Add stable marshal for storage group package

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

v2/storagegroup/marshal.go

@@ -0,0 +1,83 @@
+package storagegroup
+
+import (
+	"encoding/binary"
+
+	"github.com/nspcc-dev/neofs-api-go/util/proto"
+)
+
+const (
+	SizeField       = 1
+	HashField       = 2
+	ExpirationField = 3
+	ObjectIDsField  = 4
+)
+
+func (s *StorageGroup) StableMarshal(buf []byte) ([]byte, error) {
+	if s == nil {
+		return []byte{}, nil
+	}
+
+	if buf == nil {
+		buf = make([]byte, s.StableSize())
+	}
+
+	var (
+		offset, n int
+		prefix    uint64
+		err       error
+	)
+
+	n, err = proto.UInt64Marshal(SizeField, buf, s.size)
+	if err != nil {
+		return nil, err
+	}
+	offset += n
+
+	n, err = proto.BytesMarshal(HashField, buf[offset:], s.hash)
+	if err != nil {
+		return nil, err
+	}
+	offset += n
+
+	n, err = proto.UInt64Marshal(ExpirationField, buf[offset:], s.exp)
+	if err != nil {
+		return nil, err
+	}
+	offset += n
+
+	prefix, _ = proto.NestedStructurePrefix(ObjectIDsField)
+	for i := range s.members {
+		offset += binary.PutUvarint(buf[offset:], prefix)
+
+		n = s.members[i].StableSize()
+		offset += binary.PutUvarint(buf[offset:], uint64(n))
+
+		_, err = s.members[i].StableMarshal(buf[offset:])
+		if err != nil {
+			return nil, err
+		}
+
+		offset += n
+	}
+
+	return buf, nil
+}
+
+func (s *StorageGroup) StableSize() (size int) {
+	if s == nil {
+		return 0
+	}
+
+	size += proto.UInt64Size(SizeField, s.size)
+	size += proto.BytesSize(HashField, s.hash)
+	size += proto.UInt64Size(ExpirationField, s.exp)
+
+	_, ln := proto.NestedStructurePrefix(ObjectIDsField)
+	for i := range s.members {
+		n := s.members[i].StableSize()
+		size += ln + proto.VarUIntSize(uint64(n)) + n
+	}
+
+	return size
+}

v2/storagegroup/marshal_test.go

@@ -0,0 +1,36 @@
+package storagegroup_test
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neofs-api-go/v2/refs"
+	"github.com/nspcc-dev/neofs-api-go/v2/storagegroup"
+	grpc "github.com/nspcc-dev/neofs-api-go/v2/storagegroup/grpc"
+	"github.com/stretchr/testify/require"
+)
+
+func TestStorageGroup_StableMarshal(t *testing.T) {
+	ownerID1 := new(refs.ObjectID)
+	ownerID1.SetValue([]byte("Object ID 1"))
+	ownerID2 := new(refs.ObjectID)
+	ownerID2.SetValue([]byte("Object ID 2"))
+
+	storageGroupFrom := new(storagegroup.StorageGroup)
+	transport := new(grpc.StorageGroup)
+
+	t.Run("non empty", func(t *testing.T) {
+		storageGroupFrom.SetValidationDataSize(300)
+		storageGroupFrom.SetValidationHash([]byte("Homomorphic hash value"))
+		storageGroupFrom.SetExpirationEpoch(100)
+		storageGroupFrom.SetMembers([]*refs.ObjectID{ownerID1, ownerID2})
+
+		wire, err := storageGroupFrom.StableMarshal(nil)
+		require.NoError(t, err)
+
+		err = transport.Unmarshal(wire)
+		require.NoError(t, err)
+
+		storageGroupTo := storagegroup.StorageGroupFromGRPCMessage(transport)
+		require.Equal(t, storageGroupFrom, storageGroupTo)
+	})
+}