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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.208 by root, Mon Sep 26 20:19:08 2011 UTC vs.
Revision 1.220 by root, Sun Apr 1 17:46:02 2012 UTC

… …
168use common::sense; 168use common::sense;
169 169
170use base 'Exporter'; 170use base 'Exporter';
171 171
172BEGIN { 172BEGIN {
173 our $VERSION = '4.0'; 173 our $VERSION = '4.13';
174 174
175 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close 175 our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
176 aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx 176 aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
177 aio_scandir aio_symlink aio_readlink aio_realpath aio_sync 177 aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
178 aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_fallocate 178 aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_fallocate
179 aio_pathsync aio_readahead 179 aio_pathsync aio_readahead
180 aio_rename aio_link aio_move aio_copy aio_group 180 aio_rename aio_link aio_move aio_copy aio_group
… …
209documentation. 209documentation.
210 210
211 aio_wd $pathname, $callback->($wd) 211 aio_wd $pathname, $callback->($wd)
212 aio_open $pathname, $flags, $mode, $callback->($fh) 212 aio_open $pathname, $flags, $mode, $callback->($fh)
213 aio_close $fh, $callback->($status) 213 aio_close $fh, $callback->($status)
214 aio_seek $fh,$offset,$whence, $callback->($offs)
214 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 215 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
215 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 216 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
216 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 217 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
217 aio_readahead $fh,$offset,$length, $callback->($retval) 218 aio_readahead $fh,$offset,$length, $callback->($retval)
218 aio_stat $fh_or_path, $callback->($status) 219 aio_stat $fh_or_path, $callback->($status)
219 aio_lstat $fh, $callback->($status) 220 aio_lstat $fh, $callback->($status)
220 aio_statvfs $fh_or_path, $callback->($statvfs) 221 aio_statvfs $fh_or_path, $callback->($statvfs)
221 aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 222 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
222 aio_chown $fh_or_path, $uid, $gid, $callback->($status) 223 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
224 aio_chmod $fh_or_path, $mode, $callback->($status)
223 aio_truncate $fh_or_path, $offset, $callback->($status) 225 aio_truncate $fh_or_path, $offset, $callback->($status)
224 aio_chmod $fh_or_path, $mode, $callback->($status)
225 aio_unlink $pathname, $callback->($status) 226 aio_unlink $pathname, $callback->($status)
226 aio_mknod $path, $mode, $dev, $callback->($status) 227 aio_mknod $pathname, $mode, $dev, $callback->($status)
227 aio_link $srcpath, $dstpath, $callback->($status) 228 aio_link $srcpath, $dstpath, $callback->($status)
228 aio_symlink $srcpath, $dstpath, $callback->($status) 229 aio_symlink $srcpath, $dstpath, $callback->($status)
229 aio_readlink $path, $callback->($link) 230 aio_readlink $pathname, $callback->($link)
230 aio_realpath $path, $callback->($link) 231 aio_realpath $pathname, $callback->($link)
231 aio_rename $srcpath, $dstpath, $callback->($status) 232 aio_rename $srcpath, $dstpath, $callback->($status)
232 aio_mkdir $pathname, $mode, $callback->($status) 233 aio_mkdir $pathname, $mode, $callback->($status)
233 aio_rmdir $pathname, $callback->($status) 234 aio_rmdir $pathname, $callback->($status)
234 aio_readdir $pathname, $callback->($entries) 235 aio_readdir $pathname, $callback->($entries)
235 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 236 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
236 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST 237 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
237 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN 238 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
239 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
238 aio_load $path, $data, $callback->($status) 240 aio_load $pathname, $data, $callback->($status)
239 aio_copy $srcpath, $dstpath, $callback->($status) 241 aio_copy $srcpath, $dstpath, $callback->($status)
240 aio_move $srcpath, $dstpath, $callback->($status) 242 aio_move $srcpath, $dstpath, $callback->($status)
241 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
242 aio_rmtree $path, $callback->($status) 243 aio_rmtree $pathname, $callback->($status)
243 aio_sync $callback->($status) 244 aio_sync $callback->($status)
244 aio_syncfs $fh, $callback->($status) 245 aio_syncfs $fh, $callback->($status)
245 aio_fsync $fh, $callback->($status) 246 aio_fsync $fh, $callback->($status)
246 aio_fdatasync $fh, $callback->($status) 247 aio_fdatasync $fh, $callback->($status)
247 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 248 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
248 aio_pathsync $path, $callback->($status) 249 aio_pathsync $pathname, $callback->($status)
249 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 250 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
250 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 251 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
251 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status) 252 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
252 aio_mlockall $flags, $callback->($status) 253 aio_mlockall $flags, $callback->($status)
253 aio_group $callback->(...) 254 aio_group $callback->(...)
