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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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9 | <meta name="created" content="Fri Nov 23 06:14:47 2007" /> |
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12 | <body> |
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13 | <div class="pod"> |
13 | <div class="pod"> |
14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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96 | <div id="TIME_REPRESENTATION_CONTENT"> |
96 | <div id="TIME_REPRESENTATION_CONTENT"> |
97 | <p>Libev represents time as a single floating point number, representing the |
97 | <p>Libev represents time as a single floating point number, representing the |
98 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
98 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
99 | the beginning of 1970, details are complicated, don't ask). This type is |
99 | 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 |
100 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
101 | to the double type in C.</p> |
101 | to the <code>double</code> type in C, and when you need to do any calculations on |
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102 | it, you should treat it as such.</p> |
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103 | |
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104 | |
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105 | |
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106 | |
102 | |
107 | |
103 | </div> |
108 | </div> |
104 | <h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
109 | <h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
105 | <div id="GLOBAL_FUNCTIONS_CONTENT"> |
110 | <div id="GLOBAL_FUNCTIONS_CONTENT"> |
106 | <p>These functions can be called anytime, even before initialising the |
111 | <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> |
127 | 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, |
128 | <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 |
129 | as this indicates an incompatible change. Minor versions are usually |
125 | compatible to older versions, so a larger minor version alone is usually |
130 | compatible to older versions, so a larger minor version alone is usually |
126 | not a problem.</p> |
131 | not a problem.</p> |
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132 | <p>Example: make sure we haven't accidentally been linked against the wrong |
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133 | version:</p> |
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134 | <pre> assert (("libev version mismatch", |
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135 | ev_version_major () == EV_VERSION_MAJOR |
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136 | && ev_version_minor () >= EV_VERSION_MINOR)); |
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137 | |
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138 | </pre> |
127 | </dd> |
139 | </dd> |
128 | <dt>unsigned int ev_supported_backends ()</dt> |
140 | <dt>unsigned int ev_supported_backends ()</dt> |
129 | <dd> |
141 | <dd> |
130 | <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code> |
142 | <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 |
143 | 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 |
144 | availability on the system you are running on). See <code>ev_default_loop</code> for |
133 | a description of the set values.</p> |
145 | a description of the set values.</p> |
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146 | <p>Example: make sure we have the epoll method, because yeah this is cool and |
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147 | a must have and can we have a torrent of it please!!!11</p> |
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148 | <pre> assert (("sorry, no epoll, no sex", |
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149 | ev_supported_backends () & EVBACKEND_EPOLL)); |
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150 | |
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151 | </pre> |
134 | </dd> |
152 | </dd> |
135 | <dt>unsigned int ev_recommended_backends ()</dt> |
153 | <dt>unsigned int ev_recommended_backends ()</dt> |
136 | <dd> |
154 | <dd> |
137 | <p>Return the set of all backends compiled into this binary of libev and also |
155 | <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 |
156 | 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 |
157 | 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 |
158 | 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 |
159 | (assuming you know what you are doing). This is the set of backends that |
142 | <code>EVFLAG_AUTO</code> will probe for.</p> |
160 | libev will probe for if you specify no backends explicitly.</p> |
143 | </dd> |
161 | </dd> |
144 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
162 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
145 | <dd> |
163 | <dd> |
