Imported Upstream version 1.2upstream/1.2

11 files changed, 969 insertions, 207 deletions

diff --git a/src/pkg/encoding/json/decode.go b/src/pkg/encoding/json/decode.go
index 62ac294b8..458fb39ec 100644
--- a/src/pkg/encoding/json/decode.go
+++ b/src/pkg/encoding/json/decode.go
@@ -8,6 +8,7 @@
 package json
 
 import (
+	"encoding"
 	"encoding/base64"
 	"errors"
 	"fmt"
@@ -37,9 +38,7 @@ import (
 // keys to the keys used by Marshal (either the struct field name or its tag),
 // preferring an exact match but also accepting a case-insensitive match.
 //
-// To unmarshal JSON into an interface value, Unmarshal unmarshals
-// the JSON into the concrete value contained in the interface value.
-// If the interface value is nil, that is, has no concrete value stored in it,
+// To unmarshal JSON into an interface value,
 // Unmarshal stores one of these in the interface value:
 //
 //	bool, for JSON booleans
@@ -293,7 +292,7 @@ func (d *decodeState) value(v reflect.Value) {
 // until it gets to a non-pointer.
 // if it encounters an Unmarshaler, indirect stops and returns that.
 // if decodingNull is true, indirect stops at the last pointer so it can be set to nil.
-func (d *decodeState) indirect(v reflect.Value, decodingNull bool) (Unmarshaler, reflect.Value) {
+func (d *decodeState) indirect(v reflect.Value, decodingNull bool) (Unmarshaler, encoding.TextUnmarshaler, reflect.Value) {
 	// If v is a named type and is addressable,
 	// start with its address, so that if the type has pointer methods,
 	// we find them.
@@ -322,28 +321,38 @@ func (d *decodeState) indirect(v reflect.Value, decodingNull bool) (Unmarshaler,
 			v.Set(reflect.New(v.Type().Elem()))
 		}
 		if v.Type().NumMethod() > 0 {
-			if unmarshaler, ok := v.Interface().(Unmarshaler); ok {
-				return unmarshaler, reflect.Value{}
+			if u, ok := v.Interface().(Unmarshaler); ok {
+				return u, nil, reflect.Value{}
+			}
+			if u, ok := v.Interface().(encoding.TextUnmarshaler); ok {
+				return nil, u, reflect.Value{}
 			}
 		}
 		v = v.Elem()
 	}
-	return nil, v
+	return nil, nil, v
 }
 
 // array consumes an array from d.data[d.off-1:], decoding into the value v.
 // the first byte of the array ('[') has been read already.
 func (d *decodeState) array(v reflect.Value) {
 	// Check for unmarshaler.
-	unmarshaler, pv := d.indirect(v, false)
-	if unmarshaler != nil {
+	u, ut, pv := d.indirect(v, false)
+	if u != nil {
 		d.off--
-		err := unmarshaler.UnmarshalJSON(d.next())
+		err := u.UnmarshalJSON(d.next())
 		if err != nil {
 			d.error(err)
 		}
 		return
 	}
+	if ut != nil {
+		d.saveError(&UnmarshalTypeError{"array", v.Type()})
+		d.off--
+		d.next()
+		return
+	}
+
 	v = pv
 
 	// Check type of target.
@@ -434,15 +443,21 @@ func (d *decodeState) array(v reflect.Value) {
 // the first byte of the object ('{') has been read already.
 func (d *decodeState) object(v reflect.Value) {
 	// Check for unmarshaler.
-	unmarshaler, pv := d.indirect(v, false)
-	if unmarshaler != nil {
+	u, ut, pv := d.indirect(v, false)
+	if u != nil {
 		d.off--
-		err := unmarshaler.UnmarshalJSON(d.next())
+		err := u.UnmarshalJSON(d.next())
 		if err != nil {
 			d.error(err)
 		}
 		return
 	}
+	if ut != nil {
+		d.saveError(&UnmarshalTypeError{"object", v.Type()})
+		d.off--
+		d.next() // skip over { } in input
+		return
+	}
 	v = pv
 
 	// Decoding into nil interface?  Switch to non-reflect code.
@@ -611,14 +626,37 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 		return
 	}
 	wantptr := item[0] == 'n' // null
-	unmarshaler, pv := d.indirect(v, wantptr)
-	if unmarshaler != nil {
-		err := unmarshaler.UnmarshalJSON(item)
+	u, ut, pv := d.indirect(v, wantptr)
+	if u != nil {
+		err := u.UnmarshalJSON(item)
+		if err != nil {
+			d.error(err)
+		}
+		return
+	}
+	if ut != nil {
+		if item[0] != '"' {
+			if fromQuoted {
+				d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			} else {
+				d.saveError(&UnmarshalTypeError{"string", v.Type()})
+			}
+		}
+		s, ok := unquoteBytes(item)
+		if !ok {
+			if fromQuoted {
+				d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			} else {
+				d.error(errPhase)
+			}
+		}
+		err := ut.UnmarshalText(s)
 		if err != nil {
 			d.error(err)
 		}
 		return
 	}
+
 	v = pv
 
 	switch c := item[0]; c {
diff --git a/src/pkg/encoding/json/decode_test.go b/src/pkg/encoding/json/decode_test.go
index f845f69ab..22c5f89f7 100644
--- a/src/pkg/encoding/json/decode_test.go
+++ b/src/pkg/encoding/json/decode_test.go
@@ -6,6 +6,7 @@ package json
 
 import (
 	"bytes"
+	"encoding"
 	"fmt"
 	"image"
 	"reflect"
@@ -50,8 +51,6 @@ type tx struct {
 	x int
 }
 
-var txType = reflect.TypeOf((*tx)(nil)).Elem()
-
 // A type that can unmarshal itself.
 
 type unmarshaler struct {
@@ -59,7 +58,7 @@ type unmarshaler struct {
 }
 
 func (u *unmarshaler) UnmarshalJSON(b []byte) error {
-	*u = unmarshaler{true} // All we need to see that UnmarshalJson is called.
+	*u = unmarshaler{true} // All we need to see that UnmarshalJSON is called.
 	return nil
 }
 
@@ -67,6 +66,26 @@ type ustruct struct {
 	M unmarshaler
 }
 
+type unmarshalerText struct {
+	T bool
+}
+
+// needed for re-marshaling tests
+func (u *unmarshalerText) MarshalText() ([]byte, error) {
+	return []byte(""), nil
+}
+
+func (u *unmarshalerText) UnmarshalText(b []byte) error {
+	*u = unmarshalerText{true} // All we need to see that UnmarshalText is called.
+	return nil
+}
+
+var _ encoding.TextUnmarshaler = (*unmarshalerText)(nil)
+
+type ustructText struct {
+	M unmarshalerText
+}
+
 var (
 	um0, um1 unmarshaler // target2 of unmarshaling
 	ump      = &um1
@@ -74,6 +93,13 @@ var (
 	umslice  = []unmarshaler{{true}}
 	umslicep = new([]unmarshaler)
 	umstruct = ustruct{unmarshaler{true}}
+
+	um0T, um1T unmarshalerText // target2 of unmarshaling
+	umpT       = &um1T
+	umtrueT    = unmarshalerText{true}
+	umsliceT   = []unmarshalerText{{true}}
+	umslicepT  = new([]unmarshalerText)
+	umstructT  = ustructText{unmarshalerText{true}}
 )
 
