function _openid_dh_rand

File

modules/openid/openid.inc, line 530

Code

function _openid_dh_rand($stop) {
  $duplicate_cache =& drupal_static(__FUNCTION__, array());
  // Used as the key for the duplicate cache
  $rbytes = _openid_dh_long_to_binary($stop);
  if (isset($duplicate_cache[$rbytes])) {
    list($duplicate, $nbytes) = $duplicate_cache[$rbytes];
  }
  else {
    if ($rbytes[0] == "\x00") {
      $nbytes = strlen($rbytes) - 1;
    }
    else {
      $nbytes = strlen($rbytes);
    }
    $mxrand = _openid_math_pow(256, $nbytes);
    // If we get a number less than this, then it is in the
    // duplicated range.
    $duplicate = _openid_math_mod($mxrand, $stop);
    if (count($duplicate_cache) > 10) {
      $duplicate_cache = array();
    }
    $duplicate_cache[$rbytes] = array(
      $duplicate,
      $nbytes,
    );
  }
  do {
    $bytes = "\x00" . drupal_random_bytes($nbytes);
    $n = _openid_dh_binary_to_long($bytes);
    // Keep looping if this value is in the low duplicated range.
  } while (_openid_math_cmp($n, $duplicate) < 0);
  return _openid_math_mod($n, $stop);
}