… | |
… | |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
8 | |
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 | } |
|
|
64 | |
9 | =head1 DESCRIPTION |
65 | =head1 DESCRIPTION |
10 | |
66 | |
|
|
67 | The newest version of this document is also available as an html-formatted |
|
|
68 | web page you might find easier to navigate when reading it for the first |
|
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69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
|
|
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. |
… | |
… | |
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 | |
|
|
122 | =head1 ERROR HANDLING |
|
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123 | |
|
|
124 | Libev knows three classes of errors: operating system errors, usage errors |
|
|
125 | and internal errors (bugs). |
|
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126 | |
|
|
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 |
|
|
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 |
|
|
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 |
… | |
… | |
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 | |
|
|
158 | Sleep for the given interval: The current thread will be blocked until |
|
|
159 | either it is interrupted or the given time interval has passed. Basically |
|
|
160 | this is a sub-second-resolution C<sleep ()>. |
|
|
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 | |
|
|
172 | These version numbers refer to the ABI version of the library, not the |
|
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173 | release version. |
|
|
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 | |
… | |
… | |
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 | |
… | |
… | |
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. |
|
|
226 | |
|
|
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 |
|
|
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 | |
… | |
… | |
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); |
… | |
… | |
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 | |
284 | |
183 | If you use threads, a common model is to run the default event loop |
|
|
184 | in your main thread (or in a separate thread) and for each thread you |
|
|
185 | create, you also create another event loop. Libev itself does no locking |
|
|
186 | whatsoever, so if you mix calls to the same event loop in different |
|
|
187 | threads, make sure you lock (this is usually a bad idea, though, even if |
|
|
188 | done correctly, because it's hideous and inefficient). |
|
|
189 | |
|
|
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 | |
194 | This will initialise the default event loop if it hasn't been initialised |
289 | This will initialise the default event loop if it hasn't been initialised |
… | |
… | |
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 | |
|
|
297 | Note that this function is I<not> thread-safe, so if you want to use it |
|
|
298 | from multiple threads, you have to lock (note also that this is unlikely, |
|
|
299 | as loops cannot bes hared easily between threads anyway). |
|
|
300 | |
|
|
301 | The default loop is the only loop that can handle C<ev_signal> and |
|
|
302 | C<ev_child> watchers, and to do this, it always registers a handler |
|
|
303 | for C<SIGCHLD>. If this is a problem for your application you can either |
|
|
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
|
|
305 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
|
|
306 | C<ev_default_init>. |
|
|
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 | |
… | |
… | |
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 | |
|
|
329 | =item C<EVFLAG_FORKCHECK> |
|
|
330 | |
|
|
331 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
|
|
332 | a fork, you can also make libev check for a fork in each iteration by |
|
|
333 | enabling this flag. |
|
|
334 | |
|
|
335 | This works by calling C<getpid ()> on every iteration of the loop, |
|
|
336 | and thus this might slow down your event loop if you do a lot of loop |
|
|
337 | iterations and little real work, but is usually not noticeable (on my |
|
|
338 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
|
|
339 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
|
|
340 | C<pthread_atfork> which is even faster). |
|
|
341 | |
|
|
342 | The big advantage of this flag is that you can forget about fork (and |
|
|
343 | forget about forgetting to tell libev about forking) when you use this |
|
|
344 | flag. |
|
|
345 | |
|
|
346 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
|
|
347 | environment variable. |
|
|
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. |
|
|
356 | |
|
|
357 | To get good performance out of this backend you need a high amount of |
|
|
358 | parallelism (most of the file descriptors should be busy). If you are |
|
|
359 | writing a server, you should C<accept ()> in a loop to accept as many |
|
|
360 | connections as possible during one iteration. You might also want to have |
|
|
361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
|
|
362 | readiness notifications you get per iteration. |
230 | |
363 | |
231 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
364 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
232 | |
365 | |
233 | And this is your standard poll(2) backend. It's more complicated than |
366 | 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 |
367 | 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 |
368 | 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). |
369 | considerably with a lot of inactive fds). It scales similarly to select, |
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370 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
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371 | performance tips. |
237 | |
372 | |
238 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
373 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
239 | |
374 | |
240 | For few fds, this backend is a bit little slower than poll and select, |
375 | 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 |
376 | 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 |
377 | like O(total_fds) where n is the total number of fds (or the highest fd), |
243 | either O(1) or O(active_fds). |
378 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
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379 | of shortcomings, such as silently dropping events in some hard-to-detect |
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380 | cases and requiring a system call per fd change, no fork support and bad |
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381 | support for dup. |
244 | |
382 | |
245 | While stopping and starting an I/O watcher in the same iteration will |
383 | 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 |
384 | 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 |
385 | (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 |
386 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
249 | well if you register events for both fds. |
387 | very well if you register events for both fds. |
250 | |
388 | |
251 | Please note that epoll sometimes generates spurious notifications, so you |
389 | 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 |
390 | need to use non-blocking I/O or other means to avoid blocking when no data |
253 | (or space) is available. |
391 | (or space) is available. |
254 | |
392 | |
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393 | Best performance from this backend is achieved by not unregistering all |
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394 | watchers for a file descriptor until it has been closed, if possible, i.e. |
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395 | keep at least one watcher active per fd at all times. |
|
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396 | |
|
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397 | While nominally embeddable in other event loops, this feature is broken in |
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398 | all kernel versions tested so far. |
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399 | |
255 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
400 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
256 | |
401 | |
257 | Kqueue deserves special mention, as at the time of this writing, it |
402 | 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 |
403 | 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 |
404 | with anything but sockets and pipes, except on Darwin, where of course |
260 | completely useless). For this reason its not being "autodetected" |
405 | 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 |
406 | unless you explicitly specify it explicitly in the flags (i.e. using |
262 | C<EVBACKEND_KQUEUE>). |
407 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
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408 | system like NetBSD. |
|
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409 | |
|
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410 | You still can embed kqueue into a normal poll or select backend and use it |
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411 | only for sockets (after having made sure that sockets work with kqueue on |
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412 | the target platform). See C<ev_embed> watchers for more info. |
263 | |
413 | |
264 | It scales in the same way as the epoll backend, but the interface to the |
414 | 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 |
415 | 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 |
416 | 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 |
417 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
268 | incident, so its best to avoid that. |
418 | two event changes per incident, support for C<fork ()> is very bad and it |
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419 | drops fds silently in similarly hard-to-detect cases. |
|
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420 | |
|
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421 | This backend usually performs well under most conditions. |
|
|
422 | |
|
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423 | While nominally embeddable in other event loops, this doesn't work |
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424 | everywhere, so you might need to test for this. And since it is broken |
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425 | almost everywhere, you should only use it when you have a lot of sockets |
|
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426 | (for which it usually works), by embedding it into another event loop |
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427 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
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428 | sockets. |
269 | |
429 | |
270 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
430 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
271 | |
431 | |
272 | This is not implemented yet (and might never be). |
432 | This is not implemented yet (and might never be, unless you send me an |
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433 | implementation). According to reports, C</dev/poll> only supports sockets |
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434 | and is not embeddable, which would limit the usefulness of this backend |
|
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435 | immensely. |
273 | |
436 | |
274 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
437 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
275 | |
438 | |
276 | This uses the Solaris 10 port mechanism. As with everything on Solaris, |
439 | 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)). |
440 | it's really slow, but it still scales very well (O(active_fds)). |
278 | |
441 | |
279 | Please note that solaris ports can result in a lot of spurious |
442 | 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 |
443 | notifications, so you need to use non-blocking I/O or other means to avoid |
281 | blocking when no data (or space) is available. |
444 | blocking when no data (or space) is available. |
|
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445 | |
|
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446 | While this backend scales well, it requires one system call per active |
|
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447 | file descriptor per loop iteration. For small and medium numbers of file |
|
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448 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
|
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449 | might perform better. |
|
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450 | |
|
|
451 | On the positive side, ignoring the spurious readiness notifications, this |
|
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452 | backend actually performed to specification in all tests and is fully |
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453 | embeddable, which is a rare feat among the OS-specific backends. |
282 | |
454 | |
283 | =item C<EVBACKEND_ALL> |
455 | =item C<EVBACKEND_ALL> |
284 | |
456 | |
285 | Try all backends (even potentially broken ones that wouldn't be tried |
457 | 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 |
458 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
287 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
459 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
288 | |
460 | |
|
|
461 | It is definitely not recommended to use this flag. |
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462 | |
289 | =back |
463 | =back |
290 | |
464 | |
291 | If one or more of these are ored into the flags value, then only these |
465 | 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 |
466 | 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 |
467 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
294 | order of their flag values :) |
|
|
295 | |
468 | |
296 | The most typical usage is like this: |
469 | The most typical usage is like this: |
297 | |
470 | |
298 | if (!ev_default_loop (0)) |
471 | if (!ev_default_loop (0)) |
299 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
472 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
… | |
… | |
314 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
487 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
315 | always distinct from the default loop. Unlike the default loop, it cannot |
488 | always distinct from the default loop. Unlike the default loop, it cannot |
316 | handle signal and child watchers, and attempts to do so will be greeted by |
489 | handle signal and child watchers, and attempts to do so will be greeted by |
317 | undefined behaviour (or a failed assertion if assertions are enabled). |
490 | undefined behaviour (or a failed assertion if assertions are enabled). |
318 | |
491 | |
|
|
492 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
493 | libev with threads is indeed to create one loop per thread, and using the |
|
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494 | default loop in the "main" or "initial" thread. |
|
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495 | |
319 | Example: try to create a event loop that uses epoll and nothing else. |
496 | Example: Try to create a event loop that uses epoll and nothing else. |
320 | |
497 | |
321 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
498 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
322 | if (!epoller) |
499 | if (!epoller) |
323 | fatal ("no epoll found here, maybe it hides under your chair"); |
500 | fatal ("no epoll found here, maybe it hides under your chair"); |
324 | |
501 | |
325 | =item ev_default_destroy () |
502 | =item ev_default_destroy () |
326 | |
503 | |
327 | Destroys the default loop again (frees all memory and kernel state |
504 | 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 |
505 | 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 |
506 | 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> |
507 | responsibility to either stop all watchers cleanly yourself I<before> |
331 | calling this function, or cope with the fact afterwards (which is usually |
508 | 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 |
509 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
333 | for example). |
510 | for example). |
|
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511 | |
|
|
512 | Note that certain global state, such as signal state, will not be freed by |
|
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513 | this function, and related watchers (such as signal and child watchers) |
|
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514 | would need to be stopped manually. |
|
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515 | |
|
|
516 | In general it is not advisable to call this function except in the |
|
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517 | rare occasion where you really need to free e.g. the signal handling |
|
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518 | pipe fds. If you need dynamically allocated loops it is better to use |
|
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519 | C<ev_loop_new> and C<ev_loop_destroy>). |
334 | |
520 | |
335 | =item ev_loop_destroy (loop) |
521 | =item ev_loop_destroy (loop) |
336 | |
522 | |
337 | Like C<ev_default_destroy>, but destroys an event loop created by an |
523 | Like C<ev_default_destroy>, but destroys an event loop created by an |
338 | earlier call to C<ev_loop_new>. |
524 | earlier call to C<ev_loop_new>. |
339 | |
525 | |
340 | =item ev_default_fork () |
526 | =item ev_default_fork () |
341 | |
527 | |
|
|
528 | This function sets a flag that causes subsequent C<ev_loop> iterations |
342 | This function reinitialises the kernel state for backends that have |
529 | 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 |
530 | 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 |
531 | the child process (or both child and parent, but that again makes little |
345 | again makes little sense). |
532 | sense). You I<must> call it in the child before using any of the libev |
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533 | functions, and it will only take effect at the next C<ev_loop> iteration. |
346 | |
534 | |
347 | You I<must> call this function in the child process after forking if and |
535 | 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 |
536 | 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. |
537 | you just fork+exec, you don't have to call it at all. |
350 | |
538 | |
351 | The function itself is quite fast and it's usually not a problem to call |
539 | The function itself is quite fast and it's usually not a problem to call |
352 | it just in case after a fork. To make this easy, the function will fit in |
540 | it just in case after a fork. To make this easy, the function will fit in |
353 | quite nicely into a call to C<pthread_atfork>: |
541 | quite nicely into a call to C<pthread_atfork>: |
354 | |
542 | |
355 | pthread_atfork (0, 0, ev_default_fork); |
543 | pthread_atfork (0, 0, ev_default_fork); |
356 | |
544 | |
357 | At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use |
|
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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) |
545 | =item ev_loop_fork (loop) |
362 | |
546 | |
363 | Like C<ev_default_fork>, but acts on an event loop created by |
547 | Like C<ev_default_fork>, but acts on an event loop created by |
364 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
548 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
365 | after fork, and how you do this is entirely your own problem. |
549 | after fork, and how you do this is entirely your own problem. |
|
|
550 | |
|
|
551 | =item int ev_is_default_loop (loop) |
|
|
552 | |
|
|
553 | Returns true when the given loop actually is the default loop, false otherwise. |
|
|
554 | |
|
|
555 | =item unsigned int ev_loop_count (loop) |
|
|
556 | |
|
|
557 | Returns the count of loop iterations for the loop, which is identical to |
|
|
558 | the number of times libev did poll for new events. It starts at C<0> and |
|
|
559 | happily wraps around with enough iterations. |
|
|
560 | |
|
|
561 | This value can sometimes be useful as a generation counter of sorts (it |
|
|
562 | "ticks" the number of loop iterations), as it roughly corresponds with |
|
|
563 | C<ev_prepare> and C<ev_check> calls. |
366 | |
564 | |
367 | =item unsigned int ev_backend (loop) |
565 | =item unsigned int ev_backend (loop) |
368 | |
566 | |
369 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
567 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
370 | use. |
568 | use. |
… | |
… | |
373 | |
571 | |
374 | Returns the current "event loop time", which is the time the event loop |
572 | Returns the current "event loop time", which is the time the event loop |
375 | received events and started processing them. This timestamp does not |
573 | 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 |
574 | 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 |
575 | 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). |
576 | event occurring (or more correctly, libev finding out about it). |
379 | |
577 | |
380 | =item ev_loop (loop, int flags) |
578 | =item ev_loop (loop, int flags) |
381 | |
579 | |
