Imported Debian patch 1.5-16

[debian/pax] / tar.c

/*      $OpenBSD: tar.c,v 1.13 1998/09/26 21:29:41 millert Exp $        */
/*      $NetBSD: tar.c,v 1.5 1995/03/21 09:07:49 cgd Exp $      */

/*-
 * Copyright (c) 1992 Keith Muller.
 * Copyright (c) 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Keith Muller of the University of California, San Diego.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 */

#ifndef lint
#if 0
static char sccsid[] = "@(#)tar.c       8.2 (Berkeley) 4/18/94";
#else
static char rcsid[] = "$OpenBSD: tar.c,v 1.13 1998/09/26 21:29:41 millert Exp $";
#endif
#endif /* not lint */

#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/param.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include "pax.h"
#include "extern.h"
#include "tar.h"

/*
 * Routines for reading, writing and header identify of various versions of tar
 */

static u_long tar_chksm __P((register char *, register int));
static char *name_split __P((register char *, register int));
static int ul_oct __P((u_long, register char *, register int, int));
#ifndef NET2_STAT
static int uqd_oct __P((u_quad_t, register char *, register int, int));
#endif

/*
 * Routines common to all versions of tar
 */

static int tar_nodir;                   /* do not write dirs under old tar */

/*
 * tar_endwr()
 *      add the tar trailer of two null blocks
 * Return:
 *      0 if ok, -1 otherwise (what wr_skip returns)
 */

#ifdef __STDC__
int
tar_endwr(void)
#else
int
tar_endwr()
#endif
{
        return(wr_skip((off_t)(NULLCNT*BLKMULT)));
}

/*
 * tar_endrd()
 *      no cleanup needed here, just return size of trailer (for append)
 * Return:
 *      size of trailer (2 * BLKMULT)
 */

#ifdef __STDC__
off_t
tar_endrd(void)
#else
off_t
tar_endrd()
#endif
{
        return((off_t)(NULLCNT*BLKMULT));
}

/*
 * tar_trail()
 *      Called to determine if a header block is a valid trailer. We are passed
 *      the block, the in_sync flag (which tells us we are in resync mode;
 *      looking for a valid header), and cnt (which starts at zero) which is
 *      used to count the number of empty blocks we have seen so far.
 * Return:
 *      0 if a valid trailer, -1 if not a valid trailer, or 1 if the block
 *      could never contain a header.
 */

#ifdef __STDC__
int
tar_trail(register char *buf, register int in_resync, register int *cnt)
#else
int
tar_trail(buf, in_resync, cnt)
        register char *buf;
        register int in_resync;
        register int *cnt;
#endif
{
        register int i;

        /*
         * look for all zero, trailer is two consecutive blocks of zero
         */
        for (i = 0; i < BLKMULT; ++i) {
                if (buf[i] != '\0')
                        break;
        }

        /*
         * if not all zero it is not a trailer, but MIGHT be a header.
         */
        if (i != BLKMULT)
                return(-1);

        /*
         * When given a zero block, we must be careful!
         * If we are not in resync mode, check for the trailer. Have to watch
         * out that we do not mis-identify file data as the trailer, so we do
         * NOT try to id a trailer during resync mode. During resync mode we
         * might as well throw this block out since a valid header can NEVER be
         * a block of all 0 (we must have a valid file name).
         */
        if (!in_resync && (++*cnt >= NULLCNT))
                return(0);
        return(1);
}

/*
 * ul_oct()
 *      convert an unsigned long to an octal string. many oddball field
 *      termination characters are used by the various versions of tar in the
 *      different fields. term selects which kind to use. str is '0' padded
 *      at the front to len. we are unable to use only one format as many old
 *      tar readers are very cranky about this.
 * Return:
 *      0 if the number fit into the string, -1 otherwise
 */

#ifdef __STDC__
static int
ul_oct(u_long val, register char *str, register int len, int term)
#else
static int
ul_oct(val, str, len, term)
        u_long val;
        register char *str;
        register int len;
        int term;
#endif
{
        register char *pt;

        /*
         * term selects the appropriate character(s) for the end of the string
         */
        pt = str + len - 1;
        switch(term) {
        case 3:
                *pt-- = '\0';
                break;
        case 2:
                *pt-- = ' ';
                *pt-- = '\0';
                break;
        case 1:
                *pt-- = ' ';
                break;
        case 0:
        default:
                *pt-- = '\0';
                *pt-- = ' ';
                break;
        }

        /*
         * convert and blank pad if there is space
         */
        while (pt >= str) {
                *pt-- = '0' + (char)(val & 0x7);
                if ((val = val >> 3) == (u_long)0)
                        break;
        }

        while (pt >= str)
                *pt-- = '0';
        if (val != (u_long)0)
                return(-1);
        return(0);
}

