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// 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"
        "math"
        "math/rand"
        "reflect"
        "strings"
        "testing"
        "time"
        "unsafe"
)

// 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.
        }
        return
}

// Test basic encode/decode routines for unsigned integers
func TestUintCodec(t *testing.T) {
        defer testError(t)
        b := new(bytes.Buffer)
        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())
                }
        }
        decState := newDecodeState(b)
        for u := uint64(0); ; u = (u + 1) * 7 {
                b.Reset()
                encState.encodeUint(u)
                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(bytes.Buffer)
        encState := newEncoderState(b)
        encState.encodeInt(i)
        decState := newDecodeState(b)
        decState.buf = make([]byte, 8)
        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 *bytes.Buffer) *decoderState {
        d := new(decoderState)
        d.b = buf
        d.buf = make([]byte, uint64Size)
        return d
}

func newEncoderState(b *bytes.Buffer) *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(bytes.Buffer)

        // bool
        {
                data := struct{ a bool }{true}
                instr := &encInstr{encBool, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(boolResult, b.Bytes()) {
                        t.Errorf("bool enc instructions: expected % x got % x", boolResult, b.Bytes())
                }
        }

        // int
        {
                b.Reset()
                data := struct{ a int }{17}
                instr := &encInstr{encInt, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(signedResult, b.Bytes()) {
                        t.Errorf("int enc instructions: expected % x got % x", signedResult, b.Bytes())
                }
        }

        // uint
        {
                b.Reset()
                data := struct{ a uint }{17}
                instr := &encInstr{encUint, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(unsignedResult, b.Bytes()) {
                        t.Errorf("uint enc instructions: expected % x got % x", unsignedResult, b.Bytes())
                }
        }

        // int8
        {
                b.Reset()
                data := struct{ a int8 }{17}
                instr := &encInstr{encInt8, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(signedResult, b.Bytes()) {
                        t.Errorf("int8 enc instructions: expected % x got % x", signedResult, b.Bytes())
                }
        }

        // uint8
        {
                b.Reset()
                data := struct{ a uint8 }{17}
                instr := &encInstr{encUint8, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(unsignedResult, b.Bytes()) {
                        t.Errorf("uint8 enc instructions: expected % x got % x", unsignedResult, b.Bytes())
                }
        }

        // int16
        {
                b.Reset()
                data := struct{ a int16 }{17}
                instr := &encInstr{encInt16, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(signedResult, b.Bytes()) {
                        t.Errorf("int16 enc instructions: expected % x got % x", signedResult, b.Bytes())
                }
        }

        // uint16
        {
                b.Reset()
                data := struct{ a uint16 }{17}
                instr := &encInstr{encUint16, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(unsignedResult, b.Bytes()) {
                        t.Errorf("uint16 enc instructions: expected % x got % x", unsignedResult, b.Bytes())
                }
        }

        // int32
        {
                b.Reset()
                data := struct{ a int32 }{17}
                instr := &encInstr{encInt32, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(signedResult, b.Bytes()) {
                        t.Errorf("int32 enc instructions: expected % x got % x", signedResult, b.Bytes())
                }
        }

        // uint32
        {
                b.Reset()
                data := struct{ a uint32 }{17}
                instr := &encInstr{encUint32, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(unsignedResult, b.Bytes()) {
                        t.Errorf("uint32 enc instructions: expected % x got % x", unsignedResult, b.Bytes())
                }
        }

        // int64
        {
                b.Reset()
                data := struct{ a int64 }{17}
                instr := &encInstr{encInt64, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(signedResult, b.Bytes()) {
                        t.Errorf("int64 enc instructions: expected % x got % x", signedResult, b.Bytes())
                }
        }

        // uint64
        {
                b.Reset()
                data := struct{ a uint64 }{17}
                instr := &encInstr{encUint64, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(unsignedResult, b.Bytes()) {
                        t.Errorf("uint64 enc instructions: expected % x got % x", unsignedResult, b.Bytes())
                }
        }

