From 2ea2ef0609d7e306bf981672cda2e66782ed4db3 Mon Sep 17 00:00:00 2001
From: "jan.nijtmans" <nijtmans@users.sourceforge.net>
Date: Thu, 11 Mar 2021 12:19:14 +0000
Subject: Backport Tcl_UtfCharComplete() functionality from 8.6 for
 TCL_UTF_MAX>3. This makes Tcl_UtfCharComplete() usable to protect
 Tcl_UtfNext() calls for overflow. No change for TCL_UTF_MAX=3 (default build)

---
 generic/tclUtf.c | 19 ++++++++++++++++++-
 tests/utf.test   |  6 +++---
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/generic/tclUtf.c b/generic/tclUtf.c
index 03d0f3a..efbd383 100644
--- a/generic/tclUtf.c
+++ b/generic/tclUtf.c
@@ -76,6 +76,23 @@ static const unsigned char totalBytes[256] = {
     1,1,1,1,1,1,1,1,1,1,1
 };
 
+#if TCL_UTF_MAX > 3
+static const unsigned char complete[256] = {
+    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
+    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
+    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
+    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
+/* Tcl_UtfCharComplete() might point to 2nd byte of valid 4-byte sequence */
+    3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
+    3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
+/* End of "continuation byte section" */
+    2,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
+    3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,4,4,4,4,4,1,1,1,1,1,1,1,1,1,1,1
+};
+#else
+#   define complete totalBytes
+#endif
+
 /*
  * Functions used only in this module.
  */
@@ -492,7 +509,7 @@ Tcl_UtfCharComplete(
 				 * a complete UTF-8 character. */
     int length)			/* Length of above string in bytes. */
 {
-    return length >= totalBytes[UCHAR(*src)];
+    return length >= complete[UCHAR(*src)];
 }
 
 /*
diff --git a/tests/utf.test b/tests/utf.test
index 06ac329..76b6847 100644
--- a/tests/utf.test
+++ b/tests/utf.test
@@ -8,8 +8,8 @@
 # See the file "license.terms" for information on usage and redistribution
 # of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 
-if {[lsearch [namespace children] ::tcltest] == -1} {
-    package require tcltest 2
+if {"::tcltest" ni [namespace children]} {
+    package require tcltest 2.5
     namespace import -force ::tcltest::*
 }
 
@@ -614,7 +614,7 @@ test utf-6.117.1 {Tcl_UtfNext, read limits} {testutfnext testbytestring fullutf}
 test utf-6.118 {Tcl_UtfNext, read limits} {testutfnext testbytestring} {
     testutfnext [testbytestring \xA0]G 0
 } 0
-test utf-6.119 {Tcl_UtfNext, read limits} {testutfnext testbytestring} {
+test utf-6.119 {Tcl_UtfNext, read limits} {testutfnext testbytestring ucs2} {
     testutfnext [testbytestring \xA0]G 1
 } 1
 test utf-6.120 {Tcl_UtfNext, read limits} {testutfnext testbytestring ucs2} {
-- 
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