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2 | |
2 | |
3 | libev - a high performance full-featured event loop written in C |
3 | libev - a high performance full-featured event loop written in C |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
8 | |
8 | |
9 | =head1 DESCRIPTION |
9 | =head2 EXAMPLE PROGRAM |
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10 | |
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11 | // a single header file is required |
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12 | #include <ev.h> |
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13 | |
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14 | #include <stdio.h> // for puts |
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15 | |
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16 | // every watcher type has its own typedef'd struct |
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17 | // with the name ev_TYPE |
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18 | ev_io stdin_watcher; |
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19 | ev_timer timeout_watcher; |
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20 | |
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21 | // all watcher callbacks have a similar signature |
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22 | // this callback is called when data is readable on stdin |
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23 | static void |
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24 | stdin_cb (EV_P_ ev_io *w, int revents) |
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25 | { |
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26 | puts ("stdin ready"); |
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27 | // for one-shot events, one must manually stop the watcher |
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28 | // with its corresponding stop function. |
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29 | ev_io_stop (EV_A_ w); |
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30 | |
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31 | // this causes all nested ev_loop's to stop iterating |
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32 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
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33 | } |
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34 | |
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35 | // another callback, this time for a time-out |
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36 | static void |
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37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
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38 | { |
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39 | puts ("timeout"); |
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40 | // this causes the innermost ev_loop to stop iterating |
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41 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
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42 | } |
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43 | |
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44 | int |
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45 | main (void) |
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46 | { |
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47 | // use the default event loop unless you have special needs |
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48 | struct ev_loop *loop = ev_default_loop (0); |
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49 | |
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50 | // initialise an io watcher, then start it |
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51 | // this one will watch for stdin to become readable |
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52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
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53 | ev_io_start (loop, &stdin_watcher); |
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54 | |
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55 | // initialise a timer watcher, then start it |
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56 | // simple non-repeating 5.5 second timeout |
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57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
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58 | ev_timer_start (loop, &timeout_watcher); |
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59 | |
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60 | // now wait for events to arrive |
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61 | ev_loop (loop, 0); |
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62 | |
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63 | // unloop was called, so exit |
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64 | return 0; |
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65 | } |
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66 | |
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67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
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70 | |
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71 | The newest version of this document is also available as an html-formatted |
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72 | web page you might find easier to navigate when reading it for the first |
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73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 ABOUT LIBEV |
10 | |
84 | |
11 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
12 | file descriptor being readable or a timeout occuring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
13 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
14 | |
88 | |
15 | To do this, it must take more or less complete control over your process |
89 | To do this, it must take more or less complete control over your process |
16 | (or thread) by executing the I<event loop> handler, and will then |
90 | (or thread) by executing the I<event loop> handler, and will then |
17 | communicate events via a callback mechanism. |
91 | communicate events via a callback mechanism. |
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19 | You register interest in certain events by registering so-called I<event |
93 | You register interest in certain events by registering so-called I<event |
20 | watchers>, which are relatively small C structures you initialise with the |
94 | watchers>, which are relatively small C structures you initialise with the |
21 | details of the event, and then hand it over to libev by I<starting> the |
95 | details of the event, and then hand it over to libev by I<starting> the |
22 | watcher. |
96 | watcher. |
23 | |
97 | |
24 | =head1 FEATURES |
98 | =head2 FEATURES |
25 | |
99 | |
26 | Libev supports select, poll, the linux-specific epoll and the bsd-specific |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
27 | kqueue mechanisms for file descriptor events, relative timers, absolute |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
28 | timers with customised rescheduling, signal events, process status change |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
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103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
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104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
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105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
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106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
29 | events (related to SIGCHLD), and event watchers dealing with the event |
107 | change events (C<ev_child>), and event watchers dealing with the event |
30 | loop mechanism itself (idle, prepare and check watchers). It also is quite |
108 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
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109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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110 | limited support for fork events (C<ev_fork>). |
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111 | |
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112 | It also is quite fast (see this |
31 | fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing |
113 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
32 | it to libevent for example). |
114 | for example). |
33 | |
115 | |
34 | =head1 CONVENTIONS |
116 | =head2 CONVENTIONS |
35 | |
117 | |
36 | Libev is very configurable. In this manual the default configuration |
118 | Libev is very configurable. In this manual the default (and most common) |
37 | will be described, which supports multiple event loops. For more info |
119 | configuration will be described, which supports multiple event loops. For |
38 | about various configuration options please have a look at the file |
120 | more info about various configuration options please have a look at |
39 | F<README.embed> in the libev distribution. If libev was configured without |
121 | B<EMBED> section in this manual. If libev was configured without support |
40 | support for multiple event loops, then all functions taking an initial |
122 | for multiple event loops, then all functions taking an initial argument of |
41 | argument of name C<loop> (which is always of type C<struct ev_loop *>) |
123 | name C<loop> (which is always of type C<ev_loop *>) will not have |
42 | will not have this argument. |
124 | this argument. |
43 | |
125 | |
44 | =head1 TIME AND OTHER GLOBAL FUNCTIONS |
126 | =head2 TIME REPRESENTATION |
45 | |
127 | |
46 | Libev represents time as a single floating point number, representing the |
128 | Libev represents time as a single floating point number, representing |
47 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
129 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
48 | the beginning of 1970, details are complicated, don't ask). This type is |
130 | near the beginning of 1970, details are complicated, don't ask). This |
49 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
131 | type is called C<ev_tstamp>, which is what you should use too. It usually |
50 | to the double type in C. |
132 | aliases to the C<double> type in C. When you need to do any calculations |
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133 | on it, you should treat it as some floating point value. Unlike the name |
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134 | component C<stamp> might indicate, it is also used for time differences |
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135 | throughout libev. |
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136 | |
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137 | =head1 ERROR HANDLING |
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138 | |
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139 | Libev knows three classes of errors: operating system errors, usage errors |
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140 | and internal errors (bugs). |
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141 | |
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142 | When libev catches an operating system error it cannot handle (for example |
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143 | a system call indicating a condition libev cannot fix), it calls the callback |
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144 | set via C<ev_set_syserr_cb>, which is supposed to fix the problem or |
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145 | abort. The default is to print a diagnostic message and to call C<abort |
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146 | ()>. |
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147 | |
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148 | When libev detects a usage error such as a negative timer interval, then |
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149 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
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150 | so C<NDEBUG> will disable this checking): these are programming errors in |
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151 | the libev caller and need to be fixed there. |
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152 | |
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153 | Libev also has a few internal error-checking C<assert>ions, and also has |
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154 | extensive consistency checking code. These do not trigger under normal |
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155 | circumstances, as they indicate either a bug in libev or worse. |
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156 | |
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157 | |
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158 | =head1 GLOBAL FUNCTIONS |
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159 | |
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160 | These functions can be called anytime, even before initialising the |
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161 | library in any way. |
51 | |
162 | |
52 | =over 4 |
163 | =over 4 |
53 | |
164 | |
54 | =item ev_tstamp ev_time () |
165 | =item ev_tstamp ev_time () |
55 | |
166 | |
56 | Returns the current time as libev would use it. |
167 | Returns the current time as libev would use it. Please note that the |
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168 | C<ev_now> function is usually faster and also often returns the timestamp |
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169 | you actually want to know. |
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170 | |
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171 | =item ev_sleep (ev_tstamp interval) |
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172 | |
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173 | Sleep for the given interval: The current thread will be blocked until |
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174 | either it is interrupted or the given time interval has passed. Basically |
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175 | this is a sub-second-resolution C<sleep ()>. |
57 | |
176 | |
58 | =item int ev_version_major () |
177 | =item int ev_version_major () |
59 | |
178 | |
60 | =item int ev_version_minor () |
179 | =item int ev_version_minor () |
61 | |
180 | |
62 | You can find out the major and minor version numbers of the library |
181 | You can find out the major and minor ABI version numbers of the library |
63 | you linked against by calling the functions C<ev_version_major> and |
182 | you linked against by calling the functions C<ev_version_major> and |
64 | C<ev_version_minor>. If you want, you can compare against the global |
183 | C<ev_version_minor>. If you want, you can compare against the global |
65 | symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the |
184 | symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the |
66 | version of the library your program was compiled against. |
185 | version of the library your program was compiled against. |
67 | |
186 | |
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187 | These version numbers refer to the ABI version of the library, not the |
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188 | release version. |
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189 | |
68 | Usually, it's a good idea to terminate if the major versions mismatch, |
190 | Usually, it's a good idea to terminate if the major versions mismatch, |
69 | as this indicates an incompatible change. Minor versions are usually |
191 | as this indicates an incompatible change. Minor versions are usually |
70 | compatible to older versions, so a larger minor version alone is usually |
192 | compatible to older versions, so a larger minor version alone is usually |
71 | not a problem. |
193 | not a problem. |
72 | |
194 | |
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195 | Example: Make sure we haven't accidentally been linked against the wrong |
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196 | version. |
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197 | |
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198 | assert (("libev version mismatch", |
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199 | ev_version_major () == EV_VERSION_MAJOR |
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200 | && ev_version_minor () >= EV_VERSION_MINOR)); |
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201 | |
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202 | =item unsigned int ev_supported_backends () |
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203 | |
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204 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
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205 | value) compiled into this binary of libev (independent of their |
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206 | availability on the system you are running on). See C<ev_default_loop> for |
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207 | a description of the set values. |
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208 | |
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209 | Example: make sure we have the epoll method, because yeah this is cool and |
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210 | a must have and can we have a torrent of it please!!!11 |
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211 | |
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212 | assert (("sorry, no epoll, no sex", |
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213 | ev_supported_backends () & EVBACKEND_EPOLL)); |
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214 | |
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215 | =item unsigned int ev_recommended_backends () |
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216 | |
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217 | Return the set of all backends compiled into this binary of libev and also |
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218 | recommended for this platform. This set is often smaller than the one |
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219 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
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220 | most BSDs and will not be auto-detected unless you explicitly request it |
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221 | (assuming you know what you are doing). This is the set of backends that |
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222 | libev will probe for if you specify no backends explicitly. |
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223 | |
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224 | =item unsigned int ev_embeddable_backends () |
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225 | |
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226 | Returns the set of backends that are embeddable in other event loops. This |
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227 | is the theoretical, all-platform, value. To find which backends |
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228 | might be supported on the current system, you would need to look at |
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229 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
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230 | recommended ones. |
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231 | |
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232 | See the description of C<ev_embed> watchers for more info. |
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233 | |
73 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
234 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
74 | |
235 | |
75 | Sets the allocation function to use (the prototype is similar to the |
236 | Sets the allocation function to use (the prototype is similar - the |
76 | realloc C function, the semantics are identical). It is used to allocate |
237 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
77 | and free memory (no surprises here). If it returns zero when memory |
238 | used to allocate and free memory (no surprises here). If it returns zero |
78 | needs to be allocated, the library might abort or take some potentially |
239 | when memory needs to be allocated (C<size != 0>), the library might abort |
79 | destructive action. The default is your system realloc function. |
240 | or take some potentially destructive action. |
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241 | |
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242 | Since some systems (at least OpenBSD and Darwin) fail to implement |
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243 | correct C<realloc> semantics, libev will use a wrapper around the system |
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244 | C<realloc> and C<free> functions by default. |
80 | |
245 | |
81 | You could override this function in high-availability programs to, say, |
246 | You could override this function in high-availability programs to, say, |
82 | free some memory if it cannot allocate memory, to use a special allocator, |
247 | free some memory if it cannot allocate memory, to use a special allocator, |
83 | or even to sleep a while and retry until some memory is available. |
248 | or even to sleep a while and retry until some memory is available. |
84 | |
249 | |
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250 | Example: Replace the libev allocator with one that waits a bit and then |
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251 | retries (example requires a standards-compliant C<realloc>). |
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252 | |
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253 | static void * |
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254 | persistent_realloc (void *ptr, size_t size) |
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255 | { |
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256 | for (;;) |
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257 | { |
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258 | void *newptr = realloc (ptr, size); |
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259 | |
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260 | if (newptr) |
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261 | return newptr; |
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262 | |
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263 | sleep (60); |
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264 | } |
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265 | } |
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266 | |
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267 | ... |
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268 | ev_set_allocator (persistent_realloc); |
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269 | |
85 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
270 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
86 | |
271 | |
87 | Set the callback function to call on a retryable syscall error (such |
272 | Set the callback function to call on a retryable system call error (such |
88 | as failed select, poll, epoll_wait). The message is a printable string |
273 | as failed select, poll, epoll_wait). The message is a printable string |
89 | indicating the system call or subsystem causing the problem. If this |
274 | indicating the system call or subsystem causing the problem. If this |
90 | callback is set, then libev will expect it to remedy the sitution, no |
275 | callback is set, then libev will expect it to remedy the situation, no |
91 | matter what, when it returns. That is, libev will generally retry the |
276 | matter what, when it returns. That is, libev will generally retry the |
92 | requested operation, or, if the condition doesn't go away, do bad stuff |
277 | requested operation, or, if the condition doesn't go away, do bad stuff |
93 | (such as abort). |
278 | (such as abort). |
94 | |
279 | |
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280 | Example: This is basically the same thing that libev does internally, too. |
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281 | |
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282 | static void |
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283 | fatal_error (const char *msg) |
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284 | { |
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285 | perror (msg); |
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286 | abort (); |
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287 | } |
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288 | |
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289 | ... |
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290 | ev_set_syserr_cb (fatal_error); |
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291 | |
95 | =back |
292 | =back |
96 | |
293 | |
97 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
294 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
98 | |
295 | |
99 | An event loop is described by a C<struct ev_loop *>. The library knows two |
296 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
100 | types of such loops, the I<default> loop, which supports signals and child |
297 | is I<not> optional in this case, as there is also an C<ev_loop> |
101 | events, and dynamically created loops which do not. |
298 | I<function>). |
102 | |
299 | |
103 | If you use threads, a common model is to run the default event loop |
300 | The library knows two types of such loops, the I<default> loop, which |
104 | in your main thread (or in a separate thrad) and for each thread you |
301 | supports signals and child events, and dynamically created loops which do |
105 | create, you also create another event loop. Libev itself does no locking |
302 | not. |
106 | whatsoever, so if you mix calls to the same event loop in different |
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107 | threads, make sure you lock (this is usually a bad idea, though, even if |
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108 | done correctly, because it's hideous and inefficient). |
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109 | |
303 | |
110 | =over 4 |
304 | =over 4 |
111 | |
305 | |
112 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
306 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
113 | |
307 | |
114 | This will initialise the default event loop if it hasn't been initialised |
308 | This will initialise the default event loop if it hasn't been initialised |
115 | yet and return it. If the default loop could not be initialised, returns |
309 | yet and return it. If the default loop could not be initialised, returns |
116 | false. If it already was initialised it simply returns it (and ignores the |
310 | false. If it already was initialised it simply returns it (and ignores the |
117 | flags). |
311 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
118 | |
312 | |
119 | If you don't know what event loop to use, use the one returned from this |
313 | If you don't know what event loop to use, use the one returned from this |
120 | function. |
314 | function. |
121 | |
315 | |
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316 | Note that this function is I<not> thread-safe, so if you want to use it |
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317 | from multiple threads, you have to lock (note also that this is unlikely, |
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318 | as loops cannot be shared easily between threads anyway). |
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319 | |
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320 | The default loop is the only loop that can handle C<ev_signal> and |
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321 | C<ev_child> watchers, and to do this, it always registers a handler |
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322 | for C<SIGCHLD>. If this is a problem for your application you can either |
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323 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
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324 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
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325 | C<ev_default_init>. |
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326 | |
122 | The flags argument can be used to specify special behaviour or specific |
327 | The flags argument can be used to specify special behaviour or specific |
123 | backends to use, and is usually specified as 0 (or EVFLAG_AUTO). |
328 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
124 | |
329 | |
125 | It supports the following flags: |
330 | The following flags are supported: |
126 | |
331 | |
127 | =over 4 |
332 | =over 4 |
128 | |
333 | |
129 | =item C<EVFLAG_AUTO> |
334 | =item C<EVFLAG_AUTO> |
130 | |
335 | |
131 | The default flags value. Use this if you have no clue (it's the right |
336 | The default flags value. Use this if you have no clue (it's the right |
132 | thing, believe me). |
337 | thing, believe me). |
133 | |
338 | |
134 | =item C<EVFLAG_NOENV> |
339 | =item C<EVFLAG_NOENV> |
135 | |
340 | |
136 | If this flag bit is ored into the flag value (or the program runs setuid |
341 | If this flag bit is or'ed into the flag value (or the program runs setuid |
137 | or setgid) then libev will I<not> look at the environment variable |
342 | or setgid) then libev will I<not> look at the environment variable |
138 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
343 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
139 | override the flags completely if it is found in the environment. This is |
344 | override the flags completely if it is found in the environment. This is |
140 | useful to try out specific backends to test their performance, or to work |
345 | useful to try out specific backends to test their performance, or to work |
141 | around bugs. |
346 | around bugs. |
142 | |
347 | |
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348 | =item C<EVFLAG_FORKCHECK> |
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349 | |
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350 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
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351 | a fork, you can also make libev check for a fork in each iteration by |
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352 | enabling this flag. |
|
|
353 | |
|
|
354 | This works by calling C<getpid ()> on every iteration of the loop, |
|
|
355 | and thus this might slow down your event loop if you do a lot of loop |
|
|
356 | iterations and little real work, but is usually not noticeable (on my |
|
|
357 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
|
|
