Fixes #64, error parsing raw data ending on a packet boundary

simplefix/errors.py

@@ -42,6 +42,10 @@ class RawLengthNotNumberError(ParsingError, ValueError):
     """Raw length value could not be converted to integer."""
 
 
+class RawDataNotFollowedByFieldSeparator(ParsingError):
+    """Raw data field isn't followed by SOH field separator."""
+
+
 class FieldOrderError(ParsingError):
     """Field not found where required by standard."""
 

simplefix/parser.py

@@ -1,7 +1,7 @@
 #! /usr/bin/env python
 ########################################################################
 # SimpleFIX
-# Copyright (C) 2016-2023, David Arnold.
+# Copyright (C) 2016-2026, David Arnold.
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -262,7 +262,7 @@ def get_buffer(self):
         """Return a reference to the internal buffer."""
         return self.buf
 
-    def get_message(self):
+    def get_message(self):  # skipcq: PY-R1000
         """Process the accumulated buffer and return the first message.
 
         If the buffer starts with FIX fields other than BeginString
@@ -299,12 +299,17 @@ def get_message(self):
                         raise errors.TagNotNumberError(*e.args)
 
                     if tag in self.raw_data_tags and self.raw_len > 0:
-                        # Try to extract the data value.
-                        if self.raw_len > len(self.buf) - point:
-                            # The buffer doesn't yet contain all the raw data,
-                            # so wait for more to be added.
+                        # Try to extract the data value (and its SOH,
+                        # although that's then ignored)
+                        if self.raw_len + 1 > len(self.buf) - point:
+                            # The buffer doesn't yet contain all the raw data
+                            # plus the following SOH, so wait for more to be added.
                             break
 
+                        # Check for SOH after raw data.
+                        if self.buf[point + self.raw_len] != SOH_BYTE:
+                            raise errors.RawDataNotFollowedByFieldSeparator(tag_string)
+
                         # We've got enough buffer to extract the raw data value.
                         value = self.buf[point:point + self.raw_len]
                         self.buf = self.buf[point + self.raw_len + 1:]

test/test_parser.py

@@ -1,7 +1,7 @@
 #! /usr/bin/env python
 ########################################################################
 # SimpleFIX
-# Copyright (C) 2016-2023, David Arnold.
+# Copyright (C) 2016-2026, David Arnold.
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -23,33 +23,28 @@
 #
 ########################################################################
 
-import sys
 import unittest
 
 from simplefix import FixMessage, FixParser, SOH_STR, errors
 
 
-def make_str(s):
-    if sys.version_info.major == 2:
-        return bytes(s)
-
-    return bytes(s, 'ASCII')
-
-
 # Python 2.6's unittest.TestCase doesn't have assertIsNone()
 def test_none(_, other):  # skipcq: PYL-R1719
+    """Check for None."""
     return other is None
 
 
 # Python 2.6's unittest.TestCase doesn't have assertIsNotNone()
 def test_not_none(_, other):  # skipcq: PYL-R1719
+    """Check is not None."""
     return other is not None
 
 
 class ParserTests(unittest.TestCase):
-
+    """Tests for FIX tag-value parser."""
 
     def setUp(self):
+        """Initialize the test suite."""
         if not hasattr(self, "assertIsNotNone"):
             ParserTests.assertIsNotNone = test_not_none
         if not hasattr(self, "assertIsNone"):
@@ -553,6 +548,35 @@ def test_begin_string_config(self):
         else:
             self.fail("These keywords together should fail validation.")
 
+    def test_raw_data_ending_on_packet_boundary(self):
+        """Check parsing when raw data field ends on a packet boundary."""
+        b1 = b"8=FIX.4.2" + SOH_STR + \
+             b"9=169" + SOH_STR + \
+             b"35=A" + SOH_STR + \
+             b"52=20171213-01:41:08.063" + SOH_STR + \
+             b"49=HelloWorld" + SOH_STR + \
+             b"56=1234" + SOH_STR + \
+             b"34=1" + SOH_STR + \
+             b"95=6" + SOH_STR + \
+             b"96=ABC=DE"
+
+        # Packet boundary between end of data and SOH, as in
+        # https://github.com/da4089/simplefix/issues/64
+
+        b2 = SOH_STR + \
+             b"98=0" + SOH_STR + \
+             b"108=30" + SOH_STR + \
+             b"10=166" + SOH_STR
+
+        parser = FixParser()
+        parser.append_buffer(b1)
+        msg = parser.get_message()
+        self.assertIsNone(msg)
+
+        parser.append_buffer(b2)
+        msg = parser.get_message()
+        self.assertIsNotNone(msg)
+
 
 # b"2018-05-06 12:34:56.789 RECV "