encoding/gob: support new generic interfaces in package encoding

R=r
CC=golang-dev
https://golang.org/cl/12681044

src/pkg/encoding/gob/debug.go

@@ -415,6 +415,16 @@ func (deb *debugger) typeDefinition(indent tab, id typeId) {
 		deb.delta(1)
 		com := deb.common()
 		wire.GobEncoderT = &gobEncoderType{com}
+	case 5: // BinaryMarshaler type, one field of {{Common}}
+		// Field number 0 is CommonType
+		deb.delta(1)
+		com := deb.common()
+		wire.BinaryMarshalerT = &gobEncoderType{com}
+	case 6: // TextMarshaler type, one field of {{Common}}
+		// Field number 0 is CommonType
+		deb.delta(1)
+		com := deb.common()
+		wire.TextMarshalerT = &gobEncoderType{com}
 	default:
 		errorf("bad field in type %d", fieldNum)
 	}

src/pkg/encoding/gob/decode.go

@@ -9,6 +9,7 @@ package gob
 
 import (
 	"bytes"
+	"encoding"
 	"errors"
 	"io"
 	"math"
@@ -767,15 +768,22 @@ func (dec *Decoder) ignoreInterface(state *decoderState) {
 
 // decodeGobDecoder decodes something implementing the GobDecoder interface.
 // The data is encoded as a byte slice.
-func (dec *Decoder) decodeGobDecoder(state *decoderState, v reflect.Value) {
+func (dec *Decoder) decodeGobDecoder(ut *userTypeInfo, state *decoderState, v reflect.Value) {
 	// Read the bytes for the value.
 	b := make([]byte, state.decodeUint())
 	_, err := state.b.Read(b)
 	if err != nil {
 		error_(err)
 	}
-	// We know it's a GobDecoder, so just call the method directly.
+	// We know it's one of these.
+	switch ut.externalDec {
+	case xGob:
 		err = v.Interface().(GobDecoder).GobDecode(b)
+	case xBinary:
+		err = v.Interface().(encoding.BinaryUnmarshaler).UnmarshalBinary(b)
+	case xText:
+		err = v.Interface().(encoding.TextUnmarshaler).UnmarshalText(b)
+	}
 	if err != nil {
 		error_(err)
 	}
@@ -825,9 +833,10 @@ var decIgnoreOpMap = map[typeId]decOp{
 func (dec *Decoder) decOpFor(wireId typeId, rt reflect.Type, name string, inProgress map[reflect.Type]*decOp) (*decOp, int) {
 	ut := userType(rt)
 	// If the type implements GobEncoder, we handle it without further processing.
-	if ut.isGobDecoder {
+	if ut.externalDec != 0 {
 		return dec.gobDecodeOpFor(ut)
 	}
+
 	// If this type is already in progress, it's a recursive type (e.g. map[string]*T).
 	// Return the pointer to the op we're already building.
 	if opPtr := inProgress[rt]; opPtr != nil {
@@ -954,7 +963,7 @@ func (dec *Decoder) decIgnoreOpFor(wireId typeId) decOp {
 				state.dec.ignoreStruct(*enginePtr)
 			}
 
-		case wire.GobEncoderT != nil:
+		case wire.GobEncoderT != nil, wire.BinaryMarshalerT != nil, wire.TextMarshalerT != nil:
 			op = func(i *decInstr, state *decoderState, p unsafe.Pointer) {
 				state.dec.ignoreGobDecoder(state)
 			}
@@ -993,7 +1002,7 @@ func (dec *Decoder) gobDecodeOpFor(ut *userTypeInfo) (*decOp, int) {
 		} else {
 			v = reflect.NewAt(rcvrType, p).Elem()
 		}
-		state.dec.decodeGobDecoder(state, v)
+		state.dec.decodeGobDecoder(ut, state, v)
 	}
 	return &op, int(ut.indir)
 
