Support for defining CompositeTypes with custom inner types.

E.g.: Given the following custom type:

Class MyDateType(CassandraType):
	@staticmethod
	def pack(v, *args, **kwargs):
		"""custom pack implementation"""

	@staticmethod
	def unpack(v, *args, **kwargs):
		"""custom unpack implementation"""

You can now do the following:

	c = CompositeType(MyDateType, LongType)

And the following:

	cf = ColumnFamily(pool, 'MyColumnFamily')
	cf.column_name_class = CompositeType(MyDateType, LongType)

pycassa/marshal.py

@@ -74,8 +74,13 @@ def _to_timestamp(v):
         converted = v * 1e3
     return long(converted)
 
-def get_composite_packer(typestr):
-    packers = map(packer_for, _get_inner_types(typestr))
+def get_composite_packer(typestr=None, composite_type=None):
+    assert (typestr or composite_type), "Must provide typestr or " + \
+            "CompositeType instance"
+    if typestr:
+        packers = map(packer_for, _get_inner_types(typestr))
+    elif composite_type:
+        packers = [c.pack for c in composite_type.components] 
 
     if _have_struct:
         len_packer = _short_packer.pack
@@ -104,8 +109,13 @@ def pack_composite(items, slice_start=None):
 
     return pack_composite
 
-def get_composite_unpacker(typestr):
-    unpackers = map(unpacker_for, _get_inner_types(typestr))
+def get_composite_unpacker(typestr=None, composite_type=None):
+    assert (typestr or composite_type), "Must provide typestr or " + \
+            "CompositeType instance"
+    if typestr:
+        unpackers = map(unpacker_for, _get_inner_types(typestr))
+    elif composite_type:
+        unpackers = [c.unpack for c in composite_type.components]
 
     if _have_struct:
         len_unpacker = lambda v: _short_packer.unpack(v)[0]

pycassa/types.py

@@ -226,3 +226,11 @@ def __init__(self, *components):
 
     def __str__(self):
         return "CompositeType(" + ", ".join(map(str, self.components)) + ")"
+
+    @property
+    def pack(self):
+        return marshal.get_composite_packer(composite_type=self)
+
+    @property
+    def unpack(self):
+        return marshal.get_composite_unpacker(composite_type=self)