[chaz/tar] / src / buffer.c

/* Buffer management for tar.
   Copyright (C) 1988, 92, 93, 94, 96, 97 Free Software Foundation, Inc.
   Written by John Gilmore, on 1985-08-25.

   This program 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 2, or (at your option) any later
   version.

   This program 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, write to the Free Software Foundation, Inc.,
   59 Place - Suite 330, Boston, MA 02111-1307, USA.  */

#include "system.h"

#include <signal.h>
#include <time.h>
time_t time ();

#if MSDOS
# include <process.h>
#endif

#if XENIX
# include <sys/inode.h>
#endif

#ifndef FNM_LEADING_DIR
# include <fnmatch.h>
#endif

#include "common.h"
#include "rmt.h"

#define DEBUG_FORK 0            /* if nonzero, childs are born stopped */

#define STDIN 0                 /* standard input  file descriptor */
#define STDOUT 1                /* standard output file descriptor */

#define PREAD 0                 /* read file descriptor from pipe() */
#define PWRITE 1                /* write file descriptor from pipe() */

/* Number of retries before giving up on read.  */
#define READ_ERROR_MAX 10

/* Globbing pattern to append to volume label if initial match failed.  */
#define VOLUME_LABEL_APPEND " Volume [1-9]*"
\f
/* Variables.  */

static tarlong total_written;   /* bytes written on all volumes */
static tarlong bytes_written;   /* bytes written on this volume */

/* FIXME: The following four variables should ideally be static to this
   module.  However, this cannot be done yet, as update.c uses the first
   three a lot, and compare.c uses the fourth.  The cleanup continues!  */

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 */
static struct stat archive_stat; /* stat block for archive file */

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

/* Where we write list messages (not errors, not interactions) to.  Stdout
   unless we're writing a pipe, in which case stderr.  */
FILE *stdlis;

static void backspace_output PARAMS ((void));
static int new_volume PARAMS ((enum access_mode));
static void write_error PARAMS ((int));
static void read_error PARAMS ((void));

#if !MSDOS
/* Obnoxious test to see if dimwit is trying to dump the archive.  */
dev_t ar_dev;
ino_t ar_ino;
#endif

/* PID of child program, if compress_option or remote archive access.  */
static int child_pid = 0;

/* Error recovery stuff  */
static int read_error_count;

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

/* Checkpointing counter */
static int checkpoint;

/* We're reading, but we just read the last block and its time to update.  */
/* As least EXTERN like this one as possible.  FIXME!  */
extern int time_to_start_writing;

int file_to_switch_to = -1;     /* if remote update, close archive, and use
                                   this descriptor to write to */

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

/* The pointer save_name, which is set in function dump_file() of module
   create.c, points to the original long filename instead of the new,
   shorter mangled name that is set in start_header() of module create.c.
   The pointer save_name is only used in multi-volume mode when the file
   being processed is non-sparse; if a file is split between volumes, the
   save_name is used in generating the LF_MULTIVOL record on the second
   volume.  (From Pierce Cantrell, 1991-08-13.)  */

char *save_name;                /* name of the file we are currently writing */
long save_totsize;              /* total size of file we are writing, only
                                   valid if save_name is non NULL */
long save_sizeleft;             /* where we are in the file we are writing,
                                   only valid if save_name is nonzero */

int write_archive_to_stdout = 0;

/* Used by flush_read and flush_write to store the real info about saved
   names.  */
static char *real_s_name = NULL;
static long real_s_totsize;
static long real_s_sizeleft;
\f
/* Functions.  */

#if DEBUG_FORK

static pid_t
myfork (void)
{
  pid_t result = fork();

  if (result == 0)
    kill (getpid (), SIGSTOP);
  return result;
}

# define fork myfork

#endif /* DEBUG FORK */

void
init_total_written (void)
{
  clear_tarlong (total_written);
  clear_tarlong (bytes_written);
}

void
print_total_written (void)
{
  fprintf (stderr, _("Total bytes written: "));
  print_tarlong (total_written, stderr);
  fprintf (stderr, "\n");
}

/*--------------------------------------------------------.
| Compute and return the block ordinal at current_block.  |
`--------------------------------------------------------*/

long
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 = 0;
      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 NULL for EOF.  Once we have returned NULL, 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 = 1;
          return NULL;
        }
    }
  return current_block;
}

/*------------------------------------------------------.
| Indicate that we have used all blocks up thru BLOCK.  |
|                                                       |
| FIXME: should the arg have an off-by-1?               |
`------------------------------------------------------*/

void
set_next_block_after (union block *block)
{
  while (block >= current_block)
    current_block++;

  /* 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 previous find_next_block call.                       |
`------------------------------------------------------------------------*/

int
available_space_after (union block *pointer)
{
  return (int) (record_end->buffer - pointer->buffer);
}

/*------------------------------------------------------------------.
| Close file having descriptor FD, and abort if close unsucessful.  |
`------------------------------------------------------------------*/

static void
xclose (int fd)
{
  if (close (fd) < 0)
    FATAL_ERROR ((0, errno, _("Cannot close file #%d"), fd));
}

