… | |
… | |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
14 | // every watcher type has its own typedef'd struct |
14 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
15 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
16 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
17 | ev_timer timeout_watcher; |
18 | |
18 | |
19 | // all watcher callbacks have a similar signature |
19 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
20 | // this callback is called when data is readable on stdin |
21 | static void |
21 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
22 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
23 | { |
24 | puts ("stdin ready"); |
24 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
25 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
26 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
27 | ev_io_stop (EV_A_ w); |
… | |
… | |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
31 | } |
31 | } |
32 | |
32 | |
33 | // another callback, this time for a time-out |
33 | // another callback, this time for a time-out |
34 | static void |
34 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
35 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
36 | { |
37 | puts ("timeout"); |
37 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
38 | // this causes the innermost ev_loop to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
40 | } |
40 | } |
41 | |
41 | |
42 | int |
42 | int |
43 | main (void) |
43 | main (void) |
44 | { |
44 | { |
45 | // use the default event loop unless you have special needs |
45 | // use the default event loop unless you have special needs |
46 | struct ev_loop *loop = ev_default_loop (0); |
46 | ev_loop *loop = ev_default_loop (0); |
47 | |
47 | |
48 | // initialise an io watcher, then start it |
48 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
49 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
51 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
103 | Libev is very configurable. In this manual the default (and most common) |
103 | Libev is very configurable. In this manual the default (and most common) |
104 | configuration will be described, which supports multiple event loops. For |
104 | configuration will be described, which supports multiple event loops. For |
105 | more info about various configuration options please have a look at |
105 | more info about various configuration options please have a look at |
106 | B<EMBED> section in this manual. If libev was configured without support |
106 | B<EMBED> section in this manual. If libev was configured without support |
107 | for multiple event loops, then all functions taking an initial argument of |
107 | for multiple event loops, then all functions taking an initial argument of |
108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
108 | name C<loop> (which is always of type C<ev_loop *>) will not have |
109 | this argument. |
109 | this argument. |
110 | |
110 | |
111 | =head2 TIME REPRESENTATION |
111 | =head2 TIME REPRESENTATION |
112 | |
112 | |
113 | Libev represents time as a single floating point number, representing the |
113 | Libev represents time as a single floating point number, representing the |
… | |
… | |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
215 | recommended ones. |
215 | recommended ones. |
216 | |
216 | |
217 | See the description of C<ev_embed> watchers for more info. |
217 | See the description of C<ev_embed> watchers for more info. |
218 | |
218 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
220 | |
220 | |
221 | Sets the allocation function to use (the prototype is similar - the |
221 | Sets the allocation function to use (the prototype is similar - the |
222 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
222 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
223 | used to allocate and free memory (no surprises here). If it returns zero |
223 | used to allocate and free memory (no surprises here). If it returns zero |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
250 | } |
250 | } |
251 | |
251 | |
252 | ... |
252 | ... |
253 | ev_set_allocator (persistent_realloc); |
253 | ev_set_allocator (persistent_realloc); |
254 | |
254 | |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
256 | |
256 | |
257 | Set the callback function to call on a retryable system call error (such |
257 | Set the callback function to call on a retryable system call error (such |
258 | as failed select, poll, epoll_wait). The message is a printable string |
258 | as failed select, poll, epoll_wait). The message is a printable string |
259 | indicating the system call or subsystem causing the problem. If this |
259 | indicating the system call or subsystem causing the problem. If this |
260 | callback is set, then libev will expect it to remedy the situation, no |
260 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
276 | |
276 | |
277 | =back |
277 | =back |
278 | |
278 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
280 | |
280 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
281 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
282 | types of such loops, the I<default> loop, which supports signals and child |
282 | is I<not> optional in this case, as there is also an C<ev_loop> |
283 | events, and dynamically created loops which do not. |
283 | I<function>). |
|
|
284 | |
|
|
285 | The library knows two types of such loops, the I<default> loop, which |
|
|
286 | supports signals and child events, and dynamically created loops which do |
|
|
287 | not. |
284 | |
288 | |
285 | =over 4 |
289 | =over 4 |
286 | |
290 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
291 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
292 | |
… | |
… | |
685 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
689 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
686 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
690 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
687 | |
691 | |
688 | This "unloop state" will be cleared when entering C<ev_loop> again. |
692 | This "unloop state" will be cleared when entering C<ev_loop> again. |
689 | |
693 | |
|
|
694 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
695 | |
690 | =item ev_ref (loop) |
696 | =item ev_ref (loop) |
691 | |
697 | |
692 | =item ev_unref (loop) |
698 | =item ev_unref (loop) |
693 | |
699 | |
694 | Ref/unref can be used to add or remove a reference count on the event |
700 | Ref/unref can be used to add or remove a reference count on the event |
… | |
… | |
708 | respectively). |
714 | respectively). |
709 | |
715 | |
710 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
716 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
711 | running when nothing else is active. |
717 | running when nothing else is active. |
712 | |
718 | |
713 | struct ev_signal exitsig; |
719 | ev_signal exitsig; |
714 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
720 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
715 | ev_signal_start (loop, &exitsig); |
721 | ev_signal_start (loop, &exitsig); |
716 | evf_unref (loop); |
722 | evf_unref (loop); |
717 | |
723 | |
718 | Example: For some weird reason, unregister the above signal handler again. |
724 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
766 | they fire on, say, one-second boundaries only. |
772 | they fire on, say, one-second boundaries only. |
767 | |
773 | |
768 | =item ev_loop_verify (loop) |
774 | =item ev_loop_verify (loop) |
769 | |
775 | |
770 | This function only does something when C<EV_VERIFY> support has been |
776 | This function only does something when C<EV_VERIFY> support has been |
771 | compiled in. which is the default for non-minimal builds. It tries to go |
777 | compiled in, which is the default for non-minimal builds. It tries to go |
772 | through all internal structures and checks them for validity. If anything |
778 | through all internal structures and checks them for validity. If anything |
773 | is found to be inconsistent, it will print an error message to standard |
779 | is found to be inconsistent, it will print an error message to standard |
774 | error and call C<abort ()>. |
780 | error and call C<abort ()>. |
775 | |
781 | |
776 | This can be used to catch bugs inside libev itself: under normal |
782 | This can be used to catch bugs inside libev itself: under normal |
… | |
… | |
780 | =back |
786 | =back |
781 | |
787 | |
782 | |
788 | |
783 | =head1 ANATOMY OF A WATCHER |
789 | =head1 ANATOMY OF A WATCHER |
784 | |
790 | |
|
|
791 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
792 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
793 | watchers and C<ev_io_start> for I/O watchers. |
|
|
794 | |
785 | A watcher is a structure that you create and register to record your |
795 | A watcher is a structure that you create and register to record your |
786 | interest in some event. For instance, if you want to wait for STDIN to |
796 | interest in some event. For instance, if you want to wait for STDIN to |
787 | become readable, you would create an C<ev_io> watcher for that: |
797 | become readable, you would create an C<ev_io> watcher for that: |
788 | |
798 | |
789 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
799 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
790 | { |
800 | { |
791 | ev_io_stop (w); |
801 | ev_io_stop (w); |
792 | ev_unloop (loop, EVUNLOOP_ALL); |
802 | ev_unloop (loop, EVUNLOOP_ALL); |
793 | } |
803 | } |
794 | |
804 | |
795 | struct ev_loop *loop = ev_default_loop (0); |
805 | struct ev_loop *loop = ev_default_loop (0); |
|
|
806 | |