382 | Finally, this is it, the event handler. This function usually is called |
580 | 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 |
581 | 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 |
593 | 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 |
594 | 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. |
595 | case there are no events and will return after one iteration of the loop. |
398 | |
596 | |
399 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
597 | 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 |
598 | 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 |
599 | 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 |
600 | 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 |
601 | 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 |
602 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
405 | usually a better approach for this kind of thing. |
603 | usually a better approach for this kind of thing. |
406 | |
604 | |
407 | Here are the gory details of what C<ev_loop> does: |
605 | Here are the gory details of what C<ev_loop> does: |
408 | |
606 | |
409 | * If there are no active watchers (reference count is zero), return. |
607 | - Before the first iteration, call any pending watchers. |
410 | - Queue prepare watchers and then call all outstanding watchers. |
608 | * If EVFLAG_FORKCHECK was used, check for a fork. |
|
|
609 | - If a fork was detected, queue and call all fork watchers. |
|
|
610 | - Queue and call all prepare watchers. |
411 | - If we have been forked, recreate the kernel state. |
611 | - If we have been forked, recreate the kernel state. |
412 | - Update the kernel state with all outstanding changes. |
612 | - Update the kernel state with all outstanding changes. |
413 | - Update the "event loop time". |
613 | - Update the "event loop time". |
414 | - Calculate for how long to block. |
614 | - Calculate for how long to sleep or block, if at all |
|
|
615 | (active idle watchers, EVLOOP_NONBLOCK or not having |
|
|
616 | any active watchers at all will result in not sleeping). |
|
|
617 | - Sleep if the I/O and timer collect interval say so. |
415 | - Block the process, waiting for any events. |
618 | - Block the process, waiting for any events. |
416 | - Queue all outstanding I/O (fd) events. |
619 | - Queue all outstanding I/O (fd) events. |
417 | - Update the "event loop time" and do time jump handling. |
620 | - Update the "event loop time" and do time jump handling. |
418 | - Queue all outstanding timers. |
621 | - Queue all outstanding timers. |
419 | - Queue all outstanding periodics. |
622 | - Queue all outstanding periodics. |
420 | - If no events are pending now, queue all idle watchers. |
623 | - If no events are pending now, queue all idle watchers. |
421 | - Queue all check watchers. |
624 | - Queue all check watchers. |
422 | - Call all queued watchers in reverse order (i.e. check watchers first). |
625 | - 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 |
626 | Signals and child watchers are implemented as I/O watchers, and will |
424 | be handled here by queueing them when their watcher gets executed. |
627 | be handled here by queueing them when their watcher gets executed. |
425 | - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
628 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
426 | were used, return, otherwise continue with step *. |
629 | were used, or there are no active watchers, return, otherwise |
|
|
630 | continue with step *. |
427 | |
631 | |
428 | Example: queue some jobs and then loop until no events are outsanding |
632 | Example: Queue some jobs and then loop until no events are outstanding |
429 | anymore. |
633 | anymore. |
430 | |
634 | |
431 | ... queue jobs here, make sure they register event watchers as long |
635 | ... 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..) |
636 | ... as they still have work to do (even an idle watcher will do..) |
433 | ev_loop (my_loop, 0); |
637 | ev_loop (my_loop, 0); |
… | |
… | |
437 | |
641 | |
438 | Can be used to make a call to C<ev_loop> return early (but only after it |
642 | 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 |
643 | 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 |
644 | 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. |
645 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
|
|
646 | |
|
|
647 | This "unloop state" will be cleared when entering C<ev_loop> again. |
442 | |
648 | |
443 | =item ev_ref (loop) |
649 | =item ev_ref (loop) |
444 | |
650 | |
445 | =item ev_unref (loop) |
651 | =item ev_unref (loop) |
446 | |
652 | |
… | |
… | |
451 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
657 | 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 |
658 | 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 |
659 | 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 |
660 | 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 |
661 | 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>. |
662 | libraries. Just remember to I<unref after start> and I<ref before stop> |
|
|
663 | (but only if the watcher wasn't active before, or was active before, |
|
|
664 | respectively). |
457 | |
665 | |
458 | Example: create a signal watcher, but keep it from keeping C<ev_loop> |
666 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
459 | running when nothing else is active. |
667 | running when nothing else is active. |
460 | |
668 | |
461 | struct dv_signal exitsig; |
669 | struct ev_signal exitsig; |
462 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
670 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
463 | ev_signal_start (myloop, &exitsig); |
671 | ev_signal_start (loop, &exitsig); |
464 | evf_unref (myloop); |
672 | evf_unref (loop); |
465 | |
673 | |
466 | Example: for some weird reason, unregister the above signal handler again. |
674 | Example: For some weird reason, unregister the above signal handler again. |
467 | |
675 | |
468 | ev_ref (myloop); |
676 | ev_ref (loop); |
469 | ev_signal_stop (myloop, &exitsig); |
677 | ev_signal_stop (loop, &exitsig); |
|
|
678 | |
|
|
679 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
|
|
680 | |
|
|
681 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
|
|
682 | |
|
|
683 | These advanced functions influence the time that libev will spend waiting |
|
|
684 | for events. Both are by default C<0>, meaning that libev will try to |
|
|
685 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
|
|
686 | |
|
|
687 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
|
|
688 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
|
|
689 | increase efficiency of loop iterations. |
|
|
690 | |
|
|
691 | The background is that sometimes your program runs just fast enough to |
|
|
692 | handle one (or very few) event(s) per loop iteration. While this makes |
|
|
693 | the program responsive, it also wastes a lot of CPU time to poll for new |
|
|
694 | events, especially with backends like C<select ()> which have a high |
|
|
695 | overhead for the actual polling but can deliver many events at once. |
|
|
696 | |
|
|
697 | By setting a higher I<io collect interval> you allow libev to spend more |
|
|
698 | time collecting I/O events, so you can handle more events per iteration, |
|
|
699 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
|
|
700 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
|
|
701 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
|
|
702 | |
|
|
703 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
|
|
704 | to spend more time collecting timeouts, at the expense of increased |
|
|
705 | latency (the watcher callback will be called later). C<ev_io> watchers |
|
|
706 | will not be affected. Setting this to a non-null value will not introduce |
|
|
707 | any overhead in libev. |
|
|
708 | |
|
|
709 | Many (busy) programs can usually benefit by setting the I/O collect |
|
|
710 | interval to a value near C<0.1> or so, which is often enough for |
|
|
711 | interactive servers (of course not for games), likewise for timeouts. It |
|
|
712 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
|
|
713 | as this approaches the timing granularity of most systems. |
|
|
714 | |
|
|
715 | =item ev_loop_verify (loop) |
|
|
716 | |
|
|
717 | This function only does something when C<EV_VERIFY> support has been |
|
|
718 | compiled in. It tries to go through all internal structures and checks |
|
|
719 | them for validity. If anything is found to be inconsistent, it will print |
|
|
720 | an error message to standard error and call C<abort ()>. |
|
|
721 | |
|
|
722 | This can be used to catch bugs inside libev itself: under normal |
|
|
723 | circumstances, this function will never abort as of course libev keeps its |
|
|
724 | data structures consistent. |
470 | |
725 | |
471 | =back |
726 | =back |
472 | |
727 | |
473 | |
728 | |
474 | =head1 ANATOMY OF A WATCHER |
729 | =head1 ANATOMY OF A WATCHER |
… | |
… | |
494 | watcher structures (and it is usually a bad idea to do this on the stack, |
749 | watcher structures (and it is usually a bad idea to do this on the stack, |
495 | although this can sometimes be quite valid). |
750 | although this can sometimes be quite valid). |
496 | |
751 | |
497 | Each watcher structure must be initialised by a call to C<ev_init |
752 | Each watcher structure must be initialised by a call to C<ev_init |
498 | (watcher *, callback)>, which expects a callback to be provided. This |
753 | (watcher *, callback)>, which expects a callback to be provided. This |
499 | callback gets invoked each time the event occurs (or, in the case of io |
754 | callback gets invoked each time the event occurs (or, in the case of I/O |
500 | watchers, each time the event loop detects that the file descriptor given |
755 | watchers, each time the event loop detects that the file descriptor given |
501 | is readable and/or writable). |
756 | is readable and/or writable). |
502 | |
757 | |
503 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
758 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
504 | with arguments specific to this watcher type. There is also a macro |
759 | with arguments specific to this watcher type. There is also a macro |
… | |
… | |
544 | The signal specified in the C<ev_signal> watcher has been received by a thread. |
799 | The signal specified in the C<ev_signal> watcher has been received by a thread. |
545 | |
800 | |
546 | =item C<EV_CHILD> |
801 | =item C<EV_CHILD> |
547 | |
802 | |
548 | The pid specified in the C<ev_child> watcher has received a status change. |
803 | The pid specified in the C<ev_child> watcher has received a status change. |
|
|
804 | |
|
|
805 | =item C<EV_STAT> |
|
|
806 | |
|
|
807 | The path specified in the C<ev_stat> watcher changed its attributes somehow. |
549 | |
808 | |
550 | =item C<EV_IDLE> |
809 | =item C<EV_IDLE> |
551 | |
810 | |
552 | The C<ev_idle> watcher has determined that you have nothing better to do. |
811 | The C<ev_idle> watcher has determined that you have nothing better to do. |
553 | |
812 | |
… | |
… | |
561 | received events. Callbacks of both watcher types can start and stop as |
820 | received events. Callbacks of both watcher types can start and stop as |
562 | many watchers as they want, and all of them will be taken into account |
821 | many watchers as they want, and all of them will be taken into account |
563 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
822 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
564 | C<ev_loop> from blocking). |
823 | C<ev_loop> from blocking). |
565 | |
824 | |
|
|
825 | =item C<EV_EMBED> |
|
|
826 | |
|
|
827 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
|
|
828 | |
|
|
829 | =item C<EV_FORK> |
|
|
830 | |
|
|
831 | The event loop has been resumed in the child process after fork (see |
|
|
832 | C<ev_fork>). |
|
|
833 | |
|
|
834 | =item C<EV_ASYNC> |
|
|
835 | |
|
|
836 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
837 | |
566 | =item C<EV_ERROR> |
838 | =item C<EV_ERROR> |
567 | |
839 | |
568 | An unspecified error has occured, the watcher has been stopped. This might |
840 | An unspecified error has occurred, the watcher has been stopped. This might |
569 | happen because the watcher could not be properly started because libev |
841 | happen because the watcher could not be properly started because libev |
570 | ran out of memory, a file descriptor was found to be closed or any other |
842 | ran out of memory, a file descriptor was found to be closed or any other |
571 | problem. You best act on it by reporting the problem and somehow coping |
843 | problem. You best act on it by reporting the problem and somehow coping |
572 | with the watcher being stopped. |
844 | with the watcher being stopped. |
573 | |
845 | |
574 | Libev will usually signal a few "dummy" events together with an error, |
846 | Libev will usually signal a few "dummy" events together with an error, |
575 | for example it might indicate that a fd is readable or writable, and if |
847 | for example it might indicate that a fd is readable or writable, and if |
576 | your callbacks is well-written it can just attempt the operation and cope |
848 | your callbacks is well-written it can just attempt the operation and cope |
577 | with the error from read() or write(). This will not work in multithreaded |
849 | with the error from read() or write(). This will not work in multi-threaded |
578 | programs, though, so beware. |
850 | programs, though, so beware. |
579 | |
851 | |
580 | =back |
852 | =back |
581 | |
853 | |
582 | =head2 GENERIC WATCHER FUNCTIONS |
854 | =head2 GENERIC WATCHER FUNCTIONS |
… | |
… | |
612 | Although some watcher types do not have type-specific arguments |
884 | Although some watcher types do not have type-specific arguments |
613 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
885 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
614 | |
886 | |
615 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
887 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
616 | |
888 | |
617 | This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
889 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
618 | calls into a single call. This is the most convinient method to initialise |
890 | calls into a single call. This is the most convenient method to initialise |
619 | a watcher. The same limitations apply, of course. |
891 | a watcher. The same limitations apply, of course. |
620 | |
892 | |
621 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
893 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
622 | |
894 | |
623 | Starts (activates) the given watcher. Only active watchers will receive |
895 | Starts (activates) the given watcher. Only active watchers will receive |
… | |
… | |
641 | =item bool ev_is_pending (ev_TYPE *watcher) |
913 | =item bool ev_is_pending (ev_TYPE *watcher) |
642 | |
914 | |
643 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
915 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
644 | events but its callback has not yet been invoked). As long as a watcher |
916 | events but its callback has not yet been invoked). As long as a watcher |
645 | is pending (but not active) you must not call an init function on it (but |
917 | is pending (but not active) you must not call an init function on it (but |
646 | C<ev_TYPE_set> is safe) and you must make sure the watcher is available to |
918 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
647 | libev (e.g. you cnanot C<free ()> it). |
919 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
920 | it). |
648 | |
921 | |
649 | =item callback = ev_cb (ev_TYPE *watcher) |
922 | =item callback ev_cb (ev_TYPE *watcher) |
650 | |
923 | |
651 | Returns the callback currently set on the watcher. |
924 | Returns the callback currently set on the watcher. |
652 | |
925 | |
653 | =item ev_cb_set (ev_TYPE *watcher, callback) |
926 | =item ev_cb_set (ev_TYPE *watcher, callback) |
654 | |
927 | |
655 | Change the callback. You can change the callback at virtually any time |
928 | Change the callback. You can change the callback at virtually any time |
656 | (modulo threads). |
929 | (modulo threads). |
|
|
930 | |
|
|
931 | =item ev_set_priority (ev_TYPE *watcher, priority) |
|
|
932 | |
|
|
933 | =item int ev_priority (ev_TYPE *watcher) |
|
|
934 | |
|
|
935 | Set and query the priority of the watcher. The priority is a small |
|
|
936 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
937 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
938 | before watchers with lower priority, but priority will not keep watchers |
|
|
939 | from being executed (except for C<ev_idle> watchers). |
|
|
940 | |
|
|
941 | This means that priorities are I<only> used for ordering callback |
|
|
942 | invocation after new events have been received. This is useful, for |
|
|
943 | example, to reduce latency after idling, or more often, to bind two |
|
|
944 | watchers on the same event and make sure one is called first. |
|
|
945 | |
|
|
946 | If you need to suppress invocation when higher priority events are pending |
|
|
947 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
948 | |
|
|
949 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
950 | pending. |
|
|
951 | |
|
|
952 | The default priority used by watchers when no priority has been set is |
|
|
953 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
954 | |
|
|
955 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
956 | fine, as long as you do not mind that the priority value you query might |
|
|
957 | or might not have been adjusted to be within valid range. |
|
|
958 | |
|
|
959 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
960 | |
|
|
961 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
962 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
963 | can deal with that fact. |
|
|
964 | |
|
|
965 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
966 | |
|
|
967 | If the watcher is pending, this function returns clears its pending status |
|
|
968 | and returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
969 | watcher isn't pending it does nothing and returns C<0>. |
657 | |
970 | |
658 | =back |
971 | =back |
659 | |
972 | |
660 | |
973 | |
661 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
974 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
… | |
… | |
682 | { |
995 | { |
683 | struct my_io *w = (struct my_io *)w_; |
996 | struct my_io *w = (struct my_io *)w_; |
684 | ... |
997 | ... |
685 | } |
998 | } |
686 | |
999 | |
687 | More interesting and less C-conformant ways of catsing your callback type |
1000 | More interesting and less C-conformant ways of casting your callback type |
688 | have been omitted.... |
1001 | instead have been omitted. |
|
|
1002 | |
|
|
1003 | Another common scenario is having some data structure with multiple |
|
|
1004 | watchers: |
|
|
1005 | |
|
|
1006 | struct my_biggy |
|
|
1007 | { |
|
|
1008 | int some_data; |
|
|
1009 | ev_timer t1; |
|
|
1010 | ev_timer t2; |
|
|
1011 | } |
|
|
1012 | |
|
|
1013 | In this case getting the pointer to C<my_biggy> is a bit more complicated, |
|
|
1014 | you need to use C<offsetof>: |
|
|
1015 | |
|
|
1016 | #include <stddef.h> |
|
|
1017 | |
|
|
1018 | static void |
|
|
1019 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
1020 | { |
|
|
1021 | struct my_biggy big = (struct my_biggy * |
|
|
1022 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1023 | } |
|
|
1024 | |
|
|
1025 | static void |
|
|
1026 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
1027 | { |
|
|
1028 | struct my_biggy big = (struct my_biggy * |
|
|
1029 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1030 | } |
689 | |
1031 | |
690 | |
1032 | |
691 | =head1 WATCHER TYPES |
1033 | =head1 WATCHER TYPES |
692 | |
1034 | |
693 | This section describes each watcher in detail, but will not repeat |
1035 | This section describes each watcher in detail, but will not repeat |
694 | information given in the last section. |
1036 | information given in the last section. Any initialisation/set macros, |
|
|
1037 | functions and members specific to the watcher type are explained. |
|
|
1038 | |
|
|
1039 | Members are additionally marked with either I<[read-only]>, meaning that, |
|
|
1040 | while the watcher is active, you can look at the member and expect some |
|
|
1041 | sensible content, but you must not modify it (you can modify it while the |
|
|
1042 | watcher is stopped to your hearts content), or I<[read-write]>, which |
|
|
1043 | means you can expect it to have some sensible content while the watcher |
|
|
1044 | is active, but you can also modify it. Modifying it may not do something |
|
|
1045 | sensible or take immediate effect (or do anything at all), but libev will |
|
|
1046 | not crash or malfunction in any way. |
695 | |
1047 | |
696 | |
1048 | |
697 | =head2 C<ev_io> - is this file descriptor readable or writable? |
1049 | =head2 C<ev_io> - is this file descriptor readable or writable? |
698 | |
1050 | |
699 | I/O watchers check whether a file descriptor is readable or writable |
1051 | I/O watchers check whether a file descriptor is readable or writable |
… | |
… | |
707 | In general you can register as many read and/or write event watchers per |
1059 | In general you can register as many read and/or write event watchers per |
708 | fd as you want (as long as you don't confuse yourself). Setting all file |
1060 | fd as you want (as long as you don't confuse yourself). Setting all file |
