Unleashed v1.3

[unleashed.git] / bin / pax / ar_subs.c

/*      $OpenBSD: ar_subs.c,v 1.48 2016/08/26 05:06:14 guenther Exp $   */
/*      $NetBSD: ar_subs.c,v 1.5 1995/03/21 09:07:06 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. 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 <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "pax.h"
#include "extern.h"

static void wr_archive(ARCHD *, int is_app);
static int get_arc(void);
static int next_head(ARCHD *);
extern sigset_t s_mask;

/*
 * Routines which control the overall operation modes of pax as specified by
 * the user: list, append, read ...
 */

static char hdbuf[BLKMULT];             /* space for archive header on read */
u_long flcnt;                           /* number of files processed */

/*
 * list()
 *      list the contents of an archive which match user supplied pattern(s)
 *      (no pattern matches all).
 */

void
list(void)
{
        ARCHD *arcn;
        int res;
        ARCHD archd;
        time_t now;

        arcn = &archd;
        /*
         * figure out archive type; pass any format specific options to the
         * archive option processing routine; call the format init routine. We
         * also save current time for ls_list() so we do not make a system
         * call for each file we need to print. If verbose (vflag) start up
         * the name and group caches.
         */
        if ((get_arc() < 0) || ((*frmt->options)() < 0) ||
            ((*frmt->st_rd)() < 0))
                return;

        now = time(NULL);

        /*
         * step through the archive until the format says it is done
         */
        while (next_head(arcn) == 0) {
                if (arcn->type == PAX_GLL || arcn->type == PAX_GLF) {
                        /*
                         * we need to read, to get the real filename
                         */
                        off_t cnt;
                        if (!rd_wrfile(arcn, arcn->type == PAX_GLF
                            ? -1 : -2, &cnt))
                                (void)rd_skip(cnt + arcn->pad);
                        continue;
                }

                /*
                 * check for pattern, and user specified options match.
                 * When all patterns are matched we are done.
                 */
                if ((res = pat_match(arcn)) < 0)
                        break;

                if ((res == 0) && (sel_chk(arcn) == 0)) {
                        /*
                         * pattern resulted in a selected file
                         */
                        if (pat_sel(arcn) < 0)
                                break;

                        /*
                         * modify the name as requested by the user if name
                         * survives modification, do a listing of the file
                         */
                        if ((res = mod_name(arcn)) < 0)
                                break;
                        if (res == 0)
                                ls_list(arcn, now, stdout);
                }

                /*
                 * skip to next archive format header using values calculated
                 * by the format header read routine
                 */
                if (rd_skip(arcn->skip + arcn->pad) == 1)
                        break;
        }

        /*
         * all done, let format have a chance to cleanup, and make sure that
         * the patterns supplied by the user were all matched
         */
        (void)(*frmt->end_rd)();
        (void)sigprocmask(SIG_BLOCK, &s_mask, NULL);
        ar_close(0);
        pat_chk();
}

static int
cmp_file_times(int mtime_flag, int ctime_flag, ARCHD *arcn, struct stat *sbp)
{
        struct stat sb;

        if (sbp == NULL) {
                if (lstat(arcn->name, &sb) != 0)
                        return (0);
                sbp = &sb;
        }

        if (ctime_flag && mtime_flag)
                return (timespeccmp(&arcn->sb.st_mtim, &sbp->st_mtim, <=) &&
                        timespeccmp(&arcn->sb.st_ctim, &sbp->st_ctim, <=));
        else if (ctime_flag)
                return (timespeccmp(&arcn->sb.st_ctim, &sbp->st_ctim, <=));
        else
                return (timespeccmp(&arcn->sb.st_mtim, &sbp->st_mtim, <=));
}

/*
 * extract()
 *      extract the member(s) of an archive as specified by user supplied
 *      pattern(s) (no patterns extracts all members)
 */

void
extract(void)
{
        ARCHD *arcn;
        int res;
        off_t cnt;
        ARCHD archd;
        int fd;
        time_t now;

        sltab_start();

        arcn = &archd;
        /*
         * figure out archive type; pass any format specific options to the
         * archive option processing routine; call the format init routine;
         * start up the directory modification time and access mode database
         */
        if ((get_arc() < 0) || ((*frmt->options)() < 0) ||
            ((*frmt->st_rd)() < 0) || (dir_start() < 0))
                return;

