ev_io - is this file descriptor readable or writableev_timer - relative and optionally recurring timeoutsev_periodic - to cron or not to cronev_signal - signal me when a signal gets signalledev_child - wait for pid status changesev_idle - when you've got nothing better to doev_prepare and ev_check - customise your event loopev_embed - when one backend isn't enoughev_io - is this file descriptor readable or writable?ev_timer - relative and optionally repeating timeoutsev_periodic - to cron or not to cron?ev_signal - signal me when a signal gets signalled!ev_child - watch out for process status changesev_stat - did the file attributes just change?ev_idle - when you've got nothing better to do...ev_prepare and ev_check - customise your event loop!ev_embed - when one backend isn't enough...ev_fork - the audacity to resume the event loop after a forkev_tstamp, which is what you should use too. It usually alia
to the double type in C, and when you need to do any calculations on
it, you should treat it as such.
-
-
-
-
The pid specified in the ev_child watcher has received a status change.
EV_STATThe path specified in the ev_stat watcher changed its attributes somehow.
EV_IDLEThe ev_idle watcher has determined that you have nothing better to do.
ev_prepare watcher might start an idle watcher to keep
ev_loop from blocking).
+ EV_EMBEDThe embedded event loop specified in the ev_embed watcher needs attention.
EV_FORKThe event loop has been resumed in the child process after fork (see
+ev_fork).
EV_ERRORIn the following description, TYPE stands for the watcher type,
e.g. timer for ev_timer watchers and io for ev_io watchers.
ev_TYPE_init mac
which rolls both calls into one.
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.
-The callbakc is always of type The callback is always of type void (*)(ev_loop *loop, ev_TYPE *watcher,
+ void (*)(ev_loop *loop, ev_TYPE *watcher,
int revents).ev_TYPE_set (ev_TYPE *, [args])
This section describes each watcher in detail, but will not repeat -information given in the last section.
+information given in the last section. Any initialisation/set macros, +functions and members specific to the watcher type are explained. +Members are additionally marked with either [read-only], 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 [read-write], 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.
ev_io - is this file descriptor readable or writableev_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 (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).
+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.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 @@ -739,28 +778,39 @@ required if you know what you are doing).
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 +to the same underlying file/socket/etc. description (that is, they share the same underlying "file open").
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 EVBACKEND_SELECT and
EVBACKEND_POLL).
Another thing you have to watch out for is that it is quite easy to
+receive "spurious" readyness notifications, that is your callback might
+be called with EV_READ but a subsequent read(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 read(2) returning
+EAGAIN is far preferable to a program hanging until some data arrives.
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).
Configures an ev_io watcher. The fd is the file descriptor to rceeive
-events for and events is either EV_READ, EV_WRITE or EV_READ |
-EV_WRITE to receive the given events.
Please note that most of the more scalable backend mechanisms (for example
-epoll and solaris ports) can result in spurious readyness notifications
-for file descriptors, so you practically need to use non-blocking I/O (and
-treat callback invocation as hint only), or retest separately with a safe
-interface before doing I/O (XLib can do this), or force the use of either
-EVBACKEND_SELECT or EVBACKEND_POLL, which don't suffer from this
-problem. Also note that it is quite easy to have your callback invoked
-when the readyness condition is no longer valid even when employing
-typical ways of handling events, so its a good idea to use non-blocking
-I/O unconditionally.
Configures an ev_io watcher. The fd is the file descriptor to
+rceeive events for and events is either EV_READ, EV_WRITE or
+EV_READ | EV_WRITE to receive the given events.
The file descriptor being watched.
+The events being watched.
Example: call stdin_readable_cb when STDIN_FILENO has become, well
@@ -786,7 +836,7 @@ attempt to read a whole line in the callback:
ev_timer - relative and optionally recurring timeoutsev_timer - relative and optionally repeating timeoutsTimer watchers are simple relative timers that generate an event after a given time, and optionally repeating in regular intervals after that.
@@ -828,13 +878,34 @@ repeating. The exact semantics are:If the timer is repeating, either start it if necessary (with the repeat value), or reset the running timer to the repeat value.
