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4 | <head> |
4 | <head> |
5 | <title>libev</title> |
5 | <title>libev</title> |
6 | <meta name="description" content="Pod documentation for libev" /> |
6 | <meta name="description" content="Pod documentation for libev" /> |
7 | <meta name="inputfile" content="<standard input>" /> |
7 | <meta name="inputfile" content="<standard input>" /> |
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9 | <meta name="created" content="Mon Nov 12 08:58:02 2007" /> |
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13 | <div class="pod"> |
13 | <div class="pod"> |
14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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24 | <li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> |
24 | <li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> |
25 | <ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> |
25 | <ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> |
26 | </ul> |
26 | </ul> |
27 | </li> |
27 | </li> |
28 | <li><a href="#WATCHER_TYPES">WATCHER TYPES</a> |
28 | <li><a href="#WATCHER_TYPES">WATCHER TYPES</a> |
29 | <ul><li><a href="#struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</a></li> |
29 | <ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li> |
30 | <li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</a></li> |
30 | <li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li> |
31 | <li><a href="#ev_periodic">ev_periodic</a></li> |
31 | <li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li> |
32 | <li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</a></li> |
32 | <li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li> |
33 | <li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</a></li> |
33 | <li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> |
34 | <li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</a></li> |
34 | <li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li> |
35 | <li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li> |
35 | <li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li> |
36 | </ul> |
36 | </ul> |
37 | </li> |
37 | </li> |
38 | <li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
38 | <li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
39 | <li><a href="#AUTHOR">AUTHOR</a> |
39 | <li><a href="#AUTHOR">AUTHOR</a> |
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55 | </div> |
55 | </div> |
56 | <h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
56 | <h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
57 | <div id="DESCRIPTION_CONTENT"> |
57 | <div id="DESCRIPTION_CONTENT"> |
58 | <p>Libev is an event loop: you register interest in certain events (such as a |
58 | <p>Libev is an event loop: you register interest in certain events (such as a |
59 | file descriptor being readable or a timeout occuring), and it will manage |
59 | file descriptor being readable or a timeout occuring), and it will manage |
60 | these event sources and provide your program events.</p> |
60 | these event sources and provide your program with events.</p> |
61 | <p>To do this, it must take more or less complete control over your process |
61 | <p>To do this, it must take more or less complete control over your process |
62 | (or thread) by executing the <i>event loop</i> handler, and will then |
62 | (or thread) by executing the <i>event loop</i> handler, and will then |
63 | communicate events via a callback mechanism.</p> |
63 | communicate events via a callback mechanism.</p> |
64 | <p>You register interest in certain events by registering so-called <i>event |
64 | <p>You register interest in certain events by registering so-called <i>event |
65 | watchers</i>, which are relatively small C structures you initialise with the |
65 | watchers</i>, which are relatively small C structures you initialise with the |
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71 | <div id="FEATURES_CONTENT"> |
71 | <div id="FEATURES_CONTENT"> |
72 | <p>Libev supports select, poll, the linux-specific epoll and the bsd-specific |
72 | <p>Libev supports select, poll, the linux-specific epoll and the bsd-specific |
73 | kqueue mechanisms for file descriptor events, relative timers, absolute |
73 | kqueue mechanisms for file descriptor events, relative timers, absolute |
74 | timers with customised rescheduling, signal events, process status change |
74 | timers with customised rescheduling, signal events, process status change |
75 | events (related to SIGCHLD), and event watchers dealing with the event |
75 | events (related to SIGCHLD), and event watchers dealing with the event |
76 | loop mechanism itself (idle, prepare and check watchers).</p> |
76 | loop mechanism itself (idle, prepare and check watchers). It also is quite |
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77 | fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing |
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78 | it to libevent for example).</p> |
77 | |
79 | |
78 | </div> |
80 | </div> |
79 | <h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
81 | <h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
80 | <div id="CONVENTIONS_CONTENT"> |
82 | <div id="CONVENTIONS_CONTENT"> |
81 | <p>Libev is very configurable. In this manual the default configuration |
83 | <p>Libev is very configurable. In this manual the default configuration |
82 | will be described, which supports multiple event loops. For more info |
84 | will be described, which supports multiple event loops. For more info |
83 | about various configuraiton options please have a look at the file |
85 | about various configuration options please have a look at the file |
84 | <cite>README.embed</cite> in the libev distribution. If libev was configured without |
86 | <cite>README.embed</cite> in the libev distribution. If libev was configured without |
85 | support for multiple event loops, then all functions taking an initial |
87 | support for multiple event loops, then all functions taking an initial |
86 | argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) |
88 | argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) |
87 | will not have this argument.</p> |
89 | will not have this argument.</p> |
88 | |
90 | |
89 | </div> |
91 | </div> |
90 | <h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
92 | <h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
91 | <div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> |
93 | <div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> |
92 | <p>Libev represents time as a single floating point number. This type is |
94 | <p>Libev represents time as a single floating point number, representing the |
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95 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
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96 | the beginning of 1970, details are complicated, don't ask). This type is |
93 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
97 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
94 | to the double type in C.</p> |
98 | to the double type in C.</p> |
95 | <dl> |
99 | <dl> |
96 | <dt>ev_tstamp ev_time ()</dt> |
100 | <dt>ev_tstamp ev_time ()</dt> |
