native: reuse stackitem.(De)Serialize more for data structures

Less code bloat, no functional changes.

pkg/core/native/native_neo.go

@@ -20,7 +20,6 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
 	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
 	"github.com/nspcc-dev/neo-go/pkg/encoding/bigint"
-	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/manifest"
@@ -903,10 +902,9 @@ func (n *NEO) getAccountState(ic *interop.Context, args []stackitem.Item) stacki
 		return stackitem.Null{}
 	}
 
-	r := io.NewBinReaderFromBuf(si)
-	item := stackitem.DecodeBinary(r)
-	if r.Err != nil {
-		panic(r.Err) // no errors are expected but we better be sure
+	item, err := stackitem.Deserialize(si)
+	if err != nil {
+		panic(err) // no errors are expected but we better be sure
 	}
 	return item
 }

pkg/core/native/native_neo_candidate.go

@@ -3,7 +3,6 @@ package native
 import (
 	"math/big"
 
-	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
 
@@ -14,17 +13,18 @@ type candidate struct {
 
 // Bytes marshals c to byte array.
 func (c *candidate) Bytes() []byte {
-	w := io.NewBufBinWriter()
-	stackitem.EncodeBinary(c.toStackItem(), w.BinWriter)
-	return w.Bytes()
+	res, err := stackitem.Serialize(c.toStackItem())
+	if err != nil {
+		panic(err)
+	}
+	return res
 }
 
 // FromBytes unmarshals candidate from byte array.
 func (c *candidate) FromBytes(data []byte) *candidate {
-	r := io.NewBinReaderFromBuf(data)
-	item := stackitem.DecodeBinary(r)
-	if r.Err != nil {
-		panic(r.Err)
+	item, err := stackitem.Deserialize(data)
+	if err != nil {
+		panic(err)
 	}
 	return c.fromStackItem(item)
 }

pkg/core/native/neo_types.go

@@ -6,7 +6,6 @@ import (
 	"math/big"
 
 	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
-	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
 
@@ -84,21 +83,18 @@ func (k *keysWithVotes) fromStackItem(item stackitem.Item) error {
 
 // Bytes serializes keys with votes slice.
 func (k keysWithVotes) Bytes() []byte {
-	var it = k.toStackItem()
-	var w = io.NewBufBinWriter()
-	stackitem.EncodeBinary(it, w.BinWriter)
-	if w.Err != nil {
-		panic(w.Err)
+	buf, err := stackitem.Serialize(k.toStackItem())
+	if err != nil {
+		panic(err)
 	}
-	return w.Bytes()
+	return buf
 }
 
 // DecodeBytes deserializes keys and votes slice.
 func (k *keysWithVotes) DecodeBytes(data []byte) error {
-	var r = io.NewBinReaderFromBuf(data)
-	var it = stackitem.DecodeBinary(r)
-	if r.Err != nil {
-		return r.Err
+	it, err := stackitem.Deserialize(data)
+	if err != nil {
+		return err
 	}
 	return k.fromStackItem(it)
 }

pkg/core/native/oracle.go

@@ -359,12 +359,10 @@ func (o *Oracle) RequestInternal(ic *interop.Context, url string, filter *string
 		return err
 	}
 
-	w := io.NewBufBinWriter()
-	stackitem.EncodeBinary(userData, w.BinWriter)
-	if w.Err != nil {
-		return w.Err
+	data, err := stackitem.Serialize(userData)
+	if err != nil {
+		return err
 	}
-	data := w.Bytes()
 	if len(data) > maxUserDataLength {
 		return ErrBigArgument
 	}

pkg/core/native/std_test.go

@@ -11,7 +11,6 @@ import (
 	"github.com/mr-tron/base58"
 	"github.com/nspcc-dev/neo-go/pkg/core/interop"
 	base58neogo "github.com/nspcc-dev/neo-go/pkg/encoding/base58"
-	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/nspcc-dev/neo-go/pkg/vm"
 	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 	"github.com/stretchr/testify/assert"
@@ -275,11 +274,8 @@ func TestStdLibSerialize(t *testing.T) {
 			actualSerialized = s.serialize(ic, []stackitem.Item{stackitem.Make(42)})
 		})
 
-		w := io.NewBufBinWriter()
-		stackitem.EncodeBinary(stackitem.Make(42), w.BinWriter)
-		require.NoError(t, w.Err)
-
-		encoded := w.Bytes()
+		encoded, err := stackitem.Serialize(stackitem.Make(42))
+		require.NoError(t, err)
 		require.Equal(t, stackitem.Make(encoded), actualSerialized)
 
 		require.NotPanics(t, func() {