… | |
… | |
45 | Unlike the name component C<stamp> might indicate, it is also used for |
45 | Unlike the name component C<stamp> might indicate, it is also used for |
46 | time differences throughout libeio. |
46 | time differences throughout libeio. |
47 | |
47 | |
48 | =head2 FORK SUPPORT |
48 | =head2 FORK SUPPORT |
49 | |
49 | |
50 | Calling C<fork ()> is fully supported by this module. It is implemented in these steps: |
50 | Calling C<fork ()> is fully supported by this module - but you must not |
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51 | rely on this. It is currently implemented in these steps: |
51 | |
52 | |
52 | 1. wait till all requests in "execute" state have been handled |
53 | 1. wait till all requests in "execute" state have been handled |
53 | (basically requests that are already handed over to the kernel). |
54 | (basically requests that are already handed over to the kernel). |
54 | 2. fork |
55 | 2. fork |
55 | 3. in the parent, continue business as usual, done |
56 | 3. in the parent, continue business as usual, done |
56 | 4. in the child, destroy all ready and pending requests and free the |
57 | 4. in the child, destroy all ready and pending requests and free the |
57 | memory used by the worker threads. This gives you a fully empty |
58 | memory used by the worker threads. This gives you a fully empty |
58 | libeio queue. |
59 | libeio queue. |
59 | |
60 | |
60 | Note, however, since libeio does use threads, thr above guarantee doesn't |
61 | Note, however, since libeio does use threads, the above guarantee doesn't |
61 | cover your libc, for example, malloc and other libc functions are not |
62 | cover your libc, for example, malloc and other libc functions are not |
62 | fork-safe, so there is very little you can do after a fork, and in fatc, |
63 | fork-safe, so there is very little you can do after a fork, and in fact, |
63 | the above might crash, and thus change. |
64 | the above might crash, and thus change. |
64 | |
65 | |
65 | =head1 INITIALISATION/INTEGRATION |
66 | =head1 INITIALISATION/INTEGRATION |
66 | |
67 | |
67 | Before you can call any eio functions you first have to initialise the |
68 | Before you can call any eio functions you first have to initialise the |
… | |
… | |
124 | =back |
125 | =back |
125 | |
126 | |
126 | For libev, you would typically use an C<ev_async> watcher: the |
127 | 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 |
128 | 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 |
129 | 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 |
130 | ()>. |
130 | all requests have been handled yet). The race is taken care of because |
131 | |
131 | libev resets/rearms the async watcher before calling your callback, |
132 | 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) |
133 | (i.e. it returns C<-1>) then you should start an idle watcher that calls |
133 | spurious wake-ups, but is generally harmless. |
134 | C<eio_poll> until it returns something C<!= -1>. |
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135 | |
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136 | A full-featured connector between libeio and libev would look as follows |
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137 | (if C<eio_poll> is handling all requests, it can of course be simplified a |
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138 | lot by removing the idle watcher logic): |
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139 | |
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140 | static struct ev_loop *loop; |
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141 | static ev_idle repeat_watcher; |
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142 | static ev_async ready_watcher; |
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143 | |
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144 | /* idle watcher callback, only used when eio_poll */ |
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145 | /* didn't handle all results in one call */ |
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146 | static void |
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147 | repeat (EV_P_ ev_idle *w, int revents) |
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148 | { |
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149 | if (eio_poll () != -1) |
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150 | ev_idle_stop (EV_A_ w); |
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151 | } |
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152 | |
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153 | /* eio has some results, process them */ |
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154 | static void |
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155 | ready (EV_P_ ev_async *w, int revents) |
