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2 | |
2 | |
3 | libev - a high performance full-featured event loop written in C |
3 | libev - a high performance full-featured event loop written in C |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
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8 | |
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9 | =head2 EXAMPLE PROGRAM |
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10 | |
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11 | // a single header file is required |
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12 | #include <ev.h> |
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13 | |
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14 | // every watcher type has its own typedef'd struct |
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15 | // with the name ev_<type> |
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16 | ev_io stdin_watcher; |
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17 | ev_timer timeout_watcher; |
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18 | |
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19 | // all watcher callbacks have a similar signature |
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20 | // this callback is called when data is readable on stdin |
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21 | static void |
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22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
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23 | { |
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24 | puts ("stdin ready"); |
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25 | // for one-shot events, one must manually stop the watcher |
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26 | // with its corresponding stop function. |
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27 | ev_io_stop (EV_A_ w); |
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28 | |
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29 | // this causes all nested ev_loop's to stop iterating |
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30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
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31 | } |
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32 | |
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33 | // another callback, this time for a time-out |
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34 | static void |
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35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
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36 | { |
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37 | puts ("timeout"); |
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38 | // this causes the innermost ev_loop to stop iterating |
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39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
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40 | } |
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41 | |
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42 | int |
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43 | main (void) |
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44 | { |
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45 | // use the default event loop unless you have special needs |
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46 | struct ev_loop *loop = ev_default_loop (0); |
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47 | |
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48 | // initialise an io watcher, then start it |
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49 | // this one will watch for stdin to become readable |
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50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
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51 | ev_io_start (loop, &stdin_watcher); |
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52 | |
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53 | // initialise a timer watcher, then start it |
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54 | // simple non-repeating 5.5 second timeout |
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55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
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56 | ev_timer_start (loop, &timeout_watcher); |
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57 | |
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58 | // now wait for events to arrive |
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59 | ev_loop (loop, 0); |
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60 | |
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61 | // unloop was called, so exit |
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62 | return 0; |
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63 | } |
8 | |
64 | |
9 | =head1 DESCRIPTION |
65 | =head1 DESCRIPTION |
10 | |
66 | |
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67 | The newest version of this document is also available as an html-formatted |
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68 | web page you might find easier to navigate when reading it for the first |
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69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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70 | |
11 | Libev is an event loop: you register interest in certain events (such as a |
71 | Libev is an event loop: you register interest in certain events (such as a |
12 | file descriptor being readable or a timeout occuring), and it will manage |
72 | file descriptor being readable or a timeout occurring), and it will manage |
13 | these event sources and provide your program with events. |
73 | these event sources and provide your program with events. |
14 | |
74 | |
15 | To do this, it must take more or less complete control over your process |
75 | To do this, it must take more or less complete control over your process |
16 | (or thread) by executing the I<event loop> handler, and will then |
76 | (or thread) by executing the I<event loop> handler, and will then |
17 | communicate events via a callback mechanism. |
77 | communicate events via a callback mechanism. |
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19 | You register interest in certain events by registering so-called I<event |
79 | You register interest in certain events by registering so-called I<event |
20 | watchers>, which are relatively small C structures you initialise with the |
80 | watchers>, which are relatively small C structures you initialise with the |
21 | details of the event, and then hand it over to libev by I<starting> the |
81 | details of the event, and then hand it over to libev by I<starting> the |
22 | watcher. |
82 | watcher. |
23 | |
83 | |
24 | =head1 FEATURES |
84 | =head2 FEATURES |
25 | |
85 | |
26 | Libev supports select, poll, the linux-specific epoll and the bsd-specific |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
27 | kqueue mechanisms for file descriptor events, relative timers, absolute |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
28 | timers with customised rescheduling, signal events, process status change |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
29 | events (related to SIGCHLD), and event watchers dealing with the event |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
30 | loop mechanism itself (idle, prepare and check watchers). It also is quite |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
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91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
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92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
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93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
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94 | file watchers (C<ev_stat>) and even limited support for fork events |
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95 | (C<ev_fork>). |
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96 | |
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97 | It also is quite fast (see this |
31 | fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
32 | it to libevent for example). |
99 | for example). |
33 | |
100 | |
34 | =head1 CONVENTIONS |
101 | =head2 CONVENTIONS |
35 | |
102 | |
36 | Libev is very configurable. In this manual the default configuration |
103 | Libev is very configurable. In this manual the default (and most common) |
37 | will be described, which supports multiple event loops. For more info |
104 | configuration will be described, which supports multiple event loops. For |
38 | about various configuration options please have a look at the file |
105 | more info about various configuration options please have a look at |
39 | F<README.embed> in the libev distribution. If libev was configured without |
106 | B<EMBED> section in this manual. If libev was configured without support |
40 | support for multiple event loops, then all functions taking an initial |
107 | for multiple event loops, then all functions taking an initial argument of |
41 | argument of name C<loop> (which is always of type C<struct ev_loop *>) |
108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
42 | will not have this argument. |
109 | this argument. |
43 | |
110 | |
44 | =head1 TIME REPRESENTATION |
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 C<double> type in C, and when you need to do any calculations on |
117 | to the C<double> type in C, and when you need to do any calculations on |
51 | it, you should treat it as such. |
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. |
52 | |
141 | |
53 | |
142 | |
54 | =head1 GLOBAL FUNCTIONS |
143 | =head1 GLOBAL FUNCTIONS |
55 | |
144 | |
56 | These functions can be called anytime, even before initialising the |
145 | These functions can be called anytime, even before initialising the |
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62 | |
151 | |
63 | Returns the current time as libev would use it. Please note that the |
152 | Returns the current time as libev would use it. Please note that the |
64 | C<ev_now> function is usually faster and also often returns the timestamp |
153 | C<ev_now> function is usually faster and also often returns the timestamp |
65 | you actually want to know. |
154 | you actually want to know. |
66 | |
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 ()>. |
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161 | |
67 | =item int ev_version_major () |
162 | =item int ev_version_major () |
68 | |
163 | |
69 | =item int ev_version_minor () |
164 | =item int ev_version_minor () |
70 | |
165 | |
71 | 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 |
72 | 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 |
73 | 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 |
74 | 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 |
75 | version of the library your program was compiled against. |
170 | version of the library your program was compiled against. |
76 | |
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 | |
77 | 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, |
78 | as this indicates an incompatible change. Minor versions are usually |
176 | as this indicates an incompatible change. Minor versions are usually |
79 | 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 |
80 | not a problem. |
178 | not a problem. |
81 | |
179 | |
82 | Example: make sure we haven't accidentally been linked against the wrong |
180 | Example: Make sure we haven't accidentally been linked against the wrong |
83 | version: |
181 | version. |
84 | |
182 | |
85 | assert (("libev version mismatch", |
183 | assert (("libev version mismatch", |
86 | ev_version_major () == EV_VERSION_MAJOR |
184 | ev_version_major () == EV_VERSION_MAJOR |
87 | && ev_version_minor () >= EV_VERSION_MINOR)); |
185 | && ev_version_minor () >= EV_VERSION_MINOR)); |
88 | |
186 | |
89 | =item unsigned int ev_supported_backends () |
187 | =item unsigned int ev_supported_backends () |
90 | |
188 | |
91 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
189 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
92 | value) compiled into this binary of libev (independent of their |
190 | value) compiled into this binary of libev (independent of their |
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94 | a description of the set values. |
192 | a description of the set values. |
95 | |
193 | |
96 | Example: make sure we have the epoll method, because yeah this is cool and |
194 | Example: make sure we have the epoll method, because yeah this is cool and |
97 | a must have and can we have a torrent of it please!!!11 |
195 | a must have and can we have a torrent of it please!!!11 |
98 | |
196 | |
99 | assert (("sorry, no epoll, no sex", |
197 | assert (("sorry, no epoll, no sex", |
100 | ev_supported_backends () & EVBACKEND_EPOLL)); |
198 | ev_supported_backends () & EVBACKEND_EPOLL)); |
101 | |
199 | |
102 | =item unsigned int ev_recommended_backends () |
200 | =item unsigned int ev_recommended_backends () |
103 | |
201 | |
104 | Return the set of all backends compiled into this binary of libev and also |
202 | Return the set of all backends compiled into this binary of libev and also |
105 | recommended for this platform. This set is often smaller than the one |
203 | recommended for this platform. This set is often smaller than the one |
106 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
204 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
107 | most BSDs and will not be autodetected unless you explicitly request it |
205 | most BSDs and will not be auto-detected unless you explicitly request it |
108 | (assuming you know what you are doing). This is the set of backends that |
206 | (assuming you know what you are doing). This is the set of backends that |
109 | libev will probe for if you specify no backends explicitly. |
207 | libev will probe for if you specify no backends explicitly. |
110 | |
208 | |
111 | =item unsigned int ev_embeddable_backends () |
209 | =item unsigned int ev_embeddable_backends () |
112 | |
210 | |
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118 | |
216 | |
119 | See the description of C<ev_embed> watchers for more info. |
217 | See the description of C<ev_embed> watchers for more info. |
120 | |
218 | |
121 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
122 | |
220 | |
123 | Sets the allocation function to use (the prototype is similar to the |
221 | Sets the allocation function to use (the prototype is similar - the |
124 | 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 |
125 | 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 |
126 | 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 |
127 | 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. |
128 | |
230 | |
129 | You could override this function in high-availability programs to, say, |
231 | You could override this function in high-availability programs to, say, |
130 | 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, |
131 | 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. |
132 | |
234 | |
133 | Example: replace the libev allocator with one that waits a bit and then |
235 | Example: Replace the libev allocator with one that waits a bit and then |
134 | retries: better than mine). |
236 | retries (example requires a standards-compliant C<realloc>). |
135 | |
237 | |
136 | static void * |
238 | static void * |
137 | persistent_realloc (void *ptr, long size) |
239 | persistent_realloc (void *ptr, size_t size) |
138 | { |
240 | { |
139 | for (;;) |
241 | for (;;) |
140 | { |
242 | { |
141 | void *newptr = realloc (ptr, size); |
243 | void *newptr = realloc (ptr, size); |
142 | |
244 | |
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150 | ... |
252 | ... |
151 | ev_set_allocator (persistent_realloc); |
253 | ev_set_allocator (persistent_realloc); |
152 | |
254 | |
153 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
154 | |
256 | |
155 | 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 |
156 | 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 |
157 | indicating the system call or subsystem causing the problem. If this |
259 | indicating the system call or subsystem causing the problem. If this |
158 | 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 |
159 | 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 |
160 | 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 |
161 | (such as abort). |
263 | (such as abort). |
162 | |
264 | |
163 | Example: do the same thing as libev does internally: |
265 | Example: This is basically the same thing that libev does internally, too. |
164 | |
266 | |
165 | static void |
267 | static void |
166 | fatal_error (const char *msg) |
268 | fatal_error (const char *msg) |
167 | { |
269 | { |
168 | perror (msg); |
270 | perror (msg); |
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177 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
178 | |
280 | |
179 | An event loop is described by a C<struct ev_loop *>. The library knows two |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
180 | types of such loops, the I<default> loop, which supports signals and child |
282 | types of such loops, the I<default> loop, which supports signals and child |
181 | events, and dynamically created loops which do not. |
283 | events, and dynamically created loops which do not. |
182 | |
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183 | If you use threads, a common model is to run the default event loop |
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184 | in your main thread (or in a separate thread) and for each thread you |
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185 | create, you also create another event loop. Libev itself does no locking |
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186 | whatsoever, so if you mix calls to the same event loop in different |
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187 | threads, make sure you lock (this is usually a bad idea, though, even if |
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188 | done correctly, because it's hideous and inefficient). |
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189 | |
284 | |
190 | =over 4 |
285 | =over 4 |
191 | |
286 | |
192 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
193 | |
288 | |
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197 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
292 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
198 | |
293 | |
199 | If you don't know what event loop to use, use the one returned from this |
294 | If you don't know what event loop to use, use the one returned from this |
200 | function. |
295 | function. |
201 | |
296 | |
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297 | Note that this function is I<not> thread-safe, so if you want to use it |
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298 | from multiple threads, you have to lock (note also that this is unlikely, |
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299 | as loops cannot bes hared easily between threads anyway). |
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300 | |
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301 | The default loop is the only loop that can handle C<ev_signal> and |
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302 | C<ev_child> watchers, and to do this, it always registers a handler |
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303 | for C<SIGCHLD>. If this is a problem for your application you can either |
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304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
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305 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
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306 | C<ev_default_init>. |
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307 | |
202 | The flags argument can be used to specify special behaviour or specific |
308 | The flags argument can be used to specify special behaviour or specific |
203 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
309 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
204 | |
310 | |
205 | The following flags are supported: |
311 | The following flags are supported: |
206 | |
312 | |
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211 | The default flags value. Use this if you have no clue (it's the right |
317 | The default flags value. Use this if you have no clue (it's the right |
212 | thing, believe me). |
318 | thing, believe me). |
213 | |
319 | |
214 | =item C<EVFLAG_NOENV> |
320 | =item C<EVFLAG_NOENV> |
215 | |
321 | |
216 | If this flag bit is ored into the flag value (or the program runs setuid |
322 | If this flag bit is or'ed into the flag value (or the program runs setuid |
217 | or setgid) then libev will I<not> look at the environment variable |
323 | or setgid) then libev will I<not> look at the environment variable |
218 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
324 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
219 | override the flags completely if it is found in the environment. This is |
325 | override the flags completely if it is found in the environment. This is |
220 | useful to try out specific backends to test their performance, or to work |
326 | useful to try out specific backends to test their performance, or to work |
221 | around bugs. |
327 | around bugs. |
222 | |
328 | |
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329 | =item C<EVFLAG_FORKCHECK> |
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330 | |
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331 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
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332 | a fork, you can also make libev check for a fork in each iteration by |
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333 | enabling this flag. |
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334 | |
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335 | This works by calling C<getpid ()> on every iteration of the loop, |
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336 | and thus this might slow down your event loop if you do a lot of loop |
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337 | iterations and little real work, but is usually not noticeable (on my |
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338 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
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339 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
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340 | C<pthread_atfork> which is even faster). |
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341 | |
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342 | The big advantage of this flag is that you can forget about fork (and |
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343 | forget about forgetting to tell libev about forking) when you use this |
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344 | flag. |
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345 | |
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346 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
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347 | environment variable. |
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348 | |
223 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
349 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
224 | |
350 | |
225 | This is your standard select(2) backend. Not I<completely> standard, as |
351 | This is your standard select(2) backend. Not I<completely> standard, as |
226 | libev tries to roll its own fd_set with no limits on the number of fds, |
352 | libev tries to roll its own fd_set with no limits on the number of fds, |
227 | but if that fails, expect a fairly low limit on the number of fds when |
353 | but if that fails, expect a fairly low limit on the number of fds when |
228 | using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
354 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
229 | the fastest backend for a low number of fds. |
355 | usually the fastest backend for a low number of (low-numbered :) fds. |
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356 | |
|
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357 | To get good performance out of this backend you need a high amount of |
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358 | parallelism (most of the file descriptors should be busy). If you are |
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359 | writing a server, you should C<accept ()> in a loop to accept as many |
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360 | connections as possible during one iteration. You might also want to have |
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361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
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362 | readiness notifications you get per iteration. |
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363 | |
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364 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
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365 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
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366 | C<exceptfds> set on that platform). |
230 | |
367 | |
231 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
368 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
232 | |
369 | |
233 | And this is your standard poll(2) backend. It's more complicated than |
370 | And this is your standard poll(2) backend. It's more complicated |
234 | select, but handles sparse fds better and has no artificial limit on the |
371 | than select, but handles sparse fds better and has no artificial |
235 | number of fds you can use (except it will slow down considerably with a |
372 | limit on the number of fds you can use (except it will slow down |
236 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds). |
373 | considerably with a lot of inactive fds). It scales similarly to select, |
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374 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
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375 | performance tips. |
|
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376 | |
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377 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
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378 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
237 | |
379 | |
238 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
380 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
