// Newx returns a NONSTANDARD UUID(lower probability of conflict).
func Newx() (uuid [16]byte) {
var (
timestamp = uuidTimestamp()
sequence uint32
)
gxMutex.Lock() // Lock
switch {
case timestamp > gxLastTimestamp:
sequence = gxSequenceStart
gxLastTimestamp = timestamp
gxLastSequence = sequence
gxMutex.Unlock() // Unlock
case timestamp == gxLastTimestamp:
sequence = (gxLastSequence + 1) & xSequenceMask
if sequence == gxSequenceStart {
timestamp = tillNext100nano(timestamp)
gxLastTimestamp = timestamp
}
gxLastSequence = sequence
gxMutex.Unlock() // Unlock
default: // timestamp < xLastTimestamp
gxSequenceStart = rand.Uint32() & xSequenceMask // NOTE
sequence = gxSequenceStart
gxLastTimestamp = timestamp
gxLastSequence = sequence
gxMutex.Unlock() // Unlock
}
// time_low
uuid[0] = byte(timestamp >> 24)
uuid[1] = byte(timestamp >> 16)
uuid[2] = byte(timestamp >> 8)
uuid[3] = byte(timestamp)
// time_mid
uuid[4] = byte(timestamp >> 40)
uuid[5] = byte(timestamp >> 32)
// time_hi_and_pid_low
uuid[6] = byte(timestamp >> 52)
uuid[7] = byte(timestamp>>48) << 4
uuid[7] |= pid & 0x0F // pid, 4bits
// clk_seq_hi_pid
uuid[8] = byte(sequence>>8) & 0x3F
uuid[8] |= (pid << 2) & 0xC0 // // pid, 2bits
// clk_seq_low
uuid[9] = byte(sequence)
// node
copy(uuid[10:], xNode)
return
}
// New returns a STANDARD version 1 UUID.
func New() (uuid [16]byte) {
var (
timestamp = uuidTimestamp()
sequence uint32
)
gMutex.Lock() // Lock
switch {
case timestamp > gLastTimestamp:
sequence = gSequenceStart
gLastTimestamp = timestamp
gLastSequence = sequence
gMutex.Unlock() // Unlock
case timestamp == gLastTimestamp:
sequence = (gLastSequence + 1) & sequenceMask
if sequence == gSequenceStart {
timestamp = tillNext100nano(timestamp)
gLastTimestamp = timestamp
}
gLastSequence = sequence
gMutex.Unlock() // Unlock
default: // timestamp < lastTimestamp
gSequenceStart = rand.Uint32() & sequenceMask // NOTE
sequence = gSequenceStart
gLastTimestamp = timestamp
gLastSequence = sequence
gMutex.Unlock() // Unlock
}
// time_low
uuid[0] = byte(timestamp >> 24)
uuid[1] = byte(timestamp >> 16)
uuid[2] = byte(timestamp >> 8)
uuid[3] = byte(timestamp)
// time_mid
uuid[4] = byte(timestamp >> 40)
uuid[5] = byte(timestamp >> 32)
// time_hi_and_version
uuid[6] = byte(timestamp>>56) & 0x0F
uuid[6] |= 0x10 // version 1, 4bits
uuid[7] = byte(timestamp >> 48)
// clk_seq_hi_res
uuid[8] = byte(sequence>>8) & 0x3F
uuid[8] |= 0x80 // variant, 2bits
// clk_seq_low
uuid[9] = byte(sequence)
// node
copy(uuid[10:], node)
return
}
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
var pid = byte(hash(uint64(os.Getpid()))) // 6-bit hash of os.Getpid(), read only.
