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] == "\0") {
$nbytes = strlen($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 {
$bytes = "\0" . _openid_get_bytes($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);
}