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Revision 1.55 by root, Tue Nov 27 20:38:07 2007 UTC vs.
Revision 1.62 by root, Thu Nov 29 17:28:13 2007 UTC

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63details of the event, and then hand it over to libev by I<starting> the 63details of the event, and then hand it over to libev by I<starting> the
64watcher. 64watcher.
65 65
66=head1 FEATURES 66=head1 FEATURES
67 67
68Libev supports C<select>, C<poll>, the linux-specific C<epoll>, the 68Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
69bsd-specific C<kqueue> and the solaris-specific event port mechanisms 69BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70for file descriptor events (C<ev_io>), relative timers (C<ev_timer>), 70for file descriptor events (C<ev_io>), the Linux C<inotify> interface
71(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
71absolute timers with customised rescheduling (C<ev_periodic>), synchronous 72with customised rescheduling (C<ev_periodic>), synchronous signals
72signals (C<ev_signal>), process status change events (C<ev_child>), and 73(C<ev_signal>), process status change events (C<ev_child>), and event
73event watchers dealing with the event loop mechanism itself (C<ev_idle>, 74watchers dealing with the event loop mechanism itself (C<ev_idle>,
74C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as 75C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
75file watchers (C<ev_stat>) and even limited support for fork events 76file watchers (C<ev_stat>) and even limited support for fork events
76(C<ev_fork>). 77(C<ev_fork>).
77 78
78It also is quite fast (see this 79It also is quite fast (see this
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162C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for 163C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
163recommended ones. 164recommended ones.
164 165
165See the description of C<ev_embed> watchers for more info. 166See the description of C<ev_embed> watchers for more info.
166 167
167=item ev_set_allocator (void *(*cb)(void *ptr, size_t size)) 168=item ev_set_allocator (void *(*cb)(void *ptr, long size))
168 169
169Sets the allocation function to use (the prototype and semantics are 170Sets the allocation function to use (the prototype is similar - the
170identical to the realloc C function). It is used to allocate and free 171semantics is identical - to the realloc C function). It is used to
171memory (no surprises here). If it returns zero when memory needs to be 172allocate and free memory (no surprises here). If it returns zero when
172allocated, the library might abort or take some potentially destructive 173memory needs to be allocated, the library might abort or take some
173action. The default is your system realloc function. 174potentially destructive action. The default is your system realloc
175function.
174 176
175You could override this function in high-availability programs to, say, 177You could override this function in high-availability programs to, say,
176free some memory if it cannot allocate memory, to use a special allocator, 178free some memory if it cannot allocate memory, to use a special allocator,
177or even to sleep a while and retry until some memory is available. 179or even to sleep a while and retry until some memory is available.
178 180
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263or setgid) then libev will I<not> look at the environment variable 265or setgid) then libev will I<not> look at the environment variable
264C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will 266C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
265override the flags completely if it is found in the environment. This is 267override the flags completely if it is found in the environment. This is
266useful to try out specific backends to test their performance, or to work 268useful to try out specific backends to test their performance, or to work
267around bugs. 269around bugs.
270
271=item C<EVFLAG_FORKCHECK>
272
273Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
274a fork, you can also make libev check for a fork in each iteration by
275enabling this flag.
276
277This works by calling C<getpid ()> on every iteration of the loop,
278and thus this might slow down your event loop if you do a lot of loop
279iterations and little real work, but is usually not noticable (on my
280Linux system for example, C<getpid> is actually a simple 5-insn sequence
281without a syscall and thus I<very> fast, but my Linux system also has
282C<pthread_atfork> which is even faster).
283
284The big advantage of this flag is that you can forget about fork (and
285forget about forgetting to tell libev about forking) when you use this
286flag.
287
288This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
289environment variable.
268 290
269=item C<EVBACKEND_SELECT> (value 1, portable select backend) 291=item C<EVBACKEND_SELECT> (value 1, portable select backend)
270 292
271This is your standard select(2) backend. Not I<completely> standard, as 293This is your standard select(2) backend. Not I<completely> standard, as
272libev tries to roll its own fd_set with no limits on the number of fds, 294libev tries to roll its own fd_set with no limits on the number of fds,
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914=item ev_timer_again (loop) 936=item ev_timer_again (loop)
915 937
916This will act as if the timer timed out and restart it again if it is 938This will act as if the timer timed out and restart it again if it is
917repeating. The exact semantics are: 939repeating. The exact semantics are:
918 940
941If the timer is pending, its pending status is cleared.
942
919If the timer is started but nonrepeating, stop it. 943If the timer is started but nonrepeating, stop it (as if it timed out).
920 944
921If the timer is repeating, either start it if necessary (with the repeat 945If the timer is repeating, either start it if necessary (with the
922value), or reset the running timer to the repeat value. 946C<repeat> value), or reset the running timer to the C<repeat> value.
923 947
924This sounds a bit complicated, but here is a useful and typical 948This sounds a bit complicated, but here is a useful and typical
925example: Imagine you have a tcp connection and you want a so-called 949example: Imagine you have a tcp connection and you want a so-called idle
926idle timeout, that is, you want to be called when there have been, 950timeout, that is, you want to be called when there have been, say, 60
927say, 60 seconds of inactivity on the socket. The easiest way to do 951seconds of inactivity on the socket. The easiest way to do this is to
928this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling 952configure an C<ev_timer> with a C<repeat> value of C<60> and then call
929C<ev_timer_again> each time you successfully read or write some data. If 953C<ev_timer_again> each time you successfully read or write some data. If
930you go into an idle state where you do not expect data to travel on the 954you go into an idle state where you do not expect data to travel on the
931socket, you can stop the timer, and again will automatically restart it if 955socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
932need be. 956automatically restart it if need be.
933 957
934You can also ignore the C<after> value and C<ev_timer_start> altogether 958That means you can ignore the C<after> value and C<ev_timer_start>
935and only ever use the C<repeat> value: 959altogether and only ever use the C<repeat> value and C<ev_timer_again>:
936 960
937 ev_timer_init (timer, callback, 0., 5.); 961 ev_timer_init (timer, callback, 0., 5.);
938 ev_timer_again (loop, timer); 962 ev_timer_again (loop, timer);
939 ... 963 ...
940 timer->again = 17.; 964 timer->again = 17.;
941 ev_timer_again (loop, timer); 965 ev_timer_again (loop, timer);
942 ... 966 ...
943 timer->again = 10.; 967 timer->again = 10.;
944 ev_timer_again (loop, timer); 968 ev_timer_again (loop, timer);
945 969
946This is more efficient then stopping/starting the timer eahc time you want 970This is more slightly efficient then stopping/starting the timer each time
947to modify its timeout value. 971you want to modify its timeout value.
948 972
949=item ev_tstamp repeat [read-write] 973=item ev_tstamp repeat [read-write]
950 974
951The current C<repeat> value. Will be used each time the watcher times out 975The current C<repeat> value. Will be used each time the watcher times out
952or C<ev_timer_again> is called and determines the next timeout (if any), 976or C<ev_timer_again> is called and determines the next timeout (if any),
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1221not exist" is a status change like any other. The condition "path does 1245not exist" is a status change like any other. The condition "path does
1222not exist" is signified by the C<st_nlink> field being zero (which is 1246not exist" is signified by the C<st_nlink> field being zero (which is
1223otherwise always forced to be at least one) and all the other fields of 1247otherwise always forced to be at least one) and all the other fields of
1224the stat buffer having unspecified contents. 1248the stat buffer having unspecified contents.
1225 1249
1250The path I<should> be absolute and I<must not> end in a slash. If it is
1251relative and your working directory changes, the behaviour is undefined.
