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
index b382a04..b4bb97f 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -1 +1,9 @@
 Paul Borman <borman@google.com>
+bmatsuo
+shawnps
+theory
+jboverfelt
+dsymonds
+cd1
+wallclockbuilder
+dansouza
diff --git a/README.md b/README.md
index 7e176d9..d5cc534 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,11 @@
 # uuid ![build status](https://travis-ci.org/google/uuid.svg?branch=master)
 The uuid package generates and inspects UUIDs based on [RFC 412](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`
 
diff --git a/dce.go b/dce.go
index 50a0f2d..8523659 100755
--- a/dce.go
+++ b/dce.go
@@ -1,4 +1,4 @@
-// Copyright 2011 Google Inc.  All rights reserved.
+// 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.
 
@@ -29,21 +29,21 @@
 //
 // 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 {
-	uuid := NewUUID()
-	if uuid != nil {
+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
+	return uuid, err
 }
 
 // NewDCEPerson returns a DCE Security (Version 2) UUID in the person
 // domain with the id returned by os.Getuid.
 //
 //  NewDCEPerson(Person, uint32(os.Getuid()))
-func NewDCEPerson() UUID {
+func NewDCEPerson() (UUID, error) {
 	return NewDCESecurity(Person, uint32(os.Getuid()))
 }
 
@@ -51,24 +51,20 @@
 // domain with the id returned by os.Getgid.
 //
 //  NewDCEGroup(Group, uint32(os.Getgid()))
-func NewDCEGroup() UUID {
+func NewDCEGroup() (UUID, error) {
 	return NewDCESecurity(Group, uint32(os.Getgid()))
 }
 
-// Domain returns the domain for a Version 2 UUID or false.
-func (uuid UUID) Domain() (Domain, bool) {
-	if v, _ := uuid.Version(); v != 2 {
-		return 0, false
-	}
-	return Domain(uuid[9]), true
+// 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 or false.
-func (uuid UUID) Id() (uint32, bool) {
-	if v, _ := uuid.Version(); v != 2 {
-		return 0, false
-	}
-	return binary.BigEndian.Uint32(uuid[0:4]), true
+// Id returns the id for a Version 2 UUID. Ids are only defined for Vrsion 2
+// UUIDs.
+func (uuid UUID) Id() uint32 {
+	return binary.BigEndian.Uint32(uuid[0:4])
 }
 
 func (d Domain) String() string {
diff --git a/doc.go b/doc.go
index d8bd013..5b8a4b9 100755
--- a/doc.go
+++ b/doc.go
@@ -1,8 +1,12 @@
-// Copyright 2011 Google Inc.  All rights reserved.
+// 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.
 
-// The uuid package generates and inspects UUIDs.
+// Package uuid generates and inspects UUIDs.
 //
-// UUIDs are based on RFC 4122 and DCE 1.1: Authentication and Security Services.
+// 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/hash.go b/hash.go
index a0420c1..56db407 100644
--- a/hash.go
+++ b/hash.go
@@ -1,4 +1,4 @@
-// Copyright 2011 Google Inc.  All rights reserved.
+// 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.
 
@@ -10,13 +10,13 @@
 	"hash"
 )
 
-// Well known Name Space IDs and UUIDs
+// Well known namespace IDs and UUIDs
 var (
-	NameSpace_DNS  = Parse("6ba7b810-9dad-11d1-80b4-00c04fd430c8")
-	NameSpace_URL  = Parse("6ba7b811-9dad-11d1-80b4-00c04fd430c8")
-	NameSpace_OID  = Parse("6ba7b812-9dad-11d1-80b4-00c04fd430c8")
-	NameSpace_X500 = Parse("6ba7b814-9dad-11d1-80b4-00c04fd430c8")
-	NIL            = Parse("00000000-0000-0000-0000-000000000000")
+	NameSpace_DNS  = MustParse("6ba7b810-9dad-11d1-80b4-00c04fd430c8")
+	NameSpace_URL  = MustParse("6ba7b811-9dad-11d1-80b4-00c04fd430c8")
+	NameSpace_OID  = MustParse("6ba7b812-9dad-11d1-80b4-00c04fd430c8")
+	NameSpace_X500 = MustParse("6ba7b814-9dad-11d1-80b4-00c04fd430c8")
+	NIL            UUID // empty UUID, all zeros
 )
 
