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Revision 1.8 by root, Sun Jun 5 22:45:49 2011 UTC vs.
Revision 1.15 by root, Tue Jul 5 16:57:41 2011 UTC

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124=back 124=back
125 125
126For libev, you would typically use an C<ev_async> watcher: the 126For libev, you would typically use an C<ev_async> watcher: the
127C<want_poll> callback would invoke C<ev_async_send> to wake up the event 127C<want_poll> callback would invoke C<ev_async_send> to wake up the event
128loop. Inside the callback set for the watcher, one would call C<eio_poll 128loop. 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()>.
130all requests have been handled yet). The race is taken care of because 130
131libev resets/rearms the async watcher before calling your callback, 131If C<eio_poll ()> is configured to not handle all results in one go
132and 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
133spurious wake-ups, but is generally harmless. 133C<eio_poll> until it returns something C<!= -1>.
134
135A full-featured wrapper would look as follows (if C<eio_poll> is handling
136all requests, it can of course be simplified a lot by removing the idle
137watcher logic):
138
139 static struct ev_loop *loop;
140 static ev_idle repeat_watcher;
141 static ev_async ready_watcher;
142
143 /* idle watcher callback, only used when eio_poll */
144 /* didn't handle all results in one call */
145 static void
146 repeat (EV_P_ ev_idle *w, int revents)
147 {
148 if (eio_poll () != -1)
149 ev_idle_stop (EV_A_ w);
150 }
151
152 /* eio has some results, process them */
153 static void
154 ready (EV_P_ ev_async *w, int revents)
155 {
156 if (eio_poll () == -1)
157 ev_idle_start (EV_A_ &repeat_watcher);
158 }
159
160 /* wake up the event loop */
161 static void
162 want_poll (void)
163 {
164 ev_async_send (loop, &ready_watcher)
165 }
166
167 void
168 my_init_eio ()
169 {
170 loop = EV_DEFAULT;
171
172 ev_idle_init (&repeat_watcher, repeat);
173 ev_async_init (&ready_watcher, ready);
174 ev_async_start (loop &watcher);
175
176 eio_init (want_poll, 0);
177 }
134 178
135For most other event loops, you would typically use a pipe - the event 179For most other event loops, you would typically use a pipe - the event
136loop should be told to wait for read readiness on the read end. In 180loop should be told to wait for read readiness on the read end. In
137C<want_poll> you would write a single byte, in C<done_poll> you would try 181C<want_poll> you would write a single byte, in C<done_poll> you would try
138to read that byte, and in the callback for the read end, you would call 182to read that byte, and in the callback for the read end, you would call
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153 197
154You submit a request by calling the relevant C<eio_TYPE> function with the 198You submit a request by calling the relevant C<eio_TYPE> function with the
155required parameters, a callback of type C<int (*eio_cb)(eio_req *req)> 199required 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
158The return value will either be 0 202The return value will either be 0, in case something went really wrong
203(which can basically only happen on very fatal errors, such as C<malloc>
204returning 0, which is rather unlikely), or a pointer to the newly-created
205and submitted C<eio_req *>.
159 206
160The callback will be called with an C<eio_req *> which contains the 207The callback will be called with an C<eio_req *> which contains the
161results of the request. The members you can access inside that structure 208results of the request. The members you can access inside that structure
162vary from request to request, except for: 209vary from request to request, except for:
163 210
… …
226custom data value as C<data>. 273custom data value as C<data>.
227 274
228=head3 POSIX API WRAPPERS 275=head3 POSIX API WRAPPERS
229 276
230These requests simply wrap the POSIX call of the same name, with the same 277These requests simply wrap the POSIX call of the same name, with the same
231arguments: 278arguments. If a function is not implemented by the OS and cannot be emulated
279in some way, then all of these return C<-1> and set C<errorno> to C<ENOSYS>.
