… | |
… | |
174 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
175 | |
175 | |
176 | Returns the current time as libev would use it. Please note that the |
176 | Returns the current time as libev would use it. Please note that the |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
178 | you actually want to know. Also interesting is the combination of |
178 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
179 | C<ev_now_update> and C<ev_now>. |
180 | |
180 | |
181 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
182 | |
182 | |
183 | Sleep for the given interval: The current thread will be blocked |
183 | Sleep for the given interval: The current thread will be blocked |
184 | until either it is interrupted or the given time interval has |
184 | until either it is interrupted or the given time interval has |
… | |
… | |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
249 | |
249 | |
250 | See the description of C<ev_embed> watchers for more info. |
250 | See the description of C<ev_embed> watchers for more info. |
251 | |
251 | |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
253 | |
253 | |
254 | Sets the allocation function to use (the prototype is similar - the |
254 | Sets the allocation function to use (the prototype is similar - the |
255 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
255 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
256 | used to allocate and free memory (no surprises here). If it returns zero |
256 | used to allocate and free memory (no surprises here). If it returns zero |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
283 | } |
283 | } |
284 | |
284 | |
285 | ... |
285 | ... |
286 | ev_set_allocator (persistent_realloc); |
286 | ev_set_allocator (persistent_realloc); |
287 | |
287 | |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
289 | |
289 | |
290 | Set the callback function to call on a retryable system call error (such |
290 | Set the callback function to call on a retryable system call error (such |
291 | as failed select, poll, epoll_wait). The message is a printable string |
291 | as failed select, poll, epoll_wait). The message is a printable string |
292 | indicating the system call or subsystem causing the problem. If this |
292 | indicating the system call or subsystem causing the problem. If this |
293 | callback is set, then libev will expect it to remedy the situation, no |
293 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
567 | |
567 | |
568 | It scales in the same way as the epoll backend, but the interface to the |
568 | It scales in the same way as the epoll backend, but the interface to the |
569 | kernel is more efficient (which says nothing about its actual speed, of |
569 | 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 |
570 | 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 |
571 | 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 (but |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
573 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
574 | cases |
574 | drops fds silently in similarly hard-to-detect cases |
575 | |
575 | |
576 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
577 | |
577 | |
578 | While nominally embeddable in other event loops, this doesn't work |
578 | 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 |
579 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
792 | without a previous call to C<ev_suspend>. |
792 | without a previous call to C<ev_suspend>. |
793 | |
793 | |
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
795 | event loop time (see C<ev_now_update>). |
795 | event loop time (see C<ev_now_update>). |
796 | |
796 | |
797 | =item ev_run (loop, int flags) |
797 | =item bool ev_run (loop, int flags) |
798 | |
798 | |
799 | Finally, this is it, the event handler. This function usually is called |
799 | Finally, this is it, the event handler. This function usually is called |
800 | after you have initialised all your watchers and you want to start |
800 | after you have initialised all your watchers and you want to start |
801 | handling events. It will ask the operating system for any new events, call |
801 | handling events. It will ask the operating system for any new events, call |
802 | the watcher callbacks, an then repeat the whole process indefinitely: This |
802 | the watcher callbacks, and then repeat the whole process indefinitely: This |
803 | is why event loops are called I<loops>. |
803 | is why event loops are called I<loops>. |
804 | |
804 | |
805 | If the flags argument is specified as C<0>, it will keep handling events |
805 | If the flags argument is specified as C<0>, it will keep handling events |
806 | until either no event watchers are active anymore or C<ev_break> was |
806 | until either no event watchers are active anymore or C<ev_break> was |
807 | called. |
807 | called. |
|
|
808 | |
|
|
809 | The return value is false if there are no more active watchers (which |
|
|
810 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
811 | (which usually means " you should call C<ev_run> again"). |
808 | |
812 | |
809 | Please note that an explicit C<ev_break> is usually better than |
813 | Please note that an explicit C<ev_break> is usually better than |
810 | relying on all watchers to be stopped when deciding when a program has |
814 | relying on all watchers to be stopped when deciding when a program has |
811 | finished (especially in interactive programs), but having a program |
815 | finished (especially in interactive programs), but having a program |
812 | that automatically loops as long as it has to and no longer by virtue |
816 | that automatically loops as long as it has to and no longer by virtue |
813 | of relying on its watchers stopping correctly, that is truly a thing of |
817 | of relying on its watchers stopping correctly, that is truly a thing of |
814 | beauty. |
818 | beauty. |
815 | |
819 | |
816 | This function is also I<mostly> exception-safe - you can break out of |
820 | This function is I<mostly> exception-safe - you can break out of a |
817 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
821 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
818 | exception and so on. This does not decrement the C<ev_depth> value, nor |
822 | exception and so on. This does not decrement the C<ev_depth> value, nor |
819 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
823 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
820 | |
824 | |
821 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
825 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
822 | those events and any already outstanding ones, but will not wait and |
826 | those events and any already outstanding ones, but will not wait and |
… | |
… | |
1012 | invoke the actual watchers inside another context (another thread etc.). |
1016 | invoke the actual watchers inside another context (another thread etc.). |
1013 | |
1017 | |
1014 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1018 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1015 | callback. |
1019 | callback. |
1016 | |
1020 | |
1017 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1021 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
1018 | |
1022 | |
1019 | Sometimes you want to share the same loop between multiple threads. This |
1023 | Sometimes you want to share the same loop between multiple threads. This |
1020 | can be done relatively simply by putting mutex_lock/unlock calls around |
1024 | can be done relatively simply by putting mutex_lock/unlock calls around |
1021 | each call to a libev function. |
1025 | each call to a libev function. |
1022 | |
1026 | |
1023 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1027 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1024 | to wait for it to return. One way around this is to wake up the event |
1028 | to wait for it to return. One way around this is to wake up the event |
1025 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1029 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
1026 | I<release> and I<acquire> callbacks on the loop. |
1030 | I<release> and I<acquire> callbacks on the loop. |
1027 | |
1031 | |
1028 | When set, then C<release> will be called just before the thread is |
1032 | When set, then C<release> will be called just before the thread is |
1029 | suspended waiting for new events, and C<acquire> is called just |
1033 | suspended waiting for new events, and C<acquire> is called just |
1030 | afterwards. |
1034 | afterwards. |
… | |
… | |
1771 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1775 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1772 | monotonic clock option helps a lot here). |
1776 | monotonic clock option helps a lot here). |
1773 | |
1777 | |
1774 | The callback is guaranteed to be invoked only I<after> its timeout has |
1778 | 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 |
1779 | 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 |
1780 | might introduce a small delay, see "the special problem of being too |
|
|
1781 | 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 |
1782 | 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 |
1783 | 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). |
1784 | longer true when a callback calls C<ev_run> recursively). |
1780 | |
1785 | |
1781 | =head3 Be smart about timeouts |
1786 | =head3 Be smart about timeouts |
1782 | |
1787 | |
1783 | Many real-world problems involve some kind of timeout, usually for error |
1788 | 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, |
1789 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1859 | |
1864 | |
1860 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1865 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1861 | but remember the time of last activity, and check for a real timeout only |
