 | an example that does that for some fictitious SIGUSR1 handler: |
2223 | |
3487 | |
2224 | static ev_async mysig; |
3488 | static ev_async mysig; |
2225 | |
3489 | |
2226 | static void |
3490 | static void |
2227 | sigusr1_handler (void) |
3491 | sigusr1_handler (void) |
… | |
… | |
2293 | =over 4 |
3557 | =over 4 |
2294 | |
3558 | |
2295 | =item ev_async_init (ev_async *, callback) |
3559 | =item ev_async_init (ev_async *, callback) |
2296 | |
3560 | |
2297 | Initialises and configures the async watcher - it has no parameters of any |
3561 | Initialises and configures the async watcher - it has no parameters of any |
2298 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3562 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2299 | believe me. |
3563 | trust me. |
2300 | |
3564 | |
2301 | =item ev_async_send (loop, ev_async *) |
3565 | =item ev_async_send (loop, ev_async *) |
2302 | |
3566 | |
2303 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3567 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2304 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3568 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3569 | returns. |
|
|
3570 | |
2305 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
3571 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
2306 | similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding |
3572 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
2307 | section below on what exactly this means). |
3573 | embedding section below on what exactly this means). |
2308 | |
3574 | |
2309 | This call incurs the overhead of a syscall only once per loop iteration, |
3575 | Note that, as with other watchers in libev, multiple events might get |
2310 | so while the overhead might be noticable, it doesn't apply to repeated |
3576 | compressed into a single callback invocation (another way to look at |
2311 | calls to C<ev_async_send>. |
3577 | this is that C<ev_async> watchers are level-triggered: they are set on |
|
|
3578 | C<ev_async_send>, reset when the event loop detects that). |
|
|
3579 | |
|
|
3580 | This call incurs the overhead of at most one extra system call per event |
|
|
3581 | loop iteration, if the event loop is blocked, and no syscall at all if |
|
|
3582 | the event loop (or your program) is processing events. That means that |
|
|
3583 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3584 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3585 | zero) under load. |
2312 | |
3586 | |
2313 | =item bool = ev_async_pending (ev_async *) |
3587 | =item bool = ev_async_pending (ev_async *) |
2314 | |
3588 | |
2315 | Returns a non-zero value when C<ev_async_send> has been called on the |
3589 | Returns a non-zero value when C<ev_async_send> has been called on the |
2316 | watcher but the event has not yet been processed (or even noted) by the |
3590 | watcher but the event has not yet been processed (or even noted) by the |
2317 | event loop. |
3591 | event loop. |
2318 | |
3592 | |
2319 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3593 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2320 | the loop iterates next and checks for the watcher to have become active, |
3594 | the loop iterates next and checks for the watcher to have become active, |
2321 | it will reset the flag again. C<ev_async_pending> can be used to very |
3595 | it will reset the flag again. C<ev_async_pending> can be used to very |
2322 | quickly check wether invoking the loop might be a good idea. |
3596 | quickly check whether invoking the loop might be a good idea. |
2323 | |
3597 | |
2324 | Not that this does I<not> check wether the watcher itself is pending, only |
3598 | Not that this does I<not> check whether the watcher itself is pending, |
2325 | wether it has been requested to make this watcher pending. |
3599 | only whether it has been requested to make this watcher pending: there |
|
|
3600 | is a time window between the event loop checking and resetting the async |
|
|
3601 | notification, and the callback being invoked. |
2326 | |
3602 | |
2327 | =back |
3603 | =back |
2328 | |
3604 | |
2329 | |
3605 | |
2330 | =head1 OTHER FUNCTIONS |
3606 | =head1 OTHER FUNCTIONS |
2331 | |
3607 | |
2332 | There are some other functions of possible interest. Described. Here. Now. |
3608 | There are some other functions of possible interest. Described. Here. Now. |
2333 | |
3609 | |
2334 | =over 4 |
3610 | =over 4 |
2335 | |
3611 | |
2336 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3612 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
2337 | |
3613 | |
2338 | This function combines a simple timer and an I/O watcher, calls your |
3614 | This function combines a simple timer and an I/O watcher, calls your |
2339 | callback on whichever event happens first and automatically stop both |
3615 | callback on whichever event happens first and automatically stops both |
2340 | watchers. This is useful if you want to wait for a single event on an fd |
3616 | watchers. This is useful if you want to wait for a single event on an fd |
2341 | or timeout without having to allocate/configure/start/stop/free one or |
3617 | or timeout without having to allocate/configure/start/stop/free one or |
2342 | more watchers yourself. |
3618 | more watchers yourself. |
2343 | |
3619 | |
2344 | If C<fd> is less than 0, then no I/O watcher will be started and events |
3620 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2345 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
3621 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2346 | C<events> set will be craeted and started. |
3622 | the given C<fd> and C<events> set will be created and started. |
2347 | |
3623 | |
2348 | If C<timeout> is less than 0, then no timeout watcher will be |
3624 | If C<timeout> is less than 0, then no timeout watcher will be |
2349 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3625 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2350 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
3626 | repeat = 0) will be started. C<0> is a valid timeout. |
2351 | dubious value. |
|
|
2352 | |
3627 | |
2353 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3628 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2354 | passed an C<revents> set like normal event callbacks (a combination of |
3629 | passed an C<revents> set like normal event callbacks (a combination of |
2355 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3630 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2356 | value passed to C<ev_once>: |
3631 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
3632 | a timeout and an io event at the same time - you probably should give io |
|
|
3633 | events precedence. |
2357 | |
3634 | |
|
|
3635 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
|
|
3636 | |
2358 | static void stdin_ready (int revents, void *arg) |
3637 | static void stdin_ready (int revents, void *arg) |
|
|
3638 | { |
|
|
3639 | if (revents & EV_READ) |
|
|
3640 | /* stdin might have data for us, joy! */; |
|
|
3641 | else if (revents & EV_TIMER) |
|
|
3642 | /* doh, nothing entered */; |
|
|
3643 | } |
|
|
3644 | |
|
|
3645 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
|
|
3646 | |
|
|
3647 | =item ev_feed_fd_event (loop, int fd, int revents) |
|
|
3648 | |
|
|
3649 | Feed an event on the given fd, as if a file descriptor backend detected |
|
|
3650 | the given events. |
|
|
3651 | |
|
|
3652 | =item ev_feed_signal_event (loop, int signum) |
|
|
3653 | |
|
|
3654 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
|
|
3655 | which is async-safe. |
|
|
3656 | |
|
|
3657 | =back |
|
|
3658 | |
|
|
3659 | |
|
|
3660 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3661 | |
|
|
3662 | This section explains some common idioms that are not immediately |
|
|
3663 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3664 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3665 | |
|
|
3666 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3667 | |
|
|
3668 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3669 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3670 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3671 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3672 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3673 | data: |
|
|
3674 | |
|
|
3675 | struct my_io |
|
|
3676 | { |
|
|
3677 | ev_io io; |
|
|
3678 | int otherfd; |
|
|
3679 | void *somedata; |
|
|
3680 | struct whatever *mostinteresting; |
|
|
3681 | }; |
|
|
3682 | |
|
|
3683 | ... |
|
|
3684 | struct my_io w; |
|
|
3685 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3686 | |
|
|
3687 | And since your callback will be called with a pointer to the watcher, you |
|
|
3688 | can cast it back to your own type: |
|
|
3689 | |
|
|
3690 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3691 | { |
|
|
3692 | struct my_io *w = (struct my_io *)w_; |
|
|
3693 | ... |
|
|
3694 | } |
|
|
3695 | |
|
|
3696 | More interesting and less C-conformant ways of casting your callback |
|
|
3697 | function type instead have been omitted. |
|
|
3698 | |
|
|
3699 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3700 | |
|
|
3701 | Another common scenario is to use some data structure with multiple |
|
|
3702 | embedded watchers, in effect creating your own watcher that combines |
|
|
3703 | multiple libev event sources into one "super-watcher": |
|
|
3704 | |
|
|
3705 | struct my_biggy |
|
|
3706 | { |
|
|
3707 | int some_data; |
|
|
3708 | ev_timer t1; |
|
|
3709 | ev_timer t2; |
|
|
3710 | } |
|
|
3711 | |
|
|
3712 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3713 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3714 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3715 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3716 | real programmers): |
|
|
3717 | |
|
|
3718 | #include <stddef.h> |
|
|
3719 | |
|
|
3720 | static void |
|
|
3721 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3722 | { |
|
|
3723 | struct my_biggy big = (struct my_biggy *) |
|
|
3724 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3725 | } |
|
|
3726 | |
|
|
3727 | static void |
|
|
3728 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3729 | { |
|
|
3730 | struct my_biggy big = (struct my_biggy *) |
|
|
3731 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3732 | } |
|
|
3733 | |
|
|
3734 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3735 | |
|
|
3736 | Often you have structures like this in event-based programs: |
|
|
3737 | |
|
|
3738 | callback () |
2359 | { |
3739 | { |
2360 | if (revents & EV_TIMEOUT) |
3740 | free (request); |
2361 | /* doh, nothing entered */; |
|
|
2362 | else if (revents & EV_READ) |
|
|
2363 | /* stdin might have data for us, joy! */; |
|
|
2364 | } |
3741 | } |
2365 | |
3742 | |
2366 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3743 | request = start_new_request (..., callback); |
2367 | |
3744 | |
2368 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
3745 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3746 | used to cancel the operation, or do other things with it. |
2369 | |
3747 | |
2370 | Feeds the given event set into the event loop, as if the specified event |
3748 | It's not uncommon to have code paths in C<start_new_request> that |
2371 | had happened for the specified watcher (which must be a pointer to an |
3749 | immediately invoke the callback, for example, to report errors. Or you add |
2372 | initialised but not necessarily started event watcher). |
3750 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3751 | operation and simply invoke the callback with the result. |
2373 | |
3752 | |
2374 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3753 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3754 | has returned, so C<request> is not set. |
2375 | |
3755 | |
2376 | Feed an event on the given fd, as if a file descriptor backend detected |
3756 | Even if you pass the request by some safer means to the callback, you |
2377 | the given events it. |
3757 | might want to do something to the request after starting it, such as |
|
|
3758 | canceling it, which probably isn't working so well when the callback has |
|
|
3759 | already been invoked. |
2378 | |
3760 | |
2379 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3761 | A common way around all these issues is to make sure that |
|
|
3762 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3763 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3764 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3765 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3766 | pushing it into the pending queue: |
2380 | |
3767 | |
2381 | Feed an event as if the given signal occured (C<loop> must be the default |
3768 | ev_set_cb (watcher, callback); |
2382 | loop!). |
3769 | ev_feed_event (EV_A_ watcher, 0); |
2383 | |
3770 | |
2384 | =back |
3771 | This way, C<start_new_request> can safely return before the callback is |
|
|
3772 | invoked, while not delaying callback invocation too much. |
|
|
3773 | |
|
|
3774 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3775 | |
|
|
3776 | Often (especially in GUI toolkits) there are places where you have |
|
|
3777 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3778 | invoking C<ev_run>. |
|
|
3779 | |
|
|
3780 | This brings the problem of exiting - a callback might want to finish the |
|
|
3781 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3782 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3783 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3784 | other combination: In these cases, a simple C<ev_break> will not work. |
|
|
3785 | |
|
|
3786 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3787 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3788 | triggered, using C<EVRUN_ONCE>: |
|
|
3789 | |
|
|
3790 | // main loop |
|
|
3791 | int exit_main_loop = 0; |
|
|
3792 | |
|
|
3793 | while (!exit_main_loop) |
|
|
3794 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3795 | |
|
|
3796 | // in a modal watcher |
|
|
3797 | int exit_nested_loop = 0; |
|
|
3798 | |
|
|
3799 | while (!exit_nested_loop) |
|
|
3800 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3801 | |
|
|
3802 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3803 | |
|
|
3804 | // exit modal loop |
|
|
3805 | exit_nested_loop = 1; |
|
|
3806 | |
|
|
3807 | // exit main program, after modal loop is finished |
|
|
3808 | exit_main_loop = 1; |
|
|
3809 | |
|
|
3810 | // exit both |
|
|
3811 | exit_main_loop = exit_nested_loop = 1; |
|
|
3812 | |
|
|
3813 | =head2 THREAD LOCKING EXAMPLE |
|
|
3814 | |
|
|
3815 | Here is a fictitious example of how to run an event loop in a different |
|
|
3816 | thread from where callbacks are being invoked and watchers are |
|
|
3817 | created/added/removed. |
|
|
3818 | |
|
|
3819 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3820 | which uses exactly this technique (which is suited for many high-level |
|
|
3821 | languages). |
|
|
3822 | |
|
|
3823 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3824 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3825 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3826 | |
|
|
3827 | First, you need to associate some data with the event loop: |
|
|
3828 | |
|
|
3829 | typedef struct { |
|
|
3830 | mutex_t lock; /* global loop lock */ |
|
|
3831 | ev_async async_w; |
|
|
3832 | thread_t tid; |
|
|
3833 | cond_t invoke_cv; |
|
|
3834 | } userdata; |
|
|
3835 | |
|
|
3836 | void prepare_loop (EV_P) |
|
|
3837 | { |
|
|
3838 | // for simplicity, we use a static userdata struct. |
|
|
3839 | static userdata u; |
|
|
3840 | |
|
|
3841 | ev_async_init (&u->async_w, async_cb); |
|
|
3842 | ev_async_start (EV_A_ &u->async_w); |