97 | <dd> |
101 | <dd> |
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103 | <p>You can find out the major and minor version numbers of the library |
107 | <p>You can find out the major and minor version numbers of the library |
104 | you linked against by calling the functions <code>ev_version_major</code> and |
108 | you linked against by calling the functions <code>ev_version_major</code> and |
105 | <code>ev_version_minor</code>. If you want, you can compare against the global |
109 | <code>ev_version_minor</code>. If you want, you can compare against the global |
106 | symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the |
110 | symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the |
107 | version of the library your program was compiled against.</p> |
111 | version of the library your program was compiled against.</p> |
108 | <p>Usually, its a good idea to terminate if the major versions mismatch, |
112 | <p>Usually, it's a good idea to terminate if the major versions mismatch, |
109 | as this indicates an incompatible change. Minor versions are usually |
113 | as this indicates an incompatible change. Minor versions are usually |
110 | compatible to older versions, so a larger minor version alone is usually |
114 | compatible to older versions, so a larger minor version alone is usually |
111 | not a problem.</p> |
115 | not a problem.</p> |
112 | </dd> |
116 | </dd> |
113 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
117 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
114 | <dd> |
118 | <dd> |
115 | <p>Sets the allocation function to use (the prototype is similar to the |
119 | <p>Sets the allocation function to use (the prototype is similar to the |
116 | realloc function). It is used to allocate and free memory (no surprises |
120 | realloc C function, the semantics are identical). It is used to allocate |
117 | here). If it returns zero when memory needs to be allocated, the library |
121 | and free memory (no surprises here). If it returns zero when memory |
118 | might abort or take some potentially destructive action. The default is |
122 | needs to be allocated, the library might abort or take some potentially |
119 | your system realloc function.</p> |
123 | destructive action. The default is your system realloc function.</p> |
120 | <p>You could override this function in high-availability programs to, say, |
124 | <p>You could override this function in high-availability programs to, say, |
121 | free some memory if it cannot allocate memory, to use a special allocator, |
125 | free some memory if it cannot allocate memory, to use a special allocator, |
122 | or even to sleep a while and retry until some memory is available.</p> |
126 | or even to sleep a while and retry until some memory is available.</p> |
123 | </dd> |
127 | </dd> |
124 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
128 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
125 | <dd> |
129 | <dd> |
126 | <p>Set the callback function to call on a retryable syscall error (such |
130 | <p>Set the callback function to call on a retryable syscall error (such |
127 | as failed select, poll, epoll_wait). The message is a printable string |
131 | as failed select, poll, epoll_wait). The message is a printable string |
128 | indicating the system call or subsystem causing the problem. If this |
132 | indicating the system call or subsystem causing the problem. If this |
129 | callback is set, then libev will expect it to remedy the sitution, no |
133 | callback is set, then libev will expect it to remedy the sitution, no |
130 | matter what, when it returns. That is, libev will geenrally retry the |
134 | matter what, when it returns. That is, libev will generally retry the |
131 | requested operation, or, if the condition doesn't go away, do bad stuff |
135 | requested operation, or, if the condition doesn't go away, do bad stuff |
132 | (such as abort).</p> |
136 | (such as abort).</p> |
133 | </dd> |
137 | </dd> |
134 | </dl> |
138 | </dl> |
135 | |
139 | |
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139 | <p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two |
143 | <p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two |
140 | types of such loops, the <i>default</i> loop, which supports signals and child |
144 | types of such loops, the <i>default</i> loop, which supports signals and child |
141 | events, and dynamically created loops which do not.</p> |
145 | events, and dynamically created loops which do not.</p> |
142 | <p>If you use threads, a common model is to run the default event loop |
146 | <p>If you use threads, a common model is to run the default event loop |
143 | in your main thread (or in a separate thrad) and for each thread you |
147 | in your main thread (or in a separate thrad) and for each thread you |
144 | create, you also create another event loop. Libev itself does no lockign |
148 | create, you also create another event loop. Libev itself does no locking |
145 | whatsoever, so if you mix calls to different event loops, make sure you |
149 | whatsoever, so if you mix calls to the same event loop in different |
146 | lock (this is usually a bad idea, though, even if done right).</p> |
150 | threads, make sure you lock (this is usually a bad idea, though, even if |
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151 | done correctly, because it's hideous and inefficient).</p> |
147 | <dl> |
152 | <dl> |
148 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
153 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
149 | <dd> |
154 | <dd> |
150 | <p>This will initialise the default event loop if it hasn't been initialised |
155 | <p>This will initialise the default event loop if it hasn't been initialised |
151 | yet and return it. If the default loop could not be initialised, returns |
156 | yet and return it. If the default loop could not be initialised, returns |
152 | false. If it already was initialised it simply returns it (and ignores the |
157 | false. If it already was initialised it simply returns it (and ignores the |
153 | flags).</p> |
158 | flags).</p> |
154 | <p>If you don't know what event loop to use, use the one returned from this |
159 | <p>If you don't know what event loop to use, use the one returned from this |
155 | function.</p> |
160 | function.</p> |
156 | <p>The flags argument can be used to specify special behaviour or specific |
161 | <p>The flags argument can be used to specify special behaviour or specific |
157 | backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p> |
162 | backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> |
158 | <p>It supports the following flags:</p> |
163 | <p>It supports the following flags:</p> |
159 | <p> |
164 | <p> |
160 | <dl> |
165 | <dl> |
161 | <dt>EVFLAG_AUTO</dt> |
166 | <dt><code>EVFLAG_AUTO</code></dt> |
162 | <dd> |
167 | <dd> |
163 | <p>The default flags value. Use this if you have no clue (its the right |
168 | <p>The default flags value. Use this if you have no clue (it's the right |
164 | thing, believe me).</p> |
169 | thing, believe me).</p> |
165 | </dd> |
170 | </dd> |
166 | <dt>EVFLAG_NOENV</dt> |
171 | <dt><code>EVFLAG_NOENV</code></dt> |
