NAME

CheckDigits::M16_001 - compute check digits for ISAN

SYNOPSIS

  use Algorithm::CheckDigits;
  $isan = CheckDigits('isan');
  if ($isan->is_valid('123A567B8912E01A')) {
        # do something
  }
  $cn = $isan->complete('123A567B8912E01');
  # $cn = '123A567B8912E01A'
  $cd = $isan->checkdigit('123A567B8912E01A');
  # $cd = '4'
  $bn = $isan->basenumber('123A567B8912E01A');
  # $bn = '123A567B8912E01'

DESCRIPTION

ALGORITHM

1.

"a(1) = 16"

"b(i) = a(i) % 17 +d(i)", where d(i) is the decimal value of the hexdigit at position i.

"c(i) = b(i) % 16"

"a(i) = c(i-1) * 2", for i greater than 1

2.

Beginning left for each i = 1..16, "a", "b", "c" are computed.

3.

The check digit is the value for "d(16)" where "c(16)" equals 1.

4.

The check digit is appended as hexadecimal value to the number.

METHODS

is_valid($number): Returns true only if $number consists solely of numbers and the last digit is a valid check digit according to the algorithm given above.
Returns false otherwise,
complete($number): The check digit for $number is computed and concatenated to the end of $number.
Returns the complete number with check digit or '' if $number does not consist solely of digits and spaces.
basenumber($number): Returns the basenumber of $number if $number has a valid check digit.
Return '' otherwise.
checkdigit($number): Returns the checkdigit of $number if $number has a valid check digit.
Return '' otherwise.

EXPORT

None by default.

AUTHOR

Mathias Weidner, <mathias@weidner.in-bad-schmiedeberg.de>