| … | |
… | |
| 1102 | |
1102 | |
| 1103 | Prepare and check watchers are usually (but not always) used in tandem: |
1103 | Prepare and check watchers are usually (but not always) used in tandem: |
| 1104 | prepare watchers get invoked before the process blocks and check watchers |
1104 | prepare watchers get invoked before the process blocks and check watchers |
| 1105 | afterwards. |
1105 | afterwards. |
| 1106 | |
1106 | |
|
|
1107 | You I<must not> call C<ev_loop> or similar functions that enter |
|
|
1108 | the current event loop from either C<ev_prepare> or C<ev_check> |
|
|
1109 | watchers. Other loops than the current one are fine, however. The |
|
|
1110 | rationale behind this is that you do not need to check for recursion in |
|
|
1111 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
|
|
1112 | C<ev_check> so if you have one watcher of each kind they will always be |
|
|
1113 | called in pairs bracketing the blocking call. |
|
|
1114 | |
| 1107 | Their main purpose is to integrate other event mechanisms into libev and |
1115 | Their main purpose is to integrate other event mechanisms into libev and |
| 1108 | their use is somewhat advanced. This could be used, for example, to track |
1116 | their use is somewhat advanced. This could be used, for example, to track |
| 1109 | variable changes, implement your own watchers, integrate net-snmp or a |
1117 | variable changes, implement your own watchers, integrate net-snmp or a |
| 1110 | coroutine library and lots more. |
1118 | coroutine library and lots more. They are also occasionally useful if |
|
|
1119 | you cache some data and want to flush it before blocking (for example, |
|
|
1120 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
|
|
1121 | watcher). |
| 1111 | |
1122 | |
| 1112 | This is done by examining in each prepare call which file descriptors need |
1123 | This is done by examining in each prepare call which file descriptors need |
| 1113 | to be watched by the other library, registering C<ev_io> watchers for |
1124 | to be watched by the other library, registering C<ev_io> watchers for |
| 1114 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
1125 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
| 1115 | provide just this functionality). Then, in the check watcher you check for |
1126 | provide just this functionality). Then, in the check watcher you check for |
| … | |
… | |
| 1137 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1148 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
| 1138 | macros, but using them is utterly, utterly and completely pointless. |
1149 | macros, but using them is utterly, utterly and completely pointless. |
| 1139 | |
1150 | |
| 1140 | =back |
1151 | =back |
| 1141 | |
1152 | |
| 1142 | Example: *TODO*. |
1153 | Example: To include a library such as adns, you would add IO watchers |
|
|
1154 | and a timeout watcher in a prepare handler, as required by libadns, and |
|
|
1155 | in a check watcher, destroy them and call into libadns. What follows is |
|
|
1156 | pseudo-code only of course: |
|
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1157 | |
|
|
1158 | static ev_io iow [nfd]; |
|
|
1159 | static ev_timer tw; |
|
|
1160 | |
|
|
1161 | static void |
|
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1162 | io_cb (ev_loop *loop, ev_io *w, int revents) |
|
|
1163 | { |
|
|
1164 | // set the relevant poll flags |
|
|
1165 | struct pollfd *fd = (struct pollfd *)w->data; |
|
|
1166 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1167 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1168 | } |
|
|
1169 | |
|
|
1170 | // create io watchers for each fd and a timer before blocking |
|
|
1171 | static void |
|
|
1172 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
|
|
1173 | { |
|
|
1174 | int timeout = 3600000;truct pollfd fds [nfd]; |
|
|
1175 | // actual code will need to loop here and realloc etc. |
|
|
1176 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
|
|
1177 | |
|
|
1178 | /* the callback is illegal, but won't be called as we stop during check */ |
|
|
1179 | ev_timer_init (&tw, 0, timeout * 1e-3); |
|
|
1180 | ev_timer_start (loop, &tw); |
|
|
1181 | |
|
|
1182 | // create on ev_io per pollfd |
|
|
1183 | for (int i = 0; i < nfd; ++i) |
|
|
1184 | { |
|
|
1185 | ev_io_init (iow + i, io_cb, fds [i].fd, |
|
|
1186 | ((fds [i].events & POLLIN ? EV_READ : 0) |
|
|
1187 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
|
|
1188 | |
|
|
1189 | fds [i].revents = 0; |
|
|
1190 | iow [i].data = fds + i; |
|
|
1191 | ev_io_start (loop, iow + i); |
|
|
1192 | } |
|
|
1193 | } |
|
|
1194 | |
|
|
1195 | // stop all watchers after blocking |
|
|
1196 | static void |
|
|
1197 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
|
|
1198 | { |
|
|
1199 | ev_timer_stop (loop, &tw); |
|
|
1200 | |
|
|
1201 | for (int i = 0; i < nfd; ++i) |
|
|
1202 | ev_io_stop (loop, iow + i); |
|
|
1203 | |
|
|
1204 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
1205 | } |
| 1143 | |
1206 | |
| 1144 | |
1207 | |
| 1145 | =head2 C<ev_embed> - when one backend isn't enough... |
1208 | =head2 C<ev_embed> - when one backend isn't enough... |
| 1146 | |
1209 | |
| 1147 | This is a rather advanced watcher type that lets you embed one event loop |
1210 | This is a rather advanced watcher type that lets you embed one event loop |
