create interfaces for v1 and v2 data model

image/common.py

@@ -0,0 +1,68 @@
+import tarfile
+from util.registry.gzipwrap import GzipWrap
+
+
+class TarImageFormatter(object):
+  """
+  Base class for classes which produce a tar containing image and layer data.
+  """
+
+  def build_stream(self, namespace, repository, tag, synthetic_image_id, layer_json,
+                   get_image_iterator, get_layer_iterator, get_image_json):
+    """
+    Builds and streams a synthetic .tar.gz that represents the formatted tar created by this class's
+    implementation.
+    """
+    return GzipWrap(self.stream_generator(namespace, repository, tag,
+                                          synthetic_image_id, layer_json,
+                                          get_image_iterator, get_layer_iterator,
+                                          get_image_json))
+
+  def stream_generator(self, namespace, repository, tag, synthetic_image_id,
+                       layer_json, get_image_iterator, get_layer_iterator, get_image_json):
+    raise NotImplementedError
+
+  def tar_file(self, name, contents, mtime=None):
+    """
+    Returns the tar binary representation for a file with the given name and file contents.
+    """
+    length = len(contents)
+    tar_data = self.tar_file_header(name, length, mtime=mtime)
+    tar_data += contents
+    tar_data += self.tar_file_padding(length)
+    return tar_data
+
+  def tar_file_padding(self, length):
+    """
+    Returns tar file padding for file data of the given length.
+    """
+    if length % 512 != 0:
+      return '\0' * (512 - (length % 512))
+
+    return ''
+
+  def tar_file_header(self, name, file_size, mtime=None):
+    """
+    Returns tar file header data for a file with the given name and size.
+    """
+    info = tarfile.TarInfo(name=name)
+    info.type = tarfile.REGTYPE
+    info.size = file_size
+
+    if mtime is not None:
+      info.mtime = mtime
+    return info.tobuf()
+
+  def tar_folder(self, name, mtime=None):
+    """
+    Returns tar file header data for a folder with the given name.
+    """
+    info = tarfile.TarInfo(name=name)
+    info.type = tarfile.DIRTYPE
+
+    if mtime is not None:
+      info.mtime = mtime
+
+    # allow the directory to be readable by non-root users
+    info.mode = 0755
+    return info.tobuf()