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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.265 by root, Mon Jul 18 08:03:22 2016 UTC vs.
Revision 1.278 by root, Sun Oct 1 07:24:34 2017 UTC

171use common::sense; 171use common::sense;
172 172
173use base 'Exporter'; 173use base 'Exporter';
174 174
175BEGIN { 175BEGIN {
176 our $VERSION = 4.34; 176 our $VERSION = 4.35;
177 177
178 our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close 178 our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
179 aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx 179 aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
180 aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl 180 aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
181 aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range 181 aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
182 aio_pathsync aio_readahead aio_fiemap aio_allocate 182 aio_pathsync aio_readahead aio_fiemap aio_allocate
183 aio_rename aio_link aio_move aio_copy aio_group 183 aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
184 aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown 184 aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
185 aio_chmod aio_utime aio_truncate 185 aio_chmod aio_utime aio_truncate
186 aio_msync aio_mtouch aio_mlock aio_mlockall 186 aio_msync aio_mtouch aio_mlock aio_mlockall
187 aio_statvfs 187 aio_statvfs
188 aio_wd); 188 aio_wd);
233 aio_link $srcpath, $dstpath, $callback->($status) 233 aio_link $srcpath, $dstpath, $callback->($status)
234 aio_symlink $srcpath, $dstpath, $callback->($status) 234 aio_symlink $srcpath, $dstpath, $callback->($status)
235 aio_readlink $pathname, $callback->($link) 235 aio_readlink $pathname, $callback->($link)
236 aio_realpath $pathname, $callback->($path) 236 aio_realpath $pathname, $callback->($path)
237 aio_rename $srcpath, $dstpath, $callback->($status) 237 aio_rename $srcpath, $dstpath, $callback->($status)
238 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
238 aio_mkdir $pathname, $mode, $callback->($status) 239 aio_mkdir $pathname, $mode, $callback->($status)
239 aio_rmdir $pathname, $callback->($status) 240 aio_rmdir $pathname, $callback->($status)
240 aio_readdir $pathname, $callback->($entries) 241 aio_readdir $pathname, $callback->($entries)
241 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 242 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
242 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST 243 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
252 aio_syncfs $fh, $callback->($status) 253 aio_syncfs $fh, $callback->($status)
253 aio_fsync $fh, $callback->($status) 254 aio_fsync $fh, $callback->($status)
254 aio_fdatasync $fh, $callback->($status) 255 aio_fdatasync $fh, $callback->($status)
255 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 256 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
256 aio_pathsync $pathname, $callback->($status) 257 aio_pathsync $pathname, $callback->($status)
257 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 258 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
258 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 259 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
259 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status) 260 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
260 aio_mlockall $flags, $callback->($status) 261 aio_mlockall $flags, $callback->($status)
261 aio_group $callback->(...) 262 aio_group $callback->(...)
262 aio_nop $callback->() 263 aio_nop $callback->()
276 IO::AIO::idle_timeout $seconds 277 IO::AIO::idle_timeout $seconds
277 IO::AIO::max_outstanding $maxreqs 278 IO::AIO::max_outstanding $maxreqs
278 IO::AIO::nreqs 279 IO::AIO::nreqs
279 IO::AIO::nready 280 IO::AIO::nready
280 IO::AIO::npending 281 IO::AIO::npending
282 $nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
283 IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
281 284
282 IO::AIO::sendfile $ofh, $ifh, $offset, $count 285 IO::AIO::sendfile $ofh, $ifh, $offset, $count
283 IO::AIO::fadvise $fh, $offset, $len, $advice 286 IO::AIO::fadvise $fh, $offset, $len, $advice
284 IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]] 287 IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
285 IO::AIO::munmap $scalar 288 IO::AIO::munmap $scalar
445=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 448=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
446 449
447=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 450=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
448 451
449Reads or writes C<$length> bytes from or to the specified C<$fh> and 452Reads or writes C<$length> bytes from or to the specified C<$fh> and
450C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> 453C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
451and calls the callback without the actual number of bytes read (or -1 on 454calls the callback with the actual number of bytes transferred (or -1 on
452error, just like the syscall). 455error, just like the syscall).
453 456
454C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to 457C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
455offset plus the actual number of bytes read. 458offset plus the actual number of bytes read.
456 459
739C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate 742C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
740space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>, 743space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
741to deallocate a file range. 744to deallocate a file range.
742 745
743IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range 746IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
744(without leaving a hole) and C<FALLOC_FL_ZERO_RANGE>, to zero a range (see 747(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
745your L<fallocate(2)> manpage). 748C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
749to unshare shared blocks (see your L<fallocate(2)> manpage).
