[ViewVC] Diff of: cvs/IO-AIO/AIO.pm

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.120 by root, Sun Dec 2 21:51:36 2007 UTC vs.
Revision 1.148 by root, Sat Jun 6 17:25:13 2009 UTC

  $req->cancel; # cancel request if still in queue
  my $grp = aio_group sub { print "all stats done\n" };
  add $grp aio_stat "..." for ...;
- # AnyEvent integration (EV, Event, Glib, Tk, urxvt, pureperl...)
+ # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
- open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
+ use AnyEvent::AIO;
- my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
  # EV integration
  my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
  # Event integration
 use strict 'vars';
 use base 'Exporter';
 BEGIN {
-   our $VERSION = '2.6';
+   our $VERSION = '3.19';
    our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
-                     aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir
+                     aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
                      aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
-                     aio_fdatasync aio_pathsync aio_readahead
+                     aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
                      aio_rename aio_link aio_move aio_copy aio_group
                      aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
                      aio_chmod aio_utime aio_truncate);
-   our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
+   our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
    our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
                        min_parallel max_parallel max_idle
                        nreqs nready npending nthreads
                        max_poll_time max_poll_reqs);
+   push @AIO_REQ, qw(aio_busy); # not exported
    @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
    require XSLoader;
    XSLoader::load ("IO::AIO", $VERSION);
 All the C<aio_*> calls are more or less thin wrappers around the syscall
 with the same name (sans C<aio_>). The arguments are similar or identical,
 and they all accept an additional (and optional) C<$callback> argument
 which must be a code reference. This code reference will get called with
 the syscall return code (e.g. most syscalls return C<-1> on error, unlike
-perl, which usually delivers "false") as it's sole argument when the given
+perl, which usually delivers "false") as its sole argument after the given
 syscall has been executed asynchronously.
 All functions expecting a filehandle keep a copy of the filehandle
 internally until the request has finished.
 your pathnames to the locale (or other) encoding in effect in the user
 environment, d) use Glib::filename_from_unicode on unicode filenames or e)
 use something else to ensure your scalar has the correct contents.
 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
-handles correctly wether it is set or not.
+handles correctly whether it is set or not.
 =over 4
 =item $prev_pri = aioreq_pri [$pri]
 Asynchronously close a file and call the callback with the result
 code.
 Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
-closing the file descriptor associated with the filehandle itself. Here is
+closing the file descriptor associated with the filehandle itself.
-what aio_close will try:
-   1. dup()licate the fd
+Therefore, C<aio_close> will not close the filehandle - instead it will
-   2. asynchronously close() the duplicated fd
+use dup2 to overwrite the file descriptor with the write-end of a pipe
-   3. dup()licate the fd once more
+(the pipe fd will be created on demand and will be cached).
-   4. let perl close() the filehandle
-   5. asynchronously close the duplicated fd
-The idea is that the first close() flushes stuff to disk that closing an
+Or in other words: the file descriptor will be closed, but it will not be
-fd will flush, so when perl closes the fd, nothing much will need to be
+free for reuse until the perl filehandle is closed.
-flushed.  The second async. close() will then flush stuff to disk that
-closing the last fd to the file will flush.
-Just FYI, SuSv3 has this to say on close:
-   All outstanding record locks owned by the process on the file
-   associated with the file descriptor shall be removed.
-   If fildes refers to a socket, close() shall cause the socket to be
-   destroyed. ... close() shall block for up to the current linger
-   interval until all data is transmitted.
-   [this actually sounds like a specification bug, but who knows]
-And at least Linux additionally actually flushes stuff on every close,
-even when the file itself is still open.
-Sounds enourmously inefficient and complicated? Yes... please show me how
-to nuke perl's fd out of existence...
 =cut
-sub aio_close($;$) {
-   aio_block {
-      my ($fh, $cb) = @_;
-      my $pri = aioreq_pri;
-      my $grp = aio_group $cb;
-      my $fd = fileno $fh;
-      defined $fd or Carp::croak "aio_close called with fd-less filehandle";
-      # if the dups fail we will simply get EBADF
-      my $fd2 = _dup $fd;
-      aioreq_pri $pri;
-      add $grp _aio_close $fd2, sub {
-         my $fd2 = _dup $fd;
-         close $fh;
-         aioreq_pri $pri;
-         add $grp _aio_close $fd2, sub {
-            $grp->result ($_[0]);
-         };
-      };
-      $grp
-   }
-}
 =item aio_read  $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
 =item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
-Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
+Reads or writes C<$length> bytes from or to the specified C<$fh> and
-into the scalar given by C<$data> and offset C<$dataoffset> and calls the
+C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
-callback without the actual number of bytes read (or -1 on error, just
+and calls the callback without the actual number of bytes read (or -1 on
-like the syscall).
