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[wolnelektury.git] / apps / catalogue / utils.py

diff --git a/apps/catalogue/utils.py b/apps/catalogue/utils.py
index d1cee50..e44b379 100644 (file)
--- a/apps/catalogue/utils.py
+++ b/apps/catalogue/utils.py
@@ -1,4 +1,28 @@
 # -*- coding: utf-8 -*-
+# 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.utils.hashcompat import sha_constructor
+from django.conf import settings
+
+
+# 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()
 
 
 def split_tags(tags):