bpo-33361: Fix bug with seeking in StreamRecoders (GH-8278)
(cherry picked from commit a6ec1ce1ac05b1258931422e96eac215b6a05459)
Co-authored-by: Ammar Askar <ammar_askar@hotmail.com>
diff --git a/Lib/codecs.py b/Lib/codecs.py
index 3cd78fc..cfca5d3 100644
--- a/Lib/codecs.py
+++ b/Lib/codecs.py
@@ -847,6 +847,12 @@
self.reader.reset()
self.writer.reset()
+ def seek(self, offset, whence=0):
+ # Seeks must be propagated to both the readers and writers
+ # as they might need to reset their internal buffers.
+ self.reader.seek(offset, whence)
+ self.writer.seek(offset, whence)
+
def __getattr__(self, name,
getattr=getattr):
diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index a3a2f65..248ef6f 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -3318,6 +3318,31 @@
sr.write(text.encode('latin1'))
self.assertEqual(bio.getvalue(), text.encode('utf-8'))
+ def test_seeking_read(self):
+ bio = io.BytesIO('line1\nline2\nline3\n'.encode('utf-16-le'))
+ sr = codecs.EncodedFile(bio, 'utf-8', 'utf-16-le')
+
+ self.assertEqual(sr.readline(), b'line1\n')
+ sr.seek(0)
+ self.assertEqual(sr.readline(), b'line1\n')
+ self.assertEqual(sr.readline(), b'line2\n')
+ self.assertEqual(sr.readline(), b'line3\n')
+ self.assertEqual(sr.readline(), b'')
+
+ def test_seeking_write(self):
+ bio = io.BytesIO('123456789\n'.encode('utf-16-le'))
+ sr = codecs.EncodedFile(bio, 'utf-8', 'utf-16-le')
+
+ # Test that seek() only resets its internal buffer when offset
+ # and whence are zero.
+ sr.seek(2)
+ sr.write(b'\nabc\n')
+ self.assertEqual(sr.readline(), b'789\n')
+ sr.seek(0)
+ self.assertEqual(sr.readline(), b'1\n')
+ self.assertEqual(sr.readline(), b'abc\n')
+ self.assertEqual(sr.readline(), b'789\n')
+
if __name__ == "__main__":
unittest.main()