+error, just like the syscall).
+C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
+offset plus the actual number of bytes read.
 If C<$offset> is undefined, then the current file descriptor offset will
 be used (and updated), otherwise the file descriptor offset will not be
 changed by these calls.
-If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
+If C<$length> is undefined in C<aio_write>, use the remaining length of
+C<$data>.
 If C<$dataoffset> is less than zero, it will be counted from the end of
 C<$data>.
 The C<$data> scalar I<MUST NOT> be modified in any way while the request
 Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
 directory (i.e. opendir + readdir + closedir). The entries will not be
 sorted, and will B<NOT> include the C<.> and C<..> entries.
-The callback a single argument which is either C<undef> or an array-ref
+The callback is passed a single argument which is either C<undef> or an
-with the filenames.
+array-ref with the filenames.
+=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
+Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune
+behaviour and output format. In case of an error, C<$entries> will be
+C<undef>.
+The flags are a combination of the following constants, ORed together (the
+flags will also be passed to the callback, possibly modified):
+=over 4
+=item AIO::READDIR_DENTS
+When this flag is off, then the callback gets an arrayref with of names
+only (as with C<aio_readdir>), otherwise it gets an arrayref with
+C<[$name, $inode, $type]> arrayrefs, each describing a single directory
+entry in more detail.
+C<$name> is the name of the entry.
+C<$inode> is the inode number (which might not be exact on systems with 64
+bit inode numbers and 32 bit perls). On systems that do not deliver the
+inode information, this will always be zero.
+C<$type> is one of the C<AIO::DT_xxx> constants:
+C<AIO::DT_UNKNOWN>, C<AIO::DT_FIFO>, C<AIO::DT_CHR>, C<AIO::DT_DIR>,
+C<AIO::DT_BLK>, C<AIO::DT_REG>, C<AIO::DT_LNK>, C<AIO::DT_SOCK>,
+C<AIO::DT_WHT>.
+C<AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
+know, you have to run stat yourself. Also, for speed reasons, the C<$type>
+scalars are read-only: you can not modify them.
+=item AIO::READDIR_DIRS_FIRST
+When this flag is set, then the names will be returned in an order where
+likely directories come first. This is useful when you need to quickly
+find directories, or you want to find all directories while avoiding to
+stat() each entry.
+=item AIO::READDIR_STAT_ORDER
+When this flag is set, then the names will be returned in an order
+suitable for stat()'ing each one. That is, when you plan to stat()
+all files in the given directory, then the returned order will likely
+be fastest.
+If both this flag and IO::READDIR_DIRS_FIRST are specified, then the
+likely dirs come first, resulting in a less optimal stat order.
+=item AIO::READDIR_FOUND_UNKNOWN
+This flag should not be set when calling C<aio_readdirx>. Instead, it
+is being set by C<aio_readdirx>, when any of the C<$type>'s found were
+C<AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all
+C<$type>'s are known, which can be used to speed up some algorithms.
+=back
 =item aio_load $path, $data, $callback->($status)
 This is a composite request that tries to fully load the given file into
 memory. Status is the same as with aio_read.
 =cut
 sub aio_load($$;$) {
-   aio_block {
-      my ($path, undef, $cb) = @_;
+   my ($path, undef, $cb) = @_;
-      my $data = \$_[1];
+   my $data = \$_[1];
-      my $pri = aioreq_pri;
+   my $pri = aioreq_pri;
-      my $grp = aio_group $cb;
+   my $grp = aio_group $cb;
+   aioreq_pri $pri;
+   add $grp aio_open $path, O_RDONLY, 0, sub {
+      my $fh = shift
+         or return $grp->result (-1);
       aioreq_pri $pri;
-      add $grp aio_open $path, O_RDONLY, 0, sub {
-         my $fh = shift
-            or return $grp->result (-1);
-         aioreq_pri $pri;
-         add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
+      add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
-            $grp->result ($_[0]);
+         $grp->result ($_[0]);
-         };
       };
-      $grp
-   }
+   };
+   $grp
 }
 =item aio_copy $srcpath, $dstpath, $callback->($status)
 Try to copy the I<file> (directories not supported as either source or
 destination) from C<$srcpath> to C<$dstpath> and call the callback with
 the C<0> (error) or C<-1> ok.