        /*
         * When we are doing interactive rename, we store the mapping of names
         * so we can fix up hard links files later in the archive.
         */
        if (iflag && (name_start() < 0))
                return;

        now = time(NULL);

        /*
         * step through each entry on the archive until the format read routine
         * says it is done
         */
        while (next_head(arcn) == 0) {
                if (arcn->type == PAX_GLL || arcn->type == PAX_GLF) {
                        /*
                         * we need to read, to get the real filename
                         */
                        if (!rd_wrfile(arcn, arcn->type == PAX_GLF
                            ? -1 : -2, &cnt))
                                (void)rd_skip(cnt + arcn->pad);
                        continue;
                }

                /*
                 * check for pattern, and user specified options match. When
                 * all the patterns are matched we are done
                 */
                if ((res = pat_match(arcn)) < 0)
                        break;

                if ((res > 0) || (sel_chk(arcn) != 0)) {
                        /*
                         * file is not selected. skip past any file data and
                         * padding and go back for the next archive member
                         */
                        (void)rd_skip(arcn->skip + arcn->pad);
                        continue;
                }

                /*
                 * with -u or -D only extract when the archive member is newer
                 * than the file with the same name in the file system (no
                 * test of being the same type is required).
                 * NOTE: this test is done BEFORE name modifications as
                 * specified by pax. this operation can be confusing to the
                 * user who might expect the test to be done on an existing
                 * file AFTER the name mod. In honesty the pax spec is probably
                 * flawed in this respect.
                 */
                if ((uflag || Dflag) &&
                    cmp_file_times(uflag, Dflag, arcn, NULL)) {
                        (void)rd_skip(arcn->skip + arcn->pad);
                        continue;
                }

                /*
                 * this archive member is now been selected. modify the name.
                 */
                if ((pat_sel(arcn) < 0) || ((res = mod_name(arcn)) < 0))
                        break;
                if (res > 0) {
                        /*
                         * a bad name mod, skip and purge name from link table
                         */
                        purg_lnk(arcn);
                        (void)rd_skip(arcn->skip + arcn->pad);
                        continue;
                }

                /*
                 * Non standard -Y and -Z flag. When the existing file is
                 * same age or newer skip
                 */
                if ((Yflag || Zflag) &&
                    cmp_file_times(Yflag, Zflag, arcn, NULL)) {
                        (void)rd_skip(arcn->skip + arcn->pad);
                        continue;
                }

                if (vflag) {
                        if (vflag > 1)
                                ls_list(arcn, now, listf);
                        else {
                                (void)safe_print(arcn->name, listf);
                                vfpart = 1;
                        }
                }

                /*
                 * if required, chdir around.
                 */
                if ((arcn->pat != NULL) && (arcn->pat->chdname != NULL))
                        if (chdir(arcn->pat->chdname) != 0)
                                syswarn(1, errno, "Cannot chdir to %s",
                                    arcn->pat->chdname);

                /*
                 * all ok, extract this member based on type
                 */
                if (!PAX_IS_REG(arcn->type)) {
                        /*
                         * process archive members that are not regular files.
                         * throw out padding and any data that might follow the
                         * header (as determined by the format).
                         */
                        if (PAX_IS_HARDLINK(arcn->type))
                                res = lnk_creat(arcn);
                        else
                                res = node_creat(arcn);

                        (void)rd_skip(arcn->skip + arcn->pad);
                        if (res < 0)
                                purg_lnk(arcn);

                        if (vflag && vfpart) {
                                (void)putc('\n', listf);
                                vfpart = 0;
                        }
                        goto popd;
                }
                /*
                 * we have a file with data here. If we can not create it, skip
                 * over the data and purge the name from hard link table
                 */
                if ((fd = file_creat(arcn)) < 0) {
                        (void)rd_skip(arcn->skip + arcn->pad);
                        purg_lnk(arcn);
                        goto popd;
                }
                /*
                 * extract the file from the archive and skip over padding and
                 * any unprocessed data
                 */
                res = rd_wrfile(arcn, fd, &cnt);
                file_close(arcn, fd);
                if (vflag && vfpart) {
                        (void)putc('\n', listf);
                        vfpart = 0;
                }
                if (!res)
                        (void)rd_skip(cnt + arcn->pad);

popd:
                /*
                 * if required, chdir around.
                 */
                if ((arcn->pat != NULL) && (arcn->pat->chdname != NULL))
                        if (fchdir(cwdfd) != 0)
                                syswarn(1, errno,
                                    "Can't fchdir to starting directory");
        }

        /*
         * all done, restore directory modes and times as required; make sure
         * all patterns supplied by the user were matched; block off signals
         * to avoid chance for multiple entry into the cleanup code.
         */
        (void)(*frmt->end_rd)();
        (void)sigprocmask(SIG_BLOCK, &s_mask, NULL);
        ar_close(0);
        sltab_process(0);
        proc_dir(0);
        pat_chk();
}

/*
 * wr_archive()
 *      Write an archive. used in both creating a new archive and appends on
 *      previously written archive.
 */

static void
wr_archive(ARCHD *arcn, int is_app)
{
        int res;
        int hlk;
        int wr_one;
        off_t cnt;
        int (*wrf)(ARCHD *);
        int fd = -1;
        time_t now;

        /*
         * if this format supports hard link storage, start up the database
         * that detects them.
         */
        if (((hlk = frmt->hlk) == 1) && (lnk_start() < 0))
                return;

        /*
         * if this is not append, and there are no files, we do not write a
         * trailer
         */
        wr_one = is_app;

        /*
         * start up the file traversal code and format specific write
         */
        if (ftree_start() < 0) {
                if (is_app)
                        goto trailer;
                return;
        } else if (((*frmt->st_wr)() < 0))
                return;

        wrf = frmt->wr;

        /*
         * When we are doing interactive rename, we store the mapping of names
         * so we can fix up hard links files later in the archive.
         */
        if (iflag && (name_start() < 0))
                return;

        now = time(NULL);

        /*
         * while there are files to archive, process them one at at time
         */
        while (next_file(arcn) == 0) {
                /*
                 * check if this file meets user specified options match.
                 */
                if (sel_chk(arcn) != 0)
                        continue;
                fd = -1;
                if (uflag) {
                        /*
                         * only archive if this file is newer than a file with
                         * the same name that is already stored on the archive
                         */
                        if ((res = chk_ftime(arcn)) < 0)
                                break;
                        if (res > 0) {
                                ftree_skipped_newer(arcn);
                                continue;
                        }
                }

                /*
                 * this file is considered selected now. see if this is a hard
                 * link to a file already stored
                 */
                ftree_sel(arcn);
                if (hlk && (chk_lnk(arcn) < 0))
                        break;

                if (PAX_IS_REG(arcn->type) || (arcn->type == PAX_HRG)) {
                        /*
                         * we will have to read this file. by opening it now we
                         * can avoid writing a header to the archive for a file
                         * we were later unable to read (we also purge it from
                         * the link table).
                         */
                        if ((fd = open(arcn->org_name, O_RDONLY, 0)) < 0) {
                                syswarn(1,errno, "Unable to open %s to read",
                                        arcn->org_name);
                                purg_lnk(arcn);
                                continue;
                        }
                }

                /*
                 * Now modify the name as requested by the user
                 */
                if ((res = mod_name(arcn)) < 0) {
                        /*
                         * name modification says to skip this file, close the
                         * file and purge link table entry
                         */
                        rdfile_close(arcn, &fd);
                        purg_lnk(arcn);
                        break;
                }

                if ((res > 0) || (docrc && (set_crc(arcn, fd) < 0))) {
                        /*
                         * unable to obtain the crc we need, close the file,
                         * purge link table entry
                         */
                        rdfile_close(arcn, &fd);
                        purg_lnk(arcn);
                        continue;
                }

                if (vflag) {
                        if (vflag > 1)
                                ls_list(arcn, now, listf);
                        else {
                                (void)safe_print(arcn->name, listf);
                                vfpart = 1;
                        }
                }
                ++flcnt;