#ifndef NET2_STAT
/*
 * uqd_oct()
 *      convert an u_quad_t to an octal string. one of many oddball field
 *      termination characters are used by the various versions of tar in the
 *      different fields. term selects which kind to use. str is '0' padded
 *      at the front to len. we are unable to use only one format as many old
 *      tar readers are very cranky about this.
 * Return:
 *      0 if the number fit into the string, -1 otherwise
 */

#ifdef __STDC__
static int
uqd_oct(u_quad_t val, register char *str, register int len, int term)
#else
static int
uqd_oct(val, str, len, term)
        u_quad_t val;
        register char *str;
        register int len;
        int term;
#endif
{
        register char *pt;

        /*
         * term selects the appropriate character(s) for the end of the string
         */
        pt = str + len - 1;
        switch(term) {
        case 3:
                *pt-- = '\0';
                break;
        case 2:
                *pt-- = ' ';
                *pt-- = '\0';
                break;
        case 1:
                *pt-- = ' ';
                break;
        case 0:
        default:
                *pt-- = '\0';
                *pt-- = ' ';
                break;
        }

        /*
         * convert and blank pad if there is space
         */
        while (pt >= str) {
                *pt-- = '0' + (char)(val & 0x7);
                if ((val = val >> 3) == 0)
                        break;
        }

        while (pt >= str)
                *pt-- = '0';
        if (val != (u_quad_t)0)
                return(-1);
        return(0);
}
#endif

/*
 * tar_chksm()
 *      calculate the checksum for a tar block counting the checksum field as
 *      all blanks (BLNKSUM is that value pre-calculated, the sume of 8 blanks).
 *      NOTE: we use len to short circuit summing 0's on write since we ALWAYS
 *      pad headers with 0.
 * Return:
 *      unsigned long checksum
 */

#ifdef __STDC__
static u_long
tar_chksm(register char *blk, register int len)
#else
static u_long
tar_chksm(blk, len)
        register char *blk;
        register int len;
#endif
{
        register char *stop;
        register char *pt;
        u_long chksm = BLNKSUM; /* inital value is checksum field sum */

        /*
         * add the part of the block before the checksum field
         */
        pt = blk;
        stop = blk + CHK_OFFSET;
        while (pt < stop)
                chksm += (u_long)(*pt++ & 0xff);
        /*
         * move past the checksum field and keep going, spec counts the
         * checksum field as the sum of 8 blanks (which is pre-computed as
         * BLNKSUM).
         * ASSUMED: len is greater than CHK_OFFSET. (len is where our 0 padding
         * starts, no point in summing zero's)
         */
        pt += CHK_LEN;
        stop = blk + len;
        while (pt < stop)
                chksm += (u_long)(*pt++ & 0xff);
        return(chksm);
}

/*
 * Routines for old BSD style tar (also made portable to sysV tar)
 */

/*
 * tar_id()
 *      determine if a block given to us is a valid tar header (and not a USTAR
 *      header). We have to be on the lookout for those pesky blocks of all
 *      zero's.
 * Return:
 *      0 if a tar header, -1 otherwise
 */

#ifdef __STDC__
int
tar_id(register char *blk, int size)
#else
int
tar_id(blk, size)
        register char *blk;
        int size;
#endif
{
        register HD_TAR *hd;
        register HD_USTAR *uhd;

        if (size < BLKMULT)
                return(-1);
        hd = (HD_TAR *)blk;
        uhd = (HD_USTAR *)blk;

        /*
         * check for block of zero's first, a simple and fast test, then make
         * sure this is not a ustar header by looking for the ustar magic
         * cookie. We should use TMAGLEN, but some USTAR archive programs are
         * wrong and create archives missing the \0. Last we check the
         * checksum. If this is ok we have to assume it is a valid header.
         */
        if (hd->name[0] == '\0')
                return(-1);
        if (strncmp(uhd->magic, TMAGIC, TMAGLEN - 1) == 0)
                return(-1);
        if (asc_ul(hd->chksum,sizeof(hd->chksum),OCT) != tar_chksm(blk,BLKMULT))
                return(-1);
        return(0);
}

/*
 * tar_opt()
 *      handle tar format specific -o options
 * Return:
 *      0 if ok -1 otherwise
 */

#ifdef __STDC__
int
tar_opt(void)
#else
int
tar_opt()
#endif
{
        OPLIST *opt;

        while ((opt = opt_next()) != NULL) {
                if (strcmp(opt->name, TAR_OPTION) ||
                    strcmp(opt->value, TAR_NODIR)) {
                        paxwarn(1, "Unknown tar format -o option/value pair %s=%s",
                            opt->name, opt->value);
                        paxwarn(1,"%s=%s is the only supported tar format option",
                            TAR_OPTION, TAR_NODIR);
                        return(-1);
                }