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 ev_timer with after=repeat=60 and calling ev_timer_again each
-time you successfully read or write some data. If you go into an idle
-state where you do not expect data to travel on the socket, you can stop
-the timer, and again will automatically restart it if need be.
ev_timer with after=repeat=60 and calling
+ev_timer_again each time you successfully read or write some data. If
+you go into an idle state where you do not expect data to travel on the
+socket, you can stop the timer, and again will automatically restart it if
+need be.
+ You can also ignore the after value and ev_timer_start altogether
+and only ever use the repeat value:
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); + ++
This is more efficient then stopping/starting the timer eahc time you want +to modify its timeout value.
+ +The current repeat value. Will be used each time the watcher times out
+or ev_timer_again is called and determines the next timeout (if any),
+which is also when any modifications are taken into account.
Example: create a timer that fires after 60 seconds.
@@ -872,15 +943,15 @@ inactivity.ev_periodic - to cron or not to cronev_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).
Unlike ev_timer'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 "at" some specific point in time. For example, if you tell a
-periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()
-+ 10.>) and then reset your system clock to the last year, then it will
+periodic watcher to trigger in 10 seconds (by specifiying e.g. ev_now ()
++ 10.) and then reset your system clock to the last year, then it will
take a year to trigger the event (unlike an ev_timer, which would trigger
roughly 10 seconds later and of course not if you reset your system time
again).
The current interval value. Can be modified any time, but changes only
+take effect when the periodic timer fires or ev_periodic_again is being
+called.
The current reschedule callback, or 0, if this functionality is
+switched off. Can be changed any time, but changes only take effect when
+the periodic timer fires or ev_periodic_again is being called.
Example: call a callback every hour, or, more precisely, whenever the system clock is divisible by 3600. The callback invocation times have @@ -1001,7 +1084,7 @@ potentially a lot of jittering, but good long-term stability.
ev_signal - signal me when a signal gets signalledev_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 @@ -1020,6 +1103,10 @@ SIG_DFL (regardless of what it was set to before).
Configures the watcher to trigger on the given signal number (usually one
of the SIGxxx constants).
The signal the watcher watches out for.
+SIGxxx constants).
ev_child - wait for pid status changesev_child - watch out for process status changesChild watchers trigger when your process receives a SIGCHLD in response to some child status changes (most typically when a child of yours dies).
sys/wait.h and see your system
waitpid documentation). The rpid member contains the pid of the
process causing the status change.
+ The process id this watcher watches out for, or 0, meaning any process id.
The process id that detected a status change.
+The process exit/trace status caused by rpid (see your systems
+waitpid and sys/wait.h documentation for details).
Example: try to exit cleanly on SIGINT and SIGTERM.
static void @@ -1060,7 +1160,100 @@ process causing the status change.
ev_idle - when you've got nothing better to doev_stat - did the file attributes just change?This watches a filesystem path for attribute changes. That is, it calls
+stat regularly (or when the OS says it changed) and sees if it changed
+compared to the last time, invoking the callback if it did.
The path does not need to exist: changing from "path exists" to "path does
+not exist" is a status change like any other. The condition "path does
+not exist" is signified by the st_nlink 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.
Since there is no standard to do this, the portable implementation simply
+calls stat (2) 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 0 (highly recommended!) then a suitable,
+unspecified default 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 0.1, but thats
+usually overkill.
This watcher type is not meant for massive numbers of stat watchers, +as even with OS-supported change notifications, this can be +resource-intensive.
+At the time of this writing, no specific OS backends are implemented, but +if demand increases, at least a kqueue and inotify backend will be added.
+Configures the watcher to wait for status changes of the given
+path. The interval is a hint on how quickly a change is expected to
+be detected and should normally be specified as 0 to let libev choose
+a suitable value. The memory pointed to by path must point to the same
+path for as long as the watcher is active.
The callback will be receive EV_STAT when a change was detected,
+relative to the attributes at the time the watcher was started (or the
+last change was detected).
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.
+The most-recently detected attributes of the file. Although the type is of
+ev_statdata, this is usually the (or one of the) struct stat types
+suitable for your system. If the st_nlink member is 0, then there
+was some error while stating the file.
The previous attributes of the file. The callback gets invoked whenever
+prev != attr.
The specified interval.
+The filesystem path that is being watched.
+Example: Watch /etc/passwd for attribute changes.
