buffer.c

gnu tar 源码包。 tar 软件是 Unix 系统下的一个打包软件

    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, record_start->buffer, record_size))
	 == SAFE_READ_ERROR)
    archive_read_error ();

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

  header = find_next_block ();
  if (!header)
    return false;

  switch (header->header.typeflag)
    {
    case XGLTYPE:
      {
	if (!read_header0 (&dummy))
	  return false;
	xheader_decode (&dummy); /* decodes values from the global header */
	tar_stat_destroy (&dummy);
	if (!real_s_name)
	  {
	    /* We have read the extended header of the first member in
	       this volume. Put it back, so next read_header works as
	       expected. */
	    current_block = record_start;
	  }
	break;
      }

    case GNUTYPE_VOLHDR:
      if (!read_header0 (&dummy))
	return false;
      tar_stat_destroy (&dummy);
      assign_string (&volume_label, current_header->header.name);
      set_next_block_after (header);
      header = find_next_block ();
      if (header->header.typeflag != GNUTYPE_MULTIVOL)
	break;
      /* FALL THROUGH */

    case GNUTYPE_MULTIVOL:
      if (!read_header0 (&dummy))
	return false;
      tar_stat_destroy (&dummy);
      assign_string (&continued_file_name, current_header->header.name);
      continued_file_size =
	UINTMAX_FROM_HEADER (current_header->header.size);
      continued_file_offset =
	UINTMAX_FROM_HEADER (current_header->oldgnu_header.offset);
      break;

    default:
      break;
    }

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

      s = continued_file_size + continued_file_offset;

      if (real_s_totsize != s || s < continued_file_offset)
	{
	  char totsizebuf[UINTMAX_STRSIZE_BOUND];
	  char s1buf[UINTMAX_STRSIZE_BOUND];
	  char s2buf[UINTMAX_STRSIZE_BOUND];

	  WARN ((0, 0, _("%s is the wrong size (%s != %s + %s)"),
		 quote (continued_file_name),
		 STRINGIFY_BIGINT (save_totsize, totsizebuf),
		 STRINGIFY_BIGINT (continued_file_size, s1buf),
		 STRINGIFY_BIGINT (continued_file_offset, s2buf)));
	  return false;
	}

      if (real_s_totsize - real_s_sizeleft != continued_file_offset)
	{
	  WARN ((0, 0, _("This volume is out of sequence")));
	  return false;
	}
    }

  increase_volume_number ();
  return true;
}


/* 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 bool
check_label_pattern (union block *label)
{
  char *string;
  bool result;

  if (! memchr (label->header.name, '\0', sizeof label->header.name))
    return false;

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

  if (!multi_volume_option)
    return false;

  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;
}

/* 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)
{
  union block *label = find_next_block ();

  if (!label)
    FATAL_ERROR ((0, 0, _("Archive not labeled to match %s"),
		  quote (volume_label_option)));
  if (!check_label_pattern (label))
    FATAL_ERROR ((0, 0, _("Volume %s does not match %s"),
		  quote_n (0, label->header.name),
		  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 ();

      memset (label, 0, BLOCKSIZE);

      strcpy (label->header.name, volume_label_option);
      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);
    }
}

#define VOL_SUFFIX "Volume"

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

static void
add_chunk_header ()
{
  if (archive_format == POSIX_FORMAT)
    {
      off_t block_ordinal;
      union block *blk;
      struct tar_stat_info st;
      static size_t real_s_part_no; /* FIXME */

      real_s_part_no++;
      memset (&st, 0, sizeof st);
      st.orig_file_name = st.file_name = real_s_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.%p/%f.%n",
					       real_s_part_no);
      st.file_name = st.orig_file_name;
      st.archive_file_size = st.stat.st_size = real_s_sizeleft;

      block_ordinal = current_block_ordinal ();
      blk = start_header (&st);
      if (!blk)
	abort (); /* FIXME */
      finish_header (&st, blk, block_ordinal);
      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 (void)
{
  int tmp;
  union block *block = find_next_block ();

  if (strlen (real_s_name) > NAME_FIELD_SIZE)
    WARN ((0, 0,
	   _("%s: file name too long to be stored in a GNU multivolume header, truncated"),
	   quotearg_colon (real_s_name)));

  memset (block, 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.  */

  strncpy (block->header.name, real_s_name, NAME_FIELD_SIZE);
  block->header.typeflag = GNUTYPE_MULTIVOL;

