manyi/venv/Lib/site-packages/tornado/platform/common.py

"""Lowest-common-denominator implementations of platform functionality."""
from __future__ import absolute_import, division, print_function

import errno
import socket
import time

from tornado.platform import interface
from tornado.util import errno_from_exception


def try_close(f):
    # Avoid issue #875 (race condition when using the file in another
    # thread).
    for i in range(10):
        try:
            f.close()
        except IOError:
            # Yield to another thread
            time.sleep(1e-3)
        else:
            break
    # Try a last time and let raise
    f.close()


class Waker(interface.Waker):
    """Create an OS independent asynchronous pipe.

    For use on platforms that don't have os.pipe() (or where pipes cannot
    be passed to select()), but do have sockets.  This includes Windows
    and Jython.
    """
    def __init__(self):
        from .auto import set_close_exec
        # Based on Zope select_trigger.py:
        # https://github.com/zopefoundation/Zope/blob/master/src/ZServer/medusa/thread/select_trigger.py

        self.writer = socket.socket()
        set_close_exec(self.writer.fileno())
        # Disable buffering -- pulling the trigger sends 1 byte,
        # and we want that sent immediately, to wake up ASAP.
        self.writer.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)

        count = 0
        while 1:
            count += 1
            # Bind to a local port; for efficiency, let the OS pick
            # a free port for us.
            # Unfortunately, stress tests showed that we may not
            # be able to connect to that port ("Address already in
            # use") despite that the OS picked it.  This appears
            # to be a race bug in the Windows socket implementation.
            # So we loop until a connect() succeeds (almost always
            # on the first try).  See the long thread at
            # http://mail.zope.org/pipermail/zope/2005-July/160433.html
            # for hideous details.
            a = socket.socket()
            set_close_exec(a.fileno())
            a.bind(("127.0.0.1", 0))
            a.listen(1)
            connect_address = a.getsockname()  # assigned (host, port) pair
            try:
                self.writer.connect(connect_address)
                break    # success
            except socket.error as detail:
                if (not hasattr(errno, 'WSAEADDRINUSE') or
                        errno_from_exception(detail) != errno.WSAEADDRINUSE):
                    # "Address already in use" is the only error
                    # I've seen on two WinXP Pro SP2 boxes, under
                    # Pythons 2.3.5 and 2.4.1.
                    raise
                # (10048, 'Address already in use')
                # assert count <= 2 # never triggered in Tim's tests
                if count >= 10:  # I've never seen it go above 2
                    a.close()
                    self.writer.close()
                    raise socket.error("Cannot bind trigger!")
                # Close `a` and try again.  Note:  I originally put a short
                # sleep() here, but it didn't appear to help or hurt.
                a.close()

        self.reader, addr = a.accept()
        set_close_exec(self.reader.fileno())
        self.reader.setblocking(0)
        self.writer.setblocking(0)
        a.close()
        self.reader_fd = self.reader.fileno()

    def fileno(self):
        return self.reader.fileno()

    def write_fileno(self):
        return self.writer.fileno()

    def wake(self):
        try:
            self.writer.send(b"x")
        except (IOError, socket.error, ValueError):
            pass

    def consume(self):
        try:
            while True:
                result = self.reader.recv(1024)
                if not result:
                    break
        except (IOError, socket.error):
            pass

    def close(self):
        self.reader.close()
        try_close(self.writer)