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ar_io.c

/*    $OpenBSD: ar_io.c,v 1.38 2008/06/11 00:49:08 pvalchev Exp $ */
/*    $NetBSD: ar_io.c,v 1.5 1996/03/26 23:54:13 mrg 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.
 */

#ifndef lint
#if 0
static const char sccsid[] = "@(#)ar_io.c 8.2 (Berkeley) 4/18/94";
#else
static const char rcsid[] = "$OpenBSD: ar_io.c,v 1.38 2008/06/11 00:49:08 pvalchev Exp $";
#endif
#endif /* not lint */

#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/mtio.h>
#include <sys/param.h>
#include <sys/wait.h>
#include <signal.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <err.h>
#include "pax.h"
#include "options.h"
#include "extern.h"

/*
 * Routines which deal directly with the archive I/O device/file.
 */

#define DMOD            0666        /* default mode of created archives */
#define EXT_MODE  O_RDONLY    /* open mode for list/extract */
#define AR_MODE         (O_WRONLY | O_CREAT | O_TRUNC)      /* mode for archive */
#define APP_MODE  O_RDWR            /* mode for append */
#define STDO            "<STDOUT>"  /* pseudo name for stdout */
#define STDN            "<STDIN>"   /* pseudo name for stdin */
static int arfd = -1;               /* archive file descriptor */
static int artyp = ISREG;           /* archive type: file/FIFO/tape */
static int arvol = 1;               /* archive volume number */
static int lstrval = -1;            /* return value from last i/o */
static int io_ok;             /* i/o worked on volume after resync */
static int did_io;                  /* did i/o ever occur on volume? */
static int done;              /* set via tty termination */
static struct stat arsb;            /* stat of archive device at open */
static int invld_rec;               /* tape has out of spec record size */
static int wr_trail = 1;            /* trailer was rewritten in append */
static int can_unlnk = 0;           /* do we unlink null archives?  */
const char *arcname;                /* printable name of archive */
const char *gzip_program;           /* name of gzip program */
static pid_t zpid = -1;             /* pid of child process */
int force_one_volume;               /* 1 if we ignore volume changes */

static int get_phys(void);
extern sigset_t s_mask;
static void ar_start_gzip(int, const char *, int);

/*
 * ar_open()
 *    Opens the next archive volume. Determines the type of the device and
 *    sets up block sizes as required by the archive device and the format.
 *    Note: we may be called with name == NULL on the first open only.
 * Return:
 *    -1 on failure, 0 otherwise
 */

int
ar_open(const char *name)
{
      struct mtget mb;

      if (arfd != -1)
            (void)close(arfd);
      arfd = -1;
      can_unlnk = did_io = io_ok = invld_rec = 0;
      artyp = ISREG;
      flcnt = 0;

      /*
       * open based on overall operation mode
       */
      switch (act) {
      case LIST:
      case EXTRACT:
            if (name == NULL) {
                  arfd = STDIN_FILENO;
                  arcname = STDN;
            } else if ((arfd = open(name, EXT_MODE, DMOD)) < 0)
                  syswarn(1, errno, "Failed open to read on %s", name);
            if (arfd != -1 && gzip_program != NULL)
                  ar_start_gzip(arfd, gzip_program, 0);
            break;
      case ARCHIVE:
            if (name == NULL) {
                  arfd = STDOUT_FILENO;
                  arcname = STDO;
            } else if ((arfd = open(name, AR_MODE, DMOD)) < 0)
                  syswarn(1, errno, "Failed open to write on %s", name);
            else
                  can_unlnk = 1;
            if (arfd != -1 && gzip_program != NULL)
                  ar_start_gzip(arfd, gzip_program, 1);
            break;
      case APPND:
            if (name == NULL) {
                  arfd = STDOUT_FILENO;
                  arcname = STDO;
            } else if ((arfd = open(name, APP_MODE, DMOD)) < 0)
                  syswarn(1, errno, "Failed open to read/write on %s",
                        name);
            break;
      case COPY:
            /*
             * arfd not used in COPY mode
             */
            arcname = "<NONE>";
            lstrval = 1;
            return(0);
      }
      if (arfd < 0)
            return(-1);

      if (chdname != NULL)
            if (chdir(chdname) != 0) {
                  syswarn(1, errno, "Failed chdir to %s", chdname);
                  return(-1);
            }
      /*
       * set up is based on device type
       */
      if (fstat(arfd, &arsb) < 0) {
            syswarn(1, errno, "Failed stat on %s", arcname);
            (void)close(arfd);
            arfd = -1;
            can_unlnk = 0;
            return(-1);
      }
      if (S_ISDIR(arsb.st_mode)) {
            paxwarn(0, "Cannot write an archive on top of a directory %s",
                arcname);
            (void)close(arfd);
            arfd = -1;
            can_unlnk = 0;
            return(-1);
      }

