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reviewbot/third_party/google-api-python-client/oauth2client/multistore_file.py

-# Copyright 2011 Google Inc. All Rights Reserved.
-
-"""Multi-credential file store with lock support.
-
-This module implements a JSON credential store where multiple
-credentials can be stored in one file. That file supports locking
-both in a single process and across processes.
-
-The credential themselves are keyed off of:
-* client_id
-* user_agent
-* scope
-
-The format of the stored data is like so:
-{
-  'file_version': 1,
-  'data': [
-    {
-      'key': {
-        'clientId': '<client id>',
-        'userAgent': '<user agent>',
-        'scope': '<scope>'
-      },
-      'credential': {
-        # JSON serialized Credentials.
-      }
-    }
-  ]
-}
-"""
-
-__author__ = 'jbeda@google.com (Joe Beda)'
-
-import base64
-import errno
-import logging
-import os
-import threading
-
-from anyjson import simplejson
-from oauth2client.client import Storage as BaseStorage
-from oauth2client.client import Credentials
-from oauth2client import util
-from locked_file import LockedFile
-
-logger = logging.getLogger(__name__)
-
-# A dict from 'filename'->_MultiStore instances
-_multistores = {}
-_multistores_lock = threading.Lock()
-
-
-class Error(Exception):
-  """Base error for this module."""
-  pass
-
-
-class NewerCredentialStoreError(Error):
-  """The credential store is a newer version that supported."""
-  pass
-
-
-@util.positional(4)
-def get_credential_storage(filename, client_id, user_agent, scope,
-                           warn_on_readonly=True):
-  """Get a Storage instance for a credential.
-
-  Args:
-    filename: The JSON file storing a set of credentials
-    client_id: The client_id for the credential
-    user_agent: The user agent for the credential
-    scope: string or iterable of strings, Scope(s) being requested
-    warn_on_readonly: if True, log a warning if the store is readonly
-
-  Returns:
-    An object derived from client.Storage for getting/setting the
-    credential.
-  """
-  # Recreate the legacy key with these specific parameters
-  key = {'clientId': client_id, 'userAgent': user_agent,
-         'scope': util.scopes_to_string(scope)}
-  return get_credential_storage_custom_key(
-      filename, key, warn_on_readonly=warn_on_readonly)
-
-
-@util.positional(2)
-def get_credential_storage_custom_string_key(
-    filename, key_string, warn_on_readonly=True):
-  """Get a Storage instance for a credential using a single string as a key.
-
-  Allows you to provide a string as a custom key that will be used for
-  credential storage and retrieval.
-
-  Args:
-    filename: The JSON file storing a set of credentials
-    key_string: A string to use as the key for storing this credential.
-    warn_on_readonly: if True, log a warning if the store is readonly
-
-  Returns:
-    An object derived from client.Storage for getting/setting the
-    credential.
-  """
-  # Create a key dictionary that can be used
-  key_dict = {'key': key_string}
-  return get_credential_storage_custom_key(
-      filename, key_dict, warn_on_readonly=warn_on_readonly)
-
-
-@util.positional(2)
-def get_credential_storage_custom_key(
-    filename, key_dict, warn_on_readonly=True):
-  """Get a Storage instance for a credential using a dictionary as a key.
-
-  Allows you to provide a dictionary as a custom key that will be used for
-  credential storage and retrieval.
-
-  Args:
-    filename: The JSON file storing a set of credentials
-    key_dict: A dictionary to use as the key for storing this credential. There
-      is no ordering of the keys in the dictionary. Logically equivalent
-      dictionaries will produce equivalent storage keys.
-    warn_on_readonly: if True, log a warning if the store is readonly
-
-  Returns:
-    An object derived from client.Storage for getting/setting the
-    credential.
-  """
-  filename = os.path.expanduser(filename)
-  _multistores_lock.acquire()
-  try:
-    multistore = _multistores.setdefault(
-        filename, _MultiStore(filename, warn_on_readonly=warn_on_readonly))
-  finally:
-    _multistores_lock.release()
-  key = util.dict_to_tuple_key(key_dict)
-  return multistore._get_storage(key)
-
-
-class _MultiStore(object):
-  """A file backed store for multiple credentials."""
-
-  @util.positional(2)
-  def __init__(self, filename, warn_on_readonly=True):
-    """Initialize the class.
-
-    This will create the file if necessary.
-    """
-    self._file = LockedFile(filename, 'r+b', 'rb')
-    self._thread_lock = threading.Lock()
-    self._read_only = False
-    self._warn_on_readonly = warn_on_readonly
-
-    self._create_file_if_needed()
-
-    # Cache of deserialized store. This is only valid after the
-    # _MultiStore is locked or _refresh_data_cache is called. This is
-    # of the form of:
-    #
-    # ((key, value), (key, value)...) -> OAuth2Credential
-    #
-    # If this is None, then the store hasn't been read yet.
-    self._data = None
-
-  class _Storage(BaseStorage):
-    """A Storage object that knows how to read/write a single credential."""
-
-    def __init__(self, multistore, key):
-      self._multistore = multistore
-      self._key = key
-
-    def acquire_lock(self):
-      """Acquires any lock necessary to access this Storage.
-
-      This lock is not reentrant.
