#28047: Fix calculation of base64 line length.

This is buggy in the old email code as well, but it doesn't affect anything
there because only the default line length is ever used there.

1 files changed, 5 insertions, 4 deletions

diff --git a/Lib/email/contentmanager.py b/Lib/email/contentmanager.py
index d3636529b6..b98ce27184 100644
--- a/Lib/email/contentmanager.py
+++ b/Lib/email/contentmanager.py
@@ -126,12 +126,13 @@ def _finalize_set(msg, disposition, filename, cid, params):
             msg.set_param(key, value)
 
 
-# XXX: This is a cleaned-up version of base64mime.body_encode.  It would
-# be nice to drop both this and quoprimime.body_encode in favor of
-# enhanced binascii routines that accepted a max_line_length parameter.
+# XXX: This is a cleaned-up version of base64mime.body_encode (including a bug
+# fix in the calculation of unencoded_bytes_per_line).  It would be nice to
+# drop both this and quoprimime.body_encode in favor of enhanced binascii
+# routines that accepted a max_line_length parameter.
 def _encode_base64(data, max_line_length):
     encoded_lines = []
-    unencoded_bytes_per_line = max_line_length * 3 // 4
+    unencoded_bytes_per_line = max_line_length // 4 * 3
     for i in range(0, len(data), unencoded_bytes_per_line):
         thisline = data[i:i+unencoded_bytes_per_line]
         encoded_lines.append(binascii.b2a_base64(thisline).decode('ascii'))