 // Test data structures for anonymous fields.
@@ -184,6 +210,12 @@ type Ambig struct {
 	Second int `json:"Hello"`
 }
 
+type XYZ struct {
+	X interface{}
+	Y interface{}
+	Z interface{}
+}
+
 var unmarshalTests = []unmarshalTest{
 	// basic types
 	{in: `true`, ptr: new(bool), out: true},
@@ -263,6 +295,13 @@ var unmarshalTests = []unmarshalTest{
 	{in: `[{"T":false}]`, ptr: &umslicep, out: &umslice},
 	{in: `{"M":{"T":false}}`, ptr: &umstruct, out: umstruct},
 
+	// UnmarshalText interface test
+	{in: `"X"`, ptr: &um0T, out: umtrueT}, // use "false" so test will fail if custom unmarshaler is not called
+	{in: `"X"`, ptr: &umpT, out: &umtrueT},
+	{in: `["X"]`, ptr: &umsliceT, out: umsliceT},
+	{in: `["X"]`, ptr: &umslicepT, out: &umsliceT},
+	{in: `{"M":"X"}`, ptr: &umstructT, out: umstructT},
+
 	{
 		in: `{
 			"Level0": 1,
@@ -391,17 +430,23 @@ func TestMarshal(t *testing.T) {
 	}
 }
 
+var badUTF8 = []struct {
+	in, out string
+}{
+	{"hello\xffworld", `"hello\ufffdworld"`},
+	{"", `""`},
+	{"\xff", `"\ufffd"`},
+	{"\xff\xff", `"\ufffd\ufffd"`},
+	{"a\xffb", `"a\ufffdb"`},
+	{"\xe6\x97\xa5\xe6\x9c\xac\xff\xaa\x9e", `"日本\ufffd\ufffd\ufffd"`},
+}
+
 func TestMarshalBadUTF8(t *testing.T) {
-	s := "hello\xffworld"
-	b, err := Marshal(s)
-	if err == nil {
-		t.Fatal("Marshal bad UTF8: no error")
-	}
-	if len(b) != 0 {
-		t.Fatal("Marshal returned data")
-	}
-	if _, ok := err.(*InvalidUTF8Error); !ok {
-		t.Fatalf("Marshal did not return InvalidUTF8Error: %T %v", err, err)
+	for _, tt := range badUTF8 {
+		b, err := Marshal(tt.in)
+		if string(b) != tt.out || err != nil {
+			t.Errorf("Marshal(%q) = %#q, %v, want %#q, nil", tt.in, b, err, tt.out)
+		}
 	}
 }
 
@@ -417,6 +462,45 @@ func TestMarshalNumberZeroVal(t *testing.T) {
 	}
 }
 
+func TestMarshalEmbeds(t *testing.T) {
+	top := &Top{
+		Level0: 1,
+		Embed0: Embed0{
+			Level1b: 2,
+			Level1c: 3,
+		},
+		Embed0a: &Embed0a{
+			Level1a: 5,
+			Level1b: 6,
+		},
+		Embed0b: &Embed0b{
+			Level1a: 8,
+			Level1b: 9,
+			Level1c: 10,
+			Level1d: 11,
+			Level1e: 12,
+		},
+		Loop: Loop{
+			Loop1: 13,
+			Loop2: 14,
+		},
+		Embed0p: Embed0p{
+			Point: image.Point{X: 15, Y: 16},
+		},
+		Embed0q: Embed0q{
+			Point: Point{Z: 17},
+		},
+	}
+	b, err := Marshal(top)
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "{\"Level0\":1,\"Level1b\":2,\"Level1c\":3,\"Level1a\":5,\"LEVEL1B\":6,\"e\":{\"Level1a\":8,\"Level1b\":9,\"Level1c\":10,\"Level1d\":11,\"x\":12},\"Loop1\":13,\"Loop2\":14,\"X\":15,\"Y\":16,\"Z\":17}"
+	if string(b) != want {
+		t.Errorf("Wrong marshal result.\n got: %q\nwant: %q", b, want)
+	}
+}
+
 func TestUnmarshal(t *testing.T) {
 	for i, tt := range unmarshalTests {
 		var scan scanner
@@ -432,7 +516,7 @@ func TestUnmarshal(t *testing.T) {
 		}
 		// v = new(right-type)
 		v := reflect.New(reflect.TypeOf(tt.ptr).Elem())
-		dec := NewDecoder(bytes.NewBuffer(in))
+		dec := NewDecoder(bytes.NewReader(in))
 		if tt.useNumber {
 			dec.UseNumber()
 		}
@@ -457,16 +541,18 @@ func TestUnmarshal(t *testing.T) {
 				continue
 			}
 			vv := reflect.New(reflect.TypeOf(tt.ptr).Elem())
-			dec = NewDecoder(bytes.NewBuffer(enc))
+			dec = NewDecoder(bytes.NewReader(enc))
 			if tt.useNumber {
 				dec.UseNumber()
 			}
 			if err := dec.Decode(vv.Interface()); err != nil {
-				t.Errorf("#%d: error re-unmarshaling: %v", i, err)
+				t.Errorf("#%d: error re-unmarshaling %#q: %v", i, enc, err)
 				continue
 			}
 			if !reflect.DeepEqual(v.Elem().Interface(), vv.Elem().Interface()) {
 				t.Errorf("#%d: mismatch\nhave: %#+v\nwant: %#+v", i, v.Elem().Interface(), vv.Elem().Interface())
+				t.Errorf("     In: %q", strings.Map(noSpace, string(in)))
+				t.Errorf("Marshal: %q", strings.Map(noSpace, string(enc)))
 				continue
 			}
 		}
@@ -568,14 +654,14 @@ func TestUnmarshalPtrPtr(t *testing.T) {
 }
 
 func TestEscape(t *testing.T) {
-	const input = `"foobar"<html>`
-	const expected = `"\"foobar\"\u003chtml\u003e"`
+	const input = `"foobar"<html>` + " [\u2028 \u2029]"
+	const expected = `"\"foobar\"\u003chtml\u003e [\u2028 \u2029]"`
 	b, err := Marshal(input)
 	if err != nil {
 		t.Fatalf("Marshal error: %v", err)
 	}
 	if s := string(b); s != expected {
-		t.Errorf("Encoding of [%s] was [%s], want [%s]", input, s, expected)
+		t.Errorf("Encoding of [%s]:\n got [%s]\nwant [%s]", input, s, expected)
 	}
 }
 