… …
276 IO::AIO::madvise $scalar, $offset, $length, $advice 277 IO::AIO::madvise $scalar, $offset, $length, $advice
277 IO::AIO::mprotect $scalar, $offset, $length, $protect 278 IO::AIO::mprotect $scalar, $offset, $length, $protect
278 IO::AIO::munlock $scalar, $offset = 0, $length = undef 279 IO::AIO::munlock $scalar, $offset = 0, $length = undef
279 IO::AIO::munlockall 280 IO::AIO::munlockall
280 281
281=head2 AIO REQUEST FUNCTIONS 282=head2 API NOTES
282 283
283All the C<aio_*> calls are more or less thin wrappers around the syscall 284All the C<aio_*> calls are more or less thin wrappers around the syscall
284with the same name (sans C<aio_>). The arguments are similar or identical, 285with the same name (sans C<aio_>). The arguments are similar or identical,
285and they all accept an additional (and optional) C<$callback> argument 286and they all accept an additional (and optional) C<$callback> argument
286which must be a code reference. This code reference will get called with 287which must be a code reference. This code reference will be called after
287the syscall return code (e.g. most syscalls return C<-1> on error, unlike 288the syscall has been executed in an asynchronous fashion. The results
288perl, which usually delivers "false") as its sole argument after the given 289of the request will be passed as arguments to the callback (and, if an
289syscall has been executed asynchronously. 290error occured, in C<$!>) - for most requests the syscall return code (e.g.
291most syscalls return C<-1> on error, unlike perl, which usually delivers
292"false").
293
294Some requests (such as C<aio_readdir>) pass the actual results and
295communicate failures by passing C<undef>.
290 296
291All functions expecting a filehandle keep a copy of the filehandle 297All functions expecting a filehandle keep a copy of the filehandle
292internally until the request has finished. 298internally until the request has finished.
293 299
294All functions return request objects of type L<IO::AIO::REQ> that allow 300All functions return request objects of type L<IO::AIO::REQ> that allow
295further manipulation of those requests while they are in-flight. 301further manipulation of those requests while they are in-flight.
296 302
297The pathnames you pass to these routines I<must> be absolute and 303The pathnames you pass to these routines I<should> be absolute. The
298encoded as octets. The reason for the former is that at the time the 304reason for this is that at the time the request is being executed, the
299request is being executed, the current working directory could have 305current working directory could have changed. Alternatively, you can
300changed. Alternatively, you can make sure that you never change the 306make sure that you never change the current working directory anywhere
301current working directory anywhere in the program and then use relative 307in the program and then use relative paths. You can also take advantage
302paths. 308of IO::AIOs working directory abstraction, that lets you specify paths
309relative to some previously-opened "working directory object" - see the
310description of the C<IO::AIO::WD> class later in this document.
303 311
304To encode pathnames as octets, either make sure you either: a) always pass 312To encode pathnames as octets, either make sure you either: a) always pass
305in filenames you got from outside (command line, readdir etc.) without 313in filenames you got from outside (command line, readdir etc.) without
306tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode 314tinkering, b) are in your native filesystem encoding, c) use the Encode
307your pathnames to the locale (or other) encoding in effect in the user 315module and encode your pathnames to the locale (or other) encoding in
308environment, d) use Glib::filename_from_unicode on unicode filenames or e) 316effect in the user environment, d) use Glib::filename_from_unicode on
309use something else to ensure your scalar has the correct contents. 317unicode filenames or e) use something else to ensure your scalar has the
318correct contents.
