Lib/asyncio/windows_utils.py

"""
Various Windows specific bits and pieces
"""

import sys

if sys.platform != 'win32':  # pragma: no cover
    raise ImportError('win32 only')

import socket
import itertools
import msvcrt
import os
import subprocess
import tempfile
import _winapi


__all__ = ['socketpair', 'pipe', 'Popen', 'PIPE', 'PipeHandle']

#
# Constants/globals
#

BUFSIZE = 8192
PIPE = subprocess.PIPE
_mmap_counter = itertools.count()

#
# Replacement for socket.socketpair()
#

def socketpair(family=socket.AF_INET, type=socket.SOCK_STREAM, proto=0):
    """A socket pair usable as a self-pipe, for Windows.

    Origin: https://gist.github.com/4325783, by Geert Jansen.  Public domain.
    """
    # We create a connected TCP socket. Note the trick with setblocking(0)
    # that prevents us from having to create a thread.
    lsock = socket.socket(family, type, proto)
    lsock.bind(('localhost', 0))
    lsock.listen(1)
    addr, port = lsock.getsockname()
    csock = socket.socket(family, type, proto)
    csock.setblocking(False)
    try:
        csock.connect((addr, port))
    except (BlockingIOError, InterruptedError):
        pass
    except Exception:
        lsock.close()
        csock.close()
        raise
    ssock, _ = lsock.accept()
    csock.setblocking(True)
    lsock.close()
    return (ssock, csock)

#
# Replacement for os.pipe() using handles instead of fds
#

def pipe(*, duplex=False, overlapped=(True, True), bufsize=BUFSIZE):
    """Like os.pipe() but with overlapped support and using handles not fds."""
    address = tempfile.mktemp(prefix=r'\\.\pipe\python-pipe-%d-%d-' %
                              (os.getpid(), next(_mmap_counter)))

    if duplex:
        openmode = _winapi.PIPE_ACCESS_DUPLEX
        access = _winapi.GENERIC_READ | _winapi.GENERIC_WRITE
        obsize, ibsize = bufsize, bufsize
    else:
        openmode = _winapi.PIPE_ACCESS_INBOUND
        access = _winapi.GENERIC_WRITE
        obsize, ibsize = 0, bufsize

    openmode |= _winapi.FILE_FLAG_FIRST_PIPE_INSTANCE

    if overlapped[0]:
        openmode |= _winapi.FILE_FLAG_OVERLAPPED

    if overlapped[1]:
        flags_and_attribs = _winapi.FILE_FLAG_OVERLAPPED
    else:
        flags_and_attribs = 0

    h1 = h2 = None
    try:
        h1 = _winapi.CreateNamedPipe(
            address, openmode, _winapi.PIPE_WAIT,
            1, obsize, ibsize, _winapi.NMPWAIT_WAIT_FOREVER, _winapi.NULL)

        h2 = _winapi.CreateFile(
            address, access, 0, _winapi.NULL, _winapi.OPEN_EXISTING,
            flags_and_attribs, _winapi.NULL)

        ov = _winapi.ConnectNamedPipe(h1, overlapped=True)
        ov.GetOverlappedResult(True)
        return h1, h2
    except:
        if h1 is not None:
            _winapi.CloseHandle(h1)
        if h2 is not None:
            _winapi.CloseHandle(h2)
        raise

#
# Wrapper for a pipe handle
#

class PipeHandle:
    """Wrapper for an overlapped pipe handle which is vaguely file-object like.

    The IOCP event loop can use these instead of socket objects.
    """
    def __init__(self, handle):
        self._handle = handle

    @property
    def handle(self):
        return self._handle

    def fileno(self):
        return self._handle

    def close(self, *, CloseHandle=_winapi.CloseHandle):
        if self._handle != -1:
            CloseHandle(self._handle)
            self._handle = -1

    __del__ = close

    def __enter__(self):
        return self

    def __exit__(self, t, v, tb):
        self.close()

#
# Replacement for subprocess.Popen using overlapped pipe handles
#

class Popen(subprocess.Popen):
    """Replacement for subprocess.Popen using overlapped pipe handles.

    The stdin, stdout, stderr are None or instances of PipeHandle.
    """
    def __init__(self, args, stdin=None, stdout=None, stderr=None, **kwds):
        stdin_rfd = stdout_wfd = stderr_wfd = None
        stdin_wh = stdout_rh = stderr_rh = None
        if stdin == PIPE:
            stdin_rh, stdin_wh = pipe(overlapped=(False, True))
            stdin_rfd = msvcrt.open_osfhandle(stdin_rh, os.O_RDONLY)
        if stdout == PIPE:
            stdout_rh, stdout_wh = pipe(overlapped=(True, False))
            stdout_wfd = msvcrt.open_osfhandle(stdout_wh, 0)
        if stderr == PIPE:
            stderr_rh, stderr_wh = pipe(overlapped=(True, False))
            stderr_wfd = msvcrt.open_osfhandle(stderr_wh, 0)
        try:
            super().__init__(args, bufsize=0, universal_newlines=False,
                             stdin=stdin_rfd, stdout=stdout_wfd,
                             stderr=stderr_wfd, **kwds)
        except:
            for h in (stdin_wh, stdout_rh, stderr_rh):
                _winapi.CloseHandle(h)
            raise
        else:
            if stdin_wh is not None:
                self.stdin = PipeHandle(stdin_wh)
            if stdout_rh is not None:
                self.stdout = PipeHandle(stdout_rh)
            if stderr_rh is not None:
                self.stderr = PipeHandle(stderr_rh)
        finally:
            if stdin == PIPE:
                os.close(stdin_rfd)
            if stdout == PIPE:
                os.close(stdout_wfd)
            if stderr == PIPE:
                os.close(stderr_wfd)