146 | <p>Sets the allocation function to use (the prototype is similar to the |
164 | <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 |
165 | 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 |
167 | needs to be allocated, the library might abort or take some potentially |
150 | destructive action. The default is your system realloc function.</p> |
168 | destructive action. The default is your system realloc function.</p> |
151 | <p>You could override this function in high-availability programs to, say, |
169 | <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, |
170 | 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> |
171 | or even to sleep a while and retry until some memory is available.</p> |
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172 | <p>Example: replace the libev allocator with one that waits a bit and then |
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173 | retries: better than mine).</p> |
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174 | <pre> static void * |
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175 | persistent_realloc (void *ptr, long size) |
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176 | { |
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177 | for (;;) |
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178 | { |
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179 | void *newptr = realloc (ptr, size); |
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180 | |
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181 | if (newptr) |
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182 | return newptr; |
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183 | |
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184 | sleep (60); |
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185 | } |
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186 | } |
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187 | |
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188 | ... |
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189 | ev_set_allocator (persistent_realloc); |
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190 | |
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191 | </pre> |
154 | </dd> |
192 | </dd> |
155 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
193 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
156 | <dd> |
194 | <dd> |
157 | <p>Set the callback function to call on a retryable syscall error (such |
195 | <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 |
196 | as failed select, poll, epoll_wait). The message is a printable string |
159 | indicating the system call or subsystem causing the problem. If this |
197 | 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 |
198 | 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 |
199 | 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 |
200 | requested operation, or, if the condition doesn't go away, do bad stuff |
163 | (such as abort).</p> |
201 | (such as abort).</p> |
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202 | <p>Example: do the same thing as libev does internally:</p> |
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203 | <pre> static void |
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204 | fatal_error (const char *msg) |
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205 | { |
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206 | perror (msg); |
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207 | abort (); |
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208 | } |
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209 | |
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210 | ... |
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211 | ev_set_syserr_cb (fatal_error); |
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212 | |
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213 | </pre> |
164 | </dd> |
214 | </dd> |
165 | </dl> |
215 | </dl> |
166 | |
216 | |
167 | </div> |
217 | </div> |
168 | <h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> |
218 | <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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184 | false. If it already was initialised it simply returns it (and ignores the |
234 | false. If it already was initialised it simply returns it (and ignores the |
185 | flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p> |
235 | flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p> |
186 | <p>If you don't know what event loop to use, use the one returned from this |
236 | <p>If you don't know what event loop to use, use the one returned from this |
187 | function.</p> |
237 | function.</p> |
188 | <p>The flags argument can be used to specify special behaviour or specific |
238 | <p>The flags argument can be used to specify special behaviour or specific |
189 | backends to use, and is usually specified as <code>0</code> (or EVFLAG_AUTO).</p> |
239 | backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p> |
