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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_ 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_ 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 | 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<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)) [NOT REENTRANT] |
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)); [NOT REENTRANT] |
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 C<struct> |
100 | types of such loops, the I<default> loop, which supports signals and child |
282 | is I<not> optional in this case, as there is also an C<ev_loop> |
101 | events, and dynamically created loops which do not. |
283 | I<function>). |
102 | |
284 | |
103 | If you use threads, a common model is to run the default event loop |
285 | The library knows two types of such loops, the I<default> loop, which |
104 | in your main thread (or in a separate thrad) and for each thread you |
286 | supports signals and child events, and dynamically created loops which do |
105 | create, you also create another event loop. Libev itself does no locking |
287 | not. |
106 | whatsoever, so if you mix calls to the same event loop in different |
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107 | threads, make sure you lock (this is usually a bad idea, though, even if |
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108 | done correctly, because it's hideous and inefficient). |
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109 | |
288 | |
110 | =over 4 |
289 | =over 4 |
111 | |
290 | |
112 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
291 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
113 | |
292 | |
114 | This will initialise the default event loop if it hasn't been initialised |
293 | 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 |
294 | 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 |
295 | false. If it already was initialised it simply returns it (and ignores the |
117 | flags). |
296 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
118 | |
297 | |
119 | If you don't know what event loop to use, use the one returned from this |
298 | If you don't know what event loop to use, use the one returned from this |
120 | function. |
299 | function. |
121 | |
300 | |
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301 | Note that this function is I<not> thread-safe, so if you want to use it |
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302 | from multiple threads, you have to lock (note also that this is unlikely, |
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303 | as loops cannot be shared easily between threads anyway). |
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304 | |
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305 | The default loop is the only loop that can handle C<ev_signal> and |
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306 | C<ev_child> watchers, and to do this, it always registers a handler |
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307 | for C<SIGCHLD>. If this is a problem for your application you can either |
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308 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
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309 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
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310 | C<ev_default_init>. |
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311 | |
122 | The flags argument can be used to specify special behaviour or specific |
312 | 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). |
313 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
124 | |
314 | |
125 | It supports the following flags: |
315 | The following flags are supported: |
126 | |
316 | |
127 | =over 4 |
317 | =over 4 |
128 | |
318 | |
129 | =item C<EVFLAG_AUTO> |
319 | =item C<EVFLAG_AUTO> |
130 | |
320 | |
131 | The default flags value. Use this if you have no clue (it's the right |
321 | The default flags value. Use this if you have no clue (it's the right |
132 | thing, believe me). |
322 | thing, believe me). |
133 | |
323 | |
134 | =item C<EVFLAG_NOENV> |
324 | =item C<EVFLAG_NOENV> |
135 | |
325 | |
136 | If this flag bit is ored into the flag value (or the program runs setuid |
326 | 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 |
327 | or setgid) then libev will I<not> look at the environment variable |
138 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
328 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
139 | override the flags completely if it is found in the environment. This is |
329 | 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 |
330 | useful to try out specific backends to test their performance, or to work |
141 | around bugs. |
331 | around bugs. |
142 | |
332 | |
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333 | =item C<EVFLAG_FORKCHECK> |
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334 | |
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335 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
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336 | a fork, you can also make libev check for a fork in each iteration by |
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337 | enabling this flag. |
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338 | |
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339 | This works by calling C<getpid ()> on every iteration of the loop, |
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340 | and thus this might slow down your event loop if you do a lot of loop |
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341 | iterations and little real work, but is usually not noticeable (on my |
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342 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
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343 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
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344 | C<pthread_atfork> which is even faster). |
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345 | |
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346 | The big advantage of this flag is that you can forget about fork (and |
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347 | forget about forgetting to tell libev about forking) when you use this |
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348 | flag. |
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349 | |
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350 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
|
|
351 | environment variable. |
|
|
352 | |
143 | =item C<EVMETHOD_SELECT> (portable select backend) |
353 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
144 | |
354 | |
|
|
355 | This is your standard select(2) backend. Not I<completely> standard, as |
|
|
356 | libev tries to roll its own fd_set with no limits on the number of fds, |
|
|
357 | but if that fails, expect a fairly low limit on the number of fds when |
|
|
358 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
|
|
359 | usually the fastest backend for a low number of (low-numbered :) fds. |
|
|
360 | |
|
|
361 | To get good performance out of this backend you need a high amount of |
|
|
362 | parallelism (most of the file descriptors should be busy). If you are |
|
|
363 | writing a server, you should C<accept ()> in a loop to accept as many |
|
|
364 | connections as possible during one iteration. You might also want to have |
|
|
365 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
|
|
366 | readiness notifications you get per iteration. |
|
|
367 | |
|
|
368 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
|
|
369 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
|
|
370 | C<exceptfds> set on that platform). |
|
|
371 | |
145 | =item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows) |
372 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
146 | |
373 | |
147 | =item C<EVMETHOD_EPOLL> (linux only) |
374 | And this is your standard poll(2) backend. It's more complicated |
|
|
375 | than select, but handles sparse fds better and has no artificial |
|
|
376 | limit on the number of fds you can use (except it will slow down |
|
|
377 | considerably with a lot of inactive fds). It scales similarly to select, |
|
|
378 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
|
|
379 | performance tips. |
148 | |
380 | |
149 | =item C<EVMETHOD_KQUEUE> (some bsds only) |
381 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
|
|
382 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
150 | |
383 | |
151 | =item C<EVMETHOD_DEVPOLL> (solaris 8 only) |
384 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
152 | |
385 | |
153 | =item C<EVMETHOD_PORT> (solaris 10 only) |
386 | For few fds, this backend is a bit little slower than poll and select, |
|
|
387 | but it scales phenomenally better. While poll and select usually scale |
|
|
388 | like O(total_fds) where n is the total number of fds (or the highest fd), |
|
|
389 | epoll scales either O(1) or O(active_fds). |
154 | |
390 | |
155 | If one or more of these are ored into the flags value, then only these |
391 | The epoll mechanism deserves honorable mention as the most misdesigned |
156 | backends will be tried (in the reverse order as given here). If one are |
392 | of the more advanced event mechanisms: mere annoyances include silently |
157 | specified, any backend will do. |
393 | dropping file descriptors, requiring a system call per change per file |
|
|
394 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
395 | so on. The biggest issue is fork races, however - if a program forks then |
|
|
396 | I<both> parent and child process have to recreate the epoll set, which can |
|
|
397 | take considerable time (one syscall per file descriptor) and is of course |
|
|
398 | hard to detect. |
|
|
399 | |
|
|
400 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
|
|
401 | of course I<doesn't>, and epoll just loves to report events for totally |
|
|
402 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
403 | even remove them from the set) than registered in the set (especially |
|
|
404 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
405 | employing an additional generation counter and comparing that against the |
|
|
406 | events to filter out spurious ones, recreating the set when required. |
|
|
407 | |
|
|
408 | While stopping, setting and starting an I/O watcher in the same iteration |
|
|
409 | will result in some caching, there is still a system call per such |
|
|
410 | incident (because the same I<file descriptor> could point to a different |
|
|
411 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
|
|
412 | file descriptors might not work very well if you register events for both |
|
|
413 | file descriptors. |
|
|
414 | |
|
|
415 | Best performance from this backend is achieved by not unregistering all |
|
|
416 | watchers for a file descriptor until it has been closed, if possible, |
|
|
417 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
418 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
419 | extra overhead. A fork can both result in spurious notifications as well |
|
|
420 | as in libev having to destroy and recreate the epoll object, which can |
|
|
421 | take considerable time and thus should be avoided. |
|
|
422 | |
|
|
423 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
424 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
425 | the usage. So sad. |
|
|
426 | |
|
|
427 | While nominally embeddable in other event loops, this feature is broken in |
|
|
428 | all kernel versions tested so far. |
|
|
429 | |
|
|
430 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
431 | C<EVBACKEND_POLL>. |
|
|
432 | |
|
|
433 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
|
|
434 | |
|
|
435 | Kqueue deserves special mention, as at the time of this writing, it |
|
|
436 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
|
|
437 | with anything but sockets and pipes, except on Darwin, where of course |
|
|
438 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
439 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
440 | without API changes to existing programs. For this reason it's not being |
|
|
441 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
|
|
442 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
443 | system like NetBSD. |
|
|
444 | |
|
|
445 | You still can embed kqueue into a normal poll or select backend and use it |
|
|
446 | only for sockets (after having made sure that sockets work with kqueue on |
|
|
447 | the target platform). See C<ev_embed> watchers for more info. |
|
|
448 | |
|
|
449 | It scales in the same way as the epoll backend, but the interface to the |
|
|
450 | kernel is more efficient (which says nothing about its actual speed, of |
|
|
451 | course). While stopping, setting and starting an I/O watcher does never |
|
|
452 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
|
|
453 | two event changes per incident. Support for C<fork ()> is very bad (but |
|
|
454 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
455 | cases |
|
|
456 | |
|
|
457 | This backend usually performs well under most conditions. |
|
|
458 | |
|
|
459 | While nominally embeddable in other event loops, this doesn't work |
|
|
460 | everywhere, so you might need to test for this. And since it is broken |
|
|
461 | almost everywhere, you should only use it when you have a lot of sockets |
|
|
462 | (for which it usually works), by embedding it into another event loop |
|
|
463 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
|
|
464 | using it only for sockets. |
|
|
465 | |
|
|
466 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
467 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
468 | C<NOTE_EOF>. |
|
|
469 | |
|
|
470 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
|
|
471 | |
|
|
472 | This is not implemented yet (and might never be, unless you send me an |
|
|
473 | implementation). According to reports, C</dev/poll> only supports sockets |
|
|
474 | and is not embeddable, which would limit the usefulness of this backend |
|
|
475 | immensely. |
|
|
476 | |
|
|
477 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
|
|
478 | |
|
|
479 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
|
|
480 | it's really slow, but it still scales very well (O(active_fds)). |
|
|
481 | |
|
|
482 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
483 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
484 | blocking when no data (or space) is available. |
|
|
485 | |
|
|
486 | While this backend scales well, it requires one system call per active |
|
|
487 | file descriptor per loop iteration. For small and medium numbers of file |
|
|
488 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
|
|
489 | might perform better. |
|
|
490 | |
|
|
491 | On the positive side, with the exception of the spurious readiness |
|
|
492 | notifications, this backend actually performed fully to specification |
|
|
493 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
494 | OS-specific backends (I vastly prefer correctness over speed hacks). |
|
|
495 | |
|
|
496 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
497 | C<EVBACKEND_POLL>. |
|
|
498 | |
|
|
499 | =item C<EVBACKEND_ALL> |
|
|
500 | |
|
|
501 | Try all backends (even potentially broken ones that wouldn't be tried |
|
|
502 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
|
|
503 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
|
|
504 | |
|
|
505 | It is definitely not recommended to use this flag. |
158 | |
506 | |
159 | =back |
507 | =back |
|
|
508 | |
|
|
509 | If one or more of these are or'ed into the flags value, then only these |
|
|
510 | backends will be tried (in the reverse order as listed here). If none are |
|
|
511 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
|
|
512 | |
|
|
513 | Example: This is the most typical usage. |
|
|
514 | |
|
|
515 | if (!ev_default_loop (0)) |
|
|
516 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
517 | |
|
|
518 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
519 | environment settings to be taken into account: |
|
|
520 | |
|
|
521 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
522 | |
|
|
523 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
524 | used if available (warning, breaks stuff, best use only with your own |
|
|
525 | private event loop and only if you know the OS supports your types of |
|
|
526 | fds): |
|
|
527 | |
|
|
528 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
160 | |
529 | |
161 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
530 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
162 | |
531 | |
163 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
532 | 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 |
533 | 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 |
534 | 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). |
535 | undefined behaviour (or a failed assertion if assertions are enabled). |
167 | |
536 | |
|
|
537 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
538 | libev with threads is indeed to create one loop per thread, and using the |
|
|
539 | default loop in the "main" or "initial" thread. |
|
|
540 | |
|
|
541 | Example: Try to create a event loop that uses epoll and nothing else. |
|
|
542 | |
|
|
543 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
|
|
544 | if (!epoller) |
|
|
545 | fatal ("no epoll found here, maybe it hides under your chair"); |
|
|
546 | |
168 | =item ev_default_destroy () |
547 | =item ev_default_destroy () |
169 | |
548 | |
170 | Destroys the default loop again (frees all memory and kernel state |
549 | Destroys the default loop again (frees all memory and kernel state |
171 | etc.). This stops all registered event watchers (by not touching them in |
550 | etc.). None of the active event watchers will be stopped in the normal |
172 | any way whatsoever, although you cannot rely on this :). |
551 | sense, so e.g. C<ev_is_active> might still return true. It is your |
|
|
552 | responsibility to either stop all watchers cleanly yourself I<before> |
|
|
553 | calling this function, or cope with the fact afterwards (which is usually |
|
|
554 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
|
|
555 | for example). |
|
|
556 | |
|
|
557 | Note that certain global state, such as signal state (and installed signal |
|
|
558 | handlers), will not be freed by this function, and related watchers (such |
|
|
559 | as signal and child watchers) would need to be stopped manually. |
|
|
560 | |
|
|
561 | In general it is not advisable to call this function except in the |
|
|
562 | rare occasion where you really need to free e.g. the signal handling |
|
|
563 | pipe fds. If you need dynamically allocated loops it is better to use |
|
|
564 | C<ev_loop_new> and C<ev_loop_destroy>). |
173 | |
565 | |
174 | =item ev_loop_destroy (loop) |
566 | =item ev_loop_destroy (loop) |
175 | |
567 | |
176 | Like C<ev_default_destroy>, but destroys an event loop created by an |
568 | Like C<ev_default_destroy>, but destroys an event loop created by an |
177 | earlier call to C<ev_loop_new>. |
569 | earlier call to C<ev_loop_new>. |
178 | |
570 | |
179 | =item ev_default_fork () |
571 | =item ev_default_fork () |
180 | |
572 | |
|
|
573 | This function sets a flag that causes subsequent C<ev_loop> iterations |
181 | This function reinitialises the kernel state for backends that have |
574 | 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 |
575 | 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 |
576 | the child process (or both child and parent, but that again makes little |
184 | again makes little sense). |
577 | sense). You I<must> call it in the child before using any of the libev |
|
|
578 | functions, and it will only take effect at the next C<ev_loop> iteration. |
185 | |
579 | |
186 | You I<must> call this function after forking if and only if you want to |
580 | 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 |
581 | process if and only if you want to use the event library in the child. If |
188 | have to call it. |
582 | you just fork+exec, you don't have to call it at all. |
189 | |
583 | |
190 | The function itself is quite fast and it's usually not a problem to call |
584 | 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 |
585 | 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>: |
586 | quite nicely into a call to C<pthread_atfork>: |
193 | |
587 | |
… | |
… | |
195 | |
589 | |
196 | =item ev_loop_fork (loop) |
590 | =item ev_loop_fork (loop) |
197 | |
591 | |
198 | Like C<ev_default_fork>, but acts on an event loop created by |
592 | 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 |
593 | 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. |
594 | after fork that you want to re-use in the child, and how you do this is |
|
|
595 | entirely your own problem. |
201 | |
596 | |
|
|
597 | =item int ev_is_default_loop (loop) |
|
|
598 | |
|
|
599 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
600 | otherwise. |
|
|
601 | |
|
|
602 | =item unsigned int ev_loop_count (loop) |
|
|
603 | |
|
|
604 | Returns the count of loop iterations for the loop, which is identical to |
|
|
605 | the number of times libev did poll for new events. It starts at C<0> and |
|
|
606 | happily wraps around with enough iterations. |
|
|
607 | |
|
|
608 | This value can sometimes be useful as a generation counter of sorts (it |
|
|
609 | "ticks" the number of loop iterations), as it roughly corresponds with |
|
|
610 | C<ev_prepare> and C<ev_check> calls. |
|
|
611 | |
202 | =item unsigned int ev_method (loop) |
612 | =item unsigned int ev_backend (loop) |
203 | |
613 | |
204 | Returns one of the C<EVMETHOD_*> flags indicating the event backend in |
614 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
205 | use. |
615 | use. |
206 | |
616 | |
207 | =item ev_tstamp ev_now (loop) |
617 | =item ev_tstamp ev_now (loop) |
208 | |
618 | |
209 | Returns the current "event loop time", which is the time the event loop |
619 | 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 |
620 | 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 |
621 | 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 |
622 | 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). |
623 | event occurring (or more correctly, libev finding out about it). |
|
|
624 | |
|
|
625 | =item ev_now_update (loop) |
|
|
626 | |
|
|
627 | Establishes the current time by querying the kernel, updating the time |
|
|
628 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
629 | is usually done automatically within C<ev_loop ()>. |
|
|
630 | |
|
|
631 | This function is rarely useful, but when some event callback runs for a |
|
|
632 | very long time without entering the event loop, updating libev's idea of |
|
|
633 | the current time is a good idea. |
|
|
634 | |
|
|
635 | See also "The special problem of time updates" in the C<ev_timer> section. |
214 | |
636 | |
215 | =item ev_loop (loop, int flags) |
637 | =item ev_loop (loop, int flags) |
216 | |
638 | |
217 | Finally, this is it, the event handler. This function usually is called |
639 | 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 |
640 | after you initialised all your watchers and you want to start handling |
