1 // Copyright 2016 Google Inc. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package uuid 6 7 import ( 8 "sync" 9 ) 10 11 var ( 12 nodeMu sync.Mutex 13 ifname string // name of interface being used 14 nodeID [6]byte // hardware for version 1 UUIDs 15 zeroID [6]byte // nodeID with only 0's 16 ) 17 18 // NodeInterface returns the name of the interface from which the NodeID was 19 // derived. The interface "user" is returned if the NodeID was set by 20 // SetNodeID. 21 func NodeInterface() string { 22 defer nodeMu.Unlock() 23 nodeMu.Lock() 24 return ifname 25 } 26 27 // SetNodeInterface selects the hardware address to be used for Version 1 UUIDs. 28 // If name is "" then the first usable interface found will be used or a random 29 // Node ID will be generated. If a named interface cannot be found then false 30 // is returned. 31 // 32 // SetNodeInterface never fails when name is "". 33 func SetNodeInterface(name string) bool { 34 defer nodeMu.Unlock() 35 nodeMu.Lock() 36 return setNodeInterface(name) 37 } 38 39 func setNodeInterface(name string) bool { 40 iname, addr := getHardwareInterface(name) // null implementation for js 41 if iname != "" && addr != nil { 42 ifname = iname 43 copy(nodeID[:], addr) 44 return true 45 } 46 47 // We found no interfaces with a valid hardware address. If name 48 // does not specify a specific interface generate a random Node ID 49 // (section 4.1.6) 50 if name == "" { 51 ifname = "random" 52 randomBits(nodeID[:]) 53 return true 54 } 55 return false 56 } 57 58 // NodeID returns a slice of a copy of the current Node ID, setting the Node ID 59 // if not already set. 60 func NodeID() []byte { 61 defer nodeMu.Unlock() 62 nodeMu.Lock() 63 if nodeID == zeroID { 64 setNodeInterface("") 65 } 66 nid := nodeID 67 return nid[:] 68 } 69 70 // SetNodeID sets the Node ID to be used for Version 1 UUIDs. The first 6 bytes 71 // of id are used. If id is less than 6 bytes then false is returned and the 72 // Node ID is not set. 73 func SetNodeID(id []byte) bool { 74 if len(id) < 6 { 75 return false 76 } 77 defer nodeMu.Unlock() 78 nodeMu.Lock() 79 copy(nodeID[:], id) 80 ifname = "user" 81 return true 82 } 83 84 // NodeID returns the 6 byte node id encoded in uuid. It returns nil if uuid is 85 // not valid. The NodeID is only well defined for version 1 and 2 UUIDs. 86 func (uuid UUID) NodeID() []byte { 87 var node [6]byte 88 copy(node[:], uuid[10:]) 89 return node[:] 90 } 91