Function wait

Lib/multiprocessing/connection.py:1044–1120

Wait till an object in object_list is ready/readable. Returns list of those objects in object_list which are ready/readable.

(object_list, timeout=None)

    _ready_errors = {_winapi.ERROR_BROKEN_PIPE, _winapi.ERROR_NETNAME_DELETED}

    def wait(object_list, timeout=None):
        '''
        Wait till an object in object_list is ready/readable.

        Returns list of those objects in object_list which are ready/readable.
        '''
        if timeout is None:
            timeout = INFINITE
        elif timeout < 0:
            timeout = 0
        else:
            timeout = int(timeout * 1000 + 0.5)

        object_list = list(object_list)
        waithandle_to_obj = {}
        ov_list = []
        ready_objects = set()
        ready_handles = set()

        try:
            for o in object_list:
                try:
                    fileno = getattr(o, 'fileno')
                except AttributeError:
                    waithandle_to_obj[o.__index__()] = o
                else:
                    # start an overlapped read of length zero
                    try:
                        ov, err = _winapi.ReadFile(fileno(), 0, True)
                    except OSError as e:
                        ov, err = None, e.winerror
                        if err not in _ready_errors:
                            raise
                    if err == _winapi.ERROR_IO_PENDING:
                        ov_list.append(ov)
                        waithandle_to_obj[ov.event] = o
                    else:
                        # If o.fileno() is an overlapped pipe handle and
                        # err == 0 then there is a zero length message
                        # in the pipe, but it HAS NOT been consumed...
                        if ov and sys.getwindowsversion()[:2] >= (6, 2):
                            # ... except on Windows 8 and later, where
                            # the message HAS been consumed.
                            try:
                                _, err = ov.GetOverlappedResult(False)
                            except OSError as e:
                                err = e.winerror
                            if not err and hasattr(o, '_got_empty_message'):
                                o._got_empty_message = True
                        ready_objects.add(o)
                        timeout = 0

            ready_handles = _exhaustive_wait(waithandle_to_obj.keys(), timeout)
        finally:
            # request that overlapped reads stop
            for ov in ov_list:
                ov.cancel()