                /*
                 * looks safe to store the file, have the format specific
                 * routine write routine store the file header on the archive
                 */
                if ((res = (*wrf)(arcn)) < 0) {
                        rdfile_close(arcn, &fd);
                        break;
                }
                wr_one = 1;
                if (res > 0) {
                        /*
                         * format write says no file data needs to be stored
                         * so we are done messing with this file
                         */
                        if (vflag && vfpart) {
                                (void)putc('\n', listf);
                                vfpart = 0;
                        }
                        rdfile_close(arcn, &fd);
                        continue;
                }

                /*
                 * Add file data to the archive, quit on write error. if we
                 * cannot write the entire file contents to the archive we
                 * must pad the archive to replace the missing file data
                 * (otherwise during an extract the file header for the file
                 * which FOLLOWS this one will not be where we expect it to
                 * be).
                 */
                res = wr_rdfile(arcn, fd, &cnt);
                rdfile_close(arcn, &fd);
                if (vflag && vfpart) {
                        (void)putc('\n', listf);
                        vfpart = 0;
                }
                if (res < 0)
                        break;

                /*
                 * pad as required, cnt is number of bytes not written
                 */
                if (((cnt > 0) && (wr_skip(cnt) < 0)) ||
                    ((arcn->pad > 0) && (wr_skip(arcn->pad) < 0)))
                        break;
        }

trailer:
        /*
         * tell format to write trailer; pad to block boundary; reset directory
         * mode/access times, and check if all patterns supplied by the user
         * were matched. block off signals to avoid chance for multiple entry
         * into the cleanup code
         */
        if (wr_one) {
                (*frmt->end_wr)();
                wr_fin();
        }
        (void)sigprocmask(SIG_BLOCK, &s_mask, NULL);
        ar_close(0);
        if (tflag)
                proc_dir(0);
        ftree_chk();
}

/*
 * append()
 *      Add file to previously written archive. Archive format specified by the
 *      user must agree with archive. The archive is read first to collect
 *      modification times (if -u) and locate the archive trailer. The archive
 *      is positioned in front of the record with the trailer and wr_archive()
 *      is called to add the new members.
 *      PAX IMPLEMENTATION DETAIL NOTE:
 *      -u is implemented by adding the new members to the end of the archive.
 *      Care is taken so that these do not end up as links to the older
 *      version of the same file already stored in the archive. It is expected
 *      when extraction occurs these newer versions will over-write the older
 *      ones stored "earlier" in the archive (this may be a bad assumption as
 *      it depends on the implementation of the program doing the extraction).
 *      It is really difficult to splice in members without either re-writing
 *      the entire archive (from the point were the old version was), or having
 *      assistance of the format specification in terms of a special update
 *      header that invalidates a previous archive record. The posix spec left
 *      the method used to implement -u unspecified. This pax is able to
 *      over write existing files that it creates.
 */

void
append(void)
{
        ARCHD *arcn;
        int res;
        ARCHD archd;
        FSUB *orgfrmt;
        int udev;
        off_t tlen;

        arcn = &archd;
        orgfrmt = frmt;

        /*
         * Do not allow an append operation if the actual archive is of a
         * different format than the user specified format.
         */
        if (get_arc() < 0)
                return;
        if ((orgfrmt != NULL) && (orgfrmt != frmt)) {
                paxwarn(1, "Cannot mix current archive format %s with %s",
                    frmt->name, orgfrmt->name);
                return;
        }

        /*
         * pass the format any options and start up format
         */
        if (((*frmt->options)() < 0) || ((*frmt->st_rd)() < 0))
                return;

        /*
         * if we only are adding members that are newer, we need to save the
         * mod times for all files we see.
         */
        if (uflag && (ftime_start() < 0))
                return;

        /*
         * some archive formats encode hard links by recording the device and
         * file serial number (inode) but copy the file anyway (multiple times)
         * to the archive. When we append, we run the risk that newly added
         * files may have the same device and inode numbers as those recorded
         * on the archive but during a previous run. If this happens, when the
         * archive is extracted we get INCORRECT hard links. We avoid this by
         * remapping the device numbers so that newly added files will never
         * use the same device number as one found on the archive. remapping
         * allows new members to safely have links among themselves. remapping
         * also avoids problems with file inode (serial number) truncations
         * when the inode number is larger than storage space in the archive
         * header. See the remap routines for more details.
         */
        if ((udev = frmt->udev) && (dev_start() < 0))
                return;

