Additional comments.

python/fusion_engine_client/parsers/fast_indexer.py

@@ -66,10 +66,13 @@ def _search_blocks_for_fe(input_path: str, block_starts: List[int]):
 
             num_syncs += len(sync_matches)
 
-            # To do the CRC check and find a p1_time the full message needs to be parsed.
+            # To do the CRC check and find a p1_time the full message needs to be parsed. This
+            # section is not particularly optimized. The chance of the preamble appearing in data
+            # is relatively low, so this code is in a much less hot path then the preamble sync above.
             for i in sync_matches:
                 absolute_offset = i + block_offset
-                # Don't check preambles found inside other valid messages.
+                # Don't check preambles found inside other valid messages. Generally, this didn't
+                # provide much speed up, but could prevent wasting cycles if the message size is large.
                 if absolute_offset < message_end:
                     continue