|
|
3843 | |
|
|
3844 | pthread_mutex_init (&u->lock, 0); |
|
|
3845 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3846 | |
|
|
3847 | // now associate this with the loop |
|
|
3848 | ev_set_userdata (EV_A_ u); |
|
|
3849 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3850 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3851 | |
|
|
3852 | // then create the thread running ev_run |
|
|
3853 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3854 | } |
|
|
3855 | |
|
|
3856 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3857 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3858 | that might have been added: |
|
|
3859 | |
|
|
3860 | static void |
|
|
3861 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3862 | { |
|
|
3863 | // just used for the side effects |
|
|
3864 | } |
|
|
3865 | |
|
|
3866 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3867 | protecting the loop data, respectively. |
|
|
3868 | |
|
|
3869 | static void |
|
|
3870 | l_release (EV_P) |
|
|
3871 | { |
|
|
3872 | userdata *u = ev_userdata (EV_A); |
|
|
3873 | pthread_mutex_unlock (&u->lock); |
|
|
3874 | } |
|
|
3875 | |
|
|
3876 | static void |
|
|
3877 | l_acquire (EV_P) |
|
|
3878 | { |
|
|
3879 | userdata *u = ev_userdata (EV_A); |
|
|
3880 | pthread_mutex_lock (&u->lock); |
|
|
3881 | } |
|
|
3882 | |
|
|
3883 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3884 | into C<ev_run>: |
|
|
3885 | |
|
|
3886 | void * |
|
|
3887 | l_run (void *thr_arg) |
|
|
3888 | { |
|
|
3889 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3890 | |
|
|
3891 | l_acquire (EV_A); |
|
|
3892 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3893 | ev_run (EV_A_ 0); |
|
|
3894 | l_release (EV_A); |
|
|
3895 | |
|
|
3896 | return 0; |
|
|
3897 | } |
|
|
3898 | |
|
|
3899 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3900 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3901 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3902 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3903 | and b) skipping inter-thread-communication when there are no pending |
|
|
3904 | watchers is very beneficial): |
|
|
3905 | |
|
|
3906 | static void |
|
|
3907 | l_invoke (EV_P) |
|
|
3908 | { |
|
|
3909 | userdata *u = ev_userdata (EV_A); |
|
|
3910 | |
|
|
3911 | while (ev_pending_count (EV_A)) |
|
|
3912 | { |
|
|
3913 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3914 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3915 | } |
|
|
3916 | } |
|
|
3917 | |
|
|
3918 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3919 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3920 | thread to continue: |
|
|
3921 | |
|
|
3922 | static void |
|
|
3923 | real_invoke_pending (EV_P) |
|
|
3924 | { |
|
|
3925 | userdata *u = ev_userdata (EV_A); |
|
|
3926 | |
|
|
3927 | pthread_mutex_lock (&u->lock); |
|
|
3928 | ev_invoke_pending (EV_A); |
|
|
3929 | pthread_cond_signal (&u->invoke_cv); |
|
|
3930 | pthread_mutex_unlock (&u->lock); |
|
|
3931 | } |
|
|
3932 | |
|
|
3933 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3934 | event loop, you will now have to lock: |
|
|
3935 | |
|
|
3936 | ev_timer timeout_watcher; |
|
|
3937 | userdata *u = ev_userdata (EV_A); |
|
|
3938 | |
|
|
3939 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3940 | |
|
|
3941 | pthread_mutex_lock (&u->lock); |
|
|
3942 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3943 | ev_async_send (EV_A_ &u->async_w); |
|
|
3944 | pthread_mutex_unlock (&u->lock); |
|
|
3945 | |
|
|
3946 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3947 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3948 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3949 | watchers in the next event loop iteration. |
|
|
3950 | |
|
|
3951 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3952 | |
|
|
3953 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3954 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3955 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3956 | doesn't need callbacks anymore. |
|
|
3957 | |
|
|
3958 | Imagine you have coroutines that you can switch to using a function |
|
|
3959 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3960 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3961 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3962 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3963 | the differing C<;> conventions): |
|
|
3964 | |
|
|
3965 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3966 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3967 | |
|
|
3968 | That means instead of having a C callback function, you store the |
|
|
3969 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3970 | your callback, you instead have it switch to that coroutine. |
|
|
3971 | |
|
|
3972 | A coroutine might now wait for an event with a function called |
|
|
3973 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3974 | matter when, or whether the watcher is active or not when this function is |
|
|
3975 | called): |
|
|
3976 | |
|
|
3977 | void |
|
|
3978 | wait_for_event (ev_watcher *w) |
|
|
3979 | { |
|
|
3980 | ev_set_cb (w, current_coro); |
|
|
3981 | switch_to (libev_coro); |
|
|
3982 | } |
|
|
3983 | |
|
|
3984 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3985 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3986 | this or any other coroutine. |
|
|
3987 | |
|
|
3988 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3989 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3990 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3991 | any waiters. |
|
|
3992 | |
|
|
3993 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
|
|
3994 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3995 | |
|
|
3996 | // my_ev.h |
|
|
3997 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3998 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3999 | #include "../libev/ev.h" |
|
|
4000 | |
|
|
4001 | // my_ev.c |
|
|
4002 | #define EV_H "my_ev.h" |
|
|
4003 | #include "../libev/ev.c" |
|
|
4004 | |
|
|
4005 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
4006 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
4007 | can even use F<ev.h> as header file name directly. |
2385 | |
4008 | |
2386 | |
4009 | |
2387 | =head1 LIBEVENT EMULATION |
4010 | =head1 LIBEVENT EMULATION |
2388 | |
4011 | |
2389 | Libev offers a compatibility emulation layer for libevent. It cannot |
4012 | Libev offers a compatibility emulation layer for libevent. It cannot |
2390 | emulate the internals of libevent, so here are some usage hints: |
4013 | emulate the internals of libevent, so here are some usage hints: |
2391 | |
4014 | |
2392 | =over 4 |
4015 | =over 4 |
|
|
4016 | |
|
|
4017 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
4018 | |
|
|
4019 | This was the newest libevent version available when libev was implemented, |
|
|
4020 | and is still mostly unchanged in 2010. |
2393 | |
4021 | |
2394 | =item * Use it by including <event.h>, as usual. |
4022 | =item * Use it by including <event.h>, as usual. |
2395 | |
4023 | |
2396 | =item * The following members are fully supported: ev_base, ev_callback, |
4024 | =item * The following members are fully supported: ev_base, ev_callback, |
2397 | ev_arg, ev_fd, ev_res, ev_events. |
4025 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
2403 | =item * Priorities are not currently supported. Initialising priorities |
4031 | =item * Priorities are not currently supported. Initialising priorities |
2404 | will fail and all watchers will have the same priority, even though there |
4032 | will fail and all watchers will have the same priority, even though there |
2405 | is an ev_pri field. |
4033 | is an ev_pri field. |
2406 | |
4034 | |
2407 | =item * In libevent, the last base created gets the signals, in libev, the |
4035 | =item * In libevent, the last base created gets the signals, in libev, the |
2408 | first base created (== the default loop) gets the signals. |
4036 | base that registered the signal gets the signals. |
2409 | |
4037 | |
2410 | =item * Other members are not supported. |
4038 | =item * Other members are not supported. |
2411 | |
4039 | |
2412 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
4040 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2413 | to use the libev header file and library. |
4041 | to use the libev header file and library. |
2414 | |
4042 | |
2415 | =back |
4043 | =back |
2416 | |
4044 | |
2417 | =head1 C++ SUPPORT |
4045 | =head1 C++ SUPPORT |
2418 | |
4046 | |
|
|
4047 | =head2 C API |
|
|
4048 | |
|
|
4049 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
4050 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
4051 | will work fine. |
|
|
4052 | |
|
|
4053 | Proper exception specifications might have to be added to callbacks passed |
|
|
4054 | to libev: exceptions may be thrown only from watcher callbacks, all other |
|
|
4055 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
|
|
4056 | callbacks) must not throw exceptions, and might need a C<noexcept> |
|
|
4057 | specification. If you have code that needs to be compiled as both C and |
|
|
4058 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
|
|
4059 | |
|
|
4060 | static void |
|
|
4061 | fatal_error (const char *msg) EV_NOEXCEPT |
|
|
4062 | { |
|
|
4063 | perror (msg); |
|
|
4064 | abort (); |
|
|
4065 | } |
|
|
4066 | |
|
|
4067 | ... |
|
|
4068 | ev_set_syserr_cb (fatal_error); |
|
|
4069 | |
|
|
4070 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
4071 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
4072 | because it runs cleanup watchers). |
|
|
4073 | |
|
|
4074 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
4075 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
4076 | throwing exceptions through C libraries (most do). |
|
|
4077 | |
|
|
4078 | =head2 C++ API |
|
|
4079 | |
2419 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
4080 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
2420 | you to use some convinience methods to start/stop watchers and also change |
4081 | you to use some convenience methods to start/stop watchers and also change |
2421 | the callback model to a model using method callbacks on objects. |
4082 | the callback model to a model using method callbacks on objects. |
2422 | |
4083 | |
2423 | To use it, |
4084 | To use it, |
2424 | |
4085 | |
2425 | #include <ev++.h> |
4086 | #include <ev++.h> |
2426 | |
4087 | |
2427 | This automatically includes F<ev.h> and puts all of its definitions (many |
4088 | This automatically includes F<ev.h> and puts all of its definitions (many |
2428 | of them macros) into the global namespace. All C++ specific things are |
4089 | of them macros) into the global namespace. All C++ specific things are |
2429 | put into the C<ev> namespace. It should support all the same embedding |
4090 | put into the C<ev> namespace. It should support all the same embedding |
2430 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
4091 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
… | |
… | |
2432 | Care has been taken to keep the overhead low. The only data member the C++ |
4093 | Care has been taken to keep the overhead low. The only data member the C++ |
2433 | classes add (compared to plain C-style watchers) is the event loop pointer |
4094 | classes add (compared to plain C-style watchers) is the event loop pointer |
2434 | that the watcher is associated with (or no additional members at all if |
4095 | that the watcher is associated with (or no additional members at all if |
2435 | you disable C<EV_MULTIPLICITY> when embedding libev). |
4096 | you disable C<EV_MULTIPLICITY> when embedding libev). |
2436 | |
4097 | |
2437 | Currently, functions, and static and non-static member functions can be |
4098 | Currently, functions, static and non-static member functions and classes |
2438 | used as callbacks. Other types should be easy to add as long as they only |
4099 | with C<operator ()> can be used as callbacks. Other types should be easy |
2439 | need one additional pointer for context. If you need support for other |
4100 | to add as long as they only need one additional pointer for context. If |
2440 | types of functors please contact the author (preferably after implementing |
4101 | you need support for other types of functors please contact the author |
2441 | it). |
4102 | (preferably after implementing it). |
|
|
4103 | |
|
|
4104 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4105 | conventions as your C compiler (for static member functions), or you have |
|
|
4106 | to embed libev and compile libev itself as C++. |
2442 | |
4107 | |
2443 | Here is a list of things available in the C<ev> namespace: |
4108 | Here is a list of things available in the C<ev> namespace: |
2444 | |
4109 | |
2445 | =over 4 |
4110 | =over 4 |
2446 | |
4111 | |
… | |
… | |
2456 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4121 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
2457 | |
4122 | |
2458 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4123 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
2459 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4124 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
2460 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4125 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
2461 | defines by many implementations. |
4126 | defined by many implementations. |
2462 | |
4127 | |
2463 | All of those classes have these methods: |
4128 | All of those classes have these methods: |
2464 | |
4129 | |
2465 | =over 4 |
4130 | =over 4 |
2466 | |
4131 | |
2467 | =item ev::TYPE::TYPE () |
4132 | =item ev::TYPE::TYPE () |
2468 | |
4133 | |
2469 | =item ev::TYPE::TYPE (struct ev_loop *) |
4134 | =item ev::TYPE::TYPE (loop) |
2470 | |
4135 | |
2471 | =item ev::TYPE::~TYPE |
4136 | =item ev::TYPE::~TYPE |
2472 | |
4137 | |
2473 | The constructor (optionally) takes an event loop to associate the watcher |
4138 | The constructor (optionally) takes an event loop to associate the watcher |
2474 | with. If it is omitted, it will use C<EV_DEFAULT>. |
4139 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2497 | your compiler is good :), then the method will be fully inlined into the |
4162 | your compiler is good :), then the method will be fully inlined into the |
2498 | thunking function, making it as fast as a direct C callback. |
4163 | thunking function, making it as fast as a direct C callback. |
2499 | |
4164 | |
2500 | Example: simple class declaration and watcher initialisation |
4165 | Example: simple class declaration and watcher initialisation |
2501 | |
4166 | |
2502 | struct myclass |
4167 | struct myclass |
2503 | { |
4168 | { |
2504 | void io_cb (ev::io &w, int revents) { } |
4169 | void io_cb (ev::io &w, int revents) { } |
2505 | } |
4170 | } |
2506 | |
4171 | |
2507 | myclass obj; |
4172 | myclass obj; |
2508 | ev::io iow; |
4173 | ev::io iow; |
2509 | iow.set <myclass, &myclass::io_cb> (&obj); |
4174 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
4175 | |
|
|
4176 | =item w->set (object *) |
|
|
4177 | |
|
|
4178 | This is a variation of a method callback - leaving out the method to call |
|
|
4179 | will default the method to C<operator ()>, which makes it possible to use |
|
|
4180 | functor objects without having to manually specify the C<operator ()> all |
|
|
4181 | the time. Incidentally, you can then also leave out the template argument |
|
|
4182 | list. |
|
|
4183 | |
|
|
4184 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
4185 | int revents)>. |
|
|
4186 | |
|
|
4187 | See the method-C<set> above for more details. |
|
|
4188 | |
|
|
4189 | Example: use a functor object as callback. |
|
|
4190 | |
|
|
