make sure the tmp is not be covered

rlp/encbuffer.go

@@ -359,11 +359,16 @@ func (w *EncoderBuffer) ToBytes() []byte {
 }
 
 // AppendToBytes appends the encoded bytes to dst.
-func (w *EncoderBuffer) AppendToBytes(dst []byte) []byte {
+func (w *EncoderBuffer) AppendToBytes(dst *[]byte) {
 	size := w.buf.size()
-	out := append(dst, make([]byte, size)...)
-	w.buf.copyTo(out[len(dst):])
-	return out
+	tmp, length := *dst, len(*dst)
+	if cap(tmp) >= size+length {
+		tmp = tmp[:size+length]
+	} else {
+		tmp = append(tmp, make([]byte, size)...)
+	}
+	*dst = tmp
+	w.buf.copyTo(tmp[length:])
 }
 
 // Write appends b directly to the encoder output.

rlp/encode_test.go

@@ -435,7 +435,7 @@ func TestEncodeToBytes(t *testing.T) {
 }
 
 func TestEncodeAppendToBytes(t *testing.T) {
-	buffer := make([]byte, 20)
+	buffer := make([]byte, 3)
 	runEncTests(t, func(val interface{}) ([]byte, error) {
 		w := NewEncoderBuffer(nil)
 		defer w.Flush()
@@ -444,8 +444,9 @@ func TestEncodeAppendToBytes(t *testing.T) {
 		if err != nil {
 			return nil, err
 		}
-		output := w.AppendToBytes(buffer[:0])
-		return output, nil
+		buffer = buffer[:0]
+		w.AppendToBytes(&buffer)
+		return buffer, nil
 	})
 }
 

trie/hasher.go

@@ -181,7 +181,8 @@ func (h *hasher) encodeFullNode(n *fullNode) []byte {
 // This convention exists because node.encode can only be inlined/escape-analyzed when
 // called on a concrete receiver type.
 func (h *hasher) encodedBytes() []byte {
-	h.tmp = h.encbuf.AppendToBytes(h.tmp[:0])
+	h.tmp = h.tmp[:0]
+	h.encbuf.AppendToBytes(&h.tmp)
 	h.encbuf.Reset(nil)
 	return h.tmp
 }