loading com db only once

avoid loading db multiple times by caching it.

capa/rules/__init__.py

@@ -16,6 +16,7 @@
 import binascii
 import collections
 from enum import Enum
+from typing import Literal
 from pathlib import Path
 
 from capa.helpers import assert_never
@@ -202,23 +203,37 @@ def __repr__(self):
     "interface": {"db_path": "assets/interfaces.json.gz", "prefix": "IID_"},
 }
 
+com_db_cache: Dict[str, Dict[str, List[str]]] = {}
 
-def translate_com_feature(com_name: str, com_type: str) -> ceng.Or:
-    if com_type not in VALID_COM_TYPES:
-        raise InvalidRule(f"Invalid COM type present {com_type}")
 
-    CD = Path(__file__).resolve().parent.parent.parent
-    com_db_path = CD / VALID_COM_TYPES[com_type]["db_path"]
+def load_com_database(com_type: Literal["class", "interface"]) -> Dict[str, List[str]]:
+    com_db_path = capa.main.get_default_root() / VALID_COM_TYPES[com_type]["db_path"]
+
+    if com_type in com_db_cache:
+        # If the com database is already in the cache, return it
+        return com_db_cache[com_type]
+
     if not com_db_path.exists():
-        logger.error("Using COM %s database '%s', but it doesn't exist", com_type, com_db_path)
         raise IOError(f"COM database path '{com_db_path}' does not exist or cannot be accessed")
 
-    with gzip.open(com_db_path, "rb") as gzfile:
-        com_db: Dict[str, List[str]] = json.loads(gzfile.read().decode("utf-8"))
-        guid_strings: Optional[List[str]] = com_db.get(com_name)
-        if guid_strings is None or len(guid_strings) == 0:
-            logger.error(" %s doesn't exist in COM %s database", com_name, com_type)
-            raise InvalidRule(f"'{com_name}' doesn't exist in COM {com_type} database")
+    try:
+        with gzip.open(com_db_path, "rb") as gzfile:
+            com_db: Dict[str, List[str]] = json.loads(gzfile.read().decode("utf-8"))
+            com_db_cache[com_type] = com_db  # Cache the loaded database
+            return com_db
+    except Exception as e:
+        raise IOError(f"Error loading COM database from '{com_db_path}'") from e
+
+
+def translate_com_feature(com_name: str, com_type: Literal["class", "interface"]) -> ceng.Or:
+    if com_type not in VALID_COM_TYPES:
+        raise InvalidRule(f"Invalid COM type present {com_type}")
+
+    com_db = load_com_database(com_type)
+    guid_strings: Optional[List[str]] = com_db.get(com_name)
+    if guid_strings is None or len(guid_strings) == 0:
+        logger.error(" %s doesn't exist in COM %s database", com_name, com_type)
+        raise InvalidRule(f"'{com_name}' doesn't exist in COM {com_type} database")
 
     com_features: List = []
     for guid_string in guid_strings: