X-Git-Url: https://git.llucax.com/software/libev.git/blobdiff_plain/97710f65c4339600b822e15e7e78841ae445f0f5..1e251ffd9e2bf720df7759c2eb3c807f5b0d474f:/ev.3?ds=inline diff --git a/ev.3 b/ev.3 index fa733cf..7c9695c 100644 --- a/ev.3 +++ b/ev.3 @@ -129,7 +129,7 @@ .\" ======================================================================== .\" .IX Title """ 1" -.TH "" 1 "2007-11-24" "perl v5.8.8" "User Contributed Perl Documentation" +.TH "" 1 "2007-11-29" "perl v5.8.8" "User Contributed Perl Documentation" .SH "NAME" libev \- a high performance full\-featured event loop written in C .SH "SYNOPSIS" @@ -137,6 +137,65 @@ libev \- a high performance full\-featured event loop written in C .Vb 1 \& #include .Ve +.SH "EXAMPLE PROGRAM" +.IX Header "EXAMPLE PROGRAM" +.Vb 1 +\& #include +.Ve +.PP +.Vb 2 +\& ev_io stdin_watcher; +\& ev_timer timeout_watcher; +.Ve +.PP +.Vb 8 +\& /* called when data readable on stdin */ +\& static void +\& stdin_cb (EV_P_ struct ev_io *w, int revents) +\& { +\& /* puts ("stdin ready"); */ +\& ev_io_stop (EV_A_ w); /* just a syntax example */ +\& ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */ +\& } +.Ve +.PP +.Vb 6 +\& static void +\& timeout_cb (EV_P_ struct ev_timer *w, int revents) +\& { +\& /* puts ("timeout"); */ +\& ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */ +\& } +.Ve +.PP +.Vb 4 +\& int +\& main (void) +\& { +\& struct ev_loop *loop = ev_default_loop (0); +.Ve +.PP +.Vb 3 +\& /* initialise an io watcher, then start it */ +\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); +\& ev_io_start (loop, &stdin_watcher); +.Ve +.PP +.Vb 3 +\& /* simple non-repeating 5.5 second timeout */ +\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); +\& ev_timer_start (loop, &timeout_watcher); +.Ve +.PP +.Vb 2 +\& /* loop till timeout or data ready */ +\& ev_loop (loop, 0); +.Ve +.PP +.Vb 2 +\& return 0; +\& } +.Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" Libev is an event loop: you register interest in certain events (such as a @@ -153,22 +212,28 @@ details of the event, and then hand it over to libev by \fIstarting\fR the watcher. .SH "FEATURES" .IX Header "FEATURES" -Libev supports select, poll, the linux-specific epoll and the bsd-specific -kqueue mechanisms for file descriptor events, relative timers, absolute -timers with customised rescheduling, signal events, process status change -events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event -loop mechanism itself (idle, prepare and check watchers). It also is quite -fast (see this benchmark comparing -it to libevent for example). +Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the +BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms +for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface +(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers +with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals +(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event +watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, +\&\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 +file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events +(\f(CW\*(C`ev_fork\*(C'\fR). +.PP +It also is quite fast (see this +benchmark comparing it to libevent +for example). .SH "CONVENTIONS" .IX Header "CONVENTIONS" -Libev is very configurable. In this manual the default configuration -will be described, which supports multiple event loops. For more info -about various configuration options please have a look at the file -\&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without -support for multiple event loops, then all functions taking an initial -argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) -will not have this argument. +Libev is very configurable. In this manual the default configuration will +be described, which supports multiple event loops. For more info about +various configuration options please have a look at \fB\s-1EMBED\s0\fR section in +this manual. If libev was configured without support for multiple event +loops, then all functions taking an initial argument of name \f(CW\*(C`loop\*(C'\fR +(which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument. .SH "TIME REPRESENTATION" .IX Header "TIME REPRESENTATION" Libev represents time as a single floating point number, representing the @@ -203,8 +268,8 @@ as this indicates an incompatible change. Minor versions are usually compatible to older versions, so a larger minor version alone is usually not a problem. .Sp -Example: make sure we haven't accidentally been linked against the wrong -version: +Example: Make sure we haven't accidentally been linked against the wrong +version. .Sp .Vb 3 \& assert (("libev version mismatch", @@ -244,22 +309,23 @@ recommended ones. See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" -Sets the allocation function to use (the prototype is similar to the -realloc C function, the semantics are identical). It is used to allocate -and free memory (no surprises here). If it returns zero when memory -needs to be allocated, the library might abort or take some potentially -destructive action. The default is your system realloc function. +Sets the allocation function to use (the prototype is similar \- the +semantics is identical \- to the realloc C function). It is used to +allocate and free memory (no surprises here). If it returns zero when +memory needs to be allocated, the library might abort or take some +potentially destructive action. The default is your system realloc +function. .Sp You could override this function in high-availability programs to, say, free some memory if it cannot allocate memory, to use a special allocator, or even to sleep a while and retry until some memory is available. .Sp -Example: replace the libev allocator with one that waits a bit and then -retries: better than mine). +Example: Replace the libev allocator with one that waits a bit and then +retries). .Sp .Vb 6 \& static void * -\& persistent_realloc (void *ptr, long size) +\& persistent_realloc (void *ptr, size_t size) \& { \& for (;;) \& { @@ -291,7 +357,7 @@ matter what, when it returns. That is, libev will generally retry the requested operation, or, if the condition doesn't go away, do bad stuff (such as abort). .Sp -Example: do the same thing as libev does internally: +Example: This is basically the same thing that libev does internally, too. .Sp .Vb 6 \& static void @@ -347,6 +413,26 @@ or setgid) then libev will \fInot\fR look at the environment variable override the flags completely if it is found in the environment. This is useful to try out specific backends to test their performance, or to work around bugs. +.ie n .IP """EVFLAG_FORKCHECK""" 4 +.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4 +.IX Item "EVFLAG_FORKCHECK" +Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after +a fork, you can also make libev check for a fork in each iteration by +enabling this flag. +.Sp +This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop, +and thus this might slow down your event loop if you do a lot of loop +iterations and little real work, but is usually not noticable (on my +Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence +without a syscall and thus \fIvery\fR fast, but my Linux system also has +\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). +.Sp +The big advantage of this flag is that you can forget about fork (and +forget about forgetting to tell libev about forking) when you use this +flag. +.Sp +This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR +environment variable. .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" @@ -450,7 +536,7 @@ always distinct from the default loop. Unlike the default loop, it cannot handle signal and child watchers, and attempts to do so will be greeted by undefined behaviour (or a failed assertion if assertions are enabled). .Sp -Example: try to create a event loop that uses epoll and nothing else. +Example: Try to create a event loop that uses epoll and nothing else. .Sp .Vb 3 \& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); @@ -558,7 +644,7 @@ Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: \& were used, return, otherwise continue with step *. .Ve .Sp -Example: queue some jobs and then loop until no events are outsanding +Example: Queue some jobs and then loop until no events are outsanding anymore. .Sp .Vb 4 @@ -590,21 +676,21 @@ no event watchers registered by it are active. It is also an excellent way to do this for generic recurring timers or from within third-party libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. .Sp -Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR +Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR running when nothing else is active. .Sp .Vb 4 -\& struct dv_signal exitsig; +\& struct ev_signal exitsig; \& ev_signal_init (&exitsig, sig_cb, SIGINT); -\& ev_signal_start (myloop, &exitsig); -\& evf_unref (myloop); +\& ev_signal_start (loop, &exitsig); +\& evf_unref (loop); .Ve .Sp -Example: for some weird reason, unregister the above signal handler again. +Example: For some weird reason, unregister the above signal handler again. .Sp .Vb 2 -\& ev_ref (myloop); -\& ev_signal_stop (myloop, &exitsig); +\& ev_ref (loop); +\& ev_signal_stop (loop, &exitsig); .Ve .SH "ANATOMY OF A WATCHER" .IX Header "ANATOMY OF A WATCHER" @@ -686,6 +772,10 @@ The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been receive .el .IP "\f(CWEV_CHILD\fR" 4 .IX Item "EV_CHILD" The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. +.ie n .IP """EV_STAT""" 4 +.el .IP "\f(CWEV_STAT\fR" 4 +.IX Item "EV_STAT" +The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow. .ie