src/libip/classmask.c

#include <u.h>
#include <libc.h>
#include <ip.h>

uchar classmask[4][16] = {
	0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0x00,0x00,0x00,
	0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0x00,0x00,0x00,
	0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0xff,0x00,0x00,
	0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0x00,
};

uchar*
defmask(uchar *ip)
{
	return classmask[ip[IPv4off]>>6];
}

void
maskip(uchar *from, uchar *mask, uchar *to)
{
	int i;

	for(i = 0; i < IPaddrlen; i++)
		to[i] = from[i] & mask[i];
}