1866 | but remember the time of last activity, and check for a real timeout only |
1862 | within the callback: |
1867 | within the callback: |
1863 | |
1868 | |
|
|
1869 | ev_tstamp timeout = 60.; |
1864 | ev_tstamp last_activity; // time of last activity |
1870 | ev_tstamp last_activity; // time of last activity |
|
|
1871 | ev_timer timer; |
1865 | |
1872 | |
1866 | static void |
1873 | static void |
1867 | callback (EV_P_ ev_timer *w, int revents) |
1874 | callback (EV_P_ ev_timer *w, int revents) |
1868 | { |
1875 | { |
1869 | ev_tstamp now = ev_now (EV_A); |
1876 | // calculate when the timeout would happen |
1870 | ev_tstamp timeout = last_activity + 60.; |
1877 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1871 | |
1878 | |
1872 | // if last_activity + 60. is older than now, we did time out |
1879 | // if negative, it means we the timeout already occurred |
1873 | if (timeout < now) |
1880 | if (after < 0.) |
1874 | { |
1881 | { |
1875 | // timeout occurred, take action |
1882 | // timeout occurred, take action |
1876 | } |
1883 | } |
1877 | else |
1884 | else |
1878 | { |
1885 | { |
1879 | // callback was invoked, but there was some activity, re-arm |
1886 | // callback was invoked, but there was some recent |
1880 | // the watcher to fire in last_activity + 60, which is |
1887 | // activity. simply restart the timer to time out |
1881 | // guaranteed to be in the future, so "again" is positive: |
1888 | // after "after" seconds, which is the earliest time |
1882 | w->repeat = timeout - now; |
1889 | // the timeout can occur. |
|
|
1890 | ev_timer_set (w, after, 0.); |
1883 | ev_timer_again (EV_A_ w); |
1891 | ev_timer_start (EV_A_ w); |
1884 | } |
1892 | } |
1885 | } |
1893 | } |
1886 | |
1894 | |
1887 | To summarise the callback: first calculate the real timeout (defined |
1895 | To summarise the callback: first calculate in how many seconds the |
1888 | as "60 seconds after the last activity"), then check if that time has |
1896 | timeout will occur (by calculating the absolute time when it would occur, |
1889 | been reached, which means something I<did>, in fact, time out. Otherwise |
1897 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1890 | the callback was invoked too early (C<timeout> is in the future), so |
1898 | (EV_A)> from that). |
1891 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1892 | a timeout then. |
|
|
1893 | |
1899 | |
1894 | Note how C<ev_timer_again> is used, taking advantage of the |
1900 | If this value is negative, then we are already past the timeout, i.e. we |
1895 | C<ev_timer_again> optimisation when the timer is already running. |
1901 | timed out, and need to do whatever is needed in this case. |
|
|
1902 | |
|
|
1903 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1904 | and simply start the timer with this timeout value. |
|
|
1905 | |
|
|
1906 | In other words, each time the callback is invoked it will check whether |
|
|
1907 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1908 | again at the earliest time it could time out. Rinse. Repeat. |
1896 | |
1909 | |
1897 | This scheme causes more callback invocations (about one every 60 seconds |
1910 | This scheme causes more callback invocations (about one every 60 seconds |
1898 | minus half the average time between activity), but virtually no calls to |
1911 | minus half the average time between activity), but virtually no calls to |
1899 | libev to change the timeout. |
1912 | libev to change the timeout. |
1900 | |
1913 | |
1901 | To start the timer, simply initialise the watcher and set C<last_activity> |
1914 | To start the machinery, simply initialise the watcher and set |
1902 | to the current time (meaning we just have some activity :), then call the |
1915 | C<last_activity> to the current time (meaning there was some activity just |
1903 | callback, which will "do the right thing" and start the timer: |
1916 | now), then call the callback, which will "do the right thing" and start |
|
|
1917 | the timer: |
1904 | |
1918 | |
|
|
1919 | last_activity = ev_now (EV_A); |
1905 | ev_init (timer, callback); |
1920 | ev_init (&timer, callback); |
1906 | last_activity = ev_now (loop); |
1921 | callback (EV_A_ &timer, 0); |
1907 | callback (loop, timer, EV_TIMER); |
|
|
1908 | |
1922 | |
1909 | And when there is some activity, simply store the current time in |
1923 | When there is some activity, simply store the current time in |
1910 | C<last_activity>, no libev calls at all: |
1924 | C<last_activity>, no libev calls at all: |
1911 | |
1925 | |
|
|
1926 | if (activity detected) |
1912 | last_activity = ev_now (loop); |
1927 | last_activity = ev_now (EV_A); |
|
|
1928 | |
|
|
1929 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1930 | providing a new value, stopping the timer and calling the callback, which |
|
|
1931 | will again do the right thing (for example, time out immediately :). |
