Make the BOM constants in codecs.py bytes.

Make the buffered input for decoders a bytes object.

Fix some of the codec tests.
diff --git a/Lib/codecs.py b/Lib/codecs.py
index 909a651..982c282 100644
--- a/Lib/codecs.py
+++ b/Lib/codecs.py
@@ -33,19 +33,19 @@
 #
 
 # UTF-8
-BOM_UTF8 = '\xef\xbb\xbf'
+BOM_UTF8 = b'\xef\xbb\xbf'
 
 # UTF-16, little endian
-BOM_LE = BOM_UTF16_LE = '\xff\xfe'
+BOM_LE = BOM_UTF16_LE = b'\xff\xfe'
 
 # UTF-16, big endian
-BOM_BE = BOM_UTF16_BE = '\xfe\xff'
+BOM_BE = BOM_UTF16_BE = b'\xfe\xff'
 
 # UTF-32, little endian
-BOM_UTF32_LE = '\xff\xfe\x00\x00'
+BOM_UTF32_LE = b'\xff\xfe\x00\x00'
 
 # UTF-32, big endian
-BOM_UTF32_BE = '\x00\x00\xfe\xff'
+BOM_UTF32_BE = b'\x00\x00\xfe\xff'
 
 if sys.byteorder == 'little':
 
@@ -261,7 +261,7 @@
         Return the current state of the decoder. This must be a
         (buffered_input, additional_state_info) tuple.
         """
-        return ("", 0)
+        return (b"", 0)
 
     def setstate(self, state):
         """
@@ -278,7 +278,7 @@
     def __init__(self, errors='strict'):
         IncrementalDecoder.__init__(self, errors)
         # undecoded input that is kept between calls to decode()
-        self.buffer = ""
+        self.buffer = b""
 
     def _buffer_decode(self, input, errors, final):
         # Overwrite this method in subclasses: It must decode input
@@ -295,7 +295,7 @@
 
     def reset(self):
         IncrementalDecoder.reset(self)
-        self.buffer = ""
+        self.buffer = b""
 
     def getstate(self):
         # additional state info is always 0
@@ -402,7 +402,7 @@
         """
         self.stream = stream
         self.errors = errors
-        self.bytebuffer = ""
+        self.bytebuffer = b""
         # For str->str decoding this will stay a str
         # For str->unicode decoding the first read will promote it to unicode
         self.charbuffer = ""
@@ -588,7 +588,7 @@
             from decoding errors.
 
         """
-        self.bytebuffer = ""
+        self.bytebuffer = b""
         self.charbuffer = ""
         self.linebuffer = None
 
@@ -1005,7 +1005,7 @@
         output = decoder.decode(input)
         if output:
             yield output
-    output = decoder.decode("", True)
+    output = decoder.decode(b"", True)
     if output:
         yield output
 
diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index 991b44a..10e4c36 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -1,14 +1,14 @@
 from test import test_support
 import unittest
 import codecs
-import sys, StringIO, _testcapi
+import sys, cStringIO, _testcapi
 
 class Queue(object):
     """
     queue: write bytes at one end, read bytes from the other end
     """
-    def __init__(self):
-        self._buffer = ""
+    def __init__(self, buffer):
+        self._buffer = buffer
 
     def write(self, chars):
         self._buffer += chars
@@ -16,7 +16,7 @@
     def read(self, size=-1):
         if size<0:
             s = self._buffer
-            self._buffer = ""
+            self._buffer = self._buffer[:0] # make empty
             return s
         else:
             s = self._buffer[:size]
@@ -62,48 +62,48 @@
         # of input to the reader byte by byte. Read every available from
         # the StreamReader and check that the results equal the appropriate
         # entries from partialresults.
-        q = Queue()
+        q = Queue(b"")
         r = codecs.getreader(self.encoding)(q)
         result = ""
         for (c, partialresult) in zip(input.encode(self.encoding), partialresults):
-            q.write(c)
+            q.write(bytes([c]))
             result += r.read()
             self.assertEqual(result, partialresult)
         # check that there's nothing left in the buffers
         self.assertEqual(r.read(), "")
-        self.assertEqual(r.bytebuffer, "")
+        self.assertEqual(r.bytebuffer, b"")
         self.assertEqual(r.charbuffer, "")
 
