src/buffer.c - master - niceSOFT/tar

src/buffer.c
2 013 строк50 KB
Paul Eggert
Prefer UNNAMED to MAYBE_UNUSED
22 мар 2026, 22:23
22 мар 2026, 22:239280aa3
/* Buffer management for tar.

   Copyright 1988-2026 Free Software Foundation, Inc.

   This file is part of GNU tar.

   GNU tar is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   GNU tar is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.

   Written by John Gilmore, on 1985-08-25.  */

#include <system.h>

#include <signal.h>

#include <alignalloc.h>
#include <c-ctype.h>
#include <closeout.h>
#include <fnmatch.h>
#include <human.h>
#include <quotearg.h>

#include "common.h"
#include <rmt.h>

#include <stdcountof.h>

/* Work around GCC bug 117236.  */
# if 13 <= __GNUC__
#  pragma GCC diagnostic ignored "-Wnull-dereference"
# endif

/* Number of retries before giving up on read.  */
enum { READ_ERROR_MAX = 10 };

/* Variables.  */

static tarlong prev_written;    /* bytes written on previous volumes */
static tarlong bytes_written;   /* bytes written on this volume */
static void *record_buffer[2];  /* allocated memory */
static bool record_index;
static idx_t short_read_slop;	/* excess bytes at end of short read */

/* FIXME: The following variables should ideally be static to this
   module.  However, this cannot be done yet.  The cleanup continues!  */

int archive;
struct timespec start_time;
struct timespec volume_start_time;
struct tar_stat_info current_stat_info;
struct stat archive_stat;

bool seekable_archive;

union block *record_start;      /* start of record of archive */
union block *record_end;        /* last+1 block of archive record */
union block *current_block;     /* current block of archive */
enum access_mode access_mode;   /* how do we handle the archive */
off_t records_read;             /* number of records read from this archive */
off_t records_written;          /* likewise, for records written */
static off_t start_offset;	/* start offset in the archive */

/* When file status was last computed.  */
static struct timespec last_stat_time;

static off_t record_start_block; /* block ordinal at record_start */

/* Where we write list messages (not errors, not interactions) to.  */
FILE *stdlis;

static void backspace_output (void);
static _Noreturn void write_fatal_details (char const *, ssize_t, idx_t);

/* PID of child program, if compress_option or remote archive access.  */
static pid_t child_pid;

/* Error recovery stuff  */
static int read_error_count;

/* Have we hit EOF yet?  */
static bool hit_eof;

static bool read_full_records = false;

bool write_archive_to_stdout;

static void (*flush_write_ptr) (idx_t);
static void (*flush_read_ptr) (void);


char *volume_label;
char *continued_file_name;
off_t continued_file_size;
off_t continued_file_offset;


static intmax_t volno = 1;	/* which volume of a multi-volume tape we're
                                   on */
static intmax_t global_volno = 1; /* volume number to print in external
                                     messages */

bool write_archive_to_stdout;


/* Multi-volume tracking support */

/* When creating a multi-volume archive, each 'bufmap' represents
   a member stored (perhaps partly) in the current record buffer.
   Bufmaps are form a single-linked list in chronological order.

   After flushing the record to the output media, all bufmaps that
   represent fully written members are removed from the list, the
   nblocks and sizeleft values in the bufmap_head and start values
   in all remaining bufmaps are updated.  The information stored
   in bufmap_head is used to form the volume header.

   When reading from a multi-volume archive, the list degrades to a
   single element, which keeps information about the member currently
   being read.  In that case the sizeleft member is updated explicitly
   from the extractor code by calling the mv_size_left function.  The
   information from bufmap_head is compared with the volume header data
   to ensure that subsequent volumes are fed in the right order.
*/

struct bufmap
{
  struct bufmap *next;          /* Pointer to the next map entry */
  idx_t start;			/* Offset of the first data block */
  char *file_name;              /* Name of the stored file */
  off_t sizetotal;              /* Size of the stored file */
  off_t sizeleft;               /* Size left to read/write */
  idx_t nblocks;		/* Number of blocks written since reset */
};
static struct bufmap *bufmap_head, *bufmap_tail;

/* This variable, when set, inhibits updating the bufmap chain after
   a write.  This is necessary when writing extended POSIX headers. */
static bool inhibit_map;

void
mv_begin_write (const char *file_name, off_t totsize, off_t sizeleft)
{
  if (multi_volume_option)
    {
      struct bufmap *bp = xmalloc (sizeof bp[0]);
      if (bufmap_tail)
	bufmap_tail->next = bp;
      else
	bufmap_head = bp;
      bufmap_tail = bp;

      bp->next = NULL;
      bp->start = current_block - record_start;
      bp->file_name = xstrdup (file_name);
      bp->sizetotal = totsize;
      bp->sizeleft = sizeleft;
      bp->nblocks = 0;
    }
}

static struct bufmap *
bufmap_locate (idx_t off)
{
  struct bufmap *map;

  for (map = bufmap_head; map; map = map->next)
    {
      if (!map->next || off < map->next->start * BLOCKSIZE)
	break;
    }
  return map;
}

static void
bufmap_free (struct bufmap *mark)
{
  struct bufmap *map;
  for (map = bufmap_head; map && map != mark; )
    {
      struct bufmap *next = map->next;
      free (map->file_name);
      free (map);
      map = next;
    }
  bufmap_head = map;
  if (!bufmap_head)
    bufmap_tail = bufmap_head;
}

static void
bufmap_reset (struct bufmap *map, ptrdiff_t fixup)
{
  bufmap_free (map);
  if (map)
    {
      for (; map; map = map->next)
	{
	  map->start += fixup;
	  map->nblocks = 0;
	}
    }
}


static struct tar_stat_info dummy;

void
buffer_write_global_xheader (void)
{
  xheader_write_global (&dummy.xhdr);
}

void
mv_begin_read (struct tar_stat_info *st)
{
  mv_begin_write (st->orig_file_name, st->stat.st_size, st->stat.st_size);
}

void
mv_end (void)
{
  if (multi_volume_option)
    bufmap_free (NULL);
}

void
mv_size_left (off_t size)
{
  if (bufmap_head)
    bufmap_head->sizeleft = size;
}


/* Functions.  */

void
clear_read_error_count (void)
{
  read_error_count = 0;
}


/* Time-related functions */

/* Time consumed during run.  It is counted in ns to lessen rounding error.  */
static double duration_ns;

void
set_start_time (void)
{
  gettime (&start_time);
  volume_start_time = start_time;
  last_stat_time = start_time;
}

static void
set_volume_start_time (void)
{
  gettime (&volume_start_time);
  last_stat_time = volume_start_time;
}

double
compute_duration_ns (void)
{
  struct timespec now = current_timespec ();

