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package guuid
import (
"crypto/rand"
"encoding/hex"
"errors"
"io"
"strings"
)
const (
UUIDByteCount = 16
uuidDashCount = 4
uuidEncodedLength = (UUIDByteCount * 2) + uuidDashCount
)
var (
dashIndexes = []int { 8, 13, 18, 23 }
emptyUUID = UUID {}
)
var (
BadLengthError = errors.New("guuid: str isn't of the correct length")
BadDashCountError = errors.New("guuid: Bad count of dashes in string")
BadDashPositionError = errors.New("guuid: Bad char in string")
)
type UUID [UUIDByteCount]byte
func NewFrom(r io.Reader) (UUID, error) {
var uuid UUID
_, err := io.ReadFull(r, uuid[:])
if err != nil {
return emptyUUID, 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(rand.Reader)
if err != nil {
panic(err)
}
return uuid
}
func (uuid UUID) String() string {
dst := [uuidEncodedLength]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) != uuidEncodedLength {
return emptyUUID, BadLengthError
}
if strings.Count(str, "-") != uuidDashCount {
return emptyUUID, BadDashCountError
}
for _, idx := range dashIndexes {
if str[idx] != '-' {
return emptyUUID, BadDashPositionError
}
}
hexstr := strings.Join(strings.Split(str, "-"), "")
data, err := hex.DecodeString(hexstr)
if err != nil {
return emptyUUID, err
}
return [UUIDByteCount]byte(data), nil
}
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