358 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
|
|
359 | C<pthread_atfork> which is even faster). |
|
|
360 | |
|
|
361 | The big advantage of this flag is that you can forget about fork (and |
|
|
362 | forget about forgetting to tell libev about forking) when you use this |
|
|
363 | flag. |
|
|
364 | |
|
|
365 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
|
|
366 | environment variable. |
|
|
367 | |
|
|
368 | =item C<EVFLAG_NOINOTIFY> |
|
|
369 | |
|
|
370 | When this flag is specified, then libev will not attempt to use the |
|
|
371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
|
|
372 | testing, this flag can be useful to conserve inotify file descriptors, as |
|
|
373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
|
|
374 | |
|
|
375 | =item C<EVFLAG_NOSIGFD> |
|
|
376 | |
|
|
377 | When this flag is specified, then libev will not attempt to use the |
|
|
378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is |
|
|
379 | probably only useful to work around any bugs in libev. Consequently, this |
|
|
380 | flag might go away once the signalfd functionality is considered stable, |
|
|
381 | so it's useful mostly in environment variables and not in program code. |
|
|
382 | |
143 | =item C<EVMETHOD_SELECT> (portable select backend) |
383 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
144 | |
384 | |
|
|
385 | This is your standard select(2) backend. Not I<completely> standard, as |
|
|
386 | libev tries to roll its own fd_set with no limits on the number of fds, |
|
|
387 | but if that fails, expect a fairly low limit on the number of fds when |
|
|
388 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
|
|
389 | usually the fastest backend for a low number of (low-numbered :) fds. |
|
|
390 | |
|
|
391 | To get good performance out of this backend you need a high amount of |
|
|
392 | parallelism (most of the file descriptors should be busy). If you are |
|
|
393 | writing a server, you should C<accept ()> in a loop to accept as many |
|
|
394 | connections as possible during one iteration. You might also want to have |
|
|
395 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
|
|
396 | readiness notifications you get per iteration. |
|
|
397 | |
|
|
398 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
|
|
399 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
|
|
400 | C<exceptfds> set on that platform). |
|
|
401 | |
145 | =item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows) |
402 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
146 | |
403 | |
147 | =item C<EVMETHOD_EPOLL> (linux only) |
404 | And this is your standard poll(2) backend. It's more complicated |
|
|
405 | than select, but handles sparse fds better and has no artificial |
|
|
406 | limit on the number of fds you can use (except it will slow down |
|
|
407 | considerably with a lot of inactive fds). It scales similarly to select, |
|
|
408 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
|
|
409 | performance tips. |
148 | |
410 | |
149 | =item C<EVMETHOD_KQUEUE> (some bsds only) |
411 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
|
|
412 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
150 | |
413 | |
151 | =item C<EVMETHOD_DEVPOLL> (solaris 8 only) |
414 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
152 | |
415 | |
153 | =item C<EVMETHOD_PORT> (solaris 10 only) |
416 | For few fds, this backend is a bit little slower than poll and select, |
|
|
417 | but it scales phenomenally better. While poll and select usually scale |
|
|
418 | like O(total_fds) where n is the total number of fds (or the highest fd), |
|
|
419 | epoll scales either O(1) or O(active_fds). |
154 | |
420 | |
155 | If one or more of these are ored into the flags value, then only these |
421 | The epoll mechanism deserves honorable mention as the most misdesigned |
156 | backends will be tried (in the reverse order as given here). If one are |
422 | of the more advanced event mechanisms: mere annoyances include silently |
157 | specified, any backend will do. |
423 | dropping file descriptors, requiring a system call per change per file |
|
|
424 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
425 | so on. The biggest issue is fork races, however - if a program forks then |
|
|
426 | I<both> parent and child process have to recreate the epoll set, which can |
|
|
427 | take considerable time (one syscall per file descriptor) and is of course |
|
|
428 | hard to detect. |
|
|
429 | |
|
|
430 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
|
|
431 | of course I<doesn't>, and epoll just loves to report events for totally |
|
|
432 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
433 | even remove them from the set) than registered in the set (especially |
|
|
434 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
435 | employing an additional generation counter and comparing that against the |
|
|
436 | events to filter out spurious ones, recreating the set when required. |
|
|
437 | |
|
|
438 | While stopping, setting and starting an I/O watcher in the same iteration |
|
|
439 | will result in some caching, there is still a system call per such |
|
|
440 | incident (because the same I<file descriptor> could point to a different |
|
|
441 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
|
|
442 | file descriptors might not work very well if you register events for both |
|
|
443 | file descriptors. |
|
|
444 | |
|
|
445 | Best performance from this backend is achieved by not unregistering all |
|
|
446 | watchers for a file descriptor until it has been closed, if possible, |
|
|
447 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
448 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
449 | extra overhead. A fork can both result in spurious notifications as well |
|
|
450 | as in libev having to destroy and recreate the epoll object, which can |
|
|
451 | take considerable time and thus should be avoided. |
|
|
452 | |
|
|
453 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
454 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
455 | the usage. So sad. |
|
|
456 | |
|
|
457 | While nominally embeddable in other event loops, this feature is broken in |
|
|
458 | all kernel versions tested so far. |
|
|
459 | |
|
|
460 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
461 | C<EVBACKEND_POLL>. |
|
|
462 | |
|
|
463 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
|
|
464 | |
|
|
465 | Kqueue deserves special mention, as at the time of this writing, it |
|
|
466 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
|
|
467 | with anything but sockets and pipes, except on Darwin, where of course |
|
|
468 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
469 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
470 | without API changes to existing programs. For this reason it's not being |
|
|
471 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
|
|
472 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
473 | system like NetBSD. |
|
|
474 | |
|
|
475 | You still can embed kqueue into a normal poll or select backend and use it |
|
|
476 | only for sockets (after having made sure that sockets work with kqueue on |
|
|
477 | the target platform). See C<ev_embed> watchers for more info. |
|
|
478 | |
|
|
479 | It scales in the same way as the epoll backend, but the interface to the |
|
|
480 | kernel is more efficient (which says nothing about its actual speed, of |
|
|
481 | course). While stopping, setting and starting an I/O watcher does never |
|
|
482 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
|
|
483 | two event changes per incident. Support for C<fork ()> is very bad (but |
|
|
484 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
485 | cases |
|
|
486 | |
|
|
487 | This backend usually performs well under most conditions. |
|
|
488 | |
|
|
489 | While nominally embeddable in other event loops, this doesn't work |
|
|
490 | everywhere, so you might need to test for this. And since it is broken |
|
|
491 | almost everywhere, you should only use it when you have a lot of sockets |
|
|
492 | (for which it usually works), by embedding it into another event loop |
|
|
493 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
|
|
494 | also broken on OS X)) and, did I mention it, using it only for sockets. |
|
|
495 | |
|
|
496 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
497 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
498 | C<NOTE_EOF>. |
|
|
499 | |
|
|
500 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
|
|
501 | |
|
|
502 | This is not implemented yet (and might never be, unless you send me an |
|
|
503 | implementation). According to reports, C</dev/poll> only supports sockets |
|
|
504 | and is not embeddable, which would limit the usefulness of this backend |
|
|
505 | immensely. |
|
|
506 | |
|
|
507 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
|
|
508 | |
|
|
509 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
|
|
510 | it's really slow, but it still scales very well (O(active_fds)). |
|
|
511 | |
|
|
512 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
513 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
514 | blocking when no data (or space) is available. |
|
|
515 | |
|
|
516 | While this backend scales well, it requires one system call per active |
|
|
517 | file descriptor per loop iteration. For small and medium numbers of file |
|
|
518 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
|
|
519 | might perform better. |
|
|
520 | |
|
|
521 | On the positive side, with the exception of the spurious readiness |
|
|
522 | notifications, this backend actually performed fully to specification |
|
|
523 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
524 | OS-specific backends (I vastly prefer correctness over speed hacks). |
|
|
525 | |
|
|
526 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
527 | C<EVBACKEND_POLL>. |
|
|
528 | |
|
|
529 | =item C<EVBACKEND_ALL> |
|
|
530 | |
|
|
531 | Try all backends (even potentially broken ones that wouldn't be tried |
|
|
532 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
|
|
533 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
|
|
534 | |
|
|
535 | It is definitely not recommended to use this flag. |
158 | |
536 | |
159 | =back |
537 | =back |
|
|
538 | |
|
|
539 | If one or more of the backend flags are or'ed into the flags value, |
|
|
540 | then only these backends will be tried (in the reverse order as listed |
|
|
541 | here). If none are specified, all backends in C<ev_recommended_backends |
|
|
542 | ()> will be tried. |
|
|
543 | |
|
|
544 | Example: This is the most typical usage. |
|
|
545 | |
|
|
546 | if (!ev_default_loop (0)) |
|
|
547 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
548 | |
|
|
549 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
550 | environment settings to be taken into account: |
|
|
551 | |
|
|
552 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
553 | |
|
|
554 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
555 | used if available (warning, breaks stuff, best use only with your own |
|
|
556 | private event loop and only if you know the OS supports your types of |
|
|
557 | fds): |
|
|
558 | |
|
|
559 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
160 | |
560 | |
161 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
561 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
162 | |
562 | |
163 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
563 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
164 | always distinct from the default loop. Unlike the default loop, it cannot |
564 | always distinct from the default loop. Unlike the default loop, it cannot |
165 | handle signal and child watchers, and attempts to do so will be greeted by |
565 | handle signal and child watchers, and attempts to do so will be greeted by |
166 | undefined behaviour (or a failed assertion if assertions are enabled). |
566 | undefined behaviour (or a failed assertion if assertions are enabled). |
167 | |
567 | |
|
|
568 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
569 | libev with threads is indeed to create one loop per thread, and using the |
|
|
570 | default loop in the "main" or "initial" thread. |
|
|
571 | |
|
|
572 | Example: Try to create a event loop that uses epoll and nothing else. |
|
|
573 | |
|
|
574 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
|
|
575 | if (!epoller) |
|
|
576 | fatal ("no epoll found here, maybe it hides under your chair"); |
|
|
577 | |
168 | =item ev_default_destroy () |
578 | =item ev_default_destroy () |
169 | |
579 | |
170 | Destroys the default loop again (frees all memory and kernel state |
580 | Destroys the default loop again (frees all memory and kernel state |
171 | etc.). This stops all registered event watchers (by not touching them in |
581 | etc.). None of the active event watchers will be stopped in the normal |
172 | any way whatsoever, although you cannot rely on this :). |
582 | sense, so e.g. C<ev_is_active> might still return true. It is your |
|
|
583 | responsibility to either stop all watchers cleanly yourself I<before> |
|
|
584 | calling this function, or cope with the fact afterwards (which is usually |
|
|
585 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
|
|
586 | for example). |
|
|
587 | |
|
|
588 | Note that certain global state, such as signal state (and installed signal |
|
|
589 | handlers), will not be freed by this function, and related watchers (such |
|
|
590 | as signal and child watchers) would need to be stopped manually. |
|
|
591 | |
|
|
592 | In general it is not advisable to call this function except in the |
|
|
593 | rare occasion where you really need to free e.g. the signal handling |
|
|
594 | pipe fds. If you need dynamically allocated loops it is better to use |
|
|
595 | C<ev_loop_new> and C<ev_loop_destroy>. |
173 | |
596 | |
174 | =item ev_loop_destroy (loop) |
597 | =item ev_loop_destroy (loop) |
175 | |
598 | |
176 | Like C<ev_default_destroy>, but destroys an event loop created by an |
599 | Like C<ev_default_destroy>, but destroys an event loop created by an |
177 | earlier call to C<ev_loop_new>. |
600 | earlier call to C<ev_loop_new>. |
178 | |
601 | |
179 | =item ev_default_fork () |
602 | =item ev_default_fork () |
180 | |
603 | |
|
|
604 | This function sets a flag that causes subsequent C<ev_loop> iterations |
181 | This function reinitialises the kernel state for backends that have |
605 | to reinitialise the kernel state for backends that have one. Despite the |
182 | one. Despite the name, you can call it anytime, but it makes most sense |
606 | name, you can call it anytime, but it makes most sense after forking, in |
183 | after forking, in either the parent or child process (or both, but that |
607 | the child process (or both child and parent, but that again makes little |
184 | again makes little sense). |
608 | sense). You I<must> call it in the child before using any of the libev |
|
|
609 | functions, and it will only take effect at the next C<ev_loop> iteration. |
185 | |
610 | |
186 | You I<must> call this function after forking if and only if you want to |
611 | On the other hand, you only need to call this function in the child |
187 | use the event library in both processes. If you just fork+exec, you don't |
612 | process if and only if you want to use the event library in the child. If |
188 | have to call it. |
613 | you just fork+exec, you don't have to call it at all. |
189 | |
614 | |
190 | The function itself is quite fast and it's usually not a problem to call |
615 | The function itself is quite fast and it's usually not a problem to call |
191 | it just in case after a fork. To make this easy, the function will fit in |
616 | it just in case after a fork. To make this easy, the function will fit in |
192 | quite nicely into a call to C<pthread_atfork>: |
617 | quite nicely into a call to C<pthread_atfork>: |
193 | |
618 | |
… | |
… | |
195 | |
620 | |
196 | =item ev_loop_fork (loop) |
621 | =item ev_loop_fork (loop) |
197 | |
622 | |
198 | Like C<ev_default_fork>, but acts on an event loop created by |
623 | Like C<ev_default_fork>, but acts on an event loop created by |
199 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
624 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
200 | after fork, and how you do this is entirely your own problem. |
625 | after fork that you want to re-use in the child, and how you do this is |
|
|
626 | entirely your own problem. |
201 | |
627 | |
|
|
628 | =item int ev_is_default_loop (loop) |
|
|
629 | |
|
|
630 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
631 | otherwise. |
|
|
632 | |
|
|
633 | =item unsigned int ev_loop_count (loop) |
|
|
634 | |
|
|
635 | Returns the count of loop iterations for the loop, which is identical to |
|
|
636 | the number of times libev did poll for new events. It starts at C<0> and |
|
|
637 | happily wraps around with enough iterations. |
|
|
638 | |
|
|
639 | This value can sometimes be useful as a generation counter of sorts (it |
|
|
640 | "ticks" the number of loop iterations), as it roughly corresponds with |
|
|
641 | C<ev_prepare> and C<ev_check> calls. |
|
|
642 | |
|
|
643 | =item unsigned int ev_loop_depth (loop) |
|
|
644 | |
|
|
645 | Returns the number of times C<ev_loop> was entered minus the number of |
|
|
646 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
647 | |
|
|
648 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
|
|
649 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
|
|
650 | in which case it is higher. |
|
|
651 | |
|
|
652 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
653 | etc.), doesn't count as exit. |
|
|
654 | |
202 | =item unsigned int ev_method (loop) |
655 | =item unsigned int ev_backend (loop) |
203 | |
656 | |
204 | Returns one of the C<EVMETHOD_*> flags indicating the event backend in |
657 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
205 | use. |
658 | use. |
206 | |
659 | |
207 | =item ev_tstamp ev_now (loop) |
660 | =item ev_tstamp ev_now (loop) |
208 | |
661 | |
209 | Returns the current "event loop time", which is the time the event loop |
662 | Returns the current "event loop time", which is the time the event loop |
210 | got events and started processing them. This timestamp does not change |
663 | received events and started processing them. This timestamp does not |
211 | as long as callbacks are being processed, and this is also the base time |
664 | change as long as callbacks are being processed, and this is also the base |
212 | used for relative timers. You can treat it as the timestamp of the event |
665 | time used for relative timers. You can treat it as the timestamp of the |
213 | occuring (or more correctly, the mainloop finding out about it). |
666 | event occurring (or more correctly, libev finding out about it). |
|
|
667 | |
|
|
668 | =item ev_now_update (loop) |
|
|
669 | |
|
|
670 | Establishes the current time by querying the kernel, updating the time |
|
|
671 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
672 | is usually done automatically within C<ev_loop ()>. |
|
|
673 | |
|
|
674 | This function is rarely useful, but when some event callback runs for a |
|
|
675 | very long time without entering the event loop, updating libev's idea of |
|
|
676 | the current time is a good idea. |
|
|
677 | |
|
|
678 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
679 | |
|
|
680 | =item ev_suspend (loop) |
|
|
681 | |
|
|
682 | =item ev_resume (loop) |
|
|
683 | |
|
|
684 | These two functions suspend and resume a loop, for use when the loop is |
|
|
685 | not used for a while and timeouts should not be processed. |
|
|
686 | |
|
|
687 | A typical use case would be an interactive program such as a game: When |
|
|
688 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
689 | would be best to handle timeouts as if no time had actually passed while |
|
|
690 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
691 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
692 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
693 | |
|
|
694 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
695 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
696 | will be rescheduled (that is, they will lose any events that would have |
|
|
697 | occured while suspended). |
|
|
698 | |
|
|
699 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
700 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
701 | without a previous call to C<ev_suspend>. |
|
|
702 | |
|
|
703 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
704 | event loop time (see C<ev_now_update>). |
214 | |
705 | |
215 | =item ev_loop (loop, int flags) |
706 | =item ev_loop (loop, int flags) |
216 | |
707 | |
217 | Finally, this is it, the event handler. This function usually is called |
708 | Finally, this is it, the event handler. This function usually is called |
218 | after you initialised all your watchers and you want to start handling |
709 | after you have initialised all your watchers and you want to start |
219 | events. |
710 | handling events. |
220 | |
711 | |
221 | If the flags argument is specified as 0, it will not return until either |
712 | If the flags argument is specified as C<0>, it will not return until |
222 | no event watchers are active anymore or C<ev_unloop> was called. |
713 | either no event watchers are active anymore or C<ev_unloop> was called. |
|
|
714 | |
|
|
715 | Please note that an explicit C<ev_unloop> is usually better than |
|
|
716 | relying on all watchers to be stopped when deciding when a program has |
|
|
717 | finished (especially in interactive programs), but having a program |
|
|
718 | that automatically loops as long as it has to and no longer by virtue |
|
|
719 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
720 | beauty. |
223 | |
721 | |
224 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
722 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
225 | those events and any outstanding ones, but will not block your process in |
723 | those events and any already outstanding ones, but will not block your |
226 | case there are no events and will return after one iteration of the loop. |
724 | process in case there are no events and will return after one iteration of |
|
|
725 | the loop. |
227 | |
726 | |
228 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
727 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
229 | neccessary) and will handle those and any outstanding ones. It will block |
728 | necessary) and will handle those and any already outstanding ones. It |
230 | your process until at least one new event arrives, and will return after |
729 | will block your process until at least one new event arrives (which could |
|
|
730 | be an event internal to libev itself, so there is no guarantee that a |
|
|
731 | user-registered callback will be called), and will return after one |
231 | one iteration of the loop. |
732 | iteration of the loop. |
232 | |
733 | |
233 | This flags value could be used to implement alternative looping |
734 | This is useful if you are waiting for some external event in conjunction |
234 | constructs, but the C<prepare> and C<check> watchers provide a better and |
735 | with something not expressible using other libev watchers (i.e. "roll your |
235 | more generic mechanism. |
736 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
|
|
737 | usually a better approach for this kind of thing. |
|
|
738 | |
|
|
739 | Here are the gory details of what C<ev_loop> does: |
|
|
740 | |
|
|
741 | - Before the first iteration, call any pending watchers. |
|
|
742 | * If EVFLAG_FORKCHECK was used, check for a fork. |
|
|
743 | - If a fork was detected (by any means), queue and call all fork watchers. |
|
|
744 | - Queue and call all prepare watchers. |
|
|
745 | - If we have been forked, detach and recreate the kernel state |
|
|
746 | as to not disturb the other process. |
|
|
747 | - Update the kernel state with all outstanding changes. |
|
|
748 | - Update the "event loop time" (ev_now ()). |
|
|
749 | - Calculate for how long to sleep or block, if at all |
|
|
750 | (active idle watchers, EVLOOP_NONBLOCK or not having |
|
|
751 | any active watchers at all will result in not sleeping). |
|
|
752 | - Sleep if the I/O and timer collect interval say so. |
|
|
753 | - Block the process, waiting for any events. |
|
|
754 | - Queue all outstanding I/O (fd) events. |
|
|
755 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
|
|
756 | - Queue all expired timers. |
|
|
757 | - Queue all expired periodics. |
|
|
758 | - Unless any events are pending now, queue all idle watchers. |
|
|
759 | - Queue all check watchers. |
|
|
760 | - Call all queued watchers in reverse order (i.e. check watchers first). |
|
|
761 | Signals and child watchers are implemented as I/O watchers, and will |
|
|
762 | be handled here by queueing them when their watcher gets executed. |
|
|
763 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
|
|
764 | were used, or there are no active watchers, return, otherwise |
|
|
765 | continue with step *. |
|
|
766 | |
|
|
767 | Example: Queue some jobs and then loop until no events are outstanding |
|
|
768 | anymore. |
|
|
769 | |
|
|
770 | ... queue jobs here, make sure they register event watchers as long |
|
|
771 | ... as they still have work to do (even an idle watcher will do..) |
|
|
772 | ev_loop (my_loop, 0); |
|
|
773 | ... jobs done or somebody called unloop. yeah! |
236 | |
774 | |
237 | =item ev_unloop (loop, how) |
775 | =item ev_unloop (loop, how) |
238 | |
776 | |
239 | Can be used to make a call to C<ev_loop> return early (but only after it |
777 | Can be used to make a call to C<ev_loop> return early (but only after it |
240 | has processed all outstanding events). The C<how> argument must be either |
778 | has processed all outstanding events). The C<how> argument must be either |
241 | C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or |
779 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
242 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
780 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
|
|
781 | |
|
|
782 | This "unloop state" will be cleared when entering C<ev_loop> again. |
|
|
783 | |
|
|
784 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
243 | |
785 | |
244 | =item ev_ref (loop) |
786 | =item ev_ref (loop) |
245 | |
787 | |
246 | =item ev_unref (loop) |
788 | =item ev_unref (loop) |
247 | |
789 | |
248 | Ref/unref can be used to add or remove a reference count on the event |
790 | Ref/unref can be used to add or remove a reference count on the event |
249 | loop: Every watcher keeps one reference, and as long as the reference |
791 | loop: Every watcher keeps one reference, and as long as the reference |
250 | count is nonzero, C<ev_loop> will not return on its own. If you have |
792 | count is nonzero, C<ev_loop> will not return on its own. |
|
|
793 | |
251 | a watcher you never unregister that should not keep C<ev_loop> from |
794 | If you have a watcher you never unregister that should not keep C<ev_loop> |
252 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
795 | from returning, call ev_unref() after starting, and ev_ref() before |
|
|
796 | stopping it. |
|
|
797 | |
253 | example, libev itself uses this for its internal signal pipe: It is not |
798 | As an example, libev itself uses this for its internal signal pipe: It |
254 | visible to the libev user and should not keep C<ev_loop> from exiting if |
799 | is not visible to the libev user and should not keep C<ev_loop> from |
255 | no event watchers registered by it are active. It is also an excellent |
800 | exiting if no event watchers registered by it are active. It is also an |
256 | way to do this for generic recurring timers or from within third-party |
801 | excellent way to do this for generic recurring timers or from within |
257 | libraries. Just remember to I<unref after start> and I<ref before stop>. |
802 | third-party libraries. Just remember to I<unref after start> and I<ref |
|
|
803 | before stop> (but only if the watcher wasn't active before, or was active |
|
|
804 | before, respectively. Note also that libev might stop watchers itself |
|
|
805 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
806 | in the callback). |
|
|
807 | |
|
|
808 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
|
|
809 | running when nothing else is active. |
|
|
810 | |
|
|
811 | ev_signal exitsig; |
|
|
812 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
|
|
813 | ev_signal_start (loop, &exitsig); |
|
|
814 | evf_unref (loop); |
|
|
815 | |
|
|
816 | Example: For some weird reason, unregister the above signal handler again. |
|
|
817 | |
|
|
818 | ev_ref (loop); |
|
|
819 | ev_signal_stop (loop, &exitsig); |
|
|
820 | |
|
|
821 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
|
|
822 | |
|
|
823 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
|
|
824 | |
|
|
825 | These advanced functions influence the time that libev will spend waiting |
|
|
826 | for events. Both time intervals are by default C<0>, meaning that libev |
|
|
827 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
828 | latency. |
|
|
829 | |
|
|
830 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
|
|
831 | allows libev to delay invocation of I/O and timer/periodic callbacks |
|
|
832 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
833 | opportunities). |
|
|
834 | |
|
|
835 | The idea is that sometimes your program runs just fast enough to handle |
|
|
836 | one (or very few) event(s) per loop iteration. While this makes the |
|
|
837 | program responsive, it also wastes a lot of CPU time to poll for new |
|
|
838 | events, especially with backends like C<select ()> which have a high |
|
|
839 | overhead for the actual polling but can deliver many events at once. |
|
|
840 | |
|
|
841 | By setting a higher I<io collect interval> you allow libev to spend more |
|
|
842 | time collecting I/O events, so you can handle more events per iteration, |
|
|
843 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
|
|
844 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
|
|
845 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
846 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
847 | once per this interval, on average. |
|
|
848 | |
|
|
849 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
|
|
850 | to spend more time collecting timeouts, at the expense of increased |
|
|
851 | latency/jitter/inexactness (the watcher callback will be called |
|
|
852 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
|
|
853 | value will not introduce any overhead in libev. |
|
|
854 | |
|
|
855 | Many (busy) programs can usually benefit by setting the I/O collect |
|
|
856 | interval to a value near C<0.1> or so, which is often enough for |
|
|
857 | interactive servers (of course not for games), likewise for timeouts. It |
|
|
858 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
|
|
859 | as this approaches the timing granularity of most systems. Note that if |
|
|
860 | you do transactions with the outside world and you can't increase the |
|
|
861 | parallelity, then this setting will limit your transaction rate (if you |
|
|
862 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
863 | then you can't do more than 100 transations per second). |
|
|
864 | |
|
|
865 | Setting the I<timeout collect interval> can improve the opportunity for |
