add wcsnlen()

wcsnlen() is strnlen()'s counterpart for wide-character strings. both
were added to ieee std 1003.1 in issue 7.

from freebsd

XXX documentation missing!

include/wchar.h

@@ -154,6 +154,7 @@ int wcsncasecmp(const wchar_t *, const wchar_t *, size_t);
 
 size_t mbsnrtowcs(wchar_t * __restrict, const char ** __restrict, size_t,
     size_t, mbstate_t * __restrict);
+size_t  wcsnlen(const wchar_t *, size_t);
 size_t wcsnrtombs(char * __restrict, const wchar_t ** __restrict, size_t,
     size_t, mbstate_t * __restrict);
 #endif

lib/libc/string/Makefile.inc

@@ -11,7 +11,7 @@ SRCS+=	explicit_bzero.c memccpy.c memmem.c memrchr.c stpcpy.c stpncpy.c \
 	wcslcpy.c wcslen.c wcsncat.c wcsncmp.c wcsncpy.c wcspbrk.c wcsrchr.c \
 	wcsspn.c wcsstr.c wcstok.c wcswcs.c wcswidth.c wcsxfrm.c wmemchr.c \
 	wmemcmp.c wmemcpy.c wmemmove.c wmemset.c wcsdup.c \
-	timingsafe_bcmp.c wcscasecmp.c wcsncasecmp.c
+	timingsafe_bcmp.c wcscasecmp.c wcsncasecmp.c wcsnlen.c
 
 # machine-dependent net sources
 # m-d Makefile.inc must include sources for:

lib/libc/string/wcsnlen.c

@@ -0,0 +1,39 @@
+/*-
+ * Copyright (c) 2009 David Schultz <das@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <wchar.h>
+
+size_t
+wcsnlen(const wchar_t *s, size_t maxlen)
+{
+	size_t len;
+
+	for (len = 0; len < maxlen; len++, s++) {
+		if (!*s)
+			break;
+	}
+	return (len);
+}