… | |
… | |
441 | example) that can't properly initialise their signal masks. |
441 | example) that can't properly initialise their signal masks. |
442 | |
442 | |
443 | =item C<EVFLAG_NOSIGMASK> |
443 | =item C<EVFLAG_NOSIGMASK> |
444 | |
444 | |
445 | When this flag is specified, then libev will avoid to modify the signal |
445 | When this flag is specified, then libev will avoid to modify the signal |
446 | mask. Specifically, this means you ahve to make sure signals are unblocked |
446 | mask. Specifically, this means you have to make sure signals are unblocked |
447 | when you want to receive them. |
447 | when you want to receive them. |
448 | |
448 | |
449 | This behaviour is useful when you want to do your own signal handling, or |
449 | This behaviour is useful when you want to do your own signal handling, or |
450 | want to handle signals only in specific threads and want to avoid libev |
450 | want to handle signals only in specific threads and want to avoid libev |
451 | unblocking the signals. |
451 | unblocking the signals. |
… | |
… | |
512 | totally I<different> file descriptors (even already closed ones, so |
512 | totally I<different> file descriptors (even already closed ones, so |
513 | one cannot even remove them from the set) than registered in the set |
513 | one cannot even remove them from the set) than registered in the set |
514 | (especially on SMP systems). Libev tries to counter these spurious |
514 | (especially on SMP systems). Libev tries to counter these spurious |
515 | notifications by employing an additional generation counter and comparing |
515 | notifications by employing an additional generation counter and comparing |
516 | that against the events to filter out spurious ones, recreating the set |
516 | that against the events to filter out spurious ones, recreating the set |
517 | when required. Epoll also errornously rounds down timeouts, but gives you |
517 | when required. Epoll also erroneously rounds down timeouts, but gives you |
518 | no way to know when and by how much, so sometimes you have to busy-wait |
518 | no way to know when and by how much, so sometimes you have to busy-wait |
519 | because epoll returns immediately despite a nonzero timeout. And last |
519 | because epoll returns immediately despite a nonzero timeout. And last |
520 | not least, it also refuses to work with some file descriptors which work |
520 | not least, it also refuses to work with some file descriptors which work |
521 | perfectly fine with C<select> (files, many character devices...). |
521 | perfectly fine with C<select> (files, many character devices...). |
522 | |
522 | |
… | |
… | |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
609 | hacks). |
609 | hacks). |
610 | |
610 | |
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
612 | even sun itself gets it wrong in their code examples: The event polling |
612 | even sun itself gets it wrong in their code examples: The event polling |
613 | function sometimes returning events to the caller even though an error |
613 | function sometimes returns events to the caller even though an error |
614 | occurred, but with no indication whether it has done so or not (yes, it's |
614 | occurred, but with no indication whether it has done so or not (yes, it's |
615 | even documented that way) - deadly for edge-triggered interfaces where |
615 | even documented that way) - deadly for edge-triggered interfaces where you |
616 | you absolutely have to know whether an event occurred or not because you |
616 | absolutely have to know whether an event occurred or not because you have |
617 | have to re-arm the watcher. |
617 | to re-arm the watcher. |
618 | |
618 | |
619 | Fortunately libev seems to be able to work around these idiocies. |
619 | Fortunately libev seems to be able to work around these idiocies. |
620 | |
620 | |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
622 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
… | |
… | |
1386 | |
1386 | |
1387 | =over 4 |
1387 | =over 4 |
1388 | |
1388 | |
1389 | =item initialiased |
1389 | =item initialiased |
1390 | |
1390 | |
1391 | Before a watcher can be registered with the event looop it has to be |
1391 | Before a watcher can be registered with the event loop it has to be |
1392 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1392 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1393 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1393 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1394 | |
1394 | |
1395 | In this state it is simply some block of memory that is suitable for |
1395 | In this state it is simply some block of memory that is suitable for |
1396 | use in an event loop. It can be moved around, freed, reused etc. at |
1396 | use in an event loop. It can be moved around, freed, reused etc. at |
… | |
… | |
1771 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1771 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1772 | monotonic clock option helps a lot here). |
1772 | monotonic clock option helps a lot here). |
1773 | |
1773 | |
1774 | The callback is guaranteed to be invoked only I<after> its timeout has |
1774 | The callback is guaranteed to be invoked only I<after> its timeout has |
1775 | passed (not I<at>, so on systems with very low-resolution clocks this |
1775 | passed (not I<at>, so on systems with very low-resolution clocks this |
1776 | might introduce a small delay). If multiple timers become ready during the |
1776 | might introduce a small delay, see "the special problem of being too |
|
|
1777 | early", below). If multiple timers become ready during the same loop |
1777 | same loop iteration then the ones with earlier time-out values are invoked |
1778 | iteration then the ones with earlier time-out values are invoked before |
1778 | before ones of the same priority with later time-out values (but this is |
1779 | ones of the same priority with later time-out values (but this is no |
1779 | no longer true when a callback calls C<ev_run> recursively). |
1780 | longer true when a callback calls C<ev_run> recursively). |
1780 | |
1781 | |
1781 | =head3 Be smart about timeouts |
1782 | =head3 Be smart about timeouts |
1782 | |
1783 | |
1783 | Many real-world problems involve some kind of timeout, usually for error |
1784 | Many real-world problems involve some kind of timeout, usually for error |
