265 lines
7.4 KiB
Go
265 lines
7.4 KiB
Go
// Copyright (C) 2013-2018 by Maxim Bublis <b@codemonkey.ru>
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//
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// Permission is hereby granted, free of charge, to any person obtaining
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// a copy of this software and associated documentation files (the
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// "Software"), to deal in the Software without restriction, including
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// without limitation the rights to use, copy, modify, merge, publish,
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// distribute, sublicense, and/or sell copies of the Software, and to
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// permit persons to whom the Software is furnished to do so, subject to
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// the following conditions:
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//
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// The above copyright notice and this permission notice shall be
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// included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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package uuid
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import (
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"crypto/md5"
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"crypto/rand"
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"crypto/sha1"
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"encoding/binary"
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"fmt"
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"hash"
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"io"
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"net"
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"sync"
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"time"
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)
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// Difference in 100-nanosecond intervals between
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// UUID epoch (October 15, 1582) and Unix epoch (January 1, 1970).
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const epochStart = 122192928000000000
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type epochFunc func() time.Time
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// HWAddrFunc is the function type used to provide hardware (MAC) addresses.
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type HWAddrFunc func() (net.HardwareAddr, error)
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// DefaultGenerator is the default UUID Generator used by this package.
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var DefaultGenerator Generator = NewGen()
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// NewV1 returns a UUID based on the current timestamp and MAC address.
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func NewV1() (UUID, error) {
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return DefaultGenerator.NewV1()
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}
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// NewV3 returns a UUID based on the MD5 hash of the namespace UUID and name.
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func NewV3(ns UUID, name string) UUID {
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return DefaultGenerator.NewV3(ns, name)
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}
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// NewV4 returns a randomly generated UUID.
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func NewV4() (UUID, error) {
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return DefaultGenerator.NewV4()
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}
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// NewV5 returns a UUID based on SHA-1 hash of the namespace UUID and name.
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func NewV5(ns UUID, name string) UUID {
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return DefaultGenerator.NewV5(ns, name)
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}
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// Generator provides an interface for generating UUIDs.
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type Generator interface {
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NewV1() (UUID, error)
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NewV3(ns UUID, name string) UUID
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NewV4() (UUID, error)
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NewV5(ns UUID, name string) UUID
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}
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// Gen is a reference UUID generator based on the specifications laid out in
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// RFC-4122 and DCE 1.1: Authentication and Security Services. This type
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// satisfies the Generator interface as defined in this package.
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//
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// For consumers who are generating V1 UUIDs, but don't want to expose the MAC
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// address of the node generating the UUIDs, the NewGenWithHWAF() function has been
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// provided as a convenience. See the function's documentation for more info.
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//
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// The authors of this package do not feel that the majority of users will need
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// to obfuscate their MAC address, and so we recommend using NewGen() to create
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// a new generator.
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type Gen struct {
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clockSequenceOnce sync.Once
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hardwareAddrOnce sync.Once
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storageMutex sync.Mutex
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rand io.Reader
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epochFunc epochFunc
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hwAddrFunc HWAddrFunc
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lastTime uint64
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clockSequence uint16
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hardwareAddr [6]byte
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}
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// interface check -- build will fail if *Gen doesn't satisfy Generator
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var _ Generator = (*Gen)(nil)
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// NewGen returns a new instance of Gen with some default values set. Most
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// people should use this.
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func NewGen() *Gen {
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return NewGenWithHWAF(defaultHWAddrFunc)
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}
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// NewGenWithHWAF builds a new UUID generator with the HWAddrFunc provided. Most
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// consumers should use NewGen() instead.
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//
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// This is used so that consumers can generate their own MAC addresses, for use
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// in the generated UUIDs, if there is some concern about exposing the physical
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// address of the machine generating the UUID.
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//
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// The Gen generator will only invoke the HWAddrFunc once, and cache that MAC
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// address for all the future UUIDs generated by it. If you'd like to switch the
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// MAC address being used, you'll need to create a new generator using this
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// function.
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func NewGenWithHWAF(hwaf HWAddrFunc) *Gen {
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return &Gen{
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epochFunc: time.Now,
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hwAddrFunc: hwaf,
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rand: rand.Reader,
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}
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}
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// NewV1 returns a UUID based on the current timestamp and MAC address.
