1 files changed, 35 insertions, 3 deletions

diff --git a/src/lib/libc/string/wcslen.3 b/src/lib/libc/string/wcslen.3
index 12f81763ba..b6d9aafc41 100644
--- a/src/lib/libc/string/wcslen.3
+++ b/src/lib/libc/string/wcslen.3
@@ -1,4 +1,4 @@
-.\"     $OpenBSD: wcslen.3,v 1.3 2013/06/05 03:39:23 tedu Exp $
+.\"     $OpenBSD: wcslen.3,v 1.4 2024/07/14 09:51:18 jca Exp $
 .\"
 .\" Copyright (c) 1990, 1991 The Regents of the University of California.
 .\" All rights reserved.
@@ -31,26 +31,50 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: June 5 2013 $
+.Dd $Mdocdate: July 14 2024 $
 .Dt WCSLEN 3
 .Os
 .Sh NAME
-.Nm wcslen
+.Nm wcslen ,
+.Nm wcsnlen
 .Nd find length of a wide string
 .Sh SYNOPSIS
 .In wchar.h
 .Ft size_t
 .Fn wcslen "const wchar_t *s"
+.Ft size_t
+.Fn wcsnlen "const wchar_t *s" "size_t maxlen"
 .Sh DESCRIPTION
 The
 .Fn wcslen
 function computes the length of the wide string
 .Fa s .
+The
+.Fn wcsnlen
+function computes the length of the wide string
+.Fa s ,
+up to
+.Fa maxlen
+wide characters.
+The
+.Fn wcsnlen
+function will never attempt to address more than
+.Fa maxlen
+wide characters, making it suitable for use with wide character arrays
+that are not guaranteed to be NUL-terminated.
 .Sh RETURN VALUES
 The
 .Fn wcslen
 function returns the number of wide characters that precede the terminating
 null wide character.
+.Pp
+The
+.Fn wcsnlen
+function returns the number of wide characters that precede the terminating
+null wide character
+or
+.Fa maxlen ,
+whichever is smaller.
 .Sh SEE ALSO
 .Xr strlen 3 ,
 .Xr wcswidth 3
@@ -61,6 +85,10 @@ function conforms to
 .St -isoC-99
 and was first introduced in
 .St -isoC-amd1 .
+The
+.Fn wcsnlen
+function conforms to
+.St -p1003.1-2008 .
 .Sh HISTORY
 The
 .Fn wcslen
@@ -68,3 +96,7 @@ function was ported from
 .Nx
 and first appeared in
 .Ox 3.8 .
+The
+.Fn wcsnlen
+function first appeared in
+.Ox 7.6 .