    """
    PickleRPC provides a Server object for connection to Pickle-RPC servers
    for the purpose of making requests and receiving the responses.

        >>> from MiscUtils.PickleRPC import Server
        >>> server = Server('http://localhost/cgi-bin/WebKit.cgi/Examples/PickleRPCExample')
        >>> server.multiply(10,20)
        200
        >>> server.add(10,20)
        30

    See also: Server, Webkit.PickleRPCServlet, WebKit.Examples.PickleRPCExample

    UNDER THE HOOD

    Requests look like this:
        {
            'version':    1,  # default
            'action':     'call',  # default
            'methodName': 'NAME',
            'args':       (A, B, ...), # default = (,)
            'keywords':   {'A': A, 'B': B, ...}  # default = {}
        }

    Only 'methodName' is required since that is the only key without a
    default value.

    Responses look like this:
        {
            'timeReceived': N,
            'timeReponded': M,
            'value': V,
            'exception': E,
            'requestError': E,
        }

    TimeReceived is the time the initial request was received.
    TimeResponded is the time at which the response was finished, as
    close to transmission as possible. The times are expressed as
    number of seconds since the Epoch, e.g., time.time().

    Value is whatever the method happened to return.

    Exception may be 'occurred' to indicate that an exception
    occurred, the specific exception, such as "KeyError: foo" or the
    entire traceback (as a string), at the discretion of the server.
    It will always be a non-empty string if it is present.

    RequestError is an exception such as "Missing method
    in request." (with no traceback) that indicates a problem with the
    actual request received by the Pickle-RPC server.

    Value, exception and requestError are all exclusive to each other.

    SECURITY

    Pickle RPC uses the SafeUnpickler class (in this module) to
    prevent unpickling of unauthorized classes.  By default, it
    doesn't allow _any_ classes to be unpickled.  You can override
    allowedGlobals() or findGlobal() in a subclass as needed to
    allow specific class instances to be unpickled.

    Note that both Transport in this module and PickleRPCServlet in
    WebKit are derived from SafeUnpickler.

    CREDIT

    The implementation of this module was taken directly from Python 2.2's
    xmlrpclib and then transformed from XML-orientation to Pickle-orientation.

    The zlib compression was adapted from code by Skip Montanaro that I found
    here: http://manatee.mojam.com/~skip/python/
    """

    __version__ = 1   # version of PickleRPC protocol

    import types

    try:
        from cPickle import dumps, Unpickler, UnpicklingError
    except ImportError:
        from pickle import dumps, Unpickler, UnpicklingError

    try:
        import zlib
    except ImportError:
        zlib = None

    try:
        from cStringIO import StringIO
    except ImportError:
        from StringIO import StringIO

    class Error(Exception):
        """
        The abstract exception/error class for all PickleRPC errors.
        """
        pass

    class ResponseError(Error):
        """
        These are unhandled exceptions raised when the server was computing
        a response. These will indicate errors such as:
            * exception in the actual target method on the server
            * malformed responses
            * non "200 OK" status code responses
        """
        pass

    # Sometimes xmlrpclib is installed as a package, sometimes not.  So we'll
    # make sure it works either way.
    try:
        from xmlrpclib.xmlrpclib import ProtocolError as _PE
    except ImportError:
        from xmlrpclib import ProtocolError as _PE
    # @@ 2002-01-31 ce: should this be caught somewhere for special handling? Perhaps in XMLRPCServlet?

    class ProtocolError(ResponseError, _PE):
        pass

    class RequestError(Error):
        """
        These are errors originally raised by the server complaining about
        malformed requests.
        """
        pass

    class InvalidContentTypeError(ResponseError):

        def __init__(self, headers, content):
            Exception.__init__(self) #, headers, content)
            self.headers = headers
            self.content = content

        def __repr__(self):
            content = self.content
            return '%s: Content type is not text/x-python-pickled-dict\nheaders = %s\ncontent =\n%s' % (
                self.__class__.__name__, self.headers, content)

        __str__ = __repr__

    class SafeUnpickler:
        """
        For security reasons, we don't want to allow just anyone to unpickle
        anything.  That can cause arbitrary code to be executed.
        So this SafeUnpickler base class is used to control
        what can be unpickled.  By default it doesn't let you unpickle
        any class instances at all, but you can create subclass that
        overrides allowedGlobals().