219 | events. |
641 | events. |
220 | |
642 | |
221 | If the flags argument is specified as 0, it will not return until either |
643 | 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. |
644 | either no event watchers are active anymore or C<ev_unloop> was called. |
|
|
645 | |
|
|
646 | Please note that an explicit C<ev_unloop> is usually better than |
|
|
647 | relying on all watchers to be stopped when deciding when a program has |
|
|
648 | finished (especially in interactive programs), but having a program |
|
|
649 | that automatically loops as long as it has to and no longer by virtue |
|
|
650 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
651 | beauty. |
223 | |
652 | |
224 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
653 | 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 |
654 | those events and any already outstanding ones, but will not block your |
226 | case there are no events and will return after one iteration of the loop. |
655 | process in case there are no events and will return after one iteration of |
|
|
656 | the loop. |
227 | |
657 | |
228 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
658 | 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 |
659 | necessary) and will handle those and any already outstanding ones. It |
230 | your process until at least one new event arrives, and will return after |
660 | will block your process until at least one new event arrives (which could |
|
|
661 | be an event internal to libev itself, so there is no guarantee that a |
|
|
662 | user-registered callback will be called), and will return after one |
231 | one iteration of the loop. |
663 | iteration of the loop. |
232 | |
664 | |
233 | This flags value could be used to implement alternative looping |
665 | This is useful if you are waiting for some external event in conjunction |
234 | constructs, but the C<prepare> and C<check> watchers provide a better and |
666 | with something not expressible using other libev watchers (i.e. "roll your |
235 | more generic mechanism. |
667 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
|
|
668 | usually a better approach for this kind of thing. |
|
|
669 | |
|
|
670 | Here are the gory details of what C<ev_loop> does: |
|
|
671 | |
|
|
672 | - Before the first iteration, call any pending watchers. |
|
|
673 | * If EVFLAG_FORKCHECK was used, check for a fork. |
|
|
674 | - If a fork was detected (by any means), queue and call all fork watchers. |
|
|
675 | - Queue and call all prepare watchers. |
|
|
676 | - If we have been forked, detach and recreate the kernel state |
|
|
677 | as to not disturb the other process. |
|
|
678 | - Update the kernel state with all outstanding changes. |
|
|
679 | - Update the "event loop time" (ev_now ()). |
|
|
680 | - Calculate for how long to sleep or block, if at all |
|
|
681 | (active idle watchers, EVLOOP_NONBLOCK or not having |
|
|
682 | any active watchers at all will result in not sleeping). |
|
|
683 | - Sleep if the I/O and timer collect interval say so. |
|
|
684 | - Block the process, waiting for any events. |
|
|
685 | - Queue all outstanding I/O (fd) events. |
|
|
686 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
|
|
687 | - Queue all expired timers. |
|
|
688 | - Queue all expired periodics. |
|
|
689 | - Unless any events are pending now, queue all idle watchers. |
|
|
690 | - Queue all check watchers. |
|
|
691 | - Call all queued watchers in reverse order (i.e. check watchers first). |
|
|
692 | Signals and child watchers are implemented as I/O watchers, and will |
|
|
693 | be handled here by queueing them when their watcher gets executed. |
|
|
694 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
|
|
695 | were used, or there are no active watchers, return, otherwise |
|
|
696 | continue with step *. |
|
|
697 | |
|
|
698 | Example: Queue some jobs and then loop until no events are outstanding |
|
|
699 | anymore. |
|
|
700 | |
|
|
701 | ... queue jobs here, make sure they register event watchers as long |
|
|
702 | ... as they still have work to do (even an idle watcher will do..) |
|
|
703 | ev_loop (my_loop, 0); |
|
|
704 | ... jobs done or somebody called unloop. yeah! |
236 | |
705 | |
237 | =item ev_unloop (loop, how) |
706 | =item ev_unloop (loop, how) |
238 | |
707 | |
239 | Can be used to make a call to C<ev_loop> return early (but only after it |
708 | 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 |
709 | 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 |
710 | 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. |
711 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
|
|
712 | |
|
|
713 | This "unloop state" will be cleared when entering C<ev_loop> again. |
|
|
714 | |
|
|
715 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
243 | |
716 | |
244 | =item ev_ref (loop) |
717 | =item ev_ref (loop) |
245 | |
718 | |
246 | =item ev_unref (loop) |
719 | =item ev_unref (loop) |
247 | |
720 | |
248 | Ref/unref can be used to add or remove a reference count on the event |
721 | Ref/unref can be used to add or remove a reference count on the event |
249 | loop: Every watcher keeps one reference, and as long as the reference |
722 | loop: Every watcher keeps one reference, and as long as the reference |
250 | count is nonzero, C<ev_loop> will not return on its own. If you have |
723 | count is nonzero, C<ev_loop> will not return on its own. |
|
|
724 | |
251 | a watcher you never unregister that should not keep C<ev_loop> from |
725 | If you have a watcher you never unregister that should not keep C<ev_loop> |
252 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
726 | from returning, call ev_unref() after starting, and ev_ref() before |
|
|
727 | stopping it. |
|
|
728 | |
253 | example, libev itself uses this for its internal signal pipe: It is not |
729 | As an example, libev itself uses this for its internal signal pipe: It is |
254 | visible to the libev user and should not keep C<ev_loop> from exiting if |
730 | not visible to the libev user and should not keep C<ev_loop> from exiting |
255 | no event watchers registered by it are active. It is also an excellent |
731 | if 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 |
732 | 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>. |
733 | libraries. Just remember to I<unref after start> and I<ref before stop> |
|
|
734 | (but only if the watcher wasn't active before, or was active before, |
|
|
735 | respectively). |
|
|
736 | |
|
|
737 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
|
|
738 | running when nothing else is active. |
|
|
739 | |
|
|
740 | ev_signal exitsig; |
|
|
741 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
|
|
742 | ev_signal_start (loop, &exitsig); |
|
|
743 | evf_unref (loop); |
|
|
744 | |
|
|
745 | Example: For some weird reason, unregister the above signal handler again. |
|
|
746 | |
|
|
747 | ev_ref (loop); |
|
|
748 | ev_signal_stop (loop, &exitsig); |
|
|
749 | |
|
|
750 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
|
|
751 | |
|
|
752 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
|
|
753 | |
|
|
754 | These advanced functions influence the time that libev will spend waiting |
|
|
755 | for events. Both time intervals are by default C<0>, meaning that libev |
|
|
756 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
757 | latency. |
|
|
758 | |
|
|
759 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
|
|
760 | allows libev to delay invocation of I/O and timer/periodic callbacks |
|
|
761 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
762 | opportunities). |
|
|
763 | |
|
|
764 | The idea is that sometimes your program runs just fast enough to handle |
|
|
765 | one (or very few) event(s) per loop iteration. While this makes the |
|
|
766 | program responsive, it also wastes a lot of CPU time to poll for new |
|
|
767 | events, especially with backends like C<select ()> which have a high |
|
|
768 | overhead for the actual polling but can deliver many events at once. |
|
|
769 | |
|
|
770 | By setting a higher I<io collect interval> you allow libev to spend more |
|
|
771 | time collecting I/O events, so you can handle more events per iteration, |
|
|
772 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
|
|
773 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
|
|
774 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
|
|
775 | |
|
|
776 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
|
|
777 | to spend more time collecting timeouts, at the expense of increased |
|
|
778 | latency/jitter/inexactness (the watcher callback will be called |
|
|
779 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
|
|
780 | value will not introduce any overhead in libev. |
|
|
781 | |
|
|
782 | Many (busy) programs can usually benefit by setting the I/O collect |
|
|
783 | interval to a value near C<0.1> or so, which is often enough for |
|
|
784 | interactive servers (of course not for games), likewise for timeouts. It |
|
|
785 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
|
|
786 | as this approaches the timing granularity of most systems. |
|
|
787 | |
|
|
788 | Setting the I<timeout collect interval> can improve the opportunity for |
|
|
789 | saving power, as the program will "bundle" timer callback invocations that |
|
|
790 | are "near" in time together, by delaying some, thus reducing the number of |
|
|
791 | times the process sleeps and wakes up again. Another useful technique to |
|
|
792 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
|
|
793 | they fire on, say, one-second boundaries only. |
|
|
794 | |
|
|
795 | =item ev_loop_verify (loop) |
|
|
796 | |
|
|
797 | This function only does something when C<EV_VERIFY> support has been |
|
|
798 | compiled in, which is the default for non-minimal builds. It tries to go |
|
|
799 | through all internal structures and checks them for validity. If anything |
|
|
800 | is found to be inconsistent, it will print an error message to standard |
|
|
801 | error and call C<abort ()>. |
|
|
802 | |
|
|
803 | This can be used to catch bugs inside libev itself: under normal |
|
|
804 | circumstances, this function will never abort as of course libev keeps its |
|
|
805 | data structures consistent. |
258 | |
806 | |
259 | =back |
807 | =back |
260 | |
808 | |
|
|
809 | |
261 | =head1 ANATOMY OF A WATCHER |
810 | =head1 ANATOMY OF A WATCHER |
|
|
811 | |
|
|
812 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
813 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
814 | watchers and C<ev_io_start> for I/O watchers. |
262 | |
815 | |
263 | A watcher is a structure that you create and register to record your |
816 | 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 |
817 | 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: |
818 | become readable, you would create an C<ev_io> watcher for that: |
266 | |
819 | |
267 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
820 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
268 | { |
821 | { |
269 | ev_io_stop (w); |
822 | ev_io_stop (w); |
270 | ev_unloop (loop, EVUNLOOP_ALL); |
823 | ev_unloop (loop, EVUNLOOP_ALL); |
271 | } |
824 | } |
272 | |
825 | |
273 | struct ev_loop *loop = ev_default_loop (0); |
826 | struct ev_loop *loop = ev_default_loop (0); |
|
|
827 | |
274 | struct ev_io stdin_watcher; |
828 | ev_io stdin_watcher; |
|
|
829 | |
275 | ev_init (&stdin_watcher, my_cb); |
830 | ev_init (&stdin_watcher, my_cb); |
276 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
831 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
277 | ev_io_start (loop, &stdin_watcher); |
832 | ev_io_start (loop, &stdin_watcher); |
|
|
833 | |
278 | ev_loop (loop, 0); |
834 | ev_loop (loop, 0); |
279 | |
835 | |
280 | As you can see, you are responsible for allocating the memory for your |
836 | 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, |
837 | watcher structures (and it is I<usually> a bad idea to do this on the |
282 | although this can sometimes be quite valid). |
838 | stack). |
|
|
839 | |
|
|
840 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
841 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
283 | |
842 | |
284 | Each watcher structure must be initialised by a call to C<ev_init |
843 | Each watcher structure must be initialised by a call to C<ev_init |
285 | (watcher *, callback)>, which expects a callback to be provided. This |
844 | (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 |
845 | 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 |
846 | watchers, each time the event loop detects that the file descriptor given |
288 | is readable and/or writable). |
847 | is readable and/or writable). |
289 | |
848 | |
290 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
849 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
291 | with arguments specific to this watcher type. There is also a macro |
850 | macro to configure it, with arguments specific to the watcher type. There |
292 | to combine initialisation and setting in one call: C<< ev_<type>_init |
851 | is also a macro to combine initialisation and setting in one call: C<< |
293 | (watcher *, callback, ...) >>. |
852 | ev_TYPE_init (watcher *, callback, ...) >>. |
294 | |
853 | |
295 | To make the watcher actually watch out for events, you have to start it |
854 | To make the watcher actually watch out for events, you have to start it |
296 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
855 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
297 | *) >>), and you can stop watching for events at any time by calling the |
856 | *) >>), and you can stop watching for events at any time by calling the |
298 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
857 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
299 | |
858 | |
300 | As long as your watcher is active (has been started but not stopped) you |
859 | 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 |
860 | must not touch the values stored in it. Most specifically you must never |
302 | reinitialise it or call its set method. |
861 | reinitialise it or call its C<ev_TYPE_set> macro. |
303 | |
|
|
304 | You cna check whether an event is active by calling the C<ev_is_active |
|
|
305 | (watcher *)> macro. To see whether an event is outstanding (but the |
|
|
306 | callback for it has not been called yet) you cna use the C<ev_is_pending |
|
|
307 | (watcher *)> macro. |
|
|
308 | |
862 | |
309 | Each and every callback receives the event loop pointer as first, the |
863 | 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 |
864 | registered watcher structure as second, and a bitset of received events as |
311 | third argument. |
865 | third argument. |
312 | |
866 | |
313 | The rceeived events usually include a single bit per event type received |
867 | 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 |
868 | (you can receive multiple events at the same time). The possible bit masks |
315 | are: |
869 | are: |
316 | |
870 | |
317 | =over 4 |
871 | =over 4 |
318 | |
872 | |
… | |
… | |
336 | The signal specified in the C<ev_signal> watcher has been received by a thread. |
890 | The signal specified in the C<ev_signal> watcher has been received by a thread. |
337 | |
891 | |
338 | =item C<EV_CHILD> |
892 | =item C<EV_CHILD> |
339 | |
893 | |
340 | The pid specified in the C<ev_child> watcher has received a status change. |
894 | The pid specified in the C<ev_child> watcher has received a status change. |
|
|
895 | |
|
|
896 | =item C<EV_STAT> |
|
|
897 | |
|
|
898 | The path specified in the C<ev_stat> watcher changed its attributes somehow. |
341 | |
899 | |
342 | =item C<EV_IDLE> |
900 | =item C<EV_IDLE> |
343 | |
901 | |
344 | The C<ev_idle> watcher has determined that you have nothing better to do. |
902 | The C<ev_idle> watcher has determined that you have nothing better to do. |
345 | |
903 | |
… | |
… | |
353 | received events. Callbacks of both watcher types can start and stop as |
911 | 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 |
912 | 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 |
913 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
356 | C<ev_loop> from blocking). |
914 | C<ev_loop> from blocking). |
357 | |
915 | |
|
|
916 | =item C<EV_EMBED> |
|
|
917 | |
|
|
918 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
|
|
919 | |
|
|
920 | =item C<EV_FORK> |
|
|
921 | |
|
|
922 | The event loop has been resumed in the child process after fork (see |
|
|
923 | C<ev_fork>). |
|
|
924 | |
|
|
925 | =item C<EV_ASYNC> |
|
|
926 | |
|
|
927 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
928 | |
358 | =item C<EV_ERROR> |
929 | =item C<EV_ERROR> |
359 | |
930 | |
360 | An unspecified error has occured, the watcher has been stopped. This might |
931 | An unspecified error has occurred, the watcher has been stopped. This might |
361 | happen because the watcher could not be properly started because libev |
932 | 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 |
933 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
934 | problem. Libev considers these application bugs. |
|
|
935 | |
363 | problem. You best act on it by reporting the problem and somehow coping |
936 | You best act on it by reporting the problem and somehow coping with the |
364 | with the watcher being stopped. |
937 | watcher being stopped. Note that well-written programs should not receive |
|
|
938 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
939 | bug in your program. |
365 | |
940 | |
366 | Libev will usually signal a few "dummy" events together with an error, |
941 | Libev will usually signal a few "dummy" events together with an error, for |
367 | for example it might indicate that a fd is readable or writable, and if |
942 | example it might indicate that a fd is readable or writable, and if your |
368 | your callbacks is well-written it can just attempt the operation and cope |
943 | callbacks is well-written it can just attempt the operation and cope with |
369 | with the error from read() or write(). This will not work in multithreaded |
944 | the error from read() or write(). This will not work in multi-threaded |
370 | programs, though, so beware. |
945 | programs, though, as the fd could already be closed and reused for another |
|
|
946 | thing, so beware. |
371 | |
947 | |
372 | =back |
948 | =back |
373 | |
949 | |
|
|
950 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
951 | |
|
|
952 | =over 4 |
|
|
953 | |
|
|
954 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
955 | |
|
|
956 | This macro initialises the generic portion of a watcher. The contents |
|
|
957 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
958 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
959 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
960 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
961 | which rolls both calls into one. |
|
|
962 | |
|
|
963 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
964 | (or never started) and there are no pending events outstanding. |
|
|
965 | |
|
|
966 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
967 | int revents)>. |
|
|
968 | |
|
|
969 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
970 | |
|
|
971 | ev_io w; |
|
|
972 | ev_init (&w, my_cb); |
|
|
973 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
974 | |
|
|
975 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
|
|
976 | |
|
|
977 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
978 | call C<ev_init> at least once before you call this macro, but you can |
|
|
979 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
980 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
981 | difference to the C<ev_init> macro). |
|
|
982 | |
|
|
983 | Although some watcher types do not have type-specific arguments |
|
|
984 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
985 | |
|
|
986 | See C<ev_init>, above, for an example. |
|
|
987 | |
|
|
988 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
989 | |
|
|
990 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
991 | calls into a single call. This is the most convenient method to initialise |
|
|
992 | a watcher. The same limitations apply, of course. |
|
|
993 | |
|
|
994 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
995 | |
|
|
996 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
997 | |
|
|
998 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
|
|
999 | |
|
|
1000 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1001 | events. If the watcher is already active nothing will happen. |
|
|
1002 | |
|
|
1003 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1004 | whole section. |
|
|
1005 | |
|
|
1006 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1007 | |
|
|
1008 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
|
|
1009 | |
|
|
1010 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1011 | the watcher was active or not). |
|
|
1012 | |
|
|
1013 | It is possible that stopped watchers are pending - for example, |
|
|
1014 | non-repeating timers are being stopped when they become pending - but |
|
|
1015 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1016 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1017 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1018 | |
|
|
1019 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1020 | |
|
|
1021 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1022 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1023 | it. |
|
|
1024 | |
|
|
1025 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1026 | |
|
|
1027 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1028 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1029 | is pending (but not active) you must not call an init function on it (but |
|
|
1030 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1031 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1032 | it). |
|
|
1033 | |
|
|
1034 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1035 | |
|
|
1036 | Returns the callback currently set on the watcher. |
|
|
1037 | |
|
|
1038 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
1039 | |
|
|
1040 | Change the callback. You can change the callback at virtually any time |
|
|
1041 | (modulo threads). |
|
|
1042 | |
|
|
1043 | =item ev_set_priority (ev_TYPE *watcher, priority) |
|
|
1044 | |
|
|
1045 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1046 | |
|
|
1047 | Set and query the priority of the watcher. The priority is a small |
|
|
1048 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1049 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1050 | before watchers with lower priority, but priority will not keep watchers |
|
|
1051 | from being executed (except for C<ev_idle> watchers). |
|
|
1052 | |
|
|
1053 | This means that priorities are I<only> used for ordering callback |
|
|
1054 | invocation after new events have been received. This is useful, for |
|
|
1055 | example, to reduce latency after idling, or more often, to bind two |
|
|
1056 | watchers on the same event and make sure one is called first. |
|
|
1057 | |
|
|
1058 | If you need to suppress invocation when higher priority events are pending |
|
|
1059 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1060 | |
|
|
1061 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1062 | pending. |
|
|
1063 | |
|
|
1064 | The default priority used by watchers when no priority has been set is |
|
|