/*-----------------------------------------------------------------------.
| Duplicate file descriptor FROM into becoming INTO, or else, issue      |
| MESSAGE.  INTO is closed first and has to be the next available slot.  |
`-----------------------------------------------------------------------*/

static void
xdup2 (int from, int into, const char *message)
{
  if (from != into)
    {
      int status = close (into);

      if (status < 0 && errno != EBADF)
        FATAL_ERROR ((0, errno, _("Cannot close descriptor %d"), into));
      status = dup (from);
      if (status != into)
        FATAL_ERROR ((0, errno, _("Cannot properly duplicate %s"), message));
      xclose (from);
    }
}

#if MSDOS

/*-------------------------------------------------------.
| Set ARCHIVE for writing, then compressing an archive.  |
`-------------------------------------------------------*/

static void
child_open_for_compress (void)
{
  FATAL_ERROR ((0, 0, _("Cannot use compressed or remote archives")));
}

/*---------------------------------------------------------.
| Set ARCHIVE for uncompressing, then reading an archive.  |
`---------------------------------------------------------*/

static void
child_open_for_uncompress (void)
{
  FATAL_ERROR ((0, 0, _("Cannot use compressed or remote archives")));
}

#else /* not MSDOS */

/*---------------------------------------------------------------------.
| Return nonzero if NAME is the name of a regular file, or if the file |
| does not exist (so it would be created as a regular file).           |
`---------------------------------------------------------------------*/

static int
is_regular_file (const char *name)
{
  struct stat stbuf;

  if (stat (name, &stbuf) < 0)
    return 1;

  if (S_ISREG (stbuf.st_mode))
    return 1;

  return 0;
}

/*-------------------------------------------------------.
| Set ARCHIVE for writing, then compressing an archive.  |
`-------------------------------------------------------*/

static void
child_open_for_compress (void)
{
  int parent_pipe[2];
  int child_pipe[2];
  int grandchild_pid;

  if (pipe (parent_pipe) < 0)
    FATAL_ERROR ((0, errno, _("Cannot open pipe")));

  child_pid = fork ();
  if (child_pid < 0)
    FATAL_ERROR ((0, errno, _("Cannot fork")));

  if (child_pid > 0)
    {
      /* The parent tar is still here!  Just clean up.  */

      archive = parent_pipe[PWRITE];
      xclose (parent_pipe[PREAD]);
      return;
    }

  /* The new born child tar is here!  */

  program_name = _("tar (child)");

  xdup2 (parent_pipe[PREAD], STDIN, _("(child) Pipe to stdin"));
  xclose (parent_pipe[PWRITE]);

  /* Check if we need a grandchild tar.  This happens only if either:
     a) we are writing stdout: to force reblocking;
     b) the file is to be accessed by rmt: compressor doesn't know how;
     c) the file is not a plain file.  */

  if (strcmp (archive_name_array[0], "-") != 0
      && !_remdev (archive_name_array[0])
      && is_regular_file (archive_name_array[0]))
    {
      if (backup_option)
        maybe_backup_file (archive_name_array[0], 1);

      /* We don't need a grandchild tar.  Open the archive and launch the
         compressor.  */

      archive = creat (archive_name_array[0], 0666);
      if (archive < 0)
        {
          int saved_errno = errno;

          if (backup_option)
            undo_last_backup ();
          FATAL_ERROR ((0, saved_errno, _("Cannot open archive %s"),
                        archive_name_array[0]));
        }
      xdup2 (archive, STDOUT, _("Archive to stdout"));
      execlp (use_compress_program_option, use_compress_program_option,
              (char *) 0);
      FATAL_ERROR ((0, errno, _("Cannot exec %s"),
                    use_compress_program_option));
    }

  /* We do need a grandchild tar.  */

  if (pipe (child_pipe) < 0)
    FATAL_ERROR ((0, errno, _("Cannot open pipe")));

  grandchild_pid = fork ();
  if (grandchild_pid < 0)
    FATAL_ERROR ((0, errno, _("Child cannot fork")));

  if (grandchild_pid > 0)
    {
      /* The child tar is still here!  Launch the compressor.  */

      xdup2 (child_pipe[PWRITE], STDOUT, _("((child)) Pipe to stdout"));
      xclose (child_pipe[PREAD]);
      execlp (use_compress_program_option, use_compress_program_option,
              (char *) 0);
      FATAL_ERROR ((0, errno, _("Cannot exec %s"),
                    use_compress_program_option));
    }

  /* The new born grandchild tar is here!  */

  program_name = _("tar (grandchild)");

  /* Prepare for reblocking the data from the compressor into the archive.  */

  xdup2 (child_pipe[PREAD], STDIN, _("(grandchild) Pipe to stdin"));
  xclose (child_pipe[PWRITE]);

  if (strcmp (archive_name_array[0], "-") == 0)
    archive = STDOUT;
  else
    archive = rmtcreat (archive_name_array[0], 0666, rsh_command_option);
  if (archive < 0)
    FATAL_ERROR ((0, errno, _("Cannot open archive %s"),
                  archive_name_array[0]));

  /* Let's read out of the stdin pipe and write an archive.  */

  while (1)
    {
      int status = 0;
      char *cursor;
      int length;

