Split up util.get_file_details()

securesystemslib/util.py

@@ -81,13 +81,53 @@ def get_file_details(filepath, hash_algorithms=['sha256'],
   if storage_backend is None:
     storage_backend = securesystemslib.storage.FilesystemBackend()
 
-  # The returned file hashes of 'filepath'.
-  file_hashes = {}
+  file_length = get_file_length(filepath, storage_backend)
+  file_hashes = get_file_hashes(filepath, hash_algorithms, storage_backend)
+
+  return file_length, file_hashes
+
+
+def get_file_hashes(filepath, hash_algorithms=['sha256'],
+    storage_backend=None):
+  """
+  <Purpose>
+    Compute hash(es) of the file at filepath using each of the specified
+    hash algorithms. If no algorithms are specified, then the hash is
+    computed using the SHA-256 algorithm.
+
+  <Arguments>
+    filepath:
+      Absolute file path of a file.
+
+    hash_algorithms:
+      A list of hash algorithms with which the file's hash should be computed.
+      Defaults to ['sha256']
+
+    storage_backend:
+      An object which implements
+      securesystemslib.storage.StorageBackendInterface. When no object is
+      passed a FilesystemBackend will be instantiated and used.
+
+  <Exceptions>
+    securesystemslib.exceptions.FormatError: If hash of the file does not match
+    HASHDICT_SCHEMA.
+
+    securesystemslib.exceptions.Error: If 'filepath' does not exist.
+
+  <Returns>
+    A dictionary conforming to securesystemslib.formats.HASHDICT_SCHEMA
+    containing information about the hashes of the file at "filepath".
+  """
+
+  # Making sure that the format of 'filepath' is a path string.
+  # 'securesystemslib.exceptions.FormatError' is raised on incorrect format.
+  securesystemslib.formats.PATH_SCHEMA.check_match(filepath)
+  securesystemslib.formats.HASHALGORITHMS_SCHEMA.check_match(hash_algorithms)
 
-  filepath = os.path.abspath(filepath)
+  if storage_backend is None:
+    storage_backend = securesystemslib.storage.FilesystemBackend()
 
-  # Obtaining length of the file.
-  file_length = storage_backend.getsize(filepath)
+  file_hashes = {}
 
   with storage_backend.get(filepath) as fileobj:
     # Obtaining hash of the file.
@@ -99,7 +139,39 @@ def get_file_details(filepath, hash_algorithms=['sha256'],
   # Raise 'securesystemslib.exceptions.FormatError' if there is a mismatch.
   securesystemslib.formats.HASHDICT_SCHEMA.check_match(file_hashes)
 
-  return file_length, file_hashes
+  return file_hashes
+
+
+
+def get_file_length(filepath, storage_backend=None):
+  """
+  <Purpose>
+    To get file's length information.
+
+  <Arguments>
+    filepath:
+      Absolute file path of a file.
+
+    storage_backend:
+      An object which implements
+      securesystemslib.storage.StorageBackendInterface. When no object is
+      passed a FilesystemBackend will be instantiated and used.
+
+  <Exceptions>
+    securesystemslib.exceptions.Error: If 'filepath' does not exist.
+
+  <Returns>
+    The length, in bytes, of the file at 'filepath'.
+  """
+
+  # Making sure that the format of 'filepath' is a path string.
+  # 'securesystemslib.exceptions.FormatError' is raised on incorrect format.
+  securesystemslib.formats.PATH_SCHEMA.check_match(filepath)
+
+  if storage_backend is None:
+      storage_backend = securesystemslib.storage.FilesystemBackend()
+
+  return storage_backend.getsize(filepath)
 
 
 def persist_temp_file(temp_file, persist_path, storage_backend=None,

tests/test_util.py

@@ -85,7 +85,62 @@ def test_B1_get_file_details(self):
 
 
 
-  def  test_B2_ensure_parent_dir(self):
+  def test_B2_get_file_hashes(self):
+    # Goal: Verify proper output given certain expected/unexpected input.
+
+    # Making a temporary file.
+    filepath = self.make_temp_data_file()
+
+    # Computing the hash of the tempfile.
+    digest_object = securesystemslib.hash.digest_filename(filepath, algorithm='sha256')
+    file_hash = {'sha256' : digest_object.hexdigest()}
+
+    # Test: Expected input.
+    self.assertEqual(securesystemslib.util.get_file_hashes(filepath),
+        file_hash)
+
+    # Test: Incorrect input.
+    bogus_inputs = [self.random_string(), 1234, [self.random_string()],
+        {'a': 'b'}, None]
+
+    for bogus_input in bogus_inputs:
+      if isinstance(bogus_input, six.string_types):
+        self.assertRaises(securesystemslib.exceptions.Error,
+            securesystemslib.util.get_file_hashes, bogus_input)
+      else:
+        self.assertRaises(securesystemslib.exceptions.FormatError,
+            securesystemslib.util.get_file_hashes, bogus_input)
+
+
+
+  def test_B3_get_file_length(self):
+    # Goal: Verify proper output given certain expected/unexpected input.
+
+    # Making a temporary file.
+    filepath = self.make_temp_data_file()
+
+    # Computing the length of the tempfile.
+    digest_object = securesystemslib.hash.digest_filename(filepath, algorithm='sha256')
+    file_length = os.path.getsize(filepath)
+
+    # Test: Expected input.
+    self.assertEqual(securesystemslib.util.get_file_length(filepath), file_length)
+
+    # Test: Incorrect input.
+    bogus_inputs = [self.random_string(), 1234, [self.random_string()],
+        {'a': 'b'}, None]
+
+    for bogus_input in bogus_inputs:
+      if isinstance(bogus_input, six.string_types):
+        self.assertRaises(securesystemslib.exceptions.Error,
+            securesystemslib.util.get_file_length, bogus_input)
+      else:
+        self.assertRaises(securesystemslib.exceptions.FormatError,
+            securesystemslib.util.get_file_length, bogus_input)
+
+
+
+  def  test_B4_ensure_parent_dir(self):
     existing_parent_dir = self.make_temp_directory()
     non_existing_parent_dir = os.path.join(existing_parent_dir, 'a', 'b')
 
@@ -100,7 +155,7 @@ def  test_B2_ensure_parent_dir(self):
 
 
 
-  def  test_B3_file_in_confined_directories(self):
+  def  test_B5_file_in_confined_directories(self):
     # Goal: Provide invalid input for 'filepath' and 'confined_directories'.
     # Include inputs like: '[1, 2, "a"]' and such...
     # Reference to 'file_in_confined_directories()' to improve readability.
@@ -131,7 +186,7 @@ def  test_B3_file_in_confined_directories(self):
     self.assertTrue(in_confined_directory('a/b/c/..', ['a/']))
 
 
-  def test_B4_import_json(self):
+  def test_B6_import_json(self):
     self.assertTrue('json' in sys.modules)
     json_module = securesystemslib.util.import_json()
     self.assertTrue(json_module is not None)
@@ -142,7 +197,7 @@ def test_B4_import_json(self):
 
 
 
-  def  test_B5_load_json_string(self):
+  def  test_B7_load_json_string(self):
     # Test normal case.
     data = ['a', {'b': ['c', None, 30.3, 29]}]
     json_string = securesystemslib.util.json.dumps(data)
@@ -157,7 +212,7 @@ def  test_B5_load_json_string(self):
 
 
 
-  def  test_B6_load_json_file(self):
+  def  test_B8_load_json_file(self):
     data = ['a', {'b': ['c', None, 30.3, 29]}]
     filepath = self.make_temp_file()
     fileobj = open(filepath, 'wt')
@@ -185,7 +240,7 @@ def  test_B6_load_json_file(self):
 
 
 
-  def test_B7_persist_temp_file(self):
+  def test_B9_persist_temp_file(self):
     # Destination directory to save the temporary file in.
     dest_temp_dir = self.make_temp_directory()