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\n", (long)w->attr.st_size);
+ printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
+ printf ("passwd current mtime %ld\n", (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\n");
+ }
+
+ ...
+ ev_stat passwd;
+
+ ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
+ ev_stat_start (loop, &passwd);
+
+
+
+
+
+
+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 @@ -1103,15 +1296,25 @@ callback, free it. Alos, use no error checking, as usual.
ev_prepare and ev_check - customise your event loopev_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.
+You must not call ev_loop or similar functions that enter
+the current event loop from either ev_prepare or ev_check
+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 ev_prepare, blocking,
+ev_check so if you have one watcher of each kind they will always be
+called in pairs bracketing the blocking call.
Their main purpose is to integrate other event mechanisms into libev and their use is somewhat advanced. This could be used, for example, to track variable changes, implement your own watchers, integrate net-snmp or a -coroutine library and lots more.
+coroutine library and lots more. They are also occasionally useful if +you cache some data and want to flush it before blocking (for example, +in X programs you might want to do anXFlush () in an ev_prepare
+watcher).
This is done by examining in each prepare call which file descriptors need
to be watched by the other library, registering ev_io watchers for
them and starting an ev_timer watcher for any timeouts (many libraries
@@ -1137,14 +1340,67 @@ parameters of any kind. There are ev_prepare_set and ev_check
macros, but using them is utterly, utterly and completely pointless.
Example: *TODO*.
+Example: To include a library such as adns, you would add IO 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:
+ static ev_io iow [nfd];
+ static ev_timer tw;
+
+ 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;
+ }
+
+ // 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 ()));
+
+ /* 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);
+
+ // 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)));
+
+ fds [i].revents = 0;
+ iow [i].data = fds + i;
+ ev_io_start (loop, iow + i);
+ }
+ }
+
+ // stop all watchers after blocking
+ static void
+ adns_check_cb (ev_loop *loop, ev_check *w, int revents)
+ {
+ ev_timer_stop (loop, &tw);
+
+ for (int i = 0; i < nfd; ++i)
+ ev_io_stop (loop, iow + i);
+
+ adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
+ }
+
ev_embed - when one backend isn't enoughev_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 ev_io events are supported in the embedded
@@ -1222,6 +1478,33 @@ if you do not want thta, you need to temporarily stop the embed watcher).
ev_loop (embedded_loop, EVLOOP_NONBLOCK), but in the most
apropriate way for embedded loops.
+ The embedded event loop.
+ev_fork - the audacity to resume the event loop after a forkFork watchers are called when a fork () was detected (usually because
+whoever is a good citizen cared to tell libev about it by calling
+ev_default_fork or ev_loop_fork). The invocation is done before the
+event loop blocks next and before ev_check watchers are being called,
+and only in the child after the fork. If whoever good citizen calling
+ev_default_fork cheats and calls it in the wrong process, the fork
+handlers will be invoked, too, of course.
Initialises and configures the fork watcher - it has no parameters of any
+kind. There is a ev_fork_set macro, but using it is utterly pointless,
+believe me.
TBD.
+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.
+To use it,
+#include <ev++.h> + ++
(it is not installed by default). This automatically includes ev.h
+and puts all of its definitions (many of them macros) into the global
+namespace. All C++ specific things are put into the ev namespace.
It should support all the same embedding options as ev.h, most notably
+EV_MULTIPLICITY.
Here is a list of things available in the ev namespace:
ev::READ, ev::WRITE etc.These are just enum values with the same values as the EV_READ etc.
+macros from ev.h.
ev::tstamp, ev::nowAliases to the same types/functions as with the ev_ prefix.
ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc.For each ev_TYPE watcher in ev.h there is a corresponding class of
+the same name in the ev namespace, with the exception of ev_signal
+which is called ev::sig to avoid clashes with the signal macro
+defines by many implementations.
All of those classes have these methods:
++
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
+ev_init for you, which means you have to call the set method
+before starting it. If you do not specify a loop then the constructor
+automatically associates the default loop with this watcher.
The destructor automatically stops the watcher if it is active.
+Associates a different struct ev_loop with this watcher. You can only
+do this when the watcher is inactive (and not pending either).
Basically the same as ev_TYPE_set, with the same args. Must be
+called at least once. Unlike the C counterpart, an active watcher gets
+automatically stopped and restarted.