        Note that the PickleRPCServlet class in WebKit is derived from this class
        and uses its load() and loads() methods to do all unpickling.
        """
        def allowedGlobals(self):
            """
            Must return a list of (moduleName, klassName) tuples for all
            classes that you want to allow to be unpickled.

            Example:
                return [('mx.DateTime', '_DT')]
            allows mx.DateTime instances to be unpickled.
            """
            return []

        def findGlobal(self, module, klass):
            if (module, klass) not in self.allowedGlobals():
                raise UnpicklingError, 'For security reasons, you can\'t unpickle objects from module %s with type %s' % (module, klass)
            globals = {}
            exec 'from %s import %s as theClass' % (module, klass) in globals
            return globals['theClass']

        def load(self, file):
            safeUnpickler = Unpickler(file)
            safeUnpickler.find_global = self.findGlobal
            return safeUnpickler.load()

        def loads(self, str):
            return self.load(StringIO(str))

    # @@ 2002-01-31 ce: Could we reduce code duplication and automatically
    # inherit future improvements by actually importing and using the
    # xmlrpclib classes below either as base classes or mix-ins?

    class Server:
        """uri [,options] -> a logical connection to an XML-RPC server

        uri is the connection point on the server, given as
        scheme://host/target.

        The standard implementation always supports the "http" scheme.  If
        SSL socket support is available (Python 2.0), it also supports
        "https".

        If the target part and the slash preceding it are both omitted,
        "/PickleRPC" is assumed.

        See the module doc string for more information.
        """

        def __init__(self, uri, transport=None, verbose=0, binary=1, compressRequest=1, acceptCompressedResponse=1):
            # establish a "logical" server connection

            # get the url
            import urllib
            type, uri = urllib.splittype(uri)
            if type not in ("http", "https"):
                raise IOError, "unsupported Pickle-RPC protocol"
            self.__host, self.__handler = urllib.splithost(uri)
            if not self.__handler:
                self.__handler = "/PickleRPC"

            if transport is None:
                if type == "https":
                    transport = SafeTransport()
                else:
                    transport = Transport()
            self.__transport = transport

            self.__verbose = verbose
            self.__binary = binary
            self.__compressRequest = compressRequest
            self.__acceptCompressedResponse = acceptCompressedResponse

        def _request(self, methodName, args, keywords):
            """
            Call a method on the remote server.
            """
            request = {
                'version':    1,
                'action':     'call',
                'methodName': methodName,
                'args':       args,
                'keywords':   keywords,
            }
            if self.__binary:
                request = dumps(request, 1)
            else:
                request = dumps(request)
            if zlib is not None and self.__compressRequest and len(request) > 1000:
                request = zlib.compress(request, 1)
                compressed = 1
            else:
                compressed = 0

            response = self.__transport.request(
                self.__host,
                self.__handler,
                request,
                verbose=self.__verbose,
                binary=self.__binary,
                compressed=compressed,
                acceptCompressedResponse=self.__acceptCompressedResponse
                )

            return response

        def __requestValue(self, methodName, args, keywords):
            dict = self._request(methodName, args, keywords)
            if dict.has_key('value'):
                return dict['value']
            elif dict.has_key('exception'):
                raise ResponseError, dict['exception']
            elif dict.has_key('requestError'):
                raise RequestError, dict['requestError']
            else:
                raise RequestError, 'Response does not have a value, expection or requestError.'

        def __repr__(self):
            return "<%s for %s%s>" % (self.__class__.__name__, self.__host, self.__handler)

        __str__ = __repr__

        def __getattr__(self, name):
            # magic method dispatcher
            return _Method(self.__requestValue, name)

        # note: to call a remote object with an non-standard name, use
        # result getattr(server, "strange-python-name")(args)