 // NewHash returns a new UUID derived from the hash of space concatenated with
@@ -26,18 +26,18 @@
 // NewMD5 and NewSHA1.
 func NewHash(h hash.Hash, space UUID, data []byte, version int) UUID {
 	h.Reset()
-	h.Write(space)
+	h.Write(space[:])
 	h.Write([]byte(data))
 	s := h.Sum(nil)
-	uuid := make([]byte, 16)
-	copy(uuid, s)
+	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.
+// supplied name space and data.  It is the same as calling:
 //
 //  NewHash(md5.New(), space, data, 3)
 func NewMD5(space UUID, data []byte) UUID {
@@ -45,7 +45,7 @@
 }
 
 // NewSHA1 returns a new SHA1 (Version 5) UUID based on the
-// supplied name space and data.
+// supplied name space and data.  It is the same as calling:
 //
 //  NewHash(sha1.New(), space, data, 5)
 func NewSHA1(space UUID, data []byte) UUID {
diff --git a/json_test.go b/json_test.go
index 2866b8d..4140cee 100644
--- a/json_test.go
+++ b/json_test.go
@@ -1,4 +1,4 @@
-// Copyright 2014 Google Inc.  All rights reserved.
+// 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.
 
@@ -10,7 +10,7 @@
 	"testing"
 )
 
-var testUUID = Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
+var testUUID = MustParse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
 
 func TestJSON(t *testing.T) {
 	type S struct {
@@ -35,9 +35,10 @@
 	x := &struct {
 		UUID UUID `json:"uuid"`
 	}{}
-	x.UUID = Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
-	if x.UUID == nil {
-		b.Fatal("invalid 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)
diff --git a/marshal.go b/marshal.go
new file mode 100644
index 0000000..435ca7c
--- /dev/null
+++ b/marshal.go
@@ -0,0 +1,42 @@
+// 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"
+	"unsafe"
+)
+
+// MarshalText implements encoding.TextMarshaler.
+func (u UUID) MarshalText() ([]byte, error) {
+	var js [36]byte
+	encodeHex(js[:], u)
+	return js[:], nil
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler.
+func (u *UUID) UnmarshalText(data []byte) error {
+	// See comment in ParseBytes why we do this.
+	// id, err := ParseBytes(data)
+        id, err := Parse(*(*string)(unsafe.Pointer(&data)))
+	if err == nil {
+		*u = id
+	}
+	return err
+}
+
+// MarshalBinary implements encoding.BinaryMarshaler.
+func (u UUID) MarshalBinary() ([]byte, error) {
+	return u[:], nil
+}
+
+// UnmarshalBinary implements encoding.BinaryUnmarshaler.
+func (u *UUID) UnmarshalBinary(data []byte) error {
+	if len(data) != 16 {
+		return fmt.Errorf("invalid UUID (got %d bytes)", len(data))
+	}
+	copy(u[:], data)
+	return nil
+}
diff --git a/node.go b/node.go
index 42d60da..5f0156a 100755
--- a/node.go
+++ b/node.go
@@ -1,4 +1,4 @@
-// Copyright 2011 Google Inc.  All rights reserved.
+// 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.
 
@@ -13,7 +13,8 @@
 	nodeMu     sync.Mutex
 	interfaces []net.Interface // cached list of interfaces
 	ifname     string          // name of interface being used
-	nodeID     []byte          // hardware for version 1 UUIDs
+	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
@@ -48,10 +49,9 @@
 
 	for _, ifs := range interfaces {
 		if len(ifs.HardwareAddr) >= 6 && (name == "" || name == ifs.Name) {
-			if setNodeID(ifs.HardwareAddr) {
-				ifname = ifs.Name
-				return true
-			}
+			copy(nodeID[:], ifs.HardwareAddr)
+			ifname = ifs.Name
+			return true
 		}
 	}
 
@@ -59,10 +59,7 @@
 	// does not specify a specific interface generate a random Node ID
 	// (section 4.1.6)
 	if name == "" {
-		if nodeID == nil {
-			nodeID = make([]byte, 6)
-		}
-		randomBits(nodeID)
+		randomBits(nodeID[:])
 		return true
 	}
 	return false
@@ -73,35 +70,24 @@
 func NodeID() []byte {
 	defer nodeMu.Unlock()
 	nodeMu.Lock()
-	if nodeID == nil {
+	if nodeID == zeroID {
 		setNodeInterface("")
 	}
-	nid := make([]byte, 6)
-	copy(nid, nodeID)
-	return nid
+	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 {
-	defer nodeMu.Unlock()
-	nodeMu.Lock()
-	if setNodeID(id) {
-		ifname = "user"
-		return true
-	}
-	return false
-}
-
-func setNodeID(id []byte) bool {
 	if len(id) < 6 {
 		return false
 	}
-	if nodeID == nil {
-		nodeID = make([]byte, 6)
-	}
-	copy(nodeID, id)
+	defer nodeMu.Unlock()
+	nodeMu.Lock()
+	copy(nodeID[:], id)
+	ifname = "user"
 	return true
 }
 