n .IP """EV_IDLE""" 4 .el .IP "\f(CWEV_IDLE\fR" 4 .IX Item "EV_IDLE" @@ -705,6 +795,15 @@ received events. Callbacks of both watcher types can start and stop as many watchers as they want, and all of them will be taken into account (for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep \&\f(CW\*(C`ev_loop\*(C'\fR from blocking). +.ie n .IP """EV_EMBED""" 4 +.el .IP "\f(CWEV_EMBED\fR" 4 +.IX Item "EV_EMBED" +The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention. +.ie n .IP """EV_FORK""" 4 +.el .IP "\f(CWEV_FORK\fR" 4 +.IX Item "EV_FORK" +The event loop has been resumed in the child process after fork (see +\&\f(CW\*(C`ev_fork\*(C'\fR). .ie n .IP """EV_ERROR""" 4 .el .IP "\f(CWEV_ERROR\fR" 4 .IX Item "EV_ERROR" @@ -781,8 +880,8 @@ events but its callback has not yet been invoked). As long as a watcher is pending (but not active) you must not call an init function on it (but \&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it). -.IP "callback = ev_cb (ev_TYPE *watcher)" 4 -.IX Item "callback = ev_cb (ev_TYPE *watcher)" +.IP "callback ev_cb (ev_TYPE *watcher)" 4 +.IX Item "callback ev_cb (ev_TYPE *watcher)" Returns the callback currently set on the watcher. .IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 .IX Item "ev_cb_set (ev_TYPE *watcher, callback)" @@ -818,12 +917,59 @@ can cast it back to your own type: \& } .Ve .PP -More interesting and less C\-conformant ways of catsing your callback type -have been omitted.... +More interesting and less C\-conformant ways of casting your callback type +instead have been omitted. +.PP +Another common scenario is having some data structure with multiple +watchers: +.PP +.Vb 6 +\& struct my_biggy +\& { +\& int some_data; +\& ev_timer t1; +\& ev_timer t2; +\& } +.Ve +.PP +In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated, +you need to use \f(CW\*(C`offsetof\*(C'\fR: +.PP +.Vb 1 +\& #include +.Ve +.PP +.Vb 6 +\& static void +\& t1_cb (EV_P_ struct ev_timer *w, int revents) +\& { +\& struct my_biggy big = (struct my_biggy * +\& (((char *)w) - offsetof (struct my_biggy, t1)); +\& } +.Ve +.PP +.Vb 6 +\& static void +\& t2_cb (EV_P_ struct ev_timer *w, int revents) +\& { +\& struct my_biggy big = (struct my_biggy * +\& (((char *)w) - offsetof (struct my_biggy, t2)); +\& } +.Ve .SH "WATCHER TYPES" .IX Header "WATCHER TYPES" This section describes each watcher in detail, but will not repeat -information given in the last section. +information given in the last section. Any initialisation/set macros, +functions and members specific to the watcher type are explained. +.PP +Members are additionally marked with either \fI[read\-only]\fR, meaning that, +while the watcher is active, you can look at the member and expect some +sensible content, but you must not modify it (you can modify it while the +watcher is stopped to your hearts content), or \fI[read\-write]\fR, which +means you can expect it to have some sensible content while the watcher +is active, but you can also modify it. Modifying it may not do something +sensible or take immediate effect (or do anything at all), but libev will +not crash or malfunction in any way. .ie n .Sh """ev_io"" \- is this file descriptor readable or writable?" .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?" .IX Subsection "ev_io - is this file descriptor readable or writable?" @@ -873,10 +1019,16 @@ its own, so its quite safe to use). Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events. -.PP -Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well +.IP "int fd [read\-only]" 4 +.IX Item "int fd [read-only]" +The file descriptor being watched. +.IP "int events [read\-only]" 4 +.IX Item "int events [read-only]" +The events being watched. +.PP +Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well readable, but only once. Since it is likely line\-buffered, you could -attempt to read a whole line in the callback: +attempt to read a whole line in the callback. .PP .Vb 6 \& static void @@ -941,21 +1093,46 @@ timer will not fire more than once per event loop iteration. This will act as if the timer timed out and restart it again if it is repeating. The exact semantics are: .Sp -If the timer is started but nonrepeating, stop it. +If the timer is pending, its pending status is cleared. +.Sp +If the timer is started but nonrepeating, stop it (as if it timed out). .Sp -If the timer is repeating, either start it if necessary (with the repeat -value), or reset the running timer to the repeat value. +If the timer is repeating, either start it if necessary (with the +\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. .Sp This sounds a bit complicated, but here is a useful and typical example: Imagine you have a tcp connection and you want a so-called idle timeout, that is, you want to be called when there have been, say, 60 seconds of