239 | |
381 | |
240 | For few fds, this backend is a bit little slower than poll and select, |
382 | For few fds, this backend is a bit little slower than poll and select, |
241 | but it scales phenomenally better. While poll and select usually scale like |
383 | but it scales phenomenally better. While poll and select usually scale |
242 | O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
384 | like O(total_fds) where n is the total number of fds (or the highest fd), |
243 | either O(1) or O(active_fds). |
385 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
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386 | of shortcomings, such as silently dropping events in some hard-to-detect |
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387 | cases and requiring a system call per fd change, no fork support and bad |
|
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388 | support for dup. |
244 | |
389 | |
245 | While stopping and starting an I/O watcher in the same iteration will |
390 | While stopping, setting and starting an I/O watcher in the same iteration |
246 | result in some caching, there is still a syscall per such incident |
391 | will result in some caching, there is still a system call per such incident |
247 | (because the fd could point to a different file description now), so its |
392 | (because the fd could point to a different file description now), so its |
248 | best to avoid that. Also, dup()ed file descriptors might not work very |
393 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
249 | well if you register events for both fds. |
394 | very well if you register events for both fds. |
250 | |
395 | |
251 | Please note that epoll sometimes generates spurious notifications, so you |
396 | Please note that epoll sometimes generates spurious notifications, so you |
252 | need to use non-blocking I/O or other means to avoid blocking when no data |
397 | need to use non-blocking I/O or other means to avoid blocking when no data |
253 | (or space) is available. |
398 | (or space) is available. |
254 | |
399 | |
|
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400 | Best performance from this backend is achieved by not unregistering all |
|
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401 | watchers for a file descriptor until it has been closed, if possible, i.e. |
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402 | keep at least one watcher active per fd at all times. |
|
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403 | |
|
|
404 | While nominally embeddable in other event loops, this feature is broken in |
|
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405 | all kernel versions tested so far. |
|
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406 | |
|
|
407 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
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408 | C<EVBACKEND_POLL>. |
|
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409 | |
255 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
410 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
256 | |
411 | |
257 | Kqueue deserves special mention, as at the time of this writing, it |
412 | Kqueue deserves special mention, as at the time of this writing, it |
258 | was broken on all BSDs except NetBSD (usually it doesn't work with |
413 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
259 | anything but sockets and pipes, except on Darwin, where of course its |
414 | with anything but sockets and pipes, except on Darwin, where of course |
260 | completely useless). For this reason its not being "autodetected" |
415 | it's completely useless). For this reason it's not being "auto-detected" |
261 | unless you explicitly specify it explicitly in the flags (i.e. using |
416 | unless you explicitly specify it explicitly in the flags (i.e. using |
262 | C<EVBACKEND_KQUEUE>). |
417 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
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418 | system like NetBSD. |
|
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419 | |
|
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420 | You still can embed kqueue into a normal poll or select backend and use it |
|
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421 | only for sockets (after having made sure that sockets work with kqueue on |
|
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422 | the target platform). See C<ev_embed> watchers for more info. |
263 | |
423 | |
264 | It scales in the same way as the epoll backend, but the interface to the |
424 | It scales in the same way as the epoll backend, but the interface to the |
265 | kernel is more efficient (which says nothing about its actual speed, of |
425 | kernel is more efficient (which says nothing about its actual speed, of |
266 | course). While starting and stopping an I/O watcher does not cause an |
426 | course). While stopping, setting and starting an I/O watcher does never |
267 | extra syscall as with epoll, it still adds up to four event changes per |
427 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
268 | incident, so its best to avoid that. |
428 | two event changes per incident, support for C<fork ()> is very bad and it |
|
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429 | drops fds silently in similarly hard-to-detect cases. |
|
|
430 | |
|
|
431 | This backend usually performs well under most conditions. |
|
|
432 | |
|
|
433 | While nominally embeddable in other event loops, this doesn't work |
|
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434 | everywhere, so you might need to test for this. And since it is broken |
|
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435 | almost everywhere, you should only use it when you have a lot of sockets |
|
|
436 | (for which it usually works), by embedding it into another event loop |
|
|
437 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
|
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438 | sockets. |
|
|
439 | |
|
|
440 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
441 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
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442 | C<NOTE_EOF>. |
269 | |
443 | |
270 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
444 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
271 | |
445 | |
272 | This is not implemented yet (and might never be). |
446 | This is not implemented yet (and might never be, unless you send me an |
|
|
447 | implementation). According to reports, C</dev/poll> only supports sockets |
|
|
448 | and is not embeddable, which would limit the usefulness of this backend |
|
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449 | immensely. |
273 | |
450 | |
274 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
451 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
275 | |
452 | |
276 | This uses the Solaris 10 port mechanism. As with everything on Solaris, |
453 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
277 | it's really slow, but it still scales very well (O(active_fds)). |
454 | it's really slow, but it still scales very well (O(active_fds)). |
278 | |
455 | |
279 | Please note that solaris ports can result in a lot of spurious |
456 | Please note that Solaris event ports can deliver a lot of spurious |
280 | notifications, so you need to use non-blocking I/O or other means to avoid |
457 | notifications, so you need to use non-blocking I/O or other means to avoid |
281 | blocking when no data (or space) is available. |
458 | blocking when no data (or space) is available. |
|
|
459 | |
|
|
460 | While this backend scales well, it requires one system call per active |
|
|
461 | file descriptor per loop iteration. For small and medium numbers of file |
|
|
462 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
|
|
463 | might perform better. |
|
|
464 | |
|
|
465 | On the positive side, ignoring the spurious readiness notifications, this |
|
|
466 | backend actually performed to specification in all tests and is fully |
|
|
467 | embeddable, which is a rare feat among the OS-specific backends. |
|
|
468 | |
|
|
469 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
470 | C<EVBACKEND_POLL>. |
282 | |
471 | |
283 | =item C<EVBACKEND_ALL> |
472 | =item C<EVBACKEND_ALL> |
284 | |
473 | |
285 | Try all backends (even potentially broken ones that wouldn't be tried |
474 | Try all backends (even potentially broken ones that wouldn't be tried |
286 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
475 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
287 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
476 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
288 | |
477 | |
|
|
478 | It is definitely not recommended to use this flag. |
|
|
479 | |
289 | =back |
480 | =back |
290 | |
481 | |
291 | If one or more of these are ored into the flags value, then only these |
482 | If one or more of these are or'ed into the flags value, then only these |
292 | backends will be tried (in the reverse order as given here). If none are |
483 | backends will be tried (in the reverse order as listed here). If none are |
293 | specified, most compiled-in backend will be tried, usually in reverse |
484 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
294 | order of their flag values :) |
|
|
295 | |
485 | |
296 | The most typical usage is like this: |
486 | The most typical usage is like this: |
297 | |
487 | |
298 | if (!ev_default_loop (0)) |
488 | if (!ev_default_loop (0)) |
299 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
489 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
300 | |
490 | |
301 | Restrict libev to the select and poll backends, and do not allow |
491 | Restrict libev to the select and poll backends, and do not allow |
302 | environment settings to be taken into account: |
492 | environment settings to be taken into account: |
303 | |
493 | |
304 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
494 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
305 | |
495 | |
306 | Use whatever libev has to offer, but make sure that kqueue is used if |
496 | Use whatever libev has to offer, but make sure that kqueue is used if |
307 | available (warning, breaks stuff, best use only with your own private |
497 | available (warning, breaks stuff, best use only with your own private |
308 | event loop and only if you know the OS supports your types of fds): |
498 | event loop and only if you know the OS supports your types of fds): |
309 | |
499 | |
310 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
500 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
311 | |
501 | |
312 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
502 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
313 | |
503 | |
314 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
504 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
315 | always distinct from the default loop. Unlike the default loop, it cannot |
505 | always distinct from the default loop. Unlike the default loop, it cannot |
316 | handle signal and child watchers, and attempts to do so will be greeted by |
506 | handle signal and child watchers, and attempts to do so will be greeted by |
317 | undefined behaviour (or a failed assertion if assertions are enabled). |
507 | undefined behaviour (or a failed assertion if assertions are enabled). |
318 | |
508 | |
|
|
509 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
510 | libev with threads is indeed to create one loop per thread, and using the |
|
|
511 | default loop in the "main" or "initial" thread. |
|
|
512 | |
319 | Example: try to create a event loop that uses epoll and nothing else. |
513 | Example: Try to create a event loop that uses epoll and nothing else. |
320 | |
514 | |
321 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
515 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
322 | if (!epoller) |
516 | if (!epoller) |
323 | fatal ("no epoll found here, maybe it hides under your chair"); |
517 | fatal ("no epoll found here, maybe it hides under your chair"); |
324 | |
518 | |
325 | =item ev_default_destroy () |
519 | =item ev_default_destroy () |
326 | |
520 | |
327 | Destroys the default loop again (frees all memory and kernel state |
521 | Destroys the default loop again (frees all memory and kernel state |
328 | etc.). None of the active event watchers will be stopped in the normal |
522 | etc.). None of the active event watchers will be stopped in the normal |
329 | sense, so e.g. C<ev_is_active> might still return true. It is your |
523 | sense, so e.g. C<ev_is_active> might still return true. It is your |
330 | responsibility to either stop all watchers cleanly yoursef I<before> |
524 | responsibility to either stop all watchers cleanly yourself I<before> |
331 | calling this function, or cope with the fact afterwards (which is usually |
525 | calling this function, or cope with the fact afterwards (which is usually |
332 | the easiest thing, youc na just ignore the watchers and/or C<free ()> them |
526 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
333 | for example). |
527 | for example). |
|
|
528 | |
|
|
529 | Note that certain global state, such as signal state, will not be freed by |
|
|
530 | this function, and related watchers (such as signal and child watchers) |
|
|
531 | would need to be stopped manually. |
|
|
532 | |
|
|
533 | In general it is not advisable to call this function except in the |
|
|
534 | rare occasion where you really need to free e.g. the signal handling |
|
|
535 | pipe fds. If you need dynamically allocated loops it is better to use |
|
|
536 | C<ev_loop_new> and C<ev_loop_destroy>). |
334 | |
537 | |
335 | =item ev_loop_destroy (loop) |
538 | =item ev_loop_destroy (loop) |
336 | |
539 | |
337 | Like C<ev_default_destroy>, but destroys an event loop created by an |
540 | Like C<ev_default_destroy>, but destroys an event loop created by an |
338 | earlier call to C<ev_loop_new>. |
541 | earlier call to C<ev_loop_new>. |
339 | |
542 | |
340 | =item ev_default_fork () |
543 | =item ev_default_fork () |
341 | |
544 | |
|
|
545 | This function sets a flag that causes subsequent C<ev_loop> iterations |
342 | This function reinitialises the kernel state for backends that have |
546 | to reinitialise the kernel state for backends that have one. Despite the |
343 | one. Despite the name, you can call it anytime, but it makes most sense |
547 | name, you can call it anytime, but it makes most sense after forking, in |
344 | after forking, in either the parent or child process (or both, but that |
548 | the child process (or both child and parent, but that again makes little |
345 | again makes little sense). |
549 | sense). You I<must> call it in the child before using any of the libev |
|
|
550 | functions, and it will only take effect at the next C<ev_loop> iteration. |
346 | |
551 | |
347 | You I<must> call this function in the child process after forking if and |
552 | On the other hand, you only need to call this function in the child |
348 | only if you want to use the event library in both processes. If you just |
553 | process if and only if you want to use the event library in the child. If |
349 | fork+exec, you don't have to call it. |
554 | you just fork+exec, you don't have to call it at all. |
350 | |
555 | |
351 | The function itself is quite fast and it's usually not a problem to call |
556 | The function itself is quite fast and it's usually not a problem to call |
352 | it just in case after a fork. To make this easy, the function will fit in |
557 | it just in case after a fork. To make this easy, the function will fit in |
353 | quite nicely into a call to C<pthread_atfork>: |
558 | quite nicely into a call to C<pthread_atfork>: |
354 | |
559 | |
355 | pthread_atfork (0, 0, ev_default_fork); |
560 | pthread_atfork (0, 0, ev_default_fork); |
356 | |
561 | |
357 | At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use |
|
|
358 | without calling this function, so if you force one of those backends you |
|
|
359 | do not need to care. |
|
|
360 | |
|
|
361 | =item ev_loop_fork (loop) |
562 | =item ev_loop_fork (loop) |
362 | |
563 | |
363 | Like C<ev_default_fork>, but acts on an event loop created by |
564 | Like C<ev_default_fork>, but acts on an event loop created by |
364 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
565 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
365 | after fork, and how you do this is entirely your own problem. |
566 | after fork, and how you do this is entirely your own problem. |
|
|
567 | |
|
|
568 | =item int ev_is_default_loop (loop) |
|
|
569 | |
|
|
570 | Returns true when the given loop actually is the default loop, false otherwise. |
|
|
571 | |
|
|
572 | =item unsigned int ev_loop_count (loop) |
|
|
573 | |
|
|
574 | Returns the count of loop iterations for the loop, which is identical to |
|
|
575 | the number of times libev did poll for new events. It starts at C<0> and |
|
|
576 | happily wraps around with enough iterations. |
|
|
577 | |
|
|
578 | This value can sometimes be useful as a generation counter of sorts (it |
|
|
579 | "ticks" the number of loop iterations), as it roughly corresponds with |
|
|
580 | C<ev_prepare> and C<ev_check> calls. |
366 | |
581 | |
367 | =item unsigned int ev_backend (loop) |
582 | =item unsigned int ev_backend (loop) |
368 | |
583 | |
369 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
584 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
370 | use. |
585 | use. |
… | |
… | |
373 | |
588 | |
374 | Returns the current "event loop time", which is the time the event loop |
589 | Returns the current "event loop time", which is the time the event loop |
375 | received events and started processing them. This timestamp does not |
590 | received events and started processing them. This timestamp does not |
376 | change as long as callbacks are being processed, and this is also the base |
591 | change as long as callbacks are being processed, and this is also the base |
377 | time used for relative timers. You can treat it as the timestamp of the |
592 | time used for relative timers. You can treat it as the timestamp of the |
378 | event occuring (or more correctly, libev finding out about it). |
593 | event occurring (or more correctly, libev finding out about it). |
|
|
594 | |
|
|
595 | =item ev_now_update (loop) |
|
|
596 | |
|
|
597 | Establishes the current time by querying the kernel, updating the time |
|
|
598 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
599 | is usually done automatically within C<ev_loop ()>. |
|
|
600 | |
|
|
601 | This function is rarely useful, but when some event callback runs for a |
|
|
602 | very long time without entering the event loop, updating libev's idea of |
|
|
603 | the current time is a good idea. |
|
|
604 | |
|
|
605 | See also "The special problem of time updates" in the C<ev_timer> section. |
379 | |
606 | |
380 | =item ev_loop (loop, int flags) |
607 | =item ev_loop (loop, int flags) |
381 | |
608 | |
382 | Finally, this is it, the event handler. This function usually is called |
609 | Finally, this is it, the event handler. This function usually is called |
383 | after you initialised all your watchers and you want to start handling |
610 | after you initialised all your watchers and you want to start handling |
… | |
… | |
395 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
622 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
396 | those events and any outstanding ones, but will not block your process in |
623 | those events and any outstanding ones, but will not block your process in |
397 | case there are no events and will return after one iteration of the loop. |
624 | case there are no events and will return after one iteration of the loop. |
398 | |
625 | |
399 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
626 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
400 | neccessary) and will handle those and any outstanding ones. It will block |
627 | necessary) and will handle those and any outstanding ones. It will block |
401 | your process until at least one new event arrives, and will return after |
628 | your process until at least one new event arrives, and will return after |
402 | one iteration of the loop. This is useful if you are waiting for some |
629 | one iteration of the loop. This is useful if you are waiting for some |
403 | external event in conjunction with something not expressible using other |
630 | external event in conjunction with something not expressible using other |
404 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
631 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
405 | usually a better approach for this kind of thing. |
632 | usually a better approach for this kind of thing. |
406 | |
633 | |
407 | Here are the gory details of what C<ev_loop> does: |
634 | Here are the gory details of what C<ev_loop> does: |
408 | |
635 | |
409 | * If there are no active watchers (reference count is zero), return. |
636 | - Before the first iteration, call any pending watchers. |
410 | - Queue prepare watchers and then call all outstanding watchers. |
637 | * If EVFLAG_FORKCHECK was used, check for a fork. |
|
|
638 | - If a fork was detected (by any means), queue and call all fork watchers. |
|
|
639 | - Queue and call all prepare watchers. |
411 | - If we have been forked, recreate the kernel state. |
640 | - If we have been forked, detach and recreate the kernel state |
|
|
641 | as to not disturb the other process. |
412 | - Update the kernel state with all outstanding changes. |
642 | - Update the kernel state with all outstanding changes. |
413 | - Update the "event loop time". |
643 | - Update the "event loop time" (ev_now ()). |
414 | - Calculate for how long to block. |
644 | - Calculate for how long to sleep or block, if at all |
|
|
645 | (active idle watchers, EVLOOP_NONBLOCK or not having |
|
|
646 | any active watchers at all will result in not sleeping). |
|
|
647 | - Sleep if the I/O and timer collect interval say so. |
415 | - Block the process, waiting for any events. |
648 | - Block the process, waiting for any events. |
416 | - Queue all outstanding I/O (fd) events. |
649 | - Queue all outstanding I/O (fd) events. |
417 | - Update the "event loop time" and do time jump handling. |
650 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
418 | - Queue all outstanding timers. |
651 | - Queue all outstanding timers. |
419 | - Queue all outstanding periodics. |
652 | - Queue all outstanding periodics. |
420 | - If no events are pending now, queue all idle watchers. |
653 | - Unless any events are pending now, queue all idle watchers. |
421 | - Queue all check watchers. |
654 | - Queue all check watchers. |
422 | - Call all queued watchers in reverse order (i.e. check watchers first). |
655 | - Call all queued watchers in reverse order (i.e. check watchers first). |
423 | Signals and child watchers are implemented as I/O watchers, and will |
656 | Signals and child watchers are implemented as I/O watchers, and will |
424 | be handled here by queueing them when their watcher gets executed. |
657 | be handled here by queueing them when their watcher gets executed. |
425 | - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
658 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
426 | were used, return, otherwise continue with step *. |
659 | were used, or there are no active watchers, return, otherwise |
|
|
660 | continue with step *. |
427 | |
661 | |
428 | Example: queue some jobs and then loop until no events are outsanding |
662 | Example: Queue some jobs and then loop until no events are outstanding |
429 | anymore. |
663 | anymore. |
430 | |
664 | |
431 | ... queue jobs here, make sure they register event watchers as long |
665 | ... queue jobs here, make sure they register event watchers as long |
432 | ... as they still have work to do (even an idle watcher will do..) |
666 | ... as they still have work to do (even an idle watcher will do..) |
433 | ev_loop (my_loop, 0); |
667 | ev_loop (my_loop, 0); |
434 | ... jobs done. yeah! |
668 | ... jobs done or somebody called unloop. yeah! |
435 | |
669 | |
436 | =item ev_unloop (loop, how) |
670 | =item ev_unloop (loop, how) |
437 | |
671 | |
438 | Can be used to make a call to C<ev_loop> return early (but only after it |
672 | Can be used to make a call to C<ev_loop> return early (but only after it |
439 | has processed all outstanding events). The C<how> argument must be either |
673 | has processed all outstanding events). The C<how> argument must be either |
440 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
674 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
441 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
675 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
|
|
676 | |
|
|
677 | This "unloop state" will be cleared when entering C<ev_loop> again. |
442 | |
678 | |
443 | =item ev_ref (loop) |
679 | =item ev_ref (loop) |
444 | |
680 | |
445 | =item ev_unref (loop) |
681 | =item ev_unref (loop) |
446 | |
682 | |
… | |
… | |
451 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
687 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
452 | example, libev itself uses this for its internal signal pipe: It is not |
688 | example, libev itself uses this for its internal signal pipe: It is not |
453 | visible to the libev user and should not keep C<ev_loop> from exiting if |
689 | visible to the libev user and should not keep C<ev_loop> from exiting if |
454 | no event watchers registered by it are active. It is also an excellent |
690 | no event watchers registered by it are active. It is also an excellent |
455 | way to do this for generic recurring timers or from within third-party |
691 | way to do this for generic recurring timers or from within third-party |
456 | libraries. Just remember to I<unref after start> and I<ref before stop>. |
692 | libraries. Just remember to I<unref after start> and I<ref before stop> |
|
|
693 | (but only if the watcher wasn't active before, or was active before, |
|
|
694 | respectively). |
457 | |
695 | |
458 | Example: create a signal watcher, but keep it from keeping C<ev_loop> |
696 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
459 | running when nothing else is active. |
697 | running when nothing else is active. |
460 | |
698 | |
461 | struct dv_signal exitsig; |
699 | struct ev_signal exitsig; |
462 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
700 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
463 | ev_signal_start (myloop, &exitsig); |
701 | ev_signal_start (loop, &exitsig); |
464 | evf_unref (myloop); |
702 | evf_unref (loop); |
465 | |
703 | |
466 | Example: for some weird reason, unregister the above signal handler again. |
704 | Example: For some weird reason, unregister the above signal handler again. |
467 | |
705 | |
468 | ev_ref (myloop); |
706 | ev_ref (loop); |
469 | ev_signal_stop (myloop, &exitsig); |
707 | ev_signal_stop (loop, &exitsig); |
|
|
708 | |
|
|
709 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