  /* If the clock moves back, treat it as duration 0.
     This works even if time_t is unsigned.  */
  if (timespec_cmp (last_stat_time, now) < 0)
    duration_ns += (1e9 * (now.tv_sec - last_stat_time.tv_sec)
		    + (now.tv_nsec - last_stat_time.tv_nsec));

  last_stat_time = current_timespec ();
  return duration_ns;
}


/* Compression detection */

enum compress_type {
  ct_none,             /* Unknown compression type */
  ct_tar,              /* Plain tar file */
  ct_compress,
  ct_gzip,
  ct_bzip2,
  ct_lzip,
  ct_lzma,
  ct_lzop,
  ct_xz,
  ct_zstd
};

static enum compress_type archive_compression_type = ct_none;

struct zip_magic
{
  enum compress_type type;
  char length;
  char const *magic;
};

struct zip_program
{
  enum compress_type type;
  char const *program;
  char const *option;
};

static struct zip_magic const magic[] = {
  { ct_none,     0, NULL },
  { ct_tar,      0, NULL },
  { ct_compress, 2, "\037\235" },
  { ct_gzip,     2, "\037\213" },
  { ct_bzip2,    3, "BZh" },
  { ct_lzip,     4, "LZIP" },
  { ct_lzma,     6, "\xFFLZMA" },
  { ct_lzma,     3, "\x5d\x00\x00" },
  { ct_lzop,     4, "\211LZO" },
  { ct_xz,       6, "\xFD" "7zXZ" },
  { ct_zstd,     4, "\x28\xB5\x2F\xFD" },
};

static struct zip_program zip_program[] = {
  { ct_compress, COMPRESS_PROGRAM, "-Z" },
  { ct_compress, GZIP_PROGRAM,     "-z" },
  { ct_gzip,     GZIP_PROGRAM,     "-z" },
  { ct_bzip2,    BZIP2_PROGRAM,    "-j" },
  { ct_bzip2,    "lbzip2",         "-j" },
  { ct_lzip,     LZIP_PROGRAM,     "--lzip" },
  { ct_lzma,     LZMA_PROGRAM,     "--lzma" },
  { ct_lzma,     XZ_PROGRAM,       "-J" },
  { ct_lzop,     LZOP_PROGRAM,     "--lzop" },
  { ct_xz,       XZ_PROGRAM,       "-J" },
  { ct_zstd,     ZSTD_PROGRAM,     "--zstd" },
};

static struct zip_program const *
find_zip_program (enum compress_type type, int *pstate)
{
  int i;

  for (i = *pstate; i < countof (zip_program); i++)
    {
      if (zip_program[i].type == type)
	{
	  *pstate = i + 1;
	  return zip_program + i;
	}
    }
  *pstate = i;
  return NULL;
}

const char *
first_decompress_program (int *pstate)
{
  struct zip_program const *zp;

  *pstate = countof (zip_program);

  if (use_compress_program_option)
    return use_compress_program_option;

  if (archive_compression_type == ct_none)
    return NULL;

  *pstate = 0;
  zp = find_zip_program (archive_compression_type, pstate);
  return zp ? zp->program : NULL;
}

const char *
next_decompress_program (int *pstate)
{
  struct zip_program const *zp;

  zp = find_zip_program (archive_compression_type, pstate);
  return zp ? zp->program : NULL;
}

static const char *
compress_option (enum compress_type type)
{
  int i = 0;
  struct zip_program const *zp = find_zip_program (type, &i);
  return zp ? zp->option : NULL;
}

/* Check if the file ARCHIVE is a compressed archive. */
static enum compress_type
check_compressed_archive (bool *pshort)
{
  struct zip_magic const *p;
  bool sfr;
  bool temp;

  if (!pshort)
    pshort = &temp;

  /* Prepare global data needed for find_next_block: */
  record_end = record_start; /* set up for 1st record = # 0 */
  sfr = read_full_records;
  read_full_records = true; /* Suppress fatal error on reading a partial
                               record */
  *pshort = !find_next_block ();

  /* Restore global values */
  read_full_records = sfr;

  if (record_start != record_end /* no files smaller than BLOCKSIZE */
      && (memeq (record_start->header.magic, TMAGIC, sizeof TMAGIC)
          || memeq (record_start->buffer + offsetof (struct posix_header,
						     magic),
		    OLDGNU_MAGIC, sizeof OLDGNU_MAGIC))
      && tar_checksum (record_start, true) == HEADER_SUCCESS)
    /* Probably a valid header */
    return ct_tar;

  for (p = magic + 2; p < magic + countof (magic); p++)
    if (memeq (record_start->buffer, p->magic, p->length))
      return p->type;

  return ct_none;
}

/* Open an archive named archive_name_array[0]. Detect if it is
   a compressed archive of known type and use corresponding decompression
   program if so */
static int
open_compressed_archive (void)
{
  archive = rmtopen (archive_name_array[0], O_RDONLY | O_BINARY,
                     MODE_RW, rsh_command_option);
  if (archive < 0)
    return archive;

  if (!multi_volume_option)
    {
      if (!use_compress_program_option)
        {
          bool shortfile;
          enum compress_type type = check_compressed_archive (&shortfile);

          switch (type)
            {
            case ct_tar:
              if (shortfile)
		paxerror (0, _("This does not look like a tar archive"));
              return archive;

            case ct_none:
              if (shortfile)
		paxerror (0, _("This does not look like a tar archive"));
              set_compression_program_by_suffix (archive_name_array[0], NULL,
						 false);
              if (!use_compress_program_option)
		return archive;
              break;

            default:
              archive_compression_type = type;
              break;
            }
        }

      /* FD is not needed any more */
      rmtclose (archive);

      hit_eof = false; /* It might have been set by find_next_block in
                          check_compressed_archive */

      /* Open compressed archive */
      child_pid = sys_child_open_for_uncompress ();
      read_full_records = true;
    }

  records_read = 0;
  record_end = record_start; /* set up for 1st record = # 0 */

  return archive;
}

static intmax_t
print_stats (FILE *fp, const char *text, tarlong numbytes)
{
  char abbr[LONGEST_HUMAN_READABLE + 1];
  int human_opts = human_autoscale | human_base_1024 | human_SI | human_B;
  double ulim = UINTMAX_MAX + 1.0;

  intmax_t n = fprintf (fp, "%s: "TARLONG_FORMAT" (", gettext (text), numbytes);

  if (numbytes < ulim)
    n = add_printf (n, fprintf (fp, "%s", human_readable (numbytes, abbr,
							  human_opts, 1, 1)));
  else
    n = add_printf (n, fprintf (fp, "%g", numbytes));

  if (!duration_ns)
    n = add_printf (n, ! (fputc (')', fp) < 0));
  else
    {
      double rate = 1e9 * numbytes / duration_ns;
      n = add_printf (n, (rate < ulim
			  ? fprintf (fp, ", %s/s)",
				     human_readable (rate, abbr, human_opts,
						     1, 1))
			  : fprintf (fp, ", %g/s)", rate)));
    }

  return n;
}

/* Format totals to file FP.  FORMATS is an array of strings to output
   before each data item (bytes read, written, deleted, in that order).
   EOR is a delimiter to output after each item (used only if deleting
   from the archive), EOL is a delimiter to add at the end of the output
   line. */
intmax_t
format_total_stats (FILE *fp, char const *const *formats, char eor, char eol)
{
  intmax_t n;

  switch (subcommand_option)
    {
    case CREATE_SUBCOMMAND:
    case CAT_SUBCOMMAND:
    case UPDATE_SUBCOMMAND:
    case APPEND_SUBCOMMAND:
      n = print_stats (fp, formats[TF_WRITE],
		       prev_written + bytes_written);
      break;

    case DELETE_SUBCOMMAND:
      {
        n = print_stats (fp, formats[TF_READ],
			 records_read * record_size);

	n = add_printf (n, ! (fputc (eor, fp) < 0));

	n = add_printf (n, print_stats (fp, formats[TF_WRITE],
					prev_written + bytes_written));

	intmax_t deleted = ((records_read - records_skipped) * record_size
			    - (prev_written + bytes_written));
	n = add_printf (n, fprintf (fp, "%c%s: %jd", eor,
				    gettext (formats[TF_DELETED]), deleted));
      }
      break;

    case EXTRACT_SUBCOMMAND:
    case LIST_SUBCOMMAND:
    case DIFF_SUBCOMMAND:
      n = print_stats (fp, _(formats[TF_READ]),
		       records_read * record_size);
      break;

    default:
      abort ();
    }
  if (eol)
    n = add_printf (n, ! (fputc (eol, fp) < 0));
  return n;
}

static char const *const default_total_format[] = {
  N_("Total bytes read"),
  /* Amanda 2.4.1p1 looks for "Total bytes written: [0-9][0-9]*".  */
  N_("Total bytes written"),
  N_("Total bytes deleted")
};

void
print_total_stats (void)
{
  format_total_stats (stderr, default_total_format, '\n', '\n');
}

/* Compute and return the block ordinal at current_block.  */
off_t
current_block_ordinal (void)
{
  return record_start_block + (current_block - record_start);
}

/* If the EOF flag is set, reset it, as well as current_block, etc.  */
void
reset_eof (void)
{
  if (hit_eof)
    {
      hit_eof = false;
      current_block = record_start;
      record_end = record_start + blocking_factor;
      access_mode = ACCESS_WRITE;
    }
}

/* Return the location of the next available input or output block.
   Return zero for EOF.  Once we have returned zero, we just keep returning
   it, to avoid accidentally going on to the next file on the tape.  */
union block *
find_next_block (void)
{
  if (current_block == record_end)
    {
      if (hit_eof)
        return NULL;
      flush_archive ();
      if (current_block == record_end)
        {
          hit_eof = true;
          return NULL;
        }
    }
  return current_block;
}

/* Indicate that we have used all blocks up thru the block addressed by PTR,
   which may point to any of the bytes in the addressed block.
   This does nothing if PTR points before the current block.  */
void
set_next_block_after (void *ptr)
{
  char *p = ptr;
  ptrdiff_t offset = p - charptr (current_block);
  if (0 <= offset)
    current_block += (offset >> LG_BLOCKSIZE) + 1;

  /* Do *not* flush the archive here.  If we do, the same argument to
     set_next_block_after could mean the next block (if the input record
     is exactly one block long), which is not what is intended.  */

  if (current_block > record_end)
    abort ();
}

/* Return the number of bytes comprising the space between POINTER
   through the end of the current buffer of blocks.  This space is
   available for filling with data, or taking data from.  POINTER is
   usually (but not always) the result of previous find_next_block call.  */
idx_t
available_space_after (union block *pointer)
{
  return charptr (record_end) - charptr (pointer);
}

static void
init_buffer (void)
{
  if (! record_buffer[record_index])
    record_buffer[record_index] = xalignalloc (getpagesize (), record_size);

  record_start = record_buffer[record_index];
  current_block = record_start;
  record_end = record_start + blocking_factor;
}

static void
check_tty (enum access_mode mode)
{
  /* Refuse to read archive from and write it to a tty. */
  if (streq (archive_name_array[0], "-")
      && isatty (mode == ACCESS_READ ? STDIN_FILENO : STDOUT_FILENO))
    {
      paxfatal (0, (mode == ACCESS_READ
		    ? _("Refusing to read archive contents from terminal "
			"(missing -f option?)")
		    : _("Refusing to write archive contents to terminal "
			"(missing -f option?)")));
    }
}

/* Fetch the status of the archive, accessed via WANTED_STATUS.  */

static void
get_archive_status (enum access_mode wanted_access, bool backed_up_flag)
{
  if (!sys_get_archive_stat ())
    {
      int saved_errno = errno;

      if (backed_up_flag)
        undo_last_backup ();
      errno = saved_errno;
      open_fatal (archive_name_array[0]);
    }

  seekable_archive
    = (! (multi_volume_option || use_compress_program_option)
       && (seek_option < 0
	   ? (_isrmt (archive)
	      || ! (S_ISFIFO (archive_stat.st_mode)
		    || S_ISSOCK (archive_stat.st_mode)))
	   : seek_option != 0));

  if (wanted_access == ACCESS_READ)
    {
      if (seekable_archive)
	{
	  start_offset = (lseek (archive, 0, SEEK_CUR)
			  - (record_end - record_start) * BLOCKSIZE
			  - short_read_slop);
	  if (start_offset < 0)
	    seekable_archive = false;
	}
    }
  else
    sys_detect_dev_null_output ();

  SET_BINARY_MODE (archive);
}

/* Open an archive file.  The argument specifies whether we are
   reading or writing, or both.  */
static void
_open_archive (enum access_mode wanted_access)
{
  bool backed_up_flag = false;

  if (record_size == 0)
    paxfatal (0, _("Invalid value for record_size"));

  if (archive_names == 0)
    paxfatal (0, _("No archive name given"));

  tar_stat_destroy (&current_stat_info);

  record_index = false;
  init_buffer ();

