Add a wcswidth man page (based on FreeBSD), and fix the implementation

to return -1 in case of an unprintable character.
ok nicm jmc

src/lib/libc/string/Makefile.inc

@@ -1,4 +1,4 @@
-#	$OpenBSD: Makefile.inc,v 1.23 2010/09/24 13:33:00 matthew Exp $
+#	$OpenBSD: Makefile.inc,v 1.24 2011/04/04 18:16:24 stsp Exp $
 
 # string sources
 .PATH: ${LIBCSRCDIR}/arch/${MACHINE_CPU}/string ${LIBCSRCDIR}/string
@@ -144,7 +144,7 @@ MAN+=	bm.3 bcmp.3 bcopy.3 bstring.3 bzero.3 ffs.3 memccpy.3 memchr.3 \
 	strchr.3 strcmp.3 strcoll.3 strcpy.3 strcspn.3 strerror.3 \
 	string.3 strlen.3 strmode.3 strdup.3 strpbrk.3 strrchr.3 strsep.3 \
 	strsignal.3 strspn.3 strstr.3 strtok.3 strxfrm.3 swab.3 strlcpy.3 \
-	wcstok.3 wmemchr.3
+	wcstok.3 wmemchr.3 wcswidth.3
 
 MLINKS+=bm.3 bm_comp.3 bm.3 bm_exec.3 bm.3 bm_free.3
 MLINKS+=memchr.3 memrchr.3

src/lib/libc/string/wcswidth.3

@@ -0,0 +1,60 @@
+.\" $OpenBSD: wcswidth.3,v 1.1 2011/04/04 18:16:24 stsp Exp $
+.\" Copyright (c) 2002 Tim J. Robbins
+.\" 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.
+.\"
+.\"
+.Dd $Mdocdate: April 4 2011 $
+.Dt WCSWIDTH 3
+.Os
+.Sh NAME
+.Nm wcswidth
+.Nd number of column positions in wide-character string
+.Sh SYNOPSIS
+.In wchar.h
+.Ft int
+.Fn wcswidth "const wchar_t *pwcs" "size_t n"
+.Sh DESCRIPTION
+The
+.Fn wcswidth
+function determines the number of column positions required for the first
+.Fa n
+characters of
+.Fa pwcs ,
+or until a null wide character (L'\e0') is encountered.
+.Sh RETURN VALUES
+The
+.Fn wcswidth
+function returns 0 if
+.Fa pwcs
+is an empty string (L""),
+\-1 if a non-printing wide character is encountered,
+otherwise it returns the number of column positions occupied.
+.Sh SEE ALSO
+.Xr iswprint 3 ,
+.Xr wcwidth 3
+.Sh STANDARDS
+The
+.Fn wcswidth
+function conforms to
+.St -p1003.1-2001 .

src/lib/libc/string/wcswidth.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: wcswidth.c,v 1.3 2005/08/08 08:05:37 espie Exp $	*/
+/*	$OpenBSD: wcswidth.c,v 1.4 2011/04/04 18:16:24 stsp Exp $	*/
 /*	$NetBSD: wcswidth.c,v 1.2 2001/01/03 14:29:37 lukem Exp $	*/
 
 /*-
@@ -34,11 +34,14 @@
 int
 wcswidth(const wchar_t *s, size_t n)
 {
-	int w;
+	int w, q;
 
 	w = 0;
 	while (n && *s) {
-		w += wcwidth(*s);
+		q = wcwidth(*s);
+		if (q == -1)
+			return (-1);
+		w += q;
 		s++;
 		n--;
 	}