From b780a64b4d2506ebf134c3bae767d45470023175 Mon Sep 17 00:00:00 2001
From: Evgeniy Stratonikov <evgeniy@nspcc.ru>
Date: Fri, 5 Mar 2021 14:16:34 +0300
Subject: [PATCH] emit: allow to emit `big.Int`

---
 pkg/vm/emit/emit.go      | 19 ++++++++++++++-----
 pkg/vm/emit/emit_test.go | 10 +++++++++-
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/pkg/vm/emit/emit.go b/pkg/vm/emit/emit.go
index 31ea60697..00f7c1b44 100644
--- a/pkg/vm/emit/emit.go
+++ b/pkg/vm/emit/emit.go
@@ -59,14 +59,21 @@ func Int(w *io.BinWriter, i int64) {
 		val := opcode.Opcode(int(opcode.PUSH1) - 1 + int(i))
 		Opcodes(w, val)
 	default:
-		buf := bigint.ToPreallocatedBytes(big.NewInt(i), make([]byte, 0, 32))
-		// l != 0 becase of switch
-		padSize := byte(8 - bits.LeadingZeros8(byte(len(buf)-1)))
-		Opcodes(w, opcode.PUSHINT8+opcode.Opcode(padSize))
-		w.WriteBytes(padRight(1<<padSize, buf))
+		bigInt(w, big.NewInt(i))
 	}
 }
 
+func bigInt(w *io.BinWriter, n *big.Int) {
+	buf := bigint.ToPreallocatedBytes(n, make([]byte, 0, 32))
+	if len(buf) == 0 {
+		Opcodes(w, opcode.PUSH0)
+		return
+	}
+	padSize := byte(8 - bits.LeadingZeros8(byte(len(buf)-1)))
+	Opcodes(w, opcode.PUSHINT8+opcode.Opcode(padSize))
+	w.WriteBytes(padRight(1<<padSize, buf))
+}
+
 // Array emits array of elements to the given buffer.
 func Array(w *io.BinWriter, es ...interface{}) {
 	for i := len(es) - 1; i >= 0; i-- {
@@ -75,6 +82,8 @@ func Array(w *io.BinWriter, es ...interface{}) {
 			Array(w, e...)
 		case int64:
 			Int(w, e)
+		case *big.Int:
+			bigInt(w, e)
 		case string:
 			String(w, e)
 		case util.Uint160:
diff --git a/pkg/vm/emit/emit_test.go b/pkg/vm/emit/emit_test.go
index 7d1fd9aa2..ea5c996a1 100644
--- a/pkg/vm/emit/emit_test.go
+++ b/pkg/vm/emit/emit_test.go
@@ -3,6 +3,8 @@ package emit
 import (
 	"encoding/binary"
 	"errors"
+	"math"
+	"math/big"
 	"testing"
 
 	"github.com/nspcc-dev/neo-go/pkg/core/interop/interopnames"
@@ -144,7 +146,10 @@ func TestBytes(t *testing.T) {
 func TestEmitArray(t *testing.T) {
 	t.Run("good", func(t *testing.T) {
 		buf := io.NewBufBinWriter()
-		Array(buf.BinWriter, []interface{}{int64(1), int64(2)}, nil, int64(1), "str", true, []byte{0xCA, 0xFE})
+		veryBig := new(big.Int).SetUint64(math.MaxUint64)
+		veryBig.Add(veryBig, big.NewInt(1))
+		Array(buf.BinWriter, big.NewInt(0), veryBig,
+			[]interface{}{int64(1), int64(2)}, nil, int64(1), "str", true, []byte{0xCA, 0xFE})
 		require.NoError(t, buf.Err)
 
 		res := buf.Bytes()
@@ -163,6 +168,9 @@ func TestEmitArray(t *testing.T) {
 		assert.EqualValues(t, opcode.PUSH1, res[15])
 		assert.EqualValues(t, opcode.PUSH2, res[16])
 		assert.EqualValues(t, opcode.PACK, res[17])
+		assert.EqualValues(t, opcode.PUSHINT128, res[18])
+		assert.EqualValues(t, veryBig, bigint.FromBytes(res[19:35]))
+		assert.EqualValues(t, opcode.PUSH0, res[35])
 	})
 
 	t.Run("empty", func(t *testing.T) {