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1 | =encoding utf-8 |
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2 | |
1 | =head1 NAME |
3 | =head1 NAME |
2 | |
4 | |
3 | libev - a high performance full-featured event loop written in C |
5 | libev - a high performance full-featured event loop written in C |
4 | |
6 | |
5 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
… | |
… | |
396 | |
398 | |
397 | If this flag bit is or'ed into the flag value (or the program runs setuid |
399 | If this flag bit is or'ed into the flag value (or the program runs setuid |
398 | or setgid) then libev will I<not> look at the environment variable |
400 | or setgid) then libev will I<not> look at the environment variable |
399 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
401 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
400 | override the flags completely if it is found in the environment. This is |
402 | override the flags completely if it is found in the environment. This is |
401 | useful to try out specific backends to test their performance, or to work |
403 | useful to try out specific backends to test their performance, to work |
402 | around bugs. |
404 | around bugs, or to make libev threadsafe (accessing environment variables |
|
|
405 | cannot be done in a threadsafe way, but usually it works if no other |
|
|
406 | thread modifies them). |
403 | |
407 | |
404 | =item C<EVFLAG_FORKCHECK> |
408 | =item C<EVFLAG_FORKCHECK> |
405 | |
409 | |
406 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
410 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
407 | make libev check for a fork in each iteration by enabling this flag. |
411 | make libev check for a fork in each iteration by enabling this flag. |
… | |
… | |
569 | kernel is more efficient (which says nothing about its actual speed, of |
573 | kernel is more efficient (which says nothing about its actual speed, of |
570 | course). While stopping, setting and starting an I/O watcher does never |
574 | course). While stopping, setting and starting an I/O watcher does never |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
575 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
576 | two event changes per incident. Support for C<fork ()> is very bad (you |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
577 | might have to leak fd's on fork, but it's more sane than epoll) and it |
574 | drops fds silently in similarly hard-to-detect cases |
578 | drops fds silently in similarly hard-to-detect cases. |
575 | |
579 | |
576 | This backend usually performs well under most conditions. |
580 | This backend usually performs well under most conditions. |
577 | |
581 | |
578 | While nominally embeddable in other event loops, this doesn't work |
582 | While nominally embeddable in other event loops, this doesn't work |
579 | everywhere, so you might need to test for this. And since it is broken |
583 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
684 | reinitialise the kernel state for backends that have one. Despite the |
688 | reinitialise the kernel state for backends that have one. Despite the |
685 | name, you can call it anytime, but it makes most sense after forking, in |
689 | name, you can call it anytime, but it makes most sense after forking, in |
686 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
690 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
687 | child before resuming or calling C<ev_run>. |
691 | child before resuming or calling C<ev_run>. |
688 | |
692 | |
689 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
693 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
690 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
694 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
691 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
695 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
692 | during fork. |
696 | during fork. |
693 | |
697 | |
694 | On the other hand, you only need to call this function in the child |
698 | On the other hand, you only need to call this function in the child |
… | |
… | |
1393 | transition between them will be described in more detail - and while these |
1397 | transition between them will be described in more detail - and while these |
1394 | rules might look complicated, they usually do "the right thing". |
1398 | rules might look complicated, they usually do "the right thing". |
1395 | |
1399 | |
1396 | =over 4 |
1400 | =over 4 |
1397 | |
1401 | |
1398 | =item initialiased |
1402 | =item initialised |
1399 | |
1403 | |
1400 | Before a watcher can be registered with the event loop it has to be |
1404 | Before a watcher can be registered with the event loop it has to be |
1401 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1405 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1402 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1406 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1403 | |
1407 | |
… | |
… | |
2606 | |
2610 | |
2607 | =head2 C<ev_stat> - did the file attributes just change? |
2611 | =head2 C<ev_stat> - did the file attributes just change? |
2608 | |
2612 | |
2609 | This watches a file system path for attribute changes. That is, it calls |
2613 | This watches a file system path for attribute changes. That is, it calls |
2610 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2614 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2611 | and sees if it changed compared to the last time, invoking the callback if |
2615 | and sees if it changed compared to the last time, invoking the callback |
2612 | it did. |