796 | struct ev_io stdin_watcher; |
807 | ev_io stdin_watcher; |
|
|
808 | |
797 | ev_init (&stdin_watcher, my_cb); |
809 | ev_init (&stdin_watcher, my_cb); |
798 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
810 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
799 | ev_io_start (loop, &stdin_watcher); |
811 | ev_io_start (loop, &stdin_watcher); |
|
|
812 | |
800 | ev_loop (loop, 0); |
813 | ev_loop (loop, 0); |
801 | |
814 | |
802 | As you can see, you are responsible for allocating the memory for your |
815 | As you can see, you are responsible for allocating the memory for your |
803 | watcher structures (and it is usually a bad idea to do this on the stack, |
816 | watcher structures (and it is I<usually> a bad idea to do this on the |
804 | although this can sometimes be quite valid). |
817 | stack). |
|
|
818 | |
|
|
819 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
820 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
805 | |
821 | |
806 | Each watcher structure must be initialised by a call to C<ev_init |
822 | Each watcher structure must be initialised by a call to C<ev_init |
807 | (watcher *, callback)>, which expects a callback to be provided. This |
823 | (watcher *, callback)>, which expects a callback to be provided. This |
808 | callback gets invoked each time the event occurs (or, in the case of I/O |
824 | callback gets invoked each time the event occurs (or, in the case of I/O |
809 | watchers, each time the event loop detects that the file descriptor given |
825 | watchers, each time the event loop detects that the file descriptor given |
810 | is readable and/or writable). |
826 | is readable and/or writable). |
811 | |
827 | |
812 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
828 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
813 | with arguments specific to this watcher type. There is also a macro |
829 | macro to configure it, with arguments specific to the watcher type. There |
814 | to combine initialisation and setting in one call: C<< ev_<type>_init |
830 | is also a macro to combine initialisation and setting in one call: C<< |
815 | (watcher *, callback, ...) >>. |
831 | ev_TYPE_init (watcher *, callback, ...) >>. |
816 | |
832 | |
817 | To make the watcher actually watch out for events, you have to start it |
833 | To make the watcher actually watch out for events, you have to start it |
818 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
834 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
819 | *) >>), and you can stop watching for events at any time by calling the |
835 | *) >>), and you can stop watching for events at any time by calling the |
820 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
836 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
821 | |
837 | |
822 | As long as your watcher is active (has been started but not stopped) you |
838 | As long as your watcher is active (has been started but not stopped) you |
823 | must not touch the values stored in it. Most specifically you must never |
839 | must not touch the values stored in it. Most specifically you must never |
824 | reinitialise it or call its C<set> macro. |
840 | reinitialise it or call its C<ev_TYPE_set> macro. |
825 | |
841 | |
826 | Each and every callback receives the event loop pointer as first, the |
842 | Each and every callback receives the event loop pointer as first, the |
827 | registered watcher structure as second, and a bitset of received events as |
843 | registered watcher structure as second, and a bitset of received events as |
828 | third argument. |
844 | third argument. |
829 | |
845 | |
… | |
… | |
892 | =item C<EV_ERROR> |
908 | =item C<EV_ERROR> |
893 | |
909 | |
894 | An unspecified error has occurred, the watcher has been stopped. This might |
910 | An unspecified error has occurred, the watcher has been stopped. This might |
895 | happen because the watcher could not be properly started because libev |
911 | happen because the watcher could not be properly started because libev |
896 | ran out of memory, a file descriptor was found to be closed or any other |
912 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
913 | problem. Libev considers these application bugs. |
|
|
914 | |
897 | problem. You best act on it by reporting the problem and somehow coping |
915 | You best act on it by reporting the problem and somehow coping with the |
898 | with the watcher being stopped. |
916 | watcher being stopped. Note that well-written programs should not receive |
|
|
917 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
918 | bug in your program. |
899 | |
919 | |
900 | Libev will usually signal a few "dummy" events together with an error, for |
920 | Libev will usually signal a few "dummy" events together with an error, for |
901 | example it might indicate that a fd is readable or writable, and if your |
921 | example it might indicate that a fd is readable or writable, and if your |
902 | callbacks is well-written it can just attempt the operation and cope with |
922 | callbacks is well-written it can just attempt the operation and cope with |
903 | the error from read() or write(). This will not work in multi-threaded |
923 | the error from read() or write(). This will not work in multi-threaded |
… | |
… | |
906 | |
926 | |
907 | =back |
927 | =back |
908 | |
928 | |
909 | =head2 GENERIC WATCHER FUNCTIONS |
929 | =head2 GENERIC WATCHER FUNCTIONS |
910 | |
930 | |
911 | In the following description, C<TYPE> stands for the watcher type, |
|
|
912 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
913 | |
|
|
914 | =over 4 |
931 | =over 4 |
915 | |
932 | |
916 | =item C<ev_init> (ev_TYPE *watcher, callback) |
933 | =item C<ev_init> (ev_TYPE *watcher, callback) |
917 | |
934 | |
918 | This macro initialises the generic portion of a watcher. The contents |
935 | This macro initialises the generic portion of a watcher. The contents |
… | |
… | |
923 | which rolls both calls into one. |
940 | which rolls both calls into one. |
924 | |
941 | |
925 | You can reinitialise a watcher at any time as long as it has been stopped |
942 | You can reinitialise a watcher at any time as long as it has been stopped |
926 | (or never started) and there are no pending events outstanding. |
943 | (or never started) and there are no pending events outstanding. |
927 | |
944 | |
928 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
945 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
929 | int revents)>. |
946 | int revents)>. |
930 | |
947 | |
931 | Example: Initialise an C<ev_io> watcher in two steps. |
948 | Example: Initialise an C<ev_io> watcher in two steps. |
932 | |
949 | |
933 | ev_io w; |
950 | ev_io w; |
… | |
… | |
967 | |
984 | |
968 | ev_io_start (EV_DEFAULT_UC, &w); |
985 | ev_io_start (EV_DEFAULT_UC, &w); |
969 | |
986 | |
970 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
987 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
971 | |
988 | |
972 | Stops the given watcher again (if active) and clears the pending |
989 | Stops the given watcher if active, and clears the pending status (whether |
|
|
990 | the watcher was active or not). |
|
|
991 | |
973 | status. It is possible that stopped watchers are pending (for example, |
992 | It is possible that stopped watchers are pending - for example, |
974 | non-repeating timers are being stopped when they become pending), but |
993 | non-repeating timers are being stopped when they become pending - but |
975 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
994 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
976 | you want to free or reuse the memory used by the watcher it is therefore a |
995 | pending. If you want to free or reuse the memory used by the watcher it is |
977 | good idea to always call its C<ev_TYPE_stop> function. |
996 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
978 | |
997 | |
979 | =item bool ev_is_active (ev_TYPE *watcher) |
998 | =item bool ev_is_active (ev_TYPE *watcher) |
980 | |
999 | |
981 | Returns a true value iff the watcher is active (i.e. it has been started |
1000 | Returns a true value iff the watcher is active (i.e. it has been started |
982 | and not yet been stopped). As long as a watcher is active you must not modify |
1001 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
1024 | The default priority used by watchers when no priority has been set is |
1043 | The default priority used by watchers when no priority has been set is |
1025 | always C<0>, which is supposed to not be too high and not be too low :). |
1044 | always C<0>, which is supposed to not be too high and not be too low :). |
1026 | |
1045 | |
1027 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1046 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1028 | fine, as long as you do not mind that the priority value you query might |
1047 | fine, as long as you do not mind that the priority value you query might |
1029 | or might not have been adjusted to be within valid range. |
1048 | or might not have been clamped to the valid range. |
1030 | |
1049 | |
1031 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1050 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1032 | |
1051 | |
1033 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1052 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1034 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1053 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1056 | member, you can also "subclass" the watcher type and provide your own |
1075 | member, you can also "subclass" the watcher type and provide your own |
1057 | data: |
1076 | data: |
1058 | |
