Import google/uuid v1.3.0HEADmastermain

Change-Id: I97acfcec78d5cbe6ca6aedc81591e6adac431e6b

28 files changed, 2323 insertions, 0 deletions

diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..d8156a6
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,9 @@
+language: go
+
+go:
+  - 1.4.3
+  - 1.5.3
+  - tip
+
+script:
+  - go test -v ./...
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..04fdf09
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,10 @@
+# How to contribute
+
+We definitely welcome patches and contribution to this project!
+
+### Legal requirements
+
+In order to protect both you and ourselves, you will need to sign the
+[Contributor License Agreement](https://cla.developers.google.com/clas).
+
+You may have already signed it for other Google projects.
diff --git a/CONTRIBUTORS b/CONTRIBUTORS
new file mode 100644
index 0000000..b4bb97f
--- /dev/null
+++ b/CONTRIBUTORS
@@ -0,0 +1,9 @@
+Paul Borman <borman@google.com>
+bmatsuo
+shawnps
+theory
+jboverfelt
+dsymonds
+cd1
+wallclockbuilder
+dansouza
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..5dc6826
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,27 @@
+Copyright (c) 2009,2014 Google Inc. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..22d6543
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,14 @@
+name: "uuid"
+description:
+    "Go package for UUIDs based on RFC 4122 and DCE 1.1: Authentication and "
+    "Security Services."
+
+third_party {
+  url {
+    type: GIT
+    value: "https://github.com/google/uuid"
+  }
+  version: "v1.3.0"
+  last_upgrade_date { year: 2023 month: 3 day: 17 }
+  license_type: NOTICE
+}
diff --git a/MODULE_LICENSE_BSD b/MODULE_LICENSE_BSD
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_BSD
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..68bdac0
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1,2 @@
+dwillemsen@google.com
+ryantao@google.com
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..f765a46
--- /dev/null
+++ b/README.md
@@ -0,0 +1,19 @@
+# uuid ![build status](https://travis-ci.org/google/uuid.svg?branch=master)
+The uuid package generates and inspects UUIDs based on
+[RFC 4122](http://tools.ietf.org/html/rfc4122)
+and DCE 1.1: Authentication and Security Services. 
+
+This package is based on the github.com/pborman/uuid package (previously named
+code.google.com/p/go-uuid).  It differs from these earlier packages in that
+a UUID is a 16 byte array rather than a byte slice.  One loss due to this
+change is the ability to represent an invalid UUID (vs a NIL UUID).
+
+###### Install
+`go get github.com/google/uuid`
+
+###### Documentation 
+[![GoDoc](https://godoc.org/github.com/google/uuid?status.svg)](http://godoc.org/github.com/google/uuid)
+
+Full `go doc` style documentation for the package can be viewed online without
+installing this package by using the GoDoc site here: 
+http://pkg.go.dev/github.com/google/uuid
diff --git a/dce.go b/dce.go
new file mode 100644
index 0000000..fa820b9
--- /dev/null
+++ b/dce.go
@@ -0,0 +1,80 @@
+// 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"
+	"fmt"
+	"os"
+)
+
+// A Domain represents a Version 2 domain
+type Domain byte
+
+// Domain constants for DCE Security (Version 2) UUIDs.
+const (
+	Person = Domain(0)
+	Group  = Domain(1)
+	Org    = Domain(2)
+)
+
+// NewDCESecurity returns a DCE Security (Version 2) UUID.
+//
+// The domain should be one of Person, Group or Org.
+// On a POSIX system the id should be the users UID for the Person
+// domain and the users GID for the Group.  The meaning of id for
+// the domain Org or on non-POSIX systems is site defined.
+//
+// For a given domain/id pair the same token may be returned for up to
+// 7 minutes and 10 seconds.
+func NewDCESecurity(domain Domain, id uint32) (UUID, error) {
+	uuid, err := NewUUID()
+	if err == nil {
+		uuid[6] = (uuid[6] & 0x0f) | 0x20 // Version 2
+		uuid[9] = byte(domain)
+		binary.BigEndian.PutUint32(uuid[0:], id)
+	}
+	return uuid, err
+}
+
+// NewDCEPerson returns a DCE Security (Version 2) UUID in the person
+// domain with the id returned by os.Getuid.
+//
+//  NewDCESecurity(Person, uint32(os.Getuid()))
+func NewDCEPerson() (UUID, error) {
+	return NewDCESecurity(Person, uint32(os.Getuid()))
+}
+
+// NewDCEGroup returns a DCE Security (Version 2) UUID in the group
+// domain with the id returned by os.Getgid.
+//
+//  NewDCESecurity(Group, uint32(os.Getgid()))
+func NewDCEGroup() (UUID, error) {
+	return NewDCESecurity(Group, uint32(os.Getgid()))
+}
+
+// Domain returns the domain for a Version 2 UUID.  Domains are only defined
+// for Version 2 UUIDs.
+func (uuid UUID) Domain() Domain {
+	return Domain(uuid[9])
+}
+
+// ID returns the id for a Version 2 UUID. IDs are only defined for Version 2
+// UUIDs.
+func (uuid UUID) ID() uint32 {
+	return binary.BigEndian.Uint32(uuid[0:4])
+}
+
+func (d Domain) String() string {
+	switch d {
+	case Person:
+		return "Person"
+	case Group:
+		return "Group"
+	case Org:
+		return "Org"
+	}
+	return fmt.Sprintf("Domain%d", int(d))
+}
diff --git a/doc.go b/doc.go
new file mode 100644
index 0000000..5b8a4b9
--- /dev/null
+++ b/doc.go
@@ -0,0 +1,12 @@
+// 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 generates and inspects UUIDs.
+//
+// UUIDs are based on RFC 4122 and DCE 1.1: Authentication and Security
+// Services.
+//
+// A UUID is a 16 byte (128 bit) array.  UUIDs may be used as keys to
+// maps or compared directly.
+package uuid
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..fc84cd7
--- /dev/null
+++ b/go.mod
@@ -0,0 +1 @@
+module github.com/google/uuid
diff --git a/hash.go b/hash.go
new file mode 100644
index 0000000..b404f4b
--- /dev/null
+++ b/hash.go
@@ -0,0 +1,53 @@
+// 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 (
+	"crypto/md5"
+	"crypto/sha1"
+	"hash"
+)
+
+// Well known namespace IDs and UUIDs
+var (
+	NameSpaceDNS  = Must(Parse("6ba7b810-9dad-11d1-80b4-00c04fd430c8"))
+	NameSpaceURL  = Must(Parse("6ba7b811-9dad-11d1-80b4-00c04fd430c8"))
+	NameSpaceOID  = Must(Parse("6ba7b812-9dad-11d1-80b4-00c04fd430c8"))
+	NameSpaceX500 = Must(Parse("6ba7b814-9dad-11d1-80b4-00c04fd430c8"))
+	Nil           UUID // empty UUID, all zeros
+)
+
+// NewHash returns a new UUID derived from the hash of space concatenated with
+// data generated by h.  The hash should be at least 16 byte in length.  The
+// first 16 bytes of the hash are used to form the UUID.  The version of the
+// UUID will be the lower 4 bits of version.  NewHash is used to implement
+// NewMD5 and NewSHA1.
+func NewHash(h hash.Hash, space UUID, data []byte, version int) UUID {
+	h.Reset()
+	h.Write(space[:]) //nolint:errcheck
+	h.Write(data)     //nolint:errcheck
+	s := h.Sum(nil)
+	var uuid UUID
+	copy(uuid[:], s)
+	uuid[6] = (uuid[6] & 0x0f) | uint8((version&0xf)<<4)
+	uuid[8] = (uuid[8] & 0x3f) | 0x80 // RFC 4122 variant
+	return uuid
+}
+
+// NewMD5 returns a new MD5 (Version 3) UUID based on the
+// supplied name space and data.  It is the same as calling:
+//
+//  NewHash(md5.New(), space, data, 3)
+func NewMD5(space UUID, data []byte) UUID {
+	return NewHash(md5.New(), space, data, 3)
+}
+
+// NewSHA1 returns a new SHA1 (Version 5) UUID based on the
+// supplied name space and data.  It is the same as calling:
+//
+//  NewHash(sha1.New(), space, data, 5)
+func NewSHA1(space UUID, data []byte) UUID {
+	return NewHash(sha1.New(), space, data, 5)
+}
diff --git a/json_test.go b/json_test.go
new file mode 100644
index 0000000..245f91e
--- /dev/null
+++ b/json_test.go
@@ -0,0 +1,62 @@
+// 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/json"
+	"reflect"
+	"testing"
+)
+
+var testUUID = Must(Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479"))
+
+func TestJSON(t *testing.T) {
+	type S struct {
+		ID1 UUID
+		ID2 UUID
+	}
+	s1 := S{ID1: testUUID}
+	data, err := json.Marshal(&s1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var s2 S
+	if err := json.Unmarshal(data, &s2); err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(&s1, &s2) {
+		t.Errorf("got %#v, want %#v", s2, s1)
+	}
+}
+
+func BenchmarkUUID_MarshalJSON(b *testing.B) {
+	x := &struct {
+		UUID UUID `json:"uuid"`
+	}{}
+	var err error
+	x.UUID, err = Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
+	if err != nil {
+		b.Fatal(err)
+	}
+	for i := 0; i < b.N; i++ {
+		js, err := json.Marshal(x)
+		if err != nil {
+			b.Fatalf("marshal json: %#v (%v)", js, err)
+		}
+	}
+}
+
+func BenchmarkUUID_UnmarshalJSON(b *testing.B) {
+	js := []byte(`{"uuid":"f47ac10b-58cc-0372-8567-0e02b2c3d479"}`)
+	var x *struct {
+		UUID UUID `json:"uuid"`
+	}
+	for i := 0; i < b.N; i++ {
+		err := json.Unmarshal(js, &x)
+		if err != nil {
+			b.Fatalf("marshal json: %#v (%v)", js, err)
+		}
+	}
+}
diff --git a/marshal.go b/marshal.go
new file mode 100644
index 0000000..14bd340
--- /dev/null
+++ b/marshal.go
@@ -0,0 +1,38 @@
+// 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 "fmt"
+
+// MarshalText implements encoding.TextMarshaler.
