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/*
This file is part of Anastasis
Copyright (C) 2020, 2021 Anastasis SARL
Anastasis is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 3, or (at your option) any later version.
Anastasis is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
Anastasis; see the file COPYING.GPL. If not, see <http://www.gnu.org/licenses/>
*/
/**
* @file reducer/validation_DE_TIN.c
* @brief validation logic for German taxpayer identification numbers
* @author Christian Grothoff
*/
#include <string.h>
#include <stdbool.h>
/**
* Function to validate a German Taxpayer identification number.
*
* See https://de.wikipedia.org/wiki/Steuerliche_Identifikationsnummer
* for the structure!
*
* @param tin_number tax number to validate (input)
* @return true if validation passed, else false
*/
bool
DE_TIN_check (const char *tin_number)
{
unsigned int csum;
unsigned int product = 10;
if (strlen (tin_number) != 11)
return false;
for (unsigned int i = 0; i<10; i++)
{
unsigned int sum = ((tin_number[i] - '0') + product) % 10;
if (0 == sum)
sum = 10;
product = sum * 2 % 11;
}
csum = 11 - product;
if (10 == csum)
csum = 0;
if (tin_number[10] != '0' + csum)
return false;
if (tin_number[0] == '0')
return false;
return true;
}
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