|
|
1932 | |
|
|
1933 | timeout = new_value; |
|
|
1934 | ev_timer_stop (EV_A_ &timer); |
|
|
1935 | callback (EV_A_ &timer, 0); |
1913 | |
1936 | |
1914 | This technique is slightly more complex, but in most cases where the |
1937 | This technique is slightly more complex, but in most cases where the |
1915 | time-out is unlikely to be triggered, much more efficient. |
1938 | time-out is unlikely to be triggered, much more efficient. |
1916 | |
|
|
1917 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1918 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1919 | fix things for you. |
|
|
1920 | |
1939 | |
1921 | =item 4. Wee, just use a double-linked list for your timeouts. |
1940 | =item 4. Wee, just use a double-linked list for your timeouts. |
1922 | |
1941 | |
1923 | If there is not one request, but many thousands (millions...), all |
1942 | If there is not one request, but many thousands (millions...), all |
1924 | employing some kind of timeout with the same timeout value, then one can |
1943 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1951 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1970 | 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 |
1971 | 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 |
1972 | off after the first million or so of active timers, i.e. it's usually |
1954 | overkill :) |
1973 | overkill :) |
1955 | |
1974 | |
|
|
1975 | =head3 The special problem of being too early |
|
|
1976 | |
|
|
1977 | If you ask a timer to call your callback after three seconds, then |
|
|
1978 | you expect it to be invoked after three seconds - but of course, this |
|
|
1979 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1980 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1981 | process with a STOP signal for a few hours for example. |
|
|
1982 | |
|
|
1983 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1984 | delay has occurred, but cannot guarantee this. |
|
|
1985 | |
|
|
1986 | A less obvious failure mode is calling your callback too early: many event |
|
|
1987 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1988 | this can cause your callback to be invoked much earlier than you would |
|
|
1989 | expect. |
|
|
1990 | |
|
|
1991 | To see why, imagine a system with a clock that only offers full second |
|
|
1992 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1993 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1994 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
1995 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
1996 | |
|
|
1997 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
1998 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
1999 | one-second delay was requested - this is being "too early", despite best |
|
|
2000 | intentions. |
|
|
2001 | |
|
|
2002 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2003 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2004 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2005 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2006 | |
|
|
2007 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2008 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2009 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2010 | late" side of things. |
|
|
2011 | |
1956 | =head3 The special problem of time updates |
2012 | =head3 The special problem of time updates |
1957 | |
2013 | |
1958 | Establishing the current time is a costly operation (it usually takes at |
2014 | Establishing the current time is a costly operation (it usually takes |
1959 | least two system calls): EV therefore updates its idea of the current |
2015 | 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 |
2016 | 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 |
2017 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1962 | lots of events in one iteration. |
2018 | lots of events in one iteration. |
1963 | |
2019 | |
1964 | The relative timeouts are calculated relative to the C<ev_now ()> |
2020 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1970 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2026 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1971 | |
2027 | |
1972 | If the event loop is suspended for a long time, you can also force an |
2028 | 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 |
2029 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1974 | ()>. |
2030 | ()>. |
|
|
2031 | |
|
|
2032 | =head3 The special problem of unsynchronised clocks |
|
|
2033 | |
|
|
2034 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2035 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2036 | jumps). |
|
|
2037 | |
|
|
2038 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2039 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2040 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2041 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2042 | than a directly following call to C<time>. |