2616 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2617 | happen after the watcher has been started will be reported. |
2613 | |
2618 | |
2614 | The path does not need to exist: changing from "path exists" to "path does |
2619 | The path does not need to exist: changing from "path exists" to "path does |
2615 | not exist" is a status change like any other. The condition "path does not |
2620 | not exist" is a status change like any other. The condition "path does not |
2616 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2621 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2617 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2622 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2962 | |
2967 | |
2963 | Using an C<ev_check> watcher is almost enough: it will be called on the |
2968 | Using an C<ev_check> watcher is almost enough: it will be called on the |
2964 | next event loop iteration. However, that isn't as soon as possible - |
2969 | next event loop iteration. However, that isn't as soon as possible - |
2965 | without external events, your C<ev_check> watcher will not be invoked. |
2970 | without external events, your C<ev_check> watcher will not be invoked. |
2966 | |
2971 | |
2967 | |
|
|
2968 | This is where C<ev_idle> watchers come in handy - all you need is a |
2972 | This is where C<ev_idle> watchers come in handy - all you need is a |
2969 | single global idle watcher that is active as long as you have one active |
2973 | single global idle watcher that is active as long as you have one active |
2970 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
2974 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
2971 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
2975 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
2972 | invoked. Neither watcher alone can do that. |
2976 | invoked. Neither watcher alone can do that. |
… | |
… | |
3178 | |
3182 | |
3179 | =over 4 |
3183 | =over 4 |
3180 | |
3184 | |
3181 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3185 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3182 | |
3186 | |
3183 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3187 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
3184 | |
3188 | |
3185 | Configures the watcher to embed the given loop, which must be |
3189 | Configures the watcher to embed the given loop, which must be |
3186 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3190 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3187 | invoked automatically, otherwise it is the responsibility of the callback |
3191 | invoked automatically, otherwise it is the responsibility of the callback |
3188 | to invoke it (it will continue to be called until the sweep has been done, |
3192 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3251 | |
3255 | |
3252 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3256 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3253 | |
3257 | |
3254 | Fork watchers are called when a C<fork ()> was detected (usually because |
3258 | Fork watchers are called when a C<fork ()> was detected (usually because |
3255 | whoever is a good citizen cared to tell libev about it by calling |
3259 | whoever is a good citizen cared to tell libev about it by calling |
3256 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3260 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3257 | event loop blocks next and before C<ev_check> watchers are being called, |
3261 | and before C<ev_check> watchers are being called, and only in the child |
3258 | and only in the child after the fork. If whoever good citizen calling |
3262 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3259 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3263 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3260 | handlers will be invoked, too, of course. |
3264 | of course. |
3261 | |
3265 | |
3262 | =head3 The special problem of life after fork - how is it possible? |
3266 | =head3 The special problem of life after fork - how is it possible? |
3263 | |
3267 | |
3264 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3268 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3265 | up/change the process environment, followed by a call to C<exec()>. This |
3269 | up/change the process environment, followed by a call to C<exec()>. This |
… | |
… | |
3659 | already been invoked. |
3663 | already been invoked. |
3660 | |
3664 | |
3661 | A common way around all these issues is to make sure that |
3665 | A common way around all these issues is to make sure that |
3662 | C<start_new_request> I<always> returns before the callback is invoked. If |
3666 | C<start_new_request> I<always> returns before the callback is invoked. If |
3663 | C<start_new_request> immediately knows the result, it can artificially |
3667 | C<start_new_request> immediately knows the result, it can artificially |
3664 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
3668 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
3665 | for example, or more sneakily, by reusing an existing (stopped) watcher |
3669 | example, or more sneakily, by reusing an existing (stopped) watcher and |
3666 | and pushing it into the pending queue: |
3670 | pushing it into the pending queue: |
3667 | |
3671 | |
3668 | ev_set_cb (watcher, callback); |
3672 | ev_set_cb (watcher, callback); |
3669 | ev_feed_event (EV_A_ watcher, 0); |
3673 | ev_feed_event (EV_A_ watcher, 0); |
3670 | |
3674 | |
3671 | This way, C<start_new_request> can safely return before the callback is |
3675 | This way, C<start_new_request> can safely return before the callback is |
… | |
… | |