|
|
710 | |
|
|
711 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
|
|
712 | |
|
|
713 | These advanced functions influence the time that libev will spend waiting |
|
|
714 | for events. Both time intervals are by default C<0>, meaning that libev |
|
|
715 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
716 | latency. |
|
|
717 | |
|
|
718 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
|
|
719 | allows libev to delay invocation of I/O and timer/periodic callbacks |
|
|
720 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
721 | opportunities). |
|
|
722 | |
|
|
723 | The background is that sometimes your program runs just fast enough to |
|
|
724 | handle one (or very few) event(s) per loop iteration. While this makes |
|
|
725 | the program responsive, it also wastes a lot of CPU time to poll for new |
|
|
726 | events, especially with backends like C<select ()> which have a high |
|
|
727 | overhead for the actual polling but can deliver many events at once. |
|
|
728 | |
|
|
729 | By setting a higher I<io collect interval> you allow libev to spend more |
|
|
730 | time collecting I/O events, so you can handle more events per iteration, |
|
|
731 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
|
|
732 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
|
|
733 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
|
|
734 | |
|
|
735 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
|
|
736 | to spend more time collecting timeouts, at the expense of increased |
|
|
737 | latency (the watcher callback will be called later). C<ev_io> watchers |
|
|
738 | will not be affected. Setting this to a non-null value will not introduce |
|
|
739 | any overhead in libev. |
|
|
740 | |
|
|
741 | Many (busy) programs can usually benefit by setting the I/O collect |
|
|
742 | interval to a value near C<0.1> or so, which is often enough for |
|
|
743 | interactive servers (of course not for games), likewise for timeouts. It |
|
|
744 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
|
|
745 | as this approaches the timing granularity of most systems. |
|
|
746 | |
|
|
747 | Setting the I<timeout collect interval> can improve the opportunity for |
|
|
748 | saving power, as the program will "bundle" timer callback invocations that |
|
|
749 | are "near" in time together, by delaying some, thus reducing the number of |
|
|
750 | times the process sleeps and wakes up again. Another useful technique to |
|
|
751 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
|
|
752 | they fire on, say, one-second boundaries only. |
|
|
753 | |
|
|
754 | =item ev_loop_verify (loop) |
|
|
755 | |
|
|
756 | This function only does something when C<EV_VERIFY> support has been |
|
|
757 | compiled in. It tries to go through all internal structures and checks |
|
|
758 | them for validity. If anything is found to be inconsistent, it will print |
|
|
759 | an error message to standard error and call C<abort ()>. |
|
|
760 | |
|
|
761 | This can be used to catch bugs inside libev itself: under normal |
|
|
762 | circumstances, this function will never abort as of course libev keeps its |
|
|
763 | data structures consistent. |
470 | |
764 | |
471 | =back |
765 | =back |
|
|
766 | |
472 | |
767 | |
473 | =head1 ANATOMY OF A WATCHER |
768 | =head1 ANATOMY OF A WATCHER |
474 | |
769 | |
475 | A watcher is a structure that you create and register to record your |
770 | A watcher is a structure that you create and register to record your |
476 | interest in some event. For instance, if you want to wait for STDIN to |
771 | interest in some event. For instance, if you want to wait for STDIN to |
477 | become readable, you would create an C<ev_io> watcher for that: |
772 | become readable, you would create an C<ev_io> watcher for that: |
478 | |
773 | |
479 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
774 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
480 | { |
775 | { |
481 | ev_io_stop (w); |
776 | ev_io_stop (w); |
482 | ev_unloop (loop, EVUNLOOP_ALL); |
777 | ev_unloop (loop, EVUNLOOP_ALL); |
483 | } |
778 | } |
484 | |
779 | |
485 | struct ev_loop *loop = ev_default_loop (0); |
780 | struct ev_loop *loop = ev_default_loop (0); |
486 | struct ev_io stdin_watcher; |
781 | struct ev_io stdin_watcher; |
487 | ev_init (&stdin_watcher, my_cb); |
782 | ev_init (&stdin_watcher, my_cb); |
488 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
783 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
489 | ev_io_start (loop, &stdin_watcher); |
784 | ev_io_start (loop, &stdin_watcher); |
490 | ev_loop (loop, 0); |
785 | ev_loop (loop, 0); |
491 | |
786 | |
492 | As you can see, you are responsible for allocating the memory for your |
787 | As you can see, you are responsible for allocating the memory for your |
493 | watcher structures (and it is usually a bad idea to do this on the stack, |
788 | watcher structures (and it is usually a bad idea to do this on the stack, |
494 | although this can sometimes be quite valid). |
789 | although this can sometimes be quite valid). |
495 | |
790 | |
496 | Each watcher structure must be initialised by a call to C<ev_init |
791 | Each watcher structure must be initialised by a call to C<ev_init |
497 | (watcher *, callback)>, which expects a callback to be provided. This |
792 | (watcher *, callback)>, which expects a callback to be provided. This |
498 | callback gets invoked each time the event occurs (or, in the case of io |
793 | callback gets invoked each time the event occurs (or, in the case of I/O |
499 | watchers, each time the event loop detects that the file descriptor given |
794 | watchers, each time the event loop detects that the file descriptor given |
500 | is readable and/or writable). |
795 | is readable and/or writable). |
501 | |
796 | |
502 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
797 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
503 | with arguments specific to this watcher type. There is also a macro |
798 | with arguments specific to this watcher type. There is also a macro |
… | |
… | |
543 | The signal specified in the C<ev_signal> watcher has been received by a thread. |
838 | The signal specified in the C<ev_signal> watcher has been received by a thread. |
544 | |
839 | |
545 | =item C<EV_CHILD> |
840 | =item C<EV_CHILD> |
546 | |
841 | |
547 | The pid specified in the C<ev_child> watcher has received a status change. |
842 | The pid specified in the C<ev_child> watcher has received a status change. |
|
|
843 | |
|
|
844 | =item C<EV_STAT> |
|
|
845 | |
|
|
846 | The path specified in the C<ev_stat> watcher changed its attributes somehow. |
548 | |
847 | |
549 | =item C<EV_IDLE> |
848 | =item C<EV_IDLE> |
550 | |
849 | |
551 | The C<ev_idle> watcher has determined that you have nothing better to do. |
850 | The C<ev_idle> watcher has determined that you have nothing better to do. |
552 | |
851 | |
… | |
… | |
560 | received events. Callbacks of both watcher types can start and stop as |
859 | received events. Callbacks of both watcher types can start and stop as |
561 | many watchers as they want, and all of them will be taken into account |
860 | many watchers as they want, and all of them will be taken into account |
562 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
861 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
563 | C<ev_loop> from blocking). |
862 | C<ev_loop> from blocking). |
564 | |
863 | |
|
|
864 | =item C<EV_EMBED> |
|
|
865 | |
|
|
866 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
|
|
867 | |
|
|
868 | =item C<EV_FORK> |
|
|
869 | |
|
|
870 | The event loop has been resumed in the child process after fork (see |
|
|
871 | C<ev_fork>). |
|
|
872 | |
|
|
873 | =item C<EV_ASYNC> |
|
|
874 | |
|
|
875 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
876 | |
565 | =item C<EV_ERROR> |
877 | =item C<EV_ERROR> |
566 | |
878 | |
567 | An unspecified error has occured, the watcher has been stopped. This might |
879 | An unspecified error has occurred, the watcher has been stopped. This might |
568 | happen because the watcher could not be properly started because libev |
880 | happen because the watcher could not be properly started because libev |
569 | ran out of memory, a file descriptor was found to be closed or any other |
881 | ran out of memory, a file descriptor was found to be closed or any other |
570 | problem. You best act on it by reporting the problem and somehow coping |
882 | problem. You best act on it by reporting the problem and somehow coping |
571 | with the watcher being stopped. |
883 | with the watcher being stopped. |
572 | |
884 | |
573 | Libev will usually signal a few "dummy" events together with an error, |
885 | Libev will usually signal a few "dummy" events together with an error, |
574 | for example it might indicate that a fd is readable or writable, and if |
886 | for example it might indicate that a fd is readable or writable, and if |
575 | your callbacks is well-written it can just attempt the operation and cope |
887 | your callbacks is well-written it can just attempt the operation and cope |
576 | with the error from read() or write(). This will not work in multithreaded |
888 | with the error from read() or write(). This will not work in multi-threaded |
577 | programs, though, so beware. |
889 | programs, though, so beware. |
578 | |
890 | |
579 | =back |
891 | =back |
580 | |
892 | |
581 | =head2 SUMMARY OF GENERIC WATCHER FUNCTIONS |
893 | =head2 GENERIC WATCHER FUNCTIONS |
582 | |
894 | |
583 | In the following description, C<TYPE> stands for the watcher type, |
895 | In the following description, C<TYPE> stands for the watcher type, |
584 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
896 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
585 | |
897 | |
586 | =over 4 |
898 | =over 4 |
… | |
… | |
595 | which rolls both calls into one. |
907 | which rolls both calls into one. |
596 | |
908 | |
597 | You can reinitialise a watcher at any time as long as it has been stopped |
909 | You can reinitialise a watcher at any time as long as it has been stopped |
598 | (or never started) and there are no pending events outstanding. |
910 | (or never started) and there are no pending events outstanding. |
599 | |
911 | |
600 | The callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
912 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
601 | int revents)>. |
913 | int revents)>. |
602 | |
914 | |
603 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
915 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
604 | |
916 | |
605 | This macro initialises the type-specific parts of a watcher. You need to |
917 | This macro initialises the type-specific parts of a watcher. You need to |
… | |
… | |
611 | Although some watcher types do not have type-specific arguments |
923 | Although some watcher types do not have type-specific arguments |
612 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
924 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
613 | |
925 | |
614 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
926 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
615 | |
927 | |
616 | This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
928 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
617 | calls into a single call. This is the most convinient method to initialise |
929 | calls into a single call. This is the most convenient method to initialise |
618 | a watcher. The same limitations apply, of course. |
930 | a watcher. The same limitations apply, of course. |
619 | |
931 | |
620 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
932 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
621 | |
933 | |
622 | Starts (activates) the given watcher. Only active watchers will receive |
934 | Starts (activates) the given watcher. Only active watchers will receive |
… | |
… | |
640 | =item bool ev_is_pending (ev_TYPE *watcher) |
952 | =item bool ev_is_pending (ev_TYPE *watcher) |
641 | |
953 | |
642 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
954 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
643 | events but its callback has not yet been invoked). As long as a watcher |
955 | events but its callback has not yet been invoked). As long as a watcher |
644 | is pending (but not active) you must not call an init function on it (but |
956 | is pending (but not active) you must not call an init function on it (but |
645 | C<ev_TYPE_set> is safe) and you must make sure the watcher is available to |
957 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
646 | libev (e.g. you cnanot C<free ()> it). |
958 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
959 | it). |
647 | |
960 | |
648 | =item callback = ev_cb (ev_TYPE *watcher) |
961 | =item callback ev_cb (ev_TYPE *watcher) |
649 | |
962 | |
650 | Returns the callback currently set on the watcher. |
963 | Returns the callback currently set on the watcher. |
651 | |
964 | |
652 | =item ev_cb_set (ev_TYPE *watcher, callback) |
965 | =item ev_cb_set (ev_TYPE *watcher, callback) |
653 | |
966 | |
654 | Change the callback. You can change the callback at virtually any time |
967 | Change the callback. You can change the callback at virtually any time |
655 | (modulo threads). |
968 | (modulo threads). |
|
|
969 | |
|
|
970 | =item ev_set_priority (ev_TYPE *watcher, priority) |
|
|
971 | |
|
|
972 | =item int ev_priority (ev_TYPE *watcher) |
|
|
973 | |
|
|
974 | Set and query the priority of the watcher. The priority is a small |
|
|
975 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
976 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
977 | before watchers with lower priority, but priority will not keep watchers |
|
|
978 | from being executed (except for C<ev_idle> watchers). |
|
|
979 | |
|
|
980 | This means that priorities are I<only> used for ordering callback |
|
|
981 | invocation after new events have been received. This is useful, for |
|
|
982 | example, to reduce latency after idling, or more often, to bind two |
|
|
983 | watchers on the same event and make sure one is called first. |
|
|
984 | |
|
|
985 | If you need to suppress invocation when higher priority events are pending |
|
|
986 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
987 | |
|
|
988 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
989 | pending. |
|
|
990 | |
|
|
991 | The default priority used by watchers when no priority has been set is |
|
|
992 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
993 | |
|
|
994 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
995 | fine, as long as you do not mind that the priority value you query might |
|
|
996 | or might not have been adjusted to be within valid range. |
|
|
997 | |
|
|
998 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
999 | |
|
|
1000 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1001 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1002 | can deal with that fact. |
|
|
1003 | |
|
|
1004 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1005 | |
|
|
1006 | If the watcher is pending, this function returns clears its pending status |
|
|
1007 | and returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1008 | watcher isn't pending it does nothing and returns C<0>. |
656 | |
1009 | |
657 | =back |
1010 | =back |
658 | |
1011 | |
659 | |
1012 | |
660 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1013 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
… | |
… | |
664 | to associate arbitrary data with your watcher. If you need more data and |
1017 | to associate arbitrary data with your watcher. If you need more data and |
665 | don't want to allocate memory and store a pointer to it in that data |
1018 | don't want to allocate memory and store a pointer to it in that data |
666 | member, you can also "subclass" the watcher type and provide your own |
1019 | member, you can also "subclass" the watcher type and provide your own |
667 | data: |
1020 | data: |
668 | |
1021 | |
669 | struct my_io |
1022 | struct my_io |
670 | { |
1023 | { |
671 | struct ev_io io; |
1024 | struct ev_io io; |
672 | int otherfd; |
1025 | int otherfd; |
673 | void *somedata; |
1026 | void *somedata; |
674 | struct whatever *mostinteresting; |
1027 | struct whatever *mostinteresting; |
675 | } |
1028 | }; |
|
|
1029 | |
|
|
1030 | ... |
|
|
1031 | struct my_io w; |
|
|
1032 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
676 | |
1033 | |
677 | And since your callback will be called with a pointer to the watcher, you |
1034 | And since your callback will be called with a pointer to the watcher, you |
678 | can cast it back to your own type: |
1035 | can cast it back to your own type: |
679 | |
1036 | |
680 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1037 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
681 | { |
1038 | { |
682 | struct my_io *w = (struct my_io *)w_; |
1039 | struct my_io *w = (struct my_io *)w_; |
683 | ... |
1040 | ... |
684 | } |
1041 | } |
685 | |
1042 | |
686 | More interesting and less C-conformant ways of catsing your callback type |
1043 | More interesting and less C-conformant ways of casting your callback type |
687 | have been omitted.... |
1044 | instead have been omitted. |
|
|
1045 | |
|
|
1046 | Another common scenario is to use some data structure with multiple |
|
|
1047 | embedded watchers: |
|
|
1048 | |
|
|
1049 | struct my_biggy |
|
|
1050 | { |
|
|
1051 | int some_data; |
|
|
1052 | ev_timer t1; |
|
|
1053 | ev_timer t2; |
|
|
1054 | } |
|
|
1055 | |
|
|
1056 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1057 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1058 | in the C<data> member of the watcher, or you need to use some pointer |
|
|
1059 | arithmetic using C<offsetof> inside your watchers: |
|
|
1060 | |
|
|
1061 | #include <stddef.h> |
|
|
1062 | |
|
|
1063 | static void |
|
|
1064 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
1065 | { |
|
|
1066 | struct my_biggy big = (struct my_biggy * |
|
|
1067 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1068 | } |
|
|
1069 | |
|
|
1070 | static void |
|
|
1071 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
1072 | { |
|
|
1073 | struct my_biggy big = (struct my_biggy * |
|
|
1074 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1075 | } |
688 | |
1076 | |
689 | |
1077 | |
690 | =head1 WATCHER TYPES |
1078 | =head1 WATCHER TYPES |
691 | |
1079 | |
692 | This section describes each watcher in detail, but will not repeat |
1080 | This section describes each watcher in detail, but will not repeat |
693 | information given in the last section. |
1081 | information given in the last section. Any initialisation/set macros, |
|
|
1082 | functions and members specific to the watcher type are explained. |
694 | |
1083 | |
|
|
1084 | Members are additionally marked with either I<[read-only]>, meaning that, |
|
|
1085 | while the watcher is active, you can look at the member and expect some |
|
|
1086 | sensible content, but you must not modify it (you can modify it while the |
|
|
1087 | watcher is stopped to your hearts content), or I<[read-write]>, which |
|
|
1088 | means you can expect it to have some sensible content while the watcher |
|
|
1089 | is active, but you can also modify it. Modifying it may not do something |
|
|
1090 | sensible or take immediate effect (or do anything at all), but libev will |
|
|
1091 | not crash or malfunction in any way. |
695 | |
1092 | |
|
|
1093 | |
696 | =head2 C<ev_io> - is this file descriptor readable or writable |
1094 | =head2 C<ev_io> - is this file descriptor readable or writable? |
697 | |
1095 | |
698 | I/O watchers check whether a file descriptor is readable or writable |
1096 | I/O watchers check whether a file descriptor is readable or writable |
699 | in each iteration of the event loop (This behaviour is called |
1097 | in each iteration of the event loop, or, more precisely, when reading |
700 | level-triggering because you keep receiving events as long as the |
1098 | would not block the process and writing would at least be able to write |
701 | condition persists. Remember you can stop the watcher if you don't want to |
1099 | some data. This behaviour is called level-triggering because you keep |
702 | act on the event and neither want to receive future events). |
1100 | receiving events as long as the condition persists. Remember you can stop |
|
|
1101 | the watcher if you don't want to act on the event and neither want to |
|
|
1102 | receive future events. |
703 | |
1103 | |
704 | In general you can register as many read and/or write event watchers per |
1104 | In general you can register as many read and/or write event watchers per |
705 | fd as you want (as long as you don't confuse yourself). Setting all file |
1105 | fd as you want (as long as you don't confuse yourself). Setting all file |
706 | descriptors to non-blocking mode is also usually a good idea (but not |
1106 | descriptors to non-blocking mode is also usually a good idea (but not |
707 | required if you know what you are doing). |
1107 | required if you know what you are doing). |
708 | |
1108 | |
709 | You have to be careful with dup'ed file descriptors, though. Some backends |
|
|
710 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
|
|
711 | descriptors correctly if you register interest in two or more fds pointing |
|
|
712 | to the same underlying file/socket etc. description (that is, they share |
|
|
713 | the same underlying "file open"). |
|
|
714 | |
|
|
715 | If you must do this, then force the use of a known-to-be-good backend |
1109 | If you must do this, then force the use of a known-to-be-good backend |
716 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1110 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
717 | C<EVBACKEND_POLL>). |
1111 | C<EVBACKEND_POLL>). |
718 | |
1112 | |
|
|
1113 | Another thing you have to watch out for is that it is quite easy to |
|
|
1114 | receive "spurious" readiness notifications, that is your callback might |
|
|
1115 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
|
|
1116 | because there is no data. Not only are some backends known to create a |
|
|
1117 | lot of those (for example Solaris ports), it is very easy to get into |
|
|
1118 | this situation even with a relatively standard program structure. Thus |
|
|
1119 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1120 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
|
|
1121 | |
|
|
1122 | If you cannot run the fd in non-blocking mode (for example you should not |
|
|
1123 | play around with an Xlib connection), then you have to separately re-test |
|
|
1124 | whether a file descriptor is really ready with a known-to-be good interface |
|
|
1125 | such as poll (fortunately in our Xlib example, Xlib already does this on |
|
|
1126 | its own, so its quite safe to use). |
|
|
1127 | |
|
|
1128 | =head3 The special problem of disappearing file descriptors |
|
|
1129 | |
|
|
1130 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
|
|
1131 | descriptor (either by calling C<close> explicitly or by any other means, |
|
|
1132 | such as C<dup>). The reason is that you register interest in some file |
|
|
1133 | descriptor, but when it goes away, the operating system will silently drop |
|
|
1134 | this interest. If another file descriptor with the same number then is |
|
|
1135 | registered with libev, there is no efficient way to see that this is, in |
|
|
1136 | fact, a different file descriptor. |
|
|
1137 | |
|
|
1138 | To avoid having to explicitly tell libev about such cases, libev follows |
|
|
1139 | the following policy: Each time C<ev_io_set> is being called, libev |
|
|
1140 | will assume that this is potentially a new file descriptor, otherwise |
|
|
1141 | it is assumed that the file descriptor stays the same. That means that |
|
|
1142 | you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the |
|
|
1143 | descriptor even if the file descriptor number itself did not change. |
|
|
1144 | |
|
|
1145 | This is how one would do it normally anyway, the important point is that |
|
|
1146 | the libev application should not optimise around libev but should leave |
|
|
1147 | optimisations to libev. |
|
|
1148 | |
|
|
1149 | =head3 The special problem of dup'ed file descriptors |
|
|
1150 | |
|
|
1151 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
1152 | but only events for the underlying file descriptions. That means when you |
|
|
1153 | have C<dup ()>'ed file descriptors or weirder constellations, and register |
|
|
1154 | events for them, only one file descriptor might actually receive events. |
|
|
1155 | |
|
|
1156 | There is no workaround possible except not registering events |
|
|
1157 | for potentially C<dup ()>'ed file descriptors, or to resort to |
|
|
1158 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
|
|
1159 | |
|
|
1160 | =head3 The special problem of fork |
|
|
1161 | |
|
|
1162 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
|
|
1163 | useless behaviour. Libev fully supports fork, but needs to be told about |
|
|
1164 | it in the child. |
|
|
1165 | |
|
|
1166 | To support fork in your programs, you either have to call |
|
|
1167 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
|
|
1168 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
|
|
1169 | C<EVBACKEND_POLL>. |
|
|
1170 | |
|
|
1171 | =head3 The special problem of SIGPIPE |
|
|
1172 | |
|
|
1173 | While not really specific to libev, it is easy to forget about SIGPIPE: |
|
|
1174 | when writing to a pipe whose other end has been closed, your program gets |
|
|
1175 | send a SIGPIPE, which, by default, aborts your program. For most programs |
|
|
1176 | this is sensible behaviour, for daemons, this is usually undesirable. |
|
|
1177 | |
|
|
1178 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1179 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1180 | somewhere, as that would have given you a big clue). |
|
|
1181 | |
|
|
1182 | |
|
|
1183 | =head3 Watcher-Specific Functions |
|
|
1184 | |
719 | =over 4 |
1185 | =over 4 |
720 | |
1186 | |
721 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1187 | =item ev_io_init (ev_io *, callback, int fd, int events) |
722 | |
1188 | |
723 | =item ev_io_set (ev_io *, int fd, int events) |
1189 | =item ev_io_set (ev_io *, int fd, int events) |
724 | |
1190 | |
725 | Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive |
1191 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
726 | events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ | |
1192 | receive events for and events is either C<EV_READ>, C<EV_WRITE> or |
727 | EV_WRITE> to receive the given events. |
1193 | C<EV_READ | EV_WRITE> to receive the given events. |
728 | |
1194 | |
729 | Please note that most of the more scalable backend mechanisms (for example |
1195 | =item int fd [read-only] |
730 | epoll and solaris ports) can result in spurious readyness notifications |
1196 | |
731 | for file descriptors, so you practically need to use non-blocking I/O (and |
1197 | The file descriptor being watched. |
732 | treat callback invocation as hint only), or retest separately with a safe |
