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R3600/modules/elmsubmit/lib/elmsubmit_filename_generator.py
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elmsubmit_filename_generator.py
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# -*- coding: utf-8 -*-
##
## $Id$
##
## This file is part of the CERN Document Server Software (CDSware).
## Copyright (C) 2002, 2003, 2004, 2005, 2006 CERN.
##
## The CDSware is free software; you can redistribute it and/or
## modify it under the terms of the GNU General Public License as
## published by the Free Software Foundation; either version 2 of the
## License, or (at your option) any later version.
##
## The CDSware is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with CDSware; if not, write to the Free Software Foundation, Inc.,
## 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
import sys
import os.path
_this_module = sys.modules[__name__]
_this_module_dir = os.path.abspath(os.path.dirname(_this_module.__file__))
import random
import tempfile
import re
import os
import mimetypes
try:
import magic.magic as magic
_got_magic = True
except ImportError:
import mimetypes
_got_magic = False
import gzip
import bz2
from cdsware.elmsubmit_misc import open_tempfile as _open_tempfile
from cdsware.elmsubmit_misc import random_alphanum_string as _random_alphanum_string
from cdsware.elmsubmit_misc import remove_tempfile as _remove_tempfile
def generate_filename(filename=None, file=None, content_type=None, no_rand_chars=8, prefix='', postfix=''):
name_stub = _random_alphanum_string(no_rand_chars)
name_ext = calculate_filename_extension(filename, file, content_type)
return prefix + name_stub + postfix + '.' + name_ext
def calculate_filename_extension(filename=None, file=None, content_type=None):
# If libmagic is installed and ./magic/magic.so has been
# successfully built, then we use a python interface to libmagic
# (man libmagic) to calculate a file extension using a specially
# prepared magic data file (./magic/magic.ext) which maps
# magic tests to file extensions. Otherwise we use the mimetypes
# module from the standard Python distribution.
if (filename is None) and (file is None) and (content_type is None):
raise TypeError('at least one of filename, file or content_type must be specified')
elif (file is None) and (filename is None):
# We only have content_type:
return calculate_filename_ext_mimetypes(content_type)
# We have at least one of file and filename, so we try to use libmagic
elif _got_magic:
return calculate_filename_ext_libmagic(filename, file)
# We haven't got libmagic, so must use mimetypes:
else:
# But mimetypes requires content_type:
if content_type is None:
raise ImportError('Failed to import magic module. If no content-type is given, then magic module is required.')
else:
return calculate_filename_ext_mimetypes(content_type)
def calculate_filename_ext_libmagic(filename=None, file=None):
# See comments in magic/magic.ext for details of the format
# of the data file. All file extensions if recognized by a magic
# test will be returned in the form "file_ext:{xyz}"; this lets us
# detect the "file_ext:{}" marker and know we have a successful
# guess at the correct extension. The reason we need this marker
# is that libmagic has many tests whose return value is not
# governed through the magic data file and so we need some way of
# being sure a file extension has been returned. eg:
# >>> magician.file('/etc/init.d')
# "symbolic link to `rc.d/init.d'"
if filename is None and file is None: raise ValueError('at least one of file or content_type must be specified')
if not _got_magic: raise ImportError('magic module did not import successfully')
magician = magic.open(magic.MAGIC_NONE)
magic_data_file = os.path.join(_this_module_dir, 'magic/magic.ext')
ret_load = magician.load(magic_data_file)
# Throw private error if the magic data file is corrupt, or
# doesn't exist.
if ret_load != 0: raise _MagicDataError()
if filename is None:
# then we have only been given file as binary string.
# Get a temporary file and write file variable out to it
# because the magic module expects to be handed the name of a
# real file.
tf, tf_name = _open_tempfile(mode='wb')
tf.write(file)
tf.close()
delete_file = True
else:
os.stat(filename) # Make sure we can stat the file.
tf_name = filename
delete_file = False
ext_info = magician.file(tf_name)
# Now process ext_info to see if we can find a file extension
# contained in it.
file_ext_re = re.compile(r'file_ext:{(.+?)}')
file_ext_match = file_ext_re.search(ext_info)
if file_ext_match:
name_ext = file_ext_match.group(1)
# See if we have a compressed file type we can deal
# with. If so, uncompress it and call ourself to get more
# info:
# Note that we could use the magic.MAGIC_COMPRESS flag to
# get libmagic to do the decompression for us but:
# 1. It only supports gzip
# 2. The implementation has a nasty bug which has only
# been fixed in very recent releases of libmagic.
if name_ext == 'gz':
try:
# Decompress the stream:
decomp_file = gzip.open(tf_name).read()
except zlib.error:
# Couldn't decompress sucessfully, so just stick
# with extension we have.
pass
else:
# Guess an extension of the decompressed stream and
# tack current '.gz' on the end:
name_ext = calculate_filename_ext_libmagic(file=decomp_file) + '.' + name_ext
elif name_ext == 'bz2':
try:
# Decompress the file:
decomp_file = bz2.BZ2File(tf_name).read()
except IOError:
# Couldn't decompress sucessfully, so just stick
# with extension we have.
pass
else:
# Guess an extension of the decompressed stream and
# tack current '.bz2' on the end:
name_ext = calculate_filename_ext_libmagic(file=decomp_file) + '.' + name_ext
# Otherwise, look for special results from libmagic's
# 'internal tests' that we recognize:
elif ext_info.lower().rfind('tar archive') != -1:
name_ext = 'tar'
elif ext_info.lower().rfind('text') != -1:
name_ext = 'txt'
# Can't guess a filetype so use generic extension .dat
else:
name_ext = 'dat'
# Identification done so get rid of the temp file, assuming we created the file:
if delete_file: _remove_tempfile(tf_name)
return name_ext
mimetypes.types_map = {}
mimetypes.init([os.path.join(_this_module_dir, 'mime.types.edited')])
def calculate_filename_ext_mimetypes(content_type):
# mimetypes.types_map contains many 'builtin' maps. We empty
# it because we only want to use the maps from our edited
# mime.types file:
name_ext = mimetypes.guess_extension(content_type)
# Use '.dat' as generic file extension.
if name_ext is None: name_ext = '.dat'
# Remove leading dot produced by mimetypes.
name_ext = name_ext[1:]
return name_ext
# Errors:
# This module may also produce IOError from it use of temporary
# files.
# REMEMBER TO DOCUMENT THIS ERROR POTENTIAL
class _MagicDataError(Exception):
"""
Private error raised when we cannot compile and load the magic
data file successfully. This will only occur if there is a problem
with the module's installation.
"""
pass
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