… | |
… | |
411 | 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. |
412 | |
412 | |
413 | This works by calling C<getpid ()> on every iteration of the loop, |
413 | This works by calling C<getpid ()> on every iteration of the loop, |
414 | and thus this might slow down your event loop if you do a lot of loop |
414 | and thus this might slow down your event loop if you do a lot of loop |
415 | iterations and little real work, but is usually not noticeable (on my |
415 | iterations and little real work, but is usually not noticeable (on my |
416 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
416 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
417 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
417 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
418 | C<pthread_atfork> which is even faster). |
418 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
|
|
419 | versions 2.25 apparently removed the C<getpid> optimisation again). |
419 | |
420 | |
420 | The big advantage of this flag is that you can forget about fork (and |
421 | The big advantage of this flag is that you can forget about fork (and |
421 | forget about forgetting to tell libev about forking) when you use this |
422 | forget about forgetting to tell libev about forking, although you still |
422 | flag. |
423 | have to ignore C<SIGPIPE>) when you use this flag. |
423 | |
424 | |
424 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
425 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
425 | environment variable. |
426 | environment variable. |
426 | |
427 | |
427 | =item C<EVFLAG_NOINOTIFY> |
428 | =item C<EVFLAG_NOINOTIFY> |
… | |
… | |
682 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
683 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
683 | and C<ev_loop_destroy>. |
684 | and C<ev_loop_destroy>. |
684 | |
685 | |
685 | =item ev_loop_fork (loop) |
686 | =item ev_loop_fork (loop) |
686 | |
687 | |
687 | This function sets a flag that causes subsequent C<ev_run> iterations to |
688 | This function sets a flag that causes subsequent C<ev_run> iterations |
688 | reinitialise the kernel state for backends that have one. Despite the |
689 | to reinitialise the kernel state for backends that have one. Despite |
689 | name, you can call it anytime, but it makes most sense after forking, in |
690 | the name, you can call it anytime you are allowed to start or stop |
690 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
691 | watchers (except inside an C<ev_prepare> callback), but it makes most |
|
|
692 | sense after forking, in the child process. You I<must> call it (or use |
691 | child before resuming or calling C<ev_run>. |
693 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
|
|
694 | |
|
|
695 | In addition, if you want to reuse a loop (via this function or |
|
|
696 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
692 | |
697 | |
693 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
698 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
694 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
699 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
695 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
700 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
696 | during fork. |
701 | during fork. |
… | |
… | |
2028 | |
2033 | |
2029 | The relative timeouts are calculated relative to the C<ev_now ()> |
2034 | The relative timeouts are calculated relative to the C<ev_now ()> |
2030 | time. This is usually the right thing as this timestamp refers to the time |
2035 | time. This is usually the right thing as this timestamp refers to the time |
2031 | of the event triggering whatever timeout you are modifying/starting. If |
2036 | of the event triggering whatever timeout you are modifying/starting. If |
2032 | you suspect event processing to be delayed and you I<need> to base the |
2037 | you suspect event processing to be delayed and you I<need> to base the |
2033 | timeout on the current time, use something like this to adjust for this: |
2038 | timeout on the current time, use something like the following to adjust |
|
|
2039 | for it: |
2034 | |
2040 | |
2035 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2041 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
2036 | |
2042 | |
2037 | If the event loop is suspended for a long time, you can also force an |
2043 | If the event loop is suspended for a long time, you can also force an |
2038 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2044 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2039 | ()>. |
2045 | ()>, although that will push the event time of all outstanding events |
|
|
2046 | further into the future. |
2040 | |
2047 | |
2041 | =head3 The special problem of unsynchronised clocks |
2048 | =head3 The special problem of unsynchronised clocks |
2042 | |
2049 | |
2043 | Modern systems have a variety of clocks - libev itself uses the normal |
2050 | Modern systems have a variety of clocks - libev itself uses the normal |
2044 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
2051 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
… | |
… | |
2107 | |
2114 | |
2108 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2115 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2109 | |
2116 | |
2110 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2117 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2111 | |
2118 | |
2112 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2119 | Configure the timer to trigger after C<after> seconds (fractional and |
2113 | is C<0.>, then it will automatically be stopped once the timeout is |
2120 | negative values are supported). If C<repeat> is C<0.>, then it will |
2114 | reached. If it is positive, then the timer will automatically be |
2121 | automatically be stopped once the timeout is reached. If it is positive, |
2115 | configured to trigger again C<repeat> seconds later, again, and again, |
2122 | then the timer will automatically be configured to trigger again C<repeat> |
2116 | until stopped manually. |
2123 | seconds later, again, and again, until stopped manually. |
2117 | |
2124 | |
2118 | The timer itself will do a best-effort at avoiding drift, that is, if |
2125 | The timer itself will do a best-effort at avoiding drift, that is, if |
2119 | you configure a timer to trigger every 10 seconds, then it will normally |
2126 | you configure a timer to trigger every 10 seconds, then it will normally |
2120 | trigger at exactly 10 second intervals. If, however, your program cannot |
2127 | trigger at exactly 10 second intervals. If, however, your program cannot |
2121 | keep up with the timer (because it takes longer than those 10 seconds to |
2128 | keep up with the timer (because it takes longer than those 10 seconds to |
… | |
… | |
2203 | Periodic watchers are also timers of a kind, but they are very versatile |
2210 | Periodic watchers are also timers of a kind, but they are very versatile |
2204 | (and unfortunately a bit complex). |
2211 | (and unfortunately a bit complex). |
2205 | |
2212 | |
2206 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2213 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2207 | relative time, the physical time that passes) but on wall clock time |
2214 | relative time, the physical time that passes) but on wall clock time |
2208 | (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 |
2209 | difference is that wall clock time can run faster or slower than real |
2216 | difference is that wall clock time can run faster or slower than real |
2210 | time, and time jumps are not uncommon (e.g. when you adjust your |
2217 | time, and time jumps are not uncommon (e.g. when you adjust your |
2211 | wrist-watch). |
2218 | wrist-watch). |
2212 | |
2219 | |
2213 | You can tell a periodic watcher to trigger after some specific point |
2220 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
2907 | |
2914 | |
2908 | Prepare and check watchers are often (but not always) used in pairs: |
2915 | Prepare and check watchers are often (but not always) used in pairs: |
2909 | prepare watchers get invoked before the process blocks and check watchers |
2916 | prepare watchers get invoked before the process blocks and check watchers |
2910 | afterwards. |
2917 | afterwards. |
2911 | |
2918 | |
2912 | You I<must not> call C<ev_run> or similar functions that enter |
2919 | You I<must not> call C<ev_run> (or similar functions that enter the |
2913 | the current event loop from either C<ev_prepare> or C<ev_check> |
2920 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2914 | watchers. Other loops than the current one are fine, however. The |
2921 | C<ev_check> watchers. Other loops than the current one are fine, |
2915 | rationale behind this is that you do not need to check for recursion in |
2922 | however. The rationale behind this is that you do not need to check |
2916 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2923 | for recursion in those watchers, i.e. the sequence will always be |
2917 | C<ev_check> so if you have one watcher of each kind they will always be |
2924 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2918 | called in pairs bracketing the blocking call. |
2925 | kind they will always be called in pairs bracketing the blocking call. |
2919 | |
2926 | |
2920 | Their main purpose is to integrate other event mechanisms into libev and |
2927 | Their main purpose is to integrate other event mechanisms into libev and |
2921 | their use is somewhat advanced. They could be used, for example, to track |
2928 | their use is somewhat advanced. They could be used, for example, to track |
2922 | variable changes, implement your own watchers, integrate net-snmp or a |
2929 | variable changes, implement your own watchers, integrate net-snmp or a |
2923 | coroutine library and lots more. They are also occasionally useful if |
2930 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
3263 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3270 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3264 | of course. |
3271 | of course. |
3265 | |
