Add google-api-python-client in third_party/

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)