"""confused_math_bc.py
------------------------
Import hook that performs bytecode changes,
swapping BINARY_ADD and BINARY_MULTIPLY.
Note: If code contains something like a + b, or a * b, where
a and b are integer literals (e.g. 2 + 4), the operations are
done prior to the creation of a code object and thus are
not captured by this transformation.
"""
import dis
import sys
from types import CodeType
from ideas import create_hook
# The actual bytecode used can change with different Python version.
# Instead of attempting to hard-code some actual bytecode values
# we extract the actual value used in the current Python version.
if sys.version_info.minor < 11:
ADD = dis.opmap["BINARY_ADD"]
MUL = dis.opmap["BINARY_MULTIPLY"]
BINARY_OP = -1
binop_arg_add = binop_arg_mul = -1
else:
ADD = MUL = -1
BINARY_OP = dis.opmap["BINARY_OP"]
for index, op_nb in enumerate(dis._nb_ops): # noqa
if op_nb[1] == "+":
binop_arg_add = index
elif op_nb[1] == "*":
binop_arg_mul = index
[docs]
def swap_add_mul(bytecode):
"""Interchange BINARY_ADD and BINARY_MULTIPLY"""
new_bc = []
check_arg = -1
for i, b in enumerate(bytecode):
if b == ADD and i % 2 == 0:
new_bc.append(MUL)
elif b == MUL and i % 2 == 0:
new_bc.append(ADD)
elif b == BINARY_OP and i % 2 == 0:
new_bc.append(b)
check_arg = i + 1
continue
elif i == check_arg:
if b == binop_arg_add:
new_bc.append(binop_arg_mul)
elif b == binop_arg_mul:
new_bc.append(binop_arg_add)
else:
new_bc.append(b)
else:
new_bc.append(b)
return bytes(new_bc)
[docs]
def create_new_co(code_object):
"""Recursively creates new code objects from old ones, swapping
BINARY_ADD and BINARY_MULTIPLY.
"""
new_code = swap_add_mul(code_object.co_code)
new_const = []
for c in code_object.co_consts:
if isinstance(c, CodeType):
new_const.append(create_new_co(c))
else:
new_const.append(c)
if sys.version_info.minor in (6, 7):
new_code_object = CodeType(
code_object.co_argcount,
code_object.co_kwonlyargcount,
code_object.co_nlocals,
code_object.co_stacksize,
code_object.co_flags,
new_code,
tuple(new_const),
code_object.co_names,
code_object.co_varnames,
code_object.co_filename,
code_object.co_name,
code_object.co_firstlineno,
code_object.co_lnotab,
code_object.co_freevars,
code_object.co_cellvars,
)
elif sys.version_info.minor < 11:
new_code_object = CodeType(
code_object.co_argcount,
code_object.co_posonlyargcount, # new in Python 3.8
code_object.co_kwonlyargcount,
code_object.co_nlocals,
code_object.co_stacksize,
code_object.co_flags,
new_code,
tuple(new_const),
code_object.co_names,
code_object.co_varnames,
code_object.co_filename,
code_object.co_name,
code_object.co_firstlineno,
code_object.co_lnotab,
code_object.co_freevars,
code_object.co_cellvars,
)
else:
new_code_object = CodeType( # noqa
code_object.co_argcount,
code_object.co_posonlyargcount,
code_object.co_kwonlyargcount,
code_object.co_nlocals,
code_object.co_stacksize,
code_object.co_flags,
new_code,
tuple(new_const),
code_object.co_names,
code_object.co_varnames,
code_object.co_filename,
code_object.co_name,
code_object.co_qualname, # new in 3.11
code_object.co_firstlineno,
code_object.co_lnotab, # deprecated in 3.12
code_object.co_exceptiontable, # new in 3.11
code_object.co_freevars,
code_object.co_cellvars,
)
return new_code_object
[docs]
def add_hook(**_kwargs):
"""Creates and automatically adds the import hook in sys.meta_path"""
hook = create_hook(
name=__name__,
transform_bytecode=transform_bytecode,
)
return hook