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156 | { |
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157 | if (eio_poll () == -1) |
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158 | ev_idle_start (EV_A_ &repeat_watcher); |
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159 | } |
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160 | |
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161 | /* wake up the event loop */ |
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162 | static void |
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163 | want_poll (void) |
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164 | { |
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165 | ev_async_send (loop, &ready_watcher) |
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166 | } |
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167 | |
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168 | void |
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169 | my_init_eio () |
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170 | { |
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171 | loop = EV_DEFAULT; |
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172 | |
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173 | ev_idle_init (&repeat_watcher, repeat); |
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174 | ev_async_init (&ready_watcher, ready); |
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175 | ev_async_start (loop &watcher); |
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176 | |
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177 | eio_init (want_poll, 0); |
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178 | } |
134 | |
179 | |
135 | For most other event loops, you would typically use a pipe - the event |
180 | 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 |
181 | 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 |
182 | 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 |
183 | 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 |
184 | C<eio_poll>. |
140 | your callback again and again until the byte has been read (as the pipe |
185 | |
141 | read callback does not read it, only C<done_poll>). |
186 | You don't have to take special care in the case C<eio_poll> doesn't handle |
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187 | all requests, as the done callback will not be invoked, so the event loop |
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188 | will still signal readiness for the pipe until I<all> results have been |
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189 | processed. |
142 | |
190 | |
143 | |
191 | |
144 | =head1 HIGH LEVEL REQUEST API |
192 | =head1 HIGH LEVEL REQUEST API |
145 | |
193 | |
146 | Libeio has both a high-level API, which consists of calling a request |
194 | Libeio has both a high-level API, which consists of calling a request |
… | |
… | |
153 | |
201 | |
154 | You submit a request by calling the relevant C<eio_TYPE> function with the |
202 | 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)> |
203 | 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. |
204 | (called C<eio_cb> below) and a freely usable C<void *data> argument. |
157 | |
205 | |
158 | The return value will either be 0 |
206 | The return value will either be 0, in case something went really wrong |
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207 | (which can basically only happen on very fatal errors, such as C<malloc> |
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208 | returning 0, which is rather unlikely), or a pointer to the newly-created |
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209 | and submitted C<eio_req *>. |
159 | |
210 | |
160 | The callback will be called with an C<eio_req *> which contains the |
211 | 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 |
212 | results of the request. The members you can access inside that structure |
162 | vary from request to request, except for: |
213 | vary from request to request, except for: |
163 | |
214 | |
… | |
… | |
210 | } |
261 | } |
211 | |
262 | |
212 | /* the first three arguments are passed to open(2) */ |
263 | /* the first three arguments are passed to open(2) */ |
213 | /* the remaining are priority, callback and data */ |
264 | /* the remaining are priority, callback and data */ |
214 | if (!eio_open ("/etc/passwd", O_RDONLY, 0, 0, file_open_done, 0)) |
265 | if (!eio_open ("/etc/passwd", O_RDONLY, 0, 0, file_open_done, 0)) |
215 | abort (); /* something ent wrong, we will all die!!! */ |
266 | abort (); /* something went wrong, we will all die!!! */ |
216 | |
267 | |
217 | Note that you additionally need to call C<eio_poll> when the C<want_cb> |