      if (S_ISCHR(arsb.st_mode))
            artyp = ioctl(arfd, MTIOCGET, &mb) ? ISCHR : ISTAPE;
      else if (S_ISBLK(arsb.st_mode))
            artyp = ISBLK;
      else if ((lseek(arfd, (off_t)0L, SEEK_CUR) == -1) && (errno == ESPIPE))
            artyp = ISPIPE;
      else
            artyp = ISREG;

      /*
       * make sure we beyond any doubt that we only can unlink regular files
       * we created
       */
      if (artyp != ISREG)
            can_unlnk = 0;
      /*
       * if we are writing, we are done
       */
      if (act == ARCHIVE) {
            blksz = rdblksz = wrblksz;
            lstrval = 1;
            return(0);
      }

      /*
       * set default blksz on read. APPNDs writes rdblksz on the last volume
       * On all new archive volumes, we shift to wrblksz (if the user
       * specified one, otherwise we will continue to use rdblksz). We
       * must set blocksize based on what kind of device the archive is
       * stored.
       */
      switch (artyp) {
      case ISTAPE:
            /*
             * Tape drives come in at least two flavors. Those that support
             * variable sized records and those that have fixed sized
             * records. They must be treated differently. For tape drives
             * that support variable sized records, we must make large
             * reads to make sure we get the entire record, otherwise we
             * will just get the first part of the record (up to size we
             * asked). Tapes with fixed sized records may or may not return
             * multiple records in a single read. We really do not care
             * what the physical record size is UNLESS we are going to
             * append. (We will need the physical block size to rewrite
             * the trailer). Only when we are appending do we go to the
             * effort to figure out the true PHYSICAL record size.
             */
            blksz = rdblksz = MAXBLK;
            break;
      case ISPIPE:
      case ISBLK:
      case ISCHR:
            /*
             * Blocksize is not a major issue with these devices (but must
             * be kept a multiple of 512). If the user specified a write
             * block size, we use that to read. Under append, we must
             * always keep blksz == rdblksz. Otherwise we go ahead and use
             * the device optimal blocksize as (and if) returned by stat
             * and if it is within pax specs.
             */
            if ((act == APPND) && wrblksz) {
                  blksz = rdblksz = wrblksz;
                  break;
            }

            if ((arsb.st_blksize > 0) && (arsb.st_blksize < MAXBLK) &&
                ((arsb.st_blksize % BLKMULT) == 0))
                  rdblksz = arsb.st_blksize;
            else
                  rdblksz = DEVBLK;
            /*
             * For performance go for large reads when we can without harm
             */
            if ((act == APPND) || (artyp == ISCHR))
                  blksz = rdblksz;
            else
                  blksz = MAXBLK;
            break;
      case ISREG:
            /*
             * if the user specified wrblksz works, use it. Under appends
             * we must always keep blksz == rdblksz
             */
            if ((act == APPND) && wrblksz && ((arsb.st_size%wrblksz)==0)){
                  blksz = rdblksz = wrblksz;
                  break;
            }
            /*
             * See if we can find the blocking factor from the file size
             */
            for (rdblksz = MAXBLK; rdblksz > 0; rdblksz -= BLKMULT)
                  if ((arsb.st_size % rdblksz) == 0)
                        break;
            /*
             * When we cannot find a match, we may have a flawed archive.
             */
            if (rdblksz <= 0)
                  rdblksz = FILEBLK;
            /*
             * for performance go for large reads when we can
             */
            if (act == APPND)
                  blksz = rdblksz;
            else
                  blksz = MAXBLK;
            break;
      default:
            /*
             * should never happen, worst case, slow...
             */
            blksz = rdblksz = BLKMULT;
            break;
      }
      lstrval = 1;
      return(0);
}

/*
 * ar_close()
 *    closes archive device, increments volume number, and prints i/o summary
 */
void
ar_close(void)
{
      int status;

      if (arfd < 0) {
            did_io = io_ok = flcnt = 0;
            return;
      }

      /*
       * Close archive file. This may take a LONG while on tapes (we may be
       * forced to wait for the rewind to complete) so tell the user what is
       * going on (this avoids the user hitting control-c thinking pax is
       * broken).
       */
      if (vflag && (artyp == ISTAPE)) {
            if (vfpart)
                  (void)putc('\n', listf);
            (void)fprintf(listf,
                  "%s: Waiting for tape drive close to complete...",
                  argv0);
            (void)fflush(listf);
      }