+func (uuid UUID) MarshalText() ([]byte, error) {
+	var js [36]byte
+	encodeHex(js[:], uuid)
+	return js[:], nil
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler.
+func (uuid *UUID) UnmarshalText(data []byte) error {
+	id, err := ParseBytes(data)
+	if err != nil {
+		return err
+	}
+	*uuid = id
+	return nil
+}
+
+// MarshalBinary implements encoding.BinaryMarshaler.
+func (uuid UUID) MarshalBinary() ([]byte, error) {
+	return uuid[:], nil
+}
+
+// UnmarshalBinary implements encoding.BinaryUnmarshaler.
+func (uuid *UUID) UnmarshalBinary(data []byte) error {
+	if len(data) != 16 {
+		return fmt.Errorf("invalid UUID (got %d bytes)", len(data))
+	}
+	copy(uuid[:], data)
+	return nil
+}
diff --git a/node.go b/node.go
new file mode 100644
index 0000000..d651a2b
--- /dev/null
+++ b/node.go
@@ -0,0 +1,90 @@
+// 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 (
+	"sync"
+)
+
+var (
+	nodeMu sync.Mutex
+	ifname string  // name of interface being used
+	nodeID [6]byte // hardware for version 1 UUIDs
+	zeroID [6]byte // nodeID with only 0's
+)
+
+// NodeInterface returns the name of the interface from which the NodeID was
+// derived.  The interface "user" is returned if the NodeID was set by
+// SetNodeID.
+func NodeInterface() string {
+	defer nodeMu.Unlock()
+	nodeMu.Lock()
+	return ifname
+}
+
+// SetNodeInterface selects the hardware address to be used for Version 1 UUIDs.
+// If name is "" then the first usable interface found will be used or a random
+// Node ID will be generated.  If a named interface cannot be found then false
+// is returned.
+//
+// SetNodeInterface never fails when name is "".
+func SetNodeInterface(name string) bool {
+	defer nodeMu.Unlock()
+	nodeMu.Lock()
+	return setNodeInterface(name)
+}
+
+func setNodeInterface(name string) bool {
+	iname, addr := getHardwareInterface(name) // null implementation for js
+	if iname != "" && addr != nil {
+		ifname = iname
+		copy(nodeID[:], addr)
+		return true
+	}
+
+	// We found no interfaces with a valid hardware address.  If name
+	// does not specify a specific interface generate a random Node ID
+	// (section 4.1.6)
+	if name == "" {
+		ifname = "random"
+		randomBits(nodeID[:])
+		return true
+	}
+	return false
+}
+
+// NodeID returns a slice of a copy of the current Node ID, setting the Node ID
+// if not already set.
+func NodeID() []byte {
+	defer nodeMu.Unlock()
+	nodeMu.Lock()
+	if nodeID == zeroID {
+		setNodeInterface("")
+	}
+	nid := nodeID
+	return nid[:]
+}
+
+// SetNodeID sets the Node ID to be used for Version 1 UUIDs.  The first 6 bytes
+// of id are used.  If id is less than 6 bytes then false is returned and the
+// Node ID is not set.
+func SetNodeID(id []byte) bool {
+	if len(id) < 6 {
+		return false
+	}
+	defer nodeMu.Unlock()
+	nodeMu.Lock()
+	copy(nodeID[:], id)
+	ifname = "user"
+	return true
+}
+
+// NodeID returns the 6 byte node id encoded in uuid.  It returns nil if uuid is
+// not valid.  The NodeID is only well defined for version 1 and 2 UUIDs.
+func (uuid UUID) NodeID() []byte {
+	var node [6]byte
+	copy(node[:], uuid[10:])
+	return node[:]
+}
diff --git a/node_js.go b/node_js.go
new file mode 100644
index 0000000..24b78ed
--- /dev/null
+++ b/node_js.go
@@ -0,0 +1,12 @@
+// 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
+
+// getHardwareInterface returns nil values for the JS version of the code.
+// This remvoves the "net" dependency, because it is not used in the browser.
+// Using the "net" library inflates the size of the transpiled JS code by 673k bytes.
+func getHardwareInterface(name string) (string, []byte) { return "", nil }
diff --git a/node_net.go b/node_net.go
new file mode 100644
index 0000000..0cbbcdd
--- /dev/null
+++ b/node_net.go
@@ -0,0 +1,33 @@
+// 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
+}
diff --git a/null.go b/null.go
new file mode 100644
index 0000000..d7fcbf2
--- /dev/null
+++ b/null.go
@@ -0,0 +1,118 @@
+// Copyright 2021 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 (
+	"bytes"
+	"database/sql/driver"
+	"encoding/json"
+	"fmt"
+)
+
+var jsonNull = []byte("null")
+
+// NullUUID represents a UUID that may be null.
+// NullUUID implements the SQL driver.Scanner interface so
+// it can be used as a scan destination:
+//
+//  var u uuid.NullUUID
+//  err := db.QueryRow("SELECT name FROM foo WHERE id=?", id).Scan(&u)
+//  ...
+//  if u.Valid {
+//     // use u.UUID
+//  } else {
+//     // NULL value
+//  }
+//
+type NullUUID struct {
+	UUID  UUID
+	Valid bool // Valid is true if UUID is not NULL
+}
+
+// Scan implements the SQL driver.Scanner interface.
+func (nu *NullUUID) Scan(value interface{}) error {
+	if value == nil {
+		nu.UUID, nu.Valid = Nil, false
+		return nil
+	}
+
+	err := nu.UUID.Scan(value)
+	if err != nil {
+		nu.Valid = false
+		return err
+	}
+
+	nu.Valid = true
+	return nil
+}
+
+// Value implements the driver Valuer interface.
+func (nu NullUUID) Value() (driver.Value, error) {
+	if !nu.Valid {
+		return nil, nil
+	}
+	// Delegate to UUID Value function
+	return nu.UUID.Value()
+}
+
+// MarshalBinary implements encoding.BinaryMarshaler.
+func (nu NullUUID) MarshalBinary() ([]byte, error) {
+	if nu.Valid {
+		return nu.UUID[:], nil
+	}
+
+	return []byte(nil), nil
+}
+
+// UnmarshalBinary implements encoding.BinaryUnmarshaler.
+func (nu *NullUUID) UnmarshalBinary(data []byte) error {
+	if len(data) != 16 {
+		return fmt.Errorf("invalid UUID (got %d bytes)", len(data))
+	}
+	copy(nu.UUID[:], data)
+	nu.Valid = true
+	return nil
+}
+
+// MarshalText implements encoding.TextMarshaler.
+func (nu NullUUID) MarshalText() ([]byte, error) {
+	if nu.Valid {
+		return nu.UUID.MarshalText()
+	}
+
+	return jsonNull, nil
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler.
+func (nu *NullUUID) UnmarshalText(data []byte) error {
+	id, err := ParseBytes(data)
+	if err != nil {
+		nu.Valid = false
+		return err
+	}
+	nu.UUID = id
+	nu.Valid = true
+	return nil
+}
+
+// MarshalJSON implements json.Marshaler.
