misc.c

gnu tar 源码包。 tar 软件是 Unix 系统下的一个打包软件

	    size_t entrylen;

	    if (! directory)
	      return 0;

	    for (entry = directory;
		 (entrylen = strlen (entry)) != 0;
		 entry += entrylen + 1)
	      {
		char *file_name_buffer = new_name (file_name, entry);
		int r = remove_any_file (file_name_buffer,
                                         RECURSIVE_REMOVE_OPTION);
		int e = errno;
		free (file_name_buffer);

		if (! r)
		  {
		    free (directory);
		    errno = e;
		    return 0;
		  }
	      }

	    free (directory);
	    return safer_rmdir (file_name) == 0;
	  }
	}
      break;
    }

  return 0;
}

/* Check if FILE_NAME already exists and make a backup of it right now.
   Return success (nonzero) only if the backup is either unneeded, or
   successful.  For now, directories are considered to never need
   backup.  If THIS_IS_THE_ARCHIVE is nonzero, this is the archive and
   so, we do not have to backup block or character devices, nor remote
   entities.  */
bool
maybe_backup_file (const char *file_name, bool this_is_the_archive)
{
  struct stat file_stat;

  /* Check if we really need to backup the file.  */

  if (this_is_the_archive && _remdev (file_name))
    return true;

  if (stat (file_name, &file_stat))
    {
      if (errno == ENOENT)
	return true;

      stat_error (file_name);
      return false;
    }

  if (S_ISDIR (file_stat.st_mode))
    return true;

  if (this_is_the_archive
      && (S_ISBLK (file_stat.st_mode) || S_ISCHR (file_stat.st_mode)))
    return true;

  assign_string (&before_backup_name, file_name);

  /* A run situation may exist between Emacs or other GNU programs trying to
     make a backup for the same file simultaneously.  If theoretically
     possible, real problems are unlikely.  Doing any better would require a
     convention, GNU-wide, for all programs doing backups.  */

  assign_string (&after_backup_name, 0);
  after_backup_name = find_backup_file_name (file_name, backup_type);
  if (! after_backup_name)
    xalloc_die ();

  if (rename (before_backup_name, after_backup_name) == 0)
    {
      if (verbose_option)
	fprintf (stdlis, _("Renaming %s to %s\n"),
		 quote_n (0, before_backup_name),
		 quote_n (1, after_backup_name));
      return true;
    }
  else
    {
      /* The backup operation failed.  */
      int e = errno;
      ERROR ((0, e, _("%s: Cannot rename to %s"),
	      quotearg_colon (before_backup_name),
	      quote_n (1, after_backup_name)));
      assign_string (&after_backup_name, 0);
      return false;
    }
}

/* Try to restore the recently backed up file to its original name.
   This is usually only needed after a failed extraction.  */
void
undo_last_backup (void)
{
  if (after_backup_name)
    {
      if (rename (after_backup_name, before_backup_name) != 0)
	{
	  int e = errno;
	  ERROR ((0, e, _("%s: Cannot rename to %s"),
		  quotearg_colon (after_backup_name),
		  quote_n (1, before_backup_name)));
	}
      if (verbose_option)
	fprintf (stdlis, _("Renaming %s back to %s\n"),
		 quote_n (0, after_backup_name),
		 quote_n (1, before_backup_name));
      assign_string (&after_backup_name, 0);
    }
}

/* Depending on DEREF, apply either stat or lstat to (NAME, BUF).  */
int
deref_stat (bool deref, char const *name, struct stat *buf)
{
  return deref ? stat (name, buf) : lstat (name, buf);
}

/* Set FD's (i.e., FILE's) access time to TIMESPEC[0].  If that's not
   possible to do by itself, set its access and data modification
   times to TIMESPEC[0] and TIMESPEC[1], respectively.  */
int
set_file_atime (int fd, char const *file, struct timespec const timespec[2])
{
#ifdef _FIOSATIME
  if (0 <= fd)
    {
      struct timeval timeval;
      timeval.tv_sec = timespec[0].tv_sec;
      timeval.tv_usec = timespec[0].tv_nsec / 1000;
      if (ioctl (fd, _FIOSATIME, &timeval) == 0)
	return 0;
    }
#endif

  return gl_futimens (fd, file, timespec);
}

/* A description of a working directory.  */
struct wd
{
  char const *name;
  int saved;
  struct saved_cwd saved_cwd;
};

/* A vector of chdir targets.  wd[0] is the initial working directory.  */
static struct wd *wd;

/* The number of working directories in the vector.  */
static size_t wds;

/* The allocated size of the vector.  */
static size_t wd_alloc;

