… | |
… | |
47 | |
47 | |
48 | return 0; |
48 | return 0; |
49 | } |
49 | } |
50 | |
50 | |
51 | =head1 DESCRIPTION |
51 | =head1 DESCRIPTION |
|
|
52 | |
|
|
53 | The newest version of this document is also available as a html-formatted |
|
|
54 | web page you might find easier to navigate when reading it for the first |
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55 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
52 | |
56 | |
53 | Libev is an event loop: you register interest in certain events (such as a |
57 | Libev is an event loop: you register interest in certain events (such as a |
54 | file descriptor being readable or a timeout occuring), and it will manage |
58 | file descriptor being readable or a timeout occuring), and it will manage |
55 | these event sources and provide your program with events. |
59 | these event sources and provide your program with events. |
56 | |
60 | |
… | |
… | |
744 | =item ev_cb_set (ev_TYPE *watcher, callback) |
748 | =item ev_cb_set (ev_TYPE *watcher, callback) |
745 | |
749 | |
746 | Change the callback. You can change the callback at virtually any time |
750 | Change the callback. You can change the callback at virtually any time |
747 | (modulo threads). |
751 | (modulo threads). |
748 | |
752 | |
|
|
753 | =item ev_set_priority (ev_TYPE *watcher, priority) |
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|
754 | |
|
|
755 | =item int ev_priority (ev_TYPE *watcher) |
|
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756 | |
|
|
757 | Set and query the priority of the watcher. The priority is a small |
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758 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
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759 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
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760 | before watchers with lower priority, but priority will not keep watchers |
|
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761 | from being executed (except for C<ev_idle> watchers). |
|
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762 | |
|
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763 | This means that priorities are I<only> used for ordering callback |
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764 | invocation after new events have been received. This is useful, for |
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765 | example, to reduce latency after idling, or more often, to bind two |
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766 | watchers on the same event and make sure one is called first. |
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767 | |
|
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768 | If you need to suppress invocation when higher priority events are pending |
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769 | you need to look at C<ev_idle> watchers, which provide this functionality. |
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770 | |
|
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771 | The default priority used by watchers when no priority has been set is |
|
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772 | always C<0>, which is supposed to not be too high and not be too low :). |
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773 | |
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774 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
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775 | fine, as long as you do not mind that the priority value you query might |
|
|
776 | or might not have been adjusted to be within valid range. |
|
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777 | |
749 | =back |
778 | =back |
750 | |
779 | |
751 | |
780 | |
752 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
781 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
753 | |
782 | |
… | |
… | |
858 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
887 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
859 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
888 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
860 | |
889 | |
861 | If you cannot run the fd in non-blocking mode (for example you should not |
890 | If you cannot run the fd in non-blocking mode (for example you should not |
862 | play around with an Xlib connection), then you have to seperately re-test |
891 | play around with an Xlib connection), then you have to seperately re-test |
863 | wether a file descriptor is really ready with a known-to-be good interface |
892 | whether a file descriptor is really ready with a known-to-be good interface |
864 | such as poll (fortunately in our Xlib example, Xlib already does this on |
893 | such as poll (fortunately in our Xlib example, Xlib already does this on |
865 | its own, so its quite safe to use). |
894 | its own, so its quite safe to use). |
866 | |
895 | |
867 | =over 4 |
896 | =over 4 |
868 | |
897 | |
… | |
… | |
1351 | ev_stat_start (loop, &passwd); |
1380 | ev_stat_start (loop, &passwd); |
1352 | |
1381 | |
1353 | |
1382 | |
1354 | =head2 C<ev_idle> - when you've got nothing better to do... |
1383 | =head2 C<ev_idle> - when you've got nothing better to do... |
1355 | |
1384 | |
1356 | Idle watchers trigger events when there are no other events are pending |
1385 | Idle watchers trigger events when no other events of the same or higher |
1357 | (prepare, check and other idle watchers do not count). That is, as long |
1386 | priority are pending (prepare, check and other idle watchers do not |
1358 | as your process is busy handling sockets or timeouts (or even signals, |
1387 | count). |
1359 | imagine) it will not be triggered. But when your process is idle all idle |
1388 | |
1360 | watchers are being called again and again, once per event loop iteration - |
1389 | That is, as long as your process is busy handling sockets or timeouts |
|
|
1390 | (or even signals, imagine) of the same or higher priority it will not be |
|
|
1391 | triggered. But when your process is idle (or only lower-priority watchers |
|
|
1392 | are pending), the idle watchers are being called once per event loop |
1361 | until stopped, that is, or your process receives more events and becomes |
1393 | iteration - until stopped, that is, or your process receives more events |
1362 | busy. |
1394 | and becomes busy again with higher priority stuff. |
1363 | |
1395 | |
1364 | The most noteworthy effect is that as long as any idle watchers are |
1396 | The most noteworthy effect is that as long as any idle watchers are |
1365 | active, the process will not block when waiting for new events. |