1784 | recovery. A typical example is an HTTP request - if the other side hangs, |
1785 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1951 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1952 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1952 | rather complicated, but extremely efficient, something that really pays |
1953 | rather complicated, but extremely efficient, something that really pays |
1953 | off after the first million or so of active timers, i.e. it's usually |
1954 | off after the first million or so of active timers, i.e. it's usually |
1954 | overkill :) |
1955 | overkill :) |
1955 | |
1956 | |
|
|
1957 | =head3 The special problem of being too early |
|
|
1958 | |
|
|
1959 | If you ask a timer to call your callback after three seconds, then |
|
|
1960 | you expect it to be invoked after three seconds - but of course, this |
|
|
1961 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1962 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1963 | process a STOP signal for a few hours for example. |
|
|
1964 | |
|
|
1965 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1966 | delay has occurred, but cannot guarantee this. |
|
|
1967 | |
|
|
1968 | A less obvious failure mode is calling your callback too early: many event |
|
|
1969 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1970 | this can cause your callback to be invoked much earlier than you would |
|
|
1971 | expect. |
|
|
1972 | |
|
|
1973 | To see why, imagine a system with a clock that only offers full second |
|
|
1974 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1975 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1976 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
1977 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
1978 | |
|
|
1979 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
1980 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
1981 | one-second delay was requested - this is being "too early", despite best |
|
|
1982 | intentions. |
|
|
1983 | |
|
|
1984 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
1985 | delay equals the requested delay, but only when the elapsed delay is |
|
|
1986 | larger than the requested delay. In the example above, libev would only invoke |
|
|
1987 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
1988 | |
|
|
1989 | So, while libev cannot guarantee that your callback will be invoked |
|
|
1990 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
1991 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
1992 | late" side of things. |
|
|
1993 | |
1956 | =head3 The special problem of time updates |
1994 | =head3 The special problem of time updates |
1957 | |
1995 | |
1958 | Establishing the current time is a costly operation (it usually takes at |
1996 | Establishing the current time is a costly operation (it usually takes |
1959 | least two system calls): EV therefore updates its idea of the current |
1997 | at least one system call): EV therefore updates its idea of the current |
1960 | time only before and after C<ev_run> collects new events, which causes a |
1998 | time only before and after C<ev_run> collects new events, which causes a |
1961 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1999 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1962 | lots of events in one iteration. |
2000 | lots of events in one iteration. |
1963 | |
2001 | |
1964 | The relative timeouts are calculated relative to the C<ev_now ()> |
2002 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1970 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2008 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1971 | |
2009 | |
1972 | If the event loop is suspended for a long time, you can also force an |
2010 | If the event loop is suspended for a long time, you can also force an |
1973 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2011 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1974 | ()>. |
2012 | ()>. |
|
|
2013 | |
|
|
2014 | =head3 The special problem of unsynchronised clocks |
|
|
2015 | |
|
|
2016 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2017 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2018 | jumps). |
|
|
2019 | |
|
|
2020 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2021 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2022 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2023 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2024 | than a directly following call to C<time>. |
|
|
2025 | |
|
|
2026 | The moral of this is to only compare libev-related timestamps with |
|
|
2027 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2028 | a second or so. |
|
|
2029 | |
|
|
2030 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2031 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2032 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2033 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2034 | |
|
|
2035 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2036 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2037 | I<measured according to the real time>, not the system clock. |
|
|
2038 | |
|
|
2039 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2040 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2041 | exactly the right behaviour. |
|
|
2042 | |
|
|
2043 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2044 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2045 | time, where your comparisons will always generate correct results. |
1975 | |
2046 | |
1976 | =head3 The special problems of suspended animation |
2047 | =head3 The special problems of suspended animation |
1977 | |
2048 | |
1978 | When you leave the server world it is quite customary to hit machines that |
2049 | When you leave the server world it is quite customary to hit machines that |
1979 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2050 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
2023 | keep up with the timer (because it takes longer than those 10 seconds to |
2094 | keep up with the timer (because it takes longer than those 10 seconds to |
2024 | do stuff) the timer will not fire more than once per event loop iteration. |
2095 | do stuff) the timer will not fire more than once per event loop iteration. |
2025 | |
2096 | |
2026 | =item ev_timer_again (loop, ev_timer *) |