      /*
       * if nothing was written to the archive (and we created it), we remove
       * it
       */
      if (can_unlnk && (fstat(arfd, &arsb) == 0) && (S_ISREG(arsb.st_mode)) &&
          (arsb.st_size == 0)) {
            (void)unlink(arcname);
            can_unlnk = 0;
      }

      /*
       * for a quick extract/list, pax frequently exits before the child
       * process is done
       */
      if ((act == LIST || act == EXTRACT) && nflag && zpid > 0)
            kill(zpid, SIGINT);

      (void)close(arfd);

      /* Do not exit before child to ensure data integrity */
      if (zpid > 0)
            waitpid(zpid, &status, 0);

      if (vflag && (artyp == ISTAPE)) {
            (void)fputs("done.\n", listf);
            vfpart = 0;
            (void)fflush(listf);
      }
      arfd = -1;

      if (!io_ok && !did_io) {
            flcnt = 0;
            return;
      }
      did_io = io_ok = 0;

      /*
       * The volume number is only increased when the last device has data
       * and we have already determined the archive format.
       */
      if (frmt != NULL)
            ++arvol;

      if (!vflag) {
            flcnt = 0;
            return;
      }

      /*
       * Print out a summary of I/O for this archive volume.
       */
      if (vfpart) {
            (void)putc('\n', listf);
            vfpart = 0;
      }

      /*
       * If we have not determined the format yet, we just say how many bytes
       * we have skipped over looking for a header to id. there is no way we
       * could have written anything yet.
       */
      if (frmt == NULL) {
#     ifdef LONG_OFF_T
            (void)fprintf(listf, "%s: unknown format, %lu bytes skipped.\n",
#     else
            (void)fprintf(listf, "%s: unknown format, %qu bytes skipped.\n",
#     endif
                argv0, rdcnt);
            (void)fflush(listf);
            flcnt = 0;
            return;
      }

      if (strcmp(NM_CPIO, argv0) == 0)
            (void)fprintf(listf, "%qu blocks\n", (rdcnt ? rdcnt : wrcnt) / 5120);
      else if (strcmp(NM_TAR, argv0) != 0)
            (void)fprintf(listf,
#     ifdef LONG_OFF_T
                "%s: %s vol %d, %lu files, %lu bytes read, %lu bytes written.\n",
#     else
                "%s: %s vol %d, %lu files, %qu bytes read, %qu bytes written.\n",
#     endif
                argv0, frmt->name, arvol-1, flcnt, rdcnt, wrcnt);
      (void)fflush(listf);
      flcnt = 0;
}

/*
 * ar_drain()
 *    drain any archive format independent padding from an archive read
 *    from a socket or a pipe. This is to prevent the process on the
 *    other side of the pipe from getting a SIGPIPE (pax will stop
 *    reading an archive once a format dependent trailer is detected).
 */
void
ar_drain(void)
{
      int res;
      char drbuf[MAXBLK];

      /*
       * we only drain from a pipe/socket. Other devices can be closed
       * without reading up to end of file. We sure hope that pipe is closed
       * on the other side so we will get an EOF.
       */
      if ((artyp != ISPIPE) || (lstrval <= 0))
            return;

      /*
       * keep reading until pipe is drained
       */
      while ((res = read(arfd, drbuf, sizeof(drbuf))) > 0)
            ;
      lstrval = res;
}

/*
 * ar_set_wr()
 *    Set up device right before switching from read to write in an append.
 *    device dependent code (if required) to do this should be added here.
 *    For all archive devices we are already positioned at the place we want
 *    to start writing when this routine is called.
 * Return:
 *    0 if all ready to write, -1 otherwise
 */

int
ar_set_wr(void)
{
      off_t cpos;

      /*
       * we must make sure the trailer is rewritten on append, ar_next()
       * will stop us if the archive containing the trailer was not written
       */
      wr_trail = 0;

      /*
       * Add any device dependent code as required here
       */
      if (artyp != ISREG)
            return(0);
      /*
       * Ok we have an archive in a regular file. If we were rewriting a
       * file, we must get rid of all the stuff after the current offset
       * (it was not written by pax).
       */
      if (((cpos = lseek(arfd, (off_t)0L, SEEK_CUR)) < 0) ||
          (ftruncate(arfd, cpos) < 0)) {
            syswarn(1, errno, "Unable to truncate archive file");
            return(-1);
      }
      return(0);
}

