Crc : module
{
	PATH : con "/dis/lib/crc.dis";

	CRCstate : adt {
		crc : int;
		crctab : array of int;
		reg : int;
	};

	# setup crc table with given polynomial (if 0 default polynomial used) 
	# (the polynomial has an implicit top bit set)
	# reg is the initial value of the CRC register 
	# (usually 0 but 16rfffffffrf in the CRC32 algorithm for example)
	init : fn(poly : int, reg : int) : ref CRCstate;

	# calculate crc of first nb bytes in given array of bytes and return its value
	# may be called repeatedly to calculate crc of a series of arrays of bytes
	crc :	fn(state: ref CRCstate, buf : array of byte, nb : int) : int;

	# reset crc state to its initial value
	reset : fn(state : ref CRCstate);
};