                /*
                 * we only support one option, and only when writing
                 */
                if ((act != APPND) && (act != ARCHIVE)) {
                        paxwarn(1, "%s=%s is only supported when writing.",
                            opt->name, opt->value);
                        return(-1);
                }
                tar_nodir = 1;
        }
        return(0);
}


/*
 * tar_rd()
 *      extract the values out of block already determined to be a tar header.
 *      store the values in the ARCHD parameter.
 * Return:
 *      0
 */

#ifdef __STDC__
int
tar_rd(register ARCHD *arcn, register char *buf)
#else
int
tar_rd(arcn, buf)
        register ARCHD *arcn;
        register char *buf;
#endif
{
        register HD_TAR *hd;
        register char *pt;

        /*
         * we only get proper sized buffers passed to us
         */
        if (tar_id(buf, BLKMULT) < 0)
                return(-1);
        arcn->org_name = arcn->name;
        arcn->sb.st_nlink = 1;
        arcn->pat = NULL;

        /*
         * copy out the name and values in the stat buffer
         */
        hd = (HD_TAR *)buf;
        arcn->nlen = l_strncpy(arcn->name, hd->name, sizeof(arcn->name) - 1);
        arcn->name[arcn->nlen] = '\0';
        arcn->sb.st_mode = (mode_t)(asc_ul(hd->mode,sizeof(hd->mode),OCT) &
            0xfff);
        arcn->sb.st_uid = (uid_t)asc_ul(hd->uid, sizeof(hd->uid), OCT);
        arcn->sb.st_gid = (gid_t)asc_ul(hd->gid, sizeof(hd->gid), OCT);
        arcn->sb.st_size = (size_t)asc_ul(hd->size, sizeof(hd->size), OCT);
        arcn->sb.st_mtime = (time_t)asc_ul(hd->mtime, sizeof(hd->mtime), OCT);
        arcn->sb.st_ctime = arcn->sb.st_atime = arcn->sb.st_mtime;

        /*
         * have to look at the last character, it may be a '/' and that is used
         * to encode this as a directory
         */
        pt = &(arcn->name[arcn->nlen - 1]);
        arcn->pad = 0;
        arcn->skip = 0;
        switch(hd->linkflag) {
        case SYMTYPE:
                /*
                 * symbolic link, need to get the link name and set the type in
                 * the st_mode so -v printing will look correct.
                 */
                arcn->type = PAX_SLK;
                arcn->ln_nlen = l_strncpy(arcn->ln_name, hd->linkname,
                        sizeof(arcn->ln_name) - 1);
                arcn->ln_name[arcn->ln_nlen] = '\0';
                arcn->sb.st_mode |= S_IFLNK;
                break;
        case LNKTYPE:
                /*
                 * hard link, need to get the link name, set the type in the
                 * st_mode and st_nlink so -v printing will look better.
                 */
                arcn->type = PAX_HLK;
                arcn->sb.st_nlink = 2;
                arcn->ln_nlen = l_strncpy(arcn->ln_name, hd->linkname,
                        sizeof(arcn->ln_name) - 1);
                arcn->ln_name[arcn->ln_nlen] = '\0';

                /*
                 * no idea of what type this thing really points at, but
                 * we set something for printing only.
                 */
                arcn->sb.st_mode |= S_IFREG;
                break;
        case DIRTYPE:
                /*
                 * It is a directory, set the mode for -v printing
                 */
                arcn->type = PAX_DIR;
                arcn->sb.st_mode |= S_IFDIR;
                arcn->sb.st_nlink = 2;
                arcn->ln_name[0] = '\0';
                arcn->ln_nlen = 0;
                break;
        case AREGTYPE:
        case REGTYPE:
        default:
                /*
                 * If we have a trailing / this is a directory and NOT a file.
                 */
                arcn->ln_name[0] = '\0';
                arcn->ln_nlen = 0;
                if (*pt == '/') {
                        /*
                         * it is a directory, set the mode for -v printing
                         */
                        arcn->type = PAX_DIR;
                        arcn->sb.st_mode |= S_IFDIR;
                        arcn->sb.st_nlink = 2;
                } else {
                        /*
                         * have a file that will be followed by data. Set the
                         * skip value to the size field and caluculate the size
                         * of the padding.
                         */
                        arcn->type = PAX_REG;
                        arcn->sb.st_mode |= S_IFREG;
                        arcn->pad = TAR_PAD(arcn->sb.st_size);
                        arcn->skip = arcn->sb.st_size;
                }
                break;
        }