4191 | struct myfunctor |
|
|
4192 | { |
|
|
4193 | void operator() (ev::io &w, int revents) |
|
|
4194 | { |
|
|
4195 | ... |
|
|
4196 | } |
|
|
4197 | } |
|
|
4198 | |
|
|
4199 | myfunctor f; |
|
|
4200 | |
|
|
4201 | ev::io w; |
|
|
4202 | w.set (&f); |
2510 | |
4203 | |
2511 | =item w->set<function> (void *data = 0) |
4204 | =item w->set<function> (void *data = 0) |
2512 | |
4205 | |
2513 | Also sets a callback, but uses a static method or plain function as |
4206 | Also sets a callback, but uses a static method or plain function as |
2514 | callback. The optional C<data> argument will be stored in the watcher's |
4207 | callback. The optional C<data> argument will be stored in the watcher's |
… | |
… | |
2516 | |
4209 | |
2517 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
4210 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2518 | |
4211 | |
2519 | See the method-C<set> above for more details. |
4212 | See the method-C<set> above for more details. |
2520 | |
4213 | |
2521 | Example: |
4214 | Example: Use a plain function as callback. |
2522 | |
4215 | |
2523 | static void io_cb (ev::io &w, int revents) { } |
4216 | static void io_cb (ev::io &w, int revents) { } |
2524 | iow.set <io_cb> (); |
4217 | iow.set <io_cb> (); |
2525 | |
4218 | |
2526 | =item w->set (struct ev_loop *) |
4219 | =item w->set (loop) |
2527 | |
4220 | |
2528 | Associates a different C<struct ev_loop> with this watcher. You can only |
4221 | Associates a different C<struct ev_loop> with this watcher. You can only |
2529 | do this when the watcher is inactive (and not pending either). |
4222 | do this when the watcher is inactive (and not pending either). |
2530 | |
4223 | |
2531 | =item w->set ([args]) |
4224 | =item w->set ([arguments]) |
2532 | |
4225 | |
2533 | Basically the same as C<ev_TYPE_set>, with the same args. Must be |
4226 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
|
|
4227 | with the same arguments. Either this method or a suitable start method |
2534 | called at least once. Unlike the C counterpart, an active watcher gets |
4228 | must be called at least once. Unlike the C counterpart, an active watcher |
2535 | automatically stopped and restarted when reconfiguring it with this |
4229 | gets automatically stopped and restarted when reconfiguring it with this |
2536 | method. |
4230 | method. |
|
|
4231 | |
|
|
4232 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4233 | clashing with the C<set (loop)> method. |
2537 | |
4234 | |
2538 | =item w->start () |
4235 | =item w->start () |
2539 | |
4236 | |
2540 | Starts the watcher. Note that there is no C<loop> argument, as the |
4237 | Starts the watcher. Note that there is no C<loop> argument, as the |
2541 | constructor already stores the event loop. |
4238 | constructor already stores the event loop. |
2542 | |
4239 | |
|
|
4240 | =item w->start ([arguments]) |
|
|
4241 | |
|
|
4242 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
4243 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
4244 | the configure C<set> method of the watcher. |
|
|
4245 | |
2543 | =item w->stop () |
4246 | =item w->stop () |
2544 | |
4247 | |
2545 | Stops the watcher if it is active. Again, no C<loop> argument. |
4248 | Stops the watcher if it is active. Again, no C<loop> argument. |
2546 | |
4249 | |
2547 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
4250 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
2559 | |
4262 | |
2560 | =back |
4263 | =back |
2561 | |
4264 | |
2562 | =back |
4265 | =back |
2563 | |
4266 | |
2564 | Example: Define a class with an IO and idle watcher, start one of them in |
4267 | Example: Define a class with two I/O and idle watchers, start the I/O |
2565 | the constructor. |
4268 | watchers in the constructor. |
2566 | |
4269 | |
2567 | class myclass |
4270 | class myclass |
2568 | { |
4271 | { |
2569 | ev::io io; void io_cb (ev::io &w, int revents); |
4272 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
4273 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
2570 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
4274 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2571 | |
4275 | |
2572 | myclass (int fd) |
4276 | myclass (int fd) |
2573 | { |
4277 | { |
2574 | io .set <myclass, &myclass::io_cb > (this); |
4278 | io .set <myclass, &myclass::io_cb > (this); |
|
|
4279 | io2 .set <myclass, &myclass::io2_cb > (this); |
2575 | idle.set <myclass, &myclass::idle_cb> (this); |
4280 | idle.set <myclass, &myclass::idle_cb> (this); |
2576 | |
4281 | |
2577 | io.start (fd, ev::READ); |
4282 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
4283 | io.start (); // start it whenever convenient |
|
|
4284 | |
|
|
4285 | io2.start (fd, ev::READ); // set + start in one call |
2578 | } |
4286 | } |
2579 | }; |
4287 | }; |
2580 | |
4288 | |
2581 | |
4289 | |
2582 | =head1 OTHER LANGUAGE BINDINGS |
4290 | =head1 OTHER LANGUAGE BINDINGS |
2583 | |
4291 | |
2584 | Libev does not offer other language bindings itself, but bindings for a |
4292 | Libev does not offer other language bindings itself, but bindings for a |
2585 | numbe rof languages exist in the form of third-party packages. If you know |
4293 | number of languages exist in the form of third-party packages. If you know |
2586 | any interesting language binding in addition to the ones listed here, drop |
4294 | any interesting language binding in addition to the ones listed here, drop |
2587 | me a note. |
4295 | me a note. |
2588 | |
4296 | |
2589 | =over 4 |
4297 | =over 4 |
2590 | |
4298 | |
2591 | =item Perl |
4299 | =item Perl |
2592 | |
4300 | |
2593 | The EV module implements the full libev API and is actually used to test |
4301 | The EV module implements the full libev API and is actually used to test |
2594 | libev. EV is developed together with libev. Apart from the EV core module, |
4302 | libev. EV is developed together with libev. Apart from the EV core module, |
2595 | there are additional modules that implement libev-compatible interfaces |
4303 | there are additional modules that implement libev-compatible interfaces |
2596 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
4304 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2597 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
4305 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
4306 | and C<EV::Glib>). |
2598 | |
4307 | |
2599 | It can be found and installed via CPAN, its homepage is found at |
4308 | It can be found and installed via CPAN, its homepage is at |
2600 | L<http://software.schmorp.de/pkg/EV>. |
4309 | L<http://software.schmorp.de/pkg/EV>. |
2601 | |
4310 | |
|
|
4311 | =item Python |
|
|
4312 | |
|
|
4313 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
|
|
4314 | seems to be quite complete and well-documented. |
|
|
4315 | |
2602 | =item Ruby |
4316 | =item Ruby |
2603 | |
4317 | |
2604 | Tony Arcieri has written a ruby extension that offers access to a subset |
4318 | Tony Arcieri has written a ruby extension that offers access to a subset |
2605 | of the libev API and adds filehandle abstractions, asynchronous DNS and |
4319 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2606 | more on top of it. It can be found via gem servers. Its homepage is at |
4320 | more on top of it. It can be found via gem servers. Its homepage is at |
2607 | L<http://rev.rubyforge.org/>. |
4321 | L<http://rev.rubyforge.org/>. |
2608 | |
4322 | |
|
|
4323 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
4324 | makes rev work even on mingw. |
|
|
4325 | |
|
|
4326 | =item Haskell |
|
|
4327 | |
|
|
4328 | A haskell binding to libev is available at |
|
|
4329 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
4330 | |
2609 | =item D |
4331 | =item D |
2610 | |
4332 | |
2611 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4333 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2612 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
4334 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
|
|
4335 | |
|
|
4336 | =item Ocaml |
|
|
4337 | |
|
|
4338 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
4339 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
4340 | |
|
|
4341 | =item Lua |
|
|
4342 | |
|
|
4343 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
4344 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
4345 | L<http://github.com/brimworks/lua-ev>. |
|
|
4346 | |
|
|
4347 | =item Javascript |
|
|
4348 | |
|
|
4349 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4350 | |
|
|
4351 | =item Others |
|
|
4352 | |
|
|
4353 | There are others, and I stopped counting. |
2613 | |
4354 | |
2614 | =back |
4355 | =back |
2615 | |
4356 | |
2616 | |
4357 | |
2617 | =head1 MACRO MAGIC |
4358 | =head1 MACRO MAGIC |
2618 | |
4359 | |
2619 | Libev can be compiled with a variety of options, the most fundamantal |
4360 | Libev can be compiled with a variety of options, the most fundamental |
2620 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
4361 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2621 | functions and callbacks have an initial C<struct ev_loop *> argument. |
4362 | functions and callbacks have an initial C<struct ev_loop *> argument. |
2622 | |
4363 | |
2623 | To make it easier to write programs that cope with either variant, the |
4364 | To make it easier to write programs that cope with either variant, the |
2624 | following macros are defined: |
4365 | following macros are defined: |
… | |
… | |
2629 | |
4370 | |
2630 | This provides the loop I<argument> for functions, if one is required ("ev |
4371 | This provides the loop I<argument> for functions, if one is required ("ev |
2631 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
4372 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
2632 | C<EV_A_> is used when other arguments are following. Example: |
4373 | C<EV_A_> is used when other arguments are following. Example: |
2633 | |
4374 | |
2634 | ev_unref (EV_A); |
4375 | ev_unref (EV_A); |
2635 | ev_timer_add (EV_A_ watcher); |
4376 | ev_timer_add (EV_A_ watcher); |
2636 | ev_loop (EV_A_ 0); |
4377 | ev_run (EV_A_ 0); |
2637 | |
4378 | |
2638 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
4379 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
2639 | which is often provided by the following macro. |
4380 | which is often provided by the following macro. |
2640 | |
4381 | |
2641 | =item C<EV_P>, C<EV_P_> |
4382 | =item C<EV_P>, C<EV_P_> |
2642 | |
4383 | |
2643 | This provides the loop I<parameter> for functions, if one is required ("ev |
4384 | This provides the loop I<parameter> for functions, if one is required ("ev |
2644 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
4385 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
2645 | C<EV_P_> is used when other parameters are following. Example: |
4386 | C<EV_P_> is used when other parameters are following. Example: |
2646 | |
4387 | |
2647 | // this is how ev_unref is being declared |
4388 | // this is how ev_unref is being declared |
2648 | static void ev_unref (EV_P); |
4389 | static void ev_unref (EV_P); |
2649 | |
4390 | |
2650 | // this is how you can declare your typical callback |
4391 | // this is how you can declare your typical callback |
2651 | static void cb (EV_P_ ev_timer *w, int revents) |
4392 | static void cb (EV_P_ ev_timer *w, int revents) |
2652 | |
4393 | |
2653 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
4394 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
2654 | suitable for use with C<EV_A>. |
4395 | suitable for use with C<EV_A>. |
2655 | |
4396 | |
2656 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4397 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2657 | |
4398 | |
2658 | Similar to the other two macros, this gives you the value of the default |
4399 | Similar to the other two macros, this gives you the value of the default |
2659 | loop, if multiple loops are supported ("ev loop default"). |
4400 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4401 | will be initialised if it isn't already initialised. |
|
|
4402 | |
|
|
4403 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4404 | to initialise the loop somewhere. |
2660 | |
4405 | |
2661 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4406 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
2662 | |
4407 | |
2663 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4408 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
2664 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4409 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
2672 | |
4417 | |
2673 | Example: Declare and initialise a check watcher, utilising the above |
4418 | Example: Declare and initialise a check watcher, utilising the above |
2674 | macros so it will work regardless of whether multiple loops are supported |
4419 | macros so it will work regardless of whether multiple loops are supported |
2675 | or not. |
4420 | or not. |
2676 | |
4421 | |
2677 | static void |
4422 | static void |
2678 | check_cb (EV_P_ ev_timer *w, int revents) |
4423 | check_cb (EV_P_ ev_timer *w, int revents) |
2679 | { |
4424 | { |
2680 | ev_check_stop (EV_A_ w); |
4425 | ev_check_stop (EV_A_ w); |
2681 | } |
4426 | } |
2682 | |
4427 | |
2683 | ev_check check; |
4428 | ev_check check; |
2684 | ev_check_init (&check, check_cb); |
4429 | ev_check_init (&check, check_cb); |
2685 | ev_check_start (EV_DEFAULT_ &check); |
4430 | ev_check_start (EV_DEFAULT_ &check); |
2686 | ev_loop (EV_DEFAULT_ 0); |
4431 | ev_run (EV_DEFAULT_ 0); |
2687 | |
4432 | |
2688 | =head1 EMBEDDING |
4433 | =head1 EMBEDDING |
2689 | |
4434 | |
2690 | Libev can (and often is) directly embedded into host |
4435 | Libev can (and often is) directly embedded into host |
2691 | applications. Examples of applications that embed it include the Deliantra |
4436 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
2698 | libev somewhere in your source tree). |
4443 | libev somewhere in your source tree). |
2699 | |
4444 | |
2700 | =head2 FILESETS |
4445 | =head2 FILESETS |
2701 | |
4446 | |
2702 | Depending on what features you need you need to include one or more sets of files |
4447 | Depending on what features you need you need to include one or more sets of files |
2703 | in your app. |
4448 | in your application. |
2704 | |
4449 | |
2705 | =head3 CORE EVENT LOOP |
4450 | =head3 CORE EVENT LOOP |
2706 | |
4451 | |
2707 | To include only the libev core (all the C<ev_*> functions), with manual |
4452 | To include only the libev core (all the C<ev_*> functions), with manual |
2708 | configuration (no autoconf): |
4453 | configuration (no autoconf): |
2709 | |
4454 | |
2710 | #define EV_STANDALONE 1 |
4455 | #define EV_STANDALONE 1 |
2711 | #include "ev.c" |
4456 | #include "ev.c" |
2712 | |
4457 | |
2713 | This will automatically include F<ev.h>, too, and should be done in a |
4458 | This will automatically include F<ev.h>, too, and should be done in a |
2714 | single C source file only to provide the function implementations. To use |
4459 | single C source file only to provide the function implementations. To use |
2715 | it, do the same for F<ev.h> in all files wishing to use this API (best |
4460 | it, do the same for F<ev.h> in all files wishing to use this API (best |
2716 | done by writing a wrapper around F<ev.h> that you can include instead and |
4461 | done by writing a wrapper around F<ev.h> that you can include instead and |
2717 | where you can put other configuration options): |
4462 | where you can put other configuration options): |
2718 | |
4463 | |
2719 | #define EV_STANDALONE 1 |
4464 | #define EV_STANDALONE 1 |
2720 | #include "ev.h" |
4465 | #include "ev.h" |
2721 | |
4466 | |
2722 | Both header files and implementation files can be compiled with a C++ |