|
|
866 | saving power, as the program will "bundle" timer callback invocations that |
|
|
867 | are "near" in time together, by delaying some, thus reducing the number of |
|
|
868 | times the process sleeps and wakes up again. Another useful technique to |
|
|
869 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
|
|
870 | they fire on, say, one-second boundaries only. |
|
|
871 | |
|
|
872 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
873 | more often than 100 times per second: |
|
|
874 | |
|
|
875 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
876 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
877 | |
|
|
878 | =item ev_invoke_pending (loop) |
|
|
879 | |
|
|
880 | This call will simply invoke all pending watchers while resetting their |
|
|
881 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
|
882 | but when overriding the invoke callback this call comes handy. |
|
|
883 | |
|
|
884 | =item int ev_pending_count (loop) |
|
|
885 | |
|
|
886 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
887 | are pending. |
|
|
888 | |
|
|
889 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
890 | |
|
|
891 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
892 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
893 | this callback instead. This is useful, for example, when you want to |
|
|
894 | invoke the actual watchers inside another context (another thread etc.). |
|
|
895 | |
|
|
896 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
897 | callback. |
|
|
898 | |
|
|
899 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
900 | |
|
|
901 | Sometimes you want to share the same loop between multiple threads. This |
|
|
902 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
903 | each call to a libev function. |
|
|
904 | |
|
|
905 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
906 | wait for it to return. One way around this is to wake up the loop via |
|
|
907 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
908 | and I<acquire> callbacks on the loop. |
|
|
909 | |
|
|
910 | When set, then C<release> will be called just before the thread is |
|
|
911 | suspended waiting for new events, and C<acquire> is called just |
|
|
912 | afterwards. |
|
|
913 | |
|
|
914 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
915 | C<acquire> will just call the mutex_lock function again. |
|
|
916 | |
|
|
917 | While event loop modifications are allowed between invocations of |
|
|
918 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
919 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
920 | have no effect on the set of file descriptors being watched, or the time |
|
|
921 | waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
922 | to take note of any changes you made. |
|
|
923 | |
|
|
924 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
925 | invocations of C<release> and C<acquire>. |
|
|
926 | |
|
|
927 | See also the locking example in the C<THREADS> section later in this |
|
|
928 | document. |
|
|
929 | |
|
|
930 | =item ev_set_userdata (loop, void *data) |
|
|
931 | |
|
|
932 | =item ev_userdata (loop) |
|
|
933 | |
|
|
934 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
935 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
936 | C<0.> |
|
|
937 | |
|
|
938 | These two functions can be used to associate arbitrary data with a loop, |
|
|
939 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
940 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
941 | any other purpose as well. |
|
|
942 | |
|
|
943 | =item ev_loop_verify (loop) |
|
|
944 | |
|
|
945 | This function only does something when C<EV_VERIFY> support has been |
|
|
946 | compiled in, which is the default for non-minimal builds. It tries to go |
|
|
947 | through all internal structures and checks them for validity. If anything |
|
|
948 | is found to be inconsistent, it will print an error message to standard |
|
|
949 | error and call C<abort ()>. |
|
|
950 | |
|
|
951 | This can be used to catch bugs inside libev itself: under normal |
|
|
952 | circumstances, this function will never abort as of course libev keeps its |
|
|
953 | data structures consistent. |
258 | |
954 | |
259 | =back |
955 | =back |
260 | |
956 | |
|
|
957 | |
261 | =head1 ANATOMY OF A WATCHER |
958 | =head1 ANATOMY OF A WATCHER |
|
|
959 | |
|
|
960 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
961 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
962 | watchers and C<ev_io_start> for I/O watchers. |
262 | |
963 | |
263 | A watcher is a structure that you create and register to record your |
964 | A watcher is a structure that you create and register to record your |
264 | interest in some event. For instance, if you want to wait for STDIN to |
965 | interest in some event. For instance, if you want to wait for STDIN to |
265 | become readable, you would create an C<ev_io> watcher for that: |
966 | become readable, you would create an C<ev_io> watcher for that: |
266 | |
967 | |
267 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
968 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
268 | { |
969 | { |
269 | ev_io_stop (w); |
970 | ev_io_stop (w); |
270 | ev_unloop (loop, EVUNLOOP_ALL); |
971 | ev_unloop (loop, EVUNLOOP_ALL); |
271 | } |
972 | } |
272 | |
973 | |
273 | struct ev_loop *loop = ev_default_loop (0); |
974 | struct ev_loop *loop = ev_default_loop (0); |
|
|
975 | |
274 | struct ev_io stdin_watcher; |
976 | ev_io stdin_watcher; |
|
|
977 | |
275 | ev_init (&stdin_watcher, my_cb); |
978 | ev_init (&stdin_watcher, my_cb); |
276 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
979 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
277 | ev_io_start (loop, &stdin_watcher); |
980 | ev_io_start (loop, &stdin_watcher); |
|
|
981 | |
278 | ev_loop (loop, 0); |
982 | ev_loop (loop, 0); |
279 | |
983 | |
280 | As you can see, you are responsible for allocating the memory for your |
984 | As you can see, you are responsible for allocating the memory for your |
281 | watcher structures (and it is usually a bad idea to do this on the stack, |
985 | watcher structures (and it is I<usually> a bad idea to do this on the |
282 | although this can sometimes be quite valid). |
986 | stack). |
|
|
987 | |
|
|
988 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
989 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
283 | |
990 | |
284 | Each watcher structure must be initialised by a call to C<ev_init |
991 | Each watcher structure must be initialised by a call to C<ev_init |
285 | (watcher *, callback)>, which expects a callback to be provided. This |
992 | (watcher *, callback)>, which expects a callback to be provided. This |
286 | callback gets invoked each time the event occurs (or, in the case of io |
993 | callback gets invoked each time the event occurs (or, in the case of I/O |
287 | watchers, each time the event loop detects that the file descriptor given |
994 | watchers, each time the event loop detects that the file descriptor given |
288 | is readable and/or writable). |
995 | is readable and/or writable). |
289 | |
996 | |
290 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
997 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
291 | with arguments specific to this watcher type. There is also a macro |
998 | macro to configure it, with arguments specific to the watcher type. There |
292 | to combine initialisation and setting in one call: C<< ev_<type>_init |
999 | is also a macro to combine initialisation and setting in one call: C<< |
293 | (watcher *, callback, ...) >>. |
1000 | ev_TYPE_init (watcher *, callback, ...) >>. |
294 | |
1001 | |
295 | To make the watcher actually watch out for events, you have to start it |
1002 | To make the watcher actually watch out for events, you have to start it |
296 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
1003 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
297 | *) >>), and you can stop watching for events at any time by calling the |
1004 | *) >>), and you can stop watching for events at any time by calling the |
298 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
1005 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
299 | |
1006 | |
300 | As long as your watcher is active (has been started but not stopped) you |
1007 | As long as your watcher is active (has been started but not stopped) you |
301 | must not touch the values stored in it. Most specifically you must never |
1008 | must not touch the values stored in it. Most specifically you must never |
302 | reinitialise it or call its set method. |
1009 | reinitialise it or call its C<ev_TYPE_set> macro. |
303 | |
|
|
304 | You cna check whether an event is active by calling the C<ev_is_active |
|
|
305 | (watcher *)> macro. To see whether an event is outstanding (but the |
|
|
306 | callback for it has not been called yet) you cna use the C<ev_is_pending |
|
|
307 | (watcher *)> macro. |
|
|
308 | |
1010 | |
309 | Each and every callback receives the event loop pointer as first, the |
1011 | Each and every callback receives the event loop pointer as first, the |
310 | registered watcher structure as second, and a bitset of received events as |
1012 | registered watcher structure as second, and a bitset of received events as |
311 | third argument. |
1013 | third argument. |
312 | |
1014 | |
313 | The rceeived events usually include a single bit per event type received |
1015 | The received events usually include a single bit per event type received |
314 | (you can receive multiple events at the same time). The possible bit masks |
1016 | (you can receive multiple events at the same time). The possible bit masks |
315 | are: |
1017 | are: |
316 | |
1018 | |
317 | =over 4 |
1019 | =over 4 |
318 | |
1020 | |
… | |
… | |
336 | The signal specified in the C<ev_signal> watcher has been received by a thread. |
1038 | The signal specified in the C<ev_signal> watcher has been received by a thread. |
337 | |
1039 | |
338 | =item C<EV_CHILD> |
1040 | =item C<EV_CHILD> |
339 | |
1041 | |
340 | The pid specified in the C<ev_child> watcher has received a status change. |
1042 | The pid specified in the C<ev_child> watcher has received a status change. |
|
|
1043 | |
|
|
1044 | =item C<EV_STAT> |
|
|
1045 | |
|
|
1046 | The path specified in the C<ev_stat> watcher changed its attributes somehow. |
341 | |
1047 | |
342 | =item C<EV_IDLE> |
1048 | =item C<EV_IDLE> |
343 | |
1049 | |
344 | The C<ev_idle> watcher has determined that you have nothing better to do. |
1050 | The C<ev_idle> watcher has determined that you have nothing better to do. |
345 | |
1051 | |
… | |
… | |
353 | received events. Callbacks of both watcher types can start and stop as |
1059 | received events. Callbacks of both watcher types can start and stop as |
354 | many watchers as they want, and all of them will be taken into account |
1060 | many watchers as they want, and all of them will be taken into account |
355 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1061 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
356 | C<ev_loop> from blocking). |
1062 | C<ev_loop> from blocking). |
357 | |
1063 | |
|
|
1064 | =item C<EV_EMBED> |
|
|
1065 | |
|
|
1066 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
|
|
1067 | |
|
|
1068 | =item C<EV_FORK> |
|
|
1069 | |
|
|
1070 | The event loop has been resumed in the child process after fork (see |
|
|
1071 | C<ev_fork>). |
|
|
1072 | |
|
|
1073 | =item C<EV_ASYNC> |
|
|
1074 | |
|
|
1075 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
1076 | |
|
|
1077 | =item C<EV_CUSTOM> |
|
|
1078 | |
|
|
1079 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1080 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
1081 | |
358 | =item C<EV_ERROR> |
1082 | =item C<EV_ERROR> |
359 | |
1083 | |
360 | An unspecified error has occured, the watcher has been stopped. This might |
1084 | An unspecified error has occurred, the watcher has been stopped. This might |
361 | happen because the watcher could not be properly started because libev |
1085 | happen because the watcher could not be properly started because libev |
362 | ran out of memory, a file descriptor was found to be closed or any other |
1086 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1087 | problem. Libev considers these application bugs. |
|
|
1088 | |
363 | problem. You best act on it by reporting the problem and somehow coping |
1089 | You best act on it by reporting the problem and somehow coping with the |
364 | with the watcher being stopped. |
1090 | watcher being stopped. Note that well-written programs should not receive |
|
|
1091 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1092 | bug in your program. |
365 | |
1093 | |
366 | Libev will usually signal a few "dummy" events together with an error, |
1094 | Libev will usually signal a few "dummy" events together with an error, for |
367 | for example it might indicate that a fd is readable or writable, and if |
1095 | example it might indicate that a fd is readable or writable, and if your |
368 | your callbacks is well-written it can just attempt the operation and cope |
1096 | callbacks is well-written it can just attempt the operation and cope with |
369 | with the error from read() or write(). This will not work in multithreaded |
1097 | the error from read() or write(). This will not work in multi-threaded |
370 | programs, though, so beware. |
1098 | programs, though, as the fd could already be closed and reused for another |
|
|
1099 | thing, so beware. |
371 | |
1100 | |
372 | =back |
1101 | =back |
373 | |
1102 | |
|
|
1103 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1104 | |
|
|
1105 | =over 4 |
|
|
1106 | |
|
|
1107 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1108 | |
|
|
1109 | This macro initialises the generic portion of a watcher. The contents |
|
|
1110 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1111 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1112 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1113 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1114 | which rolls both calls into one. |
|
|
1115 | |
|
|
1116 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1117 | (or never started) and there are no pending events outstanding. |
|
|
1118 | |
|
|
1119 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1120 | int revents)>. |
|
|
1121 | |
|
|
1122 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1123 | |
|
|
1124 | ev_io w; |
|
|
1125 | ev_init (&w, my_cb); |
|
|
1126 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1127 | |
|
|
1128 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
|
|
1129 | |
|
|
1130 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1131 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1132 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1133 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1134 | difference to the C<ev_init> macro). |
|
|
1135 | |
|
|
1136 | Although some watcher types do not have type-specific arguments |
|
|
1137 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1138 | |
|
|
1139 | See C<ev_init>, above, for an example. |
|
|
1140 | |
|
|
1141 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1142 | |
|
|
1143 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1144 | calls into a single call. This is the most convenient method to initialise |
|
|
1145 | a watcher. The same limitations apply, of course. |
|
|
1146 | |
|
|
1147 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1148 | |
|
|
1149 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1150 | |
|
|
1151 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
|
|
1152 | |
|
|
1153 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1154 | events. If the watcher is already active nothing will happen. |
|
|
1155 | |
|
|
1156 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1157 | whole section. |
|
|
1158 | |
|
|
1159 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1160 | |
|
|
1161 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
|
|
1162 | |
|
|
1163 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1164 | the watcher was active or not). |
|
|
1165 | |
|
|
1166 | It is possible that stopped watchers are pending - for example, |
|
|
1167 | non-repeating timers are being stopped when they become pending - but |
|
|
1168 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1169 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1170 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1171 | |
|
|
1172 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1173 | |
|
|
1174 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1175 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1176 | it. |
|
|
1177 | |
|
|
1178 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1179 | |
|
|
1180 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1181 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1182 | is pending (but not active) you must not call an init function on it (but |
|
|
1183 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1184 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1185 | it). |
|
|
1186 | |
|
|
1187 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1188 | |
|
|
1189 | Returns the callback currently set on the watcher. |
|
|
1190 | |
|
|
1191 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
1192 | |
|
|
1193 | Change the callback. You can change the callback at virtually any time |
|
|
1194 | (modulo threads). |
|
|
1195 | |
|
|
1196 | =item ev_set_priority (ev_TYPE *watcher, priority) |
|
|
1197 | |
|
|
1198 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1199 | |
|
|
1200 | Set and query the priority of the watcher. The priority is a small |
|
|
1201 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1202 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1203 | before watchers with lower priority, but priority will not keep watchers |
|
|
1204 | from being executed (except for C<ev_idle> watchers). |
|
|
1205 | |
|
|
1206 | If you need to suppress invocation when higher priority events are pending |
|
|
1207 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1208 | |
|
|
1209 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1210 | pending. |
|
|
1211 | |
|
|
1212 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1213 | fine, as long as you do not mind that the priority value you query might |
|
|
1214 | or might not have been clamped to the valid range. |
|
|
1215 | |
|
|
1216 | The default priority used by watchers when no priority has been set is |
|
|
1217 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1218 | |
|
|
1219 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1220 | priorities. |
|
|
1221 | |
|
|
1222 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1223 | |
|
|
1224 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1225 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1226 | can deal with that fact, as both are simply passed through to the |
|
|
1227 | callback. |
|
|
1228 | |
|
|
1229 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1230 | |
|
|
1231 | If the watcher is pending, this function clears its pending status and |
|
|
1232 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1233 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1234 | |
|
|
1235 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1236 | callback to be invoked, which can be accomplished with this function. |
|
|
1237 | |
|
|
1238 | =back |
|
|
1239 | |
|
|
1240 | |
374 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1241 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
375 | |
1242 | |
376 | Each watcher has, by default, a member C<void *data> that you can change |
1243 | Each watcher has, by default, a member C<void *data> that you can change |
377 | and read at any time, libev will completely ignore it. This cna be used |
1244 | and read at any time: libev will completely ignore it. This can be used |
378 | to associate arbitrary data with your watcher. If you need more data and |
1245 | to associate arbitrary data with your watcher. If you need more data and |
379 | don't want to allocate memory and store a pointer to it in that data |
1246 | don't want to allocate memory and store a pointer to it in that data |
380 | member, you can also "subclass" the watcher type and provide your own |
1247 | member, you can also "subclass" the watcher type and provide your own |
381 | data: |
1248 | data: |
382 | |
1249 | |
383 | struct my_io |
1250 | struct my_io |
384 | { |
1251 | { |
385 | struct ev_io io; |
1252 | ev_io io; |
386 | int otherfd; |
1253 | int otherfd; |
387 | void *somedata; |
1254 | void *somedata; |
388 | struct whatever *mostinteresting; |
1255 | struct whatever *mostinteresting; |
389 | } |
1256 | }; |
|
|
1257 | |
|
|
1258 | ... |
|
|
1259 | struct my_io w; |
|
|
1260 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
390 | |
1261 | |
391 | And since your callback will be called with a pointer to the watcher, you |
1262 | And since your callback will be called with a pointer to the watcher, you |
392 | can cast it back to your own type: |
1263 | can cast it back to your own type: |
393 | |
1264 | |
394 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1265 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
395 | { |
1266 | { |
396 | struct my_io *w = (struct my_io *)w_; |
1267 | struct my_io *w = (struct my_io *)w_; |
397 | ... |
1268 | ... |
398 | } |
1269 | } |
399 | |
1270 | |
400 | More interesting and less C-conformant ways of catsing your callback type |
1271 | More interesting and less C-conformant ways of casting your callback type |
401 | have been omitted.... |
1272 | instead have been omitted. |
|
|
1273 | |
|
|
1274 | Another common scenario is to use some data structure with multiple |
|
|
1275 | embedded watchers: |
|
|
1276 | |
|
|
1277 | struct my_biggy |
|
|
1278 | { |
|
|
1279 | int some_data; |
|
|
1280 | ev_timer t1; |
|
|
1281 | ev_timer t2; |
|
|
1282 | } |
|
|
1283 | |
|
|
1284 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1285 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1286 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1287 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1288 | programmers): |
|
|
1289 | |
|
|
1290 | #include <stddef.h> |
|
|
1291 | |
|
|
1292 | static void |
|
|
1293 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1294 | { |
|
|
1295 | struct my_biggy big = (struct my_biggy *) |
|
|
1296 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1297 | } |
|
|
1298 | |
|
|
1299 | static void |
|
|
1300 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1301 | { |
|
|
1302 | struct my_biggy big = (struct my_biggy *) |
|
|
1303 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1304 | } |
|
|
1305 | |
|
|
1306 | =head2 WATCHER PRIORITY MODELS |
|
|
1307 | |
|
|
1308 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1309 | integers that influence the ordering of event callback invocation |
|
|
1310 | between watchers in some way, all else being equal. |
|
|
1311 | |
|
|
1312 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1313 | description for the more technical details such as the actual priority |
|
|
1314 | range. |
|
|
1315 | |
|
|
1316 | There are two common ways how these these priorities are being interpreted |
|
|
1317 | by event loops: |
|
|
1318 | |
|
|
1319 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1320 | of lower priority watchers, which means as long as higher priority |
|
|
1321 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1322 | |
|
|
1323 | The less common only-for-ordering model uses priorities solely to order |
|
|
1324 | callback invocation within a single event loop iteration: Higher priority |
|
|
1325 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1326 | before polling for new events. |
|
|
1327 | |
|
|
1328 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1329 | except for idle watchers (which use the lock-out model). |
|
|
1330 | |
|
|
1331 | The rationale behind this is that implementing the lock-out model for |
|
|
1332 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1333 | libraries will just poll for the same events again and again as long as |
|
|
1334 | their callbacks have not been executed, which is very inefficient in the |
|
|
1335 | common case of one high-priority watcher locking out a mass of lower |
|
|
1336 | priority ones. |
|
|
1337 | |
|
|
1338 | Static (ordering) priorities are most useful when you have two or more |
|
|
1339 | watchers handling the same resource: a typical usage example is having an |
|
|
1340 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1341 | timeouts. Under load, data might be received while the program handles |
|
|
1342 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1343 | handler will be executed before checking for data. In that case, giving |
|
|
1344 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1345 | handled first even under adverse conditions (which is usually, but not |
|
|
1346 | always, what you want). |
|
|
1347 | |
|
|
1348 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1349 | will only be executed when no same or higher priority watchers have |
|
|
1350 | received events, they can be used to implement the "lock-out" model when |
|
|
1351 | required. |
|
|
1352 | |
|
|
1353 | For example, to emulate how many other event libraries handle priorities, |
|
|
1354 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1355 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1356 | processing is done in the idle watcher callback. This causes libev to |
|
|
1357 | continously poll and process kernel event data for the watcher, but when |
|
|
1358 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1359 | workable. |
|
|
1360 | |
|
|
1361 | Usually, however, the lock-out model implemented that way will perform |
|
|
1362 | miserably under the type of load it was designed to handle. In that case, |
|
|
1363 | it might be preferable to stop the real watcher before starting the |
|
|
1364 | idle watcher, so the kernel will not have to process the event in case |
|
|
1365 | the actual processing will be delayed for considerable time. |
|
|
1366 | |
|
|
1367 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1368 | priority than the default, and which should only process data when no |
|
|
1369 | other events are pending: |
|
|
1370 | |
|
|
1371 | ev_idle idle; // actual processing watcher |
|
|
1372 | ev_io io; // actual event watcher |
|
|
1373 | |
|
|
1374 | static void |
|
|
1375 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1376 | { |
|
|
1377 | // stop the I/O watcher, we received the event, but |
|
|
1378 | // are not yet ready to handle it. |
|
|
1379 | ev_io_stop (EV_A_ w); |
|
|
1380 | |
|
|
1381 | // start the idle watcher to ahndle the actual event. |
|
|
1382 | // it will not be executed as long as other watchers |
|
|
1383 | // with the default priority are receiving events. |
|
|
1384 | ev_idle_start (EV_A_ &idle); |
|
|
1385 | } |
|
|
1386 | |
|
|
1387 | static void |
|
|
1388 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1389 | { |
|
|
1390 | // actual processing |
|
|
1391 | read (STDIN_FILENO, ...); |
|
|
1392 | |
|
|
1393 | // have to start the I/O watcher again, as |
|
|
1394 | // we have handled the event |
|
|
1395 | ev_io_start (EV_P_ &io); |
|
|
1396 | } |
|
|
1397 | |
|
|
1398 | // initialisation |
|
|
1399 | ev_idle_init (&idle, idle_cb); |
|
|
1400 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1401 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1402 | |
|
|
1403 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1404 | low-priority connections can not be locked out forever under load. This |
|
|
1405 | enables your program to keep a lower latency for important connections |
|
|
1406 | during short periods of high load, while not completely locking out less |
|
|
1407 | important ones. |
402 | |
1408 | |
403 | |
1409 | |
404 | =head1 WATCHER TYPES |
1410 | =head1 WATCHER TYPES |
405 | |
1411 | |
406 | This section describes each watcher in detail, but will not repeat |
1412 | This section describes each watcher in detail, but will not repeat |
407 | information given in the last section. |
1413 | information given in the last section. Any initialisation/set macros, |
|
|
1414 | functions and members specific to the watcher type are explained. |
408 | |
1415 | |
|
|
1416 | Members are additionally marked with either I<[read-only]>, meaning that, |
|
|
1417 | while the watcher is active, you can look at the member and expect some |
|
|
1418 | sensible content, but you must not modify it (you can modify it while the |
|
|
1419 | watcher is stopped to your hearts content), or I<[read-write]>, which |
|
|
1420 | means you can expect it to have some sensible content while the watcher |
|
|
1421 | is active, but you can also modify it. Modifying it may not do something |
|
|
1422 | sensible or take immediate effect (or do anything at all), but libev will |
|
|
1423 | not crash or malfunction in any way. |
|
|
1424 | |
|
|
1425 | |
409 | =head2 C<ev_io> - is this file descriptor readable or writable |
1426 | =head2 C<ev_io> - is this file descriptor readable or writable? |
410 | |
1427 | |
411 | I/O watchers check whether a file descriptor is readable or writable |
1428 | I/O watchers check whether a file descriptor is readable or writable |
412 | in each iteration of the event loop (This behaviour is called |
1429 | in each iteration of the event loop, or, more precisely, when reading |
413 | level-triggering because you keep receiving events as long as the |
1430 | would not block the process and writing would at least be able to write |
414 | condition persists. Remember you cna stop the watcher if you don't want to |
1431 | some data. This behaviour is called level-triggering because you keep |
415 | act on the event and neither want to receive future events). |
1432 | receiving events as long as the condition persists. Remember you can stop |
|
|
1433 | the watcher if you don't want to act on the event and neither want to |
|
|
1434 | receive future events. |
416 | |
1435 | |
417 | In general you can register as many read and/or write event watchers oer |
1436 | In general you can register as many read and/or write event watchers per |
418 | fd as you want (as long as you don't confuse yourself). Setting all file |
1437 | fd as you want (as long as you don't confuse yourself). Setting all file |
419 | descriptors to non-blocking mode is also usually a good idea (but not |
1438 | descriptors to non-blocking mode is also usually a good idea (but not |
420 | required if you know what you are doing). |
1439 | required if you know what you are doing). |
421 | |
1440 | |
422 | You have to be careful with dup'ed file descriptors, though. Some backends |
1441 | If you cannot use non-blocking mode, then force the use of a |
423 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
1442 | known-to-be-good backend (at the time of this writing, this includes only |
424 | descriptors correctly if you register interest in two or more fds pointing |
1443 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
425 | to the same file/socket etc. description. |
1444 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1445 | files) - libev doesn't guarentee any specific behaviour in that case. |
426 | |
1446 | |
427 | If you must do this, then force the use of a known-to-be-good backend |
1447 | Another thing you have to watch out for is that it is quite easy to |
428 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
1448 | receive "spurious" readiness notifications, that is your callback might |
429 | EVMETHOD_POLL). |
1449 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
|
|
1450 | because there is no data. Not only are some backends known to create a |
|
|
1451 | lot of those (for example Solaris ports), it is very easy to get into |
|
|
1452 | this situation even with a relatively standard program structure. Thus |
|
|
1453 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1454 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
|
|
1455 | |
|
|
1456 | If you cannot run the fd in non-blocking mode (for example you should |
|
|
1457 | not play around with an Xlib connection), then you have to separately |
|
|
1458 | re-test whether a file descriptor is really ready with a known-to-be good |
|
|
1459 | interface such as poll (fortunately in our Xlib example, Xlib already |
|
|
1460 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1461 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1462 | indefinitely. |
|
|
1463 | |
|
|
1464 | But really, best use non-blocking mode. |
|
|
1465 | |
|
|
1466 | =head3 The special problem of disappearing file descriptors |
|
|
1467 | |
|
|
1468 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
|
|
1469 | descriptor (either due to calling C<close> explicitly or any other means, |
|
|
1470 | such as C<dup2>). The reason is that you register interest in some file |
|
|
1471 | descriptor, but when it goes away, the operating system will silently drop |
|
|
1472 | this interest. If another file descriptor with the same number then is |
|
|
1473 | registered with libev, there is no efficient way to see that this is, in |
|
|
1474 | fact, a different file descriptor. |
|
|
1475 | |
|
|
1476 | To avoid having to explicitly tell libev about such cases, libev follows |
|
|
1477 | the following policy: Each time C<ev_io_set> is being called, libev |
|
|
1478 | will assume that this is potentially a new file descriptor, otherwise |
|
|
1479 | it is assumed that the file descriptor stays the same. That means that |
|
|
1480 | you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the |
|
|
1481 | descriptor even if the file descriptor number itself did not change. |
|
|
1482 | |
|
|
1483 | This is how one would do it normally anyway, the important point is that |
|
|
1484 | the libev application should not optimise around libev but should leave |
|
|
1485 | optimisations to libev. |
|
|
1486 | |
|
|
1487 | =head3 The special problem of dup'ed file descriptors |
|
|
1488 | |
|
|
1489 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
1490 | but only events for the underlying file descriptions. That means when you |
|
|
1491 | have C<dup ()>'ed file descriptors or weirder constellations, and register |
|
|
1492 | events for them, only one file descriptor might actually receive events. |
|
|
1493 | |
|
|
1494 | There is no workaround possible except not registering events |
|
|
1495 | for potentially C<dup ()>'ed file descriptors, or to resort to |
|
|
1496 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
|
|
1497 | |
|
|
1498 | =head3 The special problem of fork |
|
|
1499 | |
|
|
1500 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
|
|
1501 | useless behaviour. Libev fully supports fork, but needs to be told about |
|
|
1502 | it in the child. |
|
|
1503 | |
|
|
1504 | To support fork in your programs, you either have to call |
|
|
1505 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
|
|
1506 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
|
|
1507 | C<EVBACKEND_POLL>. |
|
|
1508 | |
|
|
1509 | =head3 The special problem of SIGPIPE |
|
|
1510 | |
|
|
1511 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
|
|
1512 | when writing to a pipe whose other end has been closed, your program gets |
|
|
1513 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
|
|
1514 | this is sensible behaviour, for daemons, this is usually undesirable. |
|
|
1515 | |
|
|
1516 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1517 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1518 | somewhere, as that would have given you a big clue). |
|
|
1519 | |
|
|
1520 | |
|
|
1521 | =head3 Watcher-Specific Functions |
430 | |
1522 | |
431 | =over 4 |
1523 | =over 4 |
432 | |
1524 | |
433 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1525 | =item ev_io_init (ev_io *, callback, int fd, int events) |
434 | |
1526 | |
435 | =item ev_io_set (ev_io *, int fd, int events) |
1527 | =item ev_io_set (ev_io *, int fd, int events) |
436 | |
1528 | |
437 | Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive |
1529 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
438 | events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ | |
1530 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
439 | EV_WRITE> to receive the given events. |
1531 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
|
|
1532 | |
|
|
1533 | =item int fd [read-only] |
|
|
1534 | |
|
|
1535 | The file descriptor being watched. |
|
|
1536 | |
|
|
1537 | =item int events [read-only] |
|
|
1538 | |
|
|
1539 | The events being watched. |
440 | |
1540 | |
441 | =back |
1541 | =back |
442 | |
1542 | |
|
|
1543 | =head3 Examples |
|
|
1544 | |
|
|
1545 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
|
|
1546 | readable, but only once. Since it is likely line-buffered, you could |
|
|
1547 | attempt to read a whole line in the callback. |
|
|
1548 | |
|
|
1549 | static void |
|
|
1550 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
|
|
1551 | { |
|
|
1552 | ev_io_stop (loop, w); |
|
|
1553 | .. read from stdin here (or from w->fd) and handle any I/O errors |
|
|
1554 | } |
|
|
1555 | |
|
|
1556 | ... |
|
|
1557 | struct ev_loop *loop = ev_default_init (0); |
|
|
1558 | ev_io stdin_readable; |
|
|
1559 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
|
|
1560 | ev_io_start (loop, &stdin_readable); |
|
|
1561 | ev_loop (loop, 0); |
|
|
1562 | |
|
|
1563 | |
443 | =head2 C<ev_timer> - relative and optionally recurring timeouts |
1564 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
444 | |
1565 | |
445 | Timer watchers are simple relative timers that generate an event after a |
1566 | Timer watchers are simple relative timers that generate an event after a |
446 | given time, and optionally repeating in regular intervals after that. |
1567 | given time, and optionally repeating in regular intervals after that. |
447 | |
1568 | |
448 | The timers are based on real time, that is, if you register an event that |
1569 | The timers are based on real time, that is, if you register an event that |
449 | times out after an hour and youreset your system clock to last years |
1570 | times out after an hour and you reset your system clock to January last |
450 | time, it will still time out after (roughly) and hour. "Roughly" because |
1571 | year, it will still time out after (roughly) one hour. "Roughly" because |
451 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
1572 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
452 | monotonic clock option helps a lot here). |
1573 | monotonic clock option helps a lot here). |
|
|
1574 | |
|
|
1575 | The callback is guaranteed to be invoked only I<after> its timeout has |
|
|
1576 | passed (not I<at>, so on systems with very low-resolution clocks this |
|
|
1577 | might introduce a small delay). If multiple timers become ready during the |
|
|
1578 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1579 | before ones of the same priority with later time-out values (but this is |
|
|
1580 | no longer true when a callback calls C<ev_loop> recursively). |
|
|
1581 | |
|
|
1582 | =head3 Be smart about timeouts |
|
|
1583 | |
|
|
1584 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1585 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1586 | you want to raise some error after a while. |
|
|
1587 | |
|
|
1588 | What follows are some ways to handle this problem, from obvious and |
|
|
1589 | inefficient to smart and efficient. |
|
|
1590 | |
|
|
1591 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1592 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1593 | data or other life sign was received). |
|
|
1594 | |
|
|
1595 | =over 4 |
|
|
1596 | |
|
|
1597 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1598 | |
|
|
1599 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1600 | start the watcher: |
|
|
1601 | |
|
|
1602 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1603 | ev_timer_start (loop, timer); |
|
|
1604 | |
|
|
1605 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1606 | and start it again: |
|
|
1607 | |
|
|
1608 | ev_timer_stop (loop, timer); |
|
|
1609 | ev_timer_set (timer, 60., 0.); |
|
|
1610 | ev_timer_start (loop, timer); |
|
|
1611 | |
|
|
1612 | This is relatively simple to implement, but means that each time there is |
|
|
1613 | some activity, libev will first have to remove the timer from its internal |
|
|
1614 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1615 | still not a constant-time operation. |
|
|
1616 | |
|
|
1617 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1618 | |
|
|
1619 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1620 | C<ev_timer_start>. |
|
|
1621 | |
|
|
1622 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1623 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1624 | successfully read or write some data. If you go into an idle state where |
|
|
1625 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1626 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1627 | |
|
|
1628 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1629 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1630 | member and C<ev_timer_again>. |
|
|
1631 | |
|
|
1632 | At start: |
|
|
1633 | |
|
|
1634 | ev_init (timer, callback); |
|
|
1635 | timer->repeat = 60.; |
|
|
1636 | ev_timer_again (loop, timer); |
|
|
1637 | |
|
|
1638 | Each time there is some activity: |
|
|
1639 | |
|
|
1640 | ev_timer_again (loop, timer); |
|
|
1641 | |
|
|
1642 | It is even possible to change the time-out on the fly, regardless of |
|
|
1643 | whether the watcher is active or not: |
|
|
1644 | |
|
|
1645 | timer->repeat = 30.; |
|
|
1646 | ev_timer_again (loop, timer); |
|
|
1647 | |
|
|
1648 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1649 | you want to modify its timeout value, as libev does not have to completely |
|
|
1650 | remove and re-insert the timer from/into its internal data structure. |
|
|
1651 | |
|
|
1652 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1653 | |
|
|
1654 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1655 | |
|
|
1656 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1657 | relatively long compared to the intervals between other activity - in |
|
|
1658 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1659 | associated activity resets. |
|
|
1660 | |
|
|
1661 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1662 | but remember the time of last activity, and check for a real timeout only |
|
|
1663 | within the callback: |
|
|
1664 | |
|
|
1665 | ev_tstamp last_activity; // time of last activity |
|
|
1666 | |
|
|
1667 | static void |
|
|
1668 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1669 | { |
|
|
1670 | ev_tstamp now = ev_now (EV_A); |
|
|
1671 | ev_tstamp timeout = last_activity + 60.; |
|
|
1672 | |
|
|
1673 | // if last_activity + 60. is older than now, we did time out |
|
|
1674 | if (timeout < now) |
|
|
1675 | { |
|
|
1676 | // timeout occured, take action |
|
|
1677 | } |
|
|
1678 | else |
|
|
1679 | { |
|
|
1680 | // callback was invoked, but there was some activity, re-arm |
|
|
1681 | // the watcher to fire in last_activity + 60, which is |
|
|
1682 | // guaranteed to be in the future, so "again" is positive: |
|
|
1683 | w->repeat = timeout - now; |
|
|
1684 | ev_timer_again (EV_A_ w); |
|
|
1685 | } |
|
|
1686 | } |
|
|
1687 | |
|
|
1688 | To summarise the callback: first calculate the real timeout (defined |
|
|
1689 | as "60 seconds after the last activity"), then check if that time has |
|
|
1690 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1691 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1692 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1693 | a timeout then. |
|
|
1694 | |
|
|
1695 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1696 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1697 | |
|
|
1698 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1699 | minus half the average time between activity), but virtually no calls to |
|
|
1700 | libev to change the timeout. |
|
|
1701 | |
|
|
1702 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1703 | to the current time (meaning we just have some activity :), then call the |
|
|
1704 | callback, which will "do the right thing" and start the timer: |
|
|
1705 | |
|
|
1706 | ev_init (timer, callback); |
|
|
1707 | last_activity = ev_now (loop); |
|
|
1708 | callback (loop, timer, EV_TIMEOUT); |
|
|
1709 | |
|
|
1710 | And when there is some activity, simply store the current time in |
|
|
1711 | C<last_activity>, no libev calls at all: |
|
|
1712 | |
|
|
1713 | last_actiivty = ev_now (loop); |
|
|
1714 | |
|
|
1715 | This technique is slightly more complex, but in most cases where the |
|
|
1716 | time-out is unlikely to be triggered, much more efficient. |
|
|
1717 | |
|
|
1718 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1719 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1720 | fix things for you. |
|
|
1721 | |
|
|
1722 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1723 | |
|
|
1724 | If there is not one request, but many thousands (millions...), all |
|
|
1725 | employing some kind of timeout with the same timeout value, then one can |
|
|
1726 | do even better: |
|
|
1727 | |
|
|
1728 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1729 | at the I<end> of the list. |
|
|
1730 | |
|
|
1731 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1732 | the list is expected to fire (for example, using the technique #3). |
|
|
1733 | |
|
|
1734 | When there is some activity, remove the timer from the list, recalculate |
|
|
1735 | the timeout, append it to the end of the list again, and make sure to |
|
|
1736 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1737 | |
|
|
1738 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1739 | starting, stopping and updating the timers, at the expense of a major |
|
|
1740 | complication, and having to use a constant timeout. The constant timeout |
|
|
1741 | ensures that the list stays sorted. |
|
|
1742 | |
|
|
1743 | =back |
|
|
1744 | |
|
|
1745 | So which method the best? |
|
|
1746 | |
|
|
1747 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1748 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1749 | better, and isn't very complicated either. In most case, choosing either |
|
|
1750 | one is fine, with #3 being better in typical situations. |
|
|
1751 | |
|
|
1752 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1753 | rather complicated, but extremely efficient, something that really pays |
|
|
1754 | off after the first million or so of active timers, i.e. it's usually |
|
|
1755 | overkill :) |
|
|
1756 | |
|
|
1757 | =head3 The special problem of time updates |
|
|
1758 | |
|
|
1759 | Establishing the current time is a costly operation (it usually takes at |
|
|
1760 | least two system calls): EV therefore updates its idea of the current |
|
|
1761 | time only before and after C<ev_loop> collects new events, which causes a |
|
|
1762 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
1763 | lots of events in one iteration. |
453 | |
1764 | |
454 | The relative timeouts are calculated relative to the C<ev_now ()> |
1765 | The relative timeouts are calculated relative to the C<ev_now ()> |
455 | time. This is usually the right thing as this timestamp refers to the time |
1766 | time. This is usually the right thing as this timestamp refers to the time |
456 | of the event triggering whatever timeout you are modifying/starting. If |
1767 | of the event triggering whatever timeout you are modifying/starting. If |
457 | you suspect event processing to be delayed and you *need* to base the timeout |
1768 | you suspect event processing to be delayed and you I<need> to base the |
458 | ion the current time, use something like this to adjust for this: |
1769 | timeout on the current time, use something like this to adjust for this: |
459 | |
1770 | |
460 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1771 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
461 | |
1772 | |
|
|
1773 | If the event loop is suspended for a long time, you can also force an |
|
|
1774 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
|
|
1775 | ()>. |
|
|
1776 | |
|
|
1777 | =head3 The special problems of suspended animation |
|
|
1778 | |
|
|
1779 | When you leave the server world it is quite customary to hit machines that |
|
|
1780 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1781 | |
|
|
1782 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1783 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1784 | to run until the system is suspended, but they will not advance while the |
|
|
1785 | system is suspended. That means, on resume, it will be as if the program |
|
|
1786 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1787 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1788 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1789 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1790 | be adjusted accordingly. |
|
|
1791 | |
|
|
1792 | I would not be surprised to see different behaviour in different between |
|
|
1793 | operating systems, OS versions or even different hardware. |
|
|
1794 | |
|
|
1795 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1796 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1797 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1798 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1799 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1800 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1801 | |
|
|
1802 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1803 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1804 | deterministic behaviour in this case (you can do nothing against |
|
|
1805 | C<SIGSTOP>). |
|
|
1806 | |
|
|
1807 | =head3 Watcher-Specific Functions and Data Members |
|
|
1808 | |
462 | =over 4 |
1809 | =over 4 |
463 | |
1810 | |
464 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1811 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
465 | |
1812 | |
466 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1813 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
467 | |
1814 | |
468 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1815 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
469 | C<0.>, then it will automatically be stopped. If it is positive, then the |
1816 | is C<0.>, then it will automatically be stopped once the timeout is |
470 | timer will automatically be configured to trigger again C<repeat> seconds |
1817 | reached. If it is positive, then the timer will automatically be |
471 | later, again, and again, until stopped manually. |
1818 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1819 | until stopped manually. |
472 | |
1820 | |
473 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1821 | The timer itself will do a best-effort at avoiding drift, that is, if |
474 | configure a timer to trigger every 10 seconds, then it will trigger at |
1822 | you configure a timer to trigger every 10 seconds, then it will normally |
475 | exactly 10 second intervals. If, however, your program cannot keep up with |
1823 | trigger at exactly 10 second intervals. If, however, your program cannot |
476 | the timer (ecause it takes longer than those 10 seconds to do stuff) the |
1824 | keep up with the timer (because it takes longer than those 10 seconds to |
477 | timer will not fire more than once per event loop iteration. |
1825 | do stuff) the timer will not fire more than once per event loop iteration. |
478 | |
1826 | |
479 | =item ev_timer_again (loop) |
1827 | =item ev_timer_again (loop, ev_timer *) |
480 | |
1828 | |
481 | This will act as if the timer timed out and restart it again if it is |
1829 | This will act as if the timer timed out and restart it again if it is |
482 | repeating. The exact semantics are: |
1830 | repeating. The exact semantics are: |
483 | |
1831 | |
|
|
1832 | If the timer is pending, its pending status is cleared. |
|
|
1833 | |
484 | If the timer is started but nonrepeating, stop it. |
1834 | If the timer is started but non-repeating, stop it (as if it timed out). |
485 | |
1835 | |
486 | If the timer is repeating, either start it if necessary (with the repeat |
1836 | If the timer is repeating, either start it if necessary (with the |
487 | value), or reset the running timer to the repeat value. |
1837 | C<repeat> value), or reset the running timer to the C<repeat> value. |
488 | |
1838 | |
489 | This sounds a bit complicated, but here is a useful and typical |
1839 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
490 | example: Imagine you have a tcp connection and you want a so-called idle |
1840 | usage example. |
491 | timeout, that is, you want to be called when there have been, say, 60 |
1841 | |
492 | seconds of inactivity on the socket. The easiest way to do this is to |
1842 | =item ev_timer_remaining (loop, ev_timer *) |
493 | configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each |
1843 | |
494 | time you successfully read or write some data. If you go into an idle |
1844 | Returns the remaining time until a timer fires. If the timer is active, |
495 | state where you do not expect data to travel on the socket, you can stop |
1845 | then this time is relative to the current event loop time, otherwise it's |
496 | the timer, and again will automatically restart it if need be. |
1846 | the timeout value currently configured. |
|
|
1847 | |
|
|
1848 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
1849 | C<5>. When the timer is started and one second passes, C<ev_timer_remain> |
|
|
1850 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1851 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1852 | too), and so on. |
|
|
1853 | |
|
|
1854 | =item ev_tstamp repeat [read-write] |
|
|
1855 | |
|
|
1856 | The current C<repeat> value. Will be used each time the watcher times out |
|
|
1857 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
|
|
1858 | which is also when any modifications are taken into account. |
497 | |
1859 | |
498 | =back |
1860 | =back |
499 | |
1861 | |
|
|
1862 | =head3 Examples |
|
|
1863 | |
|
|
1864 | Example: Create a timer that fires after 60 seconds. |
|
|
1865 | |
|
|
1866 | static void |
|
|
1867 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
|
|
1868 | { |
|
|
1869 | .. one minute over, w is actually stopped right here |
|
|
1870 | } |
|
|
1871 | |
|
|
1872 | ev_timer mytimer; |
|
|
1873 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
|
|
1874 | ev_timer_start (loop, &mytimer); |
|
|
1875 | |
|
|
1876 | Example: Create a timeout timer that times out after 10 seconds of |
|
|
1877 | inactivity. |
|
|
1878 | |
|
|
1879 | static void |
|
|
1880 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
|
|
1881 | { |
|
|
1882 | .. ten seconds without any activity |
|
|
1883 | } |
|
|
1884 | |
|
|
1885 | ev_timer mytimer; |
|
|
1886 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
|
|
1887 | ev_timer_again (&mytimer); /* start timer */ |
|
|
1888 | ev_loop (loop, 0); |
|
|
1889 | |
|
|
1890 | // and in some piece of code that gets executed on any "activity": |
|
|
1891 | // reset the timeout to start ticking again at 10 seconds |
|
|
1892 | ev_timer_again (&mytimer); |
|
|
1893 | |
|
|
1894 | |
500 | =head2 C<ev_periodic> - to cron or not to cron it |
1895 | =head2 C<ev_periodic> - to cron or not to cron? |
501 | |
1896 | |
502 | Periodic watchers are also timers of a kind, but they are very versatile |
1897 | Periodic watchers are also timers of a kind, but they are very versatile |
503 | (and unfortunately a bit complex). |
1898 | (and unfortunately a bit complex). |
504 | |
1899 | |
505 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1900 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
506 | but on wallclock time (absolute time). You can tell a periodic watcher |
1901 | relative time, the physical time that passes) but on wall clock time |
507 | to trigger "at" some specific point in time. For example, if you tell a |
1902 | (absolute time, the thing you can read on your calender or clock). The |
508 | periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () |
1903 | difference is that wall clock time can run faster or slower than real |
509 | + 10.>) and then reset your system clock to the last year, then it will |
1904 | time, and time jumps are not uncommon (e.g. when you adjust your |
510 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1905 | wrist-watch). |
511 | roughly 10 seconds later and of course not if you reset your system time |
|
|
512 | again). |
|
|
513 | |
1906 | |
514 | They can also be used to implement vastly more complex timers, such as |
1907 | You can tell a periodic watcher to trigger after some specific point |
|
|
1908 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1909 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1910 | not a delay) and then reset your system clock to January of the previous |
|
|
1911 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1912 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1913 | it, as it uses a relative timeout). |
|
|
1914 | |
|
|
1915 | C<ev_periodic> watchers can also be used to implement vastly more complex |
515 | triggering an event on eahc midnight, local time. |
1916 | timers, such as triggering an event on each "midnight, local time", or |
|
|
1917 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1918 | those cannot react to time jumps. |
|
|
1919 | |
|
|
1920 | As with timers, the callback is guaranteed to be invoked only when the |
|
|
1921 | point in time where it is supposed to trigger has passed. If multiple |
|
|
1922 | timers become ready during the same loop iteration then the ones with |
|
|
1923 | earlier time-out values are invoked before ones with later time-out values |
|
|
1924 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
|
|
1925 | |
|
|
1926 | =head3 Watcher-Specific Functions and Data Members |
516 | |
1927 | |
517 | =over 4 |
1928 | =over 4 |
518 | |
1929 | |
519 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1930 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
520 | |
1931 | |
521 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1932 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
522 | |
1933 | |
523 | Lots of arguments, lets sort it out... There are basically three modes of |
1934 | Lots of arguments, let's sort it out... There are basically three modes of |
524 | operation, and we will explain them from simplest to complex: |
1935 | operation, and we will explain them from simplest to most complex: |
525 | |
|
|
526 | |
1936 | |
527 | =over 4 |
1937 | =over 4 |
528 | |
1938 | |
529 | =item * absolute timer (interval = reschedule_cb = 0) |
1939 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
530 | |
1940 | |
531 | In this configuration the watcher triggers an event at the wallclock time |
1941 | In this configuration the watcher triggers an event after the wall clock |
532 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1942 | time C<offset> has passed. It will not repeat and will not adjust when a |
533 | that is, if it is to be run at January 1st 2011 then it will run when the |
1943 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
534 | system time reaches or surpasses this time. |
1944 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1945 | this point in time. |
535 | |
1946 | |
536 | =item * non-repeating interval timer (interval > 0, reschedule_cb = 0) |
1947 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
537 | |
1948 | |
538 | In this mode the watcher will always be scheduled to time out at the next |
1949 | In this mode the watcher will always be scheduled to time out at the next |
539 | C<at + N * interval> time (for some integer N) and then repeat, regardless |
1950 | C<offset + N * interval> time (for some integer N, which can also be |
540 | of any time jumps. |
1951 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1952 | argument is merely an offset into the C<interval> periods. |
541 | |
1953 | |
542 | This can be used to create timers that do not drift with respect to system |
1954 | This can be used to create timers that do not drift with respect to the |
543 | time: |
1955 | system clock, for example, here is an C<ev_periodic> that triggers each |
|
|
1956 | hour, on the hour (with respect to UTC): |
544 | |
1957 | |
545 | ev_periodic_set (&periodic, 0., 3600., 0); |
1958 | ev_periodic_set (&periodic, 0., 3600., 0); |
546 | |
1959 | |
547 | This doesn't mean there will always be 3600 seconds in between triggers, |
1960 | This doesn't mean there will always be 3600 seconds in between triggers, |
548 | but only that the the callback will be called when the system time shows a |
1961 | but only that the callback will be called when the system time shows a |
549 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1962 | full hour (UTC), or more correctly, when the system time is evenly divisible |
550 | by 3600. |
1963 | by 3600. |
551 | |
1964 | |
552 | Another way to think about it (for the mathematically inclined) is that |
1965 | Another way to think about it (for the mathematically inclined) is that |
553 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1966 | C<ev_periodic> will try to run the callback in this mode at the next possible |
554 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1967 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
555 | |
1968 | |
|
|
1969 | For numerical stability it is preferable that the C<offset> value is near |
|
|
1970 | C<ev_now ()> (the current time), but there is no range requirement for |
|
|
1971 | this value, and in fact is often specified as zero. |
|
|
1972 | |
|
|
1973 | Note also that there is an upper limit to how often a timer can fire (CPU |
|
|
1974 | speed for example), so if C<interval> is very small then timing stability |
|
|
1975 | will of course deteriorate. Libev itself tries to be exact to be about one |
|
|
1976 | millisecond (if the OS supports it and the machine is fast enough). |
|
|
1977 | |
556 | =item * manual reschedule mode (reschedule_cb = callback) |
1978 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
557 | |
1979 | |
558 | In this mode the values for C<interval> and C<at> are both being |
1980 | In this mode the values for C<interval> and C<offset> are both being |
559 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1981 | ignored. Instead, each time the periodic watcher gets scheduled, the |
560 | reschedule callback will be called with the watcher as first, and the |
1982 | reschedule callback will be called with the watcher as first, and the |
561 | current time as second argument. |
1983 | current time as second argument. |
562 | |
1984 | |
