loop: add LoopInfo.is_bound_to helper

Add a helper that will check if the loop devices is backed by
the file identified via the stat(2) result, i.e. the inode on
the correspoding device.
Add a correspoding test for the new helper.

osbuild/loop.py

@@ -43,6 +43,11 @@ class LoopInfo(ctypes.Structure):
         """Return if `LO_FLAGS_AUTOCLEAR` is set in `lo_flags`"""
         return bool(self.lo_flags & Loop.LO_FLAGS_AUTOCLEAR)
 
+    def is_bound_to(self, info: os.stat_result) -> bool:
+        """Return if the loop device is bound to the file `info`"""
+        return (self.lo_device == info.st_dev and
+                self.lo_inode == info.st_ino)
+
 
 class Loop:
     """Loopback device

test/mod/test_loop.py

@@ -4,7 +4,7 @@
 
 import contextlib
 import os
-from tempfile import TemporaryDirectory
+from tempfile import TemporaryDirectory, TemporaryFile
 
 import pytest
 
@@ -46,6 +46,16 @@ def test_basic(tempdir):
         assert info.lo_inode == sb.st_ino
         assert info.lo_number == lo.minor
 
+        # check for `LoopInfo.is_bound_to` helper
+        assert info.is_bound_to(sb)
+
+        with TemporaryFile(dir=tempdir) as t:
+            t.write(b"")
+            t.flush()
+
+            st = os.fstat(t.fileno())
+            assert not info.is_bound_to(st)
+
         # check for autoclear flags setting and helpers
         assert info.autoclear