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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" /> |
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13 | <div class="pod"> |
13 | <div class="pod"> |
14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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32 | <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="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li> |
33 | <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="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li> |
34 | <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="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> |
35 | <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="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li> |
36 | <li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li> |
36 | <li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li> |
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37 | <li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li> |
37 | </ul> |
38 | </ul> |
38 | </li> |
39 | </li> |
39 | <li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
40 | <li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
40 | <li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> |
41 | <li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> |
41 | <li><a href="#C_SUPPORT">C++ SUPPORT</a></li> |
42 | <li><a href="#C_SUPPORT">C++ SUPPORT</a></li> |
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96 | <div id="TIME_REPRESENTATION_CONTENT"> |
97 | <div id="TIME_REPRESENTATION_CONTENT"> |
97 | <p>Libev represents time as a single floating point number, representing the |
98 | <p>Libev represents time as a single floating point number, representing the |
98 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
99 | the beginning of 1970, details are complicated, don't ask). This type is |
100 | the beginning of 1970, details are complicated, don't ask). This type is |
100 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
101 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
101 | to the double type in C.</p> |
102 | to the <code>double</code> type in C, and when you need to do any calculations on |
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103 | it, you should treat it as such.</p> |
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104 | |
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105 | |
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106 | |
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107 | |
102 | |
108 | |
103 | </div> |
109 | </div> |
104 | <h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
110 | <h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
105 | <div id="GLOBAL_FUNCTIONS_CONTENT"> |
111 | <div id="GLOBAL_FUNCTIONS_CONTENT"> |
106 | <p>These functions can be called anytime, even before initialising the |
112 | <p>These functions can be called anytime, even before initialising the |
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122 | version of the library your program was compiled against.</p> |
128 | version of the library your program was compiled against.</p> |
123 | <p>Usually, it's a good idea to terminate if the major versions mismatch, |
129 | <p>Usually, it's a good idea to terminate if the major versions mismatch, |
124 | as this indicates an incompatible change. Minor versions are usually |
130 | as this indicates an incompatible change. Minor versions are usually |
125 | compatible to older versions, so a larger minor version alone is usually |
131 | compatible to older versions, so a larger minor version alone is usually |
126 | not a problem.</p> |
132 | not a problem.</p> |
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133 | <p>Example: make sure we haven't accidentally been linked against the wrong |
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134 | version:</p> |
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135 | <pre> assert (("libev version mismatch", |
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136 | ev_version_major () == EV_VERSION_MAJOR |
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137 | && ev_version_minor () >= EV_VERSION_MINOR)); |
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138 | |
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139 | </pre> |
127 | </dd> |
140 | </dd> |
128 | <dt>unsigned int ev_supported_backends ()</dt> |
141 | <dt>unsigned int ev_supported_backends ()</dt> |
129 | <dd> |
142 | <dd> |
130 | <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code> |
143 | <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code> |
131 | value) compiled into this binary of libev (independent of their |
144 | value) compiled into this binary of libev (independent of their |
132 | availability on the system you are running on). See <code>ev_default_loop</code> for |
145 | availability on the system you are running on). See <code>ev_default_loop</code> for |
133 | a description of the set values.</p> |
146 | a description of the set values.</p> |
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147 | <p>Example: make sure we have the epoll method, because yeah this is cool and |