268 | Note that you additionally need to call C<eio_poll> when the C<want_cb> |
218 | indicates that requests are ready to be processed. |
269 | indicates that requests are ready to be processed. |
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270 | |
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271 | =head2 CANCELLING REQUESTS |
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272 | |
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273 | Sometimes the need for a request goes away before the request is |
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274 | finished. In that case, one can cancel the request by a call to |
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275 | C<eio_cancel>: |
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276 | |
|
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277 | =over 4 |
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278 | |
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279 | =item eio_cancel (eio_req *req) |
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280 | |
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281 | Cancel the request (and all its subrequests). If the request is currently |
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282 | executing it might still continue to execute, and in other cases it might |
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283 | still take a while till the request is cancelled. |
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284 | |
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285 | Even if cancelled, the finish callback will still be invoked - the |
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286 | callbacks of all cancellable requests need to check whether the request |
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287 | has been cancelled by calling C<EIO_CANCELLED (req)>: |
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288 | |
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289 | static int |
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290 | my_eio_cb (eio_req *req) |
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291 | { |
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292 | if (EIO_CANCELLED (req)) |
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293 | return 0; |
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294 | } |
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295 | |
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296 | In addition, cancelled requests will I<either> have C<< req->result >> |
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297 | set to C<-1> and C<errno> to C<ECANCELED>, or I<otherwise> they were |
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298 | successfully executed, despite being cancelled (e.g. when they have |
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299 | already been executed at the time they were cancelled). |
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300 | |
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301 | C<EIO_CANCELLED> is still true for requests that have successfully |
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302 | executed, as long as C<eio_cancel> was called on them at some point. |
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303 | |
|
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304 | =back |
219 | |
305 | |
220 | =head2 AVAILABLE REQUESTS |
306 | =head2 AVAILABLE REQUESTS |
221 | |
307 | |
222 | The following request functions are available. I<All> of them return the |
308 | The following request functions are available. I<All> of them return the |
223 | C<eio_req *> on success and C<0> on failure, and I<all> of them have the |
309 | C<eio_req *> on success and C<0> on failure, and I<all> of them have the |
… | |
… | |
226 | custom data value as C<data>. |
312 | custom data value as C<data>. |
227 | |
313 | |
228 | =head3 POSIX API WRAPPERS |
314 | =head3 POSIX API WRAPPERS |
229 | |
315 | |
230 | These requests simply wrap the POSIX call of the same name, with the same |
316 | These requests simply wrap the POSIX call of the same name, with the same |
231 | arguments: |
317 | arguments. If a function is not implemented by the OS and cannot be emulated |
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318 | in some way, then all of these return C<-1> and set C<errorno> to C<ENOSYS>. |
232 | |
319 | |
233 | =over 4 |
320 | =over 4 |
234 | |
321 | |
235 | =item eio_open (const char *path, int flags, mode_t mode, int pri, eio_cb cb, void *data) |
322 | =item eio_open (const char *path, int flags, mode_t mode, int pri, eio_cb cb, void *data) |
236 | |
323 | |
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324 | =item eio_truncate (const char *path, off_t offset, int pri, eio_cb cb, void *data) |
