extract.c

gnu tar 源码包。 tar 软件是 Unix 系统下的一个打包软件

  link_name = current_stat_info.link_name;
  
  if (! absolute_names_option && contains_dot_dot (link_name))
    return create_placeholder_file (file_name, false, &interdir_made);

  do
    {
      struct stat st1, st2;
      int e;
      int status = link (link_name, file_name);
      e = errno;

      if (status == 0)
	{
	  struct delayed_link *ds = delayed_link_head;
	  if (ds && lstat (link_name, &st1) == 0)
	    for (; ds; ds = ds->next)
	      if (ds->dev == st1.st_dev
		  && ds->ino == st1.st_ino
		  && timespec_cmp (ds->mtime, get_stat_mtime (&st1)) == 0)
		{
		  struct string_list *p =  xmalloc (offsetof (struct string_list, string)
						    + strlen (file_name) + 1);
		  strcpy (p->string, file_name);
		  p->next = ds->sources;
		  ds->sources = p;
		  break;
		}
	  return 0;
	}
      else if ((e == EEXIST && strcmp (link_name, file_name) == 0)
	       || (lstat (link_name, &st1) == 0
		   && lstat (file_name, &st2) == 0
		   && st1.st_dev == st2.st_dev
		   && st1.st_ino == st2.st_ino))
	return 0;

      errno = e;
    }
  while (maybe_recoverable (file_name, &interdir_made));

  if (!(incremental_option && errno == EEXIST))
    {
      link_error (link_name, file_name);
      return 1;
    }
  return 0;
}

static int
extract_symlink (char *file_name, int typeflag)
{
#ifdef HAVE_SYMLINK
  int status;
  int interdir_made = 0;

  transform_member_name (&current_stat_info.link_name, xform_symlink);

  if (! absolute_names_option
      && (IS_ABSOLUTE_FILE_NAME (current_stat_info.link_name)
	  || contains_dot_dot (current_stat_info.link_name)))
    return create_placeholder_file (file_name, true, &interdir_made);

  while ((status = symlink (current_stat_info.link_name, file_name)))
    if (!maybe_recoverable (file_name, &interdir_made))
      break;

  if (status == 0)
    set_stat (file_name, &current_stat_info, NULL, 0, 0, SYMTYPE);
  else
    symlink_error (current_stat_info.link_name, file_name);
  return status;

#else
  static int warned_once;

  if (!warned_once)
    {
      warned_once = 1;
      WARN ((0, 0, _("Attempting extraction of symbolic links as hard links")));
    }
  return extract_link (file_name, typeflag);
#endif
}

#if S_IFCHR || S_IFBLK
static int
extract_node (char *file_name, int typeflag)
{
  int status;
  int interdir_made = 0;
  mode_t mode = current_stat_info.stat.st_mode & ~ current_umask;
  mode_t invert_permissions =
    0 < same_owner_option ? mode & (S_IRWXG | S_IRWXO) : 0;

  do
    status = mknod (file_name, mode ^ invert_permissions,
		    current_stat_info.stat.st_rdev);
  while (status && maybe_recoverable (file_name, &interdir_made));

  if (status != 0)
    mknod_error (file_name);
  else
    set_stat (file_name, &current_stat_info, NULL, invert_permissions,
	      ARCHIVED_PERMSTATUS, typeflag);
  return status;
}
#endif

#if HAVE_MKFIFO || defined mkfifo
static int
extract_fifo (char *file_name, int typeflag)
{
  int status;
  int interdir_made = 0;
  mode_t mode = current_stat_info.stat.st_mode & ~ current_umask;
  mode_t invert_permissions =
    0 < same_owner_option ? mode & (S_IRWXG | S_IRWXO) : 0;

  while ((status = mkfifo (file_name, mode)) != 0)
    if (!maybe_recoverable (file_name, &interdir_made))
      break;

  if (status == 0)
    set_stat (file_name, &current_stat_info, NULL, invert_permissions,
	      ARCHIVED_PERMSTATUS, typeflag);
  else
    mkfifo_error (file_name);
  return status;
}
#endif

static int
extract_volhdr (char *file_name, int typeflag)
{
  if (verbose_option)
    fprintf (stdlis, _("Reading %s\n"), quote (current_stat_info.file_name));
  skip_member ();
  return 0;
}

static int
extract_failure (char *file_name, int typeflag)
{
  return 1;
}

typedef int (*tar_extractor_t) (char *file_name, int typeflag);



