Fix reading of central trigger object in case of new mono trigger

.github/workflows/release_drafter.yml

@@ -4,7 +4,7 @@ on:
   push:
     # branches to consider in the event; optional, defaults to all
     branches:
-      - master
+      - main
 
 jobs:
   update_release_draft:

src/eventio/simtel/objects.py

@@ -1,4 +1,5 @@
 ''' Implementations of the simtel_array EventIO object types '''
+import sys
 import numpy as np
 from io import BytesIO
 import struct
@@ -20,13 +21,16 @@
     unsigned_varint_arrays_differential,
     varint_array,
     varint,
+    unsigned_varint_array,
 )
 from ..version_handling import (
     assert_exact_version,
     assert_max_version,
     assert_version_in
 )
 
+H_MAX_TRIG_TYPES = 4
+
 
 def read_remaining_with_check(byte_stream, length):
     pos = byte_stream.tell()
@@ -37,6 +41,15 @@
 
 
 _s_int32 = struct.Struct('<i')
+_s_float32 = struct.Struct('<f')
+
+
+if sys.version_info < (3, 10):
+    def bit_count(num):
+        return bin(num).count("1")
+else:
+    def bit_count(num):
+        return num.bit_count()
 
 
 class TelescopeObject(EventIOObject):
@@ -595,20 +608,23 @@
             )
 
         if version >= 2:
-            # konrad saves the trigger mask as crazy int, but it uses only 4 bits
-            # so it should be indentical to a normal unsigned int with 1 byte
-            event_info['teltrg_type_mask'] = read_array(
-                byte_stream, count=tels_trigger, dtype='uint8'
+            # read remaining data as varint_array only works with bytes, not a fileobj
+            data = read_remaining_with_check(byte_stream, self.header.content_size)
+            event_info['teltrg_type_mask'], bytes_read = unsigned_varint_array(
+                data, n_elements=tels_trigger,
             )
-            assert np.all(event_info['teltrg_type_mask'] < 128), 'Unexpected trigger mask'
+            # back into a BytesIO to simplify code below
+            byte_stream = BytesIO(data[bytes_read:])
 
             event_info['teltrg_time_by_type'] = {}
             it = zip(event_info['triggered_telescopes'], event_info['teltrg_type_mask'])
+
             for tel_id, mask in it:
-                # trigger times are only written if more than one trigger is there
-                if mask not in {0b001, 0b010, 0b100}:
+                # check the lowest 4 bits, individual times are only stored
+                # if more than one trigger fired
+                if bit_count(int(mask) & 0b1111) > 1:
                     event_info['teltrg_time_by_type'][tel_id] = {}
-                    for trigger in range(3):
+                    for trigger in range(H_MAX_TRIG_TYPES):
                         if bool_bit_from_pos(mask, trigger):
                             t = read_float(byte_stream)
                             event_info['teltrg_time_by_type'][tel_id][trigger] = t

tests/simtel/test_simtel_objects.py

@@ -5,7 +5,9 @@
 from eventio.search_utils import (
     yield_toplevel_of_type,
     yield_n_subobjects,
+    yield_subobjects,
 )
+from eventio.simtel.objects import TriggerInformation
 
 prod2_file = 'tests/resources/gamma_test.simtel.gz'
 camorgan_v2_file = 'tests/resources/test_camorganv2.simtel.gz'
@@ -824,3 +826,10 @@ def test_2034():
             assert isinstance(telescope_data, TelescopeData)
             photo_electrons = next(telescope_data)
             assert isinstance(photo_electrons, PhotoElectrons)
+
+
+def test_mono_trigger():
+    """Regression test for #261"""
+    with EventIOFile("tests/resources/mono_trigger.simtel.zst") as f:
+        for trigger in yield_subobjects(f, TriggerInformation):
+            trigger.parse()