nmigen/tracer.py

   1 import traceback
   2 import inspect
   3 from opcode import opname
   4
   5
   6 __all__ = ["NameNotFound", "get_var_name", "get_src_loc"]
   7
   8
   9 class NameNotFound(Exception):
  10     pass
  11
  12
  13 def get_var_name(depth=2):
  14     frame = inspect.currentframe()
  15     for _ in range(depth):
  16         frame = frame.f_back
  17
  18     code = frame.f_code
  19     call_index = frame.f_lasti
  20     call_opc   = opname[code.co_code[call_index]]
  21     if call_opc not in ("CALL_FUNCTION", "CALL_FUNCTION_KW", "CALL_FUNCTION_EX", "CALL_METHOD"):
  22         return None
  23
  24     index = call_index + 2
  25     while True:
  26         opc = opname[code.co_code[index]]
  27         if opc in ("STORE_NAME", "STORE_ATTR"):
  28             name_index = int(code.co_code[index + 1])
  29             return code.co_names[name_index]
  30         elif opc == "STORE_FAST":
  31             name_index = int(code.co_code[index + 1])
  32             return code.co_varnames[name_index]
  33         elif opc == "STORE_DEREF":
  34             name_index = int(code.co_code[index + 1])
  35             return code.co_cellvars[name_index]
  36         elif opc in ("LOAD_GLOBAL", "LOAD_ATTR", "LOAD_FAST", "LOAD_DEREF",
  37                      "DUP_TOP", "BUILD_LIST"):
  38             index += 2
  39         else:
  40             raise NameNotFound
  41
  42
  43 def get_src_loc(src_loc_at=0):
  44     # n-th  frame: get_src_loc()
  45     # n-1th frame: caller of get_src_loc() (usually constructor)
  46     # n-2th frame: caller of caller (usually user code)
  47     # Python returns the stack frames reversed, so it is enough to set limit and grab the very
  48     # first one in the array.
  49     tb = traceback.extract_stack(limit=3 + src_loc_at)
  50     return (tb[0].filename, tb[0].lineno)