@@ -111,7 +97,7 @@
 	if len(uuid) != 16 {
 		return nil
 	}
-	node := make([]byte, 6)
-	copy(node, uuid[10:])
-	return node
+	var node [6]byte
+	copy(node[:], uuid[10:])
+	return node[:]
 }
diff --git a/seq_test.go b/seq_test.go
index 3b3d143..e340f9d 100644
--- a/seq_test.go
+++ b/seq_test.go
@@ -1,4 +1,4 @@
-// Copyright 2014 Google Inc.  All rights reserved.
+// 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.
 
@@ -42,7 +42,7 @@
 				select {
 				case <-done:
 					return
-				case ch <- NewUUID():
+				case ch <- MustNewUUID():
 				}
 			}
 		}()
diff --git a/sql.go b/sql.go
index d015bfd..528ad0d 100644
--- a/sql.go
+++ b/sql.go
@@ -1,4 +1,4 @@
-// Copyright 2015 Google Inc.  All rights reserved.
+// 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.
 
@@ -6,7 +6,6 @@
 
 import (
 	"database/sql/driver"
-	"errors"
 	"fmt"
 )
 
@@ -21,14 +20,14 @@
 			return nil
 		}
 
-		// see uuid.Parse for required string format
-		parsed := Parse(src.(string))
+		// see Parse for required string format
+		u, err := Parse(src.(string))
 
-		if parsed == nil {
-			return errors.New("Scan: invalid UUID format")
+		if err != nil {
+			return fmt.Errorf("Scan: %v", err)
 		}
 
-		*uuid = parsed
+		*uuid = u
 	case []byte:
 		b := src.([]byte)
 
@@ -39,17 +38,10 @@
 
 		// assumes a simple slice of bytes if 16 bytes
 		// otherwise attempts to parse
-		if len(b) == 16 {
-			*uuid = UUID(b)
-		} else {
-			u := Parse(string(b))
-
-			if u == nil {
-				return errors.New("Scan: invalid UUID format")
-			}
-
-			*uuid = u
+		if len(b) != 16 {
+			return uuid.Scan(string(b))
 		}
+		copy((*uuid)[:], b)
 
 	default:
 		return fmt.Errorf("Scan: unable to scan type %T into UUID", src)
diff --git a/sql_test.go b/sql_test.go
index 1030951..d53d58c 100644
--- a/sql_test.go
+++ b/sql_test.go
@@ -1,4 +1,4 @@
-// Copyright 2015 Google Inc.  All rights reserved.
+// 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.
 
@@ -11,10 +11,13 @@
 
 func TestScan(t *testing.T) {
 	var stringTest string = "f47ac10b-58cc-0372-8567-0e02b2c3d479"
-	var byteTest []byte = Parse(stringTest)
 	var badTypeTest int = 6
 	var invalidTest string = "f47ac10b-58cc-0372-8567-0e02b2c3d4"
 
+	byteTest := make([]byte, 16)
+	byteTestUUID := MustParse(stringTest)
+	copy(byteTest, byteTestUUID[:])
+
 	// sunny day tests
 
 	var uuid UUID
@@ -63,32 +66,35 @@
 
 	// empty tests
 
-	uuid = nil
+	uuid = UUID{}
 	var emptySlice []byte
 	err = (&uuid).Scan(emptySlice)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	if uuid != nil {
-		t.Error("UUID was not nil after scanning empty byte slice")
+	for _, v := range uuid {
+		if v != 0 {
+			t.Error("UUID was not nil after scanning empty byte slice")
+		}
 	}
 
