snj doesn't like my accent, so use proper English month names.

[netbsd-mini2440.git] / bin / pax / buf_subs.c

/*      $NetBSD: buf_subs.c,v 1.27 2006/02/11 10:43:18 dsl 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.
 */

#if HAVE_NBTOOL_CONFIG_H
#include "nbtool_config.h"
#endif

#include <sys/cdefs.h>
#if !defined(lint)
#if 0
static char sccsid[] = "@(#)buf_subs.c  8.2 (Berkeley) 4/18/94";
#else
__RCSID("$NetBSD: buf_subs.c,v 1.27 2006/02/11 10:43:18 dsl Exp $");
#endif
#endif /* not lint */

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

/*
 * routines which implement archive and file buffering
 */

#define MINFBSZ         512             /* default block size for hole detect */
#define MAXFLT          10              /* default media read error limit */

/*
 * Need to change bufmem to dynamic allocation when the upper
 * limit on blocking size is removed (though that will violate pax spec)
 * MAXBLK define and tests will also need to be updated.
 */
static char bufmem[MAXBLK+BLKMULT];     /* i/o buffer + pushback id space */
static char *buf;                       /* normal start of i/o buffer */
static char *bufend;                    /* end or last char in i/o buffer */
static char *bufpt;                     /* read/write point in i/o buffer */
int blksz = MAXBLK;                     /* block input/output size in bytes */
int wrblksz;                            /* user spec output size in bytes */
int maxflt = MAXFLT;                    /* MAX consecutive media errors */
int rdblksz;                            /* first read blksize (tapes only) */
off_t wrlimit;                          /* # of bytes written per archive vol */
off_t wrcnt;                            /* # of bytes written on current vol */
off_t rdcnt;                            /* # of bytes read on current vol */

/*
 * wr_start()
 *      set up the buffering system to operate in a write mode
 * Return:
 *      0 if ok, -1 if the user specified write block size violates pax spec
 */

int
wr_start(void)
{
        buf = &(bufmem[BLKMULT]);
        /*
         * Check to make sure the write block size meets pax specs. If the user
         * does not specify a blocksize, we use the format default blocksize.
         * We must be picky on writes, so we do not allow the user to create an
         * archive that might be hard to read elsewhere. If all ok, we then
         * open the first archive volume
         */
        if (!wrblksz)
                wrblksz = frmt->bsz;
        if (wrblksz > MAXBLK) {
                tty_warn(1, "Write block size of %d too large, maximum is: %d",
                        wrblksz, MAXBLK);
                return -1;
        }
        if (wrblksz % BLKMULT) {
                tty_warn(1, "Write block size of %d is not a %d byte multiple",
                    wrblksz, BLKMULT);
                return -1;
        }

        /*
         * we only allow wrblksz to be used with all archive operations
         */
        blksz = rdblksz = wrblksz;
        if ((ar_open(arcname) < 0) && (ar_next() < 0))
                return -1;
        wrcnt = 0;
        bufend = buf + wrblksz;
        bufpt = buf;
        return 0;
}

/*
 * rd_start()
 *      set up buffering system to read an archive
 * Return:
 *      0 if ok, -1 otherwise
 */

int
rd_start(void)
{
        /*
         * leave space for the header pushback (see get_arc()). If we are
         * going to append and user specified a write block size, check it
         * right away
         */
        buf = &(bufmem[BLKMULT]);
        if ((act == APPND) && wrblksz) {
                if (wrblksz > MAXBLK) {
                        tty_warn(1,
                            "Write block size %d too large, maximum is: %d",
                            wrblksz, MAXBLK);
                        return -1;
                }
                if (wrblksz % BLKMULT) {
                        tty_warn(1,
                            "Write block size %d is not a %d byte multiple",
                            wrblksz, BLKMULT);
                        return -1;
                }
        }

        /*
         * open the archive
         */
        if ((ar_open(arcname) < 0) && (ar_next() < 0))
                return -1;
        bufend = buf + rdblksz;
        bufpt = bufend;
        rdcnt = 0;
        return 0;
}

/*
 * cp_start()
 *      set up buffer system for copying within the file system
 */

void
cp_start(void)
{
        buf = &(bufmem[BLKMULT]);
        rdblksz = blksz = MAXBLK;
}

