package GreekFile;

=head1 NAME

GreekFile -- for transliterating Greek file names in MS-Windows

=head1 SYNOPSIS

 gr_open( FILEHANDLE, $mode, $utf8name );
 gr_opendir( DIRHANDLE, $utf8name );
 $utf8_name = gr_readdir( DIRHANDLE );
 @utf8_names = gr_readdir( DIRHANDLE );
 @utf8_names = gr_glob( $utf8glob );

=head1 DESCRIPTION

On a Windows system that uses single-byte CP1253 Greek characters
(similar to ISO-8859-7) for naming files and directories, the
functions provided by this module will allow a utf8-based application
to work smoothly, by automatically converting file name strings
between these two encodings as needed.

This is presented as a "trial" or "proof-of-concept" version; it is
limited in many ways, and does not support a lot of the flexibility of
Perl's "open" and "opendir" functions.  For example, it does not
support the use of lexically-scoped scalar variables as file handles.
The limitations could be fixed with some looking up in manuals...

The gr_open and gr_opendir return the same success or failure values
that the normal "open" and "opendir" functions would return.
Likewise, gr_readdir behaves like normal readdir: it will return
either a single file name or a list of file names, depending on
whether it is called in a scalar or array context.

The functions that take utf8 strings as input parameters (gr_open,
gr_opendir and gr_glob), will do the conversion to CP1253 inside an
eval block.  If the conversion fails (either because the input string
was not valid utf8, or because it contained valid characters that fall
outside the CP1253 character set), they will return undef, and $! will
contain an error message from the failure (i.e. the value of $@ that
resulted from the failed eval).

Error checking is not done on the file names that are read via readdir
and glob.  At worst, if a file name on disk contains single-byte
characters that are not defined in the CP1253 character map, the
conversion to utf8 will include "\x{FFFD}" for each such character.

=cut

use Exporter;
use Encode qw(from_to);

@ISA = qw(Exporter);
@EXPORT_OK = qw(gr_open gr_opendir gr_readdir gr_glob);

use strict;
use warnings;

sub gr_open
{
    my ( $fh, $mode, $name ) = @_;
    eval { from_to( $name, "utf8", "cp1253", Encode::FB_CROAK ) };
    if ( $@ ) {
        $! = $@;
        return;
    }
    open( $fh, $mode, $name );
}

sub gr_opendir
{
    my ( $dh, $name ) = @_;
    eval { from_to( $name, "utf8", "cp1253", Encode::FB_CROAK ) };
    opendir( $dh, $name );
}

sub gr_readdir
{
    my ( @names, $name );
    my ( $dh ) = @_;
    if ( wantarray ) {
        @names = readdir( DH );
        from_to( $_, "cp1253", "utf8" ) for ( @names );
        return @names;
    } else {
        $name = readdir( DH );
        from_to( $name, "cp1253", "utf8" );
        return $name;
    }
}

sub gr_glob
{
    my ( $glb ) = @_;
    eval { from_to( $glb, "utf8", "cp1253", Encode::FB_CROAK ) };
    if ( $@ ) {
        $! = $@;
        return;
    }
    my @names = glob( $glb );
    from_to( $_, "cp1253", "utf8" ) for ( @names );
    return @names;
}
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