709 | descriptors to non-blocking mode is also usually a good idea (but not |
1061 | descriptors to non-blocking mode is also usually a good idea (but not |
710 | required if you know what you are doing). |
1062 | required if you know what you are doing). |
711 | |
1063 | |
712 | You have to be careful with dup'ed file descriptors, though. Some backends |
|
|
713 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
|
|
714 | descriptors correctly if you register interest in two or more fds pointing |
|
|
715 | to the same underlying file/socket/etc. description (that is, they share |
|
|
716 | the same underlying "file open"). |
|
|
717 | |
|
|
718 | If you must do this, then force the use of a known-to-be-good backend |
1064 | If you must do this, then force the use of a known-to-be-good backend |
719 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1065 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
720 | C<EVBACKEND_POLL>). |
1066 | C<EVBACKEND_POLL>). |
721 | |
1067 | |
722 | Another thing you have to watch out for is that it is quite easy to |
1068 | Another thing you have to watch out for is that it is quite easy to |
723 | receive "spurious" readyness notifications, that is your callback might |
1069 | receive "spurious" readiness notifications, that is your callback might |
724 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1070 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
725 | because there is no data. Not only are some backends known to create a |
1071 | because there is no data. Not only are some backends known to create a |
726 | lot of those (for example solaris ports), it is very easy to get into |
1072 | lot of those (for example Solaris ports), it is very easy to get into |
727 | this situation even with a relatively standard program structure. Thus |
1073 | this situation even with a relatively standard program structure. Thus |
728 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1074 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
729 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1075 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
730 | |
1076 | |
731 | If you cannot run the fd in non-blocking mode (for example you should not |
1077 | If you cannot run the fd in non-blocking mode (for example you should not |
732 | play around with an Xlib connection), then you have to seperately re-test |
1078 | play around with an Xlib connection), then you have to separately re-test |
733 | wether a file descriptor is really ready with a known-to-be good interface |
1079 | whether a file descriptor is really ready with a known-to-be good interface |
734 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1080 | such as poll (fortunately in our Xlib example, Xlib already does this on |
735 | its own, so its quite safe to use). |
1081 | its own, so its quite safe to use). |
736 | |
1082 | |
|
|
1083 | =head3 The special problem of disappearing file descriptors |
|
|
1084 | |
|
|
1085 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
|
|
1086 | descriptor (either by calling C<close> explicitly or by any other means, |
|
|
1087 | such as C<dup>). The reason is that you register interest in some file |
|
|
1088 | descriptor, but when it goes away, the operating system will silently drop |
|
|
1089 | this interest. If another file descriptor with the same number then is |
|
|
1090 | registered with libev, there is no efficient way to see that this is, in |
|
|
1091 | fact, a different file descriptor. |
|
|
1092 | |
|
|
1093 | To avoid having to explicitly tell libev about such cases, libev follows |
|
|
1094 | the following policy: Each time C<ev_io_set> is being called, libev |
|
|
1095 | will assume that this is potentially a new file descriptor, otherwise |
|
|
1096 | it is assumed that the file descriptor stays the same. That means that |
|
|
1097 | you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the |
|
|
1098 | descriptor even if the file descriptor number itself did not change. |
|
|
1099 | |
|
|
1100 | This is how one would do it normally anyway, the important point is that |
|
|
1101 | the libev application should not optimise around libev but should leave |
|
|
1102 | optimisations to libev. |
|
|
1103 | |
|
|
1104 | =head3 The special problem of dup'ed file descriptors |
|
|
1105 | |
|
|
1106 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
1107 | but only events for the underlying file descriptions. That means when you |
|
|
1108 | have C<dup ()>'ed file descriptors or weirder constellations, and register |
|
|
1109 | events for them, only one file descriptor might actually receive events. |
|
|
1110 | |
|
|
1111 | There is no workaround possible except not registering events |
|
|
1112 | for potentially C<dup ()>'ed file descriptors, or to resort to |
|
|
1113 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
|
|
1114 | |
|
|
1115 | =head3 The special problem of fork |
|
|
1116 | |
|
|
1117 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
|
|
1118 | useless behaviour. Libev fully supports fork, but needs to be told about |
|
|
1119 | it in the child. |
|
|
1120 | |
|
|
1121 | To support fork in your programs, you either have to call |
|
|
1122 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
|
|
1123 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
|
|
1124 | C<EVBACKEND_POLL>. |
|
|
1125 | |
|
|
1126 | =head3 The special problem of SIGPIPE |
|
|
1127 | |
|
|
1128 | While not really specific to libev, it is easy to forget about SIGPIPE: |
|
|
1129 | when reading from a pipe whose other end has been closed, your program |
|
|
1130 | gets send a SIGPIPE, which, by default, aborts your program. For most |
|
|
1131 | programs this is sensible behaviour, for daemons, this is usually |
|
|
1132 | undesirable. |
|
|
1133 | |
|
|
1134 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1135 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1136 | somewhere, as that would have given you a big clue). |
|
|
1137 | |
|
|
1138 | |
|
|
1139 | =head3 Watcher-Specific Functions |
|
|
1140 | |
737 | =over 4 |
1141 | =over 4 |
738 | |
1142 | |
739 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1143 | =item ev_io_init (ev_io *, callback, int fd, int events) |
740 | |
1144 | |
741 | =item ev_io_set (ev_io *, int fd, int events) |
1145 | =item ev_io_set (ev_io *, int fd, int events) |
742 | |
1146 | |
743 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1147 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
744 | rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1148 | receive events for and events is either C<EV_READ>, C<EV_WRITE> or |
745 | C<EV_READ | EV_WRITE> to receive the given events. |
1149 | C<EV_READ | EV_WRITE> to receive the given events. |
746 | |
1150 | |
|
|
1151 | =item int fd [read-only] |
|
|
1152 | |
|
|
1153 | The file descriptor being watched. |
|
|
1154 | |
|
|
1155 | =item int events [read-only] |
|
|
1156 | |
|
|
1157 | The events being watched. |
|
|
1158 | |
747 | =back |
1159 | =back |
748 | |
1160 | |
|
|
1161 | =head3 Examples |
|
|
1162 | |
749 | Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1163 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
750 | readable, but only once. Since it is likely line-buffered, you could |
1164 | readable, but only once. Since it is likely line-buffered, you could |
751 | attempt to read a whole line in the callback: |
1165 | attempt to read a whole line in the callback. |
752 | |
1166 | |
753 | static void |
1167 | static void |
754 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1168 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
755 | { |
1169 | { |
756 | ev_io_stop (loop, w); |
1170 | ev_io_stop (loop, w); |
… | |
… | |
769 | |
1183 | |
770 | Timer watchers are simple relative timers that generate an event after a |
1184 | Timer watchers are simple relative timers that generate an event after a |
771 | given time, and optionally repeating in regular intervals after that. |
1185 | given time, and optionally repeating in regular intervals after that. |
772 | |
1186 | |
773 | The timers are based on real time, that is, if you register an event that |
1187 | The timers are based on real time, that is, if you register an event that |
774 | times out after an hour and you reset your system clock to last years |
1188 | times out after an hour and you reset your system clock to January last |
775 | time, it will still time out after (roughly) and hour. "Roughly" because |
1189 | year, it will still time out after (roughly) and hour. "Roughly" because |
776 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1190 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
777 | monotonic clock option helps a lot here). |
1191 | monotonic clock option helps a lot here). |
778 | |
1192 | |
779 | The relative timeouts are calculated relative to the C<ev_now ()> |
1193 | The relative timeouts are calculated relative to the C<ev_now ()> |
780 | time. This is usually the right thing as this timestamp refers to the time |
1194 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
782 | you suspect event processing to be delayed and you I<need> to base the timeout |
1196 | you suspect event processing to be delayed and you I<need> to base the timeout |
783 | on the current time, use something like this to adjust for this: |
1197 | on the current time, use something like this to adjust for this: |
784 | |
1198 | |
785 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1199 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
786 | |
1200 | |
787 | The callback is guarenteed to be invoked only when its timeout has passed, |
1201 | The callback is guaranteed to be invoked only after its timeout has passed, |
788 | but if multiple timers become ready during the same loop iteration then |
1202 | but if multiple timers become ready during the same loop iteration then |
789 | order of execution is undefined. |
1203 | order of execution is undefined. |
790 | |
1204 | |
|
|
1205 | =head3 Watcher-Specific Functions and Data Members |
|
|
1206 | |
791 | =over 4 |
1207 | =over 4 |
792 | |
1208 | |
793 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1209 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
794 | |
1210 | |
795 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1211 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
796 | |
1212 | |
797 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1213 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
798 | C<0.>, then it will automatically be stopped. If it is positive, then the |
1214 | is C<0.>, then it will automatically be stopped once the timeout is |
799 | timer will automatically be configured to trigger again C<repeat> seconds |
1215 | reached. If it is positive, then the timer will automatically be |
800 | later, again, and again, until stopped manually. |
1216 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1217 | until stopped manually. |
801 | |
1218 | |
802 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1219 | The timer itself will do a best-effort at avoiding drift, that is, if |
803 | configure a timer to trigger every 10 seconds, then it will trigger at |
1220 | you configure a timer to trigger every 10 seconds, then it will normally |
804 | exactly 10 second intervals. If, however, your program cannot keep up with |
1221 | trigger at exactly 10 second intervals. If, however, your program cannot |
805 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1222 | keep up with the timer (because it takes longer than those 10 seconds to |
806 | timer will not fire more than once per event loop iteration. |
1223 | do stuff) the timer will not fire more than once per event loop iteration. |
807 | |
1224 | |
808 | =item ev_timer_again (loop) |
1225 | =item ev_timer_again (loop, ev_timer *) |
809 | |
1226 | |
810 | This will act as if the timer timed out and restart it again if it is |
1227 | This will act as if the timer timed out and restart it again if it is |
811 | repeating. The exact semantics are: |
1228 | repeating. The exact semantics are: |
812 | |
1229 | |
|
|
1230 | If the timer is pending, its pending status is cleared. |
|
|
1231 | |
813 | If the timer is started but nonrepeating, stop it. |
1232 | If the timer is started but non-repeating, stop it (as if it timed out). |
814 | |
1233 | |
815 | If the timer is repeating, either start it if necessary (with the repeat |
1234 | If the timer is repeating, either start it if necessary (with the |
816 | value), or reset the running timer to the repeat value. |
1235 | C<repeat> value), or reset the running timer to the C<repeat> value. |
817 | |
1236 | |
818 | This sounds a bit complicated, but here is a useful and typical |
1237 | This sounds a bit complicated, but here is a useful and typical |
819 | example: Imagine you have a tcp connection and you want a so-called idle |
1238 | example: Imagine you have a TCP connection and you want a so-called idle |
820 | timeout, that is, you want to be called when there have been, say, 60 |
1239 | timeout, that is, you want to be called when there have been, say, 60 |
821 | seconds of inactivity on the socket. The easiest way to do this is to |
1240 | seconds of inactivity on the socket. The easiest way to do this is to |
822 | configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each |
1241 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
823 | time you successfully read or write some data. If you go into an idle |
1242 | C<ev_timer_again> each time you successfully read or write some data. If |
824 | state where you do not expect data to travel on the socket, you can stop |
1243 | you go into an idle state where you do not expect data to travel on the |
825 | the timer, and again will automatically restart it if need be. |
1244 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1245 | automatically restart it if need be. |
|
|
1246 | |
|
|
1247 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1248 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1249 | |
|
|
1250 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1251 | ev_timer_again (loop, timer); |
|
|
1252 | ... |
|
|
1253 | timer->again = 17.; |
|
|
1254 | ev_timer_again (loop, timer); |
|
|
1255 | ... |
|
|
1256 | timer->again = 10.; |
|
|
1257 | ev_timer_again (loop, timer); |
|
|
1258 | |
|
|
1259 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1260 | you want to modify its timeout value. |
|
|
1261 | |
|
|
1262 | =item ev_tstamp repeat [read-write] |
|
|
1263 | |
|
|
1264 | The current C<repeat> value. Will be used each time the watcher times out |
|
|
1265 | or C<ev_timer_again> is called and determines the next timeout (if any), |
|
|
1266 | which is also when any modifications are taken into account. |
826 | |
1267 | |
827 | =back |
1268 | =back |
828 | |
1269 | |
|
|
1270 | =head3 Examples |
|
|
1271 | |
829 | Example: create a timer that fires after 60 seconds. |
1272 | Example: Create a timer that fires after 60 seconds. |
830 | |
1273 | |
831 | static void |
1274 | static void |
832 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1275 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
833 | { |
1276 | { |
834 | .. one minute over, w is actually stopped right here |
1277 | .. one minute over, w is actually stopped right here |
… | |
… | |
836 | |
1279 | |
837 | struct ev_timer mytimer; |
1280 | struct ev_timer mytimer; |
838 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1281 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
839 | ev_timer_start (loop, &mytimer); |
1282 | ev_timer_start (loop, &mytimer); |
840 | |
1283 | |
841 | Example: create a timeout timer that times out after 10 seconds of |
1284 | Example: Create a timeout timer that times out after 10 seconds of |
842 | inactivity. |
1285 | inactivity. |
843 | |
1286 | |
844 | static void |
1287 | static void |
845 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1288 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
846 | { |
1289 | { |
… | |
… | |
861 | |
1304 | |
862 | Periodic watchers are also timers of a kind, but they are very versatile |
1305 | Periodic watchers are also timers of a kind, but they are very versatile |
863 | (and unfortunately a bit complex). |
1306 | (and unfortunately a bit complex). |
864 | |
1307 | |
865 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1308 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
866 | but on wallclock time (absolute time). You can tell a periodic watcher |
1309 | but on wall clock time (absolute time). You can tell a periodic watcher |
867 | to trigger "at" some specific point in time. For example, if you tell a |
1310 | to trigger after some specific point in time. For example, if you tell a |
868 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1311 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
869 | + 10.>) and then reset your system clock to the last year, then it will |
1312 | + 10.>, that is, an absolute time not a delay) and then reset your system |
|
|
1313 | clock to January of the previous year, then it will take more than year |
870 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1314 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
871 | roughly 10 seconds later and of course not if you reset your system time |
1315 | roughly 10 seconds later as it uses a relative timeout). |
872 | again). |
|
|
873 | |
1316 | |
874 | They can also be used to implement vastly more complex timers, such as |
1317 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
875 | triggering an event on eahc midnight, local time. |
1318 | such as triggering an event on each "midnight, local time", or other |
|
|
1319 | complicated, rules. |
876 | |
1320 | |
877 | As with timers, the callback is guarenteed to be invoked only when the |
1321 | As with timers, the callback is guaranteed to be invoked only when the |
878 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1322 | time (C<at>) has passed, but if multiple periodic timers become ready |
879 | during the same loop iteration then order of execution is undefined. |
1323 | during the same loop iteration then order of execution is undefined. |
|
|
1324 | |
|
|
1325 | =head3 Watcher-Specific Functions and Data Members |
880 | |
1326 | |
881 | =over 4 |
1327 | =over 4 |
882 | |
1328 | |
883 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1329 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
884 | |
1330 | |
… | |
… | |
887 | Lots of arguments, lets sort it out... There are basically three modes of |
1333 | Lots of arguments, lets sort it out... There are basically three modes of |
888 | operation, and we will explain them from simplest to complex: |
1334 | operation, and we will explain them from simplest to complex: |
889 | |
1335 | |
890 | =over 4 |
1336 | =over 4 |
891 | |
1337 | |
892 | =item * absolute timer (interval = reschedule_cb = 0) |
1338 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
893 | |
1339 | |
894 | In this configuration the watcher triggers an event at the wallclock time |
1340 | In this configuration the watcher triggers an event after the wall clock |
895 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1341 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
896 | that is, if it is to be run at January 1st 2011 then it will run when the |
1342 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
897 | system time reaches or surpasses this time. |
1343 | run when the system time reaches or surpasses this time. |
898 | |
1344 | |
899 | =item * non-repeating interval timer (interval > 0, reschedule_cb = 0) |
1345 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
900 | |
1346 | |
901 | In this mode the watcher will always be scheduled to time out at the next |
1347 | In this mode the watcher will always be scheduled to time out at the next |
902 | C<at + N * interval> time (for some integer N) and then repeat, regardless |
1348 | C<at + N * interval> time (for some integer N, which can also be negative) |
903 | of any time jumps. |
1349 | and then repeat, regardless of any time jumps. |
904 | |
1350 | |
905 | This can be used to create timers that do not drift with respect to system |
1351 | This can be used to create timers that do not drift with respect to system |
906 | time: |
1352 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
|
|
1353 | the hour: |
907 | |
1354 | |
908 | ev_periodic_set (&periodic, 0., 3600., 0); |
1355 | ev_periodic_set (&periodic, 0., 3600., 0); |
909 | |
1356 | |
910 | This doesn't mean there will always be 3600 seconds in between triggers, |
1357 | This doesn't mean there will always be 3600 seconds in between triggers, |
911 | but only that the the callback will be called when the system time shows a |
1358 | but only that the callback will be called when the system time shows a |
912 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1359 | full hour (UTC), or more correctly, when the system time is evenly divisible |
913 | by 3600. |
1360 | by 3600. |
914 | |
1361 | |
915 | Another way to think about it (for the mathematically inclined) is that |
1362 | Another way to think about it (for the mathematically inclined) is that |
916 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1363 | C<ev_periodic> will try to run the callback in this mode at the next possible |
917 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1364 | time where C<time = at (mod interval)>, regardless of any time jumps. |
918 | |
