common: make Value encodable with package rlp

Value.{Encode,Decode} are gone. It implements rlp.Encoder and rlp.Decoder
instead, so Value can be decoded into directly.

common/rlp_test.go

@@ -5,6 +5,8 @@ import (
 	"math/big"
 	"reflect"
 	"testing"
+
+	"github.com/ethereum/go-ethereum/rlp"
 )
 
 func TestNonInterfaceSlice(t *testing.T) {
@@ -19,13 +21,16 @@ func TestNonInterfaceSlice(t *testing.T) {
 
 func TestRlpValueEncoding(t *testing.T) {
 	val := EmptyValue()
-	val.AppendList().Append(1).Append(2).Append(3)
-	val.Append("4").AppendList().Append(5)
+	val.AppendList().Append(byte(1)).Append(byte(2)).Append(byte(3))
+	val.Append("4").AppendList().Append(byte(5))
 
-	res := val.Encode()
+	res, err := rlp.EncodeToBytes(val)
+	if err != nil {
+		t.Fatalf("encode error: %v", err)
+	}
 	exp := Encode([]interface{}{[]interface{}{1, 2, 3}, "4", []interface{}{5}})
 	if bytes.Compare(res, exp) != 0 {
-		t.Errorf("expected %q, got %q", res, exp)
+		t.Errorf("expected %x, got %x", exp, res)
 	}
 }
 
@@ -57,9 +62,7 @@ func TestValueSlice(t *testing.T) {
 func TestLargeData(t *testing.T) {
 	data := make([]byte, 100000)
 	enc := Encode(data)
-	value := NewValue(enc)
-	value.Decode()
-
+	value := NewValueFromBytes(enc)
 	if value.Len() != len(data) {
 		t.Error("Expected data to be", len(data), "got", value.Len())
 	}
@@ -133,15 +136,16 @@ func TestEncodeDecodeBigInt(t *testing.T) {
 }
 
 func TestEncodeDecodeBytes(t *testing.T) {
-	b := NewValue([]interface{}{[]byte{1, 2, 3, 4, 5}, byte(6)})
-	val := NewValueFromBytes(b.Encode())
-	if !b.Cmp(val) {
-		t.Errorf("Expected %v, got %v", val, b)
+	bv := NewValue([]interface{}{[]byte{1, 2, 3, 4, 5}, []byte{6}})
+	b, _ := rlp.EncodeToBytes(bv)
+	val := NewValueFromBytes(b)
+	if !bv.Cmp(val) {
+		t.Errorf("Expected %#v, got %#v", bv, val)
 	}
 }
 
 func TestEncodeZero(t *testing.T) {
-	b := NewValue(0).Encode()
+	b, _ := rlp.EncodeToBytes(NewValue(0))
 	exp := []byte{0xc0}
 	if bytes.Compare(b, exp) == 0 {
 		t.Error("Expected", exp, "got", b)

common/value.go

@@ -3,14 +3,29 @@ package common
 import (
 	"bytes"
 	"fmt"
+	"io"
 	"math/big"
 	"reflect"
 	"strconv"
+
+	"github.com/ethereum/go-ethereum/rlp"
 )
 
-// Data values are returned by the rlp decoder. The data values represents
-// one item within the rlp data structure. It's responsible for all the casting
-// It always returns something valid
+// Value can hold values of certain basic types and provides ways to
+// convert between types without bothering to check whether the
+// conversion is actually meaningful.
+//
+// It currently supports the following types:
+//
+//    - int{,8,16,32,64}
+//    - uint{,8,16,32,64}
+//    - *big.Int
+//    - []byte, string
+//    - []interface{}
+//
+// Value is useful whenever you feel that Go's types limit your
+// ability to express yourself. In these situations, use Value and
+// forget about this strong typing nonsense.
 type Value struct {
 	Val  interface{}
 	kind reflect.Value
@@ -260,26 +275,34 @@ func (self *Value) DeepCmp(o *Value) bool {
 	return bytes.Compare(self.Bytes(), o.Bytes()) == 0
 }
 
-func (val *Value) Encode() []byte {
-	return Encode(val.Val)
+func (self *Value) DecodeRLP(s *rlp.Stream) error {
+	var v interface{}
+	if err := s.Decode(&v); err != nil {
+		return err
+	}
+	self.Val = v
+	return nil
 }
 
-// Assume that the data we have is encoded
-func (self *Value) Decode() {
-	v, _ := Decode(self.Bytes(), 0)
-	self.Val = v
-	//self.Val = DecodeWithReader(bytes.NewBuffer(self.Bytes()))
+func (self *Value) EncodeRLP(w io.Writer) error {
+	if self == nil {
+		w.Write(rlp.EmptyList)
+		return nil
+	} else {
+		return rlp.Encode(w, self.Val)
+	}
 }
 
+// NewValueFromBytes decodes RLP data.
+// The contained value will be nil if data contains invalid RLP.
 func NewValueFromBytes(data []byte) *Value {
+	v := new(Value)
 	if len(data) != 0 {
-		value := NewValue(data)
-		value.Decode()
-
-		return value
+		if err := rlp.DecodeBytes(data, v); err != nil {
+			v.Val = nil
+		}
 	}
-
-	return NewValue(nil)
+	return v
 }
 
 // Value setters