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124 | =back |
124 | =back |
125 | |
125 | |
126 | For libev, you would typically use an C<ev_async> watcher: the |
126 | For libev, you would typically use an C<ev_async> watcher: the |
127 | C<want_poll> callback would invoke C<ev_async_send> to wake up the event |
127 | C<want_poll> callback would invoke C<ev_async_send> to wake up the event |
128 | loop. Inside the callback set for the watcher, one would call C<eio_poll |
128 | loop. Inside the callback set for the watcher, one would call C<eio_poll |
129 | ()> (followed by C<ev_async_send> again if C<eio_poll> indicates that not |
129 | ()>. |
130 | all requests have been handled yet). The race is taken care of because |
130 | |
131 | libev resets/rearms the async watcher before calling your callback, |
131 | If C<eio_poll ()> is configured to not handle all results in one go |
132 | and therefore, before calling C<eio_poll>. This might result in (some) |
132 | (i.e. it returns C<-1>) then you should start an idle watcher that calls |
133 | spurious wake-ups, but is generally harmless. |
133 | C<eio_poll> until it returns something C<!= -1>. |
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134 | |
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135 | A full-featured wrapper would look as follows (if C<eio_poll> is handling |
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136 | all requests, it can of course be simplified a lot by removing the idle |
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137 | watcher logic): |
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138 | |
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139 | static struct ev_loop *loop; |
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140 | static ev_idle repeat_watcher; |
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141 | static ev_async ready_watcher; |
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142 | |
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143 | /* idle watcher callback, only used when eio_poll */ |
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144 | /* didn't handle all results in one call */ |
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145 | static void |
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146 | repeat (EV_P_ ev_idle *w, int revents) |
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147 | { |
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148 | if (eio_poll () != -1) |
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149 | ev_idle_stop (EV_A_ w); |
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150 | } |
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151 | |
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152 | /* eio has some results, process them */ |
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153 | static void |
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154 | ready (EV_P_ ev_async *w, int revents) |
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155 | { |
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156 | if (eio_poll () == -1) |
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157 | ev_idle_start (EV_A_ &repeat_watcher); |
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158 | } |
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159 | |
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160 | /* wake up the event loop */ |
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161 | static void |
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162 | want_poll (void) |
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163 | { |
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164 | ev_async_send (loop, &ready_watcher) |
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165 | } |
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166 | |
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167 | void |
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168 | my_init_eio () |
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169 | { |
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170 | loop = EV_DEFAULT; |
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171 | |
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172 | ev_idle_init (&repeat_watcher, repeat); |
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173 | ev_async_init (&ready_watcher, ready); |
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174 | ev_async_start (loop &watcher); |
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175 | |
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176 | eio_init (want_poll, 0); |
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177 | } |
134 | |
178 | |
135 | For most other event loops, you would typically use a pipe - the event |
179 | For most other event loops, you would typically use a pipe - the event |
136 | loop should be told to wait for read readiness on the read end. In |
180 | loop should be told to wait for read readiness on the read end. In |
137 | C<want_poll> you would write a single byte, in C<done_poll> you would try |
181 | C<want_poll> you would write a single byte, in C<done_poll> you would try |
138 | to read that byte, and in the callback for the read end, you would call |
182 | to read that byte, and in the callback for the read end, you would call |
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153 | |
197 | |
154 | You submit a request by calling the relevant C<eio_TYPE> function with the |
198 | You submit a request by calling the relevant C<eio_TYPE> function with the |
155 | required parameters, a callback of type C<int (*eio_cb)(eio_req *req)> |
199 | required parameters, a callback of type C<int (*eio_cb)(eio_req *req)> |
