50 lines
1,013 B
Go
50 lines
1,013 B
Go
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package damm
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import (
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"strconv"
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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, 3, 1, 7, 5, 9, 8, 6, 4, 2},
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{7, 0, 9, 2, 1, 5, 4, 8, 6, 3},
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{4, 2, 0, 6, 8, 7, 1, 3, 5, 9},
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{1, 7, 5, 0, 9, 8, 3, 4, 2, 6},
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{6, 1, 2, 3, 0, 4, 5, 9, 7, 8},
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{3, 6, 7, 4, 2, 0, 9, 5, 8, 1},
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{5, 8, 6, 9, 7, 2, 0, 1, 3, 4},
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{8, 9, 4, 5, 3, 6, 2, 0, 1, 7},
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{9, 4, 3, 8, 6, 1, 7, 2, 0, 5},
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{2, 5, 8, 1, 4, 3, 6, 7, 9, 0},
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}
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// Check number is correct by damm algorithm
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func Check(number string) error {
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c := 0
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for _, ch := range number {
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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][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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for _, ch := range number {
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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][num]
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}
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return strconv.Itoa(c), nil
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}
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