Starts the watcher. Note that there is no loop argument as the
+constructor already takes the loop.
Stops the watcher if it is active. Again, no loop argument.
ev::timer, ev::periodic onlyFor ev::timer and ev::periodic, this invokes the corresponding
+ev_TYPE_again function.
ev::embed onlyInvokes ev_embed_sweep.
ev::stat onlyInvokes ev_stat_stat.
Example: Define a class with an IO and idle watcher, start one of them in +the constructor.
+ class myclass
+ {
+ ev_io io; void io_cb (ev::io &w, int revents);
+ ev_idle idle void idle_cb (ev::idle &w, int revents);
+
+ myclass ();
+ }
+
+ myclass::myclass (int fd)
+ : io (this, &myclass::io_cb),
+ idle (this, &myclass::idle_cb)
+ {
+ io.start (fd, ev::READ);
+ }
+
+
+
+
+
+
+Libev can be compiled with a variety of options, the most fundemantal is
+EV_MULTIPLICITY. This option determines wether (most) functions and
+callbacks have an initial struct ev_loop * argument.
To make it easier to write programs that cope with either variant, the +following macros are defined:
+EV_A, EV_A_This provides the loop argument for functions, if one is required ("ev
+loop argument"). The EV_A form is used when this is the sole argument,
+EV_A_ is used when other arguments are following. Example:
ev_unref (EV_A); + ev_timer_add (EV_A_ watcher); + ev_loop (EV_A_ 0); + ++
It assumes the variable loop of type struct ev_loop * is in scope,
+which is often provided by the following macro.
EV_P, EV_P_This provides the loop parameter for functions, if one is required ("ev
+loop parameter"). The EV_P form is used when this is the sole parameter,
+EV_P_ is used when other parameters are following. Example:
// this is how ev_unref is being declared + static void ev_unref (EV_P); + + // this is how you can declare your typical callback + static void cb (EV_P_ ev_timer *w, int revents) + ++
It declares a parameter loop of type struct ev_loop *, quite
+suitable for use with EV_A.
EV_DEFAULT, EV_DEFAULT_Similar to the other two macros, this gives you the value of the default +loop, if multiple loops are supported ("ev loop default").
+Example: Declare and initialise a check watcher, working regardless of +wether multiple loops are supported or not.
+ static void
+ check_cb (EV_P_ ev_timer *w, int revents)
+ {
+ ev_check_stop (EV_A_ w);
+ }
+
+ ev_check check;
+ ev_check_init (&check, check_cb);
+ ev_check_start (EV_DEFAULT_ &check);
+ ev_loop (EV_DEFAULT_ 0);
+
+
+
+
+
+
+Libev can (and often is) directly embedded into host +applications. Examples of applications that embed it include the Deliantra +Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) +and rxvt-unicode.
+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).
+ +Depending on what features you need you need to include one or more sets of files +in your app.
+ +To include only the libev core (all the ev_* functions), with manual
+configuration (no autoconf):
#define EV_STANDALONE 1 + #include "ev.c" + ++
This will automatically include ev.h, too, and should be done in a +single C source file only to provide the function implementations. To use +it, do the same for ev.h in all files wishing to use this API (best +done by writing a wrapper around ev.h that you can include instead and +where you can put other configuration options):
+#define EV_STANDALONE 1 + #include "ev.h" + ++
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).
+You need the following files in your source tree, or in a directory +in your include path (e.g. in libev/ when using -Ilibev):
+ev.h + ev.c + ev_vars.h + ev_wrap.h + + ev_win32.c required on win32 platforms only + + 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) + ++
ev.c includes the backend files directly when enabled, so you only need +to compile this single file.
+ +To include the libevent compatibility API, also include:
+#include "event.c" + ++
in the file including ev.c, and:
+#include "event.h" + ++
in the files that want to use the libevent API. This also includes ev.h.
+You need the following additional files for this:
+event.h + event.c + ++ +
Instead of using EV_STANDALONE=1 and providing your config in
+whatever way you want, you can also m4_include([libev.m4]) in your
+configure.ac and leave EV_STANDALONE undefined. ev.c will then
+include config.h and configure itself accordingly.
For this of course you need the m4 file:
+libev.m4 + ++ +
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.