@@ -1010,12 +1019,18 @@ func (dec *Decoder) compatibleType(fr reflect.Type, fw typeId, inProgress map[re
 	inProgress[fr] = fw
 	ut := userType(fr)
 	wire, ok := dec.wireType[fw]
-	// If fr is a GobDecoder, the wire type must be GobEncoder.
-	// And if fr is not a GobDecoder, the wire type must not be either.
-	if ut.isGobDecoder != (ok && wire.GobEncoderT != nil) { // the parentheses look odd but are correct.
+	// If wire was encoded with an encoding method, fr must have that method.
+	// And if not, it must not.
+	// At most one of the booleans in ut is set.
+	// We could possibly relax this constraint in the future in order to
+	// choose the decoding method using the data in the wireType.
+	// The parentheses look odd but are correct.
+	if (ut.externalDec == xGob) != (ok && wire.GobEncoderT != nil) ||
+		(ut.externalDec == xBinary) != (ok && wire.BinaryMarshalerT != nil) ||
+		(ut.externalDec == xText) != (ok && wire.TextMarshalerT != nil) {
 		return false
 	}
-	if ut.isGobDecoder { // This test trumps all others.
+	if ut.externalDec != 0 { // This test trumps all others.
 		return true
 	}
 	switch t := ut.base; t.Kind() {
@@ -1114,8 +1129,7 @@ func (dec *Decoder) compileIgnoreSingle(remoteId typeId) (engine *decEngine, err
 func (dec *Decoder) compileDec(remoteId typeId, ut *userTypeInfo) (engine *decEngine, err error) {
 	rt := ut.base
 	srt := rt
-	if srt.Kind() != reflect.Struct ||
-		ut.isGobDecoder {
+	if srt.Kind() != reflect.Struct || ut.externalDec != 0 {
 		return dec.compileSingle(remoteId, ut)
 	}
 	var wireStruct *structType
@@ -1223,7 +1237,7 @@ func (dec *Decoder) decodeValue(wireId typeId, val reflect.Value) {
 		return
 	}
 	engine := *enginePtr
-	if st := base; st.Kind() == reflect.Struct && !ut.isGobDecoder {
+	if st := base; st.Kind() == reflect.Struct && ut.externalDec == 0 {
 		if engine.numInstr == 0 && st.NumField() > 0 && len(dec.wireType[wireId].StructT.Field) > 0 {
 			name := base.Name()
 			errorf("type mismatch: no fields matched compiling decoder for %s", name)

src/pkg/encoding/gob/doc.go

@@ -67,19 +67,28 @@ point values may be received into any floating point variable.  However,
 the destination variable must be able to represent the value or the decode
 operation will fail.
 
-Structs, arrays and slices are also supported.  Structs encode and
-decode only exported fields. Strings and arrays of bytes are supported
-with a special, efficient representation (see below).  When a slice
-is decoded, if the existing slice has capacity the slice will be
-extended in place; if not, a new array is allocated.  Regardless,
-the length of the resulting slice reports the number of elements
-decoded.
-
-Functions and channels cannot be sent in a gob.  Attempting
-to encode a value that contains one will fail.
-
-The rest of this comment documents the encoding, details that are not important
-for most users.  Details are presented bottom-up.
+Structs, arrays and slices are also supported. Structs encode and decode only
+exported fields. Strings and arrays of bytes are supported with a special,
+efficient representation (see below). When a slice is decoded, if the existing
+slice has capacity the slice will be extended in place; if not, a new array is
+allocated. Regardless, the length of the resulting slice reports the number of
+elements decoded.
+
+Functions and channels cannot be sent in a gob. Attempting to encode a value
+that contains one will fail.
+
+Gob can encode a value of any type implementing the GobEncoder,
+encoding.BinaryMarshaler, or encoding.TextMarshaler interfaces by calling the
+corresponding method, in that order of preference.
+
+Gob can decode a value of any type implementing the GobDecoder,
+encoding.BinaryUnmarshaler, or encoding.TextUnmarshaler interfaces by calling
+the corresponding method, again in that order of preference.
+
+Encoding Details
+
+This section documents the encoding, details that are not important for most
+users. Details are presented bottom-up.
 