1077 | |
1059 | struct my_io |
1078 | struct my_io |
1060 | { |
1079 | { |
1061 | struct ev_io io; |
1080 | ev_io io; |
1062 | int otherfd; |
1081 | int otherfd; |
1063 | void *somedata; |
1082 | void *somedata; |
1064 | struct whatever *mostinteresting; |
1083 | struct whatever *mostinteresting; |
1065 | }; |
1084 | }; |
1066 | |
1085 | |
… | |
… | |
1069 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1088 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1070 | |
1089 | |
1071 | And since your callback will be called with a pointer to the watcher, you |
1090 | And since your callback will be called with a pointer to the watcher, you |
1072 | can cast it back to your own type: |
1091 | can cast it back to your own type: |
1073 | |
1092 | |
1074 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1093 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1075 | { |
1094 | { |
1076 | struct my_io *w = (struct my_io *)w_; |
1095 | struct my_io *w = (struct my_io *)w_; |
1077 | ... |
1096 | ... |
1078 | } |
1097 | } |
1079 | |
1098 | |
… | |
… | |
1097 | programmers): |
1116 | programmers): |
1098 | |
1117 | |
1099 | #include <stddef.h> |
1118 | #include <stddef.h> |
1100 | |
1119 | |
1101 | static void |
1120 | static void |
1102 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1121 | t1_cb (EV_P_ ev_timer *w, int revents) |
1103 | { |
1122 | { |
1104 | struct my_biggy big = (struct my_biggy * |
1123 | struct my_biggy big = (struct my_biggy * |
1105 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1124 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1106 | } |
1125 | } |
1107 | |
1126 | |
1108 | static void |
1127 | static void |
1109 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1128 | t2_cb (EV_P_ ev_timer *w, int revents) |
1110 | { |
1129 | { |
1111 | struct my_biggy big = (struct my_biggy * |
1130 | struct my_biggy big = (struct my_biggy * |
1112 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1131 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1113 | } |
1132 | } |
1114 | |
1133 | |
… | |
… | |
1249 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1268 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1250 | readable, but only once. Since it is likely line-buffered, you could |
1269 | readable, but only once. Since it is likely line-buffered, you could |
1251 | attempt to read a whole line in the callback. |
1270 | attempt to read a whole line in the callback. |
1252 | |
1271 | |
1253 | static void |
1272 | static void |
1254 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1273 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1255 | { |
1274 | { |
1256 | ev_io_stop (loop, w); |
1275 | ev_io_stop (loop, w); |
1257 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1276 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1258 | } |
1277 | } |
1259 | |
1278 | |
1260 | ... |
1279 | ... |
1261 | struct ev_loop *loop = ev_default_init (0); |
1280 | struct ev_loop *loop = ev_default_init (0); |
1262 | struct ev_io stdin_readable; |
1281 | ev_io stdin_readable; |
1263 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1282 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1264 | ev_io_start (loop, &stdin_readable); |
1283 | ev_io_start (loop, &stdin_readable); |
1265 | ev_loop (loop, 0); |
1284 | ev_loop (loop, 0); |
1266 | |
1285 | |
1267 | |
1286 | |
… | |
… | |
1278 | |
1297 | |
1279 | The callback is guaranteed to be invoked only I<after> its timeout has |
1298 | The callback is guaranteed to be invoked only I<after> its timeout has |
1280 | passed, but if multiple timers become ready during the same loop iteration |
1299 | passed, but if multiple timers become ready during the same loop iteration |
1281 | then order of execution is undefined. |
1300 | then order of execution is undefined. |
1282 | |
1301 | |
|
|
1302 | =head3 Be smart about timeouts |
|
|
1303 | |
|
|
1304 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1305 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1306 | you want to raise some error after a while. |
|
|
1307 | |
|
|
1308 | What follows are some ways to handle this problem, from obvious and |
|
|
1309 | inefficient to smart and efficient. |
|
|
1310 | |
|
|
1311 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1312 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1313 | data or other life sign was received). |
|
|
1314 | |
|
|
1315 | =over 4 |
|
|
1316 | |
|
|
1317 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1318 | |
|
|
1319 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1320 | start the watcher: |
|
|
1321 | |
|
|
1322 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1323 | ev_timer_start (loop, timer); |
|
|
1324 | |
|
|
1325 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1326 | and start it again: |
|
|
1327 | |
|
|
1328 | ev_timer_stop (loop, timer); |
|
|
1329 | ev_timer_set (timer, 60., 0.); |
|
|
1330 | ev_timer_start (loop, timer); |
|
|
1331 | |
|
|
1332 | This is relatively simple to implement, but means that each time there is |
|
|
1333 | some activity, libev will first have to remove the timer from its internal |
|
|
1334 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1335 | still not a constant-time operation. |
|
|
1336 | |
|
|
1337 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1338 | |
|
|
1339 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1340 | C<ev_timer_start>. |
|
|
1341 | |
|
|
1342 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1343 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1344 | successfully read or write some data. If you go into an idle state where |
|
|
1345 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1346 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1347 | |
|
|
1348 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1349 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1350 | member and C<ev_timer_again>. |
|
|
1351 | |
|
|
1352 | At start: |
|
|
1353 | |
|
|
1354 | ev_timer_init (timer, callback); |
|
|
1355 | timer->repeat = 60.; |
|
|
1356 | ev_timer_again (loop, timer); |
|
|
1357 | |
|
|
1358 | Each time there is some activity: |
|
|
1359 | |
|
|
1360 | ev_timer_again (loop, timer); |
|
|
1361 | |
|
|
1362 | It is even possible to change the time-out on the fly, regardless of |
|
|
1363 | whether the watcher is active or not: |
|
|
1364 | |
|
|
1365 | timer->repeat = 30.; |
|
|
1366 | ev_timer_again (loop, timer); |
|
|
1367 | |
|
|
1368 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1369 | you want to modify its timeout value, as libev does not have to completely |
|
|
1370 | remove and re-insert the timer from/into its internal data structure. |
|
|
1371 | |
|
|
1372 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1373 | |
|
|
1374 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1375 | |
|
|
1376 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1377 | relatively long compared to the intervals between other activity - in |
|
|
1378 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1379 | associated activity resets. |
|
|
1380 | |
|
|
1381 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1382 | but remember the time of last activity, and check for a real timeout only |
|
|
1383 | within the callback: |
|
|
1384 | |
|
|
1385 | ev_tstamp last_activity; // time of last activity |
|
|
1386 | |
|
|
1387 | static void |
|
|
1388 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1389 | { |
|
|
1390 | ev_tstamp now = ev_now (EV_A); |
|
|
1391 | ev_tstamp timeout = last_activity + 60.; |
|
|
1392 | |
|
|
1393 | // if last_activity + 60. is older than now, we did time out |
|
|
1394 | if (timeout < now) |
|
|
1395 | { |
|
|
1396 | // timeout occured, take action |
|
|
1397 | } |
|
|
1398 | else |
|
|
1399 | { |
|
|
1400 | // callback was invoked, but there was some activity, re-arm |
|
|
1401 | // the watcher to fire in last_activity + 60, which is |
|
|
1402 | // guaranteed to be in the future, so "again" is positive: |
|
|
1403 | w->again = timeout - now; |
|
|
1404 | ev_timer_again (EV_A_ w); |
|
|
1405 | } |
|
|
1406 | } |
|
|
1407 | |
|
|
1408 | To summarise the callback: first calculate the real timeout (defined |
|
|
1409 | as "60 seconds after the last activity"), then check if that time has |
|
|
1410 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1411 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1412 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1413 | a timeout then. |
|
|
1414 | |
|
|
1415 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1416 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1417 | |
|
|
1418 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1419 | minus half the average time between activity), but virtually no calls to |
|
|
1420 | libev to change the timeout. |
|
|
1421 | |
|
|
1422 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1423 | to the current time (meaning we just have some activity :), then call the |
|
|
1424 | callback, which will "do the right thing" and start the timer: |
|
|
1425 | |
|
|
1426 | ev_timer_init (timer, callback); |
|
|
1427 | last_activity = ev_now (loop); |
|
|
1428 | callback (loop, timer, EV_TIMEOUT); |
|
|
1429 | |
|
|
1430 | And when there is some activity, simply store the current time in |
|
|
1431 | C<last_activity>, no libev calls at all: |
|
|
1432 | |
|
|
1433 | last_actiivty = ev_now (loop); |
|
|
1434 | |
|
|
1435 | This technique is slightly more complex, but in most cases where the |
|
|
1436 | time-out is unlikely to be triggered, much more efficient. |
|
|
1437 | |
|
|