167 | <dd> |
172 | <dd> |
168 | <p>If this flag bit is ored into the flag value then libev will <i>not</i> look |
173 | <p>If this flag bit is ored into the flag value (or the program runs setuid |
169 | at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this |
174 | or setgid) then libev will <i>not</i> look at the environment variable |
170 | environment variable will override the flags completely. This is useful |
175 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
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176 | override the flags completely if it is found in the environment. This is |
171 | to try out specific backends to tets their performance, or to work around |
177 | useful to try out specific backends to test their performance, or to work |
172 | bugs.</p> |
178 | around bugs.</p> |
173 | </dd> |
179 | </dd> |
174 | <dt>EVMETHOD_SELECT portable select backend</dt> |
180 | <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt> |
175 | <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> |
181 | <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt> |
176 | <dt>EVMETHOD_EPOLL linux only</dt> |
182 | <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt> |
177 | <dt>EVMETHOD_KQUEUE some bsds only</dt> |
183 | <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt> |
178 | <dt>EVMETHOD_DEVPOLL solaris 8 only</dt> |
184 | <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt> |
179 | <dt>EVMETHOD_PORT solaris 10 only</dt> |
185 | <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt> |
180 | <dd> |
186 | <dd> |
181 | <p>If one or more of these are ored into the flags value, then only these |
187 | <p>If one or more of these are ored into the flags value, then only these |
182 | backends will be tried (in the reverse order as given here). If one are |
188 | backends will be tried (in the reverse order as given here). If one are |
183 | specified, any backend will do.</p> |
189 | specified, any backend will do.</p> |
184 | </dd> |
190 | </dd> |
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194 | </dd> |
200 | </dd> |
195 | <dt>ev_default_destroy ()</dt> |
201 | <dt>ev_default_destroy ()</dt> |
196 | <dd> |
202 | <dd> |
197 | <p>Destroys the default loop again (frees all memory and kernel state |
203 | <p>Destroys the default loop again (frees all memory and kernel state |
198 | etc.). This stops all registered event watchers (by not touching them in |
204 | etc.). This stops all registered event watchers (by not touching them in |
199 | any way whatsoever, although you cnanot rely on this :).</p> |
205 | any way whatsoever, although you cannot rely on this :).</p> |
200 | </dd> |
206 | </dd> |
201 | <dt>ev_loop_destroy (loop)</dt> |
207 | <dt>ev_loop_destroy (loop)</dt> |
202 | <dd> |
208 | <dd> |
203 | <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an |
209 | <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an |
204 | earlier call to <code>ev_loop_new</code>.</p> |
210 | earlier call to <code>ev_loop_new</code>.</p> |
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210 | after forking, in either the parent or child process (or both, but that |
216 | after forking, in either the parent or child process (or both, but that |
211 | again makes little sense).</p> |
217 | again makes little sense).</p> |
212 | <p>You <i>must</i> call this function after forking if and only if you want to |
218 | <p>You <i>must</i> call this function after forking if and only if you want to |
213 | use the event library in both processes. If you just fork+exec, you don't |
219 | use the event library in both processes. If you just fork+exec, you don't |
214 | have to call it.</p> |
220 | have to call it.</p> |
215 | <p>The function itself is quite fast and its usually not a problem to call |
221 | <p>The function itself is quite fast and it's usually not a problem to call |
216 | it just in case after a fork. To make this easy, the function will fit in |
222 | it just in case after a fork. To make this easy, the function will fit in |
217 | quite nicely into a call to <code>pthread_atfork</code>:</p> |
223 | quite nicely into a call to <code>pthread_atfork</code>:</p> |
218 | <pre> pthread_atfork (0, 0, ev_default_fork); |
224 | <pre> pthread_atfork (0, 0, ev_default_fork); |
219 | |
225 | |
220 | </pre> |
226 | </pre> |
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228 | <dt>unsigned int ev_method (loop)</dt> |
234 | <dt>unsigned int ev_method (loop)</dt> |
229 | <dd> |
235 | <dd> |
230 | <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in |
236 | <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in |
231 | use.</p> |
237 | use.</p> |
232 | </dd> |
238 | </dd> |
233 | <dt>ev_tstamp = ev_now (loop)</dt> |
239 | <dt>ev_tstamp ev_now (loop)</dt> |
234 | <dd> |
240 | <dd> |
235 | <p>Returns the current "event loop time", which is the time the event loop |
241 | <p>Returns the current "event loop time", which is the time the event loop |
236 | got events and started processing them. This timestamp does not change |
242 | got events and started processing them. This timestamp does not change |
237 | as long as callbacks are being processed, and this is also the base time |
243 | as long as callbacks are being processed, and this is also the base time |
238 | used for relative timers. You can treat it as the timestamp of the event |
244 | used for relative timers. You can treat it as the timestamp of the event |
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245 | events.</p> |
251 | events.</p> |
246 | <p>If the flags argument is specified as 0, it will not return until either |
252 | <p>If the flags argument is specified as 0, it will not return until either |
247 | no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
253 | no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
248 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
254 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
249 | those events and any outstanding ones, but will not block your process in |
255 | those events and any outstanding ones, but will not block your process in |
250 | case there are no events.</p> |
256 | case there are no events and will return after one iteration of the loop.</p> |
251 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
257 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
252 | neccessary) and will handle those and any outstanding ones. It will block |
258 | neccessary) and will handle those and any outstanding ones. It will block |
253 | your process until at least one new event arrives.</p> |
259 | your process until at least one new event arrives, and will return after |
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260 | one iteration of the loop.</p> |
254 | <p>This flags value could be used to implement alternative looping |
261 | <p>This flags value could be used to implement alternative looping |
255 | constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and |
262 | constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and |
256 | more generic mechanism.</p> |
263 | more generic mechanism.</p> |
257 | </dd> |
264 | </dd> |
258 | <dt>ev_unloop (loop, how)</dt> |
265 | <dt>ev_unloop (loop, how)</dt> |