1065 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1066 | |
|
|
1067 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1068 | fine, as long as you do not mind that the priority value you query might |
|
|
1069 | or might not have been clamped to the valid range. |
|
|
1070 | |
|
|
1071 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1072 | |
|
|
1073 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1074 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1075 | can deal with that fact, as both are simply passed through to the |
|
|
1076 | callback. |
|
|
1077 | |
|
|
1078 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1079 | |
|
|
1080 | If the watcher is pending, this function clears its pending status and |
|
|
1081 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1082 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1083 | |
|
|
1084 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1085 | callback to be invoked, which can be accomplished with this function. |
|
|
1086 | |
|
|
1087 | =back |
|
|
1088 | |
|
|
1089 | |
374 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1090 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
375 | |
1091 | |
376 | Each watcher has, by default, a member C<void *data> that you can change |
1092 | 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 |
1093 | 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 |
1094 | 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 |
1095 | 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 |
1096 | member, you can also "subclass" the watcher type and provide your own |
381 | data: |
1097 | data: |
382 | |
1098 | |
383 | struct my_io |
1099 | struct my_io |
384 | { |
1100 | { |
385 | struct ev_io io; |
1101 | ev_io io; |
386 | int otherfd; |
1102 | int otherfd; |
387 | void *somedata; |
1103 | void *somedata; |
388 | struct whatever *mostinteresting; |
1104 | struct whatever *mostinteresting; |
389 | } |
1105 | }; |
|
|
1106 | |
|
|
1107 | ... |
|
|
1108 | struct my_io w; |
|
|
1109 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
390 | |
1110 | |
391 | And since your callback will be called with a pointer to the watcher, you |
1111 | And since your callback will be called with a pointer to the watcher, you |
392 | can cast it back to your own type: |
1112 | can cast it back to your own type: |
393 | |
1113 | |
394 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1114 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
395 | { |
1115 | { |
396 | struct my_io *w = (struct my_io *)w_; |
1116 | struct my_io *w = (struct my_io *)w_; |
397 | ... |
1117 | ... |
398 | } |
1118 | } |
399 | |
1119 | |
400 | More interesting and less C-conformant ways of catsing your callback type |
1120 | More interesting and less C-conformant ways of casting your callback type |
401 | have been omitted.... |
1121 | instead have been omitted. |
|
|
1122 | |
|
|
1123 | Another common scenario is to use some data structure with multiple |
|
|
1124 | embedded watchers: |
|
|
1125 | |
|
|
1126 | struct my_biggy |
|
|
1127 | { |
|
|
1128 | int some_data; |
|
|
1129 | ev_timer t1; |
|
|
1130 | ev_timer t2; |
|
|
1131 | } |
|
|
1132 | |
|
|
1133 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1134 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1135 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1136 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1137 | programmers): |
|
|
1138 | |
|
|
1139 | #include <stddef.h> |
|
|
1140 | |
|
|
1141 | static void |
|
|
1142 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1143 | { |
|
|
1144 | struct my_biggy big = (struct my_biggy * |
|
|
1145 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1146 | } |
|
|
1147 | |
|
|
1148 | static void |
|
|
1149 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1150 | { |
|
|
1151 | struct my_biggy big = (struct my_biggy * |
|
|
1152 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1153 | } |
402 | |
1154 | |
403 | |
1155 | |
404 | =head1 WATCHER TYPES |
1156 | =head1 WATCHER TYPES |
405 | |
1157 | |
406 | This section describes each watcher in detail, but will not repeat |
1158 | This section describes each watcher in detail, but will not repeat |
407 | information given in the last section. |
1159 | information given in the last section. Any initialisation/set macros, |
|
|
1160 | functions and members specific to the watcher type are explained. |
408 | |
1161 | |
|
|
1162 | Members are additionally marked with either I<[read-only]>, meaning that, |
|
|
1163 | while the watcher is active, you can look at the member and expect some |
|
|
1164 | sensible content, but you must not modify it (you can modify it while the |
|
|
1165 | watcher is stopped to your hearts content), or I<[read-write]>, which |
|
|
1166 | means you can expect it to have some sensible content while the watcher |
|
|
1167 | is active, but you can also modify it. Modifying it may not do something |
|
|
1168 | sensible or take immediate effect (or do anything at all), but libev will |
|
|
1169 | not crash or malfunction in any way. |
|
|
1170 | |
|
|
1171 | |
409 | =head2 C<ev_io> - is this file descriptor readable or writable |
1172 | =head2 C<ev_io> - is this file descriptor readable or writable? |
410 | |
1173 | |
411 | I/O watchers check whether a file descriptor is readable or writable |
1174 | I/O watchers check whether a file descriptor is readable or writable |
412 | in each iteration of the event loop (This behaviour is called |
1175 | in each iteration of the event loop, or, more precisely, when reading |
413 | level-triggering because you keep receiving events as long as the |
1176 | 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 |
1177 | some data. This behaviour is called level-triggering because you keep |
415 | act on the event and neither want to receive future events). |
1178 | receiving events as long as the condition persists. Remember you can stop |
|
|
1179 | the watcher if you don't want to act on the event and neither want to |
|
|
1180 | receive future events. |
416 | |
1181 | |
417 | In general you can register as many read and/or write event watchers oer |
1182 | 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 |
1183 | 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 |
1184 | descriptors to non-blocking mode is also usually a good idea (but not |
420 | required if you know what you are doing). |
1185 | required if you know what you are doing). |
421 | |
1186 | |
422 | You have to be careful with dup'ed file descriptors, though. Some backends |
1187 | If you cannot use non-blocking mode, then force the use of a |
423 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
1188 | known-to-be-good backend (at the time of this writing, this includes only |
424 | descriptors correctly if you register interest in two or more fds pointing |
1189 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
425 | to the same file/socket etc. description. |
|
|
426 | |
1190 | |
427 | If you must do this, then force the use of a known-to-be-good backend |
1191 | Another thing you have to watch out for is that it is quite easy to |
428 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
1192 | receive "spurious" readiness notifications, that is your callback might |
429 | EVMETHOD_POLL). |
1193 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
|
|
1194 | because there is no data. Not only are some backends known to create a |
|
|
1195 | lot of those (for example Solaris ports), it is very easy to get into |
|
|
1196 | this situation even with a relatively standard program structure. Thus |
|
|
1197 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1198 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
|
|
1199 | |
|
|
1200 | If you cannot run the fd in non-blocking mode (for example you should |
|
|
1201 | not play around with an Xlib connection), then you have to separately |
|
|
1202 | re-test whether a file descriptor is really ready with a known-to-be good |
|
|
1203 | interface such as poll (fortunately in our Xlib example, Xlib already |
|
|
1204 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1205 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1206 | indefinitely. |
|
|
1207 | |
|
|
1208 | But really, best use non-blocking mode. |
|
|
1209 | |
|
|
1210 | =head3 The special problem of disappearing file descriptors |
|
|
1211 | |
|
|
1212 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
|
|
1213 | descriptor (either due to calling C<close> explicitly or any other means, |
|
|
1214 | such as C<dup2>). The reason is that you register interest in some file |
|
|
1215 | descriptor, but when it goes away, the operating system will silently drop |
|
|
1216 | this interest. If another file descriptor with the same number then is |
|
|
1217 | registered with libev, there is no efficient way to see that this is, in |
|
|
1218 | fact, a different file descriptor. |
|
|
1219 | |
|
|
1220 | To avoid having to explicitly tell libev about such cases, libev follows |
|
|
1221 | the following policy: Each time C<ev_io_set> is being called, libev |
|
|
1222 | will assume that this is potentially a new file descriptor, otherwise |
|
|
1223 | it is assumed that the file descriptor stays the same. That means that |
|
|
1224 | you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the |
|
|
1225 | descriptor even if the file descriptor number itself did not change. |
|
|
1226 | |
|
|
1227 | This is how one would do it normally anyway, the important point is that |
|
|
1228 | the libev application should not optimise around libev but should leave |
|
|
1229 | optimisations to libev. |
|
|
1230 | |
|
|
1231 | =head3 The special problem of dup'ed file descriptors |
|
|
1232 | |
|
|
1233 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
1234 | but only events for the underlying file descriptions. That means when you |
|
|
1235 | have C<dup ()>'ed file descriptors or weirder constellations, and register |
|
|
1236 | events for them, only one file descriptor might actually receive events. |
|
|
1237 | |
|
|
1238 | There is no workaround possible except not registering events |
|
|
1239 | for potentially C<dup ()>'ed file descriptors, or to resort to |
|
|
1240 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
|
|
1241 | |
|
|
1242 | =head3 The special problem of fork |
|
|
1243 | |
|
|
1244 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
|
|
1245 | useless behaviour. Libev fully supports fork, but needs to be told about |
|
|
1246 | it in the child. |
|
|
1247 | |
|
|
1248 | To support fork in your programs, you either have to call |
|
|
1249 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
|
|
1250 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
|
|
1251 | C<EVBACKEND_POLL>. |
|
|
1252 | |
|
|
1253 | =head3 The special problem of SIGPIPE |
|
|
1254 | |
|
|
1255 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
|
|
1256 | when writing to a pipe whose other end has been closed, your program gets |
|
|
1257 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
|
|
1258 | this is sensible behaviour, for daemons, this is usually undesirable. |
|
|
1259 | |
|
|
1260 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1261 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1262 | somewhere, as that would have given you a big clue). |
|
|
1263 | |
|
|
1264 | |
|
|
1265 | =head3 Watcher-Specific Functions |
430 | |
1266 | |
431 | =over 4 |
1267 | =over 4 |
432 | |
1268 | |
433 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1269 | =item ev_io_init (ev_io *, callback, int fd, int events) |
434 | |
1270 | |
435 | =item ev_io_set (ev_io *, int fd, int events) |
1271 | =item ev_io_set (ev_io *, int fd, int events) |
436 | |
1272 | |
437 | Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive |
1273 | 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 | |
1274 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
439 | EV_WRITE> to receive the given events. |
1275 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
|
|
1276 | |
|
|
1277 | =item int fd [read-only] |
|
|
1278 | |
|
|
1279 | The file descriptor being watched. |
|
|
1280 | |
|
|
1281 | =item int events [read-only] |
|
|
1282 | |
|
|
1283 | The events being watched. |
440 | |
1284 | |
441 | =back |
1285 | =back |
442 | |
1286 | |
|
|
1287 | =head3 Examples |
|
|
1288 | |
|
|
1289 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
|
|
1290 | readable, but only once. Since it is likely line-buffered, you could |
|
|
1291 | attempt to read a whole line in the callback. |
|
|
1292 | |
|
|
1293 | static void |
|
|
1294 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
|
|
1295 | { |
|
|
1296 | ev_io_stop (loop, w); |
|
|
1297 | .. read from stdin here (or from w->fd) and handle any I/O errors |
|
|
1298 | } |
|
|
1299 | |
|
|
1300 | ... |
|
|
1301 | struct ev_loop *loop = ev_default_init (0); |
|
|
1302 | ev_io stdin_readable; |
|
|
1303 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
|
|
1304 | ev_io_start (loop, &stdin_readable); |
|
|
1305 | ev_loop (loop, 0); |
|
|
1306 | |
|
|
1307 | |
443 | =head2 C<ev_timer> - relative and optionally recurring timeouts |
1308 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
444 | |
1309 | |
445 | Timer watchers are simple relative timers that generate an event after a |
1310 | Timer watchers are simple relative timers that generate an event after a |
446 | given time, and optionally repeating in regular intervals after that. |
1311 | given time, and optionally repeating in regular intervals after that. |
447 | |
1312 | |
448 | The timers are based on real time, that is, if you register an event that |
1313 | 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 |
1314 | 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 |
1315 | year, it will still time out after (roughly) one hour. "Roughly" because |
451 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
1316 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
452 | monotonic clock option helps a lot here). |
1317 | monotonic clock option helps a lot here). |
|
|
1318 | |
|
|
1319 | The callback is guaranteed to be invoked only I<after> its timeout has |
|
|
1320 | passed, but if multiple timers become ready during the same loop iteration |
|
|
1321 | then order of execution is undefined. |
|
|
1322 | |
|
|
1323 | =head3 Be smart about timeouts |
|
|
1324 | |
|
|
1325 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1326 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1327 | you want to raise some error after a while. |
|
|
1328 | |
|
|
1329 | What follows are some ways to handle this problem, from obvious and |
|
|
1330 | inefficient to smart and efficient. |
|
|
1331 | |
|
|
1332 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1333 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1334 | data or other life sign was received). |
|
|
1335 | |
|
|
1336 | =over 4 |
|
|
1337 | |
|
|
1338 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1339 | |
|
|
1340 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1341 | start the watcher: |
|
|
1342 | |
|
|
1343 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1344 | ev_timer_start (loop, timer); |
|
|
1345 | |
|
|
1346 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1347 | and start it again: |
|
|
1348 | |
|
|
1349 | ev_timer_stop (loop, timer); |
|
|
1350 | ev_timer_set (timer, 60., 0.); |
|
|
1351 | ev_timer_start (loop, timer); |
|
|
1352 | |
|
|
1353 | This is relatively simple to implement, but means that each time there is |
|
|
1354 | some activity, libev will first have to remove the timer from its internal |
|
|
1355 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1356 | still not a constant-time operation. |
|
|
1357 | |
|
|
1358 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1359 | |
|
|
1360 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1361 | C<ev_timer_start>. |
|
|
1362 | |
|
|
1363 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1364 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1365 | successfully read or write some data. If you go into an idle state where |
|
|
1366 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1367 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1368 | |
|
|
1369 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1370 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1371 | member and C<ev_timer_again>. |
|
|
1372 | |
|
|
1373 | At start: |
|
|
1374 | |
|
|
1375 | ev_timer_init (timer, callback); |
|
|
1376 | timer->repeat = 60.; |
|
|
1377 | ev_timer_again (loop, timer); |
|
|
1378 | |
|
|
1379 | Each time there is some activity: |
|
|
1380 | |
|
|
1381 | ev_timer_again (loop, timer); |
|
|
1382 | |
|
|
1383 | It is even possible to change the time-out on the fly, regardless of |
|
|
1384 | whether the watcher is active or not: |
|
|
1385 | |
|
|
1386 | timer->repeat = 30.; |
|
|
1387 | ev_timer_again (loop, timer); |
|
|
1388 | |
|
|
1389 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1390 | you want to modify its timeout value, as libev does not have to completely |
|
|
1391 | remove and re-insert the timer from/into its internal data structure. |
|
|
1392 | |
|
|
1393 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1394 | |
|
|
1395 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1396 | |
|
|
1397 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1398 | relatively long compared to the intervals between other activity - in |
|
|
1399 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1400 | associated activity resets. |
|
|
1401 | |
|
|
1402 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1403 | but remember the time of last activity, and check for a real timeout only |
|
|
1404 | within the callback: |
|
|
1405 | |
|
|
1406 | ev_tstamp last_activity; // time of last activity |
|
|
1407 | |
|
|
1408 | static void |
|
|
1409 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1410 | { |
|
|
1411 | ev_tstamp now = ev_now (EV_A); |
|
|
1412 | ev_tstamp timeout = last_activity + 60.; |
|
|
1413 | |
|
|
1414 | // if last_activity + 60. is older than now, we did time out |
|
|
1415 | if (timeout < now) |
|
|
1416 | { |
|
|
1417 | // timeout occured, take action |
|
|
1418 | } |
|
|
1419 | else |
|
|
1420 | { |
|
|
1421 | // callback was invoked, but there was some activity, re-arm |
|
|
1422 | // the watcher to fire in last_activity + 60, which is |
|
|
1423 | // guaranteed to be in the future, so "again" is positive: |
|
|
1424 | w->repeat = timeout - now; |
|
|
1425 | ev_timer_again (EV_A_ w); |
|
|
1426 | } |
|
|
1427 | } |
|
|
1428 | |
|
|
1429 | To summarise the callback: first calculate the real timeout (defined |
|
|
1430 | as "60 seconds after the last activity"), then check if that time has |
|
|
1431 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1432 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1433 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1434 | a timeout then. |
|
|
1435 | |
|
|
1436 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1437 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1438 | |
|
|
1439 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1440 | minus half the average time between activity), but virtually no calls to |
|
|
1441 | libev to change the timeout. |
|
|
1442 | |
|
|
1443 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1444 | to the current time (meaning we just have some activity :), then call the |
|
|
1445 | callback, which will "do the right thing" and start the timer: |
|
|
1446 | |
|
|
1447 | ev_timer_init (timer, callback); |
|
|
1448 | last_activity = ev_now (loop); |
|
|
1449 | callback (loop, timer, EV_TIMEOUT); |
|
|
1450 | |
|
|
1451 | And when there is some activity, simply store the current time in |
|
|
1452 | C<last_activity>, no libev calls at all: |
|
|
1453 | |
|
|
1454 | last_actiivty = ev_now (loop); |
|
|
1455 | |
|
|
1456 | This technique is slightly more complex, but in most cases where the |
|
|
1457 | time-out is unlikely to be triggered, much more efficient. |
|
|
1458 | |
|
|
1459 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1460 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1461 | fix things for you. |
|
|
1462 | |
|
|
1463 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1464 | |
|
|
1465 | If there is not one request, but many thousands (millions...), all |
|
|
1466 | employing some kind of timeout with the same timeout value, then one can |
|
|
1467 | do even better: |
|
|
1468 | |
|
|
1469 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1470 | at the I<end> of the list. |
|
|
1471 | |
|
|
1472 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1473 | the list is expected to fire (for example, using the technique #3). |
|
|
1474 | |
|
|
1475 | When there is some activity, remove the timer from the list, recalculate |
|
|
1476 | the timeout, append it to the end of the list again, and make sure to |
|
|
1477 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1478 | |
|
|
1479 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1480 | starting, stopping and updating the timers, at the expense of a major |
|
|
1481 | complication, and having to use a constant timeout. The constant timeout |
|
|
1482 | ensures that the list stays sorted. |
|
|
1483 | |
|
|
1484 | =back |
|
|
1485 | |
|
|
1486 | So which method the best? |
|
|
1487 | |
|
|
1488 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1489 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1490 | better, and isn't very complicated either. In most case, choosing either |
|
|
1491 | one is fine, with #3 being better in typical situations. |
|
|
1492 | |
|
|
1493 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1494 | rather complicated, but extremely efficient, something that really pays |
|
|
1495 | off after the first million or so of active timers, i.e. it's usually |
|
|
1496 | overkill :) |
|
|
1497 | |
|
|
1498 | =head3 The special problem of time updates |
|
|
1499 | |
|
|
1500 | Establishing the current time is a costly operation (it usually takes at |
|
|
1501 | least two system calls): EV therefore updates its idea of the current |
|
|
1502 | time only before and after C<ev_loop> collects new events, which causes a |
|
|
1503 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
1504 | lots of events in one iteration. |
453 | |
1505 | |
454 | The relative timeouts are calculated relative to the C<ev_now ()> |
1506 | 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 |
1507 | 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 |
1508 | 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 |
1509 | 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: |
1510 | timeout on the current time, use something like this to adjust for this: |
459 | |
1511 | |
460 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1512 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
461 | |
1513 | |
|
|
1514 | If the event loop is suspended for a long time, you can also force an |
|
|
1515 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
|
|
1516 | ()>. |
|
|
1517 | |
|
|
1518 | =head3 Watcher-Specific Functions and Data Members |
|
|
1519 | |
462 | =over 4 |
1520 | =over 4 |
463 | |
1521 | |
464 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1522 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
465 | |
1523 | |
466 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1524 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