4467 | Both header files and implementation files can be compiled with a C++ |
2723 | compiler (at least, thats a stated goal, and breakage will be treated |
4468 | compiler (at least, that's a stated goal, and breakage will be treated |
2724 | as a bug). |
4469 | as a bug). |
2725 | |
4470 | |
2726 | You need the following files in your source tree, or in a directory |
4471 | You need the following files in your source tree, or in a directory |
2727 | in your include path (e.g. in libev/ when using -Ilibev): |
4472 | in your include path (e.g. in libev/ when using -Ilibev): |
2728 | |
4473 | |
2729 | ev.h |
4474 | ev.h |
2730 | ev.c |
4475 | ev.c |
2731 | ev_vars.h |
4476 | ev_vars.h |
2732 | ev_wrap.h |
4477 | ev_wrap.h |
2733 | |
4478 | |
2734 | ev_win32.c required on win32 platforms only |
4479 | ev_win32.c required on win32 platforms only |
2735 | |
4480 | |
2736 | ev_select.c only when select backend is enabled (which is enabled by default) |
4481 | ev_select.c only when select backend is enabled |
2737 | ev_poll.c only when poll backend is enabled (disabled by default) |
4482 | ev_poll.c only when poll backend is enabled |
2738 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4483 | ev_epoll.c only when the epoll backend is enabled |
|
|
4484 | ev_linuxaio.c only when the linux aio backend is enabled |
2739 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4485 | ev_kqueue.c only when the kqueue backend is enabled |
2740 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4486 | ev_port.c only when the solaris port backend is enabled |
2741 | |
4487 | |
2742 | F<ev.c> includes the backend files directly when enabled, so you only need |
4488 | F<ev.c> includes the backend files directly when enabled, so you only need |
2743 | to compile this single file. |
4489 | to compile this single file. |
2744 | |
4490 | |
2745 | =head3 LIBEVENT COMPATIBILITY API |
4491 | =head3 LIBEVENT COMPATIBILITY API |
2746 | |
4492 | |
2747 | To include the libevent compatibility API, also include: |
4493 | To include the libevent compatibility API, also include: |
2748 | |
4494 | |
2749 | #include "event.c" |
4495 | #include "event.c" |
2750 | |
4496 | |
2751 | in the file including F<ev.c>, and: |
4497 | in the file including F<ev.c>, and: |
2752 | |
4498 | |
2753 | #include "event.h" |
4499 | #include "event.h" |
2754 | |
4500 | |
2755 | in the files that want to use the libevent API. This also includes F<ev.h>. |
4501 | in the files that want to use the libevent API. This also includes F<ev.h>. |
2756 | |
4502 | |
2757 | You need the following additional files for this: |
4503 | You need the following additional files for this: |
2758 | |
4504 | |
2759 | event.h |
4505 | event.h |
2760 | event.c |
4506 | event.c |
2761 | |
4507 | |
2762 | =head3 AUTOCONF SUPPORT |
4508 | =head3 AUTOCONF SUPPORT |
2763 | |
4509 | |
2764 | Instead of using C<EV_STANDALONE=1> and providing your config in |
4510 | Instead of using C<EV_STANDALONE=1> and providing your configuration in |
2765 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
4511 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
2766 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
4512 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
2767 | include F<config.h> and configure itself accordingly. |
4513 | include F<config.h> and configure itself accordingly. |
2768 | |
4514 | |
2769 | For this of course you need the m4 file: |
4515 | For this of course you need the m4 file: |
2770 | |
4516 | |
2771 | libev.m4 |
4517 | libev.m4 |
2772 | |
4518 | |
2773 | =head2 PREPROCESSOR SYMBOLS/MACROS |
4519 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2774 | |
4520 | |
2775 | Libev can be configured via a variety of preprocessor symbols you have to |
4521 | Libev can be configured via a variety of preprocessor symbols you have to |
2776 | define before including any of its files. The default in the absense of |
4522 | define before including (or compiling) any of its files. The default in |
2777 | autoconf is noted for every option. |
4523 | the absence of autoconf is documented for every option. |
|
|
4524 | |
|
|
4525 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
4526 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
4527 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
4528 | to a compiled library. All other symbols change the ABI, which means all |
|
|
4529 | users of libev and the libev code itself must be compiled with compatible |
|
|
4530 | settings. |
2778 | |
4531 | |
2779 | =over 4 |
4532 | =over 4 |
2780 | |
4533 | |
|
|
4534 | =item EV_COMPAT3 (h) |
|
|
4535 | |
|
|
4536 | Backwards compatibility is a major concern for libev. This is why this |
|
|
4537 | release of libev comes with wrappers for the functions and symbols that |
|
|
4538 | have been renamed between libev version 3 and 4. |
|
|
4539 | |
|
|
4540 | You can disable these wrappers (to test compatibility with future |
|
|
4541 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
4542 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
4543 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
4544 | typedef in that case. |
|
|
4545 | |
|
|
4546 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
4547 | and in some even more future version the compatibility code will be |
|
|
4548 | removed completely. |
|
|
4549 | |
2781 | =item EV_STANDALONE |
4550 | =item EV_STANDALONE (h) |
2782 | |
4551 | |
2783 | Must always be C<1> if you do not use autoconf configuration, which |
4552 | Must always be C<1> if you do not use autoconf configuration, which |
2784 | keeps libev from including F<config.h>, and it also defines dummy |
4553 | keeps libev from including F<config.h>, and it also defines dummy |
2785 | implementations for some libevent functions (such as logging, which is not |
4554 | implementations for some libevent functions (such as logging, which is not |
2786 | supported). It will also not define any of the structs usually found in |
4555 | supported). It will also not define any of the structs usually found in |
2787 | F<event.h> that are not directly supported by the libev core alone. |
4556 | F<event.h> that are not directly supported by the libev core alone. |
2788 | |
4557 | |
|
|
4558 | In standalone mode, libev will still try to automatically deduce the |
|
|
4559 | configuration, but has to be more conservative. |
|
|
4560 | |
|
|
4561 | =item EV_USE_FLOOR |
|
|
4562 | |
|
|
4563 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4564 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4565 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4566 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4567 | function is not available will fail, so the safe default is to not enable |
|
|
4568 | this. |
|
|
4569 | |
2789 | =item EV_USE_MONOTONIC |
4570 | =item EV_USE_MONOTONIC |
2790 | |
4571 | |
2791 | If defined to be C<1>, libev will try to detect the availability of the |
4572 | If defined to be C<1>, libev will try to detect the availability of the |
2792 | monotonic clock option at both compiletime and runtime. Otherwise no use |
4573 | monotonic clock option at both compile time and runtime. Otherwise no |
2793 | of the monotonic clock option will be attempted. If you enable this, you |
4574 | use of the monotonic clock option will be attempted. If you enable this, |
2794 | usually have to link against librt or something similar. Enabling it when |
4575 | you usually have to link against librt or something similar. Enabling it |
2795 | the functionality isn't available is safe, though, although you have |
4576 | when the functionality isn't available is safe, though, although you have |
2796 | to make sure you link against any libraries where the C<clock_gettime> |
4577 | to make sure you link against any libraries where the C<clock_gettime> |
2797 | function is hiding in (often F<-lrt>). |
4578 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2798 | |
4579 | |
2799 | =item EV_USE_REALTIME |
4580 | =item EV_USE_REALTIME |
2800 | |
4581 | |
2801 | If defined to be C<1>, libev will try to detect the availability of the |
4582 | If defined to be C<1>, libev will try to detect the availability of the |
2802 | realtime clock option at compiletime (and assume its availability at |
4583 | real-time clock option at compile time (and assume its availability |
2803 | runtime if successful). Otherwise no use of the realtime clock option will |
4584 | at runtime if successful). Otherwise no use of the real-time clock |
2804 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
4585 | option will be attempted. This effectively replaces C<gettimeofday> |
2805 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
4586 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2806 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
4587 | correctness. See the note about libraries in the description of |
|
|
4588 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
4589 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
4590 | |
|
|
4591 | =item EV_USE_CLOCK_SYSCALL |
|
|
4592 | |
|
|
4593 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
4594 | of calling the system-provided C<clock_gettime> function. This option |
|
|
4595 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
4596 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
4597 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
4598 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
4599 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
4600 | higher, as it simplifies linking (no need for C<-lrt>). |
2807 | |
4601 | |
2808 | =item EV_USE_NANOSLEEP |
4602 | =item EV_USE_NANOSLEEP |
2809 | |
4603 | |
2810 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
4604 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2811 | and will use it for delays. Otherwise it will use C<select ()>. |
4605 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
2819 | 2.7 or newer, otherwise disabled. |
4613 | 2.7 or newer, otherwise disabled. |
2820 | |
4614 | |
2821 | =item EV_USE_SELECT |
4615 | =item EV_USE_SELECT |
2822 | |
4616 | |
2823 | If undefined or defined to be C<1>, libev will compile in support for the |
4617 | If undefined or defined to be C<1>, libev will compile in support for the |
2824 | C<select>(2) backend. No attempt at autodetection will be done: if no |
4618 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
2825 | other method takes over, select will be it. Otherwise the select backend |
4619 | other method takes over, select will be it. Otherwise the select backend |
2826 | will not be compiled in. |
4620 | will not be compiled in. |
2827 | |
4621 | |
2828 | =item EV_SELECT_USE_FD_SET |
4622 | =item EV_SELECT_USE_FD_SET |
2829 | |
4623 | |
2830 | If defined to C<1>, then the select backend will use the system C<fd_set> |
4624 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2831 | structure. This is useful if libev doesn't compile due to a missing |
4625 | structure. This is useful if libev doesn't compile due to a missing |
2832 | C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on |
4626 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
2833 | exotic systems. This usually limits the range of file descriptors to some |
4627 | on exotic systems. This usually limits the range of file descriptors to |
2834 | low limit such as 1024 or might have other limitations (winsocket only |
4628 | some low limit such as 1024 or might have other limitations (winsocket |
2835 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
4629 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
2836 | influence the size of the C<fd_set> used. |
4630 | configures the maximum size of the C<fd_set>. |
2837 | |
4631 | |
2838 | =item EV_SELECT_IS_WINSOCKET |
4632 | =item EV_SELECT_IS_WINSOCKET |
2839 | |
4633 | |
2840 | When defined to C<1>, the select backend will assume that |
4634 | When defined to C<1>, the select backend will assume that |
2841 | select/socket/connect etc. don't understand file descriptors but |
4635 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
2843 | be used is the winsock select). This means that it will call |
4637 | be used is the winsock select). This means that it will call |
2844 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
4638 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
2845 | it is assumed that all these functions actually work on fds, even |
4639 | it is assumed that all these functions actually work on fds, even |
2846 | on win32. Should not be defined on non-win32 platforms. |
4640 | on win32. Should not be defined on non-win32 platforms. |
2847 | |
4641 | |
2848 | =item EV_FD_TO_WIN32_HANDLE |
4642 | =item EV_FD_TO_WIN32_HANDLE(fd) |
2849 | |
4643 | |
2850 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
4644 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
2851 | file descriptors to socket handles. When not defining this symbol (the |
4645 | file descriptors to socket handles. When not defining this symbol (the |
2852 | default), then libev will call C<_get_osfhandle>, which is usually |
4646 | default), then libev will call C<_get_osfhandle>, which is usually |
2853 | correct. In some cases, programs use their own file descriptor management, |
4647 | correct. In some cases, programs use their own file descriptor management, |
2854 | in which case they can provide this function to map fds to socket handles. |
4648 | in which case they can provide this function to map fds to socket handles. |
2855 | |
4649 | |
|
|
4650 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
4651 | |
|
|
4652 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
4653 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
4654 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
4655 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
4656 | |
|
|
4657 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
4658 | |
|
|
4659 | If programs implement their own fd to handle mapping on win32, then this |
|
|
4660 | macro can be used to override the C<close> function, useful to unregister |
|
|
4661 | file descriptors again. Note that the replacement function has to close |
|
|
4662 | the underlying OS handle. |
|
|
4663 | |
|
|
4664 | =item EV_USE_WSASOCKET |
|
|
4665 | |
|
|
4666 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4667 | communication socket, which works better in some environments. Otherwise, |
|
|
4668 | the normal C<socket> function will be used, which works better in other |
|
|
4669 | environments. |
|
|
4670 | |
2856 | =item EV_USE_POLL |
4671 | =item EV_USE_POLL |
2857 | |
4672 | |
2858 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4673 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
2859 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4674 | backend. Otherwise it will be enabled on non-win32 platforms. It |
2860 | takes precedence over select. |
4675 | takes precedence over select. |
… | |
… | |
2864 | If defined to be C<1>, libev will compile in support for the Linux |
4679 | If defined to be C<1>, libev will compile in support for the Linux |
2865 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4680 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2866 | otherwise another method will be used as fallback. This is the preferred |
4681 | otherwise another method will be used as fallback. This is the preferred |
2867 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4682 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
2868 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4683 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4684 | |
|
|
4685 | =item EV_USE_LINUXAIO |
|
|
4686 | |
|
|
4687 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