inactivity on the socket. The easiest way to do this is to -configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each -time you successfully read or write some data. If you go into an idle -state where you do not expect data to travel on the socket, you can stop -the timer, and again will automatically restart it if need be. +configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call +\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If +you go into an idle state where you do not expect data to travel on the +socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will +automatically restart it if need be. +.Sp +That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR +altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR: +.Sp +.Vb 8 +\& ev_timer_init (timer, callback, 0., 5.); +\& ev_timer_again (loop, timer); +\& ... +\& timer->again = 17.; +\& ev_timer_again (loop, timer); +\& ... +\& timer->again = 10.; +\& ev_timer_again (loop, timer); +.Ve +.Sp +This is more slightly efficient then stopping/starting the timer each time +you want to modify its timeout value. +.IP "ev_tstamp repeat [read\-write]" 4 +.IX Item "ev_tstamp repeat [read-write]" +The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out +or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any), +which is also when any modifications are taken into account. .PP -Example: create a timer that fires after 60 seconds. +Example: Create a timer that fires after 60 seconds. .PP .Vb 5 \& static void @@ -971,7 +1148,7 @@ Example: create a timer that fires after 60 seconds. \& ev_timer_start (loop, &mytimer); .Ve .PP -Example: create a timeout timer that times out after 10 seconds of +Example: Create a timeout timer that times out after 10 seconds of inactivity. .PP .Vb 5 @@ -1095,8 +1272,18 @@ Simply stops and restarts the periodic watcher again. This is only useful when you changed some parameters or the reschedule callback would return a different time than the last time it was called (e.g. in a crond like program when the crontabs have changed). -.PP -Example: call a callback every hour, or, more precisely, whenever the +.IP "ev_tstamp interval [read\-write]" 4 +.IX Item "ev_tstamp interval [read-write]" +The current interval value. Can be modified any time, but changes only +take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being +called. +.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4 +.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]" +The current reschedule callback, or \f(CW0\fR, if this functionality is +switched off. Can be changed any time, but changes only take effect when +the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. +.PP +Example: Call a callback every hour, or, more precisely, whenever the system clock is divisible by 3600. The callback invocation times have potentially a lot of jittering, but good long-term stability. .PP @@ -1114,7 +1301,7 @@ potentially a lot of jittering, but good long-term stability. \& ev_periodic_start (loop, &hourly_tick); .Ve .PP -Example: the same as above, but use a reschedule callback to do it: +Example: The same as above, but use a reschedule callback to do it: .PP .Vb 1 \& #include @@ -1132,7 +1319,7 @@ Example: the same as above, but use a reschedule callback to do it: \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); .Ve .PP -Example: call a callback every hour, starting now: +Example: Call a callback every hour, starting now: .PP .Vb 4 \& struct ev_periodic hourly_tick; @@ -1162,6 +1349,9 @@ watcher for a signal is stopped libev will reset the signal handler to .PD Configures the watcher to trigger on the given signal number (usually one of the \f(CW\*(C`SIGxxx\*(C'\fR constants). +.IP "int signum [read\-only]" 4 +.IX Item "int signum [read-only]" +The signal the watcher watches out for. .ie n .Sh """ev_child"" \- watch out for process status changes" .el .Sh "\f(CWev_child\fP \- watch out for process status changes" .IX Subsection "ev_child - watch out for process status changes" @@ -1179,8 +1369,18 @@ at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watche the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems \&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the process causing the status change. -.PP -Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. +.IP "int pid [read\-only]" 4 +.IX Item "int pid [read-only]" +The process id this watcher watches out for, or \f(CW0\fR, meaning any process id. +.IP "int rpid [read\-write]" 4 +.IX Item "int rpid [read-write]" +The process id that detected a status change. +.IP "int rstatus [read\-write]" 4 +.IX Item "int rstatus [read-write]" +The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems +\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details). +.PP +Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. .PP .Vb 5 \& static void @@ -1195,6 +1395,109 @@ Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); \& ev_signal_start (loop, &sigint_cb); .Ve +.ie n .Sh """ev_stat"" \- did the file attributes just change?" +.