selectors.py 文件源码

def _syscall_wrapper(func, recalc_timeout, *args, **kwargs):
    """ Wrapper function for syscalls that could fail due to EINTR.
    All functions should be retried if there is time left in the timeout
    in accordance with PEP 475. """
    timeout = kwargs.get("timeout", None)
    if timeout is None:
        expires = None
        recalc_timeout = False
    else:
        timeout = float(timeout)
        if timeout < 0.0:  # Timeout less than 0 treated as no timeout.
            expires = None
        else:
            expires = monotonic() + timeout

    args = list(args)
    if recalc_timeout and "timeout" not in kwargs:
        raise ValueError(
            "Timeout must be in args or kwargs to be recalculated")

    result = _SYSCALL_SENTINEL
    while result is _SYSCALL_SENTINEL:
        try:
            result = func(*args, **kwargs)
        # OSError is thrown by select.select
        # IOError is thrown by select.epoll.poll
        # select.error is thrown by select.poll.poll
        # Aren't we thankful for Python 3.x rework for exceptions?
        except (OSError, IOError, select.error) as e:
            # select.error wasn't a subclass of OSError in the past.
            errcode = None
            if hasattr(e, "errno"):
                errcode = e.errno
            elif hasattr(e, "args"):
                errcode = e.args[0]

            # Also test for the Windows equivalent of EINTR.
            is_interrupt = (errcode == errno.EINTR or (hasattr(errno, "WSAEINTR") and
                                                       errcode == errno.WSAEINTR))

            if is_interrupt:
                if expires is not None:
                    current_time = monotonic()
                    if current_time > expires:
                        raise OSError(errno=errno.ETIMEDOUT)
                    if recalc_timeout:
                        if "timeout" in kwargs:
                            kwargs["timeout"] = expires - current_time
                continue
            if errcode:
                raise SelectorError(errcode)
            else:
                raise
    return result