implement NCD detection; fix file deletion on Windows

Author: JKB

sigmf/sigmffile.py

@@ -558,6 +558,12 @@ def set_data_file(self, data_file=None, data_buffer=None, skip_checksum=False, o
             self._memmap = raveled.reshape(mapped_reshape)
             self.shape = self._memmap.shape if (self._return_type is None) else self._memmap.shape[:-1]
 
+        if self.data_file is not None:
+            file_name = path.split(self.data_file)[1]
+            ext = path.splitext(file_name)[1]
+            if ext.lower() != SIGMF_DATASET_EXT:
+                self.set_global_field(SigMFFile.DATASET_KEY, file_name)
+
         if skip_checksum:
             return None
         return self.calculate_hash()
@@ -937,7 +943,7 @@ def get_dataset_filename_from_metadata(meta_fn, metadata=None):
         3. None (may be a metadata only distribution)
     """
     compliant_filename = get_sigmf_filenames(meta_fn)["data_fn"]
-    noncompliant_filename = metadata["global"].get("core:dataset", None)
+    noncompliant_filename = metadata["global"].get(SigMFFile.DATASET_KEY, None)
 
     if path.isfile(compliant_filename):
         if noncompliant_filename:

tests/test_ncd.py

@@ -47,8 +47,6 @@ def test_load_ncd(self, subdir: str) -> None:
         # create metadata file
         ncd_metadata = copy.deepcopy(TEST_METADATA)
         meta = SigMFFile(metadata=ncd_metadata, data_file=data_path)
-        # tell SigMF that the data is noncompliant
-        meta.set_global_field(SigMFFile.DATASET_KEY, data_path.name)
         meta.validate()
         meta.tofile(meta_path)
 
@@ -57,7 +55,11 @@ def test_load_ncd(self, subdir: str) -> None:
         self.assertTrue(np.array_equal(TEST_FLOAT32_DATA, meta_loopback.read_samples()))
         self.assertTrue(np.array_equal(TEST_FLOAT32_DATA, meta_loopback[:]))
 
-        # delete the non-conforming dataset and ensure error is raised due to missing dataset
+        # delete the non-conforming dataset and ensure error is raised due to missing dataset;
+        # in Windows the SigMFFile instances need to be garbage collected first,
+        # otherwise the np.memmap instances (stored in self._memmap) block the deletion
+        meta = None
+        meta_loopback = None
         os.remove(data_path)
         with self.assertRaises(SigMFFileError):
             _ = fromfile(meta_path)