buffer.c

gnu tar 源码包。 tar 软件是 Unix 系统下的一个打包软件

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

	if (check_compressed_archive (NULL) != ct_none)
	  FATAL_ERROR ((0, 0,
			_("Cannot update compressed archives")));
	break;
      }

  if (archive < 0
      || (! _isrmt (archive) && !sys_get_archive_stat ()))
    {
      int saved_errno = errno;

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

  sys_detect_dev_null_output ();
  sys_save_archive_dev_ino ();
  SET_BINARY_MODE (archive);

  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.  */
ssize_t
_flush_write (void)
{
  ssize_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 ();
  
  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)
    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;
}

static void
short_read (size_t status)
{
  size_t left;			/* bytes left */
  char *more;			/* pointer to next byte to read */

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

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

      if (status == 0)
	break;

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

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

      /* User warned us about this.  Fix up.  */

      left -= status;
      more += status;
    }

  /* FIXME: for size=0, multi-volume support.  On the first record, warn
     about the problem.  */

  if (!read_full_records && verbose_option > 1
      && record_start_block == 0 && status != 0)
    {
      unsigned long rsize = (record_size - left) / BLOCKSIZE;
      WARN ((0, 0,
	     ngettext ("Record size = %lu block",
		       "Record size = %lu blocks",
		       rsize),
	     rsize));
    }

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

/*  Flush the current buffer to/from the archive.  */
void
flush_archive (void)
{
  size_t buffer_level = current_block->buffer - record_start->buffer;
  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 = false;
      backspace_output ();
    }

  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)
{
#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, (off_t) 0, SEEK_CUR);

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

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

	WARN ((0, 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->buffer, 0,
		  output_start - record_start->buffer);
      }
  }
}

off_t
seek_archive (off_t size)
{
  off_t start = current_block_ordinal ();
  off_t offset;
  off_t nrec, nblk;
  off_t skipped = (blocking_factor - (current_block - record_start));

  size -= skipped * BLOCKSIZE;

  if (size < record_size)
    return 0;
  /* FIXME: flush? */

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

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

  /* Convert to number of records */
  offset /= 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)
    {
      flush_archive ();
      if (current_block > record_start)
	flush_archive ();
    }

  sys_drain_input_pipe ();

  compute_duration ();
  if (verify_option)
    verify_volume ();

  if (rmtclose (archive) != 0)
    close_error (*archive_name_cursor);

  sys_wait_for_child (child_pid);

  tar_stat_destroy (&current_stat_info);
  if (save_name)
    free (save_name);
  if (real_s_name)
    free (real_s_name);
  free (record_buffer[0]);
  free (record_buffer[1]);
}

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

  if (file)
    {
      if (fscanf (file, "%d", &global_volno) != 1
	  || global_volno < 0)
	FATAL_ERROR ((0, 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, "%d\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 ()
{
  global_volno++;
  if (global_volno < 0)
    FATAL_ERROR ((0, 0, _("Volume number overflow")));
  volno++;
}

void
change_tape_menu (FILE *read_file)
{
  char *input_buffer = NULL;
  size_t size = 0;
  bool stop = false;
  
  while (!stop)
    {
      fputc ('\007', stderr);
      fprintf (stderr,
	       _("Prepare volume #%d for %s and hit return: "),
	       global_volno + 1, quote (*archive_name_cursor));
      fflush (stderr);

      if (getline (&input_buffer, &size, read_file) <= 0)
	{
	  WARN ((0, 0, _("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")));

	  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.  */

	  WARN ((0, 0, _("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")));

	  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++)
	      ;
	    *cursor = '\0';

	    if (name[0])
	      {
		/* FIXME: the following allocation is never reclaimed.  */
		*archive_name_cursor = xstrdup (name);
		stop = true;
	      }
	    else
	      fprintf (stderr, "%s",
		       _("File name not specified. Try again.\n"));
	  }
	  break;

	case '!':
	  if (!restrict_option)
	    {
	      sys_spawn_shell ();
	      break;
	    }
	  /* FALL THROUGH */

	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 nonzero on success.
*/
static bool
new_volume (enum access_mode mode)
{
  static FILE *read_file;
  static int looped;
  int prompt;

  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_string (&volume_label, NULL);
  assign_string (&continued_file_name, NULL);
  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 = 1;
    }
  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))
	    FATAL_ERROR ((0, 0, _("%s command failed"),
			  quote (info_script_option)));
	}
      else
	change_tape_menu (read_file);
    }

  if (strcmp (archive_name_cursor[0], "-") == 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 = 1;
      goto tryagain;
    }

  SET_BINARY_MODE (archive);

  return true;
}

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

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

bool
try_new_volume ()
{
  size_t status;
  union block *header;
  enum access_mode acc;
  
  switch (subcommand_option)
    {