4688 | aio backend. Due to it's currenbt limitations it has to be requested |
|
|
4689 | explicitly. If undefined, it will be enabled on linux, otherwise |
|
|
4690 | disabled. |
2869 | |
4691 | |
2870 | =item EV_USE_KQUEUE |
4692 | =item EV_USE_KQUEUE |
2871 | |
4693 | |
2872 | If defined to be C<1>, libev will compile in support for the BSD style |
4694 | If defined to be C<1>, libev will compile in support for the BSD style |
2873 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4695 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
2886 | otherwise another method will be used as fallback. This is the preferred |
4708 | otherwise another method will be used as fallback. This is the preferred |
2887 | backend for Solaris 10 systems. |
4709 | backend for Solaris 10 systems. |
2888 | |
4710 | |
2889 | =item EV_USE_DEVPOLL |
4711 | =item EV_USE_DEVPOLL |
2890 | |
4712 | |
2891 | reserved for future expansion, works like the USE symbols above. |
4713 | Reserved for future expansion, works like the USE symbols above. |
2892 | |
4714 | |
2893 | =item EV_USE_INOTIFY |
4715 | =item EV_USE_INOTIFY |
2894 | |
4716 | |
2895 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4717 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2896 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4718 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2897 | be detected at runtime. If undefined, it will be enabled if the headers |
4719 | be detected at runtime. If undefined, it will be enabled if the headers |
2898 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4720 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2899 | |
4721 | |
|
|
4722 | =item EV_NO_SMP |
|
|
4723 | |
|
|
4724 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4725 | between threads, that is, threads can be used, but threads never run on |
|
|
4726 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4727 | and makes libev faster. |
|
|
4728 | |
|
|
4729 | =item EV_NO_THREADS |
|
|
4730 | |
|
|
4731 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4732 | different threads (that includes signal handlers), which is a stronger |
|
|
4733 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4734 | libev faster. |
|
|
4735 | |
2900 | =item EV_ATOMIC_T |
4736 | =item EV_ATOMIC_T |
2901 | |
4737 | |
2902 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4738 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2903 | access is atomic with respect to other threads or signal contexts. No such |
4739 | access is atomic with respect to other threads or signal contexts. No |
2904 | type is easily found in the C language, so you can provide your own type |
4740 | such type is easily found in the C language, so you can provide your own |
2905 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4741 | type that you know is safe for your purposes. It is used both for signal |
2906 | as well as for signal and thread safety in C<ev_async> watchers. |
4742 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4743 | watchers. |
2907 | |
4744 | |
2908 | In the absense of this define, libev will use C<sig_atomic_t volatile> |
4745 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
2909 | (from F<signal.h>), which is usually good enough on most platforms. |
4746 | (from F<signal.h>), which is usually good enough on most platforms. |
2910 | |
4747 | |
2911 | =item EV_H |
4748 | =item EV_H (h) |
2912 | |
4749 | |
2913 | The name of the F<ev.h> header file used to include it. The default if |
4750 | The name of the F<ev.h> header file used to include it. The default if |
2914 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4751 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2915 | used to virtually rename the F<ev.h> header file in case of conflicts. |
4752 | used to virtually rename the F<ev.h> header file in case of conflicts. |
2916 | |
4753 | |
2917 | =item EV_CONFIG_H |
4754 | =item EV_CONFIG_H (h) |
2918 | |
4755 | |
2919 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
4756 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
2920 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
4757 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
2921 | C<EV_H>, above. |
4758 | C<EV_H>, above. |
2922 | |
4759 | |
2923 | =item EV_EVENT_H |
4760 | =item EV_EVENT_H (h) |
2924 | |
4761 | |
2925 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
4762 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
2926 | of how the F<event.h> header can be found, the default is C<"event.h">. |
4763 | of how the F<event.h> header can be found, the default is C<"event.h">. |
2927 | |
4764 | |
2928 | =item EV_PROTOTYPES |
4765 | =item EV_PROTOTYPES (h) |
2929 | |
4766 | |
2930 | If defined to be C<0>, then F<ev.h> will not define any function |
4767 | If defined to be C<0>, then F<ev.h> will not define any function |
2931 | prototypes, but still define all the structs and other symbols. This is |
4768 | prototypes, but still define all the structs and other symbols. This is |
2932 | occasionally useful if you want to provide your own wrapper functions |
4769 | occasionally useful if you want to provide your own wrapper functions |
2933 | around libev functions. |
4770 | around libev functions. |
… | |
… | |
2938 | will have the C<struct ev_loop *> as first argument, and you can create |
4775 | will have the C<struct ev_loop *> as first argument, and you can create |
2939 | additional independent event loops. Otherwise there will be no support |
4776 | additional independent event loops. Otherwise there will be no support |
2940 | for multiple event loops and there is no first event loop pointer |
4777 | for multiple event loops and there is no first event loop pointer |
2941 | argument. Instead, all functions act on the single default loop. |
4778 | argument. Instead, all functions act on the single default loop. |
2942 | |
4779 | |
|
|
4780 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4781 | default loop when multiplicity is switched off - you always have to |
|
|
4782 | initialise the loop manually in this case. |
|
|
4783 | |
2943 | =item EV_MINPRI |
4784 | =item EV_MINPRI |
2944 | |
4785 | |
2945 | =item EV_MAXPRI |
4786 | =item EV_MAXPRI |
2946 | |
4787 | |
2947 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4788 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
2952 | When doing priority-based operations, libev usually has to linearly search |
4793 | When doing priority-based operations, libev usually has to linearly search |
2953 | all the priorities, so having many of them (hundreds) uses a lot of space |
4794 | all the priorities, so having many of them (hundreds) uses a lot of space |
2954 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
4795 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
2955 | fine. |
4796 | fine. |
2956 | |
4797 | |
2957 | If your embedding app does not need any priorities, defining these both to |
4798 | If your embedding application does not need any priorities, defining these |
2958 | C<0> will save some memory and cpu. |
4799 | both to C<0> will save some memory and CPU. |
2959 | |
4800 | |
2960 | =item EV_PERIODIC_ENABLE |
4801 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
4802 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
4803 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
2961 | |
4804 | |
2962 | If undefined or defined to be C<1>, then periodic timers are supported. If |
4805 | If undefined or defined to be C<1> (and the platform supports it), then |
2963 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
4806 | the respective watcher type is supported. If defined to be C<0>, then it |
2964 | code. |
4807 | is not. Disabling watcher types mainly saves code size. |
2965 | |
4808 | |
2966 | =item EV_IDLE_ENABLE |
4809 | =item EV_FEATURES |
2967 | |
|
|
2968 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
2969 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
2970 | code. |
|
|
2971 | |
|
|
2972 | =item EV_EMBED_ENABLE |
|
|
2973 | |
|
|
2974 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
2975 | defined to be C<0>, then they are not. |
|
|
2976 | |
|
|
2977 | =item EV_STAT_ENABLE |
|
|
2978 | |
|
|
2979 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
2980 | defined to be C<0>, then they are not. |
|
|
2981 | |
|
|
2982 | =item EV_FORK_ENABLE |
|
|
2983 | |
|
|
2984 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
2985 | defined to be C<0>, then they are not. |
|
|
2986 | |
|
|
2987 | =item EV_ASYNC_ENABLE |
|
|
2988 | |
|
|
2989 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
2990 | defined to be C<0>, then they are not. |
|
|
2991 | |
|
|
2992 | =item EV_MINIMAL |
|
|
2993 | |
4810 | |
2994 | If you need to shave off some kilobytes of code at the expense of some |
4811 | If you need to shave off some kilobytes of code at the expense of some |
2995 | speed, define this symbol to C<1>. Currently this is used to override some |
4812 | speed (but with the full API), you can define this symbol to request |
2996 | inlining decisions, saves roughly 30% codesize of amd64. It also selects a |
4813 | certain subsets of functionality. The default is to enable all features |
2997 | much smaller 2-heap for timer management over the default 4-heap. |
4814 | that can be enabled on the platform. |
|
|
4815 | |
|
|
4816 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
4817 | with some broad features you want) and then selectively re-enable |
|
|
4818 | additional parts you want, for example if you want everything minimal, |
|
|
4819 | but multiple event loop support, async and child watchers and the poll |
|
|
4820 | backend, use this: |
|
|
4821 | |
|
|
4822 | #define EV_FEATURES 0 |
|
|
4823 | #define EV_MULTIPLICITY 1 |
|
|
4824 | #define EV_USE_POLL 1 |
|
|
4825 | #define EV_CHILD_ENABLE 1 |
|
|
4826 | #define EV_ASYNC_ENABLE 1 |
|
|
4827 | |
|
|
4828 | The actual value is a bitset, it can be a combination of the following |
|
|
4829 | values (by default, all of these are enabled): |
|
|
4830 | |
|
|
4831 | =over 4 |
|
|
4832 | |
|
|
4833 | =item C<1> - faster/larger code |
|
|
4834 | |
|
|
4835 | Use larger code to speed up some operations. |
|
|
4836 | |
|
|
4837 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4838 | code size by roughly 30% on amd64). |
|
|
4839 | |
|
|
4840 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
4841 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
4842 | assertions. |
|
|
4843 | |
|
|
4844 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4845 | (e.g. gcc with C<-Os>). |
|
|
4846 | |
|
|
4847 | =item C<2> - faster/larger data structures |
|
|
4848 | |
|
|
4849 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
4850 | hash table sizes and so on. This will usually further increase code size |
|
|
4851 | and can additionally have an effect on the size of data structures at |
|
|
4852 | runtime. |
|
|
4853 | |
|
|
4854 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4855 | (e.g. gcc with C<-Os>). |
|
|
4856 | |
|
|
4857 | =item C<4> - full API configuration |
|
|
4858 | |
|
|
4859 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
4860 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
4861 | |
|
|
4862 | =item C<8> - full API |
|
|
4863 | |
|
|
4864 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
4865 | details on which parts of the API are still available without this |
|
|
4866 | feature, and do not complain if this subset changes over time. |
|
|
4867 | |
|
|
4868 | =item C<16> - enable all optional watcher types |
|
|
4869 | |
|
|
4870 | Enables all optional watcher types. If you want to selectively enable |
|
|
4871 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4872 | embed, async, child...) you can enable them manually by defining |
|
|
4873 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
4874 | |
|
|
4875 | =item C<32> - enable all backends |
|
|
4876 | |
|
|
4877 | This enables all backends - without this feature, you need to enable at |
|
|
4878 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
4879 | |
|
|
4880 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4881 | |
|
|
4882 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4883 | default. |
|
|
4884 | |
|
|
4885 | =back |
|
|
4886 | |
|
|
4887 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4888 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4889 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4890 | watchers, timers and monotonic clock support. |
|
|
4891 | |
|
|
4892 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4893 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4894 | your program might be left out as well - a binary starting a timer and an |
|
|
4895 | I/O watcher then might come out at only 5Kb. |
|
|
4896 | |
|
|
4897 | =item EV_API_STATIC |
|
|
4898 | |
|
|
4899 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4900 | will have static linkage. This means that libev will not export any |
|
|
4901 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4902 | when you embed libev, only want to use libev functions in a single file, |
|
|
4903 | and do not want its identifiers to be visible. |
|
|
4904 | |
|
|
4905 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4906 | wants to use libev. |
|
|
4907 | |
|
|
4908 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4909 | doesn't support the required declaration syntax. |
|
|
4910 | |
|
|
4911 | =item EV_AVOID_STDIO |
|
|
4912 | |
|
|
4913 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4914 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4915 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4916 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4917 | big. |
|
|
4918 | |
|
|
4919 | Note that error messages might become less precise when this option is |
|
|
4920 | enabled. |
|
|
4921 | |
|
|
4922 | =item EV_NSIG |
|
|
4923 | |
|
|
4924 | The highest supported signal number, +1 (or, the number of |
|
|
4925 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4926 | automatically, but sometimes this fails, in which case it can be |
|
|
4927 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4928 | good for about any system in existence) can save some memory, as libev |
|
|
4929 | statically allocates some 12-24 bytes per signal number. |
2998 | |
4930 | |
2999 | =item EV_PID_HASHSIZE |
4931 | =item EV_PID_HASHSIZE |
3000 | |
4932 | |
3001 | C<ev_child> watchers use a small hash table to distribute workload by |
4933 | C<ev_child> watchers use a small hash table to distribute workload by |
3002 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4934 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3003 | than enough. If you need to manage thousands of children you might want to |
4935 | usually more than enough. If you need to manage thousands of children you |
3004 | increase this value (I<must> be a power of two). |
4936 | might want to increase this value (I<must> be a power of two). |
3005 | |
4937 | |
3006 | =item EV_INOTIFY_HASHSIZE |
4938 | =item EV_INOTIFY_HASHSIZE |
3007 | |
4939 | |
3008 | C<ev_stat> watchers use a small hash table to distribute workload by |
4940 | C<ev_stat> watchers use a small hash table to distribute workload by |
3009 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4941 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3010 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4942 | disabled), usually more than enough. If you need to manage thousands of |
3011 | watchers you might want to increase this value (I<must> be a power of |
4943 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3012 | two). |
4944 | power of two). |
3013 | |
4945 | |
3014 | =item EV_USE_4HEAP |
4946 | =item EV_USE_4HEAP |
3015 | |
4947 | |