// hash uint64 to a 6-bit integer value.
func hash(x uint64) uint64 {
return (x ^ x>>6 ^ x>>12 ^ x>>18 ^ x>>24 ^ x>>30 ^ x>>36 ^ x>>42 ^ x>>48 ^ x>>54 ^ x>>60) & 0x3f
}
var xNode = internal.MAC[:] // read only.
const xSequenceMask uint32 = 0x3FFF // 14bits
var (
gxMutex sync.Mutex
gxSequenceStart uint32 = rand.Uint32() & xSequenceMask
gxLastTimestamp int64 = -1
gxLastSequence uint32 = gxSequenceStart
)
// Newx returns a NONSTANDARD UUID(lower probability of conflict).
func Newx() (uuid [16]byte) {
var (
timestamp = uuidTimestamp()
sequence uint32
)
gxMutex.Lock() // Lock
switch {
case timestamp > gxLastTimestamp:
sequence = gxSequenceStart
// New returns a unique 32-byte url-safe string.
func New() string {
var (
timeNow = time.Now()
timeNowUnix = timeNow.Unix()
timestamp = unix100nano(timeNow)
sequence uint32
saltShouldUpdate = false
saltSequence uint32
)
gMutex.Lock() // Lock
switch {
case timestamp > gLastTimestamp:
sequence = gSequenceStart
gLastTimestamp = timestamp
gLastSequence = sequence
case timestamp == gLastTimestamp:
sequence = (gLastSequence + 1) & sequenceMask
if sequence == gSequenceStart {
timestamp = tillNext100nano(timestamp)
gLastTimestamp = timestamp
}
gLastSequence = sequence
default:
gSequenceStart = rand.Uint32() & sequenceMask // NOTE
sequence = gSequenceStart
gLastTimestamp = timestamp
gLastSequence = sequence
}
if timeNowUnix >= gSaltLastUpdateTimestamp+saltUpdateInterval {
saltShouldUpdate = true
gSaltLastUpdateTimestamp = timeNowUnix
}
gSaltSequence++
saltSequence = gSaltSequence
gMutex.Unlock() // Unlock
// 56bits unix100ns + 12bits pid + 12bits sequence + 48bits node + 64bits hashsum
var idx [24]byte
// time_low
idx[0] = byte(timestamp >> 24)
idx[1] = byte(timestamp >> 16)
idx[2] = byte(timestamp >> 8)
idx[3] = byte(timestamp)
// time_mid
idx[4] = byte(timestamp >> 40)
idx[5] = byte(timestamp >> 32)
// time_hi_and_pid_low
idx[6] = byte(timestamp >> 48)
idx[7] = byte(pid)
// clk_seq_hi_pid
idx[8] = byte(sequence>>8) & 0x0f
idx[8] |= byte(pid>>8) << 4
// clk_seq_low
idx[9] = byte(sequence)
// node
copy(idx[10:], node)
// hashsum
if saltShouldUpdate {
rand.Read(gSalt)
copy(idx[16:], gSalt)
} else {
var src [8 + 4 + saltLen]byte // 8+4+43==55
src[0] = byte(timestamp >> 56)
src[1] = byte(timestamp >> 48)
src[2] = byte(timestamp >> 40)
src[3] = byte(timestamp >> 32)
src[4] = byte(timestamp >> 24)
src[5] = byte(timestamp >> 16)
src[6] = byte(timestamp >> 8)
src[7] = byte(timestamp)
src[8] = byte(saltSequence >> 24)
src[9] = byte(saltSequence >> 16)
src[10] = byte(saltSequence >> 8)
src[11] = byte(saltSequence)
copy(src[12:], gSalt)
hashsum := sha1.Sum(src[:])
copy(idx[16:], hashsum[:])
}
id := make([]byte, 32)
base64.URLEncoding.Encode(id, idx[:])
return string(id)
}
}
var node = internal.MAC[:] // read only
const (
sequenceMask = 0xfff // 12bits
saltLen = 43 // see New(), 8+4+43==55<56, Best performance for sha1.
saltUpdateInterval = 3600 // seconds
)
var (
gSalt = make([]byte, saltLen)
gMutex sync.Mutex // protect following
gSequenceStart uint32 = rand.Uint32() & sequenceMask
gLastTimestamp int64 = -1
gLastSequence uint32 = gSequenceStart
gSaltLastUpdateTimestamp int64 = -saltUpdateInterval
gSaltSequence uint32 = rand.Uint32()
)
// New returns a unique 32-byte url-safe string.
func New() string {
var (
timeNow = time.Now()
timeNowUnix = timeNow.Unix()
timestamp = unix100nano(timeNow)
sequence uint32
