Here's an example implementation to further illustrate my point.
Regards,
Anthony Liguori
Anthony Liguori wrote:
One of the first things I noticed is that the spec defines some
extended types. This is a bit challenging in XML-RPC. It's unclear
to me how 64 bit integer is represented (since XML-RPC only defines 32
bit integers). Also, defining void to an empty string is
understandable but requires some special casing that really shouldn't
be necessary.
Here's what I propose:
As a convention, we never use <struct>'s on the wire to directly
represent structures. By convention, structs always appear as:
<struct>
<member><name>kind</name><value><string>[typename]</string></value></member>
<member><name>value</name><value>[typevalue]</value></member>
</struct>
Where typename is the string representation of the type and typevalue
is the type-specific value.
Some common types would be:
struct - use this to represent actual structs. typevalue is the
normal encoding of a struct
long - 64 bit representation of struct. typevalue is the string
representation
void - use to represent None. typevalue is ignored.
What's nice about this sort of consistent approach is that we can
write a marshalling/unmarshalling wrapper for Python that
automagically does this conversion. Furthermore, if we did decide to
support objects (as the current spec does), we could automagically
marshal/unmarshal these over the wire.
The general idea here is that this is an extensible typing system for
XML-RPC.
Another thing to consider is having a type of exception. I like
exception based APIs (i'll say that for another email) however the
format of the standard XML-RPC exception leaves a lot to be desired.
Thoughts?
Regards,
Anthony Liguori
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import xmlrpclib
import SimpleXMLRPCServer
from types import DictType, NoneType
class Marshaller(xmlrpclib.Marshaller):
def dump_struct(self, value, write, escape=xmlrpclib.escape):
write("""<value><struct>
<member>
<name>type</name>
<value>struct</value>
</member>
<member>
<name>value</name>
""")
self.__dump_struct(self, value, write, escape)
write('</member></struct></value>\n')
def __init__(self, encoding=None, allow_none=0):
xmlrpclib.Marshaller.__init__(self, encoding, allow_none)
self.__dump_struct = self.dispatch[DictType]
self.dispatch[DictType] = Marshaller.dump_struct
class Unmarshaller(xmlrpclib.Unmarshaller):
dispatch_ext = {}
def ext_struct(self, value):
return value
dispatch_ext['struct'] = ext_struct
def end_struct(self, data):
self.__end_struct(self, data)
if self._on:
a = self._stack[-1]
if self.dispatch_ext.has_key(a['type']):
a = self.dispatch_ext[a['type']](self, a['value'])
self._stack[-1] = a
self._on = not self._on
def __init__(self, *args):
xmlrpclib.Unmarshaller.__init__(self)
self.__end_struct = self.dispatch["struct"]
self.dispatch["struct"] = Unmarshaller.end_struct
self._on = False
xmlrpclib.FastMarshaller = Marshaller
xmlrpclib.FastParser = xmlrpclib.ExpatParser
xmlrpclib.FastUnmarshaller = Unmarshaller
a = xmlrpclib.ServerProxy("http://localhost:8001/RPC2";)
print a.ident({'z': 'z', 'foo': {'poo': 'foo'}, 'doo': {'da': 'qe'}, 'a': 'b'})
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