259 | <dd> |
266 | <dd> |
260 | <p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument |
267 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
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268 | has processed all outstanding events). The <code>how</code> argument must be either |
261 | must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> |
269 | <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or |
262 | call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> |
270 | <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
263 | calls return.</p> |
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264 | </dd> |
271 | </dd> |
265 | <dt>ev_ref (loop)</dt> |
272 | <dt>ev_ref (loop)</dt> |
266 | <dt>ev_unref (loop)</dt> |
273 | <dt>ev_unref (loop)</dt> |
267 | <dd> |
274 | <dd> |
268 | <p>Ref/unref can be used to add or remove a refcount on the event loop: Every |
275 | <p>Ref/unref can be used to add or remove a reference count on the event |
269 | watcher keeps one reference. If you have a long-runing watcher you never |
276 | loop: Every watcher keeps one reference, and as long as the reference |
270 | unregister that should not keep ev_loop from running, ev_unref() after |
277 | count is nonzero, <code>ev_loop</code> will not return on its own. If you have |
271 | starting, and ev_ref() before stopping it. Libev itself uses this for |
278 | a watcher you never unregister that should not keep <code>ev_loop</code> from |
272 | example for its internal signal pipe: It is not visible to you as a user |
279 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
273 | and should not keep <code>ev_loop</code> from exiting if the work is done. It is |
280 | example, libev itself uses this for its internal signal pipe: It is not |
274 | also an excellent way to do this for generic recurring timers or from |
281 | visible to the libev user and should not keep <code>ev_loop</code> from exiting if |
275 | within third-party libraries. Just remember to unref after start and ref |
282 | no event watchers registered by it are active. It is also an excellent |
276 | before stop.</p> |
283 | way to do this for generic recurring timers or from within third-party |
|
|
284 | libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> |
277 | </dd> |
285 | </dd> |
278 | </dl> |
286 | </dl> |
279 | |
287 | |
280 | </div> |
288 | </div> |
281 | <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> |
289 | <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> |
282 | <div id="ANATOMY_OF_A_WATCHER_CONTENT"> |
290 | <div id="ANATOMY_OF_A_WATCHER_CONTENT"> |
283 | <p>A watcher is a structure that you create and register to record your |
291 | <p>A watcher is a structure that you create and register to record your |
284 | interest in some event. For instance, if you want to wait for STDIN to |
292 | interest in some event. For instance, if you want to wait for STDIN to |
285 | become readable, you would create an ev_io watcher for that:</p> |
293 | become readable, you would create an <code>ev_io</code> watcher for that:</p> |
286 | <pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
294 | <pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
287 | { |
295 | { |
288 | ev_io_stop (w); |
296 | ev_io_stop (w); |
289 | ev_unloop (loop, EVUNLOOP_ALL); |
297 | ev_unloop (loop, EVUNLOOP_ALL); |
290 | } |
298 | } |
… | |
… | |
314 | *)</code>), and you can stop watching for events at any time by calling the |
322 | *)</code>), and you can stop watching for events at any time by calling the |
315 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
323 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
316 | <p>As long as your watcher is active (has been started but not stopped) you |
324 | <p>As long as your watcher is active (has been started but not stopped) you |
317 | must not touch the values stored in it. Most specifically you must never |
325 | must not touch the values stored in it. Most specifically you must never |
318 | reinitialise it or call its set method.</p> |
326 | reinitialise it or call its set method.</p> |
319 | <p>You cna check wether an event is active by calling the <code>ev_is_active |
327 | <p>You can check whether an event is active by calling the <code>ev_is_active |
320 | (watcher *)</code> macro. To see wether an event is outstanding (but the |
328 | (watcher *)</code> macro. To see whether an event is outstanding (but the |
321 | callback for it has not been called yet) you cna use the <code>ev_is_pending |
329 | callback for it has not been called yet) you can use the <code>ev_is_pending |
322 | (watcher *)</code> macro.</p> |
330 | (watcher *)</code> macro.</p> |
323 | <p>Each and every callback receives the event loop pointer as first, the |
331 | <p>Each and every callback receives the event loop pointer as first, the |
324 | registered watcher structure as second, and a bitset of received events as |
332 | registered watcher structure as second, and a bitset of received events as |
325 | third argument.</p> |
333 | third argument.</p> |
326 | <p>The rceeived events usually include a single bit per event type received |
334 | <p>The received events usually include a single bit per event type received |
327 | (you can receive multiple events at the same time). The possible bit masks |
335 | (you can receive multiple events at the same time). The possible bit masks |
328 | are:</p> |
336 | are:</p> |
329 | <dl> |
337 | <dl> |
330 | <dt>EV_READ</dt> |
338 | <dt><code>EV_READ</code></dt> |
331 | <dt>EV_WRITE</dt> |
339 | <dt><code>EV_WRITE</code></dt> |
332 | <dd> |
340 | <dd> |
333 | <p>The file descriptor in the ev_io watcher has become readable and/or |
341 | <p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or |
334 | writable.</p> |
342 | writable.</p> |
335 | </dd> |
343 | </dd> |
336 | <dt>EV_TIMEOUT</dt> |
344 | <dt><code>EV_TIMEOUT</code></dt> |
337 | <dd> |
|
|
338 | <p>The ev_timer watcher has timed out.</p> |
|
|
339 | </dd> |
345 | <dd> |
340 | <dt>EV_PERIODIC</dt> |
346 | <p>The <code>ev_timer</code> watcher has timed out.</p> |
341 | <dd> |
347 | </dd> |
342 | <p>The ev_periodic watcher has timed out.</p> |
348 | <dt><code>EV_PERIODIC</code></dt> |
343 | </dd> |
349 | <dd> |
344 | <dt>EV_SIGNAL</dt> |
350 | <p>The <code>ev_periodic</code> watcher has timed out.</p> |
345 | <dd> |
351 | </dd> |
|
|
352 | <dt><code>EV_SIGNAL</code></dt> |
|
|
353 | <dd> |
346 | <p>The signal specified in the ev_signal watcher has been received by a thread.</p> |
354 | <p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p> |
347 | </dd> |
|
|
348 | <dt>EV_CHILD</dt> |
|
|
349 | <dd> |
355 | </dd> |
|
|
356 | <dt><code>EV_CHILD</code></dt> |
|
|
357 | <dd> |
350 | <p>The pid specified in the ev_child watcher has received a status change.</p> |
358 | <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> |
351 | </dd> |
|
|
352 | <dt>EV_IDLE</dt> |
|
|
353 | <dd> |
359 | </dd> |
|
|
360 | <dt><code>EV_IDLE</code></dt> |
|
|
361 | <dd> |
354 | <p>The ev_idle watcher has determined that you have nothing better to do.</p> |
362 | <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> |
355 | </dd> |
|
|
356 | <dt>EV_PREPARE</dt> |
|
|
357 | <dt>EV_CHECK</dt> |
