minor int_to_bytes performance increase (#3490)

* minor int_to_bytes performance increase

* why is Python 2.6 supported anyway...

* keep py2k version

1 files changed, 13 insertions, 7 deletions

diff --git a/src/cryptography/utils.py b/src/cryptography/utils.py
index ab3c84e1..6d304856 100644
--- a/src/cryptography/utils.py
+++ b/src/cryptography/utils.py
@@ -51,13 +51,19 @@ else:
         return int(bytes(data).encode('hex'), 16)
 
 
-def int_to_bytes(integer, length=None):
-    hex_string = '%x' % integer
-    if length is None:
-        n = len(hex_string)
-    else:
-        n = length * 2
-    return binascii.unhexlify(hex_string.zfill(n + (n & 1)))
+if hasattr(int, "to_bytes"):
+    def int_to_bytes(integer, length=None):
+        return integer.to_bytes(
+            length or (integer.bit_length() + 7) // 8 or 1, 'big'
+        )
+else:
+    def int_to_bytes(integer, length=None):
+        hex_string = '%x' % integer
+        if length is None:
+            n = len(hex_string)
+        else:
+            n = length * 2
+        return binascii.unhexlify(hex_string.zfill(n + (n & 1)))
 
 
 class InterfaceNotImplemented(Exception):