-This is a composite request that it creates the destination file with
+This is a composite request that creates the destination file with
 mode 0200 and copies the contents of the source file into it using
 C<aio_sendfile>, followed by restoring atime, mtime, access mode and
 uid/gid, in that order.
 If an error occurs, the partial destination file will be unlinked, if
 errors are being ignored.
 =cut
 sub aio_copy($$;$) {
-   aio_block {
-      my ($src, $dst, $cb) = @_;
+   my ($src, $dst, $cb) = @_;
-      my $pri = aioreq_pri;
+   my $pri = aioreq_pri;
-      my $grp = aio_group $cb;
+   my $grp = aio_group $cb;
-      aioreq_pri $pri;
+   aioreq_pri $pri;
-      add $grp aio_open $src, O_RDONLY, 0, sub {
+   add $grp aio_open $src, O_RDONLY, 0, sub {
-         if (my $src_fh = $_[0]) {
+      if (my $src_fh = $_[0]) {
-            my @stat = stat $src_fh;
+         my @stat = stat $src_fh; # hmm, might bock over nfs?
-            aioreq_pri $pri;
+         aioreq_pri $pri;
-            add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
+         add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
-               if (my $dst_fh = $_[0]) {
+            if (my $dst_fh = $_[0]) {
-                  aioreq_pri $pri;
+               aioreq_pri $pri;
-                  add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
+               add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
-                     if ($_[0] == $stat[7]) {
+                  if ($_[0] == $stat[7]) {
-                        $grp->result (0);
+                     $grp->result (0);
-                        close $src_fh;
+                     close $src_fh;
-                        # those should not normally block. should. should.
+                     my $ch = sub {
-                        utime $stat[8], $stat[9], $dst;
-                        chmod $stat[2] & 07777, $dst_fh;
-                        chown $stat[4], $stat[5], $dst_fh;
                         aioreq_pri $pri;
+                        add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
+                           aioreq_pri $pri;
+                           add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
+                              aioreq_pri $pri;
-                        add $grp aio_close $dst_fh;
+                              add $grp aio_close $dst_fh;
-                     } else {
+                           }
-                        $grp->result (-1);
-                        close $src_fh;
-                        close $dst_fh;
-                        aioreq $pri;
+                        };
-                        add $grp aio_unlink $dst;
-                     }
+                     };
+                     aioreq_pri $pri;
+                     add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
+                        if ($_[0] < 0 && $! == ENOSYS) {
+                           aioreq_pri $pri;
+                           add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
+                        } else {
+                           $ch->();
+                        }
+                     };
+                  } else {
+                     $grp->result (-1);
+                     close $src_fh;
+                     close $dst_fh;
+                     aioreq $pri;
+                     add $grp aio_unlink $dst;
-                  };
+                  }
-               } else {
-                  $grp->result (-1);
-               }
+               };
+            } else {
+               $grp->result (-1);
-            },
+            }
-         } else {
-            $grp->result (-1);
-         }
+         },
+      } else {
+         $grp->result (-1);
-      };
+      }
-      $grp
-   }
+   };
+   $grp
 }
 =item aio_move $srcpath, $dstpath, $callback->($status)
 Try to move the I<file> (directories not supported as either source or
 destination) from C<$srcpath> to C<$dstpath> and call the callback with
 the C<0> (error) or C<-1> ok.
-This is a composite request that tries to rename(2) the file first. If
+This is a composite request that tries to rename(2) the file first; if
-rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
+rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
-that is successful, unlinking the C<$srcpath>.
+that is successful, unlinks the C<$srcpath>.