    ServerProxy = Server # be like xmlrpclib for those who might guess or expect it

    class _Method:
        """
        Some magic to bind a Pickle-RPC method to an RPC server.
        Supports "nested" methods (e.g. examples.getStateName).
        """

        def __init__(self, send, name):
            self.__send = send
            self.__name = name

        def __getattr__(self, name):
            return _Method(self.__send, "%s.%s" % (self.__name, name))

        def __call__(self, *args, **keywords):  # note that keywords are supported
            return self.__send(self.__name, args, keywords)

    class Transport(SafeUnpickler):
        """
        Handles an HTTP transaction to a Pickle-RPC server.
        """

        # client identifier (may be overridden)
        user_agent = "PickleRPC/%s (by http://webware.sf.net/)" % __version__

        def request(self, host, handler, request_body, verbose=0, binary=0, compressed=0,
                    acceptCompressedResponse=0):
            # issue Pickle-RPC request

            h = self.make_connection(host)
            if verbose:
                h.set_debuglevel(1)

            self.send_request(h, handler, request_body)
            self.send_host(h, host)
            self.send_user_agent(h)
            self.send_content(h, request_body, binary, compressed, acceptCompressedResponse)

            errcode, errmsg, headers = h.getreply()

            if errcode != 200:
                raise ProtocolError(
                    host + handler,
                    errcode, errmsg,
                    headers
                    )

            self.verbose = verbose

            if h.headers['content-type'] not in ['text/x-python-pickled-dict', 'application/x-python-binary-pickled-dict']:
                headers = h.headers.headers
                content = h.getfile().read()
                raise InvalidContentTypeError(headers, content)

            try:
                content_encoding = headers["content-encoding"]
                if content_encoding and content_encoding == "x-gzip":
                    return self.parse_response_gzip(h.getfile())
                elif content_encoding:
                    raise ProtocolError(host + handler,
                                        500,
                                        "Unknown encoding type: %s" %
                                        content_encoding,
                                        headers)
                else:
                    return self.parse_response(h.getfile())
            except KeyError:
                return self.parse_response(h.getfile())

        def make_connection(self, host):
            # create a HTTP connection object from a host descriptor
            import httplib
            return httplib.HTTP(host)

        def send_request(self, connection, handler, request_body):
            connection.putrequest("POST", handler)

        def send_host(self, connection, host):
            connection.putheader("Host", host)

        def send_user_agent(self, connection):
            connection.putheader("User-Agent", self.user_agent)

        def send_content(self, connection, request_body, binary=0, compressed=0,
                         acceptCompressedResponse=0):
            if binary:
                connection.putheader("Content-Type", "application/x-python-binary-pickled-dict")
            else:
                connection.putheader("Content-Type", "text/x-python-pickled-dict")
            connection.putheader("Content-Length", str(len(request_body)))
            if compressed:
                connection.putheader("Content-Encoding", "x-gzip")
            if zlib is not None and acceptCompressedResponse:
                connection.putheader("Accept-Encoding", "gzip")
            connection.endheaders()
            if request_body:
                connection.send(request_body)

        def parse_response(self, f):
            return self.load(f)

        def parse_response_gzip(self, f):
            # read response from input file, decompress it, and parse it
            # @@ gat: could this be made more memory-efficient?
            return self.loads(zlib.decompress(f.read()))

    class SafeTransport(Transport):
        """
        Handles an HTTPS transaction to a Pickle-RPC server.
        """

        def make_connection(self, host):
            # create a HTTPS connection object from a host descriptor
            # host may be a string, or a (host, x509-dict) tuple
            import httplib
            if isinstance(host, types.TupleType):
                host, x509 = host
            else:
                x509 = {}
            try:
                HTTPS = httplib.HTTPS
            except AttributeError:
                raise NotImplementedError,\
                      "your version of httplib doesn't support HTTPS"
            else:
                return apply(HTTPS, (host, None), x509)

        def send_host(self, connection, host):
            if isinstance(host, types.TupleType):
                host, x509 = host
            connection.putheader("Host", host)