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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> |
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8 | |
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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 | // every watcher type has its own typedef'd struct |
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15 | // with the name ev_<type> |
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16 | ev_io stdin_watcher; |
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17 | ev_timer timeout_watcher; |
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18 | |
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19 | // all watcher callbacks have a similar signature |
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20 | // this callback is called when data is readable on stdin |
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21 | static void |
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22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
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23 | { |
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24 | puts ("stdin ready"); |
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25 | // for one-shot events, one must manually stop the watcher |
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26 | // with its corresponding stop function. |
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27 | ev_io_stop (EV_A_ w); |
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28 | |
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29 | // this causes all nested ev_loop's to stop iterating |
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30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
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31 | } |
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32 | |
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33 | // another callback, this time for a time-out |
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34 | static void |
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35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
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36 | { |
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37 | puts ("timeout"); |
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38 | // this causes the innermost ev_loop to stop iterating |
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39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
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40 | } |
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41 | |
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42 | int |
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43 | main (void) |
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44 | { |
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45 | // use the default event loop unless you have special needs |
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46 | struct ev_loop *loop = ev_default_loop (0); |
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47 | |
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48 | // initialise an io watcher, then start it |
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49 | // this one will watch for stdin to become readable |
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50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
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51 | ev_io_start (loop, &stdin_watcher); |
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52 | |
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53 | // initialise a timer watcher, then start it |
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54 | // simple non-repeating 5.5 second timeout |
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55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
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56 | ev_timer_start (loop, &timeout_watcher); |
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57 | |
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58 | // now wait for events to arrive |
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59 | ev_loop (loop, 0); |
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60 | |
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61 | // unloop was called, so exit |
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62 | return 0; |
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63 | } |
8 | |
64 | |
9 | =head1 DESCRIPTION |
65 | =head1 DESCRIPTION |
10 | |
66 | |
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67 | The newest version of this document is also available as an html-formatted |
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68 | web page you might find easier to navigate when reading it for the first |
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69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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70 | |
11 | Libev is an event loop: you register interest in certain events (such as a |
71 | 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 |
72 | file descriptor being readable or a timeout occurring), and it will manage |
13 | these event sources and provide your program with events. |
73 | these event sources and provide your program with events. |
14 | |
74 | |
15 | To do this, it must take more or less complete control over your process |
75 | 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 |
76 | (or thread) by executing the I<event loop> handler, and will then |
17 | communicate events via a callback mechanism. |
77 | communicate events via a callback mechanism. |
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19 | You register interest in certain events by registering so-called I<event |
79 | You register interest in certain events by registering so-called I<event |
20 | watchers>, which are relatively small C structures you initialise with the |
80 | 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 |
81 | details of the event, and then hand it over to libev by I<starting> the |
22 | watcher. |
82 | watcher. |
23 | |
83 | |
24 | =head1 FEATURES |
84 | =head2 FEATURES |
25 | |
85 | |
26 | Libev supports select, poll, the linux-specific epoll and the bsd-specific |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
27 | kqueue mechanisms for file descriptor events, relative timers, absolute |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
28 | timers with customised rescheduling, signal events, process status change |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
29 | events (related to SIGCHLD), and event watchers dealing with the event |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
30 | loop mechanism itself (idle, prepare and check watchers). It also is quite |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
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91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
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92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
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93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
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94 | file watchers (C<ev_stat>) and even limited support for fork events |
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95 | (C<ev_fork>). |
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96 | |
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97 | It also is quite fast (see this |
31 | fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
32 | it to libevent for example). |
99 | for example). |
33 | |
100 | |
34 | =head1 CONVENTIONS |
101 | =head2 CONVENTIONS |
35 | |
102 | |
36 | Libev is very configurable. In this manual the default configuration |
103 | Libev is very configurable. In this manual the default (and most common) |
37 | will be described, which supports multiple event loops. For more info |
104 | configuration will be described, which supports multiple event loops. For |
38 | about various configuration options please have a look at the file |
105 | more info about various configuration options please have a look at |
39 | F<README.embed> in the libev distribution. If libev was configured without |
106 | B<EMBED> section in this manual. If libev was configured without support |
40 | support for multiple event loops, then all functions taking an initial |
107 | 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 *>) |
108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
42 | will not have this argument. |
109 | this argument. |
43 | |
110 | |
44 | =head1 TIME AND OTHER GLOBAL FUNCTIONS |
111 | =head2 TIME REPRESENTATION |
45 | |
112 | |
46 | Libev represents time as a single floating point number, representing the |
113 | Libev represents time as a single floating point number, representing the |
47 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
48 | the beginning of 1970, details are complicated, don't ask). This type is |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
49 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
50 | to the double type in C. |
117 | to the C<double> type in C, and when you need to do any calculations on |
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118 | it, you should treat it as some floating point value. Unlike the name |
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119 | component C<stamp> might indicate, it is also used for time differences |
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120 | throughout libev. |
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121 | |
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122 | =head1 ERROR HANDLING |
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123 | |
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124 | Libev knows three classes of errors: operating system errors, usage errors |
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125 | and internal errors (bugs). |
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126 | |
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127 | When libev catches an operating system error it cannot handle (for example |
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128 | a system call indicating a condition libev cannot fix), it calls the callback |
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129 | set via C<ev_set_syserr_cb>, which is supposed to fix the problem or |
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130 | abort. The default is to print a diagnostic message and to call C<abort |
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131 | ()>. |
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132 | |
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133 | When libev detects a usage error such as a negative timer interval, then |
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134 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
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135 | so C<NDEBUG> will disable this checking): these are programming errors in |
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136 | the libev caller and need to be fixed there. |
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137 | |
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138 | Libev also has a few internal error-checking C<assert>ions, and also has |
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139 | extensive consistency checking code. These do not trigger under normal |
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140 | circumstances, as they indicate either a bug in libev or worse. |
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141 | |
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142 | |
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143 | =head1 GLOBAL FUNCTIONS |
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144 | |
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145 | These functions can be called anytime, even before initialising the |
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146 | library in any way. |
51 | |
147 | |
52 | =over 4 |
148 | =over 4 |
53 | |
149 | |
54 | =item ev_tstamp ev_time () |
150 | =item ev_tstamp ev_time () |
55 | |
151 | |
56 | Returns the current time as libev would use it. |
152 | Returns the current time as libev would use it. Please note that the |
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153 | C<ev_now> function is usually faster and also often returns the timestamp |
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154 | you actually want to know. |
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155 | |
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156 | =item ev_sleep (ev_tstamp interval) |
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157 | |
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158 | Sleep for the given interval: The current thread will be blocked until |
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159 | either it is interrupted or the given time interval has passed. Basically |
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160 | this is a sub-second-resolution C<sleep ()>. |
57 | |
161 | |
58 | =item int ev_version_major () |
162 | =item int ev_version_major () |
59 | |
163 | |
60 | =item int ev_version_minor () |
164 | =item int ev_version_minor () |
61 | |
165 | |
62 | You can find out the major and minor version numbers of the library |
166 | 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 |
167 | 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 |
168 | 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 |
169 | symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the |
66 | version of the library your program was compiled against. |
170 | version of the library your program was compiled against. |
67 | |
171 | |
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172 | These version numbers refer to the ABI version of the library, not the |
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173 | release version. |
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174 | |
68 | Usually, it's a good idea to terminate if the major versions mismatch, |
175 | Usually, it's a good idea to terminate if the major versions mismatch, |
69 | as this indicates an incompatible change. Minor versions are usually |
176 | as this indicates an incompatible change. Minor versions are usually |
70 | compatible to older versions, so a larger minor version alone is usually |
177 | compatible to older versions, so a larger minor version alone is usually |
71 | not a problem. |
178 | not a problem. |
72 | |
179 | |
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180 | Example: Make sure we haven't accidentally been linked against the wrong |
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181 | version. |
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182 | |
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183 | assert (("libev version mismatch", |
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184 | ev_version_major () == EV_VERSION_MAJOR |
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185 | && ev_version_minor () >= EV_VERSION_MINOR)); |
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186 | |
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187 | =item unsigned int ev_supported_backends () |
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188 | |
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189 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
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190 | value) compiled into this binary of libev (independent of their |
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191 | availability on the system you are running on). See C<ev_default_loop> for |
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192 | a description of the set values. |
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193 | |
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194 | Example: make sure we have the epoll method, because yeah this is cool and |
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195 | a must have and can we have a torrent of it please!!!11 |
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196 | |
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197 | assert (("sorry, no epoll, no sex", |
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198 | ev_supported_backends () & EVBACKEND_EPOLL)); |
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199 | |
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200 | =item unsigned int ev_recommended_backends () |
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201 | |
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202 | Return the set of all backends compiled into this binary of libev and also |
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203 | recommended for this platform. This set is often smaller than the one |
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204 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
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205 | most BSDs and will not be auto-detected unless you explicitly request it |
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206 | (assuming you know what you are doing). This is the set of backends that |
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207 | libev will probe for if you specify no backends explicitly. |
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208 | |
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209 | =item unsigned int ev_embeddable_backends () |
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210 | |
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211 | Returns the set of backends that are embeddable in other event loops. This |
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212 | is the theoretical, all-platform, value. To find which backends |
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213 | might be supported on the current system, you would need to look at |
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214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
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215 | recommended ones. |
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216 | |
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217 | See the description of C<ev_embed> watchers for more info. |
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218 | |
73 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
74 | |
220 | |
75 | Sets the allocation function to use (the prototype is similar to the |
221 | Sets the allocation function to use (the prototype is similar - the |
76 | realloc C function, the semantics are identical). It is used to allocate |
222 | 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 |
223 | 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 |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
79 | destructive action. The default is your system realloc function. |
225 | or take some potentially destructive action. |
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226 | |
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227 | Since some systems (at least OpenBSD and Darwin) fail to implement |
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228 | correct C<realloc> semantics, libev will use a wrapper around the system |
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229 | C<realloc> and C<free> functions by default. |
80 | |
230 | |
81 | You could override this function in high-availability programs to, say, |
231 | 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, |
232 | 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. |
233 | or even to sleep a while and retry until some memory is available. |
84 | |
234 | |
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235 | Example: Replace the libev allocator with one that waits a bit and then |
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236 | retries (example requires a standards-compliant C<realloc>). |
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237 | |
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238 | static void * |
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239 | persistent_realloc (void *ptr, size_t size) |
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240 | { |
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241 | for (;;) |
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242 | { |
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243 | void *newptr = realloc (ptr, size); |
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244 | |
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245 | if (newptr) |
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246 | return newptr; |
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247 | |
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248 | sleep (60); |
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249 | } |
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250 | } |
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251 | |
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252 | ... |
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253 | ev_set_allocator (persistent_realloc); |
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254 | |
85 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
86 | |
256 | |
87 | Set the callback function to call on a retryable syscall error (such |
257 | 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 |
258 | as failed select, poll, epoll_wait). The message is a printable string |
89 | indicating the system call or subsystem causing the problem. If this |
259 | 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 |
260 | 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 |
261 | 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 |
262 | requested operation, or, if the condition doesn't go away, do bad stuff |
93 | (such as abort). |
263 | (such as abort). |
94 | |
264 | |
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265 | Example: This is basically the same thing that libev does internally, too. |
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266 | |
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267 | static void |
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268 | fatal_error (const char *msg) |
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269 | { |
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270 | perror (msg); |
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271 | abort (); |
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272 | } |
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273 | |
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274 | ... |
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275 | ev_set_syserr_cb (fatal_error); |
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276 | |
95 | =back |
277 | =back |
96 | |
278 | |
97 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
98 | |
280 | |
99 | An event loop is described by a C<struct ev_loop *>. The library knows two |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
100 | types of such loops, the I<default> loop, which supports signals and child |
282 | types of such loops, the I<default> loop, which supports signals and child |
101 | events, and dynamically created loops which do not. |
283 | events, and dynamically created loops which do not. |
102 | |
284 | |
103 | If you use threads, a common model is to run the default event loop |
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104 | in your main thread (or in a separate thrad) and for each thread you |
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105 | create, you also create another event loop. Libev itself does no locking |
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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 | |
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110 | =over 4 |
285 | =over 4 |
111 | |
286 | |
112 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
113 | |
288 | |
114 | This will initialise the default event loop if it hasn't been initialised |
289 | 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 |
290 | 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 |
291 | false. If it already was initialised it simply returns it (and ignores the |
117 | flags). |
292 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
118 | |
293 | |
119 | If you don't know what event loop to use, use the one returned from this |
294 | If you don't know what event loop to use, use the one returned from this |
120 | function. |
295 | function. |
121 | |
296 | |
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297 | Note that this function is I<not> thread-safe, so if you want to use it |
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298 | from multiple threads, you have to lock (note also that this is unlikely, |
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299 | as loops cannot bes hared easily between threads anyway). |
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300 | |
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301 | The default loop is the only loop that can handle C<ev_signal> and |
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302 | C<ev_child> watchers, and to do this, it always registers a handler |
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303 | for C<SIGCHLD>. If this is a problem for your application you can either |
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304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
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305 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
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306 | C<ev_default_init>. |
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307 | |
122 | The flags argument can be used to specify special behaviour or specific |
308 | 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). |
309 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
124 | |
310 | |
125 | It supports the following flags: |
311 | The following flags are supported: |
126 | |
312 | |
127 | =over 4 |
313 | =over 4 |
128 | |
314 | |
129 | =item C<EVFLAG_AUTO> |
315 | =item C<EVFLAG_AUTO> |
130 | |
316 | |
131 | The default flags value. Use this if you have no clue (it's the right |
317 | The default flags value. Use this if you have no clue (it's the right |
132 | thing, believe me). |
318 | thing, believe me). |
133 | |
319 | |
134 | =item C<EVFLAG_NOENV> |
320 | =item C<EVFLAG_NOENV> |
135 | |
321 | |
136 | If this flag bit is ored into the flag value (or the program runs setuid |
322 | 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 |
323 | or setgid) then libev will I<not> look at the environment variable |
138 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
324 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
139 | override the flags completely if it is found in the environment. This is |
325 | 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 |
326 | useful to try out specific backends to test their performance, or to work |
141 | around bugs. |
327 | around bugs. |
142 | |
328 | |
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329 | =item C<EVFLAG_FORKCHECK> |
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330 | |
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331 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
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332 | a fork, you can also make libev check for a fork in each iteration by |
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333 | enabling this flag. |
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334 | |
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335 | This works by calling C<getpid ()> on every iteration of the loop, |
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336 | and thus this might slow down your event loop if you do a lot of loop |
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337 | iterations and little real work, but is usually not noticeable (on my |
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338 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
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339 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
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340 | C<pthread_atfork> which is even faster). |
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341 | |
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342 | The big advantage of this flag is that you can forget about fork (and |
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343 | forget about forgetting to tell libev about forking) when you use this |
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344 | flag. |
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345 | |
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346 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
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347 | environment variable. |
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348 | |
143 | =item C<EVMETHOD_SELECT> (portable select backend) |
349 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
144 | |
350 | |
|
|
351 | This is your standard select(2) backend. Not I<completely> standard, as |
|
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352 | libev tries to roll its own fd_set with no limits on the number of fds, |
|
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353 | but if that fails, expect a fairly low limit on the number of fds when |
|
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354 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
|
|
355 | usually the fastest backend for a low number of (low-numbered :) fds. |
|
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356 | |
|
|
357 | To get good performance out of this backend you need a high amount of |
|
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358 | parallelism (most of the file descriptors should be busy). If you are |
|
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359 | writing a server, you should C<accept ()> in a loop to accept as many |
|
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360 | connections as possible during one iteration. You might also want to have |
|
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361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
|
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362 | readiness notifications you get per iteration. |
|
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363 | |
145 | =item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows) |
364 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
146 | |
365 | |
147 | =item C<EVMETHOD_EPOLL> (linux only) |
366 | And this is your standard poll(2) backend. It's more complicated |
|
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367 | than select, but handles sparse fds better and has no artificial |
|
|
368 | limit on the number of fds you can use (except it will slow down |
|
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369 | considerably with a lot of inactive fds). It scales similarly to select, |
|
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370 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
|
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371 | performance tips. |
148 | |
372 | |
149 | =item C<EVMETHOD_KQUEUE> (some bsds only) |
373 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
150 | |
374 | |
151 | =item C<EVMETHOD_DEVPOLL> (solaris 8 only) |
375 | For few fds, this backend is a bit little slower than poll and select, |
|
|
376 | but it scales phenomenally better. While poll and select usually scale |
|
|
377 | like O(total_fds) where n is the total number of fds (or the highest fd), |
|
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378 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
|
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379 | of shortcomings, such as silently dropping events in some hard-to-detect |
|
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380 | cases and requiring a system call per fd change, no fork support and bad |
|
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381 | support for dup. |
152 | |
382 | |
153 | =item C<EVMETHOD_PORT> (solaris 10 only) |
383 | While stopping, setting and starting an I/O watcher in the same iteration |
|
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384 | will result in some caching, there is still a system call per such incident |
|
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385 | (because the fd could point to a different file description now), so its |
|
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386 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
|
|
387 | very well if you register events for both fds. |
154 | |
388 | |
155 | If one or more of these are ored into the flags value, then only these |
389 | Please note that epoll sometimes generates spurious notifications, so you |
156 | backends will be tried (in the reverse order as given here). If one are |
390 | need to use non-blocking I/O or other means to avoid blocking when no data |
157 | specified, any backend will do. |
391 | (or space) is available. |
|
|
392 | |
|
|
393 | Best performance from this backend is achieved by not unregistering all |
|
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394 | watchers for a file descriptor until it has been closed, if possible, i.e. |
|
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395 | keep at least one watcher active per fd at all times. |
|
|
396 | |
|
|
397 | While nominally embeddable in other event loops, this feature is broken in |
|
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398 | all kernel versions tested so far. |
|
|
399 | |
|
|
400 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
|
|
401 | |
|
|
402 | Kqueue deserves special mention, as at the time of this writing, it |
|
|
403 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
|
|
404 | with anything but sockets and pipes, except on Darwin, where of course |
|
|
405 | it's completely useless). For this reason it's not being "auto-detected" |
|
|
406 | unless you explicitly specify it explicitly in the flags (i.e. using |
|
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407 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
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408 | system like NetBSD. |
|
|
409 | |
|
|
410 | You still can embed kqueue into a normal poll or select backend and use it |
|
|
411 | only for sockets (after having made sure that sockets work with kqueue on |
|
|
412 | the target platform). See C<ev_embed> watchers for more info. |
|
|
413 | |
|
|
414 | It scales in the same way as the epoll backend, but the interface to the |
|
|
415 | kernel is more efficient (which says nothing about its actual speed, of |
|
|
416 | course). While stopping, setting and starting an I/O watcher does never |
|
|
417 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
|
|
418 | two event changes per incident, support for C<fork ()> is very bad and it |
|
|
419 | drops fds silently in similarly hard-to-detect cases. |
|
|
420 | |
|
|
421 | This backend usually performs well under most conditions. |
|
|
422 | |
|
|
423 | While nominally embeddable in other event loops, this doesn't work |
|
|
424 | everywhere, so you might need to test for this. And since it is broken |
|
|
425 | almost everywhere, you should only use it when you have a lot of sockets |
|
|
426 | (for which it usually works), by embedding it into another event loop |
|
|
427 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
|
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428 | sockets. |
|
|
429 | |
|
|
430 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
|
|
431 | |
|
|
432 | This is not implemented yet (and might never be, unless you send me an |
|
|
433 | implementation). According to reports, C</dev/poll> only supports sockets |
|
|
434 | and is not embeddable, which would limit the usefulness of this backend |
|
|
435 | immensely. |
|
|
436 | |
|
|
437 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
|
|
438 | |
|
|
439 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
|
|
440 | it's really slow, but it still scales very well (O(active_fds)). |
|
|
441 | |
|
|
442 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
443 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
444 | blocking when no data (or space) is available. |
|
|
445 | |
|
|
446 | While this backend scales well, it requires one system call per active |
|
|
447 | file descriptor per loop iteration. For small and medium numbers of file |
|
|
448 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
|
|
449 | might perform better. |
|
|
450 | |
|
|
451 | On the positive side, ignoring the spurious readiness notifications, this |
|
|
452 | backend actually performed to specification in all tests and is fully |
|
|
453 | embeddable, which is a rare feat among the OS-specific backends. |
|
|
454 | |
|
|
455 | =item C<EVBACKEND_ALL> |
|
|
456 | |
|
|
457 | Try all backends (even potentially broken ones that wouldn't be tried |
|
|
458 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
|
|
459 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
|
|
460 | |
|
|
461 | It is definitely not recommended to use this flag. |
158 | |
462 | |
159 | =back |
463 | =back |
|
|
464 | |
|
|
465 | If one or more of these are or'ed into the flags value, then only these |
|
|
466 | backends will be tried (in the reverse order as listed here). If none are |
|
|
467 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
|
|
468 | |
|
|
469 | The most typical usage is like this: |
|
|
470 | |
|
|
471 | if (!ev_default_loop (0)) |
|
|
472 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
473 | |
|
|
474 | Restrict libev to the select and poll backends, and do not allow |
|
|
475 | environment settings to be taken into account: |
|
|
476 | |
|
|
477 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
478 | |
|
|
479 | Use whatever libev has to offer, but make sure that kqueue is used if |
|
|
480 | available (warning, breaks stuff, best use only with your own private |
|
|
481 | event loop and only if you know the OS supports your types of fds): |
|
|
482 | |
|
|
483 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
160 | |
484 | |
161 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
485 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
162 | |
486 | |
163 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
487 | 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 |
488 | 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 |
489 | 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). |
490 | undefined behaviour (or a failed assertion if assertions are enabled). |
167 | |
491 | |
|
|
492 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
493 | libev with threads is indeed to create one loop per thread, and using the |
|
|
494 | default loop in the "main" or "initial" thread. |
|
|
495 | |
|
|
496 | Example: Try to create a event loop that uses epoll and nothing else. |
|
|
497 | |
|
|
498 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
|
|
499 | if (!epoller) |
|
|
500 | fatal ("no epoll found here, maybe it hides under your chair"); |
|
|
501 | |
168 | =item ev_default_destroy () |
502 | =item ev_default_destroy () |
169 | |
503 | |
170 | Destroys the default loop again (frees all memory and kernel state |
504 | Destroys the default loop again (frees all memory and kernel state |
171 | etc.). This stops all registered event watchers (by not touching them in |
505 | etc.). None of the active event watchers will be stopped in the normal |
172 | any way whatsoever, although you cannot rely on this :). |
506 | sense, so e.g. C<ev_is_active> might still return true. It is your |
|
|
507 | responsibility to either stop all watchers cleanly yourself I<before> |
|
|
508 | calling this function, or cope with the fact afterwards (which is usually |
|
|
509 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
|
|
510 | for example). |
|
|
511 | |
|
|
512 | Note that certain global state, such as signal state, will not be freed by |
|
|
513 | this function, and related watchers (such as signal and child watchers) |
|
|
514 | would need to be stopped manually. |
|
|
515 | |
|
|
516 | In general it is not advisable to call this function except in the |
|
|
517 | rare occasion where you really need to free e.g. the signal handling |
|
|
518 | pipe fds. If you need dynamically allocated loops it is better to use |
|
|
519 | C<ev_loop_new> and C<ev_loop_destroy>). |
173 | |
520 | |
174 | =item ev_loop_destroy (loop) |
521 | =item ev_loop_destroy (loop) |
175 | |
522 | |
176 | Like C<ev_default_destroy>, but destroys an event loop created by an |
523 | Like C<ev_default_destroy>, but destroys an event loop created by an |
177 | earlier call to C<ev_loop_new>. |
524 | earlier call to C<ev_loop_new>. |
178 | |
525 | |
179 | =item ev_default_fork () |
526 | =item ev_default_fork () |
180 | |
527 | |
|
|
528 | This function sets a flag that causes subsequent C<ev_loop> iterations |
181 | This function reinitialises the kernel state for backends that have |
529 | 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 |
530 | 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 |
531 | the child process (or both child and parent, but that again makes little |
184 | again makes little sense). |
532 | sense). You I<must> call it in the child before using any of the libev |
|
|
533 | functions, and it will only take effect at the next C<ev_loop> iteration. |
185 | |
534 | |
186 | You I<must> call this function after forking if and only if you want to |
535 | 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 |
536 | process if and only if you want to use the event library in the child. If |
188 | have to call it. |
537 | you just fork+exec, you don't have to call it at all. |
189 | |
538 | |
190 | The function itself is quite fast and it's usually not a problem to call |
539 | 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 |
540 | 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>: |
541 | quite nicely into a call to C<pthread_atfork>: |
193 | |
542 | |
… | |
… | |
197 | |
546 | |
198 | Like C<ev_default_fork>, but acts on an event loop created by |
547 | 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 |
548 | 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. |
549 | after fork, and how you do this is entirely your own problem. |
201 | |
550 | |
|
|
551 | =item int ev_is_default_loop (loop) |
|
|
552 | |
|
|
553 | Returns true when the given loop actually is the default loop, false otherwise. |
|
|
554 | |
|
|
555 | =item unsigned int ev_loop_count (loop) |
|
|
556 | |
|
|
557 | Returns the count of loop iterations for the loop, which is identical to |
|
|
558 | the number of times libev did poll for new events. It starts at C<0> and |
|
|
559 | happily wraps around with enough iterations. |
|
|
560 | |
|
|
561 | This value can sometimes be useful as a generation counter of sorts (it |
|
|
562 | "ticks" the number of loop iterations), as it roughly corresponds with |
|
|
563 | C<ev_prepare> and C<ev_check> calls. |
|
|
564 | |
202 | =item unsigned int ev_method (loop) |
565 | =item unsigned int ev_backend (loop) |
203 | |
566 | |
204 | Returns one of the C<EVMETHOD_*> flags indicating the event backend in |
567 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
205 | use. |
568 | use. |
206 | |
569 | |
207 | =item ev_tstamp ev_now (loop) |
570 | =item ev_tstamp ev_now (loop) |
208 | |
571 | |
209 | Returns the current "event loop time", which is the time the event loop |
572 | 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 |
573 | 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 |
574 | 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 |
575 | 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). |
576 | event occurring (or more correctly, libev finding out about it). |
|
|
577 | |
|
|
578 | =item ev_now_update (loop) |
|
|
579 | |
|
|
580 | Establishes the current time by querying the kernel, updating the time |
|
|
581 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
582 | is usually done automatically within C<ev_loop ()>. |
|
|
583 | |
|
|
584 | This function is rarely useful, but when some event callback runs for a |
|
|
585 | very long time without entering the event loop, updating libev's idea of |
|
|
586 | the current time is a good idea. |
|
|
587 | |
|
|
588 | See also "The special problem of time updates" in the C<ev_timer> section. |
214 | |
589 | |
215 | =item ev_loop (loop, int flags) |
590 | =item ev_loop (loop, int flags) |
216 | |
591 | |
217 | Finally, this is it, the event handler. This function usually is called |
592 | 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 |
593 | after you initialised all your watchers and you want to start handling |
219 | events. |
594 | events. |
220 | |
595 | |
221 | If the flags argument is specified as 0, it will not return until either |
596 | 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. |
597 | either no event watchers are active anymore or C<ev_unloop> was called. |
|
|
598 | |
|
|
599 | Please note that an explicit C<ev_unloop> is usually better than |
|
|
600 | relying on all watchers to be stopped when deciding when a program has |
|
|
601 | finished (especially in interactive programs), but having a program that |
|
|
602 | automatically loops as long as it has to and no longer by virtue of |
|
|
603 | relying on its watchers stopping correctly is a thing of beauty. |
223 | |
604 | |
224 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
605 | 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 |
606 | those events and any outstanding ones, but will not block your process in |
226 | case there are no events and will return after one iteration of the loop. |
607 | case there are no events and will return after one iteration of the loop. |
227 | |
608 | |
228 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
609 | 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 |
610 | necessary) and will handle those and any outstanding ones. It will block |
230 | your process until at least one new event arrives, and will return after |
611 | your process until at least one new event arrives, and will return after |
231 | one iteration of the loop. |
612 | one iteration of the loop. This is useful if you are waiting for some |
|
|
613 | external event in conjunction with something not expressible using other |
|
|
614 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
|
|
615 | usually a better approach for this kind of thing. |
232 | |
616 | |
233 | This flags value could be used to implement alternative looping |
617 | Here are the gory details of what C<ev_loop> does: |
234 | constructs, but the C<prepare> and C<check> watchers provide a better and |
618 | |
235 | more generic mechanism. |
619 | - Before the first iteration, call any pending watchers. |
|
|
620 | * If EVFLAG_FORKCHECK was used, check for a fork. |
|
|
621 | - If a fork was detected (by any means), queue and call all fork watchers. |
|
|
622 | - Queue and call all prepare watchers. |
|
|
623 | - If we have been forked, detach and recreate the kernel state |
|
|
624 | as to not disturb the other process. |
|
|
625 | - Update the kernel state with all outstanding changes. |
|
|
626 | - Update the "event loop time" (ev_now ()). |
|
|
627 | - Calculate for how long to sleep or block, if at all |
|
|
628 | (active idle watchers, EVLOOP_NONBLOCK or not having |
|
|
629 | any active watchers at all will result in not sleeping). |
|
|
630 | - Sleep if the I/O and timer collect interval say so. |
|
|
631 | - Block the process, waiting for any events. |
|
|
632 | - Queue all outstanding I/O (fd) events. |
|
|
633 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
|
|
634 | - Queue all outstanding timers. |
|
|
635 | - Queue all outstanding periodics. |
|
|
636 | - Unless any events are pending now, queue all idle watchers. |
|
|
637 | - Queue all check watchers. |
|
|
638 | - Call all queued watchers in reverse order (i.e. check watchers first). |
|
|
639 | Signals and child watchers are implemented as I/O watchers, and will |
|
|
640 | be handled here by queueing them when their watcher gets executed. |
|
|
641 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
|
|
642 | were used, or there are no active watchers, return, otherwise |
|
|
643 | continue with step *. |
|
|
644 | |
|
|
645 | Example: Queue some jobs and then loop until no events are outstanding |
|
|
646 | anymore. |
|
|
647 | |
|
|
648 | ... queue jobs here, make sure they register event watchers as long |
|
|
649 | ... as they still have work to do (even an idle watcher will do..) |
|
|
650 | ev_loop (my_loop, 0); |
|
|
651 | ... jobs done or somebody called unloop. yeah! |
236 | |
652 | |
237 | =item ev_unloop (loop, how) |
653 | =item ev_unloop (loop, how) |
238 | |
654 | |
239 | Can be used to make a call to C<ev_loop> return early (but only after it |
655 | 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 |
656 | 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 |
657 | 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. |
658 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
|
|
659 | |
|
|
660 | This "unloop state" will be cleared when entering C<ev_loop> again. |
243 | |
661 | |
244 | =item ev_ref (loop) |
662 | =item ev_ref (loop) |
245 | |
663 | |
246 | =item ev_unref (loop) |
664 | =item ev_unref (loop) |
247 | |
665 | |
… | |
… | |
252 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
670 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
253 | example, libev itself uses this for its internal signal pipe: It is not |
671 | example, libev itself uses this for its internal signal pipe: It is not |
254 | visible to the libev user and should not keep C<ev_loop> from exiting if |
672 | visible to the libev user and should not keep C<ev_loop> from exiting if |
255 | no event watchers registered by it are active. It is also an excellent |
673 | no event watchers registered by it are active. It is also an excellent |
256 | way to do this for generic recurring timers or from within third-party |
674 | way to do this for generic recurring timers or from within third-party |
257 | libraries. Just remember to I<unref after start> and I<ref before stop>. |
675 | libraries. Just remember to I<unref after start> and I<ref before stop> |
|
|
676 | (but only if the watcher wasn't active before, or was active before, |
|
|
677 | respectively). |
|
|
678 | |
|
|
679 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
|
|
680 | running when nothing else is active. |
|
|
681 | |
|
|
682 | struct ev_signal exitsig; |
|
|
683 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
|
|
684 | ev_signal_start (loop, &exitsig); |
|
|
685 | evf_unref (loop); |
|
|
686 | |
|
|
687 | Example: For some weird reason, unregister the above signal handler again. |
|
|
688 | |
|
|
689 | ev_ref (loop); |
|
|
690 | ev_signal_stop (loop, &exitsig); |
|
|
691 | |
|
|
692 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
|
|
693 | |
|
|
694 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
|
|
695 | |
|
|
696 | These advanced functions influence the time that libev will spend waiting |
|
|
697 | for events. Both time intervals are by default C<0>, meaning that libev |
|
|
698 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
699 | latency. |
|
|
700 | |
|
|
701 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
|
|
702 | allows libev to delay invocation of I/O and timer/periodic callbacks |
|
|
703 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
704 | opportunities). |
|
|
705 | |
|
|
706 | The background is that sometimes your program runs just fast enough to |
|
|
707 | handle one (or very few) event(s) per loop iteration. While this makes |
|
|
708 | the program responsive, it also wastes a lot of CPU time to poll for new |
|
|
709 | events, especially with backends like C<select ()> which have a high |
|
|
710 | overhead for the actual polling but can deliver many events at once. |
|
|
711 | |
|
|
712 | By setting a higher I<io collect interval> you allow libev to spend more |
|
|
713 | time collecting I/O events, so you can handle more events per iteration, |
|
|
714 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
|
|
715 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
|
|
716 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
|
|
717 | |
|
|
718 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
|
|
719 | to spend more time collecting timeouts, at the expense of increased |
|
|
720 | latency (the watcher callback will be called later). C<ev_io> watchers |
|
|
721 | will not be affected. Setting this to a non-null value will not introduce |
|
|
722 | any overhead in libev. |
|
|
723 | |
|
|
724 | Many (busy) programs can usually benefit by setting the I/O collect |
|
|
725 | interval to a value near C<0.1> or so, which is often enough for |
|
|
726 | interactive servers (of course not for games), likewise for timeouts. It |
|
|
727 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
|
|
728 | as this approaches the timing granularity of most systems. |
|
|
729 | |
|
|
730 | Setting the I<timeout collect interval> can improve the opportunity for |
|
|
731 | saving power, as the program will "bundle" timer callback invocations that |
|
|
732 | are "near" in time together, by delaying some, thus reducing the number of |
|
|
733 | times the process sleeps and wakes up again. Another useful technique to |
|
|
734 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
|
|
735 | they fire on, say, one-second boundaries only. |
|
|
736 | |
|
|
737 | =item ev_loop_verify (loop) |
|
|
738 | |
|
|
739 | This function only does something when C<EV_VERIFY> support has been |
|
|
740 | compiled in. It tries to go through all internal structures and checks |
|
|
741 | them for validity. If anything is found to be inconsistent, it will print |
|
|
742 | an error message to standard error and call C<abort ()>. |
|
|
743 | |
|
|
744 | This can be used to catch bugs inside libev itself: under normal |
|
|
745 | circumstances, this function will never abort as of course libev keeps its |
|
|
746 | data structures consistent. |
258 | |
747 | |
259 | =back |
748 | =back |
|
|
749 | |
260 | |
750 | |
261 | =head1 ANATOMY OF A WATCHER |
751 | =head1 ANATOMY OF A WATCHER |
262 | |
752 | |
263 | A watcher is a structure that you create and register to record your |
753 | 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 |
754 | 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: |
755 | become readable, you would create an C<ev_io> watcher for that: |
266 | |
756 | |
267 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
757 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
268 | { |
758 | { |
269 | ev_io_stop (w); |
759 | ev_io_stop (w); |
270 | ev_unloop (loop, EVUNLOOP_ALL); |
760 | ev_unloop (loop, EVUNLOOP_ALL); |
271 | } |
761 | } |
272 | |
762 | |
273 | struct ev_loop *loop = ev_default_loop (0); |
763 | struct ev_loop *loop = ev_default_loop (0); |
274 | struct ev_io stdin_watcher; |
764 | struct ev_io stdin_watcher; |
275 | ev_init (&stdin_watcher, my_cb); |
765 | ev_init (&stdin_watcher, my_cb); |
276 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
766 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
277 | ev_io_start (loop, &stdin_watcher); |
767 | ev_io_start (loop, &stdin_watcher); |
278 | ev_loop (loop, 0); |
768 | ev_loop (loop, 0); |
279 | |
769 | |
280 | As you can see, you are responsible for allocating the memory for your |
770 | 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, |
771 | watcher structures (and it is usually a bad idea to do this on the stack, |
282 | although this can sometimes be quite valid). |
772 | although this can sometimes be quite valid). |
283 | |
773 | |
284 | Each watcher structure must be initialised by a call to C<ev_init |
774 | Each watcher structure must be initialised by a call to C<ev_init |
285 | (watcher *, callback)>, which expects a callback to be provided. This |
775 | (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 |
776 | 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 |
777 | watchers, each time the event loop detects that the file descriptor given |
288 | is readable and/or writable). |
778 | is readable and/or writable). |
289 | |
779 | |
290 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
780 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
291 | with arguments specific to this watcher type. There is also a macro |
781 | with arguments specific to this watcher type. There is also a macro |
… | |
… | |
297 | *) >>), and you can stop watching for events at any time by calling the |
787 | *) >>), and you can stop watching for events at any time by calling the |
298 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
788 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
299 | |
789 | |
300 | As long as your watcher is active (has been started but not stopped) you |
790 | 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 |
791 | must not touch the values stored in it. Most specifically you must never |
302 | reinitialise it or call its set method. |
792 | reinitialise it or call its C<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 | |
793 | |
309 | Each and every callback receives the event loop pointer as first, the |
794 | 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 |
795 | registered watcher structure as second, and a bitset of received events as |
311 | third argument. |
796 | third argument. |
312 | |
797 | |
313 | The rceeived events usually include a single bit per event type received |
798 | 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 |
799 | (you can receive multiple events at the same time). The possible bit masks |
315 | are: |
800 | are: |
316 | |
801 | |
317 | =over 4 |
802 | =over 4 |
318 | |
803 | |
… | |
… | |
336 | The signal specified in the C<ev_signal> watcher has been received by a thread. |
821 | The signal specified in the C<ev_signal> watcher has been received by a thread. |
337 | |
822 | |
338 | =item C<EV_CHILD> |
823 | =item C<EV_CHILD> |
339 | |
824 | |
340 | The pid specified in the C<ev_child> watcher has received a status change. |
825 | The pid specified in the C<ev_child> watcher has received a status change. |
|
|
826 | |
|
|
827 | =item C<EV_STAT> |
|
|
828 | |
|
|
829 | The path specified in the C<ev_stat> watcher changed its attributes somehow. |
341 | |
830 | |
342 | =item C<EV_IDLE> |
831 | =item C<EV_IDLE> |
343 | |
832 | |
344 | The C<ev_idle> watcher has determined that you have nothing better to do. |
833 | The C<ev_idle> watcher has determined that you have nothing better to do. |
345 | |
834 | |
… | |
… | |
353 | received events. Callbacks of both watcher types can start and stop as |
842 | 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 |
843 | 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 |
844 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
356 | C<ev_loop> from blocking). |
845 | C<ev_loop> from blocking). |
357 | |
846 | |
|
|
847 | =item C<EV_EMBED> |
|
|
848 | |
|
|
849 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
|
|
850 | |
|
|
851 | =item C<EV_FORK> |
|
|
852 | |
|
|
853 | The event loop has been resumed in the child process after fork (see |
|
|
854 | C<ev_fork>). |
|
|
855 | |
|
|
856 | =item C<EV_ASYNC> |
|
|
857 | |
|
|
858 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
859 | |
358 | =item C<EV_ERROR> |
860 | =item C<EV_ERROR> |
359 | |
861 | |
360 | An unspecified error has occured, the watcher has been stopped. This might |
862 | An unspecified error has occurred, the watcher has been stopped. This might |
361 | happen because the watcher could not be properly started because libev |
863 | 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 |
864 | ran out of memory, a file descriptor was found to be closed or any other |
363 | problem. You best act on it by reporting the problem and somehow coping |
865 | problem. You best act on it by reporting the problem and somehow coping |
364 | with the watcher being stopped. |
866 | with the watcher being stopped. |
365 | |
867 | |
366 | Libev will usually signal a few "dummy" events together with an error, |
868 | Libev will usually signal a few "dummy" events together with an error, |
367 | for example it might indicate that a fd is readable or writable, and if |
869 | for example it might indicate that a fd is readable or writable, and if |
368 | your callbacks is well-written it can just attempt the operation and cope |
870 | your callbacks is well-written it can just attempt the operation and cope |
369 | with the error from read() or write(). This will not work in multithreaded |
871 | with the error from read() or write(). This will not work in multi-threaded |
370 | programs, though, so beware. |
872 | programs, though, so beware. |
371 | |
873 | |
372 | =back |
874 | =back |
373 | |
875 | |
|
|
876 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
877 | |
|
|
878 | In the following description, C<TYPE> stands for the watcher type, |
|
|
879 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
880 | |
|
|
881 | =over 4 |
|
|
882 | |
|
|
883 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
884 | |
|
|
885 | This macro initialises the generic portion of a watcher. The contents |
|
|
886 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
887 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
888 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
889 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
890 | which rolls both calls into one. |
|
|
891 | |
|
|
892 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
893 | (or never started) and there are no pending events outstanding. |
|
|
894 | |
|
|
895 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
|
|
896 | int revents)>. |
|
|
897 | |
|
|
898 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
|
|
899 | |
|
|
900 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
901 | call C<ev_init> at least once before you call this macro, but you can |
|
|
902 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
903 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
904 | difference to the C<ev_init> macro). |
|
|
905 | |
|
|
906 | Although some watcher types do not have type-specific arguments |
|
|
907 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
908 | |
|
|
909 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
910 | |
|
|
911 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
912 | calls into a single call. This is the most convenient method to initialise |
|
|
913 | a watcher. The same limitations apply, of course. |
|
|
914 | |
|
|
915 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
|
|
916 | |
|
|
917 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
918 | events. If the watcher is already active nothing will happen. |
|
|
919 | |
|
|
920 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
|
|
921 | |
|
|
922 | Stops the given watcher again (if active) and clears the pending |
|
|
923 | status. It is possible that stopped watchers are pending (for example, |
|
|
924 | non-repeating timers are being stopped when they become pending), but |
|
|
925 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
|
|
926 | you want to free or reuse the memory used by the watcher it is therefore a |
|
|
927 | good idea to always call its C<ev_TYPE_stop> function. |
|
|
928 | |
|
|
929 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
930 | |
|
|
931 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
932 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
933 | it. |
|
|
934 | |
|
|
935 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
936 | |
|
|
937 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
938 | events but its callback has not yet been invoked). As long as a watcher |
|
|
939 | is pending (but not active) you must not call an init function on it (but |
|
|
940 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
941 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
942 | it). |
|
|
943 | |
|
|
944 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
945 | |
|
|
946 | Returns the callback currently set on the watcher. |
|
|
947 | |
|
|
948 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
949 | |
|
|
950 | Change the callback. You can change the callback at virtually any time |
|
|
951 | (modulo threads). |
|
|
952 | |
|
|
953 | =item ev_set_priority (ev_TYPE *watcher, priority) |
|
|
954 | |
|
|
955 | =item int ev_priority (ev_TYPE *watcher) |
|
|
956 | |
|
|
957 | Set and query the priority of the watcher. The priority is a small |
|
|
958 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
959 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
960 | before watchers with lower priority, but priority will not keep watchers |
|
|
961 | from being executed (except for C<ev_idle> watchers). |
|
|
962 | |
|
|
963 | This means that priorities are I<only> used for ordering callback |
|
|
964 | invocation after new events have been received. This is useful, for |
|
|
965 | example, to reduce latency after idling, or more often, to bind two |
|
|
966 | watchers on the same event and make sure one is called first. |
|
|
967 | |
|
|
968 | If you need to suppress invocation when higher priority events are pending |
|
|
969 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
970 | |
|
|
971 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
972 | pending. |
|
|
973 | |
|
|
974 | The default priority used by watchers when no priority has been set is |
|
|
975 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
976 | |
|
|
977 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
978 | fine, as long as you do not mind that the priority value you query might |
|
|
979 | or might not have been adjusted to be within valid range. |
|
|
980 | |
|
|
981 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
982 | |
|
|
983 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
984 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
985 | can deal with that fact. |
|
|
986 | |
|
|
987 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
988 | |
|
|
989 | If the watcher is pending, this function returns clears its pending status |
|
|
990 | and returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
991 | watcher isn't pending it does nothing and returns C<0>. |
|
|
992 | |
|
|
993 | =back |
|
|
994 | |
|
|
995 | |
374 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
996 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
375 | |
997 | |
376 | Each watcher has, by default, a member C<void *data> that you can change |
998 | 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 |
999 | 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 |
1000 | 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 |
1001 | 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 |
1002 | member, you can also "subclass" the watcher type and provide your own |
381 | data: |
1003 | data: |
382 | |
1004 | |
383 | struct my_io |
1005 | struct my_io |
384 | { |
1006 | { |
385 | struct ev_io io; |
1007 | struct ev_io io; |
386 | int otherfd; |
1008 | int otherfd; |
387 | void *somedata; |
1009 | void *somedata; |
388 | struct whatever *mostinteresting; |
1010 | struct whatever *mostinteresting; |
389 | } |
1011 | }; |
|
|
1012 | |
|
|
1013 | ... |
|
|
1014 | struct my_io w; |
|
|
1015 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
390 | |
1016 | |
391 | And since your callback will be called with a pointer to the watcher, you |
1017 | And since your callback will be called with a pointer to the watcher, you |
392 | can cast it back to your own type: |
1018 | can cast it back to your own type: |
393 | |
1019 | |
394 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1020 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
395 | { |
1021 | { |
396 | struct my_io *w = (struct my_io *)w_; |
1022 | struct my_io *w = (struct my_io *)w_; |
397 | ... |
1023 | ... |
398 | } |
1024 | } |
399 | |
1025 | |
400 | More interesting and less C-conformant ways of catsing your callback type |
1026 | More interesting and less C-conformant ways of casting your callback type |
401 | have been omitted.... |
1027 | instead have been omitted. |
|
|
1028 | |
|
|
1029 | Another common scenario is to use some data structure with multiple |
|
|
1030 | embedded watchers: |
|
|
1031 | |
|
|
1032 | struct my_biggy |
|
|
1033 | { |
|
|
1034 | int some_data; |
|
|
1035 | ev_timer t1; |
|
|
1036 | ev_timer t2; |
|
|
1037 | } |
|
|
1038 | |
|
|
1039 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1040 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1041 | in the C<data> member of the watcher, or you need to use some pointer |
|
|
1042 | arithmetic using C<offsetof> inside your watchers: |
|
|
1043 | |
|
|
1044 | #include <stddef.h> |
|
|
1045 | |
|
|
1046 | static void |
|
|
1047 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
1048 | { |
|
|
1049 | struct my_biggy big = (struct my_biggy * |
|
|
1050 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1051 | } |
|
|
1052 | |
|
|
1053 | static void |
|
|
1054 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
1055 | { |
|
|
1056 | struct my_biggy big = (struct my_biggy * |
|
|
1057 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1058 | } |
402 | |
1059 | |
403 | |
1060 | |
404 | =head1 WATCHER TYPES |
1061 | =head1 WATCHER TYPES |
405 | |
1062 | |
406 | This section describes each watcher in detail, but will not repeat |
1063 | This section describes each watcher in detail, but will not repeat |
407 | information given in the last section. |
1064 | information given in the last section. Any initialisation/set macros, |
|
|
1065 | functions and members specific to the watcher type are explained. |
408 | |
1066 | |
|
|
1067 | Members are additionally marked with either I<[read-only]>, meaning that, |
|
|
1068 | while the watcher is active, you can look at the member and expect some |
|
|
1069 | sensible content, but you must not modify it (you can modify it while the |
|
|
1070 | watcher is stopped to your hearts content), or I<[read-write]>, which |
|
|
1071 | means you can expect it to have some sensible content while the watcher |
|
|
1072 | is active, but you can also modify it. Modifying it may not do something |
|
|
1073 | sensible or take immediate effect (or do anything at all), but libev will |
|
|
1074 | not crash or malfunction in any way. |
|
|
1075 | |
|
|
1076 | |
409 | =head2 C<ev_io> - is this file descriptor readable or writable |
1077 | =head2 C<ev_io> - is this file descriptor readable or writable? |
410 | |
1078 | |
411 | I/O watchers check whether a file descriptor is readable or writable |
1079 | I/O watchers check whether a file descriptor is readable or writable |
412 | in each iteration of the event loop (This behaviour is called |
1080 | in each iteration of the event loop, or, more precisely, when reading |
413 | level-triggering because you keep receiving events as long as the |
1081 | 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 |
1082 | some data. This behaviour is called level-triggering because you keep |
415 | act on the event and neither want to receive future events). |
1083 | receiving events as long as the condition persists. Remember you can stop |
|
|
1084 | the watcher if you don't want to act on the event and neither want to |
|
|
1085 | receive future events. |
416 | |
1086 | |
417 | In general you can register as many read and/or write event watchers oer |
1087 | 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 |
1088 | 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 |
1089 | descriptors to non-blocking mode is also usually a good idea (but not |
420 | required if you know what you are doing). |
1090 | required if you know what you are doing). |
421 | |
1091 | |
422 | You have to be careful with dup'ed file descriptors, though. Some backends |
|
|
423 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
|
|
424 | descriptors correctly if you register interest in two or more fds pointing |
|
|
425 | to the same file/socket etc. description. |
|
|
426 | |
|
|
427 | If you must do this, then force the use of a known-to-be-good backend |
1092 | If you must do this, then force the use of a known-to-be-good backend |
428 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
1093 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
429 | EVMETHOD_POLL). |
1094 | C<EVBACKEND_POLL>). |
|
|
1095 | |
|
|
1096 | Another thing you have to watch out for is that it is quite easy to |
|
|
1097 | receive "spurious" readiness notifications, that is your callback might |
|
|
1098 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
|
|
1099 | because there is no data. Not only are some backends known to create a |
|
|
1100 | lot of those (for example Solaris ports), it is very easy to get into |
|
|
1101 | this situation even with a relatively standard program structure. Thus |
|
|
1102 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1103 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
