Class _MultiStore

Create an empty file if necessary.

This method will not initialize the file. Instead it implements a
simple version of "touch" to ensure the file has been created.

Get the raw content of the multistore file.

The multistore must be locked when this is called.

Returns:
  The contents of the multistore decoded as JSON.

Write a JSON serializable data structure to the multistore.

The multistore must be locked when this is called.

Args:
  data: The data to be serialized and written.

Refresh the contents of the multistore.

The multistore must be locked when this is called.

Raises:
  NewerCredentialStoreError: Raised when a newer client has written the
    store.

Load a credential from our JSON serialization.

Args:
  cred_entry: A dict entry from the data member of our format

Returns:
  (key, cred) where the key is the key tuple and the cred is the
    OAuth2Credential object.

Write the cached data back out.

The multistore must be locked.

Gets all the registered credential keys in the multistore.

Returns:
  A list of dictionaries corresponding to all the keys currently registered

Get a credential from the multistore.

The multistore must be locked.

Args:
  key: The key used to retrieve the credential

Returns:
  The credential specified or None if not present

Update a credential and write the multistore.

This must be called when the multistore is locked.

Args:
  key: The key used to retrieve the credential
  cred: The OAuth2Credential to update/set

Delete a credential and write the multistore.

This must be called when the multistore is locked.

Args:
  key: The key used to retrieve the credential

Get a Storage object to get/set a credential.

This Storage is a 'view' into the multistore.

Args:
  key: The key used to retrieve the credential

Returns:
  A Storage object that can be used to get/set this cred