Refactor the util directory to use subpackages.

util/registry/tarfileappender.py

@@ -0,0 +1,56 @@
+import tarfile
+
+from cStringIO import StringIO
+
+from util.registry.tarlayerformat import TarLayerFormat
+from util.registry.gzipwrap import GzipWrap
+
+class TarfileAppender(TarLayerFormat):
+  """ Helper class which allows for appending entries to a gzipped-tarfile and doing so
+      in a streaming manner.
+  """
+  def __init__(self, base_tar_file, entries):
+    super(TarfileAppender, self).__init__(self._get_tar_iterator)
+    self.entries = entries
+    self.base_tar_file = base_tar_file
+    self.first_info = None
+
+  def get_stream(self):
+    return GzipWrap(self.get_generator())
+
+  def after_tar_layer(self, current_layer):
+    pass
+
+  def check_tar_info(self, tar_info):
+    if not self.first_info:
+      self.first_info = tar_info
+    return True
+
+  def _get_tar_iterator(self):
+    # Yield the contents of the base tar.
+    yield self.base_tar_file
+
+    # Construct an in-memory tar containing the entries to append, and then yield
+    # its data.
+    def add_entry(arch, dir_path, contents=None):
+      info = tarfile.TarInfo(dir_path)
+      info.uid = self.first_info.uid
+      info.gid = self.first_info.gid
+      info.mode = self.first_info.mode
+      info.mtime = self.first_info.mtime
+
+      info.type = tarfile.REGTYPE if contents else tarfile.DIRTYPE
+
+      if contents:
+        info.size = len(contents)
+
+      arch.addfile(info, fileobj=StringIO(contents) if contents else None)
+
+    append_tarball = StringIO()
+    with tarfile.open(fileobj=append_tarball, mode='w') as updated_archive:
+      for entry in self.entries:
+        add_entry(updated_archive, entry, self.entries[entry])
+
+    # To make tarfile happy.
+    append_tarball.seek(0)
+    yield append_tarball