}
	}

	maxInt64 := uint64(1<<63 - 1)
	if d.directorySize > maxInt64 || d.directoryOffset > maxInt64 {
		return nil, 0, ErrFormat
	}

	baseOffset = directoryEndOffset - int64(d.directorySize) - int64(d.directoryOffset)

	// Make sure directoryOffset points to somewhere in our file.
	if o := baseOffset + int64(d.directoryOffset); o < 0 || o >= size {
		return nil, 0, ErrFormat
	}

		}
		if _, err := io.Copy(io.Discard, r); err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
	}
}

func TestBaseOffsetPlusOverflow(t *testing.T) {
	// directoryOffset > maxInt64 && size-directoryOffset < 0
	data := []byte{
		0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
		0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
		0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,