grokify/mogo

package bigint

import (
    "errors"
    "fmt"
    "math/big"
)

var ErrBaseInvalid = errors.New("invalid base - must be between [2,62]")

// EncodeToString uses [0-9a-zA-Z] for base62.
func EncodeToString(base int, s []byte) (string, error) {
    if base < 2 || base > 62 {
        return "", ErrBaseInvalid
    }
    var i big.Int
    i.SetBytes(s)
    return i.Text(base), nil
}

// MustEncodeToString uses [0-9a-zA-Z] for base62.
func MustEncodeToString(base int, s []byte) string {
    var i big.Int
    i.SetBytes(s)
    return i.Text(base)
}

func DecodeString(base int, s string) ([]byte, error) {
    if base < 2 || base > 62 {
        return []byte{}, ErrBaseInvalid
    }
    var i big.Int
    _, ok := i.SetString(s, base)
    if !ok {
        return []byte{}, fmt.Errorf("cannot parse base(%d) (%q)", base, s)
    }
    return i.Bytes(), nil
}