Add strnlen() function and configure check

Add configure check for strnlen() function and provide our own
implementation for systems that doesn't support it.

Co-Authored-By: Benny Baumann <[email protected]>
Signed-off-by: Kang-Che Sung <[email protected]>

Author: Explorer09

XUtils.c

@@ -224,6 +224,17 @@ size_t String_safeStrncpy(char* restrict dest, const char* restrict src, size_t
    return i;
 }
 
+#ifndef HAVE_STRNLEN
+size_t strnlen(const char* str, size_t maxLen) {
+   for (size_t len = 0; len < maxLen; len++) {
+      if (!str[len]) {
+         return len;
+      }
+   }
+   return maxLen;
+}
+#endif
+
 int xAsprintf(char** strp, const char* fmt, ...) {
    va_list vl;
    va_start(vl, fmt);

XUtils.h

@@ -102,6 +102,10 @@ static inline char* String_strchrnul(const char* s, int c) {
 ATTR_NONNULL ATTR_ACCESS3_W(1, 3) ATTR_ACCESS3_R(2, 3)
 size_t String_safeStrncpy(char* restrict dest, const char* restrict src, size_t size);
 
+#ifndef HAVE_STRNLEN
+size_t strnlen(const char* str, size_t maxLen);
+#endif
+
 ATTR_FORMAT(printf, 2, 3) ATTR_NONNULL_N(1, 2)
 int xAsprintf(char** strp, const char* fmt, ...);
 

configure.ac

@@ -372,6 +372,7 @@ AC_CHECK_FUNCS([ \
     readlinkat \
     sched_getscheduler \
     sched_setscheduler \
+    strnlen \
    ])
 
 # strchrnul is available in macOS since 15.4, but the user may specify an older