From b75e44afb38bef99bc932942ff4ba4286b774507 Mon Sep 17 00:00:00 2001
From: default <nobody@localhost>
Date: Thu, 15 Feb 2024 17:44:28 +0100
Subject: Backport from xs.

---
 xs_unicode.h | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

(limited to 'xs_unicode.h')

diff --git a/xs_unicode.h b/xs_unicode.h
index 036c843..47e1101 100644
--- a/xs_unicode.h
+++ b/xs_unicode.h
@@ -5,6 +5,7 @@
 #define _XS_UNICODE_H
 
  int _xs_utf8_enc(char buf[4], unsigned int cpoint);
+ int xs_is_utf8_cont_byte(char c);
  unsigned int xs_utf8_dec(char **str);
  int xs_unicode_width(unsigned int cpoint);
  int xs_is_surrogate(unsigned int cpoint);
@@ -58,6 +59,13 @@ int _xs_utf8_enc(char buf[4], unsigned int cpoint)
 }
 
 
+int xs_is_utf8_cont_byte(char c)
+/* returns true if c is an utf8 continuation byte */
+{
+    return ((c & 0xc0) == 0x80);
+}
+
+
 unsigned int xs_utf8_dec(char **str)
 /* decodes an utf-8 char inside str and updates the pointer */
 {
@@ -86,7 +94,7 @@ unsigned int xs_utf8_dec(char **str)
     }
 
     /* process the continuation bytes */
-    while (cb > 0 && *p && (*p & 0xc0) == 0x80)
+    while (cb > 0 && *p && xs_is_utf8_cont_byte(*p))
         cpoint |= (*p++ & 0x3f) << (--cb * 6);
 
     /* incomplete or broken? */
-- 
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