PasswordHash::gensalt_extended

	function gensalt_extended($input)
	{
		$count_log2 = min($this->iteration_count_log2 + 8, 24);
		# This should be odd to not reveal weak DES keys, and the
		# maximum valid value is (2**24 - 1) which is odd anyway.
		$count = (1 << $count_log2) - 1;

		$output = '_';
		$output .= $this->itoa64[$count & 0x3f];
		$output .= $this->itoa64[($count >> 6) & 0x3f];
		$output .= $this->itoa64[($count >> 12) & 0x3f];
		$output .= $this->itoa64[($count >> 18) & 0x3f];

		$output .= $this->encode64($input, 3);

		return $output;
	}