         # do the check again, this time using a incremental decoder
         d = codecs.getincrementaldecoder(self.encoding)()
         result = ""
         for (c, partialresult) in zip(input.encode(self.encoding), partialresults):
-            result += d.decode(c)
+            result += d.decode(bytes([c]))
             self.assertEqual(result, partialresult)
         # check that there's nothing left in the buffers
-        self.assertEqual(d.decode("", True), "")
-        self.assertEqual(d.buffer, "")
+        self.assertEqual(d.decode(b"", True), "")
+        self.assertEqual(d.buffer, b"")
 
-        # Check whether the rest method works properly
+        # Check whether the reset method works properly
         d.reset()
         result = ""
         for (c, partialresult) in zip(input.encode(self.encoding), partialresults):
-            result += d.decode(c)
+            result += d.decode(bytes([c]))
             self.assertEqual(result, partialresult)
         # check that there's nothing left in the buffers
-        self.assertEqual(d.decode("", True), "")
-        self.assertEqual(d.buffer, "")
+        self.assertEqual(d.decode(b"", True), "")
+        self.assertEqual(d.buffer, b"")
 
         # check iterdecode()
         encoded = input.encode(self.encoding)
         self.assertEqual(
             input,
-            "".join(codecs.iterdecode(encoded, self.encoding))
+            "".join(codecs.iterdecode([bytes([c]) for c in encoded], self.encoding))
         )
 
     def test_readline(self):
         def getreader(input):
-            stream = StringIO.StringIO(input.encode(self.encoding))
+            stream = cStringIO.StringIO(input.encode(self.encoding))
             return codecs.getreader(self.encoding)(stream)
 
         def readalllines(input, keepends=True, size=None):
@@ -215,13 +215,13 @@
             '                break\r\n',
             '                \r\n',
         ]
-        stream = StringIO.StringIO("".join(s).encode(self.encoding))
+        stream = cStringIO.StringIO("".join(s).encode(self.encoding))
         reader = codecs.getreader(self.encoding)(stream)
         for (i, line) in enumerate(reader):
             self.assertEqual(line, s[i])
 
     def test_readlinequeue(self):
-        q = Queue()
+        q = Queue(b"")
         writer = codecs.getwriter(self.encoding)(q)
         reader = codecs.getreader(self.encoding)(q)
 
@@ -253,7 +253,7 @@
         s3 = "next line.\r\n"
 
         s = (s1+s2+s3).encode(self.encoding)
-        stream = StringIO.StringIO(s)
+        stream = cStringIO.StringIO(s)
         reader = codecs.getreader(self.encoding)(stream)
         self.assertEqual(reader.readline(), s1)
         self.assertEqual(reader.readline(), s2)
@@ -268,7 +268,7 @@
         s5 = "againokay.\r\n"
 
         s = (s1+s2+s3+s4+s5).encode(self.encoding)
-        stream = StringIO.StringIO(s)
+        stream = cStringIO.StringIO(s)
         reader = codecs.getreader(self.encoding)(stream)
         self.assertEqual(reader.readline(), s1)
         self.assertEqual(reader.readline(), s2)
@@ -280,13 +280,13 @@
 class UTF16Test(ReadTest):
     encoding = "utf-16"
 
-    spamle = '\xff\xfes\x00p\x00a\x00m\x00s\x00p\x00a\x00m\x00'
-    spambe = '\xfe\xff\x00s\x00p\x00a\x00m\x00s\x00p\x00a\x00m'
+    spamle = b'\xff\xfes\x00p\x00a\x00m\x00s\x00p\x00a\x00m\x00'
+    spambe = b'\xfe\xff\x00s\x00p\x00a\x00m\x00s\x00p\x00a\x00m'
 
     def test_only_one_bom(self):
         _,_,reader,writer = codecs.lookup(self.encoding)
         # encode some stream
-        s = StringIO.StringIO()
+        s = cStringIO.StringIO()
         f = writer(s)
         f.write("spam")
         f.write("spam")
@@ -294,16 +294,16 @@
         # check whether there is exactly one BOM in it
         self.assert_(d == self.spamle or d == self.spambe)
         # try to read it back
-        s = StringIO.StringIO(d)
+        s = cStringIO.StringIO(d)
         f = reader(s)
         self.assertEquals(f.read(), "spamspam")
 
     def test_badbom(self):
-        s = StringIO.StringIO("\xff\xff")
+        s = cStringIO.StringIO(b"\xff\xff")
         f = codecs.getreader(self.encoding)(s)
         self.assertRaises(UnicodeError, f.read)
 
-        s = StringIO.StringIO("\xff\xff\xff\xff")
+        s = cStringIO.StringIO(b"\xff\xff\xff\xff")
         f = codecs.getreader(self.encoding)(s)
         self.assertRaises(UnicodeError, f.read)
 
