/*      $OpenBSD: unexpand.c,v 1.13 2016/10/11 16:22:15 millert Exp $   */
/*      $NetBSD: unexpand.c,v 1.5 1994/12/24 17:08:05 cgd Exp $ */

/*-
 * Copyright (c) 1980, 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.
 */

/*
 * unexpand - put tabs into a file replacing blanks
 */
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

char    genbuf[BUFSIZ];
char    linebuf[BUFSIZ];

void tabify(bool);

int
main(int argc, char *argv[])
{
        bool all = false;
        char *cp;

        if (pledge("stdio rpath", NULL) == -1) {
                perror("pledge");
                exit(1);
        }

        argc--, argv++;
        if (argc > 0 && argv[0][0] == '-') {
                if (strcmp(argv[0], "-a") != 0) {
                        fprintf(stderr, "usage: unexpand [-a] [file ...]\n");
                        exit(1);
                }
                all = true;
                argc--, argv++;
        }
        do {
                if (argc > 0) {
                        if (freopen(argv[0], "r", stdin) == NULL) {
                                perror(argv[0]);
                                exit(1);
                        }
                        argc--, argv++;
                }
                while (fgets(genbuf, BUFSIZ, stdin) != NULL) {
                        for (cp = linebuf; *cp; cp++)
                                continue;
                        if (cp > linebuf)
                                cp[-1] = 0;
                        tabify(all);
                        printf("%s", linebuf);
                }
        } while (argc > 0);
        exit(0);
}

void
tabify(bool all)
{
        char *cp, *dp;
        int dcol;
        int ocol;
        size_t len;

        ocol = 0;
        dcol = 0;
        cp = genbuf;
        dp = linebuf;
        len = sizeof linebuf;

        for (;;) {
                switch (*cp) {

                case ' ':
                        dcol++;
                        break;

                case '\t':
                        dcol += 8;
                        dcol &= ~07;
                        break;

                default:
                        while (((ocol + 8) &~ 07) <= dcol) {
                                if (ocol + 1 == dcol)
                                        break;
                                if (len > 1) {
                                        *dp++ = '\t';
                                        len--;
                                }
                                ocol += 8;
                                ocol &= ~07;
                        }
                        while (ocol < dcol) {
                                if (len > 1) {
                                        *dp++ = ' ';
                                        len--;
                                }
                                ocol++;
                        }
                        if (*cp == '\0' || !all) {
                                strlcpy(dp, cp, len);
                                return;
                        }
                        *dp++ = *cp;
                        len--;
                        ocol++;
                        dcol++;
                }
                cp++;
        }
}