@@ -934,15 +1020,20 @@ func TestRefUnmarshal(t *testing.T) {
 		// Ref is defined in encode_test.go.
 		R0 Ref
 		R1 *Ref
+		R2 RefText
+		R3 *RefText
 	}
 	want := S{
 		R0: 12,
 		R1: new(Ref),
+		R2: 13,
+		R3: new(RefText),
 	}
 	*want.R1 = 12
+	*want.R3 = 13
 
 	var got S
-	if err := Unmarshal([]byte(`{"R0":"ref","R1":"ref"}`), &got); err != nil {
+	if err := Unmarshal([]byte(`{"R0":"ref","R1":"ref","R2":"ref","R3":"ref"}`), &got); err != nil {
 		t.Fatalf("Unmarshal: %v", err)
 	}
 	if !reflect.DeepEqual(got, want) {
@@ -1064,7 +1155,6 @@ func TestUnmarshalNulls(t *testing.T) {
 
 func TestStringKind(t *testing.T) {
 	type stringKind string
-	type aMap map[stringKind]int
 
 	var m1, m2 map[stringKind]int
 	m1 = map[stringKind]int{
@@ -1191,3 +1281,38 @@ func TestSkipArrayObjects(t *testing.T) {
 		t.Errorf("got error %q, want nil", err)
 	}
 }
+
+// Test semantics of pre-filled struct fields and pre-filled map fields.
+// Issue 4900.
+func TestPrefilled(t *testing.T) {
+	ptrToMap := func(m map[string]interface{}) *map[string]interface{} { return &m }
+
+	// Values here change, cannot reuse table across runs.
+	var prefillTests = []struct {
+		in  string
+		ptr interface{}
+		out interface{}
+	}{
+		{
+			in:  `{"X": 1, "Y": 2}`,
+			ptr: &XYZ{X: float32(3), Y: int16(4), Z: 1.5},
+			out: &XYZ{X: float64(1), Y: float64(2), Z: 1.5},
+		},
+		{
+			in:  `{"X": 1, "Y": 2}`,
+			ptr: ptrToMap(map[string]interface{}{"X": float32(3), "Y": int16(4), "Z": 1.5}),
+			out: ptrToMap(map[string]interface{}{"X": float64(1), "Y": float64(2), "Z": 1.5}),
+		},
+	}
+
+	for _, tt := range prefillTests {
+		ptrstr := fmt.Sprintf("%v", tt.ptr)
+		err := Unmarshal([]byte(tt.in), tt.ptr) // tt.ptr edited here
+		if err != nil {
+			t.Errorf("Unmarshal: %v", err)
+		}
+		if !reflect.DeepEqual(tt.ptr, tt.out) {
+			t.Errorf("Unmarshal(%#q, %s): have %v, want %v", tt.in, ptrstr, tt.ptr, tt.out)
+		}
+	}
+}
diff --git a/src/pkg/encoding/json/encode.go b/src/pkg/encoding/json/encode.go
index 85727ba61..7d6c71d7a 100644
--- a/src/pkg/encoding/json/encode.go
+++ b/src/pkg/encoding/json/encode.go
@@ -12,6 +12,7 @@ package json
 
 import (
 	"bytes"
+	"encoding"
 	"encoding/base64"
 	"math"
 	"reflect"
@@ -149,14 +150,14 @@ func MarshalIndent(v interface{}, prefix, indent string) ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
-// HTMLEscape appends to dst the JSON-encoded src with <, >, and &
-// characters inside string literals changed to \u003c, \u003e, \u0026
+// HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029
+// characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029
 // so that the JSON will be safe to embed inside HTML <script> tags.
 // For historical reasons, web browsers don't honor standard HTML
 // escaping within <script> tags, so an alternative JSON encoding must
 // be used.
 func HTMLEscape(dst *bytes.Buffer, src []byte) {
-	// < > & can only appear in string literals,
+	// The characters can only appear in string literals,
 	// so just scan the string one byte at a time.
 	start := 0
 	for i, c := range src {
@@ -169,6 +170,15 @@ func HTMLEscape(dst *bytes.Buffer, src []byte) {
 			dst.WriteByte(hex[c&0xF])
 			start = i + 1
 		}
+		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
+		if c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u202`)
+			dst.WriteByte(hex[src[i+2]&0xF])
+			start = i + 3
+		}
 	}
 	if start < len(src) {
 		dst.Write(src[start:])
@@ -200,8 +210,12 @@ func (e *UnsupportedValueError) Error() string {
 	return "json: unsupported value: " + e.Str
 }
 
-// An InvalidUTF8Error is returned by Marshal when attempting
-// to encode a string value with invalid UTF-8 sequences.
+// Before Go 1.2, an InvalidUTF8Error was returned by Marshal when
+// attempting to encode a string value with invalid UTF-8 sequences.
+// As of Go 1.2, Marshal instead coerces the string to valid UTF-8 by
+// replacing invalid bytes with the Unicode replacement rune U+FFFD.
+// This error is no longer generated but is kept for backwards compatibility
+// with programs that might mention it.
 type InvalidUTF8Error struct {
 	S string // the whole string value that caused the error
 }
@@ -227,12 +241,35 @@ type encodeState struct {
 	scratch      [64]byte
 }
 
+// TODO(bradfitz): use a sync.Cache here
+var encodeStatePool = make(chan *encodeState, 8)
+
+func newEncodeState() *encodeState {
+	select {
+	case e := <-encodeStatePool:
+		e.Reset()
+		return e
+	default:
+		return new(encodeState)
+	}
+}
+
+func putEncodeState(e *encodeState) {
+	select {
+	case encodeStatePool <- e:
+	default:
+	}
+}
+
 func (e *encodeState) marshal(v interface{}) (err error) {
 	defer func() {
 		if r := recover(); r != nil {
 			if _, ok := r.(runtime.Error); ok {
 				panic(r)
 			}
+			if s, ok := r.(string); ok {
+				panic(s)
+			}
 			err = r.(error)
 		}
 	}()
@@ -265,186 +302,438 @@ func isEmptyValue(v reflect.Value) bool {
 }
 
 func (e *encodeState) reflectValue(v reflect.Value) {
-	e.reflectValueQuoted(v, false)
+	valueEncoder(v)(e, v, false)
+}
+
+type encoderFunc func(e *encodeState, v reflect.Value, quoted bool)
+
+var encoderCache struct {
+	sync.RWMutex
+	m map[reflect.Type]encoderFunc
 }
 