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148 | a must have and can we have a torrent of it please!!!11</p> |
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149 | <pre> assert (("sorry, no epoll, no sex", |
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150 | ev_supported_backends () & EVBACKEND_EPOLL)); |
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151 | |
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152 | </pre> |
134 | </dd> |
153 | </dd> |
135 | <dt>unsigned int ev_recommended_backends ()</dt> |
154 | <dt>unsigned int ev_recommended_backends ()</dt> |
136 | <dd> |
155 | <dd> |
137 | <p>Return the set of all backends compiled into this binary of libev and also |
156 | <p>Return the set of all backends compiled into this binary of libev and also |
138 | recommended for this platform. This set is often smaller than the one |
157 | recommended for this platform. This set is often smaller than the one |
139 | returned by <code>ev_supported_backends</code>, as for example kqueue is broken on |
158 | returned by <code>ev_supported_backends</code>, as for example kqueue is broken on |
140 | most BSDs and will not be autodetected unless you explicitly request it |
159 | most BSDs and will not be autodetected unless you explicitly request it |
141 | (assuming you know what you are doing). This is the set of backends that |
160 | (assuming you know what you are doing). This is the set of backends that |
142 | libev will probe for if you specify no backends explicitly.</p> |
161 | libev will probe for if you specify no backends explicitly.</p> |
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162 | </dd> |
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163 | <dt>unsigned int ev_embeddable_backends ()</dt> |
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164 | <dd> |
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165 | <p>Returns the set of backends that are embeddable in other event loops. This |
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166 | is the theoretical, all-platform, value. To find which backends |
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167 | might be supported on the current system, you would need to look at |
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168 | <code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for |
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169 | recommended ones.</p> |
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170 | <p>See the description of <code>ev_embed</code> watchers for more info.</p> |
143 | </dd> |
171 | </dd> |
144 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
172 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
145 | <dd> |
173 | <dd> |
146 | <p>Sets the allocation function to use (the prototype is similar to the |
174 | <p>Sets the allocation function to use (the prototype is similar to the |
147 | realloc C function, the semantics are identical). It is used to allocate |
175 | realloc C function, the semantics are identical). It is used to allocate |
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149 | needs to be allocated, the library might abort or take some potentially |
177 | needs to be allocated, the library might abort or take some potentially |
150 | destructive action. The default is your system realloc function.</p> |
178 | destructive action. The default is your system realloc function.</p> |
151 | <p>You could override this function in high-availability programs to, say, |
179 | <p>You could override this function in high-availability programs to, say, |
152 | free some memory if it cannot allocate memory, to use a special allocator, |
180 | free some memory if it cannot allocate memory, to use a special allocator, |
153 | or even to sleep a while and retry until some memory is available.</p> |
181 | or even to sleep a while and retry until some memory is available.</p> |
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182 | <p>Example: replace the libev allocator with one that waits a bit and then |
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183 | retries: better than mine).</p> |
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184 | <pre> static void * |
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185 | persistent_realloc (void *ptr, long size) |
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186 | { |
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187 | for (;;) |
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188 | { |
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189 | void *newptr = realloc (ptr, size); |
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190 | |
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191 | if (newptr) |
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192 | return newptr; |
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193 | |
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194 | sleep (60); |
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195 | } |
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196 | } |
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197 | |