      /* Assemble a record.  */

      for (length = 0, cursor = record_start->buffer;
           length < record_size;
           length += status, cursor += status)
        {
          int size = record_size - length;

          if (size < BLOCKSIZE)
            size = BLOCKSIZE;
          status = read (STDIN, cursor, (size_t) size);
          if (status <= 0)
            break;
        }

      if (status < 0)
        FATAL_ERROR ((0, errno, _("Cannot read from compression program")));

      /* Copy the record.  */

      if (status == 0)
        {
          /* We hit the end of the file.  Write last record at
             full length, as the only role of the grandchild is
             doing proper reblocking.  */

          if (length > 0)
            {
              memset (record_start->buffer + length, 0,
                      (size_t) record_size - length);
              status = rmtwrite (archive, record_start->buffer,
                                 (unsigned int) record_size);
              if (status != record_size)
                write_error (status);
            }

          /* There is nothing else to read, break out.  */
          break;
        }

      status = rmtwrite (archive, record_start->buffer,
                         (unsigned int) record_size);
      if (status != record_size)
        write_error (status);
    }

#if 0
  close_archive ();
#endif
  exit (exit_status);
}

/*---------------------------------------------------------.
| Set ARCHIVE for uncompressing, then reading an archive.  |
`---------------------------------------------------------*/

static void
child_open_for_uncompress (void)
{
  int parent_pipe[2];
  int child_pipe[2];
  int grandchild_pid;

  if (pipe (parent_pipe) < 0)
    FATAL_ERROR ((0, errno, _("Cannot open pipe")));

  child_pid = fork ();
  if (child_pid < 0)
    FATAL_ERROR ((0, errno, _("Cannot fork")));

  if (child_pid > 0)
    {
      /* The parent tar is still here!  Just clean up.  */

      read_full_records_option = 1;
      archive = parent_pipe[PREAD];
      xclose (parent_pipe[PWRITE]);
      return;
    }

  /* The new born child tar is here!  */

  program_name = _("tar (child)");

  xdup2 (parent_pipe[PWRITE], STDOUT, _("(child) Pipe to stdout"));
  xclose (parent_pipe[PREAD]);

  /* Check if we need a grandchild tar.  This happens only if either:
     a) we're reading stdin: to force unblocking;
     b) the file is to be accessed by rmt: compressor doesn't know how;
     c) the file is not a plain file.  */

  if (strcmp (archive_name_array[0], "-") != 0
      && !_remdev (archive_name_array[0])
      && is_regular_file (archive_name_array[0]))
    {
      /* We don't need a grandchild tar.  Open the archive and lauch the
         uncompressor.  */

      archive = open (archive_name_array[0], O_RDONLY | O_BINARY, 0666);
      if (archive < 0)
        FATAL_ERROR ((0, errno, _("Cannot open archive %s"),
                      archive_name_array[0]));
      xdup2 (archive, STDIN, _("Archive to stdin"));
      execlp (use_compress_program_option, use_compress_program_option,
              "-d", (char *) 0);
      FATAL_ERROR ((0, errno, _("Cannot exec %s"),
                    use_compress_program_option));
    }

  /* We do need a grandchild tar.  */

  if (pipe (child_pipe) < 0)
    FATAL_ERROR ((0, errno, _("Cannot open pipe")));

  grandchild_pid = fork ();
  if (grandchild_pid < 0)
    FATAL_ERROR ((0, errno, _("Child cannot fork")));

  if (grandchild_pid > 0)
    {
      /* The child tar is still here!  Launch the uncompressor.  */

      xdup2 (child_pipe[PREAD], STDIN, _("((child)) Pipe to stdin"));
      xclose (child_pipe[PWRITE]);
      execlp (use_compress_program_option, use_compress_program_option,
              "-d", (char *) 0);
      FATAL_ERROR ((0, errno, _("Cannot exec %s"),
                    use_compress_program_option));
    }

  /* The new born grandchild tar is here!  */

  program_name = _("tar (grandchild)");

  /* Prepare for unblocking the data from the archive into the uncompressor.  */

  xdup2 (child_pipe[PWRITE], STDOUT, _("(grandchild) Pipe to stdout"));
  xclose (child_pipe[PREAD]);

  if (strcmp (archive_name_array[0], "-") == 0)
    archive = STDIN;
  else
    archive = rmtopen (archive_name_array[0], O_RDONLY | O_BINARY,
                       0666, rsh_command_option);
  if (archive < 0)
    FATAL_ERROR ((0, errno, _("Cannot open archive %s"),
                  archive_name_array[0]));

  /* Let's read the archive and pipe it into stdout.  */

  while (1)
    {
      char *cursor;
      int maximum;
      int count;
      int status;

      read_error_count = 0;

    error_loop:
      status = rmtread (archive, record_start->buffer,
                        (unsigned int) (record_size));
      if (status < 0)
        {
          read_error ();
          goto error_loop;
        }
      if (status == 0)
        break;
      cursor = record_start->buffer;
      maximum = status;
      while (maximum)
        {
          count = maximum < BLOCKSIZE ? maximum : BLOCKSIZE;
          status = write (STDOUT, cursor, (size_t) count);
          if (status < 0)
            FATAL_ERROR ((0, errno, _("\
Cannot write to compression program")));

          if (status != count)
            {
              ERROR ((0, 0, _("\
Write to compression program short %d bytes"),
                      count - status));
              count = status;
            }

          cursor += count;
          maximum -= count;
        }
    }

#if 0
  close_archive ();
#endif
  exit (exit_status);
}

#endif /* not MSDOS */

/*--------------------------------------------------------------------------.
| Check the LABEL block 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 int
check_label_pattern (union block *label)
{
  char *string;
  int result;

  if (fnmatch (volume_label_option, label->header.name, 0) == 0)
    return 1;

  if (!multi_volume_option)
    return 0;

  string = xmalloc (strlen (volume_label_option)
                    + sizeof VOLUME_LABEL_APPEND + 1);
  strcpy (string, volume_label_option);
  strcat (string, VOLUME_LABEL_APPEND);
  result = fnmatch (string, label->header.name, 0) == 0;
  free (string);
  return result;
}

