#include <stdio.h>

static unsigned long crctable[256];

void calc_crc_table(void)
{
	unsigned long poly = 0xedb88320, 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;
	}
}

unsigned long calc_crc(unsigned char *buf, unsigned long buflen)
{
	unsigned long crc = 0xffffffff;
	while (buflen--)
		crc = (crc >> 8) ^ crctable[*buf++ ^ crc & 0xff];
	return ~crc;
}

unsigned char mkhex(char c)
{
	char oc = c;
	
	if (c < '0')
		goto err;
	c -= '0';
	if (c <= 9)
		return c;
	if (c < 'A'-'0')
		goto err;
	c -= 'A'-'0';
	if (c <= 6)
		return 10+c;
	if (c < 'a'-'A')
		goto err;
	c -= 'a' - 'A';
	if (c <= 6)
		return 10+c;
err:
	fprintf(stderr, "invalid character %c (%hhx)\n", oc, oc);
	exit(1);
}

unsigned long interpol(char *src, char *dst, const unsigned long dstlen)
{
	unsigned long i=0;
	register char c;
	
	while (*src && i < dstlen) {
		if ((c = *src++) == '\\')
			if ((c = *src++) == 'x') {
				c = mkhex(*src++) << 4;
				c |= mkhex(*src++);
			} else if (!c)
				break;
		dst[i++] = c;
	}
	return i;
}

int main(int argc, char **argv)
{
	int i;
	char buf[256];
	unsigned long buflen = 256;
	
	calc_crc_table();

	if (argc > 1) {
		buflen = interpol(argv[1], buf, buflen);
		printf("%d crc: %.8X\n", buflen, calc_crc((unsigned char *)buf, buflen));
	} else
		for (i=0 ; i<256 ; i+=16)
		printf("%.8X %.8X %.8X %.8X %.8X %.8X %.8X %.8X %.8X %.8X %.8X %.8X %.8X %.8X %.8X %.8X\n",
		crctable[i], crctable[i+1], crctable[i+2], crctable[i+3],
		crctable[i+4], crctable[i+5], crctable[i+6], crctable[i+7],
		crctable[i+8], crctable[i+9], crctable[i+10], crctable[i+11],
		crctable[i+12], crctable[i+13], crctable[i+14], crctable[i+15]);
	return 0;
}