 =cut
 sub aio_move($$;$) {
-   aio_block {
-      my ($src, $dst, $cb) = @_;
+   my ($src, $dst, $cb) = @_;
-      my $pri = aioreq_pri;
+   my $pri = aioreq_pri;
-      my $grp = aio_group $cb;
+   my $grp = aio_group $cb;
-      aioreq_pri $pri;
+   aioreq_pri $pri;
-      add $grp aio_rename $src, $dst, sub {
+   add $grp aio_rename $src, $dst, sub {
-         if ($_[0] && $! == EXDEV) {
+      if ($_[0] && $! == EXDEV) {
-            aioreq_pri $pri;
+         aioreq_pri $pri;
-            add $grp aio_copy $src, $dst, sub {
+         add $grp aio_copy $src, $dst, sub {
-               $grp->result ($_[0]);
-               if (!$_[0]) {
-                  aioreq_pri $pri;
-                  add $grp aio_unlink $src;
-               }
-            };
-         } else {
             $grp->result ($_[0]);
+            if (!$_[0]) {
+               aioreq_pri $pri;
+               add $grp aio_unlink $src;
+            }
-         }
+         };
+      } else {
+         $grp->result ($_[0]);
-      };
+      }
-      $grp
-   }
+   };
+   $grp
 }
 =item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
 Scans a directory (similar to C<aio_readdir>) but additionally tries to
 directory counting heuristic.
 =cut
 sub aio_scandir($$;$) {
-   aio_block {
-      my ($path, $maxreq, $cb) = @_;
+   my ($path, $maxreq, $cb) = @_;
-      my $pri = aioreq_pri;
+   my $pri = aioreq_pri;
-      my $grp = aio_group $cb;
+   my $grp = aio_group $cb;
-      $maxreq = 4 if $maxreq <= 0;
+   $maxreq = 4 if $maxreq <= 0;
-      # stat once
+   # stat once
+   aioreq_pri $pri;
+   add $grp aio_stat $path, sub {
+      return $grp->result () if $_[0];
+      my $now = time;
+      my $hash1 = join ":", (stat _)[0,1,3,7,9];
+      # read the directory entries
       aioreq_pri $pri;
-      add $grp aio_stat $path, sub {
+      add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {
+         my $entries = shift
-         return $grp->result () if $_[0];
+            or return $grp->result ();
-         my $now = time;
-         my $hash1 = join ":", (stat _)[0,1,3,7,9];
-         # read the directory entries
+         # stat the dir another time
          aioreq_pri $pri;
-         add $grp aio_readdir $path, sub {
-            my $entries = shift
-               or return $grp->result ();
-            # stat the dir another time
-            aioreq_pri $pri;
-            add $grp aio_stat $path, sub {
+         add $grp aio_stat $path, sub {
-               my $hash2 = join ":", (stat _)[0,1,3,7,9];
+            my $hash2 = join ":", (stat _)[0,1,3,7,9];
-               my $ndirs;
+            my $ndirs;
-               # take the slow route if anything looks fishy
+            # take the slow route if anything looks fishy
-               if ($hash1 ne $hash2 or (stat _)[9] == $now) {
+            if ($hash1 ne $hash2 or (stat _)[9] == $now) {
-                  $ndirs = -1;
+               $ndirs = -1;
-               } else {
+            } else {
-                  # if nlink == 2, we are finished
+               # if nlink == 2, we are finished
-                  # on non-posix-fs's, we rely on nlink < 2
+               # on non-posix-fs's, we rely on nlink < 2
-                  $ndirs = (stat _)[3] - 2
+               $ndirs = (stat _)[3] - 2
-                     or return $grp->result ([], $entries);
+                  or return $grp->result ([], $entries);
-               }
+            }
-               # sort into likely dirs and likely nondirs
+            # sort into likely dirs and likely nondirs
-               # dirs == files without ".", short entries first
+            # dirs == files without ".", short entries first
-               $entries = [map $_->[0],
+            $entries = [map $_->[0],
-                              sort { $b->[1] cmp $a->[1] }
+                           sort { $b->[1] cmp $a->[1] }
-                                 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
+                              map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
-                                    @$entries];
+                                 @$entries];
-               my (@dirs, @nondirs);
+            my (@dirs, @nondirs);
-               my $statgrp = add $grp aio_group sub {
+            my $statgrp = add $grp aio_group sub {
-                  $grp->result (\@dirs, \@nondirs);
+               $grp->result (\@dirs, \@nondirs);
-               };
+            };
-               limit $statgrp $maxreq;
+            limit $statgrp $maxreq;
-               feed $statgrp sub {
+            feed $statgrp sub {
-                  return unless @$entries;
+               return unless @$entries;
-                  my $entry = pop @$entries;
+               my $entry = pop @$entries;
-                  aioreq_pri $pri;
+               aioreq_pri $pri;
-                  add $statgrp aio_stat "$path/$entry/.", sub {
+               add $statgrp aio_stat "$path/$entry/.", sub {
