text: // Copyright 2017 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.
  
  // +build !js
  
  package uuid
  
  import "net"
  
  var interfaces []net.Interface // cached list of interfaces
  
  // getHardwareInterface returns the name and hardware address of interface name.
  // If name is "" then the name and hardware address of one of the system's
  // interfaces is returned.  If no interfaces are found (name does not exist or
  // there are no interfaces) then "", nil is returned.
  //
  // Only addresses of at least 6 bytes are returned.
  func getHardwareInterface(name string) (string, []byte) {
  	if interfaces == nil {
  		var err error
  		interfaces, err = net.Interfaces()
  		if err != nil {
  			return "", nil
  		}
  	}
  	for _, ifs := range interfaces {
  		if len(ifs.HardwareAddr) >= 6 && (name == "" || name == ifs.Name) {
  			return ifs.Name, ifs.HardwareAddr
  		}
  	}
  	return "", nil
  }
  