1365 | |
|
|
1366 | For numerical stability it is preferable that the C<at> value is near |
|
|
1367 | C<ev_now ()> (the current time), but there is no range requirement for |
|
|
1368 | this value, and in fact is often specified as zero. |
|
|
1369 | |
|
|
1370 | Note also that there is an upper limit to how often a timer can fire (CPU |
|
|
1371 | speed for example), so if C<interval> is very small then timing stability |
|
|
1372 | will of course deteriorate. Libev itself tries to be exact to be about one |
|
|
1373 | millisecond (if the OS supports it and the machine is fast enough). |
|
|
1374 | |
919 | =item * manual reschedule mode (reschedule_cb = callback) |
1375 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
920 | |
1376 | |
921 | In this mode the values for C<interval> and C<at> are both being |
1377 | In this mode the values for C<interval> and C<at> are both being |
922 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1378 | ignored. Instead, each time the periodic watcher gets scheduled, the |
923 | reschedule callback will be called with the watcher as first, and the |
1379 | reschedule callback will be called with the watcher as first, and the |
924 | current time as second argument. |
1380 | current time as second argument. |
925 | |
1381 | |
926 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1382 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
927 | ever, or make any event loop modifications>. If you need to stop it, |
1383 | ever, or make ANY event loop modifications whatsoever>. |
928 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
|
|
929 | starting a prepare watcher). |
|
|
930 | |
1384 | |
|
|
1385 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
1386 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
1387 | only event loop modification you are allowed to do). |
|
|
1388 | |
931 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1389 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
932 | ev_tstamp now)>, e.g.: |
1390 | *w, ev_tstamp now)>, e.g.: |
933 | |
1391 | |
934 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1392 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
935 | { |
1393 | { |
936 | return now + 60.; |
1394 | return now + 60.; |
937 | } |
1395 | } |
… | |
… | |
939 | It must return the next time to trigger, based on the passed time value |
1397 | It must return the next time to trigger, based on the passed time value |
940 | (that is, the lowest time value larger than to the second argument). It |
1398 | (that is, the lowest time value larger than to the second argument). It |
941 | will usually be called just before the callback will be triggered, but |
1399 | will usually be called just before the callback will be triggered, but |
942 | might be called at other times, too. |
1400 | might be called at other times, too. |
943 | |
1401 | |
944 | NOTE: I<< This callback must always return a time that is later than the |
1402 | NOTE: I<< This callback must always return a time that is higher than or |
945 | passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. |
1403 | equal to the passed C<now> value >>. |
946 | |
1404 | |
947 | This can be used to create very complex timers, such as a timer that |
1405 | This can be used to create very complex timers, such as a timer that |
948 | triggers on each midnight, local time. To do this, you would calculate the |
1406 | triggers on "next midnight, local time". To do this, you would calculate the |
949 | next midnight after C<now> and return the timestamp value for this. How |
1407 | next midnight after C<now> and return the timestamp value for this. How |
950 | you do this is, again, up to you (but it is not trivial, which is the main |
1408 | you do this is, again, up to you (but it is not trivial, which is the main |
951 | reason I omitted it as an example). |
1409 | reason I omitted it as an example). |
952 | |
1410 | |
953 | =back |
1411 | =back |
… | |
… | |
957 | Simply stops and restarts the periodic watcher again. This is only useful |
1415 | Simply stops and restarts the periodic watcher again. This is only useful |
958 | when you changed some parameters or the reschedule callback would return |
1416 | when you changed some parameters or the reschedule callback would return |
959 | a different time than the last time it was called (e.g. in a crond like |
1417 | a different time than the last time it was called (e.g. in a crond like |
960 | program when the crontabs have changed). |
1418 | program when the crontabs have changed). |
961 | |
1419 | |
|
|
1420 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
1421 | |
|
|
1422 | When active, returns the absolute time that the watcher is supposed to |
|
|
1423 | trigger next. |
|
|
1424 | |
|
|
1425 | =item ev_tstamp offset [read-write] |
|
|
1426 | |
|
|
1427 | When repeating, this contains the offset value, otherwise this is the |
|
|
1428 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
|
|
1429 | |
|
|
1430 | Can be modified any time, but changes only take effect when the periodic |
|
|
1431 | timer fires or C<ev_periodic_again> is being called. |
|
|
1432 | |
|
|
1433 | =item ev_tstamp interval [read-write] |
|
|
1434 | |
|
|
1435 | The current interval value. Can be modified any time, but changes only |
|
|
1436 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
|
|
1437 | called. |
|
|
1438 | |
|
|
1439 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
|
|
1440 | |
|
|
1441 | The current reschedule callback, or C<0>, if this functionality is |
|
|
1442 | switched off. Can be changed any time, but changes only take effect when |
|
|
1443 | the periodic timer fires or C<ev_periodic_again> is being called. |
|
|
1444 | |
962 | =back |
1445 | =back |
963 | |
1446 | |
|
|
1447 | =head3 Examples |
|
|
1448 | |
964 | Example: call a callback every hour, or, more precisely, whenever the |
1449 | Example: Call a callback every hour, or, more precisely, whenever the |
965 | system clock is divisible by 3600. The callback invocation times have |
1450 | system clock is divisible by 3600. The callback invocation times have |
966 | potentially a lot of jittering, but good long-term stability. |
1451 | potentially a lot of jitter, but good long-term stability. |
967 | |
1452 | |
968 | static void |
1453 | static void |
969 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1454 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
970 | { |
1455 | { |
971 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1456 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
… | |
… | |
973 | |
1458 | |
974 | struct ev_periodic hourly_tick; |
1459 | struct ev_periodic hourly_tick; |
975 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1460 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
976 | ev_periodic_start (loop, &hourly_tick); |
1461 | ev_periodic_start (loop, &hourly_tick); |
977 | |
1462 | |
978 | Example: the same as above, but use a reschedule callback to do it: |
1463 | Example: The same as above, but use a reschedule callback to do it: |
979 | |
1464 | |
980 | #include <math.h> |
1465 | #include <math.h> |
981 | |
1466 | |
982 | static ev_tstamp |
1467 | static ev_tstamp |
983 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1468 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
… | |
… | |
985 | return fmod (now, 3600.) + 3600.; |
1470 | return fmod (now, 3600.) + 3600.; |
986 | } |
1471 | } |
987 | |
1472 | |
988 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1473 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
989 | |
1474 | |
990 | Example: call a callback every hour, starting now: |
1475 | Example: Call a callback every hour, starting now: |
991 | |
1476 | |
992 | struct ev_periodic hourly_tick; |
1477 | struct ev_periodic hourly_tick; |
993 | ev_periodic_init (&hourly_tick, clock_cb, |
1478 | ev_periodic_init (&hourly_tick, clock_cb, |
994 | fmod (ev_now (loop), 3600.), 3600., 0); |
1479 | fmod (ev_now (loop), 3600.), 3600., 0); |
995 | ev_periodic_start (loop, &hourly_tick); |
1480 | ev_periodic_start (loop, &hourly_tick); |
… | |
… | |
1007 | with the kernel (thus it coexists with your own signal handlers as long |
1492 | with the kernel (thus it coexists with your own signal handlers as long |
1008 | as you don't register any with libev). Similarly, when the last signal |
1493 | as you don't register any with libev). Similarly, when the last signal |
1009 | watcher for a signal is stopped libev will reset the signal handler to |
1494 | watcher for a signal is stopped libev will reset the signal handler to |
1010 | SIG_DFL (regardless of what it was set to before). |
1495 | SIG_DFL (regardless of what it was set to before). |
1011 | |
1496 | |
|
|
1497 | If possible and supported, libev will install its handlers with |
|
|
1498 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
|
|
1499 | interrupted. If you have a problem with system calls getting interrupted by |
|
|
1500 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1501 | them in an C<ev_prepare> watcher. |
|
|
1502 | |
|
|
1503 | =head3 Watcher-Specific Functions and Data Members |
|
|
1504 | |
1012 | =over 4 |
1505 | =over 4 |
1013 | |
1506 | |
1014 | =item ev_signal_init (ev_signal *, callback, int signum) |
1507 | =item ev_signal_init (ev_signal *, callback, int signum) |
1015 | |
1508 | |
1016 | =item ev_signal_set (ev_signal *, int signum) |
1509 | =item ev_signal_set (ev_signal *, int signum) |
1017 | |
1510 | |
1018 | Configures the watcher to trigger on the given signal number (usually one |
1511 | Configures the watcher to trigger on the given signal number (usually one |
1019 | of the C<SIGxxx> constants). |
1512 | of the C<SIGxxx> constants). |
1020 | |
1513 | |
|
|
1514 | =item int signum [read-only] |
|
|
1515 | |
|
|
1516 | The signal the watcher watches out for. |
|
|
1517 | |
1021 | =back |
1518 | =back |
1022 | |
1519 | |
|
|
1520 | =head3 Examples |
|
|
1521 | |
|
|
1522 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
|
|
1523 | |
|
|
1524 | static void |
|
|
1525 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
1526 | { |
|
|
1527 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1528 | } |
|
|
1529 | |
|
|
1530 | struct ev_signal signal_watcher; |
|
|
1531 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1532 | ev_signal_start (loop, &sigint_cb); |
|
|
1533 | |
1023 | |
1534 | |
1024 | =head2 C<ev_child> - watch out for process status changes |
1535 | =head2 C<ev_child> - watch out for process status changes |
1025 | |
1536 | |
1026 | Child watchers trigger when your process receives a SIGCHLD in response to |
1537 | Child watchers trigger when your process receives a SIGCHLD in response to |
1027 | some child status changes (most typically when a child of yours dies). |
1538 | some child status changes (most typically when a child of yours dies). It |
|
|
1539 | is permissible to install a child watcher I<after> the child has been |
|
|
1540 | forked (which implies it might have already exited), as long as the event |
|
|
1541 | loop isn't entered (or is continued from a watcher). |
|
|
1542 | |
|
|
1543 | Only the default event loop is capable of handling signals, and therefore |
|
|
1544 | you can only register child watchers in the default event loop. |
|
|
1545 | |
|
|
1546 | =head3 Process Interaction |
|
|
1547 | |
|
|
1548 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
1549 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
1550 | the first child watcher is started after the child exits. The occurrence |
|
|
1551 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
1552 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
1553 | children, even ones not watched. |
|
|
1554 | |
|
|
1555 | =head3 Overriding the Built-In Processing |
|
|
1556 | |
|
|
1557 | Libev offers no special support for overriding the built-in child |
|
|
1558 | processing, but if your application collides with libev's default child |
|
|
1559 | handler, you can override it easily by installing your own handler for |
|
|
1560 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
1561 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
1562 | event-based approach to child reaping and thus use libev's support for |
|
|
1563 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
1564 | |
|
|
1565 | =head3 Watcher-Specific Functions and Data Members |
1028 | |
1566 | |
1029 | =over 4 |
1567 | =over 4 |
1030 | |
1568 | |
1031 | =item ev_child_init (ev_child *, callback, int pid) |
1569 | =item ev_child_init (ev_child *, callback, int pid, int trace) |
1032 | |
1570 | |
1033 | =item ev_child_set (ev_child *, int pid) |
1571 | =item ev_child_set (ev_child *, int pid, int trace) |
1034 | |
1572 | |
1035 | Configures the watcher to wait for status changes of process C<pid> (or |
1573 | Configures the watcher to wait for status changes of process C<pid> (or |
1036 | I<any> process if C<pid> is specified as C<0>). The callback can look |
1574 | I<any> process if C<pid> is specified as C<0>). The callback can look |
1037 | at the C<rstatus> member of the C<ev_child> watcher structure to see |
1575 | at the C<rstatus> member of the C<ev_child> watcher structure to see |
1038 | the status word (use the macros from C<sys/wait.h> and see your systems |
1576 | the status word (use the macros from C<sys/wait.h> and see your systems |
1039 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
1577 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
1040 | process causing the status change. |
1578 | process causing the status change. C<trace> must be either C<0> (only |
|
|
1579 | activate the watcher when the process terminates) or C<1> (additionally |
|
|
1580 | activate the watcher when the process is stopped or continued). |
|
|
1581 | |
|
|
1582 | =item int pid [read-only] |
|
|
1583 | |
|
|
1584 | The process id this watcher watches out for, or C<0>, meaning any process id. |
|
|
1585 | |
|
|
1586 | =item int rpid [read-write] |
|
|
1587 | |
|
|
1588 | The process id that detected a status change. |
|
|
1589 | |
|
|
1590 | =item int rstatus [read-write] |
|
|
1591 | |
|
|
1592 | The process exit/trace status caused by C<rpid> (see your systems |
|
|
1593 | C<waitpid> and C<sys/wait.h> documentation for details). |
1041 | |
1594 | |
1042 | =back |
1595 | =back |
1043 | |
1596 | |
1044 | Example: try to exit cleanly on SIGINT and SIGTERM. |
1597 | =head3 Examples |
|
|
1598 | |
|
|
1599 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
1600 | its completion. |
|
|
1601 | |
|
|
1602 | ev_child cw; |
1045 | |
1603 | |
1046 | static void |
1604 | static void |
1047 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1605 | child_cb (EV_P_ struct ev_child *w, int revents) |
1048 | { |
1606 | { |
1049 | ev_unloop (loop, EVUNLOOP_ALL); |
1607 | ev_child_stop (EV_A_ w); |
|
|
1608 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1050 | } |
1609 | } |
1051 | |
1610 | |
1052 | struct ev_signal signal_watcher; |
1611 | pid_t pid = fork (); |
1053 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1612 | |
1054 | ev_signal_start (loop, &sigint_cb); |
1613 | if (pid < 0) |
|
|
1614 | // error |
|
|
1615 | else if (pid == 0) |
|
|
1616 | { |
|
|
1617 | // the forked child executes here |
|
|
1618 | exit (1); |
|
|
1619 | } |
|
|
1620 | else |
|
|
1621 | { |
|
|
1622 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
1623 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
1624 | } |
|
|
1625 | |
|
|
1626 | |
|
|
1627 | =head2 C<ev_stat> - did the file attributes just change? |
|
|
1628 | |
|
|
1629 | This watches a file system path for attribute changes. That is, it calls |
|
|
1630 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
|
|
1631 | compared to the last time, invoking the callback if it did. |
|
|
1632 | |
|
|
1633 | The path does not need to exist: changing from "path exists" to "path does |
|
|
1634 | not exist" is a status change like any other. The condition "path does |
|
|
1635 | not exist" is signified by the C<st_nlink> field being zero (which is |
|
|
1636 | otherwise always forced to be at least one) and all the other fields of |
|
|
1637 | the stat buffer having unspecified contents. |
|
|
1638 | |
|
|
1639 | The path I<should> be absolute and I<must not> end in a slash. If it is |
|
|
1640 | relative and your working directory changes, the behaviour is undefined. |
|
|
1641 | |
|
|
1642 | Since there is no standard to do this, the portable implementation simply |
|
|
1643 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
|
|
1644 | can specify a recommended polling interval for this case. If you specify |
|
|
1645 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
|
|
1646 | unspecified default> value will be used (which you can expect to be around |
|
|
1647 | five seconds, although this might change dynamically). Libev will also |
|
|
1648 | impose a minimum interval which is currently around C<0.1>, but thats |
|
|
1649 | usually overkill. |
|
|
1650 | |
|
|
1651 | This watcher type is not meant for massive numbers of stat watchers, |
|
|
1652 | as even with OS-supported change notifications, this can be |
|
|
1653 | resource-intensive. |
|
|
1654 | |
|
|
1655 | At the time of this writing, only the Linux inotify interface is |
|
|
1656 | implemented (implementing kqueue support is left as an exercise for the |
|
|
1657 | reader, note, however, that the author sees no way of implementing ev_stat |
|
|
1658 | semantics with kqueue). Inotify will be used to give hints only and should |
|
|
1659 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1660 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1661 | but changes are usually detected immediately, and if the file exists there |
|
|
1662 | will be no polling. |
|
|
1663 | |
|
|
1664 | =head3 ABI Issues (Largefile Support) |
|
|
1665 | |
|
|
1666 | Libev by default (unless the user overrides this) uses the default |
|
|
1667 | compilation environment, which means that on systems with optionally |
|
|
1668 | disabled large file support, you get the 32 bit version of the stat |
|
|
1669 | structure. When using the library from programs that change the ABI to |
|
|
1670 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
1671 | compile libev with the same flags to get binary compatibility. This is |
|
|
1672 | obviously the case with any flags that change the ABI, but the problem is |
|
|
1673 | most noticeably with ev_stat and large file support. |
|
|
1674 | |
|
|
1675 | =head3 Inotify |
|
|
1676 | |
|
|
1677 | When C<inotify (7)> support has been compiled into libev (generally only |
|
|
1678 | available on Linux) and present at runtime, it will be used to speed up |
|
|
1679 | change detection where possible. The inotify descriptor will be created lazily |
|
|
1680 | when the first C<ev_stat> watcher is being started. |
|
|
1681 | |
|
|
1682 | Inotify presence does not change the semantics of C<ev_stat> watchers |
|
|
1683 | except that changes might be detected earlier, and in some cases, to avoid |
|
|
1684 | making regular C<stat> calls. Even in the presence of inotify support |
|
|
1685 | there are many cases where libev has to resort to regular C<stat> polling. |
|
|
1686 | |
|
|
1687 | (There is no support for kqueue, as apparently it cannot be used to |
|
|
1688 | implement this functionality, due to the requirement of having a file |
|
|
1689 | descriptor open on the object at all times). |
|
|
1690 | |
|
|
1691 | =head3 The special problem of stat time resolution |
|
|
1692 | |
|
|
1693 | The C<stat ()> system call only supports full-second resolution portably, and |
|
|
1694 | even on systems where the resolution is higher, many file systems still |
|
|
1695 | only support whole seconds. |
|
|
1696 | |
|
|
1697 | That means that, if the time is the only thing that changes, you can |
|
|
1698 | easily miss updates: on the first update, C<ev_stat> detects a change and |
|
|
1699 | calls your callback, which does something. When there is another update |
|
|
1700 | within the same second, C<ev_stat> will be unable to detect it as the stat |
|
|
1701 | data does not change. |
|
|
1702 | |
|
|
1703 | The solution to this is to delay acting on a change for slightly more |
|
|
1704 | than a second (or till slightly after the next full second boundary), using |
|
|
1705 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
|
|
1706 | ev_timer_again (loop, w)>). |
|
|
1707 | |
|
|
1708 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
1709 | of some operating systems (where the second counter of the current time |
|
|
1710 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
1711 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
1712 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
1713 | update file times then there will be a small window where the kernel uses |
|
|
1714 | the previous second to update file times but libev might already execute |
|
|
1715 | the timer callback). |
|
|
1716 | |
|
|
1717 | =head3 Watcher-Specific Functions and Data Members |
|
|
1718 | |
|
|
1719 | =over 4 |
|
|
1720 | |
|
|
1721 | =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) |
|
|
1722 | |
|
|
1723 | =item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval) |
|
|
1724 | |
|
|
1725 | Configures the watcher to wait for status changes of the given |
|
|
1726 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
|
|
1727 | be detected and should normally be specified as C<0> to let libev choose |
|
|