|
|
358 | <dd> |
363 | </dd> |
|
|
364 | <dt><code>EV_PREPARE</code></dt> |
|
|
365 | <dt><code>EV_CHECK</code></dt> |
|
|
366 | <dd> |
359 | <p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts |
367 | <p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts |
360 | to gather new events, and all ev_check watchers are invoked just after |
368 | to gather new events, and all <code>ev_check</code> watchers are invoked just after |
361 | <code>ev_loop</code> has gathered them, but before it invokes any callbacks for any |
369 | <code>ev_loop</code> has gathered them, but before it invokes any callbacks for any |
362 | received events. Callbacks of both watcher types can start and stop as |
370 | received events. Callbacks of both watcher types can start and stop as |
363 | many watchers as they want, and all of them will be taken into account |
371 | many watchers as they want, and all of them will be taken into account |
364 | (for example, a ev_prepare watcher might start an idle watcher to keep |
372 | (for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep |
365 | <code>ev_loop</code> from blocking).</p> |
373 | <code>ev_loop</code> from blocking).</p> |
366 | </dd> |
374 | </dd> |
367 | <dt>EV_ERROR</dt> |
375 | <dt><code>EV_ERROR</code></dt> |
368 | <dd> |
376 | <dd> |
369 | <p>An unspecified error has occured, the watcher has been stopped. This might |
377 | <p>An unspecified error has occured, the watcher has been stopped. This might |
370 | happen because the watcher could not be properly started because libev |
378 | happen because the watcher could not be properly started because libev |
371 | ran out of memory, a file descriptor was found to be closed or any other |
379 | ran out of memory, a file descriptor was found to be closed or any other |
372 | problem. You best act on it by reporting the problem and somehow coping |
380 | problem. You best act on it by reporting the problem and somehow coping |
… | |
… | |
381 | |
389 | |
382 | </div> |
390 | </div> |
383 | <h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> |
391 | <h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> |
384 | <div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> |
392 | <div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> |
385 | <p>Each watcher has, by default, a member <code>void *data</code> that you can change |
393 | <p>Each watcher has, by default, a member <code>void *data</code> that you can change |
386 | and read at any time, libev will completely ignore it. This cna be used |
394 | and read at any time, libev will completely ignore it. This can be used |
387 | to associate arbitrary data with your watcher. If you need more data and |
395 | to associate arbitrary data with your watcher. If you need more data and |
388 | don't want to allocate memory and store a pointer to it in that data |
396 | don't want to allocate memory and store a pointer to it in that data |
389 | member, you can also "subclass" the watcher type and provide your own |
397 | member, you can also "subclass" the watcher type and provide your own |
390 | data:</p> |
398 | data:</p> |
391 | <pre> struct my_io |
399 | <pre> struct my_io |
… | |
… | |
418 | <div id="WATCHER_TYPES_CONTENT"> |
426 | <div id="WATCHER_TYPES_CONTENT"> |
419 | <p>This section describes each watcher in detail, but will not repeat |
427 | <p>This section describes each watcher in detail, but will not repeat |
420 | information given in the last section.</p> |
428 | information given in the last section.</p> |
421 | |
429 | |
422 | </div> |
430 | </div> |
423 | <h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> |
431 | <h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> |
424 | <div id="struct_ev_io_is_my_file_descriptor_r-2"> |
432 | <div id="code_ev_io_code_is_this_file_descrip-2"> |
425 | <p>I/O watchers check wether a file descriptor is readable or writable |
433 | <p>I/O watchers check whether a file descriptor is readable or writable |
426 | in each iteration of the event loop (This behaviour is called |
434 | in each iteration of the event loop (This behaviour is called |
427 | level-triggering because you keep receiving events as long as the |
435 | level-triggering because you keep receiving events as long as the |
428 | condition persists. Remember you cna stop the watcher if you don't want to |
436 | condition persists. Remember you can stop the watcher if you don't want to |
429 | act on the event and neither want to receive future events).</p> |
437 | act on the event and neither want to receive future events).</p> |
|
|
438 | <p>In general you can register as many read and/or write event watchers oer |
|
|
439 | fd as you want (as long as you don't confuse yourself). Setting all file |
|
|
440 | descriptors to non-blocking mode is also usually a good idea (but not |
|
|
441 | required if you know what you are doing).</p> |
|
|
442 | <p>You have to be careful with dup'ed file descriptors, though. Some backends |
|
|
443 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
|
|
444 | descriptors correctly if you register interest in two or more fds pointing |
|
|
445 | to the same file/socket etc. description.</p> |
|
|
446 | <p>If you must do this, then force the use of a known-to-be-good backend |
|
|
447 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
|
|
448 | EVMETHOD_POLL).</p> |
430 | <dl> |
449 | <dl> |
431 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
450 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
432 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
451 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
433 | <dd> |
452 | <dd> |
434 | <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive |
453 | <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive |
435 | events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | |
454 | events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | |
436 | EV_WRITE</code> to receive the given events.</p> |
455 | EV_WRITE</code> to receive the given events.</p> |
437 | </dd> |
456 | </dd> |
438 | </dl> |
457 | </dl> |
439 | |
458 | |
440 | </div> |
459 | </div> |
441 | <h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2> |
460 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
442 | <div id="struct_ev_timer_relative_and_optiona-2"> |
461 | <div id="code_ev_timer_code_relative_and_opti-2"> |
443 | <p>Timer watchers are simple relative timers that generate an event after a |
462 | <p>Timer watchers are simple relative timers that generate an event after a |
444 | given time, and optionally repeating in regular intervals after that.</p> |
463 | given time, and optionally repeating in regular intervals after that.</p> |
445 | <p>The timers are based on real time, that is, if you register an event that |
464 | <p>The timers are based on real time, that is, if you register an event that |
446 | times out after an hour and youreset your system clock to last years |
465 | times out after an hour and youreset your system clock to last years |
447 | time, it will still time out after (roughly) and hour. "Roughly" because |
466 | time, it will still time out after (roughly) and hour. "Roughly" because |