/*------------------------------------------------------------------------.
| Open an archive file.  The argument specifies whether we are reading or |
| writing, or both.                                                       |
`------------------------------------------------------------------------*/

void
open_archive (enum access_mode access)
{
  int backed_up_flag = 0;

  stdlis = to_stdout_option ? stderr : stdout;

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

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

  current_file_name = NULL;
  current_link_name = NULL;

  /* FIXME: According to POSIX.1, PATH_MAX may well not be a compile-time
     constant, and the value from sysconf (_SC_PATH_MAX) may well not be any
     size that is reasonable to allocate a buffer.  In the GNU system, there
     is no fixed limit.  The only correct thing to do is to use dynamic
     allocation.  (Roland McGrath)  */

  if (!real_s_name)
    real_s_name = (char *) xmalloc (PATH_MAX);
  /* FIXME: real_s_name is never freed.  */

  save_name = NULL;

  if (multi_volume_option)
    {
      record_start
        = (union block *) valloc ((unsigned) (record_size + (2 * BLOCKSIZE)));
      if (record_start)
        record_start += 2;
    }
  else
    record_start = (union block *) valloc ((unsigned) record_size);
  if (!record_start)
    FATAL_ERROR ((0, 0, _("Could not allocate memory for blocking factor %d"),
                  blocking_factor));

  current_block = record_start;
  record_end = record_start + blocking_factor;
  /* When updating the archive, we start with reading.  */
  access_mode = access == ACCESS_UPDATE ? ACCESS_READ : access;

  if (multi_volume_option && verify_option)
    FATAL_ERROR ((0, 0, _("Cannot verify multi-volume archives")));

  if (use_compress_program_option)
    {
      if (multi_volume_option)
        FATAL_ERROR ((0, 0, _("Cannot use multi-volume compressed archives")));
      if (verify_option)
        FATAL_ERROR ((0, 0, _("Cannot verify compressed archives")));

      switch (access)
        {
        case ACCESS_READ:
          child_open_for_uncompress ();
          break;

        case ACCESS_WRITE:
          child_open_for_compress ();
          break;

        case ACCESS_UPDATE:
          FATAL_ERROR ((0, 0, _("Cannot update compressed archives")));
          break;
        }

      if (access == ACCESS_WRITE && strcmp (archive_name_array[0], "-") == 0)
        stdlis = stderr;
    }
  else if (strcmp (archive_name_array[0], "-") == 0)
    {
      read_full_records_option = 1; /* could be a pipe, be safe */
      if (verify_option)
        FATAL_ERROR ((0, 0, _("Cannot verify stdin/stdout archive")));

      switch (access)
        {
        case ACCESS_READ:
          archive = STDIN;
          break;

        case ACCESS_WRITE:
          archive = STDOUT;
          stdlis = stderr;
          break;

        case ACCESS_UPDATE:
          archive = STDIN;
          stdlis = stderr;
          write_archive_to_stdout = 1;
          break;
        }
    }
  else if (verify_option)
    archive = rmtopen (archive_name_array[0], O_RDWR | O_CREAT | O_BINARY,
                       0666, rsh_command_option);
  else
    switch (access)
      {
      case ACCESS_READ:
        archive = rmtopen (archive_name_array[0], O_RDONLY | O_BINARY, 0666,
                           rsh_command_option);
        break;

      case ACCESS_WRITE:
        if (backup_option)
          {
            maybe_backup_file (archive_name_array[0], 1);
            backed_up_flag = 1;
          }
        archive = rmtcreat (archive_name_array[0], 0666, rsh_command_option);
        break;

      case ACCESS_UPDATE:
        archive = rmtopen (archive_name_array[0], O_RDWR | O_CREAT | O_BINARY,
                           0666, rsh_command_option);
        break;
      }

  if (archive < 0)
    {
      int saved_errno = errno;

      if (backed_up_flag)
        undo_last_backup ();
      FATAL_ERROR ((0, saved_errno, _("Cannot open %s"),
                    archive_name_array[0]));
    }

#if !MSDOS

  fstat (archive, &archive_stat);

  /* Detect if outputting to "/dev/null".  */
  {
    struct stat dev_null_stat;

    stat ("/dev/null", &dev_null_stat);
    dev_null_output = (S_ISCHR (archive_stat.st_mode)
                       && archive_stat.st_rdev == dev_null_stat.st_rdev);
  }

  if (!_isrmt (archive) && S_ISREG (archive_stat.st_mode))
    {
      ar_dev = archive_stat.st_dev;
      ar_ino = archive_stat.st_ino;
    }

