From f02d8b4ec4c3fd38e31994c2c1af8957e145c058 Mon Sep 17 00:00:00 2001
From: Evgeniy Stratonikov <evgeniy@nspcc.ru>
Date: Tue, 3 Aug 2021 16:29:21 +0300
Subject: [PATCH] stackitem: serialize integers to the pre-allocated slice

Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>
---
 pkg/vm/stackitem/serialization.go | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/pkg/vm/stackitem/serialization.go b/pkg/vm/stackitem/serialization.go
index b9a814e46..84e01bedc 100644
--- a/pkg/vm/stackitem/serialization.go
+++ b/pkg/vm/stackitem/serialization.go
@@ -112,8 +112,11 @@ func (w *serContext) serialize(item Item) error {
 		}
 	case *BigInteger:
 		w.data = append(w.data, byte(IntegerT))
-		data := bigint.ToBytes(t.Value().(*big.Int))
-		w.appendVarUint(uint64(len(data)))
+		v := t.Value().(*big.Int)
+		ln := len(w.data)
+		w.data = append(w.data, 0)
+		data := bigint.ToPreallocatedBytes(v, w.data[len(w.data):])
+		w.data[ln] = byte(len(data))
 		w.data = append(w.data, data...)
 	case *Interop:
 		if w.allowInvalid {