func (id *ID) Digest() Digest {
	return NewDigest((*big.Int)(id).Bytes())
}
Digest returns the C4 Digest of the ID.
package id
import (
	"bytes"
	"math/big"
)
const (
	charset = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
	base    = 58
)
var (
	lut     [256]byte
	lowbyte = []byte("1")
	prefix  = []byte{'c', '4'}
	idlen   = 90
)
func init() {
	for i := 0; i < len(lut); i++ {
		lut[i] = 0xFF
	}
	for i := 0; i < len(charset); i++ {
		lut[charset[i]] = byte(i)
	}
}
type ID big.Int
func Parse(src string) (*ID, error) {
	return parseBytesID([]byte(src))
}
func (id *ID) String() (s string) {
	return string(id.bytes())
}