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lib/Algorithm/CheckDigits/M10_001.pm  view on Meta::CPAN

sub _compute_checkdigit {
    my $self   = shift;
    my $number = shift;
    $number =~ s/\s//g;
    if ( $omitprefix{ $self->{type} } ) {
        my $pf = $prefix{ $self->{type} };
        for my $p ( @{$pf} ) {
            if ( $number =~ /^$p([0-9]+)$/ ) {
                $number = $1;
                last;
            }
        }
    }
    if ('isin' eq $self->{type}) {
        # With ISIN letters are handled differently than for instance with
        # CUSIP, so we substitute them here
        $number =~ s/([A-Z])/$ctable{$1}/ge;
    }
    elsif ('imeisv' eq $self->{type}) {
        # With IMEISV the SV (software version) is left out from the
        # computation of the checkdigit
        $number = substr( $number, 0, 14 ) if ( 'imeisv' eq $self->{type} );
    }

    my @digits =  map { $ctable{$_} } split( //, $number );
    my $even   = 1;
    my $sum    = 0;
    for ( my $i = $#digits; $i >= 0; $i-- ) {
        if ($even) {
            my $tmp = 2 * $digits[$i];
            $sum += $tmp / 10 + $tmp % 10;
        }
        else {
            $sum += $digits[$i] / 10 + $digits[$i] % 10;
        }
        $even = not $even;
    }
    return ( 10 - $sum % 10 ) % 10;
}    # _compute_checkdigit()

sub _determine_pattern {
    my $self = shift;
    if ('cusip' eq $self->{type}) {
        $self->{pattern} = qr/[0-9A-Z]{8}/io;
    }
    else {
        $self->{pattern} = qr/[0-9A-Z ]+/io;
    }
} # _determine_pattern()

# Preloaded methods go here.

1;
__END__

=head1 NAME

CheckDigits::M10_001 - compute check digits for Bahncard (DE), IMEI,
IMEISV, ISIN, Miles&More, Payback (DE), Personnummer (SE), Passport
(BR), Credit Cards, SSN (US), Samordningsnummer (SE), VAT RN (ES), VAT
RN (IT), VAT RN (SE), International Securities Identifikation Number
(ISIN), CUSIP

=head1 SYNOPSIS

  use Algorithm::CheckDigits;

  $visa = CheckDigits('visa');

  if ($visa->is_valid('4111 1111 1111 1111')) {
	# do something
  }

  $cn = $visa->complete('4111 1111 1111 111');
  # $cn = '4111 1111 1111 1111'

  $cd = $visa->checkdigit('4111 1111 1111 1111');
  # $cd = '7'

  $bn = $visa->basenumber('4111 1111 1111 1111');
  # $bn = '4111 1111 1111 111'
  
=head1 DESCRIPTION

=head2 ALGORITHM

=over 4

=item 1

Beginning right all numbers are weighted alternatively 1 and 2 (that
is the check digit is weighted 1).

=item 2

The total of the digits of all products is computed.

=item 3

The sum of step 3 ist taken modulo 10.

=item 4

The check digit is the difference between 10 and the number from step
3.

=back

To validate the total of the digits of all numbers inclusive check
digit taken modulo 10 must be 0.

=head2 METHODS

=over 4

=item is_valid($number)

Returns true only if the last digit
is a valid check digit according to the algorithm given above.