310 319
311This works, btw. independent of the internal UTF-8 bit, which IO::AIO 320This works, btw. independent of the internal UTF-8 bit, which IO::AIO
312handles correctly whether it is set or not. 321handles correctly whether it is set or not.
322
323=head2 AIO REQUEST FUNCTIONS
313 324
314=over 4 325=over 4
315 326
316=item $prev_pri = aioreq_pri [$pri] 327=item $prev_pri = aioreq_pri [$pri]
317 328
… …
399 410
400Or in other words: the file descriptor will be closed, but it will not be 411Or in other words: the file descriptor will be closed, but it will not be
401free for reuse until the perl filehandle is closed. 412free for reuse until the perl filehandle is closed.
402 413
403=cut 414=cut
415
416=item aio_seek $fh, $offset, $whence, $callback->($offs)
417
418Seeks the filehandle to the new C<$offset>, similarly to perl'S
419C<sysseek>. The C<$whence> can use the traditional values (C<0> for
420C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
421C<IO::AIO::SEEK_END>).
422
423The resulting absolute offset will be passed to the callback, or C<-1> in
424case of an error.
425
426In theory, the C<$whence> constants could be different than the
427corresponding values from L<Fcntl>, but perl guarantees they are the same,
428so don't panic.
404 429
405=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 430=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
406 431
407=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 432=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
408 433
… …
616 641
617Asynchronously unlink (delete) a file and call the callback with the 642Asynchronously unlink (delete) a file and call the callback with the
618result code. 643result code.
619 644
620 645
621=item aio_mknod $path, $mode, $dev, $callback->($status) 646=item aio_mknod $pathname, $mode, $dev, $callback->($status)
622 647
623[EXPERIMENTAL] 648[EXPERIMENTAL]
624 649
625Asynchronously create a device node (or fifo). See mknod(2). 650Asynchronously create a device node (or fifo). See mknod(2).
626 651
627The only (POSIX-) portable way of calling this function is: 652The only (POSIX-) portable way of calling this function is:
628 653
629 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 654 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
630 655
631See C<aio_stat> for info about some potentially helpful extra constants 656See C<aio_stat> for info about some potentially helpful extra constants
632and functions. 657and functions.
633 658
634=item aio_link $srcpath, $dstpath, $callback->($status) 659=item aio_link $srcpath, $dstpath, $callback->($status)
… …
641 666
642Asynchronously create a new symbolic link to the existing object at C<$srcpath> at 667Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
643the path C<$dstpath> and call the callback with the result code. 668the path C<$dstpath> and call the callback with the result code.
644 669
645 670
646=item aio_readlink $path, $callback->($link) 671=item aio_readlink $pathname, $callback->($link)
647 672
648Asynchronously read the symlink specified by C<$path> and pass it to 673Asynchronously read the symlink specified by C<$path> and pass it to
649the callback. If an error occurs, nothing or undef gets passed to the 674the callback. If an error occurs, nothing or undef gets passed to the
650callback. 675callback.
651 676
652 677
653=item aio_realpath $path, $callback->($path) 678=item aio_realpath $pathname, $callback->($path)
654 679
655Asynchronously make the path absolute and resolve any symlinks in 680Asynchronously make the path absolute and resolve any symlinks in
656C<$path>. The resulting path only consists of directories (Same as 681C<$path>. The resulting path only consists of directories (Same as
657L<Cwd::realpath>). 682L<Cwd::realpath>).
658 683
… …
753C<$type>'s are known, which can be used to speed up some algorithms. 778C<$type>'s are known, which can be used to speed up some algorithms.
754 779
755=back 780=back
756 781
757 782
758=item aio_load $path, $data, $callback->($status) 783=item aio_load $pathname, $data, $callback->($status)
759 784
760This is a composite request that tries to fully load the given file into 785This is a composite request that tries to fully load the given file into
761memory. Status is the same as with aio_read. 786memory. Status is the same as with aio_read.