#endif /* not MSDOS */

#if MSDOS
  setmode (archive, O_BINARY);
#endif

  switch (access)
    {
    case ACCESS_READ:
    case ACCESS_UPDATE:
      record_end = record_start; /* set up for 1st record = # 0 */
      find_next_block ();       /* read it in, check for EOF */

      if (volume_label_option)
        {
          union block *label = find_next_block ();

          if (!label)
            FATAL_ERROR ((0, 0, _("Archive not labelled to match `%s'"),
                          volume_label_option));
          if (!check_label_pattern (label))
            FATAL_ERROR ((0, 0, _("Volume `%s' does not match `%s'"),
                          label->header.name, volume_label_option));
        }
      break;

    case ACCESS_WRITE:
      if (volume_label_option)
        {
          memset ((void *) record_start, 0, BLOCKSIZE);
          if (multi_volume_option)
            sprintf (record_start->header.name, "%s Volume 1",
                     volume_label_option);
          else
            strcpy (record_start->header.name, volume_label_option);

          assign_string (&current_file_name, record_start->header.name);

          record_start->header.typeflag = GNUTYPE_VOLHDR;
          to_oct (time (0), 1 + 12, record_start->header.mtime);
          finish_header (record_start);
#if 0
          current_block++;
#endif
        }
      break;
    }
}

/*--------------------------------------.
| Perform a write to flush the buffer.  |
`--------------------------------------*/

void
flush_write (void)
{
  int copy_back;
  int status;

  if (checkpoint_option && !(++checkpoint % 10))
    WARN ((0, 0, _("Write checkpoint %d"), checkpoint));

  if (!zerop_tarlong (tape_length_option)
      && !lessp_tarlong (bytes_written, tape_length_option))
    {
      errno = ENOSPC;           /* FIXME: errno should be read-only */
      status = 0;
    }
  else if (dev_null_output)
    status = record_size;
  else
    status = rmtwrite (archive, record_start->buffer,
                       (unsigned int) record_size);
  if (status != record_size && !multi_volume_option)
    write_error (status);
  else if (totals_option)
    add_to_tarlong (total_written, record_size);

  if (status > 0)
    add_to_tarlong (bytes_written, status);

  if (status == record_size)
    {
      if (multi_volume_option)
        {
          char *cursor;

          if (!save_name)
            {
              real_s_name[0] = '\0';
              real_s_totsize = 0;
              real_s_sizeleft = 0;
              return;
            }

          cursor = save_name;
#if MSDOS
          if (cursor[1] == ':')
            cursor += 2;
#endif
          while (*cursor == '/')
            cursor++;

          strcpy (real_s_name, cursor);
          real_s_totsize = save_totsize;
          real_s_sizeleft = save_sizeleft;
        }
      return;
    }

  /* We're multivol.  Panic if we didn't get the right kind of response.  */

  /* ENXIO is for the UNIX PC.  */
  if (status < 0 && errno != ENOSPC && errno != EIO && errno != ENXIO)
    write_error (status);

  /* If error indicates a short write, we just move to the next tape.  */

  if (!new_volume (ACCESS_WRITE))
    return;

  clear_tarlong (bytes_written);

  if (volume_label_option && real_s_name[0])
    {
      copy_back = 2;
      record_start -= 2;
    }
  else if (volume_label_option || real_s_name[0])
    {
      copy_back = 1;
      record_start--;
    }
  else
    copy_back = 0;

  if (volume_label_option)
    {
      memset ((void *) record_start, 0, BLOCKSIZE);
      sprintf (record_start->header.name, "%s Volume %d", volume_label_option, volno);
      to_oct (time (0), 1 + 12, record_start->header.mtime);
      record_start->header.typeflag = GNUTYPE_VOLHDR;
      finish_header (record_start);
    }

  if (real_s_name[0])
    {
      int tmp;

      if (volume_label_option)
        record_start++;

      memset ((void *) record_start, 0, BLOCKSIZE);

      /* FIXME: Michael P Urban writes: [a long name file] is being written
         when a new volume rolls around [...]  Looks like the wrong value is
         being preserved in real_s_name, though.  */

      strcpy (record_start->header.name, real_s_name);
      record_start->header.typeflag = GNUTYPE_MULTIVOL;
      to_oct ((long) real_s_sizeleft, 1 + 12,
              record_start->header.size);
      to_oct ((long) real_s_totsize - real_s_sizeleft,
              1 + 12, record_start->oldgnu_header.offset);
      tmp = verbose_option;
      verbose_option = 0;
      finish_header (record_start);
      verbose_option = tmp;

      if (volume_label_option)
        record_start--;
    }

  status = rmtwrite (archive, record_start->buffer,
                     (unsigned int) record_size);
  if (status != record_size)
    write_error (status);
  else if (totals_option)
    add_to_tarlong (total_written, record_size);

  add_to_tarlong (bytes_written, record_size);
  if (copy_back)
    {
      record_start += copy_back;
      memcpy ((void *) current_block,
              (void *) (record_start + blocking_factor - copy_back),
              (size_t) (copy_back * BLOCKSIZE));
      current_block += copy_back;

      if (real_s_sizeleft >= copy_back * BLOCKSIZE)
        real_s_sizeleft -= copy_back * BLOCKSIZE;
      else if ((real_s_sizeleft + BLOCKSIZE - 1) / BLOCKSIZE <= copy_back)
        real_s_name[0] = '\0';
      else
        {
          char *cursor = save_name;