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325 | |
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326 | =item eio_chown (const char *path, uid_t uid, gid_t gid, int pri, eio_cb cb, void *data) |
|
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327 | |
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328 | =item eio_chmod (const char *path, mode_t mode, int pri, eio_cb cb, void *data) |
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329 | |
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330 | =item eio_mkdir (const char *path, mode_t mode, int pri, eio_cb cb, void *data) |
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331 | |
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332 | =item eio_rmdir (const char *path, int pri, eio_cb cb, void *data) |
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333 | |
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334 | =item eio_unlink (const char *path, int pri, eio_cb cb, void *data) |
|
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335 | |
237 | =item eio_utime (const char *path, eio_tstamp atime, eio_tstamp mtime, int pri, eio_cb cb, void *data) |
336 | =item eio_utime (const char *path, eio_tstamp atime, eio_tstamp mtime, int pri, eio_cb cb, void *data) |
238 | |
337 | |
239 | =item eio_truncate (const char *path, off_t offset, int pri, eio_cb cb, void *data) |
|
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240 | |
|
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241 | =item eio_chown (const char *path, uid_t uid, gid_t gid, int pri, eio_cb cb, void *data) |
|
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242 | |
|
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243 | =item eio_chmod (const char *path, mode_t mode, int pri, eio_cb cb, void *data) |
|
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244 | |
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245 | =item eio_mkdir (const char *path, mode_t mode, int pri, eio_cb cb, void *data) |
|
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246 | |
|
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247 | =item eio_rmdir (const char *path, int pri, eio_cb cb, void *data) |
|
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248 | |
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249 | =item eio_unlink (const char *path, int pri, eio_cb cb, void *data) |
|
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250 | |
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251 | =item eio_readlink (const char *path, int pri, eio_cb cb, void *data) /* result=ptr2 allocated dynamically */ |
|
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252 | |
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253 | =item eio_stat (const char *path, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ |
|
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254 | |
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255 | =item eio_lstat (const char *path, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ |
|
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256 | |
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257 | =item eio_statvfs (const char *path, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ |
|
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258 | |
|
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259 | =item eio_mknod (const char *path, mode_t mode, dev_t dev, int pri, eio_cb cb, void *data) |
338 | =item eio_mknod (const char *path, mode_t mode, dev_t dev, int pri, eio_cb cb, void *data) |
260 | |
339 | |
261 | =item eio_link (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
340 | =item eio_link (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
262 | |
341 | |
263 | =item eio_symlink (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
342 | =item eio_symlink (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
264 | |
343 | |
265 | =item eio_rename (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
344 | =item eio_rename (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
266 | |
345 | |
267 | =item eio_msync (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data) |
|
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268 | |
|
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269 | =item eio_mlock (void *addr, size_t length, int pri, eio_cb cb, void *data) |
346 | =item eio_mlock (void *addr, size_t length, int pri, eio_cb cb, void *data) |
270 | |
|
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271 | =item eio_mlockall (int flags, int pri, eio_cb cb, void *data) |
|
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272 | |
347 | |
273 | =item eio_close (int fd, int pri, eio_cb cb, void *data) |
348 | =item eio_close (int fd, int pri, eio_cb cb, void *data) |
274 | |
349 | |
