# Copyright (C) 2003-2007  Robey Pointer <robeypointer@gmail.com>
# Copyright 2012 Citrix Systems, Inc. Licensed under the
# Apache License, Version 2.0 (the "License"); you may not use this
# file except in compliance with the License.  Citrix Systems, Inc.
# reserves all rights not expressly granted by the License.
# You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# 
# Automatically generated by addcopyright.py at 04/03/2012
# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.

"""
Abstraction of a one-way pipe where the read end can be used in select().
Normally this is trivial, but Windows makes it nearly impossible.

The pipe acts like an Event, which can be set or cleared. When set, the pipe
will trigger as readable in select().
"""

import sys
import os
import socket


def make_pipe ():
    if sys.platform[:3] != 'win':
        p = PosixPipe()
    else:
        p = WindowsPipe()
    return p


class PosixPipe (object):
    def __init__ (self):
        self._rfd, self._wfd = os.pipe()
        self._set = False
        self._forever = False
        self._closed = False
    
    def close (self):
        os.close(self._rfd)
        os.close(self._wfd)
        # used for unit tests:
        self._closed = True
    
    def fileno (self):
        return self._rfd

    def clear (self):
        if not self._set or self._forever:
            return
        os.read(self._rfd, 1)
        self._set = False
    
    def set (self):
        if self._set or self._closed:
            return
        self._set = True
        os.write(self._wfd, '*')
    
    def set_forever (self):
        self._forever = True
        self.set()


class WindowsPipe (object):
    """
    On Windows, only an OS-level "WinSock" may be used in select(), but reads
    and writes must be to the actual socket object.
    """
    def __init__ (self):
        serv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        serv.bind(('127.0.0.1', 0))
        serv.listen(1)
    
        # need to save sockets in _rsock/_wsock so they don't get closed
        self._rsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self._rsock.connect(('127.0.0.1', serv.getsockname()[1]))
    
        self._wsock, addr = serv.accept()
        serv.close()
        self._set = False
        self._forever = False
        self._closed = False
    
    def close (self):
        self._rsock.close()
        self._wsock.close()
        # used for unit tests:
        self._closed = True
    
    def fileno (self):
        return self._rsock.fileno()

    def clear (self):
        if not self._set or self._forever:
            return
        self._rsock.recv(1)
        self._set = False
    
    def set (self):
        if self._set or self._closed:
            return
        self._set = True
        self._wsock.send('*')

    def set_forever (self):
        self._forever = True
        self.set()


class OrPipe (object):
    def __init__(self, pipe):
        self._set = False
        self._partner = None
        self._pipe = pipe
    
    def set(self):
        self._set = True
        if not self._partner._set:
            self._pipe.set()
    
    def clear(self):
        self._set = False
        if not self._partner._set:
            self._pipe.clear()


def make_or_pipe(pipe):
    """
    wraps a pipe into two pipe-like objects which are "or"d together to
    affect the real pipe. if either returned pipe is set, the wrapped pipe
    is set. when both are cleared, the wrapped pipe is cleared.
    """
    p1 = OrPipe(pipe)
    p2 = OrPipe(pipe)
    p1._partner = p2
    p2._partner = p1
    return p1, p2