vendor/github.com/pborman/uuid/version1.go


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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 (
    "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.
func NewUUID() UUID {
    if nodeID == nil {
        SetNodeInterface("")
    }

    now, seq, err := GetTime()
    if err != nil {
        return nil
    }

    uuid := make([]byte, 16)

    time_low := uint32(now & 0xffffffff)
    time_mid := uint16((now >> 32) & 0xffff)
    time_hi := uint16((now >> 48) & 0x0fff)
    time_hi |= 0x1000 // Version 1

    binary.BigEndian.PutUint32(uuid[0:], time_low)
    binary.BigEndian.PutUint16(uuid[4:], time_mid)
    binary.BigEndian.PutUint16(uuid[6:], time_hi)
    binary.BigEndian.PutUint16(uuid[8:], seq)
    copy(uuid[10:], nodeID)

    return uuid
}