  OFF_TO_CHARS (real_s_sizeleft, block->header.size);
  OFF_TO_CHARS (real_s_totsize - real_s_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 (void)
{
  if (archive_format == POSIX_FORMAT)
    {
      off_t d = real_s_totsize - real_s_sizeleft;
      xheader_store ("GNU.volume.filename", &dummy, real_s_name);
      xheader_store ("GNU.volume.size", &dummy, &real_s_sizeleft);
      xheader_store ("GNU.volume.offset", &dummy, &d);
    }
  else
    gnu_add_multi_volume_header ();
}

/* Synchronize multi-volume globals */
static void
multi_volume_sync ()
{
  if (multi_volume_option)
    {
      if (save_name)
	{
	  assign_string (&real_s_name,
			 safer_name_suffix (save_name, false,
					    absolute_names_option));
	  real_s_totsize = save_totsize;
	  real_s_sizeleft = save_sizeleft;
	}
      else
	{
	  assign_string (&real_s_name, 0);
	  real_s_totsize = 0;
	  real_s_sizeleft = 0;
	}
    }
}


/* Low-level flush functions */

/* Simple flush read (no multi-volume or label extensions) */
static void
simple_flush_read (void)
{
  size_t status;		/* result from system call */

  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;
      status = sys_write_archive_buffer ();
      archive = STDIN_FILENO;
      if (status != record_size)
	archive_write_error (status);
    }

  for (;;)
    {
      status = rmtread (archive, record_start->buffer, record_size);
      if (status == record_size)
	{
	  records_read++;
	  return;
	}
      if (status == SAFE_READ_ERROR)
	{
	  archive_read_error ();
	  continue;		/* try again */
	}
      break;
    }
  short_read (status);
}

/* Simple flush write (no multi-volume or label extensions) */
static void
simple_flush_write (size_t level __attribute__((unused)))
{
  ssize_t status;

  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)
{
  size_t status;		/* result from system call */

  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;
      status = sys_write_archive_buffer ();
      archive = STDIN_FILENO;
      if (status != record_size)
	archive_write_error (status);
    }

  multi_volume_sync ();

  for (;;)
    {
      status = rmtread (archive, record_start->buffer, record_size);
      if (status == record_size)
	{
	  records_read++;
	  return;
	}

      /* The condition below used to include
	      || (status > 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 ((status == 0
	   || (status == SAFE_READ_ERROR && errno == ENOSPC))
	  && multi_volume_option)
	{
	  while (!try_new_volume ())
	    ;
	  return;
	}
      else if (status == SAFE_READ_ERROR)
	{
	  archive_read_error ();
	  continue;
	}
      break;
    }
  short_read (status);
}

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 (size_t buffer_level)
{
  ssize_t status;
  union block *header;
  char *copy_ptr;
  size_t copy_size;
  size_t bufsize;

  status = _flush_write ();
  if (status != record_size && !multi_volume_option)
    archive_write_error (status);
  else
    {
      records_written++;
      bytes_written += status;
    }

  if (status == record_size)
    {
      multi_volume_sync ();
      return;
    }

  /* In multi-volume mode. */
  /* ENXIO is for the UNIX PC.  */
  if (status < 0 && errno != ENOSPC && errno != EIO && errno != ENXIO)
    archive_write_error (status);

  if (!new_volume (ACCESS_WRITE))
    return;

  tar_stat_destroy (&dummy);

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

  copy_ptr = record_start->buffer + status;
  copy_size = buffer_level - status;
  /* Switch to the next buffer */
  record_index = !record_index;
  init_buffer ();

  if (volume_label_option)
    add_volume_label ();

  if (real_s_name)
    add_multi_volume_header ();

  write_extended (true, &dummy, find_next_block ());
  tar_stat_destroy (&dummy);
  
  if (real_s_name)
    add_chunk_header ();
  header = find_next_block ();
  bufsize = available_space_after (header);
  while (bufsize < copy_size)
    {
      memcpy (header->buffer, copy_ptr, bufsize);
      copy_ptr += bufsize;
      copy_size -= bufsize;
      set_next_block_after (header + (bufsize - 1) / BLOCKSIZE);
      header = find_next_block ();
      bufsize = available_space_after (header);
    }
  memcpy (header->buffer, copy_ptr, copy_size);
  memset (header->buffer + copy_size, 0, bufsize - copy_size);
  set_next_block_after (header + (copy_size - 1) / BLOCKSIZE);
  find_next_block ();
}

static void
gnu_flush_write (size_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 ()
{
  flush_read_ptr ();
}

void
flush_write ()
{
  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:
      if (volume_label_option)
	match_volume_label ();
      break;

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

    default:
      break;
    }
  set_volume_start_time ();
}