-      """
-      self._multistore._lock()
-
-    def release_lock(self):
-      """Release the Storage lock.
-
-      Trying to release a lock that isn't held will result in a
-      RuntimeError.
-      """
-      self._multistore._unlock()
-
-    def locked_get(self):
-      """Retrieve credential.
-
-      The Storage lock must be held when this is called.
-
-      Returns:
-        oauth2client.client.Credentials
-      """
-      credential = self._multistore._get_credential(self._key)
-      if credential:
-        credential.set_store(self)
-      return credential
-
-    def locked_put(self, credentials):
-      """Write a credential.
-
-      The Storage lock must be held when this is called.
-
-      Args:
-        credentials: Credentials, the credentials to store.
-      """
-      self._multistore._update_credential(self._key, credentials)
-
-    def locked_delete(self):
-      """Delete a credential.
-
-      The Storage lock must be held when this is called.
-
-      Args:
-        credentials: Credentials, the credentials to store.
-      """
-      self._multistore._delete_credential(self._key)
-
-  def _create_file_if_needed(self):
-    """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.
-    """
-    if not os.path.exists(self._file.filename()):
-      old_umask = os.umask(0177)
-      try:
-        open(self._file.filename(), 'a+b').close()
-      finally:
-        os.umask(old_umask)
-
-  def _lock(self):
-    """Lock the entire multistore."""
-    self._thread_lock.acquire()
-    self._file.open_and_lock()
-    if not self._file.is_locked():
-      self._read_only = True
-      if self._warn_on_readonly:
-        logger.warn('The credentials file (%s) is not writable. Opening in '
-                    'read-only mode. Any refreshed credentials will only be '
-                    'valid for this run.' % self._file.filename())
-    if os.path.getsize(self._file.filename()) == 0:
-      logger.debug('Initializing empty multistore file')
-      # The multistore is empty so write out an empty file.
-      self._data = {}
-      self._write()
-    elif not self._read_only or self._data is None:
-      # Only refresh the data if we are read/write or we haven't
-      # cached the data yet. If we are readonly, we assume is isn't
-      # changing out from under us and that we only have to read it
-      # once. This prevents us from whacking any new access keys that
-      # we have cached in memory but were unable to write out.
-      self._refresh_data_cache()
-
-  def _unlock(self):
-    """Release the lock on the multistore."""
-    self._file.unlock_and_close()
-    self._thread_lock.release()
-
-  def _locked_json_read(self):
-    """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.
-    """
-    assert self._thread_lock.locked()
-    self._file.file_handle().seek(0)
-    return simplejson.load(self._file.file_handle())
-
-  def _locked_json_write(self, data):
-    """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.
-    """
-    assert self._thread_lock.locked()
-    if self._read_only:
-      return
-    self._file.file_handle().seek(0)
-    simplejson.dump(data, self._file.file_handle(), sort_keys=True, indent=2)
-    self._file.file_handle().truncate()
-
-  def _refresh_data_cache(self):
-    """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.
-    """
-    self._data = {}
-    try:
-      raw_data = self._locked_json_read()
-    except Exception:
-      logger.warn('Credential data store could not be loaded. '
-                  'Will ignore and overwrite.')
-      return
-
-    version = 0
-    try:
-      version = raw_data['file_version']
-    except Exception:
-      logger.warn('Missing version for credential data store. It may be '
-                  'corrupt or an old version. Overwriting.')
-    if version > 1:
-      raise NewerCredentialStoreError(
-          'Credential file has file_version of %d. '
-          'Only file_version of 1 is supported.' % version)
-
-    credentials = []
-    try:
-      credentials = raw_data['data']
-    except (TypeError, KeyError):
-      pass
-
-    for cred_entry in credentials:
-      try:
-        (key, credential) = self._decode_credential_from_json(cred_entry)
-        self._data[key] = credential
-      except:
-        # If something goes wrong loading a credential, just ignore it
-        logger.info('Error decoding credential, skipping', exc_info=True)
-
-  def _decode_credential_from_json(self, cred_entry):
-    """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.
-    """
-    raw_key = cred_entry['key']
-    key = util.dict_to_tuple_key(raw_key)
-    credential = None
-    credential = Credentials.new_from_json(simplejson.dumps(cred_entry['credential']))
-    return (key, credential)
-
-  def _write(self):
-    """Write the cached data back out.
-
-    The multistore must be locked.
-    """
-    raw_data = {'file_version': 1}
-    raw_creds = []
-    raw_data['data'] = raw_creds
-    for (cred_key, cred) in self._data.items():
-      raw_key = dict(cred_key)
-      raw_cred = simplejson.loads(cred.to_json())
-      raw_creds.append({'key': raw_key, 'credential': raw_cred})
-    self._locked_json_write(raw_data)
-
-  def _get_credential(self, key):
-    """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
-    """
-    return self._data.get(key, None)
-
-  def _update_credential(self, key, cred):
-    """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
-    """
-    self._data[key] = cred
-    self._write()
-
-  def _delete_credential(self, key):
-    """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
-    """
-    try:
-      del self._data[key]
-    except KeyError:
-      pass
-    self._write()
-
-  def _get_storage(self, key):
-    """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
-    """
-    return self._Storage(self, key)