  /* When updating the archive, we start with reading.  */
  access_mode = wanted_access == ACCESS_UPDATE ? ACCESS_READ : wanted_access;
  check_tty (access_mode);

  read_full_records = read_full_records_option;

  records_read = 0;

  if (use_compress_program_option)
    {
      switch (wanted_access)
        {
        case ACCESS_READ:
          child_pid = sys_child_open_for_uncompress ();
          read_full_records = true;
          record_end = record_start; /* set up for 1st record = # 0 */
          break;

        case ACCESS_WRITE:
          child_pid = sys_child_open_for_compress ();
          break;

        case ACCESS_UPDATE:
          abort (); /* Should not happen */
          break;
        }

      if (!index_file_name
          && wanted_access == ACCESS_WRITE
          && streq (archive_name_array[0], "-"))
        stdlis = stderr;
    }
  else if (streq (archive_name_array[0], "-"))
    {
      read_full_records = true; /* could be a pipe, be safe */
      if (verify_option)
	paxfatal (0, _("Cannot verify stdin/stdout archive"));

      switch (wanted_access)
        {
        case ACCESS_READ:
          {
            bool shortfile;
            enum compress_type type;

            archive = STDIN_FILENO;
            type = check_compressed_archive (&shortfile);
            if (type != ct_tar && type != ct_none)
	      paxfatal (0, _("Archive is compressed. Use %s option"),
			compress_option (type));
            if (shortfile)
	      paxerror (0, _("This does not look like a tar archive"));
          }
          break;

        case ACCESS_WRITE:
          archive = STDOUT_FILENO;
          if (!index_file_name)
            stdlis = stderr;
          break;

        case ACCESS_UPDATE:
          archive = STDIN_FILENO;
          write_archive_to_stdout = true;
          record_end = record_start; /* set up for 1st record = # 0 */
          if (!index_file_name)
            stdlis = stderr;
          break;
        }
    }
  else
    switch (wanted_access)
      {
      case ACCESS_READ:
        archive = open_compressed_archive ();
        break;

      case ACCESS_WRITE:
        if (backup_option)
          {
            maybe_backup_file (archive_name_array[0], 1);
            backed_up_flag = true;
          }
	if (verify_option)
	  archive = rmtopen (archive_name_array[0], O_RDWR | O_CREAT | O_BINARY,
			     MODE_RW, rsh_command_option);
	else
	  archive = rmtcreat (archive_name_array[0], MODE_RW,
			      rsh_command_option);
        break;

      case ACCESS_UPDATE:
        archive = rmtopen (archive_name_array[0],
                           O_RDWR | O_CREAT | O_BINARY,
                           MODE_RW, rsh_command_option);

        switch (check_compressed_archive (NULL))
          {
          case ct_none:
          case ct_tar:
            break;

          default:
	    paxfatal (0, _("Cannot update compressed archives"));
          }
        break;
      }

  get_archive_status (wanted_access, backed_up_flag);

  switch (wanted_access)
    {
    case ACCESS_READ:
      find_next_block ();       /* read it in, check for EOF */
      break;

    case ACCESS_UPDATE:
    case ACCESS_WRITE:
      records_written = 0;
      break;
    }
}

/* Perform a write to flush the buffer.  */
static idx_t
_flush_write (void)
{
  idx_t status;

  checkpoint_run (true);
  if (tape_length_option && tape_length_option <= bytes_written)
    {
      errno = ENOSPC;
      status = 0;
    }
  else if (dev_null_output)
    status = record_size;
  else
    status = sys_write_archive_buffer ();

  if (status && multi_volume_option && !inhibit_map)
    {
      struct bufmap *map = bufmap_locate (status);
      if (map)
	{
	  idx_t delta = status - map->start * BLOCKSIZE;
	  idx_t diff;
	  map->nblocks += delta >> LG_BLOCKSIZE;
	  if (delta > map->sizeleft)
	    delta = map->sizeleft;
	  map->sizeleft -= delta;
	  if (map->sizeleft == 0)
	    {
	      diff = map->start + map->nblocks;
	      map = map->next;
	    }
	  else
	    diff = map->start;
	  bufmap_reset (map, - diff);
	}
    }
  return status;
}

/* Handle write errors on the archive.  Write errors are always fatal.
   Hitting the end of a volume does not cause a write error unless the
   write was the first record of the volume.  */
void
archive_write_error (ssize_t status)
{
  /* It might be useful to know how much was written before the error
     occurred.  */
  if (totals_option)
    {
      int e = errno;
      print_total_stats ();
      errno = e;
    }

  write_fatal_details (*archive_name_cursor, status, record_size);
}

/* Handle read errors on the archive.  If the read should be retried,
   return to the caller.  */
void
archive_read_error (void)
{
  read_error (*archive_name_cursor);

  if (record_start_block == 0)
    paxfatal (0, _("At beginning of tape, quitting now"));

  /* Read error in mid archive.  We retry up to READ_ERROR_MAX times and
     then give up on reading the archive.  */

  if (read_error_count++ > READ_ERROR_MAX)
    paxfatal (0, _("Too many errors, quitting"));
  return;
}

static bool
archive_is_dev (void)
{
  struct stat st;

  if (fstat (archive, &st) < 0)
    {
      stat_diag (*archive_name_cursor);
      return false;
    }
  return S_ISBLK (st.st_mode) || S_ISCHR (st.st_mode);
}

static void
short_read (idx_t status)
{
  idx_t left = record_size - status;		/* bytes left to read */
  char *more = charptr (record_start) + status; /* address of next read */

  if (left && left % BLOCKSIZE == 0
      && (warning_option & WARN_RECORD_SIZE)
      && record_start_block == 0 && status != 0
      && archive_is_dev ())
    {
      idx_t rsize = status >> LG_BLOCKSIZE;
      paxwarn (0,
	       ngettext ("Record size = %td block",
			 "Record size = %td blocks",
			 rsize),
	       rsize);
    }

  while (left % BLOCKSIZE != 0
         || (left && status && read_full_records))
    {
      if (status)
	{
	  ptrdiff_t nread;
	  while ((nread = rmtread (archive, more, left)) < 0)
	    archive_read_error ();
	  status = nread;
	}

      if (status == 0)
        break;

      if (! read_full_records)
        {
          idx_t rest = record_size - left;

	  paxfatal (0, ngettext ("Unaligned block (%td byte) in archive",
				 "Unaligned block (%td bytes) in archive",
				 rest),
		    rest);
        }

      left -= status;
      more += status;
    }

  record_end = record_start + ((record_size - left) >> LG_BLOCKSIZE);
  short_read_slop = (record_size - left) & (BLOCKSIZE - 1);
  records_read++;
}

