From f01fc1cc290655b97662ef2aa3187d0747784d0b Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Fri, 6 Dec 2019 18:15:33 +0300
Subject: [PATCH] io: optimize BinWriter.WriteArray()

Replace reflect.MethodByName with a simple interface cast.
---
 pkg/io/binaryWriter.go  | 23 ++++++++---------------
 pkg/io/binaryrw_test.go |  3 +--
 pkg/io/serializable.go  |  4 ++++
 3 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/pkg/io/binaryWriter.go b/pkg/io/binaryWriter.go
index 16e9dfc77..5b6ccade9 100644
--- a/pkg/io/binaryWriter.go
+++ b/pkg/io/binaryWriter.go
@@ -39,33 +39,26 @@ func (w *BinWriter) WriteBE(v interface{}) {
 func (w *BinWriter) WriteArray(arr interface{}) {
 	switch val := reflect.ValueOf(arr); val.Kind() {
 	case reflect.Slice, reflect.Array:
-		typ := val.Type().Elem()
-		method, ok := typ.MethodByName("EncodeBinary")
-		if !ok || !isEncodeBinaryMethod(method) {
-			panic(typ.String() + " does not have EncodeBinary(*BinWriter)")
-		}
-
 		if w.Err != nil {
 			return
 		}
 
+		typ := val.Type().Elem()
+
 		w.WriteVarUint(uint64(val.Len()))
 		for i := 0; i < val.Len(); i++ {
-			method := val.Index(i).MethodByName("EncodeBinary")
-			method.Call([]reflect.Value{reflect.ValueOf(w)})
+			el, ok := val.Index(i).Interface().(encodable)
+			if !ok {
+				panic(typ.String() + "is not encodable")
+			}
+
+			el.EncodeBinary(w)
 		}
 	default:
 		panic("not an array")
 	}
 }
 
-func isEncodeBinaryMethod(method reflect.Method) bool {
-	t := method.Type
-	return t != nil &&
-		t.NumIn() == 2 && t.In(1) == reflect.TypeOf((*BinWriter)(nil)) &&
-		t.NumOut() == 0
-}
-
 // WriteVarUint writes a uint64 into the underlying writer using variable-length encoding.
 func (w *BinWriter) WriteVarUint(val uint64) {
 	if w.Err != nil {
diff --git a/pkg/io/binaryrw_test.go b/pkg/io/binaryrw_test.go
index 4ce265d2a..8c6d64c6e 100644
--- a/pkg/io/binaryrw_test.go
+++ b/pkg/io/binaryrw_test.go
@@ -267,8 +267,7 @@ func TestBinWriter_WriteArray(t *testing.T) {
 	require.Equal(t, w.Bytes(), []byte(nil))
 
 	w.Reset()
-	w.Err = errors.New("error")
-	require.Panics(t, func() { w.WriteArray([]int{}) })
+	require.Panics(t, func() { w.WriteArray([]int{1}) })
 
 	w.Reset()
 	w.Err = errors.New("error")
diff --git a/pkg/io/serializable.go b/pkg/io/serializable.go
index c878d8ddb..43e659731 100644
--- a/pkg/io/serializable.go
+++ b/pkg/io/serializable.go
@@ -14,3 +14,7 @@ type Serializable interface {
 type decodable interface {
 	DecodeBinary(*BinReader)
 }
+
+type encodable interface {
+	EncodeBinary(*BinWriter)
+}