1198 | |
733 | interface before doing I/O (XLib can do this), or force the use of either |
1199 | =item int events [read-only] |
734 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this |
1200 | |
735 | problem. Also note that it is quite easy to have your callback invoked |
1201 | The events being watched. |
736 | when the readyness condition is no longer valid even when employing |
|
|
737 | typical ways of handling events, so its a good idea to use non-blocking |
|
|
738 | I/O unconditionally. |
|
|
739 | |
1202 | |
740 | =back |
1203 | =back |
741 | |
1204 | |
|
|
1205 | =head3 Examples |
|
|
1206 | |
742 | Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1207 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
743 | readable, but only once. Since it is likely line-buffered, you could |
1208 | readable, but only once. Since it is likely line-buffered, you could |
744 | attempt to read a whole line in the callback: |
1209 | attempt to read a whole line in the callback. |
745 | |
1210 | |
746 | static void |
1211 | static void |
747 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1212 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
748 | { |
1213 | { |
749 | ev_io_stop (loop, w); |
1214 | ev_io_stop (loop, w); |
750 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1215 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
751 | } |
1216 | } |
752 | |
1217 | |
753 | ... |
1218 | ... |
754 | struct ev_loop *loop = ev_default_init (0); |
1219 | struct ev_loop *loop = ev_default_init (0); |
755 | struct ev_io stdin_readable; |
1220 | struct ev_io stdin_readable; |
756 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1221 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
757 | ev_io_start (loop, &stdin_readable); |
1222 | ev_io_start (loop, &stdin_readable); |
758 | ev_loop (loop, 0); |
1223 | ev_loop (loop, 0); |
759 | |
1224 | |
760 | |
1225 | |
761 | =head2 C<ev_timer> - relative and optionally recurring timeouts |
1226 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
762 | |
1227 | |
763 | Timer watchers are simple relative timers that generate an event after a |
1228 | Timer watchers are simple relative timers that generate an event after a |
764 | given time, and optionally repeating in regular intervals after that. |
1229 | given time, and optionally repeating in regular intervals after that. |
765 | |
1230 | |
766 | The timers are based on real time, that is, if you register an event that |
1231 | The timers are based on real time, that is, if you register an event that |
767 | times out after an hour and you reset your system clock to last years |
1232 | times out after an hour and you reset your system clock to January last |
768 | time, it will still time out after (roughly) and hour. "Roughly" because |
1233 | year, it will still time out after (roughly) and hour. "Roughly" because |
769 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1234 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
770 | monotonic clock option helps a lot here). |
1235 | monotonic clock option helps a lot here). |
|
|
1236 | |
|
|
1237 | The callback is guaranteed to be invoked only after its timeout has passed, |
|
|
1238 | but if multiple timers become ready during the same loop iteration then |
|
|
1239 | order of execution is undefined. |
|
|
1240 | |
|
|
1241 | =head3 The special problem of time updates |
|
|
1242 | |
|
|
1243 | Establishing the current time is a costly operation (it usually takes at |
|
|
1244 | least two system calls): EV therefore updates its idea of the current |
|
|
1245 | time only before and after C<ev_loop> polls for new events, which causes |
|
|
1246 | a growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
1247 | lots of events. |
771 | |
1248 | |
772 | The relative timeouts are calculated relative to the C<ev_now ()> |
1249 | The relative timeouts are calculated relative to the C<ev_now ()> |
773 | time. This is usually the right thing as this timestamp refers to the time |
1250 | time. This is usually the right thing as this timestamp refers to the time |
774 | of the event triggering whatever timeout you are modifying/starting. If |
1251 | of the event triggering whatever timeout you are modifying/starting. If |
775 | you suspect event processing to be delayed and you I<need> to base the timeout |
1252 | you suspect event processing to be delayed and you I<need> to base the |
776 | on the current time, use something like this to adjust for this: |
1253 | timeout on the current time, use something like this to adjust for this: |
777 | |
1254 | |
778 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1255 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
779 | |
1256 | |
780 | The callback is guarenteed to be invoked only when its timeout has passed, |
1257 | If the event loop is suspended for a long time, you can also force an |
781 | but if multiple timers become ready during the same loop iteration then |
1258 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
782 | order of execution is undefined. |
1259 | ()>. |
|
|
1260 | |
|
|
1261 | =head3 Watcher-Specific Functions and Data Members |
783 | |
1262 | |
784 | =over 4 |
1263 | =over 4 |
785 | |
1264 | |
786 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1265 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
787 | |
1266 | |
788 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1267 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
789 | |
1268 | |
790 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1269 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
791 | C<0.>, then it will automatically be stopped. If it is positive, then the |
1270 | is C<0.>, then it will automatically be stopped once the timeout is |
792 | timer will automatically be configured to trigger again C<repeat> seconds |
1271 | reached. If it is positive, then the timer will automatically be |
793 | later, again, and again, until stopped manually. |
1272 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1273 | until stopped manually. |
794 | |
1274 | |
795 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1275 | The timer itself will do a best-effort at avoiding drift, that is, if |
796 | configure a timer to trigger every 10 seconds, then it will trigger at |
1276 | you configure a timer to trigger every 10 seconds, then it will normally |
797 | exactly 10 second intervals. If, however, your program cannot keep up with |
1277 | trigger at exactly 10 second intervals. If, however, your program cannot |
798 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1278 | keep up with the timer (because it takes longer than those 10 seconds to |
799 | timer will not fire more than once per event loop iteration. |
1279 | do stuff) the timer will not fire more than once per event loop iteration. |
800 | |
1280 | |
801 | =item ev_timer_again (loop) |
1281 | =item ev_timer_again (loop, ev_timer *) |
802 | |
1282 | |
803 | This will act as if the timer timed out and restart it again if it is |
1283 | This will act as if the timer timed out and restart it again if it is |
804 | repeating. The exact semantics are: |
1284 | repeating. The exact semantics are: |
805 | |
1285 | |
|
|
1286 | If the timer is pending, its pending status is cleared. |
|
|
1287 | |
806 | If the timer is started but nonrepeating, stop it. |
1288 | If the timer is started but non-repeating, stop it (as if it timed out). |
807 | |
1289 | |
808 | If the timer is repeating, either start it if necessary (with the repeat |
1290 | If the timer is repeating, either start it if necessary (with the |
809 | value), or reset the running timer to the repeat value. |
1291 | C<repeat> value), or reset the running timer to the C<repeat> value. |
810 | |
1292 | |
811 | This sounds a bit complicated, but here is a useful and typical |
1293 | This sounds a bit complicated, but here is a useful and typical |
812 | example: Imagine you have a tcp connection and you want a so-called idle |
1294 | example: Imagine you have a TCP connection and you want a so-called idle |
813 | timeout, that is, you want to be called when there have been, say, 60 |
1295 | timeout, that is, you want to be called when there have been, say, 60 |
814 | seconds of inactivity on the socket. The easiest way to do this is to |
1296 | seconds of inactivity on the socket. The easiest way to do this is to |
815 | configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each |
1297 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
816 | time you successfully read or write some data. If you go into an idle |
1298 | C<ev_timer_again> each time you successfully read or write some data. If |
817 | state where you do not expect data to travel on the socket, you can stop |
1299 | you go into an idle state where you do not expect data to travel on the |
818 | the timer, and again will automatically restart it if need be. |
1300 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1301 | automatically restart it if need be. |
|
|
1302 | |
|
|
1303 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1304 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1305 | |
|
|
1306 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1307 | ev_timer_again (loop, timer); |
|
|
1308 | ... |
|
|
1309 | timer->again = 17.; |
|
|
1310 | ev_timer_again (loop, timer); |
|
|
1311 | ... |
|
|
1312 | timer->again = 10.; |
|
|
1313 | ev_timer_again (loop, timer); |
|
|
1314 | |
|
|
1315 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1316 | you want to modify its timeout value. |
|
|
1317 | |
|
|
1318 | =item ev_tstamp repeat [read-write] |
|
|
1319 | |
|
|
1320 | The current C<repeat> value. Will be used each time the watcher times out |
|
|
1321 | or C<ev_timer_again> is called and determines the next timeout (if any), |
|
|
1322 | which is also when any modifications are taken into account. |
819 | |
1323 | |
820 | =back |
1324 | =back |
821 | |
1325 | |
|
|
1326 | =head3 Examples |
|
|
1327 | |
822 | Example: create a timer that fires after 60 seconds. |
1328 | Example: Create a timer that fires after 60 seconds. |
823 | |
1329 | |
824 | static void |
1330 | static void |
825 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1331 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
826 | { |
1332 | { |
827 | .. one minute over, w is actually stopped right here |
1333 | .. one minute over, w is actually stopped right here |
828 | } |
1334 | } |
829 | |
1335 | |
830 | struct ev_timer mytimer; |
1336 | struct ev_timer mytimer; |
831 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1337 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
832 | ev_timer_start (loop, &mytimer); |
1338 | ev_timer_start (loop, &mytimer); |
833 | |
1339 | |
834 | Example: create a timeout timer that times out after 10 seconds of |
1340 | Example: Create a timeout timer that times out after 10 seconds of |
835 | inactivity. |
1341 | inactivity. |
836 | |
1342 | |
837 | static void |
1343 | static void |
838 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1344 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
839 | { |
1345 | { |
840 | .. ten seconds without any activity |
1346 | .. ten seconds without any activity |
841 | } |
1347 | } |
842 | |
1348 | |
843 | struct ev_timer mytimer; |
1349 | struct ev_timer mytimer; |
844 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1350 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
845 | ev_timer_again (&mytimer); /* start timer */ |
1351 | ev_timer_again (&mytimer); /* start timer */ |
846 | ev_loop (loop, 0); |
1352 | ev_loop (loop, 0); |
847 | |
1353 | |
848 | // and in some piece of code that gets executed on any "activity": |
1354 | // and in some piece of code that gets executed on any "activity": |
849 | // reset the timeout to start ticking again at 10 seconds |
1355 | // reset the timeout to start ticking again at 10 seconds |
850 | ev_timer_again (&mytimer); |
1356 | ev_timer_again (&mytimer); |
851 | |
1357 | |
852 | |
1358 | |
853 | =head2 C<ev_periodic> - to cron or not to cron |
1359 | =head2 C<ev_periodic> - to cron or not to cron? |
854 | |
1360 | |
855 | Periodic watchers are also timers of a kind, but they are very versatile |
1361 | Periodic watchers are also timers of a kind, but they are very versatile |
856 | (and unfortunately a bit complex). |
1362 | (and unfortunately a bit complex). |
857 | |
1363 | |
858 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1364 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
859 | but on wallclock time (absolute time). You can tell a periodic watcher |
1365 | but on wall clock time (absolute time). You can tell a periodic watcher |
860 | to trigger "at" some specific point in time. For example, if you tell a |
1366 | to trigger after some specific point in time. For example, if you tell a |
861 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1367 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
862 | + 10.>) and then reset your system clock to the last year, then it will |
1368 | + 10.>, that is, an absolute time not a delay) and then reset your system |
|
|
1369 | clock to January of the previous year, then it will take more than year |
863 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1370 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
864 | roughly 10 seconds later and of course not if you reset your system time |
1371 | roughly 10 seconds later as it uses a relative timeout). |
865 | again). |
|
|
866 | |
1372 | |
867 | They can also be used to implement vastly more complex timers, such as |
1373 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
868 | triggering an event on eahc midnight, local time. |
1374 | such as triggering an event on each "midnight, local time", or other |
|
|
1375 | complicated, rules. |
869 | |
1376 | |
870 | As with timers, the callback is guarenteed to be invoked only when the |
1377 | As with timers, the callback is guaranteed to be invoked only when the |
871 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1378 | time (C<at>) has passed, but if multiple periodic timers become ready |
872 | during the same loop iteration then order of execution is undefined. |
1379 | during the same loop iteration then order of execution is undefined. |
|
|
1380 | |
|
|
1381 | =head3 Watcher-Specific Functions and Data Members |
873 | |
1382 | |
874 | =over 4 |
1383 | =over 4 |
875 | |
1384 | |
876 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1385 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
877 | |
1386 | |
… | |
… | |
880 | Lots of arguments, lets sort it out... There are basically three modes of |
1389 | Lots of arguments, lets sort it out... There are basically three modes of |
881 | operation, and we will explain them from simplest to complex: |
1390 | operation, and we will explain them from simplest to complex: |
882 | |
1391 | |
883 | =over 4 |
1392 | =over 4 |
884 | |
1393 | |
885 | =item * absolute timer (interval = reschedule_cb = 0) |
1394 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
886 | |
1395 | |
887 | In this configuration the watcher triggers an event at the wallclock time |
1396 | In this configuration the watcher triggers an event after the wall clock |
888 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1397 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
889 | that is, if it is to be run at January 1st 2011 then it will run when the |
1398 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
890 | system time reaches or surpasses this time. |
1399 | run when the system time reaches or surpasses this time. |
891 | |
1400 | |
892 | =item * non-repeating interval timer (interval > 0, reschedule_cb = 0) |
1401 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
893 | |
1402 | |
894 | In this mode the watcher will always be scheduled to time out at the next |
1403 | In this mode the watcher will always be scheduled to time out at the next |
895 | C<at + N * interval> time (for some integer N) and then repeat, regardless |
1404 | C<at + N * interval> time (for some integer N, which can also be negative) |
896 | of any time jumps. |
1405 | and then repeat, regardless of any time jumps. |
897 | |
1406 | |
898 | This can be used to create timers that do not drift with respect to system |
1407 | This can be used to create timers that do not drift with respect to system |
899 | time: |
1408 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
|
|
1409 | the hour: |
900 | |
1410 | |
901 | ev_periodic_set (&periodic, 0., 3600., 0); |
1411 | ev_periodic_set (&periodic, 0., 3600., 0); |
902 | |
1412 | |
903 | This doesn't mean there will always be 3600 seconds in between triggers, |
1413 | This doesn't mean there will always be 3600 seconds in between triggers, |
904 | but only that the the callback will be called when the system time shows a |
1414 | but only that the callback will be called when the system time shows a |
905 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1415 | full hour (UTC), or more correctly, when the system time is evenly divisible |
906 | by 3600. |
1416 | by 3600. |
907 | |
1417 | |
908 | Another way to think about it (for the mathematically inclined) is that |
1418 | Another way to think about it (for the mathematically inclined) is that |
909 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1419 | C<ev_periodic> will try to run the callback in this mode at the next possible |
910 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1420 | time where C<time = at (mod interval)>, regardless of any time jumps. |
911 | |
1421 | |
|
|
1422 | For numerical stability it is preferable that the C<at> value is near |
|
|
1423 | C<ev_now ()> (the current time), but there is no range requirement for |
|
|
1424 | this value, and in fact is often specified as zero. |
|
|
1425 | |
|
|
1426 | Note also that there is an upper limit to how often a timer can fire (CPU |
|
|
1427 | speed for example), so if C<interval> is very small then timing stability |
|
|
1428 | will of course deteriorate. Libev itself tries to be exact to be about one |
|
|
1429 | millisecond (if the OS supports it and the machine is fast enough). |
|
|
1430 | |
912 | =item * manual reschedule mode (reschedule_cb = callback) |
1431 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
913 | |
1432 | |
914 | In this mode the values for C<interval> and C<at> are both being |
1433 | In this mode the values for C<interval> and C<at> are both being |
915 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1434 | ignored. Instead, each time the periodic watcher gets scheduled, the |
916 | reschedule callback will be called with the watcher as first, and the |
1435 | reschedule callback will be called with the watcher as first, and the |
917 | current time as second argument. |
1436 | current time as second argument. |
918 | |
1437 | |
919 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1438 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
920 | ever, or make any event loop modifications>. If you need to stop it, |
1439 | ever, or make ANY event loop modifications whatsoever>. |
921 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
|
|
922 | starting a prepare watcher). |
|
|
923 | |
1440 | |
|
|
1441 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
1442 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
1443 | only event loop modification you are allowed to do). |
|
|
1444 | |
924 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1445 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
925 | ev_tstamp now)>, e.g.: |
1446 | *w, ev_tstamp now)>, e.g.: |
926 | |
1447 | |
927 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1448 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
928 | { |
1449 | { |
929 | return now + 60.; |
1450 | return now + 60.; |
930 | } |
1451 | } |
… | |
… | |
932 | It must return the next time to trigger, based on the passed time value |
1453 | It must return the next time to trigger, based on the passed time value |
933 | (that is, the lowest time value larger than to the second argument). It |
1454 | (that is, the lowest time value larger than to the second argument). It |
934 | will usually be called just before the callback will be triggered, but |
1455 | will usually be called just before the callback will be triggered, but |
935 | might be called at other times, too. |
1456 | might be called at other times, too. |
936 | |
1457 | |
937 | NOTE: I<< This callback must always return a time that is later than the |
1458 | NOTE: I<< This callback must always return a time that is higher than or |
938 | passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. |
1459 | equal to the passed C<now> value >>. |
939 | |
1460 | |
940 | This can be used to create very complex timers, such as a timer that |
1461 | This can be used to create very complex timers, such as a timer that |
941 | triggers on each midnight, local time. To do this, you would calculate the |
1462 | triggers on "next midnight, local time". To do this, you would calculate the |
942 | next midnight after C<now> and return the timestamp value for this. How |
1463 | next midnight after C<now> and return the timestamp value for this. How |
943 | you do this is, again, up to you (but it is not trivial, which is the main |
1464 | you do this is, again, up to you (but it is not trivial, which is the main |
944 | reason I omitted it as an example). |
1465 | reason I omitted it as an example). |
945 | |
1466 | |
946 | =back |
1467 | =back |
… | |
… | |
950 | Simply stops and restarts the periodic watcher again. This is only useful |
1471 | Simply stops and restarts the periodic watcher again. This is only useful |
951 | when you changed some parameters or the reschedule callback would return |
1472 | when you changed some parameters or the reschedule callback would return |
952 | a different time than the last time it was called (e.g. in a crond like |
1473 | a different time than the last time it was called (e.g. in a crond like |
953 | program when the crontabs have changed). |
1474 | program when the crontabs have changed). |
954 | |
1475 | |
|
|
1476 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
1477 | |
|
|
1478 | When active, returns the absolute time that the watcher is supposed to |
|
|
1479 | trigger next. |
|
|
1480 | |
|
|
1481 | =item ev_tstamp offset [read-write] |
|
|
1482 | |
|
|
1483 | When repeating, this contains the offset value, otherwise this is the |
|
|
1484 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
|
|
1485 | |
|
|
1486 | Can be modified any time, but changes only take effect when the periodic |
|
|
1487 | timer fires or C<ev_periodic_again> is being called. |
|
|
1488 | |
|
|
1489 | =item ev_tstamp interval [read-write] |
|
|
1490 | |
|
|
1491 | The current interval value. Can be modified any time, but changes only |
|
|
1492 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
|
|
1493 | called. |
|
|
1494 | |
|
|
1495 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
|
|
1496 | |
|
|
1497 | The current reschedule callback, or C<0>, if this functionality is |
|
|
1498 | switched off. Can be changed any time, but changes only take effect when |
|
|
1499 | the periodic timer fires or C<ev_periodic_again> is being called. |
|
|
1500 | |
955 | =back |
1501 | =back |
956 | |
1502 | |
|
|
1503 | =head3 Examples |
|
|
1504 | |
957 | Example: call a callback every hour, or, more precisely, whenever the |
1505 | Example: Call a callback every hour, or, more precisely, whenever the |
958 | system clock is divisible by 3600. The callback invocation times have |
1506 | system clock is divisible by 3600. The callback invocation times have |
959 | potentially a lot of jittering, but good long-term stability. |
1507 | potentially a lot of jitter, but good long-term stability. |
960 | |
1508 | |
961 | static void |
1509 | static void |
962 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1510 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
963 | { |
1511 | { |
964 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1512 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
965 | } |
1513 | } |
966 | |
1514 | |
967 | struct ev_periodic hourly_tick; |
1515 | struct ev_periodic hourly_tick; |
968 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1516 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
969 | ev_periodic_start (loop, &hourly_tick); |
1517 | ev_periodic_start (loop, &hourly_tick); |
970 | |
1518 | |
971 | Example: the same as above, but use a reschedule callback to do it: |
1519 | Example: The same as above, but use a reschedule callback to do it: |
972 | |
1520 | |
973 | #include <math.h> |
1521 | #include <math.h> |
974 | |
1522 | |
975 | static ev_tstamp |
1523 | static ev_tstamp |
976 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1524 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
977 | { |
1525 | { |
978 | return fmod (now, 3600.) + 3600.; |
1526 | return fmod (now, 3600.) + 3600.; |
979 | } |
1527 | } |
980 | |
1528 | |
981 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1529 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
982 | |
1530 | |
983 | Example: call a callback every hour, starting now: |
1531 | Example: Call a callback every hour, starting now: |
984 | |
1532 | |
985 | struct ev_periodic hourly_tick; |
1533 | struct ev_periodic hourly_tick; |
986 | ev_periodic_init (&hourly_tick, clock_cb, |
1534 | ev_periodic_init (&hourly_tick, clock_cb, |
987 | fmod (ev_now (loop), 3600.), 3600., 0); |
1535 | fmod (ev_now (loop), 3600.), 3600., 0); |
988 | ev_periodic_start (loop, &hourly_tick); |
1536 | ev_periodic_start (loop, &hourly_tick); |
989 | |
1537 | |
990 | |
1538 | |
991 | =head2 C<ev_signal> - signal me when a signal gets signalled |
1539 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
992 | |
1540 | |
993 | Signal watchers will trigger an event when the process receives a specific |
1541 | Signal watchers will trigger an event when the process receives a specific |
994 | signal one or more times. Even though signals are very asynchronous, libev |
1542 | signal one or more times. Even though signals are very asynchronous, libev |
995 | will try it's best to deliver signals synchronously, i.e. as part of the |
1543 | will try it's best to deliver signals synchronously, i.e. as part of the |
996 | normal event processing, like any other event. |
1544 | normal event processing, like any other event. |
… | |
… | |
1000 | with the kernel (thus it coexists with your own signal handlers as long |
1548 | with the kernel (thus it coexists with your own signal handlers as long |
1001 | as you don't register any with libev). Similarly, when the last signal |
1549 | as you don't register any with libev). Similarly, when the last signal |
1002 | watcher for a signal is stopped libev will reset the signal handler to |
1550 | watcher for a signal is stopped libev will reset the signal handler to |
1003 | SIG_DFL (regardless of what it was set to before). |
1551 | SIG_DFL (regardless of what it was set to before). |
1004 | |
1552 | |
|
|
1553 | If possible and supported, libev will install its handlers with |