3679 | |
3683 | |
3680 | This brings the problem of exiting - a callback might want to finish the |
3684 | This brings the problem of exiting - a callback might want to finish the |
3681 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3685 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3682 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3686 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3683 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3687 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3684 | other combination: In these cases, C<ev_break> will not work alone. |
3688 | other combination: In these cases, a simple C<ev_break> will not work. |
3685 | |
3689 | |
3686 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3690 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3687 | invocation, and use a loop around C<ev_run> until the condition is |
3691 | invocation, and use a loop around C<ev_run> until the condition is |
3688 | triggered, using C<EVRUN_ONCE>: |
3692 | triggered, using C<EVRUN_ONCE>: |
3689 | |
3693 | |
… | |
… | |
3950 | libev sources can be compiled as C++. Therefore, code that uses the C API |
3954 | libev sources can be compiled as C++. Therefore, code that uses the C API |
3951 | will work fine. |
3955 | will work fine. |
3952 | |
3956 | |
3953 | Proper exception specifications might have to be added to callbacks passed |
3957 | Proper exception specifications might have to be added to callbacks passed |
3954 | to libev: exceptions may be thrown only from watcher callbacks, all |
3958 | to libev: exceptions may be thrown only from watcher callbacks, all |
3955 | other callbacks (allocator, syserr, loop acquire/release and periodioc |
3959 | other callbacks (allocator, syserr, loop acquire/release and periodic |
3956 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
3960 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
3957 | ()> specification. If you have code that needs to be compiled as both C |
3961 | ()> specification. If you have code that needs to be compiled as both C |
3958 | and C++ you can use the C<EV_THROW> macro for this: |
3962 | and C++ you can use the C<EV_THROW> macro for this: |
3959 | |
3963 | |
3960 | static void |
3964 | static void |
… | |
… | |
3980 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3984 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3981 | you to use some convenience methods to start/stop watchers and also change |
3985 | you to use some convenience methods to start/stop watchers and also change |
3982 | the callback model to a model using method callbacks on objects. |
3986 | the callback model to a model using method callbacks on objects. |
3983 | |
3987 | |
3984 | To use it, |
3988 | To use it, |
3985 | |
3989 | |
3986 | #include <ev++.h> |
3990 | #include <ev++.h> |
3987 | |
3991 | |
3988 | This automatically includes F<ev.h> and puts all of its definitions (many |
3992 | This automatically includes F<ev.h> and puts all of its definitions (many |
3989 | of them macros) into the global namespace. All C++ specific things are |
3993 | of them macros) into the global namespace. All C++ specific things are |
3990 | put into the C<ev> namespace. It should support all the same embedding |
3994 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
4121 | Associates a different C<struct ev_loop> with this watcher. You can only |
4125 | Associates a different C<struct ev_loop> with this watcher. You can only |
4122 | do this when the watcher is inactive (and not pending either). |
4126 | do this when the watcher is inactive (and not pending either). |
4123 | |
4127 | |
4124 | =item w->set ([arguments]) |
4128 | =item w->set ([arguments]) |
4125 | |
4129 | |
4126 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4130 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
4127 | method or a suitable start method must be called at least once. Unlike the |
4131 | with the same arguments. Either this method or a suitable start method |
4128 | C counterpart, an active watcher gets automatically stopped and restarted |
4132 | must be called at least once. Unlike the C counterpart, an active watcher |
4129 | when reconfiguring it with this method. |
4133 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4134 | method. |
|
|
4135 | |
|
|
4136 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4137 | clashing with the C<set (loop)> method. |
4130 | |
4138 | |
4131 | =item w->start () |
4139 | =item w->start () |
4132 | |
4140 | |
4133 | Starts the watcher. Note that there is no C<loop> argument, as the |
4141 | Starts the watcher. Note that there is no C<loop> argument, as the |
4134 | constructor already stores the event loop. |
4142 | constructor already stores the event loop. |
… | |
… | |
4237 | =item Lua |
4245 | =item Lua |
4238 | |
4246 | |
4239 | Brian Maher has written a partial interface to libev for lua (at the |
4247 | Brian Maher has written a partial interface to libev for lua (at the |
4240 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4248 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4241 | L<http://github.com/brimworks/lua-ev>. |
4249 | L<http://github.com/brimworks/lua-ev>. |
|
|
4250 | |
|
|
4251 | =item Javascript |
|
|
4252 | |
|
|
4253 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4254 | |
|
|
4255 | =item Others |
|
|
4256 | |
|
|
4257 | There are others, and I stopped counting. |
4242 | |
4258 | |
4243 | =back |
4259 | =back |
4244 | |
4260 | |
4245 | |
4261 | |
4246 | =head1 MACRO MAGIC |
4262 | =head1 MACRO MAGIC |
… | |
… | |
4545 | |
4561 | |
