Google Code Issue 215: Properly detect seekable streams

Removes the hack that tests for sys.stdin to determine if the stream
is seekable (it has tell() and seek() but it is not seekable) by
actually calling tell() and seek().

This also removes the wrapping in HTMLUnicodeInputStream, where we
do not need the ability to seek.

Author: jcarlosgarciasegovia

html5lib/inputstream.py

@@ -3,7 +3,6 @@
 
 import codecs
 import re
-import sys
 
 from .constants import EOF, spaceCharacters, asciiLetters, asciiUppercase
 from .constants import encodings, ReparseException
@@ -202,12 +201,6 @@ def openStream(self, source):
         else:
             stream = StringIO(source)
 
-        if (  # not isinstance(stream, BufferedIOBase) and
-            not(hasattr(stream, "tell") and
-                hasattr(stream, "seek")) or
-                stream is sys.stdin):
-            stream = BufferedStream(stream)
-
         return stream
 
     def _position(self, offset):
@@ -437,8 +430,9 @@ def openStream(self, source):
         else:
             stream = BytesIO(source)
 
-        if (not(hasattr(stream, "tell") and hasattr(stream, "seek")) or
-                stream is sys.stdin):
+        try:
+            stream.seek(stream.tell())
+        except:
             stream = BufferedStream(stream)
 
         return stream