|
|
1554 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
|
|
1555 | interrupted. If you have a problem with system calls getting interrupted by |
|
|
1556 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1557 | them in an C<ev_prepare> watcher. |
|
|
1558 | |
|
|
1559 | =head3 Watcher-Specific Functions and Data Members |
|
|
1560 | |
1005 | =over 4 |
1561 | =over 4 |
1006 | |
1562 | |
1007 | =item ev_signal_init (ev_signal *, callback, int signum) |
1563 | =item ev_signal_init (ev_signal *, callback, int signum) |
1008 | |
1564 | |
1009 | =item ev_signal_set (ev_signal *, int signum) |
1565 | =item ev_signal_set (ev_signal *, int signum) |
1010 | |
1566 | |
1011 | Configures the watcher to trigger on the given signal number (usually one |
1567 | Configures the watcher to trigger on the given signal number (usually one |
1012 | of the C<SIGxxx> constants). |
1568 | of the C<SIGxxx> constants). |
1013 | |
1569 | |
|
|
1570 | =item int signum [read-only] |
|
|
1571 | |
|
|
1572 | The signal the watcher watches out for. |
|
|
1573 | |
1014 | =back |
1574 | =back |
1015 | |
1575 | |
|
|
1576 | =head3 Examples |
1016 | |
1577 | |
|
|
1578 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
|
|
1579 | |
|
|
1580 | static void |
|
|
1581 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
1582 | { |
|
|
1583 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1584 | } |
|
|
1585 | |
|
|
1586 | struct ev_signal signal_watcher; |
|
|
1587 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1588 | ev_signal_start (loop, &sigint_cb); |
|
|
1589 | |
|
|
1590 | |
1017 | =head2 C<ev_child> - wait for pid status changes |
1591 | =head2 C<ev_child> - watch out for process status changes |
1018 | |
1592 | |
1019 | Child watchers trigger when your process receives a SIGCHLD in response to |
1593 | Child watchers trigger when your process receives a SIGCHLD in response to |
1020 | some child status changes (most typically when a child of yours dies). |
1594 | some child status changes (most typically when a child of yours dies). It |
|
|
1595 | is permissible to install a child watcher I<after> the child has been |
|
|
1596 | forked (which implies it might have already exited), as long as the event |
|
|
1597 | loop isn't entered (or is continued from a watcher). |
|
|
1598 | |
|
|
1599 | Only the default event loop is capable of handling signals, and therefore |
|
|
1600 | you can only register child watchers in the default event loop. |
|
|
1601 | |
|
|
1602 | =head3 Process Interaction |
|
|
1603 | |
|
|
1604 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
1605 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
1606 | the first child watcher is started after the child exits. The occurrence |
|
|
1607 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
1608 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
1609 | children, even ones not watched. |
|
|
1610 | |
|
|
1611 | =head3 Overriding the Built-In Processing |
|
|
1612 | |
|
|
1613 | Libev offers no special support for overriding the built-in child |
|
|
1614 | processing, but if your application collides with libev's default child |
|
|
1615 | handler, you can override it easily by installing your own handler for |
|
|
1616 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
1617 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
1618 | event-based approach to child reaping and thus use libev's support for |
|
|
1619 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
1620 | |
|
|
1621 | =head3 Stopping the Child Watcher |
|
|
1622 | |
|
|
1623 | Currently, the child watcher never gets stopped, even when the |
|
|
1624 | child terminates, so normally one needs to stop the watcher in the |
|
|
1625 | callback. Future versions of libev might stop the watcher automatically |
|
|
1626 | when a child exit is detected. |
|
|
1627 | |
|
|
1628 | =head3 Watcher-Specific Functions and Data Members |
1021 | |
1629 | |
1022 | =over 4 |
1630 | =over 4 |
1023 | |
1631 | |
1024 | =item ev_child_init (ev_child *, callback, int pid) |
1632 | =item ev_child_init (ev_child *, callback, int pid, int trace) |
1025 | |
1633 | |
1026 | =item ev_child_set (ev_child *, int pid) |
1634 | =item ev_child_set (ev_child *, int pid, int trace) |
1027 | |
1635 | |
1028 | Configures the watcher to wait for status changes of process C<pid> (or |
1636 | Configures the watcher to wait for status changes of process C<pid> (or |
1029 | I<any> process if C<pid> is specified as C<0>). The callback can look |
1637 | I<any> process if C<pid> is specified as C<0>). The callback can look |
1030 | at the C<rstatus> member of the C<ev_child> watcher structure to see |
1638 | at the C<rstatus> member of the C<ev_child> watcher structure to see |
1031 | the status word (use the macros from C<sys/wait.h> and see your systems |
1639 | the status word (use the macros from C<sys/wait.h> and see your systems |
1032 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
1640 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
1033 | process causing the status change. |
1641 | process causing the status change. C<trace> must be either C<0> (only |
|
|
1642 | activate the watcher when the process terminates) or C<1> (additionally |
|
|
1643 | activate the watcher when the process is stopped or continued). |
|
|
1644 | |
|
|
1645 | =item int pid [read-only] |
|
|
1646 | |
|
|
1647 | The process id this watcher watches out for, or C<0>, meaning any process id. |
|
|
1648 | |
|
|
1649 | =item int rpid [read-write] |
|
|
1650 | |
|
|
1651 | The process id that detected a status change. |
|
|
1652 | |
|
|
1653 | =item int rstatus [read-write] |
|
|
1654 | |
|
|
1655 | The process exit/trace status caused by C<rpid> (see your systems |
|
|
1656 | C<waitpid> and C<sys/wait.h> documentation for details). |
1034 | |
1657 | |
1035 | =back |
1658 | =back |
1036 | |
1659 | |
1037 | Example: try to exit cleanly on SIGINT and SIGTERM. |
1660 | =head3 Examples |
1038 | |
1661 | |
|
|
1662 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
1663 | its completion. |
|
|
1664 | |
|
|
1665 | ev_child cw; |
|
|
1666 | |
1039 | static void |
1667 | static void |
1040 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1668 | child_cb (EV_P_ struct ev_child *w, int revents) |
1041 | { |
1669 | { |
1042 | ev_unloop (loop, EVUNLOOP_ALL); |
1670 | ev_child_stop (EV_A_ w); |
|
|
1671 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1043 | } |
1672 | } |
1044 | |
1673 | |
1045 | struct ev_signal signal_watcher; |
1674 | pid_t pid = fork (); |
1046 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1047 | ev_signal_start (loop, &sigint_cb); |
|
|
1048 | |
1675 | |
|
|
1676 | if (pid < 0) |
|
|
1677 | // error |
|
|
1678 | else if (pid == 0) |
|
|
1679 | { |
|
|
1680 | // the forked child executes here |
|
|
1681 | exit (1); |
|
|
1682 | } |
|
|
1683 | else |
|
|
1684 | { |
|
|
1685 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
1686 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
1687 | } |
1049 | |
1688 | |
|
|
1689 | |
|
|
1690 | =head2 C<ev_stat> - did the file attributes just change? |
|
|
1691 | |
|
|
1692 | This watches a file system path for attribute changes. That is, it calls |
|
|
1693 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
|
|
1694 | compared to the last time, invoking the callback if it did. |
|
|
1695 | |
|
|
1696 | The path does not need to exist: changing from "path exists" to "path does |
|
|
1697 | not exist" is a status change like any other. The condition "path does |
|
|
1698 | not exist" is signified by the C<st_nlink> field being zero (which is |
|
|
1699 | otherwise always forced to be at least one) and all the other fields of |
|
|
1700 | the stat buffer having unspecified contents. |
|
|
1701 | |
|
|
1702 | The path I<should> be absolute and I<must not> end in a slash. If it is |
|
|
1703 | relative and your working directory changes, the behaviour is undefined. |
|
|
1704 | |
|
|
1705 | Since there is no standard to do this, the portable implementation simply |
|
|
1706 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
|
|
1707 | can specify a recommended polling interval for this case. If you specify |
|
|
1708 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
|
|
1709 | unspecified default> value will be used (which you can expect to be around |
|
|
1710 | five seconds, although this might change dynamically). Libev will also |
|
|
1711 | impose a minimum interval which is currently around C<0.1>, but thats |
|
|
1712 | usually overkill. |
|
|
1713 | |
|
|
1714 | This watcher type is not meant for massive numbers of stat watchers, |
|
|
1715 | as even with OS-supported change notifications, this can be |
|
|
1716 | resource-intensive. |
|
|
1717 | |
|
|
1718 | At the time of this writing, only the Linux inotify interface is |
|
|
1719 | implemented (implementing kqueue support is left as an exercise for the |
|
|
1720 | reader, note, however, that the author sees no way of implementing ev_stat |
|
|
1721 | semantics with kqueue). Inotify will be used to give hints only and should |
|
|
1722 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1723 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1724 | but changes are usually detected immediately, and if the file exists there |
|
|
1725 | will be no polling. |
|
|
1726 | |
|
|
1727 | =head3 ABI Issues (Largefile Support) |
|
|
1728 | |
|
|
1729 | Libev by default (unless the user overrides this) uses the default |
|
|
1730 | compilation environment, which means that on systems with large file |
|
|
1731 | support disabled by default, you get the 32 bit version of the stat |
|
|
1732 | structure. When using the library from programs that change the ABI to |
|
|
1733 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
1734 | compile libev with the same flags to get binary compatibility. This is |
|
|
1735 | obviously the case with any flags that change the ABI, but the problem is |
|
|
1736 | most noticeably disabled with ev_stat and large file support. |
|
|
1737 | |
|
|
1738 | The solution for this is to lobby your distribution maker to make large |
|
|
1739 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
1740 | optional. Libev cannot simply switch on large file support because it has |
|
|
1741 | to exchange stat structures with application programs compiled using the |
|
|
1742 | default compilation environment. |
|
|
1743 | |
|
|
1744 | =head3 Inotify |
|
|
1745 | |
|
|
1746 | When C<inotify (7)> support has been compiled into libev (generally only |
|
|
1747 | available on Linux) and present at runtime, it will be used to speed up |
|
|
1748 | change detection where possible. The inotify descriptor will be created lazily |
|
|
1749 | when the first C<ev_stat> watcher is being started. |
|
|
1750 | |
|
|
1751 | Inotify presence does not change the semantics of C<ev_stat> watchers |
|
|
1752 | except that changes might be detected earlier, and in some cases, to avoid |
|
|
1753 | making regular C<stat> calls. Even in the presence of inotify support |
|
|
1754 | there are many cases where libev has to resort to regular C<stat> polling. |
|
|
1755 | |
|
|
1756 | (There is no support for kqueue, as apparently it cannot be used to |
|
|
1757 | implement this functionality, due to the requirement of having a file |
|
|
1758 | descriptor open on the object at all times). |
|
|
1759 | |
|
|
1760 | =head3 The special problem of stat time resolution |
|
|
1761 | |
|
|
1762 | The C<stat ()> system call only supports full-second resolution portably, and |
|
|
1763 | even on systems where the resolution is higher, many file systems still |
|
|
1764 | only support whole seconds. |
|
|
1765 | |
|
|
1766 | That means that, if the time is the only thing that changes, you can |
|
|
1767 | easily miss updates: on the first update, C<ev_stat> detects a change and |
|
|
1768 | calls your callback, which does something. When there is another update |
|
|
1769 | within the same second, C<ev_stat> will be unable to detect it as the stat |
|
|
1770 | data does not change. |
|
|
1771 | |
|
|
1772 | The solution to this is to delay acting on a change for slightly more |
|
|
1773 | than a second (or till slightly after the next full second boundary), using |
|
|
1774 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
|
|
1775 | ev_timer_again (loop, w)>). |
|
|
1776 | |
|
|
1777 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
1778 | of some operating systems (where the second counter of the current time |
|
|
1779 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
1780 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
1781 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
1782 | update file times then there will be a small window where the kernel uses |
|
|
1783 | the previous second to update file times but libev might already execute |
|
|
1784 | the timer callback). |
|
|
1785 | |
|
|
1786 | =head3 Watcher-Specific Functions and Data Members |
|
|
1787 | |
|
|
1788 | =over 4 |
|
|
1789 | |
|
|
1790 | =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) |
|
|
1791 | |
|
|
1792 | =item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval) |
|
|
1793 | |
|
|
1794 | Configures the watcher to wait for status changes of the given |
|
|
1795 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
|
|
1796 | be detected and should normally be specified as C<0> to let libev choose |
|
|
1797 | a suitable value. The memory pointed to by C<path> must point to the same |
|
|
1798 | path for as long as the watcher is active. |
|
|
1799 | |
|
|
1800 | The callback will receive C<EV_STAT> when a change was detected, relative |
|
|
1801 | to the attributes at the time the watcher was started (or the last change |
|
|
1802 | was detected). |
|
|
1803 | |
|
|
1804 | =item ev_stat_stat (loop, ev_stat *) |
|
|
1805 | |
|
|
1806 | Updates the stat buffer immediately with new values. If you change the |
|
|
1807 | watched path in your callback, you could call this function to avoid |
|
|
1808 | detecting this change (while introducing a race condition if you are not |
|
|
1809 | the only one changing the path). Can also be useful simply to find out the |
|
|
1810 | new values. |
|
|
1811 | |
|
|
1812 | =item ev_statdata attr [read-only] |
|
|
1813 | |
|
|
1814 | The most-recently detected attributes of the file. Although the type is |
|
|
1815 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
|
|
1816 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
1817 | members to be present. If the C<st_nlink> member is C<0>, then there was |
|
|
1818 | some error while C<stat>ing the file. |
|
|
1819 | |
|
|
1820 | =item ev_statdata prev [read-only] |
|
|
1821 | |
|
|
1822 | The previous attributes of the file. The callback gets invoked whenever |
|
|
1823 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
1824 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
1825 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
|
|
1826 | |
|
|
1827 | =item ev_tstamp interval [read-only] |
|
|
1828 | |
|
|
1829 | The specified interval. |
|
|
1830 | |
|
|
1831 | =item const char *path [read-only] |
|
|
1832 | |
|
|
1833 | The file system path that is being watched. |
|
|
1834 | |
|
|
1835 | =back |
|
|
1836 | |
|
|
1837 | =head3 Examples |
|
|
1838 | |
|
|
1839 | Example: Watch C</etc/passwd> for attribute changes. |
|
|
1840 | |
|
|
1841 | static void |
|
|
1842 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
|
|
1843 | { |
|
|
1844 | /* /etc/passwd changed in some way */ |
|
|
1845 | if (w->attr.st_nlink) |
|
|
1846 | { |
|
|
1847 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
|
|
1848 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
|
|
1849 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
|
|
1850 | } |
|
|
1851 | else |
|
|
1852 | /* you shalt not abuse printf for puts */ |
|
|
1853 | puts ("wow, /etc/passwd is not there, expect problems. " |
|
|
1854 | "if this is windows, they already arrived\n"); |
|
|
1855 | } |
|
|
1856 | |
|
|
1857 | ... |
|
|
1858 | ev_stat passwd; |
|
|
1859 | |
|
|
1860 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
|
|
1861 | ev_stat_start (loop, &passwd); |
|
|
1862 | |
|
|
1863 | Example: Like above, but additionally use a one-second delay so we do not |
|
|
1864 | miss updates (however, frequent updates will delay processing, too, so |
|
|
1865 | one might do the work both on C<ev_stat> callback invocation I<and> on |
|
|
1866 | C<ev_timer> callback invocation). |
|
|
1867 | |
|
|
1868 | static ev_stat passwd; |
|
|
1869 | static ev_timer timer; |
|
|
1870 | |
|
|
1871 | static void |
|
|
1872 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1873 | { |
|
|
1874 | ev_timer_stop (EV_A_ w); |
|
|
1875 | |
|
|
1876 | /* now it's one second after the most recent passwd change */ |
|
|
1877 | } |
|
|
1878 | |
|
|
1879 | static void |
|
|
1880 | stat_cb (EV_P_ ev_stat *w, int revents) |
|
|
1881 | { |
|
|
1882 | /* reset the one-second timer */ |
|
|
1883 | ev_timer_again (EV_A_ &timer); |
|
|
1884 | } |
|
|
1885 | |
|
|
1886 | ... |
|
|
1887 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
|
|
1888 | ev_stat_start (loop, &passwd); |
|
|
1889 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
|
|
1890 | |
|
|
1891 | |
1050 | =head2 C<ev_idle> - when you've got nothing better to do |
1892 | =head2 C<ev_idle> - when you've got nothing better to do... |
1051 | |
1893 | |
1052 | Idle watchers trigger events when there are no other events are pending |
1894 | Idle watchers trigger events when no other events of the same or higher |
1053 | (prepare, check and other idle watchers do not count). That is, as long |
1895 | priority are pending (prepare, check and other idle watchers do not |
1054 | as your process is busy handling sockets or timeouts (or even signals, |
1896 | count). |
1055 | imagine) it will not be triggered. But when your process is idle all idle |
1897 | |
1056 | watchers are being called again and again, once per event loop iteration - |
1898 | That is, as long as your process is busy handling sockets or timeouts |
|
|
1899 | (or even signals, imagine) of the same or higher priority it will not be |
|
|
1900 | triggered. But when your process is idle (or only lower-priority watchers |
|
|
1901 | are pending), the idle watchers are being called once per event loop |
1057 | until stopped, that is, or your process receives more events and becomes |
1902 | iteration - until stopped, that is, or your process receives more events |
1058 | busy. |
1903 | and becomes busy again with higher priority stuff. |
1059 | |
1904 | |
1060 | The most noteworthy effect is that as long as any idle watchers are |
1905 | The most noteworthy effect is that as long as any idle watchers are |
1061 | active, the process will not block when waiting for new events. |
1906 | active, the process will not block when waiting for new events. |
1062 | |
1907 | |
1063 | Apart from keeping your process non-blocking (which is a useful |
1908 | Apart from keeping your process non-blocking (which is a useful |
1064 | effect on its own sometimes), idle watchers are a good place to do |
1909 | effect on its own sometimes), idle watchers are a good place to do |
1065 | "pseudo-background processing", or delay processing stuff to after the |
1910 | "pseudo-background processing", or delay processing stuff to after the |
1066 | event loop has handled all outstanding events. |
1911 | event loop has handled all outstanding events. |
1067 | |
1912 | |
|
|
1913 | =head3 Watcher-Specific Functions and Data Members |
|
|
1914 | |
1068 | =over 4 |
1915 | =over 4 |
1069 | |
1916 | |
1070 | =item ev_idle_init (ev_signal *, callback) |
1917 | =item ev_idle_init (ev_signal *, callback) |
1071 | |
1918 | |
1072 | Initialises and configures the idle watcher - it has no parameters of any |
1919 | Initialises and configures the idle watcher - it has no parameters of any |
1073 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1920 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1074 | believe me. |
1921 | believe me. |
1075 | |
1922 | |
1076 | =back |
1923 | =back |
1077 | |
1924 | |
|
|
1925 | =head3 Examples |
|
|
1926 | |
1078 | Example: dynamically allocate an C<ev_idle>, start it, and in the |
1927 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1079 | callback, free it. Alos, use no error checking, as usual. |
1928 | callback, free it. Also, use no error checking, as usual. |
1080 | |
1929 | |
1081 | static void |
1930 | static void |
1082 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
1931 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
1083 | { |
1932 | { |
1084 | free (w); |
1933 | free (w); |
1085 | // now do something you wanted to do when the program has |
1934 | // now do something you wanted to do when the program has |
1086 | // no longer asnything immediate to do. |
1935 | // no longer anything immediate to do. |
1087 | } |
1936 | } |
1088 | |
1937 | |
1089 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1938 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1090 | ev_idle_init (idle_watcher, idle_cb); |
1939 | ev_idle_init (idle_watcher, idle_cb); |
1091 | ev_idle_start (loop, idle_cb); |
1940 | ev_idle_start (loop, idle_cb); |
1092 | |
1941 | |
1093 | |
1942 | |
1094 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop |
1943 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1095 | |
1944 | |
1096 | Prepare and check watchers are usually (but not always) used in tandem: |
1945 | Prepare and check watchers are usually (but not always) used in tandem: |
1097 | prepare watchers get invoked before the process blocks and check watchers |
1946 | prepare watchers get invoked before the process blocks and check watchers |
1098 | afterwards. |
1947 | afterwards. |
1099 | |
1948 | |
|
|
1949 | You I<must not> call C<ev_loop> or similar functions that enter |
|
|
1950 | the current event loop from either C<ev_prepare> or C<ev_check> |
|
|
1951 | watchers. Other loops than the current one are fine, however. The |
|
|
1952 | rationale behind this is that you do not need to check for recursion in |
|
|
1953 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
|
|
1954 | C<ev_check> so if you have one watcher of each kind they will always be |
|
|
1955 | called in pairs bracketing the blocking call. |
|
|
1956 | |
1100 | Their main purpose is to integrate other event mechanisms into libev and |
1957 | Their main purpose is to integrate other event mechanisms into libev and |
1101 | their use is somewhat advanced. This could be used, for example, to track |
1958 | their use is somewhat advanced. This could be used, for example, to track |
1102 | variable changes, implement your own watchers, integrate net-snmp or a |
1959 | variable changes, implement your own watchers, integrate net-snmp or a |
1103 | coroutine library and lots more. |
1960 | coroutine library and lots more. They are also occasionally useful if |
|
|
1961 | you cache some data and want to flush it before blocking (for example, |
|
|
1962 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
|
|
1963 | watcher). |
1104 | |
1964 | |
1105 | This is done by examining in each prepare call which file descriptors need |
1965 | This is done by examining in each prepare call which file descriptors need |
1106 | to be watched by the other library, registering C<ev_io> watchers for |
1966 | to be watched by the other library, registering C<ev_io> watchers for |
1107 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
1967 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
1108 | provide just this functionality). Then, in the check watcher you check for |
1968 | provide just this functionality). Then, in the check watcher you check for |
1109 | any events that occured (by checking the pending status of all watchers |
1969 | any events that occurred (by checking the pending status of all watchers |
1110 | and stopping them) and call back into the library. The I/O and timer |
1970 | and stopping them) and call back into the library. The I/O and timer |
1111 | callbacks will never actually be called (but must be valid nevertheless, |
1971 | callbacks will never actually be called (but must be valid nevertheless, |
1112 | because you never know, you know?). |
1972 | because you never know, you know?). |
1113 | |
1973 | |
1114 | As another example, the Perl Coro module uses these hooks to integrate |
1974 | As another example, the Perl Coro module uses these hooks to integrate |
… | |
… | |
1118 | with priority higher than or equal to the event loop and one coroutine |
1978 | with priority higher than or equal to the event loop and one coroutine |
1119 | of lower priority, but only once, using idle watchers to keep the event |
1979 | of lower priority, but only once, using idle watchers to keep the event |
1120 | loop from blocking if lower-priority coroutines are active, thus mapping |
1980 | loop from blocking if lower-priority coroutines are active, thus mapping |
1121 | low-priority coroutines to idle/background tasks). |
1981 | low-priority coroutines to idle/background tasks). |
1122 | |
1982 | |
|
|
1983 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
|
|
1984 | priority, to ensure that they are being run before any other watchers |
|
|
1985 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
|
|
1986 | too) should not activate ("feed") events into libev. While libev fully |
|
|
1987 | supports this, they might get executed before other C<ev_check> watchers |
|
|
1988 | did their job. As C<ev_check> watchers are often used to embed other |
|
|
1989 | (non-libev) event loops those other event loops might be in an unusable |
|
|
1990 | state until their C<ev_check> watcher ran (always remind yourself to |
|
|
1991 | coexist peacefully with others). |
|
|
1992 | |
|
|
1993 | =head3 Watcher-Specific Functions and Data Members |
|
|
1994 | |
1123 | =over 4 |
1995 | =over 4 |
1124 | |
1996 | |
1125 | =item ev_prepare_init (ev_prepare *, callback) |
1997 | =item ev_prepare_init (ev_prepare *, callback) |
1126 | |
1998 | |
1127 | =item ev_check_init (ev_check *, callback) |
1999 | =item ev_check_init (ev_check *, callback) |
… | |
… | |
1130 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2002 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1131 | macros, but using them is utterly, utterly and completely pointless. |
2003 | macros, but using them is utterly, utterly and completely pointless. |
1132 | |
2004 | |
1133 | =back |
2005 | =back |
1134 | |
2006 | |
1135 | Example: *TODO*. |
2007 | =head3 Examples |
1136 | |
2008 | |
|
|
2009 | There are a number of principal ways to embed other event loops or modules |
|
|
2010 | into libev. Here are some ideas on how to include libadns into libev |
|
|
2011 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
|
|
2012 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
|
|
2013 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
|
|
2014 | Glib event loop). |
1137 | |
2015 | |
|
|
2016 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
|
|
2017 | and in a check watcher, destroy them and call into libadns. What follows |
|
|