275 | =item eio_sync (int pri, eio_cb cb, void *data) |
350 | =item eio_sync (int pri, eio_cb cb, void *data) |
276 | |
351 | |
… | |
… | |
305 | |
380 | |
306 | Not surprisingly, pread and pwrite are not thread-safe on Darwin (OS/X), |
381 | Not surprisingly, pread and pwrite are not thread-safe on Darwin (OS/X), |
307 | so it is advised not to submit multiple requests on the same fd on this |
382 | so it is advised not to submit multiple requests on the same fd on this |
308 | horrible pile of garbage. |
383 | horrible pile of garbage. |
309 | |
384 | |
|
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385 | =item eio_mlockall (int flags, int pri, eio_cb cb, void *data) |
|
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386 | |
|
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387 | Like C<mlockall>, but the flag value constants are called |
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388 | C<EIO_MCL_CURRENT> and C<EIO_MCL_FUTURE>. |
|
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389 | |
|
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390 | =item eio_msync (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data) |
|
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391 | |
|
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392 | Just like msync, except that the flag values are called C<EIO_MS_ASYNC>, |
|
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393 | C<EIO_MS_INVALIDATE> and C<EIO_MS_SYNC>. |
|
|
394 | |
|
|
395 | =item eio_readlink (const char *path, int pri, eio_cb cb, void *data) |
|
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396 | |
|
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397 | If successful, the path read by C<readlink(2)> can be accessed via C<< |
|
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398 | req->ptr2 >> and is I<NOT> null-terminated, with the length specified as |
|
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399 | C<< req->result >>. |
|
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400 | |
|
|
401 | if (req->result >= 0) |
|
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402 | { |
|
|
403 | char *target = strndup ((char *)req->ptr2, req->result); |
|
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404 | |
|
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405 | free (target); |
|
|
406 | } |
|
|
407 | |
|
|
408 | =item eio_realpath (const char *path, int pri, eio_cb cb, void *data) |
|
|
409 | |
|
|
410 | Similar to the realpath libc function, but unlike that one, result is |
|
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411 | C<-1> on failure and the length of the returned path in C<ptr2> (which is |
|
|
412 | not 0-terminated) - this is similar to readlink. |
|
|
413 | |
|
|
414 | =item eio_stat (const char *path, int pri, eio_cb cb, void *data) |
|
|
415 | |
|
|
416 | =item eio_lstat (const char *path, int pri, eio_cb cb, void *data) |
|
|
417 | |
310 | =item eio_fstat (int fd, int pri, eio_cb cb, void *data) |
418 | =item eio_fstat (int fd, int pri, eio_cb cb, void *data) |
311 | |
419 | |
312 | Stats a file - if C<< req->result >> indicates success, then you can |
420 | Stats a file - if C<< req->result >> indicates success, then you can |
313 | access the C<struct stat>-like structure via C<< req->ptr2 >>: |
421 | access the C<struct stat>-like structure via C<< req->ptr2 >>: |
314 | |
422 | |
315 | EIO_STRUCT_STAT *statdata = (EIO_STRUCT_STAT *)req->ptr2; |
423 | EIO_STRUCT_STAT *statdata = (EIO_STRUCT_STAT *)req->ptr2; |
316 | |
424 | |
317 | =item eio_fstatvfs (int fd, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ |
425 | =item eio_statvfs (const char *path, int pri, eio_cb cb, void *data) |
|
|
426 | |
|
|
427 | =item eio_fstatvfs (int fd, int pri, eio_cb cb, void *data) |
318 | |
428 | |
319 | Stats a filesystem - if C<< req->result >> indicates success, then you can |
429 | Stats a filesystem - if C<< req->result >> indicates success, then you can |
320 | access the C<struct statvfs>-like structure via C<< req->ptr2 >>: |
430 | access the C<struct statvfs>-like structure via C<< req->ptr2 >>: |
321 | |
431 | |
322 | EIO_STRUCT_STATVFS *statdata = (EIO_STRUCT_STATVFS *)req->ptr2; |
432 | EIO_STRUCT_STATVFS *statdata = (EIO_STRUCT_STATVFS *)req->ptr2; |
323 | |
433 | |
324 | =back |
434 | =back |
325 | |
435 | |
326 | =head3 READING DIRECTORIES |
436 | =head3 READING DIRECTORIES |
327 | |
437 | |
328 | Reading directories sounds simple, but can be rather demanding, especially |
438 | Reading directories sounds simple, but can be rather demanding, especially |
329 | if you want to do stuff such as traversing a diretcory hierarchy or |
439 | if you want to do stuff such as traversing a directory hierarchy or |
330 | processing all files in a directory. Libeio can assist thess complex tasks |
440 | processing all files in a directory. Libeio can assist these complex tasks |
331 | with it's C<eio_readdir> call. |
441 | with it's C<eio_readdir> call. |
332 | |
442 | |
333 | =over 4 |
443 | =over 4 |
334 | |
444 | |
335 | =item eio_readdir (const char *path, int flags, int pri, eio_cb cb, void *data) |
445 | =item eio_readdir (const char *path, int flags, int pri, eio_cb cb, void *data) |
… | |
… | |
338 | (via the C<opendir>, C<readdir> and C<closedir> calls) and returns either |
448 | (via the C<opendir>, C<readdir> and C<closedir> calls) and returns either |
339 | the names or an array of C<struct eio_dirent>, depending on the C<flags> |
449 | the names or an array of C<struct eio_dirent>, depending on the C<flags> |
340 | argument. |
450 | argument. |
341 | |
451 | |
342 | The C<< req->result >> indicates either the number of files found, or |
452 | The C<< req->result >> indicates either the number of files found, or |
343 | C<-1> on error. On success, zero-terminated names can be found as C<< req->ptr2 >>, |
453 | C<-1> on error. On success, null-terminated names can be found as C<< req->ptr2 >>, |
344 | and C<struct eio_dirents>, if requested by C<flags>, can be found via C<< |
454 | and C<struct eio_dirents>, if requested by C<flags>, can be found via C<< |
345 | req->ptr1 >>. |
455 | req->ptr1 >>. |
346 | |
456 | |
347 | Here is an example that prints all the names: |
457 | Here is an example that prints all the names: |
348 | |
458 | |
… | |
… | |
367 | |
477 | |
368 | If this flag is specified, then, in addition to the names in C<ptr2>, |
478 | If this flag is specified, then, in addition to the names in C<ptr2>, |
369 | also an array of C<struct eio_dirent> is returned, in C<ptr1>. A C<struct |
479 | also an array of C<struct eio_dirent> is returned, in C<ptr1>. A C<struct |
370 | eio_dirent> looks like this: |
480 | eio_dirent> looks like this: |
371 | |
481 | |
372 | struct eio_dirent |
482 | struct eio_dirent |
373 | { |
483 | { |
374 | int nameofs; /* offset of null-terminated name string in (char *)req->ptr2 */ |
484 | int nameofs; /* offset of null-terminated name string in (char *)req->ptr2 */ |
375 | unsigned short namelen; /* size of filename without trailing 0 */ |
485 | unsigned short namelen; /* size of filename without trailing 0 */ |
376 | unsigned char type; /* one of EIO_DT_* */ |
486 | unsigned char type; /* one of EIO_DT_* */ |
377 | signed char score; /* internal use */ |
487 | signed char score; /* internal use */ |
378 | ino_t inode; /* the inode number, if available, otherwise unspecified */ |
488 | ino_t inode; /* the inode number, if available, otherwise unspecified */ |
379 | }; |
489 | }; |
380 | |
490 | |
381 | The only members you normally would access are C<nameofs>, which is the |
491 | The only members you normally would access are C<nameofs>, which is the |
382 | byte-offset from C<ptr2> to the start of the name, C<namelen> and C<type>. |
492 | byte-offset from C<ptr2> to the start of the name, C<namelen> and C<type>. |
383 | |
493 | |
384 | C<type> can be one of: |
494 | C<type> can be one of: |
… | |
… | |
427 | When this flag is specified, then the names will be returned in an order |
537 | When this flag is specified, then the names will be returned in an order |
428 | suitable for stat()'ing each one. That is, when you plan to stat() |
538 | suitable for stat()'ing each one. That is, when you plan to stat() |
429 | all files in the given directory, then the returned order will likely |
539 | all files in the given directory, then the returned order will likely |
430 | be fastest. |
540 | be fastest. |
431 | |
541 | |
432 | If both this flag and C<EIO_READDIR_DIRS_FIRST> are specified, then |
542 | If both this flag and C<EIO_READDIR_DIRS_FIRST> are specified, then the |
433 | the likely dirs come first, resulting in a less optimal stat order. |
543 | likely directories come first, resulting in a less optimal stat order. |
434 | |
544 | |
435 | =item EIO_READDIR_FOUND_UNKNOWN |
545 | =item EIO_READDIR_FOUND_UNKNOWN |
436 | |
546 | |
437 | This flag should not be specified when calling C<eio_readdir>. Instead, |
547 | This flag should not be specified when calling C<eio_readdir>. Instead, |
438 | it is being set by C<eio_readdir> (you can access the C<flags> via C<< |
548 | it is being set by C<eio_readdir> (you can access the C<flags> via C<< |
439 | req->int1 >>, when any of the C<type>'s found were C<EIO_DT_UNKNOWN>. The |
549 | req->int1 >>, when any of the C<type>'s found were C<EIO_DT_UNKNOWN>. The |
440 | absense of this flag therefore indicates that all C<type>'s are known, |
550 | absence of this flag therefore indicates that all C<type>'s are known, |
441 | which can be used to speed up some algorithms. |
551 | which can be used to speed up some algorithms. |
442 | |