190 | <p>It supports the following flags:</p> |
240 | <p>The following flags are supported:</p> |
191 | <p> |
241 | <p> |
192 | <dl> |
242 | <dl> |
193 | <dt><code>EVFLAG_AUTO</code></dt> |
243 | <dt><code>EVFLAG_AUTO</code></dt> |
194 | <dd> |
244 | <dd> |
195 | <p>The default flags value. Use this if you have no clue (it's the right |
245 | <p>The default flags value. Use this if you have no clue (it's the right |
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228 | <p>While stopping and starting an I/O watcher in the same iteration will |
278 | <p>While stopping and starting an I/O watcher in the same iteration will |
229 | result in some caching, there is still a syscall per such incident |
279 | result in some caching, there is still a syscall per such incident |
230 | (because the fd could point to a different file description now), so its |
280 | (because the fd could point to a different file description now), so its |
231 | best to avoid that. Also, dup()ed file descriptors might not work very |
281 | best to avoid that. Also, dup()ed file descriptors might not work very |
232 | well if you register events for both fds.</p> |
282 | well if you register events for both fds.</p> |
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283 | <p>Please note that epoll sometimes generates spurious notifications, so you |
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284 | need to use non-blocking I/O or other means to avoid blocking when no data |
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285 | (or space) is available.</p> |
233 | </dd> |
286 | </dd> |
234 | <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt> |
287 | <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt> |
235 | <dd> |
288 | <dd> |
236 | <p>Kqueue deserves special mention, as at the time of this writing, it |
289 | <p>Kqueue deserves special mention, as at the time of this writing, it |
237 | was broken on all BSDs except NetBSD (usually it doesn't work with |
290 | was broken on all BSDs except NetBSD (usually it doesn't work with |
238 | anything but sockets and pipes, except on Darwin, where of course its |
291 | anything but sockets and pipes, except on Darwin, where of course its |
239 | completely useless). For this reason its not being "autodetected" unless |
292 | completely useless). For this reason its not being "autodetected" |
240 | you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).</p> |
293 | unless you explicitly specify it explicitly in the flags (i.e. using |
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294 | <code>EVBACKEND_KQUEUE</code>).</p> |
241 | <p>It scales in the same way as the epoll backend, but the interface to the |
295 | <p>It scales in the same way as the epoll backend, but the interface to the |
242 | kernel is more efficient (which says nothing about its actual speed, of |
296 | kernel is more efficient (which says nothing about its actual speed, of |
243 | course). While starting and stopping an I/O watcher does not cause an |
297 | course). While starting and stopping an I/O watcher does not cause an |
244 | extra syscall as with epoll, it still adds up to four event changes per |
298 | extra syscall as with epoll, it still adds up to four event changes per |
245 | incident, so its best to avoid that.</p> |
299 | incident, so its best to avoid that.</p> |
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250 | </dd> |
304 | </dd> |
251 | <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt> |
305 | <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt> |
252 | <dd> |
306 | <dd> |
253 | <p>This uses the Solaris 10 port mechanism. As with everything on Solaris, |
307 | <p>This uses the Solaris 10 port mechanism. As with everything on Solaris, |
254 | it's really slow, but it still scales very well (O(active_fds)).</p> |
308 | it's really slow, but it still scales very well (O(active_fds)).</p> |
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309 | <p>Please note that solaris ports can result in a lot of spurious |
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310 | notifications, so you need to use non-blocking I/O or other means to avoid |
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311 | blocking when no data (or space) is available.</p> |
255 | </dd> |
312 | </dd> |
256 | <dt><code>EVBACKEND_ALL</code></dt> |
313 | <dt><code>EVBACKEND_ALL</code></dt> |
257 | <dd> |
314 | <dd> |
258 | <p>Try all backends (even potentially broken ones that wouldn't be tried |
315 | <p>Try all backends (even potentially broken ones that wouldn't be tried |
259 | with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as |
316 | with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as |
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263 | </p> |
320 | </p> |
264 | <p>If one or more of these are ored into the flags value, then only these |
321 | <p>If one or more of these are ored into the flags value, then only these |
265 | backends will be tried (in the reverse order as given here). If none are |