-// reflectValueQuoted writes the value in v to the output.
-// If quoted is true, the serialization is wrapped in a JSON string.
-func (e *encodeState) reflectValueQuoted(v reflect.Value, quoted bool) {
+func valueEncoder(v reflect.Value) encoderFunc {
 	if !v.IsValid() {
-		e.WriteString("null")
-		return
+		return invalidValueEncoder
 	}
+	return typeEncoder(v.Type())
+}
 
-	m, ok := v.Interface().(Marshaler)
-	if !ok {
-		// T doesn't match the interface. Check against *T too.
-		if v.Kind() != reflect.Ptr && v.CanAddr() {
-			m, ok = v.Addr().Interface().(Marshaler)
-			if ok {
-				v = v.Addr()
-			}
-		}
+func typeEncoder(t reflect.Type) encoderFunc {
+	encoderCache.RLock()
+	f := encoderCache.m[t]
+	encoderCache.RUnlock()
+	if f != nil {
+		return f
+	}
+
+	// To deal with recursive types, populate the map with an
+	// indirect func before we build it. This type waits on the
+	// real func (f) to be ready and then calls it.  This indirect
+	// func is only used for recursive types.
+	encoderCache.Lock()
+	if encoderCache.m == nil {
+		encoderCache.m = make(map[reflect.Type]encoderFunc)
+	}
+	var wg sync.WaitGroup
+	wg.Add(1)
+	encoderCache.m[t] = func(e *encodeState, v reflect.Value, quoted bool) {
+		wg.Wait()
+		f(e, v, quoted)
+	}
+	encoderCache.Unlock()
+
+	// Compute fields without lock.
+	// Might duplicate effort but won't hold other computations back.
+	f = newTypeEncoder(t, true)
+	wg.Done()
+	encoderCache.Lock()
+	encoderCache.m[t] = f
+	encoderCache.Unlock()
+	return f
+}
+
+var (
+	marshalerType     = reflect.TypeOf(new(Marshaler)).Elem()
+	textMarshalerType = reflect.TypeOf(new(encoding.TextMarshaler)).Elem()
+)
+
+// newTypeEncoder constructs an encoderFunc for a type.
+// The returned encoder only checks CanAddr when allowAddr is true.
+func newTypeEncoder(t reflect.Type, allowAddr bool) encoderFunc {
+	if t.Implements(marshalerType) {
+		return marshalerEncoder
 	}
-	if ok && (v.Kind() != reflect.Ptr || !v.IsNil()) {
-		b, err := m.MarshalJSON()
-		if err == nil {
-			// copy JSON into buffer, checking validity.
-			err = compact(&e.Buffer, b, true)
+	if t.Kind() != reflect.Ptr && allowAddr {
+		if reflect.PtrTo(t).Implements(marshalerType) {
+			return newCondAddrEncoder(addrMarshalerEncoder, newTypeEncoder(t, false))
 		}
-		if err != nil {
-			e.error(&MarshalerError{v.Type(), err})
+	}
+
+	if t.Implements(textMarshalerType) {
+		return textMarshalerEncoder
+	}
+	if t.Kind() != reflect.Ptr && allowAddr {
+		if reflect.PtrTo(t).Implements(textMarshalerType) {
+			return newCondAddrEncoder(addrTextMarshalerEncoder, newTypeEncoder(t, false))
 		}
+	}
+
+	switch t.Kind() {
+	case reflect.Bool:
+		return boolEncoder
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return intEncoder
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return uintEncoder
+	case reflect.Float32:
+		return float32Encoder
+	case reflect.Float64:
+		return float64Encoder
+	case reflect.String:
+		return stringEncoder
+	case reflect.Interface:
+		return interfaceEncoder
+	case reflect.Struct:
+		return newStructEncoder(t)
+	case reflect.Map:
+		return newMapEncoder(t)
+	case reflect.Slice:
+		return newSliceEncoder(t)
+	case reflect.Array:
+		return newArrayEncoder(t)
+	case reflect.Ptr:
+		return newPtrEncoder(t)
+	default:
+		return unsupportedTypeEncoder
+	}
+}
+
+func invalidValueEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	e.WriteString("null")
+}
+
+func marshalerEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	if v.Kind() == reflect.Ptr && v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := v.Interface().(Marshaler)
+	b, err := m.MarshalJSON()
+	if err == nil {
+		// copy JSON into buffer, checking validity.
+		err = compact(&e.Buffer, b, true)
+	}
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err})
+	}
+}
+
+func addrMarshalerEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	va := v.Addr()
+	if va.IsNil() {
+		e.WriteString("null")
 		return
 	}
+	m := va.Interface().(Marshaler)
+	b, err := m.MarshalJSON()
+	if err == nil {
+		// copy JSON into buffer, checking validity.
+		err = compact(&e.Buffer, b, true)
+	}
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err})
+	}
+}
 
-	writeString := (*encodeState).WriteString
+func textMarshalerEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	if v.Kind() == reflect.Ptr && v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := v.Interface().(encoding.TextMarshaler)
+	b, err := m.MarshalText()
+	if err == nil {
+		_, err = e.stringBytes(b)
+	}
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err})
+	}
+}
+
+func addrTextMarshalerEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	va := v.Addr()
+	if va.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := va.Interface().(encoding.TextMarshaler)
+	b, err := m.MarshalText()
+	if err == nil {
+		_, err = e.stringBytes(b)
+	}
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err})
+	}
+}
+
+func boolEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	if quoted {
+		e.WriteByte('"')
+	}
+	if v.Bool() {
+		e.WriteString("true")
+	} else {
+		e.WriteString("false")
+	}
+	if quoted {
+		e.WriteByte('"')
+	}
+}
+
+func intEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	b := strconv.AppendInt(e.scratch[:0], v.Int(), 10)
+	if quoted {
+		e.WriteByte('"')
+	}
+	e.Write(b)
 	if quoted {
-		writeString = (*encodeState).string
+		e.WriteByte('"')
 	}
+}
 
-	switch v.Kind() {
-	case reflect.Bool:
-		x := v.Bool()
-		if x {
-			writeString(e, "true")
-		} else {
-			writeString(e, "false")
-		}
+func uintEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	b := strconv.AppendUint(e.scratch[:0], v.Uint(), 10)
+	if quoted {
+		e.WriteByte('"')
+	}
+	e.Write(b)
+	if quoted {
+		e.WriteByte('"')
+	}
+}
 