3016 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4948 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3017 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
4949 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3018 | to C<1>. The 4-heap uses more complicated (longer) code but has |
4950 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3019 | noticably faster performance with many (thousands) of watchers. |
4951 | faster performance with many (thousands) of watchers. |
3020 | |
4952 | |
3021 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4953 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3022 | (disabled). |
4954 | will be C<0>. |
3023 | |
4955 | |
3024 | =item EV_HEAP_CACHE_AT |
4956 | =item EV_HEAP_CACHE_AT |
3025 | |
4957 | |
3026 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4958 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3027 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
4959 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3028 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4960 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3029 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4961 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3030 | but avoids random read accesses on heap changes. This improves performance |
4962 | but avoids random read accesses on heap changes. This improves performance |
3031 | noticably with with many (hundreds) of watchers. |
4963 | noticeably with many (hundreds) of watchers. |
3032 | |
4964 | |
3033 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4965 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3034 | (disabled). |
4966 | will be C<0>. |
|
|
4967 | |
|
|
4968 | =item EV_VERIFY |
|
|
4969 | |
|
|
4970 | Controls how much internal verification (see C<ev_verify ()>) will |
|
|
4971 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
4972 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
4973 | called. If set to C<2>, then the internal verification code will be |
|
|
4974 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
4975 | verification code will be called very frequently, which will slow down |
|
|
4976 | libev considerably. |
|
|
4977 | |
|
|
4978 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
|
|
4979 | will be C<0>. |
3035 | |
4980 | |
3036 | =item EV_COMMON |
4981 | =item EV_COMMON |
3037 | |
4982 | |
3038 | By default, all watchers have a C<void *data> member. By redefining |
4983 | By default, all watchers have a C<void *data> member. By redefining |
3039 | this macro to a something else you can include more and other types of |
4984 | this macro to something else you can include more and other types of |
3040 | members. You have to define it each time you include one of the files, |
4985 | members. You have to define it each time you include one of the files, |
3041 | though, and it must be identical each time. |
4986 | though, and it must be identical each time. |
3042 | |
4987 | |
3043 | For example, the perl EV module uses something like this: |
4988 | For example, the perl EV module uses something like this: |
3044 | |
4989 | |
3045 | #define EV_COMMON \ |
4990 | #define EV_COMMON \ |
3046 | SV *self; /* contains this struct */ \ |
4991 | SV *self; /* contains this struct */ \ |
3047 | SV *cb_sv, *fh /* note no trailing ";" */ |
4992 | SV *cb_sv, *fh /* note no trailing ";" */ |
3048 | |
4993 | |
3049 | =item EV_CB_DECLARE (type) |
4994 | =item EV_CB_DECLARE (type) |
3050 | |
4995 | |
3051 | =item EV_CB_INVOKE (watcher, revents) |
4996 | =item EV_CB_INVOKE (watcher, revents) |
3052 | |
4997 | |
… | |
… | |
3057 | definition and a statement, respectively. See the F<ev.h> header file for |
5002 | definition and a statement, respectively. See the F<ev.h> header file for |
3058 | their default definitions. One possible use for overriding these is to |
5003 | their default definitions. One possible use for overriding these is to |
3059 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
5004 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3060 | method calls instead of plain function calls in C++. |
5005 | method calls instead of plain function calls in C++. |
3061 | |
5006 | |
|
|
5007 | =back |
|
|
5008 | |
3062 | =head2 EXPORTED API SYMBOLS |
5009 | =head2 EXPORTED API SYMBOLS |
3063 | |
5010 | |
3064 | If you need to re-export the API (e.g. via a dll) and you need a list of |
5011 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3065 | exported symbols, you can use the provided F<Symbol.*> files which list |
5012 | exported symbols, you can use the provided F<Symbol.*> files which list |
3066 | all public symbols, one per line: |
5013 | all public symbols, one per line: |
3067 | |
5014 | |
3068 | Symbols.ev for libev proper |
5015 | Symbols.ev for libev proper |
3069 | Symbols.event for the libevent emulation |
5016 | Symbols.event for the libevent emulation |
3070 | |
5017 | |
3071 | This can also be used to rename all public symbols to avoid clashes with |
5018 | This can also be used to rename all public symbols to avoid clashes with |
3072 | multiple versions of libev linked together (which is obviously bad in |
5019 | multiple versions of libev linked together (which is obviously bad in |
3073 | itself, but sometimes it is inconvinient to avoid this). |
5020 | itself, but sometimes it is inconvenient to avoid this). |
3074 | |
5021 | |
3075 | A sed command like this will create wrapper C<#define>'s that you need to |
5022 | A sed command like this will create wrapper C<#define>'s that you need to |
3076 | include before including F<ev.h>: |
5023 | include before including F<ev.h>: |
3077 | |
5024 | |
3078 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
5025 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
… | |
… | |
3095 | file. |
5042 | file. |
3096 | |
5043 | |
3097 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
5044 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3098 | that everybody includes and which overrides some configure choices: |
5045 | that everybody includes and which overrides some configure choices: |
3099 | |
5046 | |
3100 | #define EV_MINIMAL 1 |
5047 | #define EV_FEATURES 8 |
3101 | #define EV_USE_POLL 0 |
5048 | #define EV_USE_SELECT 1 |
3102 | #define EV_MULTIPLICITY 0 |
|
|
3103 | #define EV_PERIODIC_ENABLE 0 |
5049 | #define EV_PREPARE_ENABLE 1 |
|
|
5050 | #define EV_IDLE_ENABLE 1 |
3104 | #define EV_STAT_ENABLE 0 |
5051 | #define EV_SIGNAL_ENABLE 1 |
3105 | #define EV_FORK_ENABLE 0 |
5052 | #define EV_CHILD_ENABLE 1 |
|
|
5053 | #define EV_USE_STDEXCEPT 0 |
3106 | #define EV_CONFIG_H <config.h> |
5054 | #define EV_CONFIG_H <config.h> |
3107 | #define EV_MINPRI 0 |
|
|
3108 | #define EV_MAXPRI 0 |
|
|
3109 | |
5055 | |
3110 | #include "ev++.h" |
5056 | #include "ev++.h" |
3111 | |
5057 | |
3112 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
5058 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3113 | |
5059 | |
3114 | #include "ev_cpp.h" |
5060 | #include "ev_cpp.h" |
3115 | #include "ev.c" |
5061 | #include "ev.c" |
3116 | |
5062 | |
|
|
5063 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
3117 | |
5064 | |
3118 | =head1 THREADS AND COROUTINES |
5065 | =head2 THREADS AND COROUTINES |
3119 | |
5066 | |
3120 | =head2 THREADS |
5067 | =head3 THREADS |
3121 | |
5068 | |
3122 | Libev itself is completely threadsafe, but it uses no locking. This |
5069 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
5070 | documented otherwise, but libev implements no locking itself. This means |
3123 | means that you can use as many loops as you want in parallel, as long as |
5071 | that you can use as many loops as you want in parallel, as long as there |
3124 | only one thread ever calls into one libev function with the same loop |
5072 | are no concurrent calls into any libev function with the same loop |
3125 | parameter. |
5073 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
5074 | of course): libev guarantees that different event loops share no data |
|
|
5075 | structures that need any locking. |
3126 | |
5076 | |
3127 | Or put differently: calls with different loop parameters can be done in |
5077 | Or to put it differently: calls with different loop parameters can be done |
3128 | parallel from multiple threads, calls with the same loop parameter must be |
5078 | concurrently from multiple threads, calls with the same loop parameter |
3129 | done serially (but can be done from different threads, as long as only one |
5079 | must be done serially (but can be done from different threads, as long as |
3130 | thread ever is inside a call at any point in time, e.g. by using a mutex |
5080 | only one thread ever is inside a call at any point in time, e.g. by using |
3131 | per loop). |
5081 | a mutex per loop). |
3132 | |
5082 | |
3133 | If you want to know which design is best for your problem, then I cannot |
5083 | Specifically to support threads (and signal handlers), libev implements |
|
|
5084 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
5085 | concurrency on the same event loop, namely waking it up "from the |
|
|
5086 | outside". |
|
|
5087 | |
|
|
5088 | If you want to know which design (one loop, locking, or multiple loops |
|
|
5089 | without or something else still) is best for your problem, then I cannot |
3134 | help you but by giving some generic advice: |
5090 | help you, but here is some generic advice: |
3135 | |
5091 | |
3136 | =over 4 |
5092 | =over 4 |
3137 | |
5093 | |
3138 | =item * most applications have a main thread: use the default libev loop |
5094 | =item * most applications have a main thread: use the default libev loop |
3139 | in that thread, or create a seperate thread running only the default loop. |
5095 | in that thread, or create a separate thread running only the default loop. |
3140 | |
5096 | |
3141 | This helps integrating other libraries or software modules that use libev |
5097 | This helps integrating other libraries or software modules that use libev |
3142 | themselves and don't care/know about threading. |
5098 | themselves and don't care/know about threading. |
3143 | |
5099 | |
3144 | =item * one loop per thread is usually a good model. |
5100 | =item * one loop per thread is usually a good model. |
3145 | |
5101 | |
3146 | Doing this is almost never wrong, sometimes a better-performance model |
5102 | Doing this is almost never wrong, sometimes a better-performance model |
3147 | exists, but it is always a good start. |
5103 | exists, but it is always a good start. |
3148 | |
5104 | |
3149 | =item * other models exist, such as the leader/follower pattern, where one |
5105 | =item * other models exist, such as the leader/follower pattern, where one |
3150 | loop is handed through multiple threads in a kind of round-robbin fashion. |
5106 | loop is handed through multiple threads in a kind of round-robin fashion. |
3151 | |
5107 | |
3152 | Chosing a model is hard - look around, learn, know that usually you cna do |
5108 | Choosing a model is hard - look around, learn, know that usually you can do |
3153 | better than you currently do :-) |
5109 | better than you currently do :-) |
3154 | |
5110 | |
3155 | =item * often you need to talk to some other thread which blocks in the |
5111 | =item * often you need to talk to some other thread which blocks in the |
|
|
5112 | event loop. |
|
|
5113 | |
3156 | event loop - C<ev_async> watchers can be used to wake them up from other |
5114 | C<ev_async> watchers can be used to wake them up from other threads safely |
3157 | threads safely (or from signal contexts...). |
5115 | (or from signal contexts...). |
|
|
5116 | |
|
|
5117 | An example use would be to communicate signals or other events that only |
|
|
5118 | work in the default loop by registering the signal watcher with the |
|
|
5119 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
5120 | watcher callback into the event loop interested in the signal. |
3158 | |
5121 | |
3159 | =back |
5122 | =back |
3160 | |
5123 | |
|
|
5124 | See also L</THREAD LOCKING EXAMPLE>. |
|
|
5125 | |
3161 | =head2 COROUTINES |
5126 | =head3 COROUTINES |
3162 | |
5127 | |
3163 | Libev is much more accomodating to coroutines ("cooperative threads"): |
5128 | Libev is very accommodating to coroutines ("cooperative threads"): |
3164 | libev fully supports nesting calls to it's functions from different |
5129 | libev fully supports nesting calls to its functions from different |
3165 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
5130 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
3166 | different coroutines and switch freely between both coroutines running the |
5131 | different coroutines, and switch freely between both coroutines running |
3167 | loop, as long as you don't confuse yourself). The only exception is that |
5132 | the loop, as long as you don't confuse yourself). The only exception is |
3168 | you must not do this from C<ev_periodic> reschedule callbacks. |
5133 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3169 | |
5134 | |
3170 | Care has been invested into making sure that libev does not keep local |
5135 | Care has been taken to ensure that libev does not keep local state inside |
3171 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
5136 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
3172 | switches. |
5137 | they do not call any callbacks. |
3173 | |
5138 | |
|
|
5139 | =head2 COMPILER WARNINGS |
3174 | |
5140 | |
3175 | =head1 COMPLEXITIES |
5141 | Depending on your compiler and compiler settings, you might get no or a |
|
|
5142 | lot of warnings when compiling libev code. Some people are apparently |
|
|
5143 | scared by this. |
3176 | |
5144 | |
3177 | In this section the complexities of (many of) the algorithms used inside |
5145 | However, these are unavoidable for many reasons. For one, each compiler |
3178 | libev will be explained. For complexity discussions about backends see the |
5146 | has different warnings, and each user has different tastes regarding |
3179 | documentation for C<ev_default_init>. |
5147 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
5148 | targeting a specific compiler and compiler-version. |
3180 | |
5149 | |
3181 | All of the following are about amortised time: If an array needs to be |
5150 | Another reason is that some compiler warnings require elaborate |
3182 | extended, libev needs to realloc and move the whole array, but this |
5151 | workarounds, or other changes to the code that make it less clear and less |
3183 | happens asymptotically never with higher number of elements, so O(1) might |
5152 | maintainable. |
3184 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3185 | it is much faster and asymptotically approaches constant time. |
|
|
3186 | |
5153 | |
3187 | =over 4 |
5154 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
5155 | wrong (because they don't actually warn about the condition their message |
|
|
5156 | seems to warn about). For example, certain older gcc versions had some |
|
|
5157 | warnings that resulted in an extreme number of false positives. These have |
|
|
5158 | been fixed, but some people still insist on making code warn-free with |
|
|
5159 | such buggy versions. |
3188 | |
5160 | |
3189 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
5161 | While libev is written to generate as few warnings as possible, |
|
|
5162 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
5163 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
5164 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
5165 | warnings, not errors, or proof of bugs. |
3190 | |
5166 | |
3191 | This means that, when you have a watcher that triggers in one hour and |
|
|
3192 | there are 100 watchers that would trigger before that then inserting will |