322 | backends will be tried (in the reverse order as given here). If none are |
266 | specified, most compiled-in backend will be tried, usually in reverse |
323 | specified, most compiled-in backend will be tried, usually in reverse |
267 | order of their flag values :)</p> |
324 | order of their flag values :)</p> |
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325 | <p>The most typical usage is like this:</p> |
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326 | <pre> if (!ev_default_loop (0)) |
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327 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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328 | |
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329 | </pre> |
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330 | <p>Restrict libev to the select and poll backends, and do not allow |
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331 | environment settings to be taken into account:</p> |
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332 | <pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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333 | |
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334 | </pre> |
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335 | <p>Use whatever libev has to offer, but make sure that kqueue is used if |
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336 | available (warning, breaks stuff, best use only with your own private |
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337 | event loop and only if you know the OS supports your types of fds):</p> |
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338 | <pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
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339 | |
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340 | </pre> |
268 | </dd> |
341 | </dd> |
269 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
342 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
270 | <dd> |
343 | <dd> |
271 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
344 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
272 | always distinct from the default loop. Unlike the default loop, it cannot |
345 | always distinct from the default loop. Unlike the default loop, it cannot |
273 | handle signal and child watchers, and attempts to do so will be greeted by |
346 | handle signal and child watchers, and attempts to do so will be greeted by |
274 | undefined behaviour (or a failed assertion if assertions are enabled).</p> |
347 | undefined behaviour (or a failed assertion if assertions are enabled).</p> |
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348 | <p>Example: try to create a event loop that uses epoll and nothing else.</p> |
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349 | <pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
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350 | if (!epoller) |
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351 | fatal ("no epoll found here, maybe it hides under your chair"); |
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352 | |
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353 | </pre> |
275 | </dd> |
354 | </dd> |
276 | <dt>ev_default_destroy ()</dt> |
355 | <dt>ev_default_destroy ()</dt> |
277 | <dd> |
356 | <dd> |
278 | <p>Destroys the default loop again (frees all memory and kernel state |
357 | <p>Destroys the default loop again (frees all memory and kernel state |
279 | etc.). This stops all registered event watchers (by not touching them in |
358 | etc.). This stops all registered event watchers (by not touching them in |
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315 | use.</p> |
394 | use.</p> |
316 | </dd> |
395 | </dd> |
317 | <dt>ev_tstamp ev_now (loop)</dt> |
396 | <dt>ev_tstamp ev_now (loop)</dt> |
318 | <dd> |
397 | <dd> |
319 | <p>Returns the current "event loop time", which is the time the event loop |
398 | <p>Returns the current "event loop time", which is the time the event loop |
320 | got events and started processing them. This timestamp does not change |
399 | received events and started processing them. This timestamp does not |
321 | as long as callbacks are being processed, and this is also the base time |
400 | change as long as callbacks are being processed, and this is also the base |
322 | used for relative timers. You can treat it as the timestamp of the event |
401 | time used for relative timers. You can treat it as the timestamp of the |
323 | occuring (or more correctly, the mainloop finding out about it).</p> |
402 | event occuring (or more correctly, libev finding out about it).</p> |
324 | </dd> |
403 | </dd> |
325 | <dt>ev_loop (loop, int flags)</dt> |
404 | <dt>ev_loop (loop, int flags)</dt> |
326 | <dd> |
405 | <dd> |
327 | <p>Finally, this is it, the event handler. This function usually is called |
406 | <p>Finally, this is it, the event handler. This function usually is called |
328 | after you initialised all your watchers and you want to start handling |
