Read blobs from new manifest blob table where relevant

data/registry_model/registry_pre_oci_model.py

@@ -556,5 +556,33 @@ class PreOCIModel(SharedModel, RegistryDataInterface):
     """
     raise NotImplementedError('Unsupported in pre OCI model')
 
+  def get_repo_blob_by_digest(self, repository_ref, blob_digest, include_placements=False):
+    """
+    Returns the blob in the repository with the given digest, if any or None if none. Note that
+    there may be multiple records in the same repository for the same blob digest, so the return
+    value of this function may change.
+    """
+    try:
+      image_storage = model.blob.get_repository_blob_by_digest(repository_ref._db_id, blob_digest)
+    except model.BlobDoesNotExist:
+      return None
+
+    assert image_storage.cas_path is not None
+
+    placements = None
+    if include_placements:
+      placements = list(model.storage.get_storage_locations(image_storage.uuid))
+
+    return Blob.for_image_storage(image_storage,
+                                  storage_path=model.storage.get_layer_path(image_storage),
+                                  placements=placements)
+
+  def list_parsed_manifest_layers(self, repository_ref, parsed_manifest, include_placements=False):
+    """ Returns an *ordered list* of the layers found in the parsed manifest, starting at the base
+        and working towards the leaf, including the associated Blob and its placements
+        (if specified).
+    """
+    return self._list_manifest_layers(repository_ref._db_id, parsed_manifest, include_placements)
+
 
 pre_oci_model = PreOCIModel()