/* Prepare to extract a file. Find extractor function.
   Return zero if extraction should not proceed.  */

static int
prepare_to_extract (char const *file_name, int typeflag, tar_extractor_t *fun)
{
  int rc = 1;

  if (EXTRACT_OVER_PIPE)
    rc = 0;

  /* Select the extractor */
  switch (typeflag)
    {
    case GNUTYPE_SPARSE:
      *fun = extract_file;
      rc = 1;
      break;

    case AREGTYPE:
    case REGTYPE:
    case CONTTYPE:
      /* Appears to be a file.  But BSD tar uses the convention that a slash
	 suffix means a directory.  */
      if (current_stat_info.had_trailing_slash)
	*fun = extract_dir;
      else
	{
	  *fun = extract_file;
	  rc = 1;
	}
      break;

    case SYMTYPE:
      *fun = extract_symlink;
      break;

    case LNKTYPE:
      *fun = extract_link;
      break;

#if S_IFCHR
    case CHRTYPE:
      current_stat_info.stat.st_mode |= S_IFCHR;
      *fun = extract_node;
      break;
#endif

#if S_IFBLK
    case BLKTYPE:
      current_stat_info.stat.st_mode |= S_IFBLK;
      *fun = extract_node;
      break;
#endif

#if HAVE_MKFIFO || defined mkfifo
    case FIFOTYPE:
      *fun = extract_fifo;
      break;
#endif

    case DIRTYPE:
    case GNUTYPE_DUMPDIR:
      *fun = extract_dir;
      if (current_stat_info.is_dumpdir)
	delay_directory_restore_option = true;
      break;

    case GNUTYPE_VOLHDR:
      *fun = extract_volhdr;
      break;

    case GNUTYPE_MULTIVOL:
      ERROR ((0, 0,
	      _("%s: Cannot extract -- file is continued from another volume"),
	      quotearg_colon (current_stat_info.file_name)));
      *fun = extract_failure;
      break;

    case GNUTYPE_LONGNAME:
    case GNUTYPE_LONGLINK:
      ERROR ((0, 0, _("Unexpected long name header")));
      *fun = extract_failure;
      break;

    default:
      WARN ((0, 0,
	     _("%s: Unknown file type `%c', extracted as normal file"),
	     quotearg_colon (file_name), typeflag));
      *fun = extract_file;
    }

  /* Determine whether the extraction should proceed */
  if (rc == 0)
    return 0;

  switch (old_files_option)
    {
    case UNLINK_FIRST_OLD_FILES:
      if (!remove_any_file (file_name,
                            recursive_unlink_option ? RECURSIVE_REMOVE_OPTION
                                                      : ORDINARY_REMOVE_OPTION)
	  && errno && errno != ENOENT)
	{
	  unlink_error (file_name);
	  return 0;
	}
      break;

    case KEEP_NEWER_FILES:
      if (file_newer_p (file_name, &current_stat_info))
	{
	  WARN ((0, 0, _("Current %s is newer or same age"),
		 quote (file_name)));
	  return 0;
	}
      break;

    default:
      break;
    }

  return 1;
}

/* Extract a file from the archive.  */
void
extract_archive (void)
{
  char typeflag;
  tar_extractor_t fun;

  set_next_block_after (current_header);
  decode_header (current_header, &current_stat_info, &current_format, 1);
  if (!current_stat_info.file_name[0]
      || (interactive_option
	  && !confirm ("extract", current_stat_info.file_name)))
    {
      skip_member ();
      return;
    }

  /* Print the block from current_header and current_stat.  */
  if (verbose_option)
    print_header (&current_stat_info, -1);