232 280
233=over 4 281=over 4
234 282
235=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)
236 284
285=item eio_truncate (const char *path, off_t offset, int pri, eio_cb cb, void *data)
286
287=item eio_chown (const char *path, uid_t uid, gid_t gid, int pri, eio_cb cb, void *data)
288
289=item eio_chmod (const char *path, mode_t mode, int pri, eio_cb cb, void *data)
290
291=item eio_mkdir (const char *path, mode_t mode, int pri, eio_cb cb, void *data)
292
293=item eio_rmdir (const char *path, int pri, eio_cb cb, void *data)
294
295=item eio_unlink (const char *path, int pri, eio_cb cb, void *data)
296
237=item eio_utime (const char *path, eio_tstamp atime, eio_tstamp mtime, int pri, eio_cb cb, void *data) 297=item eio_utime (const char *path, eio_tstamp atime, eio_tstamp mtime, int pri, eio_cb cb, void *data)
238 298
239=item eio_truncate (const char *path, off_t offset, int pri, eio_cb cb, void *data)
240
241=item eio_chown (const char *path, uid_t uid, gid_t gid, int pri, eio_cb cb, void *data)
242
243=item eio_chmod (const char *path, mode_t mode, int pri, eio_cb cb, void *data)
244
245=item eio_mkdir (const char *path, mode_t mode, int pri, eio_cb cb, void *data)
246
247=item eio_rmdir (const char *path, int pri, eio_cb cb, void *data)
248
249=item eio_unlink (const char *path, int pri, eio_cb cb, void *data)
250
251=item eio_readlink (const char *path, int pri, eio_cb cb, void *data) /* result=ptr2 allocated dynamically */
252
253=item eio_stat (const char *path, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */
254
255=item eio_lstat (const char *path, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */
256
257=item eio_statvfs (const char *path, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */
258
259=item eio_mknod (const char *path, mode_t mode, dev_t dev, int pri, eio_cb cb, void *data) 299=item eio_mknod (const char *path, mode_t mode, dev_t dev, int pri, eio_cb cb, void *data)
260 300
261=item eio_link (const char *path, const char *new_path, int pri, eio_cb cb, void *data) 301=item eio_link (const char *path, const char *new_path, int pri, eio_cb cb, void *data)
262 302
263=item eio_symlink (const char *path, const char *new_path, int pri, eio_cb cb, void *data) 303=item eio_symlink (const char *path, const char *new_path, int pri, eio_cb cb, void *data)
264 304
265=item eio_rename (const char *path, const char *new_path, int pri, eio_cb cb, void *data) 305=item eio_rename (const char *path, const char *new_path, int pri, eio_cb cb, void *data)
266 306
267=item eio_msync (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data)
268
269=item eio_mlock (void *addr, size_t length, int pri, eio_cb cb, void *data) 307=item eio_mlock (void *addr, size_t length, int pri, eio_cb cb, void *data)
270
271=item eio_mlockall (int flags, int pri, eio_cb cb, void *data)
272 308
273=item eio_close (int fd, int pri, eio_cb cb, void *data) 309=item eio_close (int fd, int pri, eio_cb cb, void *data)
274 310
275=item eio_sync (int pri, eio_cb cb, void *data) 311=item eio_sync (int pri, eio_cb cb, void *data)
276 312
… …
305 341
306Not surprisingly, pread and pwrite are not thread-safe on Darwin (OS/X), 342Not surprisingly, pread and pwrite are not thread-safe on Darwin (OS/X),
307so it is advised not to submit multiple requests on the same fd on this 343so it is advised not to submit multiple requests on the same fd on this
308horrible pile of garbage. 344horrible pile of garbage.
309 345
346=item eio_mlockall (int flags, int pri, eio_cb cb, void *data)
347
348Like C<mlockall>, but the flag value constants are called
349C<EIO_MCL_CURRENT> and C<EIO_MCL_FUTURE>.
350
351=item eio_msync (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data)
352
353Just like msync, except that the flag values are called C<EIO_MS_ASYNC>,
354C<EIO_MS_INVALIDATE> and C<EIO_MS_SYNC>.