552 | |
443 | A typical use case would be to identify all subdirectories within a |
553 | A typical use case would be to identify all subdirectories within a |
444 | directory - you would ask C<eio_readdir> for C<EIO_READDIR_DIRS_FIRST>. If |
554 | directory - you would ask C<eio_readdir> for C<EIO_READDIR_DIRS_FIRST>. If |
445 | then this flag is I<NOT> set, then all the entries at the beginning of the |
555 | then this flag is I<NOT> set, then all the entries at the beginning of the |
… | |
… | |
480 | =item eio_sync_file_range (int fd, off_t offset, size_t nbytes, unsigned int flags, int pri, eio_cb cb, void *data) |
590 | =item eio_sync_file_range (int fd, off_t offset, size_t nbytes, unsigned int flags, int pri, eio_cb cb, void *data) |
481 | |
591 | |
482 | Calls C<sync_file_range>. If the syscall is missing, then this is the same |
592 | Calls C<sync_file_range>. If the syscall is missing, then this is the same |
483 | as calling C<fdatasync>. |
593 | as calling C<fdatasync>. |
484 | |
594 | |
|
|
595 | Flags can be any combination of C<EIO_SYNC_FILE_RANGE_WAIT_BEFORE>, |
|
|
596 | C<EIO_SYNC_FILE_RANGE_WRITE> and C<EIO_SYNC_FILE_RANGE_WAIT_AFTER>. |
|
|
597 | |
485 | =back |
598 | =back |
486 | |
599 | |
487 | =head3 LIBEIO-SPECIFIC REQUESTS |
600 | =head3 LIBEIO-SPECIFIC REQUESTS |
488 | |
601 | |
489 | These requests are specific to libeio and do not correspond to any OS call. |
602 | These requests are specific to libeio and do not correspond to any OS call. |
490 | |
603 | |
491 | =over 4 |
604 | =over 4 |
492 | |
605 | |
493 | =item eio_mtouch (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data) |
606 | =item eio_mtouch (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data) |
494 | |
607 | |
|
|
608 | Reads (C<flags == 0>) or modifies (C<flags == EIO_MT_MODIFY) the given |
|
|
609 | memory area, page-wise, that is, it reads (or reads and writes back) the |
|
|
610 | first octet of every page that spans the memory area. |
|
|
611 | |
|
|
612 | This can be used to page in some mmapped file, or dirty some pages. Note |
|
|
613 | that dirtying is an unlocked read-write access, so races can ensue when |
|
|
614 | the some other thread modifies the data stored in that memory area. |
|
|
615 | |
495 | =item eio_custom (void (*)(eio_req *) execute, int pri, eio_cb cb, void *data) |
616 | =item eio_custom (void (*)(eio_req *) execute, int pri, eio_cb cb, void *data) |
496 | |
617 | |
497 | Executes a custom request, i.e., a user-specified callback. |
618 | Executes a custom request, i.e., a user-specified callback. |
498 | |
619 | |
499 | The callback gets the C<eio_req *> as parameter and is expected to read |
620 | The callback gets the C<eio_req *> as parameter and is expected to read |
500 | and modify any request-specific members. Specifically, it should set C<< |
621 | and modify any request-specific members. Specifically, it should set C<< |
… | |
… | |
520 | req->result = open (req->data, O_RDONLY); |
641 | req->result = open (req->data, O_RDONLY); |
521 | } |
642 | } |
522 | |
643 | |
523 | eio_custom (my_open, 0, my_open_done, "/etc/passwd"); |
644 | eio_custom (my_open, 0, my_open_done, "/etc/passwd"); |
524 | |
645 | |
525 | =item eio_busy (eio_tstamp delay, int pri, eio_cb cb, void *data) |
646 | =item eio_busy (eio_tstamp delay, int pri, eio_cb cb, void *data) |
526 | |
647 | |
527 | This is a a request that takes C<delay> seconds to execute, but otherwise |
648 | This is a request that takes C<delay> seconds to execute, but otherwise |
528 | does nothing - it simply puts one of the worker threads to sleep for this |
649 | does nothing - it simply puts one of the worker threads to sleep for this |
529 | long. |
650 | long. |
530 | |
651 | |
531 | This request can be used to artificially increase load, e.g. for debugging |
652 | This request can be used to artificially increase load, e.g. for debugging |
532 | or benchmarking reasons. |
653 | or benchmarking reasons. |
533 | |
654 | |
534 | =item eio_nop (int pri, eio_cb cb, void *data) |
655 | =item eio_nop (int pri, eio_cb cb, void *data) |
535 | |
656 | |
536 | This request does nothing, except go through the whole request cycle. This |
657 | This request does nothing, except go through the whole request cycle. This |
537 | can be used to measure latency or in some cases to simplify code, but is |
658 | can be used to measure latency or in some cases to simplify code, but is |
538 | not really of much use. |
659 | not really of much use. |
539 | |
660 | |
540 | =back |
661 | =back |
541 | |
662 | |
542 | =head3 GROUPING AND LIMITING REQUESTS |
663 | =head3 GROUPING AND LIMITING REQUESTS |
543 | |
664 | |
|
|
665 | There is one more rather special request, C<eio_grp>. It is a very special |
|
|
666 | aio request: Instead of doing something, it is a container for other eio |
