392 lines
14 KiB
Python
392 lines
14 KiB
Python
# Copyright 2009-2010 10gen, Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Tools for representing files stored in GridFS."""
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import datetime
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import os
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try:
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from cStringIO import StringIO
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except ImportError:
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from StringIO import StringIO
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from gridfs.errors import (CorruptGridFile,
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NoFile,
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UnsupportedAPI)
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from pymongo.binary import Binary
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from pymongo.collection import Collection
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from pymongo.objectid import ObjectId
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try:
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_SEEK_SET = os.SEEK_SET
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_SEEK_CUR = os.SEEK_CUR
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_SEEK_END = os.SEEK_END
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except AttributeError: # before 2.5
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_SEEK_SET = 0
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_SEEK_CUR = 1
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_SEEK_END = 2
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"""Default chunk size, in bytes."""
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DEFAULT_CHUNK_SIZE = 256 * 1024
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def _create_property(field_name, docstring,
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read_only=False, closed_only=False):
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"""Helper for creating properties to read/write to files.
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"""
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def getter(self):
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if closed_only and not self._closed:
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raise AttributeError("can only get %r on a closed file" %
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field_name)
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return self._file.get(field_name, None)
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def setter(self, value):
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if self._closed:
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raise AttributeError("cannot set %r on a closed file" %
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field_name)
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self._file[field_name] = value
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if read_only:
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docstring = docstring + "\n\nThis attribute is read-only."""
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elif not closed_only:
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docstring = docstring + "\n\nThis attribute can only be set before :meth:`close` has been called."""
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else:
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docstring = docstring + "\n\nThis attribute is read-only and can only be read after :meth:`close` has been called."""
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if not read_only and not closed_only:
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return property(getter, setter, doc=docstring)
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return property(getter, doc=docstring)
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class GridIn(object):
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"""Class to write data to GridFS.
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"""
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def __init__(self, root_collection, **kwargs):
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"""Write a file to GridFS
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Application developers should generally not need to
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instantiate this class directly - instead see the methods
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provided by :class:`~gridfs.GridFS`.
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Raises :class:`TypeError` if `root_collection` is not an
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instance of :class:`~pymongo.collection.Collection`.
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Any of the file level options specified in the `GridFS Spec
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<http://dochub.mongodb.org/core/gridfsspec>`_ may be passed as
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keyword arguments. Any additional keyword arguments will be
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set as fields in the ``"metadata"`` embedded document allowed
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by the spec (overwriting any existing ``"metadata"`` field
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with the same name). Valid keyword arguments include:
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- ``"_id"``: unique ID for this file (default:
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:class:`~pymongo.objectid.ObjectId`)
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- ``"filename"``: human name for the file
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- ``"contentType"`` or ``"content_type"``: valid mime-type
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for the file
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- ``"chunkSize"`` or ``"chunk_size"``: size of each of the
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chunks, in bytes (default: 256 kb)
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- ``"aliases"``: array of alias strings
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- ``"metadata"``: document containing arbitrary metadata
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:Parameters:
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- `root_collection`: root collection to write to
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- `**kwargs` (optional): file level options (see above)
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"""
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if not isinstance(root_collection, Collection):
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raise TypeError("root_collection must be an instance of Collection")
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# Handle alternative naming
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if "content_type" in kwargs:
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kwargs["contentType"] = kwargs.pop("content_type")
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if "chunk_size" in kwargs:
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kwargs["chunkSize"] = kwargs.pop("chunk_size")
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# Move bonus kwargs into metadata
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to_move = []
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for key in kwargs:
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if key not in ["_id", "filename", "contentType",
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"chunkSize", "aliases", "metadata"]:
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to_move.append(key)
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if to_move:
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kwargs["metadata"] = kwargs.get("metadata", {})
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for key in to_move:
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kwargs["metadata"][key] = kwargs.pop(key)
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# Defaults
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kwargs["_id"] = kwargs.get("_id", ObjectId())
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kwargs["chunkSize"] = kwargs.get("chunkSize", DEFAULT_CHUNK_SIZE)
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self.__coll = root_collection
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self.__chunks = root_collection.chunks
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self._file = kwargs
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self.__buffer = StringIO()
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self.__position = 0
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self.__chunk_number = 0
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self._closed = False
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@property
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def closed(self):
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"""Is this file closed?
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"""
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return self._closed
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_id = _create_property("_id", "The ``'_id'`` value for this file.",
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read_only=True)
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name = _create_property("filename", "Name of this file.")
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content_type = _create_property("contentType", "Mime-type for this file.")
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length = _create_property("length", "Length (in bytes) of this file.",
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closed_only=True)
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chunk_size = _create_property("chunkSize", "Chunk size for this file.",
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read_only=True)
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upload_date = _create_property("uploadDate",
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"Date that this file was uploaded.",
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closed_only=True)
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aliases = _create_property("aliases", "List of aliases for this file.")
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metadata = _create_property("metadata", "Metadata attached to this file.")
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md5 = _create_property("md5", "MD5 of the contents of this file "
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"(generated on the server).",
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closed_only=True)
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def __flush_data(self, data):
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"""Flush `data` to a chunk.
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"""
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if not data:
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return
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assert(len(data) <= self.chunk_size)
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chunk = {"files_id": self._file["_id"],
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"n": self.__chunk_number,
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"data": Binary(data)}
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self.__chunks.insert(chunk)
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self.__chunk_number += 1
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self.__position += len(data)
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def __flush_buffer(self):
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"""Flush the buffer contents out to a chunk.
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"""
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self.__flush_data(self.__buffer.getvalue())
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self.__buffer.close()
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self.__buffer = StringIO()
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def __flush(self):
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"""Flush the file to the database.