@@ -326,7 +326,7 @@
 
     def test_errors(self):
         self.assertRaises(UnicodeDecodeError, codecs.utf_16_decode,
-                          "\xff", "strict", True)
+                          b"\xff", "strict", True)
 
     def test_decoder_state(self):
         self.check_state_handling_decode(self.encoding,
@@ -354,7 +354,7 @@
 
     def test_errors(self):
         self.assertRaises(UnicodeDecodeError, codecs.utf_16_le_decode,
-                          "\xff", "strict", True)
+                          b"\xff", "strict", True)
 
 class UTF16BETest(ReadTest):
     encoding = "utf-16-be"
@@ -376,7 +376,7 @@
 
     def test_errors(self):
         self.assertRaises(UnicodeDecodeError, codecs.utf_16_be_decode,
-                          "\xff", "strict", True)
+                          b"\xff", "strict", True)
 
 class UTF8Test(ReadTest):
     encoding = "utf-8"
@@ -412,7 +412,7 @@
 class UTF16ExTest(unittest.TestCase):
 
     def test_errors(self):
-        self.assertRaises(UnicodeDecodeError, codecs.utf_16_ex_decode, "\xff", "strict", 0, True)
+        self.assertRaises(UnicodeDecodeError, codecs.utf_16_ex_decode, b"\xff", "strict", 0, True)
 
     def test_bad_args(self):
         self.assertRaises(TypeError, codecs.utf_16_ex_decode)
@@ -474,7 +474,7 @@
 
     def test_bug1601501(self):
         # SF bug #1601501: check that the codec works with a buffer
-        str("\xef\xbb\xbf", "utf-8-sig")
+        str(b"\xef\xbb\xbf", "utf-8-sig")
 
     def test_bom(self):
         d = codecs.getincrementaldecoder("utf-8-sig")()
@@ -492,7 +492,7 @@
 
 class RecodingTest(unittest.TestCase):
     def test_recoding(self):
-        f = StringIO.StringIO()
+        f = cStringIO.StringIO()
         f2 = codecs.EncodedFile(f, "unicode_internal", "utf-8")
         f2.write("a")
         f2.close()
@@ -856,8 +856,7 @@
         self.assertEquals("pyth\xf6n.org.".encode("idna"), "xn--pythn-mua.org.")
 
     def test_stream(self):
-        import StringIO
-        r = codecs.getreader("idna")(StringIO.StringIO("abc"))
+        r = codecs.getreader("idna")(cStringIO.StringIO(b"abc"))
         r.read(3)
         self.assertEquals(r.read(), "")
 
@@ -922,18 +921,18 @@
 class CodecsModuleTest(unittest.TestCase):
 
     def test_decode(self):
-        self.assertEquals(codecs.decode('\xe4\xf6\xfc', 'latin-1'),
+        self.assertEquals(codecs.decode(b'\xe4\xf6\xfc', 'latin-1'),
                           '\xe4\xf6\xfc')
         self.assertRaises(TypeError, codecs.decode)
-        self.assertEquals(codecs.decode('abc'), 'abc')
-        self.assertRaises(UnicodeDecodeError, codecs.decode, '\xff', 'ascii')
+        self.assertEquals(codecs.decode(b'abc'), 'abc')
+        self.assertRaises(UnicodeDecodeError, codecs.decode, b'\xff', 'ascii')
 
     def test_encode(self):
         self.assertEquals(codecs.encode('\xe4\xf6\xfc', 'latin-1'),
-                          '\xe4\xf6\xfc')
+                          b'\xe4\xf6\xfc')
         self.assertRaises(TypeError, codecs.encode)
         self.assertRaises(LookupError, codecs.encode, "foo", "__spam__")
-        self.assertEquals(codecs.encode('abc'), 'abc')
+        self.assertEquals(codecs.encode('abc'), b'abc')
         self.assertRaises(UnicodeEncodeError, codecs.encode, '\xffff', 'ascii')
 
     def test_register(self):
@@ -965,7 +964,7 @@
 
     def setUp(self):
         self.reader = codecs.getreader('utf-8')
-        self.stream = StringIO.StringIO('\xed\x95\x9c\n\xea\xb8\x80')
+        self.stream = cStringIO.StringIO(b'\xed\x95\x9c\n\xea\xb8\x80')
 
     def test_readlines(self):
         f = self.reader(self.stream)
@@ -974,27 +973,27 @@
 class EncodedFileTest(unittest.TestCase):
 
     def test_basic(self):
-        f = StringIO.StringIO('\xed\x95\x9c\n\xea\xb8\x80')
+        f = cStringIO.StringIO(b'\xed\x95\x9c\n\xea\xb8\x80')
         ef = codecs.EncodedFile(f, 'utf-16-le', 'utf-8')
-        self.assertEquals(ef.read(), '\\\xd5\n\x00\x00\xae')
+        self.assertEquals(ef.read(), b'\\\xd5\n\x00\x00\xae')
 
