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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.107 by root, Fri Jun 1 05:52:59 2007 UTC vs.
Revision 1.143 by root, Thu Nov 20 09:01:40 2008 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, POE, urxvt, pureperl...)
+ use AnyEvent::AIO;
- # AnyEvent integration
+ # EV integration
- open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
+ my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
- my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
  # Event integration
  Event->io (fd => IO::AIO::poll_fileno,
             poll => 'r',
             cb => \&IO::AIO::poll_cb);
 etc.), but can also be used to easily do operations in parallel that are
 normally done sequentially, e.g. stat'ing many files, which is much faster
 on a RAID volume or over NFS when you do a number of stat operations
 concurrently.
-While most of this works on all types of file descriptors (for example
+While most of this works on all types of file descriptors (for
-sockets), using these functions on file descriptors that support
+example sockets), using these functions on file descriptors that
-nonblocking operation (again, sockets, pipes etc.) is very inefficient or
+support nonblocking operation (again, sockets, pipes etc.) is very
-might not work (aio_read fails on sockets/pipes/fifos). Use an event loop
+inefficient. Use an event loop for that (such as the L<Event|Event>
-for that (such as the L<Event|Event> module): IO::AIO will naturally fit
+module): IO::AIO will naturally fit into such an event loop itself.
-into such an event loop itself.
 In this version, a number of threads are started that execute your
 requests and signal their completion. You don't need thread support
 in perl, and the threads created by this module will not be visible
 to perl. In the future, this module might make use of the native aio
 not well-supported or restricted (GNU/Linux doesn't allow them on normal
 files currently, for example), and they would only support aio_read and
 aio_write, so the remaining functionality would have to be implemented
 using threads anyway.
-Although the module will work with in the presence of other (Perl-)
+Although the module will work in the presence of other (Perl-) threads,
-threads, it is currently not reentrant in any way, so use appropriate
+it is currently not reentrant in any way, so use appropriate locking
-locking yourself, always call C<poll_cb> from within the same thread, or
+yourself, always call C<poll_cb> from within the same thread, or never
-never call C<poll_cb> (or other C<aio_> functions) recursively.
+call C<poll_cb> (or other C<aio_> functions) recursively.
 =head2 EXAMPLE
 This is a simple example that uses the Event module and loads
 F</etc/passwd> asynchronously:
 =cut
 package IO::AIO;
+use Carp ();
 no warnings;
 use strict 'vars';
 use base 'Exporter';
 BEGIN {
-   our $VERSION = '2.4';
+   our $VERSION = '3.17';
-   our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
+   our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
-                     aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
+                     aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir
-                     aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
+                     aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
+                     aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
+                     aio_rename aio_link aio_move aio_copy aio_group
-                     aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
+                     aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
-                     aio_chown aio_chmod aio_utime);
+                     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]
 =item aio_close $fh, $callback->($status)
 Asynchronously close a file and call the callback with the result
-code. I<WARNING:> although accepted, you should not pass in a perl
+code.
-filehandle here, as perl will likely close the file descriptor another
-time when the filehandle is destroyed. Normally, you can safely call perls
-C<close> or just let filehandles go out of scope.
-This is supposed to be a bug in the API, so that might change. It's
+Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
-therefore best to avoid this function.
+closing the file descriptor associated with the filehandle itself.
+Therefore, C<aio_close> will not close the filehandle - instead it will
+use dup2 to overwrite the file descriptor with the write-end of a pipe
+(the pipe fd will be created on demand and will be cached).
+Or in other words: the file descriptor will be closed, but it will not be
+free for reuse until the perl filehandle is closed.
+=cut
 =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<$length> bytes from the specified C<$fh> and C<$offset>
-into the scalar given by C<data> and offset C<dataoffset> and calls the
+into the scalar given by C<$data> and offset C<$dataoffset> and calls the
 callback without the actual number of bytes read (or -1 on error, just
 like the syscall).
+If C<$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<$dataoffset> is less than zero, it will be counted from the end of
+C<$data>.
 The C<$data> scalar I<MUST NOT> be modified in any way while the request
-is outstanding. Modifying it can result in segfaults or WW3 (if the
+is outstanding. Modifying it can result in segfaults or World War III (if
-necessary/optional hardware is installed).
+the necessary/optional hardware is installed).
 Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
 offset C<0> within the scalar:
    aio_read $fh, 7, 15, $buffer, 0, sub {
    aio_chown "path", 0, -1;
    # same as above:
    aio_chown "path", 0, undef;
+=item aio_truncate $fh_or_path, $offset, $callback->($status)
+Works like truncate(2) or ftruncate(2).
 =item aio_chmod $fh_or_path, $mode, $callback->($status)
 Works like perl's C<chmod> function.
 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;
-            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.
+                     # those should not normally block. should. should.
-                        utime $stat[8], $stat[9], $dst;
+                     utime $stat[8], $stat[9], $dst;
-                        chmod $stat[2] & 07777, $dst_fh;
+                     chmod $stat[2] & 07777, $dst_fh;
-                        chown $stat[4], $stat[5], $dst_fh;
+                     chown $stat[4], $stat[5], $dst_fh;
+                     aioreq_pri $pri;
-                        close $dst_fh;
+                     add $grp aio_close $dst_fh;
-                     } else {
+                  } else {
-                        $grp->result (-1);
+                     $grp->result (-1);
-                        close $src_fh;
+                     close $src_fh;
-                        close $dst_fh;
+                     close $dst_fh;
-                        aioreq $pri;
+                     aioreq $pri;
-                        add $grp aio_unlink $dst;
+                     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_readdir $path, 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.
 =item aio_fsync $fh, $callback->($status)
 Asynchronously call fsync on the given filehandle and call the callback
 with the fsync result code.
 Asynchronously call fdatasync on the given filehandle and call the
 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 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($;$) {
+   my ($path, $cb) = @_;
+   my $pri = aioreq_pri;
+   my $grp = aio_group $cb;
+   aioreq_pri $pri;
+   add $grp aio_open $path, O_RDONLY, 0, sub {
+      my ($fh) = @_;
+      if ($fh) {
+         aioreq_pri $pri;
+         add $grp aio_fsync $fh, sub {
+            $grp->result ($_[0]);
+            aioreq_pri $pri;
+            add $grp aio_close $fh;
+         };
+      } else {
+         $grp->result (-1);
+      }
+   };
+   $grp
+}
 =item aio_group $callback->(...)
 This is a very special aio request: Instead of doing something, it is a
 container for other aio requests, which is useful if you want to bundle
 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 ...
 itself. Useful when you queued a lot of events but got a result early.
 =item $grp->result (...)
 Set the result value(s) that will be passed to the group callback when all
-subrequests have finished and set thre groups errno to the current value
+subrequests have finished and set the groups errno to the current value
 of errno (just like calling C<errno> without an error number). By default,
 no argument will be passed and errno is zero.
 =item $grp->errno ([$errno])
 =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 $maxreqs
 This is a very bad function to use in interactive programs because it
 blocks, and a bad way to reduce concurrency because it is inexact: Better
 use an C<aio_group> together with a feed callback.
 Sets the maximum number of outstanding requests to C<$nreqs>. If you
-to queue up more than this number of requests, the next call to the
+do queue up more than this number of requests, the next call to the
 C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
 function will block until the limit is no longer exceeded.
 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
 but not yet processed by poll_cb).
 =back
 =cut
-# support function to convert a fd into a perl filehandle
-sub _fd2fh {
-   return undef if $_[0] < 0;
-   # try to generate nice filehandles
-   my $sym = "IO::AIO::fd#$_[0]";
-   local *$sym;
-   open *$sym, "+<&=$_[0]"      # usually works under any unix
-      or open *$sym, "<&=$_[0]" # cygwin needs this
-      or open *$sym, ">&=$_[0]" # or this
-      or return undef;
-   *$sym
-}
 min_parallel 8;
 END { flush }
 bytes of memory. In addition, stat requests need a stat buffer (possibly
 a few hundred bytes), readdir requires a result buffer and so on. Perl
 scalars and other data passed into aio requests will also be locked and
 will consume memory till the request has entered the done state.
-This is now awfully much, so queuing lots of requests is not usually a
+This is not awfully much, so queuing lots of requests is not usually a
 problem.
 Per-thread usage:
 In the execution phase, some aio requests require more memory for
 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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Revision 1.107 by root, Fri Jun 1 05:52:59 2007 UTC vs.
Revision 1.143 by root, Thu Nov 20 09:01:40 2008 UTC