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Revision 1.55 by root, Tue Nov 27 20:38:07 2007 UTC vs.
Revision 1.61 by root, Thu Nov 29 12:21:05 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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914=item ev_timer_again (loop) 916=item ev_timer_again (loop)
915 917
916This will act as if the timer timed out and restart it again if it is 918This will act as if the timer timed out and restart it again if it is
917repeating. The exact semantics are: 919repeating. The exact semantics are:
918 920
921If the timer is pending, its pending status is cleared.
922
919If the timer is started but nonrepeating, stop it. 923If the timer is started but nonrepeating, stop it (as if it timed out).
920 924
921If the timer is repeating, either start it if necessary (with the repeat 925If the timer is repeating, either start it if necessary (with the
922value), or reset the running timer to the repeat value. 926C<repeat> value), or reset the running timer to the C<repeat> value.
923 927
924This sounds a bit complicated, but here is a useful and typical 928This sounds a bit complicated, but here is a useful and typical
925example: Imagine you have a tcp connection and you want a so-called 929example: 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, 930timeout, 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 931seconds 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 932configure 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 933C<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 934you 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 935socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
932need be. 936automatically restart it if need be.
933 937
934You can also ignore the C<after> value and C<ev_timer_start> altogether 938That means you can ignore the C<after> value and C<ev_timer_start>
935and only ever use the C<repeat> value: 939altogether and only ever use the C<repeat> value and C<ev_timer_again>:
936 940
937 ev_timer_init (timer, callback, 0., 5.); 941 ev_timer_init (timer, callback, 0., 5.);
938 ev_timer_again (loop, timer); 942 ev_timer_again (loop, timer);
939 ... 943 ...
940 timer->again = 17.; 944 timer->again = 17.;
941 ev_timer_again (loop, timer); 945 ev_timer_again (loop, timer);
942 ... 946 ...
943 timer->again = 10.; 947 timer->again = 10.;
944 ev_timer_again (loop, timer); 948 ev_timer_again (loop, timer);
945 949
946This is more efficient then stopping/starting the timer eahc time you want 950This is more slightly efficient then stopping/starting the timer each time
947to modify its timeout value. 951you want to modify its timeout value.
948 952
949=item ev_tstamp repeat [read-write] 953=item ev_tstamp repeat [read-write]
950 954
951The current C<repeat> value. Will be used each time the watcher times out 955The 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), 956or 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 1225not 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 1226not 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 1227otherwise always forced to be at least one) and all the other fields of
1224the stat buffer having unspecified contents. 1228the stat buffer having unspecified contents.
1225 1229
1230The path I<should> be absolute and I<must not> end in a slash. If it is
1231relative and your working directory changes, the behaviour is undefined.
1232
1226Since there is no standard to do this, the portable implementation simply 1233Since 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 1234calls 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 1235can specify a recommended polling interval for this case. If you specify
1229a polling interval of C<0> (highly recommended!) then a I<suitable, 1236a polling interval of C<0> (highly recommended!) then a I<suitable,
1230unspecified default> value will be used (which you can expect to be around 1237unspecified default> value will be used (which you can expect to be around
1231five seconds, although this might change dynamically). Libev will also 1238five seconds, although this might change dynamically). Libev will also
1232impose a minimum interval which is currently around C<0.1>, but thats 1239impose a minimum interval which is currently around C<0.1>, but thats
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1234 1241
1235This watcher type is not meant for massive numbers of stat watchers, 1242This watcher type is not meant for massive numbers of stat watchers,
1236as even with OS-supported change notifications, this can be 1243as even with OS-supported change notifications, this can be
1237resource-intensive. 1244resource-intensive.
1238 1245
1239At the time of this writing, no specific OS backends are implemented, but 1246At the time of this writing, only the Linux inotify interface is
1240if demand increases, at least a kqueue and inotify backend will be added. 1247implemented (implementing kqueue support is left as an exercise for the
1248reader). Inotify will be used to give hints only and should not change the
1249semantics of C<ev_stat> watchers, which means that libev sometimes needs
1250to fall back to regular polling again even with inotify, but changes are
1251usually detected immediately, and if the file exists there will be no
1252polling.
1241 1253
1242=over 4 1254=over 4
1243 1255
1244=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1256=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1245 1257
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2014 2026
2015=item EV_USE_DEVPOLL 2027=item EV_USE_DEVPOLL
2016 2028
2017reserved for future expansion, works like the USE symbols above. 2029reserved for future expansion, works like the USE symbols above.
2018 2030
2031=item EV_USE_INOTIFY
2032
2033If defined to be C<1>, libev will compile in support for the Linux inotify
2034interface to speed up C<ev_stat> watchers. Its actual availability will
2035be detected at runtime.
2036
2019=item EV_H 2037=item EV_H
2020 2038
2021The name of the F<ev.h> header file used to include it. The default if 2039The 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 2040undefined 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. 2041can be used to virtually rename the F<ev.h> header file in case of conflicts.
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2078=item EV_PID_HASHSIZE 2096=item EV_PID_HASHSIZE
2079 2097
2080C<ev_child> watchers use a small hash table to distribute workload by 2098C<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 2099pid. 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 2100than enough. If you need to manage thousands of children you might want to
2083increase this value. 2101increase this value (I<must> be a power of two).
2102
2103=item EV_INOTIFY_HASHSIZE
2104
2105C<ev_staz> watchers use a small hash table to distribute workload by
2106inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2107usually more than enough. If you need to manage thousands of C<ev_stat>
2108watchers you might want to increase this value (I<must> be a power of
2109two).
2084 2110
2085=item EV_COMMON 2111=item EV_COMMON
2086 2112
2087By default, all watchers have a C<void *data> member. By redefining 2113By 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 2114this macro to a something else you can include more and other types of
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2148 2174
2149=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2175=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2150 2176
2151=item Stopping check/prepare/idle watchers: O(1) 2177=item Stopping check/prepare/idle watchers: O(1)
2152 2178
2153=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16)) 2179=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2154 2180
2155=item Finding the next timer per loop iteration: O(1) 2181=item Finding the next timer per loop iteration: O(1)
2156 2182
2157=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2183=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2158 2184

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