From 655fbf18068626c86f487ce94771fdd22b784ae8 Mon Sep 17 00:00:00 2001
From: Antoine Pitrou <solipsis@pitrou.net>
Date: Sun, 14 Dec 2008 17:40:51 +0000
Subject: [PATCH] Backport r67759 (fix io.IncrementalNewlineDecoder for UTF-16
 et al.).

---
 Lib/io.py           |  27 +++++------
 Lib/test/test_io.py | 114 ++++++++++++++++++++++++++++----------------
 Misc/NEWS           |   4 ++
 3 files changed, 89 insertions(+), 56 deletions(-)

diff --git a/Lib/io.py b/Lib/io.py
index 110804e607f..7f938987b71 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -1292,25 +1292,23 @@ class IncrementalNewlineDecoder(codecs.IncrementalDecoder):
     """
     def __init__(self, decoder, translate, errors='strict'):
         codecs.IncrementalDecoder.__init__(self, errors=errors)
-        self.buffer = b''
         self.translate = translate
         self.decoder = decoder
         self.seennl = 0
+        self.pendingcr = False
 
     def decode(self, input, final=False):
         # decode input (with the eventual \r from a previous pass)
-        if self.buffer:
-            input = self.buffer + input
-
         output = self.decoder.decode(input, final=final)
+        if self.pendingcr and (output or final):
+            output = "\r" + output
+            self.pendingcr = False
 
         # retain last \r even when not translating data:
         # then readline() is sure to get \r\n in one pass
         if output.endswith("\r") and not final:
             output = output[:-1]
-            self.buffer = b'\r'
-        else:
-            self.buffer = b''
+            self.pendingcr = True
 
         # Record which newlines are read
         crlf = output.count('\r\n')
@@ -1329,20 +1327,19 @@ class IncrementalNewlineDecoder(codecs.IncrementalDecoder):
 
     def getstate(self):
         buf, flag = self.decoder.getstate()
-        return buf + self.buffer, flag
+        flag <<= 1
+        if self.pendingcr:
+            flag |= 1
+        return buf, flag
 
     def setstate(self, state):
         buf, flag = state
-        if buf.endswith(b'\r'):
-            self.buffer = b'\r'
-            buf = buf[:-1]
-        else:
-            self.buffer = b''
-        self.decoder.setstate((buf, flag))
+        self.pendingcr = bool(flag & 1)
+        self.decoder.setstate((buf, flag >> 1))
 
     def reset(self):
         self.seennl = 0
-        self.buffer = b''
+        self.pendingcr = False
         self.decoder.reset()
 
     _LF = 1
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index eb41d1ffa7b..8a7da60947b 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -680,8 +680,9 @@ class StatefulIncrementalDecoder(codecs.IncrementalDecoder):
     @classmethod
     def lookupTestDecoder(cls, name):
         if cls.codecEnabled and name == 'test_decoder':
+            latin1 = codecs.lookup('latin-1')
             return codecs.CodecInfo(
-                name='test_decoder', encode=None, decode=None,
+                name='test_decoder', encode=latin1.encode, decode=None,
                 incrementalencoder=None,
                 streamreader=None, streamwriter=None,
                 incrementaldecoder=cls)
@@ -840,8 +841,11 @@ class TextIOWrapperTest(unittest.TestCase):
             [ '\r\n', [ "unix\nwindows\r\n", "os9\rlast\nnonl" ] ],
             [ '\r', [ "unix\nwindows\r", "\nos9\r", "last\nnonl" ] ],
         ]
-
-        encodings = ('utf-8', 'latin-1')
+        encodings = (
+            'utf-8', 'latin-1',
+            'utf-16', 'utf-16-le', 'utf-16-be',
+            'utf-32', 'utf-32-le', 'utf-32-be',
+        )
 
         # Try a range of buffer sizes to test the case where \r is the last
         # character in TextIOWrapper._pending_line.
@@ -1195,55 +1199,83 @@ class TextIOWrapperTest(unittest.TestCase):
 
         self.assertEqual(buffer.seekable(), txt.seekable())
 
-    def test_newline_decoder(self):
-        import codecs
-        decoder = codecs.getincrementaldecoder("utf-8")()
-        decoder = io.IncrementalNewlineDecoder(decoder, translate=True)
+    def check_newline_decoder_utf8(self, decoder):
+        # UTF-8 specific tests for a newline decoder
+        def _check_decode(b, s, **kwargs):
+            # We exercise getstate() / setstate() as well as decode()
+            state = decoder.getstate()
+            self.assertEquals(decoder.decode(b, **kwargs), s)
+            decoder.setstate(state)
+            self.assertEquals(decoder.decode(b, **kwargs), s)
 
-        self.assertEquals(decoder.decode(b'\xe8\xa2\x88'), u"\u8888")
+        _check_decode(b'\xe8\xa2\x88', "\u8888")
 
-        self.assertEquals(decoder.decode(b'\xe8'), u"")
-        self.assertEquals(decoder.decode(b'\xa2'), u"")
-        self.assertEquals(decoder.decode(b'\x88'), u"\u8888")
+        _check_decode(b'\xe8', "")
+        _check_decode(b'\xa2', "")
+        _check_decode(b'\x88', "\u8888")
 