-	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		b := strconv.AppendInt(e.scratch[:0], v.Int(), 10)
-		if quoted {
-			writeString(e, string(b))
-		} else {
-			e.Write(b)
+type floatEncoder int // number of bits
+
+func (bits floatEncoder) encode(e *encodeState, v reflect.Value, quoted bool) {
+	f := v.Float()
+	if math.IsInf(f, 0) || math.IsNaN(f) {
+		e.error(&UnsupportedValueError{v, strconv.FormatFloat(f, 'g', -1, int(bits))})
+	}
+	b := strconv.AppendFloat(e.scratch[:0], f, 'g', -1, int(bits))
+	if quoted {
+		e.WriteByte('"')
+	}
+	e.Write(b)
+	if quoted {
+		e.WriteByte('"')
+	}
+}
+
+var (
+	float32Encoder = (floatEncoder(32)).encode
+	float64Encoder = (floatEncoder(64)).encode
+)
+
+func stringEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	if v.Type() == numberType {
+		numStr := v.String()
+		if numStr == "" {
+			numStr = "0" // Number's zero-val
 		}
-	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-		b := strconv.AppendUint(e.scratch[:0], v.Uint(), 10)
-		if quoted {
-			writeString(e, string(b))
-		} else {
-			e.Write(b)
+		e.WriteString(numStr)
+		return
+	}
+	if quoted {
+		sb, err := Marshal(v.String())
+		if err != nil {
+			e.error(err)
 		}
-	case reflect.Float32, reflect.Float64:
-		f := v.Float()
-		if math.IsInf(f, 0) || math.IsNaN(f) {
-			e.error(&UnsupportedValueError{v, strconv.FormatFloat(f, 'g', -1, v.Type().Bits())})
+		e.string(string(sb))
+	} else {
+		e.string(v.String())
+	}
+}
+
+func interfaceEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	e.reflectValue(v.Elem())
+}
+
+func unsupportedTypeEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	e.error(&UnsupportedTypeError{v.Type()})
+}
+
+type structEncoder struct {
+	fields    []field
+	fieldEncs []encoderFunc
+}
+
+func (se *structEncoder) encode(e *encodeState, v reflect.Value, quoted bool) {
+	e.WriteByte('{')
+	first := true
+	for i, f := range se.fields {
+		fv := fieldByIndex(v, f.index)
+		if !fv.IsValid() || f.omitEmpty && isEmptyValue(fv) {
+			continue
 		}
-		b := strconv.AppendFloat(e.scratch[:0], f, 'g', -1, v.Type().Bits())
-		if quoted {
-			writeString(e, string(b))
+		if first {
+			first = false
 		} else {
-			e.Write(b)
-		}
-	case reflect.String:
-		if v.Type() == numberType {
-			numStr := v.String()
-			if numStr == "" {
-				numStr = "0" // Number's zero-val
-			}
-			e.WriteString(numStr)
-			break
-		}
-		if quoted {
-			sb, err := Marshal(v.String())
-			if err != nil {
-				e.error(err)
-			}
-			e.string(string(sb))
-		} else {
-			e.string(v.String())
+			e.WriteByte(',')
 		}
+		e.string(f.name)
+		e.WriteByte(':')
+		se.fieldEncs[i](e, fv, f.quoted)
+	}
+	e.WriteByte('}')
+}
 
-	case reflect.Struct:
-		e.WriteByte('{')
-		first := true
-		for _, f := range cachedTypeFields(v.Type()) {
-			fv := fieldByIndex(v, f.index)
-			if !fv.IsValid() || f.omitEmpty && isEmptyValue(fv) {
-				continue
-			}
-			if first {
-				first = false
-			} else {
-				e.WriteByte(',')
-			}
-			e.string(f.name)
-			e.WriteByte(':')
-			e.reflectValueQuoted(fv, f.quoted)
-		}
-		e.WriteByte('}')
+func newStructEncoder(t reflect.Type) encoderFunc {
+	fields := cachedTypeFields(t)
+	se := &structEncoder{
+		fields:    fields,
+		fieldEncs: make([]encoderFunc, len(fields)),
+	}
+	for i, f := range fields {
+		se.fieldEncs[i] = typeEncoder(typeByIndex(t, f.index))
+	}
+	return se.encode
+}
 
-	case reflect.Map:
-		if v.Type().Key().Kind() != reflect.String {
-			e.error(&UnsupportedTypeError{v.Type()})
-		}
-		if v.IsNil() {
-			e.WriteString("null")
-			break
-		}
-		e.WriteByte('{')
-		var sv stringValues = v.MapKeys()
-		sort.Sort(sv)
-		for i, k := range sv {
-			if i > 0 {
-				e.WriteByte(',')
-			}
-			e.string(k.String())
-			e.WriteByte(':')
-			e.reflectValue(v.MapIndex(k))
-		}
-		e.WriteByte('}')
+type mapEncoder struct {
+	elemEnc encoderFunc
+}
 
-	case reflect.Slice:
-		if v.IsNil() {
-			e.WriteString("null")
-			break
-		}
-		if v.Type().Elem().Kind() == reflect.Uint8 {
-			// Byte slices get special treatment; arrays don't.
-			s := v.Bytes()
-			e.WriteByte('"')
-			if len(s) < 1024 {
-				// for small buffers, using Encode directly is much faster.
-				dst := make([]byte, base64.StdEncoding.EncodedLen(len(s)))
-				base64.StdEncoding.Encode(dst, s)
-				e.Write(dst)
-			} else {
-				// for large buffers, avoid unnecessary extra temporary
-				// buffer space.
-				enc := base64.NewEncoder(base64.StdEncoding, e)
-				enc.Write(s)
-				enc.Close()
-			}
-			e.WriteByte('"')
-			break
-		}
-		// Slices can be marshalled as nil, but otherwise are handled
-		// as arrays.
-		fallthrough
-	case reflect.Array:
-		e.WriteByte('[')
-		n := v.Len()
-		for i := 0; i < n; i++ {
-			if i > 0 {
-				e.WriteByte(',')
-			}
-			e.reflectValue(v.Index(i))
+func (me *mapEncoder) encode(e *encodeState, v reflect.Value, _ bool) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	e.WriteByte('{')
+	var sv stringValues = v.MapKeys()
+	sort.Sort(sv)
+	for i, k := range sv {
+		if i > 0 {
+			e.WriteByte(',')
 		}
-		e.WriteByte(']')
+		e.string(k.String())
+		e.WriteByte(':')
+		me.elemEnc(e, v.MapIndex(k), false)
+	}
+	e.WriteByte('}')
+}
 
