Function contigmask

tools/ipfw/ipfw2.c:1153–1165

* Returns the number of bits set (from left) in a contiguous bitmask, * or -1 if the mask is not contiguous. * XXX this needs a proper fix. * This effectively works on masks in big-endian (network) format. * when compiled on little endian architectures. * * First bit is bit 7 of the first byte -- note, for MAC addresses, * the first bit on the wire is bit 0 of the first byte. * len is the

 * len is the max length in bits.
 */
int
contigmask(const uint8_t *p, int len)
{
	int i, n;

	for (i=0; i<len ; i++)
		if ( (p[i/8] & (1 << (7 - (i%8)))) == 0) /* first bit unset */
			break;
	for (n=i+1; n < len; n++)
		if ( (p[n/8] & (1 << (7 - (n%8)))) != 0)
			return -1; /* mask not contiguous */
	return i;
}

/*
 * print flags set/clear in the two bitmasks passed as parameters.