… | |
… | |
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 conenctor between libeio and libev would look as follows |
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136 | (if C<eio_poll> is handling all requests, it can of course be simplified a |
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137 | lot by removing the idle 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 |
139 | C<eio_poll>. The race is avoided here because the event loop should invoke |
183 | C<eio_poll>. |
140 | your callback again and again until the byte has been read (as the pipe |
184 | |
141 | read callback does not read it, only C<done_poll>). |
185 | You don't have to take special care in the case C<eio_poll> doesn't handle |
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186 | all requests, as the done callback will not be invoked, so the event loop |
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187 | will still signal readyness for the pipe until I<all> results have been |
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188 | processed. |
142 | |
189 | |
143 | |
190 | |
144 | =head1 HIGH LEVEL REQUEST API |
191 | =head1 HIGH LEVEL REQUEST API |
145 | |
192 | |
146 | Libeio has both a high-level API, which consists of calling a request |
193 | Libeio has both a high-level API, which consists of calling a request |
… | |
… | |
153 | |
200 | |
154 | You submit a request by calling the relevant C<eio_TYPE> function with the |
201 | 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)> |
202 | 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. |
203 | (called C<eio_cb> below) and a freely usable C<void *data> argument. |
157 | |
204 | |
158 | The return value will either be 0 |
205 | The return value will either be 0, in case something went really wrong |
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206 | (which can basically only happen on very fatal errors, such as C<malloc> |
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207 | returning 0, which is rather unlikely), or a pointer to the newly-created |
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208 | and submitted C<eio_req *>. |
159 | |
209 | |
160 | The callback will be called with an C<eio_req *> which contains the |
210 | 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 |
211 | results of the request. The members you can access inside that structure |
162 | vary from request to request, except for: |
212 | vary from request to request, except for: |
163 | |
213 | |
… | |
… | |
226 | custom data value as C<data>. |
276 | custom data value as C<data>. |
227 | |
277 | |
228 | =head3 POSIX API WRAPPERS |
278 | =head3 POSIX API WRAPPERS |
229 | |
279 | |
230 | These requests simply wrap the POSIX call of the same name, with the same |
280 | 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 |
281 | 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>. |
282 | in some way, then all of these return C<-1> and set C<errorno> to C<ENOSYS>. |
233 | |
283 | |
234 | =over 4 |
284 | =over 4 |
235 | |
285 | |
236 | =item eio_open (const char *path, int flags, mode_t mode, int pri, eio_cb cb, void *data) |
286 | =item eio_open (const char *path, int flags, mode_t mode, int pri, eio_cb cb, void *data) |
… | |
… | |
316 | { |
366 | { |
317 | char *target = strndup ((char *)req->ptr2, req->result); |
367 | char *target = strndup ((char *)req->ptr2, req->result); |
318 | |
368 | |
319 | free (target); |
369 | free (target); |
320 | } |
370 | } |
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371 | |
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372 | =item eio_realpath (const char *path, int pri, eio_cb cb, void *data) |
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373 | |
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374 | Similar to the realpath libc function, but unlike that one, result is |
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375 | C<-1> on failure and the length of the returned path in C<ptr2> (which is |
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376 | not 0-terminated) - this is similar to readlink. |
321 | |
377 | |
322 | =item eio_stat (const char *path, int pri, eio_cb cb, void *data) |
378 | =item eio_stat (const char *path, int pri, eio_cb cb, void *data) |
323 | |
379 | |
324 | =item eio_lstat (const char *path, int pri, eio_cb cb, void *data) |
380 | =item eio_lstat (const char *path, int pri, eio_cb cb, void *data) |
325 | |
381 | |
… | |
… | |
568 | |
624 | |
569 | =back |
625 | =back |
570 | |
626 | |
571 | =head3 GROUPING AND LIMITING REQUESTS |
627 | =head3 GROUPING AND LIMITING REQUESTS |
572 | |
628 | |
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629 | There is one more rather special request, C<eio_grp>. It is a very special |
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630 | aio request: Instead of doing something, it is a container for other eio |
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631 | requests. |
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632 | |
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633 | There are two primary use cases for this: a) bundle many requests into a |
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634 | single, composite, request with a definite callback and the ability to |
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635 | cancel the whole request with its subrequests and b) limiting the number |
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636 | of "active" requests. |
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637 | |
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638 | Further below you will find more dicussion of these topics - first follows |
|
|
639 | the reference section detailing the request generator and other methods. |
|
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640 | |
|
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641 | =over 4 |
|
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642 | |
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643 | =item eio_grp (eio_cb cb, void *data) |
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644 | |
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645 | Creates and submits a group request. |
|
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646 | |
|
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647 | =back |
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648 | |
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649 | |
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650 | |
573 | #TODO |
651 | #TODO |
574 | |
652 | |
575 | /*****************************************************************************/ |
653 | /*****************************************************************************/ |
576 | /* groups */ |
654 | /* groups */ |
577 | |
655 | |