public static function random($n, $s)
{
switch (BigInt::support()) {
case 'gmp':
$result = gmp_init(0);
for ($i = 0; $i < $n; $i++) {
if (mt_rand(0, 1)) {
gmp_setbit($result, $i);
}
}
if ($s) {
gmp_setbit($result, $n - 1);
}
return $result;
case 'big_int':
$result = bi_rand($n);
if ($s) {
$result = bi_set_bit($result, $n - 1);
}
return $result;
case 'bcmath':
bcscale(0);
$t = BigInt::bcpow(2, $n);
if ($s == 1) {
$m = bcdiv($t, 2);
$t = bcsub($m, 1);
} else {
$m = 0;
$t = bcsub($t, 1);
}
$l = strlen($t);
$n = (int) ($l / 9) + 1;
$r = '';
while ($n) {
$r .= substr('000000000' . mt_rand(0, 999999999), -9);
--$n;
}
$r = substr($r, 0, $l);
while (bccomp($r, $t) == 1) {
$r = substr($r, 1, $l) . mt_rand(0, 9);
}
return bcadd($r, $m);
case '':
default:
return BigInt::_random($n, $s);
}
}
