Compatibility wrapper module to make rsa work with various versions of Python.
diff --git a/rsa/_compat.py b/rsa/_compat.py
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index 0000000..162f47e
--- /dev/null
+++ b/rsa/_compat.py
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+# -*- coding: utf-8 -*-
+#
+# Copyright 2011 Sybren A. Stüvel <sybren@stuvel.eu>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+'''Python compatibility wrappers.'''
+
+
+from __future__ import absolute_import
+
+from struct import pack
+
+try:
+ # < Python3
+ unicode_type = unicode
+ have_python3 = False
+except NameError:
+ # Python3.
+ unicode_type = str
+ have_python3 = True
+
+# Fake byte literals.
+if str is unicode_type:
+ def byte_literal(s):
+ return s.encode('latin1')
+else:
+ def byte_literal(s):
+ return s
+
+# ``long`` is no more. Do type detection using this instead.
+try:
+ integer_types = (int, long)
+except NameError:
+ integer_types = (int,)
+
+b = byte_literal
+
+try:
+ # Python 2.6 or higher.
+ bytes_type = bytes
+except NameError:
+ # Python 2.5
+ bytes_type = str
+
+
+def is_bytes(obj):
+ """
+ Determines whether the given value is a byte string.
+
+ :param obj:
+ The value to test.
+ :returns:
+ ``True`` if ``value`` is a byte string; ``False`` otherwise.
+ """
+ return isinstance(obj, bytes_type)
+
+
+def is_integer(obj):
+ """
+ Determines whether the given value is an integer.
+
+ :param obj:
+ The value to test.
+ :returns:
+ ``True`` if ``value`` is an integer; ``False`` otherwise.
+ """
+ return isinstance(obj, integer_types)
+
+
+def byte(num):
+ """
+ Converts a number between 0 and 255 (both inclusive) to a base-256 (byte)
+ representation.
+
+ Use it as a replacement for ``chr`` where you are expecting a byte
+ because this will work on all current versions of Python::
+
+ >>> byte(0)
+ '\x00'
+ >>> byte(255)
+ '\xff'
+
+ :param num:
+ An unsigned integer between 0 and 255 (both inclusive).
+ :returns:
+ A single byte.
+ """
+ return pack("B", num)
diff --git a/tests/test_compat.py b/tests/test_compat.py
new file mode 100644
index 0000000..3652c82
--- /dev/null
+++ b/tests/test_compat.py
@@ -0,0 +1,17 @@
+# -*- coding: utf-8 -*-
+
+import unittest2
+import struct
+
+from rsa._compat import is_bytes, byte
+
+class Test_byte(unittest2.TestCase):
+ def test_byte(self):
+ for i in range(256):
+ byt = byte(i)
+ self.assertTrue(is_bytes(byt))
+ self.assertEqual(ord(byt), i)
+
+ def test_raises_StructError_on_overflow(self):
+ self.assertRaises(struct.error, byte, 256)
+ self.assertRaises(struct.error, byte, -1)