448 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
467 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
449 | monotonic clock option helps a lot here).</p> |
468 | monotonic clock option helps a lot here).</p> |
|
|
469 | <p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
|
|
470 | time. This is usually the right thing as this timestamp refers to the time |
|
|
471 | of the event triggering whatever timeout you are modifying/starting. If |
|
|
472 | you suspect event processing to be delayed and you *need* to base the timeout |
|
|
473 | ion the current time, use something like this to adjust for this:</p> |
|
|
474 | <pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
|
|
475 | |
|
|
476 | </pre> |
450 | <dl> |
477 | <dl> |
451 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
478 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
452 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
479 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
453 | <dd> |
480 | <dd> |
454 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
481 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
… | |
… | |
470 | value), or reset the running timer to the repeat value.</p> |
497 | value), or reset the running timer to the repeat value.</p> |
471 | <p>This sounds a bit complicated, but here is a useful and typical |
498 | <p>This sounds a bit complicated, but here is a useful and typical |
472 | example: Imagine you have a tcp connection and you want a so-called idle |
499 | example: Imagine you have a tcp connection and you want a so-called idle |
473 | timeout, that is, you want to be called when there have been, say, 60 |
500 | timeout, that is, you want to be called when there have been, say, 60 |
474 | seconds of inactivity on the socket. The easiest way to do this is to |
501 | seconds of inactivity on the socket. The easiest way to do this is to |
475 | configure an ev_timer with after=repeat=60 and calling ev_timer_again each |
502 | configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each |
476 | time you successfully read or write some data. If you go into an idle |
503 | time you successfully read or write some data. If you go into an idle |
477 | state where you do not expect data to travel on the socket, you can stop |
504 | state where you do not expect data to travel on the socket, you can stop |
478 | the timer, and again will automatically restart it if need be.</p> |
505 | the timer, and again will automatically restart it if need be.</p> |
479 | </dd> |
506 | </dd> |
480 | </dl> |
507 | </dl> |
481 | |
508 | |
482 | </div> |
509 | </div> |
483 | <h2 id="ev_periodic">ev_periodic</h2> |
510 | <h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> |
484 | <div id="ev_periodic_CONTENT"> |
511 | <div id="code_ev_periodic_code_to_cron_or_not-2"> |
485 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
512 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
486 | (and unfortunately a bit complex).</p> |
513 | (and unfortunately a bit complex).</p> |
487 | <p>Unlike ev_timer's, they are not based on real time (or relative time) |
514 | <p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) |
488 | but on wallclock time (absolute time). You can tell a periodic watcher |
515 | but on wallclock time (absolute time). You can tell a periodic watcher |
489 | to trigger "at" some specific point in time. For example, if you tell a |
516 | to trigger "at" some specific point in time. For example, if you tell a |
490 | periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () |
517 | periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () |
491 | + 10.>) and then reset your system clock to the last year, then it will |
518 | + 10.>) and then reset your system clock to the last year, then it will |
492 | take a year to trigger the event (unlike an ev_timer, which would trigger |
519 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
493 | roughly 10 seconds later and of course not if you reset your system time |
520 | roughly 10 seconds later and of course not if you reset your system time |
494 | again).</p> |
521 | again).</p> |
495 | <p>They can also be used to implement vastly more complex timers, such as |
522 | <p>They can also be used to implement vastly more complex timers, such as |
496 | triggering an event on eahc midnight, local time.</p> |
523 | triggering an event on eahc midnight, local time.</p> |
497 | <dl> |
524 | <dl> |
… | |
… | |
523 | <pre> ev_periodic_set (&periodic, 0., 3600., 0); |
550 | <pre> ev_periodic_set (&periodic, 0., 3600., 0); |
524 | |
551 | |
525 | </pre> |
552 | </pre> |
526 | <p>This doesn't mean there will always be 3600 seconds in between triggers, |
553 | <p>This doesn't mean there will always be 3600 seconds in between triggers, |
527 | but only that the the callback will be called when the system time shows a |
554 | but only that the the callback will be called when the system time shows a |
528 | full hour (UTC), or more correct, when the system time is evenly divisible |
555 | full hour (UTC), or more correctly, when the system time is evenly divisible |
529 | by 3600.</p> |
556 | by 3600.</p> |
530 | <p>Another way to think about it (for the mathematically inclined) is that |
557 | <p>Another way to think about it (for the mathematically inclined) is that |
531 | ev_periodic will try to run the callback in this mode at the next possible |
558 | <code>ev_periodic</code> will try to run the callback in this mode at the next possible |
532 | time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
559 | time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
533 | </dd> |
560 | </dd> |
534 | <dt>* manual reschedule mode (reschedule_cb = callback)</dt> |
561 | <dt>* manual reschedule mode (reschedule_cb = callback)</dt> |
535 | <dd> |
562 | <dd> |
536 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
563 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
537 | ignored. Instead, each time the periodic watcher gets scheduled, the |
564 | ignored. Instead, each time the periodic watcher gets scheduled, the |
538 | reschedule callback will be called with the watcher as first, and the |
565 | reschedule callback will be called with the watcher as first, and the |
539 | current time as second argument.</p> |
566 | current time as second argument.</p> |
540 | <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other |
567 | <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other |
541 | periodic watcher, ever, or make any event loop modificstions</i>. If you need |
568 | periodic watcher, ever, or make any event loop modifications</i>. If you need |
542 | to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> |
569 | to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p> |
|
|
570 | <p>Also, <i>this callback must always return a time that is later than the |
|
|
571 | passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p> |
543 | <p>Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
572 | <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
544 | ev_tstamp now)>, e.g.:</p> |
573 | ev_tstamp now)</code>, e.g.:</p> |
545 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
574 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