+func (nu NullUUID) MarshalJSON() ([]byte, error) {
+	if nu.Valid {
+		return json.Marshal(nu.UUID)
+	}
+
+	return jsonNull, nil
+}
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (nu *NullUUID) UnmarshalJSON(data []byte) error {
+	if bytes.Equal(data, jsonNull) {
+		*nu = NullUUID{}
+		return nil // valid null UUID
+	}
+	err := json.Unmarshal(data, &nu.UUID)
+	nu.Valid = err == nil
+	return err
+}
diff --git a/null_test.go b/null_test.go
new file mode 100644
index 0000000..c6e5e69
--- /dev/null
+++ b/null_test.go
@@ -0,0 +1,214 @@
+// Copyright 2021 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 (
+	"bytes"
+	"encoding/json"
+	"testing"
+)
+
+func TestNullUUIDScan(t *testing.T) {
+	var u UUID
+	var nu NullUUID
+
+	uNilErr := u.Scan(nil)
+	nuNilErr := nu.Scan(nil)
+	if uNilErr != nil &&
+		nuNilErr != nil &&
+		uNilErr.Error() != nuNilErr.Error() {
+		t.Errorf("expected errors to be equal, got %s, %s", uNilErr, nuNilErr)
+	}
+
+	uInvalidStringErr := u.Scan("test")
+	nuInvalidStringErr := nu.Scan("test")
+	if uInvalidStringErr != nil &&
+		nuInvalidStringErr != nil &&
+		uInvalidStringErr.Error() != nuInvalidStringErr.Error() {
+		t.Errorf("expected errors to be equal, got %s, %s", uInvalidStringErr, nuInvalidStringErr)
+	}
+
+	valid := "12345678-abcd-1234-abcd-0123456789ab"
+	uValidErr := u.Scan(valid)
+	nuValidErr := nu.Scan(valid)
+	if uValidErr != nuValidErr {
+		t.Errorf("expected errors to be equal, got %s, %s", uValidErr, nuValidErr)
+	}
+}
+
+func TestNullUUIDValue(t *testing.T) {
+	var u UUID
+	var nu NullUUID
+
+	nuValue, nuErr := nu.Value()
+	if nuErr != nil {
+		t.Errorf("expected nil err, got err %s", nuErr)
+	}
+	if nuValue != nil {
+		t.Errorf("expected nil value, got non-nil %s", nuValue)
+	}
+
+	u = MustParse("12345678-abcd-1234-abcd-0123456789ab")
+	nu = NullUUID{
+		UUID:  MustParse("12345678-abcd-1234-abcd-0123456789ab"),
+		Valid: true,
+	}
+
+	uValue, uErr := u.Value()
+	nuValue, nuErr = nu.Value()
+	if uErr != nil {
+		t.Errorf("expected nil err, got err %s", uErr)
+	}
+	if nuErr != nil {
+		t.Errorf("expected nil err, got err %s", nuErr)
+	}
+	if uValue != nuValue {
+		t.Errorf("expected uuid %s and nulluuid %s to be equal ", uValue, nuValue)
+	}
+}
+
+func TestNullUUIDMarshalText(t *testing.T) {
+	tests := []struct {
+		nullUUID NullUUID
+	}{
+		{
+			nullUUID: NullUUID{},
+		},
+		{
+			nullUUID: NullUUID{
+				UUID:  MustParse("12345678-abcd-1234-abcd-0123456789ab"),
+				Valid: true,
+			},
+		},
+	}
+	for _, test := range tests {
+		var uText []byte
+		var uErr error
+		nuText, nuErr := test.nullUUID.MarshalText()
+		if test.nullUUID.Valid {
+			uText, uErr = test.nullUUID.UUID.MarshalText()
+		} else {
+			uText = []byte("null")
+		}
+		if nuErr != uErr {
+			t.Errorf("expected error %e, got %e", nuErr, uErr)
+		}
+		if !bytes.Equal(nuText, uText) {
+			t.Errorf("expected text data %s, got %s", string(nuText), string(uText))
+		}
+	}
+}
+
+func TestNullUUIDUnmarshalText(t *testing.T) {
+	tests := []struct {
+		nullUUID NullUUID
+	}{
+		{
+			nullUUID: NullUUID{},
+		},
+		{
+			nullUUID: NullUUID{
+				UUID:  MustParse("12345678-abcd-1234-abcd-0123456789ab"),
+				Valid: true,
+			},
+		},
+	}
+	for _, test := range tests {
+		var uText []byte
+		var uErr error
+		nuText, nuErr := test.nullUUID.MarshalText()
+		if test.nullUUID.Valid {
+			uText, uErr = test.nullUUID.UUID.MarshalText()
+		} else {
+			uText = []byte("null")
+		}
+		if nuErr != uErr {
+			t.Errorf("expected error %e, got %e", nuErr, uErr)
+		}
+		if !bytes.Equal(nuText, uText) {
+			t.Errorf("expected text data %s, got %s", string(nuText), string(uText))
+		}
+	}
+}
+
+func TestNullUUIDMarshalBinary(t *testing.T) {
+	tests := []struct {
+		nullUUID NullUUID
+	}{
+		{
+			nullUUID: NullUUID{},
+		},
+		{
+			nullUUID: NullUUID{
+				UUID:  MustParse("12345678-abcd-1234-abcd-0123456789ab"),
+				Valid: true,
+			},
+		},
+	}
+	for _, test := range tests {
+		var uBinary []byte
+		var uErr error
+		nuBinary, nuErr := test.nullUUID.MarshalBinary()
+		if test.nullUUID.Valid {
+			uBinary, uErr = test.nullUUID.UUID.MarshalBinary()
+		} else {
+			uBinary = []byte(nil)
+		}
+		if nuErr != uErr {
+			t.Errorf("expected error %e, got %e", nuErr, uErr)
+		}
+		if !bytes.Equal(nuBinary, uBinary) {
+			t.Errorf("expected binary data %s, got %s", string(nuBinary), string(uBinary))
+		}
+	}
+}
+
+func TestNullUUIDMarshalJSON(t *testing.T) {
+	jsonNull, _ := json.Marshal(nil)
+	jsonUUID, _ := json.Marshal(MustParse("12345678-abcd-1234-abcd-0123456789ab"))
+	tests := []struct {
+		nullUUID    NullUUID
+		expected    []byte
+		expectedErr error
+	}{
+		{
+			nullUUID:    NullUUID{},
+			expected:    jsonNull,
+			expectedErr: nil,
+		},
+		{
+			nullUUID: NullUUID{
+				UUID:  MustParse(string(jsonUUID)),
+				Valid: true,
+			},
+			expected:    []byte(`"12345678-abcd-1234-abcd-0123456789ab"`),
+			expectedErr: nil,
+		},
+	}
+	for _, test := range tests {
+		data, err := json.Marshal(&test.nullUUID)
+		if err != test.expectedErr {
+			t.Errorf("expected error %e, got %e", test.expectedErr, err)
+		}
+		if !bytes.Equal(data, test.expected) {
+			t.Errorf("expected json data %s, got %s", string(test.expected), string(data))
+		}
+	}
+}
+
+func TestNullUUIDUnmarshalJSON(t *testing.T) {
+	jsonNull, _ := json.Marshal(nil)
+	jsonUUID, _ := json.Marshal(MustParse("12345678-abcd-1234-abcd-0123456789ab"))
+
+	var nu NullUUID
+	err := json.Unmarshal(jsonNull, &nu)
+	if err != nil || nu.Valid {
+		t.Errorf("expected nil when unmarshaling null, got %s", err)
+	}
+	err = json.Unmarshal(jsonUUID, &nu)
+	if err != nil || !nu.Valid {
+		t.Errorf("expected nil when unmarshaling null, got %s", err)
+	}
+}
diff --git a/seq_test.go b/seq_test.go
new file mode 100644
index 0000000..4f6c549
--- /dev/null
+++ b/seq_test.go
@@ -0,0 +1,66 @@
+// 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 (
+	"flag"
+	"runtime"
+	"testing"
+	"time"
+)
+
+// This test is only run when --regressions is passed on the go test line.
+var regressions = flag.Bool("regressions", false, "run uuid regression tests")
+
+// TestClockSeqRace tests for a particular race condition of returning two
+// identical Version1 UUIDs.  The duration of 1 minute was chosen as the race
+// condition, before being fixed, nearly always occurred in under 30 seconds.
+func TestClockSeqRace(t *testing.T) {
+	if !*regressions {
+		t.Skip("skipping regression tests")
+	}
+	duration := time.Minute
+
+	done := make(chan struct{})
+	defer close(done)
+
+	ch := make(chan UUID, 10000)
+	ncpu := runtime.NumCPU()
+	switch ncpu {
+	case 0, 1:
+		// We can't run the test effectively.
+		t.Skip("skipping race test, only one CPU detected")
+		return
+	default:
+		runtime.GOMAXPROCS(ncpu)
+	}
+	for i := 0; i < ncpu; i++ {
+		go func() {
+			for {
+				select {
+				case <-done:
+					return
+				case ch <- Must(NewUUID()):
+				}
+			}
+		}()
+	}
+
+	uuids := make(map[string]bool)
+	cnt := 0
+	start := time.Now()
+	for u := range ch {
+		s := u.String()
+		if uuids[s] {
+			t.Errorf("duplicate uuid after %d in %v: %s", cnt, time.Since(start), s)
+			return
+		}
+		uuids[s] = true
+		if time.Since(start) > duration {
+			return
+		}
+		cnt++
+	}
+}
diff --git a/sql.go b/sql.go
new file mode 100644
index 0000000..2e02ec0
--- /dev/null
+++ b/sql.go
@@ -0,0 +1,59 @@
+// 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 (
+	"database/sql/driver"
+	"fmt"
+)
+
+// Scan implements sql.Scanner so UUIDs can be read from databases transparently.
+// Currently, database types that map to string and []byte are supported. Please
+// consult database-specific driver documentation for matching types.
