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 blob_reference_store as datastore
+from blob_reference_store import BlobReferenceStore
+from appengine_wrappers import blobstore
+from appengine_wrappers import files
+
+BLOBSTORE_GITHUB = 'BlobstoreGithub'
+
+class AppEngineBlobstore(object):
+  """A wrapper around the blobstore API, which stores the blob keys in
+  datastore.
+  """
+  def __init__(self):
+    self._datastore = BlobReferenceStore('blobstore')
+
+  def Set(self, key, blob, namespace):
+    """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 = namespace + '.' + key
+    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(datastore.BLOBREFERENCE_BLOBSTORE, key, blob_key)
+
+  def Get(self, key, namespace):
+    """Get a blob with version |version|.
+    """
+    key = namespace + '.' + key
+    blob_key = self._datastore.Get(datastore.BLOBREFERENCE_BLOBSTORE, key)
+    if blob_key is None:
+      return None
+    blob_reader = blobstore.BlobReader(blob_key)
+    return blob_reader.read()
+
+  def Delete(self, key, namespace):
+    """Delete the blob with version |version| if it is found.
+    """
+    key = namespace + '.' + key
+    blob_key = self._datastore.Get(datastore.BLOBREFERENCE_BLOBSTORE, key)

[not at google - send to devlin, 2012/08/10 06:02:18]

The way I read this, it's clearing the item from blobstore (since
BlobReferenceStore returns the value of the key it returns), but it doesn't
clear the reference to the key from datastore.

You could change this to call self._datastore.Delete, and make
AppEngineBlobstore.Delete return the value if it successfully deletes the item,
or None otherwise. That's pretty standard for a map API like this.

Then the code would be like

blob_key = self._datastore.Delete(datastore.BLOB_REFERENCE_BLOBSTORE, key)
if blob_key is None:
  return
blob_key.delete()

[cduvall, 2012/08/10 21:17:47]

Done.

+    if blob_key is None:
+      return
+    blob_key.delete()