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198 | ... |
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199 | ev_set_allocator (persistent_realloc); |
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200 | |
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201 | </pre> |
154 | </dd> |
202 | </dd> |
155 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
203 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
156 | <dd> |
204 | <dd> |
157 | <p>Set the callback function to call on a retryable syscall error (such |
205 | <p>Set the callback function to call on a retryable syscall error (such |
158 | as failed select, poll, epoll_wait). The message is a printable string |
206 | as failed select, poll, epoll_wait). The message is a printable string |
159 | indicating the system call or subsystem causing the problem. If this |
207 | indicating the system call or subsystem causing the problem. If this |
160 | callback is set, then libev will expect it to remedy the sitution, no |
208 | callback is set, then libev will expect it to remedy the sitution, no |
161 | matter what, when it returns. That is, libev will generally retry the |
209 | matter what, when it returns. That is, libev will generally retry the |
162 | requested operation, or, if the condition doesn't go away, do bad stuff |
210 | requested operation, or, if the condition doesn't go away, do bad stuff |
163 | (such as abort).</p> |
211 | (such as abort).</p> |
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212 | <p>Example: do the same thing as libev does internally:</p> |
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213 | <pre> static void |
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214 | fatal_error (const char *msg) |
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215 | { |
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216 | perror (msg); |
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217 | abort (); |
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218 | } |
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219 | |
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220 | ... |
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221 | ev_set_syserr_cb (fatal_error); |
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222 | |
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223 | </pre> |
164 | </dd> |
224 | </dd> |
165 | </dl> |
225 | </dl> |
166 | |
226 | |
167 | </div> |
227 | </div> |
168 | <h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> |
228 | <h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> |
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293 | <dd> |
353 | <dd> |
294 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
354 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
295 | always distinct from the default loop. Unlike the default loop, it cannot |
355 | always distinct from the default loop. Unlike the default loop, it cannot |
296 | handle signal and child watchers, and attempts to do so will be greeted by |
356 | handle signal and child watchers, and attempts to do so will be greeted by |
297 | undefined behaviour (or a failed assertion if assertions are enabled).</p> |
357 | undefined behaviour (or a failed assertion if assertions are enabled).</p> |
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358 | <p>Example: try to create a event loop that uses epoll and nothing else.</p> |
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359 | <pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
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360 | if (!epoller) |
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361 | fatal ("no epoll found here, maybe it hides under your chair"); |
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362 | |
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363 | </pre> |
298 | </dd> |
364 | </dd> |
299 | <dt>ev_default_destroy ()</dt> |
365 | <dt>ev_default_destroy ()</dt> |
300 | <dd> |
366 | <dd> |
301 | <p>Destroys the default loop again (frees all memory and kernel state |
367 | <p>Destroys the default loop again (frees all memory and kernel state |
302 | etc.). This stops all registered event watchers (by not touching them in |
368 | etc.). This stops all registered event watchers (by not touching them in |
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338 | use.</p> |
404 | use.</p> |
339 | </dd> |
405 | </dd> |
340 | <dt>ev_tstamp ev_now (loop)</dt> |
406 | <dt>ev_tstamp ev_now (loop)</dt> |
341 | <dd> |
407 | <dd> |
342 | <p>Returns the current "event loop time", which is the time the event loop |
408 | <p>Returns the current "event loop time", which is the time the event loop |
343 | got events and started processing them. This timestamp does not change |
409 | received events and started processing them. This timestamp does not |
344 | as long as callbacks are being processed, and this is also the base time |
410 | change as long as callbacks are being processed, and this is also the base |
345 | used for relative timers. You can treat it as the timestamp of the event |
411 | time used for relative timers. You can treat it as the timestamp of the |