|
|
2043 | |
|
|
2044 | The moral of this is to only compare libev-related timestamps with |
|
|
2045 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2046 | a second or so. |
|
|
2047 | |
|
|
2048 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2049 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2050 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2051 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2052 | |
|
|
2053 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2054 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2055 | I<measured according to the real time>, not the system clock. |
|
|
2056 | |
|
|
2057 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2058 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2059 | exactly the right behaviour. |
|
|
2060 | |
|
|
2061 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2062 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2063 | time, where your comparisons will always generate correct results. |
1975 | |
2064 | |
1976 | =head3 The special problems of suspended animation |
2065 | =head3 The special problems of suspended animation |
1977 | |
2066 | |
1978 | When you leave the server world it is quite customary to hit machines that |
2067 | 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? |
2068 | 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 |
2112 | 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. |
2113 | do stuff) the timer will not fire more than once per event loop iteration. |
2025 | |
2114 | |
2026 | =item ev_timer_again (loop, ev_timer *) |
2115 | =item ev_timer_again (loop, ev_timer *) |
2027 | |
2116 | |
2028 | This will act as if the timer timed out and restarts it again if it is |
2117 | This will act as if the timer timed out, and restarts it again if it is |
2029 | repeating. The exact semantics are: |
2118 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2119 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
2030 | |
2120 | |
|
|
2121 | The exact semantics are as in the following rules, all of which will be |
|
|
2122 | applied to the watcher: |
|
|
2123 | |
|
|
2124 | =over 4 |
|
|
2125 | |
2031 | If the timer is pending, its pending status is cleared. |
2126 | =item If the timer is pending, the pending status is always cleared. |
2032 | |
2127 | |
2033 | If the timer is started but non-repeating, stop it (as if it timed out). |
2128 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2129 | out, without invoking it). |
2034 | |
2130 | |
2035 | If the timer is repeating, either start it if necessary (with the |
2131 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2036 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2132 | and start the timer, if necessary. |
|
|
2133 | |
|
|
2134 | =back |
2037 | |
2135 | |
2038 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2136 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2039 | usage example. |
2137 | usage example. |
2040 | |
2138 | |
2041 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2139 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
… | |
… | |
3215 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3313 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3216 | |
3314 | |
3217 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3315 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3218 | too, are asynchronous in nature, and signals, too, will be compressed |
3316 | too, are asynchronous in nature, and signals, too, will be compressed |
3219 | (i.e. the number of callback invocations may be less than the number of |
3317 | (i.e. the number of callback invocations may be less than the number of |
3220 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3318 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3221 | of "global async watchers" by using a watcher on an otherwise unused |
3319 | 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, |
3320 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3223 | even without knowing which loop owns the signal. |
3321 | even without knowing which loop owns the signal. |
3224 | |
3322 | |
3225 | =head3 Queueing |
3323 | =head3 Queueing |
… | |
… | |
3402 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3500 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3403 | |
3501 | |
3404 | =item ev_feed_fd_event (loop, int fd, int revents) |
3502 | =item ev_feed_fd_event (loop, int fd, int revents) |
3405 | |
3503 | |
3406 | Feed an event on the given fd, as if a file descriptor backend detected |
3504 | Feed an event on the given fd, as if a file descriptor backend detected |
3407 | the given events it. |
3505 | the given events. |
3408 | |
3506 | |
3409 | =item ev_feed_signal_event (loop, int signum) |
3507 | =item ev_feed_signal_event (loop, int signum) |
3410 | |
3508 | |
