blob: a0edd82eb078de6a82781e0325cadb960bdd8325 [file] [log] [blame]
#!/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.
#
"""Implementation of Blobstore stub storage based on file system.
Contains implementation of blobstore_stub.BlobStorage that writes
blobs directly to a filesystem.
"""
import errno
import os
from google.appengine.api import blobstore
from google.appengine.api.blobstore import blobstore_stub
__all__ = ['FileBlobStorage']
import __builtin__
_local_open = __builtin__.open
class FileBlobStorage(blobstore_stub.BlobStorage):
"""Storage mechanism for storing blob data on local disk."""
def __init__(self, storage_directory, app_id):
"""Constructor.
Args:
storage_directory: Directory within which to store blobs.
app_id: App id to store blobs on behalf of.
"""
self._storage_directory = storage_directory
self._app_id = app_id
@classmethod
def _BlobKey(cls, blob_key):
"""Normalize to instance of BlobKey."""
if not isinstance(blob_key, blobstore.BlobKey):
return blobstore.BlobKey(unicode(blob_key))
return blob_key
def _DirectoryForBlob(self, blob_key):
"""Determine which directory where a blob is stored.
Each blob gets written to a directory underneath the storage objects
storage directory based on the blobs kind, app-id and first character of
its name. So blobs with blob-keys:
_ACFDEDG
_MNOPQRS
_RSTUVWX
Are stored in:
<storage-dir>/blob/myapp/A
<storage-dir>/blob/myapp/M
<storage-dir>/R
Args:
blob_key: Blob key to determine directory for.
Returns:
Directory relative to this objects storage directory to
where blob is stored or should be stored.
"""
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):
"""Calculate full filename to store blob contents in.
This method does not check to see if the file actually exists.
Args:
blob_key: Blob key of blob to calculate file for.
Returns:
Complete path for file used for storing blob.
"""
blob_key = self._BlobKey(blob_key)
return os.path.join(self._DirectoryForBlob(blob_key), str(blob_key)[1:])
def StoreBlob(self, blob_key, blob_stream):
"""Store blob stream to disk.
Args:
blob_key: Blob key of blob to store.
blob_stream: Stream or 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()
def OpenBlob(self, blob_key):
"""Open blob file for streaming.
Args:
blob_key: Blob-key of existing blob to open for reading.
Returns:
Open file stream for reading blob from disk.
"""
return _local_open(self._FileForBlob(blob_key), 'rb')
def DeleteBlob(self, blob_key):
"""Delete blob data from disk.
Deleting an unknown blob will not raise an error.
Args:
blob_key: Blob-key of existing blob to delete.
"""
try:
os.remove(self._FileForBlob(blob_key))
except OSError, e:
if e.errno != errno.ENOENT:
raise e