+func (uuid *UUID) Scan(src interface{}) error {
+	switch src := src.(type) {
+	case nil:
+		return nil
+
+	case string:
+		// if an empty UUID comes from a table, we return a null UUID
+		if src == "" {
+			return nil
+		}
+
+		// see Parse for required string format
+		u, err := Parse(src)
+		if err != nil {
+			return fmt.Errorf("Scan: %v", err)
+		}
+
+		*uuid = u
+
+	case []byte:
+		// if an empty UUID comes from a table, we return a null UUID
+		if len(src) == 0 {
+			return nil
+		}
+
+		// assumes a simple slice of bytes if 16 bytes
+		// otherwise attempts to parse
+		if len(src) != 16 {
+			return uuid.Scan(string(src))
+		}
+		copy((*uuid)[:], src)
+
+	default:
+		return fmt.Errorf("Scan: unable to scan type %T into UUID", src)
+	}
+
+	return nil
+}
+
+// Value implements sql.Valuer so that UUIDs can be written to databases
+// transparently. Currently, UUIDs map to strings. Please consult
+// database-specific driver documentation for matching types.
+func (uuid UUID) Value() (driver.Value, error) {
+	return uuid.String(), nil
+}
diff --git a/sql_test.go b/sql_test.go
new file mode 100644
index 0000000..1803dfd
--- /dev/null
+++ b/sql_test.go
@@ -0,0 +1,113 @@
+// 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 (
+	"strings"
+	"testing"
+)
+
+func TestScan(t *testing.T) {
+	stringTest := "f47ac10b-58cc-0372-8567-0e02b2c3d479"
+	badTypeTest := 6
+	invalidTest := "f47ac10b-58cc-0372-8567-0e02b2c3d4"
+
+	byteTest := make([]byte, 16)
+	byteTestUUID := Must(Parse(stringTest))
+	copy(byteTest, byteTestUUID[:])
+
+	// sunny day tests
+
+	var uuid UUID
+	err := (&uuid).Scan(stringTest)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = (&uuid).Scan([]byte(stringTest))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = (&uuid).Scan(byteTest)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// bad type tests
+
+	err = (&uuid).Scan(badTypeTest)
+	if err == nil {
+		t.Error("int correctly parsed and shouldn't have")
+	}
+	if !strings.Contains(err.Error(), "unable to scan type") {
+		t.Error("attempting to parse an int returned an incorrect error message")
+	}
+
+	// invalid/incomplete uuids
+
+	err = (&uuid).Scan(invalidTest)
+	if err == nil {
+		t.Error("invalid uuid was parsed without error")
+	}
+	if !strings.Contains(err.Error(), "invalid UUID") {
+		t.Error("attempting to parse an invalid UUID returned an incorrect error message")
+	}
+
+	err = (&uuid).Scan(byteTest[:len(byteTest)-2])
+	if err == nil {
+		t.Error("invalid byte uuid was parsed without error")
+	}
+	if !strings.Contains(err.Error(), "invalid UUID") {
+		t.Error("attempting to parse an invalid byte UUID returned an incorrect error message")
+	}
+
+	// empty tests
+
+	uuid = UUID{}
+	var emptySlice []byte
+	err = (&uuid).Scan(emptySlice)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, v := range uuid {
+		if v != 0 {
+			t.Error("UUID was not nil after scanning empty byte slice")
+		}
+	}
+
+	uuid = UUID{}
+	var emptyString string
+	err = (&uuid).Scan(emptyString)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, v := range uuid {
+		if v != 0 {
+			t.Error("UUID was not nil after scanning empty byte slice")
+		}
+	}
+
+	uuid = UUID{}
+	err = (&uuid).Scan(nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, v := range uuid {
+		if v != 0 {
+			t.Error("UUID was not nil after scanning nil")
+		}
+	}
+}
+
+func TestValue(t *testing.T) {
+	stringTest := "f47ac10b-58cc-0372-8567-0e02b2c3d479"
+	uuid := Must(Parse(stringTest))
+	val, _ := uuid.Value()
+	if val != stringTest {
+		t.Error("Value() did not return expected string")
+	}
+}
diff --git a/time.go b/time.go
new file mode 100644
index 0000000..e6ef06c
--- /dev/null
+++ b/time.go
@@ -0,0 +1,123 @@
+// 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"
+	"sync"
+	"time"
+)
+
+// A Time represents a time as the number of 100's of nanoseconds since 15 Oct
+// 1582.
+type Time int64
+
+const (
+	lillian    = 2299160          // Julian day of 15 Oct 1582
+	unix       = 2440587          // Julian day of 1 Jan 1970
+	epoch      = unix - lillian   // Days between epochs
+	g1582      = epoch * 86400    // seconds between epochs
+	g1582ns100 = g1582 * 10000000 // 100s of a nanoseconds between epochs
+)
+
+var (
+	timeMu   sync.Mutex
+	lasttime uint64 // last time we returned
+	clockSeq uint16 // clock sequence for this run
+
+	timeNow = time.Now // for testing
+)
+
+// UnixTime converts t the number of seconds and nanoseconds using the Unix
+// epoch of 1 Jan 1970.
+func (t Time) UnixTime() (sec, nsec int64) {
+	sec = int64(t - g1582ns100)
+	nsec = (sec % 10000000) * 100
+	sec /= 10000000
+	return sec, nsec
+}
+
+// GetTime returns the current Time (100s of nanoseconds since 15 Oct 1582) and
+// clock sequence as well as adjusting the clock sequence as needed.  An error
+// is returned if the current time cannot be determined.
+func GetTime() (Time, uint16, error) {
+	defer timeMu.Unlock()
+	timeMu.Lock()
+	return getTime()
+}
+
+func getTime() (Time, uint16, error) {
+	t := timeNow()
+
+	// If we don't have a clock sequence already, set one.
+	if clockSeq == 0 {
+		setClockSequence(-1)
+	}
+	now := uint64(t.UnixNano()/100) + g1582ns100
+
+	// If time has gone backwards with this clock sequence then we
+	// increment the clock sequence
+	if now <= lasttime {
+		clockSeq = ((clockSeq + 1) & 0x3fff) | 0x8000
+	}
+	lasttime = now
+	return Time(now), clockSeq, nil
+}
+
+// ClockSequence returns the current clock sequence, generating one if not
+// already set.  The clock sequence is only used for Version 1 UUIDs.
+//
+// The uuid package does not use global static storage for the clock sequence or
+// the last time a UUID was generated.  Unless SetClockSequence is used, a new
+// random clock sequence is generated the first time a clock sequence is
+// requested by ClockSequence, GetTime, or NewUUID.  (section 4.2.1.1)
+func ClockSequence() int {
+	defer timeMu.Unlock()
+	timeMu.Lock()
+	return clockSequence()
+}
+
+func clockSequence() int {
+	if clockSeq == 0 {
+		setClockSequence(-1)
+	}
+	return int(clockSeq & 0x3fff)
+}
+
+// SetClockSequence sets the clock sequence to the lower 14 bits of seq.  Setting to
+// -1 causes a new sequence to be generated.
+func SetClockSequence(seq int) {
+	defer timeMu.Unlock()
+	timeMu.Lock()
+	setClockSequence(seq)
+}
+
+func setClockSequence(seq int) {
+	if seq == -1 {
+		var b [2]byte
+		randomBits(b[:]) // clock sequence
+		seq = int(b[0])<<8 | int(b[1])
+	}
+	oldSeq := clockSeq
+	clockSeq = uint16(seq&0x3fff) | 0x8000 // Set our variant
+	if oldSeq != clockSeq {
+		lasttime = 0
+	}
+}
+
+// Time returns the time in 100s of nanoseconds since 15 Oct 1582 encoded in
+// uuid.  The time is only defined for version 1 and 2 UUIDs.
+func (uuid UUID) Time() Time {
+	time := int64(binary.BigEndian.Uint32(uuid[0:4]))
+	time |= int64(binary.BigEndian.Uint16(uuid[4:6])) << 32
+	time |= int64(binary.BigEndian.Uint16(uuid[6:8])&0xfff) << 48
+	return Time(time)
+}
+
+// ClockSequence returns the clock sequence encoded in uuid.
+// The clock sequence is only well defined for version 1 and 2 UUIDs.
+func (uuid UUID) ClockSequence() int {
+	return int(binary.BigEndian.Uint16(uuid[8:10])) & 0x3fff
+}
diff --git a/util.go b/util.go
new file mode 100644
index 0000000..5ea6c73
--- /dev/null
+++ b/util.go
@@ -0,0 +1,43 @@
+// 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 (
+	"io"
+)
+
+// randomBits completely fills slice b with random data.
+func randomBits(b []byte) {
+	if _, err := io.ReadFull(rander, b); err != nil {
+		panic(err.Error()) // rand should never fail
+	}
+}
+
+// xvalues returns the value of a byte as a hexadecimal digit or 255.
+var xvalues = [256]byte{
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255, 255, 255, 255, 255,
+	255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+}
+
+// xtob converts hex characters x1 and x2 into a byte.
+func xtob(x1, x2 byte) (byte, bool) {
+	b1 := xvalues[x1]
+	b2 := xvalues[x2]
+	return (b1 << 4) | b2, b1 != 255 && b2 != 255
+}
diff --git a/uuid.go b/uuid.go
new file mode 100644
index 0000000..a57207a
--- /dev/null
+++ b/uuid.go
@@ -0,0 +1,294 @@
+// Copyright 2018 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 (
+	"bytes"
+	"crypto/rand"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+	"sync"
+)
+
+// A UUID is a 128 bit (16 byte) Universal Unique IDentifier as defined in RFC
+// 4122.