3411 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3509 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3412 | which is async-safe. |
3510 | which is async-safe. |
… | |
… | |
3486 | { |
3584 | { |
3487 | struct my_biggy big = (struct my_biggy *) |
3585 | struct my_biggy big = (struct my_biggy *) |
3488 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3586 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3489 | } |
3587 | } |
3490 | |
3588 | |
|
|
3589 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3590 | |
|
|
3591 | Often you have structures like this in event-based programs: |
|
|
3592 | |
|
|
3593 | callback () |
|
|
3594 | { |
|
|
3595 | free (request); |
|
|
3596 | } |
|
|
3597 | |
|
|
3598 | request = start_new_request (..., callback); |
|
|
3599 | |
|
|
3600 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3601 | used to cancel the operation, or do other things with it. |
|
|
3602 | |
|
|
3603 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3604 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3605 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3606 | operation and simply invoke the callback with the result. |
|
|
3607 | |
|
|
3608 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3609 | has returned, so C<request> is not set. |
|
|
3610 | |
|
|
3611 | Even if you pass the request by some safer means to the callback, you |
|
|
3612 | might want to do something to the request after starting it, such as |
|
|
3613 | canceling it, which probably isn't working so well when the callback has |
|
|
3614 | already been invoked. |
|
|
3615 | |
|
|
3616 | A common way around all these issues is to make sure that |
|
|
3617 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3618 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3619 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
|
|
3620 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3621 | and pushing it into the pending queue: |
|
|
3622 | |
|
|
3623 | ev_set_cb (watcher, callback); |
|
|
3624 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3625 | |
|
|
3626 | This way, C<start_new_request> can safely return before the callback is |
|
|
3627 | invoked, while not delaying callback invocation too much. |
|
|
3628 | |
3491 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3629 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3492 | |
3630 | |
3493 | Often (especially in GUI toolkits) there are places where you have |
3631 | Often (especially in GUI toolkits) there are places where you have |
3494 | I<modal> interaction, which is most easily implemented by recursively |
3632 | I<modal> interaction, which is most easily implemented by recursively |
3495 | invoking C<ev_run>. |
3633 | invoking C<ev_run>. |
… | |
… | |
3508 | int exit_main_loop = 0; |
3646 | int exit_main_loop = 0; |
3509 | |
3647 | |
3510 | while (!exit_main_loop) |
3648 | while (!exit_main_loop) |
3511 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3649 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3512 | |
3650 | |
3513 | // in a model watcher |
3651 | // in a modal watcher |
3514 | int exit_nested_loop = 0; |
3652 | int exit_nested_loop = 0; |
3515 | |
3653 | |
3516 | while (!exit_nested_loop) |
3654 | while (!exit_nested_loop) |
3517 | ev_run (EV_A_ EVRUN_ONCE); |
3655 | ev_run (EV_A_ EVRUN_ONCE); |
3518 | |
3656 | |
… | |
… | |
3698 | switch_to (libev_coro); |
3836 | switch_to (libev_coro); |
3699 | } |
3837 | } |
3700 | |
3838 | |
3701 | That basically suspends the coroutine inside C<wait_for_event> and |
3839 | That basically suspends the coroutine inside C<wait_for_event> and |
3702 | continues the libev coroutine, which, when appropriate, switches back to |
3840 | continues the libev coroutine, which, when appropriate, switches back to |
3703 | this or any other coroutine. I am sure if you sue this your own :) |
3841 | this or any other coroutine. |
3704 | |
3842 | |
3705 | You can do similar tricks if you have, say, threads with an event queue - |
3843 | You can do similar tricks if you have, say, threads with an event queue - |
3706 | instead of storing a coroutine, you store the queue object and instead of |
3844 | instead of storing a coroutine, you store the queue object and instead of |
3707 | switching to a coroutine, you push the watcher onto the queue and notify |
3845 | switching to a coroutine, you push the watcher onto the queue and notify |
3708 | any waiters. |
3846 | any waiters. |
… | |
… | |
3758 | to use the libev header file and library. |
3896 | to use the libev header file and library. |
3759 | |
3897 | |
3760 | =back |
3898 | =back |
3761 | |
3899 | |
3762 | =head1 C++ SUPPORT |
3900 | =head1 C++ SUPPORT |
|
|
3901 | |
|
|
3902 | =head2 C API |
|
|
3903 | |
|
|
3904 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3905 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3906 | will work fine. |
|
|
3907 | |
|
|
3908 | Proper exception specifications might have to be added to callbacks passed |
