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Comparing libev/ev.3 (file contents):
Revision 1.30 by root, Wed Nov 28 11:27:29 2007 UTC vs.
Revision 1.35 by root, Thu Nov 29 17:28:13 2007 UTC

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127.\} 127.\}
128.rm #[ #] #H #V #F C 128.rm #[ #] #H #V #F C
129.\" ======================================================================== 129.\" ========================================================================
130.\" 130.\"
131.IX Title ""<STANDARD INPUT>" 1" 131.IX Title ""<STANDARD INPUT>" 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-28" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-11-29" "perl v5.8.8" "User Contributed Perl Documentation"
133.SH "NAME" 133.SH "NAME"
134libev \- a high performance full\-featured event loop written in C 134libev \- a high performance full\-featured event loop written in C
135.SH "SYNOPSIS" 135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS" 136.IX Header "SYNOPSIS"
137.Vb 1 137.Vb 1
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210watchers\fR, which are relatively small C structures you initialise with the 210watchers\fR, which are relatively small C structures you initialise with the
211details of the event, and then hand it over to libev by \fIstarting\fR the 211details of the event, and then hand it over to libev by \fIstarting\fR the
212watcher. 212watcher.
213.SH "FEATURES" 213.SH "FEATURES"
214.IX Header "FEATURES" 214.IX Header "FEATURES"
215Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the linux-specific \f(CW\*(C`epoll\*(C'\fR, the 215Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
216bsd-specific \f(CW\*(C`kqueue\*(C'\fR and the solaris-specific event port mechanisms 216BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
217for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), 217for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
218(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
218absolute timers with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous 219with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
219signals (\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and 220(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
220event watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, 221watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
221\&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as 222\&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as
222file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events 223file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
223(\f(CW\*(C`ev_fork\*(C'\fR). 224(\f(CW\*(C`ev_fork\*(C'\fR).
224.PP 225.PP
225It also is quite fast (see this 226It also is quite fast (see this
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304might be supported on the current system, you would need to look at 305might be supported on the current system, you would need to look at
305\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for 306\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
306recommended ones. 307recommended ones.
307.Sp 308.Sp
308See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. 309See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
309.IP "ev_set_allocator (void *(*cb)(void *ptr, size_t size))" 4 310.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
310.IX Item "ev_set_allocator (void *(*cb)(void *ptr, size_t size))" 311.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
311Sets the allocation function to use (the prototype and semantics are 312Sets the allocation function to use (the prototype is similar \- the
312identical to the realloc C function). It is used to allocate and free 313semantics is identical \- to the realloc C function). It is used to
313memory (no surprises here). If it returns zero when memory needs to be 314allocate and free memory (no surprises here). If it returns zero when
314allocated, the library might abort or take some potentially destructive 315memory needs to be allocated, the library might abort or take some
315action. The default is your system realloc function. 316potentially destructive action. The default is your system realloc
317function.
316.Sp 318.Sp
317You could override this function in high-availability programs to, say, 319You could override this function in high-availability programs to, say,
318free some memory if it cannot allocate memory, to use a special allocator, 320free some memory if it cannot allocate memory, to use a special allocator,
319or even to sleep a while and retry until some memory is available. 321or even to sleep a while and retry until some memory is available.
320.Sp 322.Sp
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409or setgid) then libev will \fInot\fR look at the environment variable 411or setgid) then libev will \fInot\fR look at the environment variable
410\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 412\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
411override the flags completely if it is found in the environment. This is 413override the flags completely if it is found in the environment. This is
412useful to try out specific backends to test their performance, or to work 414useful to try out specific backends to test their performance, or to work
413around bugs. 415around bugs.
416.ie n .IP """EVFLAG_FORKCHECK""" 4
417.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
418.IX Item "EVFLAG_FORKCHECK"
419Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
420a fork, you can also make libev check for a fork in each iteration by
421enabling this flag.
422.Sp
423This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
424and thus this might slow down your event loop if you do a lot of loop
425iterations and little real work, but is usually not noticable (on my
426Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
427without a syscall and thus \fIvery\fR fast, but my Linux system also has
428\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
429.Sp
430The big advantage of this flag is that you can forget about fork (and
431forget about forgetting to tell libev about forking) when you use this
432flag.
433.Sp
434This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
435environment variable.