1728 | a suitable value. The memory pointed to by C<path> must point to the same |
|
|
1729 | path for as long as the watcher is active. |
|
|
1730 | |
|
|
1731 | The callback will receive C<EV_STAT> when a change was detected, relative |
|
|
1732 | to the attributes at the time the watcher was started (or the last change |
|
|
1733 | was detected). |
|
|
1734 | |
|
|
1735 | =item ev_stat_stat (loop, ev_stat *) |
|
|
1736 | |
|
|
1737 | Updates the stat buffer immediately with new values. If you change the |
|
|
1738 | watched path in your callback, you could call this function to avoid |
|
|
1739 | detecting this change (while introducing a race condition if you are not |
|
|
1740 | the only one changing the path). Can also be useful simply to find out the |
|
|
1741 | new values. |
|
|
1742 | |
|
|
1743 | =item ev_statdata attr [read-only] |
|
|
1744 | |
|
|
1745 | The most-recently detected attributes of the file. Although the type is |
|
|
1746 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
|
|
1747 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
1748 | members to be present. If the C<st_nlink> member is C<0>, then there was |
|
|
1749 | some error while C<stat>ing the file. |
|
|
1750 | |
|
|
1751 | =item ev_statdata prev [read-only] |
|
|
1752 | |
|
|
1753 | The previous attributes of the file. The callback gets invoked whenever |
|
|
1754 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
1755 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
1756 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
|
|
1757 | |
|
|
1758 | =item ev_tstamp interval [read-only] |
|
|
1759 | |
|
|
1760 | The specified interval. |
|
|
1761 | |
|
|
1762 | =item const char *path [read-only] |
|
|
1763 | |
|
|
1764 | The file system path that is being watched. |
|
|
1765 | |
|
|
1766 | =back |
|
|
1767 | |
|
|
1768 | =head3 Examples |
|
|
1769 | |
|
|
1770 | Example: Watch C</etc/passwd> for attribute changes. |
|
|
1771 | |
|
|
1772 | static void |
|
|
1773 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
|
|
1774 | { |
|
|
1775 | /* /etc/passwd changed in some way */ |
|
|
1776 | if (w->attr.st_nlink) |
|
|
1777 | { |
|
|
1778 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
|
|
1779 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
|
|
1780 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
|
|
1781 | } |
|
|
1782 | else |
|
|
1783 | /* you shalt not abuse printf for puts */ |
|
|
1784 | puts ("wow, /etc/passwd is not there, expect problems. " |
|
|
1785 | "if this is windows, they already arrived\n"); |
|
|
1786 | } |
|
|
1787 | |
|
|
1788 | ... |
|
|
1789 | ev_stat passwd; |
|
|
1790 | |
|
|
1791 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
|
|
1792 | ev_stat_start (loop, &passwd); |
|
|
1793 | |
|
|
1794 | Example: Like above, but additionally use a one-second delay so we do not |
|
|
1795 | miss updates (however, frequent updates will delay processing, too, so |
|
|
1796 | one might do the work both on C<ev_stat> callback invocation I<and> on |
|
|
1797 | C<ev_timer> callback invocation). |
|
|
1798 | |
|
|
1799 | static ev_stat passwd; |
|
|
1800 | static ev_timer timer; |
|
|
1801 | |
|
|
1802 | static void |
|
|
1803 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1804 | { |
|
|
1805 | ev_timer_stop (EV_A_ w); |
|
|
1806 | |
|
|
1807 | /* now it's one second after the most recent passwd change */ |
|
|
1808 | } |
|
|
1809 | |
|
|
1810 | static void |
|
|
1811 | stat_cb (EV_P_ ev_stat *w, int revents) |
|
|
1812 | { |
|
|
1813 | /* reset the one-second timer */ |
|
|
1814 | ev_timer_again (EV_A_ &timer); |
|
|
1815 | } |
|
|
1816 | |
|
|
1817 | ... |
|
|
1818 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
|
|
1819 | ev_stat_start (loop, &passwd); |
|
|
1820 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1055 | |
1821 | |
1056 | |
1822 | |
1057 | =head2 C<ev_idle> - when you've got nothing better to do... |
1823 | =head2 C<ev_idle> - when you've got nothing better to do... |
1058 | |
1824 | |
1059 | Idle watchers trigger events when there are no other events are pending |
1825 | Idle watchers trigger events when no other events of the same or higher |
1060 | (prepare, check and other idle watchers do not count). That is, as long |
1826 | priority are pending (prepare, check and other idle watchers do not |
1061 | as your process is busy handling sockets or timeouts (or even signals, |
1827 | count). |
1062 | imagine) it will not be triggered. But when your process is idle all idle |
1828 | |
1063 | watchers are being called again and again, once per event loop iteration - |
1829 | That is, as long as your process is busy handling sockets or timeouts |
|
|
1830 | (or even signals, imagine) of the same or higher priority it will not be |
|
|
1831 | triggered. But when your process is idle (or only lower-priority watchers |
|
|
1832 | are pending), the idle watchers are being called once per event loop |
1064 | until stopped, that is, or your process receives more events and becomes |
1833 | iteration - until stopped, that is, or your process receives more events |
1065 | busy. |
1834 | and becomes busy again with higher priority stuff. |
1066 | |
1835 | |
1067 | The most noteworthy effect is that as long as any idle watchers are |
1836 | The most noteworthy effect is that as long as any idle watchers are |
1068 | active, the process will not block when waiting for new events. |
1837 | active, the process will not block when waiting for new events. |
1069 | |
1838 | |
1070 | Apart from keeping your process non-blocking (which is a useful |
1839 | Apart from keeping your process non-blocking (which is a useful |
1071 | effect on its own sometimes), idle watchers are a good place to do |
1840 | effect on its own sometimes), idle watchers are a good place to do |
1072 | "pseudo-background processing", or delay processing stuff to after the |
1841 | "pseudo-background processing", or delay processing stuff to after the |
1073 | event loop has handled all outstanding events. |
1842 | event loop has handled all outstanding events. |
1074 | |
1843 | |
|
|
1844 | =head3 Watcher-Specific Functions and Data Members |
|
|
1845 | |
1075 | =over 4 |
1846 | =over 4 |
1076 | |
1847 | |
1077 | =item ev_idle_init (ev_signal *, callback) |
1848 | =item ev_idle_init (ev_signal *, callback) |
1078 | |
1849 | |
1079 | Initialises and configures the idle watcher - it has no parameters of any |
1850 | Initialises and configures the idle watcher - it has no parameters of any |
1080 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1851 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1081 | believe me. |
1852 | believe me. |
1082 | |
1853 | |
1083 | =back |
1854 | =back |
1084 | |
1855 | |
|
|
1856 | =head3 Examples |
|
|
1857 | |
1085 | Example: dynamically allocate an C<ev_idle>, start it, and in the |
1858 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1086 | callback, free it. Alos, use no error checking, as usual. |
1859 | callback, free it. Also, use no error checking, as usual. |
1087 | |
1860 | |
1088 | static void |
1861 | static void |
1089 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
1862 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
1090 | { |
1863 | { |
1091 | free (w); |
1864 | free (w); |
1092 | // now do something you wanted to do when the program has |
1865 | // now do something you wanted to do when the program has |
1093 | // no longer asnything immediate to do. |
1866 | // no longer anything immediate to do. |
1094 | } |
1867 | } |
1095 | |
1868 | |
1096 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1869 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1097 | ev_idle_init (idle_watcher, idle_cb); |
1870 | ev_idle_init (idle_watcher, idle_cb); |
1098 | ev_idle_start (loop, idle_cb); |
1871 | ev_idle_start (loop, idle_cb); |
… | |
… | |
1102 | |
1875 | |
1103 | Prepare and check watchers are usually (but not always) used in tandem: |
1876 | Prepare and check watchers are usually (but not always) used in tandem: |
1104 | prepare watchers get invoked before the process blocks and check watchers |
1877 | prepare watchers get invoked before the process blocks and check watchers |
1105 | afterwards. |
1878 | afterwards. |
1106 | |
1879 | |
|
|
1880 | You I<must not> call C<ev_loop> or similar functions that enter |
|
|
1881 | the current event loop from either C<ev_prepare> or C<ev_check> |
|
|
1882 | watchers. Other loops than the current one are fine, however. The |
|
|
1883 | rationale behind this is that you do not need to check for recursion in |
|
|
1884 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
|
|
1885 | C<ev_check> so if you have one watcher of each kind they will always be |
|
|
1886 | called in pairs bracketing the blocking call. |
|
|
1887 | |
1107 | Their main purpose is to integrate other event mechanisms into libev and |
1888 | Their main purpose is to integrate other event mechanisms into libev and |
1108 | their use is somewhat advanced. This could be used, for example, to track |
1889 | their use is somewhat advanced. This could be used, for example, to track |
1109 | variable changes, implement your own watchers, integrate net-snmp or a |
1890 | variable changes, implement your own watchers, integrate net-snmp or a |
1110 | coroutine library and lots more. |
1891 | coroutine library and lots more. They are also occasionally useful if |
|
|
1892 | you cache some data and want to flush it before blocking (for example, |
|
|
1893 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
|
|
1894 | watcher). |
1111 | |
1895 | |
1112 | This is done by examining in each prepare call which file descriptors need |
1896 | This is done by examining in each prepare call which file descriptors need |
1113 | to be watched by the other library, registering C<ev_io> watchers for |
1897 | to be watched by the other library, registering C<ev_io> watchers for |
1114 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
1898 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
1115 | provide just this functionality). Then, in the check watcher you check for |
1899 | provide just this functionality). Then, in the check watcher you check for |
1116 | any events that occured (by checking the pending status of all watchers |
1900 | any events that occurred (by checking the pending status of all watchers |
1117 | and stopping them) and call back into the library. The I/O and timer |
1901 | and stopping them) and call back into the library. The I/O and timer |
1118 | callbacks will never actually be called (but must be valid nevertheless, |
1902 | callbacks will never actually be called (but must be valid nevertheless, |
1119 | because you never know, you know?). |
1903 | because you never know, you know?). |
1120 | |
1904 | |
1121 | As another example, the Perl Coro module uses these hooks to integrate |
1905 | As another example, the Perl Coro module uses these hooks to integrate |
… | |
… | |
1125 | with priority higher than or equal to the event loop and one coroutine |
1909 | with priority higher than or equal to the event loop and one coroutine |
1126 | of lower priority, but only once, using idle watchers to keep the event |
1910 | of lower priority, but only once, using idle watchers to keep the event |
1127 | loop from blocking if lower-priority coroutines are active, thus mapping |
1911 | loop from blocking if lower-priority coroutines are active, thus mapping |
1128 | low-priority coroutines to idle/background tasks). |
1912 | low-priority coroutines to idle/background tasks). |
1129 | |
1913 | |
|
|
1914 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
|
|
1915 | priority, to ensure that they are being run before any other watchers |
|
|
1916 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
|
|
1917 | too) should not activate ("feed") events into libev. While libev fully |
|
|
1918 | supports this, they might get executed before other C<ev_check> watchers |
|
|
1919 | did their job. As C<ev_check> watchers are often used to embed other |
|
|
1920 | (non-libev) event loops those other event loops might be in an unusable |
|
|
1921 | state until their C<ev_check> watcher ran (always remind yourself to |
|
|
1922 | coexist peacefully with others). |
|
|
1923 | |
|
|
1924 | =head3 Watcher-Specific Functions and Data Members |
|
|
1925 | |
1130 | =over 4 |
1926 | =over 4 |
1131 | |
1927 | |
1132 | =item ev_prepare_init (ev_prepare *, callback) |
1928 | =item ev_prepare_init (ev_prepare *, callback) |
1133 | |
1929 | |
1134 | =item ev_check_init (ev_check *, callback) |
1930 | =item ev_check_init (ev_check *, callback) |
… | |
… | |
1137 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1933 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1138 | macros, but using them is utterly, utterly and completely pointless. |
1934 | macros, but using them is utterly, utterly and completely pointless. |
1139 | |
1935 | |
1140 | =back |
1936 | =back |
1141 | |
1937 | |
1142 | Example: *TODO*. |
1938 | =head3 Examples |
|
|
1939 | |
|
|
1940 | There are a number of principal ways to embed other event loops or modules |
|
|
1941 | into libev. Here are some ideas on how to include libadns into libev |
|
|
1942 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
|
|
1943 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
|
|
1944 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
|
|
1945 | Glib event loop). |
|
|
1946 | |
|
|
1947 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
|
|
1948 | and in a check watcher, destroy them and call into libadns. What follows |
|
|
1949 | is pseudo-code only of course. This requires you to either use a low |
|
|
1950 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
|
|
1951 | the callbacks for the IO/timeout watchers might not have been called yet. |
|
|
1952 | |
|
|
1953 | static ev_io iow [nfd]; |
|
|
1954 | static ev_timer tw; |
|
|
1955 | |
|
|
1956 | static void |
|
|
1957 | io_cb (ev_loop *loop, ev_io *w, int revents) |
|
|
1958 | { |
|
|
1959 | } |
|
|
1960 | |
|
|
1961 | // create io watchers for each fd and a timer before blocking |
|
|
1962 | static void |
|
|
1963 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
|
|
1964 | { |
|
|
1965 | int timeout = 3600000; |
|
|
1966 | struct pollfd fds [nfd]; |
|
|
1967 | // actual code will need to loop here and realloc etc. |
|
|
1968 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
|
|
1969 | |
|
|
1970 | /* the callback is illegal, but won't be called as we stop during check */ |
|
|
1971 | ev_timer_init (&tw, 0, timeout * 1e-3); |
|
|
1972 | ev_timer_start (loop, &tw); |
|
|
1973 | |
|
|
1974 | // create one ev_io per pollfd |
|
|
1975 | for (int i = 0; i < nfd; ++i) |
|
|
1976 | { |
|
|
1977 | ev_io_init (iow + i, io_cb, fds [i].fd, |
|
|
1978 | ((fds [i].events & POLLIN ? EV_READ : 0) |
|
|
1979 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
|
|
1980 | |
|
|
1981 | fds [i].revents = 0; |
|
|
1982 | ev_io_start (loop, iow + i); |
|
|
1983 | } |
|
|
1984 | } |
|
|
1985 | |
|
|
1986 | // stop all watchers after blocking |
|
|
1987 | static void |
|
|
1988 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
|
|
1989 | { |
|
|
1990 | ev_timer_stop (loop, &tw); |
|
|
1991 | |
|
|
1992 | for (int i = 0; i < nfd; ++i) |
|
|
1993 | { |
|
|
1994 | // set the relevant poll flags |
|
|
1995 | // could also call adns_processreadable etc. here |
|
|
1996 | struct pollfd *fd = fds + i; |
|
|
1997 | int revents = ev_clear_pending (iow + i); |
|
|
1998 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1999 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
2000 | |
|
|
2001 | // now stop the watcher |
|
|
2002 | ev_io_stop (loop, iow + i); |
|
|
2003 | } |
|
|
2004 | |
|
|
2005 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
2006 | } |
|
|
2007 | |
|
|
2008 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
|
|
2009 | in the prepare watcher and would dispose of the check watcher. |
|
|
2010 | |
|
|
2011 | Method 3: If the module to be embedded supports explicit event |
|
|
2012 | notification (libadns does), you can also make use of the actual watcher |
|
|
2013 | callbacks, and only destroy/create the watchers in the prepare watcher. |
|
|
2014 | |
|
|
2015 | static void |
|
|
2016 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2017 | { |
|
|
2018 | adns_state ads = (adns_state)w->data; |
|
|
2019 | update_now (EV_A); |
|
|
2020 | |
|
|
2021 | adns_processtimeouts (ads, &tv_now); |
|
|
2022 | } |
|
|
2023 | |
|
|
2024 | static void |
|
|
2025 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
2026 | { |
|
|
2027 | adns_state ads = (adns_state)w->data; |
|
|
2028 | update_now (EV_A); |
|
|
2029 | |
|
|
2030 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
|
|
2031 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
|
|
2032 | } |
|
|
2033 | |
|
|
2034 | // do not ever call adns_afterpoll |
|
|
2035 | |
|
|
2036 | Method 4: Do not use a prepare or check watcher because the module you |
|
|
2037 | want to embed is too inflexible to support it. Instead, you can override |
|
|
2038 | their poll function. The drawback with this solution is that the main |
|
|
2039 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
|
|
2040 | this. |
|
|
2041 | |
|
|
2042 | static gint |
|
|
2043 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
2044 | { |
|
|
2045 | int got_events = 0; |
|
|
2046 | |
|
|
2047 | for (n = 0; n < nfds; ++n) |
|
|
2048 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
2049 | |
|
|
2050 | if (timeout >= 0) |
|
|
2051 | // create/start timer |
|
|
2052 | |
|
|
2053 | // poll |
|
|
2054 | ev_loop (EV_A_ 0); |
|
|
2055 | |
|
|
2056 | // stop timer again |
|
|
2057 | if (timeout >= 0) |
|
|
2058 | ev_timer_stop (EV_A_ &to); |
|
|
2059 | |
|
|
2060 | // stop io watchers again - their callbacks should have set |
|
|
2061 | for (n = 0; n < nfds; ++n) |
|
|
2062 | ev_io_stop (EV_A_ iow [n]); |
|
|
2063 | |
|
|
2064 | return got_events; |
|
|
2065 | } |
1143 | |
2066 | |
1144 | |
2067 | |
1145 | =head2 C<ev_embed> - when one backend isn't enough... |
2068 | =head2 C<ev_embed> - when one backend isn't enough... |
1146 | |
2069 | |
1147 | This is a rather advanced watcher type that lets you embed one event loop |
2070 | This is a rather advanced watcher type that lets you embed one event loop |
… | |
… | |
1189 | portable one. |
2112 | portable one. |
1190 | |
2113 | |
1191 | So when you want to use this feature you will always have to be prepared |
2114 | So when you want to use this feature you will always have to be prepared |
1192 | that you cannot get an embeddable loop. The recommended way to get around |
2115 | that you cannot get an embeddable loop. The recommended way to get around |
1193 | this is to have a separate variables for your embeddable loop, try to |
2116 | this is to have a separate variables for your embeddable loop, try to |
1194 | create it, and if that fails, use the normal loop for everything: |
2117 | create it, and if that fails, use the normal loop for everything. |
|
|
2118 | |
|
|
2119 | =head3 Watcher-Specific Functions and Data Members |
|
|
2120 | |
|
|
2121 | =over 4 |
|
|
2122 | |
|
|
2123 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
|
|
2124 | |
|
|
2125 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
|
|
2126 | |
|
|
2127 | Configures the watcher to embed the given loop, which must be |
|
|
2128 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
|
|
2129 | invoked automatically, otherwise it is the responsibility of the callback |
|
|
2130 | to invoke it (it will continue to be called until the sweep has been done, |
|
|
2131 | if you do not want that, you need to temporarily stop the embed watcher). |
|
|
2132 | |
|
|
2133 | =item ev_embed_sweep (loop, ev_embed *) |
|
|
2134 | |
|
|
2135 | Make a single, non-blocking sweep over the embedded loop. This works |
|
|
2136 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
|
|
2137 | appropriate way for embedded loops. |
|
|
2138 | |
|
|
2139 | =item struct ev_loop *other [read-only] |
|
|
2140 | |
|
|
2141 | The embedded event loop. |
|
|
2142 | |
|
|
2143 | =back |
|
|
2144 | |
|
|
2145 | =head3 Examples |
|
|
2146 | |
|
|
2147 | Example: Try to get an embeddable event loop and embed it into the default |
|
|
2148 | event loop. If that is not possible, use the default loop. The default |
|
|
2149 | loop is stored in C<loop_hi>, while the embeddable loop is stored in |
|
|
2150 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
|
|
2151 | used). |
1195 | |
2152 | |
1196 | struct ev_loop *loop_hi = ev_default_init (0); |
2153 | struct ev_loop *loop_hi = ev_default_init (0); |
1197 | struct ev_loop *loop_lo = 0; |
2154 | struct ev_loop *loop_lo = 0; |
1198 | struct ev_embed embed; |
2155 | struct ev_embed embed; |
1199 | |
2156 | |
… | |
… | |
1210 | ev_embed_start (loop_hi, &embed); |
2167 | ev_embed_start (loop_hi, &embed); |
1211 | } |
2168 | } |
1212 | else |
2169 | else |
1213 | loop_lo = loop_hi; |
2170 | loop_lo = loop_hi; |
1214 | |
2171 | |
|
|
2172 | Example: Check if kqueue is available but not recommended and create |
|
|
2173 | a kqueue backend for use with sockets (which usually work with any |
|
|
2174 | kqueue implementation). Store the kqueue/socket-only event loop in |
|
|
2175 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
|
|
2176 | |
|
|
2177 | struct ev_loop *loop = ev_default_init (0); |
|
|
2178 | struct ev_loop *loop_socket = 0; |
|
|
2179 | struct ev_embed embed; |
|
|
2180 | |
|
|
2181 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
