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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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106 | <p>These functions can be called anytime, even before initialising the |
106 | <p>These functions can be called anytime, even before initialising the |
107 | library in any way.</p> |
107 | library in any way.</p> |
108 | <dl> |
108 | <dl> |
109 | <dt>ev_tstamp ev_time ()</dt> |
109 | <dt>ev_tstamp ev_time ()</dt> |
110 | <dd> |
110 | <dd> |
111 | <p>Returns the current time as libev would use it.</p> |
111 | <p>Returns the current time as libev would use it. Please note that the |
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112 | <code>ev_now</code> function is usually faster and also often returns the timestamp |
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113 | you actually want to know.</p> |
112 | </dd> |
114 | </dd> |
113 | <dt>int ev_version_major ()</dt> |
115 | <dt>int ev_version_major ()</dt> |
114 | <dt>int ev_version_minor ()</dt> |
116 | <dt>int ev_version_minor ()</dt> |
115 | <dd> |
117 | <dd> |
116 | <p>You can find out the major and minor version numbers of the library |
118 | <p>You can find out the major and minor version numbers of the library |
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120 | version of the library your program was compiled against.</p> |
122 | version of the library your program was compiled against.</p> |
121 | <p>Usually, it's a good idea to terminate if the major versions mismatch, |
123 | <p>Usually, it's a good idea to terminate if the major versions mismatch, |
122 | as this indicates an incompatible change. Minor versions are usually |
124 | as this indicates an incompatible change. Minor versions are usually |
123 | compatible to older versions, so a larger minor version alone is usually |
125 | compatible to older versions, so a larger minor version alone is usually |
124 | not a problem.</p> |
126 | not a problem.</p> |
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127 | </dd> |
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128 | <dt>unsigned int ev_supported_backends ()</dt> |
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129 | <dd> |
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130 | <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code> |
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131 | value) compiled into this binary of libev (independent of their |
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132 | availability on the system you are running on). See <code>ev_default_loop</code> for |
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133 | a description of the set values.</p> |
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134 | </dd> |
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135 | <dt>unsigned int ev_recommended_backends ()</dt> |
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136 | <dd> |
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137 | <p>Return the set of all backends compiled into this binary of libev and also |
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138 | recommended for this platform. This set is often smaller than the one |
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139 | returned by <code>ev_supported_backends</code>, as for example kqueue is broken on |
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140 | most BSDs and will not be autodetected unless you explicitly request it |
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141 | (assuming you know what you are doing). This is the set of backends that |
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142 | libev will probe for if you specify no backends explicitly.</p> |
125 | </dd> |
143 | </dd> |
126 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
144 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
127 | <dd> |
145 | <dd> |
128 | <p>Sets the allocation function to use (the prototype is similar to the |
146 | <p>Sets the allocation function to use (the prototype is similar to the |
129 | realloc C function, the semantics are identical). It is used to allocate |
147 | realloc C function, the semantics are identical). It is used to allocate |
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162 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
180 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
163 | <dd> |
181 | <dd> |
164 | <p>This will initialise the default event loop if it hasn't been initialised |
182 | <p>This will initialise the default event loop if it hasn't been initialised |
165 | yet and return it. If the default loop could not be initialised, returns |
183 | yet and return it. If the default loop could not be initialised, returns |
166 | false. If it already was initialised it simply returns it (and ignores the |
184 | false. If it already was initialised it simply returns it (and ignores the |
167 | flags).</p> |
185 | flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p> |
168 | <p>If you don't know what event loop to use, use the one returned from this |
186 | <p>If you don't know what event loop to use, use the one returned from this |
169 | function.</p> |
187 | function.</p> |
170 | <p>The flags argument can be used to specify special behaviour or specific |
188 | <p>The flags argument can be used to specify special behaviour or specific |
171 | backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> |
189 | backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p> |
172 | <p>It supports the following flags:</p> |
190 | <p>The following flags are supported:</p> |
173 | <p> |
191 | <p> |
174 | <dl> |
192 | <dl> |
175 | <dt><code>EVFLAG_AUTO</code></dt> |
193 | <dt><code>EVFLAG_AUTO</code></dt> |
176 | <dd> |
194 | <dd> |
177 | <p>The default flags value. Use this if you have no clue (it's the right |
195 | <p>The default flags value. Use this if you have no clue (it's the right |
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184 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
202 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
185 | override the flags completely if it is found in the environment. This is |
203 | override the flags completely if it is found in the environment. This is |
186 | useful to try out specific backends to test their performance, or to work |
204 | useful to try out specific backends to test their performance, or to work |
187 | around bugs.</p> |
205 | around bugs.</p> |
188 | </dd> |
206 | </dd> |
189 | <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt> |
207 | <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> |
190 | <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt> |
208 | <dd> |
191 | <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt> |
209 | <p>This is your standard select(2) backend. Not <i>completely</i> standard, as |
