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No user-serviceable parts. ``` ```. \" fudge factors for nroff and troff ``` ```.if n \{\ ``` ```. ds #H 0 ``` ```. ds #V .8m ``` ```. ds #F .3m ``` ```. ds #[ \f1 ``` ```. ds #] \fP ``` ```.\} ``` ```.if t \{\ ``` ```. ds #H ((1u-(\\\\n(.fu%2u))*.13m) ``` ```. ds #V .6m ``` ```. ds #F 0 ``` ```. ds #[ \& ``` ```. ds #] \& ``` ```.\} ``` ```. \" simple accents for nroff and troff ``` ```.if n \{\ ``` ```. ds ' \& ``` ```. ds ` \& ``` ```. ds ^ \& ``` ```. ds , \& ``` ```. ds ~ ~ ``` ```. ds / ``` ```.\} ``` ```.if t \{\ ``` ```. ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" ``` ```. ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' ``` ```. ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' ``` ```. ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' ``` ```. ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' ``` ```. ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' ``` ```.\} ``` ```. \" troff and (daisy-wheel) nroff accents ``` ```.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' ``` ```.ds 8 \h'\*(#H'\(*b\h'-\*(#H' ``` ```.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] ``` ```.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' ``` ```.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' ``` ```.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] ``` ```.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] ``` ```.ds ae a\h'-(\w'a'u*4/10)'e ``` ```.ds Ae A\h'-(\w'A'u*4/10)'E ``` ```. \" corrections for vroff ``` ```.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' ``` ```.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' ``` ```. \" for low resolution devices (crt and lpr) ``` ```.if \n(.H>23 .if \n(.V>19 \ ``` ```\{\ ``` ```. ds : e ``` ```. ds 8 ss ``` ```. ds o a ``` ```. ds d- d\h'-1'\(ga ``` ```. ds D- D\h'-1'\(hy ``` ```. ds th \o'bp' ``` ```. ds Th \o'LP' ``` ```. ds ae ae ``` ```. ds Ae AE ``` ```.\} ``` ```.rm #[ #] #H #V #F C ``` ```.\" ======================================================================== ``` ```.\" ``` ```.IX Title """ 1" ``` ```.TH "" 1 "2007-11-27" "perl v5.8.8" "User Contributed Perl Documentation" ``` ```.SH "NAME" ``` ```libev \- a high performance full\-featured event loop written in C ``` ```.SH "SYNOPSIS" ``` ```.IX Header "SYNOPSIS" ``` ```.Vb 1 ``` ```\& #include ``` ```.Ve ``` ```.SH "DESCRIPTION" ``` ```.IX Header "DESCRIPTION" ``` ```Libev is an event loop: you register interest in certain events (such as a ``` ```file descriptor being readable or a timeout occuring), and it will manage ``` ```these event sources and provide your program with events. ``` ```.PP ``` ```To do this, it must take more or less complete control over your process ``` ```(or thread) by executing the \fIevent loop\fR handler, and will then ``` ```communicate events via a callback mechanism. ``` ```.PP ``` ```You register interest in certain events by registering so-called \fIevent ``` ```watchers\fR, which are relatively small C structures you initialise with the ``` ```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). ``` ```.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. ``` ```.SH "TIME REPRESENTATION" ``` ```.IX Header "TIME REPRESENTATION" ``` ```Libev represents time as a single floating point number, representing the ``` ```(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near ``` ```the beginning of 1970, details are complicated, don't ask). This type is ``` ```called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases ``` ```to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on ``` ```it, you should treat it as such. ``` ```.SH "GLOBAL FUNCTIONS" ``` ```.IX Header "GLOBAL FUNCTIONS" ``` ```These functions can be called anytime, even before initialising the ``` ```library in any way. ``` ```.IP "ev_tstamp ev_time ()" 4 ``` ```.IX Item "ev_tstamp ev_time ()" ``` ```Returns the current time as libev would use it. Please note that the ``` ```\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp ``` ```you actually want to know. ``` ```.IP "int ev_version_major ()" 4 ``` ```.IX Item "int ev_version_major ()" ``` ```.PD 0 ``` ```.IP "int ev_version_minor ()" 4 ``` ```.IX Item "int ev_version_minor ()" ``` ```.PD ``` ```You can find out the major and minor version numbers of the library ``` ```you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and ``` ```\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global ``` ```symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the ``` ```version of the library your program was compiled against. ``` ```.Sp ``` ```Usually, it's a good idea to terminate if the major versions mismatch, ``` ```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: ``` ```.Sp ``` ```.Vb 3 ``` ```\& assert (("libev version mismatch", ``` ```\& ev_version_major () == EV_VERSION_MAJOR ``` ```\& && ev_version_minor () >= EV_VERSION_MINOR)); ``` ```.Ve ``` ```.IP "unsigned int ev_supported_backends ()" 4 ``` ```.IX Item "unsigned int ev_supported_backends ()" ``` ```Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR ``` ```value) compiled into this binary of libev (independent of their ``` ```availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for ``` ```a description of the set values. ``` ```.Sp ``` ```Example: make sure we have the epoll method, because yeah this is cool and ``` ```a must have and can we have a torrent of it please!!!11 ``` ```.Sp ``` ```.Vb 2 ``` ```\& assert (("sorry, no epoll, no sex", ``` ```\& ev_supported_backends () & EVBACKEND_EPOLL)); ``` ```.Ve ``` ```.IP "unsigned int ev_recommended_backends ()" 4 ``` ```.IX Item "unsigned int ev_recommended_backends ()" ``` ```Return the set of all backends compiled into this binary of libev and also ``` ```recommended for this platform. This set is often smaller than the one ``` ```returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on ``` ```most BSDs and will not be autodetected unless you explicitly request it ``` ```(assuming you know what you are doing). This is the set of backends that ``` ```libev will probe for if you specify no backends explicitly. ``` ```.IP "unsigned int ev_embeddable_backends ()" 4 ``` ```.IX Item "unsigned int ev_embeddable_backends ()" ``` ```Returns the set of backends that are embeddable in other event loops. This ``` ```is the theoretical, all\-platform, value. To find which backends ``` ```might be supported on the current system, you would need to look at ``` ```\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for ``` ```recommended ones. ``` ```.Sp ``` ```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. ``` ```.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). ``` ```.Sp ``` ```.Vb 6 ``` ```\& static void * ``` ```\& persistent_realloc (void *ptr, long size) ``` ```\& { ``` ```\& for (;;) ``` ```\& { ``` ```\& void *newptr = realloc (ptr, size); ``` ```.Ve ``` ```.Sp ``` ```.Vb 2 ``` ```\& if (newptr) ``` ```\& return newptr; ``` ```.Ve ``` ```.Sp ``` ```.Vb 3 ``` ```\& sleep (60); ``` ```\& } ``` ```\& } ``` ```.Ve ``` ```.Sp ``` ```.Vb 2 ``` ```\& ... ``` ```\& ev_set_allocator (persistent_realloc); ``` ```.Ve ``` ```.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 ``` ```.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" ``` ```Set the callback function to call on a retryable syscall error (such ``` ```as failed select, poll, epoll_wait). The message is a printable string ``` ```indicating the system call or subsystem causing the problem. If this ``` ```callback is set, then libev will expect it to remedy the sitution, no ``` ```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: ``` ```.Sp ``` ```.Vb 6 ``` ```\& static void ``` ```\& fatal_error (const char *msg) ``` ```\& { ``` ```\& perror (msg); ``` ```\& abort (); ``` ```\& } ``` ```.Ve ``` ```.Sp ``` ```.Vb 2 ``` ```\& ... ``` ```\& ev_set_syserr_cb (fatal_error); ``` ```.Ve ``` ```.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" ``` ```.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" ``` ```An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two ``` ```types of such loops, the \fIdefault\fR loop, which supports signals and child ``` ```events, and dynamically created loops which do not. ``` ```.PP ``` ```If you use threads, a common model is to run the default event loop ``` ```in your main thread (or in a separate thread) and for each thread you ``` ```create, you also create another event loop. Libev itself does no locking ``` ```whatsoever, so if you mix calls to the same event loop in different ``` ```threads, make sure you lock (this is usually a bad idea, though, even if ``` ```done correctly, because it's hideous and inefficient). ``` ```.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 ``` ```.