|
|
3909 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3910 | other callbacks (allocator, syserr, loop acquire/release and periodioc |
|
|
3911 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3912 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3913 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3914 | |
|
|
3915 | static void |
|
|
3916 | fatal_error (const char *msg) EV_THROW |
|
|
3917 | { |
|
|
3918 | perror (msg); |
|
|
3919 | abort (); |
|
|
3920 | } |
|
|
3921 | |
|
|
3922 | ... |
|
|
3923 | ev_set_syserr_cb (fatal_error); |
|
|
3924 | |
|
|
3925 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3926 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
3927 | because it runs cleanup watchers). |
|
|
3928 | |
|
|
3929 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3930 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3931 | throwing exceptions through C libraries (most do). |
|
|
3932 | |
|
|
3933 | =head2 C++ API |
3763 | |
3934 | |
3764 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3935 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3765 | you to use some convenience methods to start/stop watchers and also change |
3936 | you to use some convenience methods to start/stop watchers and also change |
3766 | the callback model to a model using method callbacks on objects. |
3937 | the callback model to a model using method callbacks on objects. |
3767 | |
3938 | |
… | |
… | |
3783 | with C<operator ()> can be used as callbacks. Other types should be easy |
3954 | with C<operator ()> can be used as callbacks. Other types should be easy |
3784 | to add as long as they only need one additional pointer for context. If |
3955 | to add as long as they only need one additional pointer for context. If |
3785 | you need support for other types of functors please contact the author |
3956 | you need support for other types of functors please contact the author |
3786 | (preferably after implementing it). |
3957 | (preferably after implementing it). |
3787 | |
3958 | |
|
|
3959 | For all this to work, your C++ compiler either has to use the same calling |
|
|
3960 | conventions as your C compiler (for static member functions), or you have |
|
|
3961 | to embed libev and compile libev itself as C++. |
|
|
3962 | |
3788 | Here is a list of things available in the C<ev> namespace: |
3963 | Here is a list of things available in the C<ev> namespace: |
3789 | |
3964 | |
3790 | =over 4 |
3965 | =over 4 |
3791 | |
3966 | |
3792 | =item C<ev::READ>, C<ev::WRITE> etc. |
3967 | =item C<ev::READ>, C<ev::WRITE> etc. |
… | |
… | |
3801 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3976 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3802 | |
3977 | |
3803 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3978 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3804 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3979 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3805 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3980 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3806 | defines by many implementations. |
3981 | defined by many implementations. |
3807 | |
3982 | |
3808 | All of those classes have these methods: |
3983 | All of those classes have these methods: |
3809 | |
3984 | |
3810 | =over 4 |
3985 | =over 4 |
3811 | |
3986 | |
… | |
… | |
4370 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4545 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4371 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4546 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4372 | be detected at runtime. If undefined, it will be enabled if the headers |
4547 | be detected at runtime. If undefined, it will be enabled if the headers |
4373 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4548 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4374 | |
4549 | |
|
|
4550 | =item EV_NO_SMP |
|
|
4551 | |
|
|
4552 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4553 | between threads, that is, threads can be used, but threads never run on |
|
|
4554 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4555 | and makes libev faster. |
|
|
4556 | |
|
|
4557 | =item EV_NO_THREADS |
|
|
4558 | |
|
|
4559 | If defined to be C<1>, libev will assume that it will never be called |
|
|
4560 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
|
|
4561 | above. This reduces dependencies and makes libev faster. |
|
|
4562 | |
4375 | =item EV_ATOMIC_T |
4563 | =item EV_ATOMIC_T |
4376 | |
4564 | |
4377 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4565 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4378 | access is atomic and serialised with respect to other threads or signal |
4566 | access is atomic and serialised with respect to other threads or signal |
4379 | contexts. No such type is easily found in the C language, so you can |