-	case reflect.Interface, reflect.Ptr:
-		if v.IsNil() {
-			e.WriteString("null")
-			return
+func newMapEncoder(t reflect.Type) encoderFunc {
+	if t.Key().Kind() != reflect.String {
+		return unsupportedTypeEncoder
+	}
+	me := &mapEncoder{typeEncoder(t.Elem())}
+	return me.encode
+}
+
+func encodeByteSlice(e *encodeState, v reflect.Value, _ bool) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	s := v.Bytes()
+	e.WriteByte('"')
+	if len(s) < 1024 {
+		// for small buffers, using Encode directly is much faster.
+		dst := make([]byte, base64.StdEncoding.EncodedLen(len(s)))
+		base64.StdEncoding.Encode(dst, s)
+		e.Write(dst)
+	} else {
+		// for large buffers, avoid unnecessary extra temporary
+		// buffer space.
+		enc := base64.NewEncoder(base64.StdEncoding, e)
+		enc.Write(s)
+		enc.Close()
+	}
+	e.WriteByte('"')
+}
+
+// sliceEncoder just wraps an arrayEncoder, checking to make sure the value isn't nil.
+type sliceEncoder struct {
+	arrayEnc encoderFunc
+}
+
+func (se *sliceEncoder) encode(e *encodeState, v reflect.Value, _ bool) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	se.arrayEnc(e, v, false)
+}
+
+func newSliceEncoder(t reflect.Type) encoderFunc {
+	// Byte slices get special treatment; arrays don't.
+	if t.Elem().Kind() == reflect.Uint8 {
+		return encodeByteSlice
+	}
+	enc := &sliceEncoder{newArrayEncoder(t)}
+	return enc.encode
+}
+
+type arrayEncoder struct {
+	elemEnc encoderFunc
+}
+
+func (ae *arrayEncoder) encode(e *encodeState, v reflect.Value, _ bool) {
+	e.WriteByte('[')
+	n := v.Len()
+	for i := 0; i < n; i++ {
+		if i > 0 {
+			e.WriteByte(',')
 		}
-		e.reflectValue(v.Elem())
+		ae.elemEnc(e, v.Index(i), false)
+	}
+	e.WriteByte(']')
+}
 
-	default:
-		e.error(&UnsupportedTypeError{v.Type()})
+func newArrayEncoder(t reflect.Type) encoderFunc {
+	enc := &arrayEncoder{typeEncoder(t.Elem())}
+	return enc.encode
+}
+
+type ptrEncoder struct {
+	elemEnc encoderFunc
+}
+
+func (pe *ptrEncoder) encode(e *encodeState, v reflect.Value, _ bool) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	pe.elemEnc(e, v.Elem(), false)
+}
+
+func newPtrEncoder(t reflect.Type) encoderFunc {
+	enc := &ptrEncoder{typeEncoder(t.Elem())}
+	return enc.encode
+}
+
+type condAddrEncoder struct {
+	canAddrEnc, elseEnc encoderFunc
+}
+
+func (ce *condAddrEncoder) encode(e *encodeState, v reflect.Value, quoted bool) {
+	if v.CanAddr() {
+		ce.canAddrEnc(e, v, quoted)
+	} else {
+		ce.elseEnc(e, v, quoted)
 	}
-	return
+}
+
+// newCondAddrEncoder returns an encoder that checks whether its value
+// CanAddr and delegates to canAddrEnc if so, else to elseEnc.
+func newCondAddrEncoder(canAddrEnc, elseEnc encoderFunc) encoderFunc {
+	enc := &condAddrEncoder{canAddrEnc: canAddrEnc, elseEnc: elseEnc}
+	return enc.encode
 }
 
 func isValidTag(s string) bool {
@@ -479,6 +768,16 @@ func fieldByIndex(v reflect.Value, index []int) reflect.Value {
 	return v
 }
 
+func typeByIndex(t reflect.Type, index []int) reflect.Type {
+	for _, i := range index {
+		if t.Kind() == reflect.Ptr {
+			t = t.Elem()
+		}
+		t = t.Field(i).Type
+	}
+	return t
+}
+
 // stringValues is a slice of reflect.Value holding *reflect.StringValue.
 // It implements the methods to sort by string.
 type stringValues []reflect.Value
@@ -488,13 +787,14 @@ func (sv stringValues) Swap(i, j int)      { sv[i], sv[j] = sv[j], sv[i] }
 func (sv stringValues) Less(i, j int) bool { return sv.get(i) < sv.get(j) }
 func (sv stringValues) get(i int) string   { return sv[i].String() }
 
+// NOTE: keep in sync with stringBytes below.
 func (e *encodeState) string(s string) (int, error) {
 	len0 := e.Len()
 	e.WriteByte('"')
 	start := 0
 	for i := 0; i < len(s); {
 		if b := s[i]; b < utf8.RuneSelf {
-			if 0x20 <= b && b != '\\' && b != '"' && b != '<' && b != '>' {
+			if 0x20 <= b && b != '\\' && b != '"' && b != '<' && b != '>' && b != '&' {
 				i++
 				continue
 			}
@@ -526,7 +826,30 @@ func (e *encodeState) string(s string) (int, error) {
 		}
 		c, size := utf8.DecodeRuneInString(s[i:])
 		if c == utf8.RuneError && size == 1 {
-			e.error(&InvalidUTF8Error{s})
+			if start < i {
+				e.WriteString(s[start:i])
+			}
+			e.WriteString(`\ufffd`)
+			i += size
+			start = i
+			continue
+		}
+		// U+2028 is LINE SEPARATOR.
+		// U+2029 is PARAGRAPH SEPARATOR.
+		// They are both technically valid characters in JSON strings,
+		// but don't work in JSONP, which has to be evaluated as JavaScript,
+		// and can lead to security holes there. It is valid JSON to
+		// escape them, so we do so unconditionally.
+		// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+		if c == '\u2028' || c == '\u2029' {
+			if start < i {
+				e.WriteString(s[start:i])
+			}
+			e.WriteString(`\u202`)
+			e.WriteByte(hex[c&0xF])
+			i += size
+			start = i
+			continue
 		}
 		i += size
 	}
@@ -537,6 +860,79 @@ func (e *encodeState) string(s string) (int, error) {
 	return e.Len() - len0, nil
 }
 