3272 | |
3266 | =head3 The special problem of life after fork - how is it possible? |
3273 | =head3 The special problem of life after fork - how is it possible? |
3267 | |
3274 | |
3268 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3275 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3269 | up/change the process environment, followed by a call to C<exec()>. This |
3276 | up/change the process environment, followed by a call to C<exec()>. This |
3270 | sequence should be handled by libev without any problems. |
3277 | sequence should be handled by libev without any problems. |
3271 | |
3278 | |
3272 | This changes when the application actually wants to do event handling |
3279 | This changes when the application actually wants to do event handling |
3273 | in the child, or both parent in child, in effect "continuing" after the |
3280 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3511 | |
3518 | |
3512 | There are some other functions of possible interest. Described. Here. Now. |
3519 | There are some other functions of possible interest. Described. Here. Now. |
3513 | |
3520 | |
3514 | =over 4 |
3521 | =over 4 |
3515 | |
3522 | |
3516 | =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) |
3517 | |
3524 | |
3518 | This function combines a simple timer and an I/O watcher, calls your |
3525 | This function combines a simple timer and an I/O watcher, calls your |
3519 | callback on whichever event happens first and automatically stops both |
3526 | callback on whichever event happens first and automatically stops both |
3520 | watchers. This is useful if you want to wait for a single event on an fd |
3527 | watchers. This is useful if you want to wait for a single event on an fd |
3521 | or timeout without having to allocate/configure/start/stop/free one or |
3528 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
3897 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3904 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3898 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3905 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3899 | |
3906 | |
3900 | // my_ev.h |
3907 | // my_ev.h |
3901 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3908 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3902 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
3909 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
3903 | #include "../libev/ev.h" |
3910 | #include "../libev/ev.h" |
3904 | |
3911 | |
3905 | // my_ev.c |
3912 | // my_ev.c |
3906 | #define EV_H "my_ev.h" |
3913 | #define EV_H "my_ev.h" |
3907 | #include "../libev/ev.c" |
3914 | #include "../libev/ev.c" |
… | |
… | |
4380 | ev_vars.h |
4387 | ev_vars.h |
4381 | ev_wrap.h |
4388 | ev_wrap.h |
4382 | |
4389 | |
4383 | ev_win32.c required on win32 platforms only |
4390 | ev_win32.c required on win32 platforms only |
4384 | |
4391 | |
4385 | ev_select.c only when select backend is enabled (which is enabled by default) |
4392 | ev_select.c only when select backend is enabled |
4386 | ev_poll.c only when poll backend is enabled (disabled by default) |
4393 | ev_poll.c only when poll backend is enabled |
4387 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4394 | ev_epoll.c only when the epoll backend is enabled |
4388 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4395 | ev_kqueue.c only when the kqueue backend is enabled |
4389 | 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 |
4390 | |
4397 | |
4391 | F<ev.c> includes the backend files directly when enabled, so you only need |
4398 | F<ev.c> includes the backend files directly when enabled, so you only need |
4392 | to compile this single file. |
4399 | to compile this single file. |
4393 | |
4400 | |
4394 | =head3 LIBEVENT COMPATIBILITY API |
4401 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
5294 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5301 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5295 | assumes that the same (machine) code can be used to call any watcher |
5302 | assumes that the same (machine) code can be used to call any watcher |
5296 | callback: The watcher callbacks have different type signatures, but libev |
5303 | callback: The watcher callbacks have different type signatures, but libev |
5297 | calls them using an C<ev_watcher *> internally. |
5304 | calls them using an C<ev_watcher *> internally. |
5298 | |
5305 | |
|
|
5306 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5307 | |
|
|
5308 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5309 | relies on this setting pointers and integers to null. |
|
|
5310 | |
5299 | =item pointer accesses must be thread-atomic |
5311 | =item pointer accesses must be thread-atomic |
5300 | |
5312 | |
5301 | Accessing a pointer value must be atomic, it must both be readable and |
5313 | Accessing a pointer value must be atomic, it must both be readable and |
5302 | writable in one piece - this is the case on all current architectures. |
5314 | writable in one piece - this is the case on all current architectures. |
5303 | |
5315 | |