|
|
1104 | |
|
|
1105 | If you cannot run the fd in non-blocking mode (for example you should not |
|
|
1106 | play around with an Xlib connection), then you have to separately re-test |
|
|
1107 | whether a file descriptor is really ready with a known-to-be good interface |
|
|
1108 | such as poll (fortunately in our Xlib example, Xlib already does this on |
|
|
1109 | its own, so its quite safe to use). |
|
|
1110 | |
|
|
1111 | =head3 The special problem of disappearing file descriptors |
|
|
1112 | |
|
|
1113 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
|
|
1114 | descriptor (either by calling C<close> explicitly or by any other means, |
|
|
1115 | such as C<dup>). The reason is that you register interest in some file |
|
|
1116 | descriptor, but when it goes away, the operating system will silently drop |
|
|
1117 | this interest. If another file descriptor with the same number then is |
|
|
1118 | registered with libev, there is no efficient way to see that this is, in |
|
|
1119 | fact, a different file descriptor. |
|
|
1120 | |
|
|
1121 | To avoid having to explicitly tell libev about such cases, libev follows |
|
|
1122 | the following policy: Each time C<ev_io_set> is being called, libev |
|
|
1123 | will assume that this is potentially a new file descriptor, otherwise |
|
|
1124 | it is assumed that the file descriptor stays the same. That means that |
|
|
1125 | you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the |
|
|
1126 | descriptor even if the file descriptor number itself did not change. |
|
|
1127 | |
|
|
1128 | This is how one would do it normally anyway, the important point is that |
|
|
1129 | the libev application should not optimise around libev but should leave |
|
|
1130 | optimisations to libev. |
|
|
1131 | |
|
|
1132 | =head3 The special problem of dup'ed file descriptors |
|
|
1133 | |
|
|
1134 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
1135 | but only events for the underlying file descriptions. That means when you |
|
|
1136 | have C<dup ()>'ed file descriptors or weirder constellations, and register |
|
|
1137 | events for them, only one file descriptor might actually receive events. |
|
|
1138 | |
|
|
1139 | There is no workaround possible except not registering events |
|
|
1140 | for potentially C<dup ()>'ed file descriptors, or to resort to |
|
|
1141 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
|
|
1142 | |
|
|
1143 | =head3 The special problem of fork |
|
|
1144 | |
|
|
1145 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
|
|
1146 | useless behaviour. Libev fully supports fork, but needs to be told about |
|
|
1147 | it in the child. |
|
|
1148 | |
|
|
1149 | To support fork in your programs, you either have to call |
|
|
1150 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
|
|
1151 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
|
|
1152 | C<EVBACKEND_POLL>. |
|
|
1153 | |
|
|
1154 | =head3 The special problem of SIGPIPE |
|
|
1155 | |
|
|
1156 | While not really specific to libev, it is easy to forget about SIGPIPE: |
|
|
1157 | when writing to a pipe whose other end has been closed, your program gets |
|
|
1158 | send a SIGPIPE, which, by default, aborts your program. For most programs |
|
|
1159 | this is sensible behaviour, for daemons, this is usually undesirable. |
|
|
1160 | |
|
|
1161 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1162 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1163 | somewhere, as that would have given you a big clue). |
|
|
1164 | |
|
|
1165 | |
|
|
1166 | =head3 Watcher-Specific Functions |
430 | |
1167 | |
431 | =over 4 |
1168 | =over 4 |
432 | |
1169 | |
433 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1170 | =item ev_io_init (ev_io *, callback, int fd, int events) |
434 | |
1171 | |
435 | =item ev_io_set (ev_io *, int fd, int events) |
1172 | =item ev_io_set (ev_io *, int fd, int events) |
436 | |
1173 | |
437 | Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive |
1174 | 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 | |
1175 | receive events for and events is either C<EV_READ>, C<EV_WRITE> or |
439 | EV_WRITE> to receive the given events. |
1176 | C<EV_READ | EV_WRITE> to receive the given events. |
|
|
1177 | |
|
|
1178 | =item int fd [read-only] |
|
|
1179 | |
|
|
1180 | The file descriptor being watched. |
|
|
1181 | |
|
|
1182 | =item int events [read-only] |
|
|
1183 | |
|
|
1184 | The events being watched. |
440 | |
1185 | |
441 | =back |
1186 | =back |
442 | |
1187 | |
|
|
1188 | =head3 Examples |
|
|
1189 | |
|
|
1190 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
|
|
1191 | readable, but only once. Since it is likely line-buffered, you could |
|
|
1192 | attempt to read a whole line in the callback. |
|
|
1193 | |
|
|
1194 | static void |
|
|
1195 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
1196 | { |
|
|
1197 | ev_io_stop (loop, w); |
|
|
1198 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
|
|
1199 | } |
|
|
1200 | |
|
|
1201 | ... |
|
|
1202 | struct ev_loop *loop = ev_default_init (0); |
|
|
1203 | struct ev_io stdin_readable; |
|
|
1204 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
|
|
1205 | ev_io_start (loop, &stdin_readable); |
|
|
1206 | ev_loop (loop, 0); |
|
|
1207 | |
|
|
1208 | |
443 | =head2 C<ev_timer> - relative and optionally recurring timeouts |
1209 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
444 | |
1210 | |
445 | Timer watchers are simple relative timers that generate an event after a |
1211 | Timer watchers are simple relative timers that generate an event after a |
446 | given time, and optionally repeating in regular intervals after that. |
1212 | given time, and optionally repeating in regular intervals after that. |
447 | |
1213 | |
448 | The timers are based on real time, that is, if you register an event that |
1214 | 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 |
1215 | 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 |
1216 | year, it will still time out after (roughly) and hour. "Roughly" because |
451 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
1217 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
452 | monotonic clock option helps a lot here). |
1218 | monotonic clock option helps a lot here). |
|
|
1219 | |
|
|
1220 | The callback is guaranteed to be invoked only after its timeout has passed, |
|
|
1221 | but if multiple timers become ready during the same loop iteration then |
|
|
1222 | order of execution is undefined. |
|
|
1223 | |
|
|
1224 | =head3 The special problem of time updates |
|
|
1225 | |
|
|
1226 | Establishing the current time is a costly operation (it usually takes at |
|
|
1227 | least two system calls): EV therefore updates its idea of the current |
|
|
1228 | time only before and after C<ev_loop> polls for new events, which causes |
|
|
1229 | a growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
1230 | lots of events. |
453 | |
1231 | |
454 | The relative timeouts are calculated relative to the C<ev_now ()> |
1232 | 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 |
1233 | 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 |
1234 | 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 |
1235 | 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: |
1236 | timeout on the current time, use something like this to adjust for this: |
459 | |
1237 | |
460 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1238 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
461 | |
1239 | |
|
|
1240 | If the event loop is suspended for a long time, you can also force an |
|
|
1241 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
|
|
1242 | ()>. |
|
|
1243 | |
|
|
1244 | =head3 Watcher-Specific Functions and Data Members |
|
|
1245 | |
462 | =over 4 |
1246 | =over 4 |
463 | |
1247 | |
464 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1248 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
465 | |
1249 | |
466 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1250 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
467 | |
1251 | |
468 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1252 | 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 |
1253 | 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 |
1254 | reached. If it is positive, then the timer will automatically be |
471 | later, again, and again, until stopped manually. |
1255 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1256 | until stopped manually. |
472 | |
1257 | |
473 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1258 | 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 |
1259 | 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 |
1260 | 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 |
1261 | 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. |
1262 | do stuff) the timer will not fire more than once per event loop iteration. |
478 | |
1263 | |
479 | =item ev_timer_again (loop) |
1264 | =item ev_timer_again (loop, ev_timer *) |
480 | |
1265 | |
481 | This will act as if the timer timed out and restart it again if it is |
1266 | This will act as if the timer timed out and restart it again if it is |
482 | repeating. The exact semantics are: |
1267 | repeating. The exact semantics are: |
483 | |
1268 | |
|
|
1269 | If the timer is pending, its pending status is cleared. |
|
|
1270 | |
484 | If the timer is started but nonrepeating, stop it. |
1271 | If the timer is started but non-repeating, stop it (as if it timed out). |
485 | |
1272 | |
486 | If the timer is repeating, either start it if necessary (with the repeat |
1273 | If the timer is repeating, either start it if necessary (with the |
487 | value), or reset the running timer to the repeat value. |
1274 | C<repeat> value), or reset the running timer to the C<repeat> value. |
488 | |
1275 | |
489 | This sounds a bit complicated, but here is a useful and typical |
1276 | This sounds a bit complicated, but here is a useful and typical |
490 | example: Imagine you have a tcp connection and you want a so-called idle |
1277 | example: Imagine you have a TCP connection and you want a so-called idle |
491 | timeout, that is, you want to be called when there have been, say, 60 |
1278 | timeout, that is, you want to be called when there have been, say, 60 |
492 | seconds of inactivity on the socket. The easiest way to do this is to |
1279 | seconds of inactivity on the socket. The easiest way to do this is to |
493 | configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each |
1280 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
494 | time you successfully read or write some data. If you go into an idle |
1281 | C<ev_timer_again> each time you successfully read or write some data. If |
495 | state where you do not expect data to travel on the socket, you can stop |
1282 | you go into an idle state where you do not expect data to travel on the |
496 | the timer, and again will automatically restart it if need be. |
1283 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1284 | automatically restart it if need be. |
|
|
1285 | |
|
|
1286 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1287 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1288 | |
|
|
1289 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1290 | ev_timer_again (loop, timer); |
|
|
1291 | ... |
|
|
1292 | timer->again = 17.; |
|
|
1293 | ev_timer_again (loop, timer); |
|
|
1294 | ... |
|
|
1295 | timer->again = 10.; |
|
|
1296 | ev_timer_again (loop, timer); |
|
|
1297 | |
|
|
1298 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1299 | you want to modify its timeout value. |
|
|
1300 | |
|
|
1301 | =item ev_tstamp repeat [read-write] |
|
|
1302 | |
|
|
1303 | The current C<repeat> value. Will be used each time the watcher times out |
|
|
1304 | or C<ev_timer_again> is called and determines the next timeout (if any), |
|
|
1305 | which is also when any modifications are taken into account. |
497 | |
1306 | |
498 | =back |
1307 | =back |
499 | |
1308 | |
|
|
1309 | =head3 Examples |
|
|
1310 | |
|
|
1311 | Example: Create a timer that fires after 60 seconds. |
|
|
1312 | |
|
|
1313 | static void |
|
|
1314 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
1315 | { |
|
|
1316 | .. one minute over, w is actually stopped right here |
|
|
1317 | } |
|
|
1318 | |
|
|
1319 | struct ev_timer mytimer; |
|
|
1320 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
|
|
1321 | ev_timer_start (loop, &mytimer); |
|
|
1322 | |
|
|
1323 | Example: Create a timeout timer that times out after 10 seconds of |
|
|
1324 | inactivity. |
|
|
1325 | |
|
|
1326 | static void |
|
|
1327 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
1328 | { |
|
|
1329 | .. ten seconds without any activity |
|
|
1330 | } |
|
|
1331 | |
|
|
1332 | struct ev_timer mytimer; |
|
|
1333 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
|
|
1334 | ev_timer_again (&mytimer); /* start timer */ |
|
|
1335 | ev_loop (loop, 0); |
|
|
1336 | |
|
|
1337 | // and in some piece of code that gets executed on any "activity": |
|
|
1338 | // reset the timeout to start ticking again at 10 seconds |
|
|
1339 | ev_timer_again (&mytimer); |
|
|
1340 | |
|
|
1341 | |
500 | =head2 C<ev_periodic> - to cron or not to cron it |
1342 | =head2 C<ev_periodic> - to cron or not to cron? |
501 | |
1343 | |
502 | Periodic watchers are also timers of a kind, but they are very versatile |
1344 | Periodic watchers are also timers of a kind, but they are very versatile |
503 | (and unfortunately a bit complex). |
1345 | (and unfortunately a bit complex). |
504 | |
1346 | |
505 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1347 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
506 | but on wallclock time (absolute time). You can tell a periodic watcher |
1348 | but on wall clock time (absolute time). You can tell a periodic watcher |
507 | to trigger "at" some specific point in time. For example, if you tell a |
1349 | to trigger after some specific point in time. For example, if you tell a |
508 | periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () |
1350 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
509 | + 10.>) and then reset your system clock to the last year, then it will |
1351 | + 10.>, that is, an absolute time not a delay) and then reset your system |
|
|
1352 | clock to January of the previous year, then it will take more than year |
510 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1353 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
511 | roughly 10 seconds later and of course not if you reset your system time |
1354 | roughly 10 seconds later as it uses a relative timeout). |
512 | again). |
|
|
513 | |
1355 | |
514 | They can also be used to implement vastly more complex timers, such as |
1356 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
515 | triggering an event on eahc midnight, local time. |
1357 | such as triggering an event on each "midnight, local time", or other |
|
|
1358 | complicated, rules. |
|
|
1359 | |
|
|
1360 | As with timers, the callback is guaranteed to be invoked only when the |
|
|
1361 | time (C<at>) has passed, but if multiple periodic timers become ready |
|
|
1362 | during the same loop iteration then order of execution is undefined. |
|
|
1363 | |
|
|
1364 | =head3 Watcher-Specific Functions and Data Members |
516 | |
1365 | |
517 | =over 4 |
1366 | =over 4 |
518 | |
1367 | |
519 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1368 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
520 | |
1369 | |
521 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1370 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
522 | |
1371 | |
523 | Lots of arguments, lets sort it out... There are basically three modes of |
1372 | Lots of arguments, lets sort it out... There are basically three modes of |
524 | operation, and we will explain them from simplest to complex: |
1373 | operation, and we will explain them from simplest to complex: |
525 | |
1374 | |
526 | |
|
|
527 | =over 4 |
1375 | =over 4 |
528 | |
1376 | |
529 | =item * absolute timer (interval = reschedule_cb = 0) |
1377 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
530 | |
1378 | |
531 | In this configuration the watcher triggers an event at the wallclock time |
1379 | 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, |
1380 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
533 | that is, if it is to be run at January 1st 2011 then it will run when the |
1381 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
534 | system time reaches or surpasses this time. |
1382 | run when the system time reaches or surpasses this time. |
535 | |
1383 | |
536 | =item * non-repeating interval timer (interval > 0, reschedule_cb = 0) |
1384 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
537 | |
1385 | |
538 | In this mode the watcher will always be scheduled to time out at the next |
1386 | 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 |
1387 | C<at + N * interval> time (for some integer N, which can also be negative) |
540 | of any time jumps. |
1388 | and then repeat, regardless of any time jumps. |
541 | |
1389 | |
542 | This can be used to create timers that do not drift with respect to system |
1390 | This can be used to create timers that do not drift with respect to system |
543 | time: |
1391 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
|
|
1392 | the hour: |
544 | |
1393 | |
545 | ev_periodic_set (&periodic, 0., 3600., 0); |
1394 | ev_periodic_set (&periodic, 0., 3600., 0); |
546 | |
1395 | |
547 | This doesn't mean there will always be 3600 seconds in between triggers, |
1396 | 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 |
1397 | 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 |
1398 | full hour (UTC), or more correctly, when the system time is evenly divisible |
550 | by 3600. |
1399 | by 3600. |
551 | |
1400 | |
552 | Another way to think about it (for the mathematically inclined) is that |
1401 | 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 |
1402 | 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. |
1403 | time where C<time = at (mod interval)>, regardless of any time jumps. |
555 | |
1404 | |
|
|
1405 | For numerical stability it is preferable that the C<at> value is near |
|
|
1406 | C<ev_now ()> (the current time), but there is no range requirement for |
|
|
1407 | this value, and in fact is often specified as zero. |
|
|
1408 | |
|
|
1409 | Note also that there is an upper limit to how often a timer can fire (CPU |
|
|
1410 | speed for example), so if C<interval> is very small then timing stability |
|
|
1411 | will of course deteriorate. Libev itself tries to be exact to be about one |
|
|
1412 | millisecond (if the OS supports it and the machine is fast enough). |
|
|
1413 | |
556 | =item * manual reschedule mode (reschedule_cb = callback) |
1414 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
557 | |
1415 | |
558 | In this mode the values for C<interval> and C<at> are both being |
1416 | In this mode the values for C<interval> and C<at> are both being |
559 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1417 | ignored. Instead, each time the periodic watcher gets scheduled, the |
560 | reschedule callback will be called with the watcher as first, and the |
1418 | reschedule callback will be called with the watcher as first, and the |
561 | current time as second argument. |
1419 | current time as second argument. |
562 | |
1420 | |
563 | NOTE: I<This callback MUST NOT stop or destroy the periodic or any other |
1421 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
564 | periodic watcher, ever, or make any event loop modifications>. If you need |
1422 | ever, or make ANY event loop modifications whatsoever>. |
|
|
1423 | |
565 | to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards. |
1424 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
1425 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
1426 | only event loop modification you are allowed to do). |
566 | |
1427 | |
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, |
1428 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
571 | ev_tstamp now)>, e.g.: |
1429 | *w, ev_tstamp now)>, e.g.: |
572 | |
1430 | |
573 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1431 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
574 | { |
1432 | { |
575 | return now + 60.; |
1433 | return now + 60.; |
576 | } |
1434 | } |
… | |
… | |
578 | It must return the next time to trigger, based on the passed time value |
1436 | 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 |
1437 | (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 |
1438 | will usually be called just before the callback will be triggered, but |
581 | might be called at other times, too. |
1439 | might be called at other times, too. |
582 | |
1440 | |
|
|
1441 | NOTE: I<< This callback must always return a time that is higher than or |
|
|
1442 | equal to the passed C<now> value >>. |
|
|
1443 | |
583 | This can be used to create very complex timers, such as a timer that |
1444 | 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 |
1445 | 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 |
1446 | next midnight after C<now> and return the timestamp value for this. How |
586 | is, again, up to you (but it is not trivial). |
1447 | you do this is, again, up to you (but it is not trivial, which is the main |
|
|
1448 | reason I omitted it as an example). |
587 | |
1449 | |
588 | =back |
1450 | =back |
589 | |
1451 | |
590 | =item ev_periodic_again (loop, ev_periodic *) |
1452 | =item ev_periodic_again (loop, ev_periodic *) |
591 | |
1453 | |
592 | Simply stops and restarts the periodic watcher again. This is only useful |
1454 | Simply stops and restarts the periodic watcher again. This is only useful |
593 | when you changed some parameters or the reschedule callback would return |
1455 | 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 |
1456 | a different time than the last time it was called (e.g. in a crond like |
595 | program when the crontabs have changed). |
1457 | program when the crontabs have changed). |
596 | |
1458 | |
|
|
1459 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
1460 | |
|
|
1461 | When active, returns the absolute time that the watcher is supposed to |
|
|
1462 | trigger next. |
|
|
1463 | |
|
|
1464 | =item ev_tstamp offset [read-write] |
|
|
1465 | |
|
|
1466 | When repeating, this contains the offset value, otherwise this is the |
|
|
1467 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
|
|
1468 | |
|
|
1469 | Can be modified any time, but changes only take effect when the periodic |
|
|
1470 | timer fires or C<ev_periodic_again> is being called. |
|
|
1471 | |
|
|
1472 | =item ev_tstamp interval [read-write] |
|
|
1473 | |
|
|
1474 | The current interval value. Can be modified any time, but changes only |
|
|
1475 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
|
|
1476 | called. |
|
|
1477 | |
|
|
1478 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
|
|
1479 | |
|
|
1480 | The current reschedule callback, or C<0>, if this functionality is |
|
|
1481 | switched off. Can be changed any time, but changes only take effect when |
|
|
1482 | the periodic timer fires or C<ev_periodic_again> is being called. |
|
|
1483 | |
597 | =back |
1484 | =back |
598 | |
1485 | |
|
|
1486 | =head3 Examples |
|
|
1487 | |
|
|
1488 | Example: Call a callback every hour, or, more precisely, whenever the |
|
|
1489 | system clock is divisible by 3600. The callback invocation times have |
|
|
1490 | potentially a lot of jitter, but good long-term stability. |
|
|
1491 | |
|
|
1492 | static void |
|
|
1493 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
1494 | { |
|
|
1495 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
|
|
1496 | } |
|
|
1497 | |
|
|
1498 | struct ev_periodic hourly_tick; |
|
|
1499 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
|
|
1500 | ev_periodic_start (loop, &hourly_tick); |
|
|
1501 | |
|
|
1502 | Example: The same as above, but use a reschedule callback to do it: |
|
|
1503 | |
|
|
1504 | #include <math.h> |
|
|
1505 | |
|
|
1506 | static ev_tstamp |
|
|
1507 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
|
|
1508 | { |
|
|
1509 | return fmod (now, 3600.) + 3600.; |
|
|
1510 | } |
|
|
1511 | |
|
|
1512 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
|
|
1513 | |
|
|
1514 | Example: Call a callback every hour, starting now: |
|
|
1515 | |
|
|
1516 | struct ev_periodic hourly_tick; |
|
|
