/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1987, 1993
 *      The Regents of the University of California.  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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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 <capsicum_helpers.h>
#include <err.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

/*
 * Default expletive
 */
#define EXP     "y\n"
#define EXPLEN  strlen(EXP)

/*
 * Optimum and maximum buffer size.  The optimum is just a little less
 * than the default value of kern.ipc.pipe_mindirect; writing more than
 * that is significantly slower, but we want to get as close as possible
 * to minimize the number of system calls.  The maximum is enough for a
 * maximal command line plus a newline and terminating NUL.
 */
#define OPTBUF  8190
#define MAXBUF  (ARG_MAX + 2)

int
main(int argc, char **argv)
{
        static char buf[MAXBUF] = EXP;
        char *end = buf + sizeof(buf), *exp, *pos = buf + EXPLEN;
        size_t buflen, explen = EXPLEN;
        ssize_t wlen = 0;

        if (caph_limit_stdio() < 0 || caph_enter() < 0)
                err(1, "capsicum");

        argc -= 1;
        argv += 1;

        /* Assemble the expletive */
        if (argc > 0) {
                /* Copy positional arguments into expletive buffer */
                for (pos = buf, end = buf + sizeof(buf);
                     argc > 0 && pos < end; argc--, argv++) {
                        /* Separate with spaces */
                        if (pos > buf)
                                *pos++ = ' ';
                        exp = *argv;
                        while (*exp != '\0' && pos < end)
                                *pos++ = *exp++;
                }
                /* This should not be possible, but check anyway */
                if (pos > end - 2)
                        pos = end - 2;
                *pos++ = '\n';
                explen = pos - buf;
        }

        /*
         * Double until we're past OPTBUF, then reduce buflen to exactly
         * OPTBUF.  It doesn't matter if that's not a multiple of explen;
         * the modulo operation in the write loop will take care of that.
         */
        for (buflen = explen; buflen < OPTBUF; pos += buflen, buflen += buflen)
                memcpy(pos, buf, buflen);
        if (explen < OPTBUF && buflen > OPTBUF)
                buflen = OPTBUF;

        /* Dump it to stdout */
        end = (pos = buf) + buflen;
        do {
                pos = buf + (pos - buf + wlen) % explen;
                wlen = write(STDOUT_FILENO, pos, end - pos);
        } while (wlen > 0);
        err(1, "stdout");
        /*NOTREACHED*/
}