746 750
747The file system block size used by C<fallocate> is presumably the 751The file system block size used by C<fallocate> is presumably the
748C<f_bsize> returned by C<statvfs>. 752C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
753can dictate other limitations.
749 754
750If C<fallocate> isn't available or cannot be emulated (currently no 755If C<fallocate> isn't available or cannot be emulated (currently no
751emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>. 756emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
752 757
753 758
810rename(2) and call the callback with the result code. 815rename(2) and call the callback with the result code.
811 816
812On systems that support the AIO::WD working directory abstraction 817On systems that support the AIO::WD working directory abstraction
813natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead 818natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
814of failing, C<rename> is called on the absolute path of C<$wd>. 819of failing, C<rename> is called on the absolute path of C<$wd>.
820
821
822=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
823
824Basically a version of C<aio_rename> with an additional C<$flags>
825argument. Calling this with C<$flags=0> is the same as calling
826C<aio_rename>.
827
828Non-zero flags are currently only supported on GNU/Linux systems that
829support renameat2. Other systems fail with C<ENOSYS> in this case.
830
831The following constants are available (missing ones are, as usual C<0>),
832see renameat2(2) for details:
833
834C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
835and C<IO::AIO::RENAME_WHITEOUT>.
815 836
816 837
817=item aio_mkdir $pathname, $mode, $callback->($status) 838=item aio_mkdir $pathname, $mode, $callback->($status)
818 839
819Asynchronously mkdir (create) a directory and call the callback with 840Asynchronously mkdir (create) a directory and call the callback with
938=item aio_copy $srcpath, $dstpath, $callback->($status) 959=item aio_copy $srcpath, $dstpath, $callback->($status)
939 960
940Try to copy the I<file> (directories not supported as either source or 961Try to copy the I<file> (directories not supported as either source or
941destination) from C<$srcpath> to C<$dstpath> and call the callback with 962destination) from C<$srcpath> to C<$dstpath> and call the callback with
942a status of C<0> (ok) or C<-1> (error, see C<$!>). 963a status of C<0> (ok) or C<-1> (error, see C<$!>).
964
965Existing destination files will be truncated.
943 966
944This is a composite request that creates the destination file with 967This is a composite request that creates the destination file with
945mode 0200 and copies the contents of the source file into it using 968mode 0200 and copies the contents of the source file into it using
946C<aio_sendfile>, followed by restoring atime, mtime, access mode and 969C<aio_sendfile>, followed by restoring atime, mtime, access mode and
947uid/gid, in that order. 970uid/gid, in that order.
1057Scans a directory (similar to C<aio_readdir>) but additionally tries to 1080Scans a directory (similar to C<aio_readdir>) but additionally tries to
1058efficiently separate the entries of directory C<$path> into two sets of 1081efficiently separate the entries of directory C<$path> into two sets of
1059names, directories you can recurse into (directories), and ones you cannot 1082names, directories you can recurse into (directories), and ones you cannot
1060recurse into (everything else, including symlinks to directories). 1083recurse into (everything else, including symlinks to directories).
1061 1084
1062C<aio_scandir> is a composite request that creates of many sub requests_ 1085C<aio_scandir> is a composite request that generates many sub requests.
1063C<$maxreq> specifies the maximum number of outstanding aio requests that 1086C<$maxreq> specifies the maximum number of outstanding aio requests that
1064this function generates. If it is C<< <= 0 >>, then a suitable default 1087this function generates. If it is C<< <= 0 >>, then a suitable default
1065will be chosen (currently 4). 1088will be chosen (currently 4).
1066 1089
1067On error, the callback is called without arguments, otherwise it receives 1090On error, the callback is called without arguments, otherwise it receives
1254other processes), although if you are careful and know what you are doing, 1277other processes), although if you are careful and know what you are doing,
1255you still can. 1278you still can.
1256 1279
1257The following constants are available (missing ones are, as usual C<0>): 1280The following constants are available (missing ones are, as usual C<0>):
1258 1281
1282C<F_DUPFD_CLOEXEC>,
1283
1284C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
1285
1259C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>. 1286C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
1260 1287
1261C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>, 1288C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
1262C<FS_IOC_FIEMAP>. 1289C<FS_IOC_FIEMAP>.