+type UUID [16]byte
+
+// A Version represents a UUID's version.
+type Version byte
+
+// A Variant represents a UUID's variant.
+type Variant byte
+
+// Constants returned by Variant.
+const (
+	Invalid   = Variant(iota) // Invalid UUID
+	RFC4122                   // The variant specified in RFC4122
+	Reserved                  // Reserved, NCS backward compatibility.
+	Microsoft                 // Reserved, Microsoft Corporation backward compatibility.
+	Future                    // Reserved for future definition.
+)
+
+const randPoolSize = 16 * 16
+
+var (
+	rander      = rand.Reader // random function
+	poolEnabled = false
+	poolMu      sync.Mutex
+	poolPos     = randPoolSize     // protected with poolMu
+	pool        [randPoolSize]byte // protected with poolMu
+)
+
+type invalidLengthError struct{ len int }
+
+func (err invalidLengthError) Error() string {
+	return fmt.Sprintf("invalid UUID length: %d", err.len)
+}
+
+// IsInvalidLengthError is matcher function for custom error invalidLengthError
+func IsInvalidLengthError(err error) bool {
+	_, ok := err.(invalidLengthError)
+	return ok
+}
+
+// Parse decodes s into a UUID or returns an error.  Both the standard UUID
+// forms of xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx and
+// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx are decoded as well as the
+// Microsoft encoding {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} and the raw hex
+// encoding: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.
+func Parse(s string) (UUID, error) {
+	var uuid UUID
+	switch len(s) {
+	// xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+	case 36:
+
+	// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+	case 36 + 9:
+		if strings.ToLower(s[:9]) != "urn:uuid:" {
+			return uuid, fmt.Errorf("invalid urn prefix: %q", s[:9])
+		}
+		s = s[9:]
+
+	// {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
+	case 36 + 2:
+		s = s[1:]
+
+	// xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+	case 32:
+		var ok bool
+		for i := range uuid {
+			uuid[i], ok = xtob(s[i*2], s[i*2+1])
+			if !ok {
+				return uuid, errors.New("invalid UUID format")
+			}
+		}
+		return uuid, nil
+	default:
+		return uuid, invalidLengthError{len(s)}
+	}
+	// s is now at least 36 bytes long
+	// it must be of the form  xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+	if s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-' {
+		return uuid, errors.New("invalid UUID format")
+	}
+	for i, x := range [16]int{
+		0, 2, 4, 6,
+		9, 11,
+		14, 16,
+		19, 21,
+		24, 26, 28, 30, 32, 34} {
+		v, ok := xtob(s[x], s[x+1])
+		if !ok {
+			return uuid, errors.New("invalid UUID format")
+		}
+		uuid[i] = v
+	}
+	return uuid, nil
+}
+
+// ParseBytes is like Parse, except it parses a byte slice instead of a string.
+func ParseBytes(b []byte) (UUID, error) {
+	var uuid UUID
+	switch len(b) {
+	case 36: // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+	case 36 + 9: // urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+		if !bytes.Equal(bytes.ToLower(b[:9]), []byte("urn:uuid:")) {
+			return uuid, fmt.Errorf("invalid urn prefix: %q", b[:9])
+		}
+		b = b[9:]
+	case 36 + 2: // {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
+		b = b[1:]
+	case 32: // xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+		var ok bool
+		for i := 0; i < 32; i += 2 {
+			uuid[i/2], ok = xtob(b[i], b[i+1])
+			if !ok {
+				return uuid, errors.New("invalid UUID format")
+			}
+		}
+		return uuid, nil
+	default:
+		return uuid, invalidLengthError{len(b)}
+	}
+	// s is now at least 36 bytes long
+	// it must be of the form  xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+	if b[8] != '-' || b[13] != '-' || b[18] != '-' || b[23] != '-' {
+		return uuid, errors.New("invalid UUID format")
+	}
+	for i, x := range [16]int{
+		0, 2, 4, 6,
+		9, 11,
+		14, 16,
+		19, 21,
+		24, 26, 28, 30, 32, 34} {
+		v, ok := xtob(b[x], b[x+1])
+		if !ok {
+			return uuid, errors.New("invalid UUID format")
+		}
+		uuid[i] = v
+	}
+	return uuid, nil
+}
+
+// MustParse is like Parse but panics if the string cannot be parsed.
+// It simplifies safe initialization of global variables holding compiled UUIDs.
+func MustParse(s string) UUID {
+	uuid, err := Parse(s)
+	if err != nil {
+		panic(`uuid: Parse(` + s + `): ` + err.Error())
+	}
+	return uuid
+}
+
+// FromBytes creates a new UUID from a byte slice. Returns an error if the slice
+// does not have a length of 16. The bytes are copied from the slice.
+func FromBytes(b []byte) (uuid UUID, err error) {
+	err = uuid.UnmarshalBinary(b)
+	return uuid, err
+}
+
+// Must returns uuid if err is nil and panics otherwise.
+func Must(uuid UUID, err error) UUID {
+	if err != nil {
+		panic(err)
+	}
+	return uuid
+}
+
+// String returns the string form of uuid, xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+// , or "" if uuid is invalid.
+func (uuid UUID) String() string {
+	var buf [36]byte
+	encodeHex(buf[:], uuid)
+	return string(buf[:])
+}
+
+// URN returns the RFC 2141 URN form of uuid,
+// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx,  or "" if uuid is invalid.
+func (uuid UUID) URN() string {
+	var buf [36 + 9]byte
+	copy(buf[:], "urn:uuid:")
+	encodeHex(buf[9:], uuid)
+	return string(buf[:])
+}
+
+func encodeHex(dst []byte, uuid UUID) {
+	hex.Encode(dst, uuid[:4])
+	dst[8] = '-'
+	hex.Encode(dst[9:13], uuid[4:6])
+	dst[13] = '-'
+	hex.Encode(dst[14:18], uuid[6:8])
+	dst[18] = '-'
+	hex.Encode(dst[19:23], uuid[8:10])
+	dst[23] = '-'
+	hex.Encode(dst[24:], uuid[10:])
+}
+
+// Variant returns the variant encoded in uuid.
+func (uuid UUID) Variant() Variant {
+	switch {
+	case (uuid[8] & 0xc0) == 0x80:
+		return RFC4122
+	case (uuid[8] & 0xe0) == 0xc0:
+		return Microsoft
+	case (uuid[8] & 0xe0) == 0xe0:
+		return Future
+	default:
+		return Reserved
+	}
+}
+
+// Version returns the version of uuid.
+func (uuid UUID) Version() Version {
+	return Version(uuid[6] >> 4)
+}
+
+func (v Version) String() string {
+	if v > 15 {
+		return fmt.Sprintf("BAD_VERSION_%d", v)
+	}
+	return fmt.Sprintf("VERSION_%d", v)
+}
+
+func (v Variant) String() string {
+	switch v {
+	case RFC4122:
+		return "RFC4122"
+	case Reserved:
+		return "Reserved"
+	case Microsoft:
+		return "Microsoft"
+	case Future:
+		return "Future"
+	case Invalid:
+		return "Invalid"
+	}
+	return fmt.Sprintf("BadVariant%d", int(v))
+}
+
+// SetRand sets the random number generator to r, which implements io.Reader.
+// If r.Read returns an error when the package requests random data then
+// a panic will be issued.
+//
+// Calling SetRand with nil sets the random number generator to the default
+// generator.
+func SetRand(r io.Reader) {
+	if r == nil {
+		rander = rand.Reader
+		return
+	}
+	rander = r
+}
+
+// EnableRandPool enables internal randomness pool used for Random
+// (Version 4) UUID generation. The pool contains random bytes read from
+// the random number generator on demand in batches. Enabling the pool
+// may improve the UUID generation throughput significantly.
+//
+// Since the pool is stored on the Go heap, this feature may be a bad fit
+// for security sensitive applications.
+//
+// Both EnableRandPool and DisableRandPool are not thread-safe and should
+// only be called when there is no possibility that New or any other
+// UUID Version 4 generation function will be called concurrently.
+func EnableRandPool() {
+	poolEnabled = true
+}
+
+// DisableRandPool disables the randomness pool if it was previously
+// enabled with EnableRandPool.
+//
+// Both EnableRandPool and DisableRandPool are not thread-safe and should
+// only be called when there is no possibility that New or any other
+// UUID Version 4 generation function will be called concurrently.