/*
 * ar_app_ok()
 *    check if the last volume in the archive allows appends. We cannot check
 *    this until we are ready to write since there is no spec that says all
 *    volumes in a single archive have to be of the same type...
 * Return:
 *    0 if we can append, -1 otherwise.
 */

int
ar_app_ok(void)
{
      if (artyp == ISPIPE) {
            paxwarn(1, "Cannot append to an archive obtained from a pipe.");
            return(-1);
      }

      if (!invld_rec)
            return(0);
      paxwarn(1,"Cannot append, device record size %d does not support %s spec",
            rdblksz, argv0);
      return(-1);
}

/*
 * ar_read()
 *    read up to a specified number of bytes from the archive into the
 *    supplied buffer. When dealing with tapes we may not always be able to
 *    read what we want.
 * Return:
 *    Number of bytes in buffer. 0 for end of file, -1 for a read error.
 */

int
ar_read(char *buf, int cnt)
{
      int res = 0;

      /*
       * if last i/o was in error, no more reads until reset or new volume
       */
      if (lstrval <= 0)
            return(lstrval);

      /*
       * how we read must be based on device type
       */
      switch (artyp) {
      case ISTAPE:
            if ((res = read(arfd, buf, cnt)) > 0) {
                  /*
                   * CAUTION: tape systems may not always return the same
                   * sized records so we leave blksz == MAXBLK. The
                   * physical record size that a tape drive supports is
                   * very hard to determine in a uniform and portable
                   * manner.
                   */
                  io_ok = 1;
                  if (res != rdblksz) {
                        /*
                         * Record size changed. If this happens on
                         * any record after the first, we probably have
                         * a tape drive which has a fixed record size
                         * (we are getting multiple records in a single
                         * read). Watch out for record blocking that
                         * violates pax spec (must be a multiple of
                         * BLKMULT).
                         */
                        rdblksz = res;
                        if (rdblksz % BLKMULT)
                              invld_rec = 1;
                  }
                  return(res);
            }
            break;
      case ISREG:
      case ISBLK:
      case ISCHR:
      case ISPIPE:
      default:
            /*
             * Files are so easy to deal with. These other things cannot
             * be trusted at all. So when we are dealing with character
             * devices and pipes we just take what they have ready for us
             * and return. Trying to do anything else with them runs the
             * risk of failure.
             */
            if ((res = read(arfd, buf, cnt)) > 0) {
                  io_ok = 1;
                  return(res);
            }
            break;
      }

      /*
       * We are in trouble at this point, something is broken...
       */
      lstrval = res;
      if (res < 0)
            syswarn(1, errno, "Failed read on archive volume %d", arvol);
      else
            paxwarn(0, "End of archive volume %d reached", arvol);
      return(res);
}

/*
 * ar_write()
 *    Write a specified number of bytes in supplied buffer to the archive
 *    device so it appears as a single "block". Deals with errors and tries
 *    to recover when faced with short writes.
 * Return:
 *    Number of bytes written. 0 indicates end of volume reached and with no
 *    flaws (as best that can be detected). A -1 indicates an unrecoverable
 *    error in the archive occurred.
 */

int
ar_write(char *buf, int bsz)
{
      int res;
      off_t cpos;

      /*
       * do not allow pax to create a "bad" archive. Once a write fails on
       * an archive volume prevent further writes to it.
       */
      if (lstrval <= 0)
            return(lstrval);

      if ((res = write(arfd, buf, bsz)) == bsz) {
            wr_trail = 1;
            io_ok = 1;
            return(bsz);
      }
      /*
       * write broke, see what we can do with it. We try to send any partial
       * writes that may violate pax spec to the next archive volume.
       */
      if (res < 0)
            lstrval = res;
      else
            lstrval = 0;

      switch (artyp) {
      case ISREG:
            if ((res > 0) && (res % BLKMULT)) {
                  /*
                   * try to fix up partial writes which are not BLKMULT
                   * in size by forcing the runt record to next archive
                   * volume
                   */
                  if ((cpos = lseek(arfd, (off_t)0L, SEEK_CUR)) < 0)
                        break;
                  cpos -= (off_t)res;
                  if (ftruncate(arfd, cpos) < 0)
                        break;
                  res = lstrval = 0;
                  break;
            }
            if (res >= 0)
                  break;
            /*
             * if file is out of space, handle it like a return of 0
             */
            if ((errno == ENOSPC) || (errno == EFBIG) || (errno == EDQUOT))
                  res = lstrval = 0;
            break;
      case ISTAPE:
      case ISCHR:
      case ISBLK:
            if (res >= 0)
                  break;
            if (errno == EACCES) {
                  paxwarn(0, "Write failed, archive is write protected.");
                  res = lstrval = 0;
                  return(0);
            }
            /*
             * see if we reached the end of media, if so force a change to
             * the next volume
             */
            if ((errno == ENOSPC) || (errno == EIO) || (errno == ENXIO))
                  res = lstrval = 0;
            break;
      case ISPIPE:
      default:
            /*
             * we cannot fix errors to these devices
             */
            break;
      }

