From 882d14c514b1d7f2b36c0c0fe873a1db359694ed Mon Sep 17 00:00:00 2001
From: Jonathan Bastien-Filiatrault <joe@x2a.org>
Date: Wed, 12 Dec 2018 13:40:55 -0500
Subject: [PATCH] Avoid making a fresh slice of the whole email on each
 iteration.

An update to yesterday's patch. Should avoid copying the mail byte
string more than once.

Tested on Python 2.7 and 3.6.
---
 dkim/canonicalization.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dkim/canonicalization.py b/dkim/canonicalization.py
index 8c9ffc1..1860848 100644
--- a/dkim/canonicalization.py
+++ b/dkim/canonicalization.py
@@ -42,7 +42,7 @@ def compress_whitespace(content):
 
 def strip_trailing_lines(content):
     end = None
-    while content[:end].endswith(b"\r\n"):
+    while content.endswith(b"\r\n", 0, end):
         if end is None:
             end = -2
         else: