apps/catalogue/utils.py

   1 # -*- coding: utf-8 -*-
   2 # This file is part of Wolnelektury, licensed under GNU Affero GPLv3 or later.
   3 # Copyright © Fundacja Nowoczesna Polska. See NOTICE for more information.
   4 #
   5 from __future__ import with_statement
   6
   7 import random
   8 import time
   9 from base64 import urlsafe_b64encode
  10
  11 from django.core.files.uploadedfile import UploadedFile
  12 from django.utils.hashcompat import sha_constructor
  13 from django.conf import settings
  14 from celery.task import task
  15 from os import mkdir, path, unlink
  16 from errno import EEXIST
  17 from fcntl import flock, LOCK_EX
  18 from zipfile import ZipFile
  19
  20 from librarian import DocProvider
  21
  22
  23 # Use the system (hardware-based) random number generator if it exists.
  24 if hasattr(random, 'SystemRandom'):
  25     randrange = random.SystemRandom().randrange
  26 else:
  27     randrange = random.randrange
  28 MAX_SESSION_KEY = 18446744073709551616L     # 2 << 63
  29
  30
  31 def get_random_hash(seed):
  32     sha_digest = sha_constructor('%s%s%s%s' %
  33         (randrange(0, MAX_SESSION_KEY), time.time(), unicode(seed).encode('utf-8', 'replace'),
  34         settings.SECRET_KEY)).digest()
  35     return urlsafe_b64encode(sha_digest).replace('=', '').replace('_', '-').lower()
  36
  37
  38 def split_tags(tags):
  39     result = {}
  40     for tag in tags:
  41         result.setdefault(tag.category, []).append(tag)
  42     return result
  43
  44
  45 class ExistingFile(UploadedFile):
  46
  47     def __init__(self, path, *args, **kwargs):
  48         self.path = path
  49         return super(ExistingFile, self).__init__(*args, **kwargs)
  50
  51     def temporary_file_path(self):
  52         return self.path
  53
  54     def close(self):
  55         pass
  56
  57
  58 class BookImportDocProvider(DocProvider):
  59     """Used for joined EPUB and PDF files."""
  60
  61     def __init__(self, book):
  62         self.book = book
  63
  64     def by_slug(self, slug):
  65         if slug == self.book.slug:
  66             return self.book.xml_file
  67         else:
  68             return type(self.book).objects.get(slug=slug).xml_file
  69
  70
  71 class LockFile(object):
  72     def __init__(self, dir, objname):
  73         self.lockname = path.join(dir, objname + ".lock")
  74
  75     def __entry__(self):
  76         self.lock = open(self.lockname, 'w')
  77         flock(self.lock, LOCK_EX)
  78
  79     def __exit__(self, *err):
  80         self.lock.close()
  81         unlink(self.lockname)
  82
  83
  84 def create_zip(paths, zip_slug):
  85     # directory to store zip files
  86     zip_path = path.join(settings.MEDIA_ROOT, 'zip')
  87
  88     try:
  89         mkdir(zip_path)
  90     except OSError as oe:
  91         if oe.errno != EEXIST:
  92             raise oe
  93     zip_filename = zip_slug + ".zip"
  94
  95     with LockFile(zip_path, zip_slug):
  96         if not path.exists(path.join(zip_path, zip_filename)):
  97             with ZipFile(path.join(zip_path, zip_filename), 'w') as zipf:
  98                 for p in paths:
  99                     zipf.write(p, path.basename(p))
 100
 101         return 'zip/' + zip_filename
 102
 103
 104 def remove_zip(zip_slug):
 105     zip_file = path.join(settings.MEDIA_ROOT, 'zip', zip_slug + '.zip')
 106     try:
 107         unlink(zip_file)
 108     except OSError as oe:
 109         if oe.errno != EEXIST:
 110             raise oe
 111
 112
 113 @task
 114 def create_zip_task(*args):
 115     return create_zip(*args)