+# This file is part of Wolnelektury, licensed under GNU Affero GPLv3 or later.
+# Copyright © Fundacja Nowoczesna Polska. See NOTICE for more information.
+#
+import random
+import time
+from base64 import urlsafe_b64encode
+
+from django.core.files.uploadedfile import UploadedFile
+from django.utils.hashcompat import sha_constructor
+from django.conf import settings
+
+from librarian import DocProvider
+
+
+# Use the system (hardware-based) random number generator if it exists.
+if hasattr(random, 'SystemRandom'):
+ randrange = random.SystemRandom().randrange
+else:
+ randrange = random.randrange
+MAX_SESSION_KEY = 18446744073709551616L # 2 << 63
+
+
+def get_random_hash(seed):
+ sha_digest = sha_constructor('%s%s%s%s' %
+ (randrange(0, MAX_SESSION_KEY), time.time(), unicode(seed).encode('utf-8', 'replace'),
+ settings.SECRET_KEY)).digest()
+ return urlsafe_b64encode(sha_digest).replace('=', '').replace('_', '-').lower()