2097 | =item ev_timer_again (loop, ev_timer *) |
2027 | |
2098 | |
2028 | This will act as if the timer timed out and restart it again if it is |
2099 | This will act as if the timer timed out and restarts it again if it is |
2029 | repeating. The exact semantics are: |
2100 | repeating. The exact semantics are: |
2030 | |
2101 | |
2031 | If the timer is pending, its pending status is cleared. |
2102 | If the timer is pending, its pending status is cleared. |
2032 | |
2103 | |
2033 | If the timer is started but non-repeating, stop it (as if it timed out). |
2104 | If the timer is started but non-repeating, stop it (as if it timed out). |
… | |
… | |
3220 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3291 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3221 | of "global async watchers" by using a watcher on an otherwise unused |
3292 | of "global async watchers" by using a watcher on an otherwise unused |
3222 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3293 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3223 | even without knowing which loop owns the signal. |
3294 | even without knowing which loop owns the signal. |
3224 | |
3295 | |
3225 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
3226 | just the default loop. |
|
|
3227 | |
|
|
3228 | =head3 Queueing |
3296 | =head3 Queueing |
3229 | |
3297 | |
3230 | C<ev_async> does not support queueing of data in any way. The reason |
3298 | C<ev_async> does not support queueing of data in any way. The reason |
3231 | is that the author does not know of a simple (or any) algorithm for a |
3299 | is that the author does not know of a simple (or any) algorithm for a |
3232 | multiple-writer-single-reader queue that works in all cases and doesn't |
3300 | multiple-writer-single-reader queue that works in all cases and doesn't |
… | |
… | |
3331 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3399 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3332 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3400 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3333 | embedding section below on what exactly this means). |
3401 | embedding section below on what exactly this means). |
3334 | |
3402 | |
3335 | Note that, as with other watchers in libev, multiple events might get |
3403 | Note that, as with other watchers in libev, multiple events might get |
3336 | compressed into a single callback invocation (another way to look at this |
3404 | compressed into a single callback invocation (another way to look at |
3337 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3405 | this is that C<ev_async> watchers are level-triggered: they are set on |
3338 | reset when the event loop detects that). |
3406 | C<ev_async_send>, reset when the event loop detects that). |
3339 | |
3407 | |
3340 | This call incurs the overhead of a system call only once per event loop |
3408 | This call incurs the overhead of at most one extra system call per event |
3341 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3409 | loop iteration, if the event loop is blocked, and no syscall at all if |
3342 | repeated calls to C<ev_async_send> for the same event loop. |
3410 | the event loop (or your program) is processing events. That means that |
|
|
3411 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3412 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3413 | zero) under load. |
3343 | |
3414 | |
3344 | =item bool = ev_async_pending (ev_async *) |
3415 | =item bool = ev_async_pending (ev_async *) |
3345 | |
3416 | |
3346 | Returns a non-zero value when C<ev_async_send> has been called on the |
3417 | Returns a non-zero value when C<ev_async_send> has been called on the |
3347 | watcher but the event has not yet been processed (or even noted) by the |
3418 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3944 | watchers in the constructor. |
4015 | watchers in the constructor. |
3945 | |
4016 | |
3946 | class myclass |
4017 | class myclass |
3947 | { |
4018 | { |
3948 | ev::io io ; void io_cb (ev::io &w, int revents); |
4019 | ev::io io ; void io_cb (ev::io &w, int revents); |
3949 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4020 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3950 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4021 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3951 | |
4022 | |
3952 | myclass (int fd) |
4023 | myclass (int fd) |
3953 | { |
4024 | { |
3954 | io .set <myclass, &myclass::io_cb > (this); |
4025 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
4005 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4076 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4006 | |
4077 | |
4007 | =item D |
4078 | =item D |
4008 | |
4079 | |
4009 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4080 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4010 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4081 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
4011 | |
4082 | |
4012 | =item Ocaml |
4083 | =item Ocaml |
4013 | |
4084 | |
4014 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4085 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4015 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4086 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
4063 | suitable for use with C<EV_A>. |
4134 | suitable for use with C<EV_A>. |
4064 | |
4135 | |
4065 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4136 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4066 | |
4137 | |
4067 | Similar to the other two macros, this gives you the value of the default |
4138 | Similar to the other two macros, this gives you the value of the default |
4068 | loop, if multiple loops are supported ("ev loop default"). |
4139 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4140 | will be initialised if it isn't already initialised. |
|
|
4141 | |
|
|
4142 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4143 | to initialise the loop somewhere. |
4069 | |
4144 | |
4070 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4145 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4071 | |
4146 | |
4072 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4147 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4073 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4148 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
