can: cache DBC parsing to speed up car interface tests

opendbc/can/dbc.py

@@ -71,6 +71,37 @@ class Val:
 VAL_SPLIT_RE = re.compile(r'["]+')
 
 
+# Module-level cache for parsed DBC files
+_DBC_CACHE: dict[str, "DBC"] = {}
+
+
+def _resolve_dbc_path(name: str) -> str:
+  """Resolve a DBC name or path to an absolute path."""
+  dbc_path = name
+  if not os.path.exists(dbc_path):
+    candidate = os.path.join(DBC_PATH, name + ".dbc")
+    if os.path.exists(candidate):
+      dbc_path = candidate
+    else:
+      raise FileNotFoundError(f"DBC file not found: {name}")
+  return os.path.abspath(dbc_path)
+
+
+def get_dbc(name: str) -> "DBC":
+  """Get or create a cached DBC instance.
+
+  Args:
+    name: DBC file name (without .dbc extension) or full path to DBC file
+
+  Returns:
+    Cached DBC instance for the resolved path
+  """
+  dbc_path = _resolve_dbc_path(name)
+  if dbc_path not in _DBC_CACHE:
+    _DBC_CACHE[dbc_path] = DBC._from_file(dbc_path)
+  return _DBC_CACHE[dbc_path]
+
+
 @dataclass
 class DBC:
   name: str
@@ -79,12 +110,18 @@ class DBC:
   name_to_msg: dict[str, Msg]
   vals: list[Val]
 
-  def __init__(self, name: str):
-    dbc_path = name
-    if not os.path.exists(dbc_path):
-      dbc_path = os.path.join(DBC_PATH, name + ".dbc")
-
-    self._parse(dbc_path)
+  @classmethod
+  def _from_file(cls, path: str) -> "DBC":
+    """Internal method to create a DBC instance from a file path."""
+    dbc = cls(
+      name="",
+      msgs={},
+      addr_to_msg={},
+      name_to_msg={},
+      vals=[]
+    )
+    dbc._parse(path)
+    return dbc
 
   def _parse(self, path: str):
     self.name = os.path.basename(path).replace(".dbc", "")

opendbc/can/packer.py

@@ -1,12 +1,12 @@
 import math
 
 from opendbc.car.carlog import carlog
-from opendbc.can.dbc import DBC, Signal, SignalType
+from opendbc.can.dbc import get_dbc, Signal, SignalType
 
 
 class CANPacker:
   def __init__(self, dbc_name: str):
-    self.dbc = DBC(dbc_name)
+    self.dbc = get_dbc(dbc_name)
     self.counters: dict[int, int] = {}
 
   def pack(self, address: int, values: dict[str, float]) -> bytearray:

opendbc/can/parser.py

@@ -4,7 +4,7 @@
 from dataclasses import dataclass, field
 
 from opendbc.car.carlog import carlog
-from opendbc.can.dbc import DBC, Signal
+from opendbc.can.dbc import get_dbc, Signal
 
 
 MAX_BAD_COUNTER = 5
@@ -129,7 +129,7 @@ class CANParser:
   def __init__(self, dbc_name: str, messages: list[tuple[str | int, int]], bus: int):
     self.dbc_name: str = dbc_name
     self.bus: int = bus
-    self.dbc: DBC = DBC(dbc_name)
+    self.dbc = get_dbc(dbc_name)
 
     self.vl: dict[int | str, dict[str, float]] = VLDict(self)
     self.vl_all: dict[int | str, dict[str, list[float]]] = {}
@@ -214,6 +214,9 @@ def can_valid(self) -> bool:
     return self.can_invalid_cnt < CAN_INVALID_CNT and counters_valid
 
   def update(self, strings, sendcan: bool = False):
+    if not strings:
+      return set()
+
     if strings and not isinstance(strings[0], list | tuple):
       strings = [strings]
 
@@ -255,7 +258,7 @@ def update(self, strings, sendcan: bool = False):
 
 class CANDefine:
   def __init__(self, dbc_name: str):
-    dbc = DBC(dbc_name)
+    dbc = get_dbc(dbc_name)
 
     dv = defaultdict(dict)
     for val in dbc.vals: