static unsigned long crctable[256];
static unsigned char crcinvtable[256];
static unsigned long poly = 0xedb88320;

void set_poly(unsigned long p)
{
	poly = p;
}

unsigned long get_crc_table(unsigned long i)
{
	return crctable[i];
}

static inline unsigned char l2c(unsigned long l, int nr) { return (l >> (8*(nr-1))) & 0xff; }

void calc_crc_table(void)
{
	unsigned long value, idx, i;

	for (idx = 0 ; idx < 256 ; idx++) {
		for (value = idx, i = 0 ; i < 8 ; i++) {
			if (value & 1) {
				value >>= 1;
				value ^= poly;
			} else {
				value >>= 1;
			}
		}
		crctable[idx] = value;
		crcinvtable[l2c(value, 4)] = idx;
	}
}

unsigned long iter_crc(unsigned long c, unsigned long shiftreg)
{
	return (shiftreg >> 8) ^ crctable[(c ^ shiftreg) & 0xff];
}

unsigned long inv_iter_crc(unsigned long c, unsigned long shiftreg)
{
	unsigned long i = crcinvtable[l2c(shiftreg, 4)];
	return ((shiftreg ^ crctable[i]) << 8) | l2c(i ^ c, 1);
}

unsigned long calc_crc(unsigned char *buf, unsigned long buflen, unsigned long crc)
{
	while (buflen--)
		crc = iter_crc(*buf++, crc);
	return ~crc;
}

unsigned long solve(unsigned char *buf, unsigned long buflen, unsigned long crc, unsigned long wcrc)
{
	unsigned char a, b, c, d;
	
	while (buflen--)
		crc = iter_crc(*buf++, crc);

	wcrc = ~wcrc;

	// sequence of crc's we must have to finish with wcrc
	unsigned long c1, c2, c3, c4;
	c4 = crctable[ crcinvtable[ l2c(wcrc, 4) ] ];
	c3 = crctable[ crcinvtable[ l2c(wcrc, 3) ^ l2c(c4, 3) ] ];
	c2 = crctable[ crcinvtable[ l2c(wcrc, 2) ^ l2c(c4, 2) ^ l2c(c3, 3) ] ];
	c1 = crctable[ crcinvtable[ l2c(wcrc, 1) ^ l2c(c4, 1) ^ l2c(c3, 2) ^ l2c(c2, 3) ] ];

	a = crcinvtable[l2c(c1, 4)] ^ l2c(crc, 1);
	crc = (crc >> 8) ^ crctable[(a ^ crc) & 0xff];
	
	b = crcinvtable[l2c(c2, 4)] ^ l2c(crc, 1);
	crc = (crc >> 8) ^ crctable[(b ^ crc) & 0xff];
	
	c = crcinvtable[l2c(c3, 4)] ^ l2c(crc, 1);
	crc = (crc >> 8) ^ crctable[(c ^ crc) & 0xff];
	
	d = crcinvtable[l2c(c4, 4)] ^ l2c(crc, 1);

	crc = 0;
	crc |= d; crc <<= 8;
	crc |= c; crc <<= 8;
	crc |= b; crc <<= 8;
	crc |= a;
	return crc;
}

unsigned long not(unsigned long l)
{
	return ~l;
}