70 lines
1.5 KiB
Go
70 lines
1.5 KiB
Go
package verhoeff
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import (
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"strconv"
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"strings"
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"github.com/neonxp/checksum"
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)
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var d = [10][10]int{
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{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
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{1, 2, 3, 4, 0, 6, 7, 8, 9, 5},
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{2, 3, 4, 0, 1, 7, 8, 9, 5, 6},
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{3, 4, 0, 1, 2, 8, 9, 5, 6, 7},
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{4, 0, 1, 2, 3, 9, 5, 6, 7, 8},
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{5, 9, 8, 7, 6, 0, 4, 3, 2, 1},
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{6, 5, 9, 8, 7, 1, 0, 4, 3, 2},
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{7, 6, 5, 9, 8, 2, 1, 0, 4, 3},
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{8, 7, 6, 5, 9, 3, 2, 1, 0, 4},
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{9, 8, 7, 6, 5, 4, 3, 2, 1, 0},
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}
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var p = [8][10]int{
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{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
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{1, 5, 7, 6, 2, 8, 3, 0, 9, 4},
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{5, 8, 0, 3, 7, 9, 6, 1, 4, 2},
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{8, 9, 1, 6, 0, 4, 3, 5, 2, 7},
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{9, 4, 5, 3, 1, 2, 6, 8, 7, 0},
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{4, 2, 8, 6, 5, 7, 3, 9, 0, 1},
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{2, 7, 9, 3, 8, 0, 6, 4, 1, 5},
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{7, 0, 4, 6, 9, 1, 3, 2, 5, 8},
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}
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var inv = [10]int{0, 4, 3, 2, 1, 5, 6, 7, 8, 9}
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// Check number is correct by verhoeff algorithm
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func Check(number string) error {
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c := 0
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numbers := strings.Split(number, "")
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l := len(numbers)
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for i := l; i > 0; i-- {
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ch := numbers[i-1]
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num, err := strconv.Atoi(string(ch))
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if err != nil {
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return checksum.ErrInvalidNumber
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}
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c = d[c][p[(l-i)&7][num]]
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}
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if c != 0 {
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return checksum.ErrInvalidChecksum
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}
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return nil
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}
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// Generate checksum (must be added to number at right)
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func Generate(number string) (string, error) {
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c := 0
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numbers := strings.Split(number, "")
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l := len(numbers)
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for i := l; i > 0; i-- {
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ch := numbers[i-1]
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num, err := strconv.Atoi(string(ch))
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if err != nil {
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return "", checksum.ErrInvalidNumber
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}
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c = d[c][p[(l-i+1)&7][num]]
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}
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return strconv.Itoa(inv[c]), nil
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}
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