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This program demonstrates some sample usage of the base255 module and is the core of something called FDR (Full Duplex RPC). FDR has not been completed at this time, but the "spots" module takes most of the work off of other modules in network chatter.

Python, 254 lines
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'''Module for Send Python Object Through Socket (SPOTS).

This module implements the Zero SPOTS Protocol, the Query/Reply Protocol,
the Query/Reply Interface, and a shortcut for constructing QRI objects.'''

################################################################################

__version__ = '$Revision: 0 $'
__date__ = 'February 11, 2007'
__author__ = 'Stephen "Zero" Chappell <my.bios@gmail.com>'
__credits__ = '''\
T. Parker, for testing code that led to this module.
B. Brown, for teaching me some math courses.
G. Rossum, for allowing thread support in Python.'''

################################################################################

import base255 as _base255
import cPickle as _cPickle
import sys as _sys
import thread as _thread
import time as _time

################################################################################

class ZSP:

    'ZSP(socket) -> ZSP'

    def __init__(self, socket):
        'Initialize the Zero SPOTS Protocol object.'
        self.__sock = socket
        self.__send = _thread.allocate_lock()
        self.__recv = _thread.allocate_lock()
        self.__temp = ''

    def send(self, obj):
        'Send one object.'
        string = _base255.encode(_cPickle.dumps(obj, _cPickle.HIGHEST_PROTOCOL)) + '\0'
        self.__send.acquire()
        try:
            self.__sock.sendall(string)
        finally:
            self.__send.release()

    def recv(self):
        'Receive one object.'
        self.__recv.acquire()
        try:
            while '\0' not in self.__temp:
                temp = self.__sock.recv(2 ** 12)
                if not temp:
                    if self.__temp:
                        raise IOError
                    else:
                        raise EOFError
                self.__temp += temp
            temp, self.__temp = self.__temp.split('\0', 1)
        finally:
            self.__recv.release()
        return _cPickle.loads(_base255.decode(temp))

################################################################################

class QRP:

    'QRP(ZSP) -> QRP'

    def __init__(self, ZSP):
        'Initialize the Query/Reply Protocol object.'
        self.__ZSP = ZSP
        self.__error = None
        self.__Q_anchor = []
        self.__Q_packet = []
        self.__R_anchor = {}
        self.__Q_lock = _thread.allocate_lock()
        self.__R_lock = _thread.allocate_lock()
        _thread.start_new_thread(self.__thread, ())

    def send_Q(self, ID, obj):
        'Send one query.'
        if self.__error:
            raise self.__error
        self.__ZSP.send((False, ID, obj))

    def recv_Q(self, timeout=None):
        'Receive one query.'
        if self.__error:
            raise self.__error
        if timeout is not None:
            if not isinstance(timeout, (float, int, long)):
                raise TypeError, 'timeout must be of type float, int, or long'
            if not timeout >= 0:
                raise ValueError, 'timeout must be greater than or equal to 0'
        self.__Q_lock.acquire()
        try:
            try:
                if self.__Q_packet:
                    Q = True
                    ID, obj = self.__Q_packet.pop()
                else:
                    Q = False
                    anchor = [_thread.allocate_lock()]
                    anchor[0].acquire()
                    self.__Q_anchor.append(anchor)
            finally:
                self.__Q_lock.release()
        except AttributeError:
            raise self.__error
        if Q:
            return ID, obj
        if timeout:
            _thread.start_new_thread(self.__Q_thread, (timeout, anchor))
        anchor[0].acquire()
        try:
            Q = anchor[1]
        except IndexError:
            if self.__error:
                raise self.__error
            raise Warning
        return Q

    def send_R(self, ID, obj):
        'Send one reply.'
        if self.__error:
            raise self.__error
        self.__ZSP.send((True, ID, obj))

    def recv_R(self, ID, timeout=None):
        'Receive one reply.'
        if self.__error:
            raise self.__error
        if timeout is not None:
            if not isinstance(timeout, (float, int, long)):
                raise TypeError, 'timeout must be of type float, int, or long'
            if not timeout >= 0:
                raise ValueError, 'timeout must be greater than or equal to 0'
        anchor = [_thread.allocate_lock()]
        anchor[0].acquire()
        self.__R_lock.acquire()
        try:
            try:
                self.__R_anchor[ID] = anchor
            finally:
                self.__R_lock.release()
        except AttributeError:
            raise self.__error
        if timeout:
            _thread.start_new_thread(self.__R_thread, (timeout, ID))
        anchor[0].acquire()
        try:
            R = anchor[1]
        except IndexError:
            if self.__error:
                raise self.__error
            raise Warning
        return R

    def __thread(self):
        'Private class method.'
        try:
            while True:
                R, ID, obj = self.__ZSP.recv()
                if R:
                    self.__R_lock.acquire()
                    if self.__R_anchor.has_key(ID):
                        self.__R_anchor[ID].append(obj)
                        self.__R_anchor[ID][0].release()
                        del self.__R_anchor[ID]
                    self.__R_lock.release()
                else:
                    self.__Q_lock.acquire()
                    if self.__Q_anchor:
                        anchor = self.__Q_anchor.pop()
                        anchor.append((ID, obj))
                        anchor[0].release()
                    else:
                        self.__Q_packet.append((ID, obj))
                    self.__Q_lock.release()
        except Exception, error:
            if isinstance(error, EOFError):
                self.__error = EOFError
            else:
                self.__error = IOError
            self.__Q_lock.acquire()
            for anchor in self.__Q_anchor:
                anchor[0].release()
            del self.__Q_anchor
            del self.__Q_packet
            self.__Q_lock.release()
            self.__R_lock.acquire()
            for key in self.__R_anchor:
                self.__R_anchor[key][0].release()
            del self.__R_anchor
            self.__R_lock.release()

    def __Q_thread(self, timeout, anchor):
        'Private class method.'
        _time.sleep(timeout)
        self.__Q_lock.acquire()
        if not self.__error and anchor in self.__Q_anchor:
            anchor[0].release()
            self.__Q_anchor.remove(anchor)
        self.__Q_lock.release()

    def __R_thread(self, timeout, ID):
        'Private class method.'
        _time.sleep(timeout)
        self.__R_lock.acquire()
        if not self.__error and self.__R_anchor.has_key(ID):
            self.__R_anchor[ID][0].release()
            del self.__R_anchor[ID]
        self.__R_lock.release()

################################################################################

class QRI:

    'QRI(QRP) -> QRI'

    def __init__(self, QRP):
        'Initialize the Query/Reply Interface object.'
        self.__QRP = QRP
        self.__ID = 0
        self.__lock = _thread.allocate_lock()

    def call(self, obj, timeout=None):
        'Send one query and receive one reply.'
        self.__lock.acquire()
        ID = ''.join(chr(self.__ID >> shift & 0xFF) for shift in xrange(24, -8, -8))
        self.__ID = (self.__ID + 1) % (2 ** 32)
        self.__lock.release()
        self.__QRP.send_Q(ID, obj)
        return self.__QRP.recv_R(ID, timeout)

    def query(self, timeout=None):
        'Receive one query.'
        return self.__QRP.recv_Q(timeout)

    def reply(self, ID, obj):
        'Send one reply.'
        self.__QRP.send_R(ID, obj)

################################################################################

def qri(socket):
    'Construct a QRI object.'
    return QRI(QRP(ZSP(socket)))

################################################################################

if __name__ == '__main__':
    _sys.stdout.write('Content-Type: text/plain\n\n')
    _sys.stdout.write(file(_sys.argv[0]).read())

The QRI class is demonstrated in "Paint 1.0" to show one simple use of the "spots" module. This recipe demonstrates how network communications can be easier in a Python program by using a simple layer to handle data conversion on the fly.