 An unsigned integer is sent one of two ways.  If it is less than 128, it is sent
 as a byte with that value.  Otherwise it is sent as a minimal-length big-endian

src/pkg/encoding/gob/encode.go

@@ -6,6 +6,7 @@ package gob
 
 import (
 	"bytes"
+	"encoding"
 	"math"
 	"reflect"
 	"unsafe"
@@ -511,10 +512,20 @@ func isZero(val reflect.Value) bool {
 
 // encGobEncoder encodes a value that implements the GobEncoder interface.
 // The data is sent as a byte array.
-func (enc *Encoder) encodeGobEncoder(b *bytes.Buffer, v reflect.Value) {
+func (enc *Encoder) encodeGobEncoder(b *bytes.Buffer, ut *userTypeInfo, v reflect.Value) {
 	// TODO: should we catch panics from the called method?
-	// We know it's a GobEncoder, so just call the method directly.
-	data, err := v.Interface().(GobEncoder).GobEncode()
+
+	var data []byte
+	var err error
+	// We know it's one of these.
+	switch ut.externalEnc {
+	case xGob:
+		data, err = v.Interface().(GobEncoder).GobEncode()
+	case xBinary:
+		data, err = v.Interface().(encoding.BinaryMarshaler).MarshalBinary()
+	case xText:
+		data, err = v.Interface().(encoding.TextMarshaler).MarshalText()
+	}
 	if err != nil {
 		error_(err)
 	}
@@ -550,7 +561,7 @@ var encOpTable = [...]encOp{
 func (enc *Encoder) encOpFor(rt reflect.Type, inProgress map[reflect.Type]*encOp) (*encOp, int) {
 	ut := userType(rt)
 	// If the type implements GobEncoder, we handle it without further processing.
-	if ut.isGobEncoder {
+	if ut.externalEnc != 0 {
 		return enc.gobEncodeOpFor(ut)
 	}
 	// If this type is already in progress, it's a recursive type (e.g. map[string]*T).
@@ -661,7 +672,7 @@ func (enc *Encoder) gobEncodeOpFor(ut *userTypeInfo) (*encOp, int) {
 			return
 		}
 		state.update(i)
-		state.enc.encodeGobEncoder(state.b, v)
+		state.enc.encodeGobEncoder(state.b, ut, v)
 	}
 	return &op, int(ut.encIndir) // encIndir: op will get called with p == address of receiver.
 }
@@ -672,10 +683,10 @@ func (enc *Encoder) compileEnc(ut *userTypeInfo) *encEngine {
 	engine := new(encEngine)
 	seen := make(map[reflect.Type]*encOp)
 	rt := ut.base
-	if ut.isGobEncoder {
+	if ut.externalEnc != 0 {
 		rt = ut.user
 	}
-	if !ut.isGobEncoder &&
+	if ut.externalEnc == 0 &&
 		srt.Kind() == reflect.Struct {
 		for fieldNum, wireFieldNum := 0, 0; fieldNum < srt.NumField(); fieldNum++ {
 			f := srt.Field(fieldNum)
@@ -736,13 +747,13 @@ func (enc *Encoder) encode(b *bytes.Buffer, value reflect.Value, ut *userTypeInf
 	defer catchError(&enc.err)
 	engine := enc.lockAndGetEncEngine(ut)
 	indir := ut.indir
-	if ut.isGobEncoder {
+	if ut.externalEnc != 0 {
 		indir = int(ut.encIndir)
 	}
 	for i := 0; i < indir; i++ {
 		value = reflect.Indirect(value)
 	}
-	if !ut.isGobEncoder && value.Type().Kind() == reflect.Struct {
+	if ut.externalEnc == 0 && value.Type().Kind() == reflect.Struct {
 		enc.encodeStruct(b, engine, unsafeAddr(value))
 	} else {
 		enc.encodeSingle(b, engine, unsafeAddr(value))

