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Source file src/encoding/gob/codec_test.go

Documentation: encoding/gob

  // Copyright 2009 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package gob
  
  import (
  	"bytes"
  	"errors"
  	"flag"
  	"math"
  	"math/rand"
  	"reflect"
  	"strings"
  	"testing"
  	"time"
  )
  
  var doFuzzTests = flag.Bool("gob.fuzz", false, "run the fuzz tests, which are large and very slow")
  
  // Guarantee encoding format by comparing some encodings to hand-written values
  type EncodeT struct {
  	x uint64
  	b []byte
  }
  
  var encodeT = []EncodeT{
  	{0x00, []byte{0x00}},
  	{0x0F, []byte{0x0F}},
  	{0xFF, []byte{0xFF, 0xFF}},
  	{0xFFFF, []byte{0xFE, 0xFF, 0xFF}},
  	{0xFFFFFF, []byte{0xFD, 0xFF, 0xFF, 0xFF}},
  	{0xFFFFFFFF, []byte{0xFC, 0xFF, 0xFF, 0xFF, 0xFF}},
  	{0xFFFFFFFFFF, []byte{0xFB, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}},
  	{0xFFFFFFFFFFFF, []byte{0xFA, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}},
  	{0xFFFFFFFFFFFFFF, []byte{0xF9, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}},
  	{0xFFFFFFFFFFFFFFFF, []byte{0xF8, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}},
  	{0x1111, []byte{0xFE, 0x11, 0x11}},
  	{0x1111111111111111, []byte{0xF8, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11}},
  	{0x8888888888888888, []byte{0xF8, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88}},
  	{1 << 63, []byte{0xF8, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}},
  }
  
  // testError is meant to be used as a deferred function to turn a panic(gobError) into a
  // plain test.Error call.
  func testError(t *testing.T) {
  	if e := recover(); e != nil {
  		t.Error(e.(gobError).err) // Will re-panic if not one of our errors, such as a runtime error.
  	}
  }
  
  func newDecBuffer(data []byte) *decBuffer {
  	return &decBuffer{
  		data: data,
  	}
  }
  
  // Test basic encode/decode routines for unsigned integers
  func TestUintCodec(t *testing.T) {
  	defer testError(t)
  	b := new(encBuffer)
  	encState := newEncoderState(b)
  	for _, tt := range encodeT {
  		b.Reset()
  		encState.encodeUint(tt.x)
  		if !bytes.Equal(tt.b, b.Bytes()) {
  			t.Errorf("encodeUint: %#x encode: expected % x got % x", tt.x, tt.b, b.Bytes())
  		}
  	}
  	for u := uint64(0); ; u = (u + 1) * 7 {
  		b.Reset()
  		encState.encodeUint(u)
  		decState := newDecodeState(newDecBuffer(b.Bytes()))
  		v := decState.decodeUint()
  		if u != v {
  			t.Errorf("Encode/Decode: sent %#x received %#x", u, v)
  		}
  		if u&(1<<63) != 0 {
  			break
  		}
  	}
  }
  
  func verifyInt(i int64, t *testing.T) {
  	defer testError(t)
  	var b = new(encBuffer)
  	encState := newEncoderState(b)
  	encState.encodeInt(i)
  	decState := newDecodeState(newDecBuffer(b.Bytes()))
  	j := decState.decodeInt()
  	if i != j {
  		t.Errorf("Encode/Decode: sent %#x received %#x", uint64(i), uint64(j))
  	}
  }
  
  // Test basic encode/decode routines for signed integers
  func TestIntCodec(t *testing.T) {
  	for u := uint64(0); ; u = (u + 1) * 7 {
  		// Do positive and negative values
  		i := int64(u)
  		verifyInt(i, t)
  		verifyInt(-i, t)
  		verifyInt(^i, t)
  		if u&(1<<63) != 0 {
  			break
  		}
  	}
  	verifyInt(-1<<63, t) // a tricky case
  }
  
  // The result of encoding a true boolean with field number 7
  var boolResult = []byte{0x07, 0x01}
  
  // The result of encoding a number 17 with field number 7
  var signedResult = []byte{0x07, 2 * 17}
  var unsignedResult = []byte{0x07, 17}
  var floatResult = []byte{0x07, 0xFE, 0x31, 0x40}
  
  // The result of encoding a number 17+19i with field number 7
  var complexResult = []byte{0x07, 0xFE, 0x31, 0x40, 0xFE, 0x33, 0x40}
  
  // The result of encoding "hello" with field number 7
  var bytesResult = []byte{0x07, 0x05, 'h', 'e', 'l', 'l', 'o'}
  
  func newDecodeState(buf *decBuffer) *decoderState {
  	d := new(decoderState)
  	d.b = buf
  	return d
  }
  
  func newEncoderState(b *encBuffer) *encoderState {
  	b.Reset()
  	state := &encoderState{enc: nil, b: b}
  	state.fieldnum = -1
  	return state
  }
  
  // Test instruction execution for encoding.
  // Do not run the machine yet; instead do individual instructions crafted by hand.
  func TestScalarEncInstructions(t *testing.T) {
  	var b = new(encBuffer)
  
  	// bool
  	{
  		var data bool = true
  		instr := &encInstr{encBool, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(boolResult, b.Bytes()) {
  			t.Errorf("bool enc instructions: expected % x got % x", boolResult, b.Bytes())
  		}
  	}
  
  	// int
  	{
  		b.Reset()
  		var data int = 17
  		instr := &encInstr{encInt, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(signedResult, b.Bytes()) {
  			t.Errorf("int enc instructions: expected % x got % x", signedResult, b.Bytes())
  		}
  	}
  
  	// uint
  	{
  		b.Reset()
  		var data uint = 17
  		instr := &encInstr{encUint, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(unsignedResult, b.Bytes()) {
  			t.Errorf("uint enc instructions: expected % x got % x", unsignedResult, b.Bytes())
  		}
  	}
  
  	// int8
  	{
  		b.Reset()
  		var data int8 = 17
  		instr := &encInstr{encInt, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(signedResult, b.Bytes()) {
  			t.Errorf("int8 enc instructions: expected % x got % x", signedResult, b.Bytes())
  		}
  	}
  
  	// uint8
  	{
  		b.Reset()
  		var data uint8 = 17
  		instr := &encInstr{encUint, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(unsignedResult, b.Bytes()) {
  			t.Errorf("uint8 enc instructions: expected % x got % x", unsignedResult, b.Bytes())
  		}
  	}
  
  	// int16
  	{
  		b.Reset()
  		var data int16 = 17
  		instr := &encInstr{encInt, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(signedResult, b.Bytes()) {
  			t.Errorf("int16 enc instructions: expected % x got % x", signedResult, b.Bytes())
  		}
  	}
  
  	// uint16
  	{
  		b.Reset()
  		var data uint16 = 17
  		instr := &encInstr{encUint, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(unsignedResult, b.Bytes()) {
  			t.Errorf("uint16 enc instructions: expected % x got % x", unsignedResult, b.Bytes())
  		}
  	}
  
  	// int32
  	{
  		b.Reset()
  		var data int32 = 17
  		instr := &encInstr{encInt, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(signedResult, b.Bytes()) {
  			t.Errorf("int32 enc instructions: expected % x got % x", signedResult, b.Bytes())
  		}
  	}
  
  	// uint32
  	{
  		b.Reset()
  		var data uint32 = 17
  		instr := &encInstr{encUint, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(unsignedResult, b.Bytes()) {
  			t.Errorf("uint32 enc instructions: expected % x got % x", unsignedResult, b.Bytes())
  		}
  	}
  
  	// int64
  	{
  		b.Reset()
  		var data int64 = 17
  		instr := &encInstr{encInt, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(signedResult, b.Bytes()) {
  			t.Errorf("int64 enc instructions: expected % x got % x", signedResult, b.Bytes())
  		}
  	}
  
  	// uint64
  	{
  		b.Reset()
  		var data uint64 = 17
  		instr := &encInstr{encUint, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(unsignedResult, b.Bytes()) {
  			t.Errorf("uint64 enc instructions: expected % x got % x", unsignedResult, b.Bytes())
  		}
  	}
  
  	// float32
  	{
  		b.Reset()
  		var data float32 = 17
  		instr := &encInstr{encFloat, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(floatResult, b.Bytes()) {
  			t.Errorf("float32 enc instructions: expected % x got % x", floatResult, b.Bytes())
  		}
  	}
  
  	// float64
  	{
  		b.Reset()
  		var data float64 = 17
  		instr := &encInstr{encFloat, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(floatResult, b.Bytes()) {
  			t.Errorf("float64 enc instructions: expected % x got % x", floatResult, b.Bytes())
  		}
  	}
  
  	// bytes == []uint8
  	{
  		b.Reset()
  		data := []byte("hello")
  		instr := &encInstr{encUint8Array, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(bytesResult, b.Bytes()) {
  			t.Errorf("bytes enc instructions: expected % x got % x", bytesResult, b.Bytes())
  		}
  	}
  
  	// string
  	{
  		b.Reset()
  		var data string = "hello"
  		instr := &encInstr{encString, 6, nil, 0}
  		state := newEncoderState(b)
  		instr.op(instr, state, reflect.ValueOf(data))
  		if !bytes.Equal(bytesResult, b.Bytes()) {
  			t.Errorf("string enc instructions: expected % x got % x", bytesResult, b.Bytes())
  		}
  	}
  }
  
  func execDec(instr *decInstr, state *decoderState, t *testing.T, value reflect.Value) {
  	defer testError(t)
  	v := int(state.decodeUint())
  	if v+state.fieldnum != 6 {
  		t.Fatalf("decoding field number %d, got %d", 6, v+state.fieldnum)
  	}
  	instr.op(instr, state, value.Elem())
  	state.fieldnum = 6
  }
  
  func newDecodeStateFromData(data []byte) *decoderState {
  	b := newDecBuffer(data)
  	state := newDecodeState(b)
  	state.fieldnum = -1
  	return state
  }
  
  // Test instruction execution for decoding.
  // Do not run the machine yet; instead do individual instructions crafted by hand.
  func TestScalarDecInstructions(t *testing.T) {
  	ovfl := errors.New("overflow")
  
  	// bool
  	{
  		var data bool
  		instr := &decInstr{decBool, 6, nil, ovfl}
  		state := newDecodeStateFromData(boolResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != true {
  			t.Errorf("bool a = %v not true", data)
  		}
  	}
  	// int
  	{
  		var data int
  		instr := &decInstr{decOpTable[reflect.Int], 6, nil, ovfl}
  		state := newDecodeStateFromData(signedResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("int a = %v not 17", data)
  		}
  	}
  
  	// uint
  	{
  		var data uint
  		instr := &decInstr{decOpTable[reflect.Uint], 6, nil, ovfl}
  		state := newDecodeStateFromData(unsignedResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("uint a = %v not 17", data)
  		}
  	}
  
  	// int8
  	{
  		var data int8
  		instr := &decInstr{decInt8, 6, nil, ovfl}
  		state := newDecodeStateFromData(signedResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("int8 a = %v not 17", data)
  		}
  	}
  
  	// uint8
  	{
  		var data uint8
  		instr := &decInstr{decUint8, 6, nil, ovfl}
  		state := newDecodeStateFromData(unsignedResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("uint8 a = %v not 17", data)
  		}
  	}
  
  	// int16
  	{
  		var data int16
  		instr := &decInstr{decInt16, 6, nil, ovfl}
  		state := newDecodeStateFromData(signedResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("int16 a = %v not 17", data)
  		}
  	}
  