/*
 * appnd_start()
 *      Set up the buffering system to append new members to an archive that
 *      was just read. The last block(s) of an archive may contain a format
 *      specific trailer. To append a new member, this trailer has to be
 *      removed from the archive. The first byte of the trailer is replaced by
 *      the start of the header of the first file added to the archive. The
 *      format specific end read function tells us how many bytes to move
 *      backwards in the archive to be positioned BEFORE the trailer. Two
 *      different positions have to be adjusted, the O.S. file offset (e.g. the
 *      position of the tape head) and the write point within the data we have
 *      stored in the read (soon to become write) buffer. We may have to move
 *      back several records (the number depends on the size of the archive
 *      record and the size of the format trailer) to read up the record where
 *      the first byte of the trailer is recorded. Trailers may span (and
 *      overlap) record boundaries.
 *      We first calculate which record has the first byte of the trailer. We
 *      move the OS file offset back to the start of this record and read it
 *      up. We set the buffer write pointer to be at this byte (the byte where
 *      the trailer starts). We then move the OS file pointer back to the
 *      start of this record so a flush of this buffer will replace the record
 *      in the archive.
 *      A major problem is rewriting this last record. For archives stored
 *      on disk files, this is trivial. However, many devices are really picky
 *      about the conditions under which they will allow a write to occur.
 *      Often devices restrict the conditions where writes can be made,
 *      so it may not be feasable to append archives stored on all types of
 *      devices.
 * Return:
 *      0 for success, -1 for failure
 */

int
appnd_start(off_t skcnt)
{
        int res;
        off_t cnt;

        if (exit_val != 0) {
                tty_warn(0, "Cannot append to an archive that may have flaws.");
                return -1;
        }
        /*
         * if the user did not specify a write blocksize, inherit the size used
         * in the last archive volume read. (If a is set we still use rdblksz
         * until next volume, cannot shift sizes within a single volume).
         */
        if (!wrblksz)
                wrblksz = blksz = rdblksz;
        else
                blksz = rdblksz;

        /*
         * make sure that this volume allows appends
         */
        if (ar_app_ok() < 0)
                return -1;

        /*
         * Calculate bytes to move back and move in front of record where we
         * need to start writing from. Remember we have to add in any padding
         * that might be in the buffer after the trailer in the last block. We
         * travel skcnt + padding ROUNDED UP to blksize.
         */
        skcnt += bufend - bufpt;
        if ((cnt = (skcnt/blksz) * blksz) < skcnt)
                cnt += blksz;
        if (ar_rev((off_t)cnt) < 0)
                goto out;

        /*
         * We may have gone too far if there is valid data in the block we are
         * now in front of, read up the block and position the pointer after
         * the valid data.
         */
        if ((cnt -= skcnt) > 0) {
                /*
                 * watch out for stupid tape drives. ar_rev() will set rdblksz
                 * to be real physical blocksize so we must loop until we get
                 * the old rdblksz (now in blksz). If ar_rev() fouls up the
                 * determination of the physical block size, we will fail.
                 */
                bufpt = buf;
                bufend = buf + blksz;
                while (bufpt < bufend) {
                        if ((res = ar_read(bufpt, rdblksz)) <= 0)
                                goto out;
                        bufpt += res;
                }
                if (ar_rev((off_t)(bufpt - buf)) < 0)
                        goto out;
                bufpt = buf + cnt;
                bufend = buf + blksz;
        } else {
                /*
                 * buffer is empty
                 */
                bufend = buf + blksz;
                bufpt = buf;
        }
        rdblksz = blksz;
        rdcnt -= skcnt;
        wrcnt = 0;

        /*
         * At this point we are ready to write. If the device requires special
         * handling to write at a point were previously recorded data resides,
         * that is handled in ar_set_wr(). From now on we operate under normal
         * ARCHIVE mode (write) conditions
         */
        if (ar_set_wr() < 0)
                return -1;
        act = ARCHIVE;
        return 0;

    out:
        tty_warn(1, "Unable to rewrite archive trailer, cannot append.");
        return -1;
}