+// NOTE: keep in sync with string above.
+func (e *encodeState) stringBytes(s []byte) (int, error) {
+	len0 := e.Len()
+	e.WriteByte('"')
+	start := 0
+	for i := 0; i < len(s); {
+		if b := s[i]; b < utf8.RuneSelf {
+			if 0x20 <= b && b != '\\' && b != '"' && b != '<' && b != '>' && b != '&' {
+				i++
+				continue
+			}
+			if start < i {
+				e.Write(s[start:i])
+			}
+			switch b {
+			case '\\', '"':
+				e.WriteByte('\\')
+				e.WriteByte(b)
+			case '\n':
+				e.WriteByte('\\')
+				e.WriteByte('n')
+			case '\r':
+				e.WriteByte('\\')
+				e.WriteByte('r')
+			default:
+				// This encodes bytes < 0x20 except for \n and \r,
+				// as well as < and >. The latter are escaped because they
+				// can lead to security holes when user-controlled strings
+				// are rendered into JSON and served to some browsers.
+				e.WriteString(`\u00`)
+				e.WriteByte(hex[b>>4])
+				e.WriteByte(hex[b&0xF])
+			}
+			i++
+			start = i
+			continue
+		}
+		c, size := utf8.DecodeRune(s[i:])
+		if c == utf8.RuneError && size == 1 {
+			if start < i {
+				e.Write(s[start:i])
+			}
+			e.WriteString(`\ufffd`)
+			i += size
+			start = i
+			continue
+		}
+		// U+2028 is LINE SEPARATOR.
+		// U+2029 is PARAGRAPH SEPARATOR.
+		// They are both technically valid characters in JSON strings,
+		// but don't work in JSONP, which has to be evaluated as JavaScript,
+		// and can lead to security holes there. It is valid JSON to
+		// escape them, so we do so unconditionally.
+		// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+		if c == '\u2028' || c == '\u2029' {
+			if start < i {
+				e.Write(s[start:i])
+			}
+			e.WriteString(`\u202`)
+			e.WriteByte(hex[c&0xF])
+			i += size
+			start = i
+			continue
+		}
+		i += size
+	}
+	if start < len(s) {
+		e.Write(s[start:])
+	}
+	e.WriteByte('"')
+	return e.Len() - len0, nil
+}
+
 // A field represents a single field found in a struct.
 type field struct {
 	name      string
diff --git a/src/pkg/encoding/json/encode_test.go b/src/pkg/encoding/json/encode_test.go
index 5be0a992e..9395db7cb 100644
--- a/src/pkg/encoding/json/encode_test.go
+++ b/src/pkg/encoding/json/encode_test.go
@@ -9,6 +9,7 @@ import (
 	"math"
 	"reflect"
 	"testing"
+	"unicode"
 )
 
 type Optionals struct {
@@ -146,19 +147,46 @@ func (Val) MarshalJSON() ([]byte, error) {
 	return []byte(`"val"`), nil
 }
 
+// RefText has Marshaler and Unmarshaler methods with pointer receiver.
+type RefText int
+
+func (*RefText) MarshalText() ([]byte, error) {
+	return []byte(`"ref"`), nil
+}
+
+func (r *RefText) UnmarshalText([]byte) error {
+	*r = 13
+	return nil
+}
+
+// ValText has Marshaler methods with value receiver.
+type ValText int
+
+func (ValText) MarshalText() ([]byte, error) {
+	return []byte(`"val"`), nil
+}
+
 func TestRefValMarshal(t *testing.T) {
 	var s = struct {
 		R0 Ref
 		R1 *Ref
+		R2 RefText
+		R3 *RefText
 		V0 Val
 		V1 *Val
+		V2 ValText
+		V3 *ValText
 	}{
 		R0: 12,
 		R1: new(Ref),
+		R2: 14,
+		R3: new(RefText),
 		V0: 13,
 		V1: new(Val),
+		V2: 15,
+		V3: new(ValText),
 	}
-	const want = `{"R0":"ref","R1":"ref","V0":"val","V1":"val"}`
+	const want = `{"R0":"ref","R1":"ref","R2":"\"ref\"","R3":"\"ref\"","V0":"val","V1":"val","V2":"\"val\"","V3":"\"val\""}`
 	b, err := Marshal(&s)
 	if err != nil {
 		t.Fatalf("Marshal: %v", err)
@@ -175,15 +203,32 @@ func (C) MarshalJSON() ([]byte, error) {
 	return []byte(`"<&>"`), nil
 }
 
+// CText implements Marshaler and returns unescaped text.
+type CText int
+
+func (CText) MarshalText() ([]byte, error) {
+	return []byte(`"<&>"`), nil
+}
+
 func TestMarshalerEscaping(t *testing.T) {
 	var c C
-	const want = `"\u003c\u0026\u003e"`
+	want := `"\u003c\u0026\u003e"`
 	b, err := Marshal(c)
 	if err != nil {
-		t.Fatalf("Marshal: %v", err)
+		t.Fatalf("Marshal(c): %v", err)
 	}
 	if got := string(b); got != want {
-		t.Errorf("got %q, want %q", got, want)
+		t.Errorf("Marshal(c) = %#q, want %#q", got, want)
+	}
+
+	var ct CText
+	want = `"\"\u003c\u0026\u003e\""`
+	b, err = Marshal(ct)
+	if err != nil {
+		t.Fatalf("Marshal(ct): %v", err)
+	}
+	if got := string(b); got != want {
+		t.Errorf("Marshal(ct) = %#q, want %#q", got, want)
 	}
 }
 
@@ -310,3 +355,73 @@ func TestDuplicatedFieldDisappears(t *testing.T) {
 		t.Fatalf("Marshal: got %s want %s", got, want)
 	}
 }
+
+func TestStringBytes(t *testing.T) {
+	// Test that encodeState.stringBytes and encodeState.string use the same encoding.
+	es := &encodeState{}
+	var r []rune
+	for i := '\u0000'; i <= unicode.MaxRune; i++ {
+		r = append(r, i)
+	}
+	s := string(r) + "\xff\xff\xffhello" // some invalid UTF-8 too
+	_, err := es.string(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	esBytes := &encodeState{}
+	_, err = esBytes.stringBytes([]byte(s))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	enc := es.Buffer.String()
+	encBytes := esBytes.Buffer.String()
+	if enc != encBytes {
+		i := 0
+		for i < len(enc) && i < len(encBytes) && enc[i] == encBytes[i] {
+			i++
+		}
+		enc = enc[i:]
+		encBytes = encBytes[i:]
+		i = 0
+		for i < len(enc) && i < len(encBytes) && enc[len(enc)-i-1] == encBytes[len(encBytes)-i-1] {
+			i++
+		}
+		enc = enc[:len(enc)-i]
+		encBytes = encBytes[:len(encBytes)-i]
+
+		if len(enc) > 20 {
+			enc = enc[:20] + "..."
+		}
+		if len(encBytes) > 20 {
+			encBytes = encBytes[:20] + "..."
+		}
+
+		t.Errorf("encodings differ at %#q vs %#q", enc, encBytes)
+	}
+}
+
+func TestIssue6458(t *testing.T) {
+	type Foo struct {
+		M RawMessage
+	}
+	x := Foo{RawMessage(`"foo"`)}
+
+	b, err := Marshal(&x)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want := `{"M":"foo"}`; string(b) != want {
+		t.Errorf("Marshal(&x) = %#q; want %#q", b, want)
+	}
+
+	b, err = Marshal(x)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if want := `{"M":"ImZvbyI="}`; string(b) != want {
+		t.Errorf("Marshal(x) = %#q; want %#q", b, want)
+	}
+}
diff --git a/src/pkg/encoding/json/example_test.go b/src/pkg/encoding/json/example_test.go
index b8d150eda..ea0bc149c 100644
--- a/src/pkg/encoding/json/example_test.go
+++ b/src/pkg/encoding/json/example_test.go
@@ -81,3 +81,49 @@ func ExampleDecoder() {
 	// Sam: Go fmt who?
 	// Ed: Go fmt yourself!
 }
+
+// This example uses RawMessage to delay parsing part of a JSON message.
+func ExampleRawMessage() {
+	type Color struct {
+		Space string
+		Point json.RawMessage // delay parsing until we know the color space
+	}
+	type RGB struct {
+		R uint8
+		G uint8
+		B uint8
+	}
+	type YCbCr struct {
+		Y  uint8
+		Cb int8
+		Cr int8
+	}
+
+	var j = []byte(`[
+		{"Space": "YCbCr", "Point": {"Y": 255, "Cb": 0, "Cr": -10}},
+		{"Space": "RGB",   "Point": {"R": 98, "G": 218, "B": 255}}
+	]`)
+	var colors []Color
+	err := json.Unmarshal(j, &colors)
+	if err != nil {
+		log.Fatalln("error:", err)
+	}
+
+	for _, c := range colors {
+		var dst interface{}
+		switch c.Space {
+		case "RGB":
+			dst = new(RGB)
+		case "YCbCr":
+			dst = new(YCbCr)
+		}
+		err := json.Unmarshal(c.Point, dst)
+		if err != nil {
+			log.Fatalln("error:", err)
+		}
+		fmt.Println(c.Space, dst)
+	}
+	// Output:
+	// YCbCr &{255 0 -10}
+	// RGB &{98 218 255}
+}
diff --git a/src/pkg/encoding/json/indent.go b/src/pkg/encoding/json/indent.go
index e8dfa4ec4..11ef709cc 100644
--- a/src/pkg/encoding/json/indent.go
+++ b/src/pkg/encoding/json/indent.go
@@ -27,6 +27,15 @@ func compact(dst *bytes.Buffer, src []byte, escape bool) error {
 			dst.WriteByte(hex[c&0xF])
 			start = i + 1
 		}
+		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
+		if c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u202`)
+			dst.WriteByte(hex[src[i+2]&0xF])
+			start = i + 3
+		}
 		v := scan.step(&scan, int(c))
 		if v >= scanSkipSpace {
 			if v == scanError {
diff --git a/src/pkg/encoding/json/scanner.go b/src/pkg/encoding/json/scanner.go
index 054b6b3d5..a4609c895 100644
--- a/src/pkg/encoding/json/scanner.go
+++ b/src/pkg/encoding/json/scanner.go
@@ -390,7 +390,7 @@ func stateInStringEscU123(s *scanner, c int) int {
 	return s.error(c, "in \\u hexadecimal character escape")
 }
 