346 | occuring (or more correctly, the mainloop finding out about it).</p> |
412 | event occuring (or more correctly, libev finding out about it).</p> |
347 | </dd> |
413 | </dd> |
348 | <dt>ev_loop (loop, int flags)</dt> |
414 | <dt>ev_loop (loop, int flags)</dt> |
349 | <dd> |
415 | <dd> |
350 | <p>Finally, this is it, the event handler. This function usually is called |
416 | <p>Finally, this is it, the event handler. This function usually is called |
351 | after you initialised all your watchers and you want to start handling |
417 | after you initialised all your watchers and you want to start handling |
352 | events.</p> |
418 | events.</p> |
353 | <p>If the flags argument is specified as <code>0</code>, it will not return until |
419 | <p>If the flags argument is specified as <code>0</code>, it will not return until |
354 | either no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
420 | either no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
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421 | <p>Please note that an explicit <code>ev_unloop</code> is usually better than |
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422 | relying on all watchers to be stopped when deciding when a program has |
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423 | finished (especially in interactive programs), but having a program that |
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424 | automatically loops as long as it has to and no longer by virtue of |
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425 | relying on its watchers stopping correctly is a thing of beauty.</p> |
355 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
426 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
356 | those events and any outstanding ones, but will not block your process in |
427 | those events and any outstanding ones, but will not block your process in |
357 | case there are no events and will return after one iteration of the loop.</p> |
428 | case there are no events and will return after one iteration of the loop.</p> |
358 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
429 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
359 | neccessary) and will handle those and any outstanding ones. It will block |
430 | neccessary) and will handle those and any outstanding ones. It will block |
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381 | be handled here by queueing them when their watcher gets executed. |
452 | be handled here by queueing them when their watcher gets executed. |
382 | - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
453 | - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
383 | were used, return, otherwise continue with step *. |
454 | were used, return, otherwise continue with step *. |
384 | |
455 | |
385 | </pre> |
456 | </pre> |
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457 | <p>Example: queue some jobs and then loop until no events are outsanding |
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458 | anymore.</p> |
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459 | <pre> ... queue jobs here, make sure they register event watchers as long |
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460 | ... as they still have work to do (even an idle watcher will do..) |
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461 | ev_loop (my_loop, 0); |
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462 | ... jobs done. yeah! |
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463 | |
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464 | </pre> |
386 | </dd> |
465 | </dd> |
387 | <dt>ev_unloop (loop, how)</dt> |
466 | <dt>ev_unloop (loop, how)</dt> |
388 | <dd> |
467 | <dd> |
389 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
468 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
390 | has processed all outstanding events). The <code>how</code> argument must be either |
469 | has processed all outstanding events). The <code>how</code> argument must be either |
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402 | example, libev itself uses this for its internal signal pipe: It is not |
481 | example, libev itself uses this for its internal signal pipe: It is not |
403 | visible to the libev user and should not keep <code>ev_loop</code> from exiting if |
482 | visible to the libev user and should not keep <code>ev_loop</code> from exiting if |
404 | no event watchers registered by it are active. It is also an excellent |
483 | no event watchers registered by it are active. It is also an excellent |
405 | way to do this for generic recurring timers or from within third-party |
484 | way to do this for generic recurring timers or from within third-party |
406 | libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> |
485 | libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> |
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486 | <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> |
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487 | running when nothing else is active.</p> |
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488 | <pre> struct dv_signal exitsig; |
