IsValidEan13

IsValidEan13.go

// IsValidEan13 return true if given ean13 number is valid
func IsValidEan13(code string) bool {
	if len(code) != 13 {
		return false
	}

	oddSum := 0
	evenSum := 0
	for i, n := range code[:12] {
		digit := int(n - '0')

		if digit < 0 || 9 < digit {
			return false
		}

		if i%2 == 0 {
			evenSum += digit
		} else {
			oddSum += digit
		}
	}

	checksum := 10 - (oddSum*3+evenSum)%10
	if checksum == 10 {
		checksum = 0
	}

	return checksum == int(code[12]-'0')
}