/*
 * rd_sync()
 *      A read error occurred on this archive volume. Resync the buffer and
 *      try to reset the device (if possible) so we can continue to read. Keep
 *      trying to do this until we get a valid read, or we reach the limit on
 *      consecutive read faults (at which point we give up). The user can
 *      adjust the read error limit through a command line option.
 * Returns:
 *      0 on success, and -1 on failure
 */

int
rd_sync(void)
{
        int errcnt = 0;
        int res;

        /*
         * if the user says bail out on first fault, we are out of here...
         */
        if (maxflt == 0)
                return -1;
        if (act == APPND) {
                tty_warn(1,
                    "Unable to append when there are archive read errors.");
                return -1;
        }

        /*
         * poke at device and try to get past media error
         */
        if (ar_rdsync() < 0) {
                if (ar_next() < 0)
                        return -1;
                else
                        rdcnt = 0;
        }

        for (;;) {
                if ((res = ar_read(buf, blksz)) > 0) {
                        /*
                         * All right! got some data, fill that buffer
                         */
                        bufpt = buf;
                        bufend = buf + res;
                        rdcnt += res;
                        return 0;
                }

                /*
                 * Oh well, yet another failed read...
                 * if error limit reached, ditch. otherwise poke device to move past
                 * bad media and try again. if media is badly damaged, we ask
                 * the poor (and upset user at this point) for the next archive
                 * volume. remember the goal on reads is to get the most we
                 * can extract out of the archive.
                 */
                if ((maxflt > 0) && (++errcnt > maxflt))
                        tty_warn(0,
                            "Archive read error limit (%d) reached",maxflt);
                else if (ar_rdsync() == 0)
                        continue;
                if (ar_next() < 0)
                        break;
                rdcnt = 0;
                errcnt = 0;
        }
        return -1;
}

/*
 * pback()
 *      push the data used during the archive id phase back into the I/O
 *      buffer. This is required as we cannot be sure that the header does NOT
 *      overlap a block boundary (as in the case we are trying to recover a
 *      flawed archived). This was not designed to be used for any other
 *      purpose. (What software engineering, HA!)
 *      WARNING: do not even THINK of pback greater than BLKMULT, unless the
 *      pback space is increased.
 */

void
pback(char *pt, int cnt)
{
        bufpt -= cnt;
        memcpy(bufpt, pt, cnt);
        return;
}

/*
 * rd_skip()
 *      skip forward in the archive during an archive read. Used to get quickly
 *      past file data and padding for files the user did NOT select.
 * Return:
 *      0 if ok, -1 failure, and 1 when EOF on the archive volume was detected.
 */

int
rd_skip(off_t skcnt)
{
        off_t res;
        off_t cnt;
        off_t skipped = 0;

        /*
         * consume what data we have in the buffer. If we have to move forward
         * whole records, we call the low level skip function to see if we can
         * move within the archive without doing the expensive reads on data we
         * do not want.
         */
        if (skcnt == 0)
                return 0;
        res = MIN((bufend - bufpt), skcnt);
        bufpt += res;
        skcnt -= res;

        /*
         * if skcnt is now 0, then no additional i/o is needed
         */
        if (skcnt == 0)
                return 0;

        /*
         * We have to read more, calculate complete and partial record reads
         * based on rdblksz. we skip over "cnt" complete records
         */
        res = skcnt%rdblksz;
        cnt = (skcnt/rdblksz) * rdblksz;

        /*
         * if the skip fails, we will have to resync. ar_fow will tell us
         * how much it can skip over. We will have to read the rest.
         */
        if (ar_fow(cnt, &skipped) < 0)
                return -1;
        res += cnt - skipped;
        rdcnt += skipped;

        /*
         * what is left we have to read (which may be the whole thing if
         * ar_fow() told us the device can only read to skip records);
         */
        while (res > 0L) {
                cnt = bufend - bufpt;
                /*
                 * if the read fails, we will have to resync
                 */
                if ((cnt <= 0) && ((cnt = buf_fill()) < 0))
                        return -1;
                if (cnt == 0)
                        return 1;
                cnt = MIN(cnt, res);
                bufpt += cnt;
                res -= cnt;
        }
        return 0;
}

/*
 * wr_fin()
 *      flush out any data (and pad if required) the last block. We always pad
 *      with zero (even though we do not have to). Padding with 0 makes it a
 *      lot easier to recover if the archive is damaged. zero paddding SHOULD
 *      BE a requirement....
 */

void
wr_fin(void)
{
        if (bufpt > buf) {
                memset(bufpt, 0, bufend - bufpt);
                bufpt = bufend;
                (void)buf_flush(blksz);
        }
}

/*
 * wr_rdbuf()
 *      fill the write buffer from data passed to it in a buffer (usually used
 *      by format specific write routines to pass a file header). On failure we
 *      punt. We do not allow the user to continue to write flawed archives.
 *      We assume these headers are not very large (the memory copy we use is
 *      a bit expensive).
 * Return:
 *      0 if buffer was filled ok, -1 o.w. (buffer flush failure)
 */

int
wr_rdbuf(char *out, int outcnt)
{
        int cnt;

        /*
         * while there is data to copy copy into the write buffer. when the
         * write buffer fills, flush it to the archive and continue
         */
        while (outcnt > 0) {
                cnt = bufend - bufpt;
                if ((cnt <= 0) && ((cnt = buf_flush(blksz)) < 0))
                        return -1;
                /*
                 * only move what we have space for
                 */
                cnt = MIN(cnt, outcnt);
                memcpy(bufpt, out, cnt);
                bufpt += cnt;
                out += cnt;
                outcnt -= cnt;
        }
        return 0;
}

/*
 * rd_wrbuf()
 *      copy from the read buffer into a supplied buffer a specified number of
 *      bytes. If the read buffer is empty fill it and continue to copy.
 *      usually used to obtain a file header for processing by a format
 *      specific read routine.
 * Return
 *      number of bytes copied to the buffer, 0 indicates EOF on archive volume,
 *      -1 is a read error
 */

int
rd_wrbuf(char *in, int cpcnt)
{
        int res;
        int cnt;
        int incnt = cpcnt;

        /*
         * loop until we fill the buffer with the requested number of bytes
         */
        while (incnt > 0) {
                cnt = bufend - bufpt;
                if ((cnt <= 0) && ((cnt = buf_fill()) <= 0)) {
                        /*
                         * read error, return what we got (or the error if
                         * no data was copied). The caller must know that an
                         * error occurred and has the best knowledge what to
                         * do with it
                         */
                        if ((res = cpcnt - incnt) > 0)
                                return res;
                        return cnt;
                }

                /*
                 * calculate how much data to copy based on whats left and
                 * state of buffer
                 */
                cnt = MIN(cnt, incnt);
                memcpy(in, bufpt, cnt);
                bufpt += cnt;
                incnt -= cnt;
                in += cnt;
        }
        return cpcnt;
}

/*
 * wr_skip()
 *      skip forward during a write. In other words add padding to the file.
 *      we add zero filled padding as it makes flawed archives much easier to
 *      recover from. the caller tells us how many bytes of padding to add
 *      This routine was not designed to add HUGE amount of padding, just small
 *      amounts (a few 512 byte blocks at most)
 * Return:
 *      0 if ok, -1 if there was a buf_flush failure
 */

int
wr_skip(off_t skcnt)
{
        int cnt;

        /*
         * loop while there is more padding to add
         */
        while (skcnt > 0L) {
                cnt = bufend - bufpt;
                if ((cnt <= 0) && ((cnt = buf_flush(blksz)) < 0))
                        return -1;
                cnt = MIN(cnt, skcnt);
                memset(bufpt, 0, cnt);
                bufpt += cnt;
                skcnt -= cnt;
        }
        return 0;
}

/*
 * wr_rdfile()
 *      fill write buffer with the contents of a file. We are passed an open
 *      file descriptor to the file an the archive structure that describes the
 *      file we are storing. The variable "left" is modified to contain the
 *      number of bytes of the file we were NOT able to write to the archive.
 *      it is important that we always write EXACTLY the number of bytes that
 *      the format specific write routine told us to. The file can also get
 *      bigger, so reading to the end of file would create an improper archive,
 *      we just detect this case and warn the user. We never create a bad
 *      archive if we can avoid it. Of course trying to archive files that are
 *      active is asking for trouble. It we fail, we pass back how much we
 *      could NOT copy and let the caller deal with it.
 * Return:
 *      0 ok, -1 if archive write failure. a short read of the file returns a
 *      0, but "left" is set to be greater than zero.
 */

int
wr_rdfile(ARCHD *arcn, int ifd, off_t *left)
{
        int cnt;
        int res = 0;
        off_t size = arcn->sb.st_size;
        struct stat origsb, sb;