1397 | active, the process will not block when waiting for new events. |
1366 | |
1398 | |
1367 | Apart from keeping your process non-blocking (which is a useful |
1399 | Apart from keeping your process non-blocking (which is a useful |
… | |
… | |
1816 | |
1848 | |
1817 | |
1849 | |
1818 | =head1 MACRO MAGIC |
1850 | =head1 MACRO MAGIC |
1819 | |
1851 | |
1820 | Libev can be compiled with a variety of options, the most fundemantal is |
1852 | Libev can be compiled with a variety of options, the most fundemantal is |
1821 | C<EV_MULTIPLICITY>. This option determines wether (most) functions and |
1853 | C<EV_MULTIPLICITY>. This option determines whether (most) functions and |
1822 | callbacks have an initial C<struct ev_loop *> argument. |
1854 | callbacks have an initial C<struct ev_loop *> argument. |
1823 | |
1855 | |
1824 | To make it easier to write programs that cope with either variant, the |
1856 | To make it easier to write programs that cope with either variant, the |
1825 | following macros are defined: |
1857 | following macros are defined: |
1826 | |
1858 | |
… | |
… | |
1860 | loop, if multiple loops are supported ("ev loop default"). |
1892 | loop, if multiple loops are supported ("ev loop default"). |
1861 | |
1893 | |
1862 | =back |
1894 | =back |
1863 | |
1895 | |
1864 | Example: Declare and initialise a check watcher, utilising the above |
1896 | Example: Declare and initialise a check watcher, utilising the above |
1865 | macros so it will work regardless of wether multiple loops are supported |
1897 | macros so it will work regardless of whether multiple loops are supported |
1866 | or not. |
1898 | or not. |
1867 | |
1899 | |
1868 | static void |
1900 | static void |
1869 | check_cb (EV_P_ ev_timer *w, int revents) |
1901 | check_cb (EV_P_ ev_timer *w, int revents) |
1870 | { |
1902 | { |
… | |
… | |
2095 | will have the C<struct ev_loop *> as first argument, and you can create |
2127 | will have the C<struct ev_loop *> as first argument, and you can create |
2096 | additional independent event loops. Otherwise there will be no support |
2128 | additional independent event loops. Otherwise there will be no support |
2097 | for multiple event loops and there is no first event loop pointer |
2129 | for multiple event loops and there is no first event loop pointer |
2098 | argument. Instead, all functions act on the single default loop. |
2130 | argument. Instead, all functions act on the single default loop. |
2099 | |
2131 | |
|
|
2132 | =item EV_MINPRI |
|
|
2133 | |
|
|
2134 | =item EV_MAXPRI |
|
|
2135 | |
|
|
2136 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
|
|
2137 | C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can |
|
|
2138 | provide for more priorities by overriding those symbols (usually defined |
|
|
2139 | to be C<-2> and C<2>, respectively). |
|
|
2140 | |
|
|
2141 | When doing priority-based operations, libev usually has to linearly search |
|
|
2142 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
2143 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
|
|
2144 | fine. |
|
|
2145 | |
|
|
2146 | If your embedding app does not need any priorities, defining these both to |
|
|
2147 | C<0> will save some memory and cpu. |
|
|
2148 | |
2100 | =item EV_PERIODIC_ENABLE |
2149 | =item EV_PERIODIC_ENABLE |
2101 | |
2150 | |
2102 | If undefined or defined to be C<1>, then periodic timers are supported. If |
2151 | If undefined or defined to be C<1>, then periodic timers are supported. If |
|
|
2152 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
2153 | code. |
|
|
2154 | |
|
|
2155 | =item EV_IDLE_ENABLE |
|
|
2156 | |
|
|
2157 | If undefined or defined to be C<1>, then idle watchers are supported. If |
2103 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
2158 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
2104 | code. |
2159 | code. |
2105 | |
2160 | |
2106 | =item EV_EMBED_ENABLE |
2161 | =item EV_EMBED_ENABLE |
2107 | |
2162 | |
… | |
… | |
2204 | |
2259 | |
2205 | =over 4 |
2260 | =over 4 |
2206 | |
2261 | |
2207 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
2262 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
2208 | |
2263 | |
|
|
2264 | This means that, when you have a watcher that triggers in one hour and |
|
|
2265 | there are 100 watchers that would trigger before that then inserting will |
|
|
2266 | have to skip those 100 watchers. |
|
|
2267 | |
2209 | =item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) |
2268 | =item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) |
2210 | |
2269 | |
|
|
2270 | That means that for changing a timer costs less than removing/adding them |
|
|
2271 | as only the relative motion in the event queue has to be paid for. |
|
|
2272 | |
2211 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
2273 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
2212 | |
2274 | |
|
|
2275 | These just add the watcher into an array or at the head of a list. If |
|
|
2276 | the array needs to be extended libev needs to realloc and move the whole |
|
|
2277 | array, but this happen asymptotically less and less with more watchers, |
|
|
2278 | thus amortised O(1). |
|
|
2279 | |
2213 | =item Stopping check/prepare/idle watchers: O(1) |
2280 | =item Stopping check/prepare/idle watchers: O(1) |
2214 | |
2281 | |
2215 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2282 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2216 | |
2283 | |
|
|
2284 | These watchers are stored in lists then need to be walked to find the |
|
|
2285 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
2286 | have many watchers waiting for the same fd or signal). |
|
|
2287 | |
2217 | =item Finding the next timer per loop iteration: O(1) |
2288 | =item Finding the next timer per loop iteration: O(1) |
2218 | |
2289 | |
2219 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
2290 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
2220 | |
2291 | |
|
|
2292 | A change means an I/O watcher gets started or stopped, which requires |
|
|
2293 | libev to recalculate its status (and possibly tell the kernel). |
|
|
2294 | |
2221 | =item Activating one watcher: O(1) |
2295 | =item Activating one watcher: O(1) |
2222 | |
2296 | |
|
|
2297 | =item Priority handling: O(number_of_priorities) |
|
|
2298 | |
|
|
2299 | Priorities are implemented by allocating some space for each |
|
|
2300 | priority. When doing priority-based operations, libev usually has to |
|
|
2301 | linearly search all the priorities. |
|
|
2302 | |
2223 | =back |
2303 | =back |
2224 | |
2304 | |
2225 | |
2305 | |
2226 | =head1 AUTHOR |
2306 | =head1 AUTHOR |
2227 | |
2307 | |