        /*
         * reading the archive may take a long time. If verbose tell the user
         */
        if (vflag) {
                (void)fprintf(listf,
                        "%s: Reading archive to position at the end...", argv0);
                vfpart = 1;
        }

        /*
         * step through the archive until the format says it is done
         */
        while (next_head(arcn) == 0) {
                /*
                 * check if this file meets user specified options.
                 */
                if (sel_chk(arcn) != 0) {
                        if (rd_skip(arcn->skip + arcn->pad) == 1)
                                break;
                        continue;
                }

                if (uflag) {
                        /*
                         * see if this is the newest version of this file has
                         * already been seen, if so skip.
                         */
                        if ((res = chk_ftime(arcn)) < 0)
                                break;
                        if (res > 0) {
                                if (rd_skip(arcn->skip + arcn->pad) == 1)
                                        break;
                                continue;
                        }
                }

                /*
                 * Store this device number. Device numbers seen during the
                 * read phase of append will cause newly appended files with a
                 * device number seen in the old part of the archive to be
                 * remapped to an unused device number.
                 */
                if ((udev && (add_dev(arcn) < 0)) ||
                    (rd_skip(arcn->skip + arcn->pad) == 1))
                        break;
        }

        /*
         * done, finish up read and get the number of bytes to back up so we
         * can add new members. The format might have used the hard link table,
         * purge it.
         */
        tlen = (*frmt->end_rd)();
        lnk_end();

        /*
         * try to position for write, if this fails quit. if any error occurs,
         * we will refuse to write
         */
        if (appnd_start(tlen) < 0)
                return;

        /*
         * tell the user we are done reading.
         */
        if (vflag && vfpart) {
                (void)fputs("done.\n", listf);
                vfpart = 0;
        }

        /*
         * go to the writing phase to add the new members
         */
        wr_archive(arcn, 1);
}

/*
 * archive()
 *      write a new archive
 */

void
archive(void)
{
        ARCHD archd;

        /*
         * if we only are adding members that are newer, we need to save the
         * mod times for all files; set up for writing; pass the format any
         * options write the archive
         */
        if ((uflag && (ftime_start() < 0)) || (wr_start() < 0))
                return;
        if ((*frmt->options)() < 0)
                return;

        wr_archive(&archd, 0);
}

/*
 * copy()
 *      copy files from one part of the file system to another. this does not
 *      use any archive storage. The EFFECT OF THE COPY IS THE SAME as if an
 *      archive was written and then extracted in the destination directory
 *      (except the files are forced to be under the destination directory).
 */

void
copy(void)
{
        ARCHD *arcn;
        int res;
        int fddest;
        char *dest_pt;
        size_t dlen;
        size_t drem;
        int fdsrc = -1;
        struct stat sb;
        ARCHD archd;
        char dirbuf[PAXPATHLEN+1];

        sltab_start();

        arcn = &archd;
        /*
         * set up the destination dir path and make sure it is a directory. We
         * make sure we have a trailing / on the destination
         */
        dlen = strlcpy(dirbuf, dirptr, sizeof(dirbuf));
        if (dlen >= sizeof(dirbuf) ||
            (dlen == sizeof(dirbuf) - 1 && dirbuf[dlen - 1] != '/')) {
                paxwarn(1, "directory name is too long %s", dirptr);
                return;
        }
        dest_pt = dirbuf + dlen;
        if (*(dest_pt-1) != '/') {
                *dest_pt++ = '/';
                *dest_pt = '\0';
                ++dlen;
        }
        drem = PAXPATHLEN - dlen;

        if (stat(dirptr, &sb) < 0) {
                syswarn(1, errno, "Cannot access destination directory %s",
                        dirptr);
                return;
        }
        if (!S_ISDIR(sb.st_mode)) {
                paxwarn(1, "Destination is not a directory %s", dirptr);
                return;
        }

        /*
         * start up the hard link table; file traversal routines and the
         * modification time and access mode database
         */
        if ((lnk_start() < 0) || (ftree_start() < 0) || (dir_start() < 0))
                return;

        /*
         * When we are doing interactive rename, we store the mapping of names
         * so we can fix up hard links files later in the archive.
         */
        if (iflag && (name_start() < 0))
                return;

        /*
         * set up to cp file trees
         */
        cp_start();