        /*
         * by default, remember the previously obtained stat information
         * (in arcn->sb) for comparing the mtime after reading.
         * if Mflag is set, use the actual mtime instead.
         */
        origsb = arcn->sb;
        if (Mflag && (fstat(ifd, &origsb) < 0))
                syswarn(1, errno, "Failed stat on %s", arcn->org_name);

        /*
         * while there are more bytes to write
         */
        while (size > 0L) {
                cnt = bufend - bufpt;
                if ((cnt <= 0) && ((cnt = buf_flush(blksz)) < 0)) {
                        *left = size;
                        return -1;
                }
                cnt = MIN(cnt, size);
                if ((res = read_with_restart(ifd, bufpt, cnt)) <= 0)
                        break;
                size -= res;
                bufpt += res;
        }

        /*
         * better check the file did not change during this operation
         * or the file read failed.
         */
        if (res < 0)
                syswarn(1, errno, "Read fault on %s", arcn->org_name);
        else if (size != 0L)
                tty_warn(1, "File changed size during read %s", arcn->org_name);
        else if (fstat(ifd, &sb) < 0)
                syswarn(1, errno, "Failed stat on %s", arcn->org_name);
        else if (origsb.st_mtime != sb.st_mtime)
                tty_warn(1, "File %s was modified during copy to archive",
                        arcn->org_name);
        *left = size;
        return 0;
}

/*
 * rd_wrfile()
 *      extract the contents of a file from the archive. If we are unable to
 *      extract the entire file (due to failure to write the file) we return
 *      the numbers of bytes we did NOT process. This way the caller knows how
 *      many bytes to skip past to find the next archive header. If the failure
 *      was due to an archive read, we will catch that when we try to skip. If
 *      the format supplies a file data crc value, we calculate the actual crc
 *      so that it can be compared to the value stored in the header
 * NOTE:
 *      We call a special function to write the file. This function attempts to
 *      restore file holes (blocks of zeros) into the file. When files are
 *      sparse this saves space, and is a LOT faster. For non sparse files
 *      the performance hit is small. As of this writing, no archive supports
 *      information on where the file holes are.
 * Return:
 *      0 ok, -1 if archive read failure. if we cannot write the entire file,
 *      we return a 0 but "left" is set to be the amount unwritten
 */

int
rd_wrfile(ARCHD *arcn, int ofd, off_t *left)
{
        int cnt = 0;
        off_t size = arcn->sb.st_size;
        int res = 0;
        char *fnm = arcn->name;
        int isem = 1;
        int rem;
        int sz = MINFBSZ;
        struct stat sb;
        u_long crc = 0L;

        /*
         * pass the blocksize of the file being written to the write routine,
         * if the size is zero, use the default MINFBSZ
         */
        if (ofd < 0)
                sz = PAXPATHLEN+1;
        else if (fstat(ofd, &sb) == 0) {
                if (sb.st_blksize > 0)
                        sz = (int)sb.st_blksize;
        } else
                syswarn(0, errno,
                    "Unable to obtain block size for file %s", fnm);
        rem = sz;
        *left = 0L;

        /*
         * Copy the archive to the file the number of bytes specified. We have
         * to assume that we want to recover file holes as none of the archive
         * formats can record the location of file holes.
         */
        while (size > 0L) {
                cnt = bufend - bufpt;
                /*
                 * if we get a read error, we do not want to skip, as we may
                 * miss a header, so we do not set left, but if we get a write
                 * error, we do want to skip over the unprocessed data.
                 */
                if ((cnt <= 0) && ((cnt = buf_fill()) <= 0))
                        break;
                cnt = MIN(cnt, size);
                if ((res = file_write(ofd,bufpt,cnt,&rem,&isem,sz,fnm)) <= 0) {
                        *left = size;
                        break;
                }

                if (docrc) {
                        /*
                         * update the actual crc value
                         */
                        cnt = res;
                        while (--cnt >= 0)
                                crc += *bufpt++ & 0xff;
                } else
                        bufpt += res;
                size -= res;
        }