-                     if ($_[0] < 0) {
+                  if ($_[0] < 0) {
-                        push @nondirs, $entry;
+                     push @nondirs, $entry;
-                     } else {
+                  } else {
-                        # need to check for real directory
+                     # need to check for real directory
-                        aioreq_pri $pri;
+                     aioreq_pri $pri;
-                        add $statgrp aio_lstat "$path/$entry", sub {
+                     add $statgrp aio_lstat "$path/$entry", sub {
-                           if (-d _) {
+                        if (-d _) {
-                              push @dirs, $entry;
+                           push @dirs, $entry;
-                              unless (--$ndirs) {
+                           unless (--$ndirs) {
-                                 push @nondirs, @$entries;
+                              push @nondirs, @$entries;
-                                 feed $statgrp;
+                              feed $statgrp;
-                              }
-                           } else {
-                              push @nondirs, $entry;
                            }
+                        } else {
+                           push @nondirs, $entry;
                         }
                      }
-                  };
+                  }
                };
             };
          };
       };
-      $grp
-   }
+   };
+   $grp
 }
 =item aio_rmtree $path, $callback->($status)
 Delete a directory tree starting (and including) C<$path>, return the
 =cut
 sub aio_rmtree;
 sub aio_rmtree($;$) {
-   aio_block {
-      my ($path, $cb) = @_;
+   my ($path, $cb) = @_;
-      my $pri = aioreq_pri;
+   my $pri = aioreq_pri;
-      my $grp = aio_group $cb;
+   my $grp = aio_group $cb;
-      aioreq_pri $pri;
+   aioreq_pri $pri;
-      add $grp aio_scandir $path, 0, sub {
+   add $grp aio_scandir $path, 0, sub {
-         my ($dirs, $nondirs) = @_;
+      my ($dirs, $nondirs) = @_;
-         my $dirgrp = aio_group sub {
+      my $dirgrp = aio_group sub {
-            add $grp aio_rmdir $path, sub {
+         add $grp aio_rmdir $path, sub {
-               $grp->result ($_[0]);
+            $grp->result ($_[0]);
-            };
          };
-         (aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
-         (aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
-         add $grp $dirgrp;
       };
-      $grp
+      (aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
+      (aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
+      add $grp $dirgrp;
-   }
+   };
+   $grp
 }
 =item aio_sync $callback->($status)
 Asynchronously call sync and call the callback when finished.
 callback with the fdatasync result code.
 If this call isn't available because your OS lacks it or it couldn't be
 detected, it will be emulated by calling C<fsync> instead.
+=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
+Sync the data portion of the file specified by C<$offset> and C<$length>
+to disk (but NOT the metadata), by calling the Linux-specific
+sync_file_range call. If sync_file_range is not available or it returns
+ENOSYS, then fdatasync or fsync is being substituted.
+C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
+C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
+C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
+manpage for details.
 =item aio_pathsync $path, $callback->($status)
 This request tries to open, fsync and close the given path. This is a
-composite request intended tosync directories after directory operations
+composite request intended to sync directories after directory operations
 (E.g. rename). This might not work on all operating systems or have any
 specific effect, but usually it makes sure that directory changes get
 written to disc. It works for anything that can be opened for read-only,
 not just directories.
 Passes C<0> when everything went ok, and C<-1> on error.
 =cut
 sub aio_pathsync($;$) {
-   aio_block {
-      my ($path, $cb) = @_;
+   my ($path, $cb) = @_;
-      my $pri = aioreq_pri;
+   my $pri = aioreq_pri;
-      my $grp = aio_group $cb;
+   my $grp = aio_group $cb;
-      aioreq_pri $pri;
+   aioreq_pri $pri;
-      add $grp aio_open $path, O_RDONLY, 0, sub {
+   add $grp aio_open $path, O_RDONLY, 0, sub {
-         my ($fh) = @_;
+      my ($fh) = @_;
-         if ($fh) {
+      if ($fh) {
+         aioreq_pri $pri;
+         add $grp aio_fsync $fh, sub {
+            $grp->result ($_[0]);
             aioreq_pri $pri;
-            add $grp aio_fsync $fh, sub {
-               $grp->result ($_[0]);
-               aioreq_pri $pri;
-               add $grp aio_close $fh;
+            add $grp aio_close $fh;
-            };
-         } else {
-            $grp->result (-1);
-         }
+         };
+      } else {
+         $grp->result (-1);
-      };
+      }
-      $grp
-   }
+   };
+   $grp
 }
 =item aio_group $callback->(...)
