src/pkg/gob/encoder_test.go

// 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";
	"io";
	"os";
	"reflect";
	"strings";
	"testing";
)

type ET2 struct {
	x string;
}

type ET1 struct {
	a	int;
	et2	*ET2;
	next	*ET1;
}

// Like ET1 but with a different name for a field
type ET3 struct {
	a		int;
	et2		*ET2;
	differentNext	*ET1;
}

// Like ET1 but with a different type for a field
type ET4 struct {
	a	int;
	et2	float;
	next	int;
}

func TestEncoderDecoder(t *testing.T) {
	b := new(bytes.Buffer);
	enc := NewEncoder(b);
	et1 := new(ET1);
	et1.a = 7;
	et1.et2 = new(ET2);
	enc.Encode(et1);
	if enc.state.err != nil {
		t.Error("encoder fail:", enc.state.err)
	}
	dec := NewDecoder(b);
	newEt1 := new(ET1);
	dec.Decode(newEt1);
	if dec.state.err != nil {
		t.Fatal("error decoding ET1:", dec.state.err)
	}

	if !reflect.DeepEqual(et1, newEt1) {
		t.Fatalf("invalid data for et1: expected %+v; got %+v\n", *et1, *newEt1)
	}
	if b.Len() != 0 {
		t.Error("not at eof;", b.Len(), "bytes left")
	}

	enc.Encode(et1);
	newEt1 = new(ET1);
	dec.Decode(newEt1);
	if dec.state.err != nil {
		t.Fatal("round 2: error decoding ET1:", dec.state.err)
	}
	if !reflect.DeepEqual(et1, newEt1) {
		t.Fatalf("round 2: invalid data for et1: expected %+v; got %+v\n", *et1, *newEt1)
	}
	if b.Len() != 0 {
		t.Error("round 2: not at eof;", b.Len(), "bytes left")
	}

	// Now test with a running encoder/decoder pair that we recognize a type mismatch.
	enc.Encode(et1);
	if enc.state.err != nil {
		t.Error("round 3: encoder fail:", enc.state.err)
	}
	newEt2 := new(ET2);
	dec.Decode(newEt2);
	if dec.state.err == nil {
		t.Fatal("round 3: expected `bad type' error decoding ET2")
	}
}

// Run one value through the encoder/decoder, but use the wrong type.
// Input is always an ET1; we compare it to whatever is under 'e'.
func badTypeCheck(e interface{}, shouldFail bool, msg string, t *testing.T) {
	b := new(bytes.Buffer);
	enc := NewEncoder(b);
	et1 := new(ET1);
	et1.a = 7;
	et1.et2 = new(ET2);
	enc.Encode(et1);
	if enc.state.err != nil {
		t.Error("encoder fail:", enc.state.err)
	}
	dec := NewDecoder(b);
	dec.Decode(e);
	if shouldFail && (dec.state.err == nil) {
		t.Error("expected error for", msg)
	}
	if !shouldFail && (dec.state.err != nil) {
		t.Error("unexpected error for", msg, dec.state.err)
	}
}

// Test that we recognize a bad type the first time.
func TestWrongTypeDecoder(t *testing.T) {
	badTypeCheck(new(ET2), true, "no fields in common", t);
	badTypeCheck(new(ET3), false, "different name of field", t);
	badTypeCheck(new(ET4), true, "different type of field", t);
}

func corruptDataCheck(s string, err os.Error, t *testing.T) {
	b := bytes.NewBufferString(s);
	dec := NewDecoder(b);
	dec.Decode(new(ET2));
	if dec.state.err != err {
		t.Error("expected error", err, "got", dec.state.err)
	}
}

// Check that we survive bad data.
func TestBadData(t *testing.T) {
	corruptDataCheck("", os.EOF, t);
	corruptDataCheck("\x7Fhi", io.ErrUnexpectedEOF, t);
	corruptDataCheck("\x03now is the time for all good men", errBadType, t);
}

// Types not supported by the Encoder (only structs work at the top level).
// Basic types work implicitly.
var unsupportedValues = []interface{}{
	3,
	"hi",
	7.2,
	[]int{1, 2, 3},
	[3]int{1, 2, 3},
	make(chan int),
	func(a int) bool { return true },
	make(map[string]int),
	new(interface{}),
}

func TestUnsupported(t *testing.T) {
	var b bytes.Buffer;
	enc := NewEncoder(&b);
	for _, v := range unsupportedValues {
		err := enc.Encode(v);
		if err == nil {
			t.Errorf("expected error for %T; got none", v)
		}
	}
}

func encAndDec(in, out interface{}) os.Error {
	b := new(bytes.Buffer);
	enc := NewEncoder(b);
	enc.Encode(in);
	if enc.state.err != nil {
		return enc.state.err
	}
	dec := NewDecoder(b);
	dec.Decode(out);
	if dec.state.err != nil {
		return dec.state.err
	}
	return nil;
}

func TestTypeToPtrType(t *testing.T) {
	// Encode a T, decode a *T
	type Type0 struct {
		a int;
	}
	t0 := Type0{7};
	t0p := (*Type0)(nil);
	if err := encAndDec(t0, t0p); err != nil {
		t.Error(err)
	}
}

func TestPtrTypeToType(t *testing.T) {
	// Encode a *T, decode a T
	type Type1 struct {
		a uint;
	}
	t1p := &Type1{17};
	var t1 Type1;
	if err := encAndDec(t1, t1p); err != nil {
		t.Error(err)
	}
}

func TestTypeToPtrPtrPtrPtrType(t *testing.T) {
	type Type2 struct {
		a ****float;
	}
	t2 := Type2{};
	t2.a = new(***float);
	*t2.a = new(**float);
	**t2.a = new(*float);
	***t2.a = new(float);
	****t2.a = 27.4;
	t2pppp := new(***Type2);
	if err := encAndDec(t2, t2pppp); err != nil {
		t.Error(err)
	}
	if ****(****t2pppp).a != ****t2.a {
		t.Errorf("wrong value after decode: %g not %g", ****(****t2pppp).a, ****t2.a)
	}
}

func TestSlice(t *testing.T) {
	type Type3 struct {
		a []string;
	}
	t3p := &Type3{[]string{"hello", "world"}};
	var t3 Type3;
	if err := encAndDec(t3, t3p); err != nil {
		t.Error(err)
	}
}

func TestValueError(t *testing.T) {
	// Encode a *T, decode a T
	type Type4 struct {
		a int;
	}
	t4p := &Type4{3};
	var t4 Type4;	// note: not a pointer.
	if err := encAndDec(t4p, t4); err == nil || strings.Index(err.String(), "pointer") < 0 {
		t.Error("expected error about pointer; got", err)
	}
}

func TestArray(t *testing.T) {
	type Type5 struct {
		a [3]string;
	}
	type Type6 struct {
		a [2]string;	// can't hold t5.a
	}
	t5 := Type5{[3]string{"hello", ",", "world"}};
	var t5p Type5;
	if err := encAndDec(t5, &t5p); err != nil {
		t.Error(err)
	}
	var t6 Type6;
	if err := encAndDec(t5, &t6); err == nil {
		t.Error("should fail with mismatched array sizes")
	}
}