        /*
         * strip off any trailing slash.
         */
        if (*pt == '/') {
                *pt = '\0'; 
                --arcn->nlen;
        }
        return(0);
}

/*
 * tar_wr()
 *      write a tar header for the file specified in the ARCHD to the archive.
 *      Have to check for file types that cannot be stored and file names that
 *      are too long. Be careful of the term (last arg) to ul_oct, each field
 *      of tar has it own spec for the termination character(s).
 *      ASSUMED: space after header in header block is zero filled
 * Return:
 *      0 if file has data to be written after the header, 1 if file has NO
 *      data to write after the header, -1 if archive write failed
 */

#ifdef __STDC__
int
tar_wr(register ARCHD *arcn)
#else
int
tar_wr(arcn)
        register ARCHD *arcn;
#endif
{
        register HD_TAR *hd;
        int len;
        char hdblk[sizeof(HD_TAR)];

        /*
         * check for those file system types which tar cannot store
         */
        switch(arcn->type) {
        case PAX_DIR:
                /*
                 * user asked that dirs not be written to the archive
                 */
                if (tar_nodir)
                        return(1);
                break;
        case PAX_CHR:
                paxwarn(1, "Tar cannot archive a character device %s",
                    arcn->org_name);
                return(1);
        case PAX_BLK:
                paxwarn(1, "Tar cannot archive a block device %s", arcn->org_name);
                return(1);
        case PAX_SCK:
                paxwarn(1, "Tar cannot archive a socket %s", arcn->org_name);
                return(1);
        case PAX_FIF:
                paxwarn(1, "Tar cannot archive a fifo %s", arcn->org_name);
                return(1);
        case PAX_SLK:
        case PAX_HLK:
        case PAX_HRG:
                if (arcn->ln_nlen > sizeof(hd->linkname)) {
                        paxwarn(1,"Link name too long for tar %s", arcn->ln_name);
                        return(1);
                }
                break;
        case PAX_REG:
        case PAX_CTG:
        default:
                break;
        }

        /*
         * check file name len, remember extra char for dirs (the / at the end)
         */
        len = arcn->nlen;
        if (arcn->type == PAX_DIR)
                ++len;
        if (len >= sizeof(hd->name)) {
                paxwarn(1, "File name too long for tar %s", arcn->name);
                return(1);
        }

        /*
         * copy the data out of the ARCHD into the tar header based on the type
         * of the file. Remember many tar readers want the unused fields to be
         * padded with zero. We set the linkflag field (type), the linkname
         * (or zero if not used),the size, and set the padding (if any) to be
         * added after the file data (0 for all other types, as they only have
         * a header)
         */
        hd = (HD_TAR *)hdblk;
        l_strncpy(hd->name, arcn->name, sizeof(hd->name) - 1);
        hd->name[sizeof(hd->name) - 1] = '\0';
        arcn->pad = 0;

        if (arcn->type == PAX_DIR) {
                /*
                 * directories are the same as files, except have a filename
                 * that ends with a /, we add the slash here. No data follows,
                 * dirs, so no pad.
                 */
                hd->linkflag = AREGTYPE;
                memset(hd->linkname, 0, sizeof(hd->linkname));
                hd->name[len-1] = '/';
                if (ul_oct((u_long)0L, hd->size, sizeof(hd->size), 1))
                        goto out;
        } else if (arcn->type == PAX_SLK) {
                /*
                 * no data follows this file, so no pad
                 */
                hd->linkflag = SYMTYPE;
                l_strncpy(hd->linkname,arcn->ln_name, sizeof(hd->linkname) - 1);
                hd->linkname[sizeof(hd->linkname) - 1] = '\0';
                if (ul_oct((u_long)0L, hd->size, sizeof(hd->size), 1))
                        goto out;
        } else if ((arcn->type == PAX_HLK) || (arcn->type == PAX_HRG)) {
                /*
                 * no data follows this file, so no pad
                 */
                hd->linkflag = LNKTYPE;
                l_strncpy(hd->linkname,arcn->ln_name, sizeof(hd->linkname) - 1);
                hd->linkname[sizeof(hd->linkname) - 1] = '\0';
                if (ul_oct((u_long)0L, hd->size, sizeof(hd->size), 1))
                        goto out;
        } else {
                /*
                 * data follows this file, so set the pad
                 */
                hd->linkflag = AREGTYPE;
                memset(hd->linkname, 0, sizeof(hd->linkname));
#               ifdef NET2_STAT
                if (ul_oct((u_long)arcn->sb.st_size, hd->size,
                    sizeof(hd->size), 1)) {
#               else
                if (uqd_oct((u_quad_t)arcn->sb.st_size, hd->size,
                    sizeof(hd->size), 1)) {
#               endif
                        paxwarn(1,"File is too large for tar %s", arcn->org_name);
                        return(1);
                }
                arcn->pad = TAR_PAD(arcn->sb.st_size);
        }

