1import os
2import sys
3import signal
4
5from . import util
6
7__all__ = ['Popen']
8
9#
10# Start child process using fork
11#
12
13class Popen(object):
14    method = 'fork'
15
16    def __init__(self, process_obj):
17        sys.stdout.flush()
18        sys.stderr.flush()
19        self.returncode = None
20        self._launch(process_obj)
21
22    def duplicate_for_child(self, fd):
23        return fd
24
25    def poll(self, flag=os.WNOHANG):
26        if self.returncode is None:
27            while True:
28                try:
29                    pid, sts = os.waitpid(self.pid, flag)
30                except OSError as e:
31                    # Child process not yet created. See #1731717
32                    # e.errno == errno.ECHILD == 10
33                    return None
34                else:
35                    break
36            if pid == self.pid:
37                if os.WIFSIGNALED(sts):
38                    self.returncode = -os.WTERMSIG(sts)
39                else:
40                    assert os.WIFEXITED(sts)
41                    self.returncode = os.WEXITSTATUS(sts)
42        return self.returncode
43
44    def wait(self, timeout=None):
45        if self.returncode is None:
46            if timeout is not None:
47                from multiprocessing.connection import wait
48                if not wait([self.sentinel], timeout):
49                    return None
50            # This shouldn't block if wait() returned successfully.
51            return self.poll(os.WNOHANG if timeout == 0.0 else 0)
52        return self.returncode
53
54    def terminate(self):
55        if self.returncode is None:
56            try:
57                os.kill(self.pid, signal.SIGTERM)
58            except ProcessLookupError:
59                pass
60            except OSError:
61                if self.wait(timeout=0.1) is None:
62                    raise
63
64    def _launch(self, process_obj):
65        code = 1
66        parent_r, child_w = os.pipe()
67        self.pid = os.fork()
68        if self.pid == 0:
69            try:
70                os.close(parent_r)
71                if 'random' in sys.modules:
72                    import random
73                    random.seed()
74                code = process_obj._bootstrap()
75            finally:
76                os._exit(code)
77        else:
78            os.close(child_w)
79            util.Finalize(self, os.close, (parent_r,))
80            self.sentinel = parent_r
81