4567 | contexts. No such type is easily found in the C language, so you can |
… | |
… | |
4465 | #define EV_USE_POLL 1 |
4653 | #define EV_USE_POLL 1 |
4466 | #define EV_CHILD_ENABLE 1 |
4654 | #define EV_CHILD_ENABLE 1 |
4467 | #define EV_ASYNC_ENABLE 1 |
4655 | #define EV_ASYNC_ENABLE 1 |
4468 | |
4656 | |
4469 | The actual value is a bitset, it can be a combination of the following |
4657 | The actual value is a bitset, it can be a combination of the following |
4470 | values: |
4658 | values (by default, all of these are enabled): |
4471 | |
4659 | |
4472 | =over 4 |
4660 | =over 4 |
4473 | |
4661 | |
4474 | =item C<1> - faster/larger code |
4662 | =item C<1> - faster/larger code |
4475 | |
4663 | |
… | |
… | |
4479 | code size by roughly 30% on amd64). |
4667 | code size by roughly 30% on amd64). |
4480 | |
4668 | |
4481 | When optimising for size, use of compiler flags such as C<-Os> with |
4669 | When optimising for size, use of compiler flags such as C<-Os> with |
4482 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4670 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4483 | assertions. |
4671 | assertions. |
|
|
4672 | |
|
|
4673 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4674 | (e.g. gcc with C<-Os>). |
4484 | |
4675 | |
4485 | =item C<2> - faster/larger data structures |
4676 | =item C<2> - faster/larger data structures |
4486 | |
4677 | |
4487 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4678 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4488 | hash table sizes and so on. This will usually further increase code size |
4679 | hash table sizes and so on. This will usually further increase code size |
4489 | and can additionally have an effect on the size of data structures at |
4680 | and can additionally have an effect on the size of data structures at |
4490 | runtime. |
4681 | runtime. |
4491 | |
4682 | |
|
|
4683 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4684 | (e.g. gcc with C<-Os>). |
|
|
4685 | |
4492 | =item C<4> - full API configuration |
4686 | =item C<4> - full API configuration |
4493 | |
4687 | |
4494 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4688 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4495 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4689 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4496 | |
4690 | |
… | |
… | |
4526 | |
4720 | |
4527 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4721 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4528 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4722 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4529 | your program might be left out as well - a binary starting a timer and an |
4723 | your program might be left out as well - a binary starting a timer and an |
4530 | I/O watcher then might come out at only 5Kb. |
4724 | I/O watcher then might come out at only 5Kb. |
|
|
4725 | |
|
|
4726 | =item EV_API_STATIC |
|
|
4727 | |
|
|
4728 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4729 | will have static linkage. This means that libev will not export any |
|
|
4730 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4731 | when you embed libev, only want to use libev functions in a single file, |
|
|
4732 | and do not want its identifiers to be visible. |
|
|
4733 | |
|
|
4734 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4735 | wants to use libev. |
|
|
4736 | |
|
|
4737 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4738 | doesn't support the required declaration syntax. |
4531 | |
4739 | |
4532 | =item EV_AVOID_STDIO |
4740 | =item EV_AVOID_STDIO |
4533 | |
4741 | |
4534 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4742 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4535 | functions (printf, scanf, perror etc.). This will increase the code size |
4743 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
5061 | good enough for at least into the year 4000 with millisecond accuracy |
5269 | good enough for at least into the year 4000 with millisecond accuracy |
5062 | (the design goal for libev). This requirement is overfulfilled by |
5270 | (the design goal for libev). This requirement is overfulfilled by |
5063 | implementations using IEEE 754, which is basically all existing ones. |
5271 | implementations using IEEE 754, which is basically all existing ones. |
5064 | |
5272 | |
5065 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
5273 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
5066 | year 2255 (and millisecond accuray till the year 287396 - by then, libev |
5274 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
5067 | is either obsolete or somebody patched it to use C<long double> or |
5275 | is either obsolete or somebody patched it to use C<long double> or |
5068 | something like that, just kidding). |
5276 | something like that, just kidding). |
5069 | |
5277 | |
5070 | =back |
5278 | =back |
5071 | |
5279 | |