1 # Copyright (c) 2013 The Chromium OS Authors. All rights reserved. 2 # Use of this source code is governed by a BSD-style license that can be 3 # found in the LICENSE file. 4 5 import inspect 6 import logging 7 import sys 8 9 10 TYPE_KEY = 'xmlrpc_struct_type_key' 11 12 13 def deserialize(serialized, module=None): 14 """Deserialize an XmlRpcStruct. 15 16 Because Python XMLRPC doesn't understand anything more than basic 17 types, we're forced to reinvent type serialization. This is one way 18 to do it. 19 20 This function looks at the constructor and figures out what subset of 21 |serialized| will be accepted as arguments. 22 23 @param serialized dict representing a serialized XmlRpcStruct. 24 @param module module object to pull classes from. Defaults to 25 this file. 26 @return an XmlRpcStruct object built from |serialized|. 27 28 """ 29 if TYPE_KEY not in serialized: 30 logging.error('Failed to deserialize XmlRpcStruct because of ' 31 'missing type.') 32 logging.error('Got serialized object: %r', serialized) 33 return None 34 35 if module is None: 36 module = sys.modules[__name__] 37 klass = getattr(module, serialized[TYPE_KEY]) 38 constructor_args = inspect.getargspec(klass.__init__) 39 optional_args = [] 40 if constructor_args.defaults: 41 # Valid args should now be a list of all the parameters that have 42 # default values. 43 optional_args = constructor_args.args[-len(constructor_args.defaults):] 44 # skip to argument 1 because the first argument is always |self|. 45 required_args = constructor_args.args[1:-len(constructor_args.defaults)] 46 args = [] 47 for arg in required_args: 48 if arg not in serialized: 49 logging.error('Failed to find non-keyword argument %s', arg) 50 return None 51 52 args.append(serialized[arg]) 53 kwargs = dict(filter(lambda (k, v): k in optional_args, 54 serialized.iteritems())) 55 logging.debug('Constructing %s object with args=%r, kwargs=%r', 56 serialized[TYPE_KEY], args, kwargs) 57 return klass(*args, **kwargs) 58 59 60 class XmlRpcStruct(object): 61 """Enables deserialization by injecting the proper class type. 62 63 To make deserilization work for you, write a constructor like: 64 65 def __init__(self, arg1, arg2='foo'): 66 # It is important that self.arg1 = arg1. Otherwise arguments 67 # won't be sent over the wire correctly. 68 self.arg1 = arg1 69 self.arg2 = arg2 70 71 Serialization happens automatically when using XMLRPC proxies, since 72 Python's XMLRPC framework will take all fields from your object and drop 73 them into a dict to go over the wire. To deserialize your object on the 74 other side, call deserialize() and pass in the module defining the 75 requisite class. 76 77 serialize() is provided to allow objects to fake that they are XMLRPC 78 proxies. 79 80 """ 81 82 def __init__(self): 83 super(XmlRpcStruct, self).__init__() 84 setattr(self, TYPE_KEY, self.__class__.__name__) 85 86 87 def serialize(self): 88 """@return dict of object fields.""" 89 return self.__dict__ 90