I got some point from others.I already red and debug network.c . Now I now the basic logic behind that. But still I'm confused by arithmetic. I find some comments on that , I need some one's help.
/* * int * bitncmp(l, r, n) * compare bit masks l and r, for n bits. * return: * -1, 1, or 0 in the libc tradition. * note: * network byte order assumed. this means 220.127.116.11/28 has * 0x11110000 in its fourth octet. * author: * Paul Vixie (ISC), June 1996 */ Why we finish it in this way. Can you help me?