467 | |
1525 | |
468 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1526 | 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 |
1527 | 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 |
1528 | reached. If it is positive, then the timer will automatically be |
471 | later, again, and again, until stopped manually. |
1529 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1530 | until stopped manually. |
472 | |
1531 | |
473 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1532 | 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 |
1533 | 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 |
1534 | 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 |
1535 | 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. |
1536 | do stuff) the timer will not fire more than once per event loop iteration. |
478 | |
1537 | |
479 | =item ev_timer_again (loop) |
1538 | =item ev_timer_again (loop, ev_timer *) |
480 | |
1539 | |
481 | This will act as if the timer timed out and restart it again if it is |
1540 | This will act as if the timer timed out and restart it again if it is |
482 | repeating. The exact semantics are: |
1541 | repeating. The exact semantics are: |
483 | |
1542 | |
|
|
1543 | If the timer is pending, its pending status is cleared. |
|
|
1544 | |
484 | If the timer is started but nonrepeating, stop it. |
1545 | If the timer is started but non-repeating, stop it (as if it timed out). |
485 | |
1546 | |
486 | If the timer is repeating, either start it if necessary (with the repeat |
1547 | If the timer is repeating, either start it if necessary (with the |
487 | value), or reset the running timer to the repeat value. |
1548 | C<repeat> value), or reset the running timer to the C<repeat> value. |
488 | |
1549 | |
489 | This sounds a bit complicated, but here is a useful and typical |
1550 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
490 | example: Imagine you have a tcp connection and you want a so-called idle |
1551 | usage example. |
491 | timeout, that is, you want to be called when there have been, say, 60 |
1552 | |
492 | seconds of inactivity on the socket. The easiest way to do this is to |
1553 | =item ev_tstamp repeat [read-write] |
493 | configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each |
1554 | |
494 | time you successfully read or write some data. If you go into an idle |
1555 | The current C<repeat> value. Will be used each time the watcher times out |
495 | state where you do not expect data to travel on the socket, you can stop |
1556 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
496 | the timer, and again will automatically restart it if need be. |
1557 | which is also when any modifications are taken into account. |
497 | |
1558 | |
498 | =back |
1559 | =back |
499 | |
1560 | |
|
|
1561 | =head3 Examples |
|
|
1562 | |
|
|
1563 | Example: Create a timer that fires after 60 seconds. |
|
|
1564 | |
|
|
1565 | static void |
|
|
1566 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
|
|
1567 | { |
|
|
1568 | .. one minute over, w is actually stopped right here |
|
|
1569 | } |
|
|
1570 | |
|
|
1571 | ev_timer mytimer; |
|
|
1572 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
|
|
1573 | ev_timer_start (loop, &mytimer); |
|
|
1574 | |
|
|
1575 | Example: Create a timeout timer that times out after 10 seconds of |
|
|
1576 | inactivity. |
|
|
1577 | |
|
|
1578 | static void |
|
|
1579 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
|
|
1580 | { |
|
|
1581 | .. ten seconds without any activity |
|
|
1582 | } |
|
|
1583 | |
|
|
1584 | ev_timer mytimer; |
|
|
1585 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
|
|
1586 | ev_timer_again (&mytimer); /* start timer */ |
|
|
1587 | ev_loop (loop, 0); |
|
|
1588 | |
|
|
1589 | // and in some piece of code that gets executed on any "activity": |
|
|
1590 | // reset the timeout to start ticking again at 10 seconds |
|
|
1591 | ev_timer_again (&mytimer); |
|
|
1592 | |
|
|
1593 | |
500 | =head2 C<ev_periodic> - to cron or not to cron it |
1594 | =head2 C<ev_periodic> - to cron or not to cron? |
501 | |
1595 | |
502 | Periodic watchers are also timers of a kind, but they are very versatile |
1596 | Periodic watchers are also timers of a kind, but they are very versatile |
503 | (and unfortunately a bit complex). |
1597 | (and unfortunately a bit complex). |
504 | |
1598 | |
505 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1599 | 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 |
1600 | 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 |
1601 | 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 () |
1602 | 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 |
1603 | + 10.>, that is, an absolute time not a delay) and then reset your system |
|
|
1604 | 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 |
1605 | 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 |
1606 | roughly 10 seconds later as it uses a relative timeout). |
512 | again). |
|
|
513 | |
1607 | |
514 | They can also be used to implement vastly more complex timers, such as |
1608 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
515 | triggering an event on eahc midnight, local time. |
1609 | such as triggering an event on each "midnight, local time", or other |
|
|
1610 | complicated rules. |
|
|
1611 | |
|
|
1612 | As with timers, the callback is guaranteed to be invoked only when the |
|
|
1613 | time (C<at>) has passed, but if multiple periodic timers become ready |
|
|
1614 | during the same loop iteration, then order of execution is undefined. |
|
|
1615 | |
|
|
1616 | =head3 Watcher-Specific Functions and Data Members |
516 | |
1617 | |
517 | =over 4 |
1618 | =over 4 |
518 | |
1619 | |
519 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1620 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
520 | |
1621 | |
521 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1622 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
522 | |
1623 | |
523 | Lots of arguments, lets sort it out... There are basically three modes of |
1624 | Lots of arguments, lets sort it out... There are basically three modes of |
524 | operation, and we will explain them from simplest to complex: |
1625 | operation, and we will explain them from simplest to most complex: |
525 | |
|
|
526 | |
1626 | |
527 | =over 4 |
1627 | =over 4 |
528 | |
1628 | |
529 | =item * absolute timer (interval = reschedule_cb = 0) |
1629 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
530 | |
1630 | |
531 | In this configuration the watcher triggers an event at the wallclock time |
1631 | 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, |
1632 | time C<at> has passed. It will not repeat and 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 |
1633 | 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. |
1634 | only run when the system clock reaches or surpasses this time. |
535 | |
1635 | |
536 | =item * non-repeating interval timer (interval > 0, reschedule_cb = 0) |
1636 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
537 | |
1637 | |
538 | In this mode the watcher will always be scheduled to time out at the next |
1638 | 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 |
1639 | C<at + N * interval> time (for some integer N, which can also be negative) |
540 | of any time jumps. |
1640 | and then repeat, regardless of any time jumps. |
541 | |
1641 | |
542 | This can be used to create timers that do not drift with respect to system |
1642 | This can be used to create timers that do not drift with respect to the |
543 | time: |
1643 | system clock, for example, here is a C<ev_periodic> that triggers each |
|
|
1644 | hour, on the hour: |
544 | |
1645 | |
545 | ev_periodic_set (&periodic, 0., 3600., 0); |
1646 | ev_periodic_set (&periodic, 0., 3600., 0); |
546 | |
1647 | |
547 | This doesn't mean there will always be 3600 seconds in between triggers, |
1648 | 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 |
1649 | 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 |
1650 | full hour (UTC), or more correctly, when the system time is evenly divisible |
550 | by 3600. |
1651 | by 3600. |
551 | |
1652 | |
552 | Another way to think about it (for the mathematically inclined) is that |
1653 | 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 |
1654 | 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. |
1655 | time where C<time = at (mod interval)>, regardless of any time jumps. |
555 | |
1656 | |
|
|
1657 | For numerical stability it is preferable that the C<at> value is near |
|
|
1658 | C<ev_now ()> (the current time), but there is no range requirement for |
|
|
1659 | this value, and in fact is often specified as zero. |
|
|
1660 | |
|
|
1661 | Note also that there is an upper limit to how often a timer can fire (CPU |
|
|
1662 | speed for example), so if C<interval> is very small then timing stability |
|
|
1663 | will of course deteriorate. Libev itself tries to be exact to be about one |
|
|
1664 | millisecond (if the OS supports it and the machine is fast enough). |
|
|
1665 | |
556 | =item * manual reschedule mode (reschedule_cb = callback) |
1666 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
557 | |
1667 | |
558 | In this mode the values for C<interval> and C<at> are both being |
1668 | 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 |
1669 | ignored. Instead, each time the periodic watcher gets scheduled, the |
560 | reschedule callback will be called with the watcher as first, and the |
1670 | reschedule callback will be called with the watcher as first, and the |
561 | current time as second argument. |
1671 | current time as second argument. |
562 | |
1672 | |
563 | NOTE: I<This callback MUST NOT stop or destroy the periodic or any other |
1673 | 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 |
1674 | ever, or make ANY event loop modifications whatsoever>. |
|
|
1675 | |
565 | to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards. |
1676 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
1677 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
1678 | only event loop modification you are allowed to do). |
566 | |
1679 | |
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, |
1680 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
571 | ev_tstamp now)>, e.g.: |
1681 | *w, ev_tstamp now)>, e.g.: |
572 | |
1682 | |
|
|
1683 | static ev_tstamp |
573 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1684 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
574 | { |
1685 | { |
575 | return now + 60.; |
1686 | return now + 60.; |
576 | } |
1687 | } |
577 | |
1688 | |
578 | It must return the next time to trigger, based on the passed time value |
1689 | 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 |
1690 | (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 |
1691 | will usually be called just before the callback will be triggered, but |
581 | might be called at other times, too. |
1692 | might be called at other times, too. |
582 | |
1693 | |
|
|
1694 | NOTE: I<< This callback must always return a time that is higher than or |
|
|
1695 | equal to the passed C<now> value >>. |
|
|
1696 | |
583 | This can be used to create very complex timers, such as a timer that |
1697 | 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 |
1698 | 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 |
1699 | next midnight after C<now> and return the timestamp value for this. How |
586 | is, again, up to you (but it is not trivial). |
1700 | you do this is, again, up to you (but it is not trivial, which is the main |
|
|
1701 | reason I omitted it as an example). |
587 | |
1702 | |
588 | =back |
1703 | =back |
589 | |
1704 | |
590 | =item ev_periodic_again (loop, ev_periodic *) |
1705 | =item ev_periodic_again (loop, ev_periodic *) |
591 | |
1706 | |
592 | Simply stops and restarts the periodic watcher again. This is only useful |
1707 | Simply stops and restarts the periodic watcher again. This is only useful |
593 | when you changed some parameters or the reschedule callback would return |
1708 | 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 |
1709 | a different time than the last time it was called (e.g. in a crond like |
595 | program when the crontabs have changed). |
1710 | program when the crontabs have changed). |
596 | |
1711 | |
|
|
1712 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
1713 | |
|
|
1714 | When active, returns the absolute time that the watcher is supposed to |
|
|
1715 | trigger next. |
|
|
1716 | |
|
|
1717 | =item ev_tstamp offset [read-write] |
|
|
1718 | |
|
|
1719 | When repeating, this contains the offset value, otherwise this is the |
|
|
1720 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
|
|
1721 | |
|
|
1722 | Can be modified any time, but changes only take effect when the periodic |
|
|
1723 | timer fires or C<ev_periodic_again> is being called. |
|
|
1724 | |
|
|
1725 | =item ev_tstamp interval [read-write] |
|
|
1726 | |
|
|
1727 | The current interval value. Can be modified any time, but changes only |
|
|
1728 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
|
|
1729 | called. |
|
|
1730 | |
|
|
1731 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
|
|
1732 | |
|
|
1733 | The current reschedule callback, or C<0>, if this functionality is |
|
|
1734 | switched off. Can be changed any time, but changes only take effect when |
|
|
1735 | the periodic timer fires or C<ev_periodic_again> is being called. |
|
|
1736 | |
597 | =back |
1737 | =back |
598 | |
1738 | |
|
|
1739 | =head3 Examples |
|
|
1740 | |
|
|
1741 | Example: Call a callback every hour, or, more precisely, whenever the |
|
|
1742 | system time is divisible by 3600. The callback invocation times have |
|
|
1743 | potentially a lot of jitter, but good long-term stability. |
|
|
1744 | |
|
|
1745 | static void |
|
|
1746 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
|
|
1747 | { |
|
|
1748 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
|
|
1749 | } |
|
|
1750 | |
|
|
1751 | ev_periodic hourly_tick; |
|
|
1752 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
|
|
1753 | ev_periodic_start (loop, &hourly_tick); |
|
|
1754 | |
|
|
1755 | Example: The same as above, but use a reschedule callback to do it: |
|
|
1756 | |
|
|
1757 | #include <math.h> |
|
|
1758 | |
|
|
1759 | static ev_tstamp |
|
|
1760 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
|
|
1761 | { |
|
|
1762 | return now + (3600. - fmod (now, 3600.)); |
|
|
1763 | } |
|
|
1764 | |
|
|
1765 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
|
|
1766 | |
|
|
1767 | Example: Call a callback every hour, starting now: |
|
|
1768 | |
|
|
1769 | ev_periodic hourly_tick; |
|
|
1770 | ev_periodic_init (&hourly_tick, clock_cb, |
|
|
1771 | fmod (ev_now (loop), 3600.), 3600., 0); |
|
|
1772 | ev_periodic_start (loop, &hourly_tick); |
|
|
1773 | |
|
|
1774 | |
599 | =head2 C<ev_signal> - signal me when a signal gets signalled |
1775 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
600 | |
1776 | |
601 | Signal watchers will trigger an event when the process receives a specific |
1777 | 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 |
1778 | 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 |
1779 | will try it's best to deliver signals synchronously, i.e. as part of the |
604 | normal event processing, like any other event. |
1780 | normal event processing, like any other event. |
605 | |
1781 | |
|
|
1782 | If you want signals asynchronously, just use C<sigaction> as you would |
|
|
1783 | do without libev and forget about sharing the signal. You can even use |
|
|
1784 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
|
|
1785 | |
606 | You cna configure as many watchers as you like per signal. Only when the |
1786 | 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 |
1787 | first watcher gets started will libev actually register a signal handler |
608 | with the kernel (thus it coexists with your own signal handlers as long |
1788 | with the kernel (thus it coexists with your own signal handlers as long as |
609 | as you don't register any with libev). Similarly, when the last signal |
1789 | you don't register any with libev for the same signal). Similarly, when |
610 | watcher for a signal is stopped libev will reset the signal handler to |
1790 | the last signal watcher for a signal is stopped, libev will reset the |
611 | SIG_DFL (regardless of what it was set to before). |
1791 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1792 | |
|
|
1793 | If possible and supported, libev will install its handlers with |
|
|
1794 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
|
|
1795 | interrupted. If you have a problem with system calls getting interrupted by |
|
|
1796 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1797 | them in an C<ev_prepare> watcher. |
|
|
1798 | |
|
|
1799 | =head3 Watcher-Specific Functions and Data Members |
612 | |
1800 | |
613 | =over 4 |
1801 | =over 4 |
614 | |
1802 | |
615 | =item ev_signal_init (ev_signal *, callback, int signum) |
1803 | =item ev_signal_init (ev_signal *, callback, int signum) |
616 | |
1804 | |
617 | =item ev_signal_set (ev_signal *, int signum) |
1805 | =item ev_signal_set (ev_signal *, int signum) |
618 | |
1806 | |
619 | Configures the watcher to trigger on the given signal number (usually one |
1807 | Configures the watcher to trigger on the given signal number (usually one |
620 | of the C<SIGxxx> constants). |
1808 | of the C<SIGxxx> constants). |
621 | |
1809 | |
|
|
1810 | =item int signum [read-only] |
|
|
1811 | |
|
|
1812 | The signal the watcher watches out for. |
|
|
1813 | |
622 | =back |
1814 | =back |
623 | |
1815 | |
|
|
1816 | =head3 Examples |
|
|
1817 | |
|
|
1818 | Example: Try to exit cleanly on SIGINT. |
|
|
1819 | |
|
|
1820 | static void |
|
|
1821 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
|
|
1822 | { |
|
|
1823 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1824 | } |
|
|
1825 | |
|
|
1826 | ev_signal signal_watcher; |
|
|
1827 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1828 | ev_signal_start (loop, &signal_watcher); |
|
|
1829 | |
|
|
1830 | |
624 | =head2 C<ev_child> - wait for pid status changes |
1831 | =head2 C<ev_child> - watch out for process status changes |
625 | |
1832 | |
626 | Child watchers trigger when your process receives a SIGCHLD in response to |
1833 | 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). |
1834 | some child status changes (most typically when a child of yours dies or |
|
|
1835 | exits). It is permissible to install a child watcher I<after> the child |
|
|
1836 | has been forked (which implies it might have already exited), as long |
|
|
1837 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
1838 | forking and then immediately registering a watcher for the child is fine, |
|
|
1839 | but forking and registering a watcher a few event loop iterations later is |
|
|
1840 | not. |
|
|
1841 | |
|
|
1842 | Only the default event loop is capable of handling signals, and therefore |
|
|
1843 | you can only register child watchers in the default event loop. |
|
|
1844 | |
|
|
1845 | =head3 Process Interaction |
|
|
1846 | |
|
|
1847 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
1848 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
1849 | the first child watcher is started after the child exits. The occurrence |
|
|
1850 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
1851 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
1852 | children, even ones not watched. |
|
|
1853 | |
|
|
1854 | =head3 Overriding the Built-In Processing |
|
|
1855 | |
|
|
1856 | Libev offers no special support for overriding the built-in child |
|
|
1857 | processing, but if your application collides with libev's default child |
|
|
1858 | handler, you can override it easily by installing your own handler for |
|
|
1859 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
1860 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
1861 | event-based approach to child reaping and thus use libev's support for |
|
|
1862 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
1863 | |
|
|
1864 | =head3 Stopping the Child Watcher |
|
|
1865 | |
|
|
1866 | Currently, the child watcher never gets stopped, even when the |
|
|
1867 | child terminates, so normally one needs to stop the watcher in the |
|
|
1868 | callback. Future versions of libev might stop the watcher automatically |
|
|
1869 | when a child exit is detected. |
|
|
1870 | |
|
|
1871 | =head3 Watcher-Specific Functions and Data Members |
628 | |
1872 | |
629 | =over 4 |
1873 | =over 4 |
630 | |
1874 | |
631 | =item ev_child_init (ev_child *, callback, int pid) |
1875 | =item ev_child_init (ev_child *, callback, int pid, int trace) |
632 | |
1876 | |
633 | =item ev_child_set (ev_child *, int pid) |
1877 | =item ev_child_set (ev_child *, int pid, int trace) |
634 | |
1878 | |
635 | Configures the watcher to wait for status changes of process C<pid> (or |
1879 | 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 |
1880 | 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 |
1881 | 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 |
1882 | 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. |
1883 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
|
|
1884 | process causing the status change. C<trace> must be either C<0> (only |
|
|
1885 | activate the watcher when the process terminates) or C<1> (additionally |
|
|
1886 | activate the watcher when the process is stopped or continued). |
|
|
1887 | |
|
|
1888 | =item int pid [read-only] |
|
|
1889 | |
|
|
1890 | The process id this watcher watches out for, or C<0>, meaning any process id. |
|
|
1891 | |
|
|
1892 | =item int rpid [read-write] |
|
|
1893 | |
|
|
1894 | The process id that detected a status change. |
|
|
1895 | |
|
|
1896 | =item int rstatus [read-write] |
|
|
1897 | |
|
|
1898 | The process exit/trace status caused by C<rpid> (see your systems |
|
|
1899 | C<waitpid> and C<sys/wait.h> documentation for details). |
640 | |
1900 | |
641 | =back |
1901 | =back |
642 | |
1902 | |
|
|
1903 | =head3 Examples |
|
|
1904 | |
|
|
1905 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
1906 | its completion. |
|
|
1907 | |
|
|
1908 | ev_child cw; |
|
|
1909 | |
|
|
1910 | static void |
|
|
1911 | child_cb (EV_P_ ev_child *w, int revents) |
|
|
1912 | { |
|
|
1913 | ev_child_stop (EV_A_ w); |
|
|
1914 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
|
|
1915 | } |
|
|
1916 | |
|
|
1917 | pid_t pid = fork (); |
|
|
1918 | |
|
|
1919 | if (pid < 0) |
|
|
1920 | // error |
|
|
1921 | else if (pid == 0) |
|
|
1922 | { |
|
|
1923 | // the forked child executes here |
|
|
1924 | exit (1); |
|
|
1925 | } |
|
|
1926 | else |
|
|
1927 | { |
|
|
1928 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
1929 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
1930 | } |
|
|
1931 | |
|
|
1932 | |
|
|
1933 | =head2 C<ev_stat> - did the file attributes just change? |
|
|
1934 | |
|
|
1935 | This watches a file system path for attribute changes. That is, it calls |
|
|
1936 | C<stat> on that path in regular intervals (or when the OS says it changed) |
|
|
1937 | and sees if it changed compared to the last time, invoking the callback if |
|
|
1938 | it did. |
|
|
1939 | |
|
|
1940 | The path does not need to exist: changing from "path exists" to "path does |
|
|
1941 | not exist" is a status change like any other. The condition "path does not |
