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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.88 by root, Sun Oct 29 01:50:29 2006 UTC vs.
Revision 1.148 by root, Sat Jun 6 17:25:13 2009 UTC

 =head1 SYNOPSIS
  use IO::AIO;
  aio_open "/etc/passwd", O_RDONLY, 0, sub {
-    my ($fh) = @_;
+    my $fh = shift
+       or die "/etc/passwd: $!";
     ...
  };
  aio_unlink "/tmp/file", sub { };
  $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 this works on all types of file descriptors (for example sockets),
+While most of this works on all types of file descriptors (for
-using these functions on file descriptors that support nonblocking
+example sockets), using these functions on file descriptors that
-operation (again, sockets, pipes etc.) is very inefficient. Use an event
+support nonblocking operation (again, sockets, pipes etc.) is very
-loop for that (such as the L<Event|Event> module): IO::AIO will naturally
+inefficient. Use an event loop for that (such as the L<Event|Event>
-fit into such an event loop itself.
+module): IO::AIO will naturally fit 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:
               poll => 'r',
               cb => \&IO::AIO::poll_cb);
    # queue the request to open /etc/passwd
    aio_open "/etc/passwd", O_RDONLY, 0, sub {
-      my $fh = $_[0]
+      my $fh = shift
          or die "error while opening: $!";
       # stat'ing filehandles is generally non-blocking
       my $size = -s $fh;
 =cut
 package IO::AIO;
+use Carp ();
 no warnings;
 use strict 'vars';
 use base 'Exporter';
 BEGIN {
-   our $VERSION = '2.1';
+   our $VERSION = '3.19';
-   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_readdirx
-                     aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
+                     aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
-                     aio_copy aio_group aio_nop aio_mknod);
+                     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));
    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]
       aio_read $_[0], ..., sub {
          ...
       };
    };
 =item aioreq_nice $pri_adjust
 Similar to C<aioreq_pri>, but subtracts the given value from the current
 priority, so the effect is cumulative.
 =item aio_open $pathname, $flags, $mode, $callback->($fh)
 Asynchronously open or create a file and call the callback with a newly
 created filehandle for the file.
 list. They are the same as used by C<sysopen>.
 Likewise, C<$mode> specifies the mode of the newly created file, if it
 didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
 except that it is mandatory (i.e. use C<0> if you don't create new files,
-and C<0666> or C<0777> if you do).
+and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
+by the umask in effect then the request is being executed, so better never
+change the umask.
 Example:
    aio_open "/etc/passwd", O_RDONLY, 0, sub {
       if ($_[0]) {
       } else {
          die "open failed: $!\n";
       }
    };
 =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<$length> bytes from or to the specified C<$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<$data>.
+If C<$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 {
       $_[0] > 0 or die "read error: $!";
       print "read $_[0] bytes: <$buffer>\n";
    };
 =item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
 Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
 reading at byte offset C<$in_offset>, and starts writing at the current
 C<$in_fh> than are written, and there is no way to find out how many
 bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
 provides the number of bytes written to C<$out_fh>. Only if the result
 value equals C<$length> one can assume that C<$length> bytes have been
 read.
 =item aio_readahead $fh,$offset,$length, $callback->($retval)
 C<aio_readahead> populates the page cache with data from a file so that
 subsequent reads from that file will not block on disk I/O. The C<$offset>
 file. The current file offset of the file is left unchanged.
 If that syscall doesn't exist (likely if your OS isn't Linux) it will be
 emulated by simply reading the data, which would have a similar effect.
 =item aio_stat  $fh_or_path, $callback->($status)
 =item aio_lstat $fh, $callback->($status)
 Works like perl's C<stat> or C<lstat> in void context. The callback will
    aio_stat "/etc/passwd", sub {
       $_[0] and die "stat failed: $!";
       print "size is ", -s _, "\n";
    };
+=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
+Works like perl's C<utime> function (including the special case of $atime
+and $mtime being undef). Fractional times are supported if the underlying
+syscalls support them.
