_openid_dh_rand

1 call to _openid_dh_rand()

File

modules/openid/openid.inc, line 333

OpenID utility functions.

Code

function _openid_dh_rand($stop) {
  static $duplicate_cache = array();

  // Used as the key for the duplicate cache
  $rbytes = _openid_dh_long_to_binary($stop);

  if (array_key_exists($rbytes, $duplicate_cache)) {
    list($duplicate, $nbytes) = $duplicate_cache[$rbytes];
  }
  else {
    if ($rbytes[0] == "\x00") {
      $nbytes = strlen($rbytes) - 1;
    }
    else {
      $nbytes = strlen($rbytes);
    }

    $mxrand = bcpow(256, $nbytes);

    // If we get a number less than this, then it is in the
    // duplicated range.
    $duplicate = bcmod($mxrand, $stop);

    if (count($duplicate_cache) > 10) {
      $duplicate_cache = array();
    }

    $duplicate_cache[$rbytes] = array($duplicate, $nbytes);
  }

  do {
    $bytes = "\x00" . _openid_get_bytes($nbytes);
    $n = _openid_dh_binary_to_long($bytes);
    // Keep looping if this value is in the low duplicated range.
  } while (bccomp($n, $duplicate) < 0);

  return bcmod($n, $stop);
}