        /*
         * copy those fields that are independent of the type
         */
        if (ul_oct((u_long)arcn->sb.st_mode, hd->mode, sizeof(hd->mode), 0) ||
            ul_oct((u_long)arcn->sb.st_uid, hd->uid, sizeof(hd->uid), 0) ||
            ul_oct((u_long)arcn->sb.st_gid, hd->gid, sizeof(hd->gid), 0) ||
            ul_oct((u_long)arcn->sb.st_mtime, hd->mtime, sizeof(hd->mtime), 1))
                goto out;

        /*
         * calculate and add the checksum, then write the header. A return of
         * 0 tells the caller to now write the file data, 1 says no data needs
         * to be written
         */
        if (ul_oct(tar_chksm(hdblk, sizeof(HD_TAR)), hd->chksum,
            sizeof(hd->chksum), 3))
                goto out;
        if (wr_rdbuf(hdblk, sizeof(HD_TAR)) < 0)
                return(-1);
        if (wr_skip((off_t)(BLKMULT - sizeof(HD_TAR))) < 0)
                return(-1);
        if ((arcn->type == PAX_CTG) || (arcn->type == PAX_REG))
                return(0);
        return(1);

    out:
        /*
         * header field is out of range
         */
        paxwarn(1, "Tar header field is too small for %s", arcn->org_name);
        return(1);
}

/*
 * Routines for POSIX ustar
 */

/*
 * ustar_strd()
 *      initialization for ustar read
 * Return:
 *      0 if ok, -1 otherwise
 */

#ifdef __STDC__
int
ustar_strd(void)
#else
int
ustar_strd()
#endif
{
        if ((usrtb_start() < 0) || (grptb_start() < 0))
                return(-1);
        return(0);
}

/*
 * ustar_stwr()
 *      initialization for ustar write
 * Return:
 *      0 if ok, -1 otherwise
 */

#ifdef __STDC__
int
ustar_stwr(void)
#else
int
ustar_stwr()
#endif
{
        if ((uidtb_start() < 0) || (gidtb_start() < 0))
                return(-1);
        return(0);
}

/*
 * ustar_id()
 *      determine if a block given to us is a valid ustar header. We have to
 *      be on the lookout for those pesky blocks of all zero's
 * Return:
 *      0 if a ustar header, -1 otherwise
 */

#ifdef __STDC__
int
ustar_id(char *blk, int size)
#else
int
ustar_id(blk, size)
        char *blk;
        int size;
#endif
{
        register HD_USTAR *hd;

        if (size < BLKMULT)
                return(-1);
        hd = (HD_USTAR *)blk;

        /*
         * check for block of zero's first, a simple and fast test then check
         * ustar magic cookie. We should use TMAGLEN, but some USTAR archive
         * programs are fouled up and create archives missing the \0. Last we
         * check the checksum. If ok we have to assume it is a valid header.
         */
        if (hd->name[0] == '\0')
                return(-1);
        if (strncmp(hd->magic, TMAGIC, TMAGLEN - 1) != 0)
                return(-1);
        if (asc_ul(hd->chksum,sizeof(hd->chksum),OCT) != tar_chksm(blk,BLKMULT))
                return(-1);
        return(0);
}

/*
 * ustar_rd()
 *      extract the values out of block already determined to be a ustar header.
 *      store the values in the ARCHD parameter.
 * Return:
 *      0
 */

#ifdef __STDC__
int
ustar_rd(register ARCHD *arcn, register char *buf)
#else
int
ustar_rd(arcn, buf)
        register ARCHD *arcn;
        register char *buf;
#endif
{
        register HD_USTAR *hd;
        register char *dest;
        register int cnt = 0;
        dev_t devmajor;
        dev_t devminor;

        /*
         * we only get proper sized buffers
         */
        if (ustar_id(buf, BLKMULT) < 0)
                return(-1);
        arcn->org_name = arcn->name;
        arcn->sb.st_nlink = 1;
        arcn->pat = NULL;
        arcn->nlen = 0;
        hd = (HD_USTAR *)buf;

