GoToSocial/vendor/github.com/buckket/go-blurhash/base83/base83.go
Tobi Smethurst 98263a7de6
Grand test fixup (#138)
* start fixing up tests

* fix up tests + automate with drone

* fiddle with linting

* messing about with drone.yml

* some more fiddling

* hmmm

* add cache

* add vendor directory

* verbose

* ci updates

* update some little things

* update sig
2021-08-12 21:03:24 +02:00

59 lines
1.5 KiB
Go

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