src/pkg/encoding/gob/encoder.go

@@ -135,7 +135,7 @@ func (enc *Encoder) sendActualType(w io.Writer, state *encoderState, ut *userTyp
 // sendType sends the type info to the other side, if necessary.
 func (enc *Encoder) sendType(w io.Writer, state *encoderState, origt reflect.Type) (sent bool) {
 	ut := userType(origt)
-	if ut.isGobEncoder {
+	if ut.externalEnc != 0 {
 		// The rules are different: regardless of the underlying type's representation,
 		// we need to tell the other side that the base type is a GobEncoder.
 		return enc.sendActualType(w, state, ut, ut.base)
@@ -184,7 +184,7 @@ func (enc *Encoder) sendTypeDescriptor(w io.Writer, state *encoderState, ut *use
 	// Make sure the type is known to the other side.
 	// First, have we already sent this type?
 	rt := ut.base
-	if ut.isGobEncoder {
+	if ut.externalEnc != 0 {
 		rt = ut.user
 	}
 	if _, alreadySent := enc.sent[rt]; !alreadySent {

src/pkg/encoding/gob/gobencdec_test.go

@@ -34,6 +34,14 @@ type Gobber int
 
 type ValueGobber string // encodes with a value, decodes with a pointer.
 
+type BinaryGobber int
+
+type BinaryValueGobber string
+
+type TextGobber int
+
+type TextValueGobber string
+
 // The relevant methods
 
 func (g *ByteStruct) GobEncode() ([]byte, error) {
@@ -101,6 +109,24 @@ func (g *Gobber) GobDecode(data []byte) error {
 	return err
 }
 
+func (g *BinaryGobber) MarshalBinary() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%d", *g)), nil
+}
+
+func (g *BinaryGobber) UnmarshalBinary(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%d", (*int)(g))
+	return err
+}
+
+func (g *TextGobber) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%d", *g)), nil
+}
+
+func (g *TextGobber) UnmarshalText(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%d", (*int)(g))
+	return err
+}
+
 func (v ValueGobber) GobEncode() ([]byte, error) {
 	return []byte(fmt.Sprintf("VALUE=%s", v)), nil
 }
@@ -110,6 +136,24 @@ func (v *ValueGobber) GobDecode(data []byte) error {
 	return err
 }
 
+func (v BinaryValueGobber) MarshalBinary() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%s", v)), nil
+}
+
+func (v *BinaryValueGobber) UnmarshalBinary(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%s", (*string)(v))
+	return err
+}
+
+func (v TextValueGobber) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%s", v)), nil
+}
+
+func (v *TextValueGobber) UnmarshalText(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%s", (*string)(v))
+	return err
+}
+
 // Structs that include GobEncodable fields.
 
 type GobTest0 struct {
@@ -130,28 +174,42 @@ type GobTest2 struct {
 type GobTest3 struct {
 	X int // guarantee we have  something in common with GobTest*
 	G *Gobber
+	B *BinaryGobber
+	T *TextGobber
 }
 
 type GobTest4 struct {
 	X  int // guarantee we have  something in common with GobTest*
 	V  ValueGobber
+	BV BinaryValueGobber
+	TV TextValueGobber
 }
 
 type GobTest5 struct {
 	X  int // guarantee we have  something in common with GobTest*
 	V  *ValueGobber
+	BV *BinaryValueGobber
+	TV *TextValueGobber
 }
 
 type GobTest6 struct {
 	X  int // guarantee we have  something in common with GobTest*
 	V  ValueGobber
 	W  *ValueGobber
+	BV BinaryValueGobber
+	BW *BinaryValueGobber
+	TV TextValueGobber
+	TW *TextValueGobber
 }
 
 type GobTest7 struct {
 	X  int // guarantee we have  something in common with GobTest*
 	V  *ValueGobber
 	W  ValueGobber
+	BV *BinaryValueGobber
+	BW BinaryValueGobber
+	TV *TextValueGobber
+	TW TextValueGobber
 }
 