1438 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1439 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1440 | fix things for you. |
|
|
1441 | |
|
|
1442 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1443 | |
|
|
1444 | If there is not one request, but many thousands (millions...), all |
|
|
1445 | employing some kind of timeout with the same timeout value, then one can |
|
|
1446 | do even better: |
|
|
1447 | |
|
|
1448 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1449 | at the I<end> of the list. |
|
|
1450 | |
|
|
1451 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1452 | the list is expected to fire (for example, using the technique #3). |
|
|
1453 | |
|
|
1454 | When there is some activity, remove the timer from the list, recalculate |
|
|
1455 | the timeout, append it to the end of the list again, and make sure to |
|
|
1456 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1457 | |
|
|
1458 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1459 | starting, stopping and updating the timers, at the expense of a major |
|
|
1460 | complication, and having to use a constant timeout. The constant timeout |
|
|
1461 | ensures that the list stays sorted. |
|
|
1462 | |
|
|
1463 | =back |
|
|
1464 | |
|
|
1465 | So which method the best? |
|
|
1466 | |
|
|
1467 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1468 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1469 | better, and isn't very complicated either. In most case, choosing either |
|
|
1470 | one is fine, with #3 being better in typical situations. |
|
|
1471 | |
|
|
1472 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1473 | rather complicated, but extremely efficient, something that really pays |
|
|
1474 | off after the first million or so of active timers, i.e. it's usually |
|
|
1475 | overkill :) |
|
|
1476 | |
1283 | =head3 The special problem of time updates |
1477 | =head3 The special problem of time updates |
1284 | |
1478 | |
1285 | Establishing the current time is a costly operation (it usually takes at |
1479 | Establishing the current time is a costly operation (it usually takes at |
1286 | least two system calls): EV therefore updates its idea of the current |
1480 | least two system calls): EV therefore updates its idea of the current |
1287 | time only before and after C<ev_loop> collects new events, which causes a |
1481 | time only before and after C<ev_loop> collects new events, which causes a |
… | |
… | |
1330 | If the timer is started but non-repeating, stop it (as if it timed out). |
1524 | If the timer is started but non-repeating, stop it (as if it timed out). |
1331 | |
1525 | |
1332 | If the timer is repeating, either start it if necessary (with the |
1526 | If the timer is repeating, either start it if necessary (with the |
1333 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1527 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1334 | |
1528 | |
1335 | This sounds a bit complicated, but here is a useful and typical |
1529 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1336 | example: Imagine you have a TCP connection and you want a so-called idle |
1530 | usage example. |
1337 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1338 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1339 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1340 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1341 | you go into an idle state where you do not expect data to travel on the |
|
|
1342 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1343 | automatically restart it if need be. |
|
|
1344 | |
|
|
1345 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1346 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1347 | |
|
|
1348 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1349 | ev_timer_again (loop, timer); |
|
|
1350 | ... |
|
|
1351 | timer->again = 17.; |
|
|
1352 | ev_timer_again (loop, timer); |
|
|
1353 | ... |
|
|
1354 | timer->again = 10.; |
|
|
1355 | ev_timer_again (loop, timer); |
|
|
1356 | |
|
|
1357 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1358 | you want to modify its timeout value. |
|
|
1359 | |
|
|
1360 | Note, however, that it is often even more efficient to remember the |
|
|
1361 | time of the last activity and let the timer time-out naturally. In the |
|
|
1362 | callback, you then check whether the time-out is real, or, if there was |
|
|
1363 | some activity, you reschedule the watcher to time-out in "last_activity + |
|
|
1364 | timeout - ev_now ()" seconds. |
|
|
1365 | |
1531 | |
1366 | =item ev_tstamp repeat [read-write] |
1532 | =item ev_tstamp repeat [read-write] |
1367 | |
1533 | |
1368 | The current C<repeat> value. Will be used each time the watcher times out |
1534 | The current C<repeat> value. Will be used each time the watcher times out |
1369 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1535 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1374 | =head3 Examples |
1540 | =head3 Examples |
1375 | |
1541 | |
1376 | Example: Create a timer that fires after 60 seconds. |
1542 | Example: Create a timer that fires after 60 seconds. |
1377 | |
1543 | |
1378 | static void |
1544 | static void |
1379 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1545 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1380 | { |
1546 | { |
1381 | .. one minute over, w is actually stopped right here |
1547 | .. one minute over, w is actually stopped right here |
1382 | } |
1548 | } |
1383 | |
1549 | |
1384 | struct ev_timer mytimer; |
1550 | ev_timer mytimer; |
1385 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1551 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1386 | ev_timer_start (loop, &mytimer); |
1552 | ev_timer_start (loop, &mytimer); |
1387 | |
1553 | |
1388 | Example: Create a timeout timer that times out after 10 seconds of |
1554 | Example: Create a timeout timer that times out after 10 seconds of |
1389 | inactivity. |
1555 | inactivity. |
1390 | |
1556 | |
1391 | static void |
1557 | static void |
1392 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1558 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1393 | { |
1559 | { |
1394 | .. ten seconds without any activity |
1560 | .. ten seconds without any activity |
1395 | } |
1561 | } |
1396 | |
1562 | |
1397 | struct ev_timer mytimer; |
1563 | ev_timer mytimer; |
1398 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1564 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1399 | ev_timer_again (&mytimer); /* start timer */ |
1565 | ev_timer_again (&mytimer); /* start timer */ |
1400 | ev_loop (loop, 0); |
1566 | ev_loop (loop, 0); |
1401 | |
1567 | |
1402 | // and in some piece of code that gets executed on any "activity": |
1568 | // and in some piece of code that gets executed on any "activity": |
… | |
… | |
1488 | |
1654 | |
1489 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1655 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1490 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1656 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1491 | only event loop modification you are allowed to do). |
1657 | only event loop modification you are allowed to do). |
1492 | |
1658 | |
1493 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1659 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1494 | *w, ev_tstamp now)>, e.g.: |
1660 | *w, ev_tstamp now)>, e.g.: |
1495 | |
1661 | |
|
|
1662 | static ev_tstamp |
1496 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1663 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1497 | { |
1664 | { |
1498 | return now + 60.; |
1665 | return now + 60.; |
1499 | } |
1666 | } |
1500 | |
1667 | |
1501 | It must return the next time to trigger, based on the passed time value |
1668 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1538 | |
1705 | |
1539 | The current interval value. Can be modified any time, but changes only |
1706 | The current interval value. Can be modified any time, but changes only |
1540 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1707 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1541 | called. |
1708 | called. |
1542 | |
1709 | |
1543 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1710 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1544 | |
1711 | |
1545 | The current reschedule callback, or C<0>, if this functionality is |
1712 | The current reschedule callback, or C<0>, if this functionality is |
1546 | switched off. Can be changed any time, but changes only take effect when |
1713 | switched off. Can be changed any time, but changes only take effect when |
1547 | the periodic timer fires or C<ev_periodic_again> is being called. |
1714 | the periodic timer fires or C<ev_periodic_again> is being called. |
1548 | |
1715 | |
… | |
… | |
1553 | Example: Call a callback every hour, or, more precisely, whenever the |
1720 | Example: Call a callback every hour, or, more precisely, whenever the |
1554 | system time is divisible by 3600. The callback invocation times have |
1721 | system time is divisible by 3600. The callback invocation times have |
1555 | potentially a lot of jitter, but good long-term stability. |
1722 | potentially a lot of jitter, but good long-term stability. |
1556 | |
1723 | |
1557 | static void |
1724 | static void |
1558 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1725 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1559 | { |
1726 | { |
1560 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1727 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1561 | } |
1728 | } |
1562 | |
1729 | |
1563 | struct ev_periodic hourly_tick; |
1730 | ev_periodic hourly_tick; |
