Function _unpack_opargs

Lib/dis.py:940–969

(code)

_INT_OVERFLOW = 2 ** (_INT_BITS - 1)

def _unpack_opargs(code):
    extended_arg = 0
    extended_args_offset = 0  # Number of EXTENDED_ARG instructions preceding the current instruction
    caches = 0
    for i in range(0, len(code), 2):
        # Skip inline CACHE entries:
        if caches:
            caches -= 1
            continue
        op = code[i]
        deop = _deoptop(op)
        caches = _get_cache_size(_all_opname[deop])
        if deop in hasarg:
            arg = code[i+1] | extended_arg
            extended_arg = (arg << 8) if deop == EXTENDED_ARG else 0
            # The oparg is stored as a signed integer
            # If the value exceeds its upper limit, it will overflow and wrap
            # to a negative integer
            if extended_arg >= _INT_OVERFLOW:
                extended_arg -= 2 * _INT_OVERFLOW
        else:
            arg = None
            extended_arg = 0
        if deop == EXTENDED_ARG:
            extended_args_offset += 1
            yield (i, i, op, arg)
        else:
            start_offset = i - extended_args_offset*2
            yield (i, start_offset, op, arg)
            extended_args_offset = 0

def findlabels(code):
    """Detect all offsets in a byte code which are jump targets.