1263 1290
1350 }; 1377 };
1351 1378
1352 $grp 1379 $grp
1353} 1380}
1354 1381
1355=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 1382=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
1356 1383
1357This is a rather advanced IO::AIO call, which only works on mmap(2)ed 1384This is a rather advanced IO::AIO call, which only works on mmap(2)ed
1358scalars (see the C<IO::AIO::mmap> function, although it also works on data 1385scalars (see the C<IO::AIO::mmap> function, although it also works on data
1359scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the 1386scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
1360scalar must only be modified in-place while an aio operation is pending on 1387scalar must only be modified in-place while an aio operation is pending on
1362 1389
1363It calls the C<msync> function of your OS, if available, with the memory 1390It calls the C<msync> function of your OS, if available, with the memory
1364area starting at C<$offset> in the string and ending C<$length> bytes 1391area starting at C<$offset> in the string and ending C<$length> bytes
1365later. If C<$length> is negative, counts from the end, and if C<$length> 1392later. If C<$length> is negative, counts from the end, and if C<$length>
1366is C<undef>, then it goes till the end of the string. The flags can be 1393is C<undef>, then it goes till the end of the string. The flags can be
1367a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and 1394either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1368C<IO::AIO::MS_SYNC>. 1395C<IO::AIO::MS_INVALIDATE>.
1369 1396
1370=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 1397=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1371 1398
1372This is a rather advanced IO::AIO call, which works best on mmap(2)ed 1399This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1373scalars. 1400scalars.
1456C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>, 1483C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
1457C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>, 1484C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
1458C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or 1485C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
1459C<IO::AIO::FIEMAP_EXTENT_SHARED>. 1486C<IO::AIO::FIEMAP_EXTENT_SHARED>.
1460 1487
1461At the time of this writing (Linux 3.2), this requets is unreliable unless 1488At the time of this writing (Linux 3.2), this request is unreliable unless
1462C<$count> is C<undef>, as the kernel has all sorts of bugs preventing 1489C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
1463it to return all extents of a range for files with large number of 1490it to return all extents of a range for files with a large number of
1464extents. The code works around all these issues if C<$count> is undef. 1491extents. The code (only) works around all these issues if C<$count> is
1492C<undef>.
1465 1493
1466=item aio_group $callback->(...) 1494=item aio_group $callback->(...)
1467 1495
1468This is a very special aio request: Instead of doing something, it is a 1496This is a very special aio request: Instead of doing something, it is a
1469container for other aio requests, which is useful if you want to bundle 1497container for other aio requests, which is useful if you want to bundle
1582There are some caveats: when directories get renamed (or deleted), the 1610There are some caveats: when directories get renamed (or deleted), the
1583pathname string doesn't change, so will point to the new directory (or 1611pathname string doesn't change, so will point to the new directory (or
1584nowhere at all), while the directory fd, if available on the system, 1612nowhere at all), while the directory fd, if available on the system,
1585will still point to the original directory. Most functions accepting a 1613will still point to the original directory. Most functions accepting a
1586pathname will use the directory fd on newer systems, and the string on 1614pathname will use the directory fd on newer systems, and the string on
1587older systems. Some functions (such as realpath) will always rely on the 1615older systems. Some functions (such as C<aio_realpath>) will always rely on
1588string form of the pathname. 1616the string form of the pathname.
1589 1617
1590So this functionality is mainly useful to get some protection against 1618So this functionality is mainly useful to get some protection against
1591C<chdir>, to easily get an absolute path out of a relative path for future 1619C<chdir>, to easily get an absolute path out of a relative path for future
1592reference, and to speed up doing many operations in the same directory 1620reference, and to speed up doing many operations in the same directory
1593(e.g. when stat'ing all files in a directory). 1621(e.g. when stat'ing all files in a directory).
1985This is a very bad function to use in interactive programs because it 2013This is a very bad function to use in interactive programs because it
1986blocks, and a bad way to reduce concurrency because it is inexact: Better 2014blocks, and a bad way to reduce concurrency because it is inexact: Better
1987use an C<aio_group> together with a feed callback. 2015use an C<aio_group> together with a feed callback.
1988 2016
1989Its main use is in scripts without an event loop - when you want to stat 2017Its main use is in scripts without an event loop - when you want to stat
1990a lot of files, you can write somehting like this: 2018a lot of files, you can write something like this:
1991 2019
1992 IO::AIO::max_outstanding 32; 2020 IO::AIO::max_outstanding 32;
1993 2021
1994 for my $path (...) { 2022 for my $path (...) {
1995 aio_stat $path , ...; 2023 aio_stat $path , ...;
2040some "Advanced I/O" function not available to in Perl, without going the 2068some "Advanced I/O" function not available to in Perl, without going the
2041"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*> 2069"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
2042counterpart. 2070counterpart.
2043 2071
2044=over 4 2072=over 4
2073
2074=item $numfd = IO::AIO::get_fdlimit
2075
2076This function is I<EXPERIMENTAL> and subject to change.