192 | <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt> |
210 | libev tries to roll its own fd_set with no limits on the number of fds, |
193 | <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt> |
211 | but if that fails, expect a fairly low limit on the number of fds when |
194 | <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt> |
212 | using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
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213 | the fastest backend for a low number of fds.</p> |
195 | <dd> |
214 | </dd> |
196 | <p>If one or more of these are ored into the flags value, then only these |
215 | <dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt> |
197 | backends will be tried (in the reverse order as given here). If one are |
216 | <dd> |
198 | specified, any backend will do.</p> |
217 | <p>And this is your standard poll(2) backend. It's more complicated than |
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218 | select, but handles sparse fds better and has no artificial limit on the |
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219 | number of fds you can use (except it will slow down considerably with a |
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220 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p> |
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221 | </dd> |
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222 | <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt> |
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223 | <dd> |
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224 | <p>For few fds, this backend is a bit little slower than poll and select, |
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225 | but it scales phenomenally better. While poll and select usually scale like |
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226 | O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
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227 | either O(1) or O(active_fds).</p> |
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228 | <p>While stopping and starting an I/O watcher in the same iteration will |
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229 | result in some caching, there is still a syscall per such incident |
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230 | (because the fd could point to a different file description now), so its |
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231 | best to avoid that. Also, dup()ed file descriptors might not work very |
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232 | well if you register events for both fds.</p> |
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233 | <p>Please note that epoll sometimes generates spurious notifications, so you |
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234 | need to use non-blocking I/O or other means to avoid blocking when no data |
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235 | (or space) is available.</p> |
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236 | </dd> |
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237 | <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt> |
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238 | <dd> |
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239 | <p>Kqueue deserves special mention, as at the time of this writing, it |
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240 | was broken on all BSDs except NetBSD (usually it doesn't work with |
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241 | anything but sockets and pipes, except on Darwin, where of course its |
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242 | completely useless). For this reason its not being "autodetected" |
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243 | unless you explicitly specify it explicitly in the flags (i.e. using |
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244 | <code>EVBACKEND_KQUEUE</code>).</p> |
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245 | <p>It scales in the same way as the epoll backend, but the interface to the |
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246 | kernel is more efficient (which says nothing about its actual speed, of |
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247 | course). While starting and stopping an I/O watcher does not cause an |
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248 | extra syscall as with epoll, it still adds up to four event changes per |
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249 | incident, so its best to avoid that.</p> |
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250 | </dd> |
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251 | <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt> |
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252 | <dd> |
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253 | <p>This is not implemented yet (and might never be).</p> |
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254 | </dd> |
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255 | <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt> |
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256 | <dd> |
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257 | <p>This uses the Solaris 10 port mechanism. As with everything on Solaris, |
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258 | it's really slow, but it still scales very well (O(active_fds)).</p> |
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259 | <p>Please note that solaris ports can result in a lot of spurious |
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260 | notifications, so you need to use non-blocking I/O or other means to avoid |
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261 | blocking when no data (or space) is available.</p> |
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262 | </dd> |
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263 | <dt><code>EVBACKEND_ALL</code></dt> |
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264 | <dd> |
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265 | <p>Try all backends (even potentially broken ones that wouldn't be tried |
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266 | with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as |
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267 | <code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p> |
199 | </dd> |
268 | </dd> |
200 | </dl> |
269 | </dl> |
201 | </p> |
270 | </p> |
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271 | <p>If one or more of these are ored into the flags value, then only these |
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272 | backends will be tried (in the reverse order as given here). If none are |
