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# Copyright 2015-2017 Intel Corporation.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Loader servant module used by Loader.
Module is inteded to be private to serve only Loader itself, nevertheless
some methods are exposed outside and can be used by any other clients:
- load_modules(self, path, interface)
- load_module(self, path, interface, class_name)
Those method are stateless static members.
"""
import os
from os import sys
import imp
import fnmatch
import logging
from conf import settings
class LoaderServant(object):
"""Class implements basic dynamic import operations.
"""
_class_name = None
_path = None
_interface = None
def __init__(self, path, class_name, interface):
"""LoaderServant constructor
Intializes all data needed for import operations.
Attributes:
path: path to directory which contains implementations derived from
interface.
class_name: Class name which will be returned in get_class
method, if such definition exists in directory
represented by path,
interface: interface type. Every object which doesn't
implement this particular interface will be
filtered out.
"""
self._class_name = class_name
self._path = path
self._interface = interface
def get_class(self):
"""Returns class type based on parameters passed in __init__.
:return: Type of the found class.
None if class hasn't been found
"""
return self.load_module(path=self._path,
interface=self._interface,
class_name=self._class_name)
def get_classes(self):
"""Returns all classes in path derived from interface
:return: Dictionary with following data:
- key: String representing class name,
- value: Class type.
"""
return self.load_modules(path=self._path,
interface=self._interface)
def get_classes_printable(self):
"""Returns all classes derived from _interface found in path
:return: String - list of classes in printable format.
"""
out = self.load_modules(path=self._path,
interface=self._interface)
results = []
# sort modules to produce the same output everytime
for (name, mod) in sorted(out.items()):
desc = (mod.__doc__ or 'No description').strip().split('\n')[0]
results.append((name, desc))
header = 'Classes derived from: ' + self._interface.__name__
output = [header + '\n' + '=' * len(header) + '\n']
for (name, desc) in results:
output.append('* %-18s%s' % ('%s:' % name, desc))
output.append('')
output.append('')
return '\n'.join(output)
@staticmethod
def load_module(path, interface, class_name):
"""Imports everything from given path and returns class type
This is based on following conditions:
- Class is derived from interface,
- Class type name matches class_name.
:return: Type of the found class.
None if class hasn't been found
"""
results = LoaderServant.load_modules(
path=path, interface=interface)
if class_name in results:
logging.info(
"Class found: %s.", class_name)
return results.get(class_name)
return None
@staticmethod
def load_modules(path, interface):
"""Returns dictionary of class name/class type found in path
This is based on following conditions:
- classes found under path are derived from interface.
- class is not interface itself.
:return: Dictionary with following data:
- key: String representing class name,
- value: Class type.
"""
result = {}
for _, mod in LoaderServant._load_all_modules(path):
# find all classes derived from given interface, but suppress
# interface itself and any abstract class starting with iface name
gens = dict((k, v) for (k, v) in list(mod.__dict__.items())
if isinstance(v, type) and
issubclass(v, interface) and
not k.startswith(interface.__name__))
if gens:
for (genname, gen) in list(gens.items()):
result[genname] = gen
return result
@staticmethod
def _load_all_modules(path):
"""Load all modules from ``path`` directory.
This is based on the design used by OFTest:
https://github.com/floodlight/oftest/blob/master/oft
:param path: Path to a folder of modules.
:return: List of modules in a folder.
"""
mods = []
for root, _, filenames in os.walk(path):
# Iterate over each python file
for filename in fnmatch.filter(filenames, '[!.]*.py'):
modname = os.path.splitext(os.path.basename(filename))[0]
# skip module load if it is excluded by configuration
if modname in settings.getValue('EXCLUDE_MODULES'):
continue
try:
if modname in sys.modules:
mod = sys.modules[modname]
else:
mod = imp.load_module(
modname, *imp.find_module(modname, [root]))
except ImportError:
logging.error('Could not import file %s', filename)
raise
mods.append((modname, mod))
return mods
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