DIX: Add strncasecmp from FreeBSD, make strcasecmp args const

Add strncasecmp (as we're now using it) in case someone doesn't have it,
and also change strncasecmp args to be const, in accordance with
everything else.
(cherry picked from 11f9e3520249a603b95e64503ee759998ff17feb commit)

2 files changed, 26 insertions, 2 deletions

diff --git a/dix/strcasecmp.c b/dix/strcasecmp.c
index 58f0961e6..8f7c5c402 100644
--- a/dix/strcasecmp.c
+++ b/dix/strcasecmp.c
@@ -33,7 +33,7 @@
 
 #ifdef NEED_STRCASECMP
 int
-xstrcasecmp(char *str1,char *str2)
+xstrcasecmp(const char *str1, const char *str2)
 {
     const u_char *us1 = (const u_char *)str1, *us2 = (const u_char *)str2;
 
@@ -46,3 +46,22 @@ xstrcasecmp(char *str1,char *str2)
     return (tolower(*us1) - tolower(*us2));
 }
 #endif
+
+#ifdef NEED_STRNCASECMP
+int
+xstrncasecmp(const char *s1, const char *s2, size_t n)
+{
+    if (n != 0) {
+        const u_char *us1 = (const u_char *)s1, *us2 = (const u_char *)s2;
+
+        do {
+            if (tolower(*us1) != tolower(*us2++))
+                return (tolower(*us1) - tolower(*--us2));
+            if (*us1++ == '\0')
+                break;
+        } while (--n != 0);
+    }
+
+    return 0;
+}
+#endif
diff --git a/include/dix.h b/include/dix.h
index 0790f5847..a321757e9 100644
--- a/include/dix.h
+++ b/include/dix.h
@@ -556,7 +556,12 @@ typedef struct {
 /* strcasecmp.c */
 #if NEED_STRCASECMP
 #define strcasecmp xstrcasecmp
-extern int xstrcasecmp(char *s1, char *s2);
+extern int xstrcasecmp(const char *s1, const char *s2);
+#endif
+
+#if NEED_STRNCASECMP
+#define strncasecmp xstrncasecmp
+extern int xstrncasecmp(const char *s1, const char *s2, size_t n);
 #endif
 
 /*