        // float32
        {
                b.Reset()
                data := struct{ a float32 }{17}
                instr := &encInstr{encFloat32, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(floatResult, b.Bytes()) {
                        t.Errorf("float32 enc instructions: expected % x got % x", floatResult, b.Bytes())
                }
        }

        // float64
        {
                b.Reset()
                data := struct{ a float64 }{17}
                instr := &encInstr{encFloat64, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(floatResult, b.Bytes()) {
                        t.Errorf("float64 enc instructions: expected % x got % x", floatResult, b.Bytes())
                }
        }

        // bytes == []uint8
        {
                b.Reset()
                data := struct{ a []byte }{[]byte("hello")}
                instr := &encInstr{encUint8Array, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(bytesResult, b.Bytes()) {
                        t.Errorf("bytes enc instructions: expected % x got % x", bytesResult, b.Bytes())
                }
        }

        // string
        {
                b.Reset()
                data := struct{ a string }{"hello"}
                instr := &encInstr{encString, 6, 0, 0}
                state := newEncoderState(b)
                instr.op(instr, state, unsafe.Pointer(&data))
                if !bytes.Equal(bytesResult, b.Bytes()) {
                        t.Errorf("string enc instructions: expected % x got % x", bytesResult, b.Bytes())
                }
        }
}

func execDec(typ string, instr *decInstr, state *decoderState, t *testing.T, p unsafe.Pointer) {
        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, decIndirect(p, instr.indir))
        state.fieldnum = 6
}

func newDecodeStateFromData(data []byte) *decoderState {
        b := bytes.NewBuffer(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 struct {
                        a bool
                }
                instr := &decInstr{decBool, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(boolResult)
                execDec("bool", instr, state, t, unsafe.Pointer(&data))
                if data.a != true {
                        t.Errorf("bool a = %v not true", data.a)
                }
        }
        // int
        {
                var data struct {
                        a int
                }
                instr := &decInstr{decOpTable[reflect.Int], 6, 0, 0, ovfl}
                state := newDecodeStateFromData(signedResult)
                execDec("int", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("int a = %v not 17", data.a)
                }
        }

        // uint
        {
                var data struct {
                        a uint
                }
                instr := &decInstr{decOpTable[reflect.Uint], 6, 0, 0, ovfl}
                state := newDecodeStateFromData(unsignedResult)
                execDec("uint", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("uint a = %v not 17", data.a)
                }
        }

        // int8
        {
                var data struct {
                        a int8
                }
                instr := &decInstr{decInt8, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(signedResult)
                execDec("int8", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("int8 a = %v not 17", data.a)
                }
        }

        // uint8
        {
                var data struct {
                        a uint8
                }
                instr := &decInstr{decUint8, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(unsignedResult)
                execDec("uint8", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("uint8 a = %v not 17", data.a)
                }
        }

        // int16
        {
                var data struct {
                        a int16
                }
                instr := &decInstr{decInt16, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(signedResult)
                execDec("int16", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("int16 a = %v not 17", data.a)
                }
        }

        // uint16
        {
                var data struct {
                        a uint16
                }
                instr := &decInstr{decUint16, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(unsignedResult)
                execDec("uint16", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("uint16 a = %v not 17", data.a)
                }
        }

        // int32
        {
                var data struct {
                        a int32
                }
                instr := &decInstr{decInt32, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(signedResult)
                execDec("int32", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("int32 a = %v not 17", data.a)
                }
        }

        // uint32
        {
                var data struct {
                        a uint32
                }
                instr := &decInstr{decUint32, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(unsignedResult)
                execDec("uint32", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("uint32 a = %v not 17", data.a)
                }
        }

        // uintptr
        {
                var data struct {
                        a uintptr
                }
                instr := &decInstr{decOpTable[reflect.Uintptr], 6, 0, 0, ovfl}
                state := newDecodeStateFromData(unsignedResult)
                execDec("uintptr", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("uintptr a = %v not 17", data.a)
                }
        }