  	// uint16
  	{
  		var data uint16
  		instr := &decInstr{decUint16, 6, nil, ovfl}
  		state := newDecodeStateFromData(unsignedResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("uint16 a = %v not 17", data)
  		}
  	}
  
  	// int32
  	{
  		var data int32
  		instr := &decInstr{decInt32, 6, nil, ovfl}
  		state := newDecodeStateFromData(signedResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("int32 a = %v not 17", data)
  		}
  	}
  
  	// uint32
  	{
  		var data uint32
  		instr := &decInstr{decUint32, 6, nil, ovfl}
  		state := newDecodeStateFromData(unsignedResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("uint32 a = %v not 17", data)
  		}
  	}
  
  	// uintptr
  	{
  		var data uintptr
  		instr := &decInstr{decOpTable[reflect.Uintptr], 6, nil, ovfl}
  		state := newDecodeStateFromData(unsignedResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("uintptr a = %v not 17", data)
  		}
  	}
  
  	// int64
  	{
  		var data int64
  		instr := &decInstr{decInt64, 6, nil, ovfl}
  		state := newDecodeStateFromData(signedResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("int64 a = %v not 17", data)
  		}
  	}
  
  	// uint64
  	{
  		var data uint64
  		instr := &decInstr{decUint64, 6, nil, ovfl}
  		state := newDecodeStateFromData(unsignedResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("uint64 a = %v not 17", data)
  		}
  	}
  
  	// float32
  	{
  		var data float32
  		instr := &decInstr{decFloat32, 6, nil, ovfl}
  		state := newDecodeStateFromData(floatResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("float32 a = %v not 17", data)
  		}
  	}
  
  	// float64
  	{
  		var data float64
  		instr := &decInstr{decFloat64, 6, nil, ovfl}
  		state := newDecodeStateFromData(floatResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17 {
  			t.Errorf("float64 a = %v not 17", data)
  		}
  	}
  
  	// complex64
  	{
  		var data complex64
  		instr := &decInstr{decOpTable[reflect.Complex64], 6, nil, ovfl}
  		state := newDecodeStateFromData(complexResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17+19i {
  			t.Errorf("complex a = %v not 17+19i", data)
  		}
  	}
  
  	// complex128
  	{
  		var data complex128
  		instr := &decInstr{decOpTable[reflect.Complex128], 6, nil, ovfl}
  		state := newDecodeStateFromData(complexResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != 17+19i {
  			t.Errorf("complex a = %v not 17+19i", data)
  		}
  	}
  
  	// bytes == []uint8
  	{
  		var data []byte
  		instr := &decInstr{decUint8Slice, 6, nil, ovfl}
  		state := newDecodeStateFromData(bytesResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if string(data) != "hello" {
  			t.Errorf(`bytes a = %q not "hello"`, string(data))
  		}
  	}
  
  	// string
  	{
  		var data string
  		instr := &decInstr{decString, 6, nil, ovfl}
  		state := newDecodeStateFromData(bytesResult)
  		execDec(instr, state, t, reflect.ValueOf(&data))
  		if data != "hello" {
  			t.Errorf(`bytes a = %q not "hello"`, data)
  		}
  	}
  }
  
  func TestEndToEnd(t *testing.T) {
  	type T2 struct {
  		T string
  	}
  	type T3 struct {
  		X float64
  		Z *int
  	}
  	type T1 struct {
  		A, B, C  int
  		M        map[string]*float64
  		M2       map[int]T3
  		Mstring  map[string]string
  		Mintptr  map[int]*int
  		Mcomp    map[complex128]complex128
  		Marr     map[[2]string][2]*float64
  		EmptyMap map[string]int // to check that we receive a non-nil map.
  		N        *[3]float64
  		Strs     *[2]string
  		Int64s   *[]int64
  		RI       complex64
  		S        string
  		Y        []byte
  		T        *T2
  	}
  	pi := 3.14159
  	e := 2.71828
  	two := 2.0
  	meaning := 42
  	fingers := 5
  	s1 := "string1"
  	s2 := "string2"
  	var comp1 complex128 = complex(1.0, 1.0)
  	var comp2 complex128 = complex(1.0, 1.0)
  	var arr1 [2]string
  	arr1[0] = s1
  	arr1[1] = s2
  	var arr2 [2]string
  	arr2[0] = s2
  	arr2[1] = s1
  	var floatArr1 [2]*float64
  	floatArr1[0] = &pi
  	floatArr1[1] = &e
  	var floatArr2 [2]*float64
  	floatArr2[0] = &e
  	floatArr2[1] = &two
  	t1 := &T1{
  		A:        17,
  		B:        18,
  		C:        -5,
  		M:        map[string]*float64{"pi": &pi, "e": &e},
  		M2:       map[int]T3{4: T3{X: pi, Z: &meaning}, 10: T3{X: e, Z: &fingers}},
  		Mstring:  map[string]string{"pi": "3.14", "e": "2.71"},
  		Mintptr:  map[int]*int{meaning: &fingers, fingers: &meaning},
  		Mcomp:    map[complex128]complex128{comp1: comp2, comp2: comp1},
  		Marr:     map[[2]string][2]*float64{arr1: floatArr1, arr2: floatArr2},
  		EmptyMap: make(map[string]int),
  		N:        &[3]float64{1.5, 2.5, 3.5},
  		Strs:     &[2]string{s1, s2},
  		Int64s:   &[]int64{77, 89, 123412342134},
  		RI:       17 - 23i,
  		S:        "Now is the time",
  		Y:        []byte("hello, sailor"),
  		T:        &T2{"this is T2"},
  	}
  	b := new(bytes.Buffer)
  	err := NewEncoder(b).Encode(t1)
  	if err != nil {
  		t.Error("encode:", err)
  	}
  	var _t1 T1
  	err = NewDecoder(b).Decode(&_t1)
  	if err != nil {
  		t.Fatal("decode:", err)
  	}
  	if !reflect.DeepEqual(t1, &_t1) {
  		t.Errorf("encode expected %v got %v", *t1, _t1)
  	}
  	// Be absolutely sure the received map is non-nil.
  	if t1.EmptyMap == nil {
  		t.Errorf("nil map sent")
  	}
  	if _t1.EmptyMap == nil {
  		t.Errorf("nil map received")
  	}
  }
  
  func TestOverflow(t *testing.T) {
  	type inputT struct {
  		Maxi int64
  		Mini int64
  		Maxu uint64
  		Maxf float64
  		Minf float64
  		Maxc complex128
  		Minc complex128
  	}
  	var it inputT
  	var err error
  	b := new(bytes.Buffer)
  	enc := NewEncoder(b)
  	dec := NewDecoder(b)
  
