mpt: do not allocate NodeObject for serialization

Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>

pkg/core/mpt/base.go

@@ -23,7 +23,6 @@ type BaseNodeIface interface {
 	Hash() util.Uint256
 	Type() NodeType
 	Bytes() []byte
-	EncodeBinaryAsChild(w *io.BinWriter)
 }
 
 type flushedNode interface {
@@ -76,6 +75,15 @@ func (b *BaseNode) invalidateCache() {
 	b.hashValid = false
 }
 
+func encodeBinaryAsChild(n Node, w *io.BinWriter) {
+	if isEmpty(n) {
+		w.WriteB(byte(EmptyT))
+		return
+	}
+	w.WriteB(byte(HashT))
+	w.WriteBytes(n.Hash().BytesBE())
+}
+
 // encodeNodeWithType encodes node together with it's type.
 func encodeNodeWithType(n Node, w *io.BinWriter) {
 	switch t := n.Type(); t {

pkg/core/mpt/branch.go

@@ -48,16 +48,10 @@ func (b *BranchNode) Bytes() []byte {
 // EncodeBinary implements io.Serializable.
 func (b *BranchNode) EncodeBinary(w *io.BinWriter) {
 	for i := 0; i < childrenCount; i++ {
-		b.Children[i].EncodeBinaryAsChild(w)
+		encodeBinaryAsChild(b.Children[i], w)
 	}
 }
 
-// EncodeBinaryAsChild implements BaseNode interface.
-func (b *BranchNode) EncodeBinaryAsChild(w *io.BinWriter) {
-	n := &NodeObject{Node: NewHashNode(b.Hash())} // with type
-	n.EncodeBinary(w)
-}
-
 // DecodeBinary implements io.Serializable.
 func (b *BranchNode) DecodeBinary(r *io.BinReader) {
 	for i := 0; i < childrenCount; i++ {

pkg/core/mpt/extension.go

@@ -69,13 +69,7 @@ func (e *ExtensionNode) DecodeBinary(r *io.BinReader) {
 // EncodeBinary implements io.Serializable.
 func (e ExtensionNode) EncodeBinary(w *io.BinWriter) {
 	w.WriteVarBytes(e.key)
-	e.next.EncodeBinaryAsChild(w)
-}
-
-// EncodeBinaryAsChild implements BaseNode interface.
-func (e *ExtensionNode) EncodeBinaryAsChild(w *io.BinWriter) {
-	n := &NodeObject{Node: NewHashNode(e.Hash())} // with type
-	n.EncodeBinary(w)
+	encodeBinaryAsChild(e.next, w)
 }
 
 // MarshalJSON implements json.Marshaler.

pkg/core/mpt/hash.go

@@ -58,12 +58,6 @@ func (h HashNode) EncodeBinary(w *io.BinWriter) {
 	w.WriteBytes(h.hash[:])
 }
 
-// EncodeBinaryAsChild implements BaseNode interface.
-func (h *HashNode) EncodeBinaryAsChild(w *io.BinWriter) {
-	no := &NodeObject{Node: h} // with type
-	no.EncodeBinary(w)
-}
-
 // MarshalJSON implements json.Marshaler.
 func (h *HashNode) MarshalJSON() ([]byte, error) {
 	if !h.hashValid {

pkg/core/mpt/leaf.go

@@ -56,12 +56,6 @@ func (n LeafNode) EncodeBinary(w *io.BinWriter) {
 	w.WriteVarBytes(n.value)
 }
 
-// EncodeBinaryAsChild implements BaseNode interface.
-func (n *LeafNode) EncodeBinaryAsChild(w *io.BinWriter) {
-	no := &NodeObject{Node: NewHashNode(n.Hash())} // with type
-	no.EncodeBinary(w)
-}
-
 // MarshalJSON implements json.Marshaler.
 func (n *LeafNode) MarshalJSON() ([]byte, error) {
 	return []byte(`{"value":"` + hex.EncodeToString(n.value) + `"}`), nil