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489 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
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490 | ev_signal_start (myloop, &exitsig); |
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491 | evf_unref (myloop); |
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492 | |
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493 | </pre> |
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494 | <p>Example: for some weird reason, unregister the above signal handler again.</p> |
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495 | <pre> ev_ref (myloop); |
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496 | ev_signal_stop (myloop, &exitsig); |
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497 | |
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498 | </pre> |
407 | </dd> |
499 | </dd> |
408 | </dl> |
500 | </dl> |
409 | |
501 | |
410 | </div> |
502 | </div> |
411 | <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> |
503 | <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> |
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547 | <h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> |
639 | <h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> |
548 | <div id="WATCHER_TYPES_CONTENT"> |
640 | <div id="WATCHER_TYPES_CONTENT"> |
549 | <p>This section describes each watcher in detail, but will not repeat |
641 | <p>This section describes each watcher in detail, but will not repeat |
550 | information given in the last section.</p> |
642 | information given in the last section.</p> |
551 | |
643 | |
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644 | |
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645 | |
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646 | |
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647 | |
552 | </div> |
648 | </div> |
553 | <h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> |
649 | <h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> |
554 | <div id="code_ev_io_code_is_this_file_descrip-2"> |
650 | <div id="code_ev_io_code_is_this_file_descrip-2"> |
555 | <p>I/O watchers check whether a file descriptor is readable or writable |
651 | <p>I/O watchers check whether a file descriptor is readable or writable |
556 | in each iteration of the event loop (This behaviour is called |
652 | in each iteration of the event loop (This behaviour is called |
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586 | when the readyness condition is no longer valid even when employing |
682 | when the readyness condition is no longer valid even when employing |
587 | typical ways of handling events, so its a good idea to use non-blocking |
683 | typical ways of handling events, so its a good idea to use non-blocking |
588 | I/O unconditionally.</p> |
684 | I/O unconditionally.</p> |
589 | </dd> |
685 | </dd> |
590 | </dl> |
686 | </dl> |
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687 | <p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well |
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688 | readable, but only once. Since it is likely line-buffered, you could |
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689 | attempt to read a whole line in the callback:</p> |
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690 | <pre> static void |
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691 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
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692 | { |
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693 | ev_io_stop (loop, w); |
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694 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
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695 | } |
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696 | |
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697 | ... |
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698 | struct ev_loop *loop = ev_default_init (0); |
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699 | struct ev_io stdin_readable; |
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700 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
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701 | ev_io_start (loop, &stdin_readable); |
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702 | ev_loop (loop, 0); |
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703 | |
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704 | |
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705 | |
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706 | |
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707 | </pre> |
591 | |
708 | |
592 | </div> |
709 | </div> |
593 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
710 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
594 | <div id="code_ev_timer_code_relative_and_opti-2"> |
711 | <div id="code_ev_timer_code_relative_and_opti-2"> |
595 | <p>Timer watchers are simple relative timers that generate an event after a |
712 | <p>Timer watchers are simple relative timers that generate an event after a |