-        f = StringIO.StringIO()
+        f = cStringIO.StringIO()
         ef = codecs.EncodedFile(f, 'utf-8', 'latin1')
-        ef.write('\xc3\xbc')
-        self.assertEquals(f.getvalue(), '\xfc')
+        ef.write(b'\xc3\xbc')
+        self.assertEquals(f.getvalue(), b'\xfc')
 
 class Str2StrTest(unittest.TestCase):
 
     def test_read(self):
         sin = "\x80".encode("base64_codec")
-        reader = codecs.getreader("base64_codec")(StringIO.StringIO(sin))
+        reader = codecs.getreader("base64_codec")(cStringIO.StringIO(sin))
         sout = reader.read()
         self.assertEqual(sout, "\x80")
         self.assert_(isinstance(sout, str))
 
     def test_readline(self):
         sin = "\x80".encode("base64_codec")
-        reader = codecs.getreader("base64_codec")(StringIO.StringIO(sin))
+        reader = codecs.getreader("base64_codec")(cStringIO.StringIO(sin))
         sout = reader.readline()
         self.assertEqual(sout, "\x80")
         self.assert_(isinstance(sout, str))
@@ -1162,25 +1161,25 @@
             elif encoding == "latin_1":
                 name = "latin_1"
             self.assertEqual(encoding.replace("_", "-"), name.replace("_", "-"))
-            (bytes, size) = codecs.getencoder(encoding)(s)
+            (b, size) = codecs.getencoder(encoding)(s)
             if encoding != "unicode_internal":
                 self.assertEqual(size, len(s), "%r != %r (encoding=%r)" % (size, len(s), encoding))
-            (chars, size) = codecs.getdecoder(encoding)(bytes)
+            (chars, size) = codecs.getdecoder(encoding)(b)
             self.assertEqual(chars, s, "%r != %r (encoding=%r)" % (chars, s, encoding))
 
             if encoding not in broken_unicode_with_streams:
                 # check stream reader/writer
-                q = Queue()
+                q = Queue(b"")
                 writer = codecs.getwriter(encoding)(q)
-                encodedresult = ""
+                encodedresult = b""
                 for c in s:
                     writer.write(c)
                     encodedresult += q.read()
-                q = Queue()
+                q = Queue(b"")
                 reader = codecs.getreader(encoding)(q)
                 decodedresult = ""
                 for c in encodedresult:
-                    q.write(c)
+                    q.write(bytes([c]))
                     decodedresult += reader.read()
                 self.assertEqual(decodedresult, s, "%r != %r (encoding=%r)" % (decodedresult, s, encoding))
 
@@ -1194,26 +1193,26 @@
                     pass
                 else:
                     # check incremental decoder/encoder
-                    encodedresult = ""
+                    encodedresult = b""
                     for c in s:
                         encodedresult += encoder.encode(c)
                     encodedresult += encoder.encode("", True)
                     decoder = codecs.getincrementaldecoder(encoding)()
                     decodedresult = ""
                     for c in encodedresult:
-                        decodedresult += decoder.decode(c)
+                        decodedresult += decoder.decode(bytes([c]))
                     decodedresult += decoder.decode("", True)
                     self.assertEqual(decodedresult, s, "%r != %r (encoding=%r)" % (decodedresult, s, encoding))
 
                     # check C API
-                    encodedresult = ""
+                    encodedresult = b""
                     for c in s:
                         encodedresult += cencoder.encode(c)
                     encodedresult += cencoder.encode("", True)
                     cdecoder = _testcapi.codec_incrementaldecoder(encoding)
                     decodedresult = ""
                     for c in encodedresult:
-                        decodedresult += cdecoder.decode(c)
+                        decodedresult += cdecoder.decode(bytes([c]))
                     decodedresult += cdecoder.decode("", True)
                     self.assertEqual(decodedresult, s, "%r != %r (encoding=%r)" % (decodedresult, s, encoding))
 
