BlackrockRawIO: Fix int overflow (#1669)

* fix another overflow

* fix my own typos...

* more overflow fun

Author: zm711

neo/rawio/blackrockrawio.py

@@ -276,12 +276,19 @@ def _parse_header(self):
             self.internal_unit_ids = []  # pair of chan['packet_id'], spikes['unit_class_nb']
             for i in range(len(self.__nev_ext_header[b"NEUEVWAV"])):
 
-                channel_id = self.__nev_ext_header[b"NEUEVWAV"]["electrode_id"][i]
+                # electrode_id values are stored at uint16 which can overflow when 
+                # multiplying by 1000 below. We convert to a regular python int which 
+                # won't overflow
+                channel_id = int(self.__nev_ext_header[b"NEUEVWAV"]["electrode_id"][i])
 
                 chan_mask = spikes["packet_id"] == channel_id
                 chan_spikes = spikes[chan_mask]
+
+                # all `unit_class_nb` is uint8. Also will have issues with overflow
+                # cast this to python int
                 all_unit_id = np.unique(chan_spikes["unit_class_nb"])
                 for u, unit_id in enumerate(all_unit_id):
+                    unit_id = int(unit_id)
                     self.internal_unit_ids.append((channel_id, unit_id))
                     name = f"ch{channel_id}#{unit_id}"
                     _id = f"Unit {1000 * channel_id + unit_id}"