/* $OpenBSD: utf8.c,v 1.1 2018/07/29 11:27:15 schwarze Exp $ */
/*
 * Copyright (c) 2018 Ingo Schwarze <schwarze@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <stdlib.h>
#include <wchar.h>

/*
 * Measure the display width of the multibyte string.
 * Treat invalid bytes and non-printable characters as width 1.
 * Truncate the string to a display width of maxwidth.
 * Return the total width, possibly after truncation.
 */
int
mbswidth_truncate(char *mbs, int maxwidth)
{
        wchar_t  wc;
        int      len, width, sum;

        sum = 0;
        while (*mbs != '\0') {
                if ((len = mbtowc(&wc, mbs, MB_CUR_MAX)) == -1)
                        len = width = 1;
                else if ((width = wcwidth(wc)) < 0)
                        width = 1;
                if (sum + width > maxwidth) {
                        *mbs = '\0';
                        break;
                }
                sum += width;
                mbs += len;
        }
        return sum;
}