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Yields:

    ( '', 'a', 'b', '', 'c', '' )

=cut

sub splitdir {
    return split m|/|, $_[1], -1;  # Preserve trailing fields
}


=item catpath()

Takes volume, directory and file portions and returns an entire path. Under
Unix, $volume is ignored, and directory and file are concatenated.  A '/' is
inserted if needed (though if the directory portion doesn't start with
'/' it is not added).  On other OSs, $volume is significant.

=cut

sub catpath {
    my ($self,$volume,$directory,$file) = @_;

    if ( $directory ne ''                && 
         $file ne ''                     && 
         substr( $directory, -1 ) ne '/' && 
         substr( $file, 0, 1 ) ne '/' 
    ) {
        $directory .= "/$file" ;
    }
    else {
        $directory .= $file ;
    }

    return $directory ;
}

=item abs2rel

Takes a destination path and an optional base path returns a relative path
from the base path to the destination path:

    $rel_path = File::Spec->abs2rel( $path ) ;
    $rel_path = File::Spec->abs2rel( $path, $base ) ;

If $base is not present or '', then L<cwd()|Cwd> is used. If $base is
relative, then it is converted to absolute form using
L</rel2abs()>. This means that it is taken to be relative to
L<cwd()|Cwd>.

On systems that have a grammar that indicates filenames, this ignores the 
$base filename. Otherwise all path components are assumed to be
directories.

If $path is relative, it is converted to absolute form using L</rel2abs()>.
This means that it is taken to be relative to L<cwd()|Cwd>.

No checks against the filesystem are made.  On VMS, there is
interaction with the working environment, as logicals and
macros are expanded.

Based on code written by Shigio Yamaguchi.

=cut

sub abs2rel {
    my($self,$path,$base) = @_;

    # Clean up $path
    if ( ! $self->file_name_is_absolute( $path ) ) {
        $path = $self->rel2abs( $path ) ;
    }
    else {
        $path = $self->canonpath( $path ) ;
    }

    # Figure out the effective $base and clean it up.
    if ( !defined( $base ) || $base eq '' ) {
        $base = $self->_cwd();
    }
    elsif ( ! $self->file_name_is_absolute( $base ) ) {
        $base = $self->rel2abs( $base ) ;
    }
    else {
        $base = $self->canonpath( $base ) ;
    }

    # Now, remove all leading components that are the same
    my @pathchunks = $self->splitdir( $path);
    my @basechunks = $self->splitdir( $base);

    while (@pathchunks && @basechunks && $pathchunks[0] eq $basechunks[0]) {
        shift @pathchunks ;
        shift @basechunks ;
    }

    $path = CORE::join( '/', @pathchunks );
    $base = CORE::join( '/', @basechunks );

    # $base now contains the directories the resulting relative path 
    # must ascend out of before it can descend to $path_directory.  So, 
    # replace all names with $parentDir
    $base =~ s|[^/]+|..|g ;

    # Glue the two together, using a separator if necessary, and preventing an
    # empty result.
    if ( $path ne '' && $base ne '' ) {
        $path = "$base/$path" ;
    } else {
        $path = "$base$path" ;
    }

    return $self->canonpath( $path ) ;
}

=item rel2abs()

Converts a relative path to an absolute path. 

    $abs_path = File::Spec->rel2abs( $path ) ;
    $abs_path = File::Spec->rel2abs( $path, $base ) ;

If $base is not present or '', then L<cwd()|Cwd> is used. If $base is
relative, then it is converted to absolute form using
L</rel2abs()>. This means that it is taken to be relative to
L<cwd()|Cwd>.

On systems that have a grammar that indicates filenames, this ignores
the $base filename. Otherwise all path components are assumed to be
directories.

If $path is absolute, it is cleaned up and returned using L</canonpath()>.

No checks against the filesystem are made.  On VMS, there is
interaction with the working environment, as logicals and
macros are expanded.

Based on code written by Shigio Yamaguchi.

=cut

sub rel2abs {
    my ($self,$path,$base ) = @_;

    # Clean up $path
    if ( ! $self->file_name_is_absolute( $path ) ) {
        # Figure out the effective $base and clean it up.
        if ( !defined( $base ) || $base eq '' ) {
	    $base = $self->_cwd();
        }
        elsif ( ! $self->file_name_is_absolute( $base ) ) {
            $base = $self->rel2abs( $base ) ;
        }
        else {
            $base = $self->canonpath( $base ) ;
        }

        # Glom them together
        $path = $self->catdir( $base, $path ) ;
    }

    return $self->canonpath( $path ) ;
}

=back

=head1 SEE ALSO

L<File::Spec>

=cut

# Internal routine to File::Spec, no point in making this public since
# it is the standard Cwd interface.  Most of the platform-specific
# File::Spec subclasses use this.
sub _cwd {
    require Cwd;
    Cwd::cwd();
}

1;