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273 | specified, most compiled-in backend will be tried, usually in reverse |
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274 | order of their flag values :)</p> |
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275 | <p>The most typical usage is like this:</p> |
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276 | <pre> if (!ev_default_loop (0)) |
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277 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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278 | |
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279 | </pre> |
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280 | <p>Restrict libev to the select and poll backends, and do not allow |
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281 | environment settings to be taken into account:</p> |
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282 | <pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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283 | |
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284 | </pre> |
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285 | <p>Use whatever libev has to offer, but make sure that kqueue is used if |
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286 | available (warning, breaks stuff, best use only with your own private |
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287 | event loop and only if you know the OS supports your types of fds):</p> |
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288 | <pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
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289 | |
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290 | </pre> |
202 | </dd> |
291 | </dd> |
203 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
292 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
204 | <dd> |
293 | <dd> |
205 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
294 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
206 | always distinct from the default loop. Unlike the default loop, it cannot |
295 | always distinct from the default loop. Unlike the default loop, it cannot |
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222 | <dd> |
311 | <dd> |
223 | <p>This function reinitialises the kernel state for backends that have |
312 | <p>This function reinitialises the kernel state for backends that have |
224 | one. Despite the name, you can call it anytime, but it makes most sense |
313 | one. Despite the name, you can call it anytime, but it makes most sense |
225 | after forking, in either the parent or child process (or both, but that |
314 | after forking, in either the parent or child process (or both, but that |
226 | again makes little sense).</p> |
315 | again makes little sense).</p> |
227 | <p>You <i>must</i> call this function after forking if and only if you want to |
316 | <p>You <i>must</i> call this function in the child process after forking if and |
228 | use the event library in both processes. If you just fork+exec, you don't |
317 | only if you want to use the event library in both processes. If you just |
229 | have to call it.</p> |
318 | fork+exec, you don't have to call it.</p> |
230 | <p>The function itself is quite fast and it's usually not a problem to call |
319 | <p>The function itself is quite fast and it's usually not a problem to call |
231 | it just in case after a fork. To make this easy, the function will fit in |
320 | it just in case after a fork. To make this easy, the function will fit in |
232 | quite nicely into a call to <code>pthread_atfork</code>:</p> |
321 | quite nicely into a call to <code>pthread_atfork</code>:</p> |
233 | <pre> pthread_atfork (0, 0, ev_default_fork); |
322 | <pre> pthread_atfork (0, 0, ev_default_fork); |
234 | |
323 | |
235 | </pre> |
324 | </pre> |
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325 | <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use |
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326 | without calling this function, so if you force one of those backends you |
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327 | do not need to care.</p> |
236 | </dd> |
328 | </dd> |
237 | <dt>ev_loop_fork (loop)</dt> |
329 | <dt>ev_loop_fork (loop)</dt> |
238 | <dd> |
330 | <dd> |
239 | <p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
331 | <p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
240 | <code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
332 | <code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
241 | after fork, and how you do this is entirely your own problem.</p> |
333 | after fork, and how you do this is entirely your own problem.</p> |
242 | </dd> |
334 | </dd> |
243 | <dt>unsigned int ev_method (loop)</dt> |
335 | <dt>unsigned int ev_backend (loop)</dt> |
244 | <dd> |
336 | <dd> |
245 | <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in |
337 | <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in |
246 | use.</p> |
338 | use.</p> |
247 | </dd> |
339 | </dd> |
248 | <dt>ev_tstamp ev_now (loop)</dt> |
340 | <dt>ev_tstamp ev_now (loop)</dt> |
249 | <dd> |
341 | <dd> |
250 | <p>Returns the current "event loop time", which is the time the event loop |
342 | <p>Returns the current "event loop time", which is the time the event loop |
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256 | <dt>ev_loop (loop, int flags)</dt> |
348 | <dt>ev_loop (loop, int flags)</dt> |
257 | <dd> |
349 | <dd> |
258 | <p>Finally, this is it, the event handler. This function usually is called |
350 | <p>Finally, this is it, the event handler. This function usually is called |
259 | after you initialised all your watchers and you want to start handling |
351 | after you initialised all your watchers and you want to start handling |
260 | events.</p> |
352 | events.</p> |
261 | <p>If the flags argument is specified as 0, it will not return until either |
353 | <p>If the flags argument is specified as <code>0</code>, it will not return until |
262 | no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
354 | either no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
263 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
355 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
264 | those events and any outstanding ones, but will not block your process in |
356 | those events and any outstanding ones, but will not block your process in |
265 | case there are no events and will return after one iteration of the loop.</p> |
357 | case there are no events and will return after one iteration of the loop.</p> |
266 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
358 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
