/**
* Returns part of number $num, starting at bit
* position $start with length $length
*
* @param gmp resource $num
* @param int start
* @param int length
* @return gmp resource
* @access public
*/
function subint($num, $start, $length)
{
$start_byte = intval($start / 8);
$start_bit = $start % 8;
$byte_length = intval($length / 8);
$bit_length = $length % 8;
if ($bit_length) {
$byte_length++;
}
$bi = new Math_BigInteger($num, 10);
$divider = new Math_BigInteger(1 << $start_bit);
$res = $bi->divide($divider);
$bi = $res[0];
$tmp = _byte_strrev(_byte_substr($bi->toBytes(), $start_byte, $byte_length));
$tmp = str_pad($tmp, $byte_length, "");
$tmp = _byte_substr_replace($tmp, $tmp[$byte_length - 1] & _byte_chr(0xff >> 8 - $bit_length), $byte_length - 1, 1);
return $this->bin2int($tmp);
}
/**
* Returns part of number $num, starting at bit
* position $start with length $length
*
* @param gmp resource $num
* @param int start
* @param int length
* @return gmp resource
* @access public
*/
function subint($num, $start, $length)
{
$start_byte = intval($start / 8);
$start_bit = $start % 8;
$byte_length = intval($length / 8);
$bit_length = $length % 8;
if ($bit_length) {
$byte_length++;
}
$num = gmp_div($num, 1 << $start_bit);
$tmp = _byte_substr($this->int2bin($num), $start_byte, $byte_length);
$tmp = str_pad($tmp, $byte_length, "");
$tmp = _byte_substr_replace($tmp, $tmp[$byte_length - 1] & _byte_chr(0xff >> 8 - $bit_length), $byte_length - 1, 1);
return $this->bin2int($tmp);
}