546 | { |
575 | { |
547 | return now + 60.; |
576 | return now + 60.; |
548 | } |
577 | } |
549 | |
578 | |
… | |
… | |
568 | program when the crontabs have changed).</p> |
597 | program when the crontabs have changed).</p> |
569 | </dd> |
598 | </dd> |
570 | </dl> |
599 | </dl> |
571 | |
600 | |
572 | </div> |
601 | </div> |
573 | <h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> |
602 | <h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> |
574 | <div id="ev_signal_signal_me_when_a_signal_ge-2"> |
603 | <div id="code_ev_signal_code_signal_me_when_a-2"> |
575 | <p>Signal watchers will trigger an event when the process receives a specific |
604 | <p>Signal watchers will trigger an event when the process receives a specific |
576 | signal one or more times. Even though signals are very asynchronous, libev |
605 | signal one or more times. Even though signals are very asynchronous, libev |
577 | will try its best to deliver signals synchronously, i.e. as part of the |
606 | will try it's best to deliver signals synchronously, i.e. as part of the |
578 | normal event processing, like any other event.</p> |
607 | normal event processing, like any other event.</p> |
579 | <p>You cna configure as many watchers as you like per signal. Only when the |
608 | <p>You can configure as many watchers as you like per signal. Only when the |
580 | first watcher gets started will libev actually register a signal watcher |
609 | first watcher gets started will libev actually register a signal watcher |
581 | with the kernel (thus it coexists with your own signal handlers as long |
610 | with the kernel (thus it coexists with your own signal handlers as long |
582 | as you don't register any with libev). Similarly, when the last signal |
611 | as you don't register any with libev). Similarly, when the last signal |
583 | watcher for a signal is stopped libev will reset the signal handler to |
612 | watcher for a signal is stopped libev will reset the signal handler to |
584 | SIG_DFL (regardless of what it was set to before).</p> |
613 | SIG_DFL (regardless of what it was set to before).</p> |
… | |
… | |
590 | of the <code>SIGxxx</code> constants).</p> |
619 | of the <code>SIGxxx</code> constants).</p> |
591 | </dd> |
620 | </dd> |
592 | </dl> |
621 | </dl> |
593 | |
622 | |
594 | </div> |
623 | </div> |
595 | <h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> |
624 | <h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> |
596 | <div id="ev_child_wait_for_pid_status_changes-2"> |
625 | <div id="code_ev_child_code_wait_for_pid_stat-2"> |
597 | <p>Child watchers trigger when your process receives a SIGCHLD in response to |
626 | <p>Child watchers trigger when your process receives a SIGCHLD in response to |
598 | some child status changes (most typically when a child of yours dies).</p> |
627 | some child status changes (most typically when a child of yours dies).</p> |
599 | <dl> |
628 | <dl> |
600 | <dt>ev_child_init (ev_child *, callback, int pid)</dt> |
629 | <dt>ev_child_init (ev_child *, callback, int pid)</dt> |
601 | <dt>ev_child_set (ev_child *, int pid)</dt> |
630 | <dt>ev_child_set (ev_child *, int pid)</dt> |
602 | <dd> |
631 | <dd> |
603 | <p>Configures the watcher to wait for status changes of process <code>pid</code> (or |
632 | <p>Configures the watcher to wait for status changes of process <code>pid</code> (or |
604 | <i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look |
633 | <i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look |
605 | at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see |
634 | at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see |
606 | the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member |
635 | the status word (use the macros from <code>sys/wait.h</code> and see your systems |
|
|
636 | <code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the |
607 | contains the pid of the process causing the status change.</p> |
637 | process causing the status change.</p> |
608 | </dd> |
638 | </dd> |
609 | </dl> |
639 | </dl> |
610 | |
640 | |
611 | </div> |
641 | </div> |
612 | <h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> |
642 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> |
613 | <div id="ev_idle_when_you_ve_got_nothing_bett-2"> |
643 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
614 | <p>Idle watchers trigger events when there are no other I/O or timer (or |
644 | <p>Idle watchers trigger events when there are no other events are pending |
615 | periodic) events pending. That is, as long as your process is busy |
645 | (prepare, check and other idle watchers do not count). That is, as long |
616 | handling sockets or timeouts it will not be called. But when your process |
646 | as your process is busy handling sockets or timeouts (or even signals, |
617 | is idle all idle watchers are being called again and again - until |
647 | imagine) it will not be triggered. But when your process is idle all idle |
|
|
648 | watchers are being called again and again, once per event loop iteration - |
618 | stopped, that is, or your process receives more events.</p> |
649 | until stopped, that is, or your process receives more events and becomes |
|
|
650 | busy.</p> |
619 | <p>The most noteworthy effect is that as long as any idle watchers are |
651 | <p>The most noteworthy effect is that as long as any idle watchers are |
620 | active, the process will not block when waiting for new events.</p> |
652 | active, the process will not block when waiting for new events.</p> |
621 | <p>Apart from keeping your process non-blocking (which is a useful |
653 | <p>Apart from keeping your process non-blocking (which is a useful |
622 | effect on its own sometimes), idle watchers are a good place to do |
654 | effect on its own sometimes), idle watchers are a good place to do |
623 | "pseudo-background processing", or delay processing stuff to after the |
655 | "pseudo-background processing", or delay processing stuff to after the |
… | |
… | |
632 | </dl> |
664 | </dl> |
633 | |
665 | |
634 | </div> |
666 | </div> |
635 | <h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> |
667 | <h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> |
636 | <div id="prepare_and_check_your_hooks_into_th-2"> |
668 | <div id="prepare_and_check_your_hooks_into_th-2"> |
637 | <p>Prepare and check watchers usually (but not always) are used in |
669 | <p>Prepare and check watchers are usually (but not always) used in tandem: |
638 | tandom. Prepare watchers get invoked before the process blocks and check |
670 | Prepare watchers get invoked before the process blocks and check watchers |
639 | watchers afterwards.</p> |
671 | afterwards.</p> |
640 | <p>Their main purpose is to integrate other event mechanisms into libev. This |
672 | <p>Their main purpose is to integrate other event mechanisms into libev. This |
641 | could be used, for example, to track variable changes, implement your own |
673 | could be used, for example, to track variable changes, implement your own |
642 | watchers, integrate net-snmp or a coroutine library and lots more.</p> |
674 | watchers, integrate net-snmp or a coroutine library and lots more.</p> |