1517 | ev_periodic_init (&hourly_tick, clock_cb, |
|
|
1518 | fmod (ev_now (loop), 3600.), 3600., 0); |
|
|
1519 | ev_periodic_start (loop, &hourly_tick); |
|
|
1520 | |
|
|
1521 | |
599 | =head2 C<ev_signal> - signal me when a signal gets signalled |
1522 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
600 | |
1523 | |
601 | Signal watchers will trigger an event when the process receives a specific |
1524 | 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 |
1525 | 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 |
1526 | will try it's best to deliver signals synchronously, i.e. as part of the |
604 | normal event processing, like any other event. |
1527 | normal event processing, like any other event. |
605 | |
1528 | |
606 | You cna configure as many watchers as you like per signal. Only when the |
1529 | You can configure as many watchers as you like per signal. Only when the |
607 | first watcher gets started will libev actually register a signal watcher |
1530 | first watcher gets started will libev actually register a signal watcher |
608 | with the kernel (thus it coexists with your own signal handlers as long |
1531 | with the kernel (thus it coexists with your own signal handlers as long |
609 | as you don't register any with libev). Similarly, when the last signal |
1532 | as you don't register any with libev). Similarly, when the last signal |
610 | watcher for a signal is stopped libev will reset the signal handler to |
1533 | watcher for a signal is stopped libev will reset the signal handler to |
611 | SIG_DFL (regardless of what it was set to before). |
1534 | SIG_DFL (regardless of what it was set to before). |
612 | |
1535 | |
|
|
1536 | If possible and supported, libev will install its handlers with |
|
|
1537 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
|
|
1538 | interrupted. If you have a problem with system calls getting interrupted by |
|
|
1539 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1540 | them in an C<ev_prepare> watcher. |
|
|
1541 | |
|
|
1542 | =head3 Watcher-Specific Functions and Data Members |
|
|
1543 | |
613 | =over 4 |
1544 | =over 4 |
614 | |
1545 | |
615 | =item ev_signal_init (ev_signal *, callback, int signum) |
1546 | =item ev_signal_init (ev_signal *, callback, int signum) |
616 | |
1547 | |
617 | =item ev_signal_set (ev_signal *, int signum) |
1548 | =item ev_signal_set (ev_signal *, int signum) |
618 | |
1549 | |
619 | Configures the watcher to trigger on the given signal number (usually one |
1550 | Configures the watcher to trigger on the given signal number (usually one |
620 | of the C<SIGxxx> constants). |
1551 | of the C<SIGxxx> constants). |
621 | |
1552 | |
|
|
1553 | =item int signum [read-only] |
|
|
1554 | |
|
|
1555 | The signal the watcher watches out for. |
|
|
1556 | |
622 | =back |
1557 | =back |
623 | |
1558 | |
|
|
1559 | =head3 Examples |
|
|
1560 | |
|
|
1561 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
|
|
1562 | |
|
|
1563 | static void |
|
|
1564 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
1565 | { |
|
|
1566 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1567 | } |
|
|
1568 | |
|
|
1569 | struct ev_signal signal_watcher; |
|
|
1570 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1571 | ev_signal_start (loop, &sigint_cb); |
|
|
1572 | |
|
|
1573 | |
624 | =head2 C<ev_child> - wait for pid status changes |
1574 | =head2 C<ev_child> - watch out for process status changes |
625 | |
1575 | |
626 | Child watchers trigger when your process receives a SIGCHLD in response to |
1576 | 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). |
1577 | some child status changes (most typically when a child of yours dies). It |
|
|
1578 | is permissible to install a child watcher I<after> the child has been |
|
|
1579 | forked (which implies it might have already exited), as long as the event |
|
|
1580 | loop isn't entered (or is continued from a watcher). |
|
|
1581 | |
|
|
1582 | Only the default event loop is capable of handling signals, and therefore |
|
|
1583 | you can only register child watchers in the default event loop. |
|
|
1584 | |
|
|
1585 | =head3 Process Interaction |
|
|
1586 | |
|
|
1587 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
1588 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
1589 | the first child watcher is started after the child exits. The occurrence |
|
|
1590 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
1591 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
1592 | children, even ones not watched. |
|
|
1593 | |
|
|
1594 | =head3 Overriding the Built-In Processing |
|
|
1595 | |
|
|
1596 | Libev offers no special support for overriding the built-in child |
|
|
1597 | processing, but if your application collides with libev's default child |
|
|
1598 | handler, you can override it easily by installing your own handler for |
|
|
1599 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
1600 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
1601 | event-based approach to child reaping and thus use libev's support for |
|
|
1602 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
1603 | |
|
|
1604 | =head3 Stopping the Child Watcher |
|
|
1605 | |
|
|
1606 | Currently, the child watcher never gets stopped, even when the |
|
|
1607 | child terminates, so normally one needs to stop the watcher in the |
|
|
1608 | callback. Future versions of libev might stop the watcher automatically |
|
|
1609 | when a child exit is detected. |
|
|
1610 | |
|
|
1611 | =head3 Watcher-Specific Functions and Data Members |
628 | |
1612 | |
629 | =over 4 |
1613 | =over 4 |
630 | |
1614 | |
631 | =item ev_child_init (ev_child *, callback, int pid) |
1615 | =item ev_child_init (ev_child *, callback, int pid, int trace) |
632 | |
1616 | |
633 | =item ev_child_set (ev_child *, int pid) |
1617 | =item ev_child_set (ev_child *, int pid, int trace) |
634 | |
1618 | |
635 | Configures the watcher to wait for status changes of process C<pid> (or |
1619 | 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 |
1620 | 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 |
1621 | 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 |
1622 | 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. |
1623 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
|
|
1624 | process causing the status change. C<trace> must be either C<0> (only |
|
|
1625 | activate the watcher when the process terminates) or C<1> (additionally |
|
|
1626 | activate the watcher when the process is stopped or continued). |
|
|
1627 | |
|
|
1628 | =item int pid [read-only] |
|
|
1629 | |
|
|
1630 | The process id this watcher watches out for, or C<0>, meaning any process id. |
|
|
1631 | |
|
|
1632 | =item int rpid [read-write] |
|
|
1633 | |
|
|
1634 | The process id that detected a status change. |
|
|
1635 | |
|
|
1636 | =item int rstatus [read-write] |
|
|
1637 | |
|
|
1638 | The process exit/trace status caused by C<rpid> (see your systems |
|
|
1639 | C<waitpid> and C<sys/wait.h> documentation for details). |
640 | |
1640 | |
641 | =back |
1641 | =back |
642 | |
1642 | |
|
|
1643 | =head3 Examples |
|
|
1644 | |
|
|
1645 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
1646 | its completion. |
|
|
1647 | |
|
|
1648 | ev_child cw; |
|
|
1649 | |
|
|
1650 | static void |
|
|
1651 | child_cb (EV_P_ struct ev_child *w, int revents) |
|
|
1652 | { |
|
|
1653 | ev_child_stop (EV_A_ w); |
|
|
1654 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
|
|
1655 | } |
|
|
1656 | |
|
|
1657 | pid_t pid = fork (); |
|
|
1658 | |
|
|
1659 | if (pid < 0) |
|
|
1660 | // error |
|
|
1661 | else if (pid == 0) |
|
|
1662 | { |
|
|
1663 | // the forked child executes here |
|
|
1664 | exit (1); |
|
|
1665 | } |
|
|
1666 | else |
|
|
1667 | { |
|
|
1668 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
1669 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
1670 | } |
|
|
1671 | |
|
|
1672 | |
|
|
1673 | =head2 C<ev_stat> - did the file attributes just change? |
|
|
1674 | |
|
|
1675 | This watches a file system path for attribute changes. That is, it calls |
|
|
1676 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
|
|
1677 | compared to the last time, invoking the callback if it did. |
|
|
1678 | |
|
|
1679 | The path does not need to exist: changing from "path exists" to "path does |
|
|
1680 | not exist" is a status change like any other. The condition "path does |
|
|
1681 | not exist" is signified by the C<st_nlink> field being zero (which is |
|
|
1682 | otherwise always forced to be at least one) and all the other fields of |
|
|
1683 | the stat buffer having unspecified contents. |
|
|
1684 | |
|
|
1685 | The path I<should> be absolute and I<must not> end in a slash. If it is |
|
|
1686 | relative and your working directory changes, the behaviour is undefined. |
|
|
1687 | |
|
|
1688 | Since there is no standard to do this, the portable implementation simply |
|
|
1689 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
|
|
1690 | can specify a recommended polling interval for this case. If you specify |
|
|
1691 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
|
|
1692 | unspecified default> value will be used (which you can expect to be around |
|
|
1693 | five seconds, although this might change dynamically). Libev will also |
|
|
1694 | impose a minimum interval which is currently around C<0.1>, but thats |
|
|
1695 | usually overkill. |
|
|
1696 | |
|
|
1697 | This watcher type is not meant for massive numbers of stat watchers, |
|
|
1698 | as even with OS-supported change notifications, this can be |
|
|
1699 | resource-intensive. |
|
|
1700 | |
|
|
1701 | At the time of this writing, only the Linux inotify interface is |
|
|
1702 | implemented (implementing kqueue support is left as an exercise for the |
|
|
1703 | reader, note, however, that the author sees no way of implementing ev_stat |
|
|
1704 | semantics with kqueue). Inotify will be used to give hints only and should |
|
|
1705 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1706 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1707 | but changes are usually detected immediately, and if the file exists there |
|
|
1708 | will be no polling. |
|
|
1709 | |
|
|
1710 | =head3 ABI Issues (Largefile Support) |
|
|
1711 | |
|
|
1712 | Libev by default (unless the user overrides this) uses the default |
|
|
1713 | compilation environment, which means that on systems with large file |
|
|
1714 | support disabled by default, you get the 32 bit version of the stat |
|
|
1715 | structure. When using the library from programs that change the ABI to |
|
|
1716 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
1717 | compile libev with the same flags to get binary compatibility. This is |
|
|
1718 | obviously the case with any flags that change the ABI, but the problem is |
|
|
1719 | most noticeably disabled with ev_stat and large file support. |
|
|
1720 | |
|
|
1721 | The solution for this is to lobby your distribution maker to make large |
|
|
1722 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
1723 | optional. Libev cannot simply switch on large file support because it has |
|
|
1724 | to exchange stat structures with application programs compiled using the |
|
|
1725 | default compilation environment. |
|
|
1726 | |
|
|
1727 | =head3 Inotify |
|
|
1728 | |
|
|
1729 | When C<inotify (7)> support has been compiled into libev (generally only |
|
|
1730 | available on Linux) and present at runtime, it will be used to speed up |
|
|
1731 | change detection where possible. The inotify descriptor will be created lazily |
|
|
1732 | when the first C<ev_stat> watcher is being started. |
|
|
1733 | |
|
|
1734 | Inotify presence does not change the semantics of C<ev_stat> watchers |
|
|
1735 | except that changes might be detected earlier, and in some cases, to avoid |
|
|
1736 | making regular C<stat> calls. Even in the presence of inotify support |
|
|
1737 | there are many cases where libev has to resort to regular C<stat> polling. |
|
|
1738 | |
|
|
1739 | (There is no support for kqueue, as apparently it cannot be used to |
|
|
1740 | implement this functionality, due to the requirement of having a file |
|
|
1741 | descriptor open on the object at all times). |
|
|
1742 | |
|
|
1743 | =head3 The special problem of stat time resolution |
|
|
1744 | |
|
|
1745 | The C<stat ()> system call only supports full-second resolution portably, and |
|
|
1746 | even on systems where the resolution is higher, many file systems still |
|
|
1747 | only support whole seconds. |
|
|
1748 | |
|
|
1749 | That means that, if the time is the only thing that changes, you can |
|
|
1750 | easily miss updates: on the first update, C<ev_stat> detects a change and |
|
|
1751 | calls your callback, which does something. When there is another update |
|
|
1752 | within the same second, C<ev_stat> will be unable to detect it as the stat |
|
|
1753 | data does not change. |
|
|
1754 | |
|
|
1755 | The solution to this is to delay acting on a change for slightly more |
|
|
1756 | than a second (or till slightly after the next full second boundary), using |
|
|
1757 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
|
|
1758 | ev_timer_again (loop, w)>). |
|
|
1759 | |
|
|
1760 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
1761 | of some operating systems (where the second counter of the current time |
|
|
1762 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
1763 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
1764 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
1765 | update file times then there will be a small window where the kernel uses |
|
|
1766 | the previous second to update file times but libev might already execute |
|
|
1767 | the timer callback). |
|
|
1768 | |
|
|
1769 | =head3 Watcher-Specific Functions and Data Members |
|
|
1770 | |
|
|
1771 | =over 4 |
|
|
1772 | |
|
|
1773 | =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) |
|
|
1774 | |
|
|
1775 | =item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval) |
|
|
1776 | |
|
|
1777 | Configures the watcher to wait for status changes of the given |
|
|
1778 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
|
|
1779 | be detected and should normally be specified as C<0> to let libev choose |
|
|
1780 | a suitable value. The memory pointed to by C<path> must point to the same |
|
|
1781 | path for as long as the watcher is active. |
|
|
1782 | |
|
|
1783 | The callback will receive C<EV_STAT> when a change was detected, relative |
|
|
1784 | to the attributes at the time the watcher was started (or the last change |
|
|
1785 | was detected). |
|
|
1786 | |
|
|
1787 | =item ev_stat_stat (loop, ev_stat *) |
|
|
1788 | |
|
|
1789 | Updates the stat buffer immediately with new values. If you change the |
|
|
1790 | watched path in your callback, you could call this function to avoid |
|
|
1791 | detecting this change (while introducing a race condition if you are not |
|
|
1792 | the only one changing the path). Can also be useful simply to find out the |
|
|
1793 | new values. |
|
|
1794 | |
|
|
1795 | =item ev_statdata attr [read-only] |
|
|
1796 | |
|
|
1797 | The most-recently detected attributes of the file. Although the type is |
|
|
1798 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
|
|
1799 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
1800 | members to be present. If the C<st_nlink> member is C<0>, then there was |
|
|
1801 | some error while C<stat>ing the file. |
|
|
1802 | |
|
|
1803 | =item ev_statdata prev [read-only] |
|
|
1804 | |
|
|
1805 | The previous attributes of the file. The callback gets invoked whenever |
|
|
1806 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
1807 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
1808 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
|
|
1809 | |
|
|
1810 | =item ev_tstamp interval [read-only] |
|
|
1811 | |
|
|
1812 | The specified interval. |
|
|
1813 | |
|
|
1814 | =item const char *path [read-only] |
|
|
1815 | |
|
|
1816 | The file system path that is being watched. |
|
|
1817 | |
|
|
1818 | =back |
|
|
1819 | |
|
|
1820 | =head3 Examples |
|
|
1821 | |
|
|
1822 | Example: Watch C</etc/passwd> for attribute changes. |
|
|
1823 | |
|
|
1824 | static void |
|
|
1825 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
|
|
1826 | { |
|
|
1827 | /* /etc/passwd changed in some way */ |
|
|
1828 | if (w->attr.st_nlink) |
|
|
1829 | { |
|
|
1830 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
|
|
1831 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
|
|
1832 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
|
|
1833 | } |
|
|
1834 | else |
|
|
1835 | /* you shalt not abuse printf for puts */ |
|
|
1836 | puts ("wow, /etc/passwd is not there, expect problems. " |
|
|
1837 | "if this is windows, they already arrived\n"); |
|
|
1838 | } |
|
|
1839 | |
|
|
1840 | ... |
|
|
1841 | ev_stat passwd; |
|
|
1842 | |
|
|
1843 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
|
|
1844 | ev_stat_start (loop, &passwd); |
|
|
1845 | |
|
|
1846 | Example: Like above, but additionally use a one-second delay so we do not |
|
|
1847 | miss updates (however, frequent updates will delay processing, too, so |
|
|
1848 | one might do the work both on C<ev_stat> callback invocation I<and> on |
|
|
1849 | C<ev_timer> callback invocation). |
|
|
1850 | |
|
|
1851 | static ev_stat passwd; |
|
|
1852 | static ev_timer timer; |
|
|
1853 | |
|
|
1854 | static void |
|
|
1855 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1856 | { |
|
|
1857 | ev_timer_stop (EV_A_ w); |
|
|
1858 | |
|
|
1859 | /* now it's one second after the most recent passwd change */ |
|
|
1860 | } |
|
|
1861 | |
|
|
1862 | static void |
|
|
1863 | stat_cb (EV_P_ ev_stat *w, int revents) |
|
|
1864 | { |
|
|
1865 | /* reset the one-second timer */ |
|
|
1866 | ev_timer_again (EV_A_ &timer); |
|
|
1867 | } |
|
|
1868 | |
|
|
1869 | ... |
|
|
1870 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
|
|
1871 | ev_stat_start (loop, &passwd); |
|
|
1872 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
|
|
1873 | |
|
|
1874 | |
643 | =head2 C<ev_idle> - when you've got nothing better to do |
1875 | =head2 C<ev_idle> - when you've got nothing better to do... |
644 | |
1876 | |
645 | Idle watchers trigger events when there are no other I/O or timer (or |
1877 | 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 |
1878 | priority are pending (prepare, check and other idle watchers do not |
647 | handling sockets or timeouts it will not be called. But when your process |
1879 | count). |
648 | is idle all idle watchers are being called again and again - until |
1880 | |
|
|
1881 | That is, as long as your process is busy handling sockets or timeouts |
|
|
1882 | (or even signals, imagine) of the same or higher priority it will not be |
|
|
1883 | triggered. But when your process is idle (or only lower-priority watchers |
|
|
1884 | are pending), the idle watchers are being called once per event loop |
649 | stopped, that is, or your process receives more events. |
1885 | iteration - until stopped, that is, or your process receives more events |
|
|
1886 | and becomes busy again with higher priority stuff. |
650 | |
1887 | |
651 | The most noteworthy effect is that as long as any idle watchers are |
1888 | 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. |
1889 | active, the process will not block when waiting for new events. |
653 | |
1890 | |
654 | Apart from keeping your process non-blocking (which is a useful |
1891 | 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 |
1892 | effect on its own sometimes), idle watchers are a good place to do |
656 | "pseudo-background processing", or delay processing stuff to after the |
1893 | "pseudo-background processing", or delay processing stuff to after the |
657 | event loop has handled all outstanding events. |
1894 | event loop has handled all outstanding events. |
658 | |
1895 | |
|
|
1896 | =head3 Watcher-Specific Functions and Data Members |
|
|
1897 | |
659 | =over 4 |
1898 | =over 4 |
660 | |
1899 | |
661 | =item ev_idle_init (ev_signal *, callback) |
1900 | =item ev_idle_init (ev_signal *, callback) |
662 | |
1901 | |
663 | Initialises and configures the idle watcher - it has no parameters of any |
1902 | 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, |
1903 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
665 | believe me. |
1904 | believe me. |
666 | |
1905 | |
667 | =back |
1906 | =back |
668 | |
1907 | |
669 | =head2 prepare and check - your hooks into the event loop |
1908 | =head3 Examples |
670 | |
1909 | |
|
|
1910 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
|
|
1911 | callback, free it. Also, use no error checking, as usual. |
|
|
1912 | |
|
|
1913 | static void |
|
|
1914 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
|
|
1915 | { |
|
|
1916 | free (w); |
|
|
1917 | // now do something you wanted to do when the program has |
|
|
1918 | // no longer anything immediate to do. |
|
|
1919 | } |
|
|
1920 | |
|
|
1921 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
|
|
1922 | ev_idle_init (idle_watcher, idle_cb); |
|
|
1923 | ev_idle_start (loop, idle_cb); |
|
|
1924 | |
|
|
1925 | |
|
|
1926 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
|
|
1927 | |
671 | Prepare and check watchers usually (but not always) are used in |
1928 | Prepare and check watchers are usually (but not always) used in tandem: |
672 | tandom. Prepare watchers get invoked before the process blocks and check |
1929 | prepare watchers get invoked before the process blocks and check watchers |
673 | watchers afterwards. |
1930 | afterwards. |
674 | |
1931 | |
|
|
1932 | You I<must not> call C<ev_loop> or similar functions that enter |
|
|
1933 | the current event loop from either C<ev_prepare> or C<ev_check> |
|
|
1934 | watchers. Other loops than the current one are fine, however. The |
|
|
1935 | rationale behind this is that you do not need to check for recursion in |
|
|
1936 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
|
|
1937 | C<ev_check> so if you have one watcher of each kind they will always be |
|
|
1938 | called in pairs bracketing the blocking call. |
|
|
1939 | |
675 | Their main purpose is to integrate other event mechanisms into libev. This |
1940 | 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 |
1941 | their use is somewhat advanced. This could be used, for example, to track |
677 | watchers, integrate net-snmp or a coroutine library and lots more. |
1942 | variable changes, implement your own watchers, integrate net-snmp or a |
|
|
1943 | coroutine library and lots more. They are also occasionally useful if |
|
|
1944 | you cache some data and want to flush it before blocking (for example, |
|
|
1945 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
|
|
1946 | watcher). |
678 | |
1947 | |
679 | This is done by examining in each prepare call which file descriptors need |
1948 | This is done by examining in each prepare call which file descriptors need |
680 | to be watched by the other library, registering C<ev_io> watchers for them |
1949 | to be watched by the other library, registering C<ev_io> watchers for |
681 | and starting an C<ev_timer> watcher for any timeouts (many libraries provide |
1950 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
682 | just this functionality). Then, in the check watcher you check for any |
1951 | provide just this functionality). Then, in the check watcher you check for |
683 | events that occured (by making your callbacks set soem flags for example) |
1952 | any events that occurred (by checking the pending status of all watchers |
684 | and call back into the library. |
1953 | and stopping them) and call back into the library. The I/O and timer |
|
|
1954 | callbacks will never actually be called (but must be valid nevertheless, |
|
|
1955 | because you never know, you know?). |
685 | |
1956 | |
686 | As another example, the perl Coro module uses these hooks to integrate |
1957 | As another example, the Perl Coro module uses these hooks to integrate |
687 | coroutines into libev programs, by yielding to other active coroutines |
1958 | coroutines into libev programs, by yielding to other active coroutines |
688 | during each prepare and only letting the process block if no coroutines |
1959 | during each prepare and only letting the process block if no coroutines |
689 | are ready to run. |
1960 | are ready to run (it's actually more complicated: it only runs coroutines |
|
|
1961 | with priority higher than or equal to the event loop and one coroutine |