|
|
1942 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
|
|
1943 | C<st_nlink> field being zero (which is otherwise always forced to be at |
|
|
1944 | least one) and all the other fields of the stat buffer having unspecified |
|
|
1945 | contents. |
|
|
1946 | |
|
|
1947 | The path I<must not> end in a slash or contain special components such as |
|
|
1948 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
|
|
1949 | your working directory changes, then the behaviour is undefined. |
|
|
1950 | |
|
|
1951 | Since there is no portable change notification interface available, the |
|
|
1952 | portable implementation simply calls C<stat(2)> regularly on the path |
|
|
1953 | to see if it changed somehow. You can specify a recommended polling |
|
|
1954 | interval for this case. If you specify a polling interval of C<0> (highly |
|
|
1955 | recommended!) then a I<suitable, unspecified default> value will be used |
|
|
1956 | (which you can expect to be around five seconds, although this might |
|
|
1957 | change dynamically). Libev will also impose a minimum interval which is |
|
|
1958 | currently around C<0.1>, but that's usually overkill. |
|
|
1959 | |
|
|
1960 | This watcher type is not meant for massive numbers of stat watchers, |
|
|
1961 | as even with OS-supported change notifications, this can be |
|
|
1962 | resource-intensive. |
|
|
1963 | |
|
|
1964 | At the time of this writing, the only OS-specific interface implemented |
|
|
1965 | is the Linux inotify interface (implementing kqueue support is left as an |
|
|
1966 | exercise for the reader. Note, however, that the author sees no way of |
|
|
1967 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
|
|
1968 | |
|
|
1969 | =head3 ABI Issues (Largefile Support) |
|
|
1970 | |
|
|
1971 | Libev by default (unless the user overrides this) uses the default |
|
|
1972 | compilation environment, which means that on systems with large file |
|
|
1973 | support disabled by default, you get the 32 bit version of the stat |
|
|
1974 | structure. When using the library from programs that change the ABI to |
|
|
1975 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
1976 | compile libev with the same flags to get binary compatibility. This is |
|
|
1977 | obviously the case with any flags that change the ABI, but the problem is |
|
|
1978 | most noticeably displayed with ev_stat and large file support. |
|
|
1979 | |
|
|
1980 | The solution for this is to lobby your distribution maker to make large |
|
|
1981 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
1982 | optional. Libev cannot simply switch on large file support because it has |
|
|
1983 | to exchange stat structures with application programs compiled using the |
|
|
1984 | default compilation environment. |
|
|
1985 | |
|
|
1986 | =head3 Inotify and Kqueue |
|
|
1987 | |
|
|
1988 | When C<inotify (7)> support has been compiled into libev and present at |
|
|
1989 | runtime, it will be used to speed up change detection where possible. The |
|
|
1990 | inotify descriptor will be created lazily when the first C<ev_stat> |
|
|
1991 | watcher is being started. |
|
|
1992 | |
|
|
1993 | Inotify presence does not change the semantics of C<ev_stat> watchers |
|
|
1994 | except that changes might be detected earlier, and in some cases, to avoid |
|
|
1995 | making regular C<stat> calls. Even in the presence of inotify support |
|
|
1996 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
1997 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
1998 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
1999 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2000 | xfs are fully working) libev usually gets away without polling. |
|
|
2001 | |
|
|
2002 | There is no support for kqueue, as apparently it cannot be used to |
|
|
2003 | implement this functionality, due to the requirement of having a file |
|
|
2004 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2005 | etc. is difficult. |
|
|
2006 | |
|
|
2007 | =head3 C<stat ()> is a synchronous operation |
|
|
2008 | |
|
|
2009 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2010 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2011 | ()>, which is a synchronous operation. |
|
|
2012 | |
|
|
2013 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2014 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2015 | as the path data is suually in memory already (except when starting the |
|
|
2016 | watcher). |
|
|
2017 | |
|
|
2018 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2019 | time due to network issues, and even under good conditions, a stat call |
|
|
2020 | often takes multiple milliseconds. |
|
|
2021 | |
|
|
2022 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2023 | paths, although this is fully supported by libev. |
|
|
2024 | |
|
|
2025 | =head3 The special problem of stat time resolution |
|
|
2026 | |
|
|
2027 | The C<stat ()> system call only supports full-second resolution portably, |
|
|
2028 | and even on systems where the resolution is higher, most file systems |
|
|
2029 | still only support whole seconds. |
|
|
2030 | |
|
|
2031 | That means that, if the time is the only thing that changes, you can |
|
|
2032 | easily miss updates: on the first update, C<ev_stat> detects a change and |
|
|
2033 | calls your callback, which does something. When there is another update |
|
|
2034 | within the same second, C<ev_stat> will be unable to detect unless the |
|
|
2035 | stat data does change in other ways (e.g. file size). |
|
|
2036 | |
|
|
2037 | The solution to this is to delay acting on a change for slightly more |
|
|
2038 | than a second (or till slightly after the next full second boundary), using |
|
|
2039 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
|
|
2040 | ev_timer_again (loop, w)>). |
|
|
2041 | |
|
|
2042 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
2043 | of some operating systems (where the second counter of the current time |
|
|
2044 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
2045 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
2046 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
2047 | update file times then there will be a small window where the kernel uses |
|
|
2048 | the previous second to update file times but libev might already execute |
|
|
2049 | the timer callback). |
|
|
2050 | |
|
|
2051 | =head3 Watcher-Specific Functions and Data Members |
|
|
2052 | |
|
|
2053 | =over 4 |
|
|
2054 | |
|
|
2055 | =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) |
|
|
2056 | |
|
|
2057 | =item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval) |
|
|
2058 | |
|
|
2059 | Configures the watcher to wait for status changes of the given |
|
|
2060 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
|
|
2061 | be detected and should normally be specified as C<0> to let libev choose |
|
|
2062 | a suitable value. The memory pointed to by C<path> must point to the same |
|
|
2063 | path for as long as the watcher is active. |
|
|
2064 | |
|
|
2065 | The callback will receive an C<EV_STAT> event when a change was detected, |
|
|
2066 | relative to the attributes at the time the watcher was started (or the |
|
|
2067 | last change was detected). |
|
|
2068 | |
|
|
2069 | =item ev_stat_stat (loop, ev_stat *) |
|
|
2070 | |
|
|
2071 | Updates the stat buffer immediately with new values. If you change the |
|
|
2072 | watched path in your callback, you could call this function to avoid |
|
|
2073 | detecting this change (while introducing a race condition if you are not |
|
|
2074 | the only one changing the path). Can also be useful simply to find out the |
|
|
2075 | new values. |
|
|
2076 | |
|
|
2077 | =item ev_statdata attr [read-only] |
|
|
2078 | |
|
|
2079 | The most-recently detected attributes of the file. Although the type is |
|
|
2080 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
|
|
2081 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
2082 | members to be present. If the C<st_nlink> member is C<0>, then there was |
|
|
2083 | some error while C<stat>ing the file. |
|
|
2084 | |
|
|
2085 | =item ev_statdata prev [read-only] |
|
|
2086 | |
|
|
2087 | The previous attributes of the file. The callback gets invoked whenever |
|
|
2088 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
2089 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
2090 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
|
|
2091 | |
|
|
2092 | =item ev_tstamp interval [read-only] |
|
|
2093 | |
|
|
2094 | The specified interval. |
|
|
2095 | |
|
|
2096 | =item const char *path [read-only] |
|
|
2097 | |
|
|
2098 | The file system path that is being watched. |
|
|
2099 | |
|
|
2100 | =back |
|
|
2101 | |
|
|
2102 | =head3 Examples |
|
|
2103 | |
|
|
2104 | Example: Watch C</etc/passwd> for attribute changes. |
|
|
2105 | |
|
|
2106 | static void |
|
|
2107 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
|
|
2108 | { |
|
|
2109 | /* /etc/passwd changed in some way */ |
|
|
2110 | if (w->attr.st_nlink) |
|
|
2111 | { |
|
|
2112 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
|
|
2113 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
|
|
2114 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
|
|
2115 | } |
|
|
2116 | else |
|
|
2117 | /* you shalt not abuse printf for puts */ |
|
|
2118 | puts ("wow, /etc/passwd is not there, expect problems. " |
|
|
2119 | "if this is windows, they already arrived\n"); |
|
|
2120 | } |
|
|
2121 | |
|
|
2122 | ... |
|
|
2123 | ev_stat passwd; |
|
|
2124 | |
|
|
2125 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
|
|
2126 | ev_stat_start (loop, &passwd); |
|
|
2127 | |
|
|
2128 | Example: Like above, but additionally use a one-second delay so we do not |
|
|
2129 | miss updates (however, frequent updates will delay processing, too, so |
|
|
2130 | one might do the work both on C<ev_stat> callback invocation I<and> on |
|
|
2131 | C<ev_timer> callback invocation). |
|
|
2132 | |
|
|
2133 | static ev_stat passwd; |
|
|
2134 | static ev_timer timer; |
|
|
2135 | |
|
|
2136 | static void |
|
|
2137 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2138 | { |
|
|
2139 | ev_timer_stop (EV_A_ w); |
|
|
2140 | |
|
|
2141 | /* now it's one second after the most recent passwd change */ |
|
|
2142 | } |
|
|
2143 | |
|
|
2144 | static void |
|
|
2145 | stat_cb (EV_P_ ev_stat *w, int revents) |
|
|
2146 | { |
|
|
2147 | /* reset the one-second timer */ |
|
|
2148 | ev_timer_again (EV_A_ &timer); |
|
|
2149 | } |
|
|
2150 | |
|
|
2151 | ... |
|
|
2152 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
|
|
2153 | ev_stat_start (loop, &passwd); |
|
|
2154 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
|
|
2155 | |
|
|
2156 | |
643 | =head2 C<ev_idle> - when you've got nothing better to do |
2157 | =head2 C<ev_idle> - when you've got nothing better to do... |
644 | |
2158 | |
645 | Idle watchers trigger events when there are no other I/O or timer (or |
2159 | 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 |
2160 | priority are pending (prepare, check and other idle watchers do not count |
647 | handling sockets or timeouts it will not be called. But when your process |
2161 | as receiving "events"). |
648 | is idle all idle watchers are being called again and again - until |
2162 | |
|
|
2163 | That is, as long as your process is busy handling sockets or timeouts |
|
|
2164 | (or even signals, imagine) of the same or higher priority it will not be |
|
|
2165 | triggered. But when your process is idle (or only lower-priority watchers |
|
|
2166 | are pending), the idle watchers are being called once per event loop |
649 | stopped, that is, or your process receives more events. |
2167 | iteration - until stopped, that is, or your process receives more events |
|
|
2168 | and becomes busy again with higher priority stuff. |
650 | |
2169 | |
651 | The most noteworthy effect is that as long as any idle watchers are |
2170 | 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. |
2171 | active, the process will not block when waiting for new events. |
653 | |
2172 | |
654 | Apart from keeping your process non-blocking (which is a useful |
2173 | 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 |
2174 | effect on its own sometimes), idle watchers are a good place to do |
656 | "pseudo-background processing", or delay processing stuff to after the |
2175 | "pseudo-background processing", or delay processing stuff to after the |
657 | event loop has handled all outstanding events. |
2176 | event loop has handled all outstanding events. |
658 | |
2177 | |
|
|
2178 | =head3 Watcher-Specific Functions and Data Members |
|
|
2179 | |
659 | =over 4 |
2180 | =over 4 |
660 | |
2181 | |
661 | =item ev_idle_init (ev_signal *, callback) |
2182 | =item ev_idle_init (ev_signal *, callback) |
662 | |
2183 | |
663 | Initialises and configures the idle watcher - it has no parameters of any |
2184 | 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, |
2185 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
665 | believe me. |
2186 | believe me. |
666 | |
2187 | |
667 | =back |
2188 | =back |
668 | |
2189 | |
669 | =head2 prepare and check - your hooks into the event loop |
2190 | =head3 Examples |
670 | |
2191 | |
|
|
2192 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
|
|
2193 | callback, free it. Also, use no error checking, as usual. |
|
|
2194 | |
|
|
2195 | static void |
|
|
2196 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
|
|
2197 | { |
|
|
2198 | free (w); |
|
|
2199 | // now do something you wanted to do when the program has |
|
|
2200 | // no longer anything immediate to do. |
|
|
2201 | } |
|
|
2202 | |
|
|
2203 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
|
|
2204 | ev_idle_init (idle_watcher, idle_cb); |
|
|
2205 | ev_idle_start (loop, idle_cb); |
|
|
2206 | |
|
|
2207 | |
|
|
2208 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
|
|
2209 | |
671 | Prepare and check watchers usually (but not always) are used in |
2210 | Prepare and check watchers are usually (but not always) used in pairs: |
672 | tandom. Prepare watchers get invoked before the process blocks and check |
2211 | prepare watchers get invoked before the process blocks and check watchers |
673 | watchers afterwards. |
2212 | afterwards. |
674 | |
2213 | |
|
|
2214 | You I<must not> call C<ev_loop> or similar functions that enter |
|
|
2215 | the current event loop from either C<ev_prepare> or C<ev_check> |
|
|
2216 | watchers. Other loops than the current one are fine, however. The |
|
|
2217 | rationale behind this is that you do not need to check for recursion in |
|
|
2218 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
|
|
2219 | C<ev_check> so if you have one watcher of each kind they will always be |
|
|
2220 | called in pairs bracketing the blocking call. |
|
|
2221 | |
675 | Their main purpose is to integrate other event mechanisms into libev. This |
2222 | 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 |
2223 | their use is somewhat advanced. They could be used, for example, to track |
677 | watchers, integrate net-snmp or a coroutine library and lots more. |
2224 | variable changes, implement your own watchers, integrate net-snmp or a |
|
|
2225 | coroutine library and lots more. They are also occasionally useful if |
|
|
2226 | you cache some data and want to flush it before blocking (for example, |
|
|
2227 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
|
|
2228 | watcher). |
678 | |
2229 | |
679 | This is done by examining in each prepare call which file descriptors need |
2230 | This is done by examining in each prepare call which file descriptors |
680 | to be watched by the other library, registering C<ev_io> watchers for them |
2231 | need to be watched by the other library, registering C<ev_io> watchers |
681 | and starting an C<ev_timer> watcher for any timeouts (many libraries provide |
2232 | for them and starting an C<ev_timer> watcher for any timeouts (many |
682 | just this functionality). Then, in the check watcher you check for any |
2233 | libraries provide exactly this functionality). Then, in the check watcher, |
683 | events that occured (by making your callbacks set soem flags for example) |
2234 | you check for any events that occurred (by checking the pending status |
684 | and call back into the library. |
2235 | of all watchers and stopping them) and call back into the library. The |
|
|
2236 | I/O and timer callbacks will never actually be called (but must be valid |
|
|
2237 | nevertheless, because you never know, you know?). |
685 | |
2238 | |
686 | As another example, the perl Coro module uses these hooks to integrate |
2239 | As another example, the Perl Coro module uses these hooks to integrate |
687 | coroutines into libev programs, by yielding to other active coroutines |
2240 | coroutines into libev programs, by yielding to other active coroutines |
688 | during each prepare and only letting the process block if no coroutines |
2241 | during each prepare and only letting the process block if no coroutines |
689 | are ready to run. |
2242 | are ready to run (it's actually more complicated: it only runs coroutines |
|
|
2243 | with priority higher than or equal to the event loop and one coroutine |
|
|
2244 | of lower priority, but only once, using idle watchers to keep the event |
|
|
2245 | loop from blocking if lower-priority coroutines are active, thus mapping |
|
|
2246 | low-priority coroutines to idle/background tasks). |
|
|
2247 | |
|
|
2248 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
|
|
2249 | priority, to ensure that they are being run before any other watchers |
|
|
2250 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2251 | |
|
|
2252 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
|
|
2253 | activate ("feed") events into libev. While libev fully supports this, they |
|
|
2254 | might get executed before other C<ev_check> watchers did their job. As |
|
|
2255 | C<ev_check> watchers are often used to embed other (non-libev) event |
|
|
2256 | loops those other event loops might be in an unusable state until their |
|
|
2257 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
|
|
2258 | others). |
|
|
2259 | |
|
|
2260 | =head3 Watcher-Specific Functions and Data Members |
690 | |
2261 | |
691 | =over 4 |
2262 | =over 4 |
692 | |
2263 | |
693 | =item ev_prepare_init (ev_prepare *, callback) |
2264 | =item ev_prepare_init (ev_prepare *, callback) |
694 | |
2265 | |
695 | =item ev_check_init (ev_check *, callback) |
2266 | =item ev_check_init (ev_check *, callback) |
696 | |
2267 | |
697 | Initialises and configures the prepare or check watcher - they have no |
2268 | 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> |
2269 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
699 | macros, but using them is utterly, utterly pointless. |
2270 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2271 | pointless. |
700 | |
2272 | |
701 | =back |
2273 | =back |
702 | |
2274 | |
|
|
2275 | =head3 Examples |
|
|
2276 | |
|
|
2277 | There are a number of principal ways to embed other event loops or modules |
|
|
2278 | into libev. Here are some ideas on how to include libadns into libev |
|
|
2279 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
|
|
2280 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
|
|
2281 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
|
|
2282 | Glib event loop). |
|
|
2283 | |
|
|
2284 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
|
|
2285 | and in a check watcher, destroy them and call into libadns. What follows |
|
|
2286 | is pseudo-code only of course. This requires you to either use a low |
|
|
2287 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
|
|
2288 | the callbacks for the IO/timeout watchers might not have been called yet. |
|
|
2289 | |
|
|
2290 | static ev_io iow [nfd]; |
|
|
2291 | static ev_timer tw; |
|
|
2292 | |
|
|
2293 | static void |
|
|
2294 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
|
|
2295 | { |
|
|
2296 | } |
|
|
2297 | |
|
|
2298 | // create io watchers for each fd and a timer before blocking |
|
|
2299 | static void |
|
|
2300 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
|
|
2301 | { |
|
|
2302 | int timeout = 3600000; |
|
|
2303 | struct pollfd fds [nfd]; |
|
|
2304 | // actual code will need to loop here and realloc etc. |
|
|
2305 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
|
|
2306 | |
|
|
2307 | /* the callback is illegal, but won't be called as we stop during check */ |
|
|
2308 | ev_timer_init (&tw, 0, timeout * 1e-3); |
|
|
2309 | ev_timer_start (loop, &tw); |
|
|
2310 | |
|
|
2311 | // create one ev_io per pollfd |
|
|
2312 | for (int i = 0; i < nfd; ++i) |
|
|
2313 | { |
|
|
2314 | ev_io_init (iow + i, io_cb, fds [i].fd, |
|
|
2315 | ((fds [i].events & POLLIN ? EV_READ : 0) |
|
|
2316 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
|
|
2317 | |
|
|
2318 | fds [i].revents = 0; |
|
|
2319 | ev_io_start (loop, iow + i); |
|
|
2320 | } |
|
|
2321 | } |
|
|
2322 | |
|
|
2323 | // stop all watchers after blocking |
|
|
2324 | static void |
|
|
2325 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
|
|
2326 | { |
|
|
2327 | ev_timer_stop (loop, &tw); |
|
|
2328 | |
|
|
2329 | for (int i = 0; i < nfd; ++i) |
|
|
2330 | { |
|
|
2331 | // set the relevant poll flags |
|
|
2332 | // could also call adns_processreadable etc. here |
|
|
2333 | struct pollfd *fd = fds + i; |
|
|
2334 | int revents = ev_clear_pending (iow + i); |
|
|
2335 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
2336 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
2337 | |
|
|
2338 | // now stop the watcher |
|
|
2339 | ev_io_stop (loop, iow + i); |
|
|
2340 | } |
|
|
2341 | |
|
|
2342 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
2343 | } |
|
|
2344 | |
|
|
2345 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
|
|
2346 | in the prepare watcher and would dispose of the check watcher. |
|
|
2347 | |
|
|
2348 | Method 3: If the module to be embedded supports explicit event |
|
|
2349 | notification (libadns does), you can also make use of the actual watcher |
|
|
2350 | callbacks, and only destroy/create the watchers in the prepare watcher. |
|
|
2351 | |
|
|
2352 | static void |
|
|
2353 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2354 | { |
|
|
2355 | adns_state ads = (adns_state)w->data; |
|
|
2356 | update_now (EV_A); |
|
|
2357 | |
|
|
2358 | adns_processtimeouts (ads, &tv_now); |
|
|
2359 | } |
|
|
2360 | |
|
|
2361 | static void |
|
|
2362 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
2363 | { |
|
|
2364 | adns_state ads = (adns_state)w->data; |
|
|
2365 | update_now (EV_A); |
|
|
2366 | |
|
|
2367 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
|
|
2368 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
|
|
2369 | } |
|
|
2370 | |
|
|
2371 | // do not ever call adns_afterpoll |
|
|
2372 | |
|
|
2373 | Method 4: Do not use a prepare or check watcher because the module you |
|
|
2374 | want to embed is not flexible enough to support it. Instead, you can |
|
|
2375 | override their poll function. The drawback with this solution is that the |
|
|
2376 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
|
|
2377 | this approach, effectively embedding EV as a client into the horrible |
|
|
2378 | libglib event loop. |
|
|
2379 | |
|
|
2380 | static gint |
|
|
2381 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
2382 | { |
|
