add support for poor many's async... I don't want to tangle out

how to handle making Browse async, so I'll just restart the call
if a subfunction raises a Deferred object...  This should work
amazingly well... we may end up wrapping just the check/doUpdate
calls...

[git-p4: depot-paths = "//depot/": change = 823]

ContentDirectory.py

@@ -29,9 +29,54 @@ from elementtree.ElementTree import Element, SubElement, tostring
 from upnp import UPnPPublisher, errorCode
 from DIDLLite import DIDLElement, Container, Movie, Resource, MusicTrack
 
+from twisted.internet import defer
+from twisted.python import failure
+
 import traceback
 from urllib import quote
 
+class doRecall(defer.Deferred):
+	'''A class that will upon any callback from the Deferred object passed
+	in, recall fun(*args, **kwargs), just as if a maybeDeferred has been
+	processed.
+
+	The idea is to let something deeper called by something sync "abort"
+	the call until it's ready, and then reattempt.  This isn't the best
+	method as we throw away work, but it can be easier to implement.
+
+	Example:
+	def wrapper(five):
+		try:
+			return doacall(five)
+		except defer.Deferred, x:
+			return doRecallgen(x, wrapper, five)
+
+	If doacall works, everything is fine, but if a Deferred object is
+	raised, we put it in a doRecall class and return the deferred object
+	generated by doRecall.'''
+
+	def __init__(self, argdef, fun, *args, **kwargs):
+		self.fun = fun
+		self.args = args
+		self.kwargs = kwargs
+		self.defer = defer.Deferred()
+
+		argdef.addCallback(self._done)
+
+	def _done(self, *args, **kwargs):
+		ret = self.fun(*self.args, **self.kwargs)
+		if isinstance(ret, failure.Failure):
+			self.defer.errback(ret)
+		elif isinstance(ret, defer.Deferred):
+			# We are fruther delayed, continue.
+			ret.addCallback(self._done)
+		else:
+			self.defer.callback(ret)
+
+def doRecallgen(defer, fun, *args, **kwargs):
+        i = doRecall(defer, fun, *args, **kwargs)
+        return i.defer
+
 class ContentDirectoryControl(UPnPPublisher, dict):
 	"""This class implements the CDS actions over SOAP."""
 
@@ -123,6 +168,12 @@ class ContentDirectoryControl(UPnPPublisher, dict):
 	BrowseFlags = ('BrowseMetaData', 'BrowseDirectChildren')
 
 	def soap_Browse(self, *args):
+		try:
+			return self.thereal_soap_Browse(*args)
+		except defer.Deferred, x:
+			return doRecallgen(x, self.soap_Browse, *args)
+
+	def thereal_soap_Browse(self, *args):
 		"""Required: Incrementally browse the native heirachy of the Content
 		Directory objects exposed by the Content Directory Service."""
 
@@ -151,8 +202,14 @@ class ContentDirectoryControl(UPnPPublisher, dict):
 			# filter out the ones that don't exist anymore, we need
 			# to check against None, since some dirs might be empty
 			# (of valid content) but exist.
+			# XXX - technically if list changed, we need to get
+			# some new ones by looping till we have a complete
+			# list.
 			ochup = filter(lambda x, s = self:
 			    s[x.id].checkUpdate() is not None, ch)
+			# XXX - are we suppose to be calling addContainer
+			# for Containers instead of always addItem?
+			#log.msg('ochup:', `ochup`)
 			filter(lambda x, d = didl: d.addItem(x) and None, ochup)
 			total = len(self.getchildren(ObjectID))
 		else: