elmsubmit_filename_generator.py
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Created: Sat, May 18, 13:24

elmsubmit_filename_generator.py
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	# -- coding: utf-8 --
	##
	## $Id$
	##
	## This file is part of CDS Invenio.
	## Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007 CERN.
	##
	## CDS Invenio 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.
	##
	## CDS Invenio 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 CDS Invenio; if not, write to the Free Software Foundation, Inc.,
	## 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.

	__revision__ = "$Id$"

	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
	import zlib

	try:
	import magic.magic as magic
	_got_magic = True
	except ImportError:
	import mimetypes
	_got_magic = False

	import gzip
	try:
	import bz2
	_got_bz2 = True
	except ImportError:
	_got_bz2 = False

	from invenio.elmsubmit_misc import open_tempfile as _open_tempfile
	from invenio.elmsubmit_misc import random_alphanum_string as _random_alphanum_string
	from invenio.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:
	if not _got_bz2:
	raise ImportError('Failed to import bz2 module.')
	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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