-	uuid = nil
+	uuid = UUID{}
 	var emptyString string
 	err = (&uuid).Scan(emptyString)
 	if err != nil {
 		t.Fatal(err)
 	}
-
-	if uuid != nil {
-		t.Error("UUID was not nil after scanning empty string")
+	for _, v := range uuid {
+		if v != 0 {
+			t.Error("UUID was not nil after scanning empty byte slice")
+		}
 	}
 }
 
 func TestValue(t *testing.T) {
 	stringTest := "f47ac10b-58cc-0372-8567-0e02b2c3d479"
-	uuid := Parse(stringTest)
+	uuid := MustParse(stringTest)
 	val, _ := uuid.Value()
 	if val != stringTest {
 		t.Error("Value() did not return expected string")
diff --git a/time.go b/time.go
index eedf242..9cf8624 100755
--- a/time.go
+++ b/time.go
@@ -1,4 +1,4 @@
-// Copyright 2014 Google Inc.  All rights reserved.
+// 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.
 
@@ -70,10 +70,9 @@
 // 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 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) sequence is generated
-// for
+// 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()
@@ -109,24 +108,16 @@
 }
 
 // Time returns the time in 100s of nanoseconds since 15 Oct 1582 encoded in
-// uuid.  It returns false if uuid is not valid.  The time is only well defined
-// for version 1 and 2 UUIDs.
-func (uuid UUID) Time() (Time, bool) {
-	if len(uuid) != 16 {
-		return 0, false
-	}
+// 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), true
+	return Time(time)
 }
 
-// ClockSequence returns the clock sequence encoded in uuid.  It returns false
-// if uuid is not valid.  The clock sequence is only well defined for version 1
-// and 2 UUIDs.
-func (uuid UUID) ClockSequence() (int, bool) {
-	if len(uuid) != 16 {
-		return 0, false
-	}
-	return int(binary.BigEndian.Uint16(uuid[8:10])) & 0x3fff, true
+// 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
index fc8e052..7eaecde 100644
--- a/util.go
+++ b/util.go
@@ -1,4 +1,4 @@
-// Copyright 2011 Google Inc.  All rights reserved.
+// 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.
 
diff --git a/uuid.go b/uuid.go
index 82c9e7e..5fd83c0 100644
--- a/uuid.go
+++ b/uuid.go
@@ -1,40 +1,27 @@
-// Copyright 2011 Google Inc.  All rights reserved.
+// 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"
 	"crypto/rand"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"io"
 	"strings"
+	"unsafe"
 )
 
-// Array is a pass-by-value UUID that can be used as an effecient key in a map.
-type Array [16]byte
-
-// UUID converts uuid into a slice.
-func (uuid Array) UUID() UUID {
-	return uuid[:]
-}
-
-// String returns the string representation of uuid,
-// xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.
-func (uuid Array) String() string {
-	return uuid.UUID().String()
-}
-
 // A UUID is a 128 bit (16 byte) Universal Unique IDentifier as defined in RFC
 // 4122.
-type UUID []byte
+type UUID [16]byte
 
-// A Version represents a UUIDs version.
+// A Version represents a UUID's version.
 type Version byte
 
-// A Variant represents a UUIDs variant.
+// A Variant represents a UUID's variant.
 type Variant byte
 
 // Constants returned by Variant.
@@ -48,28 +35,23 @@
 
 var rander = rand.Reader // random function
 
-// New returns a new random (version 4) UUID as a string.  It is a convenience
-// function for NewRandom().String().
-func New() string {
-	return NewRandom().String()
-}
-
-// Parse decodes s into a UUID or returns nil.  Both the UUID form of
+// Parse decodes s into a UUID or returns an error.  Both the UUID form of
 // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx and
 // urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx are decoded.
-func Parse(s string) UUID {
-	if len(s) == 36+9 {
+func Parse(s string) (UUID, error) {
+	var uuid UUID
+	if len(s) != 36 {
+		if len(s) != 36+9 {
+			return uuid, fmt.Errorf("invalid UUID length: %d", len(s))
+		}
 		if strings.ToLower(s[:9]) != "urn:uuid:" {
-			return nil
+			return uuid, fmt.Errorf("invalid urn prefix: %q", s[:9])
 		}
 		s = s[9:]
-	} else if len(s) != 36 {
-		return nil
 	}
 	if s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-' {
-		return nil
+		return uuid, errors.New("invalid UUID format")
 	}
-	var uuid [16]byte
 	for i, x := range [16]int{
 		0, 2, 4, 6,
 		9, 11,
@@ -77,36 +59,35 @@
 		19, 21,
 		24, 26, 28, 30, 32, 34} {
 		if v, ok := xtob(s[x:]); !ok {
-			return nil
+			return uuid, errors.New("invalid UUID format")
 		} else {
 			uuid[i] = v
 		}
 	}
-	return uuid[:]
+	return uuid, nil
 }
 
