fix #4862 in _pyio: reset the decoder on seek(0)

benjaminp · benjaminp · commit 9363a65b2ceb · 2009-03-05T00:42:09.000Z
diff --git a/Lib/_pyio.py b/Lib/_pyio.py
@@ -1667,7 +1667,9 @@ def seek(self, cookie, whence=0):
         self._snapshot = None
 
         # Restore the decoder to its state from the safe start point.
-        if self._decoder or dec_flags or chars_to_skip:
+        if cookie == 0 and self._decoder:
+            self._decoder.reset()
+        elif self._decoder or dec_flags or chars_to_skip:
             self._decoder = self._decoder or self._get_decoder()
             self._decoder.setstate((b'', dec_flags))
             self._snapshot = (dec_flags, b'')
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
@@ -1706,6 +1706,8 @@ def test_encoded_writes(self):
             f.write(data)
             f.seek(0)
             self.assertEquals(f.read(), data * 2)
+            f.seek(0)
+            self.assertEquals(f.read(), data * 2)
             self.assertEquals(buf.getvalue(), (data * 2).encode(encoding))
 
     def test_read_one_by_one(self):