|
|
667 | requests. |
|
|
668 | |
|
|
669 | There are two primary use cases for this: a) bundle many requests into a |
|
|
670 | single, composite, request with a definite callback and the ability to |
|
|
671 | cancel the whole request with its subrequests and b) limiting the number |
|
|
672 | of "active" requests. |
|
|
673 | |
|
|
674 | Further below you will find more discussion of these topics - first |
|
|
675 | follows the reference section detailing the request generator and other |
|
|
676 | methods. |
|
|
677 | |
|
|
678 | =over 4 |
|
|
679 | |
|
|
680 | =item eio_req *grp = eio_grp (eio_cb cb, void *data) |
|
|
681 | |
|
|
682 | Creates, submits and returns a group request. |
|
|
683 | |
|
|
684 | =item eio_grp_add (eio_req *grp, eio_req *req) |
|
|
685 | |
|
|
686 | Adds a request to the request group. |
|
|
687 | |
|
|
688 | =item eio_grp_cancel (eio_req *grp) |
|
|
689 | |
|
|
690 | Cancels all requests I<in> the group, but I<not> the group request |
|
|
691 | itself. You can cancel the group request via a normal C<eio_cancel> call. |
|
|
692 | |
|
|
693 | |
|
|
694 | |
|
|
695 | =back |
|
|
696 | |
|
|
697 | |
|
|
698 | |
544 | #TODO |
699 | #TODO |
545 | |
700 | |
546 | /*****************************************************************************/ |
701 | /*****************************************************************************/ |
547 | /* groups */ |
702 | /* groups */ |
548 | |
703 | |
549 | eio_req *eio_grp (eio_cb cb, void *data); |
704 | eio_req *eio_grp (eio_cb cb, void *data); |
550 | void eio_grp_feed (eio_req *grp, void (*feed)(eio_req *req), int limit); |
705 | void eio_grp_feed (eio_req *grp, void (*feed)(eio_req *req), int limit); |
551 | void eio_grp_limit (eio_req *grp, int limit); |
706 | void eio_grp_limit (eio_req *grp, int limit); |
552 | void eio_grp_add (eio_req *grp, eio_req *req); |
|
|
553 | void eio_grp_cancel (eio_req *grp); /* cancels all sub requests but not the group */ |
707 | void eio_grp_cancel (eio_req *grp); /* cancels all sub requests but not the group */ |
554 | |
708 | |
555 | |
709 | |
556 | =back |
710 | =back |
557 | |
711 | |
… | |
… | |
564 | =head1 ANATOMY AND LIFETIME OF AN EIO REQUEST |
718 | =head1 ANATOMY AND LIFETIME OF AN EIO REQUEST |
565 | |
719 | |
566 | A request is represented by a structure of type C<eio_req>. To initialise |
720 | A request is represented by a structure of type C<eio_req>. To initialise |
567 | it, clear it to all zero bytes: |
721 | it, clear it to all zero bytes: |
568 | |
722 | |
569 | eio_req req; |
723 | eio_req req; |
570 | |
724 | |
571 | memset (&req, 0, sizeof (req)); |
725 | memset (&req, 0, sizeof (req)); |
572 | |
726 | |
573 | A more common way to initialise a new C<eio_req> is to use C<calloc>: |
727 | A more common way to initialise a new C<eio_req> is to use C<calloc>: |
574 | |
728 | |
575 | eio_req *req = calloc (1, sizeof (*req)); |
729 | eio_req *req = calloc (1, sizeof (*req)); |
576 | |
730 | |
577 | In either case, libeio neither allocates, initialises or frees the |
731 | In either case, libeio neither allocates, initialises or frees the |
578 | C<eio_req> structure for you - it merely uses it. |
732 | C<eio_req> structure for you - it merely uses it. |
579 | |
733 | |
580 | zero |
734 | zero |
… | |
… | |
598 | for example, in interactive programs, you might want to limit this time to |
752 | for example, in interactive programs, you might want to limit this time to |
599 | C<0.01> seconds or so. |
753 | C<0.01> seconds or so. |
600 | |
754 | |
601 | Note that: |
755 | Note that: |
602 | |
756 | |
|
|
757 | =over 4 |
|
|
758 | |
603 | a) libeio doesn't know how long your request callbacks take, so the time |
759 | =item a) libeio doesn't know how long your request callbacks take, so the |
604 | spent in C<eio_poll> is up to one callback invocation longer then this |
760 | time spent in C<eio_poll> is up to one callback invocation longer then |
605 | interval. |
761 | this interval. |
606 | |
762 | |
607 | b) this is implemented by calling C<gettimeofday> after each request, |
763 | =item b) this is implemented by calling C<gettimeofday> after each |
608 | which can be costly. |
764 | request, which can be costly. |
609 | |
765 | |
610 | c) at least one request will be handled. |
766 | =item c) at least one request will be handled. |
|
|
767 | |
|
|
768 | =back |
611 | |
769 | |
612 | =item eio_set_max_poll_reqs (unsigned int nreqs) |
770 | =item eio_set_max_poll_reqs (unsigned int nreqs) |
613 | |
771 | |
614 | When C<nreqs> is non-zero, then C<eio_poll> will not handle more than |
772 | When C<nreqs> is non-zero, then C<eio_poll> will not handle more than |
615 | C<nreqs> requests per invocation. This is a less costly way to limit the |
773 | C<nreqs> requests per invocation. This is a less costly way to limit the |