    """Dict-RPC servlets."""

    import sys, traceback
    from time import time

    try:
        from cPickle import dumps, PickleError
    except ImportError:
        from pickle import dumps, PickleError

    try:
        import zlib
    except ImportError:
        zlib = None

    from RPCServlet import RPCServlet
    from MiscUtils.PickleRPC import RequestError, SafeUnpickler

    class PickleRPCServlet(RPCServlet, SafeUnpickler):
        """PickleRPCServlet is a base class for Dict-RPC servlets.

        The "Pickle" refers to Python's pickle module. This class is
        similar to XMLRPCServlet. By using Python pickles you get their
        convenience (assuming the client is Pythonic), but lose
        language independence. Some of us don't mind that last one.  ;-)

        Conveniences over XML-RPC include the use of all of the following:
          * Any pickle-able Python type (datetime for example)
          * Python instances (aka objects)
          * None
          * Longs that are outside the 32-bit int boundaries
          * Keyword arguments

        Pickles should also be faster than XML, especially now that
        we support binary pickling and compression.

        To make your own PickleRPCServlet, create a subclass and implement a
        method which is then named in exposedMethods():

            from WebKit.PickleRPCServlet import PickleRPCServlet
            class Math(PickleRPCServlet):
                def multiply(self, x, y):
                    return x * y
                def exposedMethods(self):
                    return ['multiply']

        To make a PickleRPC call from another Python program, do this:
            from MiscUtils.PickleRPC import Server
            server = Server('http://localhost/WebKit.cgi/Context/Math')
            print server.multiply(3, 4)    # 12
            print server.multiply('-', 10) # ----------

        If a request error is raised by the server, then
        MiscUtils.PickleRPC.RequestError is raised. If an unhandled
        exception is raised by the server, or the server response is
        malformed, then MiscUtils.PickleRPC.ResponseError (or one of
        its subclasses) is raised.

        Tip: If you want callers of the RPC servlets to be able to
        introspect what methods are available, then include
        'exposedMethods' in exposedMethods().

        If you wanted the actual response dictionary for some reason:
            print server._request('multiply', 3, 4)
                # {'value': 12, 'timeReceived': ...}

        In which case, an exception is not purposefully raised if the
        dictionary contains one. Instead, examine the dictionary.

        For the dictionary formats and more information see the docs
        for MiscUtils.PickleRPC.

        """

        def respondToPost(self, trans):
            try:
                request = trans.request()
                data = request.rawInput(rewind=1)
                response = dict(timeReceived=trans.request().time())
                try:
                    try:
                        encoding = request.environ().get('HTTP_CONTENT_ENCODING')
                        if encoding == 'x-gzip':
                            if zlib is not None:
                                try:
                                    rawstring = data.read()
                                    req = self.loads(zlib.decompress(rawstring))
                                except zlib.error:
                                    raise RequestError(
                                        'Cannot uncompress compressed dict-rpc request')
                            else:
                                raise RequestError(
                                    'Cannot handle compressed dict-rpc request')
                        elif encoding:
                            raise RequestError(
                                'Cannot handle Content-Encoding of %s' % encoding)
                        else:
                            req = self.load(data)
                    except PickleError:
                        raise RequestError('Cannot unpickle dict-rpc request.')
                    if not isinstance(req, dict):
                        raise RequestError(
                            'Expecting a dictionary for dict-rpc requests, '
                            'but got %s instead.' % type(req))
                    if req.get('version', 1) != 1:
                        raise RequestError('Cannot handle version %s requests.'
                            % req['version'])
                    if req.get('action', 'call') != 'call':
                        raise RequestError(
                            'Cannot handle the request action, %r.' % req['action'])
                    try:
                        methodName = req['methodName']
                    except KeyError:
                        raise RequestError('Missing method in request')
                    args = req.get('args', ())
                    if methodName == '__methods__.__getitem__':
                        # support PythonWin autoname completion
                        response['value'] = self.exposedMethods()[args[0]]
                    else:
                        response['value'] = self.call(methodName, *args,
                            **req.get('keywords', {}))
                except RequestError, e:
                    response['requestError'] = str(e)
                    self.sendResponse(trans, response)
                    self.handleException(trans)
                except Exception, e:
                    response['exception'] = self.resultForException(e, trans)
                    self.sendResponse(trans, response)
                    self.handleException(trans)
                except: # if it's a string exception, this gets triggered
                    response['exception'] = self.resultForException(
                        sys.exc_info()[0], trans)
                    self.sendResponse(trans, response)
                    self.handleException(trans)
                else:
                    self.sendResponse(trans, response)
            except Exception:
                # internal error, report as HTTP server error
                print 'PickleRPCServlet internal error'
                print ''.join(traceback.format_exception(*sys.exc_info()))
                trans.response().setStatus(500, 'Server Error')
                self.handleException(trans)

        def sendResponse(self, trans, response):
            """Timestamp the response dict and send it."""
            # Generated a pickle string
            response['timeResponded'] = time()
            if self.useBinaryPickle():
                contentType = 'application/x-python-binary-pickled-dict'
                response = dumps(response, -1)
            else:
                contentType = 'text/x-python-pickled-dict'
                response = dumps(response, 0)

            # Get list of accepted encodings
            try:
                acceptEncoding = trans.request().environ()["HTTP_ACCEPT_ENCODING"]
                if acceptEncoding:
                    acceptEncoding = [enc.strip()
                        for enc in acceptEncoding.split(',')]
                else:
                    acceptEncoding = []
            except KeyError:
                acceptEncoding = []

            # Compress the output if we are allowed to.
            # We'll avoid compressing short responses and
            # we'll use the fastest possible compression -- level 1.
            if zlib is not None and 'gzip' in acceptEncoding and len(response) > 1000:
                contentEncoding = 'x-gzip'
                response = zlib.compress(response, 1)
            else:
                contentEncoding = None
            self.sendOK(contentType, response, trans, contentEncoding)

        @staticmethod
        def useBinaryPickle():
            """Determine whether binary pickling format shall be used.

            When this returns True, the highest available binary pickling format
            will be used. Override this to return False to use the less-efficient
            text pickling format.

            """
            return True