/* DIR is the operand of a -C option; add it to vector of chdir targets,
   and return the index of its location.  */
int
chdir_arg (char const *dir)
{
  if (wds == wd_alloc)
    {
      if (wd_alloc == 0)
	{
	  wd_alloc = 2;
	  wd = xmalloc (sizeof *wd * wd_alloc);
	}
      else
	wd = x2nrealloc (wd, &wd_alloc, sizeof *wd);

      if (! wds)
	{
	  wd[wds].name = ".";
	  wd[wds].saved = 0;
	  wds++;
	}
    }

  /* Optimize the common special case of the working directory,
     or the working directory as a prefix.  */
  if (dir[0])
    {
      while (dir[0] == '.' && ISSLASH (dir[1]))
	for (dir += 2;  ISSLASH (*dir);  dir++)
	  continue;
      if (! dir[dir[0] == '.'])
	return wds - 1;
    }

  wd[wds].name = dir;
  wd[wds].saved = 0;
  return wds++;
}

/* Change to directory I.  If I is 0, change to the initial working
   directory; otherwise, I must be a value returned by chdir_arg.  */
void
chdir_do (int i)
{
  static int previous;

  if (previous != i)
    {
      struct wd *prev = &wd[previous];
      struct wd *curr = &wd[i];

      if (! prev->saved)
	{
	  int err = 0;
	  prev->saved = 1;
	  if (save_cwd (&prev->saved_cwd) != 0)
	    err = errno;
	  else if (0 <= prev->saved_cwd.desc)
	    {
	      /* Make sure we still have at least one descriptor available.  */
	      int fd1 = prev->saved_cwd.desc;
	      int fd2 = dup (fd1);
	      if (0 <= fd2)
		close (fd2);
	      else if (errno == EMFILE)
		{
		  /* Force restore_cwd to use chdir_long.  */
		  close (fd1);
		  prev->saved_cwd.desc = -1;
		  prev->saved_cwd.name = xgetcwd ();
		}
	      else
		err = errno;
	    }

	  if (err)
	    FATAL_ERROR ((0, err, _("Cannot save working directory")));
	}

      if (curr->saved)
	{
	  if (restore_cwd (&curr->saved_cwd))
	    FATAL_ERROR ((0, 0, _("Cannot change working directory")));
	}
      else
	{
	  if (i && ! ISSLASH (curr->name[0]))
	    chdir_do (i - 1);
	  if (chdir (curr->name) != 0)
	    chdir_fatal (curr->name);
	}

      previous = i;
    }
}

void
close_diag (char const *name)
{
  if (ignore_failed_read_option)
    close_warn (name);
  else
    close_error (name);
}

void
open_diag (char const *name)
{
  if (ignore_failed_read_option)
    open_warn (name);
  else
    open_error (name);
}

void
read_diag_details (char const *name, off_t offset, size_t size)
{
  if (ignore_failed_read_option)
    read_warn_details (name, offset, size);
  else
    read_error_details (name, offset, size);
}

void
readlink_diag (char const *name)
{
  if (ignore_failed_read_option)
    readlink_warn (name);
  else
    readlink_error (name);
}

void
savedir_diag (char const *name)
{
  if (ignore_failed_read_option)
    savedir_warn (name);
  else
    savedir_error (name);
}

void
seek_diag_details (char const *name, off_t offset)
{
  if (ignore_failed_read_option)
    seek_warn_details (name, offset);
  else
    seek_error_details (name, offset);
}

void
stat_diag (char const *name)
{
  if (ignore_failed_read_option)
    stat_warn (name);
  else
    stat_error (name);
}

void
write_fatal_details (char const *name, ssize_t status, size_t size)
{
  write_error_details (name, status, size);
  fatal_exit ();
}

/* Fork, aborting if unsuccessful.  */
pid_t
xfork (void)
{
  pid_t p = fork ();
  if (p == (pid_t) -1)
    call_arg_fatal ("fork", _("child process"));
  return p;
}

/* Create a pipe, aborting if unsuccessful.  */
void
xpipe (int fd[2])
{
  if (pipe (fd) < 0)
    call_arg_fatal ("pipe", _("interprocess channel"));
}

/* Return PTR, aligned upward to the next multiple of ALIGNMENT.
   ALIGNMENT must be nonzero.  The caller must arrange for ((char *)
   PTR) through ((char *) PTR + ALIGNMENT - 1) to be addressable
   locations.  */

static inline void *
ptr_align (void *ptr, size_t alignment)
{
  char *p0 = ptr;
  char *p1 = p0 + alignment - 1;
  return p1 - (size_t) p1 % alignment;
}

/* Return the address of a page-aligned buffer of at least SIZE bytes.
   The caller should free *PTR when done with the buffer.  */

void *
page_aligned_alloc (void **ptr, size_t size)
{
  size_t alignment = getpagesize ();
  size_t size1 = size + alignment;
  if (size1 < size)
    xalloc_die ();
  *ptr = xmalloc (size1);
  return ptr_align (*ptr, alignment);
}