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?" +.IX Subsection "ev_stat - did the file attributes just change?" +This watches a filesystem path for attribute changes. That is, it calls +\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed +compared to the last time, invoking the callback if it did. +.PP +The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does +not exist\*(R" is a status change like any other. The condition \*(L"path does +not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is +otherwise always forced to be at least one) and all the other fields of +the stat buffer having unspecified contents. +.PP +The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is +relative and your working directory changes, the behaviour is undefined. +.PP +Since there is no standard to do this, the portable implementation simply +calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You +can specify a recommended polling interval for this case. If you specify +a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable, +unspecified default\fR value will be used (which you can expect to be around +five seconds, although this might change dynamically). Libev will also +impose a minimum interval which is currently around \f(CW0.1\fR, but thats +usually overkill. +.PP +This watcher type is not meant for massive numbers of stat watchers, +as even with OS-supported change notifications, this can be +resource\-intensive. +.PP +At the time of this writing, only the Linux inotify interface is +implemented (implementing kqueue support is left as an exercise for the +reader). Inotify will be used to give hints only and should not change the +semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs +to fall back to regular polling again even with inotify, but changes are +usually detected immediately, and if the file exists there will be no +polling. +.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4 +.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" +.PD 0 +.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4 +.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" +.PD +Configures the watcher to wait for status changes of the given +\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to +be detected and should normally be specified as \f(CW0\fR to let libev choose +a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same +path for as long as the watcher is active. +.Sp +The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected, +relative to the attributes at the time the watcher was started (or the +last change was detected). +.IP "ev_stat_stat (ev_stat *)" 4 +.IX Item "ev_stat_stat (ev_stat *)" +Updates the stat buffer immediately with new values. If you change the +watched path in your callback, you could call this fucntion to avoid +detecting this change (while introducing a race condition). Can also be +useful simply to find out the new values. +.IP "ev_statdata attr [read\-only]" 4 +.IX Item "ev_statdata attr [read-only]" +The most-recently detected attributes of the file. Although the type is of +\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types +suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there +was some error while \f(CW\*(C`stat\*(C'\fRing the file. +.IP "ev_statdata prev [read\-only]" 4 +.IX Item "ev_statdata prev [read-only]" +The previous attributes of the file. The callback gets invoked whenever +\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR. +.IP "ev_tstamp interval [read\-only]" 4 +.IX Item "ev_tstamp interval [read-only]" +The specified interval. +.IP "const char *path [read\-only]" 4 +.IX Item "const char *path [read-only]" +The filesystem path that is being watched. +.PP +Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes. +.PP +.Vb 15 +\& static void +\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) +\& { +\& /* /etc/passwd changed in some way */ +\& if (w->attr.st_nlink) +\& { +\& printf ("passwd current size %ld\en", (long)w->attr.st_size); +\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime); +\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime); +\& } +\& else +\& /* you shalt not abuse printf for puts */ +\& puts ("wow, /etc/passwd is not there, expect problems. " +\& "if this is windows, they already arrived\en"); +\& } +.Ve +.PP +.Vb 2 +\& ... +\& ev_stat passwd; +.Ve +.PP +.Vb 2 +\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); +\& ev_stat_start (loop, &passwd); +.Ve .ie n .Sh """ev_idle"" \- when you've got nothing better to do..." .