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1"""
2Basic subprocess implementation for POSIX which only uses os functions. Only
3implement features required by setup.py to build C extension modules when
4subprocess is unavailable. setup.py is not used on Windows.
5"""
6import os
7
8
9# distutils.spawn used by distutils.command.build_ext
10# calls subprocess.Popen().wait()
11class Popen:
12    def __init__(self, cmd, env=None):
13        self._cmd = cmd
14        self._env = env
15        self.returncode = None
16
17    def wait(self):
18        pid = os.fork()
19        if pid == 0:
20            # Child process
21            try:
22                if self._env is not None:
23                    os.execve(self._cmd[0], self._cmd, self._env)
24                else:
25                    os.execv(self._cmd[0], self._cmd)
26            finally:
27                os._exit(1)
28        else:
29            # Parent process
30            _, status = os.waitpid(pid, 0)
31            self.returncode = os.waitstatus_to_exitcode(status)
32
33        return self.returncode
34
35
36def _check_cmd(cmd):
37    # Use regex [a-zA-Z0-9./-]+: reject empty string, space, etc.
38    safe_chars = []
39    for first, last in (("a", "z"), ("A", "Z"), ("0", "9")):
40        for ch in range(ord(first), ord(last) + 1):
41            safe_chars.append(chr(ch))
42    safe_chars.append("./-")
43    safe_chars = ''.join(safe_chars)
44
45    if isinstance(cmd, (tuple, list)):
46        check_strs = cmd
47    elif isinstance(cmd, str):
48        check_strs = [cmd]
49    else:
50        return False
51
52    for arg in check_strs:
53        if not isinstance(arg, str):
54            return False
55        if not arg:
56            # reject empty string
57            return False
58        for ch in arg:
59            if ch not in safe_chars:
60                return False
61
62    return True
63
64
65# _aix_support used by distutil.util calls subprocess.check_output()
66def check_output(cmd, **kwargs):
67    if kwargs:
68        raise NotImplementedError(repr(kwargs))
69
70    if not _check_cmd(cmd):
71        raise ValueError(f"unsupported command: {cmd!r}")
72
73    tmp_filename = "check_output.tmp"
74    if not isinstance(cmd, str):
75        cmd = " ".join(cmd)
76    cmd = f"{cmd} >{tmp_filename}"
77
78    try:
79        # system() spawns a shell
80        status = os.system(cmd)
81        exitcode = os.waitstatus_to_exitcode(status)
82        if exitcode:
83            raise ValueError(f"Command {cmd!r} returned non-zero "
84                             f"exit status {exitcode!r}")
85
86        try:
87            with open(tmp_filename, "rb") as fp:
88                stdout = fp.read()
89        except FileNotFoundError:
90            stdout = b''
91    finally:
92        try:
93            os.unlink(tmp_filename)
94        except OSError:
95            pass
96
97    return stdout
98