package IO::Select;
use constant { HANDLES => 0, BITS => 1 };

sub new {
    my $package = shift;
    my $self = bless [ [], '' ], $package;
    $self->[HANDLES][fileno($_)] = $_ for @_;
    vec( $self->[BITS], fileno( $_ ), 1 ) = 1 for @_;
    return $self
}
sub add {
    my $self = shift;
    $self->[HANDLES][fileno($_)] = $_ for @_;
    vec( $self->[BITS], fileno( $_ ), 1 ) = 1 for @_;
    return $self;
}
sub remove {
    my $self = shift;
    for my $handle ( @_ ) {
        my( $bit ) = grep{
            $self->[HANDLES][ $_ ] && $self->[HANDLES][ $_ ] == $handle
        } 0 .. $#{ $self->[HANDLES] };
        warning( "Can't remove handle $handle; not found" ), next unless $bit;
        undef $self->[HANDLES][ $bit ];
        vec( $self->[BITS], $bit, 1 ) = 0;
    }
    return $self;
}
sub _mapBitsToHandles {
    my( $self, $bits ) = @_;
    map{
        vec( $bits, $_, 1 ) ? $self->[HANDLES][ $_ ] : ()
    } 0 .. ( length( $bits ) * 8 -1 );
}
sub can_read {
    my( $self, $timeout ) = @_;
    my $out = $self->[BITS];
    select( $out, undef, undef, $timeout );
    return $self->_mapBitsToHandles( $out );
}
sub can_write {
    my( $self, $timeout ) = @_;
    my $out = $self->[BITS];
    select( undef, $out, undef, $timeout );
    return $self->_mapBitsToHandles( $out );
}
sub has_exception {
    my( $self, $timeout ) = @_;
    my $out = $self->[BITS];
    select( undef, undef, $out, $timeout );
    return $self->_mapBitsToHandles( $out );
}
sub count {
    my $self = shift;
    scalar $self->handles;
}
sub handles {
    my $self = shift;
    return grep defined(), @{ $self->[HANDLES] };
}