|
2383 | int got_events = 0; |
|
|
2384 | |
|
|
2385 | for (n = 0; n < nfds; ++n) |
|
|
2386 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
2387 | |
|
|
2388 | if (timeout >= 0) |
|
|
2389 | // create/start timer |
|
|
2390 | |
|
|
2391 | // poll |
|
|
2392 | ev_loop (EV_A_ 0); |
|
|
2393 | |
|
|
2394 | // stop timer again |
|
|
2395 | if (timeout >= 0) |
|
|
2396 | ev_timer_stop (EV_A_ &to); |
|
|
2397 | |
|
|
2398 | // stop io watchers again - their callbacks should have set |
|
|
2399 | for (n = 0; n < nfds; ++n) |
|
|
2400 | ev_io_stop (EV_A_ iow [n]); |
|
|
2401 | |
|
|
2402 | return got_events; |
|
|
2403 | } |
|
|
2404 | |
|
|
2405 | |
|
|
2406 | =head2 C<ev_embed> - when one backend isn't enough... |
|
|
2407 | |
|
|
2408 | This is a rather advanced watcher type that lets you embed one event loop |
|
|
2409 | into another (currently only C<ev_io> events are supported in the embedded |
|
|
2410 | loop, other types of watchers might be handled in a delayed or incorrect |
|
|
2411 | fashion and must not be used). |
|
|
2412 | |
|
|
2413 | There are primarily two reasons you would want that: work around bugs and |
|
|
2414 | prioritise I/O. |
|
|
2415 | |
|
|
2416 | As an example for a bug workaround, the kqueue backend might only support |
|
|
2417 | sockets on some platform, so it is unusable as generic backend, but you |
|
|
2418 | still want to make use of it because you have many sockets and it scales |
|
|
2419 | so nicely. In this case, you would create a kqueue-based loop and embed |
|
|
2420 | it into your default loop (which might use e.g. poll). Overall operation |
|
|
2421 | will be a bit slower because first libev has to call C<poll> and then |
|
|
2422 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2423 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
|
|
2424 | |
|
|
2425 | As for prioritising I/O: under rare circumstances you have the case where |
|
|
2426 | some fds have to be watched and handled very quickly (with low latency), |
|
|
2427 | and even priorities and idle watchers might have too much overhead. In |
|
|
2428 | this case you would put all the high priority stuff in one loop and all |
|
|
2429 | the rest in a second one, and embed the second one in the first. |
|
|
2430 | |
|
|
2431 | As long as the watcher is active, the callback will be invoked every time |
|
|
2432 | there might be events pending in the embedded loop. The callback must then |
|
|
2433 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
|
|
2434 | their callbacks (you could also start an idle watcher to give the embedded |
|
|
2435 | loop strictly lower priority for example). You can also set the callback |
|
|
2436 | to C<0>, in which case the embed watcher will automatically execute the |
|
|
2437 | embedded loop sweep. |
|
|
2438 | |
|
|
2439 | As long as the watcher is started it will automatically handle events. The |
|
|
2440 | callback will be invoked whenever some events have been handled. You can |
|
|
2441 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2442 | interested in that. |
|
|
2443 | |
|
|
2444 | Also, there have not currently been made special provisions for forking: |
|
|
2445 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
|
|
2446 | but you will also have to stop and restart any C<ev_embed> watchers |
|
|
2447 | yourself - but you can use a fork watcher to handle this automatically, |
|
|
2448 | and future versions of libev might do just that. |
|
|
2449 | |
|
|
2450 | Unfortunately, not all backends are embeddable: only the ones returned by |
|
|
2451 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
|
|
2452 | portable one. |
|
|
2453 | |
|
|
2454 | So when you want to use this feature you will always have to be prepared |
|
|
2455 | that you cannot get an embeddable loop. The recommended way to get around |
|
|
2456 | this is to have a separate variables for your embeddable loop, try to |
|
|
2457 | create it, and if that fails, use the normal loop for everything. |
|
|
2458 | |
|
|
2459 | =head3 C<ev_embed> and fork |
|
|
2460 | |
|
|
2461 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2462 | automatically be applied to the embedded loop as well, so no special |
|
|
2463 | fork handling is required in that case. When the watcher is not running, |
|
|
2464 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2465 | as applicable. |
|
|
2466 | |
|
|
2467 | =head3 Watcher-Specific Functions and Data Members |
|
|
2468 | |
|
|
2469 | =over 4 |
|
|
2470 | |
|
|
2471 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
|
|
2472 | |
|
|
2473 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
|
|
2474 | |
|
|
2475 | Configures the watcher to embed the given loop, which must be |
|
|
2476 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
|
|
2477 | invoked automatically, otherwise it is the responsibility of the callback |
|
|
2478 | to invoke it (it will continue to be called until the sweep has been done, |
|
|
2479 | if you do not want that, you need to temporarily stop the embed watcher). |
|
|
2480 | |
|
|
2481 | =item ev_embed_sweep (loop, ev_embed *) |
|
|
2482 | |
|
|
2483 | Make a single, non-blocking sweep over the embedded loop. This works |
|
|
2484 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
|
|
2485 | appropriate way for embedded loops. |
|
|
2486 | |
|
|
2487 | =item struct ev_loop *other [read-only] |
|
|
2488 | |
|
|
2489 | The embedded event loop. |
|
|
2490 | |
|
|
2491 | =back |
|
|
2492 | |
|
|
2493 | =head3 Examples |
|
|
2494 | |
|
|
2495 | Example: Try to get an embeddable event loop and embed it into the default |
|
|
2496 | event loop. If that is not possible, use the default loop. The default |
|
|
2497 | loop is stored in C<loop_hi>, while the embeddable loop is stored in |
|
|
2498 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
|
|
2499 | used). |
|
|
2500 | |
|
|
2501 | struct ev_loop *loop_hi = ev_default_init (0); |
|
|
2502 | struct ev_loop *loop_lo = 0; |
|
|
2503 | ev_embed embed; |
|
|
2504 | |
|
|
2505 | // see if there is a chance of getting one that works |
|
|
2506 | // (remember that a flags value of 0 means autodetection) |
|
|
2507 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
2508 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
2509 | : 0; |
|
|
2510 | |
|
|
2511 | // if we got one, then embed it, otherwise default to loop_hi |
|
|
2512 | if (loop_lo) |
|
|
2513 | { |
|
|
2514 | ev_embed_init (&embed, 0, loop_lo); |
|
|
2515 | ev_embed_start (loop_hi, &embed); |
|
|
2516 | } |
|
|
2517 | else |
|
|
2518 | loop_lo = loop_hi; |
|
|
2519 | |
|
|
2520 | Example: Check if kqueue is available but not recommended and create |
|
|
2521 | a kqueue backend for use with sockets (which usually work with any |
|
|
2522 | kqueue implementation). Store the kqueue/socket-only event loop in |
|
|
2523 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
|
|
2524 | |
|
|
2525 | struct ev_loop *loop = ev_default_init (0); |
|
|
2526 | struct ev_loop *loop_socket = 0; |
|
|
2527 | ev_embed embed; |
|
|
2528 | |
|
|
2529 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
|
|
2530 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
|
|
2531 | { |
|
|
2532 | ev_embed_init (&embed, 0, loop_socket); |
|
|
2533 | ev_embed_start (loop, &embed); |
|
|
2534 | } |
|
|
2535 | |
|
|
2536 | if (!loop_socket) |
|
|
2537 | loop_socket = loop; |
|
|
2538 | |
|
|
2539 | // now use loop_socket for all sockets, and loop for everything else |
|
|
2540 | |
|
|
2541 | |
|
|
2542 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
|
|
2543 | |
|
|
2544 | Fork watchers are called when a C<fork ()> was detected (usually because |
|
|
2545 | whoever is a good citizen cared to tell libev about it by calling |
|
|
2546 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
|
|
2547 | event loop blocks next and before C<ev_check> watchers are being called, |
|
|
2548 | and only in the child after the fork. If whoever good citizen calling |
|
|
2549 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
|
|
2550 | handlers will be invoked, too, of course. |
|
|
2551 | |
|
|
2552 | =head3 Watcher-Specific Functions and Data Members |
|
|
2553 | |
|
|
2554 | =over 4 |
|
|
2555 | |
|
|
2556 | =item ev_fork_init (ev_signal *, callback) |
|
|
2557 | |
|
|
2558 | Initialises and configures the fork watcher - it has no parameters of any |
|
|
2559 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
|
|
2560 | believe me. |
|
|
2561 | |
|
|
2562 | =back |
|
|
2563 | |
|
|
2564 | |
|
|
2565 | =head2 C<ev_async> - how to wake up another event loop |
|
|
2566 | |
|
|
2567 | In general, you cannot use an C<ev_loop> from multiple threads or other |
|
|
2568 | asynchronous sources such as signal handlers (as opposed to multiple event |
|
|
2569 | loops - those are of course safe to use in different threads). |
|
|
2570 | |
|
|
2571 | Sometimes, however, you need to wake up another event loop you do not |
|
|
2572 | control, for example because it belongs to another thread. This is what |
|
|
2573 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
|
|
2574 | can signal it by calling C<ev_async_send>, which is thread- and signal |
|
|
2575 | safe. |
|
|
2576 | |
|
|
2577 | This functionality is very similar to C<ev_signal> watchers, as signals, |
|
|
2578 | too, are asynchronous in nature, and signals, too, will be compressed |
|
|
2579 | (i.e. the number of callback invocations may be less than the number of |
|
|
2580 | C<ev_async_sent> calls). |
|
|
2581 | |
|
|
2582 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
2583 | just the default loop. |
|
|
2584 | |
|
|
2585 | =head3 Queueing |
|
|
2586 | |
|
|
2587 | C<ev_async> does not support queueing of data in any way. The reason |
|
|
2588 | is that the author does not know of a simple (or any) algorithm for a |
|
|
2589 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
2590 | need elaborate support such as pthreads. |
|
|
2591 | |
|
|
2592 | That means that if you want to queue data, you have to provide your own |
|
|
2593 | queue. But at least I can tell you how to implement locking around your |
|
|
2594 | queue: |
|
|
2595 | |
|
|
2596 | =over 4 |
|
|
2597 | |
|
|
2598 | =item queueing from a signal handler context |
|
|
2599 | |
|
|
2600 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
2601 | handler but you block the signal handler in the watcher callback. Here is |
|
|
2602 | an example that does that for some fictitious SIGUSR1 handler: |
|
|
2603 | |
|
|
2604 | static ev_async mysig; |
|
|
2605 | |
|
|
2606 | static void |
|
|
2607 | sigusr1_handler (void) |
|
|
2608 | { |
|
|
2609 | sometype data; |
|
|
2610 | |
|
|
2611 | // no locking etc. |
|
|
2612 | queue_put (data); |
|
|
2613 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2614 | } |
|
|
2615 | |
|
|
2616 | static void |
|
|
2617 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2618 | { |
|
|
2619 | sometype data; |
|
|
2620 | sigset_t block, prev; |
|
|
2621 | |
|
|
2622 | sigemptyset (&block); |
|
|
2623 | sigaddset (&block, SIGUSR1); |
|
|
2624 | sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
2625 | |
|
|
2626 | while (queue_get (&data)) |
|
|
2627 | process (data); |
|
|
2628 | |
|
|
2629 | if (sigismember (&prev, SIGUSR1) |
|
|
2630 | sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
2631 | } |
|
|
2632 | |
|
|
2633 | (Note: pthreads in theory requires you to use C<pthread_setmask> |
|
|
2634 | instead of C<sigprocmask> when you use threads, but libev doesn't do it |
|
|
2635 | either...). |
|
|
2636 | |
|
|
2637 | =item queueing from a thread context |
|
|
2638 | |
|
|
2639 | The strategy for threads is different, as you cannot (easily) block |
|
|
2640 | threads but you can easily preempt them, so to queue safely you need to |
|
|
2641 | employ a traditional mutex lock, such as in this pthread example: |
|
|
2642 | |
|
|
2643 | static ev_async mysig; |
|
|
2644 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
2645 | |
|
|
2646 | static void |
|
|
2647 | otherthread (void) |
|
|
2648 | { |
|
|
2649 | // only need to lock the actual queueing operation |
|
|
2650 | pthread_mutex_lock (&mymutex); |
|
|
2651 | queue_put (data); |
|
|
2652 | pthread_mutex_unlock (&mymutex); |
|
|
2653 | |
|
|
2654 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2655 | } |
|
|
2656 | |
|
|
2657 | static void |
|
|
2658 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2659 | { |
|
|
2660 | pthread_mutex_lock (&mymutex); |
|
|
2661 | |
|
|
2662 | while (queue_get (&data)) |
|
|
2663 | process (data); |
|
|
2664 | |
|
|
2665 | pthread_mutex_unlock (&mymutex); |
|
|
2666 | } |
|
|
2667 | |
|
|
2668 | =back |
|
|
2669 | |
|
|
2670 | |
|
|
2671 | =head3 Watcher-Specific Functions and Data Members |
|
|
2672 | |
|
|
2673 | =over 4 |
|
|
2674 | |
|
|
2675 | =item ev_async_init (ev_async *, callback) |
|
|
2676 | |
|
|
2677 | Initialises and configures the async watcher - it has no parameters of any |
|
|
2678 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
|
|
2679 | trust me. |
|
|
2680 | |
|
|
2681 | =item ev_async_send (loop, ev_async *) |
|
|
2682 | |
|
|
2683 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
|
|
2684 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
|
|
2685 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
|
|
2686 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
|
|
2687 | section below on what exactly this means). |
|
|
2688 | |
|
|
2689 | This call incurs the overhead of a system call only once per loop iteration, |
|
|
2690 | so while the overhead might be noticeable, it doesn't apply to repeated |
|
|
2691 | calls to C<ev_async_send>. |
|
|
2692 | |
|
|
2693 | =item bool = ev_async_pending (ev_async *) |
|
|
2694 | |
|
|
2695 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
2696 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2697 | event loop. |
|
|
2698 | |
|
|
2699 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
2700 | the loop iterates next and checks for the watcher to have become active, |
|
|
2701 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
2702 | quickly check whether invoking the loop might be a good idea. |
|
|
2703 | |
|
|
2704 | Not that this does I<not> check whether the watcher itself is pending, only |
|
|
2705 | whether it has been requested to make this watcher pending. |
|
|
2706 | |
|
|
2707 | =back |
|
|
2708 | |
|
|
2709 | |
703 | =head1 OTHER FUNCTIONS |
2710 | =head1 OTHER FUNCTIONS |
704 | |
2711 | |
705 | There are some other fucntions of possible interest. Described. Here. Now. |
2712 | There are some other functions of possible interest. Described. Here. Now. |
706 | |
2713 | |
707 | =over 4 |
2714 | =over 4 |
708 | |
2715 | |
709 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2716 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
710 | |
2717 | |
711 | This function combines a simple timer and an I/O watcher, calls your |
2718 | This function combines a simple timer and an I/O watcher, calls your |
712 | callback on whichever event happens first and automatically stop both |
2719 | callback on whichever event happens first and automatically stops both |
713 | watchers. This is useful if you want to wait for a single event on an fd |
2720 | 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 |
2721 | or timeout without having to allocate/configure/start/stop/free one or |
715 | more watchers yourself. |
2722 | more watchers yourself. |
716 | |
2723 | |
717 | If C<fd> is less than 0, then no I/O watcher will be started and events is |
2724 | If C<fd> is less than 0, then no I/O watcher will be started and the |
718 | ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and C<events> set |
2725 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
719 | will be craeted and started. |
2726 | the given C<fd> and C<events> set will be created and started. |
720 | |
2727 | |
721 | If C<timeout> is less than 0, then no timeout watcher will be |
2728 | 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 |
2729 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
723 | = 0) will be started. |
2730 | repeat = 0) will be started. C<0> is a valid timeout. |
724 | |
2731 | |
725 | The callback has the type C<void (*cb)(int revents, void *arg)> and |
2732 | 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>, |
2733 | 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>: |
2734 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
|
|
2735 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
2736 | a timeout and an io event at the same time - you probably should give io |
|
|
2737 | events precedence. |
728 | |
2738 | |
|
|
2739 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
|
|
2740 | |
729 | static void stdin_ready (int revents, void *arg) |
2741 | static void stdin_ready (int revents, void *arg) |
730 | { |
2742 | { |
731 | if (revents & EV_TIMEOUT) |
|
|
732 | /* doh, nothing entered */ |
|
|
733 | else if (revents & EV_READ) |
2743 | if (revents & EV_READ) |
734 | /* stdin might have data for us, joy! */ |
2744 | /* stdin might have data for us, joy! */; |
|
|
2745 | else if (revents & EV_TIMEOUT) |
|
|
2746 | /* doh, nothing entered */; |
735 | } |
2747 | } |
736 | |
2748 | |
737 | ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); |
2749 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
738 | |
2750 | |
739 | =item ev_feed_event (loop, watcher, int events) |
2751 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
740 | |
2752 | |
741 | Feeds the given event set into the event loop, as if the specified event |
2753 | 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 |
2754 | had happened for the specified watcher (which must be a pointer to an |
743 | initialised but not necessarily active event watcher). |
2755 | initialised but not necessarily started event watcher). |
744 | |
2756 | |
745 | =item ev_feed_fd_event (loop, int fd, int revents) |
2757 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
746 | |
2758 | |
747 | Feed an event on the given fd, as if a file descriptor backend detected it. |
2759 | Feed an event on the given fd, as if a file descriptor backend detected |
|
|
2760 | the given events it. |
748 | |
2761 | |
749 | =item ev_feed_signal_event (loop, int signum) |
2762 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
750 | |
2763 | |
751 | Feed an event as if the given signal occured (loop must be the default loop!). |
2764 | Feed an event as if the given signal occurred (C<loop> must be the default |
|
|
2765 | loop!). |
752 | |
2766 | |
753 | =back |
2767 | =back |
754 | |
2768 | |
|
|
2769 | |
|
|
2770 | =head1 LIBEVENT EMULATION |
|
|
2771 | |
|
|
2772 | Libev offers a compatibility emulation layer for libevent. It cannot |
|
|
2773 | emulate the internals of libevent, so here are some usage hints: |
|
|
2774 | |
|
|
2775 | =over 4 |
|
|
2776 | |
|
|
2777 | =item * Use it by including <event.h>, as usual. |
|
|
2778 | |
|
|
2779 | =item * The following members are fully supported: ev_base, ev_callback, |
|
|
2780 | ev_arg, ev_fd, ev_res, ev_events. |
|
|
2781 | |
|
|
2782 | =item * Avoid using ev_flags and the EVLIST_*-macros, while it is |
|
|
2783 | maintained by libev, it does not work exactly the same way as in libevent (consider |
|
|
2784 | it a private API). |
|
|
2785 | |
|
|
2786 | =item * Priorities are not currently supported. Initialising priorities |
|
|
2787 | will fail and all watchers will have the same priority, even though there |
|
|
2788 | is an ev_pri field. |
|
|
2789 | |
|
|
2790 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
2791 | first base created (== the default loop) gets the signals. |
|
|
2792 | |
|
|
2793 | =item * Other members are not supported. |
|
|
2794 | |
|
|
2795 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
|
|
2796 | to use the libev header file and library. |
|
|
2797 | |
|
|
2798 | =back |
|
|
2799 | |
|
|
2800 | =head1 C++ SUPPORT |
|
|
2801 | |
|
|
2802 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
|
|
2803 | you to use some convenience methods to start/stop watchers and also change |
|
|
2804 | the callback model to a model using method callbacks on objects. |
|
|
2805 | |
|
|
2806 | To use it, |
|
|
2807 | |
|
|
2808 | #include <ev++.h> |
|
|
2809 | |
|
|
2810 | This automatically includes F<ev.h> and puts all of its definitions (many |
|
|
2811 | of them macros) into the global namespace. All C++ specific things are |
|
|
2812 | put into the C<ev> namespace. It should support all the same embedding |
|
|
2813 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
|
|
2814 | |
|
|
2815 | Care has been taken to keep the overhead low. The only data member the C++ |
|
|
2816 | classes add (compared to plain C-style watchers) is the event loop pointer |
|
|
2817 | that the watcher is associated with (or no additional members at all if |
|
|
2818 | you disable C<EV_MULTIPLICITY> when embedding libev). |
|
|
2819 | |
|
|
2820 | Currently, functions, and static and non-static member functions can be |
|
|
2821 | used as callbacks. Other types should be easy to add as long as they only |
|
|
2822 | need one additional pointer for context. If you need support for other |
|
|
2823 | types of functors please contact the author (preferably after implementing |
|
|
2824 | it). |
|
|
2825 | |
|
|
2826 | Here is a list of things available in the C<ev> namespace: |
|
|
2827 | |
|
|
2828 | =over 4 |
|
|
2829 | |
|
|
2830 | =item C<ev::READ>, C<ev::WRITE> etc. |
|
|
2831 | |
|
|
2832 | These are just enum values with the same values as the C<EV_READ> etc. |
|
|
2833 | macros from F<ev.h>. |
|
|
2834 | |
|
|
2835 | =item C<ev::tstamp>, C<ev::now> |
|
|
2836 | |
|
|
2837 | Aliases to the same types/functions as with the C<ev_> prefix. |
|
|
2838 | |
|
|
2839 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
|
|
2840 | |
|
|
2841 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
|
|
2842 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
|
|
2843 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
|
|
2844 | defines by many implementations. |
|
|
2845 | |
|
|
2846 | All of those classes have these methods: |
|
|
2847 | |
|
|
2848 | =over 4 |
|
|
2849 | |
|
|
2850 | =item ev::TYPE::TYPE () |
|
|
2851 | |
|
|
2852 | =item ev::TYPE::TYPE (struct ev_loop *) |
|
|
2853 | |
|
|
2854 | =item ev::TYPE::~TYPE |
|
|
2855 | |
|
|
2856 | The constructor (optionally) takes an event loop to associate the watcher |
|
|
2857 | with. If it is omitted, it will use C<EV_DEFAULT>. |
|
|
2858 | |
|
|
2859 | The constructor calls C<ev_init> for you, which means you have to call the |
|
|
2860 | C<set> method before starting it. |
|
|
2861 | |
|
|
2862 | It will not set a callback, however: You have to call the templated C<set> |
|
|
2863 | method to set a callback before you can start the watcher. |
|
|
2864 | |
|
|
2865 | (The reason why you have to use a method is a limitation in C++ which does |
|
|
2866 | not allow explicit template arguments for constructors). |
|
|
2867 | |
|
|
2868 | The destructor automatically stops the watcher if it is active. |
|
|
2869 | |
|
|
2870 | =item w->set<class, &class::method> (object *) |
|
|
2871 | |
|
|
2872 | This method sets the callback method to call. The method has to have a |
|
|
2873 | signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as |
|
|
2874 | first argument and the C<revents> as second. The object must be given as |
|
|
2875 | parameter and is stored in the C<data> member of the watcher. |
|
|
2876 | |
