Add auto mode for cnt bad chans

mne/io/cnt/cnt.py

@@ -170,7 +170,7 @@ def read_raw_cnt(
     data_format="auto",
     date_format="mm/dd/yy",
     *,
-    header="old",
+    header="auto",
     preload=False,
     verbose=None,
 ):
@@ -221,9 +221,11 @@ def read_raw_cnt(
         Defaults to ``'auto'``.
     date_format : ``'mm/dd/yy'`` | ``'dd/mm/yy'``
         Format of date in the header. Defaults to ``'mm/dd/yy'``.
-    header : ``'new'`` | ``'old'``
+    header : ``'auto'`` | ``'new'`` | ``'old'``
         Defines the header format. Used to describe how bad channels
-        are formatted.
+        are formatted. If auto, reads using old and new header and
+        if either contain a bad channel make channel bad. 
+        Defaults to ``'auto'``.
     %(preload)s
     %(verbose)s
 
@@ -352,12 +354,22 @@ def _get_cnt_info(input_fname, eog, ecg, emg, misc, data_format, date_format, he
             ch_names.append(ch_name)
 
             # Some files have bad channels marked differently in the header.
+            if header == "auto":
+                fid.seek(data_offset + 75 * ch_idx + 14)
+                if np.fromfile(fid, dtype="u1", count=1).item():
+                    bads.append(ch_name)
+                fid.seek(data_offset + 75 * ch_idx + 4)
+                if np.fromfile(fid, dtype="u1", count=1).item():
+                    bads.append(ch_name)
             if header == "new":
                 fid.seek(data_offset + 75 * ch_idx + 14)
+                if np.fromfile(fid, dtype="u1", count=1).item():
+                    bads.append(ch_name)
             if header == "old":
                 fid.seek(data_offset + 75 * ch_idx + 4)
-            if np.fromfile(fid, dtype="u1", count=1).item():
-                bads.append(ch_name)
+                if np.fromfile(fid, dtype="u1", count=1).item():
+                    bads.append(ch_name)
+
             fid.seek(data_offset + 75 * ch_idx + 19)
             xy = np.fromfile(fid, dtype="f4", count=2)
             xy[1] *= -1  # invert y-axis
@@ -462,9 +474,11 @@ class RawCNT(BaseRaw):
         Defaults to ``'auto'``.
     date_format : ``'mm/dd/yy'`` | ``'dd/mm/yy'``
         Format of date in the header. Defaults to ``'mm/dd/yy'``.
-    header : ``'new'`` | ``'old'``
+    header : ``'auto'`` | ``'new'`` | ``'old'``
         Defines the header format. Used to describe how bad channels
-        are formatted.
+        are formatted. If auto, reads using old and new header and
+        if either contain a bad channel make channel bad. 
+        Defaults to ``'auto'``.
     %(preload)s
     stim_channel : bool | None
         Add a stim channel from the events. Defaults to None to trigger a
@@ -493,7 +507,7 @@ def __init__(
         data_format="auto",
         date_format="mm/dd/yy",
         *,
-        header="old",
+        header="auto",
         preload=False,
         verbose=None,
     ):  # noqa: D102

mne/io/cnt/tests/test_cnt.py

@@ -46,6 +46,31 @@ def test_new_data():
     assert raw.info["bads"] == ["F8"]  # test bads
 
 
+@testing.requires_testing_data
+def test_auto_data():
+    """Test reading raw cnt files with automatic header."""
+    with pytest.warns(RuntimeWarning):
+        raw = read_raw_cnt(input_fname=fname_bad_spans)
+
+    assert raw.info["bads"] == ["F8"]
+
+    with pytest.warns(RuntimeWarning, match="number of bytes"):
+        raw = _test_raw_reader(
+            read_raw_cnt, input_fname=fname, eog="auto",
+            misc=["NA1", "LEFT_EAR"]
+        )
+
+    # make sure we use annotations event if we synthesized stim
+    assert len(raw.annotations) == 6
+
+    eog_chs = pick_types(raw.info, eog=True, exclude=[])
+    assert len(eog_chs) == 2  # test eog='auto'
+    assert raw.info["bads"] == ["LEFT_EAR", "VEOGR"]  # test bads
+
+    # the data has "05/10/200 17:35:31" so it is set to None
+    assert raw.info["meas_date"] is None
+
+
 @testing.requires_testing_data
 def test_compare_events_and_annotations():
     """Test comparing annotations and events."""