import io
import os

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


__all__ = ['Popen']

#
# Wrapper for an fd used while launching a process
#

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

#
# Start child process using a server process
#

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()
context.set_spawning_popen(self)
try:
reduction.dump(prep_data, buf)
reduction.dump(process_obj, buf)
finally:
context.set_spawning_popen(None)

self.sentinel, w = forkserver.connect_to_new_process(self._fds)
util.Finalize(self, os.close, (self.sentinel,))
with open(w, 'wb', closefd=True) as f:
f.write(buf.getbuffer())
self.pid = forkserver.read_unsigned(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_unsigned(self.sentinel)
except (OSError, EOFError):
# The process ended abnormally perhaps because of a signal
self.returncode = 255
return self.returncode