267 | neccessary) and will handle those and any outstanding ones. It will block |
359 | neccessary) and will handle those and any outstanding ones. It will block |
268 | your process until at least one new event arrives, and will return after |
360 | your process until at least one new event arrives, and will return after |
269 | one iteration of the loop.</p> |
361 | one iteration of the loop. This is useful if you are waiting for some |
270 | <p>This flags value could be used to implement alternative looping |
362 | external event in conjunction with something not expressible using other |
271 | constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and |
363 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
272 | more generic mechanism.</p> |
364 | usually a better approach for this kind of thing.</p> |
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365 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
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366 | <pre> * If there are no active watchers (reference count is zero), return. |
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367 | - Queue prepare watchers and then call all outstanding watchers. |
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368 | - If we have been forked, recreate the kernel state. |
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369 | - Update the kernel state with all outstanding changes. |
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370 | - Update the "event loop time". |
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371 | - Calculate for how long to block. |
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372 | - Block the process, waiting for any events. |
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373 | - Queue all outstanding I/O (fd) events. |
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374 | - Update the "event loop time" and do time jump handling. |
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375 | - Queue all outstanding timers. |
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376 | - Queue all outstanding periodics. |
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377 | - If no events are pending now, queue all idle watchers. |
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378 | - Queue all check watchers. |
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379 | - Call all queued watchers in reverse order (i.e. check watchers first). |
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380 | Signals and child watchers are implemented as I/O watchers, and will |
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381 | be handled here by queueing them when their watcher gets executed. |
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382 | - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
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383 | were used, return, otherwise continue with step *. |
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384 | |
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385 | </pre> |
273 | </dd> |
386 | </dd> |
274 | <dt>ev_unloop (loop, how)</dt> |
387 | <dt>ev_unloop (loop, how)</dt> |
275 | <dd> |
388 | <dd> |
276 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
389 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
277 | has processed all outstanding events). The <code>how</code> argument must be either |
390 | has processed all outstanding events). The <code>how</code> argument must be either |
278 | <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or |
391 | <code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or |
279 | <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
392 | <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
280 | </dd> |
393 | </dd> |
281 | <dt>ev_ref (loop)</dt> |
394 | <dt>ev_ref (loop)</dt> |
282 | <dt>ev_unref (loop)</dt> |
395 | <dt>ev_unref (loop)</dt> |
283 | <dd> |
396 | <dd> |
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330 | with a watcher-specific start function (<code>ev_<type>_start (loop, watcher |
443 | with a watcher-specific start function (<code>ev_<type>_start (loop, watcher |
331 | *)</code>), and you can stop watching for events at any time by calling the |
444 | *)</code>), and you can stop watching for events at any time by calling the |
332 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
445 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
333 | <p>As long as your watcher is active (has been started but not stopped) you |
446 | <p>As long as your watcher is active (has been started but not stopped) you |
334 | must not touch the values stored in it. Most specifically you must never |
447 | must not touch the values stored in it. Most specifically you must never |
335 | reinitialise it or call its set method.</p> |
448 | reinitialise it or call its set macro.</p> |
336 | <p>You can check whether an event is active by calling the <code>ev_is_active |
449 | <p>You can check whether an event is active by calling the <code>ev_is_active |
337 | (watcher *)</code> macro. To see whether an event is outstanding (but the |
450 | (watcher *)</code> macro. To see whether an event is outstanding (but the |
338 | callback for it has not been called yet) you can use the <code>ev_is_pending |
451 | callback for it has not been called yet) you can use the <code>ev_is_pending |
339 | (watcher *)</code> macro.</p> |
452 | (watcher *)</code> macro.</p> |
340 | <p>Each and every callback receives the event loop pointer as first, the |
453 | <p>Each and every callback receives the event loop pointer as first, the |
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452 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
565 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
453 | descriptors correctly if you register interest in two or more fds pointing |
566 | descriptors correctly if you register interest in two or more fds pointing |
454 | to the same underlying file/socket etc. description (that is, they share |
567 | to the same underlying file/socket etc. description (that is, they share |
455 | the same underlying "file open").</p> |
568 | the same underlying "file open").</p> |
456 | <p>If you must do this, then force the use of a known-to-be-good backend |
569 | <p>If you must do this, then force the use of a known-to-be-good backend |
457 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
570 | (at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and |
458 | EVMETHOD_POLL).</p> |
571 | <code>EVBACKEND_POLL</code>).</p> |
459 | <dl> |
572 | <dl> |
460 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
573 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
461 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
574 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
462 | <dd> |
575 | <dd> |