563 | NOTE: I<This callback MUST NOT stop or destroy the periodic or any other |
1985 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
564 | periodic watcher, ever, or make any event loop modifications>. If you need |
1986 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1987 | allowed by documentation here>. |
|
|
1988 | |
565 | to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards. |
1989 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
1990 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
1991 | only event loop modification you are allowed to do). |
566 | |
1992 | |
567 | Also, I<< this callback must always return a time that is later than the |
|
|
568 | passed C<now> value >>. Not even C<now> itself will be ok. |
|
|
569 | |
|
|
570 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1993 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
571 | ev_tstamp now)>, e.g.: |
1994 | *w, ev_tstamp now)>, e.g.: |
572 | |
1995 | |
|
|
1996 | static ev_tstamp |
573 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1997 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
574 | { |
1998 | { |
575 | return now + 60.; |
1999 | return now + 60.; |
576 | } |
2000 | } |
577 | |
2001 | |
578 | It must return the next time to trigger, based on the passed time value |
2002 | It must return the next time to trigger, based on the passed time value |
579 | (that is, the lowest time value larger than to the second argument). It |
2003 | (that is, the lowest time value larger than to the second argument). It |
580 | will usually be called just before the callback will be triggered, but |
2004 | will usually be called just before the callback will be triggered, but |
581 | might be called at other times, too. |
2005 | might be called at other times, too. |
582 | |
2006 | |
|
|
2007 | NOTE: I<< This callback must always return a time that is higher than or |
|
|
2008 | equal to the passed C<now> value >>. |
|
|
2009 | |
583 | This can be used to create very complex timers, such as a timer that |
2010 | This can be used to create very complex timers, such as a timer that |
584 | triggers on each midnight, local time. To do this, you would calculate the |
2011 | triggers on "next midnight, local time". To do this, you would calculate the |
585 | next midnight after C<now> and return the timestamp value for this. How you do this |
2012 | next midnight after C<now> and return the timestamp value for this. How |
586 | is, again, up to you (but it is not trivial). |
2013 | you do this is, again, up to you (but it is not trivial, which is the main |
|
|
2014 | reason I omitted it as an example). |
587 | |
2015 | |
588 | =back |
2016 | =back |
589 | |
2017 | |
590 | =item ev_periodic_again (loop, ev_periodic *) |
2018 | =item ev_periodic_again (loop, ev_periodic *) |
591 | |
2019 | |
592 | Simply stops and restarts the periodic watcher again. This is only useful |
2020 | Simply stops and restarts the periodic watcher again. This is only useful |
593 | when you changed some parameters or the reschedule callback would return |
2021 | when you changed some parameters or the reschedule callback would return |
594 | a different time than the last time it was called (e.g. in a crond like |
2022 | a different time than the last time it was called (e.g. in a crond like |
595 | program when the crontabs have changed). |
2023 | program when the crontabs have changed). |
596 | |
2024 | |
|
|
2025 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
2026 | |
|
|
2027 | When active, returns the absolute time that the watcher is supposed |
|
|
2028 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2029 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2030 | rescheduling modes. |
|
|
2031 | |
|
|
2032 | =item ev_tstamp offset [read-write] |
|
|
2033 | |
|
|
2034 | When repeating, this contains the offset value, otherwise this is the |
|
|
2035 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2036 | although libev might modify this value for better numerical stability). |
|
|
2037 | |
|
|
2038 | Can be modified any time, but changes only take effect when the periodic |
|
|
2039 | timer fires or C<ev_periodic_again> is being called. |
|
|
2040 | |
|
|
2041 | =item ev_tstamp interval [read-write] |
|
|
2042 | |
|
|
2043 | The current interval value. Can be modified any time, but changes only |
|
|
2044 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
|
|
2045 | called. |
|
|
2046 | |
|
|
2047 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
|
|
2048 | |
|
|
2049 | The current reschedule callback, or C<0>, if this functionality is |
|
|
2050 | switched off. Can be changed any time, but changes only take effect when |
|
|
2051 | the periodic timer fires or C<ev_periodic_again> is being called. |
|
|
2052 | |
597 | =back |
2053 | =back |
598 | |
2054 | |
|
|
2055 | =head3 Examples |
|
|
2056 | |
|
|
2057 | Example: Call a callback every hour, or, more precisely, whenever the |
|
|
2058 | system time is divisible by 3600. The callback invocation times have |
|
|
2059 | potentially a lot of jitter, but good long-term stability. |
|
|
2060 | |
|
|
2061 | static void |
|
|
2062 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
|
|
2063 | { |
|
|
2064 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
|
|
2065 | } |
|
|
2066 | |
|
|
2067 | ev_periodic hourly_tick; |
|
|
2068 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
|
|
2069 | ev_periodic_start (loop, &hourly_tick); |
|
|
2070 | |
|
|
2071 | Example: The same as above, but use a reschedule callback to do it: |
|
|
2072 | |
|
|
2073 | #include <math.h> |
|
|
2074 | |
|
|
2075 | static ev_tstamp |
|
|
2076 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
|
|
2077 | { |
|
|
2078 | return now + (3600. - fmod (now, 3600.)); |
|
|
2079 | } |
|
|
2080 | |
|
|
2081 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
|
|
2082 | |
|
|
2083 | Example: Call a callback every hour, starting now: |
|
|
2084 | |
|
|
2085 | ev_periodic hourly_tick; |
|
|
2086 | ev_periodic_init (&hourly_tick, clock_cb, |
|
|
2087 | fmod (ev_now (loop), 3600.), 3600., 0); |
|
|
2088 | ev_periodic_start (loop, &hourly_tick); |
|
|
2089 | |
|
|
2090 | |
599 | =head2 C<ev_signal> - signal me when a signal gets signalled |
2091 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
600 | |
2092 | |
601 | Signal watchers will trigger an event when the process receives a specific |
2093 | Signal watchers will trigger an event when the process receives a specific |
602 | signal one or more times. Even though signals are very asynchronous, libev |
2094 | signal one or more times. Even though signals are very asynchronous, libev |
603 | will try it's best to deliver signals synchronously, i.e. as part of the |
2095 | will try it's best to deliver signals synchronously, i.e. as part of the |
604 | normal event processing, like any other event. |
2096 | normal event processing, like any other event. |
605 | |
2097 | |
|
|
2098 | If you want signals to be delivered truly asynchronously, just use |
|
|
2099 | C<sigaction> as you would do without libev and forget about sharing |
|
|
2100 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2101 | synchronously wake up an event loop. |
|
|
2102 | |
606 | You cna configure as many watchers as you like per signal. Only when the |
2103 | You can configure as many watchers as you like for the same signal, but |
|
|
2104 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2105 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2106 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2107 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2108 | |
607 | first watcher gets started will libev actually register a signal watcher |
2109 | When the first watcher gets started will libev actually register something |
608 | with the kernel (thus it coexists with your own signal handlers as long |
2110 | with the kernel (thus it coexists with your own signal handlers as long as |
609 | as you don't register any with libev). Similarly, when the last signal |
2111 | you don't register any with libev for the same signal). |
610 | watcher for a signal is stopped libev will reset the signal handler to |
2112 | |
611 | SIG_DFL (regardless of what it was set to before). |
2113 | If possible and supported, libev will install its handlers with |
|
|
2114 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
|
|
2115 | not be unduly interrupted. If you have a problem with system calls getting |
|
|
2116 | interrupted by signals you can block all signals in an C<ev_check> watcher |
|
|
2117 | and unblock them in an C<ev_prepare> watcher. |
|
|
2118 | |
|
|
2119 | =head3 The special problem of inheritance over execve |
|
|
2120 | |
|
|
2121 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2122 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2123 | stopping it again), that is, libev might or might not block the signal, |
|
|
2124 | and might or might not set or restore the installed signal handler. |
|
|
2125 | |
|
|
2126 | While this does not matter for the signal disposition (libev never |
|
|
2127 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2128 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2129 | certain signals to be blocked. |
|
|
2130 | |
|
|
2131 | This means that before calling C<exec> (from the child) you should reset |
|
|
2132 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2133 | choice usually). |
|
|
2134 | |
|
|
2135 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2136 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2137 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2138 | |
|
|
2139 | In current versions of libev, you can also ensure that the signal mask is |
|
|
2140 | not blocking any signals (except temporarily, so thread users watch out) |
|
|
2141 | by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This |
|
|
2142 | is not guaranteed for future versions, however. |
|
|
2143 | |
|
|
2144 | =head3 Watcher-Specific Functions and Data Members |
612 | |
2145 | |
613 | =over 4 |
2146 | =over 4 |
614 | |
2147 | |
615 | =item ev_signal_init (ev_signal *, callback, int signum) |
2148 | =item ev_signal_init (ev_signal *, callback, int signum) |
616 | |
2149 | |
617 | =item ev_signal_set (ev_signal *, int signum) |
2150 | =item ev_signal_set (ev_signal *, int signum) |
618 | |
2151 | |
619 | Configures the watcher to trigger on the given signal number (usually one |
2152 | Configures the watcher to trigger on the given signal number (usually one |
620 | of the C<SIGxxx> constants). |
2153 | of the C<SIGxxx> constants). |
621 | |
2154 | |
|
|
2155 | =item int signum [read-only] |
|
|
2156 | |
|
|
2157 | The signal the watcher watches out for. |
|
|
2158 | |
622 | =back |
2159 | =back |
623 | |
2160 | |
|
|
2161 | =head3 Examples |
|
|
2162 | |
|
|
2163 | Example: Try to exit cleanly on SIGINT. |
|
|
2164 | |
|
|
2165 | static void |
|
|
2166 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
|
|
2167 | { |
|
|
2168 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
2169 | } |
|
|
2170 | |
|
|
2171 | ev_signal signal_watcher; |
|
|
2172 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
2173 | ev_signal_start (loop, &signal_watcher); |
|
|
2174 | |
|
|
2175 | |
624 | =head2 C<ev_child> - wait for pid status changes |
2176 | =head2 C<ev_child> - watch out for process status changes |
625 | |
2177 | |
626 | Child watchers trigger when your process receives a SIGCHLD in response to |
2178 | Child watchers trigger when your process receives a SIGCHLD in response to |
627 | some child status changes (most typically when a child of yours dies). |
2179 | some child status changes (most typically when a child of yours dies or |
|
|
2180 | exits). It is permissible to install a child watcher I<after> the child |
|
|
2181 | has been forked (which implies it might have already exited), as long |
|
|
2182 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2183 | forking and then immediately registering a watcher for the child is fine, |
|
|
2184 | but forking and registering a watcher a few event loop iterations later or |
|
|
2185 | in the next callback invocation is not. |
|
|
2186 | |
|
|
2187 | Only the default event loop is capable of handling signals, and therefore |
|
|
2188 | you can only register child watchers in the default event loop. |
|
|
2189 | |
|
|
2190 | Due to some design glitches inside libev, child watchers will always be |
|
|
2191 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2192 | libev) |
|
|
2193 | |
|
|
2194 | =head3 Process Interaction |
|
|
2195 | |
|
|
2196 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
2197 | initialised. This is necessary to guarantee proper behaviour even if the |
|
|
2198 | first child watcher is started after the child exits. The occurrence |
|
|
2199 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
2200 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
2201 | children, even ones not watched. |
|
|
2202 | |
|
|
2203 | =head3 Overriding the Built-In Processing |
|
|
2204 | |
|
|
2205 | Libev offers no special support for overriding the built-in child |
|
|
2206 | processing, but if your application collides with libev's default child |
|
|
2207 | handler, you can override it easily by installing your own handler for |
|
|
2208 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
2209 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
2210 | event-based approach to child reaping and thus use libev's support for |
|
|
2211 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
2212 | |
|
|
2213 | =head3 Stopping the Child Watcher |
|
|
2214 | |
|
|
2215 | Currently, the child watcher never gets stopped, even when the |
|
|
2216 | child terminates, so normally one needs to stop the watcher in the |
|
|
2217 | callback. Future versions of libev might stop the watcher automatically |
|
|
2218 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2219 | problem). |
|
|
2220 | |
|
|
2221 | =head3 Watcher-Specific Functions and Data Members |
628 | |
2222 | |
629 | =over 4 |
2223 | =over 4 |
630 | |
2224 | |
631 | =item ev_child_init (ev_child *, callback, int pid) |
2225 | =item ev_child_init (ev_child *, callback, int pid, int trace) |
632 | |
2226 | |
633 | =item ev_child_set (ev_child *, int pid) |
2227 | =item ev_child_set (ev_child *, int pid, int trace) |
634 | |
2228 | |
635 | Configures the watcher to wait for status changes of process C<pid> (or |
2229 | Configures the watcher to wait for status changes of process C<pid> (or |
636 | I<any> process if C<pid> is specified as C<0>). The callback can look |
2230 | I<any> process if C<pid> is specified as C<0>). The callback can look |
637 | at the C<rstatus> member of the C<ev_child> watcher structure to see |
2231 | at the C<rstatus> member of the C<ev_child> watcher structure to see |
638 | the status word (use the macros from C<sys/wait.h>). The C<rpid> member |
2232 | the status word (use the macros from C<sys/wait.h> and see your systems |
639 | contains the pid of the process causing the status change. |
2233 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
|
|
2234 | process causing the status change. C<trace> must be either C<0> (only |
|
|
2235 | activate the watcher when the process terminates) or C<1> (additionally |
|
|
2236 | activate the watcher when the process is stopped or continued). |
|
|
2237 | |
|
|
2238 | =item int pid [read-only] |
|
|
2239 | |
|
|
2240 | The process id this watcher watches out for, or C<0>, meaning any process id. |
|
|
2241 | |
|
|
2242 | =item int rpid [read-write] |
|
|
2243 | |
|
|
2244 | The process id that detected a status change. |
|
|
2245 | |
|
|
2246 | =item int rstatus [read-write] |
|
|
2247 | |
|
|
2248 | The process exit/trace status caused by C<rpid> (see your systems |
|
|
2249 | C<waitpid> and C<sys/wait.h> documentation for details). |
640 | |
2250 | |
641 | =back |
2251 | =back |
642 | |
2252 | |
|
|
2253 | =head3 Examples |
|
|
2254 | |
|
|
2255 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
2256 | its completion. |
|
|
2257 | |
|
|
2258 | ev_child cw; |
|
|
2259 | |
|
|
2260 | static void |
|
|
2261 | child_cb (EV_P_ ev_child *w, int revents) |
|
|
2262 | { |
|
|
2263 | ev_child_stop (EV_A_ w); |
|
|
2264 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
|
|
2265 | } |
|
|
2266 | |
|
|
2267 | pid_t pid = fork (); |
|
|
2268 | |
|
|
2269 | if (pid < 0) |
|
|
2270 | // error |
|
|
2271 | else if (pid == 0) |
|
|
2272 | { |
|
|
2273 | // the forked child executes here |
|
|
2274 | exit (1); |
|
|
2275 | } |
|
|
2276 | else |
|
|
2277 | { |
|
|
2278 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
2279 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
2280 | } |
|
|
2281 | |
|
|
2282 | |
|
|
2283 | =head2 C<ev_stat> - did the file attributes just change? |
|
|
2284 | |
|
|
2285 | This watches a file system path for attribute changes. That is, it calls |
|
|
2286 | C<stat> on that path in regular intervals (or when the OS says it changed) |
|
|
2287 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2288 | it did. |
|
|
2289 | |
|
|
2290 | The path does not need to exist: changing from "path exists" to "path does |
|
|
2291 | not exist" is a status change like any other. The condition "path does not |
|
|
2292 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
|
|
2293 | C<st_nlink> field being zero (which is otherwise always forced to be at |
|
|
2294 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2295 | contents. |
|
|
2296 | |
|
|
2297 | The path I<must not> end in a slash or contain special components such as |
|
|
2298 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
|
|
2299 | your working directory changes, then the behaviour is undefined. |
|
|
2300 | |
|
|
2301 | Since there is no portable change notification interface available, the |
|
|
2302 | portable implementation simply calls C<stat(2)> regularly on the path |
|
|
2303 | to see if it changed somehow. You can specify a recommended polling |
|
|
2304 | interval for this case. If you specify a polling interval of C<0> (highly |
|
|
2305 | recommended!) then a I<suitable, unspecified default> value will be used |
|
|
2306 | (which you can expect to be around five seconds, although this might |
|
|
2307 | change dynamically). Libev will also impose a minimum interval which is |
|
|
2308 | currently around C<0.1>, but that's usually overkill. |
|
|
2309 | |
|
|
2310 | This watcher type is not meant for massive numbers of stat watchers, |
|
|
2311 | as even with OS-supported change notifications, this can be |
|
|
2312 | resource-intensive. |
|
|
2313 | |
|
|
2314 | At the time of this writing, the only OS-specific interface implemented |
|
|
2315 | is the Linux inotify interface (implementing kqueue support is left as an |
|
|
2316 | exercise for the reader. Note, however, that the author sees no way of |
|
|
2317 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
|
|
2318 | |
|
|
2319 | =head3 ABI Issues (Largefile Support) |
|
|
2320 | |
|
|
2321 | Libev by default (unless the user overrides this) uses the default |
|
|
2322 | compilation environment, which means that on systems with large file |
|
|
2323 | support disabled by default, you get the 32 bit version of the stat |
|
|
2324 | structure. When using the library from programs that change the ABI to |
|
|
2325 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
2326 | compile libev with the same flags to get binary compatibility. This is |
|
|
2327 | obviously the case with any flags that change the ABI, but the problem is |
|
|
2328 | most noticeably displayed with ev_stat and large file support. |
|
|
2329 | |
|
|
2330 | The solution for this is to lobby your distribution maker to make large |
|
|
2331 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
2332 | optional. Libev cannot simply switch on large file support because it has |
|
|
2333 | to exchange stat structures with application programs compiled using the |
|
|
2334 | default compilation environment. |
|
|
2335 | |
|
|
2336 | =head3 Inotify and Kqueue |
|
|
2337 | |
|
|
2338 | When C<inotify (7)> support has been compiled into libev and present at |
|
|
2339 | runtime, it will be used to speed up change detection where possible. The |
|
|
2340 | inotify descriptor will be created lazily when the first C<ev_stat> |
|
|
2341 | watcher is being started. |
|
|
2342 | |
|
|
2343 | Inotify presence does not change the semantics of C<ev_stat> watchers |
|
|
2344 | except that changes might be detected earlier, and in some cases, to avoid |
|
|
2345 | making regular C<stat> calls. Even in the presence of inotify support |
|
|
2346 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2347 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2348 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2349 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2350 | xfs are fully working) libev usually gets away without polling. |
|
|
2351 | |
|
|
2352 | There is no support for kqueue, as apparently it cannot be used to |
|
|
2353 | implement this functionality, due to the requirement of having a file |
|
|
2354 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2355 | etc. is difficult. |
|
|
2356 | |
|
|
2357 | =head3 C<stat ()> is a synchronous operation |
|
|
2358 | |
|
|
2359 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2360 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2361 | ()>, which is a synchronous operation. |
|
|
2362 | |
|
|
2363 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2364 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2365 | as the path data is usually in memory already (except when starting the |
|
|
2366 | watcher). |
|
|
2367 | |
|
|
2368 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2369 | time due to network issues, and even under good conditions, a stat call |
|
|
2370 | often takes multiple milliseconds. |
|
|
2371 | |
|
|
2372 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2373 | paths, although this is fully supported by libev. |
|
|
2374 | |
|
|
2375 | =head3 The special problem of stat time resolution |
|
|
2376 | |
|
|
2377 | The C<stat ()> system call only supports full-second resolution portably, |
|
|
2378 | and even on systems where the resolution is higher, most file systems |
|
|
2379 | still only support whole seconds. |
|
|
2380 | |
|
|
2381 | That means that, if the time is the only thing that changes, you can |
|
|
2382 | easily miss updates: on the first update, C<ev_stat> detects a change and |
|
|
2383 | calls your callback, which does something. When there is another update |
|
|
2384 | within the same second, C<ev_stat> will be unable to detect unless the |
|
|
2385 | stat data does change in other ways (e.g. file size). |
|
|
2386 | |
|
|
2387 | The solution to this is to delay acting on a change for slightly more |
|
|
2388 | than a second (or till slightly after the next full second boundary), using |
|
|
2389 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
|
|
2390 | ev_timer_again (loop, w)>). |
|
|
2391 | |
|
|
2392 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
2393 | of some operating systems (where the second counter of the current time |
|
|
2394 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
2395 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
2396 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
2397 | update file times then there will be a small window where the kernel uses |
|
|
2398 | the previous second to update file times but libev might already execute |
|
|
2399 | the timer callback). |
|
|
2400 | |
|
|
2401 | =head3 Watcher-Specific Functions and Data Members |
|
|
2402 | |
|
|
2403 | =over 4 |
|
|
2404 | |
|
|
2405 | =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) |
|
|
2406 | |
|
|
2407 | =item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval) |
|
|
2408 | |
|
|
2409 | Configures the watcher to wait for status changes of the given |
|
|
2410 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
|
|
2411 | be detected and should normally be specified as C<0> to let libev choose |
|
|
2412 | a suitable value. The memory pointed to by C<path> must point to the same |
|
|
2413 | path for as long as the watcher is active. |
|
|
2414 | |
|
|
2415 | The callback will receive an C<EV_STAT> event when a change was detected, |
|
|
2416 | relative to the attributes at the time the watcher was started (or the |
|
|
2417 | last change was detected). |
|
|
2418 | |
|
|
2419 | =item ev_stat_stat (loop, ev_stat *) |
|
|
2420 | |
|
|
2421 | Updates the stat buffer immediately with new values. If you change the |
|
|
2422 | watched path in your callback, you could call this function to avoid |
|
|
2423 | detecting this change (while introducing a race condition if you are not |
|
|
2424 | the only one changing the path). Can also be useful simply to find out the |
|
|
2425 | new values. |
|
|
2426 | |
|
|
2427 | =item ev_statdata attr [read-only] |
|
|
2428 | |
|
|
2429 | The most-recently detected attributes of the file. Although the type is |
|
|
2430 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
|
|
2431 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
2432 | members to be present. If the C<st_nlink> member is C<0>, then there was |
|
|
2433 | some error while C<stat>ing the file. |
|
|
2434 | |
|
|
2435 | =item ev_statdata prev [read-only] |
|
|
2436 | |
|
|
2437 | The previous attributes of the file. The callback gets invoked whenever |
|
|
2438 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
2439 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
2440 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
|
|
2441 | |
|
|
2442 | =item ev_tstamp interval [read-only] |
|
|
2443 | |
|
|
2444 | The specified interval. |
|
|
2445 | |
|
|
2446 | =item const char *path [read-only] |
|
|
2447 | |
|
|
2448 | The file system path that is being watched. |
|
|
2449 | |
|
|
2450 | =back |
|
|
2451 | |
|
|
2452 | =head3 Examples |
|
|
2453 | |
|
|
2454 | Example: Watch C</etc/passwd> for attribute changes. |
|
|
2455 | |
|
|
2456 | static void |
|
|
2457 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
|
|
2458 | { |
|
|
2459 | /* /etc/passwd changed in some way */ |
|
|
2460 | if (w->attr.st_nlink) |
|
|
2461 | { |
|
|
2462 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
|
|
2463 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
|
|
2464 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
|
|
2465 | } |
|
|
2466 | else |
|
|
2467 | /* you shalt not abuse printf for puts */ |
|
|
2468 | puts ("wow, /etc/passwd is not there, expect problems. " |
|
|
2469 | "if this is windows, they already arrived\n"); |
|
|
2470 | } |
|
|
2471 | |
|
|
2472 | ... |
|
|
2473 | ev_stat passwd; |
|
|
2474 | |
|
|
2475 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
|
|
2476 | ev_stat_start (loop, &passwd); |
|
|
2477 | |
|
|
2478 | Example: Like above, but additionally use a one-second delay so we do not |
|
|
2479 | miss updates (however, frequent updates will delay processing, too, so |
|
|
2480 | one might do the work both on C<ev_stat> callback invocation I<and> on |
|
|
2481 | C<ev_timer> callback invocation). |
|
|
2482 | |
|
|
2483 | static ev_stat passwd; |
|
|
2484 | static ev_timer timer; |
|
|
2485 | |
|
|
2486 | static void |
|
|
2487 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2488 | { |
|
|
2489 | ev_timer_stop (EV_A_ w); |
|
|
2490 | |
|
|
2491 | /* now it's one second after the most recent passwd change */ |
|
|
2492 | } |
|
|
2493 | |
|
|
2494 | static void |
|
|
2495 | stat_cb (EV_P_ ev_stat *w, int revents) |
|
|
2496 | { |
|
|
2497 | /* reset the one-second timer */ |
|
|
2498 | ev_timer_again (EV_A_ &timer); |
|
|
2499 | } |
|
|
2500 | |
|
|
2501 | ... |
|
|
2502 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
|
|
2503 | ev_stat_start (loop, &passwd); |
|
|
2504 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
|
|
2505 | |
|
|
2506 | |
643 | =head2 C<ev_idle> - when you've got nothing better to do |
2507 | =head2 C<ev_idle> - when you've got nothing better to do... |
644 | |
2508 | |
645 | Idle watchers trigger events when there are no other I/O or timer (or |
2509 | Idle watchers trigger events when no other events of the same or higher |
646 | periodic) events pending. That is, as long as your process is busy |
2510 | priority are pending (prepare, check and other idle watchers do not count |
647 | handling sockets or timeouts it will not be called. But when your process |
2511 | as receiving "events"). |
648 | is idle all idle watchers are being called again and again - until |
2512 | |
|
|
2513 | That is, as long as your process is busy handling sockets or timeouts |
|
|
2514 | (or even signals, imagine) of the same or higher priority it will not be |
|
|
2515 | triggered. But when your process is idle (or only lower-priority watchers |
|
|
2516 | are pending), the idle watchers are being called once per event loop |
649 | stopped, that is, or your process receives more events. |
2517 | iteration - until stopped, that is, or your process receives more events |
|
|
2518 | and becomes busy again with higher priority stuff. |
650 | |
2519 | |
651 | The most noteworthy effect is that as long as any idle watchers are |
2520 | The most noteworthy effect is that as long as any idle watchers are |
652 | active, the process will not block when waiting for new events. |
2521 | active, the process will not block when waiting for new events. |
653 | |
2522 | |
654 | Apart from keeping your process non-blocking (which is a useful |
2523 | Apart from keeping your process non-blocking (which is a useful |
655 | effect on its own sometimes), idle watchers are a good place to do |
2524 | effect on its own sometimes), idle watchers are a good place to do |
656 | "pseudo-background processing", or delay processing stuff to after the |
2525 | "pseudo-background processing", or delay processing stuff to after the |
657 | event loop has handled all outstanding events. |
2526 | event loop has handled all outstanding events. |
658 | |
2527 | |
|
|
2528 | =head3 Watcher-Specific Functions and Data Members |
|
|
2529 | |
659 | =over 4 |
2530 | =over 4 |
660 | |
2531 | |
661 | =item ev_idle_init (ev_signal *, callback) |
2532 | =item ev_idle_init (ev_idle *, callback) |
662 | |
2533 | |
663 | Initialises and configures the idle watcher - it has no parameters of any |
2534 | Initialises and configures the idle watcher - it has no parameters of any |
664 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2535 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
665 | believe me. |
2536 | believe me. |
666 | |
2537 | |
667 | =back |
2538 | =back |
668 | |
2539 | |
669 | =head2 prepare and check - your hooks into the event loop |
2540 | =head3 Examples |
670 | |
2541 | |
|
|
2542 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
|
|
2543 | callback, free it. Also, use no error checking, as usual. |
|
|
2544 | |
|
|
2545 | static void |
|
|
2546 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
|
|
2547 | { |
|
|
2548 | free (w); |
|
|
2549 | // now do something you wanted to do when the program has |
|
|
2550 | // no longer anything immediate to do. |
|
|
2551 | } |
|
|
2552 | |
|
|
2553 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
|
|
2554 | ev_idle_init (idle_watcher, idle_cb); |
|
|
2555 | ev_idle_start (loop, idle_watcher); |
|
|
2556 | |
|
|
2557 | |
|
|
2558 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
|
|
2559 | |
671 | Prepare and check watchers usually (but not always) are used in |
2560 | Prepare and check watchers are usually (but not always) used in pairs: |
672 | tandom. Prepare watchers get invoked before the process blocks and check |
2561 | prepare watchers get invoked before the process blocks and check watchers |
673 | watchers afterwards. |
2562 | afterwards. |
674 | |
2563 | |
|
|
2564 | You I<must not> call C<ev_loop> or similar functions that enter |
|
|
2565 | the current event loop from either C<ev_prepare> or C<ev_check> |
|
|
2566 | watchers. Other loops than the current one are fine, however. The |
|
|
2567 | rationale behind this is that you do not need to check for recursion in |
|
|
2568 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
|
|
2569 | C<ev_check> so if you have one watcher of each kind they will always be |
|
|
2570 | called in pairs bracketing the blocking call. |
|
|
2571 | |
675 | Their main purpose is to integrate other event mechanisms into libev. This |
2572 | Their main purpose is to integrate other event mechanisms into libev and |
676 | could be used, for example, to track variable changes, implement your own |
2573 | their use is somewhat advanced. They could be used, for example, to track |
677 | watchers, integrate net-snmp or a coroutine library and lots more. |
2574 | variable changes, implement your own watchers, integrate net-snmp or a |
|
|
2575 | coroutine library and lots more. They are also occasionally useful if |
|
|
2576 | you cache some data and want to flush it before blocking (for example, |
|
|
2577 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
|
|
2578 | watcher). |
678 | |
2579 | |
679 | This is done by examining in each prepare call which file descriptors need |
2580 | This is done by examining in each prepare call which file descriptors |
680 | to be watched by the other library, registering C<ev_io> watchers for them |
2581 | need to be watched by the other library, registering C<ev_io> watchers |
681 | and starting an C<ev_timer> watcher for any timeouts (many libraries provide |
2582 | for them and starting an C<ev_timer> watcher for any timeouts (many |
682 | just this functionality). Then, in the check watcher you check for any |
2583 | libraries provide exactly this functionality). Then, in the check watcher, |
683 | events that occured (by making your callbacks set soem flags for example) |
2584 | you check for any events that occurred (by checking the pending status |
684 | and call back into the library. |
2585 | of all watchers and stopping them) and call back into the library. The |
|
|
2586 | I/O and timer callbacks will never actually be called (but must be valid |
|
|
2587 | nevertheless, because you never know, you know?). |
685 | |
2588 | |
686 | As another example, the perl Coro module uses these hooks to integrate |
2589 | As another example, the Perl Coro module uses these hooks to integrate |
687 | coroutines into libev programs, by yielding to other active coroutines |
2590 | coroutines into libev programs, by yielding to other active coroutines |
688 | during each prepare and only letting the process block if no coroutines |
2591 | during each prepare and only letting the process block if no coroutines |
689 | are ready to run. |
2592 | are ready to run (it's actually more complicated: it only runs coroutines |
|
|
2593 | with priority higher than or equal to the event loop and one coroutine |
|
|
2594 | of lower priority, but only once, using idle watchers to keep the event |
|
|
2595 | loop from blocking if lower-priority coroutines are active, thus mapping |
|
|
2596 | low-priority coroutines to idle/background tasks). |
|
|
2597 | |
|
|
2598 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
|
|
2599 | priority, to ensure that they are being run before any other watchers |
|
|
2600 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2601 | |
|
|
2602 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
|
|
2603 | activate ("feed") events into libev. While libev fully supports this, they |
|
|
2604 | might get executed before other C<ev_check> watchers did their job. As |
|
|
2605 | C<ev_check> watchers are often used to embed other (non-libev) event |
|
|
2606 | loops those other event loops might be in an unusable state until their |
|
|
2607 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
|
|
2608 | others). |
|
|
2609 | |
|
|
2610 | =head3 Watcher-Specific Functions and Data Members |
690 | |
2611 | |
691 | =over 4 |
2612 | =over 4 |
692 | |
2613 | |
693 | =item ev_prepare_init (ev_prepare *, callback) |
2614 | =item ev_prepare_init (ev_prepare *, callback) |
694 | |
2615 | |
695 | =item ev_check_init (ev_check *, callback) |
2616 | =item ev_check_init (ev_check *, callback) |
696 | |
2617 | |
697 | Initialises and configures the prepare or check watcher - they have no |
2618 | Initialises and configures the prepare or check watcher - they have no |
698 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2619 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
699 | macros, but using them is utterly, utterly pointless. |
2620 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2621 | pointless. |
700 | |
2622 | |
701 | =back |
2623 | =back |
702 | |
2624 | |
|
|
2625 | =head3 Examples |
|
|
2626 | |
|
|
2627 | There are a number of principal ways to embed other event loops or modules |
|
|
2628 | into libev. Here are some ideas on how to include libadns into libev |
|
|
2629 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
|
|
2630 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
|
|
2631 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
|
|
2632 | Glib event loop). |
|
|
2633 | |
|
|
2634 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
|
|
2635 | and in a check watcher, destroy them and call into libadns. What follows |
|
|
2636 | is pseudo-code only of course. This requires you to either use a low |
|
|
2637 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
|
|
2638 | the callbacks for the IO/timeout watchers might not have been called yet. |
|
|
2639 | |
|
|
2640 | static ev_io iow [nfd]; |
|
|
2641 | static ev_timer tw; |
|
|
2642 | |
|
|
2643 | static void |
|
|
2644 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
|
|
2645 | { |
|
|
2646 | } |
|
|
2647 | |
|
|
2648 | // create io watchers for each fd and a timer before blocking |
|
|
2649 | static void |
|
|
2650 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
|
|
2651 | { |
|
|
2652 | int timeout = 3600000; |
|
|
2653 | struct pollfd fds [nfd]; |
|
|
2654 | // actual code will need to loop here and realloc etc. |
|
|
2655 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
|
|
2656 | |
|
|
2657 | /* the callback is illegal, but won't be called as we stop during check */ |
|
|
2658 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
|
|
2659 | ev_timer_start (loop, &tw); |
|
|
2660 | |
|
|
2661 | // create one ev_io per pollfd |
|
|
2662 | for (int i = 0; i < nfd; ++i) |
|
|
2663 | { |
|
|
2664 | ev_io_init (iow + i, io_cb, fds [i].fd, |
|
|
2665 | ((fds [i].events & POLLIN ? EV_READ : 0) |
|
|
2666 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
|
|
2667 | |
|
|
2668 | fds [i].revents = 0; |
|
|
2669 | ev_io_start (loop, iow + i); |
|
|
2670 | } |
|
|
2671 | } |
|
|
2672 | |
|
|
2673 | // stop all watchers after blocking |
|
|
2674 | static void |
|
|
2675 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
|
|
2676 | { |
|
|
2677 | ev_timer_stop (loop, &tw); |
|
|
2678 | |
|
|
2679 | for (int i = 0; i < nfd; ++i) |
|
|
2680 | { |
|
|
2681 | // set the relevant poll flags |
|
|
2682 | // could also call adns_processreadable etc. here |
|
|
2683 | struct pollfd *fd = fds + i; |
|
|
2684 | int revents = ev_clear_pending (iow + i); |
|
|
2685 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
2686 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
2687 | |
|
|
2688 | // now stop the watcher |
|
|
2689 | ev_io_stop (loop, iow + i); |
|
|
2690 | } |
|
|
2691 | |
|
|
2692 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
2693 | } |
|
|
2694 | |
|
|
2695 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
|
|
2696 | in the prepare watcher and would dispose of the check watcher. |
|
|
2697 | |
|
|
2698 | Method 3: If the module to be embedded supports explicit event |
|
|
2699 | notification (libadns does), you can also make use of the actual watcher |
|
|
2700 | callbacks, and only destroy/create the watchers in the prepare watcher. |
|
|
2701 | |
|
|
2702 | static void |
|
|
2703 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2704 | { |
|
|
2705 | adns_state ads = (adns_state)w->data; |
|
|
2706 | update_now (EV_A); |
|
|
2707 | |
|
|
2708 | adns_processtimeouts (ads, &tv_now); |
|
|
2709 | } |
|
|
2710 | |
|
|
2711 | static void |
|
|
2712 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
2713 | { |
|
|
2714 | adns_state ads = (adns_state)w->data; |
|
|
2715 | update_now (EV_A); |
|
|
2716 | |
|
|
2717 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
|
|
2718 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
|
|
2719 | } |
|
|
2720 | |
|
|
2721 | // do not ever call adns_afterpoll |
|
|
2722 | |
|
|
2723 | Method 4: Do not use a prepare or check watcher because the module you |
|
|
2724 | want to embed is not flexible enough to support it. Instead, you can |
|
|
2725 | override their poll function. The drawback with this solution is that the |
|
|
2726 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
|
|
2727 | this approach, effectively embedding EV as a client into the horrible |
|
|
2728 | libglib event loop. |
|
|
2729 | |
|
|
2730 | static gint |
|
|
2731 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
2732 | { |
|
|
2733 | int got_events = 0; |
|
|
2734 | |
|
|
2735 | for (n = 0; n < nfds; ++n) |
|
|
2736 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
2737 | |
|
|
2738 | if (timeout >= 0) |
|
|
2739 | // create/start timer |
|
|
2740 | |
|
|
2741 | // poll |
|
|
2742 | ev_loop (EV_A_ 0); |
|
|
2743 | |
|
|
2744 | // stop timer again |
|
|
2745 | if (timeout >= 0) |
|
|
2746 | ev_timer_stop (EV_A_ &to); |
|
|
2747 | |
|
|
2748 | // stop io watchers again - their callbacks should have set |
|
|
2749 | for (n = 0; n < nfds; ++n) |
|
|
2750 | ev_io_stop (EV_A_ iow [n]); |
|
|
2751 | |
|
|
2752 | return got_events; |
|
|
2753 | } |
|
|
2754 | |
|
|
2755 | |
|
|
2756 | =head2 C<ev_embed> - when one backend isn't enough... |
|
|
2757 | |
|
|
2758 | This is a rather advanced watcher type that lets you embed one event loop |
|
|
2759 | into another (currently only C<ev_io> events are supported in the embedded |
|
|
2760 | loop, other types of watchers might be handled in a delayed or incorrect |
|
|
2761 | fashion and must not be used). |
|
|
2762 | |
|
|
2763 | There are primarily two reasons you would want that: work around bugs and |
|
|
2764 | prioritise I/O. |
|
|
2765 | |
|
|
2766 | As an example for a bug workaround, the kqueue backend might only support |
|
|
2767 | sockets on some platform, so it is unusable as generic backend, but you |
|
|
2768 | still want to make use of it because you have many sockets and it scales |
|
|
2769 | so nicely. In this case, you would create a kqueue-based loop and embed |
|
|
2770 | it into your default loop (which might use e.g. poll). Overall operation |
|
|
2771 | will be a bit slower because first libev has to call C<poll> and then |
|
|
2772 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2773 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
|
|
2774 | |
|
|
2775 | As for prioritising I/O: under rare circumstances you have the case where |
|
|
2776 | some fds have to be watched and handled very quickly (with low latency), |
|
|
2777 | and even priorities and idle watchers might have too much overhead. In |
|
|
2778 | this case you would put all the high priority stuff in one loop and all |
|
|
2779 | the rest in a second one, and embed the second one in the first. |
|
|
2780 | |
|
|
2781 | As long as the watcher is active, the callback will be invoked every |
|
|
2782 | time there might be events pending in the embedded loop. The callback |
|
|
2783 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
|
|
2784 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
|
|
2785 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
|
|
2786 | to give the embedded loop strictly lower priority for example). |
|
|
2787 | |
|
|
2788 | You can also set the callback to C<0>, in which case the embed watcher |
|
|
2789 | will automatically execute the embedded loop sweep whenever necessary. |
|
|
2790 | |
|
|
2791 | Fork detection will be handled transparently while the C<ev_embed> watcher |
|
|
2792 | is active, i.e., the embedded loop will automatically be forked when the |
|
|
2793 | embedding loop forks. In other cases, the user is responsible for calling |
|
|
2794 | C<ev_loop_fork> on the embedded loop. |
|
|
2795 | |
|
|
2796 | Unfortunately, not all backends are embeddable: only the ones returned by |
|
|
2797 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
|
|
2798 | portable one. |
|
|
2799 | |
|
|
2800 | So when you want to use this feature you will always have to be prepared |
|
|
2801 | that you cannot get an embeddable loop. The recommended way to get around |
|
|
2802 | this is to have a separate variables for your embeddable loop, try to |
|
|
2803 | create it, and if that fails, use the normal loop for everything. |
|
|
2804 | |
|
|
2805 | =head3 C<ev_embed> and fork |
|
|
2806 | |
|
|
2807 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2808 | automatically be applied to the embedded loop as well, so no special |
|
|
2809 | fork handling is required in that case. When the watcher is not running, |
|
|
2810 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2811 | as applicable. |
|
|
2812 | |
|
|
2813 | =head3 Watcher-Specific Functions and Data Members |
|
|
2814 | |
|
|
2815 | =over 4 |
|
|
2816 | |
|
|
2817 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
|
|
2818 | |
|
|
2819 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
|
|
2820 | |
|
|
2821 | Configures the watcher to embed the given loop, which must be |
|
|
2822 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
|
|
2823 | invoked automatically, otherwise it is the responsibility of the callback |
|
|
2824 | to invoke it (it will continue to be called until the sweep has been done, |
|
|
2825 | if you do not want that, you need to temporarily stop the embed watcher). |
|
|
2826 | |
|
|
2827 | =item ev_embed_sweep (loop, ev_embed *) |
|
|
2828 | |
|
|
2829 | Make a single, non-blocking sweep over the embedded loop. This works |
|
|
2830 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
|
|
2831 | appropriate way for embedded loops. |
|
|
2832 | |
|
|
2833 | =item struct ev_loop *other [read-only] |
|
|
2834 | |
|
|
2835 | The embedded event loop. |
|
|
2836 | |
|
|
2837 | =back |
|
|
2838 | |
|
|
2839 | =head3 Examples |
|
|
2840 | |
|
|
2841 | Example: Try to get an embeddable event loop and embed it into the default |
|
|
2842 | event loop. If that is not possible, use the default loop. The default |
|
|
2843 | loop is stored in C<loop_hi>, while the embeddable loop is stored in |
|
|
2844 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
|
|
2845 | used). |
|
|
2846 | |
|
|
2847 | struct ev_loop *loop_hi = ev_default_init (0); |
|
|
2848 | struct ev_loop *loop_lo = 0; |
|
|
2849 | ev_embed embed; |
|
|
2850 | |
|
|
2851 | // see if there is a chance of getting one that works |
|
|
2852 | // (remember that a flags value of 0 means autodetection) |
|
|
2853 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
2854 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
2855 | : 0; |
|
|
2856 | |
|
|
2857 | // if we got one, then embed it, otherwise default to loop_hi |
|
|
2858 | if (loop_lo) |
|
|
2859 | { |
|
|
2860 | ev_embed_init (&embed, 0, loop_lo); |
|
|
2861 | ev_embed_start (loop_hi, &embed); |
|
|
2862 | } |
|
|
2863 | else |
|
|
2864 | loop_lo = loop_hi; |
|
|
2865 | |
|
|
2866 | Example: Check if kqueue is available but not recommended and create |
|
|
2867 | a kqueue backend for use with sockets (which usually work with any |
|
|
2868 | kqueue implementation). Store the kqueue/socket-only event loop in |
|
|
2869 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
|
|
2870 | |
|
|
2871 | struct ev_loop *loop = ev_default_init (0); |
|
|
2872 | struct ev_loop *loop_socket = 0; |
|
|
2873 | ev_embed embed; |
|
|
2874 | |
|
|
2875 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
|
|
2876 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
|
|
2877 | { |
|
|
2878 | ev_embed_init (&embed, 0, loop_socket); |
|
|
2879 | ev_embed_start (loop, &embed); |
|
|
2880 | } |
|
|
2881 | |
|
|
2882 | if (!loop_socket) |
|
|
2883 | loop_socket = loop; |
|
|
2884 | |
|
|
2885 | // now use loop_socket for all sockets, and loop for everything else |
|
|
2886 | |
|
|
2887 | |
|
|
2888 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
|
|
2889 | |
|
|
2890 | Fork watchers are called when a C<fork ()> was detected (usually because |
|
|
2891 | whoever is a good citizen cared to tell libev about it by calling |
|
|
2892 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
|
|
2893 | event loop blocks next and before C<ev_check> watchers are being called, |
|
|
2894 | and only in the child after the fork. If whoever good citizen calling |
|
|
2895 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
|
|
2896 | handlers will be invoked, too, of course. |
|
|
2897 | |
|
|
2898 | =head3 The special problem of life after fork - how is it possible? |
|
|
2899 | |
|
|
2900 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2901 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2902 | sequence should be handled by libev without any problems. |
|
|
2903 | |
|
|
2904 | This changes when the application actually wants to do event handling |
|
|
2905 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2906 | fork. |
|
|
2907 | |
|
|
2908 | The default mode of operation (for libev, with application help to detect |
|
|
2909 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2910 | when I<either> the parent I<or> the child process continues. |
|
|
2911 | |
|
|
2912 | When both processes want to continue using libev, then this is usually the |
|
|
2913 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2914 | supposed to continue with all watchers in place as before, while the other |
|
|
2915 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2916 | |
|
|
2917 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2918 | simply create a new event loop, which of course will be "empty", and |
|
|
2919 | use that for new watchers. This has the advantage of not touching more |
|
|
2920 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2921 | disadvantage of having to use multiple event loops (which do not support |
|
|
2922 | signal watchers). |
|
|
2923 | |
|
|
2924 | When this is not possible, or you want to use the default loop for |
|
|
2925 | other reasons, then in the process that wants to start "fresh", call |
|
|
2926 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2927 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2928 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2929 | also that in that case, you have to re-register any signal watchers. |
|
|
2930 | |
|
|
2931 | =head3 Watcher-Specific Functions and Data Members |
|
|
2932 | |
|
|
2933 | =over 4 |
|
|
2934 | |
|
|
2935 | =item ev_fork_init (ev_signal *, callback) |
|
|
2936 | |
|
|
2937 | Initialises and configures the fork watcher - it has no parameters of any |
|
|
2938 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
|
|
2939 | believe me. |
|
|
2940 | |
|
|
2941 | =back |
|
|
2942 | |
|
|
2943 | |
|
|
2944 | =head2 C<ev_async> - how to wake up another event loop |
|
|
2945 | |
|
|
2946 | In general, you cannot use an C<ev_loop> from multiple threads or other |
|
|
2947 | asynchronous sources such as signal handlers (as opposed to multiple event |
|
|
2948 | loops - those are of course safe to use in different threads). |
|
|
2949 | |
|
|
2950 | Sometimes, however, you need to wake up another event loop you do not |
|
|
2951 | control, for example because it belongs to another thread. This is what |
|
|
2952 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
|
|
2953 | can signal it by calling C<ev_async_send>, which is thread- and signal |
|
|
2954 | safe. |
|
|
2955 | |
|
|
2956 | This functionality is very similar to C<ev_signal> watchers, as signals, |
|
|
2957 | too, are asynchronous in nature, and signals, too, will be compressed |
|
|
2958 | (i.e. the number of callback invocations may be less than the number of |
|
|
2959 | C<ev_async_sent> calls). |
|
|
2960 | |
|
|
2961 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
2962 | just the default loop. |
|
|
2963 | |
|
|
2964 | =head3 Queueing |
|
|
2965 | |
|
|
2966 | C<ev_async> does not support queueing of data in any way. The reason |
|
|
2967 | is that the author does not know of a simple (or any) algorithm for a |
|
|
2968 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
2969 | need elaborate support such as pthreads. |
|
|
2970 | |
|
|
2971 | That means that if you want to queue data, you have to provide your own |
|
|
2972 | queue. But at least I can tell you how to implement locking around your |
|
|
2973 | queue: |
|
|
2974 | |
|
|
2975 | =over 4 |
|
|
2976 | |
|
|
2977 | =item queueing from a signal handler context |
|
|
2978 | |
|
|
2979 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
2980 | handler but you block the signal handler in the watcher callback. Here is |
|
|
2981 | an example that does that for some fictitious SIGUSR1 handler: |
|
|
2982 | |
|
|
2983 | static ev_async mysig; |
|
|
2984 | |
|
|
2985 | static void |
|
|
2986 | sigusr1_handler (void) |
|
|
2987 | { |
|
|
2988 | sometype data; |
|
|
2989 | |
|
|
2990 | // no locking etc. |
|
|
2991 | queue_put (data); |
|
|
2992 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2993 | } |
|
|
2994 | |
|
|
2995 | static void |
|
|
2996 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2997 | { |
|
|
2998 | sometype data; |
|
|
2999 | sigset_t block, prev; |
|
|
3000 | |
|
|
3001 | sigemptyset (&block); |
|
|
3002 | sigaddset (&block, SIGUSR1); |
|
|
3003 | sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
3004 | |
|
|
3005 | while (queue_get (&data)) |
|
|
3006 | process (data); |
|
|
3007 | |
|
|
3008 | if (sigismember (&prev, SIGUSR1) |
|
|
3009 | sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
3010 | } |
|
|
3011 | |
|
|
3012 | (Note: pthreads in theory requires you to use C<pthread_setmask> |
|
|
3013 | instead of C<sigprocmask> when you use threads, but libev doesn't do it |
|
|
3014 | either...). |
|
|
3015 | |
|
|
3016 | =item queueing from a thread context |
|
|
3017 | |
|
|
3018 | The strategy for threads is different, as you cannot (easily) block |
|
|
3019 | threads but you can easily preempt them, so to queue safely you need to |
|
|
3020 | employ a traditional mutex lock, such as in this pthread example: |
|
|
3021 | |
|
|
3022 | static ev_async mysig; |
|
|
3023 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
3024 | |
|
|
3025 | static void |
|
|
3026 | otherthread (void) |
|
|
3027 | { |
|
|
3028 | // only need to lock the actual queueing operation |
|
|
3029 | pthread_mutex_lock (&mymutex); |
|
|
3030 | queue_put (data); |
|
|
3031 | pthread_mutex_unlock (&mymutex); |
|
|
3032 | |
|
|
3033 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
3034 | } |
|
|
3035 | |
|
|
3036 | static void |
|
|
3037 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
3038 | { |
|
|
3039 | pthread_mutex_lock (&mymutex); |
|
|
3040 | |
|
|
3041 | while (queue_get (&data)) |
|
|
3042 | process (data); |
|
|
3043 | |
|
|
3044 | pthread_mutex_unlock (&mymutex); |
|
|
3045 | } |
|
|
3046 | |
|
|
3047 | =back |
|
|
3048 | |
|
|
3049 | |
|
|
3050 | =head3 Watcher-Specific Functions and Data Members |
|
|
3051 | |
|
|
3052 | =over 4 |
|
|
3053 | |
|
|
3054 | =item ev_async_init (ev_async *, callback) |
|
|
3055 | |
|
|
3056 | Initialises and configures the async watcher - it has no parameters of any |
|
|
3057 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
|
|
3058 | trust me. |
|
|
3059 | |
|
|
3060 | =item ev_async_send (loop, ev_async *) |
|
|
3061 | |
|
|
3062 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
|
|
3063 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
|
|
3064 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
|
|
3065 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
|
|
3066 | section below on what exactly this means). |
|
|
3067 | |
|
|
3068 | Note that, as with other watchers in libev, multiple events might get |
|
|
3069 | compressed into a single callback invocation (another way to look at this |
|
|
3070 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3071 | reset when the event loop detects that). |
|
|
3072 | |
|
|
3073 | This call incurs the overhead of a system call only once per event loop |
|
|
3074 | iteration, so while the overhead might be noticeable, it doesn't apply to |
|
|
3075 | repeated calls to C<ev_async_send> for the same event loop. |
|
|
3076 | |
|
|
3077 | =item bool = ev_async_pending (ev_async *) |
|
|
3078 | |
|
|
3079 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
3080 | watcher but the event has not yet been processed (or even noted) by the |
|
|
3081 | event loop. |
|
|
3082 | |
|
|
3083 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
3084 | the loop iterates next and checks for the watcher to have become active, |
|
|
3085 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
3086 | quickly check whether invoking the loop might be a good idea. |
|
|
3087 | |
|
|
3088 | Not that this does I<not> check whether the watcher itself is pending, |
|
|
3089 | only whether it has been requested to make this watcher pending: there |
|
|
3090 | is a time window between the event loop checking and resetting the async |
|
|
3091 | notification, and the callback being invoked. |
|
|
3092 | |
|
|
3093 | =back |
|
|
3094 | |
|
|
3095 | |
703 | =head1 OTHER FUNCTIONS |
3096 | =head1 OTHER FUNCTIONS |
704 | |
3097 | |
705 | There are some other fucntions of possible interest. Described. Here. Now. |
3098 | There are some other functions of possible interest. Described. Here. Now. |
706 | |
3099 | |
707 | =over 4 |
3100 | =over 4 |
708 | |
3101 | |
709 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3102 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
710 | |
3103 | |
711 | This function combines a simple timer and an I/O watcher, calls your |
3104 | This function combines a simple timer and an I/O watcher, calls your |
712 | callback on whichever event happens first and automatically stop both |
3105 | callback on whichever event happens first and automatically stops both |
713 | watchers. This is useful if you want to wait for a single event on an fd |
3106 | watchers. This is useful if you want to wait for a single event on an fd |
714 | or timeout without havign to allocate/configure/start/stop/free one or |
3107 | or timeout without having to allocate/configure/start/stop/free one or |
715 | more watchers yourself. |
3108 | more watchers yourself. |
716 | |
3109 | |
717 | If C<fd> is less than 0, then no I/O watcher will be started and events is |
3110 | If C<fd> is less than 0, then no I/O watcher will be started and the |
718 | ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and C<events> set |
3111 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
719 | will be craeted and started. |
3112 | the given C<fd> and C<events> set will be created and started. |
720 | |
3113 | |
721 | If C<timeout> is less than 0, then no timeout watcher will be |
3114 | If C<timeout> is less than 0, then no timeout watcher will be |
722 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and repeat |
3115 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
723 | = 0) will be started. |
3116 | repeat = 0) will be started. C<0> is a valid timeout. |
724 | |
3117 | |
725 | The callback has the type C<void (*cb)(int revents, void *arg)> and |
3118 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
726 | gets passed an events set (normally a combination of C<EV_ERROR>, C<EV_READ>, |
3119 | passed an C<revents> set like normal event callbacks (a combination of |
727 | C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> value passed to C<ev_once>: |
3120 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
|
|
3121 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
3122 | a timeout and an io event at the same time - you probably should give io |
|
|
3123 | events precedence. |
728 | |
3124 | |
|
|
3125 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
|
|
3126 | |
729 | static void stdin_ready (int revents, void *arg) |
3127 | static void stdin_ready (int revents, void *arg) |
730 | { |
3128 | { |
731 | if (revents & EV_TIMEOUT) |
|
|
732 | /* doh, nothing entered */ |
|
|
733 | else if (revents & EV_READ) |
3129 | if (revents & EV_READ) |
734 | /* stdin might have data for us, joy! */ |
3130 | /* stdin might have data for us, joy! */; |
|
|
3131 | else if (revents & EV_TIMEOUT) |
|
|
3132 | /* doh, nothing entered */; |
735 | } |
3133 | } |
736 | |
3134 | |
737 | ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); |
3135 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
738 | |
3136 | |
739 | =item ev_feed_event (loop, watcher, int events) |
3137 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
740 | |
3138 | |
741 | Feeds the given event set into the event loop, as if the specified event |
3139 | Feeds the given event set into the event loop, as if the specified event |
742 | has happened for the specified watcher (which must be a pointer to an |
3140 | had happened for the specified watcher (which must be a pointer to an |
743 | initialised but not necessarily active event watcher). |
3141 | initialised but not necessarily started event watcher). |
744 | |
3142 | |
745 | =item ev_feed_fd_event (loop, int fd, int revents) |
3143 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
746 | |
3144 | |
747 | Feed an event on the given fd, as if a file descriptor backend detected it. |
3145 | Feed an event on the given fd, as if a file descriptor backend detected |
|
|
3146 | the given events it. |
748 | |
3147 | |
749 | =item ev_feed_signal_event (loop, int signum) |
3148 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
750 | |
3149 | |
751 | Feed an event as if the given signal occured (loop must be the default loop!). |
3150 | Feed an event as if the given signal occurred (C<loop> must be the default |
|
|
3151 | loop!). |
752 | |
3152 | |
753 | =back |
3153 | =back |
754 | |
3154 | |
|
|
3155 | |
|
|
3156 | =head1 LIBEVENT EMULATION |
|
|
3157 | |
|
|
3158 | Libev offers a compatibility emulation layer for libevent. It cannot |
|
|
3159 | emulate the internals of libevent, so here are some usage hints: |
|
|
3160 | |
|
|
3161 | =over 4 |
|
|
3162 | |
|
|
3163 | =item * Use it by including <event.h>, as usual. |
|
|
3164 | |
|
|
3165 | =item * The following members are fully supported: ev_base, ev_callback, |
|
|
3166 | ev_arg, ev_fd, ev_res, ev_events. |
|
|
3167 | |
|
|
3168 | =item * Avoid using ev_flags and the EVLIST_*-macros, while it is |
|
|
3169 | maintained by libev, it does not work exactly the same way as in libevent (consider |
