Re: GNOME CVS: gtk+ tml

[Tor Lillqvist <tml iki fi>]

Owen Taylor writes:
 > We probably need g_mkstemp.

Hmm, do we want it to be identical to the normal mkstemp(), or do we
want some extra features in it? Should the file be opened in binary
mode (on platforms where there is a difference)? Or should there be a
possibility to pass in extra O_ bits?

/**
 * g_mkstemp:
 *
 * Open a temporary file
 *
 * The parameter is a string that should match the rules for mktemp, i.e.
 * end in "XXXXXX". The X string will be modified to form the name
 * of a file that was created and opened.
 *
 * Return value: A file handle (as from open()) to the file file
 * opened for reading and writing. The file is opened in binary mode
 * on platforms where there is a difference. The file handle should be
 * closed with close(). In case of errors, -1 is returned.
 *
 * Code lifted from glibc.
 */
int
g_mkstemp (char *tmpl)
{
#ifdef HAVE_MKSTEMP
  return mkstemp (tmpl);
#else
  int len;
  char *XXXXXX;
  int count, fd;
  static const char letters[] =
    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  gulong value;
  GTimeVal tv;

  len = strlen (tmpl);
  if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
    return -1;

  /* This is where the Xs start.  */
  XXXXXX = &tmpl[len - 6];

  /* Get some more or less random data.  */
  g_get_current_time (&tv);
  value = (tv.tv_usec << 16) ^ tv.tv_sec;

  for (count = 0; count < 100; value += 7777, ++count)
    {
      gulong v = value;

      /* Fill in the random bits.  */
      XXXXXX[0] = letters[v % 62];
      v /= 62;
      XXXXXX[1] = letters[v % 62];
      v /= 62;
      XXXXXX[2] = letters[v % 62];
      v /= 62;
      XXXXXX[3] = letters[v % 62];
      v /= 62;
      XXXXXX[4] = letters[v % 62];
      v /= 62;
      XXXXXX[5] = letters[v % 62];

      fd = open (tmpl, O_RDWR | O_CREAT | O_EXCL | O_BINARY, 0600);

      if (fd >= 0)
	return fd;
      else if (errno != EEXIST)
	/* Any other error will apply also to other names we might
	 *  try, and there are 2^32 or so of them, so give up now.
	 */
	return -1;
    }

  /* We got out of the loop because we ran out of combinations to try.  */
  return -1;
#endif
}