463 | <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive |
576 | <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive |
464 | events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | |
577 | events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | |
465 | EV_WRITE</code> to receive the given events.</p> |
578 | EV_WRITE</code> to receive the given events.</p> |
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579 | <p>Please note that most of the more scalable backend mechanisms (for example |
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580 | epoll and solaris ports) can result in spurious readyness notifications |
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581 | for file descriptors, so you practically need to use non-blocking I/O (and |
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582 | treat callback invocation as hint only), or retest separately with a safe |
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583 | interface before doing I/O (XLib can do this), or force the use of either |
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584 | <code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this |
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585 | problem. Also note that it is quite easy to have your callback invoked |
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586 | when the readyness condition is no longer valid even when employing |
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587 | typical ways of handling events, so its a good idea to use non-blocking |
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588 | I/O unconditionally.</p> |
466 | </dd> |
589 | </dd> |
467 | </dl> |
590 | </dl> |
468 | |
591 | |
469 | </div> |
592 | </div> |
470 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
593 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
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472 | <p>Timer watchers are simple relative timers that generate an event after a |
595 | <p>Timer watchers are simple relative timers that generate an event after a |
473 | given time, and optionally repeating in regular intervals after that.</p> |
596 | given time, and optionally repeating in regular intervals after that.</p> |
474 | <p>The timers are based on real time, that is, if you register an event that |
597 | <p>The timers are based on real time, that is, if you register an event that |
475 | times out after an hour and you reset your system clock to last years |
598 | times out after an hour and you reset your system clock to last years |
476 | time, it will still time out after (roughly) and hour. "Roughly" because |
599 | time, it will still time out after (roughly) and hour. "Roughly" because |
477 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
600 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
478 | monotonic clock option helps a lot here).</p> |
601 | monotonic clock option helps a lot here).</p> |
479 | <p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
602 | <p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
480 | time. This is usually the right thing as this timestamp refers to the time |
603 | time. This is usually the right thing as this timestamp refers to the time |
481 | of the event triggering whatever timeout you are modifying/starting. If |
604 | of the event triggering whatever timeout you are modifying/starting. If |
482 | you suspect event processing to be delayed and you *need* to base the timeout |
605 | you suspect event processing to be delayed and you <i>need</i> to base the timeout |
483 | on the current time, use something like this to adjust for this:</p> |
606 | on the current time, use something like this to adjust for this:</p> |
484 | <pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
607 | <pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
485 | |
608 | |
486 | </pre> |
609 | </pre> |
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610 | <p>The callback is guarenteed to be invoked only when its timeout has passed, |
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611 | but if multiple timers become ready during the same loop iteration then |
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612 | order of execution is undefined.</p> |
487 | <dl> |
613 | <dl> |
488 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
614 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
489 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
615 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
490 | <dd> |
616 | <dd> |
491 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
617 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
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529 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
655 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
530 | roughly 10 seconds later and of course not if you reset your system time |
656 | roughly 10 seconds later and of course not if you reset your system time |
531 | again).</p> |
657 | again).</p> |
532 | <p>They can also be used to implement vastly more complex timers, such as |
658 | <p>They can also be used to implement vastly more complex timers, such as |
533 | triggering an event on eahc midnight, local time.</p> |
659 | triggering an event on eahc midnight, local time.</p> |
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660 | <p>As with timers, the callback is guarenteed to be invoked only when the |
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661 | time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
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662 | during the same loop iteration then order of execution is undefined.</p> |
534 | <dl> |
663 | <dl> |
535 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
664 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
536 | <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
665 | <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
537 | <dd> |
666 | <dd> |
538 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
667 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
539 | operation, and we will explain them from simplest to complex:</p> |
668 | operation, and we will explain them from simplest to complex:</p> |
540 | |
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541 | |
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542 | |
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543 | |
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544 | <p> |
669 | <p> |
545 | <dl> |
670 | <dl> |
546 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
671 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
547 | <dd> |
672 | <dd> |
548 | <p>In this configuration the watcher triggers an event at the wallclock time |
673 | <p>In this configuration the watcher triggers an event at the wallclock time |