1252
1226Since there is no standard to do this, the portable implementation simply 1253Since there is no standard to do this, the portable implementation simply
1227calls C<stat (2)> regulalry on the path to see if it changed somehow. You 1254calls C<stat (2)> regularly on the path to see if it changed somehow. You
1228can specify a recommended polling interval for this case. If you specify 1255can specify a recommended polling interval for this case. If you specify
1229a polling interval of C<0> (highly recommended!) then a I<suitable, 1256a polling interval of C<0> (highly recommended!) then a I<suitable,
1230unspecified default> value will be used (which you can expect to be around 1257unspecified default> value will be used (which you can expect to be around
1231five seconds, although this might change dynamically). Libev will also 1258five seconds, although this might change dynamically). Libev will also
1232impose a minimum interval which is currently around C<0.1>, but thats 1259impose a minimum interval which is currently around C<0.1>, but thats
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1234 1261
1235This watcher type is not meant for massive numbers of stat watchers, 1262This watcher type is not meant for massive numbers of stat watchers,
1236as even with OS-supported change notifications, this can be 1263as even with OS-supported change notifications, this can be
1237resource-intensive. 1264resource-intensive.
1238 1265
1239At the time of this writing, no specific OS backends are implemented, but 1266At the time of this writing, only the Linux inotify interface is
1240if demand increases, at least a kqueue and inotify backend will be added. 1267implemented (implementing kqueue support is left as an exercise for the
1268reader). Inotify will be used to give hints only and should not change the
1269semantics of C<ev_stat> watchers, which means that libev sometimes needs
1270to fall back to regular polling again even with inotify, but changes are
1271usually detected immediately, and if the file exists there will be no
1272polling.
1241 1273
1242=over 4 1274=over 4
1243 1275
1244=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1276=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1245 1277
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2014 2046
2015=item EV_USE_DEVPOLL 2047=item EV_USE_DEVPOLL
2016 2048
2017reserved for future expansion, works like the USE symbols above. 2049reserved for future expansion, works like the USE symbols above.
2018 2050
2051=item EV_USE_INOTIFY
2052
2053If defined to be C<1>, libev will compile in support for the Linux inotify
2054interface to speed up C<ev_stat> watchers. Its actual availability will
2055be detected at runtime.
2056
2019=item EV_H 2057=item EV_H
2020 2058
2021The name of the F<ev.h> header file used to include it. The default if 2059The name of the F<ev.h> header file used to include it. The default if
2022undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2060undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
2023can be used to virtually rename the F<ev.h> header file in case of conflicts. 2061can be used to virtually rename the F<ev.h> header file in case of conflicts.
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2078=item EV_PID_HASHSIZE 2116=item EV_PID_HASHSIZE
2079 2117
2080C<ev_child> watchers use a small hash table to distribute workload by 2118C<ev_child> watchers use a small hash table to distribute workload by
2081pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more 2119pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2082than enough. If you need to manage thousands of children you might want to 2120than enough. If you need to manage thousands of children you might want to
2083increase this value. 2121increase this value (I<must> be a power of two).
2122
2123=item EV_INOTIFY_HASHSIZE
2124
2125C<ev_staz> watchers use a small hash table to distribute workload by
2126inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2127usually more than enough. If you need to manage thousands of C<ev_stat>
2128watchers you might want to increase this value (I<must> be a power of
2129two).
2084 2130
2085=item EV_COMMON 2131=item EV_COMMON
2086 2132
2087By default, all watchers have a C<void *data> member. By redefining 2133By default, all watchers have a C<void *data> member. By redefining
2088this macro to a something else you can include more and other types of 2134this macro to a something else you can include more and other types of
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2148 2194
2149=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2195=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2150 2196
2151=item Stopping check/prepare/idle watchers: O(1) 2197=item Stopping check/prepare/idle watchers: O(1)
2152 2198
2153=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16)) 2199=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2154 2200
2155=item Finding the next timer per loop iteration: O(1) 2201=item Finding the next timer per loop iteration: O(1)
2156 2202
2157=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2203=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2158 2204

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