      /*
       * Better tell the user the bad news...
       * if this is a block aligned archive format, we may have a bad archive
       * if the format wants the header to start at a BLKMULT boundary.. While
       * we can deal with the mis-aligned data, it violates spec and other
       * archive readers will likely fail. if the format is not block
       * aligned, the user may be lucky (and the archive is ok).
       */
      if (res >= 0) {
            if (res > 0)
                  wr_trail = 1;
            io_ok = 1;
      }

      /*
       * If we were trying to rewrite the trailer and it didn't work, we
       * must quit right away.
       */
      if (!wr_trail && (res <= 0)) {
            paxwarn(1,"Unable to append, trailer re-write failed. Quitting.");
            return(res);
      }

      if (res == 0)
            paxwarn(0, "End of archive volume %d reached", arvol);
      else if (res < 0)
            syswarn(1, errno, "Failed write to archive volume: %d", arvol);
      else if (!frmt->blkalgn || ((res % frmt->blkalgn) == 0))
            paxwarn(0,"WARNING: partial archive write. Archive MAY BE FLAWED");
      else
            paxwarn(1,"WARNING: partial archive write. Archive IS FLAWED");
      return(res);
}

/*
 * ar_rdsync()
 *    Try to move past a bad spot on a flawed archive as needed to continue
 *    I/O. Clears error flags to allow I/O to continue.
 * Return:
 *    0 when ok to try i/o again, -1 otherwise.
 */

int
ar_rdsync(void)
{
      long fsbz;
      off_t cpos;
      off_t mpos;
      struct mtop mb;

      /*
       * Fail resync attempts at user request (done) or if this is going to be
       * an update/append to a existing archive. if last i/o hit media end,
       * we need to go to the next volume not try a resync
       */
      if ((done > 0) || (lstrval == 0))
            return(-1);

      if ((act == APPND) || (act == ARCHIVE)) {
            paxwarn(1, "Cannot allow updates to an archive with flaws.");
            return(-1);
      }
      if (io_ok)
            did_io = 1;

      switch (artyp) {
      case ISTAPE:
            /*
             * if the last i/o was a successful data transfer, we assume
             * the fault is just a bad record on the tape that we are now
             * past. If we did not get any data since the last resync try
             * to move the tape forward one PHYSICAL record past any
             * damaged tape section. Some tape drives are stubborn and need
             * to be pushed.
             */
            if (io_ok) {
                  io_ok = 0;
                  lstrval = 1;
                  break;
            }
            mb.mt_op = MTFSR;
            mb.mt_count = 1;
            if (ioctl(arfd, MTIOCTOP, &mb) < 0)
                  break;
            lstrval = 1;
            break;
      case ISREG:
      case ISCHR:
      case ISBLK:
            /*
             * try to step over the bad part of the device.
             */
            io_ok = 0;
            if (((fsbz = arsb.st_blksize) <= 0) || (artyp != ISREG))
                  fsbz = BLKMULT;
            if ((cpos = lseek(arfd, (off_t)0L, SEEK_CUR)) < 0)
                  break;
            mpos = fsbz - (cpos % (off_t)fsbz);
            if (lseek(arfd, mpos, SEEK_CUR) < 0)
                  break;
            lstrval = 1;
            break;
      case ISPIPE:
      default:
            /*
             * cannot recover on these archive device types
             */
            io_ok = 0;
            break;
      }
      if (lstrval <= 0) {
            paxwarn(1, "Unable to recover from an archive read failure.");
            return(-1);
      }
      paxwarn(0, "Attempting to recover from an archive read failure.");
      return(0);
}

/*
 * ar_fow()
 *    Move the I/O position within the archive forward the specified number of
 *    bytes as supported by the device. If we cannot move the requested
 *    number of bytes, return the actual number of bytes moved in skipped.
 * Return:
 *    0 if moved the requested distance, -1 on complete failure, 1 on
 *    partial move (the amount moved is in skipped)
 */

int
ar_fow(off_t sksz, off_t *skipped)
{
      off_t cpos;
      off_t mpos;

      *skipped = 0;
      if (sksz <= 0)
            return(0);

