IDC资讯中心
验证还取决于信用卡的类型。
**************************************
name: credit card mod 10 validation
description:this function validates if
a credit card number "appears" to be val
id, depending on the type of card, and a
lso performing a mod 10 check on the num
bers.
by: lewis moten
inputs:ascardtype – type of credit car
d. (american express, discover, visa, ma
stercard)
ancardnumber – the number appearing on the card. dashes and spaces are ok. numbers are stripped from
the data provided.
returns:returns a boolean (true/false)
determining if the number appears to be
valid or not.
assumes:the user needs to be able to lo
ok through the code and determine wich s
trings represent the cards. you can eith
er type out the entire card name (i.e. "
american express") or type in just a let
ter representing the card name (i.e. "a"
)
side effects:just because the function
returns that the card is valid, there ar
e several other things that are not bein
g validated.
date – make sure the card has not expired
active account – this script does not communicate with any banks to determine if the account number is
active
authorization – again, this script does not communicate with any banks to determine if the card has
authorization to purchase a product.
warranty:
code provided by planet source code(tm)
(www.planet-source-code.com) as is, wi
thout warranties as to performance, fitn
ess, merchantability,and any other warra
nty (whether expressed or implied).
terms of agreement:
by using this source code, you agree to
the following terms…
1) you may use this source code in per
sonal projects and may compile it into a
n .exe/.dll/.ocx and distribute it in bi
nary format freely and with no charge.
2) you may not redistribute this sourc
e code (for example to a web site) witho
ut written permission from the original
author.failure to do so is a violation o
f copyright laws.
3) you may link to this code from anot
her website, provided it is not wrapped
in a frame.
4) the author of this code may have re
tained certain additional copyright righ
ts.if so, this is indicated in the autho
rs description.
**************************************
function iscreditcard(byref ascardtype, byref ancardnumber)
performs a mod 10 check to make sure the credit card number
appears valid
developers may use the following numbers as dummy data:
visa: 430-00000-00000
american express: 372-00000-00000
mastercard: 521-00000-00000
discover: 620-00000-00000
dim lsnumber credit card number stripped of all spaces, dashes,
etc.
dim lschar an individual character
dim lntotal sum of all calculations
dim lndigit a digit found within a credit card number
dim lnposition identifies a character position in a string
dim lnsum sum of calculations for a specific set
default result is false
iscreditcard = false
====
strip all characters that are not numbers.
====
loop through each character inthe card number submited
for lnposition = 1 to len(ancardnumber)
grab the current character
lschar = mid(ancardnumber, lnposition, 1)
if the character is a number, append it to our new number
if isnumeric(lschar) then lsnumber = lsnumber & lschar
next lnposition
====
the credit card number must be between 13 and 16 digits.
====
if the length of the number is less then 13 digits, then exit the routine
if len(lsnumber) < 13 then exit function
if the length of the number is more then 16 digits, then exit the routine
if len(lsnumber) > 16 then exit function
====
the credit card number must start with:
4 for visa cards
37 for american express cards
5 for mastercards
6 for discover cards
====
choose action based on type of card
select case lcase(ascardtype)
visa
case "visa", "v"
if first digit not 4, exit function
if not left(lsnumber, 1) = "4" then exit function
american express
case "american express", "americanexpress", "american", "ax", "a"
if first 2 digits not 37, exit function
if not left(lsnumber, 2) = "37" then exit function
mastercard
case "mastercard", "master card", "master", "m"
if first digit not 5, exit function
if not left(lsnumber, 1) = "5" then exit function
discover
case "discover", "discovercard", "discover card", "d"
if first digit not 6, exit function
if not left(lsnumber, 1) = "6" then exit function
case else
end select lcase(ascardtype)
====
if the credit card number is less then 16 digits add zeros
to the beginning to make it 16 digits.
====
continue loop while the length of the number is less then 16 digits
while not len(lsnumber) = 16
insert 0 to the beginning of the number
lsnumber = "0" & lsnumber
wend not len(lsnumber) = 16
====
multiply each digit of the credit card number by the corresponding digit of
the mask, and sum the results together.
====
loop through each digit
for lnposition = 1 to 16
parse a digit from a specified position in the number
lndigit = mid(lsnumber, lnposition, 1)
determine if we multiply by:
1 (even)
2 (odd)
based on the position that we are reading the digit from
lnmultiplier = 1 + (lnposition mod 2)
calculate the sum by multiplying the digit and the multiplier
lnsum = lndigit * lnmultiplier
(single digits roll over to remain single. we manually have to do this.)
if the sum is 10 or more, subtract 9
if lnsum > 9 then lnsum = lnsum – 9
add the sum to the total of all sums
lntotal = lntotal + lnsum
next lnposition
====
once all the results are summed divide
by 10, if there is no remainder then the credit card number is valid.
====
iscreditcard = ((lntotal mod 10) = 0)
end function iscreditcard
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