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" ``` ```This will initialise the default event loop if it hasn't been initialised ``` ```yet and return it. If the default loop could not be initialised, returns ``` ```false. If it already was initialised it simply returns it (and ignores the ``` ```flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards). ``` ```.Sp ``` ```If you don't know what event loop to use, use the one returned from this ``` ```function. ``` ```.Sp ``` ```The flags argument can be used to specify special behaviour or specific ``` ```backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). ``` ```.Sp ``` ```The following flags are supported: ``` ```.RS 4 ``` ```.ie n .IP """EVFLAG_AUTO""" 4 ``` ```.el .IP "\f(CWEVFLAG_AUTO\fR" 4 ``` ```.IX Item "EVFLAG_AUTO" ``` ```The default flags value. Use this if you have no clue (it's the right ``` ```thing, believe me). ``` ```.ie n .IP """EVFLAG_NOENV""" 4 ``` ```.el .IP "\f(CWEVFLAG_NOENV\fR" 4 ``` ```.IX Item "EVFLAG_NOENV" ``` ```If this flag bit is ored into the flag value (or the program runs setuid ``` ```or setgid) then libev will \fInot\fR look at the environment variable ``` ```\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will ``` ```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 """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)" ``` ```This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as ``` ```libev tries to roll its own fd_set with no limits on the number of fds, ``` ```but if that fails, expect a fairly low limit on the number of fds when ``` ```using this backend. It doesn't scale too well (O(highest_fd)), but its usually ``` ```the fastest backend for a low number of fds. ``` ```.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 ``` ```.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 ``` ```.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" ``` ```And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than ``` ```select, but handles sparse fds better and has no artificial limit on the ``` ```number of fds you can use (except it will slow down considerably with a ``` ```lot of inactive fds). It scales similarly to select, i.e. O(total_fds). ``` ```.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 ``` ```.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 ``` ```.IX Item "EVBACKEND_EPOLL (value 4, Linux)" ``` ```For few fds, this backend is a bit little slower than poll and select, ``` ```but it scales phenomenally better. While poll and select usually scale like ``` ```O(total_fds) where n is the total number of fds (or the highest fd), epoll scales ``` ```either O(1) or O(active_fds). ``` ```.Sp ``` ```While stopping and starting an I/O watcher in the same iteration will ``` ```result in some caching, there is still a syscall per such incident ``` ```(because the fd could point to a different file description now), so its ``` ```best to avoid that. Also, \fIdup()\fRed file descriptors might not work very ``` ```well if you register events for both fds. ``` ```.Sp ``` ```Please note that epoll sometimes generates spurious notifications, so you ``` ```need to use non-blocking I/O or other means to avoid blocking when no data ``` ```(or space) is available. ``` ```.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 ``` ```.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 ``` ```.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" ``` ```Kqueue deserves special mention, as at the time of this writing, it ``` ```was broken on all BSDs except NetBSD (usually it doesn't work with ``` ```anything but sockets and pipes, except on Darwin, where of course its ``` ```completely useless). For this reason its not being \*(L"autodetected\*(R" ``` ```unless you explicitly specify it explicitly in the flags (i.e. using ``` ```\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR). ``` ```.Sp ``` ```It scales in the same way as the epoll backend, but the interface to the ``` ```kernel is more efficient (which says nothing about its actual speed, of ``` ```course). While starting and stopping an I/O watcher does not cause an ``` ```extra syscall as with epoll, it still adds up to four event changes per ``` ```incident, so its best to avoid that. ``` ```.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 ``` ```.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 ``` ```.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" ``` ```This is not implemented yet (and might never be). ``` ```.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 ``` ```.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 ``` ```.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" ``` ```This uses the Solaris 10 port mechanism. As with everything on Solaris, ``` ```it's really slow, but it still scales very well (O(active_fds)). ``` ```.Sp ``` ```Please note that solaris ports can result in a lot of spurious ``` ```notifications, so you need to use non-blocking I/O or other means to avoid ``` ```blocking when no data (or space) is available. ``` ```.ie n .IP """EVBACKEND_ALL""" 4 ``` ```.el .IP "\f(CWEVBACKEND_ALL\fR" 4 ``` ```.IX Item "EVBACKEND_ALL" ``` ```Try all backends (even potentially broken ones that wouldn't be tried ``` ```with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as ``` ```\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. ``` ```.RE ``` ```.RS 4 ``` ```.Sp ``` ```If one or more of these are ored into the flags value, then only these ``` ```backends will be tried (in the reverse order as given here). If none are ``` ```specified, most compiled-in backend will be tried, usually in reverse ``` ```order of their flag values :) ``` ```.Sp ``` ```The most typical usage is like this: ``` ```.Sp ``` ```.Vb 2 ``` ```\& if (!ev_default_loop (0)) ``` ```\& fatal ("could not initialise libev, bad \$LIBEV_FLAGS in environment?"); ``` ```.Ve ``` ```.Sp ``` ```Restrict libev to the select and poll backends, and do not allow ``` ```environment settings to be taken into account: ``` ```.Sp ``` ```.Vb 1 ``` ```\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); ``` ```.Ve ``` ```.Sp ``` ```Use whatever libev has to offer, but make sure that kqueue is used if ``` ```available (warning, breaks stuff, best use only with your own private ``` ```event loop and only if you know the \s-1OS\s0 supports your types of fds): ``` ```.Sp ``` ```.Vb 1 ``` ```\& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); ``` ```.Ve ``` ```.RE ``` ```.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 ``` ```.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" ``` ```Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is ``` ```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. ``` ```.Sp ``` ```.Vb 3 ``` ```\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); ``` ```\& if (!epoller) ``` ```\& fatal ("no epoll found here, maybe it hides under your chair"); ``` ```.Ve ``` ```.IP "ev_default_destroy ()" 4 ``` ```.IX Item "ev_default_destroy ()" ``` ```Destroys the default loop again (frees all memory and kernel state ``` ```etc.). None of the active event watchers will be stopped in the normal ``` ```sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your ``` ```responsibility to either stop all watchers cleanly yoursef \fIbefore\fR ``` ```calling this function, or cope with the fact afterwards (which is usually ``` ```the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them ``` ```for example). ``` ```.IP "ev_loop_destroy (loop)" 4 ``` ```.IX Item "ev_loop_destroy (loop)" ``` ```Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an ``` ```earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. ``` ```.IP "ev_default_fork ()" 4 ``` ```.IX Item "ev_default_fork ()" ``` ```This function reinitialises the kernel state for backends that have ``` ```one. Despite the name, you can call it anytime, but it makes most sense ``` ```after forking, in either the parent or child process (or both, but that ``` ```again makes little sense). ``` ```.Sp ``` ```You \fImust\fR call this function in the child process after forking if and ``` ```only if you want to use the event library in both processes. If you just ``` ```fork+exec, you don't have to call it. ``` ```.Sp ``` ```The function itself is quite fast and it's usually not a problem to call ``` ```it just in case after a fork. To make this easy, the function will fit in ``` ```quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: ``` ```.Sp ``` ```.Vb 1 ``` ```\& pthread_atfork (0, 0, ev_default_fork); ``` ```.Ve ``` ```.Sp ``` ```At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use ``` ```without calling this function, so if you force one of those backends you ``` ```do not need to care. ``` ```.IP "ev_loop_fork (loop)" 4 ``` ```.IX Item "ev_loop_fork (loop)" ``` ```Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by ``` ```\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop ``` ```after fork, and how you do this is entirely your own problem. ``` ```.IP "unsigned int ev_backend (loop)" 4 ``` ```.IX Item "unsigned int ev_backend (loop)" ``` ```Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in ``` ```use. ``` ```.IP "ev_tstamp ev_now (loop)" 4 ``` ```.IX Item "ev_tstamp ev_now (loop)" ``` ```Returns the current \*(L"event loop time\*(R", which is the time the event loop ``` ```received events and started processing them. This timestamp does not ``` ```change as long as callbacks are being processed, and this is also the base ``` ```time used for relative timers. You can treat it as the timestamp of the ``` ```event occuring (or more correctly, libev finding out about it). ``` ```.IP "ev_loop (loop, int flags)" 4 ``` ```.IX Item "ev_loop (loop, int flags)" ``` ```Finally, this is it, the event handler. This function usually is called ``` ```after you initialised all your watchers and you want to start handling ``` ```events. ``` ```.Sp ``` ```If the flags argument is specified as \f(CW0\fR, it will not return until ``` ```either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. ``` ```.Sp ``` ```Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than ``` ```relying on all watchers to be stopped when deciding when a program has ``` ```finished (especially in interactive programs), but having a program that ``` ```automatically loops as long as it has to and no longer by virtue of ``` ```relying on its watchers stopping correctly is a thing of beauty. ``` ```.Sp ``` ```A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle ``` ```those events and any outstanding ones, but will not block your process in ``` ```case there are no events and will return after one iteration of the loop. ``` ```.Sp ``` ```A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if ``` ```neccessary) and will handle those and any outstanding ones. It will block ``` ```your process until at least one new event arrives, and will return after ``` ```one iteration of the loop. This is useful if you are waiting for some ``` ```external event in conjunction with something not expressible using other ``` ```libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is ``` ```usually a better approach for this kind of thing. ``` ```.Sp ``` ```Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: ``` ```.Sp ``` ```.Vb 18 ``` ```\& * If there are no active watchers (reference count is zero), return. ``` ```\& - Queue prepare watchers and then call all outstanding watchers. ``` ```\& - If we have been forked, recreate the kernel state. ``` ```\& - Update the kernel state with all outstanding changes. ``` ```\& - Update the "event loop time". ``` ```\& - Calculate for how long to block. ``` ```\& - Block the process, waiting for any events. ``` ```\& - Queue all outstanding I/O (fd) events. ``` ```\& - Update the "event loop time" and do time jump handling. ``` ```\& - Queue all outstanding timers. ``` ```\& - Queue all outstanding periodics. ``` ```\& - If no events are pending now, queue all idle watchers. ``` ```\& - Queue all check watchers. ``` ```\& - Call all queued watchers in reverse order (i.e. check watchers first). ``` ```\& Signals and child watchers are implemented as I/O watchers, and will ``` ```\& be handled here by queueing them when their watcher gets executed. ``` ```\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK ``` ```\& were used, return, otherwise continue with step *. ``` ```.Ve ``` ```.Sp ``` ```Example: queue some jobs and then loop until no events are outsanding ``` ```anymore. ``` ```.Sp ``` ```.Vb 4 ``` ```\& ... queue jobs here, make sure they register event watchers as long ``` ```\& ... as they still have work to do (even an idle watcher will do..) ``` ```\& ev_loop (my_loop, 0); ``` ```\& ... jobs done. yeah! ``` ```.Ve ``` ```.IP "ev_unloop (loop, how)" 4 ``` ```.IX Item "ev_unloop (loop, how)" ``` ```Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it ``` ```has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either ``` ```\&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or ``` ```\&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. ``` ```.IP "ev_ref (loop)" 4 ``` ```.IX Item "ev_ref (loop)" ``` ```.PD 0 ``` ```.IP "ev_unref (loop)" 4 ``` ```.IX Item "ev_unref (loop)" ``` ```.PD ``` ```Ref/unref can be used to add or remove a reference count on the event ``` ```loop: Every watcher keeps one reference, and as long as the reference ``` ```count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have ``` ```a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from ``` ```returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For ``` ```example, libev itself uses this for its internal signal pipe: It is not ``` ```visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if ``` ```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 ``` ```running when nothing else is active. ``` ```.Sp ``` ```.Vb 4 ``` ```\& struct dv_signal exitsig; ``` ```\& ev_signal_init (&exitsig, sig_cb, SIGINT); ``` ```\& ev_signal_start (myloop, &exitsig); ``` ```\& evf_unref (myloop); ``` ```.Ve ``` ```.Sp ``` ```Example: for some weird reason, unregister the above signal handler again. ``` ```.Sp ``` ```.Vb 2 ``` ```\& ev_ref (myloop); ``` ```\& ev_signal_stop (myloop, &exitsig); ``` ```.Ve ``` ```.SH "ANATOMY OF A WATCHER" ``` ```.IX Header "ANATOMY OF A WATCHER" ``` ```A watcher is a structure that you create and register to record your ``` ```interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to ``` ```become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: ``` ```.PP ``` ```.Vb 5 ``` ```\& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) ``` ```\& { ``` ```\& ev_io_stop (w); ``` ```\& ev_unloop (loop, EVUNLOOP_ALL); ``` ```\& } ``` ```.Ve ``` ```.PP ``` ```.Vb 6 ``` ```\& struct ev_loop *loop = ev_default_loop (0); ``` ```\& struct ev_io stdin_watcher; ``` ```\& ev_init (&stdin_watcher, my_cb); ``` ```\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); ``` ```\& ev_io_start (loop, &stdin_watcher); ``` ```\& ev_loop (loop, 0); ``` ```.Ve ``` ```.PP ``` ```As you can see, you are responsible for allocating the memory for your ``` ```watcher structures (and it is usually a bad idea to do this on the stack, ``` ```although this can sometimes be quite valid). ``` ```.PP ``` ```Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init ``` ```(watcher *, callback)\*(C'\fR, which expects a callback to be provided. This ``` ```callback gets invoked each time the event occurs (or, in the case of io ``` ```watchers, each time the event loop detects that the file descriptor given ``` ```is readable and/or writable). ``` ```.PP ``` ```Each watcher type has its own \f(CW\*(C`ev__set (watcher *, ...)\*(C'\fR macro ``` ```with arguments specific to this watcher type. There is also a macro ``` ```to combine initialisation and setting in one call: \f(CW\*(C`ev__init ``` ```(watcher *, callback, ...)\*(C'\fR. ``` ```.PP ``` ```To make the watcher actually watch out for events, you have to start it ``` ```with a watcher-specific start function (\f(CW\*(C`ev__start (loop, watcher ``` ```*)\*(C'\fR), and you can stop watching for events at any time by calling the ``` ```corresponding stop function (\f(CW\*(C`ev__stop (loop, watcher *)\*(C'\fR. ``` ```.PP ``` ```As long as your watcher is active (has been started but not stopped) you ``` ```must not touch the values stored in it. Most specifically you must never ``` ```reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro. ``` ```.PP ``` ```Each and every callback receives the event loop pointer as first, the ``` ```registered watcher structure as second, and a bitset of received events as ``` ```third argument. ``` ```.PP ``` ```The received events usually include a single bit per event type received ``` ```(you can receive multiple events at the same time). The possible bit masks ``` ```are: ``` ```.ie n .IP """EV_READ""" 4 ``` ```.el .IP "\f(CWEV_READ\fR" 4 ``` ```.IX Item "EV_READ" ``` ```.PD 0 ``` ```.ie n .IP """EV_WRITE""" 4 ``` ```.el .IP "\f(CWEV_WRITE\fR" 4 ``` ```.IX Item "EV_WRITE" ``` ```.PD ``` ```The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or ``` ```writable. ``` ```.ie n .IP """EV_TIMEOUT""" 4 ``` ```.el .IP "\f(CWEV_TIMEOUT\fR" 4 ``` ```.IX Item "EV_TIMEOUT" ``` ```The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out. ``` ```.ie n .IP """EV_PERIODIC""" 4 ``` ```.el .IP "\f(CWEV_PERIODIC\fR" 4 ``` ```.IX Item "EV_PERIODIC" ``` ```The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out. ``` ```.ie n .IP """EV_SIGNAL""" 4 ``` ```.el .IP "\f(CWEV_SIGNAL\fR" 4 ``` ```.IX Item "EV_SIGNAL" ``` ```The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. ``` ```.ie n .IP """EV_CHILD""" 4 ``` ```.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" ``` ```The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. ``` ```.ie n .IP """EV_PREPARE""" 4 ``` ```.el .IP "\f(CWEV_PREPARE\fR" 4 ``` ```.IX Item "EV_PREPARE" ``` ```.PD 0 ``` ```.ie n .IP """EV_CHECK""" 4 ``` ```.el .IP "\f(CWEV_CHECK\fR" 4 ``` ```.IX Item "EV_CHECK" ``` ```.PD ``` ```All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts ``` ```to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after ``` ```\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any ``` ```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" ``` ```An unspecified error has occured, the watcher has been stopped. This might ``` ```happen because the watcher could not be properly started because libev ``` ```ran out of memory, a file descriptor was found to be closed or any other ``` ```problem. You best act on it by reporting the problem and somehow coping ``` ```with the watcher being stopped. ``` ```.Sp ``` ```Libev will usually signal a few \*(L"dummy\*(R" events together with an error, ``` ```for example it might indicate that a fd is readable or writable, and if ``` ```your callbacks is well-written it can just attempt the operation and cope ``` ```with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded ``` ```programs, though, so beware. ``` ```.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" ``` ```.IX Subsection "GENERIC WATCHER FUNCTIONS" ``` ```In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, ``` ```e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers. ``` ```.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 ``` ```.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 ``` ```.IX Item "ev_init (ev_TYPE *watcher, callback)" ``` ```This macro initialises the generic portion of a watcher. The contents ``` ```of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only ``` ```the generic parts of the watcher are initialised, you \fIneed\fR to call ``` ```the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the ``` ```type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro ``` ```which rolls both calls into one. ``` ```.Sp ``` ```You can reinitialise a watcher at any time as long as it has been stopped ``` ```(or never started) and there are no pending events outstanding. ``` ```.Sp ``` ```The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, ``` ```int revents)\*(C'\fR. ``` ```.