/*  Flush the current buffer to/from the archive.  */
void
flush_archive (void)
{
  idx_t buffer_level;

  if (access_mode == ACCESS_READ && time_to_start_writing)
    {
      access_mode = ACCESS_WRITE;
      time_to_start_writing = false;
      backspace_output ();
      if (record_end - record_start < blocking_factor)
	{
	  memset (record_end, 0,
		  (blocking_factor - (record_end - record_start))
		  * BLOCKSIZE);
	  record_end = record_start + blocking_factor;
	  return;
	}
    }

  buffer_level = charptr (current_block) - charptr (record_start);
  record_start_block += record_end - record_start;
  current_block = record_start;
  record_end = record_start + blocking_factor;

  switch (access_mode)
    {
    case ACCESS_READ:
      flush_read ();
      break;

    case ACCESS_WRITE:
      flush_write_ptr (buffer_level);
      break;

    case ACCESS_UPDATE:
      abort ();
    }
}

/* Backspace the archive descriptor by one record worth.  If it's a
   tape, MTIOCTOP will work.  If it's something else, try to seek on
   it.  If we can't seek, we lose!  */
static void
backspace_output (void)
{
  if (mtioseek (false, -1))
    return;

  {
    off_t position = rmtlseek (archive, 0, SEEK_CUR);

    /* Seek back to the beginning of this record and start writing there.  */

    position -= charptr (record_end) - charptr (record_start);
    if (position < 0)
      position = 0;
    if (rmtlseek (archive, position, SEEK_SET) != position)
      {
        /* Lseek failed.  Try a different method.  */

	paxwarn (0, _("Cannot backspace archive file;"
		      " it may be unreadable without -i"));

        /* Replace the first part of the record with NULs.  */

        if (record_start->buffer != output_start)
          memset (record_start, 0, output_start - charptr (record_start));
      }
  }
}

off_t
seek_archive (off_t size)
{
  off_t start = current_block_ordinal ();
  off_t offset;
  off_t nrec, nblk;

  /* If low level I/O is already at EOF, do not try to seek further.  */
  if (record_end < record_start + blocking_factor)
    return 0;

  off_t skipped = (blocking_factor - (current_block - record_start))
                  * BLOCKSIZE;

  if (size <= skipped)
    return 0;

  /* Compute number of records to skip */
  nrec = (size - skipped) / record_size;
  if (nrec == 0)
    return 0;
  offset = rmtlseek (archive, nrec * record_size, SEEK_CUR);
  if (offset < 0)
    return offset;

  offset -= start_offset;

  if (offset % record_size)
    paxfatal (0, _("rmtlseek not stopped at a record boundary"));

  /* Convert to number of records */
  offset >>= LG_BLOCKSIZE;
  /* Compute number of skipped blocks */
  nblk = offset - start;

  /* Update buffering info */
  records_read += nblk / blocking_factor;
  record_start_block = offset - blocking_factor;
  current_block = record_end;

  return nblk;
}

/* Close the archive file.  */
void
close_archive (void)
{
  if (time_to_start_writing || access_mode == ACCESS_WRITE)
    {
      do
	flush_archive ();
      while (current_block > record_start);
    }

  compute_duration_ns ();
  if (verify_option)
    verify_volume ();

  if (rmtclose (archive) < 0)
    close_error (*archive_name_cursor);

  sys_wait_for_child (child_pid, hit_eof);

  tar_stat_destroy (&current_stat_info);
  alignfree (record_buffer[0]);
  alignfree (record_buffer[1]);
  bufmap_free (NULL);
}

static void
write_fatal_details (char const *name, ssize_t status, idx_t size)
{
  write_error_details (name, status, size);
  if (rmtclose (archive) < 0)
    close_error (*archive_name_cursor);
  sys_wait_for_child (child_pid, false);
  fatal_exit ();
}

/* Called to initialize the global volume number.  */
void
init_volume_number (void)
{
  FILE *file = fopen (volno_file_option, "r");

  if (file)
    {
      if (fscanf (file, "%jd", &global_volno) != 1
          || global_volno < 0)
	paxfatal (0, _("%s: contains invalid volume number"),
		  quotearg_colon (volno_file_option));
      if (ferror (file))
        read_error (volno_file_option);
      if (fclose (file) < 0)
        close_error (volno_file_option);
    }
  else if (errno != ENOENT)
    open_error (volno_file_option);
}

/* Called to write out the closing global volume number.  */
void
closeout_volume_number (void)
{
  FILE *file = fopen (volno_file_option, "w");

  if (file)
    {
      fprintf (file, "%jd\n", global_volno);
      if (ferror (file))
        write_error (volno_file_option);
      if (fclose (file) < 0)
        close_error (volno_file_option);
    }
  else
    open_error (volno_file_option);
}


static void
increase_volume_number (void)
{
  global_volno++;
  volno++;
}

static void
change_tape_menu (FILE *read_file)
{
  char *input_buffer = NULL;
  size_t size = 0;

  while (true)
    {
      fputc ('\007', stderr);
      fprintf (stderr,
               _("Prepare volume #%jd for %s and hit return: "),
               global_volno + 1, quote (*archive_name_cursor));
      fflush (stderr);

      if (getline (&input_buffer, &size, read_file) <= 0)
        {
	  paxwarn (0, _("EOF where user reply was expected"));

          if (subcommand_option != EXTRACT_SUBCOMMAND
              && subcommand_option != LIST_SUBCOMMAND
              && subcommand_option != DIFF_SUBCOMMAND)
	    paxwarn (0, _("WARNING: Archive is incomplete"));

          fatal_exit ();
        }

      if (input_buffer[0] == '\n'
          || input_buffer[0] == 'y'
          || input_buffer[0] == 'Y')
        break;

      switch (input_buffer[0])
        {
        case '?':
          {
            fprintf (stderr, _("\
 n name        Give a new file name for the next (and subsequent) volume(s)\n\
 q             Abort tar\n\
 y or newline  Continue operation\n"));
            if (!restrict_option)
              fprintf (stderr, _(" !             Spawn a subshell\n"));
            fprintf (stderr, _(" ?             Print this list\n"));
          }
          break;

        case 'q':
          /* Quit.  */

	  paxwarn (0, _("No new volume; exiting.\n"));

          if (subcommand_option != EXTRACT_SUBCOMMAND
              && subcommand_option != LIST_SUBCOMMAND
              && subcommand_option != DIFF_SUBCOMMAND)
	    paxwarn (0, _("WARNING: Archive is incomplete"));

          fatal_exit ();

        case 'n':
          /* Get new file name.  */

          {
            char *name;
            char *cursor;

            for (name = input_buffer + 1;
                 *name == ' ' || *name == '\t';
                 name++)
              ;

            for (cursor = name; *cursor && *cursor != '\n'; cursor++)
              ;

            if (cursor != name)
              {
		memmove (input_buffer, name, cursor - name);
		input_buffer[cursor - name] = '\0';
		*archive_name_cursor = input_buffer;
		/* FIXME: *archive_name_cursor is never freed.  */
		return;
              }

	    fprintf (stderr, "%s",
		     _("File name not specified. Try again.\n"));
          }
          break;

        case '!':
          if (!restrict_option)
            {
              sys_spawn_shell ();
              break;
            }
	  FALLTHROUGH;
        default:
          fprintf (stderr, _("Invalid input. Type ? for help.\n"));
        }
    }
  free (input_buffer);
}

