add the missing file. i are senior dvlpr

1 files changed, 35 insertions, 0 deletions

diff --git a/cryptography/hazmat/backends/openssl/utils.py b/cryptography/hazmat/backends/openssl/utils.py
new file mode 100644
index 00000000..408b6146
--- /dev/null
+++ b/cryptography/hazmat/backends/openssl/utils.py
@@ -0,0 +1,35 @@
+# 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.
+
+from __future__ import absolute_import, division, print_function
+
+import six
+
+
+def _truncate_digest(digest, order_bits):
+    digest_len = len(digest)
+
+    if 8 * digest_len > order_bits:
+        digest_len = (order_bits + 7) // 8
+        digest = digest[:digest_len]
+
+    if 8 * digest_len > order_bits:
+        rshift = 8 - (order_bits & 0x7)
+        assert rshift > 0 and rshift < 8
+
+        mask = 0xFF >> rshift << rshift
+
+        # Set the bottom rshift bits to 0
+        digest = digest[:-1] + six.int2byte(six.indexbytes(digest, -1) & mask)
+
+    return digest