        /*
         * while there are files to archive, process them
         */
        while (next_file(arcn) == 0) {
                fdsrc = -1;

                /*
                 * check if this file meets user specified options
                 */
                if (sel_chk(arcn) != 0)
                        continue;

                /*
                 * if there is already a file in the destination directory with
                 * the same name and it is newer, skip the one stored on the
                 * archive.
                 * NOTE: this test is done BEFORE name modifications as
                 * specified by pax. this can be confusing to the user who
                 * might expect the test to be done on an existing file AFTER
                 * the name mod. In honesty the pax spec is probably flawed in
                 * this respect
                 */
                if (uflag || Dflag) {
                        /*
                         * create the destination name
                         */
                        if (strlcpy(dest_pt, arcn->name + (*arcn->name == '/'),
                            drem + 1) > drem) {
                                paxwarn(1, "Destination pathname too long %s",
                                        arcn->name);
                                continue;
                        }

                        /*
                         * if existing file is same age or newer skip
                         */
                        res = lstat(dirbuf, &sb);
                        *dest_pt = '\0';

                        if (res == 0) {
                                ftree_skipped_newer(arcn);
                                if (cmp_file_times(uflag, Dflag, arcn, &sb))
                                        continue;
                        }
                }

                /*
                 * this file is considered selected. See if this is a hard link
                 * to a previous file; modify the name as requested by the
                 * user; set the final destination.
                 */
                ftree_sel(arcn);
                if ((chk_lnk(arcn) < 0) || ((res = mod_name(arcn)) < 0))
                        break;
                if ((res > 0) || (set_dest(arcn, dirbuf, dlen) < 0)) {
                        /*
                         * skip file, purge from link table
                         */
                        purg_lnk(arcn);
                        continue;
                }

                /*
                 * Non standard -Y and -Z flag. When the existing file is
                 * same age or newer skip
                 */
                if ((Yflag || Zflag) &&
                    cmp_file_times(Yflag, Zflag, arcn, NULL))
                        continue;

                if (vflag) {
                        (void)safe_print(arcn->name, listf);
                        vfpart = 1;
                }
                ++flcnt;

                /*
                 * try to create a hard link to the src file if requested
                 * but make sure we are not trying to overwrite ourselves.
                 */
                if (lflag)
                        res = cross_lnk(arcn);
                else
                        res = chk_same(arcn);
                if (res <= 0) {
                        if (vflag && vfpart) {
                                (void)putc('\n', listf);
                                vfpart = 0;
                        }
                        continue;
                }

                /*
                 * have to create a new file
                 */
                if (!PAX_IS_REG(arcn->type)) {
                        /*
                         * create a link or special file
                         */
                        if (PAX_IS_HARDLINK(arcn->type))
                                res = lnk_creat(arcn);
                        else
                                res = node_creat(arcn);
                        if (res < 0)
                                purg_lnk(arcn);
                        if (vflag && vfpart) {
                                (void)putc('\n', listf);
                                vfpart = 0;
                        }
                        continue;
                }

                /*
                 * have to copy a regular file to the destination directory.
                 * first open source file and then create the destination file
                 */
                if ((fdsrc = open(arcn->org_name, O_RDONLY, 0)) < 0) {
                        syswarn(1, errno, "Unable to open %s to read",
                            arcn->org_name);
                        purg_lnk(arcn);
                        continue;
                }
                if ((fddest = file_creat(arcn)) < 0) {
                        rdfile_close(arcn, &fdsrc);
                        purg_lnk(arcn);
                        continue;
                }

                /*
                 * copy source file data to the destination file
                 */
                cp_file(arcn, fdsrc, fddest);
                file_close(arcn, fddest);
                rdfile_close(arcn, &fdsrc);

                if (vflag && vfpart) {
                        (void)putc('\n', listf);
                        vfpart = 0;
                }
        }

        /*
         * restore directory modes and times as required; make sure all
         * patterns were selected block off signals to avoid chance for
         * multiple entry into the cleanup code.
         */
        (void)sigprocmask(SIG_BLOCK, &s_mask, NULL);
        ar_close(0);
        sltab_process(0);
        proc_dir(0);
        ftree_chk();
}