+Must always be 1 if you do not use autoconf configuration, which
+keeps libev from including config.h, 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
+event.h that are not directly supported by the libev core alone.
If defined to be 1, 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 clock_gettime
+function is hiding in (often -lrt).
If defined to be 1, 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 gettimeofday by clock_get
+(CLOCK_REALTIME, ...) and will not normally affect correctness. See tzhe note about libraries
+in the description of EV_USE_MONOTONIC, though.
If undefined or defined to be 1, libev will compile in support for the
+select(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.
If defined to 1, then the select backend will use the system fd_set
+structure. This is useful if libev doesn't compile due to a missing
+NFDBITS or fd_mask 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 FD_SETSIZE macro, set before compilation, might
+influence the size of the fd_set used.
When defined to 1, 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
+_get_osfhandle on the fd to convert it to an OS handle. Otherwise,
+it is assumed that all these functions actually work on fds, even
+on win32. Should not be defined on non-win32 platforms.
If defined to be 1, libev will compile in support for the poll(2)
+backend. Otherwise it will be enabled on non-win32 platforms. It
+takes precedence over select.
If defined to be 1, libev will compile in support for the Linux
+epoll(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.
If defined to be 1, libev will compile in support for the BSD style
+kqueue(2) backend. Its actual availability will be detected at runtime,
+otherwise another method will be used as fallback. This is the preferred
+backend for BSD 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.
If defined to be 1, 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.
reserved for future expansion, works like the USE symbols above.
+The name of the ev.h header file used to include it. The default if
+undefined is <ev.h> in event.h and "ev.h" in ev.c. This
+can be used to virtually rename the ev.h header file in case of conflicts.
If EV_STANDALONE isn't 1, this variable can be used to override
+ev.c's idea of where to find the config.h file, similarly to
+EV_H, above.
Similarly to EV_H, this macro can be used to override event.c's idea
+of how the event.h header can be found.
If defined to be 0, then ev.h 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.
If undefined or defined to 1, then all event-loop-specific functions
+will have the struct ev_loop * 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.
If undefined or defined to be 1, then periodic timers are supported. If
+defined to be 0, then they are not. Disabling them saves a few kB of
+code.
If undefined or defined to be 1, then embed watchers are supported. If
+defined to be 0, then they are not.
If undefined or defined to be 1, then stat watchers are supported. If
+defined to be 0, then they are not.
If undefined or defined to be 1, then fork watchers are supported. If
+defined to be 0, then they are not.
If you need to shave off some kilobytes of code at the expense of some
+speed, define this symbol to 1. Currently only used for gcc to override
+some inlining decisions, saves roughly 30% codesize of amd64.
ev_child watchers use a small hash table to distribute workload by
+pid. The default size is 16 (or 1 with EV_MINIMAL), usually more
+than enough. If you need to manage thousands of children you might want to
+increase this value.
By default, all watchers have a void *data 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.
For example, the perl EV module uses something like this:
+#define EV_COMMON \ + SV *self; /* contains this struct */ \ + SV *cb_sv, *fh /* note no trailing ";" */ + ++
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 ev.v header file for
+their default definitions. One possible use for overriding these is to
+avoid the struct ev_loop * as first argument in all cases, or to use
+method calls instead of plain function calls in C++.
For a real-world example of a program the includes libev +verbatim, you can have a look at the EV perl module +(http://software.schmorp.de/pkg/EV.html). It has the libev files in +the libev/ subdirectory and includes them in the EV/EVAPI.h (public +interface) and EV.xs (implementation) files. Only the EV.xs file +will be compiled. It is pretty complex because it provides its own header +file.
+The usage in rxvt-unicode is simpler. It has a ev_cpp.h header file +that everybody includes and which overrides some autoconf choices:
+#define EV_USE_POLL 0 + #define EV_MULTIPLICITY 0 + #define EV_PERIODICS 0 + #define EV_CONFIG_H <config.h> + + #include "ev++.h" + ++
And a ev_cpp.C implementation file that contains libev proper and is compiled:
+#include "ev_cpp.h" + #include "ev.c" + + + + ++ +
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 ev_default_init.
+
Marc Lehmann <libev@schmorp.de>.
+Marc Lehmann <libev@schmorp.de>.