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#!/usr/bin/pike
/*
creditcheck.pike - library
Version .50
Author - Allen Bolderoff
(with copious amounts of code stolen shamelessly from
Henrik Grubbstrm <grubba@infovav.se>)
and based entirely on the algorithm supplied
with CREDIT_CARD_VALIDATION_LIB.PL v1.0
by Doug Miles dmiles@primenet.com
USAGE
This is called by doing an
inherit "creditcheck.pike";
if(creditcheck(cardnumber, cardtype))
card_is_bad() //any subroutine you wish when card is no good
else
card_is_good() // or vice versa
LICENSE - GPL-2.0 and or later
WARRANTY - NONE WHAT SO EVER - implied or otherwise.
I have used this to check many cards successfully to weed out bad numbers (most of the time.) - this just stops someone from putting in Random numbers and trying to get an Obviously false number into your system. I do not guarentee that it will help you in any way whatsoever - USE at your own risk!
*/
/*
This is some constants for number of digits per card
*/
constant hash_function = ({ 0, 2, 4, 6, 8, 1, 3, 5, 7, 9 });
constant card_digits =([ "VISA":16, "AMEX":15, "MasterCard":16 ]);
import String;
import Array;
import Stdio;
// subroutine creditcheck() starts here
int creditcheck(string ccn, string card_type)
{
// clear spaces & non numeric characters here
string number = replace(ccn, ({ " ", "-" }), ({ "", "" }));
// Check if any non numeric characters exist, and exit with 1 if no good
string validnumbers = replace(number,
({ "0","1","2","3","4","5","6","7","8","9" }),
({ "","","","","","","","","","" }));
if (validnumbers != "") {
return(1);
}
//verify card number length and exit with 1 if bad
if (card_digits[card_type] != sizeof(number)) {
return(1);
}
// reverse digits here
array digits = map(reverse(number/""), lambda(string n) { return (int)n; });
/*
double every second digit of the reversed number.
ceck whether it is more than 9 when doubled.
if it is more than 9, the we minus 9 from the doubled figure, or if it
is below 9, then we just double it.
*/
int sum=0;
for(int i=1; i<sizeof(digits); i+=2) {
if((digits[i]*2) > 9)
{
(digits[i]*=2);
(digits[i]-=9);
} else {
digits[i]*=2;
}
}
/*
add all digits (including double values & non doubled figures) together
and put in value of "sum"
*/
for(int i=0; i<sizeof(digits); i+=1) {
sum += digits[i];
}
/*
is sum divided by 10 equal to 0?
if so, then the card should be good(exit with 0),
if not, then card is bad (exit with 1)
*/
sum %= 10;
if (sum != 0)
{
return(1);
}
return(0);
}
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