  	// int8
  	b.Reset()
  	it = inputT{
  		Maxi: math.MaxInt8 + 1,
  	}
  	type outi8 struct {
  		Maxi int8
  		Mini int8
  	}
  	var o1 outi8
  	enc.Encode(it)
  	err = dec.Decode(&o1)
  	if err == nil || err.Error() != `value for "Maxi" out of range` {
  		t.Error("wrong overflow error for int8:", err)
  	}
  	it = inputT{
  		Mini: math.MinInt8 - 1,
  	}
  	b.Reset()
  	enc.Encode(it)
  	err = dec.Decode(&o1)
  	if err == nil || err.Error() != `value for "Mini" out of range` {
  		t.Error("wrong underflow error for int8:", err)
  	}
  
  	// int16
  	b.Reset()
  	it = inputT{
  		Maxi: math.MaxInt16 + 1,
  	}
  	type outi16 struct {
  		Maxi int16
  		Mini int16
  	}
  	var o2 outi16
  	enc.Encode(it)
  	err = dec.Decode(&o2)
  	if err == nil || err.Error() != `value for "Maxi" out of range` {
  		t.Error("wrong overflow error for int16:", err)
  	}
  	it = inputT{
  		Mini: math.MinInt16 - 1,
  	}
  	b.Reset()
  	enc.Encode(it)
  	err = dec.Decode(&o2)
  	if err == nil || err.Error() != `value for "Mini" out of range` {
  		t.Error("wrong underflow error for int16:", err)
  	}
  
  	// int32
  	b.Reset()
  	it = inputT{
  		Maxi: math.MaxInt32 + 1,
  	}
  	type outi32 struct {
  		Maxi int32
  		Mini int32
  	}
  	var o3 outi32
  	enc.Encode(it)
  	err = dec.Decode(&o3)
  	if err == nil || err.Error() != `value for "Maxi" out of range` {
  		t.Error("wrong overflow error for int32:", err)
  	}
  	it = inputT{
  		Mini: math.MinInt32 - 1,
  	}
  	b.Reset()
  	enc.Encode(it)
  	err = dec.Decode(&o3)
  	if err == nil || err.Error() != `value for "Mini" out of range` {
  		t.Error("wrong underflow error for int32:", err)
  	}
  
  	// uint8
  	b.Reset()
  	it = inputT{
  		Maxu: math.MaxUint8 + 1,
  	}
  	type outu8 struct {
  		Maxu uint8
  	}
  	var o4 outu8
  	enc.Encode(it)
  	err = dec.Decode(&o4)
  	if err == nil || err.Error() != `value for "Maxu" out of range` {
  		t.Error("wrong overflow error for uint8:", err)
  	}
  
  	// uint16
  	b.Reset()
  	it = inputT{
  		Maxu: math.MaxUint16 + 1,
  	}
  	type outu16 struct {
  		Maxu uint16
  	}
  	var o5 outu16
  	enc.Encode(it)
  	err = dec.Decode(&o5)
  	if err == nil || err.Error() != `value for "Maxu" out of range` {
  		t.Error("wrong overflow error for uint16:", err)
  	}
  
  	// uint32
  	b.Reset()
  	it = inputT{
  		Maxu: math.MaxUint32 + 1,
  	}
  	type outu32 struct {
  		Maxu uint32
  	}
  	var o6 outu32
  	enc.Encode(it)
  	err = dec.Decode(&o6)
  	if err == nil || err.Error() != `value for "Maxu" out of range` {
  		t.Error("wrong overflow error for uint32:", err)
  	}
  
  	// float32
  	b.Reset()
  	it = inputT{
  		Maxf: math.MaxFloat32 * 2,
  	}
  	type outf32 struct {
  		Maxf float32
  		Minf float32
  	}
  	var o7 outf32
  	enc.Encode(it)
  	err = dec.Decode(&o7)
  	if err == nil || err.Error() != `value for "Maxf" out of range` {
  		t.Error("wrong overflow error for float32:", err)
  	}
  
  	// complex64
  	b.Reset()
  	it = inputT{
  		Maxc: complex(math.MaxFloat32*2, math.MaxFloat32*2),
  	}
  	type outc64 struct {
  		Maxc complex64
  		Minc complex64
  	}
  	var o8 outc64
  	enc.Encode(it)
  	err = dec.Decode(&o8)
  	if err == nil || err.Error() != `value for "Maxc" out of range` {
  		t.Error("wrong overflow error for complex64:", err)
  	}
  }
  
  func TestNesting(t *testing.T) {
  	type RT struct {
  		A    string
  		Next *RT
  	}
  	rt := new(RT)
  	rt.A = "level1"
  	rt.Next = new(RT)
  	rt.Next.A = "level2"
  	b := new(bytes.Buffer)
  	NewEncoder(b).Encode(rt)
  	var drt RT
  	dec := NewDecoder(b)
  	err := dec.Decode(&drt)
  	if err != nil {
  		t.Fatal("decoder error:", err)
  	}
  	if drt.A != rt.A {
  		t.Errorf("nesting: encode expected %v got %v", *rt, drt)
  	}
  	if drt.Next == nil {
  		t.Errorf("nesting: recursion failed")
  	}
  	if drt.Next.A != rt.Next.A {
  		t.Errorf("nesting: encode expected %v got %v", *rt.Next, *drt.Next)
  	}
  }
  