|
|
2877 | This method synthesizes efficient thunking code to call your method from |
|
|
2878 | the C callback that libev requires. If your compiler can inline your |
|
|
2879 | callback (i.e. it is visible to it at the place of the C<set> call and |
|
|
2880 | your compiler is good :), then the method will be fully inlined into the |
|
|
2881 | thunking function, making it as fast as a direct C callback. |
|
|
2882 | |
|
|
2883 | Example: simple class declaration and watcher initialisation |
|
|
2884 | |
|
|
2885 | struct myclass |
|
|
2886 | { |
|
|
2887 | void io_cb (ev::io &w, int revents) { } |
|
|
2888 | } |
|
|
2889 | |
|
|
2890 | myclass obj; |
|
|
2891 | ev::io iow; |
|
|
2892 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
2893 | |
|
|
2894 | =item w->set<function> (void *data = 0) |
|
|
2895 | |
|
|
2896 | Also sets a callback, but uses a static method or plain function as |
|
|
2897 | callback. The optional C<data> argument will be stored in the watcher's |
|
|
2898 | C<data> member and is free for you to use. |
|
|
2899 | |
|
|
2900 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
|
|
2901 | |
|
|
2902 | See the method-C<set> above for more details. |
|
|
2903 | |
|
|
2904 | Example: Use a plain function as callback. |
|
|
2905 | |
|
|
2906 | static void io_cb (ev::io &w, int revents) { } |
|
|
2907 | iow.set <io_cb> (); |
|
|
2908 | |
|
|
2909 | =item w->set (struct ev_loop *) |
|
|
2910 | |
|
|
2911 | Associates a different C<struct ev_loop> with this watcher. You can only |
|
|
2912 | do this when the watcher is inactive (and not pending either). |
|
|
2913 | |
|
|
2914 | =item w->set ([arguments]) |
|
|
2915 | |
|
|
2916 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
|
|
2917 | called at least once. Unlike the C counterpart, an active watcher gets |
|
|
2918 | automatically stopped and restarted when reconfiguring it with this |
|
|
2919 | method. |
|
|
2920 | |
|
|
2921 | =item w->start () |
|
|
2922 | |
|
|
2923 | Starts the watcher. Note that there is no C<loop> argument, as the |
|
|
2924 | constructor already stores the event loop. |
|
|
2925 | |
|
|
2926 | =item w->stop () |
|
|
2927 | |
|
|
2928 | Stops the watcher if it is active. Again, no C<loop> argument. |
|
|
2929 | |
|
|
2930 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
|
|
2931 | |
|
|
2932 | For C<ev::timer> and C<ev::periodic>, this invokes the corresponding |
|
|
2933 | C<ev_TYPE_again> function. |
|
|
2934 | |
|
|
2935 | =item w->sweep () (C<ev::embed> only) |
|
|
2936 | |
|
|
2937 | Invokes C<ev_embed_sweep>. |
|
|
2938 | |
|
|
2939 | =item w->update () (C<ev::stat> only) |
|
|
2940 | |
|
|
2941 | Invokes C<ev_stat_stat>. |
|
|
2942 | |
|
|
2943 | =back |
|
|
2944 | |
|
|
2945 | =back |
|
|
2946 | |
|
|
2947 | Example: Define a class with an IO and idle watcher, start one of them in |
|
|
2948 | the constructor. |
|
|
2949 | |
|
|
2950 | class myclass |
|
|
2951 | { |
|
|
2952 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
2953 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
|
|
2954 | |
|
|
2955 | myclass (int fd) |
|
|
2956 | { |
|
|
2957 | io .set <myclass, &myclass::io_cb > (this); |
|
|
2958 | idle.set <myclass, &myclass::idle_cb> (this); |
|
|
2959 | |
|
|
2960 | io.start (fd, ev::READ); |
|
|
2961 | } |
|
|
2962 | }; |
|
|
2963 | |
|
|
2964 | |
|
|
2965 | =head1 OTHER LANGUAGE BINDINGS |
|
|
2966 | |
|
|
2967 | Libev does not offer other language bindings itself, but bindings for a |
|
|
2968 | number of languages exist in the form of third-party packages. If you know |
|
|
2969 | any interesting language binding in addition to the ones listed here, drop |
|
|
2970 | me a note. |
|
|
2971 | |
|
|
2972 | =over 4 |
|
|
2973 | |
|
|
2974 | =item Perl |
|
|
2975 | |
|
|
2976 | The EV module implements the full libev API and is actually used to test |
|
|
2977 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
2978 | there are additional modules that implement libev-compatible interfaces |
|
|
2979 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
|
|
2980 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
2981 | and C<EV::Glib>). |
|
|
2982 | |
|
|
2983 | It can be found and installed via CPAN, its homepage is at |
|
|
2984 | L<http://software.schmorp.de/pkg/EV>. |
|
|
2985 | |
|
|
2986 | =item Python |
|
|
2987 | |
|
|
2988 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
|
|
2989 | seems to be quite complete and well-documented. Note, however, that the |
|
|
2990 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2991 | for everybody else, and therefore, should never be applied in an installed |
|
|
2992 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2993 | libev). |
|
|
2994 | |
|
|
2995 | =item Ruby |
|
|
2996 | |
|
|
2997 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
2998 | of the libev API and adds file handle abstractions, asynchronous DNS and |
|
|
2999 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
3000 | L<http://rev.rubyforge.org/>. |
|
|
3001 | |
|
|
3002 | =item D |
|
|
3003 | |
|
|
3004 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
3005 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3006 | |
|
|
3007 | =item Ocaml |
|
|
3008 | |
|
|
3009 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3010 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3011 | |
|
|
3012 | =back |
|
|
3013 | |
|
|
3014 | |
|
|
3015 | =head1 MACRO MAGIC |
|
|
3016 | |
|
|
3017 | Libev can be compiled with a variety of options, the most fundamental |
|
|
3018 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
|
|
3019 | functions and callbacks have an initial C<struct ev_loop *> argument. |
|
|
3020 | |
|
|
3021 | To make it easier to write programs that cope with either variant, the |
|
|
3022 | following macros are defined: |
|
|
3023 | |
|
|
3024 | =over 4 |
|
|
3025 | |
|
|
3026 | =item C<EV_A>, C<EV_A_> |
|
|
3027 | |
|
|
3028 | This provides the loop I<argument> for functions, if one is required ("ev |
|
|
3029 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
|
|
3030 | C<EV_A_> is used when other arguments are following. Example: |
|
|
3031 | |
|
|
3032 | ev_unref (EV_A); |
|
|
3033 | ev_timer_add (EV_A_ watcher); |
|
|
3034 | ev_loop (EV_A_ 0); |
|
|
3035 | |
|
|
3036 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
|
|
3037 | which is often provided by the following macro. |
|
|
3038 | |
|
|
3039 | =item C<EV_P>, C<EV_P_> |
|
|
3040 | |
|
|
3041 | This provides the loop I<parameter> for functions, if one is required ("ev |
|
|
3042 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
|
|
3043 | C<EV_P_> is used when other parameters are following. Example: |
|
|
3044 | |
|
|
3045 | // this is how ev_unref is being declared |
|
|
3046 | static void ev_unref (EV_P); |
|
|
3047 | |
|
|
3048 | // this is how you can declare your typical callback |
|
|
3049 | static void cb (EV_P_ ev_timer *w, int revents) |
|
|
3050 | |
|
|
3051 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
|
|
3052 | suitable for use with C<EV_A>. |
|
|
3053 | |
|
|
3054 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
|
|
3055 | |
|
|
3056 | Similar to the other two macros, this gives you the value of the default |
|
|
3057 | loop, if multiple loops are supported ("ev loop default"). |
|
|
3058 | |
|
|
3059 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
3060 | |
|
|
3061 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
3062 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
3063 | is undefined when the default loop has not been initialised by a previous |
|
|
3064 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
3065 | |
|
|
3066 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
3067 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
|
|
3068 | |
|
|
3069 | =back |
|
|
3070 | |
|
|
3071 | Example: Declare and initialise a check watcher, utilising the above |
|
|
3072 | macros so it will work regardless of whether multiple loops are supported |
|
|
3073 | or not. |
|
|
3074 | |
|
|
3075 | static void |
|
|
3076 | check_cb (EV_P_ ev_timer *w, int revents) |
|
|
3077 | { |
|
|
3078 | ev_check_stop (EV_A_ w); |
|
|
3079 | } |
|
|
3080 | |
|
|
3081 | ev_check check; |
|
|
3082 | ev_check_init (&check, check_cb); |
|
|
3083 | ev_check_start (EV_DEFAULT_ &check); |
|
|
3084 | ev_loop (EV_DEFAULT_ 0); |
|
|
3085 | |
|
|
3086 | =head1 EMBEDDING |
|
|
3087 | |
|
|
3088 | Libev can (and often is) directly embedded into host |
|
|
3089 | applications. Examples of applications that embed it include the Deliantra |
|
|
3090 | Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
|
|
3091 | and rxvt-unicode. |
|
|
3092 | |
|
|
3093 | The goal is to enable you to just copy the necessary files into your |
|
|
3094 | source directory without having to change even a single line in them, so |
|
|
3095 | you can easily upgrade by simply copying (or having a checked-out copy of |
|
|
3096 | libev somewhere in your source tree). |
|
|
3097 | |
|
|
3098 | =head2 FILESETS |
|
|
3099 | |
|
|
3100 | Depending on what features you need you need to include one or more sets of files |
|
|
3101 | in your application. |
|
|
3102 | |
|
|
3103 | =head3 CORE EVENT LOOP |
|
|
3104 | |
|
|
3105 | To include only the libev core (all the C<ev_*> functions), with manual |
|
|
3106 | configuration (no autoconf): |
|
|
3107 | |
|
|
3108 | #define EV_STANDALONE 1 |
|
|
3109 | #include "ev.c" |
|
|
3110 | |
|
|
3111 | This will automatically include F<ev.h>, too, and should be done in a |
|
|
3112 | single C source file only to provide the function implementations. To use |
|
|
3113 | it, do the same for F<ev.h> in all files wishing to use this API (best |
|
|
3114 | done by writing a wrapper around F<ev.h> that you can include instead and |
|
|
3115 | where you can put other configuration options): |
|
|
3116 | |
|
|
3117 | #define EV_STANDALONE 1 |
|
|
3118 | #include "ev.h" |
|
|
3119 | |
|
|
3120 | Both header files and implementation files can be compiled with a C++ |
|
|
3121 | compiler (at least, that's a stated goal, and breakage will be treated |
|
|
3122 | as a bug). |
|
|
3123 | |
|
|
3124 | You need the following files in your source tree, or in a directory |
|
|
3125 | in your include path (e.g. in libev/ when using -Ilibev): |
|
|
3126 | |
|
|
3127 | ev.h |
|
|
3128 | ev.c |
|
|
3129 | ev_vars.h |
|
|
3130 | ev_wrap.h |
|
|
3131 | |
|
|
3132 | ev_win32.c required on win32 platforms only |
|
|
3133 | |
|
|
3134 | ev_select.c only when select backend is enabled (which is enabled by default) |
|
|
3135 | ev_poll.c only when poll backend is enabled (disabled by default) |
|
|
3136 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
|
|
3137 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
|
|
3138 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
|
|
3139 | |
|
|
3140 | F<ev.c> includes the backend files directly when enabled, so you only need |
|
|
3141 | to compile this single file. |
|
|
3142 | |
|
|
3143 | =head3 LIBEVENT COMPATIBILITY API |
|
|
3144 | |
|
|
3145 | To include the libevent compatibility API, also include: |
|
|
3146 | |
|
|
3147 | #include "event.c" |
|
|
3148 | |
|
|
3149 | in the file including F<ev.c>, and: |
|
|
3150 | |
|
|
3151 | #include "event.h" |
|
|
3152 | |
|
|
3153 | in the files that want to use the libevent API. This also includes F<ev.h>. |
|
|
3154 | |
|
|
3155 | You need the following additional files for this: |
|
|
3156 | |
|
|
3157 | event.h |
|
|
3158 | event.c |
|
|
3159 | |
|
|
3160 | =head3 AUTOCONF SUPPORT |
|
|
3161 | |
|
|
3162 | Instead of using C<EV_STANDALONE=1> and providing your configuration in |
|
|
3163 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
|
|
3164 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
|
|
3165 | include F<config.h> and configure itself accordingly. |
|
|
3166 | |
|
|
3167 | For this of course you need the m4 file: |
|
|
3168 | |
|
|
3169 | libev.m4 |
|
|
3170 | |
|
|
3171 | =head2 PREPROCESSOR SYMBOLS/MACROS |
|
|
3172 | |
|
|
3173 | Libev can be configured via a variety of preprocessor symbols you have to |
|
|
3174 | define before including any of its files. The default in the absence of |
|
|
3175 | autoconf is documented for every option. |
|
|
3176 | |
|
|
3177 | =over 4 |
|
|
3178 | |
|
|
3179 | =item EV_STANDALONE |
|
|
3180 | |
|
|
3181 | Must always be C<1> if you do not use autoconf configuration, which |
|
|
3182 | keeps libev from including F<config.h>, and it also defines dummy |
|
|
3183 | implementations for some libevent functions (such as logging, which is not |
|
|
3184 | supported). It will also not define any of the structs usually found in |
|
|
3185 | F<event.h> that are not directly supported by the libev core alone. |
|
|
3186 | |
|
|
3187 | =item EV_USE_MONOTONIC |
|
|
3188 | |
|
|
3189 | If defined to be C<1>, libev will try to detect the availability of the |
|
|
3190 | monotonic clock option at both compile time and runtime. Otherwise no use |
|
|
3191 | of the monotonic clock option will be attempted. If you enable this, you |
|
|
3192 | usually have to link against librt or something similar. Enabling it when |
|
|
3193 | the functionality isn't available is safe, though, although you have |
|
|
3194 | to make sure you link against any libraries where the C<clock_gettime> |
|
|
3195 | function is hiding in (often F<-lrt>). |
|
|
3196 | |
|
|
3197 | =item EV_USE_REALTIME |
|
|
3198 | |
|
|
3199 | If defined to be C<1>, libev will try to detect the availability of the |
|
|
3200 | real-time clock option at compile time (and assume its availability at |
|
|
3201 | runtime if successful). Otherwise no use of the real-time clock option will |
|
|
3202 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
|
|
3203 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
|
|
3204 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
|
|
3205 | |
|
|
3206 | =item EV_USE_NANOSLEEP |
|
|
3207 | |
|
|
3208 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
|
|
3209 | and will use it for delays. Otherwise it will use C<select ()>. |
|
|
3210 | |
|
|
3211 | =item EV_USE_EVENTFD |
|
|
3212 | |
|
|
3213 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
3214 | available and will probe for kernel support at runtime. This will improve |
|
|
3215 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
3216 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
3217 | 2.7 or newer, otherwise disabled. |
|
|
3218 | |
|
|
3219 | =item EV_USE_SELECT |
|
|
3220 | |
|
|
3221 | If undefined or defined to be C<1>, libev will compile in support for the |
|
|
3222 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
|
|
3223 | other method takes over, select will be it. Otherwise the select backend |
|
|
3224 | will not be compiled in. |
|
|
3225 | |
|
|
3226 | =item EV_SELECT_USE_FD_SET |
|
|
3227 | |
|
|
3228 | If defined to C<1>, then the select backend will use the system C<fd_set> |
|
|
3229 | structure. This is useful if libev doesn't compile due to a missing |
|
|
3230 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
|
|
3231 | exotic systems. This usually limits the range of file descriptors to some |
|
|
3232 | low limit such as 1024 or might have other limitations (winsocket only |
|
|
3233 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
|
|
3234 | influence the size of the C<fd_set> used. |
|
|
3235 | |
|
|
3236 | =item EV_SELECT_IS_WINSOCKET |
|
|
3237 | |
|
|
3238 | When defined to C<1>, the select backend will assume that |
|
|
3239 | select/socket/connect etc. don't understand file descriptors but |
|
|
3240 | wants osf handles on win32 (this is the case when the select to |
|
|
3241 | be used is the winsock select). This means that it will call |
|
|
3242 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
|
|
3243 | it is assumed that all these functions actually work on fds, even |
|
|
3244 | on win32. Should not be defined on non-win32 platforms. |
|
|
3245 | |
|
|
3246 | =item EV_FD_TO_WIN32_HANDLE |
|
|
3247 | |
|
|
3248 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
|
|
3249 | file descriptors to socket handles. When not defining this symbol (the |
|
|
3250 | default), then libev will call C<_get_osfhandle>, which is usually |
|
|
3251 | correct. In some cases, programs use their own file descriptor management, |
|
|
3252 | in which case they can provide this function to map fds to socket handles. |
|
|
3253 | |
|
|
3254 | =item EV_USE_POLL |
|
|
3255 | |
|
|
3256 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
|
|
3257 | backend. Otherwise it will be enabled on non-win32 platforms. It |
|
|
3258 | takes precedence over select. |
|
|
3259 | |
|
|
3260 | =item EV_USE_EPOLL |
|
|
3261 | |
|
|
3262 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
3263 | C<epoll>(7) backend. Its availability will be detected at runtime, |
|
|
3264 | otherwise another method will be used as fallback. This is the preferred |
|
|
3265 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
3266 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
3267 | |
|
|
3268 | =item EV_USE_KQUEUE |
|
|
3269 | |
|
|
3270 | If defined to be C<1>, libev will compile in support for the BSD style |
|
|
3271 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
|
|
3272 | otherwise another method will be used as fallback. This is the preferred |
|
|
3273 | backend for BSD and BSD-like systems, although on most BSDs kqueue only |
|
|
3274 | supports some types of fds correctly (the only platform we found that |
|
|
3275 | supports ptys for example was NetBSD), so kqueue might be compiled in, but |
|
|
3276 | not be used unless explicitly requested. The best way to use it is to find |
|
|
3277 | out whether kqueue supports your type of fd properly and use an embedded |
|
|
3278 | kqueue loop. |
|
|
3279 | |
|
|
3280 | =item EV_USE_PORT |
|
|
3281 | |
|
|
3282 | If defined to be C<1>, libev will compile in support for the Solaris |
|
|
3283 | 10 port style backend. Its availability will be detected at runtime, |
|
|
3284 | otherwise another method will be used as fallback. This is the preferred |
|
|
3285 | backend for Solaris 10 systems. |
|
|
3286 | |
|
|
3287 | =item EV_USE_DEVPOLL |
|
|
3288 | |
|
|
3289 | Reserved for future expansion, works like the USE symbols above. |
|
|
3290 | |
|
|
3291 | =item EV_USE_INOTIFY |
|
|
3292 | |
|
|
3293 | If defined to be C<1>, libev will compile in support for the Linux inotify |
|
|
3294 | interface to speed up C<ev_stat> watchers. Its actual availability will |
|
|
3295 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
3296 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
3297 | |
|
|
3298 | =item EV_ATOMIC_T |
|
|
3299 | |
|
|
3300 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
|
|
3301 | access is atomic with respect to other threads or signal contexts. No such |
|
|
3302 | type is easily found in the C language, so you can provide your own type |
|
|
3303 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
3304 | as well as for signal and thread safety in C<ev_async> watchers. |
|
|
3305 | |
|
|
3306 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
|
|
3307 | (from F<signal.h>), which is usually good enough on most platforms. |
|
|
3308 | |
|
|
3309 | =item EV_H |
|
|
3310 | |
|
|
3311 | The name of the F<ev.h> header file used to include it. The default if |
|
|
3312 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
|
|
3313 | used to virtually rename the F<ev.h> header file in case of conflicts. |
|
|
3314 | |
|
|
3315 | =item EV_CONFIG_H |
|
|
3316 | |
|
|
3317 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
|
|
3318 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
|
|
3319 | C<EV_H>, above. |
|
|
3320 | |
|
|
3321 | =item EV_EVENT_H |
|
|
3322 | |
|
|
3323 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
|
|
3324 | of how the F<event.h> header can be found, the default is C<"event.h">. |
|
|
3325 | |
|
|
3326 | =item EV_PROTOTYPES |
|
|
3327 | |
|
|
3328 | If defined to be C<0>, then F<ev.h> will not define any function |
|
|
3329 | prototypes, but still define all the structs and other symbols. This is |
|
|
3330 | occasionally useful if you want to provide your own wrapper functions |
|
|
3331 | around libev functions. |
|
|
3332 | |
|
|
3333 | =item EV_MULTIPLICITY |
|
|
3334 | |
|
|
3335 | If undefined or defined to C<1>, then all event-loop-specific functions |
|
|
3336 | will have the C<struct ev_loop *> as first argument, and you can create |
|
|
3337 | additional independent event loops. Otherwise there will be no support |
|
|
3338 | for multiple event loops and there is no first event loop pointer |
|
|
3339 | argument. Instead, all functions act on the single default loop. |
|
|
3340 | |
|
|
3341 | =item EV_MINPRI |
|
|
3342 | |
|
|
3343 | =item EV_MAXPRI |
|
|
3344 | |
|
|
3345 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
|
|
3346 | C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can |
|
|
3347 | provide for more priorities by overriding those symbols (usually defined |
|
|
3348 | to be C<-2> and C<2>, respectively). |
|
|
3349 | |
|
|
3350 | When doing priority-based operations, libev usually has to linearly search |
|
|
3351 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
3352 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
|
|
3353 | fine. |
|
|
3354 | |
|
|
3355 | If your embedding application does not need any priorities, defining these |
|
|
3356 | both to C<0> will save some memory and CPU. |
|
|
3357 | |
|
|
3358 | =item EV_PERIODIC_ENABLE |
|
|
3359 | |
|
|
3360 | If undefined or defined to be C<1>, then periodic timers are supported. If |
|
|
3361 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3362 | code. |
|
|
3363 | |
|
|
3364 | =item EV_IDLE_ENABLE |
|
|
3365 | |
|
|
3366 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3367 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3368 | code. |
|
|
3369 | |
|
|
3370 | =item EV_EMBED_ENABLE |
|
|
3371 | |
|
|
3372 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3373 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3374 | watcher types, which therefore must not be disabled. |
|
|
3375 | |
|
|
3376 | =item EV_STAT_ENABLE |
|
|
3377 | |
|
|
3378 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3379 | defined to be C<0>, then they are not. |
|
|
3380 | |
|
|
3381 | =item EV_FORK_ENABLE |
|
|
3382 | |
|
|
3383 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3384 | defined to be C<0>, then they are not. |
|
|
3385 | |
|
|
3386 | =item EV_ASYNC_ENABLE |
|
|
3387 | |
|
|
3388 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3389 | defined to be C<0>, then they are not. |
|
|
3390 | |
|
|
3391 | =item EV_MINIMAL |
|
|
3392 | |
|
|
3393 | If you need to shave off some kilobytes of code at the expense of some |
|
|
3394 | speed, define this symbol to C<1>. Currently this is used to override some |
|
|
3395 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
|
|
3396 | much smaller 2-heap for timer management over the default 4-heap. |
|
|
3397 | |
|
|
3398 | =item EV_PID_HASHSIZE |
|
|
3399 | |
|
|
3400 | C<ev_child> watchers use a small hash table to distribute workload by |
|
|
3401 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
|
|
3402 | than enough. If you need to manage thousands of children you might want to |
|
|
3403 | increase this value (I<must> be a power of two). |
|
|
3404 | |
|
|
3405 | =item EV_INOTIFY_HASHSIZE |
|
|
3406 | |
|
|
3407 | C<ev_stat> watchers use a small hash table to distribute workload by |
