Private/Test-LuhnCheck.ps1
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function Test-LuhnCheck { param( [ValidateNotNull()] [String] $Data ) # Strip hyphens and spaces $Data = $Data -replace "-", "" $Data = $Data -replace " ", "" if ([string]::IsNullOrWhiteSpace($Data)) { Write-Warning -Message ("{0} :: Provided empty data for luhn check." -f $MyInvocation.MyCommand) return $false } [regex] $digitCheck = "^[0-9]*$" if (-not $digitCheck.IsMatch($Data)) { Write-Warning -Message ("{0} :: Provided invalid, non numeric data '{1}' for luhn check." -f $MyInvocation.MyCommand, $Data) return $false } # Implementation of : https://de.wikipedia.org/wiki/Luhn-Algorithmus $sum = 0 $parity = $Data.Length % 2 for ($i = 0; $i -lt $Data.Length; $i++) { $digit = [int]::Parse($Data[$i]) # Double every other digit (starting from last digit) if ($i % 2 -eq $parity) { $digit *= 2 if ($digit -gt 9) { $digit = $digit - 9 } } $sum += $digit } return ($sum % 10) -eq 0 } |