355
356=item eio_readlink (const char *path, int pri, eio_cb cb, void *data)
357
358If successful, the path read by C<readlink(2)> can be accessed via C<<
359req->ptr2 >> and is I<NOT> null-terminated, with the length specified as
360C<< req->result >>.
361
362 if (req->result >= 0)
363 {
364 char *target = strndup ((char *)req->ptr2, req->result);
365
366 free (target);
367 }
368
369=item eio_realpath (const char *path, int pri, eio_cb cb, void *data)
370
371Similar to the realpath libc function, but unlike that one, result is
372C<-1> on failure and the length of the returned path in C<ptr2> (which is
373not 0-terminated) - this is similar to readlink.
374
375=item eio_stat (const char *path, int pri, eio_cb cb, void *data)
376
377=item eio_lstat (const char *path, int pri, eio_cb cb, void *data)
378
310=item eio_fstat (int fd, int pri, eio_cb cb, void *data) 379=item eio_fstat (int fd, int pri, eio_cb cb, void *data)
311 380
312Stats a file - if C<< req->result >> indicates success, then you can 381Stats a file - if C<< req->result >> indicates success, then you can
313access the C<struct stat>-like structure via C<< req->ptr2 >>: 382access the C<struct stat>-like structure via C<< req->ptr2 >>:
314 383
315 EIO_STRUCT_STAT *statdata = (EIO_STRUCT_STAT *)req->ptr2; 384 EIO_STRUCT_STAT *statdata = (EIO_STRUCT_STAT *)req->ptr2;
316 385
317=item eio_fstatvfs (int fd, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ 386=item eio_statvfs (const char *path, int pri, eio_cb cb, void *data)
387
388=item eio_fstatvfs (int fd, int pri, eio_cb cb, void *data)
318 389
319Stats a filesystem - if C<< req->result >> indicates success, then you can 390Stats a filesystem - if C<< req->result >> indicates success, then you can
320access the C<struct statvfs>-like structure via C<< req->ptr2 >>: 391access the C<struct statvfs>-like structure via C<< req->ptr2 >>:
321 392
322 EIO_STRUCT_STATVFS *statdata = (EIO_STRUCT_STATVFS *)req->ptr2; 393 EIO_STRUCT_STATVFS *statdata = (EIO_STRUCT_STATVFS *)req->ptr2;
… …
338(via the C<opendir>, C<readdir> and C<closedir> calls) and returns either 409(via the C<opendir>, C<readdir> and C<closedir> calls) and returns either
339the names or an array of C<struct eio_dirent>, depending on the C<flags> 410the names or an array of C<struct eio_dirent>, depending on the C<flags>
340argument. 411argument.
341 412
342The C<< req->result >> indicates either the number of files found, or 413The C<< req->result >> indicates either the number of files found, or
343C<-1> on error. On success, zero-terminated names can be found as C<< req->ptr2 >>, 414C<-1> on error. On success, null-terminated names can be found as C<< req->ptr2 >>,
344and C<struct eio_dirents>, if requested by C<flags>, can be found via C<< 415and C<struct eio_dirents>, if requested by C<flags>, can be found via C<<
345req->ptr1 >>. 416req->ptr1 >>.
346 417
347Here is an example that prints all the names: 418Here is an example that prints all the names:
348 419
… …
480=item eio_sync_file_range (int fd, off_t offset, size_t nbytes, unsigned int flags, int pri, eio_cb cb, void *data) 551=item eio_sync_file_range (int fd, off_t offset, size_t nbytes, unsigned int flags, int pri, eio_cb cb, void *data)
481 552
482Calls C<sync_file_range>. If the syscall is missing, then this is the same 553Calls C<sync_file_range>. If the syscall is missing, then this is the same
483as calling C<fdatasync>. 554as calling C<fdatasync>.
