Module mod11

mod11 is a Lua module to calculate and verify modulo11 checksums.

Modulo 11 is commonly used to prevent human errors. Common usecases are; bank account numbers, creditcard numbers, social security numbers.

Info:

  • Release: Version 1.0, mod11 module to calculate and verify checksums
  • License: mod11 is free software under the MIT license.
  • Author: Thijs Schreijer, http://www.thijsschreijer.nl
  • Copyright: 2014 Thijs Schreijer

Functions

new (verify, allowed) Creates a new object based on the given verify weights and allowed characters.
getverify (self) Returns the string with verify weights as passed to new
getallowed (self) Returns the string with allowed characters as passed to new .
calc (self, inp) Calculates the checksum.
split (self, inp) Splits a number with checksum into number and checksum.
check (self, inp) Checks a number to be a valid one.
foreach (self, text, minsize, maxsize) Iterator factory.


Functions

new (verify, allowed)
Creates a new object based on the given verify weights and allowed characters.

Parameters:

  • verify string A string of size 8, containing the digits 2-9, in some random order (no doubles).
  • allowed string (optional) A string of characters allowed in between the digits. The digits (0-9) will automatically be added to the allowed set.

Returns:

  1. mod11 object that can be used to generate and verify checksums
  2. Throws an error on invalid input

Usage:

     local mod11 = require("mod11")
 local m = mod11("25834967","-/")               -- mod11() is a shortcut to mod11:new()
 local invoicenr = "2013-12-23/013-"            -- a date and a sequential nr
 invoicenr = invoicenr..m:calc(invoicenr)       -- append the checksum
 print("Invoicenr including check:",invoicenr)
getverify (self)
Returns the string with verify weights as passed to new

Parameters:

  • self The mod11 object created by new .
getallowed (self)
Returns the string with allowed characters as passed to new . The returned string will also contain the digits (0-9), which are also allowed. Hence the string returned will not be identical to the string passed to new .

Parameters:

  • self The mod11 object created by new .
calc (self, inp)
Calculates the checksum. See new for an example.

Parameters:

  • self The mod11 object created by new .
  • inp string The string to calculate the checksum for. The string can only contain digits and 'allowed' characters

Returns:

  1. 2 values; 1) input with checksum appended, 2) checksum only
  2. Throws an error on invalid input
split (self, inp)
Splits a number with checksum into number and checksum. It will not test validity of the checksum, use check for testing validity.

Parameters:

  • self The mod11 object created by new .
  • inp The string containing the number sequence to split.

Returns:

  1. 2 strings; number and checksum. Both will be digits only, all other characters will be removed
  2. Throws an error on invalid input
check (self, inp)
Checks a number to be a valid one. The check will only succeed if the verify number used is the exact same number as the one used to create the checksum.

Parameters:

  • self The mod11 object created by new .
  • inp The string containing the number sequence to verify.

Returns:

  1. true if the checksum matches
  2. false if the checksum failed
  3. nil + error message if bad input was provided
foreach (self, text, minsize, maxsize)
Iterator factory. Return an iterator, which returns all valid numbers in the provided string. The optional minsize and maxsize parameters can be used to minimize the chance of false positives.

Parameters:

  • self The mod11 object created by new .
  • text The string to search. If text is not a string it will be 'tostring'ed
  • minsize (optional) The minimum length (in digits, excluding 'allowed' characters)
  • maxsize (optional) The maximum length (in digits, excluding 'allowed' characters)

Returns:

  1. an iterator function that will return 3 values; 1) value (incl chk nr), 2) startpos, 3) endpos
  2. Throws an error on invalid input (minsize < 2, or maxsize < minsize)

Usage:

    -- see the sample directory for an example of the iterator
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