#if MSDOS
          if (cursor[1] == ':')
            cursor += 2;
#endif
          while (*cursor == '/')
            cursor++;

          strcpy (real_s_name, cursor);
          real_s_sizeleft = save_sizeleft;
          real_s_totsize = save_totsize;
        }
      copy_back = 0;
    }
}

/*---------------------------------------------------------------------.
| 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.                            |
`---------------------------------------------------------------------*/

static void
write_error (int status)
{
  int saved_errno = errno;

  /* It might be useful to know how much was written before the error
     occured.  Beware that mere printing maybe change errno value.  */
  if (totals_option)
    print_total_written ();

  if (status < 0)
    FATAL_ERROR ((0, saved_errno, _("Cannot write to %s"),
                  *archive_name_cursor));
  else
    FATAL_ERROR ((0, 0, _("Only wrote %u of %u bytes to %s"),
                  status, record_size, *archive_name_cursor));
}

/*-------------------------------------------------------------------.
| Handle read errors on the archive.  If the read should be retried, |
| returns to the caller.                                             |
`-------------------------------------------------------------------*/

static void
read_error (void)
{
  WARN ((0, errno, _("Read error on %s"), *archive_name_cursor));

  if (record_start_block == 0)
    FATAL_ERROR ((0, 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)
    FATAL_ERROR ((0, 0, _("Too many errors, quitting")));
  return;
}

/*-------------------------------------.
| Perform a read to flush the buffer.  |
`-------------------------------------*/

void
flush_read (void)
{
  int status;                   /* result from system call */
  int left;                     /* bytes left */
  char *more;                   /* pointer to next byte to read */

  if (checkpoint_option && !(++checkpoint % 10))
    WARN ((0, 0, _("Read checkpoint %d"), checkpoint));

  /* 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)
    {
      status = rmtwrite (1, record_start->buffer, (unsigned int) record_size);
      if (status != record_size)
        write_error (status);
    }
  if (multi_volume_option)
    if (save_name)
      {
        char *cursor = save_name;

#if MSDOS
        if (cursor[1] == ':')
          cursor += 2;
#endif
        while (*cursor == '/')
          cursor++;

        strcpy (real_s_name, cursor);
        real_s_sizeleft = save_sizeleft;
        real_s_totsize = save_totsize;
      }
    else
      {
        real_s_name[0] = '\0';
        real_s_totsize = 0;
        real_s_sizeleft = 0;
      }

error_loop:
  status = rmtread (archive, record_start->buffer, (unsigned int) record_size);
  if (status == record_size)
    return;

  if ((status == 0
       || (status < 0 && errno == ENOSPC)
       || (status > 0 && !read_full_records_option))
      && multi_volume_option)
    {
      union block *cursor;

    try_volume:
      switch (subcommand_option)
        {
        case APPEND_SUBCOMMAND:
        case CAT_SUBCOMMAND:
        case UPDATE_SUBCOMMAND:
          if (!new_volume (ACCESS_UPDATE))
            return;
          break;

        default:
          if (!new_volume (ACCESS_READ))
            return;
          break;
        }

    vol_error:
      status = rmtread (archive, record_start->buffer,
                        (unsigned int) record_size);
      if (status < 0)
        {
          read_error ();
          goto vol_error;
        }
      if (status != record_size)
        goto short_read;

      cursor = record_start;

      if (cursor->header.typeflag == GNUTYPE_VOLHDR)
        {
          if (volume_label_option)
            {
              if (!check_label_pattern (cursor))
                {
                  WARN ((0, 0, _("Volume `%s' does not match `%s'"),
                         cursor->header.name, volume_label_option));
                  volno--;
                  global_volno--;
                  goto try_volume;
                }
            }
          if (verbose_option)
            fprintf (stdlis, _("Reading %s\n"), cursor->header.name);
          cursor++;
        }
      else if (volume_label_option)
        WARN ((0, 0, _("WARNING: No volume header")));

      if (real_s_name[0])
        {
          if (cursor->header.typeflag != GNUTYPE_MULTIVOL
              || strcmp (cursor->header.name, real_s_name))
            {
              WARN ((0, 0, _("%s is not continued on this volume"),
                     real_s_name));
              volno--;
              global_volno--;
              goto try_volume;
            }
          if (real_s_totsize
              != (from_oct (1 + 12, cursor->header.size)
                  + from_oct (1 + 12, cursor->oldgnu_header.offset)))
            {
              WARN ((0, 0, _("%s is the wrong size (%ld != %ld + %ld)"),
                         cursor->header.name, save_totsize,
                         from_oct (1 + 12, cursor->header.size),
                         from_oct (1 + 12, cursor->oldgnu_header.offset)));
              volno--;
              global_volno--;
              goto try_volume;
            }
          if (real_s_totsize - real_s_sizeleft
              != from_oct (1 + 12, cursor->oldgnu_header.offset))
            {
              WARN ((0, 0, _("This volume is out of sequence")));
              volno--;
              global_volno--;
              goto try_volume;
            }
          cursor++;
        }
      current_block = cursor;
      return;
    }
  else if (status < 0)
    {
      read_error ();
      goto error_loop;          /* try again */
    }