|
|
1962 | of lower priority, but only once, using idle watchers to keep the event |
|
|
1963 | loop from blocking if lower-priority coroutines are active, thus mapping |
|
|
1964 | low-priority coroutines to idle/background tasks). |
|
|
1965 | |
|
|
1966 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
|
|
1967 | priority, to ensure that they are being run before any other watchers |
|
|
1968 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
|
|
1969 | too) should not activate ("feed") events into libev. While libev fully |
|
|
1970 | supports this, they might get executed before other C<ev_check> watchers |
|
|
1971 | did their job. As C<ev_check> watchers are often used to embed other |
|
|
1972 | (non-libev) event loops those other event loops might be in an unusable |
|
|
1973 | state until their C<ev_check> watcher ran (always remind yourself to |
|
|
1974 | coexist peacefully with others). |
|
|
1975 | |
|
|
1976 | =head3 Watcher-Specific Functions and Data Members |
690 | |
1977 | |
691 | =over 4 |
1978 | =over 4 |
692 | |
1979 | |
693 | =item ev_prepare_init (ev_prepare *, callback) |
1980 | =item ev_prepare_init (ev_prepare *, callback) |
694 | |
1981 | |
695 | =item ev_check_init (ev_check *, callback) |
1982 | =item ev_check_init (ev_check *, callback) |
696 | |
1983 | |
697 | Initialises and configures the prepare or check watcher - they have no |
1984 | 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> |
1985 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
699 | macros, but using them is utterly, utterly pointless. |
1986 | macros, but using them is utterly, utterly and completely pointless. |
700 | |
1987 | |
701 | =back |
1988 | =back |
702 | |
1989 | |
|
|
1990 | =head3 Examples |
|
|
1991 | |
|
|
1992 | There are a number of principal ways to embed other event loops or modules |
|
|
1993 | into libev. Here are some ideas on how to include libadns into libev |
|
|
1994 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
|
|
1995 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
|
|
1996 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
|
|
1997 | Glib event loop). |
|
|
1998 | |
|
|
1999 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
|
|
2000 | and in a check watcher, destroy them and call into libadns. What follows |
|
|
2001 | is pseudo-code only of course. This requires you to either use a low |
|
|
2002 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
|
|
2003 | the callbacks for the IO/timeout watchers might not have been called yet. |
|
|
2004 | |
|
|
2005 | static ev_io iow [nfd]; |
|
|
2006 | static ev_timer tw; |
|
|
2007 | |
|
|
2008 | static void |
|
|
2009 | io_cb (ev_loop *loop, ev_io *w, int revents) |
|
|
2010 | { |
|
|
2011 | } |
|
|
2012 | |
|
|
2013 | // create io watchers for each fd and a timer before blocking |
|
|
2014 | static void |
|
|
2015 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
|
|
2016 | { |
|
|
2017 | int timeout = 3600000; |
|
|
2018 | struct pollfd fds [nfd]; |
|
|
2019 | // actual code will need to loop here and realloc etc. |
|
|
2020 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
|
|
2021 | |
|
|
2022 | /* the callback is illegal, but won't be called as we stop during check */ |
|
|
2023 | ev_timer_init (&tw, 0, timeout * 1e-3); |
|
|
2024 | ev_timer_start (loop, &tw); |
|
|
2025 | |
|
|
2026 | // create one ev_io per pollfd |
|
|
2027 | for (int i = 0; i < nfd; ++i) |
|
|
2028 | { |
|
|
2029 | ev_io_init (iow + i, io_cb, fds [i].fd, |
|
|
2030 | ((fds [i].events & POLLIN ? EV_READ : 0) |
|
|
2031 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
|
|
2032 | |
|
|
2033 | fds [i].revents = 0; |
|
|
2034 | ev_io_start (loop, iow + i); |
|
|
2035 | } |
|
|
2036 | } |
|
|
2037 | |
|
|
2038 | // stop all watchers after blocking |
|
|
2039 | static void |
|
|
2040 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
|
|
2041 | { |
|
|
2042 | ev_timer_stop (loop, &tw); |
|
|
2043 | |
|
|
2044 | for (int i = 0; i < nfd; ++i) |
|
|
2045 | { |
|
|
2046 | // set the relevant poll flags |
|
|
2047 | // could also call adns_processreadable etc. here |
|
|
2048 | struct pollfd *fd = fds + i; |
|
|
2049 | int revents = ev_clear_pending (iow + i); |
|
|
2050 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
2051 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
2052 | |
|
|
2053 | // now stop the watcher |
|
|
2054 | ev_io_stop (loop, iow + i); |
|
|
2055 | } |
|
|
2056 | |
|
|
2057 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
2058 | } |
|
|
2059 | |
|
|
2060 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
|
|
2061 | in the prepare watcher and would dispose of the check watcher. |
|
|
2062 | |
|
|
2063 | Method 3: If the module to be embedded supports explicit event |
|
|
2064 | notification (libadns does), you can also make use of the actual watcher |
|
|
2065 | callbacks, and only destroy/create the watchers in the prepare watcher. |
|
|
2066 | |
|
|
2067 | static void |
|
|
2068 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2069 | { |
|
|
2070 | adns_state ads = (adns_state)w->data; |
|
|
2071 | update_now (EV_A); |
|
|
2072 | |
|
|
2073 | adns_processtimeouts (ads, &tv_now); |
|
|
2074 | } |
|
|
2075 | |
|
|
2076 | static void |
|
|
2077 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
2078 | { |
|
|
2079 | adns_state ads = (adns_state)w->data; |
|
|
2080 | update_now (EV_A); |
|
|
2081 | |
|
|
2082 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
|
|
2083 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
|
|
2084 | } |
|
|
2085 | |
|
|
2086 | // do not ever call adns_afterpoll |
|
|
2087 | |
|
|
2088 | Method 4: Do not use a prepare or check watcher because the module you |
|
|
2089 | want to embed is too inflexible to support it. Instead, you can override |
|
|
2090 | their poll function. The drawback with this solution is that the main |
|
|
2091 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
|
|
2092 | this. |
|
|
2093 | |
|
|
2094 | static gint |
|
|
2095 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
2096 | { |
|
|
2097 | int got_events = 0; |
|
|
2098 | |
|
|
2099 | for (n = 0; n < nfds; ++n) |
|
|
2100 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
2101 | |
|
|
2102 | if (timeout >= 0) |
|
|
2103 | // create/start timer |
|
|
2104 | |
|
|
2105 | // poll |
|
|
2106 | ev_loop (EV_A_ 0); |
|
|
2107 | |
|
|
2108 | // stop timer again |
|
|
2109 | if (timeout >= 0) |
|
|
2110 | ev_timer_stop (EV_A_ &to); |
|
|
2111 | |
|
|
2112 | // stop io watchers again - their callbacks should have set |
|
|
2113 | for (n = 0; n < nfds; ++n) |
|
|
2114 | ev_io_stop (EV_A_ iow [n]); |
|
|
2115 | |
|
|
2116 | return got_events; |
|
|
2117 | } |
|
|
2118 | |
|
|
2119 | |
|
|
2120 | =head2 C<ev_embed> - when one backend isn't enough... |
|
|
2121 | |
|
|
2122 | This is a rather advanced watcher type that lets you embed one event loop |
|
|
2123 | into another (currently only C<ev_io> events are supported in the embedded |
|
|
2124 | loop, other types of watchers might be handled in a delayed or incorrect |
|
|
2125 | fashion and must not be used). |
|
|
2126 | |
|
|
2127 | There are primarily two reasons you would want that: work around bugs and |
|
|
2128 | prioritise I/O. |
|
|
2129 | |
|
|
2130 | As an example for a bug workaround, the kqueue backend might only support |
|
|
2131 | sockets on some platform, so it is unusable as generic backend, but you |
|
|
2132 | still want to make use of it because you have many sockets and it scales |
|
|
2133 | so nicely. In this case, you would create a kqueue-based loop and embed it |
|
|
2134 | into your default loop (which might use e.g. poll). Overall operation will |
|
|
2135 | be a bit slower because first libev has to poll and then call kevent, but |
|
|
2136 | at least you can use both at what they are best. |
|
|
2137 | |
|
|
2138 | As for prioritising I/O: rarely you have the case where some fds have |
|
|
2139 | to be watched and handled very quickly (with low latency), and even |
|
|
2140 | priorities and idle watchers might have too much overhead. In this case |
|
|
2141 | you would put all the high priority stuff in one loop and all the rest in |
|
|
2142 | a second one, and embed the second one in the first. |
|
|
2143 | |
|
|
2144 | As long as the watcher is active, the callback will be invoked every time |
|
|
2145 | there might be events pending in the embedded loop. The callback must then |
|
|
2146 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
|
|
2147 | their callbacks (you could also start an idle watcher to give the embedded |
|
|
2148 | loop strictly lower priority for example). You can also set the callback |
|
|
2149 | to C<0>, in which case the embed watcher will automatically execute the |
|
|
2150 | embedded loop sweep. |
|
|
2151 | |
|
|
2152 | As long as the watcher is started it will automatically handle events. The |
|
|
2153 | callback will be invoked whenever some events have been handled. You can |
|
|
2154 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2155 | interested in that. |
|
|
2156 | |
|
|
2157 | Also, there have not currently been made special provisions for forking: |
|
|
2158 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
|
|
2159 | but you will also have to stop and restart any C<ev_embed> watchers |
|
|
2160 | yourself. |
|
|
2161 | |
|
|
2162 | Unfortunately, not all backends are embeddable, only the ones returned by |
|
|
2163 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
|
|
2164 | portable one. |
|
|
2165 | |
|
|
2166 | So when you want to use this feature you will always have to be prepared |
|
|
2167 | that you cannot get an embeddable loop. The recommended way to get around |
|
|
2168 | this is to have a separate variables for your embeddable loop, try to |
|
|
2169 | create it, and if that fails, use the normal loop for everything. |
|
|
2170 | |
|
|
2171 | =head3 Watcher-Specific Functions and Data Members |
|
|
2172 | |
|
|
2173 | =over 4 |
|
|
2174 | |
|
|
2175 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
|
|
2176 | |
|
|
2177 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
|
|
2178 | |
|
|
2179 | Configures the watcher to embed the given loop, which must be |
|
|
2180 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
|
|
2181 | invoked automatically, otherwise it is the responsibility of the callback |
|
|
2182 | to invoke it (it will continue to be called until the sweep has been done, |
|
|
2183 | if you do not want that, you need to temporarily stop the embed watcher). |
|
|
2184 | |
|
|
2185 | =item ev_embed_sweep (loop, ev_embed *) |
|
|
2186 | |
|
|
2187 | Make a single, non-blocking sweep over the embedded loop. This works |
|
|
2188 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
|
|
2189 | appropriate way for embedded loops. |
|
|
2190 | |
|
|
2191 | =item struct ev_loop *other [read-only] |
|
|
2192 | |
|
|
2193 | The embedded event loop. |
|
|
2194 | |
|
|
2195 | =back |
|
|
2196 | |
|
|
2197 | =head3 Examples |
|
|
2198 | |
|
|
2199 | Example: Try to get an embeddable event loop and embed it into the default |
|
|
2200 | event loop. If that is not possible, use the default loop. The default |
|
|
2201 | loop is stored in C<loop_hi>, while the embeddable loop is stored in |
|
|
2202 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
|
|
2203 | used). |
|
|
2204 | |
|
|
2205 | struct ev_loop *loop_hi = ev_default_init (0); |
|
|
2206 | struct ev_loop *loop_lo = 0; |
|
|
2207 | struct ev_embed embed; |
|
|
2208 | |
|
|
2209 | // see if there is a chance of getting one that works |
|
|
2210 | // (remember that a flags value of 0 means autodetection) |
|
|
2211 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
2212 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
2213 | : 0; |
|
|
2214 | |
|
|
2215 | // if we got one, then embed it, otherwise default to loop_hi |
|
|
2216 | if (loop_lo) |
|
|
2217 | { |
|
|
2218 | ev_embed_init (&embed, 0, loop_lo); |
|
|
2219 | ev_embed_start (loop_hi, &embed); |
|
|
2220 | } |
|
|
2221 | else |
|
|
2222 | loop_lo = loop_hi; |
|
|
2223 | |
|
|
2224 | Example: Check if kqueue is available but not recommended and create |
|
|
2225 | a kqueue backend for use with sockets (which usually work with any |
|
|
2226 | kqueue implementation). Store the kqueue/socket-only event loop in |
|
|
2227 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
|
|
2228 | |
|
|
2229 | struct ev_loop *loop = ev_default_init (0); |
|
|
2230 | struct ev_loop *loop_socket = 0; |
|
|
2231 | struct ev_embed embed; |
|
|
2232 | |
|
|
2233 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
|
|
2234 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
|
|
2235 | { |
|
|
2236 | ev_embed_init (&embed, 0, loop_socket); |
|
|
2237 | ev_embed_start (loop, &embed); |
|
|
2238 | } |
|
|
2239 | |
|
|
2240 | if (!loop_socket) |
|
|
2241 | loop_socket = loop; |
|
|
2242 | |
|
|
2243 | // now use loop_socket for all sockets, and loop for everything else |
|
|
2244 | |
|
|
2245 | |
|
|
2246 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
|
|
2247 | |
|
|
2248 | Fork watchers are called when a C<fork ()> was detected (usually because |
|
|
2249 | whoever is a good citizen cared to tell libev about it by calling |
|
|
2250 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
|
|
2251 | event loop blocks next and before C<ev_check> watchers are being called, |
|
|
2252 | and only in the child after the fork. If whoever good citizen calling |
|
|
2253 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
|
|
2254 | handlers will be invoked, too, of course. |
|
|
2255 | |
|
|
2256 | =head3 Watcher-Specific Functions and Data Members |
|
|
2257 | |
|
|
2258 | =over 4 |
|
|
2259 | |
|
|
2260 | =item ev_fork_init (ev_signal *, callback) |
|
|
2261 | |
|
|
2262 | Initialises and configures the fork watcher - it has no parameters of any |
|
|
2263 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
|
|
2264 | believe me. |
|
|
2265 | |
|
|
2266 | =back |
|
|
2267 | |
|
|
2268 | |
|
|
2269 | =head2 C<ev_async> - how to wake up another event loop |
|
|
2270 | |
|
|
2271 | In general, you cannot use an C<ev_loop> from multiple threads or other |
|
|
2272 | asynchronous sources such as signal handlers (as opposed to multiple event |
|
|
2273 | loops - those are of course safe to use in different threads). |
|
|
2274 | |
|
|
2275 | Sometimes, however, you need to wake up another event loop you do not |
|
|
2276 | control, for example because it belongs to another thread. This is what |
|
|
2277 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
|
|
2278 | can signal it by calling C<ev_async_send>, which is thread- and signal |
|
|
2279 | safe. |
|
|
2280 | |
|
|
2281 | This functionality is very similar to C<ev_signal> watchers, as signals, |
|
|
2282 | too, are asynchronous in nature, and signals, too, will be compressed |
|
|
2283 | (i.e. the number of callback invocations may be less than the number of |
|
|
2284 | C<ev_async_sent> calls). |
|
|
2285 | |
|
|
2286 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
2287 | just the default loop. |
|
|
2288 | |
|
|
2289 | =head3 Queueing |
|
|
2290 | |
|
|
2291 | C<ev_async> does not support queueing of data in any way. The reason |
|
|
2292 | is that the author does not know of a simple (or any) algorithm for a |
|
|
2293 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
2294 | need elaborate support such as pthreads. |
|
|
2295 | |
|
|
2296 | That means that if you want to queue data, you have to provide your own |
|
|
2297 | queue. But at least I can tell you would implement locking around your |
|
|
2298 | queue: |
|
|
2299 | |
|
|
2300 | =over 4 |
|
|
2301 | |
|
|
2302 | =item queueing from a signal handler context |
|
|
2303 | |
|
|
2304 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
2305 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
|
|
2306 | some fictitious SIGUSR1 handler: |
|
|
2307 | |
|
|
2308 | static ev_async mysig; |
|
|
2309 | |
|
|
2310 | static void |
|
|
2311 | sigusr1_handler (void) |
|
|
2312 | { |
|
|
2313 | sometype data; |
|
|
2314 | |
|
|
2315 | // no locking etc. |
|
|
2316 | queue_put (data); |
|
|
2317 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2318 | } |
|
|
2319 | |
|
|
2320 | static void |
|
|
2321 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2322 | { |
|
|
2323 | sometype data; |
|
|
2324 | sigset_t block, prev; |
|
|
2325 | |
|
|
2326 | sigemptyset (&block); |
|
|
2327 | sigaddset (&block, SIGUSR1); |
|
|
2328 | sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
2329 | |
|
|
2330 | while (queue_get (&data)) |
|
|
2331 | process (data); |
|
|
2332 | |
|
|
2333 | if (sigismember (&prev, SIGUSR1) |
|
|
2334 | sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
2335 | } |
|
|
2336 | |
|
|
2337 | (Note: pthreads in theory requires you to use C<pthread_setmask> |
|
|
2338 | instead of C<sigprocmask> when you use threads, but libev doesn't do it |
|
|
2339 | either...). |
|
|
2340 | |
|
|
2341 | =item queueing from a thread context |
|
|
2342 | |
|
|
2343 | The strategy for threads is different, as you cannot (easily) block |
|
|
2344 | threads but you can easily preempt them, so to queue safely you need to |
|
|
2345 | employ a traditional mutex lock, such as in this pthread example: |
|
|
2346 | |
|
|
2347 | static ev_async mysig; |
|
|
2348 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
2349 | |
|
|
2350 | static void |
|
|
2351 | otherthread (void) |
|
|
2352 | { |
|
|
2353 | // only need to lock the actual queueing operation |
|
|
2354 | pthread_mutex_lock (&mymutex); |
|
|
2355 | queue_put (data); |
|
|
2356 | pthread_mutex_unlock (&mymutex); |
|
|
2357 | |
|
|
2358 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2359 | } |
|
|
2360 | |
|
|
2361 | static void |
|
|
2362 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2363 | { |
|
|
2364 | pthread_mutex_lock (&mymutex); |
|
|
2365 | |
|
|
2366 | while (queue_get (&data)) |
|
|
2367 | process (data); |
|
|
2368 | |
|
|
2369 | pthread_mutex_unlock (&mymutex); |
|
|
2370 | } |
|
|
2371 | |
|
|
2372 | =back |
|
|
2373 | |
|
|
2374 | |
|
|
2375 | =head3 Watcher-Specific Functions and Data Members |
|
|
2376 | |
|
|
2377 | =over 4 |
|
|
2378 | |
|
|
2379 | =item ev_async_init (ev_async *, callback) |
|
|
2380 | |
|
|
2381 | Initialises and configures the async watcher - it has no parameters of any |
|
|
2382 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
|
|
2383 | believe me. |
|
|
2384 | |
|
|
2385 | =item ev_async_send (loop, ev_async *) |
|
|
2386 | |
|
|
2387 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
|
|
2388 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
|
|
2389 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
|
|
2390 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
|
|
2391 | section below on what exactly this means). |
|
|
2392 | |
|
|
2393 | This call incurs the overhead of a system call only once per loop iteration, |
|
|
2394 | so while the overhead might be noticeable, it doesn't apply to repeated |
|
|
2395 | calls to C<ev_async_send>. |
|
|
2396 | |
|
|
2397 | =item bool = ev_async_pending (ev_async *) |
|
|
2398 | |
|
|
2399 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
2400 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2401 | event loop. |
|
|
2402 | |
|
|
2403 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
2404 | the loop iterates next and checks for the watcher to have become active, |
|
|
2405 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
2406 | quickly check whether invoking the loop might be a good idea. |
|
|
2407 | |
|
|
2408 | Not that this does I<not> check whether the watcher itself is pending, only |
|
|
2409 | whether it has been requested to make this watcher pending. |
|
|
2410 | |
|
|
2411 | =back |
|
|
2412 | |
|
|
2413 | |
703 | =head1 OTHER FUNCTIONS |
2414 | =head1 OTHER FUNCTIONS |
704 | |
2415 | |
705 | There are some other fucntions of possible interest. Described. Here. Now. |
2416 | There are some other functions of possible interest. Described. Here. Now. |
706 | |
2417 | |
707 | =over 4 |
2418 | =over 4 |
708 | |
2419 | |
709 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2420 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
710 | |
2421 | |
711 | This function combines a simple timer and an I/O watcher, calls your |
2422 | This function combines a simple timer and an I/O watcher, calls your |
712 | callback on whichever event happens first and automatically stop both |
2423 | callback on whichever event happens first and automatically stop both |
713 | watchers. This is useful if you want to wait for a single event on an fd |
2424 | 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 |
2425 | or timeout without having to allocate/configure/start/stop/free one or |
715 | more watchers yourself. |
2426 | more watchers yourself. |
716 | |
2427 | |
717 | If C<fd> is less than 0, then no I/O watcher will be started and events is |
2428 | If C<fd> is less than 0, then no I/O watcher will be started and events |
718 | ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and C<events> set |
2429 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
719 | will be craeted and started. |
2430 | C<events> set will be created and started. |
720 | |
2431 | |
721 | If C<timeout> is less than 0, then no timeout watcher will be |
2432 | 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 |
2433 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
723 | = 0) will be started. |
2434 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
|
|
2435 | dubious value. |
724 | |
2436 | |
725 | The callback has the type C<void (*cb)(int revents, void *arg)> and |
2437 | 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>, |
2438 | 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>: |
2439 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
|
|
2440 | value passed to C<ev_once>: |
728 | |
2441 | |
729 | static void stdin_ready (int revents, void *arg) |
2442 | static void stdin_ready (int revents, void *arg) |
730 | { |
2443 | { |
731 | if (revents & EV_TIMEOUT) |
2444 | if (revents & EV_TIMEOUT) |
732 | /* doh, nothing entered */ |
2445 | /* doh, nothing entered */; |
733 | else if (revents & EV_READ) |
2446 | else if (revents & EV_READ) |
734 | /* stdin might have data for us, joy! */ |
2447 | /* stdin might have data for us, joy! */; |
735 | } |
2448 | } |
736 | |
2449 | |
737 | ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); |
2450 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
738 | |
2451 | |
739 | =item ev_feed_event (loop, watcher, int events) |
2452 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
740 | |
2453 | |
741 | Feeds the given event set into the event loop, as if the specified event |
2454 | 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 |
2455 | had happened for the specified watcher (which must be a pointer to an |
743 | initialised but not necessarily active event watcher). |
2456 | initialised but not necessarily started event watcher). |
744 | |
2457 | |
745 | =item ev_feed_fd_event (loop, int fd, int revents) |
2458 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
746 | |
2459 | |
747 | Feed an event on the given fd, as if a file descriptor backend detected it. |
2460 | Feed an event on the given fd, as if a file descriptor backend detected |
|
|
2461 | the given events it. |
748 | |
2462 | |
749 | =item ev_feed_signal_event (loop, int signum) |
2463 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
750 | |
2464 | |
751 | Feed an event as if the given signal occured (loop must be the default loop!). |
2465 | Feed an event as if the given signal occurred (C<loop> must be the default |
|
|
2466 | loop!). |
752 | |
2467 | |
753 | =back |
2468 | =back |
754 | |
2469 | |
|
|
2470 | |
|
|
2471 | =head1 LIBEVENT EMULATION |
|
|
2472 | |
|
|
2473 | Libev offers a compatibility emulation layer for libevent. It cannot |
|
|
2474 | emulate the internals of libevent, so here are some usage hints: |
|
|
2475 | |
|
|
2476 | =over 4 |
|
|
2477 | |
|
|
2478 | =item * Use it by including <event.h>, as usual. |
|
|
2479 | |
|
|
2480 | =item * The following members are fully supported: ev_base, ev_callback, |
|
|
2481 | ev_arg, ev_fd, ev_res, ev_events. |
|
|
2482 | |
|
|
2483 | =item * Avoid using ev_flags and the EVLIST_*-macros, while it is |
|
|
2484 | maintained by libev, it does not work exactly the same way as in libevent (consider |
|
|
2485 | it a private API). |
|
|
2486 | |
|
|