|
|
3193 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3194 | |
5167 | |
3195 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
5168 | =head2 VALGRIND |
3196 | |
5169 | |
3197 | That means that changing a timer costs less than removing/adding them |
5170 | Valgrind has a special section here because it is a popular tool that is |
3198 | as only the relative motion in the event queue has to be paid for. |
5171 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3199 | |
5172 | |
3200 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
5173 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
5174 | in libev, then check twice: If valgrind reports something like: |
3201 | |
5175 | |
3202 | These just add the watcher into an array or at the head of a list. |
5176 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
5177 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
5178 | ==2274== still reachable: 256 bytes in 1 blocks. |
3203 | |
5179 | |
3204 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
5180 | Then there is no memory leak, just as memory accounted to global variables |
|
|
5181 | is not a memleak - the memory is still being referenced, and didn't leak. |
3205 | |
5182 | |
3206 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
5183 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
5184 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
5185 | although an acceptable workaround has been found here), or it might be |
|
|
5186 | confused. |
3207 | |
5187 | |
3208 | These watchers are stored in lists then need to be walked to find the |
5188 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3209 | correct watcher to remove. The lists are usually short (you don't usually |
5189 | make it into some kind of religion. |
3210 | have many watchers waiting for the same fd or signal). |
|
|
3211 | |
5190 | |
3212 | =item Finding the next timer in each loop iteration: O(1) |
5191 | If you are unsure about something, feel free to contact the mailing list |
|
|
5192 | with the full valgrind report and an explanation on why you think this |
|
|
5193 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
5194 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
5195 | of learning how to interpret valgrind properly. |
3213 | |
5196 | |
3214 | By virtue of using a binary or 4-heap, the next timer is always found at a |
5197 | If you need, for some reason, empty reports from valgrind for your project |
3215 | fixed position in the storage array. |
5198 | I suggest using suppression lists. |
3216 | |
5199 | |
3217 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3218 | |
5200 | |
3219 | A change means an I/O watcher gets started or stopped, which requires |
5201 | =head1 PORTABILITY NOTES |
3220 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3221 | on backend and wether C<ev_io_set> was used). |
|
|
3222 | |
5202 | |
3223 | =item Activating one watcher (putting it into the pending state): O(1) |
5203 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
3224 | |
5204 | |
3225 | =item Priority handling: O(number_of_priorities) |
5205 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
5206 | interfaces but I<disables> them by default. |
3226 | |
5207 | |
3227 | Priorities are implemented by allocating some space for each |
5208 | That means that libev compiled in the default environment doesn't support |
3228 | priority. When doing priority-based operations, libev usually has to |
5209 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
3229 | linearly search all the priorities, but starting/stopping and activating |
|
|
3230 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3231 | |
5210 | |
3232 | =item Sending an ev_async: O(1) |
5211 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
5212 | by enabling the large file API, which makes them incompatible with the |
|
|
5213 | standard libev compiled for their system. |
3233 | |
5214 | |
3234 | =item Processing ev_async_send: O(number_of_async_watchers) |
5215 | Likewise, libev cannot enable the large file API itself as this would |
|
|
5216 | suddenly make it incompatible to the default compile time environment, |
|
|
5217 | i.e. all programs not using special compile switches. |
3235 | |
5218 | |
3236 | =item Processing signals: O(max_signal_number) |
5219 | =head2 OS/X AND DARWIN BUGS |
3237 | |
5220 | |
3238 | Sending involves a syscall I<iff> there were no other C<ev_async_send> |
5221 | The whole thing is a bug if you ask me - basically any system interface |
3239 | calls in the current loop iteration. Checking for async and signal events |
5222 | you touch is broken, whether it is locales, poll, kqueue or even the |
3240 | involves iterating over all running async watchers or all signal numbers. |
5223 | OpenGL drivers. |
3241 | |
5224 | |
3242 | =back |
5225 | =head3 C<kqueue> is buggy |
3243 | |
5226 | |
|
|
5227 | The kqueue syscall is broken in all known versions - most versions support |
|
|
5228 | only sockets, many support pipes. |
3244 | |
5229 | |
3245 | =head1 Win32 platform limitations and workarounds |
5230 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
5231 | rotten platform, but of course you can still ask for it when creating a |
|
|
5232 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
5233 | probably going to work well. |
|
|
5234 | |
|
|
5235 | =head3 C<poll> is buggy |
|
|
5236 | |
|
|
5237 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
5238 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
5239 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
5240 | |
|
|
5241 | Libev tries to work around this by not using C<poll> by default on |
|
|
5242 | this rotten platform, but of course you can still ask for it when creating |
|
|
5243 | a loop. |
|
|
5244 | |
|
|
5245 | =head3 C<select> is buggy |
|
|
5246 | |
|
|
5247 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
5248 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
5249 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
5250 | you use more. |
|
|
5251 | |
|
|
5252 | There is an undocumented "workaround" for this - defining |
|
|
5253 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
5254 | work on OS/X. |
|
|
5255 | |
|
|
5256 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
5257 | |
|
|
5258 | =head3 C<errno> reentrancy |
|
|
5259 | |
|
|
5260 | The default compile environment on Solaris is unfortunately so |
|
|
5261 | thread-unsafe that you can't even use components/libraries compiled |
|
|
5262 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
5263 | defined by default. A valid, if stupid, implementation choice. |
|
|
5264 | |
|
|
5265 | If you want to use libev in threaded environments you have to make sure |
|
|
5266 | it's compiled with C<_REENTRANT> defined. |
|
|
5267 | |
|
|
5268 | =head3 Event port backend |
|
|
5269 | |
|
|
5270 | The scalable event interface for Solaris is called "event |
|
|
5271 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
5272 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
5273 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
5274 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
5275 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
5276 | great. |
|
|
5277 | |
|
|
5278 | If you can't get it to work, you can try running the program by setting |
|
|
5279 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
5280 | C<select> backends. |
|
|
5281 | |
|
|
5282 | =head2 AIX POLL BUG |
|
|
5283 | |
|
|
5284 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
5285 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
5286 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
5287 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
5288 | |
|
|
5289 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
5290 | |
|
|
5291 | =head3 General issues |
3246 | |
5292 | |
3247 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
5293 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3248 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5294 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3249 | model. Libev still offers limited functionality on this platform in |
5295 | model. Libev still offers limited functionality on this platform in |
3250 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5296 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3251 | descriptors. This only applies when using Win32 natively, not when using |
5297 | descriptors. This only applies when using Win32 natively, not when using |
3252 | e.g. cygwin. |
5298 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
5299 | as every compiler comes with a slightly differently broken/incompatible |
|
|
5300 | environment. |
3253 | |
5301 | |
3254 | Lifting these limitations would basically require the full |
5302 | Lifting these limitations would basically require the full |
3255 | re-implementation of the I/O system. If you are into these kinds of |
5303 | re-implementation of the I/O system. If you are into this kind of thing, |
3256 | things, then note that glib does exactly that for you in a very portable |
5304 | then note that glib does exactly that for you in a very portable way (note |
3257 | way (note also that glib is the slowest event library known to man). |
5305 | also that glib is the slowest event library known to man). |
3258 | |
5306 | |
3259 | There is no supported compilation method available on windows except |
5307 | There is no supported compilation method available on windows except |
3260 | embedding it into other applications. |
5308 | embedding it into other applications. |
|
|
5309 | |
|
|
5310 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
5311 | tries its best, but under most conditions, signals will simply not work. |
|
|
5312 | |
|
|
5313 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
5314 | accept large writes: instead of resulting in a partial write, windows will |
|
|
5315 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
|
|
5316 | so make sure you only write small amounts into your sockets (less than a |
|
|
5317 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
5318 | available). |
3261 | |
5319 | |
3262 | Due to the many, low, and arbitrary limits on the win32 platform and |
5320 | Due to the many, low, and arbitrary limits on the win32 platform and |
3263 | the abysmal performance of winsockets, using a large number of sockets |
5321 | the abysmal performance of winsockets, using a large number of sockets |
3264 | is not recommended (and not reasonable). If your program needs to use |
5322 | is not recommended (and not reasonable). If your program needs to use |
3265 | more than a hundred or so sockets, then likely it needs to use a totally |
5323 | more than a hundred or so sockets, then likely it needs to use a totally |
3266 | different implementation for windows, as libev offers the POSIX readiness |
5324 | different implementation for windows, as libev offers the POSIX readiness |
3267 | notification model, which cannot be implemented efficiently on windows |
5325 | notification model, which cannot be implemented efficiently on windows |
3268 | (microsoft monopoly games). |
5326 | (due to Microsoft monopoly games). |
3269 | |
5327 | |
3270 | =over 4 |
5328 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
5329 | section for details) and use the following F<evwrap.h> header file instead |
|
|
5330 | of F<ev.h>: |
3271 | |
5331 | |
|
|
5332 | #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
5333 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
5334 | |
|
|
5335 | #include "ev.h" |
|
|
5336 | |
|
|
5337 | And compile the following F<evwrap.c> file into your project (make sure |
|
|
5338 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
|
|
5339 | |
|
|
5340 | #include "evwrap.h" |
|
|
5341 | #include "ev.c" |
|
|
5342 | |
3272 | =item The winsocket select function |
5343 | =head3 The winsocket C<select> function |
3273 | |
5344 | |
3274 | The winsocket C<select> function doesn't follow POSIX in that it requires |
5345 | The winsocket C<select> function doesn't follow POSIX in that it |
3275 | socket I<handles> and not socket I<file descriptors>. This makes select |
5346 | requires socket I<handles> and not socket I<file descriptors> (it is |
3276 | very inefficient, and also requires a mapping from file descriptors |
5347 | also extremely buggy). This makes select very inefficient, and also |
3277 | to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>, |
5348 | requires a mapping from file descriptors to socket handles (the Microsoft |
3278 | C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor |
5349 | C runtime provides the function C<_open_osfhandle> for this). See the |
3279 | symbols for more info. |
5350 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
|
|
5351 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
3280 | |
5352 | |
3281 | The configuration for a "naked" win32 using the microsoft runtime |
5353 | The configuration for a "naked" win32 using the Microsoft runtime |
3282 | libraries and raw winsocket select is: |
5354 | libraries and raw winsocket select is: |
3283 | |
5355 | |
3284 | #define EV_USE_SELECT 1 |
5356 | #define EV_USE_SELECT 1 |
3285 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
5357 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3286 | |
5358 | |
3287 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
5359 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3288 | complexity in the O(n²) range when using win32. |
5360 | complexity in the O(n²) range when using win32. |
3289 | |
5361 | |
3290 | =item Limited number of file descriptors |
5362 | =head3 Limited number of file descriptors |
3291 | |
5363 | |
3292 | Windows has numerous arbitrary (and low) limits on things. |
5364 | Windows has numerous arbitrary (and low) limits on things. |
3293 | |
5365 | |
3294 | Early versions of winsocket's select only supported waiting for a maximum |
5366 | Early versions of winsocket's select only supported waiting for a maximum |
3295 | of C<64> handles (probably owning to the fact that all windows kernels |
5367 | of C<64> handles (probably owning to the fact that all windows kernels |
3296 | can only wait for C<64> things at the same time internally; microsoft |
5368 | can only wait for C<64> things at the same time internally; Microsoft |
3297 | recommends spawning a chain of threads and wait for 63 handles and the |
5369 | recommends spawning a chain of threads and wait for 63 handles and the |
3298 | previous thread in each. Great). |
5370 | previous thread in each. Sounds great!). |
3299 | |
5371 | |
3300 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
5372 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3301 | to some high number (e.g. C<2048>) before compiling the winsocket select |
5373 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3302 | call (which might be in libev or elsewhere, for example, perl does its own |
5374 | call (which might be in libev or elsewhere, for example, perl and many |
3303 | select emulation on windows). |
5375 | other interpreters do their own select emulation on windows). |
3304 | |
5376 | |
3305 | Another limit is the number of file descriptors in the microsoft runtime |
5377 | Another limit is the number of file descriptors in the Microsoft runtime |
3306 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
5378 | libraries, which by default is C<64> (there must be a hidden I<64> |
3307 | or something like this inside microsoft). You can increase this by calling |
5379 | fetish or something like this inside Microsoft). You can increase this |
3308 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