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 ``` ```.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 ``` ```.IX Item "ev_TYPE_set (ev_TYPE *, [args])" ``` ```This macro initialises the type-specific parts of a watcher. You need to ``` ```call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can ``` ```call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this ``` ```macro on a watcher that is active (it can be pending, however, which is a ``` ```difference to the \f(CW\*(C`ev_init\*(C'\fR macro). ``` ```.Sp ``` ```Although some watcher types do not have type-specific arguments ``` ```(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro. ``` ```.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4 ``` ```.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4 ``` ```.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])" ``` ```This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro ``` ```calls into a single call. This is the most convinient method to initialise ``` ```a watcher. The same limitations apply, of course. ``` ```.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 ``` ```.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 ``` ```.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" ``` ```Starts (activates) the given watcher. Only active watchers will receive ``` ```events. If the watcher is already active nothing will happen. ``` ```.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 ``` ```.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 ``` ```.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" ``` ```Stops the given watcher again (if active) and clears the pending ``` ```status. It is possible that stopped watchers are pending (for example, ``` ```non-repeating timers are being stopped when they become pending), but ``` ```\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If ``` ```you want to free or reuse the memory used by the watcher it is therefore a ``` ```good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. ``` ```.IP "bool ev_is_active (ev_TYPE *watcher)" 4 ``` ```.IX Item "bool ev_is_active (ev_TYPE *watcher)" ``` ```Returns a true value iff the watcher is active (i.e. it has been started ``` ```and not yet been stopped). As long as a watcher is active you must not modify ``` ```it. ``` ```.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 ``` ```.IX Item "bool ev_is_pending (ev_TYPE *watcher)" ``` ```Returns a true value iff the watcher is pending, (i.e. it has outstanding ``` ```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)" ``` ```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)" ``` ```Change the callback. You can change the callback at virtually any time ``` ```(modulo threads). ``` ```.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" ``` ```.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" ``` ```Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change ``` ```and read at any time, libev will completely ignore it. This can be used ``` ```to associate arbitrary data with your watcher. If you need more data and ``` ```don't want to allocate memory and store a pointer to it in that data ``` ```member, you can also \*(L"subclass\*(R" the watcher type and provide your own ``` ```data: ``` ```.PP ``` ```.Vb 7 ``` ```\& struct my_io ``` ```\& { ``` ```\& struct ev_io io; ``` ```\& int otherfd; ``` ```\& void *somedata; ``` ```\& struct whatever *mostinteresting; ``` ```\& } ``` ```.Ve ``` ```.PP ``` ```And since your callback will be called with a pointer to the watcher, you ``` ```can cast it back to your own type: ``` ```.PP ``` ```.Vb 5 ``` ```\& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) ``` ```\& { ``` ```\& struct my_io *w = (struct my_io *)w_; ``` ```\& ... ``` ```\& } ``` ```.Ve ``` ```.PP ``` ```More interesting and less C\-conformant ways of catsing your callback type ``` ```have been omitted.... ``` ```.SH "WATCHER TYPES" ``` ```.IX Header "WATCHER TYPES" ``` ```This section describes each watcher in detail, but will not repeat ``` ```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?" ``` ```I/O watchers check whether a file descriptor is readable or writable ``` ```in each iteration of the event loop, or, more precisely, when reading ``` ```would not block the process and writing would at least be able to write ``` ```some data. This behaviour is called level-triggering because you keep ``` ```receiving events as long as the condition persists. Remember you can stop ``` ```the watcher if you don't want to act on the event and neither want to ``` ```receive future events. ``` ```.PP ``` ```In general you can register as many read and/or write event watchers per ``` ```fd as you want (as long as you don't confuse yourself). Setting all file ``` ```descriptors to non-blocking mode is also usually a good idea (but not ``` ```required if you know what you are doing). ``` ```.PP ``` ```You have to be careful with dup'ed file descriptors, though. Some backends ``` ```(the linux epoll backend is a notable example) cannot handle dup'ed file ``` ```descriptors correctly if you register interest in two or more fds pointing ``` ```to the same underlying file/socket/etc. description (that is, they share ``` ```the same underlying \*(L"file open\*(R"). ``` ```.PP ``` ```If you must do this, then force the use of a known-to-be-good backend ``` ```(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and ``` ```\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). ``` ```.PP ``` ```Another thing you have to watch out for is that it is quite easy to ``` ```receive \*(L"spurious\*(R" readyness notifications, that is your callback might ``` ```be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block ``` ```because there is no data. Not only are some backends known to create a ``` ```lot of those (for example solaris ports), it is very easy to get into ``` ```this situation even with a relatively standard program structure. Thus ``` ```it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning ``` ```\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. ``` ```.PP ``` ```If you cannot run the fd in non-blocking mode (for example you should not ``` ```play around with an Xlib connection), then you have to seperately re-test ``` ```wether a file descriptor is really ready with a known-to-be good interface ``` ```such as poll (fortunately in our Xlib example, Xlib already does this on ``` ```its own, so its quite safe to use). ``` ```.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 ``` ```.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" ``` ```.PD 0 ``` ```.IP "ev_io_set (ev_io *, int fd, int events)" 4 ``` ```.IX Item "ev_io_set (ev_io *, int fd, int events)" ``` ```.PD ``` ```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. ``` ```.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: ``` ```.PP ``` ```.Vb 6 ``` ```\& static void ``` ```\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) ``` ```\& { ``` ```\& ev_io_stop (loop, w); ``` ```\& .. read from stdin here (or from w->fd) and haqndle any I/O errors ``` ```\& } ``` ```.Ve ``` ```.PP ``` ```.Vb 6 ``` ```\& ... ``` ```\& struct ev_loop *loop = ev_default_init (0); ``` ```\& struct ev_io stdin_readable; ``` ```\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); ``` ```\& ev_io_start (loop, &stdin_readable); ``` ```\& ev_loop (loop, 0); ``` ```.Ve ``` ```.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" ``` ```.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts" ``` ```.IX Subsection "ev_timer - relative and optionally repeating timeouts" ``` ```Timer watchers are simple relative timers that generate an event after a ``` ```given time, and optionally repeating in regular intervals after that. ``` ```.PP ``` ```The timers are based on real time, that is, if you register an event that ``` ```times out after an hour and you reset your system clock to last years ``` ```time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because ``` ```detecting time jumps is hard, and some inaccuracies are unavoidable (the ``` ```monotonic clock option helps a lot here). ``` ```.PP ``` ```The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR ``` ```time. This is usually the right thing as this timestamp refers to the time ``` ```of the event triggering whatever timeout you are modifying/starting. If ``` ```you suspect event processing to be delayed and you \fIneed\fR to base the timeout ``` ```on the current time, use something like this to adjust for this: ``` ```.PP ``` ```.Vb 1 ``` ```\& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); ``` ```.Ve ``` ```.PP ``` ```The callback is guarenteed to be invoked only when its timeout has passed, ``` ```but if multiple timers become ready during the same loop iteration then ``` ```order of execution is undefined. ``` ```.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 ``` ```.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" ``` ```.PD 0 ``` ```.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 ``` ```.