643 | <p>This is done by examining in each prepare call which file descriptors need |
675 | <p>This is done by examining in each prepare call which file descriptors need |
644 | to be watched by the other library, registering ev_io watchers for them |
676 | to be watched by the other library, registering <code>ev_io</code> watchers for |
645 | and starting an ev_timer watcher for any timeouts (many libraries provide |
677 | them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries |
646 | just this functionality). Then, in the check watcher you check for any |
678 | provide just this functionality). Then, in the check watcher you check for |
647 | events that occured (by making your callbacks set soem flags for example) |
679 | any events that occured (by checking the pending status of all watchers |
648 | and call back into the library.</p> |
680 | and stopping them) and call back into the library. The I/O and timer |
|
|
681 | callbacks will never actually be called (but must be valid neverthelles, |
|
|
682 | because you never know, you know?).</p> |
649 | <p>As another example, the perl Coro module uses these hooks to integrate |
683 | <p>As another example, the Perl Coro module uses these hooks to integrate |
650 | coroutines into libev programs, by yielding to other active coroutines |
684 | coroutines into libev programs, by yielding to other active coroutines |
651 | during each prepare and only letting the process block if no coroutines |
685 | during each prepare and only letting the process block if no coroutines |
652 | are ready to run.</p> |
686 | are ready to run (its actually more complicated, it only runs coroutines |
|
|
687 | with priority higher than the event loop and one lower priority once, |
|
|
688 | using idle watchers to keep the event loop from blocking if lower-priority |
|
|
689 | coroutines exist, thus mapping low-priority coroutines to idle/background |
|
|
690 | tasks).</p> |
653 | <dl> |
691 | <dl> |
654 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
692 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
655 | <dt>ev_check_init (ev_check *, callback)</dt> |
693 | <dt>ev_check_init (ev_check *, callback)</dt> |
656 | <dd> |
694 | <dd> |
657 | <p>Initialises and configures the prepare or check watcher - they have no |
695 | <p>Initialises and configures the prepare or check watcher - they have no |
658 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
696 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
659 | macros, but using them is utterly, utterly pointless.</p> |
697 | macros, but using them is utterly, utterly and completely pointless.</p> |
660 | </dd> |
698 | </dd> |
661 | </dl> |
699 | </dl> |
662 | |
700 | |
663 | </div> |
701 | </div> |
664 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
702 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
665 | <div id="OTHER_FUNCTIONS_CONTENT"> |
703 | <div id="OTHER_FUNCTIONS_CONTENT"> |
666 | <p>There are some other fucntions of possible interest. Described. Here. Now.</p> |
704 | <p>There are some other functions of possible interest. Described. Here. Now.</p> |
667 | <dl> |
705 | <dl> |
668 | <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
706 | <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
669 | <dd> |
707 | <dd> |
670 | <p>This function combines a simple timer and an I/O watcher, calls your |
708 | <p>This function combines a simple timer and an I/O watcher, calls your |
671 | callback on whichever event happens first and automatically stop both |
709 | callback on whichever event happens first and automatically stop both |
672 | watchers. This is useful if you want to wait for a single event on an fd |
710 | watchers. This is useful if you want to wait for a single event on an fd |
673 | or timeout without havign to allocate/configure/start/stop/free one or |
711 | or timeout without havign to allocate/configure/start/stop/free one or |
674 | more watchers yourself.</p> |
712 | more watchers yourself.</p> |
675 | <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is |
713 | <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events |
676 | ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set |
714 | is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and |
677 | will be craeted and started.</p> |
715 | <code>events</code> set will be craeted and started.</p> |
678 | <p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
716 | <p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
679 | started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat |
717 | started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and |
680 | = 0) will be started.</p> |
718 | repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of |
|
|
719 | dubious value.</p> |
681 | <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and |
720 | <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets |
682 | gets passed an events set (normally a combination of EV_ERROR, EV_READ, |
721 | passed an events set like normal event callbacks (with a combination of |
683 | EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> |
722 | <code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> |
|
|
723 | value passed to <code>ev_once</code>:</p> |
684 | <pre> static void stdin_ready (int revents, void *arg) |
724 | <pre> static void stdin_ready (int revents, void *arg) |
685 | { |
725 | { |
686 | if (revents & EV_TIMEOUT) |
726 | if (revents & EV_TIMEOUT) |
687 | /* doh, nothing entered */ |
727 | /* doh, nothing entered */; |
688 | else if (revents & EV_READ) |
728 | else if (revents & EV_READ) |
689 | /* stdin might have data for us, joy! */ |
729 | /* stdin might have data for us, joy! */; |
690 | } |
730 | } |
691 | |
731 | |
692 | ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); |
732 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
693 | |
733 | |
694 | </pre> |
734 | </pre> |
695 | </dd> |
735 | </dd> |
696 | <dt>ev_feed_event (loop, watcher, int events)</dt> |
736 | <dt>ev_feed_event (loop, watcher, int events)</dt> |
697 | <dd> |
737 | <dd> |
698 | <p>Feeds the given event set into the event loop, as if the specified event |
738 | <p>Feeds the given event set into the event loop, as if the specified event |
699 | has happened for the specified watcher (which must be a pointer to an |
739 | had happened for the specified watcher (which must be a pointer to an |
700 | initialised but not necessarily active event watcher).</p> |
740 | initialised but not necessarily started event watcher).</p> |
701 | </dd> |
741 | </dd> |
702 | <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> |
742 | <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> |
703 | <dd> |
743 | <dd> |
704 | <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> |
744 | <p>Feed an event on the given fd, as if a file descriptor backend detected |
|
|
745 | the given events it.</p> |
705 | </dd> |
746 | </dd> |
706 | <dt>ev_feed_signal_event (loop, int signum)</dt> |
747 | <dt>ev_feed_signal_event (loop, int signum)</dt> |
707 | <dd> |
748 | <dd> |
708 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
749 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
709 | </dd> |
750 | </dd> |