|
|
2182 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
|
|
2183 | { |
|
|
2184 | ev_embed_init (&embed, 0, loop_socket); |
|
|
2185 | ev_embed_start (loop, &embed); |
|
|
2186 | } |
|
|
2187 | |
|
|
2188 | if (!loop_socket) |
|
|
2189 | loop_socket = loop; |
|
|
2190 | |
|
|
2191 | // now use loop_socket for all sockets, and loop for everything else |
|
|
2192 | |
|
|
2193 | |
|
|
2194 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
|
|
2195 | |
|
|
2196 | Fork watchers are called when a C<fork ()> was detected (usually because |
|
|
2197 | whoever is a good citizen cared to tell libev about it by calling |
|
|
2198 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
|
|
2199 | event loop blocks next and before C<ev_check> watchers are being called, |
|
|
2200 | and only in the child after the fork. If whoever good citizen calling |
|
|
2201 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
|
|
2202 | handlers will be invoked, too, of course. |
|
|
2203 | |
|
|
2204 | =head3 Watcher-Specific Functions and Data Members |
|
|
2205 | |
1215 | =over 4 |
2206 | =over 4 |
1216 | |
2207 | |
1217 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2208 | =item ev_fork_init (ev_signal *, callback) |
1218 | |
2209 | |
1219 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
2210 | Initialises and configures the fork watcher - it has no parameters of any |
|
|
2211 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
|
|
2212 | believe me. |
1220 | |
2213 | |
1221 | Configures the watcher to embed the given loop, which must be |
2214 | =back |
1222 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
|
|
1223 | invoked automatically, otherwise it is the responsibility of the callback |
|
|
1224 | to invoke it (it will continue to be called until the sweep has been done, |
|
|
1225 | if you do not want thta, you need to temporarily stop the embed watcher). |
|
|
1226 | |
2215 | |
1227 | =item ev_embed_sweep (loop, ev_embed *) |
|
|
1228 | |
2216 | |
1229 | Make a single, non-blocking sweep over the embedded loop. This works |
2217 | =head2 C<ev_async> - how to wake up another event loop |
1230 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
2218 | |
1231 | apropriate way for embedded loops. |
2219 | In general, you cannot use an C<ev_loop> from multiple threads or other |
|
|
2220 | asynchronous sources such as signal handlers (as opposed to multiple event |
|
|
2221 | loops - those are of course safe to use in different threads). |
|
|
2222 | |
|
|
2223 | Sometimes, however, you need to wake up another event loop you do not |
|
|
2224 | control, for example because it belongs to another thread. This is what |
|
|
2225 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
|
|
2226 | can signal it by calling C<ev_async_send>, which is thread- and signal |
|
|
2227 | safe. |
|
|
2228 | |
|
|
2229 | This functionality is very similar to C<ev_signal> watchers, as signals, |
|
|
2230 | too, are asynchronous in nature, and signals, too, will be compressed |
|
|
2231 | (i.e. the number of callback invocations may be less than the number of |
|
|
2232 | C<ev_async_sent> calls). |
|
|
2233 | |
|
|
2234 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
2235 | just the default loop. |
|
|
2236 | |
|
|
2237 | =head3 Queueing |
|
|
2238 | |
|
|
2239 | C<ev_async> does not support queueing of data in any way. The reason |
|
|
2240 | is that the author does not know of a simple (or any) algorithm for a |
|
|
2241 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
2242 | need elaborate support such as pthreads. |
|
|
2243 | |
|
|
2244 | That means that if you want to queue data, you have to provide your own |
|
|
2245 | queue. But at least I can tell you would implement locking around your |
|
|
2246 | queue: |
|
|
2247 | |
|
|
2248 | =over 4 |
|
|
2249 | |
|
|
2250 | =item queueing from a signal handler context |
|
|
2251 | |
|
|
2252 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
2253 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
|
|
2254 | some fictitious SIGUSR1 handler: |
|
|
2255 | |
|
|
2256 | static ev_async mysig; |
|
|
2257 | |
|
|
2258 | static void |
|
|
2259 | sigusr1_handler (void) |
|
|
2260 | { |
|
|
2261 | sometype data; |
|
|
2262 | |
|
|
2263 | // no locking etc. |
|
|
2264 | queue_put (data); |
|
|
2265 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2266 | } |
|
|
2267 | |
|
|
2268 | static void |
|
|
2269 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2270 | { |
|
|
2271 | sometype data; |
|
|
2272 | sigset_t block, prev; |
|
|
2273 | |
|
|
2274 | sigemptyset (&block); |
|
|
2275 | sigaddset (&block, SIGUSR1); |
|
|
2276 | sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
2277 | |
|
|
2278 | while (queue_get (&data)) |
|
|
2279 | process (data); |
|
|
2280 | |
|
|
2281 | if (sigismember (&prev, SIGUSR1) |
|
|
2282 | sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
2283 | } |
|
|
2284 | |
|
|
2285 | (Note: pthreads in theory requires you to use C<pthread_setmask> |
|
|
2286 | instead of C<sigprocmask> when you use threads, but libev doesn't do it |
|
|
2287 | either...). |
|
|
2288 | |
|
|
2289 | =item queueing from a thread context |
|
|
2290 | |
|
|
2291 | The strategy for threads is different, as you cannot (easily) block |
|
|
2292 | threads but you can easily preempt them, so to queue safely you need to |
|
|
2293 | employ a traditional mutex lock, such as in this pthread example: |
|
|
2294 | |
|
|
2295 | static ev_async mysig; |
|
|
2296 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
2297 | |
|
|
2298 | static void |
|
|
2299 | otherthread (void) |
|
|
2300 | { |
|
|
2301 | // only need to lock the actual queueing operation |
|
|
2302 | pthread_mutex_lock (&mymutex); |
|
|
2303 | queue_put (data); |
|
|
2304 | pthread_mutex_unlock (&mymutex); |
|
|
2305 | |
|
|
2306 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2307 | } |
|
|
2308 | |
|
|
2309 | static void |
|
|
2310 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2311 | { |
|
|
2312 | pthread_mutex_lock (&mymutex); |
|
|
2313 | |
|
|
2314 | while (queue_get (&data)) |
|
|
2315 | process (data); |
|
|
2316 | |
|
|
2317 | pthread_mutex_unlock (&mymutex); |
|
|
2318 | } |
|
|
2319 | |
|
|
2320 | =back |
|
|
2321 | |
|
|
2322 | |
|
|
2323 | =head3 Watcher-Specific Functions and Data Members |
|
|
2324 | |
|
|
2325 | =over 4 |
|
|
2326 | |
|
|
2327 | =item ev_async_init (ev_async *, callback) |
|
|
2328 | |
|
|
2329 | Initialises and configures the async watcher - it has no parameters of any |
|
|
2330 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
|
|
2331 | believe me. |
|
|
2332 | |
|
|
2333 | =item ev_async_send (loop, ev_async *) |
|
|
2334 | |
|
|
2335 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
|
|
2336 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
|
|
2337 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
|
|
2338 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
|
|
2339 | section below on what exactly this means). |
|
|
2340 | |
|
|
2341 | This call incurs the overhead of a system call only once per loop iteration, |
|
|
2342 | so while the overhead might be noticeable, it doesn't apply to repeated |
|
|
2343 | calls to C<ev_async_send>. |
|
|
2344 | |
|
|
2345 | =item bool = ev_async_pending (ev_async *) |
|
|
2346 | |
|
|
2347 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
2348 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2349 | event loop. |
|
|
2350 | |
|
|
2351 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
2352 | the loop iterates next and checks for the watcher to have become active, |
|
|
2353 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
2354 | quickly check whether invoking the loop might be a good idea. |
|
|
2355 | |
|
|
2356 | Not that this does I<not> check whether the watcher itself is pending, only |
|
|
2357 | whether it has been requested to make this watcher pending. |
1232 | |
2358 | |
1233 | =back |
2359 | =back |
1234 | |
2360 | |
1235 | |
2361 | |
1236 | =head1 OTHER FUNCTIONS |
2362 | =head1 OTHER FUNCTIONS |
… | |
… | |
1247 | or timeout without having to allocate/configure/start/stop/free one or |
2373 | or timeout without having to allocate/configure/start/stop/free one or |
1248 | more watchers yourself. |
2374 | more watchers yourself. |
1249 | |
2375 | |
1250 | If C<fd> is less than 0, then no I/O watcher will be started and events |
2376 | If C<fd> is less than 0, then no I/O watcher will be started and events |
1251 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
2377 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
1252 | C<events> set will be craeted and started. |
2378 | C<events> set will be created and started. |
1253 | |
2379 | |
1254 | If C<timeout> is less than 0, then no timeout watcher will be |
2380 | If C<timeout> is less than 0, then no timeout watcher will be |
1255 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2381 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
1256 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
2382 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
1257 | dubious value. |
2383 | dubious value. |
… | |
… | |
1282 | Feed an event on the given fd, as if a file descriptor backend detected |
2408 | Feed an event on the given fd, as if a file descriptor backend detected |
1283 | the given events it. |
2409 | the given events it. |
1284 | |
2410 | |
1285 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
2411 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
1286 | |
2412 | |
1287 | Feed an event as if the given signal occured (C<loop> must be the default |
2413 | Feed an event as if the given signal occurred (C<loop> must be the default |
1288 | loop!). |
2414 | loop!). |
1289 | |
2415 | |
1290 | =back |
2416 | =back |
1291 | |
2417 | |
1292 | |
2418 | |
… | |
… | |
1308 | |
2434 | |
1309 | =item * Priorities are not currently supported. Initialising priorities |
2435 | =item * Priorities are not currently supported. Initialising priorities |
1310 | will fail and all watchers will have the same priority, even though there |
2436 | will fail and all watchers will have the same priority, even though there |
1311 | is an ev_pri field. |
2437 | is an ev_pri field. |
1312 | |
2438 | |
|
|
2439 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
2440 | first base created (== the default loop) gets the signals. |
|
|
2441 | |
1313 | =item * Other members are not supported. |
2442 | =item * Other members are not supported. |
1314 | |
2443 | |
1315 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2444 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
1316 | to use the libev header file and library. |
2445 | to use the libev header file and library. |
1317 | |
2446 | |
1318 | =back |
2447 | =back |
1319 | |
2448 | |
1320 | =head1 C++ SUPPORT |
2449 | =head1 C++ SUPPORT |
1321 | |
2450 | |
1322 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
2451 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
1323 | you to use some convinience methods to start/stop watchers and also change |
2452 | you to use some convenience methods to start/stop watchers and also change |
1324 | the callback model to a model using method callbacks on objects. |
2453 | the callback model to a model using method callbacks on objects. |
1325 | |
2454 | |
1326 | To use it, |
2455 | To use it, |
1327 | |
2456 | |
1328 | #include <ev++.h> |
2457 | #include <ev++.h> |
1329 | |
2458 | |
1330 | (it is not installed by default). This automatically includes F<ev.h> |
2459 | This automatically includes F<ev.h> and puts all of its definitions (many |
1331 | and puts all of its definitions (many of them macros) into the global |
2460 | of them macros) into the global namespace. All C++ specific things are |
1332 | namespace. All C++ specific things are put into the C<ev> namespace. |
2461 | put into the C<ev> namespace. It should support all the same embedding |
|
|
2462 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
1333 | |
2463 | |
1334 | It should support all the same embedding options as F<ev.h>, most notably |
2464 | Care has been taken to keep the overhead low. The only data member the C++ |
1335 | C<EV_MULTIPLICITY>. |
2465 | classes add (compared to plain C-style watchers) is the event loop pointer |
|
|
2466 | that the watcher is associated with (or no additional members at all if |
|
|
2467 | you disable C<EV_MULTIPLICITY> when embedding libev). |
|
|
2468 | |
|
|
2469 | Currently, functions, and static and non-static member functions can be |
|
|
2470 | used as callbacks. Other types should be easy to add as long as they only |
|
|
2471 | need one additional pointer for context. If you need support for other |
|
|
2472 | types of functors please contact the author (preferably after implementing |
|
|
2473 | it). |
1336 | |
2474 | |
1337 | Here is a list of things available in the C<ev> namespace: |
2475 | Here is a list of things available in the C<ev> namespace: |
1338 | |
2476 | |
1339 | =over 4 |
2477 | =over 4 |
1340 | |
2478 | |
… | |
… | |
1356 | |
2494 | |
1357 | All of those classes have these methods: |
2495 | All of those classes have these methods: |
1358 | |
2496 | |
1359 | =over 4 |
2497 | =over 4 |
1360 | |
2498 | |
1361 | =item ev::TYPE::TYPE (object *, object::method *) |
2499 | =item ev::TYPE::TYPE () |
1362 | |
2500 | |
1363 | =item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *) |
2501 | =item ev::TYPE::TYPE (struct ev_loop *) |
1364 | |
2502 | |
1365 | =item ev::TYPE::~TYPE |
2503 | =item ev::TYPE::~TYPE |
1366 | |
2504 | |
1367 | The constructor takes a pointer to an object and a method pointer to |
2505 | The constructor (optionally) takes an event loop to associate the watcher |
1368 | the event handler callback to call in this class. The constructor calls |
2506 | with. If it is omitted, it will use C<EV_DEFAULT>. |
1369 | C<ev_init> for you, which means you have to call the C<set> method |
2507 | |
1370 | before starting it. If you do not specify a loop then the constructor |
2508 | The constructor calls C<ev_init> for you, which means you have to call the |
1371 | automatically associates the default loop with this watcher. |
2509 | C<set> method before starting it. |
|
|
2510 | |
|
|
2511 | It will not set a callback, however: You have to call the templated C<set> |
|
|
2512 | method to set a callback before you can start the watcher. |
|
|
2513 | |
|
|
2514 | (The reason why you have to use a method is a limitation in C++ which does |
|
|
2515 | not allow explicit template arguments for constructors). |
1372 | |
2516 | |
1373 | The destructor automatically stops the watcher if it is active. |
2517 | The destructor automatically stops the watcher if it is active. |
|
|
2518 | |
|
|
2519 | =item w->set<class, &class::method> (object *) |
|
|
2520 | |
|
|
2521 | This method sets the callback method to call. The method has to have a |
|
|
2522 | signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as |
|
|
2523 | first argument and the C<revents> as second. The object must be given as |
|
|
2524 | parameter and is stored in the C<data> member of the watcher. |
|
|
2525 | |
|
|
2526 | This method synthesizes efficient thunking code to call your method from |
|
|
2527 | the C callback that libev requires. If your compiler can inline your |
|
|
2528 | callback (i.e. it is visible to it at the place of the C<set> call and |
|
|
2529 | your compiler is good :), then the method will be fully inlined into the |
|
|
2530 | thunking function, making it as fast as a direct C callback. |
|
|
2531 | |
|
|
2532 | Example: simple class declaration and watcher initialisation |
|
|
2533 | |
|
|
2534 | struct myclass |
|
|
2535 | { |
|
|
2536 | void io_cb (ev::io &w, int revents) { } |
|
|
2537 | } |
|
|
2538 | |
|
|
2539 | myclass obj; |
|
|
2540 | ev::io iow; |
|
|
2541 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
2542 | |
|
|
2543 | =item w->set<function> (void *data = 0) |
|
|
2544 | |
|
|
2545 | Also sets a callback, but uses a static method or plain function as |
|
|
2546 | callback. The optional C<data> argument will be stored in the watcher's |
|
|
2547 | C<data> member and is free for you to use. |
|
|
2548 | |
|
|
2549 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
|
|
2550 | |
|
|
2551 | See the method-C<set> above for more details. |
|
|
2552 | |
|
|
2553 | Example: |
|
|
2554 | |
|
|
2555 | static void io_cb (ev::io &w, int revents) { } |
|
|
2556 | iow.set <io_cb> (); |
1374 | |
2557 | |
1375 | =item w->set (struct ev_loop *) |
2558 | =item w->set (struct ev_loop *) |
1376 | |
2559 | |
1377 | Associates a different C<struct ev_loop> with this watcher. You can only |
2560 | Associates a different C<struct ev_loop> with this watcher. You can only |
1378 | do this when the watcher is inactive (and not pending either). |
2561 | do this when the watcher is inactive (and not pending either). |
1379 | |
2562 | |
1380 | =item w->set ([args]) |
2563 | =item w->set ([arguments]) |
1381 | |
2564 | |
1382 | Basically the same as C<ev_TYPE_set>, with the same args. Must be |
2565 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
1383 | called at least once. Unlike the C counterpart, an active watcher gets |
2566 | called at least once. Unlike the C counterpart, an active watcher gets |
1384 | automatically stopped and restarted. |
2567 | automatically stopped and restarted when reconfiguring it with this |
|
|
2568 | method. |
1385 | |
2569 | |
1386 | =item w->start () |
2570 | =item w->start () |
1387 | |
2571 | |
1388 | Starts the watcher. Note that there is no C<loop> argument as the |
2572 | Starts the watcher. Note that there is no C<loop> argument, as the |
1389 | constructor already takes the loop. |
2573 | constructor already stores the event loop. |
1390 | |
2574 | |
1391 | =item w->stop () |
2575 | =item w->stop () |
1392 | |
2576 | |
1393 | Stops the watcher if it is active. Again, no C<loop> argument. |
2577 | Stops the watcher if it is active. Again, no C<loop> argument. |
1394 | |
2578 | |
1395 | =item w->again () C<ev::timer>, C<ev::periodic> only |
2579 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
1396 | |
2580 | |
1397 | For C<ev::timer> and C<ev::periodic>, this invokes the corresponding |
2581 | For C<ev::timer> and C<ev::periodic>, this invokes the corresponding |
1398 | C<ev_TYPE_again> function. |
2582 | C<ev_TYPE_again> function. |
1399 | |
2583 | |
1400 | =item w->sweep () C<ev::embed> only |
2584 | =item w->sweep () (C<ev::embed> only) |
1401 | |
2585 | |
1402 | Invokes C<ev_embed_sweep>. |
2586 | Invokes C<ev_embed_sweep>. |
|
|
2587 | |
|
|
2588 | =item w->update () (C<ev::stat> only) |
|
|
2589 | |
|
|
2590 | Invokes C<ev_stat_stat>. |
1403 | |
2591 | |
1404 | =back |
2592 | =back |
1405 | |
2593 | |
1406 | =back |
2594 | =back |
1407 | |
2595 | |
1408 | Example: Define a class with an IO and idle watcher, start one of them in |
2596 | Example: Define a class with an IO and idle watcher, start one of them in |
1409 | the constructor. |
2597 | the constructor. |
1410 | |
2598 | |
1411 | class myclass |
2599 | class myclass |
1412 | { |
2600 | { |
1413 | ev_io io; void io_cb (ev::io &w, int revents); |
2601 | ev::io io; void io_cb (ev::io &w, int revents); |
1414 | ev_idle idle void idle_cb (ev::idle &w, int revents); |
2602 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
1415 | |
2603 | |
1416 | myclass (); |
2604 | myclass (int fd) |
|
|
2605 | { |
|
|
2606 | io .set <myclass, &myclass::io_cb > (this); |
|
|
2607 | idle.set <myclass, &myclass::idle_cb> (this); |
|
|
2608 | |
|
|
2609 | io.start (fd, ev::READ); |
|
|
2610 | } |
|
|
2611 | }; |
|
|
2612 | |
|
|
2613 | |
|
|
2614 | =head1 OTHER LANGUAGE BINDINGS |
|
|
2615 | |
|
|
2616 | Libev does not offer other language bindings itself, but bindings for a |
|
|
2617 | number of languages exist in the form of third-party packages. If you know |
|
|
2618 | any interesting language binding in addition to the ones listed here, drop |
|
|
2619 | me a note. |
|
|
2620 | |
|
|
2621 | =over 4 |
|
|
2622 | |
|
|
2623 | =item Perl |
|
|
2624 | |
|
|
2625 | The EV module implements the full libev API and is actually used to test |
|
|
2626 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
2627 | there are additional modules that implement libev-compatible interfaces |
|
|
2628 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
|
|
2629 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
|
|
2630 | |
|
|
2631 | It can be found and installed via CPAN, its homepage is found at |
|
|
2632 | L<http://software.schmorp.de/pkg/EV>. |
|
|
2633 | |
|
|
2634 | =item Ruby |
|
|
2635 | |
|
|
2636 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
2637 | of the libev API and adds file handle abstractions, asynchronous DNS and |
|
|
2638 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
2639 | L<http://rev.rubyforge.org/>. |
|
|
2640 | |
|
|
2641 | =item D |
|
|
2642 | |
|
|
2643 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
2644 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
|
|
2645 | |
|
|
2646 | =back |
|
|
2647 | |
|
|
2648 | |
|
|
2649 | =head1 MACRO MAGIC |
|
|
2650 | |
|
|
2651 | Libev can be compiled with a variety of options, the most fundamental |
|
|
2652 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
|
|
2653 | functions and callbacks have an initial C<struct ev_loop *> argument. |
|
|
2654 | |
|
|
2655 | To make it easier to write programs that cope with either variant, the |
|
|