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" ``` ```.PD ``` ```Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is ``` ```\&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the ``` ```timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds ``` ```later, again, and again, until stopped manually. ``` ```.Sp ``` ```The timer itself will do a best-effort at avoiding drift, that is, if you ``` ```configure a timer to trigger every 10 seconds, then it will trigger at ``` ```exactly 10 second intervals. If, however, your program cannot keep up with ``` ```the timer (because it takes longer than those 10 seconds to do stuff) the ``` ```timer will not fire more than once per event loop iteration. ``` ```.IP "ev_timer_again (loop)" 4 ``` ```.IX Item "ev_timer_again (loop)" ``` ```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. ``` ```.Sp ``` ```If the timer is repeating, either start it if necessary (with the repeat ``` ```value), or reset the running timer to the repeat 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 \f(CW\*(C`after\*(C'\fR=\f(CW\*(C`repeat\*(C'\fR=\f(CW60\fR and calling ``` ```\&\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 stop the timer, and again will automatically restart it if ``` ```need be. ``` ```.Sp ``` ```You can also 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: ``` ```.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 efficient then stopping/starting the timer eahc 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. ``` ```.PP ``` ```.Vb 5 ``` ```\& static void ``` ```\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) ``` ```\& { ``` ```\& .. one minute over, w is actually stopped right here ``` ```\& } ``` ```.Ve ``` ```.PP ``` ```.Vb 3 ``` ```\& struct ev_timer mytimer; ``` ```\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); ``` ```\& ev_timer_start (loop, &mytimer); ``` ```.Ve ``` ```.PP ``` ```Example: create a timeout timer that times out after 10 seconds of ``` ```inactivity. ``` ```.PP ``` ```.Vb 5 ``` ```\& static void ``` ```\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) ``` ```\& { ``` ```\& .. ten seconds without any activity ``` ```\& } ``` ```.Ve ``` ```.PP ``` ```.Vb 4 ``` ```\& struct ev_timer mytimer; ``` ```\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ ``` ```\& ev_timer_again (&mytimer); /* start timer */ ``` ```\& ev_loop (loop, 0); ``` ```.Ve ``` ```.PP ``` ```.Vb 3 ``` ```\& // and in some piece of code that gets executed on any "activity": ``` ```\& // reset the timeout to start ticking again at 10 seconds ``` ```\& ev_timer_again (&mytimer); ``` ```.Ve ``` ```.ie n .Sh """ev_periodic"" \- to cron or not to cron?" ``` ```.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" ``` ```.IX Subsection "ev_periodic - to cron or not to cron?" ``` ```Periodic watchers are also timers of a kind, but they are very versatile ``` ```(and unfortunately a bit complex). ``` ```.PP ``` ```Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) ``` ```but on wallclock time (absolute time). You can tell a periodic watcher ``` ```to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a ``` ```periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now () ``` ```+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will ``` ```take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger ``` ```roughly 10 seconds later and of course not if you reset your system time ``` ```again). ``` ```.PP ``` ```They can also be used to implement vastly more complex timers, such as ``` ```triggering an event on eahc midnight, local time. ``` ```.PP ``` ```As with timers, the callback is guarenteed to be invoked only when the ``` ```time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready ``` ```during the same loop iteration then order of execution is undefined. ``` ```.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 ``` ```.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" ``` ```.PD 0 ``` ```.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 ``` ```.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" ``` ```.PD ``` ```Lots of arguments, lets sort it out... There are basically three modes of ``` ```operation, and we will explain them from simplest to complex: ``` ```.RS 4 ``` ```.IP "* absolute timer (interval = reschedule_cb = 0)" 4 ``` ```.IX Item "absolute timer (interval = reschedule_cb = 0)" ``` ```In this configuration the watcher triggers an event at the wallclock time ``` ```\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, ``` ```that is, if it is to be run at January 1st 2011 then it will run when the ``` ```system time reaches or surpasses this time. ``` ```.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 ``` ```.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" ``` ```In this mode the watcher will always be scheduled to time out at the next ``` ```\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless ``` ```of any time jumps. ``` ```.Sp ``` ```This can be used to create timers that do not drift with respect to system ``` ```time: ``` ```.Sp ``` ```.Vb 1 ``` ```\& ev_periodic_set (&periodic, 0., 3600., 0); ``` ```.Ve ``` ```.Sp ``` ```This doesn't mean there will always be 3600 seconds in between triggers, ``` ```but only that the the callback will be called when the system time shows a ``` ```full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible ``` ```by 3600. ``` ```.Sp ``` ```Another way to think about it (for the mathematically inclined) is that ``` ```\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible ``` ```time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. ``` ```.IP "* manual reschedule mode (reschedule_cb = callback)" 4 ``` ```.IX Item "manual reschedule mode (reschedule_cb = callback)" ``` ```In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being ``` ```ignored. Instead, each time the periodic watcher gets scheduled, the ``` ```reschedule callback will be called with the watcher as first, and the ``` ```current time as second argument. ``` ```.Sp ``` ```\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, ``` ```ever, or make any event loop modifications\fR. If you need to stop it, ``` ```return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by ``` ```starting a prepare watcher). ``` ```.Sp ``` ```Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ``` ```ev_tstamp now)\*(C'\fR, e.g.: ``` ```.Sp ``` ```.Vb 4 ``` ```\& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) ``` ```\& { ``` ```\& return now + 60.; ``` ```\& } ``` ```.Ve ``` ```.Sp ``` ```It must return the next time to trigger, based on the passed time value ``` ```(that is, the lowest time value larger than to the second argument). It ``` ```will usually be called just before the callback will be triggered, but ``` ```might be called at other times, too. ``` ```.Sp ``` ```\&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the ``` ```passed \f(CI\*(C`now\*(C'\fI value\fR. Not even \f(CW\*(C`now\*(C'\fR itself will do, it \fImust\fR be larger. ``` ```.Sp ``` ```This can be used to create very complex timers, such as a timer that ``` ```triggers on each midnight, local time. To do this, you would calculate the ``` ```next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How ``` ```you do this is, again, up to you (but it is not trivial, which is the main ``` ```reason I omitted it as an example). ``` ```.RE ``` ```.RS 4 ``` ```.RE ``` ```.IP "ev_periodic_again (loop, ev_periodic *)" 4 ``` ```.IX Item "ev_periodic_again (loop, ev_periodic *)" ``` ```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). ``` ```.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 ``` ```.Vb 5 ``` ```\& static void ``` ```\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) ``` ```\& { ``` ```\& ... its now a full hour (UTC, or TAI or whatever your clock follows) ``` ```\& } ``` ```.Ve ``` ```.PP ``` ```.Vb 3 ``` ```\& struct ev_periodic hourly_tick; ``` ```\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); ``` ```\& ev_periodic_start (loop, &hourly_tick); ``` ```.Ve ``` ```.PP ``` ```Example: the same as above, but use a reschedule callback to do it: ``` ```.PP ``` ```.Vb 1 ``` ```\& #include ``` ```.Ve ``` ```.PP ``` ```.Vb 5 ``` ```\& static ev_tstamp ``` ```\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) ``` ```\& { ``` ```\& return fmod (now, 3600.) + 3600.; ``` ```\& } ``` ```.Ve ``` ```.PP ``` ```.Vb 1 ``` ```\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); ``` ```.Ve ``` ```.PP ``` ```Example: call a callback every hour, starting now: ``` ```.PP ``` ```.Vb 4 ``` ```\& struct ev_periodic hourly_tick; ``` ```\& ev_periodic_init (&hourly_tick, clock_cb, ``` ```\& fmod (ev_now (loop), 3600.), 3600., 0); ``` ```\& ev_periodic_start (loop, &hourly_tick); ``` ```.Ve ``` ```.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" ``` ```.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!" ``` ```.IX Subsection "ev_signal - signal me when a signal gets signalled!" ``` ```Signal watchers will trigger an event when the process receives a specific ``` ```signal one or more times. Even though signals are very asynchronous, libev ``` ```will try it's best to deliver signals synchronously, i.e. as part of the ``` ```normal event processing, like any other event. ``` ```.PP ``` ```You can configure as many watchers as you like per signal. Only when the ``` ```first watcher gets started will libev actually register a signal watcher ``` ```with the kernel (thus it coexists with your own signal handlers as long ``` ```as you don't register any with libev). Similarly, when the last signal ``` ```watcher for a signal is stopped libev will reset the signal handler to ``` ```\&\s-1SIG_DFL\s0 (regardless of what it was set to before). ``` ```.