117 lines
2.3 KiB
Go
117 lines
2.3 KiB
Go
package base62
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import (
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"bytes"
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"errors"
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"github.com/samber/lo"
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)
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type Base62 struct {
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characters []byte // base62 编码规则
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charactersMap map[byte]int // base62 编码规则
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}
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func GetInstance() *Base62 {
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b62 := &Base62{}
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b62.SetCharacters([]byte("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"))
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return b62
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}
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func (base62 *Base62) SetCharacters(characters []byte) (*Base62, error) {
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characters = lo.FindUniques(characters)
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charactersMap := make(map[byte]int)
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if len(characters) != 62 {
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return nil, errors.New("Invalid characters")
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}
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for i, v := range characters {
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charactersMap[v] = i
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}
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base62.characters = characters
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base62.charactersMap = charactersMap
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return base62, nil
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}
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// Encode function receives a byte slice and encodes it to a string using the alphabet provided
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func (base62 *Base62) Encode(source []byte) string {
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if len(source) == 0 {
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return ""
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}
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digits := []int{0}
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for i := 0; i < len(source); i++ {
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carry := int(source[i])
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for j := 0; j < len(digits); j++ {
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carry += digits[j] << 8
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digits[j] = carry % 62
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carry = carry / 62
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}
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for carry > 0 {
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digits = append(digits, carry%62)
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carry = carry / 62
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}
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}
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var res bytes.Buffer
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for k := 0; source[k] == 0 && k < len(source)-1; k++ {
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res.WriteByte(base62.characters[0])
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}
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for q := len(digits) - 1; q >= 0; q-- {
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res.WriteByte(base62.characters[digits[q]])
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}
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return res.String()
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}
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// Decode function decodes a string previously obtained from Encode, using the same alphabet and returns a byte slice
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// In case the input is not valid an arror will be returned
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func (base62 *Base62) Decode(source string) ([]byte, error) {
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if len(source) == 0 {
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return []byte{}, nil
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}
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runes := []byte(source)
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bytes := []byte{0}
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for i := 0; i < len(runes); i++ {
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value, ok := base62.charactersMap[runes[i]]
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if !ok {
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return nil, errors.New("Non Base Character")
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}
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carry := int(value)
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for j := 0; j < len(bytes); j++ {
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carry += int(bytes[j]) * 62
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bytes[j] = byte(carry & 0xff)
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carry >>= 8
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}
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for carry > 0 {
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bytes = append(bytes, byte(carry&0xff))
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carry >>= 8
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}
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}
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for k := 0; runes[k] == base62.characters[0] && k < len(runes)-1; k++ {
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bytes = append(bytes, 0)
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}
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// Reverse bytes
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for i, j := 0, len(bytes)-1; i < j; i, j = i+1, j-1 {
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bytes[i], bytes[j] = bytes[j], bytes[i]
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}
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return bytes, nil
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}
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