/*
 * Copyright (c) 2000 Sheldon Hearn <sheldonh@FreeBSD.org>.
 * 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.
 *
 * $FreeBSD: src/usr.bin/truncate/truncate.c,v 1.6.2.1 2000/08/04 08:05:52 sheldonh Exp $
 */

#include <sys/stat.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

static off_t    parselength(char *, off_t *);
static void     usage(void);

static int      no_create;
static int      do_relative;
static int      do_refer;
static int      got_size;

int
main(int argc, char **argv)
{
        struct stat     sb;
        mode_t  omode;
        off_t   oflow, rsize, sz, tsize;
        int     ch, error, fd, oflags;
        char   *fname, *rname;

        rsize = tsize = sz = 0;
        error = 0;
        rname = NULL;
        while ((ch = getopt(argc, argv, "cr:s:")) != -1)
                switch (ch) {
                case 'c':
                        no_create = 1;
                        break;
                case 'r':
                        do_refer = 1;
                        rname = optarg;
                        break;
                case 's':
                        if (parselength(optarg, &sz) == -1)
                                errx(EXIT_FAILURE,
                                    "invalid size argument `%s'", optarg);
                        if (*optarg == '+' || *optarg == '-')
                                do_relative = 1;
                        got_size = 1;
                        break;
                default:
                        usage();
                        /* NOTREACHED */
                }

        argv += optind;
        argc -= optind;

        /*
         * Exactly one of do_refer or got_size must be specified.  Since
         * do_relative implies got_size, do_relative and do_refer are
         * also mutually exclusive.  See usage() for allowed invocations.
         */
        if (do_refer + got_size != 1 || argc < 1)
                usage();
        if (do_refer) {
                if (stat(rname, &sb) == -1)
                        err(EXIT_FAILURE, "%s", rname);
                tsize = sb.st_size;
        } else if (do_relative)
                rsize = sz;
        else
                tsize = sz;

        if (no_create)
                oflags = O_WRONLY;
        else
                oflags = O_WRONLY | O_CREAT;
        omode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;

        while ((fname = *argv++) != NULL) {
                if ((fd = open(fname, oflags, omode)) == -1) {
                        if (errno != ENOENT) {
                                warn("%s", fname);
                                error++;
                        }
                        continue;
                }
                if (do_relative) {
                        if (fstat(fd, &sb) == -1) {
                                warn("%s", fname);
                                error++;
                                continue;
                        }
                        oflow = sb.st_size + rsize;
                        if (oflow < (sb.st_size + rsize)) {
                                errno = EFBIG;
                                warn("%s", fname);
                                error++;
                                continue;
                        }
                        tsize = oflow;
                }
                if (tsize < 0)
                        tsize = 0;

                if (ftruncate(fd, tsize) == -1) {
                        warn("%s", fname);
                        error++;
                        continue;
                }

                close(fd);
        }

        return error ? EXIT_FAILURE : EXIT_SUCCESS;
}

/*
 * Return the numeric value of a string given in the form [+-][0-9]+[GMK]
 * or -1 on format error or overflow.
 */
static off_t
parselength(char *ls, off_t *sz)
{
        off_t   length, oflow;
        int     lsign;

        length = 0;
        lsign = 1;

        switch (*ls) {
        case '-':
                lsign = -1;
                /* FALLTHROUGH */
        case '+':
                ls++;
        }

#define ASSIGN_CHK_OFLOW(x, y)  if (x < y) return -1; y = x
        /*
         * Calculate the value of the decimal digit string, failing
         * on overflow.
         */
        while (isdigit(*ls)) {
                oflow = length * 10 + *ls++ - '0';
                ASSIGN_CHK_OFLOW(oflow, length);
        }

        switch (*ls) {
        case 'T':
                oflow = length * 1024;
                ASSIGN_CHK_OFLOW(oflow, length);
                /* FALLTHROUGH */
        case 'G':
                oflow = length * 1024;
                ASSIGN_CHK_OFLOW(oflow, length);
                /* FALLTHROUGH */
        case 'M':
                oflow = length * 1024;
                ASSIGN_CHK_OFLOW(oflow, length);
                /* FALLTHROUGH */
        case 'K':
                if (ls[1] != '\0')
                        return -1;
                oflow = length * 1024;
                ASSIGN_CHK_OFLOW(oflow, length);
        case '\0':
                break;
        default:
                return -1;
        }

        *sz = length * lsign;
        return 0;
}

static void
usage(void)
{
        fprintf(stderr, "%s\n%s\n",
            "usage: truncate [-c] -s [+|-]size[K|M|G|T] file ...",
            "       truncate [-c] -r rfile file ...");
        exit(EXIT_FAILURE);
}