short_read:
  more = record_start->buffer + status;
  left = record_size - status;

again:
  if ((unsigned) left % BLOCKSIZE == 0)
    {
      /* FIXME: for size=0, multi-volume support.  On the first record, warn
         about the problem.  */

      if (!read_full_records_option && verbose_option
          && record_start_block == 0 && status > 0)
        WARN ((0, 0, _("Record size = %d blocks"), status / BLOCKSIZE));

      record_end
        = record_start + ((unsigned) (record_size - left)) / BLOCKSIZE;

      return;
    }
  if (read_full_records_option)
    {
      /* User warned us about this.  Fix up.  */

      if (left > 0)
        {
        error2loop:
          status = rmtread (archive, more, (unsigned int) left);
          if (status < 0)
            {
              read_error ();
              goto error2loop;  /* try again */
            }
          if (status == 0)
            FATAL_ERROR ((0, 0, _("Archive %s EOF not on block boundary"),
                          *archive_name_cursor));
          left -= status;
          more += status;
          goto again;
        }
    }
  else
    FATAL_ERROR ((0, 0, _("Only read %d bytes from archive %s"),
                  status, *archive_name_cursor));
}

/*-----------------------------------------------.
| Flush the current buffer to/from the archive.  |
`-----------------------------------------------*/

void
flush_archive (void)
{
  record_start_block += record_end - record_start;
  current_block = record_start;
  record_end = record_start + blocking_factor;

  if (access_mode == ACCESS_READ && time_to_start_writing)
    {
      access_mode = ACCESS_WRITE;
      time_to_start_writing = 0;

      if (file_to_switch_to >= 0)
        {
          int status = rmtclose (archive);

          if (status < 0)
            WARN ((0, errno, _("WARNING: Cannot close %s (%d, %d)"),
                   *archive_name_cursor, archive, status));

          archive = file_to_switch_to;
        }
      else
        backspace_output ();
    }

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

    case ACCESS_WRITE:
      flush_write ();
      break;

    case ACCESS_UPDATE:
      abort ();
    }
}

/*-------------------------------------------------------------------------.
| Backspace the archive descriptor by one record worth.  If its a tape,    |
| MTIOCTOP will work.  If its something else, we try to seek on it.  If we |
| can't seek, we lose!                                                     |
`-------------------------------------------------------------------------*/

static void
backspace_output (void)
{
#ifdef MTIOCTOP
  {
    struct mtop operation;

    operation.mt_op = MTBSR;
    operation.mt_count = 1;
    if (rmtioctl (archive, MTIOCTOP, (char *) &operation) >= 0)
      return;
    if (errno == EIO && rmtioctl (archive, MTIOCTOP, (char *) &operation) >= 0)
      return;
  }
#endif

  {
    off_t position = rmtlseek (archive, 0L, 1);

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

    position -= record_size;
    if (rmtlseek (archive, position, 0) != position)
      {
        /* Lseek failed.  Try a different method.  */

        WARN ((0, 0, _("\
Could not 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->buffer, 0,
                  (size_t) (output_start - record_start->buffer));
      }
  }
}

/*-------------------------.
| Close the archive file.  |
`-------------------------*/

void
close_archive (void)
{
  if (time_to_start_writing || access_mode == ACCESS_WRITE)
    flush_archive ();

#if !MSDOS

  /* Manage to fully drain a pipe we might be reading, so to not break it on
     the producer after the EOF block.  FIXME: one of these days, GNU tar
     might become clever enough to just stop working, once there is no more
     work to do, we might have to revise this area in such time.  */

  if (access_mode == ACCESS_READ && S_ISFIFO (archive_stat.st_mode))
    while (rmtread (archive, record_start->buffer, (unsigned int) record_size)
           > 0)
      continue;
#endif

  if (subcommand_option == DELETE_SUBCOMMAND)
    {
      off_t pos;

      pos = rmtlseek (archive, 0L, 1);
#if MSDOS
      rmtwrite (archive, "", 0);
#else
      ftruncate (archive, (size_t) pos);
#endif
    }
  if (verify_option)
    verify_volume ();

  {
    int status = rmtclose (archive);

    if (status < 0)
      WARN ((0, errno, _("WARNING: Cannot close %s (%d, %d)"),
             *archive_name_cursor, archive, status));
  }

#if !MSDOS

  if (child_pid)
    {
      WAIT_T wait_status;
      int child;

