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// Copyright 2011 Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package uuid
import (
// NewUUID returns a Version 1 UUID based on the current NodeID and clock
// sequence, and the current time. If the NodeID has not been set by SetNodeID
// or SetNodeInterface then it will be set automatically. If the NodeID cannot
// be set NewUUID returns nil. If clock sequence has not been set by
// SetClockSequence then it will be set automatically. If GetTime fails to
// return the current NewUUID returns nil.
func NewUUID() UUID {
now, seq, err := GetTime()
if err != nil {
return nil
uuid := make([]byte, 16)
time_low := uint32(now & 0xffffffff)
time_mid := uint16((now >> 32) & 0xffff)
time_hi := uint16((now >> 48) & 0x0fff)
time_hi |= 0x1000 // Version 1
binary.BigEndian.PutUint32(uuid[0:], time_low)
binary.BigEndian.PutUint16(uuid[4:], time_mid)
binary.BigEndian.PutUint16(uuid[6:], time_hi)
binary.BigEndian.PutUint16(uuid[8:], seq)
copy(uuid[10:], nodeID)
return uuid