Source code for google.appengine.api.blobstore.file_blob_storage
#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# 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.
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"""In-memory implementation of Blobstore stub storage based on file system.
This module contains an implementation of `blob_storage.BlobStorage` that
writes blobs directly to a file system.
"""
import errno
import os
from google.appengine.api import blobstore
from google.appengine.api.blobstore import blob_storage
__all__ = ['FileBlobStorage']
import __builtin__
_local_open = __builtin__.open
[docs]class FileBlobStorage(blob_storage.BlobStorage):
"""The storage mechanism that stores blob data on a local disk."""
def __init__(self, storage_directory, app_id):
"""Constructor.
Args:
storage_directory: Directory within which to store blobs.
app_id: The application ID on whose behalf to store blobs.
"""
self._storage_directory = storage_directory
self._app_id = app_id
@classmethod
def _BlobKey(cls, blob_key):
"""Normalizes to an instance of `BlobKey`."""
if not isinstance(blob_key, blobstore.BlobKey):
return blobstore.BlobKey(unicode(blob_key))
return blob_key
def _DirectoryForBlob(self, blob_key):
"""Determines the directory in which a blob is stored.
Each blob is written to a directory underneath the storage objects
storage directory based on the kind of blobs, application ID, and first
character of its name. For example, the following blob keys...::
_ACFDEDG
_MNOPQRS
_RSTUVWX
...are stored in the following locations::
<storage-dir>/blob/myapp/A
<storage-dir>/blob/myapp/M
<storage-dir>/R
Args:
blob_key: Blob key for which you need to determine the directory.
Returns:
A directory where the blob is stored or should be stored, relative to this
object's storage directory.
"""
blob_key = self._BlobKey(blob_key)
return os.path.join(self._storage_directory,
self._app_id,
str(blob_key)[1])
def _FileForBlob(self, blob_key):
"""Calculates the full file name in which to store blob contents.
This method does not check to see if the file already exists.
Args:
blob_key: The blob key of the blob for which to calculate the file name.
Returns:
A string that contains the complete path for the file that is used to
store the blob.
"""
blob_key = self._BlobKey(blob_key)
return os.path.join(self._DirectoryForBlob(blob_key), str(blob_key)[1:])
[docs] def StoreBlob(self, blob_key, blob_stream):
"""Stores a blob stream .
Args:
blob_key: The blob key of the blob that you want to store.
blob_stream: A stream or a stream-like object that will generate blob
content.
"""
blob_key = self._BlobKey(blob_key)
blob_directory = self._DirectoryForBlob(blob_key)
if not os.path.exists(blob_directory):
os.makedirs(blob_directory)
blob_file = self._FileForBlob(blob_key)
output = _local_open(blob_file, 'wb')
try:
while True:
block = blob_stream.read(1 << 20)
if not block:
break
output.write(block)
finally:
output.close()
[docs] def OpenBlob(self, blob_key):
"""Opens a blob file for streaming.
Args:
blob_key: The blob key of an existing blob that you want to open.
Returns:
An open file stream to read the blob.
"""
return _local_open(self._FileForBlob(blob_key), 'rb')
[docs] def DeleteBlob(self, blob_key):
"""Deletes blob data.
Deleting an unknown blob will not raise an error.
Args:
blob_key: The blob key of an existing blob that you want to delete.
"""
try:
os.remove(self._FileForBlob(blob_key))
except OSError, e:
if e.errno != errno.ENOENT:
raise e