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 ``` ```.IX Item "ev_signal_init (ev_signal *, callback, int signum)" ``` ```.PD 0 ``` ```.IP "ev_signal_set (ev_signal *, int signum)" 4 ``` ```.IX Item "ev_signal_set (ev_signal *, int signum)" ``` ```.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" ``` ```Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to ``` ```some child status changes (most typically when a child of yours dies). ``` ```.IP "ev_child_init (ev_child *, callback, int pid)" 4 ``` ```.IX Item "ev_child_init (ev_child *, callback, int pid)" ``` ```.PD 0 ``` ```.IP "ev_child_set (ev_child *, int pid)" 4 ``` ```.IX Item "ev_child_set (ev_child *, int pid)" ``` ```.PD ``` ```Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or ``` ```\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look ``` ```at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see ``` ```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. ``` ```.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 ``` ```\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) ``` ```\& { ``` ```\& ev_unloop (loop, EVUNLOOP_ALL); ``` ```\& } ``` ```.Ve ``` ```.PP ``` ```.Vb 3 ``` ```\& struct ev_signal signal_watcher; ``` ```\& 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 ``` ```Since there is no standard to do this, the portable implementation simply ``` ```calls \f(CW\*(C`stat (2)\*(C'\fR regulalry 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, no specific \s-1OS\s0 backends are implemented, but ``` ```if demand increases, at least a kqueue and inotify backend will be added. ``` ```.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..." ``` ```Idle watchers trigger events when there are no other events are pending ``` ```(prepare, check and other idle watchers do not count). That is, as long ``` ```as your process is busy handling sockets or timeouts (or even signals, ``` ```imagine) it will not be triggered. But when your process is idle all idle ``` ```watchers are being called again and again, once per event loop iteration \- ``` ```until stopped, that is, or your process receives more events and becomes ``` ```busy. ``` ```.PP ``` ```The most noteworthy effect is that as long as any idle watchers are ``` ```active, the process will not block when waiting for new events. ``` ```.PP ``` ```Apart from keeping your process non-blocking (which is a useful ``` ```effect on its own sometimes), idle watchers are a good place to do ``` ```\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the ``` ```event loop has handled all outstanding events. ``` ```.IP "ev_idle_init (ev_signal *, callback)" 4 ``` ```.IX Item "ev_idle_init (ev_signal *, callback)" ``` ```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. ``` ```.PP ``` ```.Vb 7 ``` ```\& static void ``` ```\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) ``` ```\& { ``` ```\& free (w); ``` ```\& // now do something you wanted to do when the program has ``` ```\& // no longer asnything immediate to do. ``` ```\& } ``` ```.Ve ``` ```.PP ``` ```.Vb 3 ``` ```\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); ``` ```\& ev_idle_init (idle_watcher, idle_cb); ``` ```\& ev_idle_start (loop, idle_cb); ``` ```.Ve ``` ```.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" ``` ```.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" ``` ```.IX Subsection "ev_prepare and ev_check - customise your event loop!" ``` ```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. 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 ``` ```them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries ``` ```provide just this functionality). Then, in the check watcher you check for ``` ```any events that occured (by checking the pending status of all watchers ``` ```and stopping them) and call back into the library. The I/O and timer ``` ```callbacks will never actually be called (but must be valid nevertheless, ``` ```because you never know, you know?). ``` ```.PP ``` ```As another example, the Perl Coro module uses these hooks to integrate ``` ```coroutines into libev programs, by yielding to other active coroutines ``` ```during each prepare and only letting the process block if no coroutines ``` ```are ready to run (it's actually more complicated: it only runs coroutines ``` ```with priority higher than or equal to the event loop and one coroutine ``` ```of lower priority, but only once, using idle watchers to keep the event ``` ```loop from blocking if lower-priority coroutines are active, thus mapping ``` ```low-priority coroutines to idle/background tasks). ``` ```.IP "ev_prepare_init (ev_prepare *, callback)" 4 ``` ```.IX Item "ev_prepare_init (ev_prepare *, callback)" ``` ```.PD 0 ``` ```.IP "ev_check_init (ev_check *, callback)" 4 ``` ```.IX Item "ev_check_init (ev_check *, callback)" ``` ```.PD ``` ```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: 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..." ``` ```This is a rather advanced watcher type that lets you embed one event loop ``` ```into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded ``` ```loop, other types of watchers might be handled in a delayed or incorrect ``` ```fashion and must not be used). ``` ```.PP ``` ```There are primarily two reasons you would want that: work around bugs and ``` ```prioritise I/O. ``` ```.PP ``` ```As an example for a bug workaround, the kqueue backend might only support ``` ```sockets on some platform, so it is unusable as generic backend, but you ``` ```still want to make use of it because you have many sockets and it scales ``` ```so nicely. In this case, you would create a kqueue-based loop and embed it ``` ```into your default loop (which might use e.g. poll). Overall operation will ``` ```be a bit slower because first libev has to poll and then call kevent, but ``` ```at least you can use both at what they are best. ``` ```.PP ``` ```As for prioritising I/O: rarely you have the case where some fds have ``` ```to be watched and handled very quickly (with low latency), and even ``` ```priorities and idle watchers might have too much overhead. In this case ``` ```you would put all the high priority stuff in one loop and all the rest in ``` ```a second one, and embed the second one in the first. ``` ```.PP ``` ```As long as the watcher is active, the callback will be invoked every time ``` ```there might be events pending in the embedded loop. The callback must then ``` ```call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke ``` ```their callbacks (you could also start an idle watcher to give the embedded ``` ```loop strictly lower priority for example). You can also set the callback ``` ```to \f(CW0\fR, in which case the embed watcher will automatically execute the ``` ```embedded loop sweep. ``` ```.PP ``` ```As long as the watcher is started it will automatically handle events. The ``` ```callback will be invoked whenever some events have been handled. You can ``` ```set the callback to \f(CW0\fR to avoid having to specify one if you are not ``` ```interested in that. ``` ```.PP ``` ```Also, there have not currently been made special provisions for forking: ``` ```when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops, ``` ```but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers ``` ```yourself. ``` ```.PP ``` ```Unfortunately, not all backends are embeddable, only the ones returned by ``` ```\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any ``` ```portable one. ``` ```.PP ``` ```So when you want to use this feature you will always have to be prepared ``` ```that you cannot get an embeddable loop. The recommended way to get around ``` ```this is to have a separate variables for your embeddable loop, try to ``` ```create it, and if that fails, use the normal loop for everything: ``` ```.PP ``` ```.Vb 3 ``` ```\& struct ev_loop *loop_hi = ev_default_init (0); ``` ```\& struct ev_loop *loop_lo = 0; ``` ```\& struct ev_embed embed; ``` ```.Ve ``` ```.PP ``` ```.Vb 5 ``` ```\& // see if there is a chance of getting one that works ``` ```\& // (remember that a flags value of 0 means autodetection) ``` ```\& loop_lo = ev_embeddable_backends () & ev_recommended_backends () ``` ```\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) ``` ```\& : 0; ``` ```.Ve ``` ```.PP ``` ```.Vb 8 ``` ```\& // if we got one, then embed it, otherwise default to loop_hi ``` ```\& if (loop_lo) ``` ```\& { ``` ```\& ev_embed_init (&embed, 0, loop_lo); ``` ```\& ev_embed_start (loop_hi, &embed); ``` ```\& } ``` ```\& else ``` ```\& loop_lo = loop_hi; ``` ```.Ve ``` ```.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 ``` ```.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" ``` ```.PD 0 ``` ```.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 ``` ```.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" ``` ```.PD ``` ```Configures the watcher to embed the given loop, which must be ``` ```embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be ``` ```invoked automatically, otherwise it is the responsibility of the callback ``` ```to invoke it (it will continue to be called until the sweep has been done, ``` ```if you do not want thta, you need to temporarily stop the embed watcher). ``` ```.IP "ev_embed_sweep (loop, ev_embed *)" 4 ``` ```.IX Item "ev_embed_sweep (loop, ev_embed *)" ``` ```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. ``` ```.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 ``` ```.