use ordered dict to ensure sorted order

Author: lostnihilist

bencode/__init__.py

@@ -12,7 +12,7 @@
 
 """bencode.py - bencode encoder + decoder."""
 
-from collections import deque
+from collections import deque, OrderedDict
 
 from bencode.BTL import BTFailure
 from bencode.exceptions import BencodeDecodeError
@@ -86,13 +86,30 @@ def decode_list(x, f):
     return r, f + 1
 
 
-def decode_dict(x, f):
-    r, f = {}, f + 1
+def decode_dict(x, f, force_sort=True):
+    """
+        decode bencoded data to an OrderedDict
+
+        The BitTorrent standard states that:
+            Keys must be strings and appear in sorted order (sorted as raw
+            strings, not alphanumerics)
+        - http://www.bittorrent.org/beps/bep_0003.html
+
+        Therefore, this function will force the keys to be strings (decoded
+        from utf-8), and by default the keys are (re)sorted after reading.
+        Set force_sort to False to keep the order of the dictionary as
+        represented in x, as many other encoders and decoders do not force this
+        property.
+    """
+    r, f = OrderedDict(), f + 1
 
     while x[f : f+1] != b'e':
         k, f = decode_string(x, f, force_decode_utf8=True)
         r[k], f = decode_func[x[f : f+1]](x, f)
 
+    if force_sort:
+        r = OrderedDict(sorted(r.items()))
+
     return r, f + 1
 
 
@@ -209,6 +226,7 @@ def encode_dict(x, r):
 else:
     encode_func[bool] = encode_bool
     encode_func[dict] = encode_dict
+    encode_func[OrderedDict] = encode_dict
     encode_func[int] = encode_int
     encode_func[list] = encode_list
     encode_func[str] = encode_string

tests/bencode_tests.py

@@ -3,6 +3,8 @@
 
 """bencode.py tests."""
 
+from collections import OrderedDict
+
 from bencode import BTFailure, bencode, bdecode
 
 import unittest
@@ -31,6 +33,10 @@ class KnownValues(unittest.TestCase):
             'foo': 42,
             'bar': 'spam'
         }, 'd3:bar4:spam3:fooi42ee'.encode('utf-8')),
+        (OrderedDict((
+            ('bar', 'spam'),
+            ('foo', 42)
+        )), 'd3:bar4:spam3:fooi42ee'.encode('utf-8')),
     )
 
     def testBencodeKnownValues(self):