app/melange/utils/files.py

# Copyright 2014 the Melange authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Utility functions for file operations."""

import cloudstorage

from google.appengine.api import app_identity


# Multipart/form-data forms which want to persist the uploaded files in
# Cloud Storage should have an additional hidden field whose name is equal
# to the string below.
# Existence of this field will prevent middleware from pre-processing uploaded
# files. This part does not apply to uploads which are not handled by Blobstore.
# This constant and corresponding form fields can be removed when all uploads
# are handled Cloud Storage instead of Blobstore.
DONT_USE_BLOBSTORE_MIDDLEWARE = 'dont_use_blobstore_middleware'


def saveFile(file_object, object_name=None, bucket_name=None):
  """Saves content of the specified file to Cloud Storage.

  Args:
    file_object: File whose content is saved.
    object_name: Name of the object to be saved.
    bucket_name: Optional name of the bucket in which the saved object is
      supposed to be saved. If not specified, the default bucket for
      the application is used.

  Returns:
    A string containing path under which the object was saved in Cloud Storage.
  """
  bucket_name = bucket_name or app_identity.get_default_gcs_bucket_name()
  object_path = '/' + '/'.join([bucket_name, object_name])
  options = {'x-goog-acl': 'public-read'}

  with cloudstorage.open(object_path, 'w', content_type='text/plain',
      options=options) as gcs_file:
    gcs_file.write(file_object.read())

  return object_path


def deleteFile(object_path):
  """Deletes the specified file object from Cloud Storage.

  Args:
    object_path: The full GCS file name for the object, in the format
      /bucket/object_name. Must be a full filename and can include the
      delimiter '/'.
  """
  try:
    cloudstorage.delete(object_path)
  except cloudstorage.NotFoundError:
    pass