2656 | following macros are defined: |
|
|
2657 | |
|
|
2658 | =over 4 |
|
|
2659 | |
|
|
2660 | =item C<EV_A>, C<EV_A_> |
|
|
2661 | |
|
|
2662 | This provides the loop I<argument> for functions, if one is required ("ev |
|
|
2663 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
|
|
2664 | C<EV_A_> is used when other arguments are following. Example: |
|
|
2665 | |
|
|
2666 | ev_unref (EV_A); |
|
|
2667 | ev_timer_add (EV_A_ watcher); |
|
|
2668 | ev_loop (EV_A_ 0); |
|
|
2669 | |
|
|
2670 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
|
|
2671 | which is often provided by the following macro. |
|
|
2672 | |
|
|
2673 | =item C<EV_P>, C<EV_P_> |
|
|
2674 | |
|
|
2675 | This provides the loop I<parameter> for functions, if one is required ("ev |
|
|
2676 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
|
|
2677 | C<EV_P_> is used when other parameters are following. Example: |
|
|
2678 | |
|
|
2679 | // this is how ev_unref is being declared |
|
|
2680 | static void ev_unref (EV_P); |
|
|
2681 | |
|
|
2682 | // this is how you can declare your typical callback |
|
|
2683 | static void cb (EV_P_ ev_timer *w, int revents) |
|
|
2684 | |
|
|
2685 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
|
|
2686 | suitable for use with C<EV_A>. |
|
|
2687 | |
|
|
2688 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
|
|
2689 | |
|
|
2690 | Similar to the other two macros, this gives you the value of the default |
|
|
2691 | loop, if multiple loops are supported ("ev loop default"). |
|
|
2692 | |
|
|
2693 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
2694 | |
|
|
2695 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
2696 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
2697 | is undefined when the default loop has not been initialised by a previous |
|
|
2698 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
2699 | |
|
|
2700 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
2701 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
|
|
2702 | |
|
|
2703 | =back |
|
|
2704 | |
|
|
2705 | Example: Declare and initialise a check watcher, utilising the above |
|
|
2706 | macros so it will work regardless of whether multiple loops are supported |
|
|
2707 | or not. |
|
|
2708 | |
|
|
2709 | static void |
|
|
2710 | check_cb (EV_P_ ev_timer *w, int revents) |
|
|
2711 | { |
|
|
2712 | ev_check_stop (EV_A_ w); |
1417 | } |
2713 | } |
1418 | |
2714 | |
1419 | myclass::myclass (int fd) |
2715 | ev_check check; |
1420 | : io (this, &myclass::io_cb), |
2716 | ev_check_init (&check, check_cb); |
1421 | idle (this, &myclass::idle_cb) |
2717 | ev_check_start (EV_DEFAULT_ &check); |
1422 | { |
2718 | ev_loop (EV_DEFAULT_ 0); |
1423 | io.start (fd, ev::READ); |
|
|
1424 | } |
|
|
1425 | |
2719 | |
1426 | =head1 EMBEDDING |
2720 | =head1 EMBEDDING |
1427 | |
2721 | |
1428 | Libev can (and often is) directly embedded into host |
2722 | Libev can (and often is) directly embedded into host |
1429 | applications. Examples of applications that embed it include the Deliantra |
2723 | applications. Examples of applications that embed it include the Deliantra |
1430 | Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
2724 | Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
1431 | and rxvt-unicode. |
2725 | and rxvt-unicode. |
1432 | |
2726 | |
1433 | The goal is to enable you to just copy the neecssary files into your |
2727 | The goal is to enable you to just copy the necessary files into your |
1434 | source directory without having to change even a single line in them, so |
2728 | source directory without having to change even a single line in them, so |
1435 | you can easily upgrade by simply copying (or having a checked-out copy of |
2729 | you can easily upgrade by simply copying (or having a checked-out copy of |
1436 | libev somewhere in your source tree). |
2730 | libev somewhere in your source tree). |
1437 | |
2731 | |
1438 | =head2 FILESETS |
2732 | =head2 FILESETS |
1439 | |
2733 | |
1440 | Depending on what features you need you need to include one or more sets of files |
2734 | Depending on what features you need you need to include one or more sets of files |
1441 | in your app. |
2735 | in your application. |
1442 | |
2736 | |
1443 | =head3 CORE EVENT LOOP |
2737 | =head3 CORE EVENT LOOP |
1444 | |
2738 | |
1445 | To include only the libev core (all the C<ev_*> functions), with manual |
2739 | To include only the libev core (all the C<ev_*> functions), with manual |
1446 | configuration (no autoconf): |
2740 | configuration (no autoconf): |
… | |
… | |
1469 | ev_vars.h |
2763 | ev_vars.h |
1470 | ev_wrap.h |
2764 | ev_wrap.h |
1471 | |
2765 | |
1472 | ev_win32.c required on win32 platforms only |
2766 | ev_win32.c required on win32 platforms only |
1473 | |
2767 | |
1474 | ev_select.c only when select backend is enabled (which is is by default) |
2768 | ev_select.c only when select backend is enabled (which is enabled by default) |
1475 | ev_poll.c only when poll backend is enabled (disabled by default) |
2769 | ev_poll.c only when poll backend is enabled (disabled by default) |
1476 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
2770 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
1477 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
2771 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
1478 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
2772 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
1479 | |
2773 | |
1480 | F<ev.c> includes the backend files directly when enabled, so you only need |
2774 | F<ev.c> includes the backend files directly when enabled, so you only need |
1481 | to compile a single file. |
2775 | to compile this single file. |
1482 | |
2776 | |
1483 | =head3 LIBEVENT COMPATIBILITY API |
2777 | =head3 LIBEVENT COMPATIBILITY API |
1484 | |
2778 | |
1485 | To include the libevent compatibility API, also include: |
2779 | To include the libevent compatibility API, also include: |
1486 | |
2780 | |
… | |
… | |
1497 | event.h |
2791 | event.h |
1498 | event.c |
2792 | event.c |
1499 | |
2793 | |
1500 | =head3 AUTOCONF SUPPORT |
2794 | =head3 AUTOCONF SUPPORT |
1501 | |
2795 | |
1502 | Instead of using C<EV_STANDALONE=1> and providing your config in |
2796 | Instead of using C<EV_STANDALONE=1> and providing your configuration in |
1503 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
2797 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
1504 | F<configure.ac> and leave C<EV_STANDALONE> off. F<ev.c> will then include |
2798 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
1505 | F<config.h> and configure itself accordingly. |
2799 | include F<config.h> and configure itself accordingly. |
1506 | |
2800 | |
1507 | For this of course you need the m4 file: |
2801 | For this of course you need the m4 file: |
1508 | |
2802 | |
1509 | libev.m4 |
2803 | libev.m4 |
1510 | |
2804 | |
1511 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2805 | =head2 PREPROCESSOR SYMBOLS/MACROS |
1512 | |
2806 | |
1513 | Libev can be configured via a variety of preprocessor symbols you have to define |
2807 | Libev can be configured via a variety of preprocessor symbols you have to |
1514 | before including any of its files. The default is not to build for multiplicity |
2808 | define before including any of its files. The default in the absence of |
1515 | and only include the select backend. |
2809 | autoconf is noted for every option. |
1516 | |
2810 | |
1517 | =over 4 |
2811 | =over 4 |
1518 | |
2812 | |
1519 | =item EV_STANDALONE |
2813 | =item EV_STANDALONE |
1520 | |
2814 | |
… | |
… | |
1525 | F<event.h> that are not directly supported by the libev core alone. |
2819 | F<event.h> that are not directly supported by the libev core alone. |
1526 | |
2820 | |
1527 | =item EV_USE_MONOTONIC |
2821 | =item EV_USE_MONOTONIC |
1528 | |
2822 | |
1529 | If defined to be C<1>, libev will try to detect the availability of the |
2823 | If defined to be C<1>, libev will try to detect the availability of the |
1530 | monotonic clock option at both compiletime and runtime. Otherwise no use |
2824 | monotonic clock option at both compile time and runtime. Otherwise no use |
1531 | of the monotonic clock option will be attempted. If you enable this, you |
2825 | of the monotonic clock option will be attempted. If you enable this, you |
1532 | usually have to link against librt or something similar. Enabling it when |
2826 | usually have to link against librt or something similar. Enabling it when |
1533 | the functionality isn't available is safe, though, althoguh you have |
2827 | the functionality isn't available is safe, though, although you have |
1534 | to make sure you link against any libraries where the C<clock_gettime> |
2828 | to make sure you link against any libraries where the C<clock_gettime> |
1535 | function is hiding in (often F<-lrt>). |
2829 | function is hiding in (often F<-lrt>). |
1536 | |
2830 | |
1537 | =item EV_USE_REALTIME |
2831 | =item EV_USE_REALTIME |
1538 | |
2832 | |
1539 | If defined to be C<1>, libev will try to detect the availability of the |
2833 | If defined to be C<1>, libev will try to detect the availability of the |
1540 | realtime clock option at compiletime (and assume its availability at |
2834 | real-time clock option at compile time (and assume its availability at |
1541 | runtime if successful). Otherwise no use of the realtime clock option will |
2835 | runtime if successful). Otherwise no use of the real-time clock option will |
1542 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
2836 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
1543 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries |
2837 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
1544 | in the description of C<EV_USE_MONOTONIC>, though. |
2838 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
|
|
2839 | |
|
|
2840 | =item EV_USE_NANOSLEEP |
|
|
2841 | |
|
|
2842 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
|
|
2843 | and will use it for delays. Otherwise it will use C<select ()>. |
|
|
2844 | |
|
|
2845 | =item EV_USE_EVENTFD |
|
|
2846 | |
|
|
2847 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
2848 | available and will probe for kernel support at runtime. This will improve |
|
|
2849 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
2850 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
2851 | 2.7 or newer, otherwise disabled. |
1545 | |
2852 | |
1546 | =item EV_USE_SELECT |
2853 | =item EV_USE_SELECT |
1547 | |
2854 | |
1548 | If undefined or defined to be C<1>, libev will compile in support for the |
2855 | If undefined or defined to be C<1>, libev will compile in support for the |
1549 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2856 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
1550 | other method takes over, select will be it. Otherwise the select backend |
2857 | other method takes over, select will be it. Otherwise the select backend |
1551 | will not be compiled in. |
2858 | will not be compiled in. |
1552 | |
2859 | |
1553 | =item EV_SELECT_USE_FD_SET |
2860 | =item EV_SELECT_USE_FD_SET |
1554 | |
2861 | |
1555 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2862 | If defined to C<1>, then the select backend will use the system C<fd_set> |
1556 | structure. This is useful if libev doesn't compile due to a missing |
2863 | structure. This is useful if libev doesn't compile due to a missing |
1557 | C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on |
2864 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
1558 | exotic systems. This usually limits the range of file descriptors to some |
2865 | exotic systems. This usually limits the range of file descriptors to some |
1559 | low limit such as 1024 or might have other limitations (winsocket only |
2866 | low limit such as 1024 or might have other limitations (winsocket only |
1560 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
2867 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
1561 | influence the size of the C<fd_set> used. |
2868 | influence the size of the C<fd_set> used. |
1562 | |
2869 | |
… | |
… | |
1568 | be used is the winsock select). This means that it will call |
2875 | be used is the winsock select). This means that it will call |
1569 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
2876 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
1570 | it is assumed that all these functions actually work on fds, even |
2877 | it is assumed that all these functions actually work on fds, even |
1571 | on win32. Should not be defined on non-win32 platforms. |
2878 | on win32. Should not be defined on non-win32 platforms. |
1572 | |
2879 | |
|
|
2880 | =item EV_FD_TO_WIN32_HANDLE |
|
|
2881 | |
|
|
2882 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
|
|
2883 | file descriptors to socket handles. When not defining this symbol (the |
|
|
2884 | default), then libev will call C<_get_osfhandle>, which is usually |
|
|
2885 | correct. In some cases, programs use their own file descriptor management, |
|
|
2886 | in which case they can provide this function to map fds to socket handles. |
|
|
2887 | |
1573 | =item EV_USE_POLL |
2888 | =item EV_USE_POLL |
1574 | |
2889 | |
1575 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
2890 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
1576 | backend. Otherwise it will be enabled on non-win32 platforms. It |
2891 | backend. Otherwise it will be enabled on non-win32 platforms. It |
1577 | takes precedence over select. |
2892 | takes precedence over select. |
1578 | |
2893 | |
1579 | =item EV_USE_EPOLL |
2894 | =item EV_USE_EPOLL |
1580 | |
2895 | |
1581 | If defined to be C<1>, libev will compile in support for the Linux |
2896 | If defined to be C<1>, libev will compile in support for the Linux |
1582 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2897 | C<epoll>(7) backend. Its availability will be detected at runtime, |
1583 | otherwise another method will be used as fallback. This is the |
2898 | otherwise another method will be used as fallback. This is the preferred |
1584 | preferred backend for GNU/Linux systems. |
2899 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
2900 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
1585 | |
2901 | |
1586 | =item EV_USE_KQUEUE |
2902 | =item EV_USE_KQUEUE |
1587 | |
2903 | |
1588 | If defined to be C<1>, libev will compile in support for the BSD style |
2904 | If defined to be C<1>, libev will compile in support for the BSD style |
1589 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
2905 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
1602 | otherwise another method will be used as fallback. This is the preferred |
2918 | otherwise another method will be used as fallback. This is the preferred |
1603 | backend for Solaris 10 systems. |
2919 | backend for Solaris 10 systems. |
1604 | |
2920 | |
1605 | =item EV_USE_DEVPOLL |
2921 | =item EV_USE_DEVPOLL |
1606 | |
2922 | |
1607 | reserved for future expansion, works like the USE symbols above. |
2923 | Reserved for future expansion, works like the USE symbols above. |
|
|
2924 | |
|
|
2925 | =item EV_USE_INOTIFY |
|
|
2926 | |
|
|
2927 | If defined to be C<1>, libev will compile in support for the Linux inotify |
|
|
2928 | interface to speed up C<ev_stat> watchers. Its actual availability will |
|
|
2929 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
2930 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
2931 | |
|
|
2932 | =item EV_ATOMIC_T |
|
|
2933 | |
|
|
2934 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
|
|
2935 | access is atomic with respect to other threads or signal contexts. No such |
|
|
2936 | type is easily found in the C language, so you can provide your own type |
|
|
2937 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
2938 | as well as for signal and thread safety in C<ev_async> watchers. |
|
|
2939 | |
|
|
2940 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
|
|
2941 | (from F<signal.h>), which is usually good enough on most platforms. |
1608 | |
2942 | |
1609 | =item EV_H |
2943 | =item EV_H |
1610 | |
2944 | |
1611 | The name of the F<ev.h> header file used to include it. The default if |
2945 | The name of the F<ev.h> header file used to include it. The default if |
1612 | undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This |
2946 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
1613 | can be used to virtually rename the F<ev.h> header file in case of conflicts. |
2947 | used to virtually rename the F<ev.h> header file in case of conflicts. |
1614 | |
2948 | |
1615 | =item EV_CONFIG_H |
2949 | =item EV_CONFIG_H |
1616 | |
2950 | |
1617 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
2951 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
1618 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
2952 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
1619 | C<EV_H>, above. |
2953 | C<EV_H>, above. |
1620 | |
2954 | |
1621 | =item EV_EVENT_H |
2955 | =item EV_EVENT_H |
1622 | |
2956 | |
1623 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
2957 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
1624 | of how the F<event.h> header can be found. |
2958 | of how the F<event.h> header can be found, the default is C<"event.h">. |
1625 | |
2959 | |
1626 | =item EV_PROTOTYPES |
2960 | =item EV_PROTOTYPES |
1627 | |
2961 | |
1628 | If defined to be C<0>, then F<ev.h> will not define any function |
2962 | If defined to be C<0>, then F<ev.h> will not define any function |
1629 | prototypes, but still define all the structs and other symbols. This is |
2963 | prototypes, but still define all the structs and other symbols. This is |
… | |
… | |
1636 | will have the C<struct ev_loop *> as first argument, and you can create |
2970 | will have the C<struct ev_loop *> as first argument, and you can create |
1637 | additional independent event loops. Otherwise there will be no support |
2971 | additional independent event loops. Otherwise there will be no support |
1638 | for multiple event loops and there is no first event loop pointer |
2972 | for multiple event loops and there is no first event loop pointer |
1639 | argument. Instead, all functions act on the single default loop. |
2973 | argument. Instead, all functions act on the single default loop. |
1640 | |
2974 | |
|
|
2975 | =item EV_MINPRI |
|
|
2976 | |
|
|
2977 | =item EV_MAXPRI |
|
|
2978 | |
|
|
2979 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
|
|
2980 | C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can |
|
|
2981 | provide for more priorities by overriding those symbols (usually defined |
|
|
2982 | to be C<-2> and C<2>, respectively). |
|
|
2983 | |
|
|
2984 | When doing priority-based operations, libev usually has to linearly search |
|
|
2985 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
2986 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
|
|
2987 | fine. |
|
|
2988 | |
|
|
2989 | If your embedding application does not need any priorities, defining these both to |
|
|
2990 | C<0> will save some memory and CPU. |
|
|
2991 | |
1641 | =item EV_PERIODICS |
2992 | =item EV_PERIODIC_ENABLE |
1642 | |
2993 | |
1643 | If undefined or defined to be C<1>, then periodic timers are supported, |
2994 | If undefined or defined to be C<1>, then periodic timers are supported. If |
1644 | otherwise not. This saves a few kb of code. |
2995 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
2996 | code. |
|
|
2997 | |
|
|
2998 | =item EV_IDLE_ENABLE |
|
|
2999 | |
|
|
3000 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3001 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3002 | code. |
|
|
3003 | |
|
|
3004 | =item EV_EMBED_ENABLE |
|
|
3005 | |
|
|
3006 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3007 | defined to be C<0>, then they are not. |
|
|
3008 | |
|
|
3009 | =item EV_STAT_ENABLE |
|
|
3010 | |
|
|
3011 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3012 | defined to be C<0>, then they are not. |
|
|
3013 | |
|
|
3014 | =item EV_FORK_ENABLE |
|
|
3015 | |
|
|
3016 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3017 | defined to be C<0>, then they are not. |
|
|
3018 | |
|
|
3019 | =item EV_ASYNC_ENABLE |
|
|
3020 | |
|
|
3021 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3022 | defined to be C<0>, then they are not. |
|
|
3023 | |
|
|
3024 | =item EV_MINIMAL |
|
|
3025 | |
|
|
3026 | If you need to shave off some kilobytes of code at the expense of some |
|
|
3027 | speed, define this symbol to C<1>. Currently this is used to override some |
|
|
3028 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
|
|
3029 | much smaller 2-heap for timer management over the default 4-heap. |
|
|
3030 | |
|
|
3031 | =item EV_PID_HASHSIZE |
|
|
3032 | |
|
|
3033 | C<ev_child> watchers use a small hash table to distribute workload by |
|
|
3034 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
|
|
3035 | than enough. If you need to manage thousands of children you might want to |
|
|
3036 | increase this value (I<must> be a power of two). |
|
|
3037 | |
|
|
3038 | =item EV_INOTIFY_HASHSIZE |
|
|
3039 | |
|
|
3040 | C<ev_stat> watchers use a small hash table to distribute workload by |
|
|
3041 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
|
|
3042 | usually more than enough. If you need to manage thousands of C<ev_stat> |
|
|
3043 | watchers you might want to increase this value (I<must> be a power of |
|
|
3044 | two). |
|
|
3045 | |
|
|