2018 | is pseudo-code only of course. This requires you to either use a low |
|
|
2019 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
|
|
2020 | the callbacks for the IO/timeout watchers might not have been called yet. |
|
|
2021 | |
|
|
2022 | static ev_io iow [nfd]; |
|
|
2023 | static ev_timer tw; |
|
|
2024 | |
|
|
2025 | static void |
|
|
2026 | io_cb (ev_loop *loop, ev_io *w, int revents) |
|
|
2027 | { |
|
|
2028 | } |
|
|
2029 | |
|
|
2030 | // create io watchers for each fd and a timer before blocking |
|
|
2031 | static void |
|
|
2032 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
|
|
2033 | { |
|
|
2034 | int timeout = 3600000; |
|
|
2035 | struct pollfd fds [nfd]; |
|
|
2036 | // actual code will need to loop here and realloc etc. |
|
|
2037 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
|
|
2038 | |
|
|
2039 | /* the callback is illegal, but won't be called as we stop during check */ |
|
|
2040 | ev_timer_init (&tw, 0, timeout * 1e-3); |
|
|
2041 | ev_timer_start (loop, &tw); |
|
|
2042 | |
|
|
2043 | // create one ev_io per pollfd |
|
|
2044 | for (int i = 0; i < nfd; ++i) |
|
|
2045 | { |
|
|
2046 | ev_io_init (iow + i, io_cb, fds [i].fd, |
|
|
2047 | ((fds [i].events & POLLIN ? EV_READ : 0) |
|
|
2048 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
|
|
2049 | |
|
|
2050 | fds [i].revents = 0; |
|
|
2051 | ev_io_start (loop, iow + i); |
|
|
2052 | } |
|
|
2053 | } |
|
|
2054 | |
|
|
2055 | // stop all watchers after blocking |
|
|
2056 | static void |
|
|
2057 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
|
|
2058 | { |
|
|
2059 | ev_timer_stop (loop, &tw); |
|
|
2060 | |
|
|
2061 | for (int i = 0; i < nfd; ++i) |
|
|
2062 | { |
|
|
2063 | // set the relevant poll flags |
|
|
2064 | // could also call adns_processreadable etc. here |
|
|
2065 | struct pollfd *fd = fds + i; |
|
|
2066 | int revents = ev_clear_pending (iow + i); |
|
|
2067 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
2068 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
2069 | |
|
|
2070 | // now stop the watcher |
|
|
2071 | ev_io_stop (loop, iow + i); |
|
|
2072 | } |
|
|
2073 | |
|
|
2074 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
2075 | } |
|
|
2076 | |
|
|
2077 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
|
|
2078 | in the prepare watcher and would dispose of the check watcher. |
|
|
2079 | |
|
|
2080 | Method 3: If the module to be embedded supports explicit event |
|
|
2081 | notification (libadns does), you can also make use of the actual watcher |
|
|
2082 | callbacks, and only destroy/create the watchers in the prepare watcher. |
|
|
2083 | |
|
|
2084 | static void |
|
|
2085 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2086 | { |
|
|
2087 | adns_state ads = (adns_state)w->data; |
|
|
2088 | update_now (EV_A); |
|
|
2089 | |
|
|
2090 | adns_processtimeouts (ads, &tv_now); |
|
|
2091 | } |
|
|
2092 | |
|
|
2093 | static void |
|
|
2094 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
2095 | { |
|
|
2096 | adns_state ads = (adns_state)w->data; |
|
|
2097 | update_now (EV_A); |
|
|
2098 | |
|
|
2099 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
|
|
2100 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
|
|
2101 | } |
|
|
2102 | |
|
|
2103 | // do not ever call adns_afterpoll |
|
|
2104 | |
|
|
2105 | Method 4: Do not use a prepare or check watcher because the module you |
|
|
2106 | want to embed is too inflexible to support it. Instead, you can override |
|
|
2107 | their poll function. The drawback with this solution is that the main |
|
|
2108 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
|
|
2109 | this. |
|
|
2110 | |
|
|
2111 | static gint |
|
|
2112 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
2113 | { |
|
|
2114 | int got_events = 0; |
|
|
2115 | |
|
|
2116 | for (n = 0; n < nfds; ++n) |
|
|
2117 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
2118 | |
|
|
2119 | if (timeout >= 0) |
|
|
2120 | // create/start timer |
|
|
2121 | |
|
|
2122 | // poll |
|
|
2123 | ev_loop (EV_A_ 0); |
|
|
2124 | |
|
|
2125 | // stop timer again |
|
|
2126 | if (timeout >= 0) |
|
|
2127 | ev_timer_stop (EV_A_ &to); |
|
|
2128 | |
|
|
2129 | // stop io watchers again - their callbacks should have set |
|
|
2130 | for (n = 0; n < nfds; ++n) |
|
|
2131 | ev_io_stop (EV_A_ iow [n]); |
|
|
2132 | |
|
|
2133 | return got_events; |
|
|
2134 | } |
|
|
2135 | |
|
|
2136 | |
1138 | =head2 C<ev_embed> - when one backend isn't enough |
2137 | =head2 C<ev_embed> - when one backend isn't enough... |
1139 | |
2138 | |
1140 | This is a rather advanced watcher type that lets you embed one event loop |
2139 | This is a rather advanced watcher type that lets you embed one event loop |
1141 | into another (currently only C<ev_io> events are supported in the embedded |
2140 | into another (currently only C<ev_io> events are supported in the embedded |
1142 | loop, other types of watchers might be handled in a delayed or incorrect |
2141 | loop, other types of watchers might be handled in a delayed or incorrect |
1143 | fashion and must not be used). |
2142 | fashion and must not be used). |
… | |
… | |
1182 | portable one. |
2181 | portable one. |
1183 | |
2182 | |
1184 | So when you want to use this feature you will always have to be prepared |
2183 | So when you want to use this feature you will always have to be prepared |
1185 | that you cannot get an embeddable loop. The recommended way to get around |
2184 | that you cannot get an embeddable loop. The recommended way to get around |
1186 | this is to have a separate variables for your embeddable loop, try to |
2185 | this is to have a separate variables for your embeddable loop, try to |
1187 | create it, and if that fails, use the normal loop for everything: |
2186 | create it, and if that fails, use the normal loop for everything. |
1188 | |
2187 | |
1189 | struct ev_loop *loop_hi = ev_default_init (0); |
2188 | =head3 Watcher-Specific Functions and Data Members |
1190 | struct ev_loop *loop_lo = 0; |
|
|
1191 | struct ev_embed embed; |
|
|
1192 | |
|
|
1193 | // see if there is a chance of getting one that works |
|
|
1194 | // (remember that a flags value of 0 means autodetection) |
|
|
1195 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
1196 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
1197 | : 0; |
|
|
1198 | |
|
|
1199 | // if we got one, then embed it, otherwise default to loop_hi |
|
|
1200 | if (loop_lo) |
|
|
1201 | { |
|
|
1202 | ev_embed_init (&embed, 0, loop_lo); |
|
|
1203 | ev_embed_start (loop_hi, &embed); |
|
|
1204 | } |
|
|
1205 | else |
|
|
1206 | loop_lo = loop_hi; |
|
|
1207 | |
2189 | |
1208 | =over 4 |
2190 | =over 4 |
1209 | |
2191 | |
1210 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2192 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
1211 | |
2193 | |
… | |
… | |
1213 | |
2195 | |
1214 | Configures the watcher to embed the given loop, which must be |
2196 | Configures the watcher to embed the given loop, which must be |
1215 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2197 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
1216 | invoked automatically, otherwise it is the responsibility of the callback |
2198 | invoked automatically, otherwise it is the responsibility of the callback |
1217 | to invoke it (it will continue to be called until the sweep has been done, |
2199 | to invoke it (it will continue to be called until the sweep has been done, |
1218 | if you do not want thta, you need to temporarily stop the embed watcher). |
2200 | if you do not want that, you need to temporarily stop the embed watcher). |
1219 | |
2201 | |
1220 | =item ev_embed_sweep (loop, ev_embed *) |
2202 | =item ev_embed_sweep (loop, ev_embed *) |
1221 | |
2203 | |
1222 | Make a single, non-blocking sweep over the embedded loop. This works |
2204 | Make a single, non-blocking sweep over the embedded loop. This works |
1223 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
2205 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
1224 | apropriate way for embedded loops. |
2206 | appropriate way for embedded loops. |
|
|
2207 | |
|
|
2208 | =item struct ev_loop *other [read-only] |
|
|
2209 | |
|
|
2210 | The embedded event loop. |
|
|
2211 | |
|
|
2212 | =back |
|
|
2213 | |
|
|
2214 | =head3 Examples |
|
|
2215 | |
|
|
2216 | Example: Try to get an embeddable event loop and embed it into the default |
|
|
2217 | event loop. If that is not possible, use the default loop. The default |
|
|
2218 | loop is stored in C<loop_hi>, while the embeddable loop is stored in |
|
|
2219 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
|
|
2220 | used). |
|
|
2221 | |
|
|
2222 | struct ev_loop *loop_hi = ev_default_init (0); |
|
|
2223 | struct ev_loop *loop_lo = 0; |
|
|
2224 | struct ev_embed embed; |
|
|
2225 | |
|
|
2226 | // see if there is a chance of getting one that works |
|
|
2227 | // (remember that a flags value of 0 means autodetection) |
|
|
2228 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
2229 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
2230 | : 0; |
|
|
2231 | |
|
|
2232 | // if we got one, then embed it, otherwise default to loop_hi |
|
|
2233 | if (loop_lo) |
|
|
2234 | { |
|
|
2235 | ev_embed_init (&embed, 0, loop_lo); |
|
|
2236 | ev_embed_start (loop_hi, &embed); |
|
|
2237 | } |
|
|
2238 | else |
|
|
2239 | loop_lo = loop_hi; |
|
|
2240 | |
|
|
2241 | Example: Check if kqueue is available but not recommended and create |
|
|
2242 | a kqueue backend for use with sockets (which usually work with any |
|
|
2243 | kqueue implementation). Store the kqueue/socket-only event loop in |
|
|
2244 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
|
|
2245 | |
|
|
2246 | struct ev_loop *loop = ev_default_init (0); |
|
|
2247 | struct ev_loop *loop_socket = 0; |
|
|
2248 | struct ev_embed embed; |
|
|
2249 | |
|
|
2250 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
|
|
2251 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
|
|
2252 | { |
|
|
2253 | ev_embed_init (&embed, 0, loop_socket); |
|
|
2254 | ev_embed_start (loop, &embed); |
|
|
2255 | } |
|
|
2256 | |
|
|
2257 | if (!loop_socket) |
|
|
2258 | loop_socket = loop; |
|
|
2259 | |
|
|
2260 | // now use loop_socket for all sockets, and loop for everything else |
|
|
2261 | |
|
|
2262 | |
|
|
2263 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
|
|
2264 | |
|
|
2265 | Fork watchers are called when a C<fork ()> was detected (usually because |
|
|
2266 | whoever is a good citizen cared to tell libev about it by calling |
|
|
2267 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
|
|
2268 | event loop blocks next and before C<ev_check> watchers are being called, |
|
|
2269 | and only in the child after the fork. If whoever good citizen calling |
|
|
2270 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
|
|
2271 | handlers will be invoked, too, of course. |
|
|
2272 | |
|
|
2273 | =head3 Watcher-Specific Functions and Data Members |
|
|
2274 | |
|
|
2275 | =over 4 |
|
|
2276 | |
|
|
2277 | =item ev_fork_init (ev_signal *, callback) |
|
|
2278 | |
|
|
2279 | Initialises and configures the fork watcher - it has no parameters of any |
|
|
2280 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
|
|
2281 | believe me. |
|
|
2282 | |
|
|
2283 | =back |
|
|
2284 | |
|
|
2285 | |
|
|
2286 | =head2 C<ev_async> - how to wake up another event loop |
|
|
2287 | |
|
|
2288 | In general, you cannot use an C<ev_loop> from multiple threads or other |
|
|
2289 | asynchronous sources such as signal handlers (as opposed to multiple event |
|
|
2290 | loops - those are of course safe to use in different threads). |
|
|
2291 | |
|
|
2292 | Sometimes, however, you need to wake up another event loop you do not |
|
|
2293 | control, for example because it belongs to another thread. This is what |
|
|
2294 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
|
|
2295 | can signal it by calling C<ev_async_send>, which is thread- and signal |
|
|
2296 | safe. |
|
|
2297 | |
|
|
2298 | This functionality is very similar to C<ev_signal> watchers, as signals, |
|
|
2299 | too, are asynchronous in nature, and signals, too, will be compressed |
|
|
2300 | (i.e. the number of callback invocations may be less than the number of |
|
|
2301 | C<ev_async_sent> calls). |
|
|
2302 | |
|
|
2303 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
2304 | just the default loop. |
|
|
2305 | |
|
|
2306 | =head3 Queueing |
|
|
2307 | |
|
|
2308 | C<ev_async> does not support queueing of data in any way. The reason |
|
|
2309 | is that the author does not know of a simple (or any) algorithm for a |
|
|
2310 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
2311 | need elaborate support such as pthreads. |
|
|
2312 | |
|
|
2313 | That means that if you want to queue data, you have to provide your own |
|
|
2314 | queue. But at least I can tell you would implement locking around your |
|
|
2315 | queue: |
|
|
2316 | |
|
|
2317 | =over 4 |
|
|
2318 | |
|
|
2319 | =item queueing from a signal handler context |
|
|
2320 | |
|
|
2321 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
2322 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
|
|
2323 | some fictitious SIGUSR1 handler: |
|
|
2324 | |
|
|
2325 | static ev_async mysig; |
|
|
2326 | |
|
|
2327 | static void |
|
|
2328 | sigusr1_handler (void) |
|
|
2329 | { |
|
|
2330 | sometype data; |
|
|
2331 | |
|
|
2332 | // no locking etc. |
|
|
2333 | queue_put (data); |
|
|
2334 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2335 | } |
|
|
2336 | |
|
|
2337 | static void |
|
|
2338 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2339 | { |
|
|
2340 | sometype data; |
|
|
2341 | sigset_t block, prev; |
|
|
2342 | |
|
|
2343 | sigemptyset (&block); |
|
|
2344 | sigaddset (&block, SIGUSR1); |
|
|
2345 | sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
2346 | |
|
|
2347 | while (queue_get (&data)) |
|
|
2348 | process (data); |
|
|
2349 | |
|
|
2350 | if (sigismember (&prev, SIGUSR1) |
|
|
2351 | sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
2352 | } |
|
|
2353 | |
|
|
2354 | (Note: pthreads in theory requires you to use C<pthread_setmask> |
|
|
2355 | instead of C<sigprocmask> when you use threads, but libev doesn't do it |
|
|
2356 | either...). |
|
|
2357 | |
|
|
2358 | =item queueing from a thread context |
|
|
2359 | |
|
|
2360 | The strategy for threads is different, as you cannot (easily) block |
|
|
2361 | threads but you can easily preempt them, so to queue safely you need to |
|
|
2362 | employ a traditional mutex lock, such as in this pthread example: |
|
|
2363 | |
|
|
2364 | static ev_async mysig; |
|
|
2365 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
2366 | |
|
|
2367 | static void |
|
|
2368 | otherthread (void) |
|
|
2369 | { |
|
|
2370 | // only need to lock the actual queueing operation |
|
|
2371 | pthread_mutex_lock (&mymutex); |
|
|
2372 | queue_put (data); |
|
|
2373 | pthread_mutex_unlock (&mymutex); |
|
|
2374 | |
|
|
2375 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2376 | } |
|
|
2377 | |
|
|
2378 | static void |
|
|
2379 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2380 | { |
|
|
2381 | pthread_mutex_lock (&mymutex); |
|
|
2382 | |
|
|
2383 | while (queue_get (&data)) |
|
|
2384 | process (data); |
|
|
2385 | |
|
|
2386 | pthread_mutex_unlock (&mymutex); |
|
|
2387 | } |
|
|
2388 | |
|
|
2389 | =back |
|
|
2390 | |
|
|
2391 | |
|
|
2392 | =head3 Watcher-Specific Functions and Data Members |
|
|
2393 | |
|
|
2394 | =over 4 |
|
|
2395 | |
|
|
2396 | =item ev_async_init (ev_async *, callback) |
|
|
2397 | |
|
|
2398 | Initialises and configures the async watcher - it has no parameters of any |
|
|
2399 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
|
|
2400 | believe me. |
|
|
2401 | |
|
|
2402 | =item ev_async_send (loop, ev_async *) |
|
|
2403 | |
|
|
2404 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
|
|
2405 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
|
|
2406 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
|
|
2407 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
|
|
2408 | section below on what exactly this means). |
|
|
2409 | |
|
|
2410 | This call incurs the overhead of a system call only once per loop iteration, |
|
|
2411 | so while the overhead might be noticeable, it doesn't apply to repeated |
|
|
2412 | calls to C<ev_async_send>. |
|
|
2413 | |
|
|
2414 | =item bool = ev_async_pending (ev_async *) |
|
|
2415 | |
|
|
2416 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
2417 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2418 | event loop. |
|
|
2419 | |
|
|
2420 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
2421 | the loop iterates next and checks for the watcher to have become active, |
|
|
2422 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
2423 | quickly check whether invoking the loop might be a good idea. |
|
|
2424 | |
|
|
2425 | Not that this does I<not> check whether the watcher itself is pending, only |
|
|
2426 | whether it has been requested to make this watcher pending. |
1225 | |
2427 | |
1226 | =back |
2428 | =back |
1227 | |
2429 | |
1228 | |
2430 | |
1229 | =head1 OTHER FUNCTIONS |
2431 | =head1 OTHER FUNCTIONS |
… | |
… | |
1240 | or timeout without having to allocate/configure/start/stop/free one or |
2442 | or timeout without having to allocate/configure/start/stop/free one or |
1241 | more watchers yourself. |
2443 | more watchers yourself. |
1242 | |
2444 | |
1243 | If C<fd> is less than 0, then no I/O watcher will be started and events |
2445 | If C<fd> is less than 0, then no I/O watcher will be started and events |
1244 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
2446 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
1245 | C<events> set will be craeted and started. |
2447 | C<events> set will be created and started. |
1246 | |
2448 | |
1247 | If C<timeout> is less than 0, then no timeout watcher will be |
2449 | If C<timeout> is less than 0, then no timeout watcher will be |
1248 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2450 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
1249 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
2451 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
1250 | dubious value. |
2452 | dubious value. |
… | |
… | |
1252 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2454 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
1253 | passed an C<revents> set like normal event callbacks (a combination of |
2455 | passed an C<revents> set like normal event callbacks (a combination of |
1254 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2456 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
1255 | value passed to C<ev_once>: |
2457 | value passed to C<ev_once>: |
1256 | |
2458 | |
1257 | static void stdin_ready (int revents, void *arg) |
2459 | static void stdin_ready (int revents, void *arg) |
1258 | { |
2460 | { |
1259 | if (revents & EV_TIMEOUT) |
2461 | if (revents & EV_TIMEOUT) |
1260 | /* doh, nothing entered */; |
2462 | /* doh, nothing entered */; |
1261 | else if (revents & EV_READ) |
2463 | else if (revents & EV_READ) |
1262 | /* stdin might have data for us, joy! */; |
2464 | /* stdin might have data for us, joy! */; |
1263 | } |
2465 | } |
1264 | |
2466 | |
1265 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2467 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
1266 | |
2468 | |
1267 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
2469 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
1268 | |
2470 | |
1269 | Feeds the given event set into the event loop, as if the specified event |
2471 | Feeds the given event set into the event loop, as if the specified event |
1270 | had happened for the specified watcher (which must be a pointer to an |
2472 | had happened for the specified watcher (which must be a pointer to an |
… | |
… | |
1275 | Feed an event on the given fd, as if a file descriptor backend detected |
2477 | Feed an event on the given fd, as if a file descriptor backend detected |
1276 | the given events it. |
2478 | the given events it. |
1277 | |
2479 | |
1278 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
2480 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
1279 | |
2481 | |
1280 | Feed an event as if the given signal occured (C<loop> must be the default |
2482 | Feed an event as if the given signal occurred (C<loop> must be the default |
1281 | loop!). |
2483 | loop!). |
1282 | |
2484 | |
1283 | =back |
2485 | =back |
1284 | |
2486 | |
1285 | |
2487 | |
… | |
… | |
1301 | |
2503 | |
1302 | =item * Priorities are not currently supported. Initialising priorities |
2504 | =item * Priorities are not currently supported. Initialising priorities |
1303 | will fail and all watchers will have the same priority, even though there |
2505 | will fail and all watchers will have the same priority, even though there |
1304 | is an ev_pri field. |
2506 | is an ev_pri field. |
1305 | |
2507 | |
|
|
2508 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
2509 | first base created (== the default loop) gets the signals. |
|
|
2510 | |
1306 | =item * Other members are not supported. |
2511 | =item * Other members are not supported. |
1307 | |
2512 | |
1308 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2513 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
1309 | to use the libev header file and library. |
2514 | to use the libev header file and library. |
1310 | |
2515 | |
1311 | =back |
2516 | =back |
1312 | |
2517 | |
1313 | =head1 C++ SUPPORT |
2518 | =head1 C++ SUPPORT |
1314 | |
2519 | |
1315 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
2520 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
1316 | you to use some convinience methods to start/stop watchers and also change |
2521 | you to use some convenience methods to start/stop watchers and also change |
1317 | the callback model to a model using method callbacks on objects. |
2522 | the callback model to a model using method callbacks on objects. |
1318 | |
2523 | |
1319 | To use it, |
2524 | To use it, |
1320 | |
2525 | |
1321 | #include <ev++.h> |
2526 | #include <ev++.h> |
1322 | |
2527 | |
1323 | (it is not installed by default). This automatically includes F<ev.h> |
2528 | This automatically includes F<ev.h> and puts all of its definitions (many |
1324 | and puts all of its definitions (many of them macros) into the global |
2529 | of them macros) into the global namespace. All C++ specific things are |
1325 | namespace. All C++ specific things are put into the C<ev> namespace. |
2530 | put into the C<ev> namespace. It should support all the same embedding |
|
|
2531 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
1326 | |
2532 | |
1327 | It should support all the same embedding options as F<ev.h>, most notably |
2533 | Care has been taken to keep the overhead low. The only data member the C++ |
1328 | C<EV_MULTIPLICITY>. |
2534 | classes add (compared to plain C-style watchers) is the event loop pointer |
|
|
2535 | that the watcher is associated with (or no additional members at all if |
|
|
2536 | you disable C<EV_MULTIPLICITY> when embedding libev). |
|
|
2537 | |
|
|
2538 | Currently, functions, and static and non-static member functions can be |
|
|
2539 | used as callbacks. Other types should be easy to add as long as they only |
|
|
2540 | need one additional pointer for context. If you need support for other |
|
|
2541 | types of functors please contact the author (preferably after implementing |
|
|
2542 | it). |
1329 | |
2543 | |
1330 | Here is a list of things available in the C<ev> namespace: |
2544 | Here is a list of things available in the C<ev> namespace: |
1331 | |
2545 | |
1332 | =over 4 |
2546 | =over 4 |
1333 | |
2547 | |
… | |
… | |
1349 | |
2563 | |
1350 | All of those classes have these methods: |
2564 | All of those classes have these methods: |
1351 | |
2565 | |
1352 | =over 4 |
2566 | =over 4 |
1353 | |
2567 | |
1354 | =item ev::TYPE::TYPE (object *, object::method *) |
2568 | =item ev::TYPE::TYPE () |
1355 | |
2569 | |
1356 | =item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *) |
2570 | =item ev::TYPE::TYPE (struct ev_loop *) |
1357 | |
2571 | |
1358 | =item ev::TYPE::~TYPE |
2572 | =item ev::TYPE::~TYPE |
1359 | |
2573 | |
1360 | The constructor takes a pointer to an object and a method pointer to |
2574 | The constructor (optionally) takes an event loop to associate the watcher |
1361 | the event handler callback to call in this class. The constructor calls |
2575 | with. If it is omitted, it will use C<EV_DEFAULT>. |
1362 | C<ev_init> for you, which means you have to call the C<set> method |
2576 | |
1363 | before starting it. If you do not specify a loop then the constructor |
2577 | The constructor calls C<ev_init> for you, which means you have to call the |
1364 | automatically associates the default loop with this watcher. |
2578 | C<set> method before starting it. |
|
|
2579 | |
|
|
2580 | It will not set a callback, however: You have to call the templated C<set> |
|
|
2581 | method to set a callback before you can start the watcher. |
|
|
2582 | |
|
|
2583 | (The reason why you have to use a method is a limitation in C++ which does |
|
|
2584 | not allow explicit template arguments for constructors). |
1365 | |
2585 | |
1366 | The destructor automatically stops the watcher if it is active. |
2586 | The destructor automatically stops the watcher if it is active. |
|
|
2587 | |
|
|
2588 | =item w->set<class, &class::method> (object *) |
|
|
2589 | |
|
|
2590 | This method sets the callback method to call. The method has to have a |
|
|
2591 | signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as |
|
|
2592 | first argument and the C<revents> as second. The object must be given as |
|
|
2593 | parameter and is stored in the C<data> member of the watcher. |
|
|
2594 | |
|
|
2595 | This method synthesizes efficient thunking code to call your method from |
|
|
2596 | the C callback that libev requires. If your compiler can inline your |
|
|
2597 | callback (i.e. it is visible to it at the place of the C<set> call and |
|
|
2598 | your compiler is good :), then the method will be fully inlined into the |
|
|
2599 | thunking function, making it as fast as a direct C callback. |
|
|
2600 | |
|
|
2601 | Example: simple class declaration and watcher initialisation |
|
|
2602 | |
|
|
2603 | struct myclass |
|
|
2604 | { |
|
|
2605 | void io_cb (ev::io &w, int revents) { } |
|
|
2606 | } |
|
|
2607 | |
|
|
2608 | myclass obj; |
|
|
2609 | ev::io iow; |
|
|
2610 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
2611 | |
|
|
2612 | =item w->set<function> (void *data = 0) |
|
|
2613 | |
|
|
2614 | Also sets a callback, but uses a static method or plain function as |
|
|
2615 | callback. The optional C<data> argument will be stored in the watcher's |
|
|
2616 | C<data> member and is free for you to use. |
|
|
2617 | |
|
|
2618 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
|
|
2619 | |
|
|
2620 | See the method-C<set> above for more details. |
|
|
2621 | |
|
|
2622 | Example: |
|
|
2623 | |
|
|
2624 | static void io_cb (ev::io &w, int revents) { } |