2487 | =item * Priorities are not currently supported. Initialising priorities |
|
|
2488 | will fail and all watchers will have the same priority, even though there |
|
|
2489 | is an ev_pri field. |
|
|
2490 | |
|
|
2491 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
2492 | first base created (== the default loop) gets the signals. |
|
|
2493 | |
|
|
2494 | =item * Other members are not supported. |
|
|
2495 | |
|
|
2496 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
|
|
2497 | to use the libev header file and library. |
|
|
2498 | |
|
|
2499 | =back |
|
|
2500 | |
|
|
2501 | =head1 C++ SUPPORT |
|
|
2502 | |
|
|
2503 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
|
|
2504 | you to use some convenience methods to start/stop watchers and also change |
|
|
2505 | the callback model to a model using method callbacks on objects. |
|
|
2506 | |
|
|
2507 | To use it, |
|
|
2508 | |
|
|
2509 | #include <ev++.h> |
|
|
2510 | |
|
|
2511 | This automatically includes F<ev.h> and puts all of its definitions (many |
|
|
2512 | of them macros) into the global namespace. All C++ specific things are |
|
|
2513 | put into the C<ev> namespace. It should support all the same embedding |
|
|
2514 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
|
|
2515 | |
|
|
2516 | Care has been taken to keep the overhead low. The only data member the C++ |
|
|
2517 | classes add (compared to plain C-style watchers) is the event loop pointer |
|
|
2518 | that the watcher is associated with (or no additional members at all if |
|
|
2519 | you disable C<EV_MULTIPLICITY> when embedding libev). |
|
|
2520 | |
|
|
2521 | Currently, functions, and static and non-static member functions can be |
|
|
2522 | used as callbacks. Other types should be easy to add as long as they only |
|
|
2523 | need one additional pointer for context. If you need support for other |
|
|
2524 | types of functors please contact the author (preferably after implementing |
|
|
2525 | it). |
|
|
2526 | |
|
|
2527 | Here is a list of things available in the C<ev> namespace: |
|
|
2528 | |
|
|
2529 | =over 4 |
|
|
2530 | |
|
|
2531 | =item C<ev::READ>, C<ev::WRITE> etc. |
|
|
2532 | |
|
|
2533 | These are just enum values with the same values as the C<EV_READ> etc. |
|
|
2534 | macros from F<ev.h>. |
|
|
2535 | |
|
|
2536 | =item C<ev::tstamp>, C<ev::now> |
|
|
2537 | |
|
|
2538 | Aliases to the same types/functions as with the C<ev_> prefix. |
|
|
2539 | |
|
|
2540 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
|
|
2541 | |
|
|
2542 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
|
|
2543 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
|
|
2544 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
|
|
2545 | defines by many implementations. |
|
|
2546 | |
|
|
2547 | All of those classes have these methods: |
|
|
2548 | |
|
|
2549 | =over 4 |
|
|
2550 | |
|
|
2551 | =item ev::TYPE::TYPE () |
|
|
2552 | |
|
|
2553 | =item ev::TYPE::TYPE (struct ev_loop *) |
|
|
2554 | |
|
|
2555 | =item ev::TYPE::~TYPE |
|
|
2556 | |
|
|
2557 | The constructor (optionally) takes an event loop to associate the watcher |
|
|
2558 | with. If it is omitted, it will use C<EV_DEFAULT>. |
|
|
2559 | |
|
|
2560 | The constructor calls C<ev_init> for you, which means you have to call the |
|
|
2561 | C<set> method before starting it. |
|
|
2562 | |
|
|
2563 | It will not set a callback, however: You have to call the templated C<set> |
|
|
2564 | method to set a callback before you can start the watcher. |
|
|
2565 | |
|
|
2566 | (The reason why you have to use a method is a limitation in C++ which does |
|
|
2567 | not allow explicit template arguments for constructors). |
|
|
2568 | |
|
|
2569 | The destructor automatically stops the watcher if it is active. |
|
|
2570 | |
|
|
2571 | =item w->set<class, &class::method> (object *) |
|
|
2572 | |
|
|
2573 | This method sets the callback method to call. The method has to have a |
|
|
2574 | signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as |
|
|
2575 | first argument and the C<revents> as second. The object must be given as |
|
|
2576 | parameter and is stored in the C<data> member of the watcher. |
|
|
2577 | |
|
|
2578 | This method synthesizes efficient thunking code to call your method from |
|
|
2579 | the C callback that libev requires. If your compiler can inline your |
|
|
2580 | callback (i.e. it is visible to it at the place of the C<set> call and |
|
|
2581 | your compiler is good :), then the method will be fully inlined into the |
|
|
2582 | thunking function, making it as fast as a direct C callback. |
|
|
2583 | |
|
|
2584 | Example: simple class declaration and watcher initialisation |
|
|
2585 | |
|
|
2586 | struct myclass |
|
|
2587 | { |
|
|
2588 | void io_cb (ev::io &w, int revents) { } |
|
|
2589 | } |
|
|
2590 | |
|
|
2591 | myclass obj; |
|
|
2592 | ev::io iow; |
|
|
2593 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
2594 | |
|
|
2595 | =item w->set<function> (void *data = 0) |
|
|
2596 | |
|
|
2597 | Also sets a callback, but uses a static method or plain function as |
|
|
2598 | callback. The optional C<data> argument will be stored in the watcher's |
|
|
2599 | C<data> member and is free for you to use. |
|
|
2600 | |
|
|
2601 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
|
|
2602 | |
|
|
2603 | See the method-C<set> above for more details. |
|
|
2604 | |
|
|
2605 | Example: |
|
|
2606 | |
|
|
2607 | static void io_cb (ev::io &w, int revents) { } |
|
|
2608 | iow.set <io_cb> (); |
|
|
2609 | |
|
|
2610 | =item w->set (struct ev_loop *) |
|
|
2611 | |
|
|
2612 | Associates a different C<struct ev_loop> with this watcher. You can only |
|
|
2613 | do this when the watcher is inactive (and not pending either). |
|
|
2614 | |
|
|
2615 | =item w->set ([arguments]) |
|
|
2616 | |
|
|
2617 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
|
|
2618 | called at least once. Unlike the C counterpart, an active watcher gets |
|
|
2619 | automatically stopped and restarted when reconfiguring it with this |
|
|
2620 | method. |
|
|
2621 | |
|
|
2622 | =item w->start () |
|
|
2623 | |
|
|
2624 | Starts the watcher. Note that there is no C<loop> argument, as the |
|
|
2625 | constructor already stores the event loop. |
|
|
2626 | |
|
|
2627 | =item w->stop () |
|
|
2628 | |
|
|
2629 | Stops the watcher if it is active. Again, no C<loop> argument. |
|
|
2630 | |
|
|
2631 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
|
|
2632 | |
|
|
2633 | For C<ev::timer> and C<ev::periodic>, this invokes the corresponding |
|
|
2634 | C<ev_TYPE_again> function. |
|
|
2635 | |
|
|
2636 | =item w->sweep () (C<ev::embed> only) |
|
|
2637 | |
|
|
2638 | Invokes C<ev_embed_sweep>. |
|
|
2639 | |
|
|
2640 | =item w->update () (C<ev::stat> only) |
|
|
2641 | |
|
|
2642 | Invokes C<ev_stat_stat>. |
|
|
2643 | |
|
|
2644 | =back |
|
|
2645 | |
|
|
2646 | =back |
|
|
2647 | |
|
|
2648 | Example: Define a class with an IO and idle watcher, start one of them in |
|
|
2649 | the constructor. |
|
|
2650 | |
|
|
2651 | class myclass |
|
|
2652 | { |
|
|
2653 | ev::io io; void io_cb (ev::io &w, int revents); |
|
|
2654 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
|
|
2655 | |
|
|
2656 | myclass (int fd) |
|
|
2657 | { |
|
|
2658 | io .set <myclass, &myclass::io_cb > (this); |
|
|
2659 | idle.set <myclass, &myclass::idle_cb> (this); |
|
|
2660 | |
|
|
2661 | io.start (fd, ev::READ); |
|
|
2662 | } |
|
|
2663 | }; |
|
|
2664 | |
|
|
2665 | |
|
|
2666 | =head1 OTHER LANGUAGE BINDINGS |
|
|
2667 | |
|
|
2668 | Libev does not offer other language bindings itself, but bindings for a |
|
|
2669 | number of languages exist in the form of third-party packages. If you know |
|
|
2670 | any interesting language binding in addition to the ones listed here, drop |
|
|
2671 | me a note. |
|
|
2672 | |
|
|
2673 | =over 4 |
|
|
2674 | |
|
|
2675 | =item Perl |
|
|
2676 | |
|
|
2677 | The EV module implements the full libev API and is actually used to test |
|
|
2678 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
2679 | there are additional modules that implement libev-compatible interfaces |
|
|
2680 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
|
|
2681 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
|
|
2682 | |
|
|
2683 | It can be found and installed via CPAN, its homepage is at |
|
|
2684 | L<http://software.schmorp.de/pkg/EV>. |
|
|
2685 | |
|
|
2686 | =item Python |
|
|
2687 | |
|
|
2688 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
|
|
2689 | seems to be quite complete and well-documented. Note, however, that the |
|
|
2690 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2691 | for everybody else, and therefore, should never be applied in an installed |
|
|
2692 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2693 | libev). |
|
|
2694 | |
|
|
2695 | =item Ruby |
|
|
2696 | |
|
|
2697 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
2698 | of the libev API and adds file handle abstractions, asynchronous DNS and |
|
|
2699 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
2700 | L<http://rev.rubyforge.org/>. |
|
|
2701 | |
|
|
2702 | =item D |
|
|
2703 | |
|
|
2704 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
2705 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
2706 | |
|
|
2707 | =back |
|
|
2708 | |
|
|
2709 | |
|
|
2710 | =head1 MACRO MAGIC |
|
|
2711 | |
|
|
2712 | Libev can be compiled with a variety of options, the most fundamental |
|
|
2713 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
|
|
2714 | functions and callbacks have an initial C<struct ev_loop *> argument. |
|
|
2715 | |
|
|
2716 | To make it easier to write programs that cope with either variant, the |
|
|
2717 | following macros are defined: |
|
|
2718 | |
|
|
2719 | =over 4 |
|
|
2720 | |
|
|
2721 | =item C<EV_A>, C<EV_A_> |
|
|
2722 | |
|
|
2723 | This provides the loop I<argument> for functions, if one is required ("ev |
|
|
2724 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
|
|
2725 | C<EV_A_> is used when other arguments are following. Example: |
|
|
2726 | |
|
|
2727 | ev_unref (EV_A); |
|
|
2728 | ev_timer_add (EV_A_ watcher); |
|
|
2729 | ev_loop (EV_A_ 0); |
|
|
2730 | |
|
|
2731 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
|
|
2732 | which is often provided by the following macro. |
|
|
2733 | |
|
|
2734 | =item C<EV_P>, C<EV_P_> |
|
|
2735 | |
|
|
2736 | This provides the loop I<parameter> for functions, if one is required ("ev |
|
|
2737 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
|
|
2738 | C<EV_P_> is used when other parameters are following. Example: |
|
|
2739 | |
|
|
2740 | // this is how ev_unref is being declared |
|
|
2741 | static void ev_unref (EV_P); |
|
|
2742 | |
|
|
2743 | // this is how you can declare your typical callback |
|
|
2744 | static void cb (EV_P_ ev_timer *w, int revents) |
|
|
2745 | |
|
|
2746 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
|
|
2747 | suitable for use with C<EV_A>. |
|
|
2748 | |
|
|
2749 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
|
|
2750 | |
|
|
2751 | Similar to the other two macros, this gives you the value of the default |
|
|
2752 | loop, if multiple loops are supported ("ev loop default"). |
|
|
2753 | |
|
|
2754 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
2755 | |
|
|
2756 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
2757 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
2758 | is undefined when the default loop has not been initialised by a previous |
|
|
2759 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
2760 | |
|
|
2761 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
2762 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
|
|
2763 | |
|
|
2764 | =back |
|
|
2765 | |
|
|
2766 | Example: Declare and initialise a check watcher, utilising the above |
|
|
2767 | macros so it will work regardless of whether multiple loops are supported |
|
|
2768 | or not. |
|
|
2769 | |
|
|
2770 | static void |
|
|
2771 | check_cb (EV_P_ ev_timer *w, int revents) |
|
|
2772 | { |
|
|
2773 | ev_check_stop (EV_A_ w); |
|
|
2774 | } |
|
|
2775 | |
|
|
2776 | ev_check check; |
|
|
2777 | ev_check_init (&check, check_cb); |
|
|
2778 | ev_check_start (EV_DEFAULT_ &check); |
|
|
2779 | ev_loop (EV_DEFAULT_ 0); |
|
|
2780 | |
|
|
2781 | =head1 EMBEDDING |
|
|
2782 | |
|
|
2783 | Libev can (and often is) directly embedded into host |
|
|
2784 | applications. Examples of applications that embed it include the Deliantra |
|
|
2785 | Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
|
|
2786 | and rxvt-unicode. |
|
|
2787 | |
|
|
2788 | The goal is to enable you to just copy the necessary files into your |
|
|
2789 | source directory without having to change even a single line in them, so |
|
|
2790 | you can easily upgrade by simply copying (or having a checked-out copy of |
|
|
2791 | libev somewhere in your source tree). |
|
|
2792 | |
|
|
2793 | =head2 FILESETS |
|
|
2794 | |
|
|
2795 | Depending on what features you need you need to include one or more sets of files |
|
|
2796 | in your application. |
|
|
2797 | |
|
|
2798 | =head3 CORE EVENT LOOP |
|
|
2799 | |
|
|
2800 | To include only the libev core (all the C<ev_*> functions), with manual |
|
|
2801 | configuration (no autoconf): |
|
|
2802 | |
|
|
2803 | #define EV_STANDALONE 1 |
|
|
2804 | #include "ev.c" |
|
|
2805 | |
|
|
2806 | This will automatically include F<ev.h>, too, and should be done in a |
|
|
2807 | single C source file only to provide the function implementations. To use |
|
|
2808 | it, do the same for F<ev.h> in all files wishing to use this API (best |
|
|
2809 | done by writing a wrapper around F<ev.h> that you can include instead and |
|
|
2810 | where you can put other configuration options): |
|
|
2811 | |
|
|
2812 | #define EV_STANDALONE 1 |
|
|
2813 | #include "ev.h" |
|
|
2814 | |
|
|
2815 | Both header files and implementation files can be compiled with a C++ |
|
|
2816 | compiler (at least, thats a stated goal, and breakage will be treated |
|
|
2817 | as a bug). |
|
|
2818 | |
|
|
2819 | You need the following files in your source tree, or in a directory |
|
|
2820 | in your include path (e.g. in libev/ when using -Ilibev): |
|
|
2821 | |
|
|
2822 | ev.h |
|
|
2823 | ev.c |
|
|
2824 | ev_vars.h |
|
|
2825 | ev_wrap.h |
|
|
2826 | |
|
|
2827 | ev_win32.c required on win32 platforms only |
|
|
2828 | |
|
|
2829 | ev_select.c only when select backend is enabled (which is enabled by default) |
|
|
2830 | ev_poll.c only when poll backend is enabled (disabled by default) |
|
|
2831 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
|
|
2832 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
|
|
2833 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
|
|
2834 | |
|
|
2835 | F<ev.c> includes the backend files directly when enabled, so you only need |
|
|
2836 | to compile this single file. |
|
|
2837 | |
|
|
2838 | =head3 LIBEVENT COMPATIBILITY API |
|
|
2839 | |
|
|
2840 | To include the libevent compatibility API, also include: |
|
|
2841 | |
|
|
2842 | #include "event.c" |
|
|
2843 | |
|
|
2844 | in the file including F<ev.c>, and: |
|
|
2845 | |
|
|
2846 | #include "event.h" |
|
|
2847 | |
|
|
2848 | in the files that want to use the libevent API. This also includes F<ev.h>. |
|
|
2849 | |
|
|
2850 | You need the following additional files for this: |
|
|
2851 | |
|
|
2852 | event.h |
|
|
2853 | event.c |
|
|
2854 | |
|
|
2855 | =head3 AUTOCONF SUPPORT |
|
|
2856 | |
|
|
2857 | Instead of using C<EV_STANDALONE=1> and providing your configuration in |
|
|
2858 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
|
|
2859 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
|
|
2860 | include F<config.h> and configure itself accordingly. |
|
|
2861 | |
|
|
2862 | For this of course you need the m4 file: |
|
|
2863 | |
|
|
2864 | libev.m4 |
|
|
2865 | |
|
|
2866 | =head2 PREPROCESSOR SYMBOLS/MACROS |
|
|
2867 | |
|
|
2868 | Libev can be configured via a variety of preprocessor symbols you have to |
|
|
2869 | define before including any of its files. The default in the absence of |
|
|
2870 | autoconf is noted for every option. |
|
|
2871 | |
|
|
2872 | =over 4 |
|
|
2873 | |
|
|
2874 | =item EV_STANDALONE |
|
|
2875 | |
|
|
2876 | Must always be C<1> if you do not use autoconf configuration, which |
|
|
2877 | keeps libev from including F<config.h>, and it also defines dummy |
|
|
2878 | implementations for some libevent functions (such as logging, which is not |
|
|
2879 | supported). It will also not define any of the structs usually found in |
|
|
2880 | F<event.h> that are not directly supported by the libev core alone. |
|
|
2881 | |
|
|
2882 | =item EV_USE_MONOTONIC |
|
|
2883 | |
|
|
2884 | If defined to be C<1>, libev will try to detect the availability of the |
|
|
2885 | monotonic clock option at both compile time and runtime. Otherwise no use |
|
|
2886 | of the monotonic clock option will be attempted. If you enable this, you |
|
|
2887 | usually have to link against librt or something similar. Enabling it when |
|
|
2888 | the functionality isn't available is safe, though, although you have |
|
|
2889 | to make sure you link against any libraries where the C<clock_gettime> |
|
|
2890 | function is hiding in (often F<-lrt>). |
|
|
2891 | |
|
|
2892 | =item EV_USE_REALTIME |
|
|
2893 | |
|
|
2894 | If defined to be C<1>, libev will try to detect the availability of the |
|
|
2895 | real-time clock option at compile time (and assume its availability at |
|
|
2896 | runtime if successful). Otherwise no use of the real-time clock option will |
|
|
2897 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
|
|
2898 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
|
|
2899 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
|
|
2900 | |
|
|
2901 | =item EV_USE_NANOSLEEP |
|
|
2902 | |
|
|
2903 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
|
|
2904 | and will use it for delays. Otherwise it will use C<select ()>. |
|
|
2905 | |
|
|
2906 | =item EV_USE_EVENTFD |
|
|
2907 | |
|
|
2908 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
2909 | available and will probe for kernel support at runtime. This will improve |
|
|
2910 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
2911 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
2912 | 2.7 or newer, otherwise disabled. |
|
|
2913 | |
|
|
2914 | =item EV_USE_SELECT |
|
|
2915 | |
|
|
2916 | If undefined or defined to be C<1>, libev will compile in support for the |
|
|
2917 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
|
|
2918 | other method takes over, select will be it. Otherwise the select backend |
|
|
2919 | will not be compiled in. |
|
|
2920 | |
|
|
2921 | =item EV_SELECT_USE_FD_SET |
|
|
2922 | |
|
|
2923 | If defined to C<1>, then the select backend will use the system C<fd_set> |
|
|
2924 | structure. This is useful if libev doesn't compile due to a missing |
|
|
2925 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
|
|
2926 | exotic systems. This usually limits the range of file descriptors to some |
|
|
2927 | low limit such as 1024 or might have other limitations (winsocket only |
|
|
2928 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
|
|
2929 | influence the size of the C<fd_set> used. |
|
|
2930 | |
|
|
2931 | =item EV_SELECT_IS_WINSOCKET |
|
|
2932 | |
|
|
2933 | When defined to C<1>, the select backend will assume that |
|
|
2934 | select/socket/connect etc. don't understand file descriptors but |
|
|
2935 | wants osf handles on win32 (this is the case when the select to |
|
|
2936 | be used is the winsock select). This means that it will call |
|
|
2937 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
|
|
2938 | it is assumed that all these functions actually work on fds, even |
|
|
2939 | on win32. Should not be defined on non-win32 platforms. |
|
|
2940 | |
|
|
2941 | =item EV_FD_TO_WIN32_HANDLE |
|
|
2942 | |
|
|
2943 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
|
|
2944 | file descriptors to socket handles. When not defining this symbol (the |
|
|
2945 | default), then libev will call C<_get_osfhandle>, which is usually |
|
|
2946 | correct. In some cases, programs use their own file descriptor management, |
|
|
2947 | in which case they can provide this function to map fds to socket handles. |
|
|
2948 | |
|
|
2949 | =item EV_USE_POLL |
|
|
2950 | |
|
|
2951 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
|
|
2952 | backend. Otherwise it will be enabled on non-win32 platforms. It |
|
|
2953 | takes precedence over select. |
|
|
2954 | |
|
|
2955 | =item EV_USE_EPOLL |
|
|
2956 | |
|
|
2957 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
2958 | C<epoll>(7) backend. Its availability will be detected at runtime, |
|
|
2959 | otherwise another method will be used as fallback. This is the preferred |
|
|
2960 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
2961 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
2962 | |
|
|
2963 | =item EV_USE_KQUEUE |
|
|
2964 | |
|
|
2965 | If defined to be C<1>, libev will compile in support for the BSD style |
|
|
2966 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
|
|
2967 | otherwise another method will be used as fallback. This is the preferred |
|
|
2968 | backend for BSD and BSD-like systems, although on most BSDs kqueue only |
|
|
2969 | supports some types of fds correctly (the only platform we found that |
|
|
2970 | supports ptys for example was NetBSD), so kqueue might be compiled in, but |
|
|
2971 | not be used unless explicitly requested. The best way to use it is to find |
|
|
2972 | out whether kqueue supports your type of fd properly and use an embedded |
|
|
2973 | kqueue loop. |
|
|
2974 | |
|
|
2975 | =item EV_USE_PORT |
|
|
2976 | |
|
|
2977 | If defined to be C<1>, libev will compile in support for the Solaris |
|
|
2978 | 10 port style backend. Its availability will be detected at runtime, |
|
|
2979 | otherwise another method will be used as fallback. This is the preferred |
|
|
2980 | backend for Solaris 10 systems. |
|
|
2981 | |
|
|
2982 | =item EV_USE_DEVPOLL |
|
|
2983 | |
|
|
2984 | Reserved for future expansion, works like the USE symbols above. |
|
|
2985 | |
|
|
2986 | =item EV_USE_INOTIFY |
|
|
2987 | |
|
|
2988 | If defined to be C<1>, libev will compile in support for the Linux inotify |
|
|
2989 | interface to speed up C<ev_stat> watchers. Its actual availability will |
|
|
2990 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
2991 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
2992 | |
|
|
2993 | =item EV_ATOMIC_T |
|
|
2994 | |
|
|
2995 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
|
|
2996 | access is atomic with respect to other threads or signal contexts. No such |
|
|
2997 | type is easily found in the C language, so you can provide your own type |
|
|
2998 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
2999 | as well as for signal and thread safety in C<ev_async> watchers. |
|
|
3000 | |
|
|
3001 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
|
|
3002 | (from F<signal.h>), which is usually good enough on most platforms. |
|
|
3003 | |
|
|
3004 | =item EV_H |
|
|
3005 | |
|
|
3006 | The name of the F<ev.h> header file used to include it. The default if |
|
|
3007 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
|
|
3008 | used to virtually rename the F<ev.h> header file in case of conflicts. |
|
|
3009 | |
|
|
3010 | =item EV_CONFIG_H |
|
|
3011 | |
|
|
3012 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
|
|
3013 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
|
|
3014 | C<EV_H>, above. |
|
|
3015 | |
|
|
3016 | =item EV_EVENT_H |
|
|
3017 | |
|
|
3018 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
|
|
3019 | of how the F<event.h> header can be found, the default is C<"event.h">. |
|
|
3020 | |
|
|
3021 | =item EV_PROTOTYPES |
|
|
3022 | |
|
|
3023 | If defined to be C<0>, then F<ev.h> will not define any function |
|
|
3024 | prototypes, but still define all the structs and other symbols. This is |
|
|
3025 | occasionally useful if you want to provide your own wrapper functions |
|
|
3026 | around libev functions. |
|
|
3027 | |
|
|
3028 | =item EV_MULTIPLICITY |
|
|
3029 | |
|
|
3030 | If undefined or defined to C<1>, then all event-loop-specific functions |
|
|
3031 | will have the C<struct ev_loop *> as first argument, and you can create |
|
|
3032 | additional independent event loops. Otherwise there will be no support |
|
|
3033 | for multiple event loops and there is no first event loop pointer |
|
|
3034 | argument. Instead, all functions act on the single default loop. |