      /*
       * we cannot move forward at EOF or error
       */
      if (lstrval <= 0)
            return(lstrval);

      /*
       * Safer to read forward on devices where it is hard to find the end of
       * the media without reading to it. With tapes we cannot be sure of the
       * number of physical blocks to skip (we do not know physical block
       * size at this point), so we must only read forward on tapes!
       */
      if (artyp != ISREG)
            return(0);

      /*
       * figure out where we are in the archive
       */
      if ((cpos = lseek(arfd, (off_t)0L, SEEK_CUR)) >= 0) {
            /*
             * we can be asked to move farther than there are bytes in this
             * volume, if so, just go to file end and let normal buf_fill()
             * deal with the end of file (it will go to next volume by
             * itself)
             */
            if ((mpos = cpos + sksz) > arsb.st_size) {
                  *skipped = arsb.st_size - cpos;
                  mpos = arsb.st_size;
            } else
                  *skipped = sksz;
            if (lseek(arfd, mpos, SEEK_SET) >= 0)
                  return(0);
      }
      syswarn(1, errno, "Forward positioning operation on archive failed");
      lstrval = -1;
      return(-1);
}

/*
 * ar_rev()
 *    move the i/o position within the archive backwards the specified byte
 *    count as supported by the device. With tapes drives we RESET rdblksz to
 *    the PHYSICAL blocksize.
 *    NOTE: We should only be called to move backwards so we can rewrite the
 *    last records (the trailer) of an archive (APPEND).
 * Return:
 *    0 if moved the requested distance, -1 on complete failure
 */

int
ar_rev(off_t sksz)
{
      off_t cpos;
      struct mtop mb;
      int phyblk;

      /*
       * make sure we do not have try to reverse on a flawed archive
       */
      if (lstrval < 0)
            return(lstrval);

      switch (artyp) {
      case ISPIPE:
            if (sksz <= 0)
                  break;
            /*
             * cannot go backwards on these critters
             */
            paxwarn(1, "Reverse positioning on pipes is not supported.");
            lstrval = -1;
            return(-1);
      case ISREG:
      case ISBLK:
      case ISCHR:
      default:
            if (sksz <= 0)
                  break;

            /*
             * For things other than files, backwards movement has a very
             * high probability of failure as we really do not know the
             * true attributes of the device we are talking to (the device
             * may not even have the ability to lseek() in any direction).
             * First we figure out where we are in the archive.
             */
            if ((cpos = lseek(arfd, (off_t)0L, SEEK_CUR)) < 0) {
                  syswarn(1, errno,
                     "Unable to obtain current archive byte offset");
                  lstrval = -1;
                  return(-1);
            }

            /*
             * we may try to go backwards past the start when the archive
             * is only a single record. If this happens and we are on a
             * multi-volume archive, we need to go to the end of the
             * previous volume and continue our movement backwards from
             * there.
             */
            if ((cpos -= sksz) < (off_t)0L) {
                  if (arvol > 1) {
                        /*
                         * this should never happen
                         */
                        paxwarn(1,"Reverse position on previous volume.");
                        lstrval = -1;
                        return(-1);
                  }
                  cpos = (off_t)0L;
            }
            if (lseek(arfd, cpos, SEEK_SET) < 0) {
                  syswarn(1, errno, "Unable to seek archive backwards");
                  lstrval = -1;
                  return(-1);
            }
            break;
      case ISTAPE:
            /*
             * Calculate and move the proper number of PHYSICAL tape
             * blocks. If the sksz is not an even multiple of the physical
             * tape size, we cannot do the move (this should never happen).
             * (We also cannot handle trailers spread over two vols.)
             * get_phys() also makes sure we are in front of the filemark.
             */
            if ((phyblk = get_phys()) <= 0) {
                  lstrval = -1;
                  return(-1);
            }

            /*
             * make sure future tape reads only go by physical tape block
             * size (set rdblksz to the real size).
             */
            rdblksz = phyblk;

            /*
             * if no movement is required, just return (we must be after
             * get_phys() so the physical blocksize is properly set)
             */
            if (sksz <= 0)
                  break;

            /*
             * ok we have to move. Make sure the tape drive can do it.
             */
            if (sksz % phyblk) {
                  paxwarn(1,
                      "Tape drive unable to backspace requested amount");
                  lstrval = -1;
                  return(-1);
            }

            /*
             * move backwards the requested number of bytes
             */
            mb.mt_op = MTBSR;
            mb.mt_count = sksz/phyblk;
            if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
                  syswarn(1,errno, "Unable to backspace tape %d blocks.",
                      mb.mt_count);
                  lstrval = -1;
                  return(-1);
            }
            break;
      }
      lstrval = 1;
      return(0);
}

