loop: add autoclear propert to LoopInfo

Small convenience property to check if the autoclear flag is set
in the `lo_flags` member of the `LoopInfo`.
Also add a corresponding test for it.

osbuild/loop.py

@@ -38,6 +38,11 @@ class LoopInfo(ctypes.Structure):
         ('lo_init', ctypes.c_uint64 * 2)
     ]
 
+    @property
+    def autoclear(self) -> bool:
+        """Return if `LO_FLAGS_AUTOCLEAR` is set in `lo_flags`"""
+        return bool(self.lo_flags & Loop.LO_FLAGS_AUTOCLEAR)
+
 
 class Loop:
     """Loopback device

test/mod/test_loop.py

@@ -35,7 +35,7 @@ def test_basic(tempdir):
         f = open(path, "wb+")
         f.truncate(1024)
         f.flush()
-        lo = ctl.loop_for_fd(f.fileno())
+        lo = ctl.loop_for_fd(f.fileno(), autoclear=True)
 
         sb = os.fstat(f.fileno())
 
@@ -46,6 +46,13 @@ def test_basic(tempdir):
         assert info.lo_inode == sb.st_ino
         assert info.lo_number == lo.minor
 
+        # check for autoclear flags setting and helpers
+        assert info.autoclear
+
+        lo.set_status(autoclear=False)
+        info = lo.get_status()
+        assert not info.autoclear
+
     finally:
         if lo:
             with contextlib.suppress(OSError):