diff options
| -rw-r--r-- | main.c | 27 |
1 files changed, 25 insertions, 2 deletions
@@ -57,6 +57,18 @@ countones(u32int addr) { int cnt, shift; + for(cnt = 0, shift = 31; shift >= 0; shift--) + if((addr & 1<<shift) != 0) + cnt++; + return cnt; +} + +/* returns the most-significant ones */ +int +countmsones(u32int addr) +{ + int cnt, shift; + for(cnt = 0, shift = 31; cnt < 32 && (addr & 1<<shift) != 0; cnt++, shift--) ; return cnt; @@ -82,6 +94,14 @@ getip4(char *s) return addr; } +int +checkmask(u32int mask) +{ + if(countones(mask) != countmsones(mask)) + return -1; + return 0; +} + void usage(void) { @@ -109,8 +129,11 @@ main(int argc, char *argv[]) cidr = strtol(argv[1], nil, 10); assert(cidr > 0 && cidr <= 32); mask = ~0 << (32-cidr); - }else + }else{ mask = getip4(argv[1]); + if(checkmask(mask) < 0) + sysfatal("invalid mask"); + } net.addr = addr&mask; net.mask = mask; @@ -118,7 +141,7 @@ main(int argc, char *argv[]) net.minaddr = net.addr+1; net.maxaddr = net.bcast-1; net.nhosts = net.maxaddr-net.minaddr; - net.cidr = countones(net.mask); + net.cidr = countmsones(net.mask); print("%N", net); exits(nil); |