156 | (called C<eio_cb> below) and a freely usable C<void *data> argument. |
200 | (called C<eio_cb> below) and a freely usable C<void *data> argument. |
157 | |
201 | |
158 | The return value will either be 0 |
202 | The return value will either be 0, in case something went really wrong |
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203 | (which can basically only happen on very fatal errors, such as C<malloc> |
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204 | returning 0, which is rather unlikely), or a pointer to the newly-created |
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205 | and submitted C<eio_req *>. |
159 | |
206 | |
160 | The callback will be called with an C<eio_req *> which contains the |
207 | The callback will be called with an C<eio_req *> which contains the |
161 | results of the request. The members you can access inside that structure |
208 | results of the request. The members you can access inside that structure |
162 | vary from request to request, except for: |
209 | vary from request to request, except for: |
163 | |
210 | |
… | |
… | |
226 | custom data value as C<data>. |
273 | custom data value as C<data>. |
227 | |
274 | |
228 | =head3 POSIX API WRAPPERS |
275 | =head3 POSIX API WRAPPERS |
229 | |
276 | |
230 | These requests simply wrap the POSIX call of the same name, with the same |
277 | These requests simply wrap the POSIX call of the same name, with the same |
231 | arguments. If a function is not implemented by the OS and cnanot be emulated |
278 | arguments. If a function is not implemented by the OS and cannot be emulated |
232 | in some way, then all of these return C<-1> and set C<errorno> to C<ENOSYS>. |
279 | in some way, then all of these return C<-1> and set C<errorno> to C<ENOSYS>. |
233 | |
280 | |
234 | =over 4 |
281 | =over 4 |
235 | |
282 | |
236 | =item eio_open (const char *path, int flags, mode_t mode, int pri, eio_cb cb, void *data) |
283 | =item eio_open (const char *path, int flags, mode_t mode, int pri, eio_cb cb, void *data) |
… | |
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316 | { |
363 | { |
317 | char *target = strndup ((char *)req->ptr2, req->result); |
364 | char *target = strndup ((char *)req->ptr2, req->result); |
318 | |
365 | |
319 | free (target); |
366 | free (target); |
320 | } |
367 | } |
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368 | |
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369 | =item eio_realpath (const char *path, int pri, eio_cb cb, void *data) |
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370 | |
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371 | Similar to the realpath libc function, but unlike that one, result is |
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372 | C<-1> on failure and the length of the returned path in C<ptr2> (which is |
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373 | not 0-terminated) - this is similar to readlink. |
321 | |
374 | |
322 | =item eio_stat (const char *path, int pri, eio_cb cb, void *data) |
375 | =item eio_stat (const char *path, int pri, eio_cb cb, void *data) |
323 | |
376 | |
324 | =item eio_lstat (const char *path, int pri, eio_cb cb, void *data) |
377 | =item eio_lstat (const char *path, int pri, eio_cb cb, void *data) |
325 | |
378 | |
… | |
… | |
568 | |
621 | |
569 | =back |
622 | =back |
570 | |
623 | |
571 | =head3 GROUPING AND LIMITING REQUESTS |
624 | =head3 GROUPING AND LIMITING REQUESTS |
572 | |
625 | |
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626 | There is one more rather special request, C<eio_grp>. It is a very special |
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627 | aio request: Instead of doing something, it is a container for other eio |
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628 | requests. |
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629 | |
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630 | There are two primary use cases for this: a) bundle many requests into a |
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631 | single, composite, request with a definite callback and the ability to |
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632 | cancel the whole request with its subrequests and b) limiting the number |
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633 | of "active" requests. |
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634 | |
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635 | Further below you will find more dicussion of these topics - first follows |
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636 | the reference section detailing the request generator and other methods. |
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637 | |
|
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638 | =over 4 |
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639 | |
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640 | =item eio_grp (eio_cb cb, void *data) |
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641 | |
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642 | Creates and submits a group request. |
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643 | |
|
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644 | =back |
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645 | |
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646 | |
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647 | |
573 | #TODO |
648 | #TODO |
574 | |
649 | |
575 | /*****************************************************************************/ |
650 | /*****************************************************************************/ |
576 | /* groups */ |
651 | /* groups */ |
577 | |
652 | |