|
|
3035 | |
|
|
3036 | =item EV_MINPRI |
|
|
3037 | |
|
|
3038 | =item EV_MAXPRI |
|
|
3039 | |
|
|
3040 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
|
|
3041 | C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can |
|
|
3042 | provide for more priorities by overriding those symbols (usually defined |
|
|
3043 | to be C<-2> and C<2>, respectively). |
|
|
3044 | |
|
|
3045 | When doing priority-based operations, libev usually has to linearly search |
|
|
3046 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
3047 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
|
|
3048 | fine. |
|
|
3049 | |
|
|
3050 | If your embedding application does not need any priorities, defining these both to |
|
|
3051 | C<0> will save some memory and CPU. |
|
|
3052 | |
|
|
3053 | =item EV_PERIODIC_ENABLE |
|
|
3054 | |
|
|
3055 | If undefined or defined to be C<1>, then periodic timers are supported. If |
|
|
3056 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3057 | code. |
|
|
3058 | |
|
|
3059 | =item EV_IDLE_ENABLE |
|
|
3060 | |
|
|
3061 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3062 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3063 | code. |
|
|
3064 | |
|
|
3065 | =item EV_EMBED_ENABLE |
|
|
3066 | |
|
|
3067 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3068 | defined to be C<0>, then they are not. |
|
|
3069 | |
|
|
3070 | =item EV_STAT_ENABLE |
|
|
3071 | |
|
|
3072 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3073 | defined to be C<0>, then they are not. |
|
|
3074 | |
|
|
3075 | =item EV_FORK_ENABLE |
|
|
3076 | |
|
|
3077 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3078 | defined to be C<0>, then they are not. |
|
|
3079 | |
|
|
3080 | =item EV_ASYNC_ENABLE |
|
|
3081 | |
|
|
3082 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3083 | defined to be C<0>, then they are not. |
|
|
3084 | |
|
|
3085 | =item EV_MINIMAL |
|
|
3086 | |
|
|
3087 | If you need to shave off some kilobytes of code at the expense of some |
|
|
3088 | speed, define this symbol to C<1>. Currently this is used to override some |
|
|
3089 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
|
|
3090 | much smaller 2-heap for timer management over the default 4-heap. |
|
|
3091 | |
|
|
3092 | =item EV_PID_HASHSIZE |
|
|
3093 | |
|
|
3094 | C<ev_child> watchers use a small hash table to distribute workload by |
|
|
3095 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
|
|
3096 | than enough. If you need to manage thousands of children you might want to |
|
|
3097 | increase this value (I<must> be a power of two). |
|
|
3098 | |
|
|
3099 | =item EV_INOTIFY_HASHSIZE |
|
|
3100 | |
|
|
3101 | C<ev_stat> watchers use a small hash table to distribute workload by |
|
|
3102 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
|
|
3103 | usually more than enough. If you need to manage thousands of C<ev_stat> |
|
|
3104 | watchers you might want to increase this value (I<must> be a power of |
|
|
3105 | two). |
|
|
3106 | |
|
|
3107 | =item EV_USE_4HEAP |
|
|
3108 | |
|
|
3109 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3110 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
|
|
3111 | to C<1>. The 4-heap uses more complicated (longer) code but has |
|
|
3112 | noticeably faster performance with many (thousands) of watchers. |
|
|
3113 | |
|
|
3114 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3115 | (disabled). |
|
|
3116 | |
|
|
3117 | =item EV_HEAP_CACHE_AT |
|
|
3118 | |
|
|
3119 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3120 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
|
|
3121 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3122 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3123 | but avoids random read accesses on heap changes. This improves performance |
|
|
3124 | noticeably with with many (hundreds) of watchers. |
|
|
3125 | |
|
|
3126 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3127 | (disabled). |
|
|
3128 | |
|
|
3129 | =item EV_VERIFY |
|
|
3130 | |
|
|
3131 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
|
|
3132 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
3133 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
3134 | called. If set to C<2>, then the internal verification code will be |
|
|
3135 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
3136 | verification code will be called very frequently, which will slow down |
|
|
3137 | libev considerably. |
|
|
3138 | |
|
|
3139 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
|
|
3140 | C<0.> |
|
|
3141 | |
|
|
3142 | =item EV_COMMON |
|
|
3143 | |
|
|
3144 | By default, all watchers have a C<void *data> member. By redefining |
|
|
3145 | this macro to a something else you can include more and other types of |
|
|
3146 | members. You have to define it each time you include one of the files, |
|
|
3147 | though, and it must be identical each time. |
|
|
3148 | |
|
|
3149 | For example, the perl EV module uses something like this: |
|
|
3150 | |
|
|
3151 | #define EV_COMMON \ |
|
|
3152 | SV *self; /* contains this struct */ \ |
|
|
3153 | SV *cb_sv, *fh /* note no trailing ";" */ |
|
|
3154 | |
|
|
3155 | =item EV_CB_DECLARE (type) |
|
|
3156 | |
|
|
3157 | =item EV_CB_INVOKE (watcher, revents) |
|
|
3158 | |
|
|
3159 | =item ev_set_cb (ev, cb) |
|
|
3160 | |
|
|
3161 | Can be used to change the callback member declaration in each watcher, |
|
|
3162 | and the way callbacks are invoked and set. Must expand to a struct member |
|
|
3163 | definition and a statement, respectively. See the F<ev.h> header file for |
|
|
3164 | their default definitions. One possible use for overriding these is to |
|
|
3165 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
|
|
3166 | method calls instead of plain function calls in C++. |
|
|
3167 | |
|
|
3168 | =head2 EXPORTED API SYMBOLS |
|
|
3169 | |
|
|
3170 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
|
|
3171 | exported symbols, you can use the provided F<Symbol.*> files which list |
|
|
3172 | all public symbols, one per line: |
|
|
3173 | |
|
|
3174 | Symbols.ev for libev proper |
|
|
3175 | Symbols.event for the libevent emulation |
|
|
3176 | |
|
|
3177 | This can also be used to rename all public symbols to avoid clashes with |
|
|
3178 | multiple versions of libev linked together (which is obviously bad in |
|
|
3179 | itself, but sometimes it is inconvenient to avoid this). |
|
|
3180 | |
|
|
3181 | A sed command like this will create wrapper C<#define>'s that you need to |
|
|
3182 | include before including F<ev.h>: |
|
|
3183 | |
|
|
3184 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
|
|
3185 | |
|
|
3186 | This would create a file F<wrap.h> which essentially looks like this: |
|
|
3187 | |
|
|
3188 | #define ev_backend myprefix_ev_backend |
|
|
3189 | #define ev_check_start myprefix_ev_check_start |
|
|
3190 | #define ev_check_stop myprefix_ev_check_stop |
|
|
3191 | ... |
|
|
3192 | |
|
|
3193 | =head2 EXAMPLES |
|
|
3194 | |
|
|
3195 | For a real-world example of a program the includes libev |
|
|
3196 | verbatim, you can have a look at the EV perl module |
|
|
3197 | (L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
|
|
3198 | the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public |
|
|
3199 | interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file |
|
|
3200 | will be compiled. It is pretty complex because it provides its own header |
|
|
3201 | file. |
|
|
3202 | |
|
|
3203 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
|
|
3204 | that everybody includes and which overrides some configure choices: |
|
|
3205 | |
|
|
3206 | #define EV_MINIMAL 1 |
|
|
3207 | #define EV_USE_POLL 0 |
|
|
3208 | #define EV_MULTIPLICITY 0 |
|
|
3209 | #define EV_PERIODIC_ENABLE 0 |
|
|
3210 | #define EV_STAT_ENABLE 0 |
|
|
3211 | #define EV_FORK_ENABLE 0 |
|
|
3212 | #define EV_CONFIG_H <config.h> |
|
|
3213 | #define EV_MINPRI 0 |
|
|
3214 | #define EV_MAXPRI 0 |
|
|
3215 | |
|
|
3216 | #include "ev++.h" |
|
|
3217 | |
|
|
3218 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
|
|
3219 | |
|
|
3220 | #include "ev_cpp.h" |
|
|
3221 | #include "ev.c" |
|
|
3222 | |
|
|
3223 | |
|
|
3224 | =head1 THREADS AND COROUTINES |
|
|
3225 | |
|
|
3226 | =head2 THREADS |
|
|
3227 | |
|
|
3228 | Libev itself is completely thread-safe, but it uses no locking. This |
|
|
3229 | means that you can use as many loops as you want in parallel, as long as |
|
|
3230 | only one thread ever calls into one libev function with the same loop |
|
|
3231 | parameter. |
|
|
3232 | |
|
|
3233 | Or put differently: calls with different loop parameters can be done in |
|
|
3234 | parallel from multiple threads, calls with the same loop parameter must be |
|
|
3235 | done serially (but can be done from different threads, as long as only one |
|
|
3236 | thread ever is inside a call at any point in time, e.g. by using a mutex |
|
|
3237 | per loop). |
|
|
3238 | |
|
|
3239 | If you want to know which design (one loop, locking, or multiple loops |
|
|
3240 | without or something else still) is best for your problem, then I cannot |
|
|
3241 | help you. I can give some generic advice however: |
|
|
3242 | |
|
|
3243 | =over 4 |
|
|
3244 | |
|
|
3245 | =item * most applications have a main thread: use the default libev loop |
|
|
3246 | in that thread, or create a separate thread running only the default loop. |
|
|
3247 | |
|
|
3248 | This helps integrating other libraries or software modules that use libev |
|
|
3249 | themselves and don't care/know about threading. |
|
|
3250 | |
|
|
3251 | =item * one loop per thread is usually a good model. |
|
|
3252 | |
|
|
3253 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3254 | exists, but it is always a good start. |
|
|
3255 | |
|
|
3256 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
3257 | loop is handed through multiple threads in a kind of round-robin fashion. |
|
|
3258 | |
|
|
3259 | Choosing a model is hard - look around, learn, know that usually you can do |
|
|
3260 | better than you currently do :-) |
|
|
3261 | |
|
|
3262 | =item * often you need to talk to some other thread which blocks in the |
|
|
3263 | event loop - C<ev_async> watchers can be used to wake them up from other |
|
|
3264 | threads safely (or from signal contexts...). |
|
|
3265 | |
|
|
3266 | =back |
|
|
3267 | |
|
|
3268 | =head2 COROUTINES |
|
|
3269 | |
|
|
3270 | Libev is much more accommodating to coroutines ("cooperative threads"): |
|
|
3271 | libev fully supports nesting calls to it's functions from different |
|
|
3272 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
3273 | different coroutines and switch freely between both coroutines running the |
|
|
3274 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3275 | you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
3276 | |
|
|
3277 | Care has been invested into making sure that libev does not keep local |
|
|
3278 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
|
|
3279 | switches. |
|
|
3280 | |
|
|
3281 | |
|
|
3282 | =head1 COMPLEXITIES |
|
|
3283 | |
|
|
3284 | In this section the complexities of (many of) the algorithms used inside |
|
|
3285 | libev will be explained. For complexity discussions about backends see the |
|
|
3286 | documentation for C<ev_default_init>. |
|
|
3287 | |
|
|
3288 | All of the following are about amortised time: If an array needs to be |
|
|
3289 | extended, libev needs to realloc and move the whole array, but this |
|
|
3290 | happens asymptotically never with higher number of elements, so O(1) might |
|
|
3291 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3292 | it is much faster and asymptotically approaches constant time. |
|
|
3293 | |
|
|
3294 | =over 4 |
|
|
3295 | |
|
|
3296 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
|
|
3297 | |
|
|
3298 | This means that, when you have a watcher that triggers in one hour and |
|
|
3299 | there are 100 watchers that would trigger before that then inserting will |
|
|
3300 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3301 | |
|
|
3302 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
|
|
3303 | |
|
|
3304 | That means that changing a timer costs less than removing/adding them |
|
|
3305 | as only the relative motion in the event queue has to be paid for. |
|
|
3306 | |
|
|
3307 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
|
|
3308 | |
|
|
3309 | These just add the watcher into an array or at the head of a list. |
|
|
3310 | |
|
|
3311 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
|
|
3312 | |
|
|
3313 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
|
|
3314 | |
|
|
3315 | These watchers are stored in lists then need to be walked to find the |
|
|
3316 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
3317 | have many watchers waiting for the same fd or signal). |
|
|
3318 | |
|
|
3319 | =item Finding the next timer in each loop iteration: O(1) |
|
|
3320 | |
|
|
3321 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
3322 | fixed position in the storage array. |
|
|
3323 | |
|
|
3324 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3325 | |
|
|
3326 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3327 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3328 | on backend and whether C<ev_io_set> was used). |
|
|
3329 | |
|
|
3330 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3331 | |
|
|
3332 | =item Priority handling: O(number_of_priorities) |
|
|
3333 | |
|
|
3334 | Priorities are implemented by allocating some space for each |
|
|
3335 | priority. When doing priority-based operations, libev usually has to |
|
|
3336 | linearly search all the priorities, but starting/stopping and activating |
|
|
3337 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3338 | |
|
|
3339 | =item Sending an ev_async: O(1) |
|
|
3340 | |
|
|
3341 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3342 | |
|
|
3343 | =item Processing signals: O(max_signal_number) |
|
|
3344 | |
|
|
3345 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3346 | calls in the current loop iteration. Checking for async and signal events |
|
|
3347 | involves iterating over all running async watchers or all signal numbers. |
|
|
3348 | |
|
|
3349 | =back |
|
|
3350 | |
|
|
3351 | |
|
|
3352 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
3353 | |
|
|
3354 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
|
|
3355 | requires, and its I/O model is fundamentally incompatible with the POSIX |
|
|
3356 | model. Libev still offers limited functionality on this platform in |
|
|
3357 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
|
|
3358 | descriptors. This only applies when using Win32 natively, not when using |
|
|
3359 | e.g. cygwin. |
|
|
3360 | |
|
|
3361 | Lifting these limitations would basically require the full |
|
|
3362 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3363 | things, then note that glib does exactly that for you in a very portable |
|
|
3364 | way (note also that glib is the slowest event library known to man). |
|
|
3365 | |
|
|
3366 | There is no supported compilation method available on windows except |
|
|
3367 | embedding it into other applications. |
|
|
3368 | |
|
|
3369 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
3370 | accept large writes: instead of resulting in a partial write, windows will |
|
|
3371 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
|
|
3372 | so make sure you only write small amounts into your sockets (less than a |
|
|
3373 | megabyte seems safe, but thsi apparently depends on the amount of memory |
|
|
3374 | available). |
|
|
3375 | |
|
|
3376 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
3377 | the abysmal performance of winsockets, using a large number of sockets |
|
|
3378 | is not recommended (and not reasonable). If your program needs to use |
|
|
3379 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
3380 | different implementation for windows, as libev offers the POSIX readiness |
|
|
3381 | notification model, which cannot be implemented efficiently on windows |
|
|
3382 | (Microsoft monopoly games). |
|
|
3383 | |
|
|
3384 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
3385 | section for details) and use the following F<evwrap.h> header file instead |
|
|
3386 | of F<ev.h>: |
|
|
3387 | |
|
|
3388 | #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
3389 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
3390 | |
|
|
3391 | #include "ev.h" |
|
|
3392 | |
|
|
3393 | And compile the following F<evwrap.c> file into your project (make sure |
|
|
3394 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
|
|
3395 | |
|
|
3396 | #include "evwrap.h" |
|
|
3397 | #include "ev.c" |
|
|
3398 | |
|
|
3399 | =over 4 |
|
|
3400 | |
|
|
3401 | =item The winsocket select function |
|
|
3402 | |
|
|
3403 | The winsocket C<select> function doesn't follow POSIX in that it |
|
|
3404 | requires socket I<handles> and not socket I<file descriptors> (it is |
|
|
3405 | also extremely buggy). This makes select very inefficient, and also |
|
|
3406 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
3407 | C runtime provides the function C<_open_osfhandle> for this). See the |
|
|
3408 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
|
|
3409 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
|
|
3410 | |
|
|
3411 | The configuration for a "naked" win32 using the Microsoft runtime |
|
|
3412 | libraries and raw winsocket select is: |
|
|
3413 | |
|
|
3414 | #define EV_USE_SELECT 1 |
|
|
3415 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
3416 | |
|
|
3417 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
3418 | complexity in the O(n²) range when using win32. |
|
|
3419 | |
|
|
3420 | =item Limited number of file descriptors |
|
|
3421 | |
|
|
3422 | Windows has numerous arbitrary (and low) limits on things. |
|
|
3423 | |
|
|
3424 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
3425 | of C<64> handles (probably owning to the fact that all windows kernels |
|
|
3426 | can only wait for C<64> things at the same time internally; Microsoft |
|
|
3427 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3428 | previous thread in each. Great). |
|
|
3429 | |
|
|
3430 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
|
|
3431 | to some high number (e.g. C<2048>) before compiling the winsocket select |
|
|
3432 | call (which might be in libev or elsewhere, for example, perl does its own |
|
|
3433 | select emulation on windows). |
|
|
3434 | |
|
|
3435 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
3436 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
|
|
3437 | or something like this inside Microsoft). You can increase this by calling |
|
|
3438 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
|
|
3439 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
|
|
3440 | libraries. |
|
|
3441 | |
|
|
3442 | This might get you to about C<512> or C<2048> sockets (depending on |
|
|
3443 | windows version and/or the phase of the moon). To get more, you need to |
|
|
3444 | wrap all I/O functions and provide your own fd management, but the cost of |
|
|
3445 | calling select (O(n²)) will likely make this unworkable. |
|
|
3446 | |
|
|
3447 | =back |
|
|
3448 | |
|
|
3449 | |
|
|
3450 | =head1 PORTABILITY REQUIREMENTS |
|
|
3451 | |
|
|
3452 | In addition to a working ISO-C implementation, libev relies on a few |
|
|
3453 | additional extensions: |
|
|
3454 | |
|
|
3455 | =over 4 |
|
|
3456 | |
|
|
3457 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
|
|
3458 | calling conventions regardless of C<ev_watcher_type *>. |
|
|
3459 | |
|
|
3460 | Libev assumes not only that all watcher pointers have the same internal |
|
|
3461 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
|
|
3462 | assumes that the same (machine) code can be used to call any watcher |
|
|
3463 | callback: The watcher callbacks have different type signatures, but libev |
|
|
3464 | calls them using an C<ev_watcher *> internally. |
|
|
3465 | |
|
|
3466 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
3467 | |
|
|
3468 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
3469 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
|
|
3470 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
3471 | believed to be sufficiently portable. |
|
|
3472 | |
|
|
3473 | =item C<sigprocmask> must work in a threaded environment |
|
|
3474 | |
|
|
3475 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
3476 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
3477 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
3478 | thread" or will block signals process-wide, both behaviours would |
|
|
3479 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
3480 | C<pthread_sigmask> could complicate things, however. |
|
|
3481 | |
|
|
3482 | The most portable way to handle signals is to block signals in all threads |
|
|
3483 | except the initial one, and run the default loop in the initial thread as |
|
|
3484 | well. |
|
|
3485 | |
|
|
3486 | =item C<long> must be large enough for common memory allocation sizes |
|
|
3487 | |
|
|
3488 | To improve portability and simplify using libev, libev uses C<long> |
|
|
3489 | internally instead of C<size_t> when allocating its data structures. On |
|
|
3490 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3491 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3492 | millions of watchers. |
|
|
3493 | |
|
|
3494 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
3495 | |
|
|
3496 | The type C<double> is used to represent timestamps. It is required to |
|
|
3497 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3498 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3499 | implementations implementing IEEE 754 (basically all existing ones). |
|
|
3500 | |
|
|
3501 | =back |
|
|
3502 | |
|
|
3503 | If you know of other additional requirements drop me a note. |
|
|
3504 | |
|
|
3505 | |
|
|
3506 | =head1 COMPILER WARNINGS |
|
|
3507 | |
|
|
3508 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3509 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3510 | scared by this. |
|
|
3511 | |
|
|
3512 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3513 | has different warnings, and each user has different tastes regarding |
|
|
3514 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3515 | targeting a specific compiler and compiler-version. |
|
|
3516 | |
|
|
3517 | Another reason is that some compiler warnings require elaborate |
|
|
3518 | workarounds, or other changes to the code that make it less clear and less |
|
|
3519 | maintainable. |
|
|
3520 | |
|
|
3521 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3522 | wrong (because they don't actually warn about the condition their message |
|
|
3523 | seems to warn about). |
|
|
3524 | |
|
|
3525 | While libev is written to generate as few warnings as possible, |
|
|
3526 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3527 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3528 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3529 | warnings, not errors, or proof of bugs. |
|
|
3530 | |
|
|
3531 | |
|
|
3532 | =head1 VALGRIND |
|
|
3533 | |
|
|
3534 | Valgrind has a special section here because it is a popular tool that is |
|
|
3535 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3536 | |
|
|
3537 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3538 | in libev, then check twice: If valgrind reports something like: |
|
|
3539 | |
|
|
3540 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3541 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3542 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3543 | |
|
|
3544 | Then there is no memory leak. Similarly, under some circumstances, |
|
|
3545 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3546 | might be confused (it is a very good tool, but only a tool). |
|
|
3547 | |
|
|
3548 | If you are unsure about something, feel free to contact the mailing list |
|
|
3549 | with the full valgrind report and an explanation on why you think this is |
|
|
3550 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
|
|
3551 | no bug" answer and take the chance of learning how to interpret valgrind |
|
|
3552 | properly. |
|
|
3553 | |
|
|
3554 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3555 | I suggest using suppression lists. |
|
|
3556 | |
|
|
3557 | |
755 | =head1 AUTHOR |
3558 | =head1 AUTHOR |
756 | |
3559 | |
757 | Marc Lehmann <libev@schmorp.de>. |
3560 | Marc Lehmann <libev@schmorp.de>. |
758 | |
3561 | |