wrapper for an fd used while launching a process start child process using a server process keep a duplicate of the data pipe s write end as a sentinel of the parent process used by the child process this should not happen usually but perhaps the forkserver process itself got killed wrapper for an fd used while launching a process start child process using a server process keep a duplicate of the data pipe s write end as a sentinel of the parent process used by the child process this should not happen usually but perhaps the forkserver process itself got killed
import io
import os

from .context import reduction, set_spawning_popen
if not reduction.HAVE_SEND_HANDLE:
    raise ImportError('No support for sending fds between processes')
from . import forkserver
from . import popen_fork
from . import spawn
from . import util


__all__ = ['Popen']





class _DupFd(object):
    def __init__(self, ind):
        self.ind = ind
    def detach(self):
        return forkserver.get_inherited_fds()[self.ind]





class Popen(popen_fork.Popen):
    method = 'forkserver'
    DupFd = _DupFd

    def __init__(self, process_obj):
        self._fds = []
        super().__init__(process_obj)

    def duplicate_for_child(self, fd):
        self._fds.append(fd)
        return len(self._fds) - 1

    def _launch(self, process_obj):
        prep_data = spawn.get_preparation_data(process_obj._name)
        buf = io.BytesIO()
        set_spawning_popen(self)
        try:
            reduction.dump(prep_data, buf)
            reduction.dump(process_obj, buf)
        finally:
            set_spawning_popen(None)

        self.sentinel, w = forkserver.connect_to_new_process(self._fds)
        
        
        _parent_w = os.dup(w)
        self.finalizer = util.Finalize(self, util.close_fds,
                                       (_parent_w, self.sentinel))
        with open(w, 'wb', closefd=True) as f:
            f.write(buf.getbuffer())
        self.pid = forkserver.read_signed(self.sentinel)

    def poll(self, flag=os.WNOHANG):
        if self.returncode is None:
            from multiprocessing.connection import wait
            timeout = 0 if flag == os.WNOHANG else None
            if not wait([self.sentinel], timeout):
                return None
            try:
                self.returncode = forkserver.read_signed(self.sentinel)
            except (OSError, EOFError):
                
                
                self.returncode = 255

        return self.returncode