762 787
763=cut 788=cut
… …
898 }; 923 };
899 924
900 $grp 925 $grp
901} 926}
902 927
903=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 928=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
904 929
905Scans a directory (similar to C<aio_readdir>) but additionally tries to 930Scans a directory (similar to C<aio_readdir>) but additionally tries to
906efficiently separate the entries of directory C<$path> into two sets of 931efficiently separate the entries of directory C<$path> into two sets of
907names, directories you can recurse into (directories), and ones you cannot 932names, directories you can recurse into (directories), and ones you cannot
908recurse into (everything else, including symlinks to directories). 933recurse into (everything else, including symlinks to directories).
… …
965 990
966 my $grp = aio_group $cb; 991 my $grp = aio_group $cb;
967 992
968 $maxreq = 4 if $maxreq <= 0; 993 $maxreq = 4 if $maxreq <= 0;
969 994
970 # stat once 995 # get a wd object
971 aioreq_pri $pri; 996 aioreq_pri $pri;
972 add $grp aio_stat $path, sub { 997 add $grp aio_wd $path, sub {
998 $_[0]
973 return $grp->result () if $_[0]; 999 or return $grp->result ();
974 my $now = time;
975 my $hash1 = join ":", (stat _)[0,1,3,7,9];
976 1000
977 # read the directory entries 1001 my $wd = [shift, "."];
1002
1003 # stat once
978 aioreq_pri $pri; 1004 aioreq_pri $pri;
979 add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub { 1005 add $grp aio_stat $wd, sub {
980 my $entries = shift
981 or return $grp->result (); 1006 return $grp->result () if $_[0];
1007 my $now = time;
1008 my $hash1 = join ":", (stat _)[0,1,3,7,9];
982 1009
983 # stat the dir another time 1010 # read the directory entries
984 aioreq_pri $pri; 1011 aioreq_pri $pri;
1012 add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
1013 my $entries = shift
1014 or return $grp->result ();
1015
1016 # stat the dir another time
1017 aioreq_pri $pri;
985 add $grp aio_stat $path, sub { 1018 add $grp aio_stat $wd, sub {
986 my $hash2 = join ":", (stat _)[0,1,3,7,9]; 1019 my $hash2 = join ":", (stat _)[0,1,3,7,9];
987 1020
988 my $ndirs; 1021 my $ndirs;
989 1022
990 # take the slow route if anything looks fishy 1023 # take the slow route if anything looks fishy
991 if ($hash1 ne $hash2 or (stat _)[9] == $now) { 1024 if ($hash1 ne $hash2 or (stat _)[9] == $now) {
992 $ndirs = -1; 1025 $ndirs = -1;
993 } else { 1026 } else {
994 # if nlink == 2, we are finished 1027 # if nlink == 2, we are finished
995 # for non-posix-fs's, we rely on nlink < 2 1028 # for non-posix-fs's, we rely on nlink < 2
996 $ndirs = (stat _)[3] - 2 1029 $ndirs = (stat _)[3] - 2
997 or return $grp->result ([], $entries); 1030 or return $grp->result ([], $entries);
998 } 1031 }
999 1032
1000 my (@dirs, @nondirs); 1033 my (@dirs, @nondirs);
1001 1034
1002 my $statgrp = add $grp aio_group sub { 1035 my $statgrp = add $grp aio_group sub {
1003 $grp->result (\@dirs, \@nondirs); 1036 $grp->result (\@dirs, \@nondirs);
1004 }; 1037 };
1005 1038
1006 limit $statgrp $maxreq; 1039 limit $statgrp $maxreq;
1007 feed $statgrp sub { 1040 feed $statgrp sub {
1008 return unless @$entries; 1041 return unless @$entries;
1009 my $entry = shift @$entries; 1042 my $entry = shift @$entries;
1010 1043
1011 aioreq_pri $pri; 1044 aioreq_pri $pri;
1045 $wd->[1] = "$entry/.";
1012 add $statgrp aio_stat "$path/$entry/.", sub { 1046 add $statgrp aio_stat $wd, sub {
1013 if ($_[0] < 0) { 1047 if ($_[0] < 0) {
1014 push @nondirs, $entry; 1048 push @nondirs, $entry;
1015 } else { 1049 } else {
1016 # need to check for real directory 1050 # need to check for real directory
1017 aioreq_pri $pri; 1051 aioreq_pri $pri;
1052 $wd->[1] = $entry;
1018 add $statgrp aio_lstat "$path/$entry", sub { 1053 add $statgrp aio_lstat $wd, sub {
1019 if (-d _) { 1054 if (-d _) {
1020 push @dirs, $entry; 1055 push @dirs, $entry;
1021 1056
1022 unless (--$ndirs) { 1057 unless (--$ndirs) {
1023 push @nondirs, @$entries; 1058 push @nondirs, @$entries;
1024 feed $statgrp; 1059 feed $statgrp;
1060 }
1061 } else {
1062 push @nondirs, $entry;
1025 } 1063 }
1026 } else {
1027 push @nondirs, $entry;
1028 } 1064 }
1029 } 1065 }
1030 } 1066 };
1031 }; 1067 };
1032 }; 1068 };
1033 }; 1069 };
1034 }; 1070 };
1035 }; 1071 };
1036 1072
1037 $grp 1073 $grp
1038} 1074}
1039 1075
1040=item aio_rmtree $path, $callback->($status) 1076=item aio_rmtree $pathname, $callback->($status)
1041 1077
1042Delete a directory tree starting (and including) C<$path>, return the 1078Delete a directory tree starting (and including) C<$path>, return the
1043status of the final C<rmdir> only. This is a composite request that 1079status of the final C<rmdir> only. This is a composite request that
1044uses C<aio_scandir> to recurse into and rmdir directories, and unlink 1080uses C<aio_scandir> to recurse into and rmdir directories, and unlink
1045everything else. 1081everything else.
… …
1106C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>, 1142C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1107C<IO::AIO::SYNC_FILE_RANGE_WRITE> and 1143C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1108C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range 1144C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1109manpage for details. 1145manpage for details.
1110 1146
1111=item aio_pathsync $path, $callback->($status) 1147=item aio_pathsync $pathname, $callback->($status)
1112 1148
1113This request tries to open, fsync and close the given path. This is a 1149This request tries to open, fsync and close the given path. This is a
1114composite request intended to sync directories after directory operations 1150composite request intended to sync directories after directory operations
1115(E.g. rename). This might not work on all operating systems or have any 1151(E.g. rename). This might not work on all operating systems or have any
1116specific effect, but usually it makes sure that directory changes get 1152specific effect, but usually it makes sure that directory changes get
… …
1259immense (it blocks a thread for a long time) so do not use this function 1295immense (it blocks a thread for a long time) so do not use this function
1260except to put your application under artificial I/O pressure. 1296except to put your application under artificial I/O pressure.
1261 1297
1262=back 1298=back
1263 1299
1300
1301=head2 IO::AIO::WD - multiple working directories
1302
1303Your process only has one current working directory, which is used by all
1304threads. This makes it hard to use relative paths (some other component
1305could call C<chdir> at any time, and it is hard to control when the path
1306will be used by IO::AIO).
1307
1308One solution for this is to always use absolute paths. This usually works,
1309but can be quite slow (the kernel has to walk the whole path on every
1310access), and can also be a hassle to implement.
1311
1312Newer POSIX systems have a number of functions (openat, fdopendir,
1313futimensat and so on) that make it possible to specify working directories
1314per operation.
1315
1316For portability, and because the clowns who "designed", or shall I write,
1317perpetrated this new interface were obviously half-drunk, this abstraction
1318cannot be perfect, though.
1319
1320IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
1321object. This object stores the canonicalised, absolute version of the
1322path, and on systems that allow it, also a directory file descriptor.
1323
1324Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
1325or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
1326object and a pathname instead (or the IO::AIO::WD object alone, which
1327gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
1328IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
1329to that IO::AIO::WD object.
1330
1331For example, to get a wd object for F</etc> and then stat F<passwd>
1332inside, you would write:
1333
1334 aio_wd "/etc", sub {
1335 my $etcdir = shift;
1336
1337 # although $etcdir can be undef on error, there is generally no reason
1338 # to check for errors here, as aio_stat will fail with ENOENT
1339 # when $etcdir is undef.