  // These three structures have the same data with different indirections
  type T0 struct {
  	A int
  	B int
  	C int
  	D int
  }
  type T1 struct {
  	A int
  	B *int
  	C **int
  	D ***int
  }
  type T2 struct {
  	A ***int
  	B **int
  	C *int
  	D int
  }
  
  func TestAutoIndirection(t *testing.T) {
  	// First transfer t1 into t0
  	var t1 T1
  	t1.A = 17
  	t1.B = new(int)
  	*t1.B = 177
  	t1.C = new(*int)
  	*t1.C = new(int)
  	**t1.C = 1777
  	t1.D = new(**int)
  	*t1.D = new(*int)
  	**t1.D = new(int)
  	***t1.D = 17777
  	b := new(bytes.Buffer)
  	enc := NewEncoder(b)
  	enc.Encode(t1)
  	dec := NewDecoder(b)
  	var t0 T0
  	dec.Decode(&t0)
  	if t0.A != 17 || t0.B != 177 || t0.C != 1777 || t0.D != 17777 {
  		t.Errorf("t1->t0: expected {17 177 1777 17777}; got %v", t0)
  	}
  
  	// Now transfer t2 into t0
  	var t2 T2
  	t2.D = 17777
  	t2.C = new(int)
  	*t2.C = 1777
  	t2.B = new(*int)
  	*t2.B = new(int)
  	**t2.B = 177
  	t2.A = new(**int)
  	*t2.A = new(*int)
  	**t2.A = new(int)
  	***t2.A = 17
  	b.Reset()
  	enc.Encode(t2)
  	t0 = T0{}
  	dec.Decode(&t0)
  	if t0.A != 17 || t0.B != 177 || t0.C != 1777 || t0.D != 17777 {
  		t.Errorf("t2->t0 expected {17 177 1777 17777}; got %v", t0)
  	}
  
  	// Now transfer t0 into t1
  	t0 = T0{17, 177, 1777, 17777}
  	b.Reset()
  	enc.Encode(t0)
  	t1 = T1{}
  	dec.Decode(&t1)
  	if t1.A != 17 || *t1.B != 177 || **t1.C != 1777 || ***t1.D != 17777 {
  		t.Errorf("t0->t1 expected {17 177 1777 17777}; got {%d %d %d %d}", t1.A, *t1.B, **t1.C, ***t1.D)
  	}
  
  	// Now transfer t0 into t2
  	b.Reset()
  	enc.Encode(t0)
  	t2 = T2{}
  	dec.Decode(&t2)
  	if ***t2.A != 17 || **t2.B != 177 || *t2.C != 1777 || t2.D != 17777 {
  		t.Errorf("t0->t2 expected {17 177 1777 17777}; got {%d %d %d %d}", ***t2.A, **t2.B, *t2.C, t2.D)
  	}
  
  	// Now do t2 again but without pre-allocated pointers.
  	b.Reset()
  	enc.Encode(t0)
  	***t2.A = 0
  	**t2.B = 0
  	*t2.C = 0
  	t2.D = 0
  	dec.Decode(&t2)
  	if ***t2.A != 17 || **t2.B != 177 || *t2.C != 1777 || t2.D != 17777 {
  		t.Errorf("t0->t2 expected {17 177 1777 17777}; got {%d %d %d %d}", ***t2.A, **t2.B, *t2.C, t2.D)
  	}
  }
  
  type RT0 struct {
  	A int
  	B string
  	C float64
  }
  type RT1 struct {
  	C      float64
  	B      string
  	A      int
  	NotSet string
  }
  
  func TestReorderedFields(t *testing.T) {
  	var rt0 RT0
  	rt0.A = 17
  	rt0.B = "hello"
  	rt0.C = 3.14159
  	b := new(bytes.Buffer)
  	NewEncoder(b).Encode(rt0)
  	dec := NewDecoder(b)
  	var rt1 RT1
  	// Wire type is RT0, local type is RT1.
  	err := dec.Decode(&rt1)
  	if err != nil {
  		t.Fatal("decode error:", err)
  	}
  	if rt0.A != rt1.A || rt0.B != rt1.B || rt0.C != rt1.C {
  		t.Errorf("rt1->rt0: expected %v; got %v", rt0, rt1)
  	}
  }
  
  // Like an RT0 but with fields we'll ignore on the decode side.
  type IT0 struct {
  	A        int64
  	B        string
  	Ignore_d []int
  	Ignore_e [3]float64
  	Ignore_f bool
  	Ignore_g string
  	Ignore_h []byte
  	Ignore_i *RT1
  	Ignore_m map[string]int
  	C        float64
  }
  
  func TestIgnoredFields(t *testing.T) {
  	var it0 IT0
  	it0.A = 17
  	it0.B = "hello"
  	it0.C = 3.14159
  	it0.Ignore_d = []int{1, 2, 3}
  	it0.Ignore_e[0] = 1.0
  	it0.Ignore_e[1] = 2.0
  	it0.Ignore_e[2] = 3.0
  	it0.Ignore_f = true
  	it0.Ignore_g = "pay no attention"
  	it0.Ignore_h = []byte("to the curtain")
  	it0.Ignore_i = &RT1{3.1, "hi", 7, "hello"}
  	it0.Ignore_m = map[string]int{"one": 1, "two": 2}
  
  	b := new(bytes.Buffer)
  	NewEncoder(b).Encode(it0)
  	dec := NewDecoder(b)
  	var rt1 RT1
  	// Wire type is IT0, local type is RT1.
  	err := dec.Decode(&rt1)
  	if err != nil {
  		t.Error("error: ", err)
  	}
  	if int(it0.A) != rt1.A || it0.B != rt1.B || it0.C != rt1.C {
  		t.Errorf("rt0->rt1: expected %v; got %v", it0, rt1)
  	}
  }
  
