[#226] sdk/object: Implement Tombstone type with field access and encoding

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

pkg/object/tombstone_test.go

@@ -0,0 +1,65 @@
+package object
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func generateIDList(sz int) []*ID {
+	res := make([]*ID, sz)
+	cs := [sha256.Size]byte{}
+
+	for i := 0; i < sz; i++ {
+		res[i] = NewID()
+		rand.Read(cs[:])
+		res[i].SetSHA256(cs)
+	}
+
+	return res
+}
+
+func TestTombstone(t *testing.T) {
+	ts := NewTombstone()
+
+	exp := uint64(13)
+	ts.SetExpirationEpoch(exp)
+	require.Equal(t, exp, ts.ExpirationEpoch())
+
+	splitID := NewSplitID()
+	ts.SetSplitID(splitID)
+	require.Equal(t, splitID, ts.SplitID())
+
+	members := generateIDList(3)
+	ts.SetMembers(members)
+	require.Equal(t, members, ts.Members())
+}
+
+func TestTombstoneEncoding(t *testing.T) {
+	ts := NewTombstone()
+	ts.SetExpirationEpoch(13)
+	ts.SetSplitID(NewSplitID())
+	ts.SetMembers(generateIDList(5))
+
+	t.Run("binary", func(t *testing.T) {
+		data, err := ts.Marshal()
+		require.NoError(t, err)
+
+		ts2 := NewTombstone()
+		require.NoError(t, ts2.Unmarshal(data))
+
+		require.Equal(t, ts, ts2)
+	})
+
+	t.Run("json", func(t *testing.T) {
+		data, err := ts.MarshalJSON()
+		require.NoError(t, err)
+
+		ts2 := NewTombstone()
+		require.NoError(t, ts2.UnmarshalJSON(data))
+
+		require.Equal(t, ts, ts2)
+	})
+}