BaseStreamFileLike: handle reads that return None

Fixes #555.

test/test_filelike.py

@@ -90,6 +90,15 @@ class TestLimitingStream(unittest.TestCase):
 
 
 class TestStreamSlice(unittest.TestCase):
+  def test_none_read(self):
+    class NoneReader(object):
+      def read(self, size=None):
+        return None
+
+    stream = StreamSlice(NoneReader(), 0)
+    self.assertEquals(None, stream.read(-1))
+    self.assertEquals(0, stream.tell())
+
   def test_noslice(self):
     fileobj = StringIO('this is a cool test')
     stream = StreamSlice(fileobj, 0)
@@ -123,4 +132,4 @@ class TestStreamSlice(unittest.TestCase):
 
 
 if __name__ == '__main__':
-  unittest.main()
+  unittest.main()

util/registry/filelike.py

@@ -15,6 +15,8 @@ class BaseStreamFilelike(object):
 
   def read(self, size=READ_UNTIL_END):
     buf = self._fileobj.read(size)
+    if buf is None:
+      return None
     self._cursor_position += len(buf)
     return buf