 type GobTestIgnoreEncoder struct {
@@ -198,7 +256,9 @@ func TestGobEncoderField(t *testing.T) {
 	// Now a field that's not a structure.
 	b.Reset()
 	gobber := Gobber(23)
-	err = enc.Encode(GobTest3{17, &gobber})
+	bgobber := BinaryGobber(24)
+	tgobber := TextGobber(25)
+	err = enc.Encode(GobTest3{17, &gobber, &bgobber, &tgobber})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
@@ -207,7 +267,7 @@ func TestGobEncoderField(t *testing.T) {
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
-	if *y.G != 23 {
+	if *y.G != 23 || *y.B != 24 || *y.T != 25 {
 		t.Errorf("expected '23 got %d", *y.G)
 	}
 }
@@ -357,7 +417,7 @@ func TestGobEncoderValueEncoder(t *testing.T) {
 	// first, string in field to byte in field
 	b := new(bytes.Buffer)
 	enc := NewEncoder(b)
-	err := enc.Encode(GobTest4{17, ValueGobber("hello")})
+	err := enc.Encode(GobTest4{17, ValueGobber("hello"), BinaryValueGobber("Καλημέρα"), TextValueGobber("こんにちは")})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
@@ -367,7 +427,7 @@ func TestGobEncoderValueEncoder(t *testing.T) {
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
-	if *x.V != "hello" {
+	if *x.V != "hello" || *x.BV != "Καλημέρα" || *x.TV != "こんにちは" {
 		t.Errorf("expected `hello` got %s", x.V)
 	}
 }
@@ -377,13 +437,17 @@ func TestGobEncoderValueEncoder(t *testing.T) {
 func TestGobEncoderValueThenPointer(t *testing.T) {
 	v := ValueGobber("forty-two")
 	w := ValueGobber("six-by-nine")
+	bv := BinaryValueGobber("1nanocentury")
+	bw := BinaryValueGobber("πseconds")
+	tv := TextValueGobber("gravitationalacceleration")
+	tw := TextValueGobber("π²ft/s²")
 
 	// this was a bug: encoding a GobEncoder by value before a GobEncoder
 	// pointer would cause duplicate type definitions to be sent.
 
 	b := new(bytes.Buffer)
 	enc := NewEncoder(b)
-	if err := enc.Encode(GobTest6{42, v, &w}); err != nil {
+	if err := enc.Encode(GobTest6{42, v, &w, bv, &bw, tv, &tw}); err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
@@ -391,6 +455,7 @@ func TestGobEncoderValueThenPointer(t *testing.T) {
 	if err := dec.Decode(x); err != nil {
 		t.Fatal("decode error:", err)
 	}
+
 	if got, want := x.V, v; got != want {
 		t.Errorf("v = %q, want %q", got, want)
 	}
@@ -399,6 +464,24 @@ func TestGobEncoderValueThenPointer(t *testing.T) {
 	} else if *got != want {
 		t.Errorf("w = %q, want %q", *got, want)
 	}
+
+	if got, want := x.BV, bv; got != want {
+		t.Errorf("bv = %q, want %q", got, want)
+	}
+	if got, want := x.BW, bw; got == nil {
+		t.Errorf("bw = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("bw = %q, want %q", *got, want)
+	}
+
+	if got, want := x.TV, tv; got != want {
+		t.Errorf("tv = %q, want %q", got, want)
+	}
+	if got, want := x.TW, tw; got == nil {
+		t.Errorf("tw = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("tw = %q, want %q", *got, want)
+	}
 }
 