407 | after you initialised all your watchers and you want to start handling |
329 | events.</p> |
408 | events.</p> |
330 | <p>If the flags argument is specified as 0, it will not return until either |
409 | <p>If the flags argument is specified as <code>0</code>, it will not return until |
331 | no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
410 | either no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
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411 | <p>Please note that an explicit <code>ev_unloop</code> is usually better than |
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412 | relying on all watchers to be stopped when deciding when a program has |
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413 | finished (especially in interactive programs), but having a program that |
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414 | automatically loops as long as it has to and no longer by virtue of |
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415 | relying on its watchers stopping correctly is a thing of beauty.</p> |
332 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
416 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
333 | those events and any outstanding ones, but will not block your process in |
417 | those events and any outstanding ones, but will not block your process in |
334 | case there are no events and will return after one iteration of the loop.</p> |
418 | case there are no events and will return after one iteration of the loop.</p> |
335 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
419 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
336 | neccessary) and will handle those and any outstanding ones. It will block |
420 | neccessary) and will handle those and any outstanding ones. It will block |
337 | your process until at least one new event arrives, and will return after |
421 | your process until at least one new event arrives, and will return after |
338 | one iteration of the loop.</p> |
422 | one iteration of the loop. This is useful if you are waiting for some |
339 | <p>This flags value could be used to implement alternative looping |
423 | external event in conjunction with something not expressible using other |
340 | constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and |
424 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
341 | more generic mechanism.</p> |
425 | usually a better approach for this kind of thing.</p> |
342 | <p>Here are the gory details of what ev_loop does:</p> |
426 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
343 | <pre> 1. If there are no active watchers (reference count is zero), return. |
427 | <pre> * If there are no active watchers (reference count is zero), return. |
344 | 2. Queue and immediately call all prepare watchers. |
428 | - Queue prepare watchers and then call all outstanding watchers. |
345 | 3. If we have been forked, recreate the kernel state. |
429 | - If we have been forked, recreate the kernel state. |
346 | 4. Update the kernel state with all outstanding changes. |
430 | - Update the kernel state with all outstanding changes. |
347 | 5. Update the "event loop time". |
431 | - Update the "event loop time". |
348 | 6. Calculate for how long to block. |
432 | - Calculate for how long to block. |
349 | 7. Block the process, waiting for events. |
433 | - Block the process, waiting for any events. |
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434 | - Queue all outstanding I/O (fd) events. |
350 | 8. Update the "event loop time" and do time jump handling. |
435 | - Update the "event loop time" and do time jump handling. |
351 | 9. Queue all outstanding timers. |
436 | - Queue all outstanding timers. |
352 | 10. Queue all outstanding periodics. |
437 | - Queue all outstanding periodics. |
353 | 11. If no events are pending now, queue all idle watchers. |
438 | - If no events are pending now, queue all idle watchers. |
354 | 12. Queue all check watchers. |
439 | - Queue all check watchers. |
355 | 13. Call all queued watchers in reverse order (i.e. check watchers first). |
440 | - Call all queued watchers in reverse order (i.e. check watchers first). |
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441 | Signals and child watchers are implemented as I/O watchers, and will |
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442 | be handled here by queueing them when their watcher gets executed. |
356 | 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
443 | - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
357 | was used, return, otherwise continue with step #1. |
444 | were used, return, otherwise continue with step *. |
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445 | |
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446 | </pre> |
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447 | <p>Example: queue some jobs and then loop until no events are outsanding |
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448 | anymore.</p> |
