=head1 NAME

Cache::IOString - wrapper for IO::String to use in Cache implementations

=head1 DESCRIPTION

This module implements a derived class of IO::String that handles access 
modes and allows callback on close.  It is for use by Cache implementations
and should not be used directly.

=cut
package Cache::IOString;

require 5.005;
use strict;
use warnings;
use IO::String;

our @ISA = qw(IO::String);


sub open {
    my $self = shift;
    my ($dataref, $mode, $close_callback) = @_;
    return $self->new(@_) unless ref($self);

    # check mode
    my $read;
    my $write;
    if ($mode =~ /^\+?>>?$/) {
        $write = 1;
        $read = 1 if $mode =~ /^\+/;
    }
    elsif ($mode =~ /^\+?<$/) {
        $read = 1;
        $write = 1 if $mode =~ /^\+/;
    }

    $self->SUPER::open($dataref);

    *$self->{_cache_read} = $read;
    *$self->{_cache_write} = $write;
    *$self->{_cache_close_callback} = $close_callback;

    if ($write) {
        if ($mode =~ /^\+?>>$/) {
            # append
            $self->seek(0, 2);
        }
        elsif ($mode =~ /^\+?>$/) {
            # truncate
            $self->truncate(0);
        }
    }

    return $self;
}

sub close {
    my $self = shift;
    delete *$self->{_cache_read};
    delete *$self->{_cache_write};
    *$self->{_cache_close_callback}->($self) if *$self->{_cache_close_callback};
    delete *$self->{_cache_close_callback};
    $self->SUPER::close(@_);
}

sub DESTROY {
    my $self = shift;
    *$self->{_cache_close_callback}->($self) if *$self->{_cache_close_callback};
}

sub pad {
    my $self = shift;
    return undef unless *$self->{_cache_write};
    return $self->SUPER::pad(@_);
}

sub getc {
    my $self = shift;
    return undef unless *$self->{_cache_read};
    return $self->SUPER::getc(@_);
}

sub ungetc {
    my $self = shift;
    return undef unless *$self->{_cache_read};
    return $self->SUPER::ungetc(@_);
}

sub seek {
    my $self = shift;
    # call setpos if not writing to ensure a seek past the end doesn't extend
    # the string.  Probably should really return undef in that situation.
    return $self->SUPER::setpos(@_) unless *$self->{_cache_write};
    return $self->SUPER::seek(@_);
}

sub getline {
    my $self = shift;
    return undef unless *$self->{_cache_read};
    return $self->SUPER::getline(@_);
}

sub truncate {
    my $self = shift;
    return undef unless *$self->{_cache_write};
    return $self->SUPER::truncate(@_);
}

sub read {
    my $self = shift;
    return undef unless *$self->{_cache_read};
    return $self->SUPER::read(@_);
}

sub write {
    my $self = shift;
    return undef unless *$self->{_cache_write};
    return $self->SUPER::write(@_);
}

*GETC = \&getc;
*READ = \&read;
*WRITE = \&write;
*SEEK = \&seek;
*CLOSE = \&close;


1;
__END__

=head1 SEE ALSO

Cache::Entry, Cache::File, Cache::RemovalStrategy

=head1 AUTHOR

 Chris Leishman <chris@leishman.org>
 Based on work by DeWitt Clinton <dewitt@unto.net>

=head1 COPYRIGHT

 Copyright (C) 2003 Chris Leishman.  All Rights Reserved.

This module is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND,
either expressed or implied. This program is free software; you can
redistribute or modify it under the same terms as Perl itself.

$Id: IOString.pm,v 1.1.1.1 2003/06/05 21:46:09 caleishm Exp $

=cut