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" ``` ```This function combines a simple timer and an I/O watcher, calls your ``` ```callback on whichever event happens first and automatically stop both ``` ```watchers. This is useful if you want to wait for a single event on an fd ``` ```or timeout without having to allocate/configure/start/stop/free one or ``` ```more watchers yourself. ``` ```.Sp ``` ```If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events ``` ```is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and ``` ```\&\f(CW\*(C`events\*(C'\fR set will be craeted and started. ``` ```.Sp ``` ```If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be ``` ```started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and ``` ```repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of ``` ```dubious value. ``` ```.Sp ``` ```The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets ``` ```passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of ``` ```\&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR ``` ```value passed to \f(CW\*(C`ev_once\*(C'\fR: ``` ```.Sp ``` ```.Vb 7 ``` ```\& static void stdin_ready (int revents, void *arg) ``` ```\& { ``` ```\& if (revents & EV_TIMEOUT) ``` ```\& /* doh, nothing entered */; ``` ```\& else if (revents & EV_READ) ``` ```\& /* stdin might have data for us, joy! */; ``` ```\& } ``` ```.Ve ``` ```.Sp ``` ```.Vb 1 ``` ```\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); ``` ```.Ve ``` ```.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4 ``` ```.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)" ``` ```Feeds the given event set into the event loop, as if the specified event ``` ```had happened for the specified watcher (which must be a pointer to an ``` ```initialised but not necessarily started event watcher). ``` ```.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4 ``` ```.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)" ``` ```Feed an event on the given fd, as if a file descriptor backend detected ``` ```the given events it. ``` ```.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4 ``` ```.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)" ``` ```Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default ``` ```loop!). ``` ```.SH "LIBEVENT EMULATION" ``` ```.IX Header "LIBEVENT EMULATION" ``` ```Libev offers a compatibility emulation layer for libevent. It cannot ``` ```emulate the internals of libevent, so here are some usage hints: ``` ```.IP "* Use it by including , as usual." 4 ``` ```.IX Item "Use it by including , as usual." ``` ```.PD 0 ``` ```.IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4 ``` ```.IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." ``` ```.IP "* Avoid using ev_flags and the EVLIST_*\-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private \s-1API\s0)." 4 ``` ```.IX Item "Avoid using ev_flags and the EVLIST_*-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private API)." ``` ```.IP "* Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." 4 ``` ```.IX Item "Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." ``` ```.IP "* Other members are not supported." 4 ``` ```.IX Item "Other members are not supported." ``` ```.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 ``` ```.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." ``` ```.PD ``` ```.SH "\*(C+ SUPPORT" ``` ```.IX Header " SUPPORT" ``` ```Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow ``` ```you to use some convinience methods to start/stop watchers and also change ``` ```the callback model to a model using method callbacks on objects. ``` ```.PP ``` ```To use it, ``` ```.PP ``` ```.Vb 1 ``` ```\& #include ``` ```.Ve ``` ```.PP ``` ```(it is not installed by default). This automatically includes \fIev.h\fR ``` ```and puts all of its definitions (many of them macros) into the global ``` ```namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace. ``` ```.PP ``` ```It should support all the same embedding options as \fIev.h\fR, most notably ``` ```\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. ``` ```.PP ``` ```Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: ``` ```.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 ``` ```.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 ``` ```.IX Item "ev::READ, ev::WRITE etc." ``` ```These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. ``` ```macros from \fIev.h\fR. ``` ```.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4 ``` ```.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 ``` ```.IX Item "ev::tstamp, ev::now" ``` ```Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. ``` ```.ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4 ``` ```.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 ``` ```.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." ``` ```For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of ``` ```the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR ``` ```which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro ``` ```defines by many implementations. ``` ```.Sp ``` ```All of those classes have these methods: ``` ```.RS 4 ``` ```.IP "ev::TYPE::TYPE (object *, object::method *)" 4 ``` ```.IX Item "ev::TYPE::TYPE (object *, object::method *)" ``` ```.PD 0 ``` ```.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4 ``` ```.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" ``` ```.IP "ev::TYPE::~TYPE" 4 ``` ```.IX Item "ev::TYPE::~TYPE" ``` ```.PD ``` ```The constructor takes a pointer to an object and a method pointer to ``` ```the event handler callback to call in this class. The constructor calls ``` ```\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method ``` ```before starting it. If you do not specify a loop then the constructor ``` ```automatically associates the default loop with this watcher. ``` ```.Sp ``` ```The destructor automatically stops the watcher if it is active. ``` ```.IP "w\->set (struct ev_loop *)" 4 ``` ```.IX Item "w->set (struct ev_loop *)" ``` ```Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only ``` ```do this when the watcher is inactive (and not pending either). ``` ```.IP "w\->set ([args])" 4 ``` ```.IX Item "w->set ([args])" ``` ```Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be ``` ```called at least once. Unlike the C counterpart, an active watcher gets ``` ```automatically stopped and restarted. ``` ```.IP "w\->start ()" 4 ``` ```.IX Item "w->start ()" ``` ```Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the ``` ```constructor already takes the loop. ``` ```.IP "w\->stop ()" 4 ``` ```.IX Item "w->stop ()" ``` ```Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. ``` ```.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4 ``` ```.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4 ``` ```.IX Item "w->again () ev::timer, ev::periodic only" ``` ```For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding ``` ```\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. ``` ```.ie n .IP "w\->sweep () ""ev::embed"" only" 4 ``` ```.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 ``` ```.PP ``` ```Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in ``` ```the constructor. ``` ```.PP ``` ```.Vb 4 ``` ```\& class myclass ``` ```\& { ``` ```\& ev_io io; void io_cb (ev::io &w, int revents); ``` ```\& ev_idle idle void idle_cb (ev::idle &w, int revents); ``` ```.Ve ``` ```.PP ``` ```.Vb 2 ``` ```\& myclass (); ``` ```\& } ``` ```.Ve ``` ```.PP ``` ```.Vb 6 ``` ```\& myclass::myclass (int fd) ``` ```\& : io (this, &myclass::io_cb), ``` ```\& idle (this, &myclass::idle_cb) ``` ```\& { ``` ```\& 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, working 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 ``` ```applications. Examples of applications that embed it include the Deliantra ``` ```Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe) ``` ```and rxvt\-unicode. ``` ```.PP ``` ```The goal is to enable you to just copy the neecssary files into your ``` ```source directory without having to change even a single line in them, so ``` ```you can easily upgrade by simply copying (or having a checked-out copy of ``` ```libev somewhere in your source tree). ``` ```.Sh "\s-1FILESETS\s0" ``` ```.IX Subsection "FILESETS" ``` ```Depending on what features you need you need to include one or more sets of files ``` ```in your app. ``` ```.PP ``` ```\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR ``` ```.IX Subsection "CORE EVENT LOOP" ``` ```.PP ``` ```To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual ``` ```configuration (no autoconf): ``` ```.PP ``` ```.Vb 2 ``` ```\& #define EV_STANDALONE 1 ``` ```\& #include "ev.c" ``` ```.Ve ``` ```.PP ``` ```This will automatically include \fIev.h\fR, too, and should be done in a ``` ```single C source file only to provide the function implementations. To use ``` ```it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best ``` ```done by writing a wrapper around \fIev.h\fR that you can include instead and ``` ```where you can put other configuration options): ``` ```.PP ``` ```.Vb 2 ``` ```\& #define EV_STANDALONE 1 ``` ```\& #include "ev.h" ``` ```.Ve ``` ```.PP ``` ```Both header files and implementation files can be compiled with a \*(C+ ``` ```compiler (at least, thats a stated goal, and breakage will be treated ``` ```as a bug). ``` ```.PP ``` ```You need the following files in your source tree, or in a directory ``` ```in your include path (e.g. in libev/ when using \-Ilibev): ``` ```.PP ``` ```.Vb 4 ``` ```\& ev.h ``` ```\& ev.c ``` ```\& ev_vars.h ``` ```\& ev_wrap.h ``` ```.Ve ``` ```.PP ``` ```.Vb 1 ``` ```\& ev_win32.c required on win32 platforms only ``` ```.Ve ``` ```.PP ``` ```.Vb 5 ``` ```\& ev_select.c only when select backend is enabled (which is 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) ``` ```\& ev_port.c only when the solaris port backend is enabled (disabled by default) ``` ```.Ve ``` ```.PP ``` ```\&\fIev.c\fR includes the backend files directly when enabled, so you only need ``` ```to compile this single file. ``` ```.PP ``` ```\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR ``` ```.IX Subsection "LIBEVENT COMPATIBILITY API" ``` ```.PP ``` ```To include the libevent compatibility \s-1API\s0, also include: ``` ```.PP ``` ```.Vb 1 ``` ```\& #include "event.c" ``` ```.Ve ``` ```.PP ``` ```in the file including \fIev.c\fR, and: ``` ```.PP ``` ```.Vb 1 ``` ```\& #include "event.h" ``` ```.Ve ``` ```.PP ``` ```in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR. ``` ```.PP ``` ```You need the following additional files for this: ``` ```.PP ``` ```.Vb 2 ``` ```\& event.h ``` ```\& event.c ``` ```.Ve ``` ```.PP ``` ```\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR ``` ```.IX Subsection "AUTOCONF SUPPORT" ``` ```.PP ``` ```Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in ``` ```whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your ``` ```\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then ``` ```include \fIconfig.h\fR and configure itself accordingly. ``` ```.PP ``` ```For this of course you need the m4 file: ``` ```.PP ``` ```.Vb 1 ``` ```\& libev.m4 ``` ```.Ve ``` ```.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" ``` ```.IX Subsection "PREPROCESSOR SYMBOLS/MACROS" ``` ```Libev can be configured via a variety of preprocessor symbols you have to define ``` ```before including any of its files. The default is not to build for multiplicity ``` ```and only include the select backend. ``` ```.IP "\s-1EV_STANDALONE\s0" 4 ``` ```.IX Item "EV_STANDALONE" ``` ```Must always be \f(CW1\fR if you do not use autoconf configuration, which ``` ```keeps libev from including \fIconfig.h\fR, and it also defines dummy ``` ```implementations for some libevent functions (such as logging, which is not ``` ```supported). It will also not define any of the structs usually found in ``` ```\&\fIevent.h\fR that are not directly supported by the libev core alone. ``` ```.IP "\s-1EV_USE_MONOTONIC\s0" 4 ``` ```.IX Item "EV_USE_MONOTONIC" ``` ```If defined to be \f(CW1\fR, libev will try to detect the availability of the ``` ```monotonic clock option at both compiletime and runtime. Otherwise no use ``` ```of the monotonic clock option will be attempted. If you enable this, you ``` ```usually have to link against librt or something similar. Enabling it when ``` ```the functionality isn't available is safe, though, althoguh you have ``` ```to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR ``` ```function is hiding in (often \fI\-lrt\fR). ``` ```.IP "\s-1EV_USE_REALTIME\s0" 4 ``` ```.IX Item "EV_USE_REALTIME" ``` ```If defined to be \f(CW1\fR, libev will try to detect the availability of the ``` ```realtime clock option at compiletime (and assume its availability at ``` ```runtime if successful). Otherwise no use of the realtime clock option will ``` ```be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get ``` ```(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries ``` ```in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. ``` ```.IP "\s-1EV_USE_SELECT\s0" 4 ``` ```.IX Item "EV_USE_SELECT" ``` ```If undefined or defined to be \f(CW1\fR, libev will compile in support for the ``` ```\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no ``` ```other method takes over, select will be it. Otherwise the select backend ``` ```will not be compiled in. ``` ```.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 ``` ```.IX Item "EV_SELECT_USE_FD_SET" ``` ```If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR ``` ```structure. This is useful if libev doesn't compile due to a missing ``` ```\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on ``` ```exotic systems. This usually limits the range of file descriptors to some ``` ```low limit such as 1024 or might have other limitations (winsocket only ``` ```allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might ``` ```influence the size of the \f(CW\*(C`fd_set\*(C'\fR used. ``` ```.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 ``` ```.IX Item "EV_SELECT_IS_WINSOCKET" ``` ```When defined to \f(CW1\fR, the select backend will assume that ``` ```select/socket/connect etc. don't understand file descriptors but ``` ```wants osf handles on win32 (this is the case when the select to ``` ```be used is the winsock select). This means that it will call ``` ```\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, ``` ```it is assumed that all these functions actually work on fds, even ``` ```on win32. Should not be defined on non\-win32 platforms. ``` ```.IP "\s-1EV_USE_POLL\s0" 4 ``` ```.IX Item "EV_USE_POLL" ``` ```If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) ``` ```backend. Otherwise it will be enabled on non\-win32 platforms. It ``` ```takes precedence over select. ``` ```.IP "\s-1EV_USE_EPOLL\s0" 4 ``` ```.IX Item "EV_USE_EPOLL" ``` ```If defined to be \f(CW1\fR, libev will compile in support for the Linux ``` ```\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, ``` ```otherwise another method will be used as fallback. This is the ``` ```preferred backend for GNU/Linux systems. ``` ```.IP "\s-1EV_USE_KQUEUE\s0" 4 ``` ```.IX Item "EV_USE_KQUEUE" ``` ```If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style ``` ```\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, ``` ```otherwise another method will be used as fallback. This is the preferred ``` ```backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only ``` ```supports some types of fds correctly (the only platform we found that ``` ```supports ptys for example was NetBSD), so kqueue might be compiled in, but ``` ```not be used unless explicitly requested. The best way to use it is to find ``` ```out whether kqueue supports your type of fd properly and use an embedded ``` ```kqueue loop. ``` ```.IP "\s-1EV_USE_PORT\s0" 4 ``` ```.IX Item "EV_USE_PORT" ``` ```If defined to be \f(CW1\fR, libev will compile in support for the Solaris ``` ```10 port style backend. Its availability will be detected at runtime, ``` ```otherwise another method will be used as fallback. This is the preferred ``` ```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_H\s0" 4 ``` ```.IX Item "EV_H" ``` ```The name of the \fIev.h\fR header file used to include it. The default if ``` ```undefined is \f(CW\*(C`\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This ``` ```can be used to virtually rename the \fIev.h\fR header file in case of conflicts. ``` ```.IP "\s-1EV_CONFIG_H\s0" 4 ``` ```.IX Item "EV_CONFIG_H" ``` ```If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override ``` ```\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to ``` ```\&\f(CW\*(C`EV_H\*(C'\fR, above. ``` ```.IP "\s-1EV_EVENT_H\s0" 4 ``` ```.IX Item "EV_EVENT_H" ``` ```Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea ``` ```of how the \fIevent.h\fR header can be found. ``` ```.IP "\s-1EV_PROTOTYPES\s0" 4 ``` ```.IX Item "EV_PROTOTYPES" ``` ```If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function ``` ```prototypes, but still define all the structs and other symbols. This is ``` ```occasionally useful if you want to provide your own wrapper functions ``` ```around libev functions. ``` ```.IP "\s-1EV_MULTIPLICITY\s0" 4 ``` ```.IX Item "EV_MULTIPLICITY" ``` ```If undefined or defined to \f(CW1\fR, then all event-loop-specific functions ``` ```will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create ``` ```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_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_COMMON\s0" 4 ``` ```.IX Item "EV_COMMON" ``` ```By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining ``` ```this macro to a something else you can include more and other types of ``` ```members. You have to define it each time you include one of the files, ``` ```though, and it must be identical each time. ``` ```.Sp ``` ```For example, the perl \s-1EV\s0 module uses something like this: ``` ```.Sp ``` ```.Vb 3 ``` ```\& #define EV_COMMON \e ``` ```\& 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)" ``` ```.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)" ``` ```.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 \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 ``` ```verbatim, you can have a look at the \s-1EV\s0 perl module ``` ```(). It has the libev files in ``` ```the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public ``` ```interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file ``` ```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: ``` ```.Sp ``` ```.Vb 4 ``` ```\& #define EV_USE_POLL 0 ``` ```\& #define EV_MULTIPLICITY 0 ``` ```\& #define EV_PERIODICS 0 ``` ```\& #define EV_CONFIG_H ``` ```.Ve ``` ```.Sp ``` ```.Vb 1 ``` ```\& #include "ev++.h" ``` ```.Ve ``` ```.Sp ``` ```And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled: ``` ```.Sp ``` ```.Vb 2 ``` ```\& #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 % 16))" 4 ``` ```.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))" ``` ```.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 . ```