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449 | <pre> ... queue jobs here, make sure they register event watchers as long |
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450 | ... as they still have work to do (even an idle watcher will do..) |
|
|
451 | ev_loop (my_loop, 0); |
|
|
452 | ... jobs done. yeah! |
358 | |
453 | |
359 | </pre> |
454 | </pre> |
360 | </dd> |
455 | </dd> |
361 | <dt>ev_unloop (loop, how)</dt> |
456 | <dt>ev_unloop (loop, how)</dt> |
362 | <dd> |
457 | <dd> |
… | |
… | |
376 | example, libev itself uses this for its internal signal pipe: It is not |
471 | example, libev itself uses this for its internal signal pipe: It is not |
377 | visible to the libev user and should not keep <code>ev_loop</code> from exiting if |
472 | visible to the libev user and should not keep <code>ev_loop</code> from exiting if |
378 | no event watchers registered by it are active. It is also an excellent |
473 | no event watchers registered by it are active. It is also an excellent |
379 | way to do this for generic recurring timers or from within third-party |
474 | way to do this for generic recurring timers or from within third-party |
380 | libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> |
475 | libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> |
|
|
476 | <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> |
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477 | running when nothing else is active.</p> |
|
|
478 | <pre> struct dv_signal exitsig; |
|
|
479 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
|
|
480 | ev_signal_start (myloop, &exitsig); |
|
|
481 | evf_unref (myloop); |
|
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482 | |
|
|
483 | </pre> |
|
|
484 | <p>Example: for some weird reason, unregister the above signal handler again.</p> |
|
|
485 | <pre> ev_ref (myloop); |
|
|
486 | ev_signal_stop (myloop, &exitsig); |
|
|
487 | |
|
|
488 | </pre> |
381 | </dd> |
489 | </dd> |
382 | </dl> |
490 | </dl> |
383 | |
491 | |
384 | </div> |
492 | </div> |
385 | <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> |
493 | <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> |
… | |
… | |
521 | <h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> |
629 | <h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> |
522 | <div id="WATCHER_TYPES_CONTENT"> |
630 | <div id="WATCHER_TYPES_CONTENT"> |
523 | <p>This section describes each watcher in detail, but will not repeat |
631 | <p>This section describes each watcher in detail, but will not repeat |
524 | information given in the last section.</p> |
632 | information given in the last section.</p> |
525 | |
633 | |
|
|
634 | |
|
|
635 | |
|
|
636 | |
|
|
637 | |
526 | </div> |
638 | </div> |
527 | <h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> |
639 | <h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> |
528 | <div id="code_ev_io_code_is_this_file_descrip-2"> |
640 | <div id="code_ev_io_code_is_this_file_descrip-2"> |
529 | <p>I/O watchers check whether a file descriptor is readable or writable |
641 | <p>I/O watchers check whether a file descriptor is readable or writable |
530 | in each iteration of the event loop (This behaviour is called |
642 | in each iteration of the event loop (This behaviour is called |
… | |
… | |
548 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
660 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
549 | <dd> |
661 | <dd> |
550 | <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive |
662 | <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive |
551 | events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | |
663 | events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | |
552 | EV_WRITE</code> to receive the given events.</p> |
664 | EV_WRITE</code> to receive the given events.</p> |
|
|
665 | <p>Please note that most of the more scalable backend mechanisms (for example |
|
|
666 | epoll and solaris ports) can result in spurious readyness notifications |
|
|
667 | for file descriptors, so you practically need to use non-blocking I/O (and |
|
|
668 | treat callback invocation as hint only), or retest separately with a safe |
|
|
669 | interface before doing I/O (XLib can do this), or force the use of either |
|
|
670 | <code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this |
|
|
671 | problem. Also note that it is quite easy to have your callback invoked |
|
|
672 | when the readyness condition is no longer valid even when employing |
|
|
673 | typical ways of handling events, so its a good idea to use non-blocking |
|
|
674 | I/O unconditionally.</p> |
553 | </dd> |
675 | </dd> |
554 | </dl> |
676 | </dl> |
|
|
677 | <p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well |
|
|
678 | readable, but only once. Since it is likely line-buffered, you could |
|
|
679 | attempt to read a whole line in the callback:</p> |
|
|
680 | <pre> static void |
|
|
681 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
682 | { |
|
|
683 | ev_io_stop (loop, w); |
|
|
