Add v2 version to go module name

Replace all elements from `v2` to root directory.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

tombstone/marshal.go

@@ -0,0 +1,76 @@
+package tombstone
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/v2/rpc/message"
+	tombstone "github.com/nspcc-dev/neofs-api-go/v2/tombstone/grpc"
+	"github.com/nspcc-dev/neofs-api-go/v2/util/proto"
+)
+
+const (
+	expFNum     = 1
+	splitIDFNum = 2
+	membersFNum = 3
+)
+
+// StableMarshal marshals unified tombstone message in a protobuf
+// compatible way without field order shuffle.
+func (s *Tombstone) StableMarshal(buf []byte) ([]byte, error) {
+	if s == nil {
+		return []byte{}, nil
+	}
+
+	if buf == nil {
+		buf = make([]byte, s.StableSize())
+	}
+
+	var (
+		offset, n int
+		err       error
+	)
+
+	n, err = proto.UInt64Marshal(expFNum, buf[offset:], s.exp)
+	if err != nil {
+		return nil, err
+	}
+
+	offset += n
+
+	n, err = proto.BytesMarshal(splitIDFNum, buf[offset:], s.splitID)
+	if err != nil {
+		return nil, err
+	}
+
+	offset += n
+
+	for i := range s.members {
+		n, err = proto.NestedStructureMarshal(membersFNum, buf[offset:], s.members[i])
+		if err != nil {
+			return nil, err
+		}
+
+		offset += n
+	}
+
+	return buf, nil
+}
+
+// StableSize returns size of tombstone message marshalled by StableMarshal function.
+func (s *Tombstone) StableSize() (size int) {
+	if s == nil {
+		return 0
+	}
+
+	size += proto.UInt64Size(expFNum, s.exp)
+	size += proto.BytesSize(splitIDFNum, s.splitID)
+
+	for i := range s.members {
+		size += proto.NestedStructureSize(membersFNum, s.members[i])
+	}
+
+	return size
+}
+
+// Unmarshal unmarshal tombstone message from its binary representation.
+func (s *Tombstone) Unmarshal(data []byte) error {
+	return message.Unmarshal(s, data, new(tombstone.Tombstone))
+}