5380 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3309 | arbitrary limit), but is broken in many versions of the microsoft runtime |
5381 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3310 | libraries. |
|
|
3311 | |
|
|
3312 | This might get you to about C<512> or C<2048> sockets (depending on |
5382 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3313 | windows version and/or the phase of the moon). To get more, you need to |
5383 | (depending on windows version and/or the phase of the moon). To get more, |
3314 | wrap all I/O functions and provide your own fd management, but the cost of |
5384 | you need to wrap all I/O functions and provide your own fd management, but |
3315 | calling select (O(n²)) will likely make this unworkable. |
5385 | the cost of calling select (O(n²)) will likely make this unworkable. |
3316 | |
5386 | |
3317 | =back |
|
|
3318 | |
|
|
3319 | |
|
|
3320 | =head1 PORTABILITY REQUIREMENTS |
5387 | =head2 PORTABILITY REQUIREMENTS |
3321 | |
5388 | |
3322 | In addition to a working ISO-C implementation, libev relies on a few |
5389 | In addition to a working ISO-C implementation and of course the |
3323 | additional extensions: |
5390 | backend-specific APIs, libev relies on a few additional extensions: |
3324 | |
5391 | |
3325 | =over 4 |
5392 | =over 4 |
3326 | |
5393 | |
|
|
5394 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
|
|
5395 | calling conventions regardless of C<ev_watcher_type *>. |
|
|
5396 | |
|
|
5397 | Libev assumes not only that all watcher pointers have the same internal |
|
|
5398 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
|
|
5399 | assumes that the same (machine) code can be used to call any watcher |
|
|
5400 | callback: The watcher callbacks have different type signatures, but libev |
|
|
5401 | calls them using an C<ev_watcher *> internally. |
|
|
5402 | |
|
|
5403 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5404 | |
|
|
5405 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5406 | relies on this setting pointers and integers to null. |
|
|
5407 | |
|
|
5408 | =item pointer accesses must be thread-atomic |
|
|
5409 | |
|
|
5410 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5411 | writable in one piece - this is the case on all current architectures. |
|
|
5412 | |
3327 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5413 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3328 | |
5414 | |
3329 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5415 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3330 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
5416 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
3331 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
5417 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3332 | believed to be sufficiently portable. |
5418 | believed to be sufficiently portable. |
3333 | |
5419 | |
3334 | =item C<sigprocmask> must work in a threaded environment |
5420 | =item C<sigprocmask> must work in a threaded environment |
3335 | |
5421 | |
… | |
… | |
3339 | thread" or will block signals process-wide, both behaviours would |
5425 | thread" or will block signals process-wide, both behaviours would |
3340 | be compatible with libev. Interaction between C<sigprocmask> and |
5426 | be compatible with libev. Interaction between C<sigprocmask> and |
3341 | C<pthread_sigmask> could complicate things, however. |
5427 | C<pthread_sigmask> could complicate things, however. |
3342 | |
5428 | |
3343 | The most portable way to handle signals is to block signals in all threads |
5429 | The most portable way to handle signals is to block signals in all threads |
3344 | except the initial one, and run the default loop in the initial thread as |
5430 | except the initial one, and run the signal handling loop in the initial |
3345 | well. |
5431 | thread as well. |
3346 | |
5432 | |
3347 | =item C<long> must be large enough for common memory allocation sizes |
5433 | =item C<long> must be large enough for common memory allocation sizes |
3348 | |
5434 | |
3349 | To improve portability and simplify using libev, libev uses C<long> |
5435 | To improve portability and simplify its API, libev uses C<long> internally |
3350 | internally instead of C<size_t> when allocating its data structures. On |
5436 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3351 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
5437 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3352 | is still at least 31 bits everywhere, which is enough for hundreds of |
5438 | least 31 bits everywhere, which is enough for hundreds of millions of |
3353 | millions of watchers. |
5439 | watchers. |
3354 | |
5440 | |
3355 | =item C<double> must hold a time value in seconds with enough accuracy |
5441 | =item C<double> must hold a time value in seconds with enough accuracy |
3356 | |
5442 | |
3357 | The type C<double> is used to represent timestamps. It is required to |
5443 | The type C<double> is used to represent timestamps. It is required to |
3358 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
5444 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
3359 | enough for at least into the year 4000. This requirement is fulfilled by |
5445 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
5446 | (the design goal for libev). This requirement is overfulfilled by |
3360 | implementations implementing IEEE 754 (basically all existing ones). |
5447 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5448 | |
|
|
5449 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5450 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5451 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5452 | something like that, just kidding). |
3361 | |
5453 | |
3362 | =back |
5454 | =back |
3363 | |
5455 | |
3364 | If you know of other additional requirements drop me a note. |
5456 | If you know of other additional requirements drop me a note. |
3365 | |
5457 | |
3366 | |
5458 | |
3367 | =head1 VALGRIND |
5459 | =head1 ALGORITHMIC COMPLEXITIES |
3368 | |
5460 | |
3369 | Valgrind has a special section here because it is a popular tool that is |
5461 | In this section the complexities of (many of) the algorithms used inside |
3370 | highly useful, but valgrind reports are very hard to interpret. |
5462 | libev will be documented. For complexity discussions about backends see |
|
|
5463 | the documentation for C<ev_default_init>. |
3371 | |
5464 | |
3372 | If you think you found a bug (memory leak, uninitialised data access etc.) |
5465 | All of the following are about amortised time: If an array needs to be |
3373 | in libev, then check twice: If valgrind reports something like: |
5466 | extended, libev needs to realloc and move the whole array, but this |
|
|
5467 | happens asymptotically rarer with higher number of elements, so O(1) might |
|
|
5468 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
5469 | average it is much faster and asymptotically approaches constant time. |
3374 | |
5470 | |
3375 | ==2274== definitely lost: 0 bytes in 0 blocks. |
5471 | =over 4 |
3376 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3377 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3378 | |
5472 | |
3379 | then there is no memory leak. Similarly, under some circumstances, |
5473 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3380 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3381 | might be confused (it is a very good tool, but only a tool). |
|
|
3382 | |
5474 | |
3383 | If you are unsure about something, feel free to contact the mailing list |
5475 | This means that, when you have a watcher that triggers in one hour and |
3384 | with the full valgrind report and an explanation on why you think this is |
5476 | there are 100 watchers that would trigger before that, then inserting will |
3385 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
5477 | have to skip roughly seven (C<ld 100>) of these watchers. |
3386 | no bug" answer and take the chance of learning how to interpret valgrind |
|
|
3387 | properly. |
|
|
3388 | |
5478 | |
3389 | If you need, for some reason, empty reports from valgrind for your project |
5479 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3390 | I suggest using suppression lists. |
|
|
3391 | |
5480 | |
|
|
5481 | That means that changing a timer costs less than removing/adding them, |
|
|
5482 | as only the relative motion in the event queue has to be paid for. |
|
|
5483 | |
|
|
5484 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
|
|
5485 | |
|
|
5486 | These just add the watcher into an array or at the head of a list. |
|
|
5487 | |
|
|
5488 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
|
|
5489 | |
|
|
5490 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
|
|
5491 | |
|
|
5492 | These watchers are stored in lists, so they need to be walked to find the |
|
|
5493 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
5494 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
5495 | is rare). |
|
|
5496 | |
|
|
5497 | =item Finding the next timer in each loop iteration: O(1) |
|
|
5498 | |
|
|
5499 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
5500 | fixed position in the storage array. |
|
|
5501 | |
|
|
5502 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
5503 | |
|
|
5504 | A change means an I/O watcher gets started or stopped, which requires |
|
|
5505 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
5506 | on backend and whether C<ev_io_set> was used). |
|
|
5507 | |
|
|
5508 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
5509 | |
|
|
5510 | =item Priority handling: O(number_of_priorities) |
|
|
5511 | |
|
|
5512 | Priorities are implemented by allocating some space for each |
|
|
5513 | priority. When doing priority-based operations, libev usually has to |
|
|
5514 | linearly search all the priorities, but starting/stopping and activating |
|
|
5515 | watchers becomes O(1) with respect to priority handling. |
|
|
5516 | |
|
|
5517 | =item Sending an ev_async: O(1) |
|
|
5518 | |
|
|
5519 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
5520 | |
|
|
5521 | =item Processing signals: O(max_signal_number) |
|
|
5522 | |
|
|
5523 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
5524 | calls in the current loop iteration and the loop is currently |
|
|
5525 | blocked. Checking for async and signal events involves iterating over all |
|
|
5526 | running async watchers or all signal numbers. |
|
|
5527 | |
|
|
5528 | =back |
|
|
5529 | |
|
|
5530 | |
|
|
5531 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
5532 | |
|
|
5533 | The major version 4 introduced some incompatible changes to the API. |
|
|
5534 | |
|
|
5535 | At the moment, the C<ev.h> header file provides compatibility definitions |
|
|
5536 | for all changes, so most programs should still compile. The compatibility |
|
|
5537 | layer might be removed in later versions of libev, so better update to the |
|
|
5538 | new API early than late. |
|
|
5539 | |
|
|
5540 | =over 4 |
|
|
5541 | |
|
|
5542 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5543 | |
|
|
5544 | The backward compatibility mechanism can be controlled by |
|
|
5545 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
|
|
5546 | section. |
|
|
5547 | |
|
|
5548 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5549 | |
|
|
5550 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5551 | |
|
|
5552 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5553 | ev_loop_fork (EV_DEFAULT); |
|
|
5554 | |
|
|
5555 | =item function/symbol renames |
|
|
5556 | |
|
|
5557 | A number of functions and symbols have been renamed: |
|
|
5558 | |
|
|
5559 | ev_loop => ev_run |
|
|
5560 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
5561 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5562 | |
|
|
5563 | ev_unloop => ev_break |
|
|
5564 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5565 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5566 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5567 | |
|
|
5568 | EV_TIMEOUT => EV_TIMER |
|
|
5569 | |
|
|
5570 | ev_loop_count => ev_iteration |
|
|
5571 | ev_loop_depth => ev_depth |
|
|
5572 | ev_loop_verify => ev_verify |
|
|
5573 | |
|
|
5574 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
5575 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
5576 | associated constants have been renamed to not collide with the C<struct |
|
|
5577 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
5578 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
5579 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
5580 | typedef. |
|
|
5581 | |
|
|
5582 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
5583 | |
|
|
5584 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
5585 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
5586 | and work, but the library code will of course be larger. |
|
|
5587 | |
|
|
5588 | =back |
|
|
5589 | |
|
|
5590 | |
|
|
5591 | =head1 GLOSSARY |
|
|
5592 | |
|
|
5593 | =over 4 |
|
|
5594 | |
|
|
5595 | =item active |
|
|
5596 | |
|
|
5597 | A watcher is active as long as it has been started and not yet stopped. |
|
|
5598 | See L</WATCHER STATES> for details. |
|
|
5599 | |
|
|
5600 | =item application |
|
|
5601 | |
|
|
5602 | In this document, an application is whatever is using libev. |
|
|
5603 | |
|
|
5604 | =item backend |
|
|
5605 | |
|
|
5606 | The part of the code dealing with the operating system interfaces. |
|
|
5607 | |
|
|
5608 | =item callback |
|
|
5609 | |
|
|
5610 | The address of a function that is called when some event has been |
|
|
5611 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
5612 | received the event, and the actual event bitset. |
|
|
5613 | |
|
|
5614 | =item callback/watcher invocation |
|
|
5615 | |
|
|
5616 | The act of calling the callback associated with a watcher. |
|
|
5617 | |
|
|
5618 | =item event |
|
|
5619 | |
|
|
5620 | A change of state of some external event, such as data now being available |
|
|
5621 | for reading on a file descriptor, time having passed or simply not having |
|
|
5622 | any other events happening anymore. |
|
|
5623 | |
|
|
5624 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
5625 | C<EV_TIMER>). |
|
|
5626 | |
|
|
5627 | =item event library |
|
|
5628 | |
|
|
5629 | A software package implementing an event model and loop. |
|
|
5630 | |
|
|
5631 | =item event loop |
|
|
5632 | |
|
|
5633 | An entity that handles and processes external events and converts them |
|
|
5634 | into callback invocations. |
|
|
5635 | |
|
|
5636 | =item event model |
|
|
5637 | |
|
|
5638 | The model used to describe how an event loop handles and processes |
|
|
5639 | watchers and events. |
|
|
5640 | |
|
|
5641 | =item pending |
|
|
5642 | |
|
|
5643 | A watcher is pending as soon as the corresponding event has been |
|
|
5644 | detected. See L</WATCHER STATES> for details. |
|
|
5645 | |
|
|
5646 | =item real time |
|
|
5647 | |
|
|
5648 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
5649 | |
|
|
5650 | =item wall-clock time |
|
|
5651 | |
|
|
5652 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
5653 | be wrong and jump forwards and backwards, e.g. when you adjust your |
|
|
5654 | clock. |
|
|
5655 | |
|
|
5656 | =item watcher |
|
|
5657 | |
|
|
5658 | A data structure that describes interest in certain events. Watchers need |
|
|
5659 | to be started (attached to an event loop) before they can receive events. |
|
|
5660 | |
|
|
5661 | =back |
3392 | |
5662 | |
3393 | =head1 AUTHOR |
5663 | =head1 AUTHOR |
3394 | |
5664 | |
3395 | Marc Lehmann <libev@schmorp.de>. |
5665 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5666 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
3396 | |
5667 | |