+func DisableRandPool() {
+	poolEnabled = false
+	defer poolMu.Unlock()
+	poolMu.Lock()
+	poolPos = randPoolSize
+}
diff --git a/uuid_test.go b/uuid_test.go
new file mode 100644
index 0000000..e98d0fe
--- /dev/null
+++ b/uuid_test.go
@@ -0,0 +1,702 @@
+// 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 (
+	"bytes"
+	"fmt"
+	"os"
+	"runtime"
+	"strings"
+	"testing"
+	"time"
+	"unsafe"
+)
+
+type test struct {
+	in      string
+	version Version
+	variant Variant
+	isuuid  bool
+}
+
+var tests = []test{
+	{"f47ac10b-58cc-0372-8567-0e02b2c3d479", 0, RFC4122, true},
+	{"f47ac10b-58cc-1372-8567-0e02b2c3d479", 1, RFC4122, true},
+	{"f47ac10b-58cc-2372-8567-0e02b2c3d479", 2, RFC4122, true},
+	{"f47ac10b-58cc-3372-8567-0e02b2c3d479", 3, RFC4122, true},
+	{"f47ac10b-58cc-4372-8567-0e02b2c3d479", 4, RFC4122, true},
+	{"f47ac10b-58cc-5372-8567-0e02b2c3d479", 5, RFC4122, true},
+	{"f47ac10b-58cc-6372-8567-0e02b2c3d479", 6, RFC4122, true},
+	{"f47ac10b-58cc-7372-8567-0e02b2c3d479", 7, RFC4122, true},
+	{"f47ac10b-58cc-8372-8567-0e02b2c3d479", 8, RFC4122, true},
+	{"f47ac10b-58cc-9372-8567-0e02b2c3d479", 9, RFC4122, true},
+	{"f47ac10b-58cc-a372-8567-0e02b2c3d479", 10, RFC4122, true},
+	{"f47ac10b-58cc-b372-8567-0e02b2c3d479", 11, RFC4122, true},
+	{"f47ac10b-58cc-c372-8567-0e02b2c3d479", 12, RFC4122, true},
+	{"f47ac10b-58cc-d372-8567-0e02b2c3d479", 13, RFC4122, true},
+	{"f47ac10b-58cc-e372-8567-0e02b2c3d479", 14, RFC4122, true},
+	{"f47ac10b-58cc-f372-8567-0e02b2c3d479", 15, RFC4122, true},
+
+	{"urn:uuid:f47ac10b-58cc-4372-0567-0e02b2c3d479", 4, Reserved, true},
+	{"URN:UUID:f47ac10b-58cc-4372-0567-0e02b2c3d479", 4, Reserved, true},
+	{"f47ac10b-58cc-4372-0567-0e02b2c3d479", 4, Reserved, true},
+	{"f47ac10b-58cc-4372-1567-0e02b2c3d479", 4, Reserved, true},
+	{"f47ac10b-58cc-4372-2567-0e02b2c3d479", 4, Reserved, true},
+	{"f47ac10b-58cc-4372-3567-0e02b2c3d479", 4, Reserved, true},
+	{"f47ac10b-58cc-4372-4567-0e02b2c3d479", 4, Reserved, true},
+	{"f47ac10b-58cc-4372-5567-0e02b2c3d479", 4, Reserved, true},
+	{"f47ac10b-58cc-4372-6567-0e02b2c3d479", 4, Reserved, true},
+	{"f47ac10b-58cc-4372-7567-0e02b2c3d479", 4, Reserved, true},
+	{"f47ac10b-58cc-4372-8567-0e02b2c3d479", 4, RFC4122, true},
+	{"f47ac10b-58cc-4372-9567-0e02b2c3d479", 4, RFC4122, true},
+	{"f47ac10b-58cc-4372-a567-0e02b2c3d479", 4, RFC4122, true},
+	{"f47ac10b-58cc-4372-b567-0e02b2c3d479", 4, RFC4122, true},
+	{"f47ac10b-58cc-4372-c567-0e02b2c3d479", 4, Microsoft, true},
+	{"f47ac10b-58cc-4372-d567-0e02b2c3d479", 4, Microsoft, true},
+	{"f47ac10b-58cc-4372-e567-0e02b2c3d479", 4, Future, true},
+	{"f47ac10b-58cc-4372-f567-0e02b2c3d479", 4, Future, true},
+
+	{"f47ac10b158cc-5372-a567-0e02b2c3d479", 0, Invalid, false},
+	{"f47ac10b-58cc25372-a567-0e02b2c3d479", 0, Invalid, false},
+	{"f47ac10b-58cc-53723a567-0e02b2c3d479", 0, Invalid, false},
+	{"f47ac10b-58cc-5372-a56740e02b2c3d479", 0, Invalid, false},
+	{"f47ac10b-58cc-5372-a567-0e02-2c3d479", 0, Invalid, false},
+	{"g47ac10b-58cc-4372-a567-0e02b2c3d479", 0, Invalid, false},
+
+	{"{f47ac10b-58cc-0372-8567-0e02b2c3d479}", 0, RFC4122, true},
+	{"{f47ac10b-58cc-0372-8567-0e02b2c3d479", 0, Invalid, false},
+	{"f47ac10b-58cc-0372-8567-0e02b2c3d479}", 0, Invalid, false},
+
+	{"f47ac10b58cc037285670e02b2c3d479", 0, RFC4122, true},
+	{"f47ac10b58cc037285670e02b2c3d4790", 0, Invalid, false},
+	{"f47ac10b58cc037285670e02b2c3d47", 0, Invalid, false},
+}
+
+var constants = []struct {
+	c    interface{}
+	name string
+}{
+	{Person, "Person"},
+	{Group, "Group"},
+	{Org, "Org"},
+	{Invalid, "Invalid"},
+	{RFC4122, "RFC4122"},
+	{Reserved, "Reserved"},
+	{Microsoft, "Microsoft"},
+	{Future, "Future"},
+	{Domain(17), "Domain17"},
+	{Variant(42), "BadVariant42"},
+}
+
+func testTest(t *testing.T, in string, tt test) {
+	uuid, err := Parse(in)
+	if ok := (err == nil); ok != tt.isuuid {
+		t.Errorf("Parse(%s) got %v expected %v\b", in, ok, tt.isuuid)
+	}
+	if err != nil {
+		return
+	}
+
+	if v := uuid.Variant(); v != tt.variant {
+		t.Errorf("Variant(%s) got %d expected %d\b", in, v, tt.variant)
+	}
+	if v := uuid.Version(); v != tt.version {
+		t.Errorf("Version(%s) got %d expected %d\b", in, v, tt.version)
+	}
+}
+
+func testBytes(t *testing.T, in []byte, tt test) {
+	uuid, err := ParseBytes(in)
+	if ok := (err == nil); ok != tt.isuuid {
+		t.Errorf("ParseBytes(%s) got %v expected %v\b", in, ok, tt.isuuid)
+	}
+	if err != nil {
+		return
+	}
+	suuid, _ := Parse(string(in))
+	if uuid != suuid {
+		t.Errorf("ParseBytes(%s) got %v expected %v\b", in, uuid, suuid)
+	}
+}
+
+func TestUUID(t *testing.T) {
+	for _, tt := range tests {
+		testTest(t, tt.in, tt)
+		testTest(t, strings.ToUpper(tt.in), tt)
+		testBytes(t, []byte(tt.in), tt)
+	}
+}
+
+func TestFromBytes(t *testing.T) {
+	b := []byte{
+		0x7d, 0x44, 0x48, 0x40,
+		0x9d, 0xc0,
+		0x11, 0xd1,
+		0xb2, 0x45,
+		0x5f, 0xfd, 0xce, 0x74, 0xfa, 0xd2,
+	}
+	uuid, err := FromBytes(b)
+	if err != nil {
+		t.Fatalf("%s", err)
+	}
+	for i := 0; i < len(uuid); i++ {
+		if b[i] != uuid[i] {
+			t.Fatalf("FromBytes() got %v expected %v\b", uuid[:], b)
+		}
+	}
+}
+
+func TestConstants(t *testing.T) {
+	for x, tt := range constants {
+		v, ok := tt.c.(fmt.Stringer)
+		if !ok {
+			t.Errorf("%x: %v: not a stringer", x, v)
+		} else if s := v.String(); s != tt.name {
+			v, _ := tt.c.(int)
+			t.Errorf("%x: Constant %T:%d gives %q, expected %q", x, tt.c, v, s, tt.name)
+		}
+	}
+}
+
+func TestRandomUUID(t *testing.T) {
+	m := make(map[string]bool)
+	for x := 1; x < 32; x++ {
+		uuid := New()
+		s := uuid.String()
+		if m[s] {
+			t.Errorf("NewRandom returned duplicated UUID %s", s)
+		}
+		m[s] = true
+		if v := uuid.Version(); v != 4 {
+			t.Errorf("Random UUID of version %s", v)
+		}
+		if uuid.Variant() != RFC4122 {
+			t.Errorf("Random UUID is variant %d", uuid.Variant())
+		}
+	}
+}
+
+func TestRandomUUID_Pooled(t *testing.T) {
+	defer DisableRandPool()
+	EnableRandPool()
+	m := make(map[string]bool)
+	for x := 1; x < 128; x++ {
+		uuid := New()
+		s := uuid.String()
+		if m[s] {
+			t.Errorf("NewRandom returned duplicated UUID %s", s)
+		}
+		m[s] = true
+		if v := uuid.Version(); v != 4 {
+			t.Errorf("Random UUID of version %s", v)
+		}
+		if uuid.Variant() != RFC4122 {
+			t.Errorf("Random UUID is variant %d", uuid.Variant())
+		}
+	}
+}
+
+func TestNew(t *testing.T) {
+	m := make(map[UUID]bool)
+	for x := 1; x < 32; x++ {
+		s := New()
+		if m[s] {
+			t.Errorf("New returned duplicated UUID %s", s)
+		}
+		m[s] = true
+		uuid, err := Parse(s.String())
+		if err != nil {
+			t.Errorf("New.String() returned %q which does not decode", s)
+			continue
+		}
+		if v := uuid.Version(); v != 4 {
+			t.Errorf("Random UUID of version %s", v)
+		}
+		if uuid.Variant() != RFC4122 {
+			t.Errorf("Random UUID is variant %d", uuid.Variant())
+		}
+	}
+}
+
+func TestClockSeq(t *testing.T) {
+	// Fake time.Now for this test to return a monotonically advancing time; restore it at end.
