Mini Shell

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

import sys

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

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


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


# Constants/globals


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


if hasattr(socket, 'socketpair'):
    # Since Python 3.5, socket.socketpair() is now also available on Windows
    socketpair = socket.socketpair
else:
    # 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.
        """
        if family == socket.AF_INET:
            host = '127.0.0.1'
        elif family == socket.AF_INET6:
            host = '::1'
        else:
            raise ValueError("Only AF_INET and AF_INET6 socket address "
                             "families are supported")
        if type != socket.SOCK_STREAM:
            raise ValueError("Only SOCK_STREAM socket type is supported")
        if proto != 0:
            raise ValueError("Only protocol zero is supported")

        # 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)
        try:
            lsock.bind((host, 0))
            lsock.listen(1)
            # On IPv6, ignore flow_info and scope_id
            addr, port = lsock.getsockname()[:2]
            csock = socket.socket(family, type, proto)
            try:
                csock.setblocking(False)
                try:
                    csock.connect((addr, port))
                except (BlockingIOError, InterruptedError):
                    pass
                csock.setblocking(True)
                ssock, _ = lsock.accept()
            except:
                csock.close()
                raise
        finally:
            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

    def __repr__(self):
        if self._handle is not None:
            handle = 'handle=%r' % self._handle
        else:
            handle = 'closed'
        return '<%s %s>' % (self.__class__.__name__, handle)

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

    def fileno(self):
        if self._handle is None:
            raise ValueError("I/O operatioon on closed pipe")
        return self._handle

    def close(self, *, CloseHandle=_winapi.CloseHandle):
        if self._handle is not None:
            CloseHandle(self._handle)
            self._handle = None

    def __del__(self):
        if self._handle is not None:
            warnings.warn("unclosed %r" % self, ResourceWarning)
            self.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):
        assert not kwds.get('universal_newlines')
        assert kwds.get('bufsize', 0) == 0
        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), duplex=True)
            stdin_rfd = msvcrt.open_osfhandle(stdin_rh, os.O_RDONLY)
        else:
            stdin_rfd = stdin
        if stdout == PIPE:
            stdout_rh, stdout_wh = pipe(overlapped=(True, False))
            stdout_wfd = msvcrt.open_osfhandle(stdout_wh, 0)
        else:
            stdout_wfd = stdout
        if stderr == PIPE:
            stderr_rh, stderr_wh = pipe(overlapped=(True, False))
            stderr_wfd = msvcrt.open_osfhandle(stderr_wh, 0)
        elif stderr == STDOUT:
            stderr_wfd = stdout_wfd
        else:
            stderr_wfd = stderr
        try:
            super().__init__(args, stdin=stdin_rfd, stdout=stdout_wfd,
                             stderr=stderr_wfd, **kwds)
        except:
            for h in (stdin_wh, stdout_rh, stderr_rh):
                if h is not None:
                    _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)