 // Test that we can use a pointer then a value type of a GobEncoder
@@ -406,10 +489,14 @@ func TestGobEncoderValueThenPointer(t *testing.T) {
 func TestGobEncoderPointerThenValue(t *testing.T) {
 	v := ValueGobber("forty-two")
 	w := ValueGobber("six-by-nine")
+	bv := BinaryValueGobber("1nanocentury")
+	bw := BinaryValueGobber("πseconds")
+	tv := TextValueGobber("gravitationalacceleration")
+	tw := TextValueGobber("π²ft/s²")
 
 	b := new(bytes.Buffer)
 	enc := NewEncoder(b)
-	if err := enc.Encode(GobTest7{42, &v, w}); err != nil {
+	if err := enc.Encode(GobTest7{42, &v, w, &bv, bw, &tv, tw}); err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
@@ -417,14 +504,33 @@ func TestGobEncoderPointerThenValue(t *testing.T) {
 	if err := dec.Decode(x); err != nil {
 		t.Fatal("decode error:", err)
 	}
+
 	if got, want := x.V, v; got == nil {
 		t.Errorf("v = nil, want %q", want)
 	} else if *got != want {
-		t.Errorf("v = %q, want %q", got, want)
+		t.Errorf("v = %q, want %q", *got, want)
 	}
 	if got, want := x.W, w; got != want {
 		t.Errorf("w = %q, want %q", got, want)
 	}
+
+	if got, want := x.BV, bv; got == nil {
+		t.Errorf("bv = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("bv = %q, want %q", *got, want)
+	}
+	if got, want := x.BW, bw; got != want {
+		t.Errorf("bw = %q, want %q", got, want)
+	}
+
+	if got, want := x.TV, tv; got == nil {
+		t.Errorf("tv = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("tv = %q, want %q", *got, want)
+	}
+	if got, want := x.TW, tw; got != want {
+		t.Errorf("tw = %q, want %q", got, want)
+	}
 }
 
 func TestGobEncoderFieldTypeError(t *testing.T) {
@@ -521,7 +627,9 @@ func TestGobEncoderIgnoreNonStructField(t *testing.T) {
 	// First a field that's a structure.
 	enc := NewEncoder(b)
 	gobber := Gobber(23)
-	err := enc.Encode(GobTest3{17, &gobber})
+	bgobber := BinaryGobber(24)
+	tgobber := TextGobber(25)
+	err := enc.Encode(GobTest3{17, &gobber, &bgobber, &tgobber})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}

src/pkg/encoding/gob/type.go

@@ -5,6 +5,7 @@
 package gob
 
 import (
+	"encoding"
 	"errors"
 	"fmt"
 	"os"
@@ -21,12 +22,19 @@ type userTypeInfo struct {
 	user        reflect.Type // the type the user handed us
 	base        reflect.Type // the base type after all indirections
 	indir       int          // number of indirections to reach the base type
-	isGobEncoder bool         // does the type implement GobEncoder?
-	isGobDecoder bool         // does the type implement GobDecoder?
+	externalEnc int          // xGob, xBinary, or xText
+	externalDec int          // xGob, xBinary or xText
 	encIndir    int8         // number of indirections to reach the receiver type; may be negative
 	decIndir    int8         // number of indirections to reach the receiver type; may be negative
 }
 
