Extensions Docs Server: Apps samples page

chrome/common/extensions/docs/server2/appengine_blobstore.py

+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import appengine_datastore as datastore
+from appengine_datastore import AppEngineDatastore
+from appengine_wrappers import blobstore
+from appengine_wrappers import files
+
+class AppEngineBlobstore(object):
+  """A wrapper around the blobstore API, which stores the blob keys in
+  datastore.
+  """
+  def __init__(self):
+    self._datastore = AppEngineDatastore('blobstore')
+
+  def Set(self, key, blob, version):

[not at google - send to devlin, 2012/08/09 07:52:36]

yeah, I don't really see the need to store multiple versions. What's the
difference between getting foo1.zip then later adding a foo2.zip and removing
foo1.zip, versus overwriting foo.zip with the new version?

[cduvall, 2012/08/09 19:20:08]

See comment my reply to your other version comment (other instances won't know
when to fetch a new version). Also, I added a namespace so this has the same
interface as AppEngineMemcache.

+    """Add a blob to the blobstore. |version| is used as part of the key so
+    multiple blobs with the same name can be differentiated.
+    """
+    key = key + '.' + str(version)
+    filename = files.blobstore.create()
+    with files.open(filename, 'a') as f:
+      f.write(blob)
+    files.finalize(filename)
+    blob_key = files.blobstore.get_blob_key(filename)
+    self._datastore.Set(key, blob_key, datastore.DATASTORE_BLOBSTORE)
+
+  def Get(self, key, version):
+    """Get a blob with version |version|.
+    """
+    key = key + '.' + str(version)
+    blob_key = self._datastore.Get(key, datastore.DATASTORE_BLOBSTORE)
+    if blob_key is None:
+      return None
+    blob_reader = blobstore.BlobReader(blob_key)
+    return blob_reader.read()
+
+  def Delete(self, key, version):
+    """Delete the blob with version |version| if it is found.
+    """
+    key = key + '.' + str(version)
+    blob_key = self._datastore.Get(key, datastore.DATASTORE_BLOBSTORE)
+    if blob_key is None:
+      return
+    blobstore.delete(blob_key)