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Revision 1.27 by root, Sun Jul 24 03:32:54 2011 UTC vs.
Revision 1.35 by root, Mon Aug 18 08:11:54 2014 UTC

25similar functions, as well as less rarely ones such as C<mknod>, C<futime> 25similar functions, as well as less rarely ones such as C<mknod>, C<futime>
26or C<readlink>. 26or C<readlink>.
27 27
28It also offers wrappers around C<sendfile> (Solaris, Linux, HP-UX and 28It also offers wrappers around C<sendfile> (Solaris, Linux, HP-UX and
29FreeBSD, with emulation on other platforms) and C<readahead> (Linux, with 29FreeBSD, with emulation on other platforms) and C<readahead> (Linux, with
30emulation elsewhere>). 30emulation elsewhere).
31 31
32The goal is to enable you to write fully non-blocking programs. For 32The goal is to enable you to write fully non-blocking programs. For
33example, in a game server, you would not want to freeze for a few seconds 33example, in a game server, you would not want to freeze for a few seconds
34just because the server is running a backup and you happen to call 34just because the server is running a backup and you happen to call
35C<readdir>. 35C<readdir>.
176 { 176 {
177 loop = EV_DEFAULT; 177 loop = EV_DEFAULT;
178 178
179 ev_idle_init (&repeat_watcher, repeat); 179 ev_idle_init (&repeat_watcher, repeat);
180 ev_async_init (&ready_watcher, ready); 180 ev_async_init (&ready_watcher, ready);
181 ev_async_start (loop &watcher); 181 ev_async_start (loop, &watcher);
182 182
183 eio_init (want_poll, 0); 183 eio_init (want_poll, 0);
184 } 184 }
185 185
186For most other event loops, you would typically use a pipe - the event 186For most other event loops, you would typically use a pipe - the event
233 233
234The C<void *data> member simply stores the value of the C<data> argument. 234The C<void *data> member simply stores the value of the C<data> argument.
235 235
236=back 236=back
237 237
238Members not explicitly described as accessible must not be
239accessed. Specifically, there is no guarantee that any members will still
240have the value they had when the request was submitted.
241
238The return value of the callback is normally C<0>, which tells libeio to 242The return value of the callback is normally C<0>, which tells libeio to
239continue normally. If a callback returns a nonzero value, libeio will 243continue normally. If a callback returns a nonzero value, libeio will
240stop processing results (in C<eio_poll>) and will return the value to its 244stop processing results (in C<eio_poll>) and will return the value to its
241caller. 245caller.
242 246
243Memory areas passed to libeio must stay valid as long as a request 247Memory areas passed to libeio wrappers must stay valid as long as a
244executes, with the exception of paths, which are being copied 248request executes, with the exception of paths, which are being copied
245internally. Any memory libeio itself allocates will be freed after the 249internally. Any memory libeio itself allocates will be freed after the
246finish callback has been called. If you want to manage all memory passed 250finish callback has been called. If you want to manage all memory passed
247to libeio yourself you can use the low-level API. 251to libeio yourself you can use the low-level API.
248 252
249For example, to open a file, you could do this: 253For example, to open a file, you could do this:
286 290
287Cancel the request (and all its subrequests). If the request is currently 291Cancel the request (and all its subrequests). If the request is currently
288executing it might still continue to execute, and in other cases it might 292executing it might still continue to execute, and in other cases it might
289still take a while till the request is cancelled. 293still take a while till the request is cancelled.
290 294
291Even if cancelled, the finish callback will still be invoked - the 295When cancelled, the finish callback will not be invoked.
292callbacks of all cancellable requests need to check whether the request
293has been cancelled by calling C<EIO_CANCELLED (req)>:
294
295 static int
296 my_eio_cb (eio_req *req)
297 {
298 if (EIO_CANCELLED (req))
299 return 0;
300 }
301
302In addition, cancelled requests will I<either> have C<< req->result >>
303set to C<-1> and C<errno> to C<ECANCELED>, or I<otherwise> they were
304successfully executed, despite being cancelled (e.g. when they have
305already been executed at the time they were cancelled).
