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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 (
"net"
"sync"
)
var (
nodeMu sync.Mutex
interfaces []net.Interface // cached list of interfaces
ifname string // name of interface being used
nodeID []byte // hardware for version 1 UUIDs
)
// 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()
nodeMu.Lock()
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()
nodeMu.Lock()
return setNodeInterface(name)
}
func setNodeInterface(name string) bool {
if interfaces == nil {
var err error
interfaces, err = net.Interfaces()
if err != nil && name != "" {
return false
}
}
for _, ifs := range interfaces {
if len(ifs.HardwareAddr) >= 6 && (name == "" || name == ifs.Name) {
if setNodeID(ifs.HardwareAddr) {
ifname = ifs.Name
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 == "" {
if nodeID == nil {
nodeID = make([]byte, 6)
}
randomBits(nodeID)
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()
nodeMu.Lock()
if nodeID == nil {
setNodeInterface("")
}
nid := make([]byte, 6)
copy(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 {
defer nodeMu.Unlock()
nodeMu.Lock()
if setNodeID(id) {
ifname = "user"
return true
}
return false
}
func setNodeID(id []byte) bool {
if len(id) < 6 {
return false
}
if nodeID == nil {
nodeID = make([]byte, 6)
}
copy(nodeID, id)
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 {
if len(uuid) != 16 {
return nil
}
node := make([]byte, 6)
copy(node, uuid[10:])
return node
}