event.py 文件源码

def blocking_wait_for_edge(pin, trigger, timeout=-1):
    assert trigger in [RISING, FALLING, BOTH]

    if pin in _threads:
        raise RuntimeError("Conflicting edge detection events already exist for this GPIO channel")

    try:
        sysfs.edge(pin, trigger)

        finished = False
        initial_edge = True

        with sysfs.value_descriptor(pin) as fd:
            e = select.epoll()
            e.register(fd, EPOLLIN | EPOLLET | EPOLLPRI)
            try:
                while not finished:
                    # TODO: implement bouncetime
                    events = e.poll(timeout / 1000.0, maxevents=1)
                    if initial_edge:
                        initial_edge = False
                    else:
                        finished = True

                n = len(events)
                if n == 0:
                    return None
                else:
                    return pin
            finally:
                e.unregister(fd)
                e.close()

    finally:
        sysfs.edge(pin, NONE)