+	defer func(orig func() time.Time) { timeNow = orig }(timeNow)
+	monTime := time.Now()
+	timeNow = func() time.Time {
+		monTime = monTime.Add(1 * time.Second)
+		return monTime
+	}
+
+	SetClockSequence(-1)
+	uuid1, err := NewUUID()
+	if err != nil {
+		t.Fatalf("could not create UUID: %v", err)
+	}
+	uuid2, err := NewUUID()
+	if err != nil {
+		t.Fatalf("could not create UUID: %v", err)
+	}
+
+	if s1, s2 := uuid1.ClockSequence(), uuid2.ClockSequence(); s1 != s2 {
+		t.Errorf("clock sequence %d != %d", s1, s2)
+	}
+
+	SetClockSequence(-1)
+	uuid2, err = NewUUID()
+	if err != nil {
+		t.Fatalf("could not create UUID: %v", err)
+	}
+
+	// Just on the very off chance we generated the same sequence
+	// two times we try again.
+	if uuid1.ClockSequence() == uuid2.ClockSequence() {
+		SetClockSequence(-1)
+		uuid2, err = NewUUID()
+		if err != nil {
+			t.Fatalf("could not create UUID: %v", err)
+		}
+	}
+	if s1, s2 := uuid1.ClockSequence(), uuid2.ClockSequence(); s1 == s2 {
+		t.Errorf("Duplicate clock sequence %d", s1)
+	}
+
+	SetClockSequence(0x1234)
+	uuid1, err = NewUUID()
+	if err != nil {
+		t.Fatalf("could not create UUID: %v", err)
+	}
+	if seq := uuid1.ClockSequence(); seq != 0x1234 {
+		t.Errorf("%s: expected seq 0x1234 got 0x%04x", uuid1, seq)
+	}
+}
+
+func TestCoding(t *testing.T) {
+	text := "7d444840-9dc0-11d1-b245-5ffdce74fad2"
+	urn := "urn:uuid:7d444840-9dc0-11d1-b245-5ffdce74fad2"
+	data := UUID{
+		0x7d, 0x44, 0x48, 0x40,
+		0x9d, 0xc0,
+		0x11, 0xd1,
+		0xb2, 0x45,
+		0x5f, 0xfd, 0xce, 0x74, 0xfa, 0xd2,
+	}
+	if v := data.String(); v != text {
+		t.Errorf("%x: encoded to %s, expected %s", data, v, text)
+	}
+	if v := data.URN(); v != urn {
+		t.Errorf("%x: urn is %s, expected %s", data, v, urn)
+	}
+
+	uuid, err := Parse(text)
+	if err != nil {
+		t.Errorf("Parse returned unexpected error %v", err)
+	}
+	if data != uuid {
+		t.Errorf("%s: decoded to %s, expected %s", text, uuid, data)
+	}
+}
+
+func TestVersion1(t *testing.T) {
+	uuid1, err := NewUUID()
+	if err != nil {
+		t.Fatalf("could not create UUID: %v", err)
+	}
+	uuid2, err := NewUUID()
+	if err != nil {
+		t.Fatalf("could not create UUID: %v", err)
+	}
+
+	if uuid1 == uuid2 {
+		t.Errorf("%s:duplicate uuid", uuid1)
+	}
+	if v := uuid1.Version(); v != 1 {
+		t.Errorf("%s: version %s expected 1", uuid1, v)
+	}
+	if v := uuid2.Version(); v != 1 {
+		t.Errorf("%s: version %s expected 1", uuid2, v)
+	}
+	n1 := uuid1.NodeID()
+	n2 := uuid2.NodeID()
+	if !bytes.Equal(n1, n2) {
+		t.Errorf("Different nodes %x != %x", n1, n2)
+	}
+	t1 := uuid1.Time()
+	t2 := uuid2.Time()
+	q1 := uuid1.ClockSequence()
+	q2 := uuid2.ClockSequence()
+
+	switch {
+	case t1 == t2 && q1 == q2:
+		t.Error("time stopped")
+	case t1 > t2 && q1 == q2:
+		t.Error("time reversed")
+	case t1 < t2 && q1 != q2:
+		t.Error("clock sequence changed unexpectedly")
+	}
+}
+
+func TestNode(t *testing.T) {
+	// This test is mostly to make sure we don't leave nodeMu locked.
+	ifname = ""
+	if ni := NodeInterface(); ni != "" {
+		t.Errorf("NodeInterface got %q, want %q", ni, "")
+	}
+	if SetNodeInterface("xyzzy") {
+		t.Error("SetNodeInterface succeeded on a bad interface name")
+	}
+	if !SetNodeInterface("") {
+		t.Error("SetNodeInterface failed")
+	}
+	if runtime.GOARCH != "js" {
+		if ni := NodeInterface(); ni == "" {
+			t.Error("NodeInterface returned an empty string")
+		}
+	}
+
+	ni := NodeID()
+	if len(ni) != 6 {
+		t.Errorf("ni got %d bytes, want 6", len(ni))
+	}
+	hasData := false
+	for _, b := range ni {
+		if b != 0 {
+			hasData = true
+		}
+	}
+	if !hasData {
+		t.Error("nodeid is all zeros")
+	}
+
+	id := []byte{1, 2, 3, 4, 5, 6, 7, 8}
+	SetNodeID(id)
+	ni = NodeID()
+	if !bytes.Equal(ni, id[:6]) {
+		t.Errorf("got nodeid %v, want %v", ni, id[:6])
+	}
+
+	if ni := NodeInterface(); ni != "user" {
+		t.Errorf("got interface %q, want %q", ni, "user")
+	}
+}
+
+func TestNodeAndTime(t *testing.T) {
+	// Time is February 5, 1998 12:30:23.136364800 AM GMT
+
+	uuid, err := Parse("7d444840-9dc0-11d1-b245-5ffdce74fad2")
+	if err != nil {
+		t.Fatalf("Parser returned unexpected error %v", err)
+	}
+	node := []byte{0x5f, 0xfd, 0xce, 0x74, 0xfa, 0xd2}
+
+	ts := uuid.Time()
+	c := time.Unix(ts.UnixTime())
+	want := time.Date(1998, 2, 5, 0, 30, 23, 136364800, time.UTC)
+	if !c.Equal(want) {
+		t.Errorf("Got time %v, want %v", c, want)
+	}
+	if !bytes.Equal(node, uuid.NodeID()) {
+		t.Errorf("Expected node %v got %v", node, uuid.NodeID())
+	}
+}
+
+func TestMD5(t *testing.T) {
+	uuid := NewMD5(NameSpaceDNS, []byte("python.org")).String()
+	want := "6fa459ea-ee8a-3ca4-894e-db77e160355e"
+	if uuid != want {
+		t.Errorf("MD5: got %q expected %q", uuid, want)
+	}
+}
+
+func TestSHA1(t *testing.T) {
+	uuid := NewSHA1(NameSpaceDNS, []byte("python.org")).String()
+	want := "886313e1-3b8a-5372-9b90-0c9aee199e5d"
+	if uuid != want {
+		t.Errorf("SHA1: got %q expected %q", uuid, want)
+	}
+}
+
+func TestNodeID(t *testing.T) {
+	nid := []byte{1, 2, 3, 4, 5, 6}
+	SetNodeInterface("")
+	s := NodeInterface()
+	if runtime.GOARCH != "js" {
+		if s == "" || s == "user" {
+			t.Errorf("NodeInterface %q after SetInterface", s)
+		}
+	}
+	node1 := NodeID()
+	if node1 == nil {
+		t.Error("NodeID nil after SetNodeInterface", s)
+	}
+	SetNodeID(nid)
+	s = NodeInterface()
+	if s != "user" {
+		t.Errorf("Expected NodeInterface %q got %q", "user", s)
+	}
+	node2 := NodeID()
+	if node2 == nil {
+		t.Error("NodeID nil after SetNodeID", s)
+	}
+	if bytes.Equal(node1, node2) {
+		t.Error("NodeID not changed after SetNodeID", s)
+	} else if !bytes.Equal(nid, node2) {
+		t.Errorf("NodeID is %x, expected %x", node2, nid)
+	}
+}
+
+func testDCE(t *testing.T, name string, uuid UUID, err error, domain Domain, id uint32) {
+	if err != nil {
+		t.Errorf("%s failed: %v", name, err)
+		return
+	}
+	if v := uuid.Version(); v != 2 {
+		t.Errorf("%s: %s: expected version 2, got %s", name, uuid, v)
+		return
+	}
+	if v := uuid.Domain(); v != domain {
+		t.Errorf("%s: %s: expected domain %d, got %d", name, uuid, domain, v)
+	}
+	if v := uuid.ID(); v != id {
+		t.Errorf("%s: %s: expected id %d, got %d", name, uuid, id, v)
+	}
+}
+
+func TestDCE(t *testing.T) {
+	uuid, err := NewDCESecurity(42, 12345678)
+	testDCE(t, "NewDCESecurity", uuid, err, 42, 12345678)
+	uuid, err = NewDCEPerson()
+	testDCE(t, "NewDCEPerson", uuid, err, Person, uint32(os.Getuid()))
+	uuid, err = NewDCEGroup()
+	testDCE(t, "NewDCEGroup", uuid, err, Group, uint32(os.Getgid()))
+}
+
+type badRand struct{}
+
+func (r badRand) Read(buf []byte) (int, error) {
+	for i := range buf {
+		buf[i] = byte(i)
+	}
+	return len(buf), nil
+}
+
+func TestBadRand(t *testing.T) {
+	SetRand(badRand{})
+	uuid1 := New()
+	uuid2 := New()
+	if uuid1 != uuid2 {
+		t.Errorf("expected duplicates, got %q and %q", uuid1, uuid2)
+	}
+	SetRand(nil)
+	uuid1 = New()
+	uuid2 = New()
+	if uuid1 == uuid2 {
+		t.Errorf("unexpected duplicates, got %q", uuid1)
+	}
+}
+
+func TestSetRand(t *testing.T) {