4546 | If programs implement their own fd to handle mapping on win32, then this |
4562 | If programs implement their own fd to handle mapping on win32, then this |
4547 | macro can be used to override the C<close> function, useful to unregister |
4563 | macro can be used to override the C<close> function, useful to unregister |
4548 | file descriptors again. Note that the replacement function has to close |
4564 | file descriptors again. Note that the replacement function has to close |
4549 | the underlying OS handle. |
4565 | the underlying OS handle. |
|
|
4566 | |
|
|
4567 | =item EV_USE_WSASOCKET |
|
|
4568 | |
|
|
4569 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4570 | communication socket, which works better in some environments. Otherwise, |
|
|
4571 | the normal C<socket> function will be used, which works better in other |
|
|
4572 | environments. |
4550 | |
4573 | |
4551 | =item EV_USE_POLL |
4574 | =item EV_USE_POLL |
4552 | |
4575 | |
4553 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4576 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4554 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4577 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
4599 | different cpus (or different cpu cores). This reduces dependencies |
4622 | different cpus (or different cpu cores). This reduces dependencies |
4600 | and makes libev faster. |
4623 | and makes libev faster. |
4601 | |
4624 | |
4602 | =item EV_NO_THREADS |
4625 | =item EV_NO_THREADS |
4603 | |
4626 | |
4604 | If defined to be C<1>, libev will assume that it will never be called |
4627 | If defined to be C<1>, libev will assume that it will never be called from |
4605 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
4628 | different threads (that includes signal handlers), which is a stronger |
4606 | above. This reduces dependencies and makes libev faster. |
4629 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4630 | libev faster. |
4607 | |
4631 | |
4608 | =item EV_ATOMIC_T |
4632 | =item EV_ATOMIC_T |
4609 | |
4633 | |
4610 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4634 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4611 | access is atomic and serialised with respect to other threads or signal |
4635 | access is atomic with respect to other threads or signal contexts. No |
4612 | contexts. No such type is easily found in the C language, so you can |
4636 | such type is easily found in the C language, so you can provide your own |
4613 | provide your own type that you know is safe for your purposes. It is used |
4637 | type that you know is safe for your purposes. It is used both for signal |
4614 | both for signal handler "locking" as well as for signal and thread safety |
4638 | handler "locking" as well as for signal and thread safety in C<ev_async> |
4615 | in C<ev_async> watchers. |
4639 | watchers. |
4616 | |
4640 | |
4617 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4641 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4618 | (from F<signal.h>), which is usually good enough on most platforms, |
4642 | (from F<signal.h>), which is usually good enough on most platforms. |
4619 | although strictly speaking using a type that also implies a memory fence |
|
|
4620 | is required. |
|
|
4621 | |
4643 | |
4622 | =item EV_H (h) |
4644 | =item EV_H (h) |
4623 | |
4645 | |
4624 | The name of the F<ev.h> header file used to include it. The default if |
4646 | The name of the F<ev.h> header file used to include it. The default if |
4625 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4647 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
5294 | thread" or will block signals process-wide, both behaviours would |
5316 | thread" or will block signals process-wide, both behaviours would |
5295 | be compatible with libev. Interaction between C<sigprocmask> and |
5317 | be compatible with libev. Interaction between C<sigprocmask> and |
5296 | C<pthread_sigmask> could complicate things, however. |
5318 | C<pthread_sigmask> could complicate things, however. |
5297 | |
5319 | |
5298 | The most portable way to handle signals is to block signals in all threads |
5320 | The most portable way to handle signals is to block signals in all threads |
5299 | except the initial one, and run the default loop in the initial thread as |
5321 | except the initial one, and run the signal handling loop in the initial |
5300 | well. |
5322 | thread as well. |
5301 | |
5323 | |
5302 | =item C<long> must be large enough for common memory allocation sizes |
5324 | =item C<long> must be large enough for common memory allocation sizes |
5303 | |
5325 | |
5304 | To improve portability and simplify its API, libev uses C<long> internally |
5326 | To improve portability and simplify its API, libev uses C<long> internally |
5305 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5327 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
5409 | =over 4 |
5431 | =over 4 |
5410 | |
5432 | |
5411 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5433 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5412 | |
5434 | |
5413 | The backward compatibility mechanism can be controlled by |
5435 | The backward compatibility mechanism can be controlled by |
5414 | C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING> |
5436 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
5415 | section. |
5437 | section. |
5416 | |
5438 | |
5417 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5439 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5418 | |
5440 | |
5419 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5441 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |