Refactor: Modified Class ImageLayer

First commit in a string of code refactoring commits to move some
utility modules into classes in an attempt to decouple the process
of extracting or formatting data from the actual data

- Layer is now renamed ImageLayer for clarity
- Image layer property sha is now diff_id for clarity
- Added property tar_file to point to location of the diff filesystem
tarball
- Added property created_by which is not an OCI specification but is
used in images created by Docker
- Added getters for the new properties
- Added setter for created_by
- Modified the unit tests to reflect the changes in the class

Note: This change will break the build

Signed-off-by: Nisha K <[email protected]>

classes/image_layer.py

@@ -0,0 +1,77 @@
+'''
+Copyright (c) 2017 VMware, Inc. All Rights Reserved.
+SPDX-License-Identifier: BSD-2-Clause
+'''
+
+
+class ImageLayer(object):
+ '''A representation of a container filesystem layer
+ attributes:
+ sha: the sha256 of the layer filesystem
+ packages: list of objects of type Package (package.py)
+ tar_file: the path to the layer filesystem tarball
+ created_by: sometimes the metadata will contain a created_by
+ key containing the command that created the filesystem layer
+ methods:
+ add_package: adds a package to the layer
+ remove_package: removes a package from the layer
+ to_dict: returns a dict representation of the instance
+ get_package_names: returns a list of package names'''
+ def __init__(self, diff_id, tar_file, created_by=None):
+ self.__diff_id = diff_id
+ self.__tar_file = tar_file
+ self.__created_by = created_by
+ self.__packages = []
+
+ @property
+ def diff_id(self):
+ return self.__diff_id
+
+ @property
+ def packages(self):
+ return self.__packages
+
+ @property
+ def tar_file(self):
+ return self.__tar_file
+
+ @property
+ def created_by(self):
+ return self.__created_by
+
+ @created_by.setter
+ def created_by(self, create_string):
+ self.__created_by = create_string
+
+ def add_package(self, package):
+ self.__packages.append(package)
+
+ def remove_package(self, package_name):
+ rem_index = 0
+ success = False
+ for index in range(0, len(self.__packages)):
+ if self.packages[index].name == package_name:
+ rem_index = index
+ success = True
+ break
+ if success:
+ self.__packages.remove(self.__packages[rem_index])
+ return success
+
+ def to_dict(self):
+ layer_dict = {}
+ pkg_list = []
+ for pkg in self.__packages:
+ pkg_list.append(pkg.to_dict())
+ layer_dict.update({self.diff_id: {'packages': pkg_list,
+ 'tar_file': self.__tar_file,
+ 'created_by': self.__created_by
+ }})
+ return layer_dict
+
+ def get_package_names(self):
+ '''Get the list of package names in this layer'''
+ pkg_list = []
+ for pkg in self.packages:
+ pkg_list.append(pkg.name)
+ return pkg_list

tests/test_class_image_layer.py

@@ -0,0 +1,63 @@
+'''
+Copyright (c) 2017 VMware, Inc. All Rights Reserved.
+SPDX-License-Identifier: BSD-2-Clause
+'''
+
+import unittest
+
+from classes.image_layer import ImageLayer
+from classes.package import Package
+
+
+class TestClassLayer(unittest.TestCase):
+
+ def setUp(self):
+ self.layer = ImageLayer('123abc', 'path/to/tar')
+
+ def tearDown(self):
+ del self.layer
+
+ def testInstance(self):
+ self.assertEqual(self.layer.diff_id, '123abc')
+ self.assertEqual(self.layer.tar_file, 'path/to/tar')
+ self.assertFalse(self.layer.packages)
+ self.assertFalse(self.layer.created_by)
+ self.assertRaises(AttributeError, setattr, self.layer,
+ 'diff_id', '456def')
+ self.assertRaises(AttributeError, setattr, self.layer, 'tar_file',
+ 'some/other/path')
+ self.layer.created_by = 'some string'
+ self.assertEqual(self.layer.created_by, 'some string')
+
+ def testAddPackage(self):
+ p1 = Package('x')
+ self.layer.add_package(p1)
+ self.assertEqual(len(self.layer.packages), 1)
+
+ def testRemovePackage(self):
+ p1 = Package('x')
+ p2 = Package('y')
+ self.layer.add_package(p1)
+ self.layer.add_package(p2)
+ self.assertTrue(self.layer.remove_package('y'))
+ self.assertFalse(self.layer.remove_package('y'))
+
+ def testToDict(self):
+ p1 = Package('x')
+ self.layer.add_package(p1)
+ a_dict = self.layer.to_dict()
+ print(a_dict)
+ self.assertTrue(a_dict['123abc'])
+ self.assertEqual(len(a_dict['123abc']['packages']), 1)
+ self.assertEqual(a_dict['123abc']['packages'][0]['name'], 'x')
+ self.assertEqual(a_dict['123abc']['tar_file'], 'path/to/tar')
+
+ def testGetPackageNames(self):
+ p1 = Package('x')
+ self.layer.add_package(p1)
+ pkgs = self.layer.get_package_names()
+ self.assertEqual(pkgs[0], 'x')
+
+
+if __name__ == '__main__':
+ unittest.main()