// Copyright (C) 2013-2018 by Maxim Bublis <b@codemonkey.ru>
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
package uuid
import (
"crypto/md5"
"crypto/rand"
"crypto/sha1"
"encoding/binary"
"hash"
"net"
"os"
"sync"
"time"
)
// Difference in 100-nanosecond intervals between
// UUID epoch (October 15, 1582) and Unix epoch (January 1, 1970).
const epochStart = 122192928000000000
var (
global = newDefaultGenerator()
epochFunc = unixTimeFunc
posixUID = uint32(os.Getuid())
posixGID = uint32(os.Getgid())
)
// NewV1 returns UUID based on current timestamp and MAC address.
func NewV1() UUID {
return global.NewV1()
}
// NewV2 returns DCE Security UUID based on POSIX UID/GID.
func NewV2(domain byte) UUID {
return global.NewV2(domain)
}
// NewV3 returns UUID based on MD5 hash of namespace UUID and name.
func NewV3(ns UUID, name string) UUID {
return global.NewV3(ns, name)
}
// NewV4 returns random generated UUID.
func NewV4() UUID {
return global.NewV4()
}
// NewV5 returns UUID based on SHA-1 hash of namespace UUID and name.
func NewV5(ns UUID, name string) UUID {
return global.NewV5(ns, name)
}
// Generator provides interface for generating UUIDs.
type Generator interface {
NewV1() UUID
NewV2(domain byte) UUID
NewV3(ns UUID, name string) UUID
NewV4() UUID
NewV5(ns UUID, name string) UUID
}
// Default generator implementation.
type generator struct {
storageOnce sync.Once
storageMutex sync.Mutex
lastTime uint64
clockSequence uint16
hardwareAddr [6]byte
}
func newDefaultGenerator() Generator {
return &generator{}
}
// NewV1 returns UUID based on current timestamp and MAC address.
func (g *generator) NewV1() UUID {
u := UUID{}
timeNow, clockSeq, hardwareAddr := g.getStorage()
binary.BigEndian.PutUint32(u[0:], uint32(timeNow))
binary.BigEndian.PutUint16(u[4:], uint16(timeNow>>32))
binary.BigEndian.PutUint16(u[6:], uint16(timeNow>>48))
binary.BigEndian.PutUint16(u[8:], clockSeq)
copy(u[10:], hardwareAddr)
u.SetVersion(V1)
u.SetVariant(VariantRFC4122)
return u
}
// NewV2 returns DCE Security UUID based on POSIX UID/GID.
func (g *generator) NewV2(domain byte) UUID {
u := UUID{}
timeNow, clockSeq, hardwareAddr := g.getStorage()
switch domain {
case DomainPerson:
binary.BigEndian.PutUint32(u[0:], posixUID)
case DomainGroup:
binary.BigEndian.PutUint32(u[0:], posixGID)
}
binary.BigEndian.PutUint16(u[4:], uint16(timeNow>>32))
binary.BigEndian.PutUint16(u[6:], uint16(timeNow>>48))
binary.BigEndian.PutUint16(u[8:], clockSeq)
u[9] = domain
copy(u[10:], hardwareAddr)
u.SetVersion(V2)
u.SetVariant(VariantRFC4122)
return u
}
// NewV3 returns UUID based on MD5 hash of namespace UUID and name.
func (g *generator) NewV3(ns UUID, name string) UUID {
u := newFromHash(md5.New(), ns, name)
u.SetVersion(V3)
u.SetVariant(VariantRFC4122)
return u
}
// NewV4 returns random generated UUID.
func (g *generator) NewV4() UUID {
u := UUID{}
g.safeRandom(u[:])
u.SetVersion(V4)
u.SetVariant(VariantRFC4122)
return u
}
// NewV5 returns UUID based on SHA-1 hash of namespace UUID and name.
func (g *generator) NewV5(ns UUID, name string) UUID {
u := newFromHash(sha1.New(), ns, name)
u.SetVersion(V5)
u.SetVariant(VariantRFC4122)
return u
}
func (g *generator) initStorage() {
g.initClockSequence()
g.initHardwareAddr()
}
func (g *generator) initClockSequence() {
buf := make([]byte, 2)
g.safeRandom(buf)
g.clockSequence = binary.BigEndian.Uint16(buf)
}
func (g *generator) initHardwareAddr() {
interfaces, err := net.Interfaces()
if err == nil {
for _, iface := range interfaces {
if len(iface.HardwareAddr) >= 6 {
copy(g.hardwareAddr[:], iface.HardwareAddr)
return
}
}
}
// Initialize hardwareAddr randomly in case
// of real network interfaces absence
g.safeRandom(g.hardwareAddr[:])
// Set multicast bit as recommended in RFC 4122
g.hardwareAddr[0] |= 0x01
}
func (g *generator) safeRandom(dest []byte) {
if _, err := rand.Read(dest); err != nil {
panic(err)
}
}
// Returns UUID v1/v2 storage state.
// Returns epoch timestamp, clock sequence, and hardware address.
func (g *generator) getStorage() (uint64, uint16, []byte) {
g.storageOnce.Do(g.initStorage)
g.storageMutex.Lock()
defer g.storageMutex.Unlock()
timeNow := epochFunc()
// Clock changed backwards since last UUID generation.
// Should increase clock sequence.
if timeNow <= g.lastTime {
g.clockSequence++
}
g.lastTime = timeNow
return timeNow, g.clockSequence, g.hardwareAddr[:]
}
// Returns difference in 100-nanosecond intervals between
// UUID epoch (October 15, 1582) and current time.
// This is default epoch calculation function.
func unixTimeFunc() uint64 {
return epochStart + uint64(time.Now().UnixNano()/100)
}
// Returns UUID based on hashing of namespace UUID and name.
func newFromHash(h hash.Hash, ns UUID, name string) UUID {
u := UUID{}
h.Write(ns[:])
h.Write([]byte(name))
copy(u[:], h.Sum(nil))
return u
}
