From 0bdd959a19ed224f5fa3e18c395b787400400612 Mon Sep 17 00:00:00 2001
From: Xiang Zhang <angwerzx@126.com>
Date: Mon, 22 May 2017 23:07:30 +0800
Subject: [PATCH] bpo-30003: Fix handling escape characters in HZ codec

---
 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 fdae538973d36a..a1049373a450c8 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 254bb52f9778d9..938a02955a5470 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 3bc652fefffb91..92cf06d5ffd353 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;
         }