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
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"""In-memory implementation of Blobstore stub storage based on file system.

This module contains an implementation of `blobstore_stub.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 blobstore_stub


__all__ = ['FileBlobStorage']



import __builtin__
_local_open = __builtin__.open


[docs]class FileBlobStorage(blobstore_stub.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

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