/*
 * get_phys()
 *    Determine the physical block size on a tape drive. We need the physical
 *    block size so we know how many bytes we skip over when we move with
 *    mtio commands. We also make sure we are BEFORE THE TAPE FILEMARK when
 *    return.
 *    This is one really SLOW routine...
 * Return:
 *    physical block size if ok (ok > 0), -1 otherwise
 */

static int
get_phys(void)
{
      int padsz = 0;
      int res;
      int phyblk;
      struct mtop mb;
      char scbuf[MAXBLK];

      /*
       * move to the file mark, and then back up one record and read it.
       * this should tell us the physical record size the tape is using.
       */
      if (lstrval == 1) {
            /*
             * we know we are at file mark when we get back a 0 from
             * read()
             */
            while ((res = read(arfd, scbuf, sizeof(scbuf))) > 0)
                  padsz += res;
            if (res < 0) {
                  syswarn(1, errno, "Unable to locate tape filemark.");
                  return(-1);
            }
      }

      /*
       * move backwards over the file mark so we are at the end of the
       * last record.
       */
      mb.mt_op = MTBSF;
      mb.mt_count = 1;
      if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
            syswarn(1, errno, "Unable to backspace over tape filemark.");
            return(-1);
      }

      /*
       * move backwards so we are in front of the last record and read it to
       * get physical tape blocksize.
       */
      mb.mt_op = MTBSR;
      mb.mt_count = 1;
      if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
            syswarn(1, errno, "Unable to backspace over last tape block.");
            return(-1);
      }
      if ((phyblk = read(arfd, scbuf, sizeof(scbuf))) <= 0) {
            syswarn(1, errno, "Cannot determine archive tape blocksize.");
            return(-1);
      }

      /*
       * read forward to the file mark, then back up in front of the filemark
       * (this is a bit paranoid, but should be safe to do).
       */
      while ((res = read(arfd, scbuf, sizeof(scbuf))) > 0)
            ;
      if (res < 0) {
            syswarn(1, errno, "Unable to locate tape filemark.");
            return(-1);
      }
      mb.mt_op = MTBSF;
      mb.mt_count = 1;
      if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
            syswarn(1, errno, "Unable to backspace over tape filemark.");
            return(-1);
      }

      /*
       * set lstrval so we know that the filemark has not been seen
       */
      lstrval = 1;

      /*
       * return if there was no padding
       */
      if (padsz == 0)
            return(phyblk);

      /*
       * make sure we can move backwards over the padding. (this should
       * never fail).
       */
      if (padsz % phyblk) {
            paxwarn(1, "Tape drive unable to backspace requested amount");
            return(-1);
      }

      /*
       * move backwards over the padding so the head is where it was when
       * we were first called (if required).
       */
      mb.mt_op = MTBSR;
      mb.mt_count = padsz/phyblk;
      if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
            syswarn(1,errno,"Unable to backspace tape over %d pad blocks",
                mb.mt_count);
            return(-1);
      }
      return(phyblk);
}

/*
 * ar_next()
 *    prompts the user for the next volume in this archive. For some devices
 *    we may allow the media to be changed. Otherwise a new archive is
 *    prompted for. By pax spec, if there is no controlling tty or an eof is
 *    read on tty input, we must quit pax.
 * Return:
 *    0 when ready to continue, -1 when all done
 */

int
ar_next(void)
{
      char buf[PAXPATHLEN+2];
      static int freeit = 0;
      sigset_t o_mask;

      /*
       * WE MUST CLOSE THE DEVICE. A lot of devices must see last close, (so
       * things like writing EOF etc will be done) (Watch out ar_close() can
       * also be called via a signal handler, so we must prevent a race.
       */
      if (sigprocmask(SIG_BLOCK, &s_mask, &o_mask) < 0)
            syswarn(0, errno, "Unable to set signal mask");
      ar_close();
      if (sigprocmask(SIG_SETMASK, &o_mask, NULL) < 0)
            syswarn(0, errno, "Unable to restore signal mask");

      if (done || !wr_trail || force_one_volume || strcmp(NM_TAR, argv0) == 0)
            return(-1);

      tty_prnt("\nATTENTION! %s archive volume change required.\n", argv0);

