75 lines
1.2 KiB
Go
75 lines
1.2 KiB
Go
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package langext
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import (
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"crypto/rand"
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"errors"
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"math"
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"math/big"
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"strings"
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)
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var (
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base62Base = uint64(62)
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base62CharacterSet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
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)
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func RandBase62(rlen int) string {
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bi52 := big.NewInt(int64(len(base62CharacterSet)))
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randMax := big.NewInt(math.MaxInt64)
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r := ""
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for i := 0; i < rlen; i++ {
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v, err := rand.Int(rand.Reader, randMax)
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if err != nil {
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panic(err)
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}
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r += string(base62CharacterSet[v.Mod(v, bi52).Int64()])
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}
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return r
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}
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func EncodeBase62(num uint64) string {
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if num == 0 {
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return "0"
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}
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b := make([]byte, 0)
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// loop as long the num is bigger than zero
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for num > 0 {
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r := num % base62Base
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num -= r
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num /= base62Base
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b = append([]byte{base62CharacterSet[int(r)]}, b...)
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}
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return string(b)
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}
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func DecodeBase62(str string) (uint64, error) {
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if str == "" {
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return 0, errors.New("empty string")
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}
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result := uint64(0)
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for _, v := range str {
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result *= base62Base
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pos := strings.IndexRune(base62CharacterSet, v)
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if pos == -1 {
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return 0, errors.New("invalid character: " + string(v))
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}
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result += uint64(pos)
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}
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return result, nil
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}
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