        /*
         * see if the filename is split into two parts. if, so joint the parts.
         * we copy the prefix first and add a / between the prefix and name.
         *
         * the length passed to l_strncpy must be the length of the field
         * being copied *from*, since these fields are NOT null terminated
         * when full.  the destination buffer is plenty big enough to hold
         * the longest supported ustar path length, so there's no need
         * to check against that.
         */
        dest = arcn->name;
        if (*(hd->prefix) != '\0') {
                cnt = l_strncpy(dest, hd->prefix, sizeof(hd->prefix));
                dest += cnt;
                *dest++ = '/';
                cnt++;
        }
        arcn->nlen = cnt + l_strncpy(dest, hd->name, sizeof(hd->name));
        arcn->name[arcn->nlen] = '\0';

        /*
         * follow the spec to the letter. we should only have mode bits, strip
         * off all other crud we may be passed.
         */
        arcn->sb.st_mode = (mode_t)(asc_ul(hd->mode, sizeof(hd->mode), OCT) &
            0xfff);
        arcn->sb.st_size = (size_t)asc_ul(hd->size, sizeof(hd->size), OCT);
        arcn->sb.st_mtime = (time_t)asc_ul(hd->mtime, sizeof(hd->mtime), OCT);
        arcn->sb.st_ctime = arcn->sb.st_atime = arcn->sb.st_mtime;

        /*
         * If we can find the ascii names for gname and uname in the password
         * and group files we will use the uid's and gid they bind. Otherwise
         * we use the uid and gid values stored in the header. (This is what
         * the posix spec wants).
         */
        hd->gname[sizeof(hd->gname) - 1] = '\0';
        if (gid_name(hd->gname, &(arcn->sb.st_gid)) < 0)
                arcn->sb.st_gid = (gid_t)asc_ul(hd->gid, sizeof(hd->gid), OCT);
        hd->uname[sizeof(hd->uname) - 1] = '\0';
        if (uid_name(hd->uname, &(arcn->sb.st_uid)) < 0)
                arcn->sb.st_uid = (uid_t)asc_ul(hd->uid, sizeof(hd->uid), OCT);

        /*
         * set the defaults, these may be changed depending on the file type
         */
        arcn->ln_name[0] = '\0';
        arcn->ln_nlen = 0;
        arcn->pad = 0;
        arcn->skip = 0;
        arcn->sb.st_rdev = (dev_t)0;

        /*
         * set the mode and PAX type according to the typeflag in the header
         */
        switch(hd->typeflag) {
        case FIFOTYPE:
                arcn->type = PAX_FIF;
                arcn->sb.st_mode |= S_IFIFO;
                break;
        case DIRTYPE:
                arcn->type = PAX_DIR;
                arcn->sb.st_mode |= S_IFDIR;
                arcn->sb.st_nlink = 2;

                /*
                 * Some programs that create ustar archives append a '/'
                 * to the pathname for directories. This clearly violates
                 * ustar specs, but we will silently strip it off anyway.
                 */
                if (arcn->name[arcn->nlen - 1] == '/')
                        arcn->name[--arcn->nlen] = '\0';
                break;
        case BLKTYPE:
        case CHRTYPE:
                /*
                 * this type requires the rdev field to be set.
                 */
                if (hd->typeflag == BLKTYPE) {
                        arcn->type = PAX_BLK;
                        arcn->sb.st_mode |= S_IFBLK;
                } else {
                        arcn->type = PAX_CHR;
                        arcn->sb.st_mode |= S_IFCHR;
                }
                devmajor = (dev_t)asc_ul(hd->devmajor,sizeof(hd->devmajor),OCT);
                devminor = (dev_t)asc_ul(hd->devminor,sizeof(hd->devminor),OCT);
                arcn->sb.st_rdev = TODEV(devmajor, devminor);
                break;
        case SYMTYPE:
        case LNKTYPE:
                if (hd->typeflag == SYMTYPE) {
                        arcn->type = PAX_SLK;
                        arcn->sb.st_mode |= S_IFLNK;
                } else {
                        arcn->type = PAX_HLK;
                        /*
                         * so printing looks better
                         */
                        arcn->sb.st_mode |= S_IFREG;
                        arcn->sb.st_nlink = 2;
                }
                /*
                 * copy the link name
                 *
                 * see comment above (for hd->name) regarding the length
                 * passed to l_strncpy
                 */
                arcn->ln_nlen = l_strncpy(arcn->ln_name, hd->linkname,
                        sizeof(hd->linkname));
                arcn->ln_name[arcn->ln_nlen] = '\0';
                break;
        case CONTTYPE:
        case AREGTYPE:
        case REGTYPE:
        default:
                /*
                 * these types have file data that follows. Set the skip and
                 * pad fields.
                 */
                arcn->type = PAX_REG;
                arcn->pad = TAR_PAD(arcn->sb.st_size);
                arcn->skip = arcn->sb.st_size;
                arcn->sb.st_mode |= S_IFREG;
                break;
        }
        return(0);
}

