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package uuid
import (
"crypto/rand"
"encoding/hex"
"errors"
"fmt"
"io"
"os"
"strings"
)
const (
ByteCount = 16
dashCount = 4
encodedLength = (ByteCount * 2) + dashCount
)
var (
dashIndexes = []int{ 8, 13, 18, 23 }
randomReader = rand.Reader
ErrBadLength = errors.New(
"uuid: str isn't of the correct length",
)
ErrBadDashCount = errors.New("uuid: Bad count of dashes in string")
ErrBadDashPosition = errors.New("uuid: Bad char in string")
)
type UUID [ByteCount]byte
func NewFrom(r io.Reader) (UUID, error) {
var uuid UUID
_, err := io.ReadFull(r, uuid[:])
if err != nil {
return UUID{}, err
}
uuid[6] = (uuid[6] & 0x0f) | 0x40 // v4
uuid[8] = (uuid[8] & 0x3f) | 0x80 // variant 10
return uuid, nil
}
func New() UUID {
uuid, err := NewFrom(randomReader)
if err != nil {
panic(err)
}
return uuid
}
func (uuid UUID) String() string {
dst := [encodedLength]byte {
0, 0, 0, 0,
0, 0, 0, 0,
'-',
0, 0, 0, 0,
'-',
0, 0, 0, 0,
'-',
0, 0, 0, 0,
'-',
0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0,
}
hex.Encode(dst[ 0:8], uuid[0:4])
hex.Encode(dst[ 9:13], uuid[4:6])
hex.Encode(dst[14:18], uuid[6:8])
hex.Encode(dst[19:23], uuid[8:10])
hex.Encode(dst[24:36], uuid[10:])
return string(dst[:])
}
func FromString(str string) (UUID, error) {
if len(str) != encodedLength {
return UUID{}, ErrBadLength
}
if strings.Count(str, "-") != dashCount {
return UUID{}, ErrBadDashCount
}
for _, idx := range dashIndexes {
if str[idx] != '-' {
return UUID{}, ErrBadDashPosition
}
}
hexstr := strings.Join(strings.Split(str, "-"), "")
data, err := hex.DecodeString(hexstr)
if err != nil {
return UUID{}, err
}
return [ByteCount]byte(data), nil
}
func Main() {
if len(os.Args) < 2 {
fmt.Println(New().String())
} else {
_, err := FromString(strings.TrimSpace(os.Args[1]))
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(3)
}
}
}
|
