fix AES-encrypted buffers

--HG--
branch : pmacs2

buffer/__init__.py

@@ -639,6 +639,7 @@ class FileBuffer(Buffer):
             data = f.read()
             f.close()
             self.store_checksum(data)
+            data = self.read_filter(data)
             self.codec = chardet.detect(data)['encoding'].lower()
         else:
             data = ''
@@ -654,8 +655,6 @@ class FileBuffer(Buffer):
         if '\t' in data: self.writetabs = True
         self.nl = self._detect_nl_type(data)
 
-        data = self.read_filter(data)
-
         if '\x00' in data[:8192]:
             raise BinaryDataException("binary files are not supported")