        // int64
        {
                var data struct {
                        a int64
                }
                instr := &decInstr{decInt64, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(signedResult)
                execDec("int64", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("int64 a = %v not 17", data.a)
                }
        }

        // uint64
        {
                var data struct {
                        a uint64
                }
                instr := &decInstr{decUint64, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(unsignedResult)
                execDec("uint64", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("uint64 a = %v not 17", data.a)
                }
        }

        // float32
        {
                var data struct {
                        a float32
                }
                instr := &decInstr{decFloat32, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(floatResult)
                execDec("float32", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("float32 a = %v not 17", data.a)
                }
        }

        // float64
        {
                var data struct {
                        a float64
                }
                instr := &decInstr{decFloat64, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(floatResult)
                execDec("float64", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17 {
                        t.Errorf("float64 a = %v not 17", data.a)
                }
        }

        // complex64
        {
                var data struct {
                        a complex64
                }
                instr := &decInstr{decOpTable[reflect.Complex64], 6, 0, 0, ovfl}
                state := newDecodeStateFromData(complexResult)
                execDec("complex", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17+19i {
                        t.Errorf("complex a = %v not 17+19i", data.a)
                }
        }

        // complex128
        {
                var data struct {
                        a complex128
                }
                instr := &decInstr{decOpTable[reflect.Complex128], 6, 0, 0, ovfl}
                state := newDecodeStateFromData(complexResult)
                execDec("complex", instr, state, t, unsafe.Pointer(&data))
                if data.a != 17+19i {
                        t.Errorf("complex a = %v not 17+19i", data.a)
                }
        }

        // bytes == []uint8
        {
                var data struct {
                        a []byte
                }
                instr := &decInstr{decUint8Slice, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(bytesResult)
                execDec("bytes", instr, state, t, unsafe.Pointer(&data))
                if string(data.a) != "hello" {
                        t.Errorf(`bytes a = %q not "hello"`, string(data.a))
                }
        }

        // string
        {
                var data struct {
                        a string
                }
                instr := &decInstr{decString, 6, 0, 0, ovfl}
                state := newDecodeStateFromData(bytesResult)
                execDec("bytes", instr, state, t, unsafe.Pointer(&data))
                if data.a != "hello" {
                        t.Errorf(`bytes a = %q not "hello"`, data.a)
                }
        }
}

func TestEndToEnd(t *testing.T) {
        type T2 struct {
                T string
        }
        s1 := "string1"
        s2 := "string2"
        type T1 struct {
                A, B, C  int
                M        map[string]*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
        t1 := &T1{
                A:        17,
                B:        18,
                C:        -5,
                M:        map[string]*float64{"pi": &pi, "e": &e},
                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.Index(err.Error(), "recursive") < 0 {
                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 Bad0 struct {
        CH chan int
        C  float64
}

func TestInvalidField(t *testing.T) {
        var bad0 Bad0
        bad0.CH = make(chan int)
        b := new(bytes.Buffer)
        dummyEncoder := new(Encoder) // sufficient for this purpose.
        dummyEncoder.encode(b, reflect.ValueOf(&bad0), userType(reflect.TypeOf(&bad0)))
        if err := dummyEncoder.err; err == nil {
                t.Error("expected error; got none")
        } else if strings.Index(err.Error(), "type") < 0 {
                t.Error("expected type error; got", err)
        }
}

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)
                        }
                        continue
                        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 != item2.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 != u0.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 TestDebugStruct(t *testing.T) {
        if debugFunc == nil {
                return
        }
        Register(OnTheFly{})
        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"}
        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 testing.Short() {
                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) {
        // An instance triggering a type name of length ~102 GB.
        testFuzz(t, 1328492090837718000, 100, new(float32))
}

func testFuzz(t *testing.T, seed int64, n int, input ...interface{}) {
        t.Logf("seed=%d n=%d\n", seed, n)
        for _, e := range input {
                rng := rand.New(rand.NewSource(seed))
                for i := 0; i < n; i++ {
                        encFuzzDec(rng, e)
                }
        }
}