1564 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1731 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1565 | ev_periodic_start (loop, &hourly_tick); |
1732 | ev_periodic_start (loop, &hourly_tick); |
1566 | |
1733 | |
1567 | Example: The same as above, but use a reschedule callback to do it: |
1734 | Example: The same as above, but use a reschedule callback to do it: |
1568 | |
1735 | |
1569 | #include <math.h> |
1736 | #include <math.h> |
1570 | |
1737 | |
1571 | static ev_tstamp |
1738 | static ev_tstamp |
1572 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1739 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1573 | { |
1740 | { |
1574 | return now + (3600. - fmod (now, 3600.)); |
1741 | return now + (3600. - fmod (now, 3600.)); |
1575 | } |
1742 | } |
1576 | |
1743 | |
1577 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1744 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1578 | |
1745 | |
1579 | Example: Call a callback every hour, starting now: |
1746 | Example: Call a callback every hour, starting now: |
1580 | |
1747 | |
1581 | struct ev_periodic hourly_tick; |
1748 | ev_periodic hourly_tick; |
1582 | ev_periodic_init (&hourly_tick, clock_cb, |
1749 | ev_periodic_init (&hourly_tick, clock_cb, |
1583 | fmod (ev_now (loop), 3600.), 3600., 0); |
1750 | fmod (ev_now (loop), 3600.), 3600., 0); |
1584 | ev_periodic_start (loop, &hourly_tick); |
1751 | ev_periodic_start (loop, &hourly_tick); |
1585 | |
1752 | |
1586 | |
1753 | |
… | |
… | |
1625 | |
1792 | |
1626 | =back |
1793 | =back |
1627 | |
1794 | |
1628 | =head3 Examples |
1795 | =head3 Examples |
1629 | |
1796 | |
1630 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
1797 | Example: Try to exit cleanly on SIGINT. |
1631 | |
1798 | |
1632 | static void |
1799 | static void |
1633 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1800 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1634 | { |
1801 | { |
1635 | ev_unloop (loop, EVUNLOOP_ALL); |
1802 | ev_unloop (loop, EVUNLOOP_ALL); |
1636 | } |
1803 | } |
1637 | |
1804 | |
1638 | struct ev_signal signal_watcher; |
1805 | ev_signal signal_watcher; |
1639 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1806 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1640 | ev_signal_start (loop, &sigint_cb); |
1807 | ev_signal_start (loop, &signal_watcher); |
1641 | |
1808 | |
1642 | |
1809 | |
1643 | =head2 C<ev_child> - watch out for process status changes |
1810 | =head2 C<ev_child> - watch out for process status changes |
1644 | |
1811 | |
1645 | Child watchers trigger when your process receives a SIGCHLD in response to |
1812 | Child watchers trigger when your process receives a SIGCHLD in response to |
… | |
… | |
1718 | its completion. |
1885 | its completion. |
1719 | |
1886 | |
1720 | ev_child cw; |
1887 | ev_child cw; |
1721 | |
1888 | |
1722 | static void |
1889 | static void |
1723 | child_cb (EV_P_ struct ev_child *w, int revents) |
1890 | child_cb (EV_P_ ev_child *w, int revents) |
1724 | { |
1891 | { |
1725 | ev_child_stop (EV_A_ w); |
1892 | ev_child_stop (EV_A_ w); |
1726 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1893 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1727 | } |
1894 | } |
1728 | |
1895 | |
… | |
… | |
1792 | to exchange stat structures with application programs compiled using the |
1959 | to exchange stat structures with application programs compiled using the |
1793 | default compilation environment. |
1960 | default compilation environment. |
1794 | |
1961 | |
1795 | =head3 Inotify and Kqueue |
1962 | =head3 Inotify and Kqueue |
1796 | |
1963 | |
1797 | When C<inotify (7)> support has been compiled into libev (generally only |
1964 | When C<inotify (7)> support has been compiled into libev (generally |
|
|
1965 | only available with Linux 2.6.25 or above due to bugs in earlier |
1798 | available with Linux) and present at runtime, it will be used to speed up |
1966 | implementations) and present at runtime, it will be used to speed up |
1799 | change detection where possible. The inotify descriptor will be created lazily |
1967 | change detection where possible. The inotify descriptor will be created |
1800 | when the first C<ev_stat> watcher is being started. |
1968 | lazily when the first C<ev_stat> watcher is being started. |
1801 | |
1969 | |
1802 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1970 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1803 | except that changes might be detected earlier, and in some cases, to avoid |
1971 | except that changes might be detected earlier, and in some cases, to avoid |
1804 | making regular C<stat> calls. Even in the presence of inotify support |
1972 | making regular C<stat> calls. Even in the presence of inotify support |
1805 | there are many cases where libev has to resort to regular C<stat> polling, |
1973 | there are many cases where libev has to resort to regular C<stat> polling, |
… | |
… | |
1979 | |
2147 | |
1980 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2148 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1981 | callback, free it. Also, use no error checking, as usual. |
2149 | callback, free it. Also, use no error checking, as usual. |
1982 | |
2150 | |
1983 | static void |
2151 | static void |
1984 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2152 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1985 | { |
2153 | { |
1986 | free (w); |
2154 | free (w); |
1987 | // now do something you wanted to do when the program has |
2155 | // now do something you wanted to do when the program has |
1988 | // no longer anything immediate to do. |
2156 | // no longer anything immediate to do. |
1989 | } |
2157 | } |
1990 | |
2158 | |
1991 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2159 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1992 | ev_idle_init (idle_watcher, idle_cb); |
2160 | ev_idle_init (idle_watcher, idle_cb); |
1993 | ev_idle_start (loop, idle_cb); |
2161 | ev_idle_start (loop, idle_cb); |
1994 | |
2162 | |
1995 | |
2163 | |
1996 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2164 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
… | |
… | |
2077 | |
2245 | |
2078 | static ev_io iow [nfd]; |
2246 | static ev_io iow [nfd]; |
2079 | static ev_timer tw; |
2247 | static ev_timer tw; |
2080 | |
2248 | |
2081 | static void |
2249 | static void |
2082 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2250 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2083 | { |
2251 | { |
2084 | } |
2252 | } |
2085 | |
2253 | |
2086 | // create io watchers for each fd and a timer before blocking |
2254 | // create io watchers for each fd and a timer before blocking |
2087 | static void |
2255 | static void |
2088 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2256 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2089 | { |
2257 | { |
2090 | int timeout = 3600000; |
2258 | int timeout = 3600000; |
2091 | struct pollfd fds [nfd]; |
2259 | struct pollfd fds [nfd]; |
2092 | // actual code will need to loop here and realloc etc. |
2260 | // actual code will need to loop here and realloc etc. |
2093 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2261 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
… | |
… | |
2108 | } |
2276 | } |
2109 | } |
2277 | } |
2110 | |
2278 | |
2111 | // stop all watchers after blocking |
2279 | // stop all watchers after blocking |
2112 | static void |
2280 | static void |
2113 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2281 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2114 | { |
2282 | { |
2115 | ev_timer_stop (loop, &tw); |
2283 | ev_timer_stop (loop, &tw); |
2116 | |
2284 | |
2117 | for (int i = 0; i < nfd; ++i) |
2285 | for (int i = 0; i < nfd; ++i) |
2118 | { |
2286 | { |
… | |
… | |
2242 | So when you want to use this feature you will always have to be prepared |
2410 | So when you want to use this feature you will always have to be prepared |
2243 | that you cannot get an embeddable loop. The recommended way to get around |
2411 | that you cannot get an embeddable loop. The recommended way to get around |
2244 | this is to have a separate variables for your embeddable loop, try to |
2412 | this is to have a separate variables for your embeddable loop, try to |
2245 | create it, and if that fails, use the normal loop for everything. |
2413 | create it, and if that fails, use the normal loop for everything. |
2246 | |
2414 | |
|
|
2415 | =head3 C<ev_embed> and fork |
|
|
2416 | |
|
|
2417 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2418 | automatically be applied to the embedded loop as well, so no special |
|
|
2419 | fork handling is required in that case. When the watcher is not running, |
|
|
2420 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2421 | as applicable. |
|
|
2422 | |
2247 | =head3 Watcher-Specific Functions and Data Members |
2423 | =head3 Watcher-Specific Functions and Data Members |
2248 | |
2424 | |
2249 | =over 4 |
2425 | =over 4 |
2250 | |
2426 | |
2251 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2427 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
… | |
… | |
2278 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2454 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2279 | used). |
2455 | used). |
2280 | |
2456 | |
2281 | struct ev_loop *loop_hi = ev_default_init (0); |
2457 | struct ev_loop *loop_hi = ev_default_init (0); |
2282 | struct ev_loop *loop_lo = 0; |
2458 | struct ev_loop *loop_lo = 0; |
2283 | struct ev_embed embed; |
2459 | ev_embed embed; |
2284 | |
2460 | |
2285 | // see if there is a chance of getting one that works |
2461 | // see if there is a chance of getting one that works |