3046 | =item EV_USE_4HEAP |
|
|
3047 | |
|
|
3048 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3049 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
|
|
3050 | to C<1>. The 4-heap uses more complicated (longer) code but has |
|
|
3051 | noticeably faster performance with many (thousands) of watchers. |
|
|
3052 | |
|
|
3053 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3054 | (disabled). |
|
|
3055 | |
|
|
3056 | =item EV_HEAP_CACHE_AT |
|
|
3057 | |
|
|
3058 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3059 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
|
|
3060 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3061 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3062 | but avoids random read accesses on heap changes. This improves performance |
|
|
3063 | noticeably with with many (hundreds) of watchers. |
|
|
3064 | |
|
|
3065 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3066 | (disabled). |
|
|
3067 | |
|
|
3068 | =item EV_VERIFY |
|
|
3069 | |
|
|
3070 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
|
|
3071 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
3072 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
3073 | called. If set to C<2>, then the internal verification code will be |
|
|
3074 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
3075 | verification code will be called very frequently, which will slow down |
|
|
3076 | libev considerably. |
|
|
3077 | |
|
|
3078 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
|
|
3079 | C<0.> |
1645 | |
3080 | |
1646 | =item EV_COMMON |
3081 | =item EV_COMMON |
1647 | |
3082 | |
1648 | By default, all watchers have a C<void *data> member. By redefining |
3083 | By default, all watchers have a C<void *data> member. By redefining |
1649 | this macro to a something else you can include more and other types of |
3084 | this macro to a something else you can include more and other types of |
… | |
… | |
1654 | |
3089 | |
1655 | #define EV_COMMON \ |
3090 | #define EV_COMMON \ |
1656 | SV *self; /* contains this struct */ \ |
3091 | SV *self; /* contains this struct */ \ |
1657 | SV *cb_sv, *fh /* note no trailing ";" */ |
3092 | SV *cb_sv, *fh /* note no trailing ";" */ |
1658 | |
3093 | |
1659 | =item EV_CB_DECLARE(type) |
3094 | =item EV_CB_DECLARE (type) |
1660 | |
3095 | |
1661 | =item EV_CB_INVOKE(watcher,revents) |
3096 | =item EV_CB_INVOKE (watcher, revents) |
1662 | |
3097 | |
1663 | =item ev_set_cb(ev,cb) |
3098 | =item ev_set_cb (ev, cb) |
1664 | |
3099 | |
1665 | Can be used to change the callback member declaration in each watcher, |
3100 | Can be used to change the callback member declaration in each watcher, |
1666 | and the way callbacks are invoked and set. Must expand to a struct member |
3101 | and the way callbacks are invoked and set. Must expand to a struct member |
1667 | definition and a statement, respectively. See the F<ev.v> header file for |
3102 | definition and a statement, respectively. See the F<ev.h> header file for |
1668 | their default definitions. One possible use for overriding these is to |
3103 | their default definitions. One possible use for overriding these is to |
1669 | avoid the ev_loop pointer as first argument in all cases, or to use method |
3104 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
1670 | calls instead of plain function calls in C++. |
3105 | method calls instead of plain function calls in C++. |
|
|
3106 | |
|
|
3107 | =head2 EXPORTED API SYMBOLS |
|
|
3108 | |
|
|
3109 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
|
|
3110 | exported symbols, you can use the provided F<Symbol.*> files which list |
|
|
3111 | all public symbols, one per line: |
|
|
3112 | |
|
|
3113 | Symbols.ev for libev proper |
|
|
3114 | Symbols.event for the libevent emulation |
|
|
3115 | |
|
|
3116 | This can also be used to rename all public symbols to avoid clashes with |
|
|
3117 | multiple versions of libev linked together (which is obviously bad in |
|
|
3118 | itself, but sometimes it is inconvenient to avoid this). |
|
|
3119 | |
|
|
3120 | A sed command like this will create wrapper C<#define>'s that you need to |
|
|
3121 | include before including F<ev.h>: |
|
|
3122 | |
|
|
3123 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
|
|
3124 | |
|
|
3125 | This would create a file F<wrap.h> which essentially looks like this: |
|
|
3126 | |
|
|
3127 | #define ev_backend myprefix_ev_backend |
|
|
3128 | #define ev_check_start myprefix_ev_check_start |
|
|
3129 | #define ev_check_stop myprefix_ev_check_stop |
|
|
3130 | ... |
1671 | |
3131 | |
1672 | =head2 EXAMPLES |
3132 | =head2 EXAMPLES |
1673 | |
3133 | |
1674 | For a real-world example of a program the includes libev |
3134 | For a real-world example of a program the includes libev |
1675 | verbatim, you can have a look at the EV perl module |
3135 | verbatim, you can have a look at the EV perl module |
… | |
… | |
1678 | interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file |
3138 | interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file |
1679 | will be compiled. It is pretty complex because it provides its own header |
3139 | will be compiled. It is pretty complex because it provides its own header |
1680 | file. |
3140 | file. |
1681 | |
3141 | |
1682 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3142 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
1683 | that everybody includes and which overrides some autoconf choices: |
3143 | that everybody includes and which overrides some configure choices: |
1684 | |
3144 | |
|
|
3145 | #define EV_MINIMAL 1 |
1685 | #define EV_USE_POLL 0 |
3146 | #define EV_USE_POLL 0 |
1686 | #define EV_MULTIPLICITY 0 |
3147 | #define EV_MULTIPLICITY 0 |
1687 | #define EV_PERIODICS 0 |
3148 | #define EV_PERIODIC_ENABLE 0 |
|
|
3149 | #define EV_STAT_ENABLE 0 |
|
|
3150 | #define EV_FORK_ENABLE 0 |
1688 | #define EV_CONFIG_H <config.h> |
3151 | #define EV_CONFIG_H <config.h> |
|
|
3152 | #define EV_MINPRI 0 |
|
|
3153 | #define EV_MAXPRI 0 |
1689 | |
3154 | |
1690 | #include "ev++.h" |
3155 | #include "ev++.h" |
1691 | |
3156 | |
1692 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3157 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
1693 | |
3158 | |
1694 | #include "ev_cpp.h" |
3159 | #include "ev_cpp.h" |
1695 | #include "ev.c" |
3160 | #include "ev.c" |
1696 | |
3161 | |
|
|
3162 | |
|
|
3163 | =head1 THREADS AND COROUTINES |
|
|
3164 | |
|
|
3165 | =head2 THREADS |
|
|
3166 | |
|
|
3167 | Libev itself is completely thread-safe, but it uses no locking. This |
|
|
3168 | means that you can use as many loops as you want in parallel, as long as |
|
|
3169 | only one thread ever calls into one libev function with the same loop |
|
|
3170 | parameter. |
|
|
3171 | |
|
|
3172 | Or put differently: calls with different loop parameters can be done in |
|
|
3173 | parallel from multiple threads, calls with the same loop parameter must be |
|
|
3174 | done serially (but can be done from different threads, as long as only one |
|
|
3175 | thread ever is inside a call at any point in time, e.g. by using a mutex |
|
|
3176 | per loop). |
|
|
3177 | |
|
|
3178 | If you want to know which design is best for your problem, then I cannot |
|
|
3179 | help you but by giving some generic advice: |
|
|
3180 | |
|
|
3181 | =over 4 |
|
|
3182 | |
|
|
3183 | =item * most applications have a main thread: use the default libev loop |
|
|
3184 | in that thread, or create a separate thread running only the default loop. |
|
|
3185 | |
|
|
3186 | This helps integrating other libraries or software modules that use libev |
|
|
3187 | themselves and don't care/know about threading. |
|
|
3188 | |
|
|
3189 | =item * one loop per thread is usually a good model. |
|
|
3190 | |
|
|
3191 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3192 | exists, but it is always a good start. |
|
|
3193 | |
|
|
3194 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
3195 | loop is handed through multiple threads in a kind of round-robin fashion. |
|
|
3196 | |
|
|
3197 | Choosing a model is hard - look around, learn, know that usually you can do |
|
|
3198 | better than you currently do :-) |
|
|
3199 | |
|
|
3200 | =item * often you need to talk to some other thread which blocks in the |
|
|
3201 | event loop - C<ev_async> watchers can be used to wake them up from other |
|
|
3202 | threads safely (or from signal contexts...). |
|
|
3203 | |
|
|
3204 | =back |
|
|
3205 | |
|
|
3206 | =head2 COROUTINES |
|
|
3207 | |
|
|
3208 | Libev is much more accommodating to coroutines ("cooperative threads"): |
|
|
3209 | libev fully supports nesting calls to it's functions from different |
|
|
3210 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
3211 | different coroutines and switch freely between both coroutines running the |
|
|
3212 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3213 | you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
3214 | |
|
|
3215 | Care has been invested into making sure that libev does not keep local |
|
|
3216 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
|
|
3217 | switches. |
|
|
3218 | |
|
|
3219 | |
|
|
3220 | =head1 COMPLEXITIES |
|
|
3221 | |
|
|
3222 | In this section the complexities of (many of) the algorithms used inside |
|
|
3223 | libev will be explained. For complexity discussions about backends see the |
|
|
3224 | documentation for C<ev_default_init>. |
|
|
3225 | |
|
|
3226 | All of the following are about amortised time: If an array needs to be |
|
|
3227 | extended, libev needs to realloc and move the whole array, but this |
|
|
3228 | happens asymptotically never with higher number of elements, so O(1) might |
|
|
3229 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3230 | it is much faster and asymptotically approaches constant time. |
|
|
3231 | |
|
|
3232 | =over 4 |
|
|
3233 | |
|
|
3234 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
|
|
3235 | |
|
|
3236 | This means that, when you have a watcher that triggers in one hour and |
|
|
3237 | there are 100 watchers that would trigger before that then inserting will |
|
|
3238 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3239 | |
|
|
3240 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
|
|
3241 | |
|
|
3242 | That means that changing a timer costs less than removing/adding them |
|
|
3243 | as only the relative motion in the event queue has to be paid for. |
|
|
3244 | |
|
|
3245 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
|
|
3246 | |
|
|
3247 | These just add the watcher into an array or at the head of a list. |
|
|
3248 | |
|
|
3249 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
|
|
3250 | |
|
|
3251 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
|
|
3252 | |
|
|
3253 | These watchers are stored in lists then need to be walked to find the |
|
|
3254 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
3255 | have many watchers waiting for the same fd or signal). |
|
|
3256 | |
|
|
3257 | =item Finding the next timer in each loop iteration: O(1) |
|
|
3258 | |
|
|
3259 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
3260 | fixed position in the storage array. |
|
|
3261 | |
|
|
3262 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3263 | |
|
|
3264 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3265 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3266 | on backend and whether C<ev_io_set> was used). |
|
|
3267 | |
|
|
3268 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3269 | |
|
|
3270 | =item Priority handling: O(number_of_priorities) |
|
|
3271 | |
|
|
3272 | Priorities are implemented by allocating some space for each |
|
|
3273 | priority. When doing priority-based operations, libev usually has to |
|
|
3274 | linearly search all the priorities, but starting/stopping and activating |
|
|
3275 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3276 | |
|
|
3277 | =item Sending an ev_async: O(1) |
|
|
3278 | |
|
|
3279 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3280 | |
|
|
3281 | =item Processing signals: O(max_signal_number) |
|
|
3282 | |
|
|
3283 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3284 | calls in the current loop iteration. Checking for async and signal events |
|
|
3285 | involves iterating over all running async watchers or all signal numbers. |
|
|
3286 | |
|
|
3287 | =back |
|
|
3288 | |
|
|
3289 | |
|
|
3290 | =head1 Win32 platform limitations and workarounds |
|
|
3291 | |
|
|
3292 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
|
|
3293 | requires, and its I/O model is fundamentally incompatible with the POSIX |
|
|
3294 | model. Libev still offers limited functionality on this platform in |
|
|
3295 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
|
|
3296 | descriptors. This only applies when using Win32 natively, not when using |
|
|
3297 | e.g. cygwin. |
|
|
3298 | |
|
|
3299 | Lifting these limitations would basically require the full |
|
|
3300 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3301 | things, then note that glib does exactly that for you in a very portable |
|
|
3302 | way (note also that glib is the slowest event library known to man). |
|
|
3303 | |
|
|
3304 | There is no supported compilation method available on windows except |
|
|
3305 | embedding it into other applications. |
|
|
3306 | |
|
|
3307 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
3308 | accept large writes: instead of resulting in a partial write, windows will |
|
|
3309 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
|
|
3310 | so make sure you only write small amounts into your sockets (less than a |
|
|
3311 | megabyte seems safe, but thsi apparently depends on the amount of memory |
|
|
3312 | available). |
|
|
3313 | |
|
|
3314 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
3315 | the abysmal performance of winsockets, using a large number of sockets |
|
|
3316 | is not recommended (and not reasonable). If your program needs to use |
|
|
3317 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
3318 | different implementation for windows, as libev offers the POSIX readiness |
|
|
3319 | notification model, which cannot be implemented efficiently on windows |
|
|
3320 | (Microsoft monopoly games). |
|
|
3321 | |
|
|
3322 | =over 4 |
|
|
3323 | |
|
|
3324 | =item The winsocket select function |
|
|
3325 | |
|
|
3326 | The winsocket C<select> function doesn't follow POSIX in that it |
|
|
3327 | requires socket I<handles> and not socket I<file descriptors> (it is |
|
|
3328 | also extremely buggy). This makes select very inefficient, and also |
|
|
3329 | requires a mapping from file descriptors to socket handles. See the |
|
|
3330 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
|
|
3331 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
|
|
3332 | |
|
|
3333 | The configuration for a "naked" win32 using the Microsoft runtime |
|
|
3334 | libraries and raw winsocket select is: |
|
|
3335 | |
|
|
3336 | #define EV_USE_SELECT 1 |
|
|
3337 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
3338 | |
|
|
3339 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
3340 | complexity in the O(n²) range when using win32. |
|
|
3341 | |
|
|
3342 | =item Limited number of file descriptors |
|
|
3343 | |
|
|
3344 | Windows has numerous arbitrary (and low) limits on things. |
|
|
3345 | |
|
|
3346 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
3347 | of C<64> handles (probably owning to the fact that all windows kernels |
|
|
3348 | can only wait for C<64> things at the same time internally; Microsoft |
|
|
3349 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3350 | previous thread in each. Great). |
|
|
3351 | |
|
|
3352 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
|
|
3353 | to some high number (e.g. C<2048>) before compiling the winsocket select |
|
|
3354 | call (which might be in libev or elsewhere, for example, perl does its own |
|
|
3355 | select emulation on windows). |
|
|
3356 | |
|
|
3357 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
3358 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
|
|
3359 | or something like this inside Microsoft). You can increase this by calling |
|
|
3360 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
|
|
3361 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
|
|
3362 | libraries. |
|
|
3363 | |
|
|
3364 | This might get you to about C<512> or C<2048> sockets (depending on |
|
|
3365 | windows version and/or the phase of the moon). To get more, you need to |
|
|
3366 | wrap all I/O functions and provide your own fd management, but the cost of |
|
|
3367 | calling select (O(n²)) will likely make this unworkable. |
|
|
3368 | |
|
|
3369 | =back |
|
|
3370 | |
|
|
3371 | |
|
|
3372 | =head1 PORTABILITY REQUIREMENTS |
|
|
3373 | |
|
|
3374 | In addition to a working ISO-C implementation, libev relies on a few |
|
|
3375 | additional extensions: |
|
|
3376 | |
|
|
3377 | =over 4 |
|
|
3378 | |
|
|
3379 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
3380 | |
|
|
3381 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
3382 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
|
|
3383 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
3384 | believed to be sufficiently portable. |
|
|
3385 | |
|
|
3386 | =item C<sigprocmask> must work in a threaded environment |
|
|
3387 | |
|
|
3388 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
3389 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
3390 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
3391 | thread" or will block signals process-wide, both behaviours would |
|
|
3392 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
3393 | C<pthread_sigmask> could complicate things, however. |
|
|
3394 | |
|
|
3395 | The most portable way to handle signals is to block signals in all threads |
|
|
3396 | except the initial one, and run the default loop in the initial thread as |
|
|
3397 | well. |
|
|
3398 | |
|
|
3399 | =item C<long> must be large enough for common memory allocation sizes |
|
|
3400 | |
|
|
3401 | To improve portability and simplify using libev, libev uses C<long> |
|
|
3402 | internally instead of C<size_t> when allocating its data structures. On |
|
|
3403 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3404 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3405 | millions of watchers. |
|
|
3406 | |
|
|
3407 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
3408 | |
|
|
3409 | The type C<double> is used to represent timestamps. It is required to |
|
|
3410 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3411 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3412 | implementations implementing IEEE 754 (basically all existing ones). |
|
|
3413 | |
|
|
3414 | =back |
|
|
3415 | |
|
|
3416 | If you know of other additional requirements drop me a note. |
|
|
3417 | |
|
|
3418 | |
|
|
3419 | =head1 COMPILER WARNINGS |
|
|
3420 | |
|
|
3421 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3422 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3423 | scared by this. |
|
|
3424 | |
|
|
3425 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3426 | has different warnings, and each user has different tastes regarding |
|
|
3427 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3428 | targeting a specific compiler and compiler-version. |
|
|
3429 | |
|
|
3430 | Another reason is that some compiler warnings require elaborate |
|
|
3431 | workarounds, or other changes to the code that make it less clear and less |
|
|
3432 | maintainable. |
|
|
3433 | |
|
|
3434 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3435 | wrong (because they don't actually warn about the condition their message |
|
|
3436 | seems to warn about). |
|
|
3437 | |
|
|
3438 | While libev is written to generate as few warnings as possible, |
|
|
3439 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3440 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3441 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3442 | warnings, not errors, or proof of bugs. |
|
|
3443 | |
|
|
3444 | |
|
|
3445 | =head1 VALGRIND |
|
|
3446 | |
|
|
3447 | Valgrind has a special section here because it is a popular tool that is |
|
|
3448 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3449 | |
|
|
3450 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3451 | in libev, then check twice: If valgrind reports something like: |
|
|
3452 | |
|
|
3453 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3454 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3455 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3456 | |
|
|
3457 | Then there is no memory leak. Similarly, under some circumstances, |
|
|
3458 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3459 | might be confused (it is a very good tool, but only a tool). |
|
|
3460 | |
|
|
3461 | If you are unsure about something, feel free to contact the mailing list |
|
|
3462 | with the full valgrind report and an explanation on why you think this is |
|
|
3463 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
|
|
3464 | no bug" answer and take the chance of learning how to interpret valgrind |
|
|
3465 | properly. |
|
|
3466 | |
|
|
3467 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3468 | I suggest using suppression lists. |
|
|
3469 | |
|
|
3470 | |
1697 | =head1 AUTHOR |
3471 | =head1 AUTHOR |
1698 | |
3472 | |
1699 | Marc Lehmann <libev@schmorp.de>. |
3473 | Marc Lehmann <libev@schmorp.de>. |
1700 | |
3474 | |