+// externalEncoding bits
+const (
+	xGob    = 1 + iota // GobEncoder or GobDecoder
+	xBinary            // encoding.BinaryMarshaler or encoding.BinaryUnmarshaler
+	xText              // encoding.TextMarshaler or encoding.TextUnmarshaler
+)
+
 var (
 	// Protected by an RWMutex because we read it a lot and write
 	// it only when we see a new type, typically when compiling.
@@ -75,8 +83,23 @@ func validUserType(rt reflect.Type) (ut *userTypeInfo, err error) {
 		}
 		ut.indir++
 	}
-	ut.isGobEncoder, ut.encIndir = implementsInterface(ut.user, gobEncoderInterfaceType)
-	ut.isGobDecoder, ut.decIndir = implementsInterface(ut.user, gobDecoderInterfaceType)
+
+	if ok, indir := implementsInterface(ut.user, gobEncoderInterfaceType); ok {
+		ut.externalEnc, ut.encIndir = xGob, indir
+	} else if ok, indir := implementsInterface(ut.user, binaryMarshalerInterfaceType); ok {
+		ut.externalEnc, ut.encIndir = xBinary, indir
+	} else if ok, indir := implementsInterface(ut.user, textMarshalerInterfaceType); ok {
+		ut.externalEnc, ut.encIndir = xText, indir
+	}
+
+	if ok, indir := implementsInterface(ut.user, gobDecoderInterfaceType); ok {
+		ut.externalDec, ut.decIndir = xGob, indir
+	} else if ok, indir := implementsInterface(ut.user, binaryUnmarshalerInterfaceType); ok {
+		ut.externalDec, ut.decIndir = xBinary, indir
+	} else if ok, indir := implementsInterface(ut.user, textUnmarshalerInterfaceType); ok {
+		ut.externalDec, ut.decIndir = xText, indir
+	}
+
 	userTypeCache[rt] = ut
 	return
 }
@@ -84,6 +107,10 @@ func validUserType(rt reflect.Type) (ut *userTypeInfo, err error) {
 var (
 	gobEncoderInterfaceType        = reflect.TypeOf((*GobEncoder)(nil)).Elem()
 	gobDecoderInterfaceType        = reflect.TypeOf((*GobDecoder)(nil)).Elem()
+	binaryMarshalerInterfaceType   = reflect.TypeOf((*encoding.BinaryMarshaler)(nil)).Elem()
+	binaryUnmarshalerInterfaceType = reflect.TypeOf((*encoding.BinaryUnmarshaler)(nil)).Elem()
+	textMarshalerInterfaceType     = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
+	textUnmarshalerInterfaceType   = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
 )
 
 // implementsInterface reports whether the type implements the
@@ -412,7 +439,7 @@ func newStructType(name string) *structType {
 // works through typeIds and userTypeInfos alone.
 func newTypeObject(name string, ut *userTypeInfo, rt reflect.Type) (gobType, error) {
 	// Does this type implement GobEncoder?
-	if ut.isGobEncoder {
+	if ut.externalEnc != 0 {
 		return newGobEncoderType(name), nil
 	}
 	var err error
@@ -598,6 +625,8 @@ type wireType struct {
 	StructT          *structType
 	MapT             *mapType
 	GobEncoderT      *gobEncoderType
+	BinaryMarshalerT *gobEncoderType
+	TextMarshalerT   *gobEncoderType
 }
 
 func (w *wireType) string() string {
@@ -616,6 +645,10 @@ func (w *wireType) string() string {
 		return w.MapT.Name
 	case w.GobEncoderT != nil:
 		return w.GobEncoderT.Name
+	case w.BinaryMarshalerT != nil:
+		return w.BinaryMarshalerT.Name
+	case w.TextMarshalerT != nil:
+		return w.TextMarshalerT.Name
 	}
 	return unknown
 }
@@ -631,7 +664,7 @@ var typeInfoMap = make(map[reflect.Type]*typeInfo) // protected by typeLock
 // typeLock must be held.
 func getTypeInfo(ut *userTypeInfo) (*typeInfo, error) {
 	rt := ut.base
-	if ut.isGobEncoder {
+	if ut.externalEnc != 0 {
 		// We want the user type, not the base type.
 		rt = ut.user
 	}
@@ -646,12 +679,20 @@ func getTypeInfo(ut *userTypeInfo) (*typeInfo, error) {
 	}
 	info.id = gt.id()
 
-	if ut.isGobEncoder {
+	if ut.externalEnc != 0 {
 		userType, err := getType(rt.Name(), ut, rt)
 		if err != nil {
 			return nil, err
 		}
-		info.wire = &wireType{GobEncoderT: userType.id().gobType().(*gobEncoderType)}
+		gt := userType.id().gobType().(*gobEncoderType)
+		switch ut.externalEnc {
+		case xGob:
+			info.wire = &wireType{GobEncoderT: gt}
+		case xBinary:
+			info.wire = &wireType{BinaryMarshalerT: gt}
+		case xText:
+			info.wire = &wireType{TextMarshalerT: gt}
+		}
 		typeInfoMap[ut.user] = info
 		return info, nil
 	}