2286 | // (remember that a flags value of 0 means autodetection) |
2462 | // (remember that a flags value of 0 means autodetection) |
2287 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2463 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2288 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2464 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2302 | kqueue implementation). Store the kqueue/socket-only event loop in |
2478 | kqueue implementation). Store the kqueue/socket-only event loop in |
2303 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2479 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2304 | |
2480 | |
2305 | struct ev_loop *loop = ev_default_init (0); |
2481 | struct ev_loop *loop = ev_default_init (0); |
2306 | struct ev_loop *loop_socket = 0; |
2482 | struct ev_loop *loop_socket = 0; |
2307 | struct ev_embed embed; |
2483 | ev_embed embed; |
2308 | |
2484 | |
2309 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2485 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2310 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2486 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2311 | { |
2487 | { |
2312 | ev_embed_init (&embed, 0, loop_socket); |
2488 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2376 | =over 4 |
2552 | =over 4 |
2377 | |
2553 | |
2378 | =item queueing from a signal handler context |
2554 | =item queueing from a signal handler context |
2379 | |
2555 | |
2380 | To implement race-free queueing, you simply add to the queue in the signal |
2556 | To implement race-free queueing, you simply add to the queue in the signal |
2381 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
2557 | handler but you block the signal handler in the watcher callback. Here is |
2382 | some fictitious SIGUSR1 handler: |
2558 | an example that does that for some fictitious SIGUSR1 handler: |
2383 | |
2559 | |
2384 | static ev_async mysig; |
2560 | static ev_async mysig; |
2385 | |
2561 | |
2386 | static void |
2562 | static void |
2387 | sigusr1_handler (void) |
2563 | sigusr1_handler (void) |
… | |
… | |
2494 | =over 4 |
2670 | =over 4 |
2495 | |
2671 | |
2496 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2672 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2497 | |
2673 | |
2498 | This function combines a simple timer and an I/O watcher, calls your |
2674 | This function combines a simple timer and an I/O watcher, calls your |
2499 | callback on whichever event happens first and automatically stop both |
2675 | callback on whichever event happens first and automatically stops both |
2500 | watchers. This is useful if you want to wait for a single event on an fd |
2676 | watchers. This is useful if you want to wait for a single event on an fd |
2501 | or timeout without having to allocate/configure/start/stop/free one or |
2677 | or timeout without having to allocate/configure/start/stop/free one or |
2502 | more watchers yourself. |
2678 | more watchers yourself. |
2503 | |
2679 | |
2504 | If C<fd> is less than 0, then no I/O watcher will be started and events |
2680 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2505 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
2681 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2506 | C<events> set will be created and started. |
2682 | the given C<fd> and C<events> set will be created and started. |
2507 | |
2683 | |
2508 | If C<timeout> is less than 0, then no timeout watcher will be |
2684 | If C<timeout> is less than 0, then no timeout watcher will be |
2509 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2685 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2510 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
2686 | repeat = 0) will be started. C<0> is a valid timeout. |
2511 | dubious value. |
|
|
2512 | |
2687 | |
2513 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2688 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2514 | passed an C<revents> set like normal event callbacks (a combination of |
2689 | passed an C<revents> set like normal event callbacks (a combination of |
2515 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2690 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2516 | value passed to C<ev_once>: |
2691 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
2692 | a timeout and an io event at the same time - you probably should give io |
|
|
2693 | events precedence. |
|
|
2694 | |
|
|
2695 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2517 | |
2696 | |
2518 | static void stdin_ready (int revents, void *arg) |
2697 | static void stdin_ready (int revents, void *arg) |
2519 | { |
2698 | { |
|
|
2699 | if (revents & EV_READ) |
|
|
2700 | /* stdin might have data for us, joy! */; |
2520 | if (revents & EV_TIMEOUT) |
2701 | else if (revents & EV_TIMEOUT) |
2521 | /* doh, nothing entered */; |
2702 | /* doh, nothing entered */; |
2522 | else if (revents & EV_READ) |
|
|
2523 | /* stdin might have data for us, joy! */; |
|
|
2524 | } |
2703 | } |
2525 | |
2704 | |
2526 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2705 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2527 | |
2706 | |
2528 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
2707 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
2529 | |
2708 | |
2530 | Feeds the given event set into the event loop, as if the specified event |
2709 | Feeds the given event set into the event loop, as if the specified event |
2531 | had happened for the specified watcher (which must be a pointer to an |
2710 | had happened for the specified watcher (which must be a pointer to an |
2532 | initialised but not necessarily started event watcher). |
2711 | initialised but not necessarily started event watcher). |
2533 | |
2712 | |
2534 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
2713 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
2535 | |
2714 | |
2536 | Feed an event on the given fd, as if a file descriptor backend detected |
2715 | Feed an event on the given fd, as if a file descriptor backend detected |
2537 | the given events it. |
2716 | the given events it. |
2538 | |
2717 | |
2539 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
2718 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
2540 | |
2719 | |
2541 | Feed an event as if the given signal occurred (C<loop> must be the default |
2720 | Feed an event as if the given signal occurred (C<loop> must be the default |
2542 | loop!). |
2721 | loop!). |
2543 | |
2722 | |
2544 | =back |
2723 | =back |
… | |
… | |
2778 | |
2957 | |
2779 | =item D |
2958 | =item D |
2780 | |
2959 | |
2781 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2960 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2782 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
2961 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
2962 | |
|
|
2963 | =item Ocaml |
|
|
2964 | |
|
|
2965 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
2966 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
2783 | |
2967 | |
2784 | =back |
2968 | =back |
2785 | |
2969 | |
2786 | |
2970 | |
2787 | =head1 MACRO MAGIC |
2971 | =head1 MACRO MAGIC |
… | |
… | |
3241 | definition and a statement, respectively. See the F<ev.h> header file for |
3425 | definition and a statement, respectively. See the F<ev.h> header file for |
3242 | their default definitions. One possible use for overriding these is to |
3426 | their default definitions. One possible use for overriding these is to |
3243 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3427 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3244 | method calls instead of plain function calls in C++. |
3428 | method calls instead of plain function calls in C++. |
3245 | |
3429 | |
|
|
3430 | =back |
|
|
3431 | |
3246 | =head2 EXPORTED API SYMBOLS |
3432 | =head2 EXPORTED API SYMBOLS |
3247 | |
3433 | |
3248 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3434 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3249 | exported symbols, you can use the provided F<Symbol.*> files which list |
3435 | exported symbols, you can use the provided F<Symbol.*> files which list |
3250 | all public symbols, one per line: |
3436 | all public symbols, one per line: |
… | |
… | |
3296 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3482 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3297 | |
3483 | |
3298 | #include "ev_cpp.h" |
3484 | #include "ev_cpp.h" |
3299 | #include "ev.c" |
3485 | #include "ev.c" |
3300 | |
3486 | |
|
|
3487 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3301 | |
3488 | |
3302 | =head1 THREADS AND COROUTINES |
3489 | =head2 THREADS AND COROUTINES |
3303 | |
3490 | |
3304 | =head2 THREADS |
3491 | =head3 THREADS |
3305 | |
3492 | |
3306 | Libev itself is thread-safe (unless the opposite is specifically |
3493 | All libev functions are reentrant and thread-safe unless explicitly |
3307 | documented for a function), but it uses no locking itself. This means that |
3494 | documented otherwise, but libev implements no locking itself. This means |
3308 | you can use as many loops as you want in parallel, as long as only one |
3495 | that you can use as many loops as you want in parallel, as long as there |
3309 | thread ever calls into one libev function with the same loop parameter: |
3496 | are no concurrent calls into any libev function with the same loop |
|
|
3497 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
3310 | libev guarantees that different event loops share no data structures that |
3498 | of course): libev guarantees that different event loops share no data |
3311 | need locking. |