      /*
       * if i/o is on stdin or stdout, we cannot reopen it (we do not know
       * the name), the user will be forced to type it in.
       */
      if (strcmp(arcname, STDO) && strcmp(arcname, STDN) && (artyp != ISREG)
          && (artyp != ISPIPE)) {
            if (artyp == ISTAPE) {
                  tty_prnt("%s ready for archive tape volume: %d\n",
                        arcname, arvol);
                  tty_prnt("Load the NEXT TAPE on the tape drive");
            } else {
                  tty_prnt("%s ready for archive volume: %d\n",
                        arcname, arvol);
                  tty_prnt("Load the NEXT STORAGE MEDIA (if required)");
            }

            if ((act == ARCHIVE) || (act == APPND))
                  tty_prnt(" and make sure it is WRITE ENABLED.\n");
            else
                  tty_prnt("\n");

            for (;;) {
                  tty_prnt("Type \"y\" to continue, \".\" to quit %s,",
                        argv0);
                  tty_prnt(" or \"s\" to switch to new device.\nIf you");
                  tty_prnt(" cannot change storage media, type \"s\"\n");
                  tty_prnt("Is the device ready and online? > ");

                  if ((tty_read(buf,sizeof(buf))<0) || !strcmp(buf,".")){
                        done = 1;
                        lstrval = -1;
                        tty_prnt("Quitting %s!\n", argv0);
                        vfpart = 0;
                        return(-1);
                  }

                  if ((buf[0] == '\0') || (buf[1] != '\0')) {
                        tty_prnt("%s unknown command, try again\n",buf);
                        continue;
                  }

                  switch (buf[0]) {
                  case 'y':
                  case 'Y':
                        /*
                         * we are to continue with the same device
                         */
                        if (ar_open(arcname) >= 0)
                              return(0);
                        tty_prnt("Cannot re-open %s, try again\n",
                              arcname);
                        continue;
                  case 's':
                  case 'S':
                        /*
                         * user wants to open a different device
                         */
                        tty_prnt("Switching to a different archive\n");
                        break;
                  default:
                        tty_prnt("%s unknown command, try again\n",buf);
                        continue;
                  }
                  break;
            }
      } else
            tty_prnt("Ready for archive volume: %d\n", arvol);

      /*
       * have to go to a different archive
       */
      for (;;) {
            tty_prnt("Input archive name or \".\" to quit %s.\n", argv0);
            tty_prnt("Archive name > ");

            if ((tty_read(buf, sizeof(buf)) < 0) || !strcmp(buf, ".")) {
                  done = 1;
                  lstrval = -1;
                  tty_prnt("Quitting %s!\n", argv0);
                  vfpart = 0;
                  return(-1);
            }
            if (buf[0] == '\0') {
                  tty_prnt("Empty file name, try again\n");
                  continue;
            }
            if (!strcmp(buf, "..")) {
                  tty_prnt("Illegal file name: .. try again\n");
                  continue;
            }
            if (strlen(buf) > PAXPATHLEN) {
                  tty_prnt("File name too long, try again\n");
                  continue;
            }

            /*
             * try to open new archive
             */
            if (ar_open(buf) >= 0) {
                  if (freeit) {
                        (void)free((char *)arcname);
                        freeit = 0;
                  }
                  if ((arcname = strdup(buf)) == NULL) {
                        done = 1;
                        lstrval = -1;
                        paxwarn(0, "Cannot save archive name.");
                        return(-1);
                  }
                  freeit = 1;
                  break;
            }
            tty_prnt("Cannot open %s, try again\n", buf);
            continue;
      }
      return(0);
}

/*
 * ar_start_gzip()
 * starts the compress, gzip or bzip2 compression/decompression process
 * as a child, using magic to keep the fd the same in the calling function
 * (parent).
 */
void
ar_start_gzip(int fd, const char *gzip_program, int wr)
{
      int fds[2];
      const char *gzip_flags;

      if (pipe(fds) < 0)
            err(1, "could not pipe");
      zpid = fork();
      if (zpid < 0)
            err(1, "could not fork");

      /* parent */
      if (zpid) {
            if (wr)
                  dup2(fds[1], fd);
            else
                  dup2(fds[0], fd);
            close(fds[0]);
            close(fds[1]);
      } else {
            if (wr) {
                  dup2(fds[0], STDIN_FILENO);
                  dup2(fd, STDOUT_FILENO);
                  gzip_flags = "-c";
            } else {
                  dup2(fds[1], STDOUT_FILENO);
                  dup2(fd, STDIN_FILENO);
                  gzip_flags = "-dc";
            }
            close(fds[0]);
            close(fds[1]);
            if (execlp(gzip_program, gzip_program, gzip_flags, (char *)NULL) < 0)
                  err(1, "could not exec %s", gzip_program);
            /* NOTREACHED */
      }
}

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