|
|
3408 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
|
|
3409 | usually more than enough. If you need to manage thousands of C<ev_stat> |
|
|
3410 | watchers you might want to increase this value (I<must> be a power of |
|
|
3411 | two). |
|
|
3412 | |
|
|
3413 | =item EV_USE_4HEAP |
|
|
3414 | |
|
|
3415 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3416 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
|
|
3417 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
|
|
3418 | faster performance with many (thousands) of watchers. |
|
|
3419 | |
|
|
3420 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3421 | (disabled). |
|
|
3422 | |
|
|
3423 | =item EV_HEAP_CACHE_AT |
|
|
3424 | |
|
|
3425 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3426 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
|
|
3427 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3428 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3429 | but avoids random read accesses on heap changes. This improves performance |
|
|
3430 | noticeably with many (hundreds) of watchers. |
|
|
3431 | |
|
|
3432 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3433 | (disabled). |
|
|
3434 | |
|
|
3435 | =item EV_VERIFY |
|
|
3436 | |
|
|
3437 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
|
|
3438 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
3439 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
3440 | called. If set to C<2>, then the internal verification code will be |
|
|
3441 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
3442 | verification code will be called very frequently, which will slow down |
|
|
3443 | libev considerably. |
|
|
3444 | |
|
|
3445 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
|
|
3446 | C<0>. |
|
|
3447 | |
|
|
3448 | =item EV_COMMON |
|
|
3449 | |
|
|
3450 | By default, all watchers have a C<void *data> member. By redefining |
|
|
3451 | this macro to a something else you can include more and other types of |
|
|
3452 | members. You have to define it each time you include one of the files, |
|
|
3453 | though, and it must be identical each time. |
|
|
3454 | |
|
|
3455 | For example, the perl EV module uses something like this: |
|
|
3456 | |
|
|
3457 | #define EV_COMMON \ |
|
|
3458 | SV *self; /* contains this struct */ \ |
|
|
3459 | SV *cb_sv, *fh /* note no trailing ";" */ |
|
|
3460 | |
|
|
3461 | =item EV_CB_DECLARE (type) |
|
|
3462 | |
|
|
3463 | =item EV_CB_INVOKE (watcher, revents) |
|
|
3464 | |
|
|
3465 | =item ev_set_cb (ev, cb) |
|
|
3466 | |
|
|
3467 | Can be used to change the callback member declaration in each watcher, |
|
|
3468 | and the way callbacks are invoked and set. Must expand to a struct member |
|
|
3469 | definition and a statement, respectively. See the F<ev.h> header file for |
|
|
3470 | their default definitions. One possible use for overriding these is to |
|
|
3471 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
|
|
3472 | method calls instead of plain function calls in C++. |
|
|
3473 | |
|
|
3474 | =back |
|
|
3475 | |
|
|
3476 | =head2 EXPORTED API SYMBOLS |
|
|
3477 | |
|
|
3478 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
|
|
3479 | exported symbols, you can use the provided F<Symbol.*> files which list |
|
|
3480 | all public symbols, one per line: |
|
|
3481 | |
|
|
3482 | Symbols.ev for libev proper |
|
|
3483 | Symbols.event for the libevent emulation |
|
|
3484 | |
|
|
3485 | This can also be used to rename all public symbols to avoid clashes with |
|
|
3486 | multiple versions of libev linked together (which is obviously bad in |
|
|
3487 | itself, but sometimes it is inconvenient to avoid this). |
|
|
3488 | |
|
|
3489 | A sed command like this will create wrapper C<#define>'s that you need to |
|
|
3490 | include before including F<ev.h>: |
|
|
3491 | |
|
|
3492 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
|
|
3493 | |
|
|
3494 | This would create a file F<wrap.h> which essentially looks like this: |
|
|
3495 | |
|
|
3496 | #define ev_backend myprefix_ev_backend |
|
|
3497 | #define ev_check_start myprefix_ev_check_start |
|
|
3498 | #define ev_check_stop myprefix_ev_check_stop |
|
|
3499 | ... |
|
|
3500 | |
|
|
3501 | =head2 EXAMPLES |
|
|
3502 | |
|
|
3503 | For a real-world example of a program the includes libev |
|
|
3504 | verbatim, you can have a look at the EV perl module |
|
|
3505 | (L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
|
|
3506 | the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public |
|
|
3507 | interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file |
|
|
3508 | will be compiled. It is pretty complex because it provides its own header |
|
|
3509 | file. |
|
|
3510 | |
|
|
3511 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
|
|
3512 | that everybody includes and which overrides some configure choices: |
|
|
3513 | |
|
|
3514 | #define EV_MINIMAL 1 |
|
|
3515 | #define EV_USE_POLL 0 |
|
|
3516 | #define EV_MULTIPLICITY 0 |
|
|
3517 | #define EV_PERIODIC_ENABLE 0 |
|
|
3518 | #define EV_STAT_ENABLE 0 |
|
|
3519 | #define EV_FORK_ENABLE 0 |
|
|
3520 | #define EV_CONFIG_H <config.h> |
|
|
3521 | #define EV_MINPRI 0 |
|
|
3522 | #define EV_MAXPRI 0 |
|
|
3523 | |
|
|
3524 | #include "ev++.h" |
|
|
3525 | |
|
|
3526 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
|
|
3527 | |
|
|
3528 | #include "ev_cpp.h" |
|
|
3529 | #include "ev.c" |
|
|
3530 | |
|
|
3531 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
|
|
3532 | |
|
|
3533 | =head2 THREADS AND COROUTINES |
|
|
3534 | |
|
|
3535 | =head3 THREADS |
|
|
3536 | |
|
|
3537 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
3538 | documented otherwise, but libev implements no locking itself. This means |
|
|
3539 | that you can use as many loops as you want in parallel, as long as there |
|
|
3540 | are no concurrent calls into any libev function with the same loop |
|
|
3541 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
3542 | of course): libev guarantees that different event loops share no data |
|
|
3543 | structures that need any locking. |
|
|
3544 | |
|
|
3545 | Or to put it differently: calls with different loop parameters can be done |
|
|
3546 | concurrently from multiple threads, calls with the same loop parameter |
|
|
3547 | must be done serially (but can be done from different threads, as long as |
|
|
3548 | only one thread ever is inside a call at any point in time, e.g. by using |
|
|
3549 | a mutex per loop). |
|
|
3550 | |
|
|
3551 | Specifically to support threads (and signal handlers), libev implements |
|
|
3552 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
3553 | concurrency on the same event loop, namely waking it up "from the |
|
|
3554 | outside". |
|
|
3555 | |
|
|
3556 | If you want to know which design (one loop, locking, or multiple loops |
|
|
3557 | without or something else still) is best for your problem, then I cannot |
|
|
3558 | help you, but here is some generic advice: |
|
|
3559 | |
|
|
3560 | =over 4 |
|
|
3561 | |
|
|
3562 | =item * most applications have a main thread: use the default libev loop |
|
|
3563 | in that thread, or create a separate thread running only the default loop. |
|
|
3564 | |
|
|
3565 | This helps integrating other libraries or software modules that use libev |
|
|
3566 | themselves and don't care/know about threading. |
|
|
3567 | |
|
|
3568 | =item * one loop per thread is usually a good model. |
|
|
3569 | |
|
|
3570 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3571 | exists, but it is always a good start. |
|
|
3572 | |
|
|
3573 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
3574 | loop is handed through multiple threads in a kind of round-robin fashion. |
|
|
3575 | |
|
|
3576 | Choosing a model is hard - look around, learn, know that usually you can do |
|
|
3577 | better than you currently do :-) |
|
|
3578 | |
|
|
3579 | =item * often you need to talk to some other thread which blocks in the |
|
|
3580 | event loop. |
|
|
3581 | |
|
|
3582 | C<ev_async> watchers can be used to wake them up from other threads safely |
|
|
3583 | (or from signal contexts...). |
|
|
3584 | |
|
|
3585 | An example use would be to communicate signals or other events that only |
|
|
3586 | work in the default loop by registering the signal watcher with the |
|
|
3587 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
3588 | watcher callback into the event loop interested in the signal. |
|
|
3589 | |
|
|
3590 | =back |
|
|
3591 | |
|
|
3592 | =head3 COROUTINES |
|
|
3593 | |
|
|
3594 | Libev is very accommodating to coroutines ("cooperative threads"): |
|
|
3595 | libev fully supports nesting calls to its functions from different |
|
|
3596 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
3597 | different coroutines, and switch freely between both coroutines running the |
|
|
3598 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3599 | you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
3600 | |
|
|
3601 | Care has been taken to ensure that libev does not keep local state inside |
|
|
3602 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
|
|
3603 | they do not call any callbacks. |
|
|
3604 | |
|
|
3605 | =head2 COMPILER WARNINGS |
|
|
3606 | |
|
|
3607 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3608 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3609 | scared by this. |
|
|
3610 | |
|
|
3611 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3612 | has different warnings, and each user has different tastes regarding |
|
|
3613 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3614 | targeting a specific compiler and compiler-version. |
|
|
3615 | |
|
|
3616 | Another reason is that some compiler warnings require elaborate |
|
|
3617 | workarounds, or other changes to the code that make it less clear and less |
|
|
3618 | maintainable. |
|
|
3619 | |
|
|
3620 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3621 | wrong (because they don't actually warn about the condition their message |
|
|
3622 | seems to warn about). For example, certain older gcc versions had some |
|
|
3623 | warnings that resulted an extreme number of false positives. These have |
|
|
3624 | been fixed, but some people still insist on making code warn-free with |
|
|
3625 | such buggy versions. |
|
|
3626 | |
|
|
3627 | While libev is written to generate as few warnings as possible, |
|
|
3628 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3629 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3630 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3631 | warnings, not errors, or proof of bugs. |
|
|
3632 | |
|
|
3633 | |
|
|
3634 | =head2 VALGRIND |
|
|
3635 | |
|
|
3636 | Valgrind has a special section here because it is a popular tool that is |
|
|
3637 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
|
|
3638 | |
|
|
3639 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3640 | in libev, then check twice: If valgrind reports something like: |
|
|
3641 | |
|
|
3642 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3643 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3644 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3645 | |
|
|
3646 | Then there is no memory leak, just as memory accounted to global variables |
|
|
3647 | is not a memleak - the memory is still being referenced, and didn't leak. |
|
|
3648 | |
|
|
3649 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
3650 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
3651 | although an acceptable workaround has been found here), or it might be |
|
|
3652 | confused. |
|
|
3653 | |
|
|
3654 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
|
|
3655 | make it into some kind of religion. |
|
|
3656 | |
|
|
3657 | If you are unsure about something, feel free to contact the mailing list |
|
|
3658 | with the full valgrind report and an explanation on why you think this |
|
|
3659 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
3660 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
3661 | of learning how to interpret valgrind properly. |
|
|
3662 | |
|
|
3663 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3664 | I suggest using suppression lists. |
|
|
3665 | |
|
|
3666 | |
|
|
3667 | =head1 PORTABILITY NOTES |
|
|
3668 | |
|
|
3669 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
3670 | |
|
|
3671 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
|
|
3672 | requires, and its I/O model is fundamentally incompatible with the POSIX |
|
|
3673 | model. Libev still offers limited functionality on this platform in |
|
|
3674 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
|
|
3675 | descriptors. This only applies when using Win32 natively, not when using |
|
|
3676 | e.g. cygwin. |
|
|
3677 | |
|
|
3678 | Lifting these limitations would basically require the full |
|
|
3679 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3680 | things, then note that glib does exactly that for you in a very portable |
|
|
3681 | way (note also that glib is the slowest event library known to man). |
|
|
3682 | |
|
|
3683 | There is no supported compilation method available on windows except |
|
|
3684 | embedding it into other applications. |
|
|
3685 | |
|
|
3686 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
3687 | accept large writes: instead of resulting in a partial write, windows will |
|
|
3688 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
|
|
3689 | so make sure you only write small amounts into your sockets (less than a |
|
|
3690 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
3691 | available). |
|
|
3692 | |
|
|
3693 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
3694 | the abysmal performance of winsockets, using a large number of sockets |
|
|
3695 | is not recommended (and not reasonable). If your program needs to use |
|
|
3696 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
3697 | different implementation for windows, as libev offers the POSIX readiness |
|
|
3698 | notification model, which cannot be implemented efficiently on windows |
|
|
3699 | (Microsoft monopoly games). |
|
|
3700 | |
|
|
3701 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
3702 | section for details) and use the following F<evwrap.h> header file instead |
|
|
3703 | of F<ev.h>: |
|
|
3704 | |
|
|
3705 | #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
3706 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
3707 | |
|
|
3708 | #include "ev.h" |
|
|
3709 | |
|
|
3710 | And compile the following F<evwrap.c> file into your project (make sure |
|
|
3711 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
|
|
3712 | |
|
|
3713 | #include "evwrap.h" |
|
|
3714 | #include "ev.c" |
|
|
3715 | |
|
|
3716 | =over 4 |
|
|
3717 | |
|
|
3718 | =item The winsocket select function |
|
|
3719 | |
|
|
3720 | The winsocket C<select> function doesn't follow POSIX in that it |
|
|
3721 | requires socket I<handles> and not socket I<file descriptors> (it is |
|
|
3722 | also extremely buggy). This makes select very inefficient, and also |
|
|
3723 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
3724 | C runtime provides the function C<_open_osfhandle> for this). See the |
|
|
3725 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
|
|
3726 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
|
|
3727 | |
|
|
3728 | The configuration for a "naked" win32 using the Microsoft runtime |
|
|
3729 | libraries and raw winsocket select is: |
|
|
3730 | |
|
|
3731 | #define EV_USE_SELECT 1 |
|
|
3732 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
3733 | |
|
|
3734 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
3735 | complexity in the O(n²) range when using win32. |
|
|
3736 | |
|
|
3737 | =item Limited number of file descriptors |
|
|
3738 | |
|
|
3739 | Windows has numerous arbitrary (and low) limits on things. |
|
|
3740 | |
|
|
3741 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
3742 | of C<64> handles (probably owning to the fact that all windows kernels |
|
|
3743 | can only wait for C<64> things at the same time internally; Microsoft |
|
|
3744 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3745 | previous thread in each. Great). |
|
|
3746 | |
|
|
3747 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
|
|
3748 | to some high number (e.g. C<2048>) before compiling the winsocket select |
|
|
3749 | call (which might be in libev or elsewhere, for example, perl does its own |
|
|
3750 | select emulation on windows). |
|
|
3751 | |
|
|
3752 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
3753 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
|
|
3754 | or something like this inside Microsoft). You can increase this by calling |
|
|
3755 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
|
|
3756 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
|
|
3757 | libraries. |
|
|
3758 | |
|
|
3759 | This might get you to about C<512> or C<2048> sockets (depending on |
|
|
3760 | windows version and/or the phase of the moon). To get more, you need to |
|
|
3761 | wrap all I/O functions and provide your own fd management, but the cost of |
|
|
3762 | calling select (O(n²)) will likely make this unworkable. |
|
|
3763 | |
|
|
3764 | =back |
|
|
3765 | |
|
|
3766 | =head2 PORTABILITY REQUIREMENTS |
|
|
3767 | |
|
|
3768 | In addition to a working ISO-C implementation and of course the |
|
|
3769 | backend-specific APIs, libev relies on a few additional extensions: |
|
|
3770 | |
|
|
3771 | =over 4 |
|
|
3772 | |
|
|
3773 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
|
|
3774 | calling conventions regardless of C<ev_watcher_type *>. |
|
|
3775 | |
|
|
3776 | Libev assumes not only that all watcher pointers have the same internal |
|
|
3777 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
|
|
3778 | assumes that the same (machine) code can be used to call any watcher |
|
|
3779 | callback: The watcher callbacks have different type signatures, but libev |
|
|
3780 | calls them using an C<ev_watcher *> internally. |
|
|
3781 | |
|
|
3782 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
3783 | |
|
|
3784 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
3785 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
|
|
3786 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
3787 | believed to be sufficiently portable. |
|
|
3788 | |
|
|
3789 | =item C<sigprocmask> must work in a threaded environment |
|
|
3790 | |
|
|
3791 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
3792 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
3793 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
3794 | thread" or will block signals process-wide, both behaviours would |
|
|
3795 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
3796 | C<pthread_sigmask> could complicate things, however. |
|
|
3797 | |
|
|
3798 | The most portable way to handle signals is to block signals in all threads |
|
|
3799 | except the initial one, and run the default loop in the initial thread as |
|
|
3800 | well. |
|
|
3801 | |
|
|
3802 | =item C<long> must be large enough for common memory allocation sizes |
|
|
3803 | |
|
|
3804 | To improve portability and simplify its API, libev uses C<long> internally |
|
|
3805 | instead of C<size_t> when allocating its data structures. On non-POSIX |
|
|
3806 | systems (Microsoft...) this might be unexpectedly low, but is still at |
|
|
3807 | least 31 bits everywhere, which is enough for hundreds of millions of |
|
|
3808 | watchers. |
|
|
3809 | |
|
|
3810 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
3811 | |
|
|
3812 | The type C<double> is used to represent timestamps. It is required to |
|
|
3813 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3814 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3815 | implementations implementing IEEE 754 (basically all existing ones). |
|
|
3816 | |
|
|
3817 | =back |
|
|
3818 | |
|
|
3819 | If you know of other additional requirements drop me a note. |
|
|
3820 | |
|
|
3821 | |
|
|
3822 | =head1 ALGORITHMIC COMPLEXITIES |
|
|
3823 | |
|
|
3824 | In this section the complexities of (many of) the algorithms used inside |
|
|
3825 | libev will be documented. For complexity discussions about backends see |
|
|
3826 | the documentation for C<ev_default_init>. |
|
|
3827 | |
|
|
3828 | All of the following are about amortised time: If an array needs to be |
|
|
3829 | extended, libev needs to realloc and move the whole array, but this |
|
|
3830 | happens asymptotically rarer with higher number of elements, so O(1) might |
|
|
3831 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
3832 | average it is much faster and asymptotically approaches constant time. |
|
|
3833 | |
|
|
3834 | =over 4 |
|
|
3835 | |
|
|
3836 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
|
|
3837 | |
|
|
3838 | This means that, when you have a watcher that triggers in one hour and |
|
|
3839 | there are 100 watchers that would trigger before that, then inserting will |
|
|
3840 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3841 | |
|
|
3842 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
|
|
3843 | |
|
|
3844 | That means that changing a timer costs less than removing/adding them, |
|
|
3845 | as only the relative motion in the event queue has to be paid for. |
|
|
3846 | |
|
|
3847 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
|
|
3848 | |
|
|
3849 | These just add the watcher into an array or at the head of a list. |
|
|
3850 | |
|
|
3851 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
|
|
3852 | |
|
|
3853 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
|
|
3854 | |
|
|
3855 | These watchers are stored in lists, so they need to be walked to find the |
|
|
3856 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
3857 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
3858 | is rare). |
|
|
3859 | |
|
|
3860 | =item Finding the next timer in each loop iteration: O(1) |
|
|
3861 | |
|
|
3862 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
3863 | fixed position in the storage array. |
|
|
3864 | |
|
|
3865 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3866 | |
|
|
3867 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3868 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3869 | on backend and whether C<ev_io_set> was used). |
|
|
3870 | |
|
|
3871 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3872 | |
|
|
3873 | =item Priority handling: O(number_of_priorities) |
|
|
3874 | |
|
|
3875 | Priorities are implemented by allocating some space for each |
|
|
3876 | priority. When doing priority-based operations, libev usually has to |
|
|
3877 | linearly search all the priorities, but starting/stopping and activating |
|
|
3878 | watchers becomes O(1) with respect to priority handling. |
|
|
3879 | |
|
|
3880 | =item Sending an ev_async: O(1) |
|
|
3881 | |
|
|
3882 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3883 | |
|
|
3884 | =item Processing signals: O(max_signal_number) |
|
|
3885 | |
|
|
3886 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3887 | calls in the current loop iteration. Checking for async and signal events |
|
|
3888 | involves iterating over all running async watchers or all signal numbers. |
|
|
3889 | |
|
|
3890 | =back |
|
|
3891 | |
|
|
3892 | |
755 | =head1 AUTHOR |
3893 | =head1 AUTHOR |
756 | |
3894 | |
757 | Marc Lehmann <libev@schmorp.de>. |
3895 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
758 | |
3896 | |