… | |
… | |
639 | time you successfully read or write some data. If you go into an idle |
756 | time you successfully read or write some data. If you go into an idle |
640 | state where you do not expect data to travel on the socket, you can stop |
757 | state where you do not expect data to travel on the socket, you can stop |
641 | the timer, and again will automatically restart it if need be.</p> |
758 | the timer, and again will automatically restart it if need be.</p> |
642 | </dd> |
759 | </dd> |
643 | </dl> |
760 | </dl> |
|
|
761 | <p>Example: create a timer that fires after 60 seconds.</p> |
|
|
762 | <pre> static void |
|
|
763 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
764 | { |
|
|
765 | .. one minute over, w is actually stopped right here |
|
|
766 | } |
|
|
767 | |
|
|
768 | struct ev_timer mytimer; |
|
|
769 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
|
|
770 | ev_timer_start (loop, &mytimer); |
|
|
771 | |
|
|
772 | </pre> |
|
|
773 | <p>Example: create a timeout timer that times out after 10 seconds of |
|
|
774 | inactivity.</p> |
|
|
775 | <pre> static void |
|
|
776 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
777 | { |
|
|
778 | .. ten seconds without any activity |
|
|
779 | } |
|
|
780 | |
|
|
781 | struct ev_timer mytimer; |
|
|
782 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
|
|
783 | ev_timer_again (&mytimer); /* start timer */ |
|
|
784 | ev_loop (loop, 0); |
|
|
785 | |
|
|
786 | // and in some piece of code that gets executed on any "activity": |
|
|
787 | // reset the timeout to start ticking again at 10 seconds |
|
|
788 | ev_timer_again (&mytimer); |
|
|
789 | |
|
|
790 | |
|
|
791 | |
|
|
792 | |
|
|
793 | </pre> |
644 | |
794 | |
645 | </div> |
795 | </div> |
646 | <h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> |
796 | <h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> |
647 | <div id="code_ev_periodic_code_to_cron_or_not-2"> |
797 | <div id="code_ev_periodic_code_to_cron_or_not-2"> |
648 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
798 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
… | |
… | |
732 | when you changed some parameters or the reschedule callback would return |
882 | when you changed some parameters or the reschedule callback would return |
733 | a different time than the last time it was called (e.g. in a crond like |
883 | a different time than the last time it was called (e.g. in a crond like |
734 | program when the crontabs have changed).</p> |
884 | program when the crontabs have changed).</p> |
735 | </dd> |
885 | </dd> |
736 | </dl> |
886 | </dl> |
|
|
887 | <p>Example: call a callback every hour, or, more precisely, whenever the |
|
|
888 | system clock is divisible by 3600. The callback invocation times have |
|
|
889 | potentially a lot of jittering, but good long-term stability.</p> |
|
|
890 | <pre> static void |
|
|
891 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
892 | { |
|
|
893 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
|
|
894 | } |
|
|
895 | |
|
|
896 | struct ev_periodic hourly_tick; |
|
|
897 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
|
|
898 | ev_periodic_start (loop, &hourly_tick); |
|
|
899 | |
|
|
900 | </pre> |
|
|
901 | <p>Example: the same as above, but use a reschedule callback to do it:</p> |
|
|
902 | <pre> #include <math.h> |
|
|
903 | |
|
|
904 | static ev_tstamp |
|
|
905 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
|
|
906 | { |
|
|
907 | return fmod (now, 3600.) + 3600.; |
|
|
908 | } |
|
|
909 | |
|
|
910 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
|
|
911 | |
|
|
912 | </pre> |
|
|
913 | <p>Example: call a callback every hour, starting now:</p> |
|
|
914 | <pre> struct ev_periodic hourly_tick; |
|
|
915 | ev_periodic_init (&hourly_tick, clock_cb, |
|
|
916 | fmod (ev_now (loop), 3600.), 3600., 0); |
|
|
917 | ev_periodic_start (loop, &hourly_tick); |
|
|
918 | |
|
|
919 | |
|
|
920 | |
|
|
921 | |
|
|
922 | </pre> |
737 | |
923 | |
738 | </div> |
924 | </div> |
739 | <h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> |
925 | <h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> |
740 | <div id="code_ev_signal_code_signal_me_when_a-2"> |
926 | <div id="code_ev_signal_code_signal_me_when_a-2"> |
741 | <p>Signal watchers will trigger an event when the process receives a specific |
927 | <p>Signal watchers will trigger an event when the process receives a specific |
… | |
… | |
755 | <p>Configures the watcher to trigger on the given signal number (usually one |
941 | <p>Configures the watcher to trigger on the given signal number (usually one |
756 | of the <code>SIGxxx</code> constants).</p> |
942 | of the <code>SIGxxx</code> constants).</p> |
757 | </dd> |
943 | </dd> |
758 | </dl> |
944 | </dl> |
759 | |
945 | |
|
|
946 | |
|
|
947 | |
|
|
948 | |
|
|
949 | |
760 | </div> |
950 | </div> |
761 | <h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> |
951 | <h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> |
762 | <div id="code_ev_child_code_wait_for_pid_stat-2"> |
952 | <div id="code_ev_child_code_wait_for_pid_stat-2"> |
763 | <p>Child watchers trigger when your process receives a SIGCHLD in response to |