4369 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4444 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4370 | |
4445 | |
4371 | =item EV_ATOMIC_T |
4446 | =item EV_ATOMIC_T |
4372 | |
4447 | |
4373 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4448 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4374 | access is atomic with respect to other threads or signal contexts. No such |
4449 | access is atomic and serialised with respect to other threads or signal |
4375 | type is easily found in the C language, so you can provide your own type |
4450 | contexts. No such type is easily found in the C language, so you can |
4376 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4451 | provide your own type that you know is safe for your purposes. It is used |
4377 | as well as for signal and thread safety in C<ev_async> watchers. |
4452 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4453 | in C<ev_async> watchers. |
4378 | |
4454 | |
4379 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4455 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4380 | (from F<signal.h>), which is usually good enough on most platforms. |
4456 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4457 | although strictly speaking using a type that also implies a memory fence |
|
|
4458 | is required. |
4381 | |
4459 | |
4382 | =item EV_H (h) |
4460 | =item EV_H (h) |
4383 | |
4461 | |
4384 | The name of the F<ev.h> header file used to include it. The default if |
4462 | The name of the F<ev.h> header file used to include it. The default if |
4385 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4463 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
4408 | If undefined or defined to C<1>, then all event-loop-specific functions |
4486 | If undefined or defined to C<1>, then all event-loop-specific functions |
4409 | will have the C<struct ev_loop *> as first argument, and you can create |
4487 | will have the C<struct ev_loop *> as first argument, and you can create |
4410 | additional independent event loops. Otherwise there will be no support |
4488 | additional independent event loops. Otherwise there will be no support |
4411 | for multiple event loops and there is no first event loop pointer |
4489 | for multiple event loops and there is no first event loop pointer |
4412 | argument. Instead, all functions act on the single default loop. |
4490 | argument. Instead, all functions act on the single default loop. |
|
|
4491 | |
|
|
4492 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4493 | default loop when multiplicity is switched off - you always have to |
|
|
4494 | initialise the loop manually in this case. |
4413 | |
4495 | |
4414 | =item EV_MINPRI |
4496 | =item EV_MINPRI |
4415 | |
4497 | |
4416 | =item EV_MAXPRI |
4498 | =item EV_MAXPRI |
4417 | |
4499 | |
… | |
… | |
4904 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4986 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4905 | model. Libev still offers limited functionality on this platform in |
4987 | model. Libev still offers limited functionality on this platform in |
4906 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4988 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4907 | descriptors. This only applies when using Win32 natively, not when using |
4989 | descriptors. This only applies when using Win32 natively, not when using |
4908 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4990 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4909 | as every compielr comes with a slightly differently broken/incompatible |
4991 | as every compiler comes with a slightly differently broken/incompatible |
4910 | environment. |
4992 | environment. |
4911 | |
4993 | |
4912 | Lifting these limitations would basically require the full |
4994 | Lifting these limitations would basically require the full |
4913 | re-implementation of the I/O system. If you are into this kind of thing, |
4995 | re-implementation of the I/O system. If you are into this kind of thing, |
4914 | then note that glib does exactly that for you in a very portable way (note |
4996 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
5047 | |
5129 | |
5048 | The type C<double> is used to represent timestamps. It is required to |
5130 | The type C<double> is used to represent timestamps. It is required to |
5049 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5131 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5050 | good enough for at least into the year 4000 with millisecond accuracy |
5132 | good enough for at least into the year 4000 with millisecond accuracy |
5051 | (the design goal for libev). This requirement is overfulfilled by |
5133 | (the design goal for libev). This requirement is overfulfilled by |
5052 | implementations using IEEE 754, which is basically all existing ones. With |
5134 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5135 | |
5053 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5136 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5137 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5138 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5139 | something like that, just kidding). |
5054 | |
5140 | |
5055 | =back |
5141 | =back |
5056 | |
5142 | |
5057 | If you know of other additional requirements drop me a note. |
5143 | If you know of other additional requirements drop me a note. |
5058 | |
5144 | |
… | |
… | |
5120 | =item Processing ev_async_send: O(number_of_async_watchers) |
5206 | =item Processing ev_async_send: O(number_of_async_watchers) |
5121 | |
5207 | |
5122 | =item Processing signals: O(max_signal_number) |
5208 | =item Processing signals: O(max_signal_number) |
5123 | |
5209 | |
5124 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5210 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5125 | calls in the current loop iteration. Checking for async and signal events |
5211 | calls in the current loop iteration and the loop is currently |
|
|
5212 | blocked. Checking for async and signal events involves iterating over all |
5126 | involves iterating over all running async watchers or all signal numbers. |
5213 | running async watchers or all signal numbers. |
5127 | |
5214 | |
5128 | =back |
5215 | =back |
5129 | |
5216 | |
5130 | |
5217 | |
5131 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5218 | =head1 PORTING FROM LIBEV 3.X TO 4.X |