  func TestBadRecursiveType(t *testing.T) {
  	type Rec ***Rec
  	var rec Rec
  	b := new(bytes.Buffer)
  	err := NewEncoder(b).Encode(&rec)
  	if err == nil {
  		t.Error("expected error; got none")
  	} else if !strings.Contains(err.Error(), "recursive") {
  		t.Error("expected recursive type error; got", err)
  	}
  	// Can't test decode easily because we can't encode one, so we can't pass one to a Decoder.
  }
  
  type Indirect struct {
  	A ***[3]int
  	S ***[]int
  	M ****map[string]int
  }
  
  type Direct struct {
  	A [3]int
  	S []int
  	M map[string]int
  }
  
  func TestIndirectSliceMapArray(t *testing.T) {
  	// Marshal indirect, unmarshal to direct.
  	i := new(Indirect)
  	i.A = new(**[3]int)
  	*i.A = new(*[3]int)
  	**i.A = new([3]int)
  	***i.A = [3]int{1, 2, 3}
  	i.S = new(**[]int)
  	*i.S = new(*[]int)
  	**i.S = new([]int)
  	***i.S = []int{4, 5, 6}
  	i.M = new(***map[string]int)
  	*i.M = new(**map[string]int)
  	**i.M = new(*map[string]int)
  	***i.M = new(map[string]int)
  	****i.M = map[string]int{"one": 1, "two": 2, "three": 3}
  	b := new(bytes.Buffer)
  	NewEncoder(b).Encode(i)
  	dec := NewDecoder(b)
  	var d Direct
  	err := dec.Decode(&d)
  	if err != nil {
  		t.Error("error: ", err)
  	}
  	if len(d.A) != 3 || d.A[0] != 1 || d.A[1] != 2 || d.A[2] != 3 {
  		t.Errorf("indirect to direct: d.A is %v not %v", d.A, ***i.A)
  	}
  	if len(d.S) != 3 || d.S[0] != 4 || d.S[1] != 5 || d.S[2] != 6 {
  		t.Errorf("indirect to direct: d.S is %v not %v", d.S, ***i.S)
  	}
  	if len(d.M) != 3 || d.M["one"] != 1 || d.M["two"] != 2 || d.M["three"] != 3 {
  		t.Errorf("indirect to direct: d.M is %v not %v", d.M, ***i.M)
  	}
  	// Marshal direct, unmarshal to indirect.
  	d.A = [3]int{11, 22, 33}
  	d.S = []int{44, 55, 66}
  	d.M = map[string]int{"four": 4, "five": 5, "six": 6}
  	i = new(Indirect)
  	b.Reset()
  	NewEncoder(b).Encode(d)
  	dec = NewDecoder(b)
  	err = dec.Decode(&i)
  	if err != nil {
  		t.Fatal("error: ", err)
  	}
  	if len(***i.A) != 3 || (***i.A)[0] != 11 || (***i.A)[1] != 22 || (***i.A)[2] != 33 {
  		t.Errorf("direct to indirect: ***i.A is %v not %v", ***i.A, d.A)
  	}
  	if len(***i.S) != 3 || (***i.S)[0] != 44 || (***i.S)[1] != 55 || (***i.S)[2] != 66 {
  		t.Errorf("direct to indirect: ***i.S is %v not %v", ***i.S, ***i.S)
  	}
  	if len(****i.M) != 3 || (****i.M)["four"] != 4 || (****i.M)["five"] != 5 || (****i.M)["six"] != 6 {
  		t.Errorf("direct to indirect: ****i.M is %v not %v", ****i.M, d.M)
  	}
  }
  
  // An interface with several implementations
  type Squarer interface {
  	Square() int
  }
  
  type Int int
  
  func (i Int) Square() int {
  	return int(i * i)
  }
  
  type Float float64
  
  func (f Float) Square() int {
  	return int(f * f)
  }
  
  type Vector []int
  
  func (v Vector) Square() int {
  	sum := 0
  	for _, x := range v {
  		sum += x * x
  	}
  	return sum
  }
  
  type Point struct {
  	X, Y int
  }
  
  func (p Point) Square() int {
  	return p.X*p.X + p.Y*p.Y
  }
  
  // A struct with interfaces in it.
  type InterfaceItem struct {
  	I             int
  	Sq1, Sq2, Sq3 Squarer
  	F             float64
  	Sq            []Squarer
  }
  
  // The same struct without interfaces
  type NoInterfaceItem struct {
  	I int
  	F float64
  }
  
  func TestInterface(t *testing.T) {
  	iVal := Int(3)
  	fVal := Float(5)
  	// Sending a Vector will require that the receiver define a type in the middle of
  	// receiving the value for item2.
  	vVal := Vector{1, 2, 3}
  	b := new(bytes.Buffer)
  	item1 := &InterfaceItem{1, iVal, fVal, vVal, 11.5, []Squarer{iVal, fVal, nil, vVal}}
  	// Register the types.
  	Register(Int(0))
  	Register(Float(0))
  	Register(Vector{})
  	err := NewEncoder(b).Encode(item1)
  	if err != nil {
  		t.Error("expected no encode error; got", err)
  	}
  
  	item2 := InterfaceItem{}
  	err = NewDecoder(b).Decode(&item2)
  	if err != nil {
  		t.Fatal("decode:", err)
  	}
  	if item2.I != item1.I {
  		t.Error("normal int did not decode correctly")
  	}
  	if item2.Sq1 == nil || item2.Sq1.Square() != iVal.Square() {
  		t.Error("Int did not decode correctly")
  	}
  	if item2.Sq2 == nil || item2.Sq2.Square() != fVal.Square() {
  		t.Error("Float did not decode correctly")
  	}
  	if item2.Sq3 == nil || item2.Sq3.Square() != vVal.Square() {
  		t.Error("Vector did not decode correctly")
  	}
  	if item2.F != item1.F {
  		t.Error("normal float did not decode correctly")
  	}
  	// Now check that we received a slice of Squarers correctly, including a nil element
  	if len(item1.Sq) != len(item2.Sq) {
  		t.Fatalf("[]Squarer length wrong: got %d; expected %d", len(item2.Sq), len(item1.Sq))
  	}
  	for i, v1 := range item1.Sq {
  		v2 := item2.Sq[i]
  		if v1 == nil || v2 == nil {
  			if v1 != nil || v2 != nil {
  				t.Errorf("item %d inconsistent nils", i)
  			}
  		} else if v1.Square() != v2.Square() {
  			t.Errorf("item %d inconsistent values: %v %v", i, v1, v2)
  		}
  	}
  }
  
  // A struct with all basic types, stored in interfaces.
  type BasicInterfaceItem struct {
  	Int, Int8, Int16, Int32, Int64      interface{}
  	Uint, Uint8, Uint16, Uint32, Uint64 interface{}
  	Float32, Float64                    interface{}
  	Complex64, Complex128               interface{}
  	Bool                                interface{}
  	String                              interface{}
  	Bytes                               interface{}
  }
  
  func TestInterfaceBasic(t *testing.T) {
  	b := new(bytes.Buffer)
  	item1 := &BasicInterfaceItem{
  		int(1), int8(1), int16(1), int32(1), int64(1),
  		uint(1), uint8(1), uint16(1), uint32(1), uint64(1),
  		float32(1), 1.0,
  		complex64(1i), complex128(1i),
  		true,
  		"hello",
  		[]byte("sailor"),
  	}
  	err := NewEncoder(b).Encode(item1)
  	if err != nil {
  		t.Error("expected no encode error; got", err)
  	}
  
  	item2 := &BasicInterfaceItem{}
  	err = NewDecoder(b).Decode(&item2)
  	if err != nil {
  		t.Fatal("decode:", err)
  	}
  	if !reflect.DeepEqual(item1, item2) {
  		t.Errorf("encode expected %v got %v", item1, item2)
  	}
  	// Hand check a couple for correct types.
  	if v, ok := item2.Bool.(bool); !ok || !v {
  		t.Error("boolean should be true")
  	}
  	if v, ok := item2.String.(string); !ok || v != item1.String.(string) {
  		t.Errorf("string should be %v is %v", item1.String, v)
  	}
  }
  
  type String string
  
  type PtrInterfaceItem struct {
  	Str1 interface{} // basic
  	Str2 interface{} // derived
  }
  
  // We'll send pointers; should receive values.
  // Also check that we can register T but send *T.
  func TestInterfacePointer(t *testing.T) {
  	b := new(bytes.Buffer)
  	str1 := "howdy"
  	str2 := String("kiddo")
  	item1 := &PtrInterfaceItem{
  		&str1,
  		&str2,
  	}
  	// Register the type.
  	Register(str2)
  	err := NewEncoder(b).Encode(item1)
  	if err != nil {
  		t.Error("expected no encode error; got", err)
  	}
  
  	item2 := &PtrInterfaceItem{}
  	err = NewDecoder(b).Decode(&item2)
  	if err != nil {
  		t.Fatal("decode:", err)
  	}
  	// Hand test for correct types and values.
  	if v, ok := item2.Str1.(string); !ok || v != str1 {
  		t.Errorf("basic string failed: %q should be %q", v, str1)
  	}
  	if v, ok := item2.Str2.(String); !ok || v != str2 {
  		t.Errorf("derived type String failed: %q should be %q", v, str2)
  	}
  }
  
  func TestIgnoreInterface(t *testing.T) {
  	iVal := Int(3)
  	fVal := Float(5)
  	// Sending a Point will require that the receiver define a type in the middle of
  	// receiving the value for item2.
  	pVal := Point{2, 3}
  	b := new(bytes.Buffer)
  	item1 := &InterfaceItem{1, iVal, fVal, pVal, 11.5, nil}
  	// Register the types.
  	Register(Int(0))
  	Register(Float(0))
  	Register(Point{})
  	err := NewEncoder(b).Encode(item1)
  	if err != nil {
  		t.Error("expected no encode error; got", err)
  	}
  
  	item2 := NoInterfaceItem{}
  	err = NewDecoder(b).Decode(&item2)
  	if err != nil {
  		t.Fatal("decode:", err)
  	}
  	if item2.I != item1.I {
  		t.Error("normal int did not decode correctly")
  	}
  	if item2.F != item1.F {
  		t.Error("normal float did not decode correctly")
  	}
  }
  
  type U struct {
  	A int
  	B string
  	c float64
  	D uint
  }
  
  func TestUnexportedFields(t *testing.T) {
  	var u0 U
  	u0.A = 17
  	u0.B = "hello"
  	u0.c = 3.14159
  	u0.D = 23
  	b := new(bytes.Buffer)
  	NewEncoder(b).Encode(u0)
  	dec := NewDecoder(b)
  	var u1 U
  	u1.c = 1234.
  	err := dec.Decode(&u1)
  	if err != nil {
  		t.Fatal("decode error:", err)
  	}
  	if u0.A != u1.A || u0.B != u1.B || u0.D != u1.D {
  		t.Errorf("u1->u0: expected %v; got %v", u0, u1)
  	}
  	if u1.c != 1234. {
  		t.Error("u1.c modified")
  	}
  }
  
  var singletons = []interface{}{
  	true,
  	7,
  	3.2,
  	"hello",
  	[3]int{11, 22, 33},
  	[]float32{0.5, 0.25, 0.125},
  	map[string]int{"one": 1, "two": 2},
  }
  
  func TestDebugSingleton(t *testing.T) {
  	if debugFunc == nil {
  		return
  	}
  	b := new(bytes.Buffer)
  	// Accumulate a number of values and print them out all at once.
  	for _, x := range singletons {
  		err := NewEncoder(b).Encode(x)
  		if err != nil {
  			t.Fatal("encode:", err)
  		}
  	}
  	debugFunc(b)
  }
  
  // A type that won't be defined in the gob until we send it in an interface value.
  type OnTheFly struct {
  	A int
  }
  
  type DT struct {
  	//	X OnTheFly
  	A     int
  	B     string
  	C     float64
  	I     interface{}
  	J     interface{}
  	I_nil interface{}
  	M     map[string]int
  	T     [3]int
  	S     []string
  }
  
  func newDT() DT {
  	var dt DT
  	dt.A = 17
  	dt.B = "hello"
  	dt.C = 3.14159
  	dt.I = 271828
  	dt.J = OnTheFly{3}
  	dt.I_nil = nil
  	dt.M = map[string]int{"one": 1, "two": 2}
  	dt.T = [3]int{11, 22, 33}
  	dt.S = []string{"hi", "joe"}
  	return dt
  }
  
  func TestDebugStruct(t *testing.T) {
  	if debugFunc == nil {
  		return
  	}
  	Register(OnTheFly{})
  	dt := newDT()
  	b := new(bytes.Buffer)
  	err := NewEncoder(b).Encode(dt)
  	if err != nil {
  		t.Fatal("encode:", err)
  	}
  	debugBuffer := bytes.NewBuffer(b.Bytes())
  	dt2 := &DT{}
  	err = NewDecoder(b).Decode(&dt2)
  	if err != nil {
  		t.Error("decode:", err)
  	}
  	debugFunc(debugBuffer)
  }
  
  func encFuzzDec(rng *rand.Rand, in interface{}) error {
  	buf := new(bytes.Buffer)
  	enc := NewEncoder(buf)
  	if err := enc.Encode(&in); err != nil {
  		return err
  	}
  
  	b := buf.Bytes()
  	for i, bi := range b {
  		if rng.Intn(10) < 3 {
  			b[i] = bi + uint8(rng.Intn(256))
  		}
  	}
  
  	dec := NewDecoder(buf)
  	var e interface{}
  	if err := dec.Decode(&e); err != nil {
  		return err
  	}
  	return nil
  }
  
  // This does some "fuzz testing" by attempting to decode a sequence of random bytes.
  func TestFuzz(t *testing.T) {
  	if !*doFuzzTests {
  		t.Logf("disabled; run with -gob.fuzz to enable")
  		return
  	}
  
  	// all possible inputs
  	input := []interface{}{
  		new(int),
  		new(float32),
  		new(float64),
  		new(complex128),
  		&ByteStruct{255},
  		&ArrayStruct{},
  		&StringStruct{"hello"},
  		&GobTest1{0, &StringStruct{"hello"}},
  	}
  	testFuzz(t, time.Now().UnixNano(), 100, input...)
  }
  
  func TestFuzzRegressions(t *testing.T) {
  	if !*doFuzzTests {
  		t.Logf("disabled; run with -gob.fuzz to enable")
  		return
  	}
  
  	// An instance triggering a type name of length ~102 GB.
  	testFuzz(t, 1328492090837718000, 100, new(float32))
  	// An instance triggering a type name of 1.6 GB.
  	// Note: can take several minutes to run.
  	testFuzz(t, 1330522872628565000, 100, new(int))
  }
  
  func testFuzz(t *testing.T, seed int64, n int, input ...interface{}) {
  	for _, e := range input {
  		t.Logf("seed=%d n=%d e=%T", seed, n, e)
  		rng := rand.New(rand.NewSource(seed))
  		for i := 0; i < n; i++ {
  			encFuzzDec(rng, e)
  		}
  	}
  }
  
  // TestFuzzOneByte tries to decode corrupted input sequences
  // and checks that no panic occurs.
  func TestFuzzOneByte(t *testing.T) {
  	buf := new(bytes.Buffer)
  	Register(OnTheFly{})
  	dt := newDT()
  	if err := NewEncoder(buf).Encode(dt); err != nil {
  		t.Fatal(err)
  	}
  	s := buf.String()
  
  	indices := make([]int, 0, len(s))
  	for i := 0; i < len(s); i++ {
  		switch i {
  		case 14, 167, 231, 265: // a slice length, corruptions are not handled yet.
  			continue
  		}
  		indices = append(indices, i)
  	}
  	if testing.Short() {
  		indices = []int{1, 111, 178} // known fixed panics
  	}
  	for _, i := range indices {
  		for j := 0; j < 256; j += 3 {
  			b := []byte(s)
  			b[i] ^= byte(j)
  			var e DT
  			func() {
  				defer func() {
  					if p := recover(); p != nil {
  						t.Errorf("crash for b[%d] ^= 0x%x", i, j)
  						panic(p)
  					}
  				}()
  				err := NewDecoder(bytes.NewReader(b)).Decode(&e)
  				_ = err
  			}()
  		}
  	}
  }
  
  // Don't crash, just give error with invalid type id.
  // Issue 9649.
  func TestErrorInvalidTypeId(t *testing.T) {
  	data := []byte{0x01, 0x00, 0x01, 0x00}
  	d := NewDecoder(bytes.NewReader(data))
  	// When running d.Decode(&foo) the first time the decoder stops
  	// after []byte{0x01, 0x00} and reports an errBadType. Running
  	// d.Decode(&foo) again on exactly the same input sequence should
  	// give another errBadType, but instead caused a panic because
  	// decoderMap wasn't cleaned up properly after the first error.
  	for i := 0; i < 2; i++ {
  		var foo struct{}
  		err := d.Decode(&foo)
  		if err != errBadType {
  			t.Fatalf("decode: expected %s, got %s", errBadType, err)
  		}
  	}
  }
  

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