/* We've hit the end of the old volume.  Close it and open the next one.
   Return true on success.
*/
static bool
new_volume (enum access_mode mode)
{
  static FILE *read_file;
  static bool looped;
  bool prompt;

  if (global_volno == INTMAX_MAX)
    paxfatal (0, _("Volume number overflow"));

  if (!read_file && !info_script_option)
    /* FIXME: if fopen is used, it will never be closed.  */
    read_file = archive == STDIN_FILENO ? fopen (TTY_NAME, "r") : stdin;

  if (now_verifying)
    return false;
  if (verify_option)
    verify_volume ();

  assign_null (&volume_label);
  assign_null (&continued_file_name);
  continued_file_size = continued_file_offset = 0;
  current_block = record_start;

  if (rmtclose (archive) < 0)
    close_error (*archive_name_cursor);

  archive_name_cursor++;
  if (archive_name_cursor == archive_name_array + archive_names)
    {
      archive_name_cursor = archive_name_array;
      looped = true;
    }
  prompt = looped;

 tryagain:
  if (prompt)
    {
      /* We have to prompt from now on.  */

      if (info_script_option)
        {
          if (volno_file_option)
            closeout_volume_number ();
	  if (sys_exec_info_script (archive_name_cursor, global_volno + 1) != 0)
	    paxfatal (0, _("%s command failed"), quote (info_script_option));
        }
      else
        change_tape_menu (read_file);
    }

  if (streq (archive_name_cursor[0], "-"))
    {
      read_full_records = true;
      archive = STDIN_FILENO;
    }
  else if (verify_option)
    archive = rmtopen (*archive_name_cursor, O_RDWR | O_CREAT, MODE_RW,
                       rsh_command_option);
  else
    switch (mode)
      {
      case ACCESS_READ:
        archive = rmtopen (*archive_name_cursor, O_RDONLY, MODE_RW,
                           rsh_command_option);
        break;

      case ACCESS_WRITE:
        if (backup_option)
          maybe_backup_file (*archive_name_cursor, 1);
        archive = rmtcreat (*archive_name_cursor, MODE_RW,
                            rsh_command_option);
        break;

      case ACCESS_UPDATE:
        archive = rmtopen (*archive_name_cursor, O_RDWR | O_CREAT, MODE_RW,
                           rsh_command_option);
        break;
      }

  if (archive < 0)
    {
      open_warn (*archive_name_cursor);
      if (!verify_option && mode == ACCESS_WRITE && backup_option)
        undo_last_backup ();
      prompt = true;
      goto tryagain;
    }

  get_archive_status (mode, false);

  return true;
}

static bool
read_header0 (struct tar_stat_info *info)
{
  enum read_header rc;

  tar_stat_init (info);
  rc = read_header (&current_header, info, read_header_auto);
  if (rc == HEADER_SUCCESS)
    {
      set_next_block_after (current_header);
      return true;
    }
  paxerror (0, _("This does not look like a tar archive"));
  return false;
}

static bool
try_new_volume (void)
{
  ptrdiff_t status;
  union block *header;
  enum access_mode acc;

  switch (subcommand_option)
    {
    case APPEND_SUBCOMMAND:
    case CAT_SUBCOMMAND:
    case UPDATE_SUBCOMMAND:
      acc = ACCESS_UPDATE;
      break;

    default:
      acc = ACCESS_READ;
      break;
    }

  if (!new_volume (acc))
    return true;

  while ((status = rmtread (archive, charptr (record_start), record_size))
         < 0)
    archive_read_error ();

  short_read_slop = 0;
  if (status != record_size)
    short_read (status);

  header = find_next_block ();
  if (!header)
    {
      paxwarn (0, _("This does not look like a tar archive"));
      return false;
    }

  switch (header->header.typeflag)
    {
    case XGLTYPE:
      {
	tar_stat_init (&dummy);
	if (read_header (&header, &dummy, read_header_x_global)
	    != HEADER_SUCCESS_EXTENDED)
	  {
	    paxwarn (0, _("This does not look like a tar archive"));
	    return false;
	  }

        xheader_decode (&dummy); /* decodes values from the global header */
        tar_stat_destroy (&dummy);

	/* The initial global header must be immediately followed by
	   an extended PAX header for the first member in this volume.
	   However, in some cases tar may split volumes in the middle
	   of a PAX header. This is incorrect, and should be fixed
           in the future versions. In the meantime we must be
	   prepared to correctly list and extract such archives.

	   If this happens, the following call to read_header returns
	   HEADER_FAILURE, which is ignored.

	   See also tests/multiv07.at */

	switch (read_header (&header, &dummy, read_header_auto))
	  {
	  case HEADER_SUCCESS:
	    set_next_block_after (header);
	    break;

	  case HEADER_FAILURE:
	    break;

	  default:
	    paxwarn (0, _("This does not look like a tar archive"));
	    return false;
	  }
        break;
      }

    case GNUTYPE_VOLHDR:
      if (!read_header0 (&dummy))
        return false;
      tar_stat_destroy (&dummy);
      ASSIGN_STRING_N (&volume_label, current_header->header.name);
      set_next_block_after (header);
      header = find_next_block ();
      if (! (header && header->header.typeflag == GNUTYPE_MULTIVOL))
        break;
      FALLTHROUGH;
    case GNUTYPE_MULTIVOL:
      if (!read_header0 (&dummy))
        return false;
      tar_stat_destroy (&dummy);
      ASSIGN_STRING_N (&continued_file_name, current_header->header.name);
      continued_file_size =
        OFF_FROM_HEADER (current_header->header.size);
      continued_file_offset =
        OFF_FROM_HEADER (current_header->oldgnu_header.offset);
      break;

    default:
      break;
    }

  if (bufmap_head)
    {
      if (!continued_file_name)
	{
	  paxwarn (0, _("%s is not continued on this volume"),
		   quote (bufmap_head->file_name));
	  return false;
	}

      if (!streq (continued_file_name, bufmap_head->file_name))
        {
          if ((archive_format == GNU_FORMAT || archive_format == OLDGNU_FORMAT)
              && strlen (bufmap_head->file_name) >= NAME_FIELD_SIZE
              && strncmp (continued_file_name, bufmap_head->file_name,
                          NAME_FIELD_SIZE) == 0)
	    paxwarn (0,
		     _("%s is possibly continued on this volume:"
		       " header contains truncated name"),
		     quote (bufmap_head->file_name));
          else
            {
	      paxwarn (0, _("%s is not continued on this volume"),
		       quote (bufmap_head->file_name));
              return false;
            }
        }

      off_t s;
      if (ckd_add (&s, continued_file_size, continued_file_offset)
	  || s != bufmap_head->sizetotal)
        {
	  paxwarn (0, _("%s is the wrong size (%jd != %jd + %jd)"),
		   quote (continued_file_name),
		   intmax (bufmap_head->sizetotal),
		   intmax (continued_file_size),
		   intmax (continued_file_offset));
          return false;
        }

      if (bufmap_head->sizetotal - bufmap_head->sizeleft
	  != continued_file_offset)
        {
	  paxwarn (0, _("This volume is out of sequence (%jd - %jd != %jd)"),
		   intmax (bufmap_head->sizetotal),
		   intmax (bufmap_head->sizeleft),
		   intmax (continued_file_offset));
          return false;
        }
    }

  increase_volume_number ();
  return true;
}


char *
drop_volume_label_suffix (const char *label)
{
  static char const VOLUME_TEXT[] = " Volume ";
  idx_t VOLUME_TEXT_LEN = sizeof VOLUME_TEXT - 1;
  idx_t prefix_len = 0;

  for (idx_t i = 0; label[i]; i++)
    if (!c_isdigit (label[i]))
      prefix_len = i + 1;

  ptrdiff_t len = prefix_len - VOLUME_TEXT_LEN;
  return (0 <= len && memeq (label + len, VOLUME_TEXT, VOLUME_TEXT_LEN)
	  ? ximemdup0 (label, len)
	  : NULL);
}

/* Check LABEL against the volume label, seen as a globbing
   pattern.  Return true if the pattern matches.  In case of failure,
   retry matching a volume sequence number before giving up in
   multi-volume mode.  */
static bool
check_label_pattern (const char *label)
{
  char *string;
  bool result = false;

  if (fnmatch (volume_label_option, label, 0) == 0)
    return true;

  if (!multi_volume_option)
    return false;

  string = drop_volume_label_suffix (label);
  if (string)
    {
      result = fnmatch (string, volume_label_option, 0) == 0;
      free (string);
    }
  return result;
}

/* Check if the next block contains a volume label and if this matches
   the one given in the command line */
static void
match_volume_label (void)
{
  if (!volume_label)
    {
      union block *label = find_next_block ();

      if (!label)
	paxfatal (0, _("Archive not labeled to match %s"),
		  quote (volume_label_option));
      if (label->header.typeflag == GNUTYPE_VOLHDR)
	{
	  ASSIGN_STRING_N (&volume_label, label->header.name);
	}
      else if (label->header.typeflag == XGLTYPE)
	{
	  struct tar_stat_info st;
	  tar_stat_init (&st);
	  xheader_read (&st.xhdr, label,
			OFF_FROM_HEADER (label->header.size));
	  xheader_decode (&st);
	  tar_stat_destroy (&st);
	}
    }

  if (!volume_label)
    paxfatal (0, _("Archive not labeled to match %s"),
	      quote (volume_label_option));

  if (!check_label_pattern (volume_label))
    paxfatal (0, _("Volume %s does not match %s"),
	      quote_n (0, volume_label),
	      quote_n (1, volume_label_option));
}

/* Mark the archive with volume label STR. */
static void
_write_volume_label (const char *str)
{
  if (archive_format == POSIX_FORMAT)
    xheader_store ("GNU.volume.label", &dummy, str);
  else
    {
      union block *label = find_next_block ();

      assume (label);
      memset (label, 0, BLOCKSIZE);

      strcpy (label->header.name, str);
      assign_string (&current_stat_info.file_name, label->header.name);
      current_stat_info.had_trailing_slash =
        strip_trailing_slashes (current_stat_info.file_name);

      label->header.typeflag = GNUTYPE_VOLHDR;
      TIME_TO_CHARS (start_time.tv_sec, label->header.mtime);
      finish_header (&current_stat_info, label, -1);
      set_next_block_after (label);
    }
}

/* Add a volume label to a part of multi-volume archive */
static void
add_volume_label (void)
{
  static char const VOL_SUFFIX[] = "Volume";
  char *s = xmalloc (strlen (volume_label_option) + sizeof VOL_SUFFIX
		     + INT_BUFSIZE_BOUND (intmax_t) + 2);
  sprintf (s, "%s %s %jd", volume_label_option, VOL_SUFFIX, volno);
  _write_volume_label (s);
  free (s);
}

static void
add_chunk_header (struct bufmap *map)
{
  if (archive_format == POSIX_FORMAT)
    {
      union block *blk;
      struct tar_stat_info st;

      memset (&st, 0, sizeof st);
      st.orig_file_name = st.file_name = map->file_name;
      st.stat.st_mode = S_IFREG|S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH;
      st.stat.st_uid = getuid ();
      st.stat.st_gid = getgid ();
      st.orig_file_name = xheader_format_name (&st,
                                               "%d/GNUFileParts/%f.%n",
                                               volno);
      st.file_name = st.orig_file_name;
      st.archive_file_size = st.stat.st_size = map->sizeleft;

      blk = start_header (&st);
      if (!blk)
        abort (); /* FIXME */
      simple_finish_header (write_extended (false, &st, blk));
      free (st.orig_file_name);
    }
}


/* Add a volume label to the current archive */
static void
write_volume_label (void)
{
  if (multi_volume_option)
    add_volume_label ();
  else
    _write_volume_label (volume_label_option);
}

/* Write GNU multi-volume header */
static void
gnu_add_multi_volume_header (struct bufmap *map)
{
  int tmp;
  union block *block = find_next_block ();
  idx_t len = strlen (map->file_name);

  if (len > NAME_FIELD_SIZE)
    {
      paxwarn (0,
	       _("%s: file name too long to be stored"
		 " in a GNU multivolume header, truncated"),
	       quotearg_colon (map->file_name));
      len = NAME_FIELD_SIZE;
    }

  memset (block, 0, BLOCKSIZE);

  memcpy (block->header.name, map->file_name, len);
  block->header.typeflag = GNUTYPE_MULTIVOL;