-// Equal returns true if uuid1 and uuid2 are equal.
-func Equal(uuid1, uuid2 UUID) bool {
-	return bytes.Equal(uuid1, uuid2)
+// ParseBytes is like Parse, exect it parses a byte slice instead of a string.
+func ParseBytes(b []byte) (UUID, error) {
+	// Parsing a string is actually faster than parsing a byte slice as it
+	// is cheaper to slice a string.  Further, it is not safe to convert
+	// a string into a byte slice but the opposite direction is.  These
+	// stem from the fact that a byte slice is 3 words while a string
+	// is only 2 words.
+	return Parse(*(*string)(unsafe.Pointer(&b)))
 }
 
-// Array returns an array representation of uuid that can be used as a map key.
-// Array panics if uuid is not valid.
-func (uuid UUID) Array() Array {
-	if len(uuid) != 16 {
-		panic("invalid uuid")
+func MustParse(s string) UUID {
+	u, err := Parse(s)
+	if err != nil {
+		panic(err)
 	}
-	var a Array
-	copy(a[:], uuid)
-	return a
+	return u
 }
 
 // String returns the string form of uuid, xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
 // , or "" if uuid is invalid.
 func (uuid UUID) String() string {
-	if len(uuid) != 16 {
-		return ""
-	}
 	var buf [36]byte
 	encodeHex(buf[:], uuid)
 	return string(buf[:])
@@ -115,9 +96,6 @@
 // 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 {
-	if len(uuid) != 16 {
-		return ""
-	}
 	var buf [36 + 9]byte
 	copy(buf[:], "urn:uuid:")
 	encodeHex(buf[9:], uuid)
@@ -136,12 +114,8 @@
 	hex.Encode(dst[24:], uuid[10:])
 }
 
-// Variant returns the variant encoded in uuid.  It returns Invalid if
-// uuid is invalid.
+// Variant returns the variant encoded in uuid.
 func (uuid UUID) Variant() Variant {
-	if len(uuid) != 16 {
-		return Invalid
-	}
 	switch {
 	case (uuid[8] & 0xc0) == 0x80:
 		return RFC4122
@@ -154,13 +128,10 @@
 	}
 }
 
-// Version returns the version of uuid.  It returns false if uuid is not
+// Version returns the version of uuid.
 // valid.
-func (uuid UUID) Version() (Version, bool) {
-	if len(uuid) != 16 {
-		return 0, false
-	}
-	return Version(uuid[6] >> 4), true
+func (uuid UUID) Version() Version {
+	return Version(uuid[6] >> 4)
 }
 
 func (v Version) String() string {
diff --git a/uuid_test.go b/uuid_test.go
index cb1cd5c..cc961ad 100644
--- a/uuid_test.go
+++ b/uuid_test.go
@@ -1,4 +1,4 @@
-// Copyright 2011 Google Inc.  All rights reserved.
+// 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.
 
@@ -6,6 +6,7 @@
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"os"
 	"strings"
@@ -82,26 +83,41 @@
 }
 
 func testTest(t *testing.T, in string, tt test) {
-	uuid := Parse(in)
-	if ok := (uuid != nil); ok != tt.isuuid {
+	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 uuid == nil {
+	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 {
+	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)
 	}
 }
 
@@ -120,13 +136,13 @@
 func TestRandomUUID(t *testing.T) {
 	m := make(map[string]bool)
 	for x := 1; x < 32; x++ {
-		uuid := NewRandom()
+		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 {
+		if v := uuid.Version(); v != 4 {
 			t.Errorf("Random UUID of version %s", v)
 		}
 		if uuid.Variant() != RFC4122 {
@@ -136,19 +152,19 @@
 }
 
 func TestNew(t *testing.T) {
-	m := make(map[string]bool)
+	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 := Parse(s)
-		if uuid == nil {
-			t.Errorf("New returned %q which does not decode", s)
+		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 {
+		if v := uuid.Version(); v != 4 {
 			t.Errorf("Random UUID of version %s", v)
 		}
 		if uuid.Variant() != RFC4122 {
@@ -157,14 +173,6 @@
 	}
 }
 