684 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
|
|
685 | } |
|
|
686 | |
|
|
687 | ... |
|
|
688 | struct ev_loop *loop = ev_default_init (0); |
|
|
689 | struct ev_io stdin_readable; |
|
|
690 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
|
|
691 | ev_io_start (loop, &stdin_readable); |
|
|
692 | ev_loop (loop, 0); |
|
|
693 | |
|
|
694 | |
|
|
695 | |
|
|
696 | |
|
|
697 | </pre> |
555 | |
698 | |
556 | </div> |
699 | </div> |
557 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
700 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
558 | <div id="code_ev_timer_code_relative_and_opti-2"> |
701 | <div id="code_ev_timer_code_relative_and_opti-2"> |
559 | <p>Timer watchers are simple relative timers that generate an event after a |
702 | <p>Timer watchers are simple relative timers that generate an event after a |
… | |
… | |
603 | time you successfully read or write some data. If you go into an idle |
746 | time you successfully read or write some data. If you go into an idle |
604 | state where you do not expect data to travel on the socket, you can stop |
747 | state where you do not expect data to travel on the socket, you can stop |
605 | the timer, and again will automatically restart it if need be.</p> |
748 | the timer, and again will automatically restart it if need be.</p> |
606 | </dd> |
749 | </dd> |
607 | </dl> |
750 | </dl> |
|
|
751 | <p>Example: create a timer that fires after 60 seconds.</p> |
|
|
752 | <pre> static void |
|
|
753 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
754 | { |
|
|
755 | .. one minute over, w is actually stopped right here |
|
|
756 | } |
|
|
757 | |
|
|
758 | struct ev_timer mytimer; |
|
|
759 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
|
|
760 | ev_timer_start (loop, &mytimer); |
|
|
761 | |
|
|
762 | </pre> |
|
|
763 | <p>Example: create a timeout timer that times out after 10 seconds of |
|
|
764 | inactivity.</p> |
|
|
765 | <pre> static void |
|
|
766 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
767 | { |
|
|
768 | .. ten seconds without any activity |
|
|
769 | } |
|
|
770 | |
|
|
771 | struct ev_timer mytimer; |
|
|
772 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
|
|
773 | ev_timer_again (&mytimer); /* start timer */ |
|
|
774 | ev_loop (loop, 0); |
|
|
775 | |
|
|
776 | // and in some piece of code that gets executed on any "activity": |
|
|
777 | // reset the timeout to start ticking again at 10 seconds |
|
|
778 | ev_timer_again (&mytimer); |
|
|
779 | |
|
|
780 | |
|
|
781 | |
|
|
782 | |
|
|
783 | </pre> |
608 | |
784 | |
609 | </div> |
785 | </div> |
610 | <h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> |
786 | <h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> |
611 | <div id="code_ev_periodic_code_to_cron_or_not-2"> |
787 | <div id="code_ev_periodic_code_to_cron_or_not-2"> |
612 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
788 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
… | |
… | |
696 | when you changed some parameters or the reschedule callback would return |
872 | when you changed some parameters or the reschedule callback would return |
697 | a different time than the last time it was called (e.g. in a crond like |
873 | a different time than the last time it was called (e.g. in a crond like |
698 | program when the crontabs have changed).</p> |
874 | program when the crontabs have changed).</p> |
699 | </dd> |
875 | </dd> |
700 | </dl> |
876 | </dl> |
|
|
877 | <p>Example: call a callback every hour, or, more precisely, whenever the |
|
|
878 | system clock is divisible by 3600. The callback invocation times have |
|
|
879 | potentially a lot of jittering, but good long-term stability.</p> |
|
|
880 | <pre> static void |
|
|
881 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
882 | { |
|
|
883 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
|
|
884 | } |
|
|
885 | |
|
|
886 | struct ev_periodic hourly_tick; |
|
|
887 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
|
|
888 | ev_periodic_start (loop, &hourly_tick); |
|
|
889 | |
|
|
890 | </pre> |
|
|
891 | <p>Example: the same as above, but use a reschedule callback to do it:</p> |
|
|
892 | <pre> #include <math.h> |
|
|
893 | |
|
|
894 | static ev_tstamp |
|
|
895 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
|
|
896 | { |
|
|
897 | return fmod (now, 3600.) + 3600.; |
|
|
898 | } |
|
|
899 | |
|
|
900 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
|
|
901 | |
|
|
902 | </pre> |
|
|
903 | <p>Example: call a callback every hour, starting now:</p> |
|
|
904 | <pre> struct ev_periodic hourly_tick; |
|
|
905 | ev_periodic_init (&hourly_tick, clock_cb, |
|
|
906 | fmod (ev_now (loop), 3600.), 3600., 0); |
|
|
907 | ev_periodic_start (loop, &hourly_tick); |
|
|
908 | |
|
|
909 | |
|
|
910 | |
|
|
911 | |
|
|
912 | </pre> |
701 | |
913 | |
702 | </div> |
914 | </div> |
703 | <h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> |
915 | <h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> |
704 | <div id="code_ev_signal_code_signal_me_when_a-2"> |
