59 lines
1.5 KiB
Go
59 lines
1.5 KiB
Go
package base83
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import (
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"fmt"
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"math"
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"strings"
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)
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const characters = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz#$%*+,-.:;=?@[]^_{|}~"
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// An InvalidCharacterError occurs when a characters is found which is not part of the Base83 character set.
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type InvalidCharacterError rune
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func (e InvalidCharacterError) Error() string {
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return fmt.Sprintf("base83: invalid string (character %q out of range)", rune(e))
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}
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// An InvalidLengthError occurs when a given value cannot be encoded to a string of given length.
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type InvalidLengthError int
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func (e InvalidLengthError) Error() string {
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return fmt.Sprintf("base83: invalid length (%d)", int(e))
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}
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// Encode will encode the given integer value to a Base83 string with given length.
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// If length is too short to encode the given value InvalidLengthError will be returned.
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func Encode(value, length int) (string, error) {
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divisor := int(math.Pow(83, float64(length)))
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if value/divisor != 0 {
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return "", InvalidLengthError(length)
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}
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divisor /= 83
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var str strings.Builder
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str.Grow(length)
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for i := 0; i < length; i++ {
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if divisor <= 0 {
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return "", InvalidLengthError(length)
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}
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digit := (value / divisor) % 83
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divisor /= 83
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str.WriteRune(rune(characters[digit]))
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}
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return str.String(), nil
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}
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// Decode will decode the given Base83 string to an integer.
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func Decode(str string) (value int, err error) {
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for _, r := range str {
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idx := strings.IndexRune(characters, r)
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if idx == -1 {
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return 0, InvalidCharacterError(r)
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}
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value = value*83 + idx
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}
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return value, nil
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}
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