+When called with a pathname, uses utimes(2) if available, otherwise
+utime(2). If called on a file descriptor, uses futimes(2) if available,
+otherwise returns ENOSYS, so this is not portable.
+Examples:
+   # set atime and mtime to current time (basically touch(1)):
+   aio_utime "path", undef, undef;
+   # set atime to current time and mtime to beginning of the epoch:
+   aio_utime "path", time, undef; # undef==0
+=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
+Works like perl's C<chown> function, except that C<undef> for either $uid
+or $gid is being interpreted as "do not change" (but -1 can also be used).
+Examples:
+   # same as "chown root path" in the shell:
+   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.
 =item aio_unlink $pathname, $callback->($status)
 Asynchronously unlink (delete) a file and call the callback with the
 result code.
 =item aio_mknod $path, $mode, $dev, $callback->($status)
 [EXPERIMENTAL]
 Asynchronously create a device node (or fifo). See mknod(2).
 The only (POSIX-) portable way of calling this function is:
    aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
 =item aio_link $srcpath, $dstpath, $callback->($status)
 Asynchronously create a new link to the existing object at C<$srcpath> at
 the path C<$dstpath> and call the callback with the result code.
 =item aio_symlink $srcpath, $dstpath, $callback->($status)
 Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
 the path C<$dstpath> and call the callback with the result code.
+=item aio_readlink $path, $callback->($link)
+Asynchronously read the symlink specified by C<$path> and pass it to
+the callback. If an error occurs, nothing or undef gets passed to the
+callback.
 =item aio_rename $srcpath, $dstpath, $callback->($status)
 Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
 rename(2) and call the callback with the result code.
+=item aio_mkdir $pathname, $mode, $callback->($status)
+Asynchronously mkdir (create) a directory and call the callback with
+the result code. C<$mode> will be modified by the umask at the time the
+request is executed, so do not change your umask.
 =item aio_rmdir $pathname, $callback->($status)
 Asynchronously rmdir (delete) a directory and call the callback with the
 result code.
 =item aio_readdir $pathname, $callback->($entries)
 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($$;$) {
+   my ($path, undef, $cb) = @_;
+   my $data = \$_[1];
+   my $pri = aioreq_pri;
+   my $grp = aio_group $cb;
+   aioreq_pri $pri;
+   add $grp aio_open $path, O_RDONLY, 0, sub {
+      my $fh = shift
+         or return $grp->result (-1);
+      aioreq_pri $pri;
+      add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
+         $grp->result ($_[0]);
+      };
+   };
+   $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
    my $grp = aio_group $cb;
    aioreq_pri $pri;
    add $grp aio_open $src, O_RDONLY, 0, sub {
       if (my $src_fh = $_[0]) {
-         my @stat = stat $src_fh;
+         my @stat = stat $src_fh; # hmm, might bock over nfs?
          aioreq_pri $pri;
          add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
             if (my $dst_fh = $_[0]) {
                aioreq_pri $pri;
                add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
                   if ($_[0] == $stat[7]) {
                      $grp->result (0);
                      close $src_fh;
-                     # those should not normally block. should. should.
+                     my $ch = sub {
+                        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;
+                           }
+                        };
+                     };
+                     aioreq_pri $pri;
+                     add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
+                        if ($_[0] < 0 && $! == ENOSYS) {
+                           aioreq_pri $pri;
-                     utime $stat[8], $stat[9], $dst;
+                           add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
-                     chmod $stat[2] & 07777, $dst_fh;
+                        } else {
-                     chown $stat[4], $stat[5], $dst_fh;
+                           $ch->();
+                        }
-                     close $dst_fh;
+                     };
                   } else {
                      $grp->result (-1);
                      close $src_fh;
                      close $dst_fh;
 Try to move the I<file> (directories not supported as either source or
 destination) from C<$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($$;$) {
    my ($src, $dst, $cb) = @_;
 as those tend to return 0 or 1 as link counts, which disables the
 directory counting heuristic.
 =cut
-sub aio_scandir($$$) {
+sub aio_scandir($$;$) {
    my ($path, $maxreq, $cb) = @_;
    my $pri = aioreq_pri;
    my $grp = aio_group $cb;
       my $now = time;
       my $hash1 = join ":", (stat _)[0,1,3,7,9];
       # read the directory entries
       aioreq_pri $pri;
-      add $grp aio_readdir $path, sub {
+      add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {
          my $entries = shift
             or return $grp->result ();
          # stat the dir another time
          aioreq_pri $pri;
    };
    $grp
 }
+=item aio_rmtree $path, $callback->($status)
+Delete a directory tree starting (and including) C<$path>, return the
+status of the final C<rmdir> only.  This is a composite request that
+uses C<aio_scandir> to recurse into and rmdir directories, and unlink
+everything else.
+=cut
+sub aio_rmtree;
+sub aio_rmtree($;$) {
+   my ($path, $cb) = @_;
+   my $pri = aioreq_pri;
+   my $grp = aio_group $cb;
+   aioreq_pri $pri;
+   add $grp aio_scandir $path, 0, sub {
+      my ($dirs, $nondirs) = @_;
+      my $dirgrp = aio_group sub {
+         add $grp aio_rmdir $path, sub {
+            $grp->result ($_[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
+}
+=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,
 that are being processed by C<IO::AIO::poll_cb> in one call, respectively
 the maximum amount of time (default C<0>, meaning infinity) spent in
 C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
 of time C<poll_cb> is allowed to use).
+Setting C<max_poll_time> to a non-zero value creates an overhead of one
+syscall per request processed, which is not normally a problem unless your
+callbacks are really really fast or your OS is really really slow (I am
+not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
 Setting these is useful if you want to ensure some level of
 interactiveness when perl is not fast enough to process all requests in
 time.
 For interactive programs, values such as C<0.01> to C<0.1> should be fine.
 Example: Install an Event watcher that automatically calls
-IO::AIO::poll_some with low priority, to ensure that other parts of the
+IO::AIO::poll_cb with low priority, to ensure that other parts of the
 program get the CPU sometimes even under high AIO load.
    # try not to spend much more than 0.1s in poll_cb
    IO::AIO::max_poll_time 0.1;
               poll => 'r', nice => 1,
               cb => &IO::AIO::poll_cb);
 =item IO::AIO::poll_wait
+If there are any outstanding requests and none of them in the result
-Wait till the result filehandle becomes ready for reading (simply does a
+phase, wait till the result filehandle becomes ready for reading (simply
-C<select> on the filehandle. This is useful if you want to synchronously
+does a C<select> on the filehandle. This is useful if you want to
-wait for some requests to finish).
+synchronously wait for some requests to finish).
 See C<nreqs> for an example.
 =item IO::AIO::poll
 Waits until some requests have been handled.
+Returns the number of requests processed, but is otherwise strictly
-Strictly equivalent to:
+equivalent to:
    IO::AIO::poll_wait, IO::AIO::poll_cb
-      if IO::AIO::nreqs;
 =item IO::AIO::flush
 Wait till all outstanding AIO requests have been handled.
 Strictly equivalent to:
    IO::AIO::poll_wait, IO::AIO::poll_cb
       while IO::AIO::nreqs;
+=back
 =head3 CONTROLLING THE NUMBER OF THREADS
+=over
 =item IO::AIO::min_parallel $nthreads
 Set the minimum number of AIO threads to C<$nthreads>. The current
 default is C<8>, which means eight asynchronous operations can execute
 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
+=over
 =item IO::AIO::nreqs
 Returns the number of requests currently in the ready, execute or pending
 states (i.e. for which their callback has not been invoked yet).
 =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 {
+END { flush }
-   min_parallel 1;
-   flush;
-};
 1;
 =head2 FORK BEHAVIOUR
 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 1.148 by root, Sat Jun 6 17:25:13 2009 UTC