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Comparing libev/ev.pod (file contents):
Revision 1.436 by root, Sun Oct 11 15:46:42 2015 UTC vs.
Revision 1.442 by root, Mon Jul 30 22:23:50 2018 UTC

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411make libev check for a fork in each iteration by enabling this flag. 411make libev check for a fork in each iteration by enabling this flag.
412 412
413This works by calling C<getpid ()> on every iteration of the loop, 413This works by calling C<getpid ()> on every iteration of the loop,
414and thus this might slow down your event loop if you do a lot of loop 414and thus this might slow down your event loop if you do a lot of loop
415iterations and little real work, but is usually not noticeable (on my 415iterations and little real work, but is usually not noticeable (on my
416GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence 416GNU/Linux system for example, C<getpid> is actually a simple 5-insn
417without a system call and thus I<very> fast, but my GNU/Linux system also has 417sequence without a system call and thus I<very> fast, but my GNU/Linux
418C<pthread_atfork> which is even faster). 418system also has C<pthread_atfork> which is even faster). (Update: glibc
419versions 2.25 apparently removed the C<getpid> optimisation again).
419 420
420The big advantage of this flag is that you can forget about fork (and 421The big advantage of this flag is that you can forget about fork (and
421forget about forgetting to tell libev about forking, although you still 422forget about forgetting to tell libev about forking, although you still
422have to ignore C<SIGPIPE>) when you use this flag. 423have to ignore C<SIGPIPE>) when you use this flag.
423 424
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689the name, you can call it anytime you are allowed to start or stop 690the name, you can call it anytime you are allowed to start or stop
690watchers (except inside an C<ev_prepare> callback), but it makes most 691watchers (except inside an C<ev_prepare> callback), but it makes most
691sense after forking, in the child process. You I<must> call it (or use 692sense after forking, in the child process. You I<must> call it (or use
692C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. 693C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
693 694
694In addition, if you want to reuse a loop (via this function of 695In addition, if you want to reuse a loop (via this function or
695C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. 696C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
696 697
697Again, you I<have> to call it on I<any> loop that you want to re-use after 698Again, you I<have> to call it on I<any> loop that you want to re-use after
698a fork, I<even if you do not plan to use the loop in the parent>. This is 699a fork, I<even if you do not plan to use the loop in the parent>. This is
699because some kernel interfaces *cough* I<kqueue> *cough* do funny things 700because some kernel interfaces *cough* I<kqueue> *cough* do funny things
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2209Periodic watchers are also timers of a kind, but they are very versatile 2210Periodic watchers are also timers of a kind, but they are very versatile
2210(and unfortunately a bit complex). 2211(and unfortunately a bit complex).
2211 2212
2212Unlike C<ev_timer>, periodic watchers are not based on real time (or 2213Unlike C<ev_timer>, periodic watchers are not based on real time (or
2213relative time, the physical time that passes) but on wall clock time 2214relative time, the physical time that passes) but on wall clock time
2214(absolute time, the thing you can read on your calender or clock). The 2215(absolute time, the thing you can read on your calendar or clock). The
2215difference is that wall clock time can run faster or slower than real 2216difference is that wall clock time can run faster or slower than real
2216time, and time jumps are not uncommon (e.g. when you adjust your 2217time, and time jumps are not uncommon (e.g. when you adjust your
2217wrist-watch). 2218wrist-watch).
2218 2219
2219You can tell a periodic watcher to trigger after some specific point 2220You can tell a periodic watcher to trigger after some specific point
… …
3517 3518
3518There are some other functions of possible interest. Described. Here. Now. 3519There are some other functions of possible interest. Described. Here. Now.
3519 3520
3520=over 4 3521=over 4
3521 3522
3522=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) 3523=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3523 3524
3524This function combines a simple timer and an I/O watcher, calls your 3525This function combines a simple timer and an I/O watcher, calls your
3525callback on whichever event happens first and automatically stops both 3526callback on whichever event happens first and automatically stops both
3526watchers. This is useful if you want to wait for a single event on an fd 3527watchers. This is useful if you want to wait for a single event on an fd
3527or timeout without having to allocate/configure/start/stop/free one or 3528or timeout without having to allocate/configure/start/stop/free one or
… …
4386 ev_vars.h 4387 ev_vars.h
4387 ev_wrap.h 4388 ev_wrap.h
4388 4389
4389 ev_win32.c required on win32 platforms only 4390 ev_win32.c required on win32 platforms only
4390 4391
4391 ev_select.c only when select backend is enabled (which is enabled by default) 4392 ev_select.c only when select backend is enabled
4392 ev_poll.c only when poll backend is enabled (disabled by default) 4393 ev_poll.c only when poll backend is enabled
4393 ev_epoll.c only when the epoll backend is enabled (disabled by default) 4394 ev_epoll.c only when the epoll backend is enabled
4394 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 4395 ev_kqueue.c only when the kqueue backend is enabled
4395 ev_port.c only when the solaris port backend is enabled (disabled by default) 4396 ev_port.c only when the solaris port backend is enabled
4396 4397
4397F<ev.c> includes the backend files directly when enabled, so you only need 4398F<ev.c> includes the backend files directly when enabled, so you only need
4398to compile this single file. 4399to compile this single file.
4399 4400
4400=head3 LIBEVENT COMPATIBILITY API 4401=head3 LIBEVENT COMPATIBILITY API
… …
5300structure (guaranteed by POSIX but not by ISO C for example), but it also 5301structure (guaranteed by POSIX but not by ISO C for example), but it also
5301assumes that the same (machine) code can be used to call any watcher 5302assumes that the same (machine) code can be used to call any watcher
5302callback: The watcher callbacks have different type signatures, but libev 5303callback: The watcher callbacks have different type signatures, but libev
5303calls them using an C<ev_watcher *> internally. 5304calls them using an C<ev_watcher *> internally.
5304 5305
5306=item null pointers and integer zero are represented by 0 bytes
5307
5308Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
5309relies on this setting pointers and integers to null.
5310
5305=item pointer accesses must be thread-atomic 5311=item pointer accesses must be thread-atomic
5306 5312
5307Accessing a pointer value must be atomic, it must both be readable and 5313Accessing a pointer value must be atomic, it must both be readable and
5308writable in one piece - this is the case on all current architectures. 5314writable in one piece - this is the case on all current architectures.
5309 5315

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