luhn.c

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// SPDX-FileCopyrightText: 2021 deroad <wargio@libero.it>
// SPDX-License-Identifier: LGPL-3.0-only
 
#include <rz_util.h>
 
RZ_API bool rz_calculate_luhn_value(const char *data, ut64 *result) {
    rz_return_val_if_fail(data && result, false);
    ssize_t size = strlen(data);
    if (size < 1) {
        return false;
    }
 
    int digit;
    ut64 sum = 0;
    bool parity = false;
    for (ssize_t i = size - 1; i >= 0; --i) {
        if (!IS_DIGIT(data[i])) {
            return false;
        }
 
        digit = data[i] - '0';
        if (parity) {
            digit *= 2;
        }
        digit = (digit / 10) + (digit % 10);
        sum += digit;
        parity = !parity;
    }
 
    *result = sum % 10;
    return true;
}