"""Used by the AsyncThreadedAppServer module.

This file implements an object that can force a call to select in the main
asyncore.poll loop to return. This dispatcher is added to the asyncore polling
group. It is polled for reads. We make this object available to everyone.
When we need the asyncore select loop to return, i.e., we have some data ready
to go, we call the release() method, which does a quick write to it's own socket/file-descriptor. This causes select to return.

"""

import asyncore
import asynchat

import os
import socket
import string
import thread


if os.name == 'posix':

    class SelectRelease (asyncore.file_dispatcher):
        """Version for Posix.

        In a Posix environment, we can use a file descriptor as the object
        that we include in the polling loop that we force a read on.

        """

        def __init__ (self):
            r, w = os.pipe()
            self.wpipe = w
            asyncore.file_dispatcher.__init__ (self, r)

        def readable (self):
            return 1

        def writable (self):
            return 0

        def handle_connect (self):
            pass

        def release (self):
            os.write (self.wpipe, 'x')

        def handle_read (self):
            self.recv (8192)

        def log(self,message):
            pass


else:

    class SelectRelease (asyncore.dispatcher):
        """Version for MS Windows.

        Windows can't handle file descriptors in a select poll, so a real
        socket has to be used. This method was adapted from a similar module
        in the Zope Medusa server.

        """

        address = ('127.9.9.9', 19999)

        def __init__ (self):
            a = socket.socket (socket.AF_INET, socket.SOCK_STREAM)
            w = socket.socket (socket.AF_INET, socket.SOCK_STREAM)

            w.setsockopt(socket.IPPROTO_TCP, 1, 1)

            # get a pair of connected sockets
            host='127.9.9.9'
            port=19999
            while 1:
                try:
                    self.address=(host, port)
                    a.bind(self.address)
                    break
                except:
                    if port <= 19950:
                        raise 'Bind Error', 'Cannot bind trigger!'
                    port=port - 1

            a.listen (1)
            w.setblocking (0)
            try:
                w.connect (self.address)
            except:
                pass
            r, addr = a.accept()
            a.close()
            w.setblocking (1)
            self.trigger = w

            asyncore.dispatcher.__init__ (self, r)
            self._trigger_connected = 0

        def __repr__ (self):
            return '<select-trigger (loopback) at %x>' % id(self)

        def readable (self):
            return 1

        def writable (self):
            return 0

        def handle_connect (self):
            pass

        def release (self, thunk=None):
            self.trigger.send ('x')

        def handle_read (self):
            self.recv (8192)

        def log(self, message):
            pass