function biPowMod($x, $y, $m)
{
global $biRadixBase, $biRadixBits, $biBitsPerDigit, $biRadix, $biHalfRadix, $biRadixSquared, $biMaxDigitVal, $biMaxInteger, $biMaxDigits, $biZERO_ARRAY, $biBigZero, $biBigOne, $dpl10, $lr10;
$result = $biBigOne;
$a = $x;
$k = $y;
while (true) {
if (($k->digits[0] & 1) != 0) {
$result = biMultiplyMod($result, $a, $m);
}
$k = biShiftRight($k, 1);
if ($k->digits[0] == 0 && biHighIndex($k) == 0) {
break;
}
$a = biMultiplyMod($a, $a, $m);
}
return $result;
}
function powMod($x, $y)
{
$result = new BigInt();
$result->digits[0] = 1;
$a = $x;
$k = $y;
while (true) {
if (($k->digits[0] & 1) != 0) {
$result = $this->multiplyMod($result, $a);
}
$k = biShiftRight($k, 1);
if ($k->digits[0] == 0 && biHighIndex($k) == 0) {
break;
}
$a = $this->multiplyMod($a, $a);
}
return $result;
}