      /* Loop waiting for the right child to die, or for no more kids.  */

      while ((child = wait (&wait_status), child != child_pid)
             && child != -1)
        continue;

      if (child != -1)
        if (WIFSIGNALED (wait_status)
#if 0
            && !WIFSTOPPED (wait_status)
#endif
            )
          {
            /* SIGPIPE is OK, everything else is a problem.  */

            if (WTERMSIG (wait_status) != SIGPIPE)
              ERROR ((0, 0, _("Child died with signal %d%s"),
                      WTERMSIG (wait_status),
                      WCOREDUMP (wait_status) ? _(" (core dumped)") : ""));
          }
        else
          {
            /* Child voluntarily terminated -- but why?  /bin/sh returns
               SIGPIPE + 128 if its child, then do nothing.  */

            if (WEXITSTATUS (wait_status) != (SIGPIPE + 128)
                && WEXITSTATUS (wait_status))
              ERROR ((0, 0, _("Child returned status %d"),
                      WEXITSTATUS (wait_status)));
          }
    }
#endif /* !MSDOS */

  if (current_file_name)
    free (current_file_name);
  if (current_link_name)
    free (current_link_name);
  if (save_name)
    free (save_name);
  free (multi_volume_option ? record_start - 2 : record_start);
}

/*------------------------------------------------.
| Called to initialize the global volume number.  |
`------------------------------------------------*/

void
init_volume_number (void)
{
  FILE *file = fopen (volno_file_option, "r");

  if (file)
    {
      fscanf (file, "%d", &global_volno);
      if (fclose (file) == EOF)
        ERROR ((0, errno, "%s", volno_file_option));
    }
  else if (errno != ENOENT)
    ERROR ((0, errno, "%s", 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, "%d\n", global_volno);
      if (fclose (file) == EOF)
        ERROR ((0, errno, "%s", volno_file_option));
    }
  else
    ERROR ((0, errno, "%s", volno_file_option));
}

/*-----------------------------------------------------------------------.
| We've hit the end of the old volume.  Close it and open the next one.  |
| Return nonzero on success.                                             |
`-----------------------------------------------------------------------*/

static int
new_volume (enum access_mode access)
{
  static FILE *read_file = NULL;
  static int looped = 0;

  int status;

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

  if (now_verifying)
    return 0;
  if (verify_option)
    verify_volume ();

  if (status = rmtclose (archive), status < 0)
    WARN ((0, errno, _("WARNING: Cannot close %s (%d, %d)"),
           *archive_name_cursor, archive, status));

  global_volno++;
  volno++;
  archive_name_cursor++;
  if (archive_name_cursor == archive_name_array + archive_names)
    {
      archive_name_cursor = archive_name_array;
      looped = 1;
    }

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

      if (info_script_option)
        {
          if (volno_file_option)
            closeout_volume_number ();
          system (info_script_option);
        }
      else
        while (1)
          {
            char input_buffer[80];

            fprintf (stderr,
                     _("\007Prepare volume #%d for %s and hit return: "),
                     global_volno, *archive_name_cursor);
            fflush (stderr);

            if (fgets (input_buffer, sizeof (input_buffer), read_file) == 0)
              {
                fprintf (stderr, _("EOF where user reply was expected"));

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

                exit (TAREXIT_FAILURE);
              }
            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\
 !          Spawn a subshell\n\
 ?          Print this list\n"));
                }
                break;

              case 'q':
                /* Quit.  */

                fprintf (stdlis, _("No new volume; exiting.\n"));

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

                exit (TAREXIT_FAILURE);

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

                {
                  char *name = &input_buffer[1];
                  char *cursor;

                  while (*name == ' ' || *name == '\t')
                    name++;
                  cursor = name;
                  while (*cursor && *cursor != '\n')
                    cursor++;
                  *cursor = '\0';

                  /* FIXME: the following allocation is never reclaimed.  */
                  *archive_name_cursor = xstrdup (name);
                }
                break;

              case '!':
#if MSDOS
                spawnl (P_WAIT, getenv ("COMSPEC"), "-", 0);
#else /* not MSDOS */
                switch (fork ())
                  {
                  case -1:
                    WARN ((0, errno, _("Cannot fork!")));
                    break;

                  case 0:
                    {
                      const char *shell = getenv ("SHELL");

                      if (shell == NULL)
                        shell = "/bin/sh";
                      execlp (shell, "-sh", "-i", 0);
                      FATAL_ERROR ((0, errno, _("Cannot exec a shell %s"),
                                    shell));
                    }

                  default:
                    {
                      WAIT_T wait_status;

                      wait (&wait_status);
                    }
                    break;
                  }

                /* FIXME: I'm not sure if that's all that has to be done
                   here.  (jk)  */

#endif /* not MSDOS */
                break;
              }
          }
    }

  if (verify_option)
    archive = rmtopen (*archive_name_cursor, O_RDWR | O_CREAT, 0666,
                       rsh_command_option);
  else
    switch (access)
      {
      case ACCESS_READ:
        archive = rmtopen (*archive_name_cursor, O_RDONLY, 0666,
                           rsh_command_option);
        break;

      case ACCESS_WRITE:
        if (backup_option)
          maybe_backup_file (*archive_name_cursor, 1);
        archive = rmtcreat (*archive_name_cursor, 0666, rsh_command_option);
        break;

      case ACCESS_UPDATE:
        archive = rmtopen (*archive_name_cursor, O_RDWR | O_CREAT, 0666,
                           rsh_command_option);
        break;
      }

  if (archive < 0)
    {
      WARN ((0, errno, _("Cannot open %s"), *archive_name_cursor));
      if (!verify_option && access == ACCESS_WRITE && backup_option)
        undo_last_backup ();
      goto tryagain;
    }

#if MSDOS
  setmode (archive, O_BINARY);
#endif

  return 1;
}