/*
 * next_head()
 *      try to find a valid header in the archive. Uses format specific
 *      routines to extract the header and id the trailer. Trailers may be
 *      located within a valid header or in an invalid header (the location
 *      is format specific. The inhead field from the option table tells us
 *      where to look for the trailer).
 *      We keep reading (and resyncing) until we get enough contiguous data
 *      to check for a header. If we cannot find one, we shift by a byte
 *      add a new byte from the archive to the end of the buffer and try again.
 *      If we get a read error, we throw out what we have (as we must have
 *      contiguous data) and start over again.
 *      ASSUMED: headers fit within a BLKMULT header.
 * Return:
 *      0 if we got a header, -1 if we are unable to ever find another one
 *      (we reached the end of input, or we reached the limit on retries. see
 *      the specs for rd_wrbuf() for more details)
 */

static int
next_head(ARCHD *arcn)
{
        int ret;
        char *hdend;
        int res;
        int shftsz;
        int hsz;
        int in_resync = 0;              /* set when we are in resync mode */
        int cnt = 0;                    /* counter for trailer function */
        int first = 1;                  /* on 1st read, EOF isn't premature. */

        /*
         * set up initial conditions, we want a whole frmt->hsz block as we
         * have no data yet.
         */
        res = hsz = frmt->hsz;
        hdend = hdbuf;
        shftsz = hsz - 1;
        for (;;) {
                /*
                 * keep looping until we get a contiguous FULL buffer
                 * (frmt->hsz is the proper size)
                 */
                for (;;) {
                        if ((ret = rd_wrbuf(hdend, res)) == res)
                                break;

                        /*
                         * If we read 0 bytes (EOF) from an archive when we
                         * expect to find a header, we have stepped upon
                         * an archive without the customary block of zeroes
                         * end marker.  It's just stupid to error out on
                         * them, so exit gracefully.
                         */
                        if (first && ret == 0)
                                return(-1);
                        first = 0;

                        /*
                         * some kind of archive read problem, try to resync the
                         * storage device, better give the user the bad news.
                         */
                        if ((ret == 0) || (rd_sync() < 0)) {
                                paxwarn(1,"Premature end of file on archive read");
                                return(-1);
                        }
                        if (!in_resync) {
                                if (act == APPND) {
                                        paxwarn(1,
                                          "Archive I/O error, cannot continue");
                                        return(-1);
                                }
                                paxwarn(1,"Archive I/O error. Trying to recover.");
                                ++in_resync;
                        }

                        /*
                         * oh well, throw it all out and start over
                         */
                        res = hsz;
                        hdend = hdbuf;
                }

                /*
                 * ok we have a contiguous buffer of the right size. Call the
                 * format read routine. If this was not a valid header and this
                 * format stores trailers outside of the header, call the
                 * format specific trailer routine to check for a trailer. We
                 * have to watch out that we do not mis-identify file data or
                 * block padding as a header or trailer. Format specific
                 * trailer functions must NOT check for the trailer while we
                 * are running in resync mode. Some trailer functions may tell
                 * us that this block cannot contain a valid header either, so
                 * we then throw out the entire block and start over.
                 */
                if ((*frmt->rd)(arcn, hdbuf) == 0)
                        break;

                if (!frmt->inhead) {
                        /*
                         * this format has trailers outside of valid headers
                         */
                        if ((ret = (*frmt->trail)(arcn,hdbuf,in_resync,&cnt)) == 0){
                                /*
                                 * valid trailer found, drain input as required
                                 */
                                ar_drain();
                                return(-1);
                        }

                        if (ret == 1) {
                                /*
                                 * we are in resync and we were told to throw
                                 * the whole block out because none of the
                                 * bytes in this block can be used to form a
                                 * valid header
                                 */
                                res = hsz;
                                hdend = hdbuf;
                                continue;
                        }
                }

                /*
                 * Brute force section.
                 * not a valid header. We may be able to find a header yet. So
                 * we shift over by one byte, and set up to read one byte at a
                 * time from the archive and place it at the end of the buffer.
                 * We will keep moving byte at a time until we find a header or
                 * get a read error and have to start over.
                 */
                if (!in_resync) {
                        if (act == APPND) {
                                paxwarn(1,"Unable to append, archive header flaw");
                                return(-1);
                        }
                        paxwarn(1,"Invalid header, starting valid header search.");
                        ++in_resync;
                }
                memmove(hdbuf, hdbuf+1, shftsz);
                res = 1;
                hdend = hdbuf + shftsz;
        }

