Fix spikeglx events memmap (#1790)

* delay memory access till event access on spikeglx reader

* fix tests

* black

Author: h-mayorquin

neo/rawio/spikeglxrawio.py

@@ -246,12 +246,20 @@ def _parse_header(self):
                         chan_name = local_chan
                         chan_id = f"{stream_name}#{chan_name}"
                         event_channels.append((chan_name, chan_id, "event"))
-                    # add events_memmap
-                    data = np.memmap(info["bin_file"], dtype="int16", mode="r", offset=0, order="C")
-                    data = data.reshape(-1, info["num_chan"])
-                    # The digital word is usually the last channel, after all the individual analog channels
-                    extracted_word = data[:, len(info["analog_channels"])]
-                    self._events_memmap = np.unpackbits(extracted_word.astype(np.uint8)[:, None], axis=1)
+                    # Create memmap for digital word but defer unpacking until needed
+                    # The digital word is stored as the last channel, after all the individual analog channels
+                    # For example: if there are 8 analog channels (indices 0-7), the digital word is at index 8
+                    num_samples = info["sample_length"]
+                    num_channels = info["num_chan"]
+                    data = np.memmap(
+                        info["bin_file"],
+                        dtype="int16",
+                        mode="r",
+                        shape=(num_samples, num_channels),
+                        order="C",
+                    )
+                    digital_word_channel_index = len(info["analog_channels"])
+                    self._events_memmap_digital_word = data[:, digital_word_channel_index]
         event_channels = np.array(event_channels, dtype=_event_channel_dtype)
 
         # No spikes
@@ -342,7 +350,9 @@ def _get_event_timestamps(self, block_index, seg_index, event_channel_index, t_s
         info = self.signals_info_dict[0, "nidq"]  # There are no events that are not in the nidq stream
         dig_ch = info["digital_channels"]
         if len(dig_ch) > 0:
-            event_data = self._events_memmap
+            # Unpack bits on-demand - this is when memory allocation happens
+            event_data = np.unpackbits(self._events_memmap_digital_word.astype(np.uint8)[:, None], axis=1)
+
             channel = dig_ch[event_channel_index]
             ch_idx = 7 - int(channel[2:])  # They are in the reverse order
             this_stream = event_data[:, ch_idx]
@@ -682,7 +692,12 @@ def extract_stream_info(meta_file, meta):
             info["sampling_rate"] = float(meta[k])
     info["num_chan"] = num_chan
 
-    info["sample_length"] = int(meta["fileSizeBytes"]) // 2 // num_chan
+    # Calculate sample_length from actual file size instead of metadata to handle stub/modified files
+    # The metadata fileSizeBytes may not match the actual .bin file (e.g., in test stub files)
+    # Original calculation (only correct for unmodified files):
+    # info["sample_length"] = int(meta["fileSizeBytes"]) // 2 // num_chan
+    actual_file_size = Path(meta_file).with_suffix(".bin").stat().st_size
+    info["sample_length"] = actual_file_size // 2 // num_chan  # 2 bytes per int16 sample
     info["gate_num"] = gate_num
     info["trigger_num"] = trigger_num
     info["device"] = device