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func (g *Gen) NewV1() (UUID, error) {
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u := UUID{}
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timeNow, clockSeq, err := g.getClockSequence()
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if err != nil {
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return Nil, err
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}
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binary.BigEndian.PutUint32(u[0:], uint32(timeNow))
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binary.BigEndian.PutUint16(u[4:], uint16(timeNow>>32))
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binary.BigEndian.PutUint16(u[6:], uint16(timeNow>>48))
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binary.BigEndian.PutUint16(u[8:], clockSeq)
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hardwareAddr, err := g.getHardwareAddr()
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if err != nil {
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return Nil, err
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}
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copy(u[10:], hardwareAddr)
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u.SetVersion(V1)
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u.SetVariant(VariantRFC4122)
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return u, nil
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}
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// NewV3 returns a UUID based on the MD5 hash of the namespace UUID and name.
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func (g *Gen) NewV3(ns UUID, name string) UUID {
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u := newFromHash(md5.New(), ns, name)
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u.SetVersion(V3)
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u.SetVariant(VariantRFC4122)
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return u
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}
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// NewV4 returns a randomly generated UUID.
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func (g *Gen) NewV4() (UUID, error) {
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u := UUID{}
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if _, err := io.ReadFull(g.rand, u[:]); err != nil {
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return Nil, err
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}
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u.SetVersion(V4)
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u.SetVariant(VariantRFC4122)
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return u, nil
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}
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// NewV5 returns a UUID based on SHA-1 hash of the namespace UUID and name.
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func (g *Gen) NewV5(ns UUID, name string) UUID {
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u := newFromHash(sha1.New(), ns, name)
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u.SetVersion(V5)
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u.SetVariant(VariantRFC4122)
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return u
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}
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// getClockSequence returns the epoch and clock sequence.
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func (g *Gen) getClockSequence() (uint64, uint16, error) {
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var err error
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g.clockSequenceOnce.Do(func() {
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buf := make([]byte, 2)
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if _, err = io.ReadFull(g.rand, buf); err != nil {
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return
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}
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g.clockSequence = binary.BigEndian.Uint16(buf)
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})
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if err != nil {
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return 0, 0, err
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}
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g.storageMutex.Lock()
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defer g.storageMutex.Unlock()
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timeNow := g.getEpoch()
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// Clock didn't change since last UUID generation.
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// Should increase clock sequence.
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if timeNow <= g.lastTime {
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g.clockSequence++
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}
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g.lastTime = timeNow
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return timeNow, g.clockSequence, nil
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}
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// Returns the hardware address.
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func (g *Gen) getHardwareAddr() ([]byte, error) {
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var err error
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g.hardwareAddrOnce.Do(func() {
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var hwAddr net.HardwareAddr
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if hwAddr, err = g.hwAddrFunc(); err == nil {
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copy(g.hardwareAddr[:], hwAddr)
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return
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}
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// Initialize hardwareAddr randomly in case
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// of real network interfaces absence.
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if _, err = io.ReadFull(g.rand, g.hardwareAddr[:]); err != nil {
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return
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}
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// Set multicast bit as recommended by RFC-4122
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g.hardwareAddr[0] |= 0x01
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})
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if err != nil {
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return []byte{}, err
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}
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return g.hardwareAddr[:], nil
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}
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// Returns the difference between UUID epoch (October 15, 1582)
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// and current time in 100-nanosecond intervals.
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func (g *Gen) getEpoch() uint64 {
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return epochStart + uint64(g.epochFunc().UnixNano()/100)
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}
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// Returns the UUID based on the hashing of the namespace UUID and name.
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func newFromHash(h hash.Hash, ns UUID, name string) UUID {
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u := UUID{}
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h.Write(ns[:])
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h.Write([]byte(name))
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copy(u[:], h.Sum(nil))
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return u
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}
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// Returns the hardware address.
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func defaultHWAddrFunc() (net.HardwareAddr, error) {
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ifaces, err := net.Interfaces()
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if err != nil {
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return []byte{}, err
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}
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for _, iface := range ifaces {
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if len(iface.HardwareAddr) >= 6 {
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return iface.HardwareAddr, nil
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}
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}
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return []byte{}, fmt.Errorf("uuid: no HW address found")
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}
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