/*
 * ustar_wr()
 *      write a ustar header for the file specified in the ARCHD to the archive
 *      Have to check for file types that cannot be stored and file names that
 *      are too long. Be careful of the term (last arg) to ul_oct, we only use
 *      '\0' for the termination character (this is different than picky tar)
 *      ASSUMED: space after header in header block is zero filled
 * Return:
 *      0 if file has data to be written after the header, 1 if file has NO
 *      data to write after the header, -1 if archive write failed
 */

#ifdef __STDC__
int
ustar_wr(register ARCHD *arcn)
#else
int
ustar_wr(arcn)
        register ARCHD *arcn;
#endif
{
        register HD_USTAR *hd;
        register char *pt;
        char hdblk[sizeof(HD_USTAR)];

        /*
         * check for those file system types ustar cannot store
         */
        if (arcn->type == PAX_SCK) {
                paxwarn(1, "Ustar cannot archive a socket %s", arcn->org_name);
                return(1);
        }

        /*
         * check the length of the linkname
         */
        if (((arcn->type == PAX_SLK) || (arcn->type == PAX_HLK) ||
            (arcn->type == PAX_HRG)) && (arcn->ln_nlen > sizeof(hd->linkname))){
                paxwarn(1, "Link name too long for ustar %s", arcn->ln_name);
                return(1);
        }

        /*
         * split the path name into prefix and name fields (if needed). if
         * pt != arcn->name, the name has to be split
         */
        if ((pt = name_split(arcn->name, arcn->nlen)) == NULL) {
                paxwarn(1, "File name too long for ustar %s", arcn->name);
                return(1);
        }
        hd = (HD_USTAR *)hdblk;
        arcn->pad = 0L;

        /*
         * split the name, or zero out the prefix
         */
        if (pt != arcn->name) {
                /*
                 * name was split, pt points at the / where the split is to
                 * occur, we remove the / and copy the first part to the prefix
                 */
                *pt = '\0';
                l_strncpy(hd->prefix, arcn->name, sizeof(hd->prefix));
                *pt++ = '/';
        } else
                memset(hd->prefix, 0, sizeof(hd->prefix));

        /*
         * copy the name part. this may be the whole path or the part after
         * the prefix
         */
        l_strncpy(hd->name, pt, sizeof(hd->name));

        /*
         * set the fields in the header that are type dependent
         */
        switch(arcn->type) {
        case PAX_DIR:
                hd->typeflag = DIRTYPE;
                memset(hd->linkname, 0, sizeof(hd->linkname));
                memset(hd->devmajor, 0, sizeof(hd->devmajor));
                hd->devmajor[0] = '0';
                memset(hd->devminor, 0, sizeof(hd->devminor));
                hd->devminor[0] = '0';
                if (ul_oct((u_long)0L, hd->size, sizeof(hd->size), 3))
                        goto out;
                break;
        case PAX_CHR:
        case PAX_BLK:
                if (arcn->type == PAX_CHR)
                        hd->typeflag = CHRTYPE;
                else
                        hd->typeflag = BLKTYPE;
                memset(hd->linkname, 0, sizeof(hd->linkname));
                if (ul_oct((u_long)MAJOR(arcn->sb.st_rdev), hd->devmajor,
                   sizeof(hd->devmajor), 3) ||
                   ul_oct((u_long)MINOR(arcn->sb.st_rdev), hd->devminor,
                   sizeof(hd->devminor), 3) ||
                   ul_oct((u_long)0L, hd->size, sizeof(hd->size), 3))
                        goto out;
                break;
        case PAX_FIF:
                hd->typeflag = FIFOTYPE;
                memset(hd->linkname, 0, sizeof(hd->linkname));
                memset(hd->devmajor, 0, sizeof(hd->devmajor));
                hd->devmajor[0] = '0';
                memset(hd->devminor, 0, sizeof(hd->devminor));
                hd->devminor[0] = '0';
                if (ul_oct((u_long)0L, hd->size, sizeof(hd->size), 3))
                        goto out;
                break;
        case PAX_SLK:
        case PAX_HLK:
        case PAX_HRG:
                if (arcn->type == PAX_SLK)
                        hd->typeflag = SYMTYPE;
                else
                        hd->typeflag = LNKTYPE;
                l_strncpy(hd->linkname,arcn->ln_name, sizeof(hd->linkname));
                memset(hd->devmajor, 0, sizeof(hd->devmajor));
                hd->devmajor[0] = '0';
                memset(hd->devminor, 0, sizeof(hd->devminor));
                hd->devminor[0] = '0';
                if (ul_oct((u_long)0L, hd->size, sizeof(hd->size), 3))
                        goto out;
                break;
        case PAX_REG:
        case PAX_CTG:
        default:
                /*
                 * file data with this type, set the padding
                 */
                if (arcn->type == PAX_CTG)
                        hd->typeflag = CONTTYPE;
                else
                        hd->typeflag = REGTYPE;
                memset(hd->linkname, 0, sizeof(hd->linkname));
                memset(hd->devmajor, 0, sizeof(hd->devmajor));
                hd->devmajor[0] = '0';
                memset(hd->devminor, 0, sizeof(hd->devminor));
                hd->devminor[0] = '0';
                arcn->pad = TAR_PAD(arcn->sb.st_size);
#               ifdef NET2_STAT
                if (ul_oct((u_long)arcn->sb.st_size, hd->size,
                    sizeof(hd->size), 3)) {
#               else
                if (uqd_oct((u_quad_t)arcn->sb.st_size, hd->size,
                    sizeof(hd->size), 3)) {
#               endif
                        paxwarn(1,"File is too long for ustar %s",arcn->org_name);
                        return(1);
                }
                break;
        }