|
|
2625 | iow.set <io_cb> (); |
1367 | |
2626 | |
1368 | =item w->set (struct ev_loop *) |
2627 | =item w->set (struct ev_loop *) |
1369 | |
2628 | |
1370 | Associates a different C<struct ev_loop> with this watcher. You can only |
2629 | Associates a different C<struct ev_loop> with this watcher. You can only |
1371 | do this when the watcher is inactive (and not pending either). |
2630 | do this when the watcher is inactive (and not pending either). |
1372 | |
2631 | |
1373 | =item w->set ([args]) |
2632 | =item w->set ([arguments]) |
1374 | |
2633 | |
1375 | Basically the same as C<ev_TYPE_set>, with the same args. Must be |
2634 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
1376 | called at least once. Unlike the C counterpart, an active watcher gets |
2635 | called at least once. Unlike the C counterpart, an active watcher gets |
1377 | automatically stopped and restarted. |
2636 | automatically stopped and restarted when reconfiguring it with this |
|
|
2637 | method. |
1378 | |
2638 | |
1379 | =item w->start () |
2639 | =item w->start () |
1380 | |
2640 | |
1381 | Starts the watcher. Note that there is no C<loop> argument as the |
2641 | Starts the watcher. Note that there is no C<loop> argument, as the |
1382 | constructor already takes the loop. |
2642 | constructor already stores the event loop. |
1383 | |
2643 | |
1384 | =item w->stop () |
2644 | =item w->stop () |
1385 | |
2645 | |
1386 | Stops the watcher if it is active. Again, no C<loop> argument. |
2646 | Stops the watcher if it is active. Again, no C<loop> argument. |
1387 | |
2647 | |
1388 | =item w->again () C<ev::timer>, C<ev::periodic> only |
2648 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
1389 | |
2649 | |
1390 | For C<ev::timer> and C<ev::periodic>, this invokes the corresponding |
2650 | For C<ev::timer> and C<ev::periodic>, this invokes the corresponding |
1391 | C<ev_TYPE_again> function. |
2651 | C<ev_TYPE_again> function. |
1392 | |
2652 | |
1393 | =item w->sweep () C<ev::embed> only |
2653 | =item w->sweep () (C<ev::embed> only) |
1394 | |
2654 | |
1395 | Invokes C<ev_embed_sweep>. |
2655 | Invokes C<ev_embed_sweep>. |
|
|
2656 | |
|
|
2657 | =item w->update () (C<ev::stat> only) |
|
|
2658 | |
|
|
2659 | Invokes C<ev_stat_stat>. |
1396 | |
2660 | |
1397 | =back |
2661 | =back |
1398 | |
2662 | |
1399 | =back |
2663 | =back |
1400 | |
2664 | |
1401 | Example: Define a class with an IO and idle watcher, start one of them in |
2665 | Example: Define a class with an IO and idle watcher, start one of them in |
1402 | the constructor. |
2666 | the constructor. |
1403 | |
2667 | |
1404 | class myclass |
2668 | class myclass |
1405 | { |
2669 | { |
1406 | ev_io io; void io_cb (ev::io &w, int revents); |
2670 | ev::io io; void io_cb (ev::io &w, int revents); |
1407 | ev_idle idle void idle_cb (ev::idle &w, int revents); |
2671 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
1408 | |
2672 | |
1409 | myclass (); |
2673 | myclass (int fd) |
1410 | } |
2674 | { |
|
|
2675 | io .set <myclass, &myclass::io_cb > (this); |
|
|
2676 | idle.set <myclass, &myclass::idle_cb> (this); |
1411 | |
2677 | |
1412 | myclass::myclass (int fd) |
|
|
1413 | : io (this, &myclass::io_cb), |
|
|
1414 | idle (this, &myclass::idle_cb) |
|
|
1415 | { |
|
|
1416 | io.start (fd, ev::READ); |
2678 | io.start (fd, ev::READ); |
|
|
2679 | } |
|
|
2680 | }; |
|
|
2681 | |
|
|
2682 | |
|
|
2683 | =head1 OTHER LANGUAGE BINDINGS |
|
|
2684 | |
|
|
2685 | Libev does not offer other language bindings itself, but bindings for a |
|
|
2686 | number of languages exist in the form of third-party packages. If you know |
|
|
2687 | any interesting language binding in addition to the ones listed here, drop |
|
|
2688 | me a note. |
|
|
2689 | |
|
|
2690 | =over 4 |
|
|
2691 | |
|
|
2692 | =item Perl |
|
|
2693 | |
|
|
2694 | The EV module implements the full libev API and is actually used to test |
|
|
2695 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
2696 | there are additional modules that implement libev-compatible interfaces |
|
|
2697 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
|
|
2698 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
|
|
2699 | |
|
|
2700 | It can be found and installed via CPAN, its homepage is at |
|
|
2701 | L<http://software.schmorp.de/pkg/EV>. |
|
|
2702 | |
|
|
2703 | =item Python |
|
|
2704 | |
|
|
2705 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
|
|
2706 | seems to be quite complete and well-documented. Note, however, that the |
|
|
2707 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2708 | for everybody else, and therefore, should never be applied in an installed |
|
|
2709 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2710 | libev). |
|
|
2711 | |
|
|
2712 | =item Ruby |
|
|
2713 | |
|
|
2714 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
2715 | of the libev API and adds file handle abstractions, asynchronous DNS and |
|
|
2716 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
2717 | L<http://rev.rubyforge.org/>. |
|
|
2718 | |
|
|
2719 | =item D |
|
|
2720 | |
|
|
2721 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
2722 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
2723 | |
|
|
2724 | =back |
|
|
2725 | |
|
|
2726 | |
|
|
2727 | =head1 MACRO MAGIC |
|
|
2728 | |
|
|
2729 | Libev can be compiled with a variety of options, the most fundamental |
|
|
2730 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
|
|
2731 | functions and callbacks have an initial C<struct ev_loop *> argument. |
|
|
2732 | |
|
|
2733 | To make it easier to write programs that cope with either variant, the |
|
|
2734 | following macros are defined: |
|
|
2735 | |
|
|
2736 | =over 4 |
|
|
2737 | |
|
|
2738 | =item C<EV_A>, C<EV_A_> |
|
|
2739 | |
|
|
2740 | This provides the loop I<argument> for functions, if one is required ("ev |
|
|
2741 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
|
|
2742 | C<EV_A_> is used when other arguments are following. Example: |
|
|
2743 | |
|
|
2744 | ev_unref (EV_A); |
|
|
2745 | ev_timer_add (EV_A_ watcher); |
|
|
2746 | ev_loop (EV_A_ 0); |
|
|
2747 | |
|
|
2748 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
|
|
2749 | which is often provided by the following macro. |
|
|
2750 | |
|
|
2751 | =item C<EV_P>, C<EV_P_> |
|
|
2752 | |
|
|
2753 | This provides the loop I<parameter> for functions, if one is required ("ev |
|
|
2754 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
|
|
2755 | C<EV_P_> is used when other parameters are following. Example: |
|
|
2756 | |
|
|
2757 | // this is how ev_unref is being declared |
|
|
2758 | static void ev_unref (EV_P); |
|
|
2759 | |
|
|
2760 | // this is how you can declare your typical callback |
|
|
2761 | static void cb (EV_P_ ev_timer *w, int revents) |
|
|
2762 | |
|
|
2763 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
|
|
2764 | suitable for use with C<EV_A>. |
|
|
2765 | |
|
|
2766 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
|
|
2767 | |
|
|
2768 | Similar to the other two macros, this gives you the value of the default |
|
|
2769 | loop, if multiple loops are supported ("ev loop default"). |
|
|
2770 | |
|
|
2771 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
2772 | |
|
|
2773 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
2774 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
2775 | is undefined when the default loop has not been initialised by a previous |
|
|
2776 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
2777 | |
|
|
2778 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
2779 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
|
|
2780 | |
|
|
2781 | =back |
|
|
2782 | |
|
|
2783 | Example: Declare and initialise a check watcher, utilising the above |
|
|
2784 | macros so it will work regardless of whether multiple loops are supported |
|
|
2785 | or not. |
|
|
2786 | |
|
|
2787 | static void |
|
|
2788 | check_cb (EV_P_ ev_timer *w, int revents) |
|
|
2789 | { |
|
|
2790 | ev_check_stop (EV_A_ w); |
1417 | } |
2791 | } |
|
|
2792 | |
|
|
2793 | ev_check check; |
|
|
2794 | ev_check_init (&check, check_cb); |
|
|
2795 | ev_check_start (EV_DEFAULT_ &check); |
|
|
2796 | ev_loop (EV_DEFAULT_ 0); |
1418 | |
2797 | |
1419 | =head1 EMBEDDING |
2798 | =head1 EMBEDDING |
1420 | |
2799 | |
1421 | Libev can (and often is) directly embedded into host |
2800 | Libev can (and often is) directly embedded into host |
1422 | applications. Examples of applications that embed it include the Deliantra |
2801 | applications. Examples of applications that embed it include the Deliantra |
1423 | Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
2802 | Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
1424 | and rxvt-unicode. |
2803 | and rxvt-unicode. |
1425 | |
2804 | |
1426 | The goal is to enable you to just copy the neecssary files into your |
2805 | The goal is to enable you to just copy the necessary files into your |
1427 | source directory without having to change even a single line in them, so |
2806 | source directory without having to change even a single line in them, so |
1428 | you can easily upgrade by simply copying (or having a checked-out copy of |
2807 | you can easily upgrade by simply copying (or having a checked-out copy of |
1429 | libev somewhere in your source tree). |
2808 | libev somewhere in your source tree). |
1430 | |
2809 | |
1431 | =head2 FILESETS |
2810 | =head2 FILESETS |
1432 | |
2811 | |
1433 | Depending on what features you need you need to include one or more sets of files |
2812 | Depending on what features you need you need to include one or more sets of files |
1434 | in your app. |
2813 | in your application. |
1435 | |
2814 | |
1436 | =head3 CORE EVENT LOOP |
2815 | =head3 CORE EVENT LOOP |
1437 | |
2816 | |
1438 | To include only the libev core (all the C<ev_*> functions), with manual |
2817 | To include only the libev core (all the C<ev_*> functions), with manual |
1439 | configuration (no autoconf): |
2818 | configuration (no autoconf): |
1440 | |
2819 | |
1441 | #define EV_STANDALONE 1 |
2820 | #define EV_STANDALONE 1 |
1442 | #include "ev.c" |
2821 | #include "ev.c" |
1443 | |
2822 | |
1444 | This will automatically include F<ev.h>, too, and should be done in a |
2823 | This will automatically include F<ev.h>, too, and should be done in a |
1445 | single C source file only to provide the function implementations. To use |
2824 | single C source file only to provide the function implementations. To use |
1446 | it, do the same for F<ev.h> in all files wishing to use this API (best |
2825 | it, do the same for F<ev.h> in all files wishing to use this API (best |
1447 | done by writing a wrapper around F<ev.h> that you can include instead and |
2826 | done by writing a wrapper around F<ev.h> that you can include instead and |
1448 | where you can put other configuration options): |
2827 | where you can put other configuration options): |
1449 | |
2828 | |
1450 | #define EV_STANDALONE 1 |
2829 | #define EV_STANDALONE 1 |
1451 | #include "ev.h" |
2830 | #include "ev.h" |
1452 | |
2831 | |
1453 | Both header files and implementation files can be compiled with a C++ |
2832 | Both header files and implementation files can be compiled with a C++ |
1454 | compiler (at least, thats a stated goal, and breakage will be treated |
2833 | compiler (at least, thats a stated goal, and breakage will be treated |
1455 | as a bug). |
2834 | as a bug). |
1456 | |
2835 | |
1457 | You need the following files in your source tree, or in a directory |
2836 | You need the following files in your source tree, or in a directory |
1458 | in your include path (e.g. in libev/ when using -Ilibev): |
2837 | in your include path (e.g. in libev/ when using -Ilibev): |
1459 | |
2838 | |
1460 | ev.h |
2839 | ev.h |
1461 | ev.c |
2840 | ev.c |
1462 | ev_vars.h |
2841 | ev_vars.h |
1463 | ev_wrap.h |
2842 | ev_wrap.h |
1464 | |
2843 | |
1465 | ev_win32.c required on win32 platforms only |
2844 | ev_win32.c required on win32 platforms only |
1466 | |
2845 | |
1467 | ev_select.c only when select backend is enabled (which is is by default) |
2846 | ev_select.c only when select backend is enabled (which is enabled by default) |
1468 | ev_poll.c only when poll backend is enabled (disabled by default) |
2847 | ev_poll.c only when poll backend is enabled (disabled by default) |
1469 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
2848 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
1470 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
2849 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
1471 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
2850 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
1472 | |
2851 | |
1473 | F<ev.c> includes the backend files directly when enabled, so you only need |
2852 | F<ev.c> includes the backend files directly when enabled, so you only need |
1474 | to compile a single file. |
2853 | to compile this single file. |
1475 | |
2854 | |
1476 | =head3 LIBEVENT COMPATIBILITY API |
2855 | =head3 LIBEVENT COMPATIBILITY API |
1477 | |
2856 | |
1478 | To include the libevent compatibility API, also include: |
2857 | To include the libevent compatibility API, also include: |
1479 | |
2858 | |
1480 | #include "event.c" |
2859 | #include "event.c" |
1481 | |
2860 | |
1482 | in the file including F<ev.c>, and: |
2861 | in the file including F<ev.c>, and: |
1483 | |
2862 | |
1484 | #include "event.h" |
2863 | #include "event.h" |
1485 | |
2864 | |
1486 | in the files that want to use the libevent API. This also includes F<ev.h>. |
2865 | in the files that want to use the libevent API. This also includes F<ev.h>. |
1487 | |
2866 | |
1488 | You need the following additional files for this: |
2867 | You need the following additional files for this: |
1489 | |
2868 | |
1490 | event.h |
2869 | event.h |
1491 | event.c |
2870 | event.c |
1492 | |
2871 | |
1493 | =head3 AUTOCONF SUPPORT |
2872 | =head3 AUTOCONF SUPPORT |
1494 | |
2873 | |
1495 | Instead of using C<EV_STANDALONE=1> and providing your config in |
2874 | Instead of using C<EV_STANDALONE=1> and providing your configuration in |
1496 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
2875 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
1497 | F<configure.ac> and leave C<EV_STANDALONE> off. F<ev.c> will then include |
2876 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
1498 | F<config.h> and configure itself accordingly. |
2877 | include F<config.h> and configure itself accordingly. |
1499 | |
2878 | |
1500 | For this of course you need the m4 file: |
2879 | For this of course you need the m4 file: |
1501 | |
2880 | |
1502 | libev.m4 |
2881 | libev.m4 |
1503 | |
2882 | |
1504 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2883 | =head2 PREPROCESSOR SYMBOLS/MACROS |
1505 | |
2884 | |
1506 | Libev can be configured via a variety of preprocessor symbols you have to define |
2885 | Libev can be configured via a variety of preprocessor symbols you have to |
1507 | before including any of its files. The default is not to build for multiplicity |
2886 | define before including any of its files. The default in the absence of |
1508 | and only include the select backend. |
2887 | autoconf is noted for every option. |
1509 | |
2888 | |
1510 | =over 4 |
2889 | =over 4 |
1511 | |
2890 | |
1512 | =item EV_STANDALONE |
2891 | =item EV_STANDALONE |
1513 | |
2892 | |
… | |
… | |
1518 | F<event.h> that are not directly supported by the libev core alone. |
2897 | F<event.h> that are not directly supported by the libev core alone. |
1519 | |
2898 | |
1520 | =item EV_USE_MONOTONIC |
2899 | =item EV_USE_MONOTONIC |
1521 | |
2900 | |
1522 | If defined to be C<1>, libev will try to detect the availability of the |
2901 | If defined to be C<1>, libev will try to detect the availability of the |
1523 | monotonic clock option at both compiletime and runtime. Otherwise no use |
2902 | monotonic clock option at both compile time and runtime. Otherwise no use |
1524 | of the monotonic clock option will be attempted. If you enable this, you |
2903 | of the monotonic clock option will be attempted. If you enable this, you |
1525 | usually have to link against librt or something similar. Enabling it when |
2904 | usually have to link against librt or something similar. Enabling it when |
1526 | the functionality isn't available is safe, though, althoguh you have |
2905 | the functionality isn't available is safe, though, although you have |
1527 | to make sure you link against any libraries where the C<clock_gettime> |
2906 | to make sure you link against any libraries where the C<clock_gettime> |
1528 | function is hiding in (often F<-lrt>). |
2907 | function is hiding in (often F<-lrt>). |
1529 | |
2908 | |
1530 | =item EV_USE_REALTIME |
2909 | =item EV_USE_REALTIME |
1531 | |
2910 | |
1532 | If defined to be C<1>, libev will try to detect the availability of the |
2911 | If defined to be C<1>, libev will try to detect the availability of the |
1533 | realtime clock option at compiletime (and assume its availability at |
2912 | real-time clock option at compile time (and assume its availability at |
1534 | runtime if successful). Otherwise no use of the realtime clock option will |
2913 | runtime if successful). Otherwise no use of the real-time clock option will |
1535 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
2914 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
1536 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries |
2915 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
1537 | in the description of C<EV_USE_MONOTONIC>, though. |
2916 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
|
|
2917 | |
|
|
2918 | =item EV_USE_NANOSLEEP |
|
|
2919 | |
|
|
2920 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
|
|
2921 | and will use it for delays. Otherwise it will use C<select ()>. |
|
|
2922 | |
|
|
2923 | =item EV_USE_EVENTFD |
|
|
2924 | |
|
|
2925 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
2926 | available and will probe for kernel support at runtime. This will improve |
|
|
2927 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
2928 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
2929 | 2.7 or newer, otherwise disabled. |
1538 | |
2930 | |
1539 | =item EV_USE_SELECT |
2931 | =item EV_USE_SELECT |
1540 | |
2932 | |
1541 | If undefined or defined to be C<1>, libev will compile in support for the |
2933 | If undefined or defined to be C<1>, libev will compile in support for the |
1542 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2934 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
1543 | other method takes over, select will be it. Otherwise the select backend |
2935 | other method takes over, select will be it. Otherwise the select backend |
1544 | will not be compiled in. |
2936 | will not be compiled in. |
1545 | |
2937 | |
1546 | =item EV_SELECT_USE_FD_SET |
2938 | =item EV_SELECT_USE_FD_SET |
1547 | |
2939 | |
1548 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2940 | If defined to C<1>, then the select backend will use the system C<fd_set> |
1549 | structure. This is useful if libev doesn't compile due to a missing |
2941 | structure. This is useful if libev doesn't compile due to a missing |
1550 | C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on |
2942 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
1551 | exotic systems. This usually limits the range of file descriptors to some |
2943 | exotic systems. This usually limits the range of file descriptors to some |
1552 | low limit such as 1024 or might have other limitations (winsocket only |
2944 | low limit such as 1024 or might have other limitations (winsocket only |
1553 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
2945 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
1554 | influence the size of the C<fd_set> used. |
2946 | influence the size of the C<fd_set> used. |
1555 | |
2947 | |
… | |
… | |
1561 | be used is the winsock select). This means that it will call |
2953 | be used is the winsock select). This means that it will call |
1562 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
2954 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
1563 | it is assumed that all these functions actually work on fds, even |
2955 | it is assumed that all these functions actually work on fds, even |
1564 | on win32. Should not be defined on non-win32 platforms. |
2956 | on win32. Should not be defined on non-win32 platforms. |
1565 | |
2957 | |
|
|
2958 | =item EV_FD_TO_WIN32_HANDLE |
|
|
2959 | |
|
|
2960 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
|
|
2961 | file descriptors to socket handles. When not defining this symbol (the |
|
|
2962 | default), then libev will call C<_get_osfhandle>, which is usually |
|
|
2963 | correct. In some cases, programs use their own file descriptor management, |
|
|
2964 | in which case they can provide this function to map fds to socket handles. |
|
|
2965 | |
1566 | =item EV_USE_POLL |
2966 | =item EV_USE_POLL |
1567 | |
2967 | |
1568 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
2968 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
1569 | backend. Otherwise it will be enabled on non-win32 platforms. It |
2969 | backend. Otherwise it will be enabled on non-win32 platforms. It |
1570 | takes precedence over select. |
2970 | takes precedence over select. |
1571 | |
2971 | |
1572 | =item EV_USE_EPOLL |
2972 | =item EV_USE_EPOLL |
1573 | |
2973 | |
1574 | If defined to be C<1>, libev will compile in support for the Linux |
2974 | If defined to be C<1>, libev will compile in support for the Linux |
1575 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2975 | C<epoll>(7) backend. Its availability will be detected at runtime, |
1576 | otherwise another method will be used as fallback. This is the |
2976 | otherwise another method will be used as fallback. This is the preferred |
1577 | preferred backend for GNU/Linux systems. |
2977 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
2978 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
1578 | |
2979 | |
1579 | =item EV_USE_KQUEUE |
2980 | =item EV_USE_KQUEUE |
1580 | |
2981 | |
1581 | If defined to be C<1>, libev will compile in support for the BSD style |
2982 | If defined to be C<1>, libev will compile in support for the BSD style |
1582 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
2983 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
1583 | otherwise another method will be used as fallback. This is the preferred |
2984 | otherwise another method will be used as fallback. This is the preferred |
1584 | backend for BSD and BSD-like systems, although on most BSDs kqueue only |
2985 | backend for BSD and BSD-like systems, although on most BSDs kqueue only |
1585 | supports some types of fds correctly (the only platform we found that |
2986 | supports some types of fds correctly (the only platform we found that |
1586 | supports ptys for example was NetBSD), so kqueue might be compiled in, but |
2987 | supports ptys for example was NetBSD), so kqueue might be compiled in, but |
1587 | not be used unless explicitly requested. The best way to use it is to find |
2988 | not be used unless explicitly requested. The best way to use it is to find |
1588 | out wether kqueue supports your type of fd properly and use an embedded |
2989 | out whether kqueue supports your type of fd properly and use an embedded |
1589 | kqueue loop. |
2990 | kqueue loop. |
1590 | |
2991 | |
1591 | =item EV_USE_PORT |
2992 | =item EV_USE_PORT |
1592 | |
2993 | |
1593 | If defined to be C<1>, libev will compile in support for the Solaris |
2994 | If defined to be C<1>, libev will compile in support for the Solaris |
… | |
… | |
1595 | otherwise another method will be used as fallback. This is the preferred |
2996 | otherwise another method will be used as fallback. This is the preferred |
1596 | backend for Solaris 10 systems. |
2997 | backend for Solaris 10 systems. |
1597 | |
2998 | |
1598 | =item EV_USE_DEVPOLL |
2999 | =item EV_USE_DEVPOLL |
1599 | |
3000 | |
1600 | reserved for future expansion, works like the USE symbols above. |
3001 | Reserved for future expansion, works like the USE symbols above. |
|
|
3002 | |
|
|
3003 | =item EV_USE_INOTIFY |
|
|
3004 | |
|
|
3005 | If defined to be C<1>, libev will compile in support for the Linux inotify |
|
|
3006 | interface to speed up C<ev_stat> watchers. Its actual availability will |
|
|
3007 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
3008 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
3009 | |
|
|
3010 | =item EV_ATOMIC_T |
|
|
3011 | |
|
|
3012 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
|
|
3013 | access is atomic with respect to other threads or signal contexts. No such |
|
|
3014 | type is easily found in the C language, so you can provide your own type |
|
|
3015 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
3016 | as well as for signal and thread safety in C<ev_async> watchers. |
|
|
3017 | |
|
|
3018 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
|
|
3019 | (from F<signal.h>), which is usually good enough on most platforms. |
1601 | |
3020 | |
1602 | =item EV_H |
3021 | =item EV_H |
1603 | |
3022 | |
1604 | The name of the F<ev.h> header file used to include it. The default if |
3023 | The name of the F<ev.h> header file used to include it. The default if |
1605 | undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This |
3024 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
1606 | can be used to virtually rename the F<ev.h> header file in case of conflicts. |
3025 | used to virtually rename the F<ev.h> header file in case of conflicts. |
1607 | |
3026 | |
1608 | =item EV_CONFIG_H |
3027 | =item EV_CONFIG_H |
1609 | |
3028 | |
1610 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3029 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
1611 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3030 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
1612 | C<EV_H>, above. |
3031 | C<EV_H>, above. |
1613 | |
3032 | |
1614 | =item EV_EVENT_H |
3033 | =item EV_EVENT_H |
1615 | |
3034 | |
1616 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3035 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
1617 | of how the F<event.h> header can be found. |
3036 | of how the F<event.h> header can be found, the default is C<"event.h">. |
1618 | |
3037 | |
1619 | =item EV_PROTOTYPES |
3038 | =item EV_PROTOTYPES |
1620 | |
3039 | |
1621 | If defined to be C<0>, then F<ev.h> will not define any function |
3040 | If defined to be C<0>, then F<ev.h> will not define any function |
1622 | prototypes, but still define all the structs and other symbols. This is |
3041 | prototypes, but still define all the structs and other symbols. This is |
… | |
… | |
1629 | will have the C<struct ev_loop *> as first argument, and you can create |
3048 | will have the C<struct ev_loop *> as first argument, and you can create |
1630 | additional independent event loops. Otherwise there will be no support |
3049 | additional independent event loops. Otherwise there will be no support |