306 296
307C<EIO_CANCELLED> is still true for requests that have successfully 297C<EIO_CANCELLED> is still true for requests that have successfully
308executed, as long as C<eio_cancel> was called on them at some point. 298executed, as long as C<eio_cancel> was called on them at some point.
309 299
310=back 300=back
626 616
627=over 4 617=over 4
628 618
629=item eio_mtouch (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data) 619=item eio_mtouch (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data)
630 620
631Reads (C<flags == 0>) or modifies (C<flags == EIO_MT_MODIFY) the given 621Reads (C<flags == 0>) or modifies (C<flags == EIO_MT_MODIFY>) the given
632memory area, page-wise, that is, it reads (or reads and writes back) the 622memory area, page-wise, that is, it reads (or reads and writes back) the
633first octet of every page that spans the memory area. 623first octet of every page that spans the memory area.
634 624
635This can be used to page in some mmapped file, or dirty some pages. Note 625This can be used to page in some mmapped file, or dirty some pages. Note
636that dirtying is an unlocked read-write access, so races can ensue when 626that dirtying is an unlocked read-write access, so races can ensue when
760request finish on its own. 750request finish on its own.
761 751
762=item 3) open callback adds more requests 752=item 3) open callback adds more requests
763 753
764In the open callback, if the open was not successful, copy C<< 754In the open callback, if the open was not successful, copy C<<
765req->errorno >> to C<< grp->errorno >> and set C<< grp->errorno >> to 755req->errorno >> to C<< grp->errorno >> and set C<< grp->result >> to
766C<-1> to signal an error. 756C<-1> to signal an error.
767 757
768Otherwise, malloc some memory or so and issue a read request, adding the 758Otherwise, malloc some memory or so and issue a read request, adding the
769read request to the group. 759read request to the group.
770 760
771=item 4) continue issuing requests till finished 761=item 4) continue issuing requests till finished
772 762
773In the real callback, check for errors and possibly continue with 763In the read callback, check for errors and possibly continue with
774C<eio_close> or any other eio request in the same way. 764C<eio_close> or any other eio request in the same way.
775 765
776As soon as no new requests are added the group request will finish. Make 766As soon as no new requests are added, the group request will finish. Make
777sure you I<always> set C<< grp->result >> to some sensible value. 767sure you I<always> set C<< grp->result >> to some sensible value.
778 768
779=back 769=back
780 770
781=head4 REQUEST LIMITING 771=head4 REQUEST LIMITING
783 773
784#TODO 774#TODO
785 775
786void eio_grp_limit (eio_req *grp, int limit); 776void eio_grp_limit (eio_req *grp, int limit);
787 777
788
789=back
790 778
791 779
792=head1 LOW LEVEL REQUEST API 780=head1 LOW LEVEL REQUEST API
793 781
794#TODO 782#TODO
922This symbol governs the stack size for each eio thread. Libeio itself 910This symbol governs the stack size for each eio thread. Libeio itself
923was written to use very little stackspace, but when using C<EIO_CUSTOM> 911was written to use very little stackspace, but when using C<EIO_CUSTOM>
924requests, you might want to increase this. 912requests, you might want to increase this.
925 913
926If this symbol is undefined (the default) then libeio will use its default 914If this symbol is undefined (the default) then libeio will use its default
927stack size (C<sizeof (void *) * 4096> currently). If it is defined, but 915stack size (C<sizeof (void *) * 4096> currently). In all other cases, the
928C<0>, then the default operating system stack size will be used. In all
929other cases, the value must be an expression that evaluates to the desired 916value must be an expression that evaluates to the desired stack size.
930stack size.
931 917
932=back 918=back
933 919
934 920
935=head1 PORTABILITY REQUIREMENTS 921=head1 PORTABILITY REQUIREMENTS

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