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Update EAN13.swift #5

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Update EAN13.swift #5

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20 changes: 11 additions & 9 deletions Sources/BarcodeView/Models/EAN13.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -70,16 +70,18 @@ extension EAN13 {

return digits
}

private static func verifyChecksumDigit(value: String) -> Bool {
let digits = value.map { Int(String($0))! }.dropLast()

let odd = stride(from: 1, to: digits.count, by: 2).map { digits[$0] }.reduce(0, +) * 3
let even = stride(from: 0, to: digits.count, by: 2).map { digits[$0] }.reduce(0, +)

let calculatedChecksum = 10 - ((odd + even) % 10)

return String(calculatedChecksum) == value.last.map({ String($0) })
let digits = value.compactMap { Int(String($0)) }
let lastDigit = digits.last!
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@nrivard nrivard Jan 15, 2024

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This seems inherently unsafe if after the compactMap there are zero elements in digits. Previous code was written a long time ago I should have probably made it safer long ago 😂 Haven't looked at this code in awhile so maybe there are other verification steps that make sure it's the proper number of digits but you may want to check that value.count == digits.count

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@hrabkin hrabkin Jan 15, 2024

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@nrivard yes, I've seen it, but on line 16 you checked digits, so it is actually fine:

BarcodeView/Sources/BarcodeView/Models/EAN13.swift

Line 16 in 1c18b32

guard !verifyChecksum || EAN13.verifyChecksumDigit(value: value), let digits = EAN13.digits(value: value) else { return nil }


let evenSum = stride(from: 1, to: digits.count - 1, by: 2).map { digits[$0] }.reduce(0, +) * 3
let oddSum = stride(from: 0, to: digits.count - 1, by: 2).map { digits[$0] }.reduce(0, +)
let totalSum = evenSum + oddSum

let calculatedCheckDigit = totalSum % 10 == 0 ? 0 : 10 - totalSum % 10

return calculatedCheckDigit == lastDigit
}
}

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