  /* Restore stats for all non-ancestor directories, unless
     it is an incremental archive.
     (see NOTICE in the comment to delay_set_stat above) */
  if (!delay_directory_restore_option)
    apply_nonancestor_delayed_set_stat (current_stat_info.file_name, 0);

  /* Take a safety backup of a previously existing file.  */

  if (backup_option)
    if (!maybe_backup_file (current_stat_info.file_name, 0))
      {
	int e = errno;
	ERROR ((0, e, _("%s: Was unable to backup this file"),
		quotearg_colon (current_stat_info.file_name)));
	skip_member ();
	return;
      }

  /* Extract the archive entry according to its type.  */
  /* KLUDGE */
  typeflag = sparse_member_p (&current_stat_info) ?
                  GNUTYPE_SPARSE : current_header->header.typeflag;

  if (prepare_to_extract (current_stat_info.file_name, typeflag, &fun))
    {
      if (fun && (*fun) (current_stat_info.file_name, typeflag)
	  && backup_option)
	undo_last_backup ();
    }
  else
    skip_member ();

}

/* Extract the symbolic links whose final extraction were delayed.  */
static void
apply_delayed_links (void)
{
  struct delayed_link *ds;

  for (ds = delayed_link_head; ds; )
    {
      struct string_list *sources = ds->sources;
      char const *valid_source = 0;

      for (sources = ds->sources; sources; sources = sources->next)
	{
	  char const *source = sources->string;
	  struct stat st;

	  /* Make sure the placeholder file is still there.  If not,
	     don't create a link, as the placeholder was probably
	     removed by a later extraction.  */
	  if (lstat (source, &st) == 0
	      && st.st_dev == ds->dev
	      && st.st_ino == ds->ino
	      && timespec_cmp (get_stat_mtime (&st), ds->mtime) == 0)
	    {
	      /* Unlink the placeholder, then create a hard link if possible,
		 a symbolic link otherwise.  */
	      if (unlink (source) != 0)
		unlink_error (source);
	      else if (valid_source && link (valid_source, source) == 0)
		;
	      else if (!ds->is_symlink)
		{
		  if (link (ds->target, source) != 0)
		    link_error (ds->target, source);
		}
	      else if (symlink (ds->target, source) != 0)
		symlink_error (ds->target, source);
	      else
		{
		  struct tar_stat_info st1;
		  st1.stat.st_uid = ds->uid;
		  st1.stat.st_gid = ds->gid;
		  set_stat (source, &st1, NULL, 0, 0, SYMTYPE);
		  valid_source = source;
		}
	    }
	}

      for (sources = ds->sources; sources; )
	{
	  struct string_list *next = sources->next;
	  free (sources);
	  sources = next;
	}

      {
	struct delayed_link *next = ds->next;
	free (ds);
	ds = next;
      }
    }

  delayed_link_head = 0;
}

/* Finish the extraction of an archive.  */
void
extract_finish (void)
{
  /* First, fix the status of ordinary directories that need fixing.  */
  apply_nonancestor_delayed_set_stat ("", 0);

  /* Then, apply delayed links, so that they don't affect delayed
     directory status-setting for ordinary directories.  */
  apply_delayed_links ();

  /* Finally, fix the status of directories that are ancestors
     of delayed links.  */
  apply_nonancestor_delayed_set_stat ("", 1);
}

bool
rename_directory (char *src, char *dst)
{
  if (rename (src, dst))
    {
      int e = errno;

      switch (e)
	{
	case ENOENT:
	  if (make_directories (dst))
	    {
	      if (rename (src, dst) == 0)
		return true;
	      e = errno;
	    }
	  break;

	case EXDEV:
	  /* FIXME: Fall back to recursive copying */

	default:
	  break;
	}

      ERROR ((0, e, _("Cannot rename %s to %s"),
	      quote_n (0, src),
	      quote_n (1, dst)));
      return false;
    }
  return true;
}

void
fatal_exit (void)
{
  extract_finish ();
  error (TAREXIT_FAILURE, 0, _("Error is not recoverable: exiting now"));
  abort ();
}

void
xalloc_die (void)
{
  error (0, 0, "%s", _("memory exhausted"));
  fatal_exit ();
}