@@ -1233,14 +1232,14 @@
                     except LookupError: # no IncrementalEncoder
                         pass
                     else:
-                        encodedresult = "".join(encoder.encode(c) for c in s)
+                        encodedresult = b"".join(encoder.encode(c) for c in s)
                         decoder = codecs.getincrementaldecoder(encoding)("ignore")
-                        decodedresult = "".join(decoder.decode(c) for c in encodedresult)
+                        decodedresult = "".join(decoder.decode(bytes([c])) for c in encodedresult)
                         self.assertEqual(decodedresult, s, "%r != %r (encoding=%r)" % (decodedresult, s, encoding))
 
-                        encodedresult = "".join(cencoder.encode(c) for c in s)
+                        encodedresult = b"".join(cencoder.encode(c) for c in s)
                         cdecoder = _testcapi.codec_incrementaldecoder(encoding, "ignore")
-                        decodedresult = "".join(cdecoder.decode(c) for c in encodedresult)
+                        decodedresult = "".join(cdecoder.decode(bytes([c])) for c in encodedresult)
                         self.assertEqual(decodedresult, s, "%r != %r (encoding=%r)" % (decodedresult, s, encoding))
 
     def test_seek(self):
@@ -1251,7 +1250,7 @@
                 continue
             if encoding in broken_unicode_with_streams:
                 continue
-            reader = codecs.getreader(encoding)(StringIO.StringIO(s.encode(encoding)))
+            reader = codecs.getreader(encoding)(cStringIO.StringIO(s.encode(encoding)))
             for t in xrange(5):
                 # Test that calling seek resets the internal codec state and buffers
                 reader.seek(0, 0)
@@ -1288,39 +1287,39 @@
     def test_basics(self):
         s = "abc123"
         for encoding in all_string_encodings:
-            (bytes, size) = codecs.getencoder(encoding)(s)
+            (encoded, size) = codecs.getencoder(encoding)(s)
             self.assertEqual(size, len(s))
-            (chars, size) = codecs.getdecoder(encoding)(bytes)
+            (chars, size) = codecs.getdecoder(encoding)(encoded)
             self.assertEqual(chars, s, "%r != %r (encoding=%r)" % (chars, s, encoding))
 
 class CharmapTest(unittest.TestCase):
     def test_decode_with_string_map(self):
         self.assertEquals(
-            codecs.charmap_decode("\x00\x01\x02", "strict", "abc"),
+            codecs.charmap_decode(b"\x00\x01\x02", "strict", "abc"),
             ("abc", 3)
         )
 
         self.assertEquals(
-            codecs.charmap_decode("\x00\x01\x02", "replace", "ab"),
+            codecs.charmap_decode(b"\x00\x01\x02", "replace", "ab"),
             ("ab\ufffd", 3)
         )
 
         self.assertEquals(
-            codecs.charmap_decode("\x00\x01\x02", "replace", "ab\ufffe"),
+            codecs.charmap_decode(b"\x00\x01\x02", "replace", "ab\ufffe"),
             ("ab\ufffd", 3)
         )
 
         self.assertEquals(
-            codecs.charmap_decode("\x00\x01\x02", "ignore", "ab"),
+            codecs.charmap_decode(b"\x00\x01\x02", "ignore", "ab"),
             ("ab", 3)
         )
 
         self.assertEquals(
-            codecs.charmap_decode("\x00\x01\x02", "ignore", "ab\ufffe"),
+            codecs.charmap_decode(b"\x00\x01\x02", "ignore", "ab\ufffe"),
             ("ab", 3)
         )
 
-        allbytes = "".join(chr(i) for i in xrange(256))
+        allbytes = bytes(xrange(256))
         self.assertEquals(
             codecs.charmap_decode(allbytes, "ignore", ""),
             ("", len(allbytes))
@@ -1328,12 +1327,12 @@
 
 class WithStmtTest(unittest.TestCase):
     def test_encodedfile(self):
-        f = StringIO.StringIO("\xc3\xbc")
+        f = cStringIO.StringIO(b"\xc3\xbc")
         with codecs.EncodedFile(f, "latin-1", "utf-8") as ef:
-            self.assertEquals(ef.read(), "\xfc")
+            self.assertEquals(ef.read(), b"\xfc")
 
     def test_streamreaderwriter(self):
-        f = StringIO.StringIO("\xc3\xbc")
+        f = cStringIO.StringIO(b"\xc3\xbc")
         info = codecs.lookup("utf-8")
         with codecs.StreamReaderWriter(f, info.streamreader,
                                        info.streamwriter, 'strict') as srw: