1 files changed, 63 insertions, 0 deletions
diff --git a/lib/git/utils.py b/lib/git/utils.py
index c204c432..f84c247d 100644
--- a/lib/git/utils.py
+++ b/lib/git/utils.py
@@ -24,3 +24,66 @@ def is_git_dir(d):
 				(os.path.islink(headref) and
 				os.readlink(headref).startswith('refs'))
 	return False
+	
+	
+class LazyMixin(object):
+	"""
+	Base class providing an interface to lazily retrieve attribute values upon 
+	first access. If slots are used, memory will only be reserved once the attribute
+	is actually accessed and retrieved the first time. All future accesses will 
+	return the cached value as stored in the Instance's dict or slot.
+	"""
+	__slots__ = tuple()
+	
+	def __getattr__(self, attr):
+		"""
+		Whenever an attribute is requested that we do not know, we allow it 
+		to be created and set. Next time the same attribute is reqeusted, it is simply
+		returned from our dict/slots.
+		"""
+		self._set_cache_(attr)
+		# will raise in case the cache was not created
+		return object.__getattribute__(self, attr)
+
+	def _set_cache_(self, attr):
+		""" This method should be overridden in the derived class. 
+		It should check whether the attribute named by attr can be created
+		and cached. Do nothing if you do not know the attribute or call your subclass
+		
+		The derived class may create as many additional attributes as it deems 
+		necessary in case a git command returns more information than represented 
+		in the single attribute."""
+		pass
+
+
+class Iterable(object):
+	"""
+	Defines an interface for iterable items which is to assure a uniform 
+	way to retrieve and iterate items within the git repository
+	"""
+	__slots__ = tuple()
+	
+	@classmethod
+	def list_items(cls, repo, *args, **kwargs):
+		"""
+		Find all items of this type - subclasses can specify args and kwargs differently.
+		If no args are given, subclasses are obliged to return all items if no additional 
+		arguments arg given.
+		
+		Note: Favor the iter_items method as it will 
+		
+		Returns:
+			list(Item,...) list of item instances 
+		"""
+		return list(cls.iter_items(repo, *args, **kwargs))
+		
+		
+	@classmethod
+	def iter_items(cls, repo, *args, **kwargs):
+		"""
+		For more information about the arguments, see list_items
+		Return: 
+			iterator yielding Items
+		"""
+		raise NotImplementedError("To be implemented by Subclass")
+