From 6e1b832a6c0c8f32962a196ab631ccc17471d32b Mon Sep 17 00:00:00 2001
From: Xiang Zhang <angwerzx@126.com>
Date: Tue, 23 May 2017 01:04:27 +0800
Subject: [PATCH] bpo-30003: Fix handling escape characters in HZ codec (#1720)
 (#1556)

---
 Lib/test/test_codecencodings_cn.py |  4 ++++
 Misc/NEWS                          |  3 +++
 Modules/cjkcodecs/_codecs_cn.c     | 27 ++++++++++++++-------------
 3 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/Lib/test/test_codecencodings_cn.py b/Lib/test/test_codecencodings_cn.py
index fdae538973d..a1049373a45 100644
--- a/Lib/test/test_codecencodings_cn.py
+++ b/Lib/test/test_codecencodings_cn.py
@@ -82,6 +82,10 @@ class Test_HZ(test_multibytecodec_support.TestBase, unittest.TestCase):
         (b'ab~cd', 'replace', u'ab\uFFFDd'),
         (b'ab\xffcd', 'replace', u'ab\uFFFDcd'),
         (b'ab~{\x81\x81\x41\x44~}cd', 'replace', u'ab\uFFFD\uFFFD\u804Acd'),
+        # issue 30003
+        (u'ab~cd', 'strict',  b'ab~~cd'), # escape ~
+        (b'~{Dc~~:C~}', 'strict', None),  # ~~ only in ASCII mode
+        (b'~{Dc~\n:C~}', 'strict', None), # ~\n only in ASCII mode
     )
 
 def test_main():
diff --git a/Misc/NEWS b/Misc/NEWS
index 254bb52f977..938a02955a5 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -49,6 +49,9 @@ Extension Modules
 Library
 -------
 
+- bpo-30003: Fix handling escape characters in HZ codec.  Based on patch
+  by Ma Lin.
+
 - bpo-30375: Warnings emitted when compile a regular expression now always
   point to the line in the user code.  Previously they could point into inners
   of the re module if emitted from inside of groups or conditionals.
diff --git a/Modules/cjkcodecs/_codecs_cn.c b/Modules/cjkcodecs/_codecs_cn.c
index 3bc652fefff..92cf06d5ffd 100644
--- a/Modules/cjkcodecs/_codecs_cn.c
+++ b/Modules/cjkcodecs/_codecs_cn.c
@@ -335,15 +335,17 @@ ENCODER(hz)
         DBCHAR code;
 
         if (c < 0x80) {
-            if (state->i == 0) {
-                WRITE1((unsigned char)c)
-                NEXT(1, 1)
-            }
-            else {
-                WRITE3('~', '}', (unsigned char)c)
-                NEXT(1, 3)
+            if (state->i) {
+                WRITE2('~', '}')
+                NEXT_OUT(2)
                 state->i = 0;
             }
+            WRITE1((unsigned char)c)
+            NEXT(1, 1)
+            if (c == '~') {
+                WRITE1('~')
+                NEXT_OUT(1)
+            }
             continue;
         }
 
@@ -390,20 +392,19 @@ DECODER(hz)
             unsigned char c2 = IN2;
 
             REQUIRE_INBUF(2)
-            if (c2 == '~') {
+            if (c2 == '~' && state->i == 0) {
                 WRITE1('~')
-                NEXT(2, 1)
-                continue;
+                NEXT_OUT(1)
             }
             else if (c2 == '{' && state->i == 0)
                 state->i = 1; /* set GB */
+            else if (c2 == '\n' && state->i == 0)
+                ; /* line-continuation */
             else if (c2 == '}' && state->i == 1)
                 state->i = 0; /* set ASCII */
-            else if (c2 == '\n')
-                ; /* line-continuation */
             else
                 return 2;
-            NEXT(2, 0);
+            NEXT_IN(2)
             continue;
         }