Mini Shell

package IO::Wrap;

# SEE DOCUMENTATION AT BOTTOM OF FILE

require 5.002;

use strict;
use vars qw(@ISA @EXPORT $VERSION);
@ISA = qw(Exporter);
@EXPORT = qw(wraphandle);

use FileHandle;
use Carp;

# The package version, both in 1.23 style *and* usable by MakeMaker:
$VERSION = "2.111";


#------------------------------
# wraphandle RAW
#------------------------------
sub wraphandle {
    my $raw = shift;
    new IO::Wrap $raw;
}

#------------------------------
# new STREAM
#------------------------------
sub new {
    my ($class, $stream) = @_;
    no strict 'refs';

    ### Convert raw scalar to globref:
    ref($stream) or $stream = \*$stream;

    ### Wrap globref and incomplete objects:
    if ((ref($stream) eq 'GLOB') or      ### globref
	(ref($stream) eq 'FileHandle') && !defined(&FileHandle::read)) {
	return bless \$stream, $class;
    }
    $stream;           ### already okay!
}

#------------------------------
# I/O methods...
#------------------------------
sub close {
    my $self = shift;
    return close($$self);
}
sub fileno {
    my $self = shift;
    my $fh = $$self;
    return fileno($fh);
}

sub getline {
    my $self = shift;
    my $fh = $$self;
    return scalar(<$fh>);
}
sub getlines {
    my $self = shift;
    wantarray or croak("Can't call getlines in scalar context!");
    my $fh = $$self;
    <$fh>;
}
sub print {
    my $self = shift;
    print { $$self } @_;
}
sub read {
    my $self = shift;
    return read($$self, $_[0], $_[1]);
}
sub seek {
    my $self = shift;
    return seek($$self, $_[0], $_[1]);
}
sub tell {
    my $self = shift;
    return tell($$self);
}

#------------------------------
1;
__END__


=head1 NAME

IO::Wrap - wrap raw filehandles in IO::Handle interface


=head1 SYNOPSIS

   use IO::Wrap;
       
   ### Do stuff with any kind of filehandle (including a bare globref), or 
   ### any kind of blessed object that responds to a print() message.
   ###
   sub do_stuff {
       my $fh = shift;         
       
       ### At this point, we have no idea what the user gave us... 
       ### a globref? a FileHandle? a scalar filehandle name?
       
       $fh = wraphandle($fh);  
        
       ### At this point, we know we have an IO::Handle-like object!
       
       $fh->print("Hey there!");
       ...
   }
    

=head1 DESCRIPTION

Let's say you want to write some code which does I/O, but you don't 
want to force the caller to provide you with a FileHandle or IO::Handle
object.  You want them to be able to say:

    do_stuff(\*STDOUT);
    do_stuff('STDERR');
    do_stuff($some_FileHandle_object);
    do_stuff($some_IO_Handle_object);

And even:

    do_stuff($any_object_with_a_print_method);

Sure, one way to do it is to force the caller to use tiehandle().  
But that puts the burden on them.  Another way to do it is to 
use B<IO::Wrap>, which provides you with the following functions:


=over 4

=item wraphandle SCALAR

This function will take a single argument, and "wrap" it based on
what it seems to be...

=over 4

=item *

B<A raw scalar filehandle name,> like C<"STDOUT"> or C<"Class::HANDLE">.
In this case, the filehandle name is wrapped in an IO::Wrap object, 
which is returned.

=item *

B<A raw filehandle glob,> like C<\*STDOUT>.
In this case, the filehandle glob is wrapped in an IO::Wrap object, 
which is returned.

=item *

B<A blessed FileHandle object.>
In this case, the FileHandle is wrapped in an IO::Wrap object if and only
if your FileHandle class does not support the C<read()> method.

=item *

B<Any other kind of blessed object,> which is assumed to be already
conformant to the IO::Handle interface.
In this case, you just get back that object.

=back

=back


If you get back an IO::Wrap object, it will obey a basic subset of
the IO:: interface.  That is, the following methods (note: I said
I<methods>, not named operators) should work on the thing you get back:

    close 
    getline 
    getlines 
    print ARGS...
    read BUFFER,NBYTES
    seek POS,WHENCE
    tell 



=head1 NOTES

Clearly, when wrapping a raw external filehandle (like \*STDOUT), 
I didn't want to close the file descriptor when the "wrapper" object is
destroyed... since the user might not appreciate that!  Hence,
there's no DESTROY method in this class.

When wrapping a FileHandle object, however, I believe that Perl will 
invoke the FileHandle::DESTROY when the last reference goes away,
so in that case, the filehandle is closed if the wrapped FileHandle
really was the last reference to it.


=head1 WARNINGS

This module does not allow you to wrap filehandle names which are given
as strings that lack the package they were opened in. That is, if a user 
opens FOO in package Foo, they must pass it to you either as C<\*FOO> 
or as C<"Foo::FOO">.  However, C<"STDIN"> and friends will work just fine.


=head1 VERSION

$Id: Wrap.pm,v 1.2 2005/02/10 21:21:53 dfs Exp $
    

=head1 AUTHOR

=item Primary Maintainer

Dianne Skoll (F<dfs@roaringpenguin.com>).

=item Original Author

Eryq (F<eryq@zeegee.com>).
President, ZeeGee Software Inc (F<http://www.zeegee.com>).

=cut