|
|
3170 | it a private API). |
|
|
3171 | |
|
|
3172 | =item * Priorities are not currently supported. Initialising priorities |
|
|
3173 | will fail and all watchers will have the same priority, even though there |
|
|
3174 | is an ev_pri field. |
|
|
3175 | |
|
|
3176 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
3177 | first base created (== the default loop) gets the signals. |
|
|
3178 | |
|
|
3179 | =item * Other members are not supported. |
|
|
3180 | |
|
|
3181 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
|
|
3182 | to use the libev header file and library. |
|
|
3183 | |
|
|
3184 | =back |
|
|
3185 | |
|
|
3186 | =head1 C++ SUPPORT |
|
|
3187 | |
|
|
3188 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
|
|
3189 | you to use some convenience methods to start/stop watchers and also change |
|
|
3190 | the callback model to a model using method callbacks on objects. |
|
|
3191 | |
|
|
3192 | To use it, |
|
|
3193 | |
|
|
3194 | #include <ev++.h> |
|
|
3195 | |
|
|
3196 | This automatically includes F<ev.h> and puts all of its definitions (many |
|
|
3197 | of them macros) into the global namespace. All C++ specific things are |
|
|
3198 | put into the C<ev> namespace. It should support all the same embedding |
|
|
3199 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
|
|
3200 | |
|
|
3201 | Care has been taken to keep the overhead low. The only data member the C++ |
|
|
3202 | classes add (compared to plain C-style watchers) is the event loop pointer |
|
|
3203 | that the watcher is associated with (or no additional members at all if |
|
|
3204 | you disable C<EV_MULTIPLICITY> when embedding libev). |
|
|
3205 | |
|
|
3206 | Currently, functions, and static and non-static member functions can be |
|
|
3207 | used as callbacks. Other types should be easy to add as long as they only |
|
|
3208 | need one additional pointer for context. If you need support for other |
|
|
3209 | types of functors please contact the author (preferably after implementing |
|
|
3210 | it). |
|
|
3211 | |
|
|
3212 | Here is a list of things available in the C<ev> namespace: |
|
|
3213 | |
|
|
3214 | =over 4 |
|
|
3215 | |
|
|
3216 | =item C<ev::READ>, C<ev::WRITE> etc. |
|
|
3217 | |
|
|
3218 | These are just enum values with the same values as the C<EV_READ> etc. |
|
|
3219 | macros from F<ev.h>. |
|
|
3220 | |
|
|
3221 | =item C<ev::tstamp>, C<ev::now> |
|
|
3222 | |
|
|
3223 | Aliases to the same types/functions as with the C<ev_> prefix. |
|
|
3224 | |
|
|
3225 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
|
|
3226 | |
|
|
3227 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
|
|
3228 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
|
|
3229 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
|
|
3230 | defines by many implementations. |
|
|
3231 | |
|
|
3232 | All of those classes have these methods: |
|
|
3233 | |
|
|
3234 | =over 4 |
|
|
3235 | |
|
|
3236 | =item ev::TYPE::TYPE () |
|
|
3237 | |
|
|
3238 | =item ev::TYPE::TYPE (struct ev_loop *) |
|
|
3239 | |
|
|
3240 | =item ev::TYPE::~TYPE |
|
|
3241 | |
|
|
3242 | The constructor (optionally) takes an event loop to associate the watcher |
|
|
3243 | with. If it is omitted, it will use C<EV_DEFAULT>. |
|
|
3244 | |
|
|
3245 | The constructor calls C<ev_init> for you, which means you have to call the |
|
|
3246 | C<set> method before starting it. |
|
|
3247 | |
|
|
3248 | It will not set a callback, however: You have to call the templated C<set> |
|
|
3249 | method to set a callback before you can start the watcher. |
|
|
3250 | |
|
|
3251 | (The reason why you have to use a method is a limitation in C++ which does |
|
|
3252 | not allow explicit template arguments for constructors). |
|
|
3253 | |
|
|
3254 | The destructor automatically stops the watcher if it is active. |
|
|
3255 | |
|
|
3256 | =item w->set<class, &class::method> (object *) |
|
|
3257 | |
|
|
3258 | This method sets the callback method to call. The method has to have a |
|
|
3259 | signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as |
|
|
3260 | first argument and the C<revents> as second. The object must be given as |
|
|
3261 | parameter and is stored in the C<data> member of the watcher. |
|
|
3262 | |
|
|
3263 | This method synthesizes efficient thunking code to call your method from |
|
|
3264 | the C callback that libev requires. If your compiler can inline your |
|
|
3265 | callback (i.e. it is visible to it at the place of the C<set> call and |
|
|
3266 | your compiler is good :), then the method will be fully inlined into the |
|
|
3267 | thunking function, making it as fast as a direct C callback. |
|
|
3268 | |
|
|
3269 | Example: simple class declaration and watcher initialisation |
|
|
3270 | |
|
|
3271 | struct myclass |
|
|
3272 | { |
|
|
3273 | void io_cb (ev::io &w, int revents) { } |
|
|
3274 | } |
|
|
3275 | |
|
|
3276 | myclass obj; |
|
|
3277 | ev::io iow; |
|
|
3278 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
3279 | |
|
|
3280 | =item w->set (object *) |
|
|
3281 | |
|
|
3282 | This is an B<experimental> feature that might go away in a future version. |
|
|
3283 | |
|
|
3284 | This is a variation of a method callback - leaving out the method to call |
|
|
3285 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3286 | functor objects without having to manually specify the C<operator ()> all |
|
|
3287 | the time. Incidentally, you can then also leave out the template argument |
|
|
3288 | list. |
|
|
3289 | |
|
|
3290 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3291 | int revents)>. |
|
|
3292 | |
|
|
3293 | See the method-C<set> above for more details. |
|
|
3294 | |
|
|
3295 | Example: use a functor object as callback. |
|
|
3296 | |
|
|
3297 | struct myfunctor |
|
|
3298 | { |
|
|
3299 | void operator() (ev::io &w, int revents) |
|
|
3300 | { |
|
|
3301 | ... |
|
|
3302 | } |
|
|
3303 | } |
|
|
3304 | |
|
|
3305 | myfunctor f; |
|
|
3306 | |
|
|
3307 | ev::io w; |
|
|
3308 | w.set (&f); |
|
|
3309 | |
|
|
3310 | =item w->set<function> (void *data = 0) |
|
|
3311 | |
|
|
3312 | Also sets a callback, but uses a static method or plain function as |
|
|
3313 | callback. The optional C<data> argument will be stored in the watcher's |
|
|
3314 | C<data> member and is free for you to use. |
|
|
3315 | |
|
|
3316 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
|
|
3317 | |
|
|
3318 | See the method-C<set> above for more details. |
|
|
3319 | |
|
|
3320 | Example: Use a plain function as callback. |
|
|
3321 | |
|
|
3322 | static void io_cb (ev::io &w, int revents) { } |
|
|
3323 | iow.set <io_cb> (); |
|
|
3324 | |
|
|
3325 | =item w->set (struct ev_loop *) |
|
|
3326 | |
|
|
3327 | Associates a different C<struct ev_loop> with this watcher. You can only |
|
|
3328 | do this when the watcher is inactive (and not pending either). |
|
|
3329 | |
|
|
3330 | =item w->set ([arguments]) |
|
|
3331 | |
|
|
3332 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
|
|
3333 | called at least once. Unlike the C counterpart, an active watcher gets |
|
|
3334 | automatically stopped and restarted when reconfiguring it with this |
|
|
3335 | method. |
|
|
3336 | |
|
|
3337 | =item w->start () |
|
|
3338 | |
|
|
3339 | Starts the watcher. Note that there is no C<loop> argument, as the |
|
|
3340 | constructor already stores the event loop. |
|
|
3341 | |
|
|
3342 | =item w->stop () |
|
|
3343 | |
|
|
3344 | Stops the watcher if it is active. Again, no C<loop> argument. |
|
|
3345 | |
|
|
3346 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
|
|
3347 | |
|
|
3348 | For C<ev::timer> and C<ev::periodic>, this invokes the corresponding |
|
|
3349 | C<ev_TYPE_again> function. |
|
|
3350 | |
|
|
3351 | =item w->sweep () (C<ev::embed> only) |
|
|
3352 | |
|
|
3353 | Invokes C<ev_embed_sweep>. |
|
|
3354 | |
|
|
3355 | =item w->update () (C<ev::stat> only) |
|
|
3356 | |
|
|
3357 | Invokes C<ev_stat_stat>. |
|
|
3358 | |
|
|
3359 | =back |
|
|
3360 | |
|
|
3361 | =back |
|
|
3362 | |
|
|
3363 | Example: Define a class with an IO and idle watcher, start one of them in |
|
|
3364 | the constructor. |
|
|
3365 | |
|
|
3366 | class myclass |
|
|
3367 | { |
|
|
3368 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
3369 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
|
|
3370 | |
|
|
3371 | myclass (int fd) |
|
|
3372 | { |
|
|
3373 | io .set <myclass, &myclass::io_cb > (this); |
|
|
3374 | idle.set <myclass, &myclass::idle_cb> (this); |
|
|
3375 | |
|
|
3376 | io.start (fd, ev::READ); |
|
|
3377 | } |
|
|
3378 | }; |
|
|
3379 | |
|
|
3380 | |
|
|
3381 | =head1 OTHER LANGUAGE BINDINGS |
|
|
3382 | |
|
|
3383 | Libev does not offer other language bindings itself, but bindings for a |
|
|
3384 | number of languages exist in the form of third-party packages. If you know |
|
|
3385 | any interesting language binding in addition to the ones listed here, drop |
|
|
3386 | me a note. |
|
|
3387 | |
|
|
3388 | =over 4 |
|
|
3389 | |
|
|
3390 | =item Perl |
|
|
3391 | |
|
|
3392 | The EV module implements the full libev API and is actually used to test |
|
|
3393 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
3394 | there are additional modules that implement libev-compatible interfaces |
|
|
3395 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
|
|
3396 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
3397 | and C<EV::Glib>). |
|
|
3398 | |
|
|
3399 | It can be found and installed via CPAN, its homepage is at |
|
|
3400 | L<http://software.schmorp.de/pkg/EV>. |
|
|
3401 | |
|
|
3402 | =item Python |
|
|
3403 | |
|
|
3404 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
|
|
3405 | seems to be quite complete and well-documented. |
|
|
3406 | |
|
|
3407 | =item Ruby |
|
|
3408 | |
|
|
3409 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
3410 | of the libev API and adds file handle abstractions, asynchronous DNS and |
|
|
3411 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
3412 | L<http://rev.rubyforge.org/>. |
|
|
3413 | |
|
|
3414 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3415 | makes rev work even on mingw. |
|
|
3416 | |
|
|
3417 | =item Haskell |
|
|
3418 | |
|
|
3419 | A haskell binding to libev is available at |
|
|
3420 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3421 | |
|
|
3422 | =item D |
|
|
3423 | |
|
|
3424 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
3425 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3426 | |
|
|
3427 | =item Ocaml |
|
|
3428 | |
|
|
3429 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3430 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3431 | |
|
|
3432 | =item Lua |
|
|
3433 | |
|
|
3434 | Brian Maher has written a partial interface to libev |
|
|
3435 | for lua (only C<ev_io> and C<ev_timer>), to be found at |
|
|
3436 | L<http://github.com/brimworks/lua-ev>. |
|
|
3437 | |
|
|
3438 | =back |
|
|
3439 | |
|
|
3440 | |
|
|
3441 | =head1 MACRO MAGIC |
|
|
3442 | |
|
|
3443 | Libev can be compiled with a variety of options, the most fundamental |
|
|
3444 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
|
|
3445 | functions and callbacks have an initial C<struct ev_loop *> argument. |
|
|
3446 | |
|
|
3447 | To make it easier to write programs that cope with either variant, the |
|
|
3448 | following macros are defined: |
|
|
3449 | |
|
|
3450 | =over 4 |
|
|
3451 | |
|
|
3452 | =item C<EV_A>, C<EV_A_> |
|
|
3453 | |
|
|
3454 | This provides the loop I<argument> for functions, if one is required ("ev |
|
|
3455 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
|
|
3456 | C<EV_A_> is used when other arguments are following. Example: |
|
|
3457 | |
|
|
3458 | ev_unref (EV_A); |
|
|
3459 | ev_timer_add (EV_A_ watcher); |
|
|
3460 | ev_loop (EV_A_ 0); |
|
|
3461 | |
|
|
3462 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
|
|
3463 | which is often provided by the following macro. |
|
|
3464 | |
|
|
3465 | =item C<EV_P>, C<EV_P_> |
|
|
3466 | |
|
|
3467 | This provides the loop I<parameter> for functions, if one is required ("ev |
|
|
3468 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
|
|
3469 | C<EV_P_> is used when other parameters are following. Example: |
|
|
3470 | |
|
|
3471 | // this is how ev_unref is being declared |
|
|
3472 | static void ev_unref (EV_P); |
|
|
3473 | |
|
|
3474 | // this is how you can declare your typical callback |
|
|
3475 | static void cb (EV_P_ ev_timer *w, int revents) |
|
|
3476 | |
|
|
3477 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
|
|
3478 | suitable for use with C<EV_A>. |
|
|
3479 | |
|
|
3480 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
|
|
3481 | |
|
|
3482 | Similar to the other two macros, this gives you the value of the default |
|
|
3483 | loop, if multiple loops are supported ("ev loop default"). |
|
|
3484 | |
|
|
3485 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
3486 | |
|
|
3487 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
3488 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
3489 | is undefined when the default loop has not been initialised by a previous |
|
|
3490 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
3491 | |
|
|
3492 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
3493 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
|
|
3494 | |
|
|
3495 | =back |
|
|
3496 | |
|
|
3497 | Example: Declare and initialise a check watcher, utilising the above |
|
|
3498 | macros so it will work regardless of whether multiple loops are supported |
|
|
3499 | or not. |
|
|
3500 | |
|
|
3501 | static void |
|
|
3502 | check_cb (EV_P_ ev_timer *w, int revents) |
|
|
3503 | { |
|
|
3504 | ev_check_stop (EV_A_ w); |
|
|
3505 | } |
|
|
3506 | |
|
|
3507 | ev_check check; |
|
|
3508 | ev_check_init (&check, check_cb); |
|
|
3509 | ev_check_start (EV_DEFAULT_ &check); |
|
|
3510 | ev_loop (EV_DEFAULT_ 0); |
|
|
3511 | |
|
|
3512 | =head1 EMBEDDING |
|
|
3513 | |
|
|
3514 | Libev can (and often is) directly embedded into host |
|
|
3515 | applications. Examples of applications that embed it include the Deliantra |
|
|
3516 | Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
|
|
3517 | and rxvt-unicode. |
|
|
3518 | |
|
|
3519 | The goal is to enable you to just copy the necessary files into your |
|
|
3520 | source directory without having to change even a single line in them, so |
|
|
3521 | you can easily upgrade by simply copying (or having a checked-out copy of |
|
|
3522 | libev somewhere in your source tree). |
|
|
3523 | |
|
|
3524 | =head2 FILESETS |
|
|
3525 | |
|
|
3526 | Depending on what features you need you need to include one or more sets of files |
|
|
3527 | in your application. |
|
|
3528 | |
|
|
3529 | =head3 CORE EVENT LOOP |
|
|
3530 | |
|
|
3531 | To include only the libev core (all the C<ev_*> functions), with manual |
|
|
3532 | configuration (no autoconf): |
|
|
3533 | |
|
|
3534 | #define EV_STANDALONE 1 |
|
|
3535 | #include "ev.c" |
|
|
3536 | |
|
|
3537 | This will automatically include F<ev.h>, too, and should be done in a |
|
|
3538 | single C source file only to provide the function implementations. To use |
|
|
3539 | it, do the same for F<ev.h> in all files wishing to use this API (best |
|
|
3540 | done by writing a wrapper around F<ev.h> that you can include instead and |
|
|
3541 | where you can put other configuration options): |
|
|
3542 | |
|
|
3543 | #define EV_STANDALONE 1 |
|
|
3544 | #include "ev.h" |
|
|
3545 | |
|
|
3546 | Both header files and implementation files can be compiled with a C++ |
|
|
3547 | compiler (at least, that's a stated goal, and breakage will be treated |
|
|
3548 | as a bug). |
|
|
3549 | |
|
|
3550 | You need the following files in your source tree, or in a directory |
|
|
3551 | in your include path (e.g. in libev/ when using -Ilibev): |
|
|
3552 | |
|
|
3553 | ev.h |
|
|
3554 | ev.c |
|
|
3555 | ev_vars.h |
|
|
3556 | ev_wrap.h |
|
|
3557 | |
|
|
3558 | ev_win32.c required on win32 platforms only |
|
|
3559 | |
|
|
3560 | ev_select.c only when select backend is enabled (which is enabled by default) |
|
|
3561 | ev_poll.c only when poll backend is enabled (disabled by default) |
|
|
3562 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
|
|
3563 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
|
|
3564 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
|
|
3565 | |
|
|
3566 | F<ev.c> includes the backend files directly when enabled, so you only need |
|
|
3567 | to compile this single file. |
|
|
3568 | |
|
|
3569 | =head3 LIBEVENT COMPATIBILITY API |
|
|
3570 | |
|
|
3571 | To include the libevent compatibility API, also include: |
|
|
3572 | |
|
|
3573 | #include "event.c" |
|
|
3574 | |
|
|
3575 | in the file including F<ev.c>, and: |
|
|
3576 | |
|
|
3577 | #include "event.h" |
|
|
3578 | |
|
|
3579 | in the files that want to use the libevent API. This also includes F<ev.h>. |
|
|
3580 | |
|
|
3581 | You need the following additional files for this: |
|
|
3582 | |
|
|
3583 | event.h |
|
|
3584 | event.c |
|
|
3585 | |
|
|
3586 | =head3 AUTOCONF SUPPORT |
|
|
3587 | |
|
|
3588 | Instead of using C<EV_STANDALONE=1> and providing your configuration in |
|
|
3589 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
|
|
3590 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
|
|
3591 | include F<config.h> and configure itself accordingly. |
|
|
3592 | |
|
|
3593 | For this of course you need the m4 file: |
|
|
3594 | |
|
|
3595 | libev.m4 |
|
|
3596 | |
|
|
3597 | =head2 PREPROCESSOR SYMBOLS/MACROS |
|
|
3598 | |
|
|
3599 | Libev can be configured via a variety of preprocessor symbols you have to |
|
|
3600 | define before including any of its files. The default in the absence of |
|
|
3601 | autoconf is documented for every option. |
|
|
3602 | |
|
|
3603 | =over 4 |
|
|
3604 | |
|
|
3605 | =item EV_STANDALONE |
|
|
3606 | |
|
|
3607 | Must always be C<1> if you do not use autoconf configuration, which |
|
|
3608 | keeps libev from including F<config.h>, and it also defines dummy |
|
|
3609 | implementations for some libevent functions (such as logging, which is not |
|
|
3610 | supported). It will also not define any of the structs usually found in |
|
|
3611 | F<event.h> that are not directly supported by the libev core alone. |
|
|
3612 | |
|
|
3613 | In standalone mode, libev will still try to automatically deduce the |
|
|
3614 | configuration, but has to be more conservative. |
|
|
3615 | |
|
|
3616 | =item EV_USE_MONOTONIC |
|
|
3617 | |
|
|
3618 | If defined to be C<1>, libev will try to detect the availability of the |
|
|
3619 | monotonic clock option at both compile time and runtime. Otherwise no |
|
|
3620 | use of the monotonic clock option will be attempted. If you enable this, |
|
|
3621 | you usually have to link against librt or something similar. Enabling it |
|
|
3622 | when the functionality isn't available is safe, though, although you have |
|
|
3623 | to make sure you link against any libraries where the C<clock_gettime> |
|
|
3624 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
|
|
3625 | |
|
|
3626 | =item EV_USE_REALTIME |
|
|
3627 | |
|
|
3628 | If defined to be C<1>, libev will try to detect the availability of the |
|
|
3629 | real-time clock option at compile time (and assume its availability |
|
|
3630 | at runtime if successful). Otherwise no use of the real-time clock |
|
|
3631 | option will be attempted. This effectively replaces C<gettimeofday> |
|
|
3632 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
|
|
3633 | correctness. See the note about libraries in the description of |
|
|
3634 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3635 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3636 | |
|
|
3637 | =item EV_USE_CLOCK_SYSCALL |
|
|
3638 | |
|
|
3639 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3640 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3641 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3642 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3643 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3644 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3645 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3646 | higher, as it simplifies linking (no need for C<-lrt>). |
|
|
3647 | |
|
|
3648 | =item EV_USE_NANOSLEEP |
|
|
3649 | |
|
|
3650 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
|
|
3651 | and will use it for delays. Otherwise it will use C<select ()>. |
|
|
3652 | |
|
|
3653 | =item EV_USE_EVENTFD |
|
|
3654 | |
|
|
3655 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
3656 | available and will probe for kernel support at runtime. This will improve |
|
|
3657 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
3658 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
3659 | 2.7 or newer, otherwise disabled. |
|
|
3660 | |
|
|
3661 | =item EV_USE_SELECT |
|
|
3662 | |
|
|
3663 | If undefined or defined to be C<1>, libev will compile in support for the |
|
|
3664 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
|
|
3665 | other method takes over, select will be it. Otherwise the select backend |
|
|
3666 | will not be compiled in. |
|
|
3667 | |
|
|
3668 | =item EV_SELECT_USE_FD_SET |
|
|
3669 | |
|
|
3670 | If defined to C<1>, then the select backend will use the system C<fd_set> |
|
|
3671 | structure. This is useful if libev doesn't compile due to a missing |
|
|
3672 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
|
|
3673 | on exotic systems. This usually limits the range of file descriptors to |
|
|
3674 | some low limit such as 1024 or might have other limitations (winsocket |
|
|
3675 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
|
|
3676 | configures the maximum size of the C<fd_set>. |
|
|
3677 | |
|
|
3678 | =item EV_SELECT_IS_WINSOCKET |
|
|
3679 | |
|
|
3680 | When defined to C<1>, the select backend will assume that |
|
|
3681 | select/socket/connect etc. don't understand file descriptors but |
|
|
3682 | wants osf handles on win32 (this is the case when the select to |
|
|
3683 | be used is the winsock select). This means that it will call |
|
|
3684 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
|
|
3685 | it is assumed that all these functions actually work on fds, even |
|
|
3686 | on win32. Should not be defined on non-win32 platforms. |
|
|
3687 | |
|
|
3688 | =item EV_FD_TO_WIN32_HANDLE(fd) |
|
|
3689 | |
|
|
3690 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
|
|
3691 | file descriptors to socket handles. When not defining this symbol (the |
|
|
3692 | default), then libev will call C<_get_osfhandle>, which is usually |
|
|
3693 | correct. In some cases, programs use their own file descriptor management, |
|
|
3694 | in which case they can provide this function to map fds to socket handles. |
|
|
3695 | |
|
|
3696 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3697 | |
|
|
3698 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3699 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3700 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3701 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3702 | |
|
|
3703 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3704 | |
|
|
3705 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3706 | macro can be used to override the C<close> function, useful to unregister |
|
|
3707 | file descriptors again. Note that the replacement function has to close |
|
|
3708 | the underlying OS handle. |
|
|
3709 | |
|
|
3710 | =item EV_USE_POLL |
|
|
3711 | |
|
|
3712 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
|
|
3713 | backend. Otherwise it will be enabled on non-win32 platforms. It |
|
|
3714 | takes precedence over select. |
|
|
3715 | |
|
|
3716 | =item EV_USE_EPOLL |
|
|
3717 | |
|
|
3718 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
3719 | C<epoll>(7) backend. Its availability will be detected at runtime, |
|
|
3720 | otherwise another method will be used as fallback. This is the preferred |
|
|
3721 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
3722 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
3723 | |
|
|
3724 | =item EV_USE_KQUEUE |
|
|
3725 | |
|
|
3726 | If defined to be C<1>, libev will compile in support for the BSD style |
|
|
3727 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
|
|
3728 | otherwise another method will be used as fallback. This is the preferred |
|
|
3729 | backend for BSD and BSD-like systems, although on most BSDs kqueue only |
|
|
3730 | supports some types of fds correctly (the only platform we found that |
|
|
3731 | supports ptys for example was NetBSD), so kqueue might be compiled in, but |
|
|
3732 | not be used unless explicitly requested. The best way to use it is to find |
|
|
3733 | out whether kqueue supports your type of fd properly and use an embedded |
|
|
3734 | kqueue loop. |
|
|
3735 | |
|
|
3736 | =item EV_USE_PORT |
|
|
3737 | |
|
|
3738 | If defined to be C<1>, libev will compile in support for the Solaris |
|
|
3739 | 10 port style backend. Its availability will be detected at runtime, |
|
|
3740 | otherwise another method will be used as fallback. This is the preferred |
|
|
3741 | backend for Solaris 10 systems. |
|
|
3742 | |
|
|
3743 | =item EV_USE_DEVPOLL |
|
|
3744 | |
|
|
3745 | Reserved for future expansion, works like the USE symbols above. |
|
|
3746 | |
|
|
3747 | =item EV_USE_INOTIFY |
|
|
3748 | |
|
|
3749 | If defined to be C<1>, libev will compile in support for the Linux inotify |
|
|
3750 | interface to speed up C<ev_stat> watchers. Its actual availability will |
|
|
3751 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
3752 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
3753 | |
|
|
3754 | =item EV_ATOMIC_T |
|
|
3755 | |
|
|
3756 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
|
|
3757 | access is atomic with respect to other threads or signal contexts. No such |
|
|
3758 | type is easily found in the C language, so you can provide your own type |
|
|
3759 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
3760 | as well as for signal and thread safety in C<ev_async> watchers. |
|
|
3761 | |
|
|
3762 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
|
|
3763 | (from F<signal.h>), which is usually good enough on most platforms. |
|
|
3764 | |
|
|
3765 | =item EV_H |
|
|
3766 | |
|
|
3767 | The name of the F<ev.h> header file used to include it. The default if |
|
|
3768 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
|
|
3769 | used to virtually rename the F<ev.h> header file in case of conflicts. |
|
|
3770 | |
|
|
3771 | =item EV_CONFIG_H |
|
|
3772 | |
|
|
3773 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
|
|
3774 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
|
|
3775 | C<EV_H>, above. |
|
|
3776 | |
|
|
3777 | =item EV_EVENT_H |
|
|
3778 | |
|
|
3779 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
|
|
3780 | of how the F<event.h> header can be found, the default is C<"event.h">. |
|
|
3781 | |
|
|
3782 | =item EV_PROTOTYPES |
|
|
3783 | |
|
|
3784 | If defined to be C<0>, then F<ev.h> will not define any function |
|
|
3785 | prototypes, but still define all the structs and other symbols. This is |
|
|
3786 | occasionally useful if you want to provide your own wrapper functions |
|
|
3787 | around libev functions. |
|
|
3788 | |
|
|
3789 | =item EV_MULTIPLICITY |
|
|
3790 | |
|
|
3791 | If undefined or defined to C<1>, then all event-loop-specific functions |
|
|
3792 | will have the C<struct ev_loop *> as first argument, and you can create |
|
|
3793 | additional independent event loops. Otherwise there will be no support |
|
|
3794 | for multiple event loops and there is no first event loop pointer |
|
|
3795 | argument. Instead, all functions act on the single default loop. |
|
|
3796 | |
|
|
3797 | =item EV_MINPRI |
|
|
3798 | |
|
|
3799 | =item EV_MAXPRI |
|
|
3800 | |
|
|
3801 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
|
|
3802 | C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can |
|
|
3803 | provide for more priorities by overriding those symbols (usually defined |
|
|
3804 | to be C<-2> and C<2>, respectively). |
|
|
3805 | |
|
|
3806 | When doing priority-based operations, libev usually has to linearly search |
|
|
3807 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
3808 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
|
|
3809 | fine. |
|
|
3810 | |
|
|
3811 | If your embedding application does not need any priorities, defining these |
|
|
3812 | both to C<0> will save some memory and CPU. |
|
|
3813 | |
|
|
3814 | =item EV_PERIODIC_ENABLE |
|
|
3815 | |
|
|
3816 | If undefined or defined to be C<1>, then periodic timers are supported. If |
|
|
3817 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3818 | code. |
|
|
3819 | |
|
|
3820 | =item EV_IDLE_ENABLE |
|
|
3821 | |
|
|
3822 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3823 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3824 | code. |
|
|
3825 | |
|
|
3826 | =item EV_EMBED_ENABLE |
|
|
3827 | |
|
|
3828 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3829 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3830 | watcher types, which therefore must not be disabled. |
|
|
3831 | |
|
|
3832 | =item EV_STAT_ENABLE |
|
|
3833 | |
|
|
3834 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3835 | defined to be C<0>, then they are not. |
|
|
3836 | |
|
|
3837 | =item EV_FORK_ENABLE |
|
|
3838 | |
|
|
3839 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3840 | defined to be C<0>, then they are not. |
|
|
3841 | |
|
|
3842 | =item EV_ASYNC_ENABLE |
|
|
3843 | |
|
|
3844 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3845 | defined to be C<0>, then they are not. |
|
|
3846 | |
|
|
3847 | =item EV_MINIMAL |
|
|
3848 | |
|
|
3849 | If you need to shave off some kilobytes of code at the expense of some |
|
|
3850 | speed (but with the full API), define this symbol to C<1>. Currently this |
|
|
3851 | is used to override some inlining decisions, saves roughly 30% code size |
|
|
3852 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3853 | the default 4-heap. |
|
|
3854 | |
|
|
3855 | You can save even more by disabling watcher types you do not need |
|
|
3856 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3857 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3858 | |
|
|
3859 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3860 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3861 | of the API are still available, and do not complain if this subset changes |
|
|
3862 | over time. |
|
|
3863 | |
|
|
3864 | =item EV_NSIG |
|
|
3865 | |
|
|
3866 | The highest supported signal number, +1 (or, the number of |
|
|
3867 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
3868 | automatically, but sometimes this fails, in which case it can be |
|
|
3869 | specified. Also, using a lower number than detected (C<32> should be |
|
|
3870 | good for about any system in existance) can save some memory, as libev |
|
|
3871 | statically allocates some 12-24 bytes per signal number. |
|
|
3872 | |
|
|
3873 | =item EV_PID_HASHSIZE |
|
|
3874 | |
|
|
3875 | C<ev_child> watchers use a small hash table to distribute workload by |
|
|
3876 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
|
|
3877 | than enough. If you need to manage thousands of children you might want to |
|
|
3878 | increase this value (I<must> be a power of two). |
|
|
3879 | |
|
|
3880 | =item EV_INOTIFY_HASHSIZE |
|
|
3881 | |
|
|
3882 | C<ev_stat> watchers use a small hash table to distribute workload by |
|
|