916 | <div id="code_ev_signal_code_signal_me_when_a-2"> |
705 | <p>Signal watchers will trigger an event when the process receives a specific |
917 | <p>Signal watchers will trigger an event when the process receives a specific |
… | |
… | |
736 | the status word (use the macros from <code>sys/wait.h</code> and see your systems |
948 | the status word (use the macros from <code>sys/wait.h</code> and see your systems |
737 | <code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the |
949 | <code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the |
738 | process causing the status change.</p> |
950 | process causing the status change.</p> |
739 | </dd> |
951 | </dd> |
740 | </dl> |
952 | </dl> |
|
|
953 | <p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> |
|
|
954 | <pre> static void |
|
|
955 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
956 | { |
|
|
957 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
958 | } |
|
|
959 | |
|
|
960 | struct ev_signal signal_watcher; |
|
|
961 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
962 | ev_signal_start (loop, &sigint_cb); |
|
|
963 | |
|
|
964 | |
|
|
965 | |
|
|
966 | |
|
|
967 | </pre> |
741 | |
968 | |
742 | </div> |
969 | </div> |
743 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> |
970 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> |
744 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
971 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
745 | <p>Idle watchers trigger events when there are no other events are pending |
972 | <p>Idle watchers trigger events when there are no other events are pending |
… | |
… | |
761 | <p>Initialises and configures the idle watcher - it has no parameters of any |
988 | <p>Initialises and configures the idle watcher - it has no parameters of any |
762 | kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, |
989 | kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, |
763 | believe me.</p> |
990 | believe me.</p> |
764 | </dd> |
991 | </dd> |
765 | </dl> |
992 | </dl> |
|
|
993 | <p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the |
|
|
994 | callback, free it. Alos, use no error checking, as usual.</p> |
|
|
995 | <pre> static void |
|
|
996 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
|
|
997 | { |
|
|
998 | free (w); |
|
|
999 | // now do something you wanted to do when the program has |
|
|
1000 | // no longer asnything immediate to do. |
|
|
1001 | } |
|
|
1002 | |
|
|
1003 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
|
|
1004 | ev_idle_init (idle_watcher, idle_cb); |
|
|
1005 | ev_idle_start (loop, idle_cb); |
|
|
1006 | |
|
|
1007 | |
|
|
1008 | |
|
|
1009 | |
|
|
1010 | </pre> |
766 | |
1011 | |
767 | </div> |
1012 | </div> |
768 | <h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> |
1013 | <h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> |
769 | <div id="code_ev_prepare_code_and_code_ev_che-2"> |
1014 | <div id="code_ev_prepare_code_and_code_ev_che-2"> |
770 | <p>Prepare and check watchers are usually (but not always) used in tandem: |
1015 | <p>Prepare and check watchers are usually (but not always) used in tandem: |
… | |
… | |
796 | <p>Initialises and configures the prepare or check watcher - they have no |
1041 | <p>Initialises and configures the prepare or check watcher - they have no |
797 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1042 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
798 | macros, but using them is utterly, utterly and completely pointless.</p> |
1043 | macros, but using them is utterly, utterly and completely pointless.</p> |
799 | </dd> |
1044 | </dd> |
800 | </dl> |
1045 | </dl> |
|
|
1046 | <p>Example: *TODO*.</p> |
|
|
1047 | |
|
|
1048 | |
|
|
1049 | |
|
|
1050 | |
801 | |
1051 | |
802 | </div> |
1052 | </div> |
803 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
1053 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
804 | <div id="OTHER_FUNCTIONS_CONTENT"> |
1054 | <div id="OTHER_FUNCTIONS_CONTENT"> |
805 | <p>There are some other functions of possible interest. Described. Here. Now.</p> |
1055 | <p>There are some other functions of possible interest. Described. Here. Now.</p> |
… | |
… | |
849 | <dd> |
1099 | <dd> |
850 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
1100 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
851 | </dd> |
1101 | </dd> |
852 | </dl> |
1102 | </dl> |
853 | |
1103 | |
|
|
1104 | |
|
|
1105 | |
|
|
1106 | |
|
|
1107 | |
854 | </div> |
1108 | </div> |
855 | <h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
1109 | <h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
856 | <div id="LIBEVENT_EMULATION_CONTENT"> |
1110 | <div id="LIBEVENT_EMULATION_CONTENT"> |
857 | <p>Libev offers a compatibility emulation layer for libevent. It cannot |
1111 | <p>Libev offers a compatibility emulation layer for libevent. It cannot |
858 | emulate the internals of libevent, so here are some usage hints:</p> |
1112 | emulate the internals of libevent, so here are some usage hints:</p> |