        l_strncpy(hd->magic, TMAGIC, TMAGLEN);
        l_strncpy(hd->version, TVERSION, TVERSLEN);

        /*
         * set the remaining fields. Some versions want all 16 bits of mode
         * we better humor them (they really do not meet spec though)....
         */
        if (ul_oct((u_long)arcn->sb.st_mode, hd->mode, sizeof(hd->mode), 3) ||
            ul_oct((u_long)arcn->sb.st_uid, hd->uid, sizeof(hd->uid), 3)  ||
            ul_oct((u_long)arcn->sb.st_gid, hd->gid, sizeof(hd->gid), 3) ||
            ul_oct((u_long)arcn->sb.st_mtime,hd->mtime,sizeof(hd->mtime),3))
                goto out;
        l_strncpy(hd->uname,name_uid(arcn->sb.st_uid, 0),sizeof(hd->uname));
        l_strncpy(hd->gname,name_gid(arcn->sb.st_gid, 0),sizeof(hd->gname));

        /*
         * calculate and store the checksum write the header to the archive
         * return 0 tells the caller to now write the file data, 1 says no data
         * needs to be written
         */
        if (ul_oct(tar_chksm(hdblk, sizeof(HD_USTAR)), hd->chksum,
           sizeof(hd->chksum), 3))
                goto out;
        if (wr_rdbuf(hdblk, sizeof(HD_USTAR)) < 0)
                return(-1);
        if (wr_skip((off_t)(BLKMULT - sizeof(HD_USTAR))) < 0)
                return(-1);
        if ((arcn->type == PAX_CTG) || (arcn->type == PAX_REG))
                return(0);
        return(1);

    out:
        /*
         * header field is out of range
         */
        paxwarn(1, "Ustar header field is too small for %s", arcn->org_name);
        return(1);
}

/*
 * name_split()
 *      see if the name has to be split for storage in a ustar header. We try
 *      to fit the entire name in the name field without splitting if we can.
 *      The split point is always at a /
 * Return
 *      character pointer to split point (always the / that is to be removed
 *      if the split is not needed, the points is set to the start of the file
 *      name (it would violate the spec to split there). A NULL is returned if
 *      the file name is too long
 */

#ifdef __STDC__
static char *
name_split(register char *name, register int len)
#else
static char *
name_split(name, len)
        register char *name;
        register int len;
#endif
{
        register char *start;

        /*
         * check to see if the file name is small enough to fit in the name
         * field. if so just return a pointer to the name.
         */
        if (len <= TNMSZ)
                return(name);
        if (len > (TPFSZ + TNMSZ + 1))
                return(NULL);

        /*
         * we start looking at the biggest sized piece that fits in the name
         * field. We walk foward looking for a slash to split at. The idea is
         * to find the biggest piece to fit in the name field (or the smallest
         * prefix we can find) (the -1 is correct the biggest piece would
         * include the slash between the two parts that gets thrown away)
         */
        start = name + len - TNMSZ - 1;
        while ((*start != '\0') && (*start != '/'))
                ++start;

        /*
         * if we hit the end of the string, this name cannot be split, so we
         * cannot store this file.
         */
        if (*start == '\0')
                return(NULL);
        len = start - name;

        /*
         * NOTE: /str where the length of str == TNMSZ can not be stored under
         * the p1003.1-1990 spec for ustar. We could force a prefix of / and
         * the file would then expand on extract to //str. The len == 0 below
         * makes this special case follow the spec to the letter.
         */
        if ((len > TPFSZ) || (len == 0))
                return(NULL);

        /*
         * ok have a split point, return it to the caller
         */
        return(start);
}