Differential D3192 Diff 11342 swh/deposit/file_storage.py

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swh/deposit/file_storage.py

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				# Copyright (C) 2020 The Software Heritage developers
				# Copyright (c) Django Software Foundation and individual contributors.
				# All rights reserved.
				#
				# Redistribution and use in source and binary forms, with or without modification,
				# are permitted provided that the following conditions are met:
				#
				# 1. Redistributions of source code must retain the above copyright notice,
				# this list of conditions and the following disclaimer.
				#
				# 2. Redistributions in binary form must reproduce the above copyright
				# notice, this list of conditions and the following disclaimer in the
				# documentation and/or other materials provided with the distribution.
				#
				# 3. Neither the name of Django nor the names of its contributors may be used
				# to endorse or promote products derived from this software without
				# specific prior written permission.
				#
				# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
				# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
				# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
				# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
				# ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
				# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
				# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
				# ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
				# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
				# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

				import os.path

				from django.core.exceptions import SuspiciousFileOperation
				from django.core.files.storage import FileSystemStorage
				from django.utils.crypto import get_random_string


				class PrefixedFileSystemStorage(FileSystemStorage):
				"""Subclass of FileSystemStorage, that disambiguates by adding
				a random prefix, instead of a random suffix.
				This prevents issues with compound extensions (eg. .tar.gz), as a suffix
				changes the second-to-last extension; which messages with shutil's
				file type detection.."""

				# This function is copy-pasted from
				# <https://github.com/django/django/blob/98ef3829e96ebc73d4d446f92465e671ff520d2b/django/core/files/storage.py#L63-L92>
				# with just the two computations of 'name' changed
				#
				# TODO: when we upgrade to Django 3, this whole function can be removed
				# and replaced with an override of get_alternative_name.
				def get_available_name(self, name, max_length=None):
				"""
				Return a filename that's free on the target storage system and
				available for new content to be written to.
				"""
				dir_name, file_name = os.path.split(name)
				file_root, file_ext = os.path.splitext(file_name)
				# If the filename already exists, add an underscore and a random 7
				# character alphanumeric string (before the file extension, if one
				# exists) to the filename until the generated filename doesn't exist.
				# Truncate original name if required, so the new filename does not
				# exceed the max_length.
				while self.exists(name) or (max_length and len(name) > max_length):
				# file_ext includes the dot.
				name = os.path.join(
				dir_name, "%s_%s%s" % (get_random_string(7), file_root, file_ext)
				)
				if max_length is None:
				continue
				# Truncate file_root if max_length exceeded.
				truncation = len(name) - max_length
				if truncation > 0:
				file_root = file_root[:-truncation]
				# Entire file_root was truncated in attempt to find an available
				# filename.
				if not file_root:
				raise SuspiciousFileOperation(
				'Storage can not find an available filename for "%s". '
				"Please make sure that the corresponding file field "
				'allows sufficient "max_length".' % name
				)
				name = os.path.join(
				dir_name, "%s_%s%s" % (get_random_string(7), file_root, file_ext)
				)
				return name