2077
2078Tries to find the current file descriptor limit and returns it, or
2079C<undef> and sets C<$!> in case of an error. The limit is one larger than
2080the highest valid file descriptor number.
2081
2082=item IO::AIO::min_fdlimit [$numfd]
2083
2084This function is I<EXPERIMENTAL> and subject to change.
2085
2086Try to increase the current file descriptor limit(s) to at least C<$numfd>
2087by changing the soft or hard file descriptor resource limit. If C<$numfd>
2088is missing, it will try to set a very high limit, although this is not
2089recommended when you know the actual minimum that you require.
2090
2091If the limit cannot be raised enough, the function makes a best-effort
2092attempt to increase the limit as much as possible, using various
2093tricks, while still failing. You can query the resulting limit using
2094C<IO::AIO::get_fdlimit>.
2095
2096If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
2097true.
2045 2098
2046=item IO::AIO::sendfile $ofh, $ifh, $offset, $count 2099=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
2047 2100
2048Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>, 2101Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
2049but is blocking (this makes most sense if you know the input data is 2102but is blocking (this makes most sense if you know the input data is
2066=item IO::AIO::madvise $scalar, $offset, $len, $advice 2119=item IO::AIO::madvise $scalar, $offset, $len, $advice
2067 2120
2068Simply calls the C<posix_madvise> function (see its 2121Simply calls the C<posix_madvise> function (see its
2069manpage for details). The following advice constants are 2122manpage for details). The following advice constants are
2070available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>, 2123available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
2071C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>, 2124C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
2072C<IO::AIO::MADV_FREE>. 2125C<IO::AIO::MADV_DONTNEED>.
2126
2127If C<$offset> is negative, counts from the end. If C<$length> is negative,
2128the remaining length of the C<$scalar> is used. If possible, C<$length>
2129will be reduced to fit into the C<$scalar>.
2073 2130
2074On systems that do not implement C<posix_madvise>, this function returns 2131On systems that do not implement C<posix_madvise>, this function returns
2075ENOSYS, otherwise the return value of C<posix_madvise>. 2132ENOSYS, otherwise the return value of C<posix_madvise>.
2076 2133
2077=item IO::AIO::mprotect $scalar, $offset, $len, $protect 2134=item IO::AIO::mprotect $scalar, $offset, $len, $protect
2079Simply calls the C<mprotect> function on the preferably AIO::mmap'ed 2136Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
2080$scalar (see its manpage for details). The following protect 2137$scalar (see its manpage for details). The following protect
2081constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>, 2138constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
2082C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>. 2139C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
2083 2140
2141If C<$offset> is negative, counts from the end. If C<$length> is negative,
2142the remaining length of the C<$scalar> is used. If possible, C<$length>
2143will be reduced to fit into the C<$scalar>.
2144
2084On systems that do not implement C<mprotect>, this function returns 2145On systems that do not implement C<mprotect>, this function returns
2085ENOSYS, otherwise the return value of C<mprotect>. 2146ENOSYS, otherwise the return value of C<mprotect>.
2086 2147
2087=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset] 2148=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
2088 2149
2089Memory-maps a file (or anonymous memory range) and attaches it to the 2150Memory-maps a file (or anonymous memory range) and attaches it to the
2090given C<$scalar>, which will act like a string scalar. Returns true on 2151given C<$scalar>, which will act like a string scalar. Returns true on
2091success, and false otherwise. 2152success, and false otherwise.
2092 2153
2154The scalar must exist, but its contents do not matter - this means you
2155cannot use a nonexistant array or hash element. When in doubt, C<undef>
2156the scalar first.
2157
2093The only operations allowed on the scalar are C<substr>/C<vec> that don't 2158The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
2094change the string length, and most read-only operations such as copying it 2159which don't change the string length, and most read-only operations such
2095or searching it with regexes and so on. 2160as copying it or searching it with regexes and so on.
2096 2161
2097Anything else is unsafe and will, at best, result in memory leaks. 2162Anything else is unsafe and will, at best, result in memory leaks.
2098 2163
2099The memory map associated with the C<$scalar> is automatically removed 2164The memory map associated with the C<$scalar> is automatically removed
2100when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or 2165when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
2101C<IO::AIO::munmap> functions are called. 2166or C<IO::AIO::munmap> functions are called on it.
2102 2167
2103This calls the C<mmap>(2) function internally. See your system's manual 2168This calls the C<mmap>(2) function internally. See your system's manual
2104page for details on the C<$length>, C<$prot> and C<$flags> parameters. 2169page for details on the C<$length>, C<$prot> and C<$flags> parameters.
2105 2170
2106The C<$length> must be larger than zero and smaller than the actual 2171The C<$length> must be larger than zero and smaller than the actual

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