3499 | structures that need any locking. |
3312 | |
3500 | |
3313 | Or to put it differently: calls with different loop parameters can be done |
3501 | Or to put it differently: calls with different loop parameters can be done |
3314 | concurrently from multiple threads, calls with the same loop parameter |
3502 | concurrently from multiple threads, calls with the same loop parameter |
3315 | must be done serially (but can be done from different threads, as long as |
3503 | must be done serially (but can be done from different threads, as long as |
3316 | only one thread ever is inside a call at any point in time, e.g. by using |
3504 | only one thread ever is inside a call at any point in time, e.g. by using |
3317 | a mutex per loop). |
3505 | a mutex per loop). |
3318 | |
3506 | |
3319 | Specifically to support threads (and signal handlers), libev implements |
3507 | Specifically to support threads (and signal handlers), libev implements |
3320 | so-called C<ev_async> watchers, which allow some limited form of |
3508 | so-called C<ev_async> watchers, which allow some limited form of |
3321 | concurrency on the same event loop. |
3509 | concurrency on the same event loop, namely waking it up "from the |
|
|
3510 | outside". |
3322 | |
3511 | |
3323 | If you want to know which design (one loop, locking, or multiple loops |
3512 | If you want to know which design (one loop, locking, or multiple loops |
3324 | without or something else still) is best for your problem, then I cannot |
3513 | without or something else still) is best for your problem, then I cannot |
3325 | help you. I can give some generic advice however: |
3514 | help you, but here is some generic advice: |
3326 | |
3515 | |
3327 | =over 4 |
3516 | =over 4 |
3328 | |
3517 | |
3329 | =item * most applications have a main thread: use the default libev loop |
3518 | =item * most applications have a main thread: use the default libev loop |
3330 | in that thread, or create a separate thread running only the default loop. |
3519 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3354 | default loop and triggering an C<ev_async> watcher from the default loop |
3543 | default loop and triggering an C<ev_async> watcher from the default loop |
3355 | watcher callback into the event loop interested in the signal. |
3544 | watcher callback into the event loop interested in the signal. |
3356 | |
3545 | |
3357 | =back |
3546 | =back |
3358 | |
3547 | |
3359 | =head2 COROUTINES |
3548 | =head3 COROUTINES |
3360 | |
3549 | |
3361 | Libev is much more accommodating to coroutines ("cooperative threads"): |
3550 | Libev is very accommodating to coroutines ("cooperative threads"): |
3362 | libev fully supports nesting calls to it's functions from different |
3551 | libev fully supports nesting calls to its functions from different |
3363 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3552 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3364 | different coroutines and switch freely between both coroutines running the |
3553 | different coroutines, and switch freely between both coroutines running the |
3365 | loop, as long as you don't confuse yourself). The only exception is that |
3554 | loop, as long as you don't confuse yourself). The only exception is that |
3366 | you must not do this from C<ev_periodic> reschedule callbacks. |
3555 | you must not do this from C<ev_periodic> reschedule callbacks. |
3367 | |
3556 | |
3368 | Care has been taken to ensure that libev does not keep local state inside |
3557 | Care has been taken to ensure that libev does not keep local state inside |
3369 | C<ev_loop>, and other calls do not usually allow coroutine switches. |
3558 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
|
|
3559 | they do not clal any callbacks. |
3370 | |
3560 | |
|
|
3561 | =head2 COMPILER WARNINGS |
3371 | |
3562 | |
3372 | =head1 COMPLEXITIES |
3563 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3564 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3565 | scared by this. |
3373 | |
3566 | |
3374 | In this section the complexities of (many of) the algorithms used inside |
3567 | However, these are unavoidable for many reasons. For one, each compiler |
3375 | libev will be explained. For complexity discussions about backends see the |
3568 | has different warnings, and each user has different tastes regarding |
3376 | documentation for C<ev_default_init>. |
3569 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3570 | targeting a specific compiler and compiler-version. |
3377 | |
3571 | |
3378 | All of the following are about amortised time: If an array needs to be |
3572 | Another reason is that some compiler warnings require elaborate |
3379 | extended, libev needs to realloc and move the whole array, but this |
3573 | workarounds, or other changes to the code that make it less clear and less |
3380 | happens asymptotically never with higher number of elements, so O(1) might |
3574 | maintainable. |
3381 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3382 | it is much faster and asymptotically approaches constant time. |
|
|
3383 | |
3575 | |
3384 | =over 4 |
3576 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3577 | wrong (because they don't actually warn about the condition their message |
|
|
3578 | seems to warn about). For example, certain older gcc versions had some |
|
|
3579 | warnings that resulted an extreme number of false positives. These have |
|
|
3580 | been fixed, but some people still insist on making code warn-free with |
|
|
3581 | such buggy versions. |
3385 | |
3582 | |
3386 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3583 | While libev is written to generate as few warnings as possible, |
|
|
3584 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3585 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3586 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3587 | warnings, not errors, or proof of bugs. |
3387 | |
3588 | |
3388 | This means that, when you have a watcher that triggers in one hour and |
|
|
3389 | there are 100 watchers that would trigger before that then inserting will |
|
|
3390 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3391 | |
3589 | |
3392 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3590 | =head2 VALGRIND |
3393 | |
3591 | |
3394 | That means that changing a timer costs less than removing/adding them |
3592 | Valgrind has a special section here because it is a popular tool that is |
3395 | as only the relative motion in the event queue has to be paid for. |
3593 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3396 | |
3594 | |
3397 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3595 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3596 | in libev, then check twice: If valgrind reports something like: |
3398 | |
3597 | |
3399 | These just add the watcher into an array or at the head of a list. |
3598 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3599 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3600 | ==2274== still reachable: 256 bytes in 1 blocks. |
3400 | |
3601 | |
3401 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3602 | Then there is no memory leak, just as memory accounted to global variables |
|
|
3603 | is not a memleak - the memory is still being refernced, and didn't leak. |
3402 | |
3604 | |
3403 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3605 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
3606 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
3607 | although an acceptable workaround has been found here), or it might be |
|
|
3608 | confused. |
3404 | |
3609 | |
3405 | These watchers are stored in lists then need to be walked to find the |
3610 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3406 | correct watcher to remove. The lists are usually short (you don't usually |
3611 | make it into some kind of religion. |
3407 | have many watchers waiting for the same fd or signal). |
|
|
3408 | |
3612 | |
3409 | =item Finding the next timer in each loop iteration: O(1) |
3613 | If you are unsure about something, feel free to contact the mailing list |
|
|
3614 | with the full valgrind report and an explanation on why you think this |
|
|
3615 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
3616 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
3617 | of learning how to interpret valgrind properly. |
3410 | |
3618 | |
3411 | By virtue of using a binary or 4-heap, the next timer is always found at a |
3619 | If you need, for some reason, empty reports from valgrind for your project |
3412 | fixed position in the storage array. |
3620 | I suggest using suppression lists. |
3413 | |
3621 | |
3414 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3415 | |
3622 | |
3416 | A change means an I/O watcher gets started or stopped, which requires |
3623 | =head1 PORTABILITY NOTES |
3417 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3418 | on backend and whether C<ev_io_set> was used). |
|
|
3419 | |
3624 | |
3420 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3421 | |
|
|
3422 | =item Priority handling: O(number_of_priorities) |
|
|
3423 | |
|
|
3424 | Priorities are implemented by allocating some space for each |
|
|
3425 | priority. When doing priority-based operations, libev usually has to |
|
|
3426 | linearly search all the priorities, but starting/stopping and activating |
|
|
3427 | watchers becomes O(1) with respect to priority handling. |
|
|
3428 | |
|
|
3429 | =item Sending an ev_async: O(1) |
|
|
3430 | |
|
|
3431 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3432 | |
|
|
3433 | =item Processing signals: O(max_signal_number) |
