Merge ~jbfzs/dkimpy:beautifold into dkimpy:master

[Jonathan Bastien-Filiatrault]

Better folding in general. Removes trailing whitespace and better uses the whole line length.

[Scott Kitterman (kitterman)]

Thanks. Merged. Feel free to include an appropriate ChangeLog entry in the future.

Scott K

review: Approve

diff --git a/dkim/__init__.py b/dkim/__init__.py
index ed54d1f..f68cf31 100644
--- a/dkim/__init__.py
+++ b/dkim/__init__.py
@@ -371,7 +371,7 @@ def fold(header, namelen=0):
     >>> text(fold(b'foo'))
     'foo'
     >>> text(fold(b'foo  '+b'foo'*24).splitlines()[0])
-    'foo  '
+    'foo '
     >>> text(fold(b'foo'*25).splitlines()[-1])
     ' foo'
     >>> len(fold(b'foo'*25).splitlines()[0])
@@ -386,7 +386,7 @@ def fold(header, namelen=0):
     maxleng = 72 - namelen
     if len(header) <= maxleng:
         return header
-    if len(header) - header.rfind(b"\r\n") == 2 and len(header) <= maxleng +2:
+    if header.endswith(b"\r\n") and len(header) - 2 <= maxleng:
         return header
     i = header.rfind(b"\r\n ")
     if i == -1:
@@ -399,19 +399,21 @@ def fold(header, namelen=0):
         i = header[:maxleng].rfind(b" ")
         if i == -1:
             j = maxleng
+            pre += header[:j] + b"\r\n "
         else:
             j = i + 1
-        pre += header[:j] + b"\r\n "
+            pre += header[:i] + b"\r\n "
         header = header[j:]
-        namelen = 0
-    if len(header) > 2:
-        return pre + header
-    else:
-        if pre[0] == b' ':
-            return pre[:-1]
-        else:
-            return pre + header
 
+        if header == b"\r\n":
+            # If only a CRLF is left to fold, remove the space added
+            # and we are done.
+            pre = pre[:-1]
+            header = b""
+
+        maxleng = 72
+
+    return pre + header
 
 def load_pk_from_dns(name, dnsfunc=get_txt):
   s = dnsfunc(name)
diff --git a/dkim/tests/test_arc.py b/dkim/tests/test_arc.py
index 18719a3..286b25c 100644
--- a/dkim/tests/test_arc.py
+++ b/dkim/tests/test_arc.py
@@ -74,7 +74,7 @@ Y+vtSBczUiKERHv1yRbcaQtZFh5wtiRrN04BLUTD21MycBX5jYchHjPY/wIDAQAB"""
         sig_lines = dkim.arc_sign(
             self.message, b"test", b"example.com", self.key, b"lists.example.org", timestamp="12345")
 
-        expected_sig = [b'ARC-Seal: i=1; cv=none; a=rsa-sha256; d=example.com; s=test; t=12345; \r\n b=2DTLaiAcKznJwwNOWoOG8WBsdTq+/S92TZbURDxkgjGCmsSw8czQiisf02sC92\r\n 0nswz3JItA80l70iguM00onrj3eCe41yRDzB8lQL3kbrDyM+wUewmyhPoifRTsng\r\n t9ELTFrax4kCeHv6SdNz3uJfGYwQc+WCFEchXt3szNTRM=\r\n', b'ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; \r\n d=example.com; s=test; t=12345; h=message-id : \r\n date : from : to : subject : from; \r\n bh=wE7NXSkgnx9PGiavN4OZhJztvkqPDlemV3OGuEnLwNo=; \r\n b=a0f6qc3k9eECTSR155A0TQS+LjqPFWfI/brQBA83EUz00SNxj\r\n 1wmWykvs1hhBVeM0r1kEQc6CKbzRYaBNSiFj4q8JBpRIujLz1qL\r\n yGmPuAI6ddu/Z/1hQxgpVcp/odmI1UMV2R+d+yQ7tUp3EQxF/GY\r\n Nt22rV4rNmDmANZVqJ90=\r\n', b'ARC-Authentication-Results: i=1; lists.example.org; arc=none;\r\n  spf=pass smtp.mfrom=[e-mail];\r\n  dkim=pass (1024-bit key) header.i=@d1.example;\r\n  dmarc=pass\r\n']
+        expected_sig = [b'ARC-Seal: i=1; cv=none; a=rsa-sha256; d=example.com; s=test; t=12345;\r\n b=AwwfB+haHcusCH1o5kKebsCtsGWBa2sW1jJRHPNLRv8e5fuDl8VMYtj/r5LIZRgj+2ubPc\r\n hjLhoj6/Nf3Sv5m3P6iW9nnXM/HV0CLFxD5RjLhNy0Wsi6POBHVQ2KTT85xv7AyBURBv00Np\r\n kgGt+v3g7wtDQ3T+MwquceXqPmRjM=\r\n', b'ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed;\r\n d=example.com; s=test; t=12345; h=message-id : date : from : to :\r\n subject : from; bh=wE7NXSkgnx9PGiavN4OZhJztvkqPDlemV3OGuEnLwNo=;\r\n b=a0f6qc3k9eECTSR155A0TQS+LjqPFWfI/brQBA83EUz00SNxj1wmWykvs1hhBVeM0r1kEQ\r\n c6CKbzRYaBNSiFj4q8JBpRIujLz1qLyGmPuAI6ddu/Z/1hQxgpVcp/odmI1UMV2R+d+yQ7tU\r\n p3EQxF/GYNt22rV4rNmDmANZVqJ90=\r\n', b'ARC-Authentication-Results: i=1; lists.example.org; arc=none;\r\n  spf=pass smtp.mfrom=[e-mail];\r\n  dkim=pass (1024-bit key) header.i=@d1.example;\r\n  dmarc=pass\r\n']
 
         self.assertEqual(expected_sig, sig_lines)