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"""
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self.__flush_buffer()
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md5 = self.__coll.database.command("filemd5", self._id,
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root=self.__coll.name)["md5"]
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self._file["md5"] = md5
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self._file["length"] = self.__position
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self._file["uploadDate"] = datetime.datetime.utcnow()
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return self.__coll.files.insert(self._file)
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def close(self):
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"""Flush the file and close it.
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A closed file cannot be written any more. Calling
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:meth:`close` more than once is allowed.
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"""
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if not self._closed:
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self.__flush()
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self._closed = True
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# TODO should support writing unicode to a file. this means that files will
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# need to have an encoding attribute.
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def write(self, data):
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"""Write a string to the file. There is no return value.
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Due to buffering, the string may not actually be written to
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the database until the :meth:`close` method is called. Raises
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:class:`ValueError` if this file is already closed. Raises
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:class:`TypeErrer` if `data` is not an instance of
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:class:`str`.
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:Parameters:
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- `data`: string of bytes to be written to the file
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"""
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if self._closed:
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raise ValueError("cannot write to a closed file")
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if not isinstance(data, str):
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raise TypeError("can only write strings")
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while data:
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space = self.chunk_size - self.__buffer.tell()
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if len(data) <= space:
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self.__buffer.write(data)
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break
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else:
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self.__buffer.write(data[:space])
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self.__flush_buffer()
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data = data[space:]
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def writelines(self, sequence):
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"""Write a sequence of strings to the file.
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Does not add seperators.
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"""
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for line in sequence:
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self.write(line)
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def __enter__(self):
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"""Support for the context manager protocol.
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"""
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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"""Support for the context manager protocol.
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Close the file and allow exceptions to propogate.
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"""
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self.close()
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return False # propogate exceptions
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class GridOut(object):
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"""Class to read data out of GridFS.
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"""
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def __init__(self, root_collection, file_id):
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"""Read a file from GridFS
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Application developers should generally not need to
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instantiate this class directly - instead see the methods
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provided by :class:`~gridfs.GridFS`.
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Raises :class:`TypeError` if `root_collection` is not an instance of
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:class:`~pymongo.collection.Collection`.
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:Parameters:
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- `root_collection`: root collection to read from
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- `file_id`: value of ``"_id"`` for the file to read
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"""
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if not isinstance(root_collection, Collection):
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raise TypeError("root_collection must be an instance of Collection")
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self.__chunks = root_collection.chunks
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self._file = root_collection.files.find_one({"_id": file_id})
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if not self._file:
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raise NoFile("no file in gridfs collection %r with _id %r" %
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(root_collection, file_id))
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self.__buffer = ""
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self.__position = 0
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_id = _create_property("_id", "The ``'_id'`` value for this file.", True)
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name = _create_property("filename", "Name of this file.", True)
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content_type = _create_property("contentType", "Mime-type for this file.",
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True)
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length = _create_property("length", "Length (in bytes) of this file.",
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True)
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chunk_size = _create_property("chunkSize", "Chunk size for this file.",
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True)
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upload_date = _create_property("uploadDate",
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"Date that this file was first uploaded.",
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True)
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aliases = _create_property("aliases", "List of aliases for this file.",
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True)
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metadata = _create_property("metadata", "Metadata attached to this file.",
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True)
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md5 = _create_property("md5", "MD5 of the contents of this file "
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"(generated on the server).", True)
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def read(self, size=-1):
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"""Read at most `size` bytes from the file (less if there
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isn't enough data).
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The bytes are returned as an instance of :class:`str`. If
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`size` is negative or omitted all data is read.
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:Parameters:
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- `size` (optional): the number of bytes to read
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"""
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if size == 0:
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return ""
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remainder = int(self.length) - self.__position
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if size < 0 or size > remainder:
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size = remainder
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data = self.__buffer
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chunk_number = (len(data) + self.__position) / self.chunk_size
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while len(data) < size:
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chunk = self.__chunks.find_one({"files_id": self._id,
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"n": chunk_number})
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if not chunk:
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raise CorruptGridFile("no chunk for n = " + chunk_number)
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if not data:
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data += chunk["data"][self.__position % self.chunk_size:]
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else:
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data += chunk["data"]
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chunk_number += 1
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self.__position += size
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to_return = data[:size]
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self.__buffer = data[size:]
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return to_return
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def tell(self):
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"""Return the current position of this file.
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"""
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return self.__position
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def seek(self, pos, whence=_SEEK_SET):
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"""Set the current position of this file.
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:Parameters:
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- `pos`: the position (or offset if using relative
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positioning) to seek to
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- `whence` (optional): where to seek
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from. :attr:`os.SEEK_SET` (``0``) for absolute file
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positioning, :attr:`os.SEEK_CUR` (``1``) to seek relative
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to the current position, :attr:`os.SEEK_END` (``2``) to
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seek relative to the file's end.
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"""
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if whence == _SEEK_SET:
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new_pos = pos
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elif whence == _SEEK_CUR:
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new_pos = self.__position + pos
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elif whence == _SEEK_END:
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new_pos = int(self.length) + pos
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else:
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raise IOError(22, "Invalid value for `whence`")
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if new_pos < 0:
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raise IOError(22, "Invalid value for `pos` - must be positive")
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self.__position = new_pos
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self.__buffer = ""
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class GridFile(object):
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"""No longer supported.
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.. versionchanged:: 1.5.1+
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The GridFile class is no longer supported.
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"""
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def __init__(self, *args, **kwargs):
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raise UnsupportedAPI("The GridFile class is no longer supported. "
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"Please use GridIn or GridOut instead.")
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