78 lines
1.7 KiB
Go
78 lines
1.7 KiB
Go
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package crypt
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import (
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"encoding/binary"
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"strconv"
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"strings"
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)
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// Luhn validates a number using the Luhn algorithm.
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func (s *Service) Luhn(payload string) bool {
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payload = strings.ReplaceAll(payload, " ", "")
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sum := 0
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isSecond := false
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for i := len(payload) - 1; i >= 0; i-- {
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digit, err := strconv.Atoi(string(payload[i]))
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if err != nil {
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return false // Contains non-digit
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}
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if isSecond {
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digit = digit * 2
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if digit > 9 {
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digit = digit - 9
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}
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}
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sum += digit
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isSecond = !isSecond
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}
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return sum%10 == 0
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}
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// Fletcher16 computes the Fletcher-16 checksum.
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func (s *Service) Fletcher16(payload string) uint16 {
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data := []byte(payload)
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var sum1, sum2 uint16
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for _, b := range data {
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sum1 = (sum1 + uint16(b)) % 255
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sum2 = (sum2 + sum1) % 255
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}
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return (sum2 << 8) | sum1
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}
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// Fletcher32 computes the Fletcher-32 checksum.
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func (s *Service) Fletcher32(payload string) uint32 {
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data := []byte(payload)
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// Pad with 0 to make it even length for uint16 conversion
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if len(data)%2 != 0 {
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data = append(data, 0)
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}
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var sum1, sum2 uint32
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for i := 0; i < len(data); i += 2 {
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val := binary.LittleEndian.Uint16(data[i : i+2])
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sum1 = (sum1 + uint32(val)) % 65535
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sum2 = (sum2 + sum1) % 65535
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}
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return (sum2 << 16) | sum1
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}
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// Fletcher64 computes the Fletcher-64 checksum.
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func (s *Service) Fletcher64(payload string) uint64 {
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data := []byte(payload)
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// Pad to multiple of 4
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if len(data)%4 != 0 {
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padding := 4 - (len(data) % 4)
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data = append(data, make([]byte, padding)...)
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}
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var sum1, sum2 uint64
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for i := 0; i < len(data); i += 4 {
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val := binary.LittleEndian.Uint32(data[i : i+4])
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sum1 = (sum1 + uint64(val)) % 4294967295
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sum2 = (sum2 + sum1) % 4294967295
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}
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return (sum2 << 32) | sum1
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}
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