source: code/trunk/vendor/github.com/google/uuid/version1.go@ 822

// 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 (
        "encoding/binary"
)

// 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 and an error.
//
// In most cases, New should be used.
func NewUUID() (UUID, error) {
        var uuid UUID
        now, seq, err := GetTime()
        if err != nil {
                return uuid, err
        }

        timeLow := uint32(now & 0xffffffff)
        timeMid := uint16((now >> 32) & 0xffff)
        timeHi := uint16((now >> 48) & 0x0fff)
        timeHi |= 0x1000 // Version 1

        binary.BigEndian.PutUint32(uuid[0:], timeLow)
        binary.BigEndian.PutUint16(uuid[4:], timeMid)
        binary.BigEndian.PutUint16(uuid[6:], timeHi)
        binary.BigEndian.PutUint16(uuid[8:], seq)

        nodeMu.Lock()
        if nodeID == zeroID {
                setNodeInterface("")
        }
        copy(uuid[10:], nodeID[:])
        nodeMu.Unlock()

        return uuid, nil
}