utils: add plugin loader classes

tuned/utils/pluginloader.py

@@ -0,0 +1,55 @@
+import tuned.logs
+
+__all__ = ["PluginLoader"]
+
+log = tuned.logs.get()
+
+class PluginLoader(object):
+	__slots__ = ["_namespace", "_prefix", "_interface"]
+
+	def __init__(self, namespace, prefix, interface):
+		super(self.__class__, self).__init__()
+
+		assert type(namespace) is str
+		assert type(prefix) is str
+		assert type(interface) is type and issubclass(interface, object)
+
+		self._namespace = namespace
+		self._prefix = prefix
+		self._interface = interface
+
+	@property
+	def namespace(self):
+		return self._namespace
+
+	@property
+	def prefix(self):
+		return self._prefix
+
+	@property
+	def interface(self):
+		return self._interface
+
+	def load(self, plugin_name):
+		assert type(plugin_name) is str
+
+		module_name = "%s.%s%s" % (self._namespace, self._prefix, plugin_name)
+		module = self._get_module(module_name)
+		return module
+
+	def _get_module(self, module_name):
+		log.debug("loading module %s" % module_name)
+		module = __import__(module_name)
+		path = module_name.split(".")
+		path.pop(0)
+
+		while len(path) > 0:
+			module = getattr(module, path.pop(0))
+
+		for name in module.__dict__:
+			obj = getattr(module, name)
+			if type(obj) is type and issubclass(obj, self._interface):
+				return obj
+
+		raise ImportError("Cannot find the plugin class.")
+