953 | <p>Child watchers trigger when your process receives a SIGCHLD in response to |
764 | some child status changes (most typically when a child of yours dies).</p> |
954 | some child status changes (most typically when a child of yours dies).</p> |
… | |
… | |
772 | the status word (use the macros from <code>sys/wait.h</code> and see your systems |
962 | the status word (use the macros from <code>sys/wait.h</code> and see your systems |
773 | <code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the |
963 | <code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the |
774 | process causing the status change.</p> |
964 | process causing the status change.</p> |
775 | </dd> |
965 | </dd> |
776 | </dl> |
966 | </dl> |
|
|
967 | <p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> |
|
|
968 | <pre> static void |
|
|
969 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
970 | { |
|
|
971 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
972 | } |
|
|
973 | |
|
|
974 | struct ev_signal signal_watcher; |
|
|
975 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
976 | ev_signal_start (loop, &sigint_cb); |
|
|
977 | |
|
|
978 | |
|
|
979 | |
|
|
980 | |
|
|
981 | </pre> |
777 | |
982 | |
778 | </div> |
983 | </div> |
779 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> |
984 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> |
780 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
985 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
781 | <p>Idle watchers trigger events when there are no other events are pending |
986 | <p>Idle watchers trigger events when there are no other events are pending |
… | |
… | |
797 | <p>Initialises and configures the idle watcher - it has no parameters of any |
1002 | <p>Initialises and configures the idle watcher - it has no parameters of any |
798 | kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, |
1003 | kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, |
799 | believe me.</p> |
1004 | believe me.</p> |
800 | </dd> |
1005 | </dd> |
801 | </dl> |
1006 | </dl> |
|
|
1007 | <p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the |
|
|
1008 | callback, free it. Alos, use no error checking, as usual.</p> |
|
|
1009 | <pre> static void |
|
|
1010 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
|
|
1011 | { |
|
|
1012 | free (w); |
|
|
1013 | // now do something you wanted to do when the program has |
|
|
1014 | // no longer asnything immediate to do. |
|
|
1015 | } |
|
|
1016 | |
|
|
1017 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
|
|
1018 | ev_idle_init (idle_watcher, idle_cb); |
|
|
1019 | ev_idle_start (loop, idle_cb); |
|
|
1020 | |
|
|
1021 | |
|
|
1022 | |
|
|
1023 | |
|
|
1024 | </pre> |
802 | |
1025 | |
803 | </div> |
1026 | </div> |
804 | <h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> |
1027 | <h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> |
805 | <div id="code_ev_prepare_code_and_code_ev_che-2"> |
1028 | <div id="code_ev_prepare_code_and_code_ev_che-2"> |
806 | <p>Prepare and check watchers are usually (but not always) used in tandem: |
1029 | <p>Prepare and check watchers are usually (but not always) used in tandem: |
807 | prepare watchers get invoked before the process blocks and check watchers |
1030 | prepare watchers get invoked before the process blocks and check watchers |
808 | afterwards.</p> |
1031 | afterwards.</p> |
809 | <p>Their main purpose is to integrate other event mechanisms into libev. This |
1032 | <p>Their main purpose is to integrate other event mechanisms into libev and |
810 | could be used, for example, to track variable changes, implement your own |
1033 | their use is somewhat advanced. This could be used, for example, to track |
811 | watchers, integrate net-snmp or a coroutine library and lots more.</p> |
1034 | variable changes, implement your own watchers, integrate net-snmp or a |
|
|
1035 | coroutine library and lots more.</p> |
812 | <p>This is done by examining in each prepare call which file descriptors need |
1036 | <p>This is done by examining in each prepare call which file descriptors need |
813 | to be watched by the other library, registering <code>ev_io</code> watchers for |
1037 | to be watched by the other library, registering <code>ev_io</code> watchers for |
814 | them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries |
1038 | them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries |
815 | provide just this functionality). Then, in the check watcher you check for |
1039 | provide just this functionality). Then, in the check watcher you check for |
816 | any events that occured (by checking the pending status of all watchers |
1040 | any events that occured (by checking the pending status of all watchers |
… | |
… | |
832 | <p>Initialises and configures the prepare or check watcher - they have no |
1056 | <p>Initialises and configures the prepare or check watcher - they have no |
833 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1057 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
834 | macros, but using them is utterly, utterly and completely pointless.</p> |