        /*
         * if the last block has a file hole (all zero), we must make sure this
         * gets updated in the file. We force the last block of zeros to be
         * written. just closing with the file offset moved forward may not put
         * a hole at the end of the file.
         */
        if (ofd >= 0 && isem && (arcn->sb.st_size > 0L))
                file_flush(ofd, fnm, isem);

        /*
         * if we failed from archive read, we do not want to skip
         */
        if ((size > 0L) && (*left == 0L))
                return -1;

        /*
         * some formats record a crc on file data. If so, then we compare the
         * calculated crc to the crc stored in the archive
         */
        if (docrc && (size == 0L) && (arcn->crc != crc))
                tty_warn(1,"Actual crc does not match expected crc %s",
                    arcn->name);
        return 0;
}

/*
 * cp_file()
 *      copy the contents of one file to another. used during -rw phase of pax
 *      just as in rd_wrfile() we use a special write function to write the
 *      destination file so we can properly copy files with holes.
 */

void
cp_file(ARCHD *arcn, int fd1, int fd2)
{
        int cnt;
        off_t cpcnt = 0L;
        int res = 0;
        char *fnm = arcn->name;
        int no_hole = 0;
        int isem = 1;
        int rem;
        int sz = MINFBSZ;
        struct stat sb, origsb;

        /*
         * check for holes in the source file. If none, we will use regular
         * write instead of file write.
         */
         if (((off_t)(arcn->sb.st_blocks * BLKMULT)) >= arcn->sb.st_size)
                ++no_hole;

        /*
         * by default, remember the previously obtained stat information
         * (in arcn->sb) for comparing the mtime after reading.
         * if Mflag is set, use the actual mtime instead.
         */
        origsb = arcn->sb;
        if (Mflag && (fstat(fd1, &origsb) < 0))
                syswarn(1, errno, "Failed stat on %s", arcn->org_name);

        /*
         * pass the blocksize of the file being written to the write routine,
         * if the size is zero, use the default MINFBSZ
         */
        if (fstat(fd2, &sb) == 0) {
                if (sb.st_blksize > 0)
                        sz = sb.st_blksize;
        } else
                syswarn(0, errno,
                    "Unable to obtain block size for file %s", fnm);
        rem = sz;

        /*
         * read the source file and copy to destination file until EOF
         */
        for(;;) {
                if ((cnt = read_with_restart(fd1, buf, blksz)) <= 0)
                        break;
                if (no_hole)
                        res = xwrite(fd2, buf, cnt);
                else
                        res = file_write(fd2, buf, cnt, &rem, &isem, sz, fnm);
                if (res != cnt)
                        break;
                cpcnt += cnt;
        }

        /*
         * check to make sure the copy is valid.
         */
        if (res < 0)
                syswarn(1, errno, "Failed write during copy of %s to %s",
                        arcn->org_name, arcn->name);
        else if (cpcnt != arcn->sb.st_size)
                tty_warn(1, "File %s changed size during copy to %s",
                        arcn->org_name, arcn->name);
        else if (fstat(fd1, &sb) < 0)
                syswarn(1, errno, "Failed stat of %s", arcn->org_name);
        else if (origsb.st_mtime != sb.st_mtime)
                tty_warn(1, "File %s was modified during copy to %s",
                        arcn->org_name, arcn->name);

        /*
         * if the last block has a file hole (all zero), we must make sure this
         * gets updated in the file. We force the last block of zeros to be
         * written. just closing with the file offset moved forward may not put
         * a hole at the end of the file.
         */
        if (!no_hole && isem && (arcn->sb.st_size > 0L))
                file_flush(fd2, fnm, isem);
        return;
}