-func clockSeq(t *testing.T, uuid UUID) int {
-	seq, ok := uuid.ClockSequence()
-	if !ok {
-		t.Fatalf("%s: invalid clock sequence", uuid)
-	}
-	return seq
-}
-
 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)
@@ -175,29 +183,44 @@
 	}
 
 	SetClockSequence(-1)
-	uuid1 := NewUUID()
-	uuid2 := NewUUID()
+	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 clockSeq(t, uuid1) != clockSeq(t, uuid2) {
-		t.Errorf("clock sequence %d != %d", clockSeq(t, uuid1), clockSeq(t, uuid2))
+	if s1, s2 := uuid1.ClockSequence(), uuid2.ClockSequence(); s1 != s2 {
+		t.Errorf("clock sequence %d != %d", s1, s2)
 	}
 
 	SetClockSequence(-1)
-	uuid2 = NewUUID()
+	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 clockSeq(t, uuid1) == clockSeq(t, uuid2) {
+	if uuid1.ClockSequence() == uuid2.ClockSequence() {
 		SetClockSequence(-1)
-		uuid2 = NewUUID()
+		uuid2, err = NewUUID()
+		if err != nil {
+			t.Fatalf("could not create UUID: %v", err)
+		}
 	}
-	if clockSeq(t, uuid1) == clockSeq(t, uuid2) {
-		t.Errorf("Duplicate clock sequence %d", clockSeq(t, uuid1))
+	if s1, s2 := uuid1.ClockSequence(), uuid2.ClockSequence(); s1 == s2 {
+		t.Errorf("Duplicate clock sequence %d", s1)
 	}
 
 	SetClockSequence(0x1234)
-	uuid1 = NewUUID()
-	if seq := clockSeq(t, uuid1); seq != 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)
 	}
 }
@@ -219,23 +242,32 @@
 		t.Errorf("%x: urn is %s, expected %s", data, v, urn)
 	}
 
-	uuid := Parse(text)
-	if !Equal(uuid, data) {
+	uuid, err := Parse(text)
+	if err != nil {
+		t.Errorf("Parse returned unexpected error %v", err)
+	}
+	if data != data {
 		t.Errorf("%s: decoded to %s, expected %s", text, uuid, data)
 	}
 }
 
 func TestVersion1(t *testing.T) {
-	uuid1 := NewUUID()
-	uuid2 := NewUUID()
+	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 Equal(uuid1, uuid2) {
+	if uuid1 == uuid2 {
 		t.Errorf("%s:duplicate uuid", uuid1)
 	}
-	if v, _ := uuid1.Version(); v != 1 {
+	if v := uuid1.Version(); v != 1 {
 		t.Errorf("%s: version %s expected 1", uuid1, v)
 	}
-	if v, _ := uuid2.Version(); v != 1 {
+	if v := uuid2.Version(); v != 1 {
 		t.Errorf("%s: version %s expected 1", uuid2, v)
 	}
 	n1 := uuid1.NodeID()
@@ -243,22 +275,10 @@
 	if !bytes.Equal(n1, n2) {
 		t.Errorf("Different nodes %x != %x", n1, n2)
 	}
-	t1, ok := uuid1.Time()
-	if !ok {
-		t.Errorf("%s: invalid time", uuid1)
-	}
-	t2, ok := uuid2.Time()
-	if !ok {
-		t.Errorf("%s: invalid time", uuid2)
-	}
-	q1, ok := uuid1.ClockSequence()
-	if !ok {
-		t.Errorf("%s: invalid clock sequence", uuid1)
-	}
-	q2, ok := uuid2.ClockSequence()
-	if !ok {
-		t.Errorf("%s: invalid clock sequence", uuid2)
-	}
+	t1 := uuid1.Time()
+	t2 := uuid2.Time()
+	q1 := uuid1.ClockSequence()
+	q2 := uuid2.ClockSequence()
 
 	switch {
 	case t1 == t2 && q1 == q2:
@@ -315,18 +335,17 @@
 func TestNodeAndTime(t *testing.T) {
 	// Time is February 5, 1998 12:30:23.136364800 AM GMT
 
-	uuid := Parse("7d444840-9dc0-11d1-b245-5ffdce74fad2")
+	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, ok := uuid.Time()
-	if ok {
-		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)
-		}
-	} else {
-		t.Errorf("%s: bad time", uuid)
+	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())
@@ -376,35 +395,30 @@
 	}
 }
 
-func testDCE(t *testing.T, name string, uuid UUID, domain Domain, id uint32) {
-	if uuid == nil {
-		t.Errorf("%s failed", name)
+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 {
+	if v := uuid.Version(); v != 2 {
 		t.Errorf("%s: %s: expected version 2, got %s", name, uuid, v)
 		return
 	}
-	if v, ok := uuid.Domain(); !ok || v != domain {
-		if !ok {
-			t.Errorf("%s: %d: Domain failed", name, uuid)
-		} else {
-			t.Errorf("%s: %s: expected domain %d, got %d", name, uuid, domain, v)
-		}
+	if v := uuid.Domain(); v != domain {
+		t.Errorf("%s: %s: expected domain %d, got %d", name, uuid, domain, v)
 	}
-	if v, ok := uuid.Id(); !ok || v != id {
-		if !ok {
-			t.Errorf("%s: %d: Id failed", name, uuid)
-		} else {
-			t.Errorf("%s: %s: expected id %d, got %d", name, uuid, id, 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) {
-	testDCE(t, "NewDCESecurity", NewDCESecurity(42, 12345678), 42, 12345678)
-	testDCE(t, "NewDCEPerson", NewDCEPerson(), Person, uint32(os.Getuid()))
-	testDCE(t, "NewDCEGroup", NewDCEGroup(), Group, uint32(os.Getgid()))
+	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{}
@@ -431,45 +445,86 @@
 	}
 }
 
-func TestUUID_Array(t *testing.T) {
-	expect := Array{
-		0xf4, 0x7a, 0xc1, 0x0b,
-		0x58, 0xcc,
-		0x03, 0x72,
-		0x85, 0x67,
-		0x0e, 0x02, 0xb2, 0xc3, 0xd4, 0x79,
-	}
-	uuid := Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
-	if uuid == nil {
-		t.Fatal("invalid uuid")
-	}
-	if uuid.Array() != expect {
-		t.Fatal("invalid array")
-	}
-}
-
-func TestArray_UUID(t *testing.T) {
-	array := Array{
-		0xf4, 0x7a, 0xc1, 0x0b,
-		0x58, 0xcc,
-		0x03, 0x72,
-		0x85, 0x67,
-		0x0e, 0x02, 0xb2, 0xc3, 0xd4, 0x79,
-	}
-	expect := Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
-	if expect == nil {
-		t.Fatal("invalid uuid")
-	}
-	if !bytes.Equal(array.UUID(), expect) {
-		t.Fatal("invalid uuid")
-	}
-}
+var asString = "f47ac10b-58cc-0372-8567-0e02b2c3d479"
+var asBytes = []byte(asString)
 
 func BenchmarkParse(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		uuid := Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
-		if uuid == nil {
-			b.Fatal("invalid uuid")
+		_, 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)
+		}
+	}
+}
+
+// parseBytesCopy is to benchmark not using unsafe.
+func parseBytesCopy(b []byte) (UUID, error) {
+	return Parse(string(b))
+}
+
+
+// xtobb converts the the first two hex bytes of x into a byte.
+func xtobb(x []byte) (byte, bool) {
+        b1 := xvalues[x[0]]
+        b2 := xvalues[x[1]]
+        return (b1 << 4) | b2, b1 != 255 && b2 != 255
+}
+
+// parseBytes is the same as Parse, but with byte slices.  It demonstrates
+// that it is faster to convert the byte slice into a string and then parse
+// than to parse the byte slice directly.
+func parseBytes(s []byte) (UUID, error) {
+	var uuid UUID
+	if len(s) != 36 {
+		if len(s) != 36+9 {
+			return uuid, fmt.Errorf("invalid UUID length: %d", len(s))
+		}
+		if !bytes.Equal(bytes.ToLower(s[:9]), []byte("urn:uuid:")) {
+			return uuid, fmt.Errorf("invalid urn prefix: %q", s[:9])
+		}
+		s = s[9:]
+	}
+	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} {
+		if v, ok := xtobb(s[x:]); !ok {
+			return uuid, errors.New("invalid UUID format")
+		} else {
+			uuid[i] = v
+		}
+	}
+	return uuid, nil
+}
+
+func BenchmarkParseBytesNative(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		_, err := parseBytes(asBytes)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkParseBytesCopy(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		_, err := parseBytesCopy(asBytes)
+		if err != nil {
+			b.Fatal(err)
 		}
 	}
 }
@@ -481,9 +536,9 @@
 }
 
 func BenchmarkUUID_String(b *testing.B) {
-	uuid := Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
-	if uuid == nil {
-		b.Fatal("invalid uuid")
+	uuid, err := Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
+	if err != nil {
+		b.Fatal(err)
 	}
 	for i := 0; i < b.N; i++ {
 		if uuid.String() == "" {
@@ -493,9 +548,9 @@
 }
 
 func BenchmarkUUID_URN(b *testing.B) {
-	uuid := Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
-	if uuid == nil {
-		b.Fatal("invalid uuid")
+	uuid, err := Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
+	if err != nil {
+		b.Fatal(err)
 	}
 	for i := 0; i < b.N; i++ {
 		if uuid.URN() == "" {
@@ -503,41 +558,3 @@
 		}
 	}
 }
-
-func BenchmarkUUID_Array(b *testing.B) {
-	expect := Array{
-		0xf4, 0x7a, 0xc1, 0x0b,
-		0x58, 0xcc,
-		0x03, 0x72,
-		0x85, 0x67,
-		0x0e, 0x02, 0xb2, 0xc3, 0xd4, 0x79,
-	}
-	uuid := Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
-	if uuid == nil {
-		b.Fatal("invalid uuid")
-	}
-	for i := 0; i < b.N; i++ {
-		if uuid.Array() != expect {
-			b.Fatal("invalid array")
-		}
-	}
-}
-
-func BenchmarkArray_UUID(b *testing.B) {
-	array := Array{
-		0xf4, 0x7a, 0xc1, 0x0b,
-		0x58, 0xcc,
-		0x03, 0x72,
-		0x85, 0x67,
-		0x0e, 0x02, 0xb2, 0xc3, 0xd4, 0x79,
-	}
-	expect := Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
-	if expect == nil {
-		b.Fatal("invalid uuid")
-	}
-	for i := 0; i < b.N; i++ {
-		if !bytes.Equal(array.UUID(), expect) {
-			b.Fatal("invalid uuid")
-		}
-	}
-}
diff --git a/version1.go b/version1.go
index 0127eac..17c018a 100644
--- a/version1.go
+++ b/version1.go
@@ -1,4 +1,4 @@
-// Copyright 2011 Google Inc.  All rights reserved.
+// 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.
 
@@ -14,18 +14,21 @@
 // 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("")
+//
+// In most cases, New should be used.
+func NewUUID() (UUID, error) {
+	nodeMu.Lock()
+	if nodeID == zeroID {
+		setNodeInterface("")
 	}
+	nodeMu.Unlock()
 
+	var uuid UUID
 	now, seq, err := GetTime()
 	if err != nil {
-		return nil
+		return uuid, err
 	}
 
-	uuid := make([]byte, 16)
-
 	time_low := uint32(now & 0xffffffff)
 	time_mid := uint16((now >> 32) & 0xffff)
 	time_hi := uint16((now >> 48) & 0x0fff)
@@ -35,7 +38,17 @@
 	binary.BigEndian.PutUint16(uuid[4:], time_mid)
 	binary.BigEndian.PutUint16(uuid[6:], time_hi)
 	binary.BigEndian.PutUint16(uuid[8:], seq)
-	copy(uuid[10:], nodeID)
+	copy(uuid[10:], nodeID[:])
 
+	return uuid, nil
+}
+
+// MustNewUUID returns the Verison 1 UUID from calling NewUUID, or panics
+// if NewUUID fails.
+func MustNewUUID() UUID {
+	uuid, err := NewUUID()
+	if err != nil {
+		panic(err)
+	}
 	return uuid
 }
diff --git a/version4.go b/version4.go
index b3d4a36..913d019 100644
--- a/version4.go
+++ b/version4.go
@@ -1,10 +1,10 @@
-// Copyright 2011 Google Inc.  All rights reserved.
+// 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
 
-// Random returns a Random (Version 4) UUID or panics.
+// New returns a Random (Version 4) UUID or panics.
 //
 // The strength of the UUIDs is based on the strength of the crypto/rand
 // package.
@@ -16,9 +16,9 @@
 //  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 {
-	uuid := make([]byte, 16)
-	randomBits([]byte(uuid))
+func New() UUID {
+	var uuid UUID
+	randomBits([]byte(uuid[:]))
 	uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4
 	uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10
 	return uuid