        /*
         * ok got a valid header, check for trailer if format encodes it in the
         * the header. NOTE: the parameters are different than trailer routines
         * which encode trailers outside of the header!
         */
        if (frmt->inhead && ((*frmt->trail)(arcn,NULL,0,NULL) == 0)) {
                /*
                 * valid trailer found, drain input as required
                 */
                ar_drain();
                return(-1);
        }

        ++flcnt;
        return(0);
}

/*
 * get_arc()
 *      Figure out what format an archive is. Handles archive with flaws by
 *      brute force searches for a legal header in any supported format. The
 *      format id routines have to be careful to NOT mis-identify a format.
 *      ASSUMED: headers fit within a BLKMULT header.
 * Return:
 *      0 if archive found -1 otherwise
 */

static int
get_arc(void)
{
        int i;
        int hdsz = 0;
        int res;
        int minhd = BLKMULT;
        char *hdend;
        int notice = 0;

        /*
         * find the smallest header size in all archive formats and then set up
         * to read the archive.
         */
        for (i = 0; ford[i] >= 0; ++i) {
                if (fsub[ford[i]].name != NULL && fsub[ford[i]].hsz < minhd)
                        minhd = fsub[ford[i]].hsz;
        }
        if (rd_start() < 0)
                return(-1);
        res = BLKMULT;
        hdsz = 0;
        hdend = hdbuf;
        for (;;) {
                for (;;) {
                        /*
                         * fill the buffer with at least the smallest header
                         */
                        i = rd_wrbuf(hdend, res);
                        if (i > 0)
                                hdsz += i;
                        if (hdsz >= minhd)
                                break;

                        /*
                         * if we cannot recover from a read error quit
                         */
                        if ((i == 0) || (rd_sync() < 0))
                                goto out;

                        /*
                         * when we get an error none of the data we already
                         * have can be used to create a legal header (we just
                         * got an error in the middle), so we throw it all out
                         * and refill the buffer with fresh data.
                         */
                        res = BLKMULT;
                        hdsz = 0;
                        hdend = hdbuf;
                        if (!notice) {
                                if (act == APPND)
                                        return(-1);
                                paxwarn(1,"Cannot identify format. Searching...");
                                ++notice;
                        }
                }

                /*
                 * we have at least the size of the smallest header in any
                 * archive format. Look to see if we have a match. The array
                 * ford[] is used to specify the header id order to reduce the
                 * chance of incorrectly id'ing a valid header (some formats
                 * may be subsets of each other and the order would then be
                 * important).
                 */
                for (i = 0; ford[i] >= 0; ++i) {
                        if (fsub[ford[i]].id == NULL ||
                            (*fsub[ford[i]].id)(hdbuf, hdsz) < 0)
                                continue;
                        frmt = &(fsub[ford[i]]);
                        /*
                         * yuck, to avoid slow special case code in the extract
                         * routines, just push this header back as if it was
                         * not seen. We have left extra space at start of the
                         * buffer for this purpose. This is a bit ugly, but
                         * adding all the special case code is far worse.
                         */
                        pback(hdbuf, hdsz);
                        return(0);
                }

                /*
                 * We have a flawed archive, no match. we start searching, but
                 * we never allow additions to flawed archives
                 */
                if (!notice) {
                        if (act == APPND)
                                return(-1);
                        paxwarn(1, "Cannot identify format. Searching...");
                        ++notice;
                }

                /*
                 * brute force search for a header that we can id.
                 * we shift through byte at a time. this is slow, but we cannot
                 * determine the nature of the flaw in the archive in a
                 * portable manner
                 */
                if (--hdsz > 0) {
                        memmove(hdbuf, hdbuf+1, hdsz);
                        res = BLKMULT - hdsz;
                        hdend = hdbuf + hdsz;
                } else {
                        res = BLKMULT;
                        hdend = hdbuf;
                        hdsz = 0;
                }
        }

    out:
        /*
         * we cannot find a header, bow, apologize and quit
         */
        paxwarn(1, "Sorry, unable to determine archive format.");
        return(-1);
}