|
|
3434 | |
|
|
3435 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3436 | calls in the current loop iteration. Checking for async and signal events |
|
|
3437 | involves iterating over all running async watchers or all signal numbers. |
|
|
3438 | |
|
|
3439 | =back |
|
|
3440 | |
|
|
3441 | |
|
|
3442 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3625 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3443 | |
3626 | |
3444 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3627 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3445 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3628 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3446 | model. Libev still offers limited functionality on this platform in |
3629 | model. Libev still offers limited functionality on this platform in |
3447 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3630 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
… | |
… | |
3534 | wrap all I/O functions and provide your own fd management, but the cost of |
3717 | wrap all I/O functions and provide your own fd management, but the cost of |
3535 | calling select (O(n²)) will likely make this unworkable. |
3718 | calling select (O(n²)) will likely make this unworkable. |
3536 | |
3719 | |
3537 | =back |
3720 | =back |
3538 | |
3721 | |
3539 | |
|
|
3540 | =head1 PORTABILITY REQUIREMENTS |
3722 | =head2 PORTABILITY REQUIREMENTS |
3541 | |
3723 | |
3542 | In addition to a working ISO-C implementation, libev relies on a few |
3724 | In addition to a working ISO-C implementation and of course the |
3543 | additional extensions: |
3725 | backend-specific APIs, libev relies on a few additional extensions: |
3544 | |
3726 | |
3545 | =over 4 |
3727 | =over 4 |
3546 | |
3728 | |
3547 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3729 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3548 | calling conventions regardless of C<ev_watcher_type *>. |
3730 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3573 | except the initial one, and run the default loop in the initial thread as |
3755 | except the initial one, and run the default loop in the initial thread as |
3574 | well. |
3756 | well. |
3575 | |
3757 | |
3576 | =item C<long> must be large enough for common memory allocation sizes |
3758 | =item C<long> must be large enough for common memory allocation sizes |
3577 | |
3759 | |
3578 | To improve portability and simplify using libev, libev uses C<long> |
3760 | To improve portability and simplify its API, libev uses C<long> internally |
3579 | internally instead of C<size_t> when allocating its data structures. On |
3761 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3580 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
3762 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3581 | is still at least 31 bits everywhere, which is enough for hundreds of |
3763 | least 31 bits everywhere, which is enough for hundreds of millions of |
3582 | millions of watchers. |
3764 | watchers. |
3583 | |
3765 | |
3584 | =item C<double> must hold a time value in seconds with enough accuracy |
3766 | =item C<double> must hold a time value in seconds with enough accuracy |
3585 | |
3767 | |
3586 | The type C<double> is used to represent timestamps. It is required to |
3768 | The type C<double> is used to represent timestamps. It is required to |
3587 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3769 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
… | |
… | |
3591 | =back |
3773 | =back |
3592 | |
3774 | |
3593 | If you know of other additional requirements drop me a note. |
3775 | If you know of other additional requirements drop me a note. |
3594 | |
3776 | |
3595 | |
3777 | |
3596 | =head1 COMPILER WARNINGS |
3778 | =head1 ALGORITHMIC COMPLEXITIES |
3597 | |
3779 | |
3598 | Depending on your compiler and compiler settings, you might get no or a |
3780 | In this section the complexities of (many of) the algorithms used inside |
3599 | lot of warnings when compiling libev code. Some people are apparently |
3781 | libev will be documented. For complexity discussions about backends see |
3600 | scared by this. |
3782 | the documentation for C<ev_default_init>. |
3601 | |
3783 | |
3602 | However, these are unavoidable for many reasons. For one, each compiler |
3784 | All of the following are about amortised time: If an array needs to be |
3603 | has different warnings, and each user has different tastes regarding |
3785 | extended, libev needs to realloc and move the whole array, but this |
3604 | warning options. "Warn-free" code therefore cannot be a goal except when |
3786 | happens asymptotically rarer with higher number of elements, so O(1) might |
3605 | targeting a specific compiler and compiler-version. |
3787 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
3788 | average it is much faster and asymptotically approaches constant time. |
3606 | |
3789 | |
3607 | Another reason is that some compiler warnings require elaborate |
3790 | =over 4 |
3608 | workarounds, or other changes to the code that make it less clear and less |
|
|
3609 | maintainable. |
|
|
3610 | |
3791 | |
3611 | And of course, some compiler warnings are just plain stupid, or simply |
3792 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3612 | wrong (because they don't actually warn about the condition their message |
|
|
3613 | seems to warn about). |
|
|
3614 | |
3793 | |
3615 | While libev is written to generate as few warnings as possible, |
3794 | This means that, when you have a watcher that triggers in one hour and |
3616 | "warn-free" code is not a goal, and it is recommended not to build libev |
3795 | there are 100 watchers that would trigger before that, then inserting will |
3617 | with any compiler warnings enabled unless you are prepared to cope with |
3796 | have to skip roughly seven (C<ld 100>) of these watchers. |
3618 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3619 | warnings, not errors, or proof of bugs. |
|
|
3620 | |
3797 | |
|
|
3798 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3621 | |
3799 | |
3622 | =head1 VALGRIND |
3800 | That means that changing a timer costs less than removing/adding them, |
|
|
3801 | as only the relative motion in the event queue has to be paid for. |
3623 | |
3802 | |
3624 | Valgrind has a special section here because it is a popular tool that is |
3803 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3625 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3626 | |
3804 | |
3627 | If you think you found a bug (memory leak, uninitialised data access etc.) |
3805 | These just add the watcher into an array or at the head of a list. |
3628 | in libev, then check twice: If valgrind reports something like: |
|
|
3629 | |
3806 | |
3630 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3807 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3631 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3632 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3633 | |
3808 | |
3634 | Then there is no memory leak. Similarly, under some circumstances, |
3809 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3635 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3636 | might be confused (it is a very good tool, but only a tool). |
|
|
3637 | |
3810 | |
3638 | If you are unsure about something, feel free to contact the mailing list |
3811 | These watchers are stored in lists, so they need to be walked to find the |
3639 | with the full valgrind report and an explanation on why you think this is |
3812 | correct watcher to remove. The lists are usually short (you don't usually |
3640 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
3813 | have many watchers waiting for the same fd or signal: one is typical, two |
3641 | no bug" answer and take the chance of learning how to interpret valgrind |
3814 | is rare). |
3642 | properly. |
|
|
3643 | |
3815 | |
3644 | If you need, for some reason, empty reports from valgrind for your project |
3816 | =item Finding the next timer in each loop iteration: O(1) |
3645 | I suggest using suppression lists. |
3817 | |
|
|
3818 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
3819 | fixed position in the storage array. |
|
|
3820 | |
|
|
3821 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3822 | |
|
|
3823 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3824 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3825 | on backend and whether C<ev_io_set> was used). |
|
|
3826 | |
|
|
3827 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3828 | |
|
|
3829 | =item Priority handling: O(number_of_priorities) |
|
|
3830 | |
|
|
3831 | Priorities are implemented by allocating some space for each |
|
|
3832 | priority. When doing priority-based operations, libev usually has to |
|
|
3833 | linearly search all the priorities, but starting/stopping and activating |
|
|
3834 | watchers becomes O(1) with respect to priority handling. |
|
|
3835 | |
|
|
3836 | =item Sending an ev_async: O(1) |
|
|
3837 | |
|
|
3838 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3839 | |
|
|
3840 | =item Processing signals: O(max_signal_number) |
|
|
3841 | |
|
|
3842 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3843 | calls in the current loop iteration. Checking for async and signal events |
|
|
3844 | involves iterating over all running async watchers or all signal numbers. |
|
|
3845 | |
|
|
3846 | =back |
3646 | |
3847 | |
3647 | |
3848 | |
3648 | =head1 AUTHOR |
3849 | =head1 AUTHOR |
3649 | |
3850 | |
3650 | Marc Lehmann <libev@schmorp.de>. |
3851 | Marc Lehmann <libev@schmorp.de>. |