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);
}