414.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 436.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
415.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 437.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
416.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 438.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
417This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 439This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
418libev tries to roll its own fd_set with no limits on the number of fds, 440libev tries to roll its own fd_set with no limits on the number of fds,
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1069.IP "ev_timer_again (loop)" 4 1091.IP "ev_timer_again (loop)" 4
1070.IX Item "ev_timer_again (loop)" 1092.IX Item "ev_timer_again (loop)"
1071This will act as if the timer timed out and restart it again if it is 1093This will act as if the timer timed out and restart it again if it is
1072repeating. The exact semantics are: 1094repeating. The exact semantics are:
1073.Sp 1095.Sp
1096If the timer is pending, its pending status is cleared.
1097.Sp
1074If the timer is started but nonrepeating, stop it. 1098If the timer is started but nonrepeating, stop it (as if it timed out).
1075.Sp 1099.Sp
1076If the timer is repeating, either start it if necessary (with the repeat 1100If the timer is repeating, either start it if necessary (with the
1077value), or reset the running timer to the repeat value. 1101\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
1078.Sp 1102.Sp
1079This sounds a bit complicated, but here is a useful and typical 1103This sounds a bit complicated, but here is a useful and typical
1080example: Imagine you have a tcp connection and you want a so-called 1104example: Imagine you have a tcp connection and you want a so-called idle
1081idle timeout, that is, you want to be called when there have been, 1105timeout, that is, you want to be called when there have been, say, 60
1082say, 60 seconds of inactivity on the socket. The easiest way to do 1106seconds of inactivity on the socket. The easiest way to do this is to
1083this is to configure an \f(CW\*(C`ev_timer\*(C'\fR with \f(CW\*(C`after\*(C'\fR=\f(CW\*(C`repeat\*(C'\fR=\f(CW60\fR and calling 1107configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
1084\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If 1108\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
1085you go into an idle state where you do not expect data to travel on the 1109you go into an idle state where you do not expect data to travel on the
1086socket, you can stop the timer, and again will automatically restart it if 1110socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1087need be. 1111automatically restart it if need be.
1088.Sp 1112.Sp
1089You can also ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR altogether 1113That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1090and only ever use the \f(CW\*(C`repeat\*(C'\fR value: 1114altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1091.Sp 1115.Sp
1092.Vb 8 1116.Vb 8
1093\& ev_timer_init (timer, callback, 0., 5.); 1117\& ev_timer_init (timer, callback, 0., 5.);
1094\& ev_timer_again (loop, timer); 1118\& ev_timer_again (loop, timer);
1095\& ... 1119\& ...
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1098\& ... 1122\& ...
1099\& timer->again = 10.; 1123\& timer->again = 10.;
1100\& ev_timer_again (loop, timer); 1124\& ev_timer_again (loop, timer);
1101.Ve 1125.Ve
1102.Sp 1126.Sp
1103This is more efficient then stopping/starting the timer eahc time you want 1127This is more slightly efficient then stopping/starting the timer each time
1104to modify its timeout value. 1128you want to modify its timeout value.
1105.IP "ev_tstamp repeat [read\-write]" 4 1129.IP "ev_tstamp repeat [read\-write]" 4
1106.IX Item "ev_tstamp repeat [read-write]" 1130.IX Item "ev_tstamp repeat [read-write]"
1107The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out 1131The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1108or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any), 1132or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1109which is also when any modifications are taken into account. 1133which is also when any modifications are taken into account.
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1381The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does 1405The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1382not exist\*(R" is a status change like any other. The condition \*(L"path does 1406not exist\*(R" is a status change like any other. The condition \*(L"path does
1383not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is 1407not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1384otherwise always forced to be at least one) and all the other fields of 1408otherwise always forced to be at least one) and all the other fields of
1385the stat buffer having unspecified contents. 1409the stat buffer having unspecified contents.
1410.PP
1411The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1412relative and your working directory changes, the behaviour is undefined.
1386.PP 1413.PP
1387Since there is no standard to do this, the portable implementation simply 1414Since there is no standard to do this, the portable implementation simply
1388calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You 1415calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1389can specify a recommended polling interval for this case. If you specify 1416can specify a recommended polling interval for this case. If you specify
1390a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable, 1417a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,

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