3883 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
|
|
3884 | usually more than enough. If you need to manage thousands of C<ev_stat> |
|
|
3885 | watchers you might want to increase this value (I<must> be a power of |
|
|
3886 | two). |
|
|
3887 | |
|
|
3888 | =item EV_USE_4HEAP |
|
|
3889 | |
|
|
3890 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3891 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
|
|
3892 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
|
|
3893 | faster performance with many (thousands) of watchers. |
|
|
3894 | |
|
|
3895 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3896 | (disabled). |
|
|
3897 | |
|
|
3898 | =item EV_HEAP_CACHE_AT |
|
|
3899 | |
|
|
3900 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3901 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
|
|
3902 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3903 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3904 | but avoids random read accesses on heap changes. This improves performance |
|
|
3905 | noticeably with many (hundreds) of watchers. |
|
|
3906 | |
|
|
3907 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3908 | (disabled). |
|
|
3909 | |
|
|
3910 | =item EV_VERIFY |
|
|
3911 | |
|
|
3912 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
|
|
3913 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
3914 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
3915 | called. If set to C<2>, then the internal verification code will be |
|
|
3916 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
3917 | verification code will be called very frequently, which will slow down |
|
|
3918 | libev considerably. |
|
|
3919 | |
|
|
3920 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
|
|
3921 | C<0>. |
|
|
3922 | |
|
|
3923 | =item EV_COMMON |
|
|
3924 | |
|
|
3925 | By default, all watchers have a C<void *data> member. By redefining |
|
|
3926 | this macro to a something else you can include more and other types of |
|
|
3927 | members. You have to define it each time you include one of the files, |
|
|
3928 | though, and it must be identical each time. |
|
|
3929 | |
|
|
3930 | For example, the perl EV module uses something like this: |
|
|
3931 | |
|
|
3932 | #define EV_COMMON \ |
|
|
3933 | SV *self; /* contains this struct */ \ |
|
|
3934 | SV *cb_sv, *fh /* note no trailing ";" */ |
|
|
3935 | |
|
|
3936 | =item EV_CB_DECLARE (type) |
|
|
3937 | |
|
|
3938 | =item EV_CB_INVOKE (watcher, revents) |
|
|
3939 | |
|
|
3940 | =item ev_set_cb (ev, cb) |
|
|
3941 | |
|
|
3942 | Can be used to change the callback member declaration in each watcher, |
|
|
3943 | and the way callbacks are invoked and set. Must expand to a struct member |
|
|
3944 | definition and a statement, respectively. See the F<ev.h> header file for |
|
|
3945 | their default definitions. One possible use for overriding these is to |
|
|
3946 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
|
|
3947 | method calls instead of plain function calls in C++. |
|
|
3948 | |
|
|
3949 | =back |
|
|
3950 | |
|
|
3951 | =head2 EXPORTED API SYMBOLS |
|
|
3952 | |
|
|
3953 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
|
|
3954 | exported symbols, you can use the provided F<Symbol.*> files which list |
|
|
3955 | all public symbols, one per line: |
|
|
3956 | |
|
|
3957 | Symbols.ev for libev proper |
|
|
3958 | Symbols.event for the libevent emulation |
|
|
3959 | |
|
|
3960 | This can also be used to rename all public symbols to avoid clashes with |
|
|
3961 | multiple versions of libev linked together (which is obviously bad in |
|
|
3962 | itself, but sometimes it is inconvenient to avoid this). |
|
|
3963 | |
|
|
3964 | A sed command like this will create wrapper C<#define>'s that you need to |
|
|
3965 | include before including F<ev.h>: |
|
|
3966 | |
|
|
3967 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
|
|
3968 | |
|
|
3969 | This would create a file F<wrap.h> which essentially looks like this: |
|
|
3970 | |
|
|
3971 | #define ev_backend myprefix_ev_backend |
|
|
3972 | #define ev_check_start myprefix_ev_check_start |
|
|
3973 | #define ev_check_stop myprefix_ev_check_stop |
|
|
3974 | ... |
|
|
3975 | |
|
|
3976 | =head2 EXAMPLES |
|
|
3977 | |
|
|
3978 | For a real-world example of a program the includes libev |
|
|
3979 | verbatim, you can have a look at the EV perl module |
|
|
3980 | (L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
|
|
3981 | the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public |
|
|
3982 | interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file |
|
|
3983 | will be compiled. It is pretty complex because it provides its own header |
|
|
3984 | file. |
|
|
3985 | |
|
|
3986 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
|
|
3987 | that everybody includes and which overrides some configure choices: |
|
|
3988 | |
|
|
3989 | #define EV_MINIMAL 1 |
|
|
3990 | #define EV_USE_POLL 0 |
|
|
3991 | #define EV_MULTIPLICITY 0 |
|
|
3992 | #define EV_PERIODIC_ENABLE 0 |
|
|
3993 | #define EV_STAT_ENABLE 0 |
|
|
3994 | #define EV_FORK_ENABLE 0 |
|
|
3995 | #define EV_CONFIG_H <config.h> |
|
|
3996 | #define EV_MINPRI 0 |
|
|
3997 | #define EV_MAXPRI 0 |
|
|
3998 | |
|
|
3999 | #include "ev++.h" |
|
|
4000 | |
|
|
4001 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
|
|
4002 | |
|
|
4003 | #include "ev_cpp.h" |
|
|
4004 | #include "ev.c" |
|
|
4005 | |
|
|
4006 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
|
|
4007 | |
|
|
4008 | =head2 THREADS AND COROUTINES |
|
|
4009 | |
|
|
4010 | =head3 THREADS |
|
|
4011 | |
|
|
4012 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
4013 | documented otherwise, but libev implements no locking itself. This means |
|
|
4014 | that you can use as many loops as you want in parallel, as long as there |
|
|
4015 | are no concurrent calls into any libev function with the same loop |
|
|
4016 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
4017 | of course): libev guarantees that different event loops share no data |
|
|
4018 | structures that need any locking. |
|
|
4019 | |
|
|
4020 | Or to put it differently: calls with different loop parameters can be done |
|
|
4021 | concurrently from multiple threads, calls with the same loop parameter |
|
|
4022 | must be done serially (but can be done from different threads, as long as |
|
|
4023 | only one thread ever is inside a call at any point in time, e.g. by using |
|
|
4024 | a mutex per loop). |
|
|
4025 | |
|
|
4026 | Specifically to support threads (and signal handlers), libev implements |
|
|
4027 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
4028 | concurrency on the same event loop, namely waking it up "from the |
|
|
4029 | outside". |
|
|
4030 | |
|
|
4031 | If you want to know which design (one loop, locking, or multiple loops |
|
|
4032 | without or something else still) is best for your problem, then I cannot |
|
|
4033 | help you, but here is some generic advice: |
|
|
4034 | |
|
|
4035 | =over 4 |
|
|
4036 | |
|
|
4037 | =item * most applications have a main thread: use the default libev loop |
|
|
4038 | in that thread, or create a separate thread running only the default loop. |
|
|
4039 | |
|
|
4040 | This helps integrating other libraries or software modules that use libev |
|
|
4041 | themselves and don't care/know about threading. |
|
|
4042 | |
|
|
4043 | =item * one loop per thread is usually a good model. |
|
|
4044 | |
|
|
4045 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
4046 | exists, but it is always a good start. |
|
|
4047 | |
|
|
4048 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
4049 | loop is handed through multiple threads in a kind of round-robin fashion. |
|
|
4050 | |
|
|
4051 | Choosing a model is hard - look around, learn, know that usually you can do |
|
|
4052 | better than you currently do :-) |
|
|
4053 | |
|
|
4054 | =item * often you need to talk to some other thread which blocks in the |
|
|
4055 | event loop. |
|
|
4056 | |
|
|
4057 | C<ev_async> watchers can be used to wake them up from other threads safely |
|
|
4058 | (or from signal contexts...). |
|
|
4059 | |
|
|
4060 | An example use would be to communicate signals or other events that only |
|
|
4061 | work in the default loop by registering the signal watcher with the |
|
|
4062 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
4063 | watcher callback into the event loop interested in the signal. |
|
|
4064 | |
|
|
4065 | =back |
|
|
4066 | |
|
|
4067 | =head4 THREAD LOCKING EXAMPLE |
|
|
4068 | |
|
|
4069 | Here is a fictitious example of how to run an event loop in a different |
|
|
4070 | thread than where callbacks are being invoked and watchers are |
|
|
4071 | created/added/removed. |
|
|
4072 | |
|
|
4073 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4074 | which uses exactly this technique (which is suited for many high-level |
|
|
4075 | languages). |
|
|
4076 | |
|
|
4077 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4078 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4079 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4080 | |
|
|
4081 | First, you need to associate some data with the event loop: |
|
|
4082 | |
|
|
4083 | typedef struct { |
|
|
4084 | mutex_t lock; /* global loop lock */ |
|
|
4085 | ev_async async_w; |
|
|
4086 | thread_t tid; |
|
|
4087 | cond_t invoke_cv; |
|
|
4088 | } userdata; |
|
|
4089 | |
|
|
4090 | void prepare_loop (EV_P) |
|
|
4091 | { |
|
|
4092 | // for simplicity, we use a static userdata struct. |
|
|
4093 | static userdata u; |
|
|
4094 | |
|
|
4095 | ev_async_init (&u->async_w, async_cb); |
|
|
4096 | ev_async_start (EV_A_ &u->async_w); |
|
|
4097 | |
|
|
4098 | pthread_mutex_init (&u->lock, 0); |
|
|
4099 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4100 | |
|
|
4101 | // now associate this with the loop |
|
|
4102 | ev_set_userdata (EV_A_ u); |
|
|
4103 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4104 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4105 | |
|
|
4106 | // then create the thread running ev_loop |
|
|
4107 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4108 | } |
|
|
4109 | |
|
|
4110 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4111 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4112 | that might have been added: |
|
|
4113 | |
|
|
4114 | static void |
|
|
4115 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4116 | { |
|
|
4117 | // just used for the side effects |
|
|
4118 | } |
|
|
4119 | |
|
|
4120 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4121 | protecting the loop data, respectively. |
|
|
4122 | |
|
|
4123 | static void |
|
|
4124 | l_release (EV_P) |
|
|
4125 | { |
|
|
4126 | userdata *u = ev_userdata (EV_A); |
|
|
4127 | pthread_mutex_unlock (&u->lock); |
|
|
4128 | } |
|
|
4129 | |
|
|
4130 | static void |
|
|
4131 | l_acquire (EV_P) |
|
|
4132 | { |
|
|
4133 | userdata *u = ev_userdata (EV_A); |
|
|
4134 | pthread_mutex_lock (&u->lock); |
|
|
4135 | } |
|
|
4136 | |
|
|
4137 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4138 | into C<ev_loop>: |
|
|
4139 | |
|
|
4140 | void * |
|
|
4141 | l_run (void *thr_arg) |
|
|
4142 | { |
|
|
4143 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4144 | |
|
|
4145 | l_acquire (EV_A); |
|
|
4146 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4147 | ev_loop (EV_A_ 0); |
|
|
4148 | l_release (EV_A); |
|
|
4149 | |
|
|
4150 | return 0; |
|
|
4151 | } |
|
|
4152 | |
|
|
4153 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4154 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4155 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4156 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4157 | and b) skipping inter-thread-communication when there are no pending |
|
|
4158 | watchers is very beneficial): |
|
|
4159 | |
|
|
4160 | static void |
|
|
4161 | l_invoke (EV_P) |
|
|
4162 | { |
|
|
4163 | userdata *u = ev_userdata (EV_A); |
|
|
4164 | |
|
|
4165 | while (ev_pending_count (EV_A)) |
|
|
4166 | { |
|
|
4167 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4168 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4169 | } |
|
|
4170 | } |
|
|
4171 | |
|
|
4172 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4173 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4174 | thread to continue: |
|
|
4175 | |
|
|
4176 | static void |
|
|
4177 | real_invoke_pending (EV_P) |
|
|
4178 | { |
|
|
4179 | userdata *u = ev_userdata (EV_A); |
|
|
4180 | |
|
|
4181 | pthread_mutex_lock (&u->lock); |
|
|
4182 | ev_invoke_pending (EV_A); |
|
|
4183 | pthread_cond_signal (&u->invoke_cv); |
|
|
4184 | pthread_mutex_unlock (&u->lock); |
|
|
4185 | } |
|
|
4186 | |
|
|
4187 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4188 | event loop, you will now have to lock: |
|
|
4189 | |
|
|
4190 | ev_timer timeout_watcher; |
|
|
4191 | userdata *u = ev_userdata (EV_A); |
|
|
4192 | |
|
|
4193 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4194 | |
|
|
4195 | pthread_mutex_lock (&u->lock); |
|
|
4196 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4197 | ev_async_send (EV_A_ &u->async_w); |
|
|
4198 | pthread_mutex_unlock (&u->lock); |
|
|
4199 | |
|
|
4200 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4201 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4202 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4203 | watchers in the next event loop iteration. |
|
|
4204 | |
|
|
4205 | =head3 COROUTINES |
|
|
4206 | |
|
|
4207 | Libev is very accommodating to coroutines ("cooperative threads"): |
|
|
4208 | libev fully supports nesting calls to its functions from different |
|
|
4209 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
4210 | different coroutines, and switch freely between both coroutines running |
|
|
4211 | the loop, as long as you don't confuse yourself). The only exception is |
|
|
4212 | that you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
4213 | |
|
|
4214 | Care has been taken to ensure that libev does not keep local state inside |
|
|
4215 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
|
|
4216 | they do not call any callbacks. |
|
|
4217 | |
|
|
4218 | =head2 COMPILER WARNINGS |
|
|
4219 | |
|
|
4220 | Depending on your compiler and compiler settings, you might get no or a |
|
|
4221 | lot of warnings when compiling libev code. Some people are apparently |
|
|
4222 | scared by this. |
|
|
4223 | |
|
|
4224 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
4225 | has different warnings, and each user has different tastes regarding |
|
|
4226 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
4227 | targeting a specific compiler and compiler-version. |
|
|
4228 | |
|
|
4229 | Another reason is that some compiler warnings require elaborate |
|
|
4230 | workarounds, or other changes to the code that make it less clear and less |
|
|
4231 | maintainable. |
|
|
4232 | |
|
|
4233 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
4234 | wrong (because they don't actually warn about the condition their message |
|
|
4235 | seems to warn about). For example, certain older gcc versions had some |
|
|
4236 | warnings that resulted an extreme number of false positives. These have |
|
|
4237 | been fixed, but some people still insist on making code warn-free with |
|
|
4238 | such buggy versions. |
|
|
4239 | |
|
|
4240 | While libev is written to generate as few warnings as possible, |
|
|
4241 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
4242 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
4243 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
4244 | warnings, not errors, or proof of bugs. |
|
|
4245 | |
|
|
4246 | |
|
|
4247 | =head2 VALGRIND |
|
|
4248 | |
|
|
4249 | Valgrind has a special section here because it is a popular tool that is |
|
|
4250 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
|
|
4251 | |
|
|
4252 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
4253 | in libev, then check twice: If valgrind reports something like: |
|
|
4254 | |
|
|
4255 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
4256 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
4257 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
4258 | |
|
|
4259 | Then there is no memory leak, just as memory accounted to global variables |
|
|
4260 | is not a memleak - the memory is still being referenced, and didn't leak. |
|
|
4261 | |
|
|
4262 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
4263 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
4264 | although an acceptable workaround has been found here), or it might be |
|
|
4265 | confused. |
|
|
4266 | |
|
|
4267 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
|
|
4268 | make it into some kind of religion. |
|
|
4269 | |
|
|
4270 | If you are unsure about something, feel free to contact the mailing list |
|
|
4271 | with the full valgrind report and an explanation on why you think this |
|
|
4272 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
4273 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
4274 | of learning how to interpret valgrind properly. |
|
|
4275 | |
|
|
4276 | If you need, for some reason, empty reports from valgrind for your project |
|
|
4277 | I suggest using suppression lists. |
|
|
4278 | |
|
|
4279 | |
|
|
4280 | =head1 PORTABILITY NOTES |
|
|
4281 | |
|
|
4282 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4283 | |
|
|
4284 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
|
|
4285 | requires, and its I/O model is fundamentally incompatible with the POSIX |
|
|
4286 | model. Libev still offers limited functionality on this platform in |
|
|
4287 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
|
|
4288 | descriptors. This only applies when using Win32 natively, not when using |
|
|
4289 | e.g. cygwin. |
|
|
4290 | |
|
|
4291 | Lifting these limitations would basically require the full |
|
|
4292 | re-implementation of the I/O system. If you are into these kinds of |
|
|
4293 | things, then note that glib does exactly that for you in a very portable |
|
|
4294 | way (note also that glib is the slowest event library known to man). |
|
|
4295 | |
|
|
4296 | There is no supported compilation method available on windows except |
|
|
4297 | embedding it into other applications. |
|
|
4298 | |
|
|
4299 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4300 | tries its best, but under most conditions, signals will simply not work. |
|
|
4301 | |
|
|
4302 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
4303 | accept large writes: instead of resulting in a partial write, windows will |
|
|
4304 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
|
|
4305 | so make sure you only write small amounts into your sockets (less than a |
|
|
4306 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
4307 | available). |
|
|
4308 | |
|
|
4309 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
4310 | the abysmal performance of winsockets, using a large number of sockets |
|
|
4311 | is not recommended (and not reasonable). If your program needs to use |
|
|
4312 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
4313 | different implementation for windows, as libev offers the POSIX readiness |
|
|
4314 | notification model, which cannot be implemented efficiently on windows |
|
|
4315 | (due to Microsoft monopoly games). |
|
|
4316 | |
|
|
4317 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
4318 | section for details) and use the following F<evwrap.h> header file instead |
|
|
4319 | of F<ev.h>: |
|
|
4320 | |
|
|
4321 | #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
4322 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
4323 | |
|
|
4324 | #include "ev.h" |
|
|
4325 | |
|
|
4326 | And compile the following F<evwrap.c> file into your project (make sure |
|
|
4327 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
|
|
4328 | |
|
|
4329 | #include "evwrap.h" |
|
|
4330 | #include "ev.c" |
|
|
4331 | |
|
|
4332 | =over 4 |
|
|
4333 | |
|
|
4334 | =item The winsocket select function |
|
|
4335 | |
|
|
4336 | The winsocket C<select> function doesn't follow POSIX in that it |
|
|
4337 | requires socket I<handles> and not socket I<file descriptors> (it is |
|
|
4338 | also extremely buggy). This makes select very inefficient, and also |
|
|
4339 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
4340 | C runtime provides the function C<_open_osfhandle> for this). See the |
|
|
4341 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
|
|
4342 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
|
|
4343 | |
|
|
4344 | The configuration for a "naked" win32 using the Microsoft runtime |
|
|
4345 | libraries and raw winsocket select is: |
|
|
4346 | |
|
|
4347 | #define EV_USE_SELECT 1 |
|
|
4348 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
4349 | |
|
|
4350 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
4351 | complexity in the O(n²) range when using win32. |
|
|
4352 | |
|
|
4353 | =item Limited number of file descriptors |
|
|
4354 | |
|
|
4355 | Windows has numerous arbitrary (and low) limits on things. |
|
|
4356 | |
|
|
4357 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
4358 | of C<64> handles (probably owning to the fact that all windows kernels |
|
|
4359 | can only wait for C<64> things at the same time internally; Microsoft |
|
|
4360 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
4361 | previous thread in each. Sounds great!). |
|
|
4362 | |
|
|
4363 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
|
|
4364 | to some high number (e.g. C<2048>) before compiling the winsocket select |
|
|
4365 | call (which might be in libev or elsewhere, for example, perl and many |
|
|
4366 | other interpreters do their own select emulation on windows). |
|
|
4367 | |
|
|
4368 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
4369 | libraries, which by default is C<64> (there must be a hidden I<64> |
|
|
4370 | fetish or something like this inside Microsoft). You can increase this |
|
|
4371 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
|
|
4372 | (another arbitrary limit), but is broken in many versions of the Microsoft |
|
|
4373 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
|
|
4374 | (depending on windows version and/or the phase of the moon). To get more, |
|
|
4375 | you need to wrap all I/O functions and provide your own fd management, but |
|
|
4376 | the cost of calling select (O(n²)) will likely make this unworkable. |
|
|
4377 | |
|
|
4378 | =back |
|
|
4379 | |
|
|
4380 | =head2 PORTABILITY REQUIREMENTS |
|
|
4381 | |
|
|
4382 | In addition to a working ISO-C implementation and of course the |
|
|
4383 | backend-specific APIs, libev relies on a few additional extensions: |
|
|
4384 | |
|
|
4385 | =over 4 |
|
|
4386 | |
|
|
4387 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
|
|
4388 | calling conventions regardless of C<ev_watcher_type *>. |
|
|
4389 | |
|
|
4390 | Libev assumes not only that all watcher pointers have the same internal |
|
|
4391 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
|
|
4392 | assumes that the same (machine) code can be used to call any watcher |
|
|
4393 | callback: The watcher callbacks have different type signatures, but libev |
|
|
4394 | calls them using an C<ev_watcher *> internally. |
|
|
4395 | |
|
|
4396 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
4397 | |
|
|
4398 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
4399 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
|
|
4400 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
4401 | believed to be sufficiently portable. |
|
|
4402 | |
|
|
4403 | =item C<sigprocmask> must work in a threaded environment |
|
|
4404 | |
|
|
4405 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
4406 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
4407 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
4408 | thread" or will block signals process-wide, both behaviours would |
|
|
4409 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
4410 | C<pthread_sigmask> could complicate things, however. |
|
|
4411 | |
|
|
4412 | The most portable way to handle signals is to block signals in all threads |
|
|
4413 | except the initial one, and run the default loop in the initial thread as |
|
|
4414 | well. |
|
|
4415 | |
|
|
4416 | =item C<long> must be large enough for common memory allocation sizes |
|
|
4417 | |
|
|
4418 | To improve portability and simplify its API, libev uses C<long> internally |
|
|
4419 | instead of C<size_t> when allocating its data structures. On non-POSIX |
|
|
4420 | systems (Microsoft...) this might be unexpectedly low, but is still at |
|
|
4421 | least 31 bits everywhere, which is enough for hundreds of millions of |
|
|
4422 | watchers. |
|
|
4423 | |
|
|
4424 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
4425 | |
|
|
4426 | The type C<double> is used to represent timestamps. It is required to |
|
|
4427 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
4428 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
4429 | implementations implementing IEEE 754, which is basically all existing |
|
|
4430 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4431 | 2200. |
|
|
4432 | |
|
|
4433 | =back |
|
|
4434 | |
|
|
4435 | If you know of other additional requirements drop me a note. |
|
|
4436 | |
|
|
4437 | |
|
|
4438 | =head1 ALGORITHMIC COMPLEXITIES |
|
|
4439 | |
|
|
4440 | In this section the complexities of (many of) the algorithms used inside |
|
|
4441 | libev will be documented. For complexity discussions about backends see |
|
|
4442 | the documentation for C<ev_default_init>. |
|
|
4443 | |
|
|
4444 | All of the following are about amortised time: If an array needs to be |
|
|
4445 | extended, libev needs to realloc and move the whole array, but this |
|
|
4446 | happens asymptotically rarer with higher number of elements, so O(1) might |
|
|
4447 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
4448 | average it is much faster and asymptotically approaches constant time. |
|
|
4449 | |
|
|
4450 | =over 4 |
|
|
4451 | |
|
|
4452 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
|
|
4453 | |
|
|
4454 | This means that, when you have a watcher that triggers in one hour and |
|
|
4455 | there are 100 watchers that would trigger before that, then inserting will |
|
|
4456 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
4457 | |
|
|
4458 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
|
|
4459 | |
|
|
4460 | That means that changing a timer costs less than removing/adding them, |
|
|
4461 | as only the relative motion in the event queue has to be paid for. |
|
|
4462 | |
|
|
4463 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
|
|
4464 | |
|
|
4465 | These just add the watcher into an array or at the head of a list. |
|
|
4466 | |
|
|
4467 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
|
|
4468 | |
|
|
4469 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
|
|
4470 | |
|
|
4471 | These watchers are stored in lists, so they need to be walked to find the |
|
|
4472 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
4473 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
4474 | is rare). |
|
|
4475 | |
|
|
4476 | =item Finding the next timer in each loop iteration: O(1) |
|
|
4477 | |
|
|
4478 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
4479 | fixed position in the storage array. |
|
|
4480 | |
|
|
4481 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
4482 | |
|
|
4483 | A change means an I/O watcher gets started or stopped, which requires |
|
|
4484 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
4485 | on backend and whether C<ev_io_set> was used). |
|
|
4486 | |
|
|
4487 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
4488 | |
|
|
4489 | =item Priority handling: O(number_of_priorities) |
|
|
4490 | |
|
|
4491 | Priorities are implemented by allocating some space for each |
|
|
4492 | priority. When doing priority-based operations, libev usually has to |
|
|
4493 | linearly search all the priorities, but starting/stopping and activating |
|
|
4494 | watchers becomes O(1) with respect to priority handling. |
|
|
4495 | |
|
|
4496 | =item Sending an ev_async: O(1) |
|
|
4497 | |
|
|
4498 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
4499 | |
|
|
4500 | =item Processing signals: O(max_signal_number) |
|
|
4501 | |
|
|
4502 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
4503 | calls in the current loop iteration. Checking for async and signal events |
|
|
4504 | involves iterating over all running async watchers or all signal numbers. |
|
|
4505 | |
|
|
4506 | =back |
|
|
4507 | |
|
|
4508 | |
|
|
4509 | =head1 GLOSSARY |
|
|
4510 | |
|
|
4511 | =over 4 |
|
|
4512 | |
|
|
4513 | =item active |
|
|
4514 | |
|
|
4515 | A watcher is active as long as it has been started (has been attached to |
|
|
4516 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4517 | |
|
|
4518 | =item application |
|
|
4519 | |
|
|
4520 | In this document, an application is whatever is using libev. |
|
|
4521 | |
|
|
4522 | =item callback |
|
|
4523 | |
|
|
4524 | The address of a function that is called when some event has been |
|
|
4525 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4526 | received the event, and the actual event bitset. |
|
|
4527 | |
|
|
4528 | =item callback invocation |
|
|
4529 | |
|
|
4530 | The act of calling the callback associated with a watcher. |
|
|
4531 | |
|
|
4532 | =item event |
|
|
4533 | |
|
|
4534 | A change of state of some external event, such as data now being available |
|
|
4535 | for reading on a file descriptor, time having passed or simply not having |
|
|
4536 | any other events happening anymore. |
|
|
4537 | |
|
|
4538 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4539 | C<EV_TIMEOUT>). |
|
|
4540 | |
|
|
4541 | =item event library |
|
|
4542 | |
|
|
4543 | A software package implementing an event model and loop. |
|
|
4544 | |
|
|
4545 | =item event loop |
|
|
4546 | |
|
|
4547 | An entity that handles and processes external events and converts them |
|
|
4548 | into callback invocations. |
|
|
4549 | |
|
|
4550 | =item event model |
|
|
4551 | |
|
|
4552 | The model used to describe how an event loop handles and processes |
|
|
4553 | watchers and events. |
|
|
4554 | |
|
|
4555 | =item pending |
|
|
4556 | |
|
|
4557 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4558 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4559 | pending status is explicitly cleared by the application. |
|
|
4560 | |
|
|
4561 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4562 | its pending status. |
|
|
4563 | |
|
|
4564 | =item real time |
|
|
4565 | |
|
|
4566 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4567 | |
|
|
4568 | =item wall-clock time |
|
|
4569 | |
|
|
4570 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4571 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4572 | clock. |
|
|
4573 | |
|
|
4574 | =item watcher |
|
|
4575 | |
|
|
4576 | A data structure that describes interest in certain events. Watchers need |
|
|
4577 | to be started (attached to an event loop) before they can receive events. |
|
|
4578 | |
|
|
4579 | =item watcher invocation |
|
|
4580 | |
|
|
4581 | The act of calling the callback associated with a watcher. |
|
|
4582 | |
|
|
4583 | =back |
|
|
4584 | |
755 | =head1 AUTHOR |
4585 | =head1 AUTHOR |
756 | |
4586 | |
757 | Marc Lehmann <libev@schmorp.de>. |
4587 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
758 | |
4588 | |