1631 | for multiple event loops and there is no first event loop pointer |
3050 | for multiple event loops and there is no first event loop pointer |
1632 | argument. Instead, all functions act on the single default loop. |
3051 | argument. Instead, all functions act on the single default loop. |
1633 | |
3052 | |
|
|
3053 | =item EV_MINPRI |
|
|
3054 | |
|
|
3055 | =item EV_MAXPRI |
|
|
3056 | |
|
|
3057 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
|
|
3058 | C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can |
|
|
3059 | provide for more priorities by overriding those symbols (usually defined |
|
|
3060 | to be C<-2> and C<2>, respectively). |
|
|
3061 | |
|
|
3062 | When doing priority-based operations, libev usually has to linearly search |
|
|
3063 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
3064 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
|
|
3065 | fine. |
|
|
3066 | |
|
|
3067 | If your embedding application does not need any priorities, defining these both to |
|
|
3068 | C<0> will save some memory and CPU. |
|
|
3069 | |
1634 | =item EV_PERIODICS |
3070 | =item EV_PERIODIC_ENABLE |
1635 | |
3071 | |
1636 | If undefined or defined to be C<1>, then periodic timers are supported, |
3072 | If undefined or defined to be C<1>, then periodic timers are supported. If |
1637 | otherwise not. This saves a few kb of code. |
3073 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3074 | code. |
|
|
3075 | |
|
|
3076 | =item EV_IDLE_ENABLE |
|
|
3077 | |
|
|
3078 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3079 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3080 | code. |
|
|
3081 | |
|
|
3082 | =item EV_EMBED_ENABLE |
|
|
3083 | |
|
|
3084 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3085 | defined to be C<0>, then they are not. |
|
|
3086 | |
|
|
3087 | =item EV_STAT_ENABLE |
|
|
3088 | |
|
|
3089 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3090 | defined to be C<0>, then they are not. |
|
|
3091 | |
|
|
3092 | =item EV_FORK_ENABLE |
|
|
3093 | |
|
|
3094 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3095 | defined to be C<0>, then they are not. |
|
|
3096 | |
|
|
3097 | =item EV_ASYNC_ENABLE |
|
|
3098 | |
|
|
3099 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3100 | defined to be C<0>, then they are not. |
|
|
3101 | |
|
|
3102 | =item EV_MINIMAL |
|
|
3103 | |
|
|
3104 | If you need to shave off some kilobytes of code at the expense of some |
|
|
3105 | speed, define this symbol to C<1>. Currently this is used to override some |
|
|
3106 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
|
|
3107 | much smaller 2-heap for timer management over the default 4-heap. |
|
|
3108 | |
|
|
3109 | =item EV_PID_HASHSIZE |
|
|
3110 | |
|
|
3111 | C<ev_child> watchers use a small hash table to distribute workload by |
|
|
3112 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
|
|
3113 | than enough. If you need to manage thousands of children you might want to |
|
|
3114 | increase this value (I<must> be a power of two). |
|
|
3115 | |
|
|
3116 | =item EV_INOTIFY_HASHSIZE |
|
|
3117 | |
|
|
3118 | C<ev_stat> watchers use a small hash table to distribute workload by |
|
|
3119 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
|
|
3120 | usually more than enough. If you need to manage thousands of C<ev_stat> |
|
|
3121 | watchers you might want to increase this value (I<must> be a power of |
|
|
3122 | two). |
|
|
3123 | |
|
|
3124 | =item EV_USE_4HEAP |
|
|
3125 | |
|
|
3126 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3127 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
|
|
3128 | to C<1>. The 4-heap uses more complicated (longer) code but has |
|
|
3129 | noticeably faster performance with many (thousands) of watchers. |
|
|
3130 | |
|
|
3131 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3132 | (disabled). |
|
|
3133 | |
|
|
3134 | =item EV_HEAP_CACHE_AT |
|
|
3135 | |
|
|
3136 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3137 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
|
|
3138 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3139 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3140 | but avoids random read accesses on heap changes. This improves performance |
|
|
3141 | noticeably with with many (hundreds) of watchers. |
|
|
3142 | |
|
|
3143 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3144 | (disabled). |
|
|
3145 | |
|
|
3146 | =item EV_VERIFY |
|
|
3147 | |
|
|
3148 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
|
|
3149 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
3150 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
3151 | called. If set to C<2>, then the internal verification code will be |
|
|
3152 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
3153 | verification code will be called very frequently, which will slow down |
|
|
3154 | libev considerably. |
|
|
3155 | |
|
|
3156 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
|
|
3157 | C<0.> |
1638 | |
3158 | |
1639 | =item EV_COMMON |
3159 | =item EV_COMMON |
1640 | |
3160 | |
1641 | By default, all watchers have a C<void *data> member. By redefining |
3161 | By default, all watchers have a C<void *data> member. By redefining |
1642 | this macro to a something else you can include more and other types of |
3162 | this macro to a something else you can include more and other types of |
1643 | members. You have to define it each time you include one of the files, |
3163 | members. You have to define it each time you include one of the files, |
1644 | though, and it must be identical each time. |
3164 | though, and it must be identical each time. |
1645 | |
3165 | |
1646 | For example, the perl EV module uses something like this: |
3166 | For example, the perl EV module uses something like this: |
1647 | |
3167 | |
1648 | #define EV_COMMON \ |
3168 | #define EV_COMMON \ |
1649 | SV *self; /* contains this struct */ \ |
3169 | SV *self; /* contains this struct */ \ |
1650 | SV *cb_sv, *fh /* note no trailing ";" */ |
3170 | SV *cb_sv, *fh /* note no trailing ";" */ |
1651 | |
3171 | |
1652 | =item EV_CB_DECLARE(type) |
3172 | =item EV_CB_DECLARE (type) |
1653 | |
3173 | |
1654 | =item EV_CB_INVOKE(watcher,revents) |
3174 | =item EV_CB_INVOKE (watcher, revents) |
1655 | |
3175 | |
1656 | =item ev_set_cb(ev,cb) |
3176 | =item ev_set_cb (ev, cb) |
1657 | |
3177 | |
1658 | Can be used to change the callback member declaration in each watcher, |
3178 | Can be used to change the callback member declaration in each watcher, |
1659 | and the way callbacks are invoked and set. Must expand to a struct member |
3179 | and the way callbacks are invoked and set. Must expand to a struct member |
1660 | definition and a statement, respectively. See the F<ev.v> header file for |
3180 | definition and a statement, respectively. See the F<ev.h> header file for |
1661 | their default definitions. One possible use for overriding these is to |
3181 | their default definitions. One possible use for overriding these is to |
1662 | avoid the ev_loop pointer as first argument in all cases, or to use method |
3182 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
1663 | calls instead of plain function calls in C++. |
3183 | method calls instead of plain function calls in C++. |
|
|
3184 | |
|
|
3185 | =head2 EXPORTED API SYMBOLS |
|
|
3186 | |
|
|
3187 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
|
|
3188 | exported symbols, you can use the provided F<Symbol.*> files which list |
|
|
3189 | all public symbols, one per line: |
|
|
3190 | |
|
|
3191 | Symbols.ev for libev proper |
|
|
3192 | Symbols.event for the libevent emulation |
|
|
3193 | |
|
|
3194 | This can also be used to rename all public symbols to avoid clashes with |
|
|
3195 | multiple versions of libev linked together (which is obviously bad in |
|
|
3196 | itself, but sometimes it is inconvenient to avoid this). |
|
|
3197 | |
|
|
3198 | A sed command like this will create wrapper C<#define>'s that you need to |
|
|
3199 | include before including F<ev.h>: |
|
|
3200 | |
|
|
3201 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
|
|
3202 | |
|
|
3203 | This would create a file F<wrap.h> which essentially looks like this: |
|
|
3204 | |
|
|
3205 | #define ev_backend myprefix_ev_backend |
|
|
3206 | #define ev_check_start myprefix_ev_check_start |
|
|
3207 | #define ev_check_stop myprefix_ev_check_stop |
|
|
3208 | ... |
1664 | |
3209 | |
1665 | =head2 EXAMPLES |
3210 | =head2 EXAMPLES |
1666 | |
3211 | |
1667 | For a real-world example of a program the includes libev |
3212 | For a real-world example of a program the includes libev |
1668 | verbatim, you can have a look at the EV perl module |
3213 | verbatim, you can have a look at the EV perl module |
… | |
… | |
1671 | interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file |
3216 | interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file |
1672 | will be compiled. It is pretty complex because it provides its own header |
3217 | will be compiled. It is pretty complex because it provides its own header |
1673 | file. |
3218 | file. |
1674 | |
3219 | |
1675 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3220 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
1676 | that everybody includes and which overrides some autoconf choices: |
3221 | that everybody includes and which overrides some configure choices: |
1677 | |
3222 | |
|
|
3223 | #define EV_MINIMAL 1 |
1678 | #define EV_USE_POLL 0 |
3224 | #define EV_USE_POLL 0 |
1679 | #define EV_MULTIPLICITY 0 |
3225 | #define EV_MULTIPLICITY 0 |
1680 | #define EV_PERIODICS 0 |
3226 | #define EV_PERIODIC_ENABLE 0 |
|
|
3227 | #define EV_STAT_ENABLE 0 |
|
|
3228 | #define EV_FORK_ENABLE 0 |
1681 | #define EV_CONFIG_H <config.h> |
3229 | #define EV_CONFIG_H <config.h> |
|
|
3230 | #define EV_MINPRI 0 |
|
|
3231 | #define EV_MAXPRI 0 |
1682 | |
3232 | |
1683 | #include "ev++.h" |
3233 | #include "ev++.h" |
1684 | |
3234 | |
1685 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3235 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
1686 | |
3236 | |
1687 | #include "ev_cpp.h" |
3237 | #include "ev_cpp.h" |
1688 | #include "ev.c" |
3238 | #include "ev.c" |
|
|
3239 | |
|
|
3240 | |
|
|
3241 | =head1 THREADS AND COROUTINES |
|
|
3242 | |
|
|
3243 | =head2 THREADS |
|
|
3244 | |
|
|
3245 | Libev itself is thread-safe (unless the opposite is specifically |
|
|
3246 | documented for a function), but it uses no locking itself. This means that |
|
|
3247 | you can use as many loops as you want in parallel, as long as only one |
|
|
3248 | thread ever calls into one libev function with the same loop parameter: |
|
|
3249 | libev guarentees that different event loops share no data structures that |
|
|
3250 | need locking. |
|
|
3251 | |
|
|
3252 | Or to put it differently: calls with different loop parameters can be done |
|
|
3253 | concurrently from multiple threads, calls with the same loop parameter |
|
|
3254 | must be done serially (but can be done from different threads, as long as |
|
|
3255 | only one thread ever is inside a call at any point in time, e.g. by using |
|
|
3256 | a mutex per loop). |
|
|
3257 | |
|
|
3258 | Specifically to support threads (and signal handlers), libev implements |
|
|
3259 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
3260 | concurrency on the same event loop. |
|
|
3261 | |
|
|
3262 | If you want to know which design (one loop, locking, or multiple loops |
|
|
3263 | without or something else still) is best for your problem, then I cannot |
|
|
3264 | help you. I can give some generic advice however: |
|
|
3265 | |
|
|
3266 | =over 4 |
|
|
3267 | |
|
|
3268 | =item * most applications have a main thread: use the default libev loop |
|
|
3269 | in that thread, or create a separate thread running only the default loop. |
|
|
3270 | |
|
|
3271 | This helps integrating other libraries or software modules that use libev |
|
|
3272 | themselves and don't care/know about threading. |
|
|
3273 | |
|
|
3274 | =item * one loop per thread is usually a good model. |
|
|
3275 | |
|
|
3276 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3277 | exists, but it is always a good start. |
|
|
3278 | |
|
|
3279 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
3280 | loop is handed through multiple threads in a kind of round-robin fashion. |
|
|
3281 | |
|
|
3282 | Choosing a model is hard - look around, learn, know that usually you can do |
|
|
3283 | better than you currently do :-) |
|
|
3284 | |
|
|
3285 | =item * often you need to talk to some other thread which blocks in the |
|
|
3286 | event loop - C<ev_async> watchers can be used to wake them up from other |
|
|
3287 | threads safely (or from signal contexts...). |
|
|
3288 | |
|
|
3289 | =item * some watcher types are only supported in the default loop - use |
|
|
3290 | C<ev_async> watchers to tell your other loops about any such events. |
|
|
3291 | |
|
|
3292 | =back |
|
|
3293 | |
|
|
3294 | =head2 COROUTINES |
|
|
3295 | |
|
|
3296 | Libev is much more accommodating to coroutines ("cooperative threads"): |
|
|
3297 | libev fully supports nesting calls to it's functions from different |
|
|
3298 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
3299 | different coroutines and switch freely between both coroutines running the |
|
|
3300 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3301 | you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
3302 | |
|
|
3303 | Care has been invested into making sure that libev does not keep local |
|
|
3304 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
|
|
3305 | switches. |
|
|
3306 | |
|
|
3307 | |
|
|
3308 | =head1 COMPLEXITIES |
|
|
3309 | |
|
|
3310 | In this section the complexities of (many of) the algorithms used inside |
|
|
3311 | libev will be explained. For complexity discussions about backends see the |
|
|
3312 | documentation for C<ev_default_init>. |
|
|
3313 | |
|
|
3314 | All of the following are about amortised time: If an array needs to be |
|
|
3315 | extended, libev needs to realloc and move the whole array, but this |
|
|
3316 | happens asymptotically never with higher number of elements, so O(1) might |
|
|
3317 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3318 | it is much faster and asymptotically approaches constant time. |
|
|
3319 | |
|
|
3320 | =over 4 |
|
|
3321 | |
|
|
3322 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
|
|
3323 | |
|
|
3324 | This means that, when you have a watcher that triggers in one hour and |
|
|
3325 | there are 100 watchers that would trigger before that then inserting will |
|
|
3326 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3327 | |
|
|
3328 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
|
|
3329 | |
|
|
3330 | That means that changing a timer costs less than removing/adding them |
|
|
3331 | as only the relative motion in the event queue has to be paid for. |
|
|
3332 | |
|
|
3333 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
|
|
3334 | |
|
|
3335 | These just add the watcher into an array or at the head of a list. |
|
|
3336 | |
|
|
3337 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
|
|
3338 | |
|
|
3339 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
|
|
3340 | |
|
|
3341 | These watchers are stored in lists then need to be walked to find the |
|
|
3342 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
3343 | have many watchers waiting for the same fd or signal). |
|
|
3344 | |
|
|
3345 | =item Finding the next timer in each loop iteration: O(1) |
|
|
3346 | |
|
|
3347 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
3348 | fixed position in the storage array. |
|
|
3349 | |
|
|
3350 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3351 | |
|
|
3352 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3353 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3354 | on backend and whether C<ev_io_set> was used). |
|
|
3355 | |
|
|
3356 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3357 | |
|
|
3358 | =item Priority handling: O(number_of_priorities) |
|
|
3359 | |
|
|
3360 | Priorities are implemented by allocating some space for each |
|
|
3361 | priority. When doing priority-based operations, libev usually has to |
|
|
3362 | linearly search all the priorities, but starting/stopping and activating |
|
|
3363 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3364 | |
|
|
3365 | =item Sending an ev_async: O(1) |
|
|
3366 | |
|
|
3367 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3368 | |
|
|
3369 | =item Processing signals: O(max_signal_number) |
|
|
3370 | |
|
|
3371 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3372 | calls in the current loop iteration. Checking for async and signal events |
|
|
3373 | involves iterating over all running async watchers or all signal numbers. |
|
|
3374 | |
|
|
3375 | =back |
|
|
3376 | |
|
|
3377 | |
|
|
3378 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
3379 | |
|
|
3380 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
|
|
3381 | requires, and its I/O model is fundamentally incompatible with the POSIX |
|
|
3382 | model. Libev still offers limited functionality on this platform in |
|
|
3383 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
|
|
3384 | descriptors. This only applies when using Win32 natively, not when using |
|
|
3385 | e.g. cygwin. |
|
|
3386 | |
|
|
3387 | Lifting these limitations would basically require the full |
|
|
3388 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3389 | things, then note that glib does exactly that for you in a very portable |
|
|
3390 | way (note also that glib is the slowest event library known to man). |
|
|
3391 | |
|
|
3392 | There is no supported compilation method available on windows except |
|
|
3393 | embedding it into other applications. |
|
|
3394 | |
|
|
3395 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
3396 | accept large writes: instead of resulting in a partial write, windows will |
|
|
3397 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
|
|
3398 | so make sure you only write small amounts into your sockets (less than a |
|
|
3399 | megabyte seems safe, but thsi apparently depends on the amount of memory |
|
|
3400 | available). |
|
|
3401 | |
|
|
3402 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
3403 | the abysmal performance of winsockets, using a large number of sockets |
|
|
3404 | is not recommended (and not reasonable). If your program needs to use |
|
|
3405 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
3406 | different implementation for windows, as libev offers the POSIX readiness |
|
|
3407 | notification model, which cannot be implemented efficiently on windows |
|
|
3408 | (Microsoft monopoly games). |
|
|
3409 | |
|
|
3410 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
3411 | section for details) and use the following F<evwrap.h> header file instead |
|
|
3412 | of F<ev.h>: |
|
|
3413 | |
|
|
3414 | #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
3415 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
3416 | |
|
|
3417 | #include "ev.h" |
|
|
3418 | |
|
|
3419 | And compile the following F<evwrap.c> file into your project (make sure |
|
|
3420 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
|
|
3421 | |
|
|
3422 | #include "evwrap.h" |
|
|
3423 | #include "ev.c" |
|
|
3424 | |
|
|
3425 | =over 4 |
|
|
3426 | |
|
|
3427 | =item The winsocket select function |
|
|
3428 | |
|
|
3429 | The winsocket C<select> function doesn't follow POSIX in that it |
|
|
3430 | requires socket I<handles> and not socket I<file descriptors> (it is |
|
|
3431 | also extremely buggy). This makes select very inefficient, and also |
|
|
3432 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
3433 | C runtime provides the function C<_open_osfhandle> for this). See the |
|
|
3434 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
|
|
3435 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
|
|
3436 | |
|
|
3437 | The configuration for a "naked" win32 using the Microsoft runtime |
|
|
3438 | libraries and raw winsocket select is: |
|
|
3439 | |
|
|
3440 | #define EV_USE_SELECT 1 |
|
|
3441 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
3442 | |
|
|
3443 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
3444 | complexity in the O(n²) range when using win32. |
|
|
3445 | |
|
|
3446 | =item Limited number of file descriptors |
|
|
3447 | |
|
|
3448 | Windows has numerous arbitrary (and low) limits on things. |
|
|
3449 | |
|
|
3450 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
3451 | of C<64> handles (probably owning to the fact that all windows kernels |
|
|
3452 | can only wait for C<64> things at the same time internally; Microsoft |
|
|
3453 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3454 | previous thread in each. Great). |
|
|
3455 | |
|
|
3456 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
|
|
3457 | to some high number (e.g. C<2048>) before compiling the winsocket select |
|
|
3458 | call (which might be in libev or elsewhere, for example, perl does its own |
|
|
3459 | select emulation on windows). |
|
|
3460 | |
|
|
3461 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
3462 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
|
|
3463 | or something like this inside Microsoft). You can increase this by calling |
|
|
3464 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
|
|
3465 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
|
|
3466 | libraries. |
|
|
3467 | |
|
|
3468 | This might get you to about C<512> or C<2048> sockets (depending on |
|
|
3469 | windows version and/or the phase of the moon). To get more, you need to |
|
|
3470 | wrap all I/O functions and provide your own fd management, but the cost of |
|
|
3471 | calling select (O(n²)) will likely make this unworkable. |
|
|
3472 | |
|
|
3473 | =back |
|
|
3474 | |
|
|
3475 | |
|
|
3476 | =head1 PORTABILITY REQUIREMENTS |
|
|
3477 | |
|
|
3478 | In addition to a working ISO-C implementation, libev relies on a few |
|
|
3479 | additional extensions: |
|
|
3480 | |
|
|
3481 | =over 4 |
|
|
3482 | |
|
|
3483 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
|
|
3484 | calling conventions regardless of C<ev_watcher_type *>. |
|
|
3485 | |
|
|
3486 | Libev assumes not only that all watcher pointers have the same internal |
|
|
3487 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
|
|
3488 | assumes that the same (machine) code can be used to call any watcher |
|
|
3489 | callback: The watcher callbacks have different type signatures, but libev |
|
|
3490 | calls them using an C<ev_watcher *> internally. |
|
|
3491 | |
|
|
3492 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
3493 | |
|
|
3494 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
3495 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
|
|
3496 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
3497 | believed to be sufficiently portable. |
|
|
3498 | |
|
|
3499 | =item C<sigprocmask> must work in a threaded environment |
|
|
3500 | |
|
|
3501 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
3502 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
3503 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
3504 | thread" or will block signals process-wide, both behaviours would |
|
|
3505 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
3506 | C<pthread_sigmask> could complicate things, however. |
|
|
3507 | |
|
|
3508 | The most portable way to handle signals is to block signals in all threads |
|
|
3509 | except the initial one, and run the default loop in the initial thread as |
|
|
3510 | well. |
|
|
3511 | |
|
|
3512 | =item C<long> must be large enough for common memory allocation sizes |
|
|
3513 | |
|
|
3514 | To improve portability and simplify using libev, libev uses C<long> |
|
|
3515 | internally instead of C<size_t> when allocating its data structures. On |
|
|
3516 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3517 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3518 | millions of watchers. |
|
|
3519 | |
|
|
3520 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
3521 | |
|
|
3522 | The type C<double> is used to represent timestamps. It is required to |
|
|
3523 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3524 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3525 | implementations implementing IEEE 754 (basically all existing ones). |
|
|
3526 | |
|
|
3527 | =back |
|
|
3528 | |
|
|
3529 | If you know of other additional requirements drop me a note. |
|
|
3530 | |
|
|
3531 | |
|
|
3532 | =head1 COMPILER WARNINGS |
|
|
3533 | |
|
|
3534 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3535 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3536 | scared by this. |
|
|
3537 | |
|
|
3538 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3539 | has different warnings, and each user has different tastes regarding |
|
|
3540 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3541 | targeting a specific compiler and compiler-version. |
|
|
3542 | |
|
|
3543 | Another reason is that some compiler warnings require elaborate |
|
|
3544 | workarounds, or other changes to the code that make it less clear and less |
|
|
3545 | maintainable. |
|
|
3546 | |
|
|
3547 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3548 | wrong (because they don't actually warn about the condition their message |
|
|
3549 | seems to warn about). |
|
|
3550 | |
|
|
3551 | While libev is written to generate as few warnings as possible, |
|
|
3552 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3553 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3554 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3555 | warnings, not errors, or proof of bugs. |
|
|
3556 | |
|
|
3557 | |
|
|
3558 | =head1 VALGRIND |
|
|
3559 | |
|
|
3560 | Valgrind has a special section here because it is a popular tool that is |
|
|
3561 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3562 | |
|
|
3563 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3564 | in libev, then check twice: If valgrind reports something like: |
|
|
3565 | |
|
|
3566 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3567 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3568 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3569 | |
|
|
3570 | Then there is no memory leak. Similarly, under some circumstances, |
|
|
3571 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3572 | might be confused (it is a very good tool, but only a tool). |
|
|
3573 | |
|
|
3574 | If you are unsure about something, feel free to contact the mailing list |
|
|
3575 | with the full valgrind report and an explanation on why you think this is |
|
|
3576 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
|
|
3577 | no bug" answer and take the chance of learning how to interpret valgrind |
|
|
3578 | properly. |
|
|
3579 | |
|
|
3580 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3581 | I suggest using suppression lists. |
|
|
3582 | |
1689 | |
3583 | |
1690 | =head1 AUTHOR |
3584 | =head1 AUTHOR |
1691 | |
3585 | |
1692 | Marc Lehmann <libev@schmorp.de>. |
3586 | Marc Lehmann <libev@schmorp.de>. |
1693 | |
3587 | |