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." .IX Subsection "ev_idle - when you've got nothing better to do..." @@ -1219,8 +1522,8 @@ Initialises and configures the idle watcher \- it has no parameters of any kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, believe me. .PP -Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the -callback, free it. Alos, use no error checking, as usual. +Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the +callback, free it. Also, use no error checking, as usual. .PP .Vb 7 \& static void @@ -1244,10 +1547,21 @@ Prepare and check watchers are usually (but not always) used in tandem: prepare watchers get invoked before the process blocks and check watchers afterwards. .PP +You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter +the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR +watchers. Other loops than the current one are fine, however. The +rationale behind this is that you do not need to check for recursion in +those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, +\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be +called in pairs bracketing the blocking call. +.PP Their main purpose is to integrate other event mechanisms into libev and their use is somewhat advanced. This could be used, for example, to track variable changes, implement your own watchers, integrate net-snmp or a -coroutine library and lots more. +coroutine library and lots more. They are also occasionally useful if +you cache some data and want to flush it before blocking (for example, +in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR +watcher). .PP This is done by examining in each prepare call which file descriptors need to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for @@ -1276,7 +1590,78 @@ Initialises and configures the prepare or check watcher \- they have no parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR macros, but using them is utterly, utterly and completely pointless. .PP -Example: *TODO*. +Example: To include a library such as adns, you would add \s-1IO\s0 watchers +and a timeout watcher in a prepare handler, as required by libadns, and +in a check watcher, destroy them and call into libadns. What follows is +pseudo-code only of course: +.PP +.Vb 2 +\& static ev_io iow [nfd]; +\& static ev_timer tw; +.Ve +.PP +.Vb 9 +\& static void +\& io_cb (ev_loop *loop, ev_io *w, int revents) +\& { +\& // set the relevant poll flags +\& // could also call adns_processreadable etc. here +\& struct pollfd *fd = (struct pollfd *)w->data; +\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; +\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; +\& } +.Ve +.PP +.Vb 7 +\& // create io watchers for each fd and a timer before blocking +\& static void +\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) +\& { +\& int timeout = 3600000;truct pollfd fds [nfd]; +\& // actual code will need to loop here and realloc etc. +\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); +.Ve +.PP +.Vb 3 +\& /* the callback is illegal, but won't be called as we stop during check */ +\& ev_timer_init (&tw, 0, timeout * 1e-3); +\& ev_timer_start (loop, &tw); +.Ve +.PP +.Vb 6 +\& // create on ev_io per pollfd +\& for (int i = 0; i < nfd; ++i) +\& { +\& ev_io_init (iow + i, io_cb, fds [i].fd, +\& ((fds [i].events & POLLIN ? EV_READ : 0) +\& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); +.Ve +.PP +.Vb 5 +\& fds [i].revents = 0; +\& iow [i].data = fds + i; +\& ev_io_start (loop, iow + i); +\& } +\& } +.Ve +.PP +.Vb 5 +\& // stop all watchers after blocking +\& static void +\& adns_check_cb (ev_loop *loop, ev_check *w, int revents) +\& { +\& ev_timer_stop (loop, &tw); +.Ve +.PP +.Vb 2 +\& for (int i = 0; i < nfd; ++i) +\& ev_io_stop (loop, iow + i); +.Ve +.PP +.Vb 2 +\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); +\& } +.Ve .ie n .Sh """ev_embed"" \- when one backend isn't enough..." .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." .IX Subsection "ev_embed - when one backend isn't enough..." @@ -1369,6 +1754,24 @@ if you do not want thta, you need to temporarily stop the embed watcher). Make a single, non-blocking sweep over the embedded loop. This works similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most apropriate way for embedded loops. +.IP "struct ev_loop *loop [read\-only]" 4 +.IX Item "struct ev_loop *loop [read-only]" +The embedded event loop. +.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork" +.