/*
 * buf_fill()
 *      fill the read buffer with the next record (or what we can get) from
 *      the archive volume.
 * Return:
 *      Number of bytes of data in the read buffer, -1 for read error, and
 *      0 when finished (user specified termination in ar_next()).
 */

int
buf_fill(void)
{
        int cnt;
        static int fini = 0;

        if (fini)
                return 0;

        for(;;) {
                /*
                 * try to fill the buffer. on error the next archive volume is
                 * opened and we try again.
                 */
                if ((cnt = ar_read(buf, blksz)) > 0) {
                        bufpt = buf;
                        bufend = buf + cnt;
                        rdcnt += cnt;
                        return cnt;
                }

                /*
                 * errors require resync, EOF goes to next archive
                 * but in case we have not determined yet the format,
                 * this means that we have a very short file, so we
                 * are done again.
                 */
                if (cnt < 0)
                        break;
                if (frmt == NULL || ar_next() < 0) {
                        fini = 1;
                        return 0;
                }
                rdcnt = 0;
        }
        exit_val = 1;
        return -1;
}

/*
 * buf_flush()
 *      force the write buffer to the archive. We are passed the number of
 *      bytes in the buffer at the point of the flush. When we change archives
 *      the record size might change. (either larger or smaller).
 * Return:
 *      0 if all is ok, -1 when a write error occurs.
 */

int
buf_flush(int bufcnt)
{
        int cnt;
        int push = 0;
        int totcnt = 0;

        /*
         * if we have reached the user specified byte count for each archive
         * volume, prompt for the next volume. (The non-standard -R flag).
         * NOTE: If the wrlimit is smaller than wrcnt, we will always write
         * at least one record. We always round limit UP to next blocksize.
         */
        if ((wrlimit > 0) && (wrcnt > wrlimit)) {
                tty_warn(0,
                    "User specified archive volume byte limit reached.");
                if (ar_next() < 0) {
                        wrcnt = 0;
                        exit_val = 1;
                        return -1;
                }
                wrcnt = 0;

                /*
                 * The new archive volume might have changed the size of the
                 * write blocksize. if so we figure out if we need to write
                 * (one or more times), or if there is now free space left in
                 * the buffer (it is no longer full). bufcnt has the number of
                 * bytes in the buffer, (the blocksize, at the point we were
                 * CALLED). Push has the amount of "extra" data in the buffer
                 * if the block size has shrunk from a volume change.
                 */
                bufend = buf + blksz;
                if (blksz > bufcnt)
                        return 0;
                if (blksz < bufcnt)
                        push = bufcnt - blksz;
        }

        /*
         * We have enough data to write at least one archive block
         */
        for (;;) {
                /*
                 * write a block and check if it all went out ok
                 */
                cnt = ar_write(buf, blksz);
                if (cnt == blksz) {
                        /*
                         * the write went ok
                         */
                        wrcnt += cnt;
                        totcnt += cnt;
                        if (push > 0) {
                                /* we have extra data to push to the front.
                                 * check for more than 1 block of push, and if
                                 * so we loop back to write again
                                 */
                                memcpy(buf, bufend, push);
                                bufpt = buf + push;
                                if (push >= blksz) {
                                        push -= blksz;
                                        continue;
                                }
                        } else
                                bufpt = buf;
                        return totcnt;
                } else if (cnt > 0) {
                        /*
                         * Oh drat we got a partial write!
                         * if format doesnt care about alignment let it go,
                         * we warned the user in ar_write().... but this means
                         * the last record on this volume violates pax spec....
                         */
                        totcnt += cnt;
                        wrcnt += cnt;
                        bufpt = buf + cnt;
                        cnt = bufcnt - cnt;
                        memcpy(buf, bufpt, cnt);
                        bufpt = buf + cnt;
                        if (!frmt->blkalgn || ((cnt % frmt->blkalgn) == 0))
                                return totcnt;
                        break;
                }

                /*
                 * All done, go to next archive
                 */
                wrcnt = 0;
                if (ar_next() < 0)
                        break;

                /*
                 * The new archive volume might also have changed the block
                 * size. if so, figure out if we have too much or too little
                 * data for using the new block size
                 */
                bufend = buf + blksz;
                if (blksz > bufcnt)
                        return 0;
                if (blksz < bufcnt)
                        push = bufcnt - blksz;
        }

        /*
         * write failed, stop pax. we must not create a bad archive!
         */
        exit_val = 1;
        return -1;
}