 This is a very special aio request: Instead of doing something, it is a
 Their lifetime, simplified, looks like this: when they are empty, they
 will finish very quickly. If they contain only requests that are in the
 C<done> state, they will also finish. Otherwise they will continue to
 exist.
-That means after creating a group you have some time to add requests. And
+That means after creating a group you have some time to add requests
-in the callbacks of those requests, you can add further requests to the
+(precisely before the callback has been invoked, which is only done within
-group. And only when all those requests have finished will the the group
+the C<poll_cb>). And in the callbacks of those requests, you can add
-itself finish.
+further requests to the group. And only when all those requests have
+finished will the the group itself finish.
 =over 4
 =item add $grp ...
 =item feed $grp $callback->($grp)
 Sets a feeder/generator on this group: every group can have an attached
 generator that generates requests if idle. The idea behind this is that,
 although you could just queue as many requests as you want in a group,
-this might starve other requests for a potentially long time.  For
+this might starve other requests for a potentially long time. For example,
-example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
+C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,
-requests, delaying any later requests for a long time.
+delaying any later requests for a long time.
 To avoid this, and allow incremental generation of requests, you can
 instead a group and set a feeder on it that generates those requests. The
 feed callback will be called whenever there are few enough (see C<limit>,
 below) requests active in the group itself and is expected to queue more
 not impose any limits).
 If the feed does not queue more requests when called, it will be
 automatically removed from the group.
-If the feed limit is C<0>, it will be set to C<2> automatically.
+If the feed limit is C<0> when this method is called, it will be set to
+C<2> automatically.
 Example:
    # stat all files in @files, but only ever use four aio requests concurrently:
 Sets the feeder limit for the group: The feeder will be called whenever
 the group contains less than this many requests.
 Setting the limit to C<0> will pause the feeding process.
+The default value for the limit is C<0>, but note that setting a feeder
+automatically bumps it up to C<2>.
 =back
 =head2 SUPPORT FUNCTIONS
 =head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
 See C<poll_cb> for an example.
 =item IO::AIO::poll_cb
 Process some outstanding events on the result pipe. You have to call this
-regularly. Returns the number of events processed. Returns immediately
+regularly. Returns C<0> if all events could be processed, or C<-1> if it
+returned earlier for whatever reason. Returns immediately when no events
-when no events are outstanding. The amount of events processed depends on
+are outstanding. The amount of events processed depends on the settings of
-the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
+C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
 If not all requests were processed for whatever reason, the filehandle
-will still be ready when C<poll_cb> returns.
+will still be ready when C<poll_cb> returns, so normally you don't have to
+do anything special to have it called later.
 Example: Install an Event watcher that automatically calls
 IO::AIO::poll_cb with high priority:
    Event->io (fd => IO::AIO::poll_fileno,
 The default is probably ok in most situations, especially if thread
 creation is fast. If thread creation is very slow on your system you might
 want to use larger values.
-=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
+=item IO::AIO::max_outstanding $maxreqs
 This is a very bad function to use in interactive programs because it
 blocks, and a bad way to reduce concurrency because it is inexact: Better
 use an C<aio_group> together with a feed callback.
 The default value is very large, so there is no practical limit on the
 number of outstanding requests.
 You can still queue as many requests as you want. Therefore,
-C<max_oustsanding> is mainly useful in simple scripts (with low values) or
+C<max_outstanding> is mainly useful in simple scripts (with low values) or
 as a stop gap to shield against fatal memory overflow (with large values).
 =back
 =head3 STATISTICAL INFORMATION
 Known bugs will be fixed in the next release.
 =head1 SEE ALSO
-L<Coro::AIO>.
+L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
+more natural syntax.
 =head1 AUTHOR
  Marc Lehmann <schmorp@schmorp.de>
  http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.120 by root, Sun Dec 2 21:51:36 2007 UTC vs.
Revision 1.148 by root, Sat Jun 6 17:25:13 2009 UTC