[#79] Fix panic on get empty object

Signed-off-by: Denis Kirillov <denis@nspcc.ru>

handlers/objects_test.go

@@ -0,0 +1,77 @@
+package handlers
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neofs-rest-gw/gen/restapi/operations"
+	"github.com/nspcc-dev/neofs-rest-gw/internal/util"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPrepareOffset(t *testing.T) {
+	for _, tc := range []struct {
+		err            bool
+		expectedOffset uint64
+		expectedLength uint64
+		params         operations.GetObjectInfoParams
+		objSize        uint64
+	}{
+		{
+			params: operations.GetObjectInfoParams{
+				RangeLength: util.NewInteger(1),
+				RangeOffset: util.NewInteger(0),
+			},
+			objSize:        1,
+			expectedOffset: 0,
+			expectedLength: 1,
+		},
+		{
+			params: operations.GetObjectInfoParams{
+				RangeLength: util.NewInteger(3),
+				RangeOffset: util.NewInteger(1),
+			},
+			objSize:        5,
+			expectedOffset: 1,
+			expectedLength: 3,
+		},
+		{
+			objSize:        1,
+			expectedOffset: 0,
+			expectedLength: 1,
+		},
+		{
+			err: true,
+			params: operations.GetObjectInfoParams{
+				RangeLength: util.NewInteger(1),
+				RangeOffset: nil,
+			},
+		},
+		{
+			err: true,
+			params: operations.GetObjectInfoParams{
+				RangeLength: nil,
+				RangeOffset: util.NewInteger(1),
+			},
+		},
+		{
+			err: true,
+			params: operations.GetObjectInfoParams{
+				RangeLength: util.NewInteger(1),
+				RangeOffset: util.NewInteger(0),
+			},
+			objSize: 0,
+		},
+	} {
+		t.Run("", func(t *testing.T) {
+			offset, length, err := prepareOffsetLength(tc.params, tc.objSize)
+			if tc.err {
+				require.Error(t, err)
+				return
+			}
+
+			require.NoError(t, err)
+			require.Equal(t, tc.expectedOffset, offset)
+			require.Equal(t, tc.expectedLength, length)
+		})
+	}
+}