// FromStringOrNil returns UUID parsed from string input.
// Same behavior as FromString, but returns a Nil UUID on error.
func FromStringOrNil(input string) UUID {
uuid, err := FromString(input)
if err != nil {
return Nil
}
return uuid
}
// Returns UUID v1/v2 storage state.
// Returns epoch timestamp, clock sequence, and hardware address.
func getStorage() (uint64, uint16, []byte) {
storageOnce.Do(initStorage)
storageMutex.Lock()
defer storageMutex.Unlock()
timeNow := epochFunc()
// Clock changed backwards since last UUID generation.
// Should increase clock sequence.
if timeNow <= lastTime {
clockSequence++
}
lastTime = timeNow
return timeNow, clockSequence, hardwareAddr[😏
}
// NewV1 returns UUID based on current timestamp and MAC address.
func NewV1() UUID {
u := UUID{}
timeNow, clockSeq, hardwareAddr := getStorage()
binary.BigEndian.PutUint32(u[0😏, uint32(timeNow))
binary.BigEndian.PutUint16(u[4😏, uint16(timeNow»32))
binary.BigEndian.PutUint16(u[6😏, uint16(timeNow»48))
binary.BigEndian.PutUint16(u[8😏, clockSeq)
copy(u[10😏, hardwareAddr)
u.SetVersion(1)
u.SetVariant()
return u
}
// NewV2 returns DCE Security UUID based on POSIX UID/GID.
func NewV2(domain byte) UUID {
u := UUID{}
timeNow, clockSeq, hardwareAddr := getStorage()
switch domain {
case DomainPerson:
binary.BigEndian.PutUint32(u[0😏, posixUID)
case DomainGroup:
binary.BigEndian.PutUint32(u[0😏, posixGID)
}
binary.BigEndian.PutUint16(u[4😏, uint16(timeNow»32))
binary.BigEndian.PutUint16(u[6😏, uint16(timeNow»48))
binary.BigEndian.PutUint16(u[8😏, clockSeq)
u[9] = domain
copy(u[10😏, hardwareAddr)
u.SetVersion(2)
u.SetVariant()
return u
}
// NewV3 returns UUID based on MD5 hash of namespace UUID and name.
func NewV3(ns UUID, name string) UUID {
u := newFromHash(md5.New(), ns, name)
u.SetVersion(3)
u.SetVariant()
return u
}
// NewV4 returns random generated UUID.
func NewV4() UUID {
u := UUID{}
safeRandom(u[😏)
u.SetVersion(4)
u.SetVariant()
return u
}
// NewV5 returns UUID based on SHA-1 hash of namespace UUID and name.
func NewV5(ns UUID, name string) UUID {
u := newFromHash(sha1.New(), ns, name)
u.SetVersion(5)
u.SetVariant()
return u
}
// Returns UUID based on hashing of namespace UUID and name.
func newFromHash(h hash.Hash, ns UUID, name string) UUID {
u := UUID{}
h.Write(ns[😏)
h.Write([]byte(name))
copy(u[😏, h.Sum(nil))
return u
}
func main(){
u1 := uuid.NewV4()
fmt.Printf("UUIDv4: %s\n", u1)
}