-        self.assertEquals(decoder.decode(b'\xe8'), u"")
+        _check_decode(b'\xe8', "")
+        _check_decode(b'\xa2', "")
+        _check_decode(b'\x88', "\u8888")
+
+        _check_decode(b'\xe8', "")
         self.assertRaises(UnicodeDecodeError, decoder.decode, b'', final=True)
 
-        decoder.setstate((b'', 0))
-        self.assertEquals(decoder.decode(b'\n'), u"\n")
-        self.assertEquals(decoder.decode(b'\r'), u"")
-        self.assertEquals(decoder.decode(b'', final=True), u"\n")
-        self.assertEquals(decoder.decode(b'\r', final=True), u"\n")
+        decoder.reset()
+        _check_decode(b'\n', "\n")
+        _check_decode(b'\r', "")
+        _check_decode(b'', "\n", final=True)
+        _check_decode(b'\r', "\n", final=True)
 
-        self.assertEquals(decoder.decode(b'\r'), u"")
-        self.assertEquals(decoder.decode(b'a'), u"\na")
+        _check_decode(b'\r', "")
+        _check_decode(b'a', "\na")
 
-        self.assertEquals(decoder.decode(b'\r\r\n'), u"\n\n")
-        self.assertEquals(decoder.decode(b'\r'), u"")
-        self.assertEquals(decoder.decode(b'\r'), u"\n")
-        self.assertEquals(decoder.decode(b'\na'), u"\na")
+        _check_decode(b'\r\r\n', "\n\n")
+        _check_decode(b'\r', "")
+        _check_decode(b'\r', "\n")
+        _check_decode(b'\na', "\na")
 
-        self.assertEquals(decoder.decode(b'\xe8\xa2\x88\r\n'), u"\u8888\n")
-        self.assertEquals(decoder.decode(b'\xe8\xa2\x88'), u"\u8888")
-        self.assertEquals(decoder.decode(b'\n'), u"\n")
-        self.assertEquals(decoder.decode(b'\xe8\xa2\x88\r'), u"\u8888")
-        self.assertEquals(decoder.decode(b'\n'), u"\n")
+        _check_decode(b'\xe8\xa2\x88\r\n', "\u8888\n")
+        _check_decode(b'\xe8\xa2\x88', "\u8888")
+        _check_decode(b'\n', "\n")
+        _check_decode(b'\xe8\xa2\x88\r', "\u8888")
+        _check_decode(b'\n', "\n")
 
+    def check_newline_decoder(self, decoder, encoding):
+        result = []
+        encoder = codecs.getincrementalencoder(encoding)()
+        def _decode_bytewise(s):
+            for b in encoder.encode(s):
+                result.append(decoder.decode(b))
+        self.assertEquals(decoder.newlines, None)
+        _decode_bytewise("abc\n\r")
+        self.assertEquals(decoder.newlines, '\n')
+        _decode_bytewise("\nabc")
+        self.assertEquals(decoder.newlines, ('\n', '\r\n'))
+        _decode_bytewise("abc\r")
+        self.assertEquals(decoder.newlines, ('\n', '\r\n'))
+        _decode_bytewise("abc")
+        self.assertEquals(decoder.newlines, ('\r', '\n', '\r\n'))
+        _decode_bytewise("abc\r")
+        self.assertEquals("".join(result), "abc\n\nabcabc\nabcabc")
+        decoder.reset()
+        self.assertEquals(decoder.decode("abc".encode(encoding)), "abc")
+        self.assertEquals(decoder.newlines, None)
+
+    def test_newline_decoder(self):
+        encodings = (
+            'utf-8', 'latin-1',
+            'utf-16', 'utf-16-le', 'utf-16-be',
+            'utf-32', 'utf-32-le', 'utf-32-be',
+        )
+        for enc in encodings:
+            decoder = codecs.getincrementaldecoder(enc)()
+            decoder = io.IncrementalNewlineDecoder(decoder, translate=True)
+            self.check_newline_decoder(decoder, enc)
         decoder = codecs.getincrementaldecoder("utf-8")()
         decoder = io.IncrementalNewlineDecoder(decoder, translate=True)
-        self.assertEquals(decoder.newlines, None)
-        decoder.decode(b"abc\n\r")
-        self.assertEquals(decoder.newlines, u'\n')
-        decoder.decode(b"\nabc")
-        self.assertEquals(decoder.newlines, ('\n', '\r\n'))
-        decoder.decode(b"abc\r")
-        self.assertEquals(decoder.newlines, ('\n', '\r\n'))
-        decoder.decode(b"abc")
-        self.assertEquals(decoder.newlines, ('\r', '\n', '\r\n'))
-        decoder.decode(b"abc\r")
-        decoder.reset()
-        self.assertEquals(decoder.decode(b"abc"), "abc")
-        self.assertEquals(decoder.newlines, None)
+        self.check_newline_decoder_utf8(decoder)
+
 
 # XXX Tests for open()
 
diff --git a/Misc/NEWS b/Misc/NEWS
index ea5ee13e31a..79d4493cbaf 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -74,6 +74,10 @@ Core and Builtins
 Library
 -------
 
+- Issue #4574: fix a crash in io.IncrementalNewlineDecoder when a carriage
+  return encodes to more than one byte in the source encoding (e.g. UTF-16)
+  and gets split on a chunk boundary.
+
 - Issue #4223: inspect.getsource() will now correctly display source code
   for packages loaded via zipimport (or any other conformant PEP 302
   loader). Original patch by Alexander Belopolsky.