stackitem: implement DeepCopy

pkg/vm/stackitem/item.go

@@ -1019,3 +1019,66 @@ func (i *Buffer) Convert(typ Type) (Item, error) {
 func (i *Buffer) Len() int {
 	return len(i.value)
 }
+
+// DeepCopy returns new deep copy of the provided item.
+// Values of Interop items are not deeply copied.
+// It does preserve duplicates only for non-primitive types.
+func DeepCopy(item Item) Item {
+	seen := make(map[Item]Item)
+	return deepCopy(item, seen)
+}
+
+func deepCopy(item Item, seen map[Item]Item) Item {
+	if it := seen[item]; it != nil {
+		return it
+	}
+	switch it := item.(type) {
+	case Null:
+		return Null{}
+	case *Array:
+		arr := NewArray(make([]Item, len(it.value)))
+		seen[item] = arr
+		for i := range it.value {
+			arr.value[i] = deepCopy(it.value[i], seen)
+		}
+		return arr
+	case *Struct:
+		arr := NewStruct(make([]Item, len(it.value)))
+		seen[item] = arr
+		for i := range it.value {
+			arr.value[i] = deepCopy(it.value[i], seen)
+		}
+		return arr
+	case *Map:
+		m := NewMap()
+		seen[item] = m
+		for i := range it.value {
+			key := deepCopy(it.value[i].Key, seen)
+			value := deepCopy(it.value[i].Value, seen)
+			m.Add(key, value)
+		}
+		return m
+	case *BigInteger:
+		bi := new(big.Int).SetBytes(it.value.Bytes())
+		if it.value.Sign() == -1 {
+			bi.Neg(bi)
+		}
+		return NewBigInteger(bi)
+	case *ByteArray:
+		val := make([]byte, len(it.value))
+		copy(val, it.value)
+		return NewByteArray(val)
+	case *Buffer:
+		val := make([]byte, len(it.value))
+		copy(val, it.value)
+		return NewBuffer(val)
+	case *Bool:
+		return NewBool(it.value)
+	case *Pointer:
+		return NewPointer(it.pos, it.script)
+	case *Interop:
+		return NewInterop(it.value)
+	default:
+		return nil
+	}
+}

pkg/vm/stackitem/item_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 var makeStackItemTestCases = []struct {
@@ -412,3 +413,61 @@ func TestMarshalJSON(t *testing.T) {
 		assert.Equal(t, testCase.result, actual)
 	}
 }
+
+func TestDeepCopy(t *testing.T) {
+	testCases := []struct {
+		name string
+		item Item
+	}{
+		{"Integer", NewBigInteger(big.NewInt(1))},
+		{"ByteArray", NewByteArray([]byte{1, 2, 3})},
+		{"Buffer", NewBuffer([]byte{1, 2, 3})},
+		{"Bool", NewBool(true)},
+		{"Pointer", NewPointer(1, []byte{1, 2, 3})},
+		{"Interop", NewInterop(&[]byte{1, 2})},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			actual := DeepCopy(tc.item)
+			require.Equal(t, tc.item, actual)
+			require.False(t, actual == tc.item)
+		})
+	}
+
+	t.Run("Null", func(t *testing.T) {
+		require.Equal(t, Null{}, DeepCopy(Null{}))
+	})
+
+	t.Run("Array", func(t *testing.T) {
+		arr := NewArray(make([]Item, 2))
+		arr.value[0] = NewBool(true)
+		arr.value[1] = arr
+
+		actual := DeepCopy(arr)
+		require.Equal(t, arr, actual)
+		require.False(t, arr == actual)
+		require.True(t, actual == actual.(*Array).value[1])
+	})
+
+	t.Run("Struct", func(t *testing.T) {
+		arr := NewStruct(make([]Item, 2))
+		arr.value[0] = NewBool(true)
+		arr.value[1] = arr
+
+		actual := DeepCopy(arr)
+		require.Equal(t, arr, actual)
+		require.False(t, arr == actual)
+		require.True(t, actual == actual.(*Struct).value[1])
+	})
+
+	t.Run("Map", func(t *testing.T) {
+		m := NewMapWithValue(make([]MapElement, 2))
+		m.value[0] = MapElement{Key: NewBool(true), Value: m}
+		m.value[1] = MapElement{Key: NewBigInteger(big.NewInt(1)), Value: NewByteArray([]byte{1, 2, 3})}
+
+		actual := DeepCopy(m)
+		require.Equal(t, m, actual)
+		require.False(t, m == actual)
+		require.True(t, actual == actual.(*Map).value[0].Value)
+	})
+}