  OFF_TO_CHARS (map->sizeleft, block->header.size);
  OFF_TO_CHARS (map->sizetotal - map->sizeleft,
                block->oldgnu_header.offset);

  tmp = verbose_option;
  verbose_option = 0;
  finish_header (&current_stat_info, block, -1);
  verbose_option = tmp;
  set_next_block_after (block);
}

/* Add a multi volume header to the current archive. The exact header format
   depends on the archive format. */
static void
add_multi_volume_header (struct bufmap *map)
{
  if (archive_format == POSIX_FORMAT)
    {
      off_t d = map->sizetotal - map->sizeleft;
      xheader_store ("GNU.volume.filename", &dummy, map->file_name);
      xheader_store ("GNU.volume.size", &dummy, &map->sizeleft);
      xheader_store ("GNU.volume.offset", &dummy, &d);
    }
  else
    gnu_add_multi_volume_header (map);
}


/* Low-level flush functions */

/* Simple flush read (no multi-volume or label extensions) */
static void
simple_flush_read (void)
{
  checkpoint_run (false);

  /* Clear the count of errors.  This only applies to a single call to
     flush_read.  */

  read_error_count = 0;         /* clear error count */

  if (write_archive_to_stdout && record_start_block != 0)
    {
      archive = STDOUT_FILENO;
      idx_t status = sys_write_archive_buffer ();
      archive = STDIN_FILENO;
      if (status != record_size)
        archive_write_error (status);
    }

  ptrdiff_t nread;
  while ((nread = rmtread (archive, charptr (record_start), record_size)) < 0)
    archive_read_error ();
  short_read_slop = 0;
  if (nread == record_size)
    records_read++;
  else
    short_read (nread);
}

/* Simple flush write (no multi-volume or label extensions) */
static void
simple_flush_write (idx_t UNNAMED (level))
{
  idx_t status = _flush_write ();
  if (status != record_size)
    archive_write_error (status);
  else
    {
      records_written++;
      bytes_written += status;
    }
}


/* GNU flush functions. These support multi-volume and archive labels in
   GNU and PAX archive formats. */

static void
_gnu_flush_read (void)
{
  checkpoint_run (false);

  /* Clear the count of errors.  This only applies to a single call to
     flush_read.  */

  read_error_count = 0;         /* clear error count */

  if (write_archive_to_stdout && record_start_block != 0)
    {
      archive = STDOUT_FILENO;
      idx_t status = sys_write_archive_buffer ();
      archive = STDIN_FILENO;
      if (status != record_size)
        archive_write_error (status);
    }

  ptrdiff_t nread;
  while ((nread = rmtread (archive, charptr (record_start), record_size)) < 0
	 && ! (errno == ENOSPC && multi_volume_option))
    archive_read_error ();
  /* The condition below used to include
     || (nread > 0 && !read_full_records)
     This is incorrect since even if new_volume() succeeds, the
     subsequent call to rmtread will overwrite the chunk of data
     already read in the buffer, so the processing will fail */
  if (nread <= 0 && multi_volume_option)
    {
      while (!try_new_volume ())
	continue;
      if (current_block == record_end)
	/* Necessary for blocking_factor == 1 */
	flush_archive ();
    }
  else
    {
      short_read_slop = 0;
      if (nread == record_size)
	records_read++;
      else
	short_read (nread);
    }
}

static void
gnu_flush_read (void)
{
  flush_read_ptr = simple_flush_read; /* Avoid recursion */
  _gnu_flush_read ();
  flush_read_ptr = gnu_flush_read;
}

static void
_gnu_flush_write (idx_t buffer_level)
{
  union block *header;
  char *copy_ptr;
  idx_t copy_size;
  idx_t bufsize;
  struct bufmap *map;

  idx_t status = _flush_write ();
  records_written += !!status;
  bytes_written += status;

  if (status == record_size)
    {
      return;
    }

  map = bufmap_locate (status);

  if (status % BLOCKSIZE)
    {
      int e = errno;
      paxerror (0, _("write did not end on a block boundary"));
      errno = e;
      archive_write_error (status);
    }

  /* ENXIO is for the UNIX PC.  */
  if (! (multi_volume_option
	 && (errno == ENOSPC || errno == EIO || errno == ENXIO)))
    archive_write_error (status);

  /* In multi-volume mode.  */

  if (!new_volume (ACCESS_WRITE))
    return;

  tar_stat_destroy (&dummy);

  increase_volume_number ();
  prev_written += bytes_written;
  bytes_written = 0;

  copy_ptr = charptr (record_start) + status;
  copy_size = buffer_level - status;

  /* Switch to the next buffer */
  record_index = !record_index;
  init_buffer ();

  inhibit_map = true;

  if (volume_label_option)
    add_volume_label ();

  if (map)
    add_multi_volume_header (map);

  write_extended (true, &dummy, find_next_block ());
  tar_stat_destroy (&dummy);

  if (map)
    add_chunk_header (map);
  header = find_next_block ();
  bufmap_reset (map, header - record_start);
  bufsize = available_space_after (header);
  inhibit_map = false;
  while (bufsize < copy_size)
    {
      memcpy (header, copy_ptr, bufsize);
      copy_ptr += bufsize;
      copy_size -= bufsize;
      set_next_block_after (charptr (header) + bufsize - 1);
      header = find_next_block ();
      bufsize = available_space_after (header);
    }
  memcpy (header, copy_ptr, copy_size);
  memset (charptr (header) + copy_size, 0, bufsize - copy_size);
  set_next_block_after (charptr (header) + copy_size - 1);
  find_next_block ();
}

static void
gnu_flush_write (idx_t buffer_level)
{
  flush_write_ptr = simple_flush_write; /* Avoid recursion */
  _gnu_flush_write (buffer_level);
  flush_write_ptr = gnu_flush_write;
}

void
flush_read (void)
{
  flush_read_ptr ();
}

void
flush_write (void)
{
  flush_write_ptr (record_size);
}

void
open_archive (enum access_mode wanted_access)
{
  flush_read_ptr = gnu_flush_read;
  flush_write_ptr = gnu_flush_write;

  _open_archive (wanted_access);
  switch (wanted_access)
    {
    case ACCESS_READ:
    case ACCESS_UPDATE:
      if (volume_label_option)
        match_volume_label ();
      break;

    case ACCESS_WRITE:
      records_written = 0;
      if (volume_label_option)
        write_volume_label ();
      break;
    }
  set_volume_start_time ();
}