Check read block size, fixes #15

corsikaio/file.py

@@ -22,7 +22,6 @@
 ParticleEvent = namedtuple('ParticleEvent', ['header', 'particles', 'longitudinal', 'end'])
 
 
-
 class CorsikaFile:
 
     def __init__(self, path):
@@ -67,18 +66,15 @@ def __next__(self):
             self._run_end = parse_run_end(block)
             raise StopIteration()
 
-        if len(block) < BLOCK_SIZE_BYTES:
-            raise StopIteration
-
         if block[:4] != b'EVTH':
             raise IOError('EVTH block expected but found {}'.format(block[:4]))
 
         event_header = parse_event_header(block)[0]
 
-        block = self.read_block()
         data_bytes = bytearray()
         long_bytes = bytearray()
 
+        block = self.read_block()
         while block[:4] != b'EVTE':
 
             if block[:4] == b'LONG':

corsikaio/io.py

@@ -70,4 +70,8 @@ def read_block(f, buffer_size=None):
         if (pos + 4) % (buffer_size + 8) == 0:
             f.read(8)
 
-    return f.read(BLOCK_SIZE_BYTES)
+    block = f.read(BLOCK_SIZE_BYTES)
+    if len(block) < BLOCK_SIZE_BYTES:
+        raise IOError("Read less bytes than expected, file seems to be truncated")
+
+    return block

tests/test_file.py

@@ -1,3 +1,6 @@
+import pytest
+
+
 def test_version():
     from corsikaio import CorsikaFile
 
@@ -66,3 +69,23 @@ def test_particle_longi():
         e = next(f)
 
         assert e.header['event_number'] == 1
+
+
+def test_truncated(tmp_path):
+    '''Test we raise a meaningful error for a truncated file
+
+    Truncated files might happen if corsika crashes or the disk is full.
+
+    Regression test for cta-observatory/pycorsikaio#15
+    '''
+    from corsikaio import CorsikaParticleFile
+    path = tmp_path / "truncated.dat"
+
+    with open("tests/resources/corsika757_particle", "rb") as f:
+        with path.open("wb") as out:
+            out.write(f.read(273 * 10))
+
+    with pytest.raises(IOError, match="seems to be truncated"):
+        with CorsikaParticleFile(path) as f:
+            for _ in f:
+                pass