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" +.IX Subsection "ev_fork - the audacity to resume the event loop after a fork" +Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because +whoever is a good citizen cared to tell libev about it by calling +\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the +event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, +and only in the child after the fork. If whoever good citizen calling +\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork +handlers will be invoked, too, of course. +.IP "ev_fork_init (ev_signal *, callback)" 4 +.IX Item "ev_fork_init (ev_signal *, callback)" +Initialises and configures the fork watcher \- it has no parameters of any +kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, +believe me. .SH "OTHER FUNCTIONS" .IX Header "OTHER FUNCTIONS" There are some other functions of possible interest. Described. Here. Now. @@ -1517,6 +1920,10 @@ For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes .el .IP "w\->sweep () \f(CWev::embed\fR only" 4 .IX Item "w->sweep () ev::embed only" Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. +.ie n .IP "w\->update () ""ev::stat"" only" 4 +.el .IP "w\->update () \f(CWev::stat\fR only" 4 +.IX Item "w->update () ev::stat only" +Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. .RE .RS 4 .RE @@ -1544,6 +1951,72 @@ the constructor. \& io.start (fd, ev::READ); \& } .Ve +.SH "MACRO MAGIC" +.IX Header "MACRO MAGIC" +Libev can be compiled with a variety of options, the most fundemantal is +\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines wether (most) functions and +callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. +.PP +To make it easier to write programs that cope with either variant, the +following macros are defined: +.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4 +.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 +.IX Item "EV_A, EV_A_" +This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev +loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, +\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: +.Sp +.Vb 3 +\& ev_unref (EV_A); +\& ev_timer_add (EV_A_ watcher); +\& ev_loop (EV_A_ 0); +.Ve +.Sp +It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, +which is often provided by the following macro. +.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4 +.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 +.IX Item "EV_P, EV_P_" +This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev +loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, +\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: +.Sp +.Vb 2 +\& // this is how ev_unref is being declared +\& static void ev_unref (EV_P); +.Ve +.Sp +.Vb 2 +\& // this is how you can declare your typical callback +\& static void cb (EV_P_ ev_timer *w, int revents) +.Ve +.Sp +It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite +suitable for use with \f(CW\*(C`EV_A\*(C'\fR. +.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4 +.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 +.IX Item "EV_DEFAULT, EV_DEFAULT_" +Similar to the other two macros, this gives you the value of the default +loop, if multiple loops are supported (\*(L"ev loop default\*(R"). +.PP +Example: Declare and initialise a check watcher, utilising the above +macros so it will work regardless of wether multiple loops are supported +or not. +.PP +.Vb 5 +\& static void +\& check_cb (EV_P_ ev_timer *w, int revents) +\& { +\& ev_check_stop (EV_A_ w); +\& } +.Ve +.PP +.Vb 4 +\& ev_check check; +\& ev_check_init (&check, check_cb); +\& ev_check_start (EV_DEFAULT_ &check); +\& ev_loop (EV_DEFAULT_ 0); +.Ve .SH "EMBEDDING" .IX Header "EMBEDDING" Libev can (and often is) directly embedded into host @@ -1601,7 +2074,7 @@ in your include path (e.g. in libev/ when using \-Ilibev): .Ve .PP .Vb 5 -\& ev_select.c only when select backend is enabled (which is by default) +\& ev_select.c only when select backend is enabled (which is enabled by default) \& ev_poll.c only when poll backend is enabled (disabled by default) \& ev_epoll.c only when the epoll backend is enabled (disabled by default) \& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) @@ -1732,6 +2205,11 @@ backend for Solaris 10 systems. .IP "\s-1EV_USE_DEVPOLL\s0" 4 .IX Item "EV_USE_DEVPOLL" reserved for future expansion, works like the \s-1USE\s0 symbols above. +.IP "\s-1EV_USE_INOTIFY\s0" 4 +.IX Item "EV_USE_INOTIFY" +If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify +interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will +be detected at runtime. .IP "\s-1EV_H\s0" 4 .IX Item "EV_H" The name of the \fIev.h\fR header file used to include it. The default if @@ -1759,10 +2237,41 @@ will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can additional independent event loops. Otherwise there will be no support for multiple event loops and there is no first event loop pointer argument. Instead, all functions act on the single default loop. -.IP "\s-1EV_PERIODICS\s0" 4 -.IX Item "EV_PERIODICS" -If undefined or defined to be \f(CW1\fR, then periodic timers are supported, -otherwise not. This saves a few kb of code. +.IP "\s-1EV_PERIODIC_ENABLE\s0" 4 +.IX Item "EV_PERIODIC_ENABLE" +If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If +defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of +code. +.IP "\s-1EV_EMBED_ENABLE\s0" 4 +.IX Item "EV_EMBED_ENABLE" +If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If +defined to be \f(CW0\fR, then they are not. +.IP "\s-1EV_STAT_ENABLE\s0" 4 +.IX Item "EV_STAT_ENABLE" +If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If +defined to be \f(CW0\fR, then they are not. +.IP "\s-1EV_FORK_ENABLE\s0" 4 +.IX Item "EV_FORK_ENABLE" +If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If +defined to be \f(CW0\fR, then they are not. +.IP "\s-1EV_MINIMAL\s0" 4 +.IX Item "EV_MINIMAL" +If you need to shave off some kilobytes of code at the expense of some +speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override +some inlining decisions, saves roughly 30% codesize of amd64. +.IP "\s-1EV_PID_HASHSIZE\s0" 4 +.IX Item "EV_PID_HASHSIZE" +\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by +pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more +than enough. If you need to manage thousands of children you might want to +increase this value (\fImust\fR be a power of two). +.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4 +.IX Item "EV_INOTIFY_HASHSIZE" +\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by +inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), +usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR +watchers you might want to increase this value (\fImust\fR be a power of +two). .IP "\s-1EV_COMMON\s0" 4 .IX Item "EV_COMMON" By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining @@ -1777,20 +2286,20 @@ For example, the perl \s-1EV\s0 module uses something like this: \& SV *self; /* contains this struct */ \e \& SV *cb_sv, *fh /* note no trailing ";" */ .Ve -.IP "\s-1EV_CB_DECLARE\s0(type)" 4 -.IX Item "EV_CB_DECLARE(type)" +.IP "\s-1EV_CB_DECLARE\s0 (type)" 4 +.IX Item "EV_CB_DECLARE (type)" .PD 0 -.IP "\s-1EV_CB_INVOKE\s0(watcher,revents)" 4 -.IX Item "EV_CB_INVOKE(watcher,revents)" -.IP "ev_set_cb(ev,cb)" 4 -.IX Item "ev_set_cb(ev,cb)" +.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4 +.IX Item "EV_CB_INVOKE (watcher, revents)" +.IP "ev_set_cb (ev, cb)" 4 +.IX Item "ev_set_cb (ev, cb)" .PD Can be used to change the callback member declaration in each watcher, and the way callbacks are invoked and set. Must expand to a struct member definition and a statement, respectively. See the \fIev.v\fR header file for their default definitions. One possible use for overriding these is to -avoid the ev_loop pointer as first argument in all cases, or to use method -calls instead of plain function calls in \*(C+. +avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use +method calls instead of plain function calls in \*(C+. .Sh "\s-1EXAMPLES\s0" .IX Subsection "EXAMPLES" For a real-world example of a program the includes libev @@ -1802,13 +2311,18 @@ will be compiled. It is pretty complex because it provides its own header file. .Sp The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file -that everybody includes and which overrides some autoconf choices: +that everybody includes and which overrides some configure choices: .Sp -.Vb 4 +.Vb 9 +\& #define EV_MINIMAL 1 \& #define EV_USE_POLL 0 \& #define EV_MULTIPLICITY 0 -\& #define EV_PERIODICS 0 +\& #define EV_PERIODIC_ENABLE 0 +\& #define EV_STAT_ENABLE 0 +\& #define EV_FORK_ENABLE 0 \& #define EV_CONFIG_H +\& #define EV_MINPRI 0 +\& #define EV_MAXPRI 0 .Ve .Sp .Vb 1 @@ -1821,6 +2335,32 @@ And a \fIev_cpp.C\fR implementation file that contains libev proper and is compi \& #include "ev_cpp.h" \& #include "ev.c" .Ve +.SH "COMPLEXITIES" +.IX Header "COMPLEXITIES" +In this section the complexities of (many of) the algorithms used inside +libev will be explained. For complexity discussions about backends see the +documentation for \f(CW\*(C`ev_default_init\*(C'\fR. +.RS 4 +.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 +.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" +.PD 0 +.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4 +.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" +.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4 +.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)" +.IP "Stopping check/prepare/idle watchers: O(1)" 4 +.IX Item "Stopping check/prepare/idle watchers: O(1)" +.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 +.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" +.IP "Finding the next timer per loop iteration: O(1)" 4 +.IX Item "Finding the next timer per loop iteration: O(1)" +.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 +.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" +.IP "Activating one watcher: O(1)" 4 +.IX Item "Activating one watcher: O(1)" +.RE +.RS 4 +.PD .SH "AUTHOR" .IX Header "AUTHOR" Marc Lehmann .