1340
1341 aio_stat [$etcdir, "passwd"], sub {
1342 # yay
1343 };
1344 };
1345
1346That C<aio_wd> is a request and not a normal function shows that creating
1347an IO::AIO::WD object is itself a potentially blocking operation, which is
1348why it is done asynchronously.
1349
1350To stat the directory obtained with C<aio_wd> above, one could write
1351either of the following three request calls:
1352
1353 aio_lstat "/etc" , sub { ... # pathname as normal string
1354 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1355 aio_lstat $wd , sub { ... # shorthand for the previous
1356
1357As with normal pathnames, IO::AIO keeps a copy of the working directory
1358object and the pathname string, so you could write the following without
1359causing any issues due to C<$path> getting reused:
1360
1361 my $path = [$wd, undef];
1362
1363 for my $name (qw(abc def ghi)) {
1364 $path->[1] = $name;
1365 aio_stat $path, sub {
1366 # ...
1367 };
1368 }
1369
1370There are some caveats: when directories get renamed (or deleted), the
1371pathname string doesn't change, so will point to the new directory (or
1372nowhere at all), while the directory fd, if available on the system,
1373will still point to the original directory. Most functions accepting a
1374pathname will use the directory fd on newer systems, and the string on
1375older systems. Some functions (such as realpath) will always rely on the
1376string form of the pathname.
1377
1378So this fucntionality is mainly useful to get some protection against
1379C<chdir>, to easily get an absolute path out of a relative path for future
1380reference, and to speed up doing many operations in the same directory
1381(e.g. when stat'ing all files in a directory).
1382
1383The following functions implement this working directory abstraction:
1384
1385=over 4
1386
1387=item aio_wd $pathname, $callback->($wd)
1388
1389Asynchonously canonicalise the given pathname and convert it to an
1390IO::AIO::WD object representing it. If possible and supported on the
1391system, also open a directory fd to speed up pathname resolution relative
1392to this working directory.
1393
1394If something goes wrong, then C<undef> is passwd to the callback instead
1395of a working directory object and C<$!> is set appropriately. Since
1396passing C<undef> as working directory component of a pathname fails the
1397request with C<ENOENT>, there is often no need for error checking in the
1398C<aio_wd> callback, as future requests using the value will fail in the
1399expected way.
1400
1401If this call isn't available because your OS lacks it or it couldn't be
1402detected, it will be emulated by calling C<fsync> instead.
1403
1404=item IO::AIO::CWD
1405
1406This is a compiletime constant (object) that represents the process
1407current working directory.
1408
1409Specifying this object as working directory object for a pathname is as
1410if the pathname would be specified directly, without a directory object,
1411e.g., these calls are functionally identical:
1412
1413 aio_stat "somefile", sub { ... };
1414 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1415
1416=back
1417
1418
1264=head2 IO::AIO::REQ CLASS 1419=head2 IO::AIO::REQ CLASS
1265 1420
1266All non-aggregate C<aio_*> functions return an object of this class when 1421All non-aggregate C<aio_*> functions return an object of this class when
1267called in non-void context. 1422called in non-void context.
1268 1423
… …
1385 1540
1386Sets a feeder/generator on this group: every group can have an attached 1541Sets a feeder/generator on this group: every group can have an attached
1387generator that generates requests if idle. The idea behind this is that, 1542generator that generates requests if idle. The idea behind this is that,
1388although you could just queue as many requests as you want in a group, 1543although you could just queue as many requests as you want in a group,
1389this might starve other requests for a potentially long time. For example, 1544this might starve other requests for a potentially long time. For example,
1390C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests, 1545C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1391delaying any later requests for a long time. 1546requests, delaying any later requests for a long time.
1392 1547
1393To avoid this, and allow incremental generation of requests, you can 1548To avoid this, and allow incremental generation of requests, you can
1394instead a group and set a feeder on it that generates those requests. The 1549instead a group and set a feeder on it that generates those requests. The
1395feed callback will be called whenever there are few enough (see C<limit>, 1550feed callback will be called whenever there are few enough (see C<limit>,
1396below) requests active in the group itself and is expected to queue more 1551below) requests active in the group itself and is expected to queue more

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