-// stateInStringEscU123 is the state after reading `-` during a number.
+// stateNeg is the state after reading `-` during a number.
 func stateNeg(s *scanner, c int) int {
 	if c == '0' {
 		s.step = state0
diff --git a/src/pkg/encoding/json/scanner_test.go b/src/pkg/encoding/json/scanner_test.go
index 77d3455d3..90e45ff03 100644
--- a/src/pkg/encoding/json/scanner_test.go
+++ b/src/pkg/encoding/json/scanner_test.go
@@ -63,6 +63,25 @@ func TestCompact(t *testing.T) {
 	}
 }
 
+func TestCompactSeparators(t *testing.T) {
+	// U+2028 and U+2029 should be escaped inside strings.
+	// They should not appear outside strings.
+	tests := []struct {
+		in, compact string
+	}{
+		{"{\"\u2028\": 1}", `{"\u2028":1}`},
+		{"{\"\u2029\" :2}", `{"\u2029":2}`},
+	}
+	for _, tt := range tests {
+		var buf bytes.Buffer
+		if err := Compact(&buf, []byte(tt.in)); err != nil {
+			t.Errorf("Compact(%q): %v", tt.in, err)
+		} else if s := buf.String(); s != tt.compact {
+			t.Errorf("Compact(%q) = %q, want %q", tt.in, s, tt.compact)
+		}
+	}
+}
+
 func TestIndent(t *testing.T) {
 	var buf bytes.Buffer
 	for _, tt := range examples {
diff --git a/src/pkg/encoding/json/stream.go b/src/pkg/encoding/json/stream.go
index 00f4726cf..1928abadb 100644
--- a/src/pkg/encoding/json/stream.go
+++ b/src/pkg/encoding/json/stream.go
@@ -148,7 +148,7 @@ func NewEncoder(w io.Writer) *Encoder {
 	return &Encoder{w: w}
 }
 
-// Encode writes the JSON encoding of v to the connection.
+// Encode writes the JSON encoding of v to the stream.
 //
 // See the documentation for Marshal for details about the
 // conversion of Go values to JSON.
@@ -156,8 +156,8 @@ func (enc *Encoder) Encode(v interface{}) error {
 	if enc.err != nil {
 		return enc.err
 	}
-	enc.e.Reset()
-	err := enc.e.marshal(v)
+	e := newEncodeState()
+	err := e.marshal(v)
 	if err != nil {
 		return err
 	}
@@ -168,11 +168,12 @@ func (enc *Encoder) Encode(v interface{}) error {
 	// is required if the encoded value was a number,
 	// so that the reader knows there aren't more
 	// digits coming.
-	enc.e.WriteByte('\n')
+	e.WriteByte('\n')
 
-	if _, err = enc.w.Write(enc.e.Bytes()); err != nil {
+	if _, err = enc.w.Write(e.Bytes()); err != nil {
 		enc.err = err
 	}
+	putEncodeState(e)
 	return err
 }
 
diff --git a/src/pkg/encoding/json/stream_test.go b/src/pkg/encoding/json/stream_test.go
index 07c9e1d39..b562e8769 100644
--- a/src/pkg/encoding/json/stream_test.go
+++ b/src/pkg/encoding/json/stream_test.go
@@ -191,3 +191,16 @@ func TestBlocking(t *testing.T) {
 		w.Close()
 	}
 }
+
+func BenchmarkEncoderEncode(b *testing.B) {
+	b.ReportAllocs()
+	type T struct {
+		X, Y string
+	}
+	v := &T{"foo", "bar"}
+	for i := 0; i < b.N; i++ {
+		if err := NewEncoder(ioutil.Discard).Encode(v); err != nil {
+			b.Fatal(err)
+		}
+	}
+}
diff --git a/src/pkg/encoding/json/tags.go b/src/pkg/encoding/json/tags.go
index 58cda2027..c38fd5102 100644
--- a/src/pkg/encoding/json/tags.go
+++ b/src/pkg/encoding/json/tags.go
@@ -21,7 +21,7 @@ func parseTag(tag string) (string, tagOptions) {
 	return tag, tagOptions("")
 }
 
-// Contains returns whether checks that a comma-separated list of options
+// Contains reports whether a comma-separated list of options
 // contains a particular substr flag. substr must be surrounded by a
 // string boundary or commas.
 func (o tagOptions) Contains(optionName string) bool {