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@pborman @elliott5 @kortschak @bmatsuo
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// Copyright 2016 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 (
var (
nodeMu sync.Mutex
ifname string // name of interface being used
nodeID [6]byte // hardware for version 1 UUIDs
zeroID [6]byte // nodeID with only 0's
// NodeInterface returns the name of the interface from which the NodeID was
// derived. The interface "user" is returned if the NodeID was set by
// SetNodeID.
func NodeInterface() string {
defer nodeMu.Unlock()
return ifname
// SetNodeInterface selects the hardware address to be used for Version 1 UUIDs.
// If name is "" then the first usable interface found will be used or a random
// Node ID will be generated. If a named interface cannot be found then false
// is returned.
// SetNodeInterface never fails when name is "".
func SetNodeInterface(name string) bool {
defer nodeMu.Unlock()
return setNodeInterface(name)
func setNodeInterface(name string) bool {
iname, addr := getHardwareInterface(name) // null implementation for js
if iname != "" && addr != nil {
ifname = iname
copy(nodeID[:], addr)
return true
// We found no interfaces with a valid hardware address. If name
// does not specify a specific interface generate a random Node ID
// (section 4.1.6)
if name == "" {
ifname = "random"
return true
return false
// NodeID returns a slice of a copy of the current Node ID, setting the Node ID
// if not already set.
func NodeID() []byte {
defer nodeMu.Unlock()
if nodeID == zeroID {
nid := nodeID
return nid[:]
// SetNodeID sets the Node ID to be used for Version 1 UUIDs. The first 6 bytes
// of id are used. If id is less than 6 bytes then false is returned and the
// Node ID is not set.
func SetNodeID(id []byte) bool {
if len(id) < 6 {
return false
defer nodeMu.Unlock()
copy(nodeID[:], id)
ifname = "user"
return true
// NodeID returns the 6 byte node id encoded in uuid. It returns nil if uuid is
// not valid. The NodeID is only well defined for version 1 and 2 UUIDs.
func (uuid UUID) NodeID() []byte {
var node [6]byte
copy(node[:], uuid[10:])
return node[:]
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