From 7f038bd4650340d6da0941088a4aeaa356cfad98 Mon Sep 17 00:00:00 2001
From: Anna Shaleva <shaleva.ann@nspcc.ru>
Date: Tue, 30 Mar 2021 20:35:41 +0300
Subject: [PATCH] mpt: split HashNode in two types

First type is non-empty HashNode, and the second one is an Empty node.
---
 pkg/core/mpt/base.go                | 24 ++++++++++++++++++++++--
 pkg/core/mpt/hash.go                | 15 +++------------
 pkg/core/mpt/node.go                |  1 +
 pkg/core/mpt/node_test.go           | 11 +++++++----
 pkg/rpc/response/result/mpt_test.go |  6 ++++--
 5 files changed, 37 insertions(+), 20 deletions(-)

diff --git a/pkg/core/mpt/base.go b/pkg/core/mpt/base.go
index 38645ff05..8762281d6 100644
--- a/pkg/core/mpt/base.go
+++ b/pkg/core/mpt/base.go
@@ -78,7 +78,17 @@ func (b *BaseNode) invalidateCache() {
 
 // encodeNodeWithType encodes node together with it's type.
 func encodeNodeWithType(n Node, w *io.BinWriter) {
-	w.WriteB(byte(n.Type()))
+	switch t := n.Type(); t {
+	case HashT:
+		hn := n.(*HashNode)
+		if !hn.hashValid {
+			w.WriteB(byte(EmptyT))
+			break
+		}
+		fallthrough
+	default:
+		w.WriteB(byte(t))
+	}
 	n.EncodeBinary(w)
 }
 
@@ -94,9 +104,19 @@ func DecodeNodeWithType(r *io.BinReader) Node {
 	case ExtensionT:
 		n = new(ExtensionNode)
 	case HashT:
-		n = new(HashNode)
+		n = &HashNode{
+			BaseNode: BaseNode{
+				hashValid: true,
+			},
+		}
 	case LeafT:
 		n = new(LeafNode)
+	case EmptyT:
+		n = &HashNode{
+			BaseNode: BaseNode{
+				hashValid: false,
+			},
+		}
 	default:
 		r.Err = fmt.Errorf("invalid node type: %x", typ)
 		return nil
diff --git a/pkg/core/mpt/hash.go b/pkg/core/mpt/hash.go
index 03c4fdc1d..ca24dc457 100644
--- a/pkg/core/mpt/hash.go
+++ b/pkg/core/mpt/hash.go
@@ -2,7 +2,6 @@ package mpt
 
 import (
 	"errors"
-	"fmt"
 
 	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/nspcc-dev/neo-go/pkg/util"
@@ -46,25 +45,17 @@ func (h *HashNode) Bytes() []byte {
 
 // DecodeBinary implements io.Serializable.
 func (h *HashNode) DecodeBinary(r *io.BinReader) {
-	sz := r.ReadVarUint()
-	switch sz {
-	case 0:
-		h.hashValid = false
-	case util.Uint256Size:
-		h.hashValid = true
-		r.ReadBytes(h.hash[:])
-	default:
-		r.Err = fmt.Errorf("invalid hash node size: %d", sz)
+	if h.hashValid {
+		h.hash.DecodeBinary(r)
 	}
 }
 
 // EncodeBinary implements io.Serializable.
 func (h HashNode) EncodeBinary(w *io.BinWriter) {
 	if !h.hashValid {
-		w.WriteVarUint(0)
 		return
 	}
-	w.WriteVarBytes(h.hash[:])
+	w.WriteBytes(h.hash[:])
 }
 
 // EncodeBinaryAsChild implements BaseNode interface.
diff --git a/pkg/core/mpt/node.go b/pkg/core/mpt/node.go
index befc216fd..2d2c42807 100644
--- a/pkg/core/mpt/node.go
+++ b/pkg/core/mpt/node.go
@@ -18,6 +18,7 @@ const (
 	ExtensionT NodeType = 0x01
 	LeafT      NodeType = 0x02
 	HashT      NodeType = 0x03
+	EmptyT     NodeType = 0x04
 )
 
 // NodeObject represents Node together with it's type.
diff --git a/pkg/core/mpt/node_test.go b/pkg/core/mpt/node_test.go
index 8dd65ac9d..74c0247a2 100644
--- a/pkg/core/mpt/node_test.go
+++ b/pkg/core/mpt/node_test.go
@@ -16,6 +16,9 @@ func getTestFuncEncode(ok bool, expected, actual Node) func(t *testing.T) {
 		t.Run("IO", func(t *testing.T) {
 			bs, err := testserdes.EncodeBinary(expected)
 			require.NoError(t, err)
+			if hn, ok := actual.(*HashNode); ok {
+				hn.hashValid = true // this field is set during NodeObject decoding
+			}
 			err = testserdes.DecodeBinary(bs, actual)
 			if !ok {
 				require.Error(t, err)
@@ -80,8 +83,8 @@ func TestNode_Serializable(t *testing.T) {
 		})
 		t.Run("InvalidSize", func(t *testing.T) {
 			buf := io.NewBufBinWriter()
-			buf.BinWriter.WriteVarBytes(make([]byte, 13))
-			require.Error(t, testserdes.DecodeBinary(buf.Bytes(), new(HashNode)))
+			buf.BinWriter.WriteBytes(make([]byte, 13))
+			require.Error(t, testserdes.DecodeBinary(buf.Bytes(), &HashNode{BaseNode: BaseNode{hashValid: true}}))
 		})
 	})
 
@@ -151,6 +154,6 @@ func TestRootHash(t *testing.T) {
 	b.Children[9] = l2
 
 	r1 := NewExtensionNode([]byte{0x0A, 0x0C, 0x00, 0x01}, v1)
-	require.Equal(t, "a6d1385fa2e089fd9ca79e58bee47cb4c9c949140a382580138840113412931d", r1.Hash().StringLE())
-	require.Equal(t, "62d14dc02b9f905ca6ec73fb499b1eef835e482d936744e3b6298cf9ad26ba03", r.Hash().StringLE())
+	require.Equal(t, "cedd9897dd1559fbd5dfe5cfb223464da6de438271028afb8d647e950cbd18e0", r1.Hash().StringLE())
+	require.Equal(t, "1037e779c8a0313bd0d99c4151fa70a277c43c53a549b6444079f2e67e8ffb7b", r.Hash().StringLE())
 }
diff --git a/pkg/rpc/response/result/mpt_test.go b/pkg/rpc/response/result/mpt_test.go
index 91adeaabb..e328288f8 100644
--- a/pkg/rpc/response/result/mpt_test.go
+++ b/pkg/rpc/response/result/mpt_test.go
@@ -1,10 +1,13 @@
 package result
 
 import (
+	"encoding/json"
 	"testing"
 
 	"github.com/nspcc-dev/neo-go/internal/random"
 	"github.com/nspcc-dev/neo-go/internal/testserdes"
+	"github.com/nspcc-dev/neo-go/pkg/core/mpt"
+	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/stretchr/testify/require"
 )
 
@@ -19,7 +22,6 @@ func testProofWithKey() *ProofWithKey {
 	}
 }
 
-/*
 func TestGetProof_MarshalJSON(t *testing.T) {
 	t.Run("Good", func(t *testing.T) {
 		p := testProofWithKey()
@@ -40,7 +42,7 @@ func TestGetProof_MarshalJSON(t *testing.T) {
 		}
 	})
 }
-*/
+
 func TestProofWithKey_EncodeString(t *testing.T) {
 	expected := testProofWithKey()
 	var actual ProofWithKey