+	myString := "805-9dd6-1a877cb526c678e71d38-7122-44c0-9b7c-04e7001cc78783ac3e82-47a3-4cc3-9951-13f3339d88088f5d685a-11f7-4078-ada9-de44ad2daeb7"
+
+	SetRand(strings.NewReader(myString))
+	uuid1 := New()
+	uuid2 := New()
+
+	SetRand(strings.NewReader(myString))
+	uuid3 := New()
+	uuid4 := New()
+
+	if uuid1 != uuid3 {
+		t.Errorf("expected duplicates, got %q and %q", uuid1, uuid3)
+	}
+	if uuid2 != uuid4 {
+		t.Errorf("expected duplicates, got %q and %q", uuid2, uuid4)
+	}
+}
+
+func TestRandomFromReader(t *testing.T) {
+	myString := "8059ddhdle77cb52"
+	r := bytes.NewReader([]byte(myString))
+	r2 := bytes.NewReader([]byte(myString))
+	uuid1, err := NewRandomFromReader(r)
+	if err != nil {
+		t.Errorf("failed generating UUID from a reader")
+	}
+	_, err = NewRandomFromReader(r)
+	if err == nil {
+		t.Errorf("expecting an error as reader has no more bytes. Got uuid. NewRandomFromReader may not be using the provided reader")
+	}
+	uuid3, err := NewRandomFromReader(r2)
+	if err != nil {
+		t.Errorf("failed generating UUID from a reader")
+	}
+	if uuid1 != uuid3 {
+		t.Errorf("expected duplicates, got %q and %q", uuid1, uuid3)
+	}
+}
+
+func TestRandPool(t *testing.T) {
+	myString := "8059ddhdle77cb52"
+	EnableRandPool()
+	SetRand(strings.NewReader(myString))
+	_, err := NewRandom()
+	if err == nil {
+		t.Errorf("expecting an error as reader has no more bytes")
+	}
+	DisableRandPool()
+	SetRand(strings.NewReader(myString))
+	_, err = NewRandom()
+	if err != nil {
+		t.Errorf("failed generating UUID from a reader")
+	}
+}
+
+func TestWrongLength(t *testing.T) {
+	_, err := Parse("12345")
+	if err == nil {
+		t.Errorf("expected ‘12345’ was invalid")
+	} else if err.Error() != "invalid UUID length: 5" {
+		t.Errorf("expected a different error message for an invalid length")
+	}
+}
+
+func TestIsWrongLength(t *testing.T) {
+	_, err := Parse("12345")
+	if !IsInvalidLengthError(err) {
+		t.Errorf("expected error type is invalidLengthError")
+	}
+}
+
+var asString = "f47ac10b-58cc-0372-8567-0e02b2c3d479"
+var asBytes = []byte(asString)
+
+func BenchmarkParse(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		_, err := Parse(asString)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkParseBytes(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		_, err := ParseBytes(asBytes)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+// parseBytesUnsafe is to benchmark using unsafe.
+func parseBytesUnsafe(b []byte) (UUID, error) {
+	return Parse(*(*string)(unsafe.Pointer(&b)))
+}
+
+func BenchmarkParseBytesUnsafe(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		_, err := parseBytesUnsafe(asBytes)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+// parseBytesCopy is to benchmark not using unsafe.
+func parseBytesCopy(b []byte) (UUID, error) {
+	return Parse(string(b))
+}
+
+func BenchmarkParseBytesCopy(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		_, err := parseBytesCopy(asBytes)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkNew(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		New()
+	}
+}
+
+func BenchmarkUUID_String(b *testing.B) {
+	uuid, err := Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
+	if err != nil {
+		b.Fatal(err)
+	}
+	for i := 0; i < b.N; i++ {
+		if uuid.String() == "" {
+			b.Fatal("invalid uuid")
+		}
+	}
+}
+
+func BenchmarkUUID_URN(b *testing.B) {
+	uuid, err := Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
+	if err != nil {
+		b.Fatal(err)
+	}
+	for i := 0; i < b.N; i++ {
+		if uuid.URN() == "" {
+			b.Fatal("invalid uuid")
+		}
+	}
+}
+
+func BenchmarkParseBadLength(b *testing.B) {
+	short := asString[:10]
+	for i := 0; i < b.N; i++ {
+		_, err := Parse(short)
+		if err == nil {
+			b.Fatalf("expected ‘%s’ was invalid", short)
+		}
+	}
+}
+
+func BenchmarkParseLen32Truncated(b *testing.B) {
+	partial := asString[:len(asString)-4]
+	for i := 0; i < b.N; i++ {
+		_, err := Parse(partial)
+		if err == nil {
+			b.Fatalf("expected ‘%s’ was invalid", partial)
+		}
+	}
+}
+
+func BenchmarkParseLen36Corrupted(b *testing.B) {
+	wrong := asString[:len(asString)-1] + "x"
+	for i := 0; i < b.N; i++ {
+		_, err := Parse(wrong)
+		if err == nil {
+			b.Fatalf("expected ‘%s’ was invalid", wrong)
+		}
+	}
+}
+
+func BenchmarkUUID_New(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			_, err := NewRandom()
+			if err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}
+
+func BenchmarkUUID_NewPooled(b *testing.B) {
+	EnableRandPool()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			_, err := NewRandom()
+			if err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}
diff --git a/version1.go b/version1.go
new file mode 100644
index 0000000..4631096
--- /dev/null
+++ b/version1.go
@@ -0,0 +1,44 @@
+// 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
+}
diff --git a/version4.go b/version4.go
new file mode 100644
index 0000000..7697802
--- /dev/null
+++ b/version4.go
@@ -0,0 +1,76 @@
+// 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 "io"
+
+// New creates a new random UUID or panics.  New is equivalent to
+// the expression
+//
+//    uuid.Must(uuid.NewRandom())
+func New() UUID {
+	return Must(NewRandom())
+}
+
+// NewString creates a new random UUID and returns it as a string or panics.
+// NewString is equivalent to the expression
+//
+//    uuid.New().String()
+func NewString() string {
+	return Must(NewRandom()).String()
+}
+
+// NewRandom returns a Random (Version 4) UUID.
+//
+// The strength of the UUIDs is based on the strength of the crypto/rand
+// package.
+//
+// Uses the randomness pool if it was enabled with EnableRandPool.
+//
+// A note about uniqueness derived from the UUID Wikipedia entry:
+//
+//  Randomly generated UUIDs have 122 random bits.  One's annual risk of being
+//  hit by a meteorite is estimated to be one chance in 17 billion, that
+//  means the probability is about 0.00000000006 (6 × 10−11),
+//  equivalent to the odds of creating a few tens of trillions of UUIDs in a
+//  year and having one duplicate.
+func NewRandom() (UUID, error) {
+	if !poolEnabled {
+		return NewRandomFromReader(rander)
+	}
+	return newRandomFromPool()
+}
+
+// NewRandomFromReader returns a UUID based on bytes read from a given io.Reader.
+func NewRandomFromReader(r io.Reader) (UUID, error) {
+	var uuid UUID
+	_, err := io.ReadFull(r, uuid[:])
+	if err != nil {
+		return Nil, err
+	}
+	uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4
+	uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10
+	return uuid, nil
+}
+
+func newRandomFromPool() (UUID, error) {
+	var uuid UUID
+	poolMu.Lock()
+	if poolPos == randPoolSize {
+		_, err := io.ReadFull(rander, pool[:])
+		if err != nil {
+			poolMu.Unlock()
+			return Nil, err
+		}
+		poolPos = 0
+	}
+	copy(uuid[:], pool[poolPos:(poolPos+16)])
+	poolPos += 16
+	poolMu.Unlock()
+
+	uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4
+	uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10
+	return uuid, nil
+}