Issue #6268: More bugfixes about BOM, UTF-16 and UTF-32

 * Fix seek() method of codecs.open(), don't write the BOM twice after seek(0)
 * Fix reset() method of codecs, UTF-16, UTF-32 and StreamWriter classes
 * test_codecs: use "w+" mode instead of "wt+". "t" mode is not supported by
   Solaris or Windows, but does it really exist? I found it the in the issue.

1 files changed, 10 insertions, 3 deletions

diff --git a/Lib/codecs.py b/Lib/codecs.py
index e903f2e..f4cd60a 100644
--- a/Lib/codecs.py
+++ b/Lib/codecs.py
@@ -370,6 +370,11 @@ class StreamWriter(Codec):
         """
         pass
 
+    def seek(self, offset, whence=0):
+        self.stream.seek(offset, whence)
+        if whence == 0 and offset == 0:
+            self.reset()
+
     def __getattr__(self, name,
                     getattr=getattr):
 
@@ -601,8 +606,8 @@ class StreamReader(Codec):
 
             Resets the codec buffers used for keeping state.
         """
-        self.reset()
         self.stream.seek(offset, whence)
+        self.reset()
 
     def next(self):
 
@@ -695,8 +700,10 @@ class StreamReaderWriter:
         self.writer.reset()
 
     def seek(self, offset, whence=0):
-        self.reader.seek(offset, whence)
-        self.writer.seek(offset, whence)
+        self.stream.seek(offset, whence)
+        self.reader.reset()
+        if whence == 0 and offset == 0:
+            self.writer.reset()
 
     def __getattr__(self, name,
                     getattr=getattr):