1058 | macros, but using them is utterly, utterly and completely pointless.</p> |
835 | </dd> |
1059 | </dd> |
836 | </dl> |
1060 | </dl> |
|
|
1061 | <p>Example: *TODO*.</p> |
|
|
1062 | |
|
|
1063 | |
|
|
1064 | |
|
|
1065 | |
|
|
1066 | |
|
|
1067 | </div> |
|
|
1068 | <h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> |
|
|
1069 | <div id="code_ev_embed_code_when_one_backend_-2"> |
|
|
1070 | <p>This is a rather advanced watcher type that lets you embed one event loop |
|
|
1071 | into another.</p> |
|
|
1072 | <p>There are primarily two reasons you would want that: work around bugs and |
|
|
1073 | prioritise I/O.</p> |
|
|
1074 | <p>As an example for a bug workaround, the kqueue backend might only support |
|
|
1075 | sockets on some platform, so it is unusable as generic backend, but you |
|
|
1076 | still want to make use of it because you have many sockets and it scales |
|
|
1077 | so nicely. In this case, you would create a kqueue-based loop and embed it |
|
|
1078 | into your default loop (which might use e.g. poll). Overall operation will |
|
|
1079 | be a bit slower because first libev has to poll and then call kevent, but |
|
|
1080 | at least you can use both at what they are best.</p> |
|
|
1081 | <p>As for prioritising I/O: rarely you have the case where some fds have |
|
|
1082 | to be watched and handled very quickly (with low latency), and even |
|
|
1083 | priorities and idle watchers might have too much overhead. In this case |
|
|
1084 | you would put all the high priority stuff in one loop and all the rest in |
|
|
1085 | a second one, and embed the second one in the first.</p> |
|
|
1086 | <p>As long as the watcher is started it will automatically handle events. The |
|
|
1087 | callback will be invoked whenever some events have been handled. You can |
|
|
1088 | set the callback to <code>0</code> to avoid having to specify one if you are not |
|
|
1089 | interested in that.</p> |
|
|
1090 | <p>Also, there have not currently been made special provisions for forking: |
|
|
1091 | when you fork, you not only have to call <code>ev_loop_fork</code> on both loops, |
|
|
1092 | but you will also have to stop and restart any <code>ev_embed</code> watchers |
|
|
1093 | yourself.</p> |
|
|
1094 | <p>Unfortunately, not all backends are embeddable, only the ones returned by |
|
|
1095 | <code>ev_embeddable_backends</code> are, which, unfortunately, does not include any |
|
|
1096 | portable one.</p> |
|
|
1097 | <p>So when you want to use this feature you will always have to be prepared |
|
|
1098 | that you cannot get an embeddable loop. The recommended way to get around |
|
|
1099 | this is to have a separate variables for your embeddable loop, try to |
|
|
1100 | create it, and if that fails, use the normal loop for everything:</p> |
|
|
1101 | <pre> struct ev_loop *loop_hi = ev_default_init (0); |
|
|
1102 | struct ev_loop *loop_lo = 0; |
|
|
1103 | struct ev_embed embed; |
|
|
1104 | |
|
|
1105 | // see if there is a chance of getting one that works |
|
|
1106 | // (remember that a flags value of 0 means autodetection) |
|
|
1107 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
1108 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
1109 | : 0; |
|
|
1110 | |
|
|
1111 | // if we got one, then embed it, otherwise default to loop_hi |
|
|
1112 | if (loop_lo) |
|
|
1113 | { |
|
|
1114 | ev_embed_init (&embed, 0, loop_lo); |
|
|
1115 | ev_embed_start (loop_hi, &embed); |
|
|
1116 | } |
|
|
1117 | else |
|
|
1118 | loop_lo = loop_hi; |
|
|
1119 | |
|
|
1120 | </pre> |
|
|
1121 | <dl> |
|
|
1122 | <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *loop)</dt> |
|
|
1123 | <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *loop)</dt> |
|
|
1124 | <dd> |
|
|
1125 | <p>Configures the watcher to embed the given loop, which must be embeddable.</p> |
|
|
1126 | </dd> |
|
|
1127 | </dl> |
|
|
1128 | |
|
|
1129 | |
|
|
1130 | |
|
|
1131 | |
837 | |
1132 | |
838 | </div> |
1133 | </div> |
839 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
1134 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
840 | <div id="OTHER_FUNCTIONS_CONTENT"> |
1135 | <div id="OTHER_FUNCTIONS_CONTENT"> |
841 | <p>There are some other functions of possible interest. Described. Here. Now.</p> |
1136 | <p>There are some other functions of possible interest. Described. Here. Now.</p> |
… | |
… | |
885 | <dd> |
1180 | <dd> |
886 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
1181 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
887 | </dd> |
1182 | </dd> |
888 | </dl> |
1183 | </dl> |
889 | |
1184 | |
|
|
1185 | |
|
|
1186 | |
|
|
1187 | |
|
|
1188 | |
890 | </div> |
1189 | </div> |
891 | <h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
1190 | <h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
892 | <div id="LIBEVENT_EMULATION_CONTENT"> |
1191 | <div id="LIBEVENT_EMULATION_CONTENT"> |
893 | <p>Libev offers a compatibility emulation layer for libevent. It cannot |
1192 | <p>Libev offers a compatibility emulation layer for libevent. It cannot |
894 | emulate the internals of libevent, so here are some usage hints:</p> |
1193 | emulate the internals of libevent, so here are some usage hints:</p> |