484 555
556Flags can be any combination of C<EIO_SYNC_FILE_RANGE_WAIT_BEFORE>,
557C<EIO_SYNC_FILE_RANGE_WRITE> and C<EIO_SYNC_FILE_RANGE_WAIT_AFTER>.
558
485=back 559=back
486 560
487=head3 LIBEIO-SPECIFIC REQUESTS 561=head3 LIBEIO-SPECIFIC REQUESTS
488 562
489These requests are specific to libeio and do not correspond to any OS call. 563These requests are specific to libeio and do not correspond to any OS call.
490 564
491=over 4 565=over 4
492 566
493=item eio_mtouch (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data) 567=item eio_mtouch (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data)
494 568
569Reads (C<flags == 0>) or modifies (C<flags == EIO_MT_MODIFY) the given
570memory area, page-wise, that is, it reads (or reads and writes back) the
571first octet of every page that spans the memory area.
572
573This can be used to page in some mmapped file, or dirty some pages. Note
574that dirtying is an unlocked read-write access, so races can ensue when
575the some other thread modifies the data stored in that memory area.
576
495=item eio_custom (void (*)(eio_req *) execute, int pri, eio_cb cb, void *data) 577=item eio_custom (void (*)(eio_req *) execute, int pri, eio_cb cb, void *data)
496 578
497Executes a custom request, i.e., a user-specified callback. 579Executes a custom request, i.e., a user-specified callback.
498 580
499The callback gets the C<eio_req *> as parameter and is expected to read 581The callback gets the C<eio_req *> as parameter and is expected to read
500and modify any request-specific members. Specifically, it should set C<< 582and modify any request-specific members. Specifically, it should set C<<
… …
520 req->result = open (req->data, O_RDONLY); 602 req->result = open (req->data, O_RDONLY);
521 } 603 }
522 604
523 eio_custom (my_open, 0, my_open_done, "/etc/passwd"); 605 eio_custom (my_open, 0, my_open_done, "/etc/passwd");
524 606
525=item eio_busy (eio_tstamp delay, int pri, eio_cb cb, void *data) 607=item eio_busy (eio_tstamp delay, int pri, eio_cb cb, void *data)
526 608
527This is a a request that takes C<delay> seconds to execute, but otherwise 609This is a a request that takes C<delay> seconds to execute, but otherwise
528does nothing - it simply puts one of the worker threads to sleep for this 610does nothing - it simply puts one of the worker threads to sleep for this
529long. 611long.
530 612
531This request can be used to artificially increase load, e.g. for debugging 613This request can be used to artificially increase load, e.g. for debugging
532or benchmarking reasons. 614or benchmarking reasons.
533 615
534=item eio_nop (int pri, eio_cb cb, void *data) 616=item eio_nop (int pri, eio_cb cb, void *data)
535 617
536This request does nothing, except go through the whole request cycle. This 618This request does nothing, except go through the whole request cycle. This
537can be used to measure latency or in some cases to simplify code, but is 619can be used to measure latency or in some cases to simplify code, but is
538not really of much use. 620not really of much use.
539 621
540=back 622=back
541 623
542=head3 GROUPING AND LIMITING REQUESTS 624=head3 GROUPING AND LIMITING REQUESTS
625
626There is one more rather special request, C<eio_grp>. It is a very special
627aio request: Instead of doing something, it is a container for other eio
628requests.
629
630There are two primary use cases for this: a) bundle many requests into a
631single, composite, request with a definite callback and the ability to
632cancel the whole request with its subrequests and b) limiting the number
633of "active" requests.
634
635Further below you will find more dicussion of these topics - first follows
636the reference section detailing the request generator and other methods.
637
638=over 4
639
640=item eio_grp (eio_cb cb, void *data)
641
642Creates and submits a group request.
643
644=back
645
646
543 647
544#TODO 648#TODO
545 649
546/*****************************************************************************/ 650/*****************************************************************************/
547/* groups */ 651/* groups */

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