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// group ip list from stdout into subnets
// ip list must be pre-uniqued
#include <stdio.h>
#include <stdlib.h>
#include "qsort.h"
#define ALLOC_STEP 16384
#define PCTMULT 3/4
typedef unsigned int uint;
typedef unsigned char uchar;
int ucmp (const void * a,const void * b, void *arg)
{
if (*(uint*)a < *(uint*)b)
return -1;
else if (*(uint*)a > *(uint*)b)
return 1;
else
return 0;
}
uint mask_from_bitcount(uint zct)
{
return ~((1<<zct)-1);
}
int main()
{
uint u1,u2,u3,u4,ip;
uint ipct=0,iplist_size=0,*iplist=NULL,*iplist_new;
uint pos=0,p;
uint i,zct,subnet_ct,end_ip;
while (!feof(stdin))
if (scanf("%u.%u.%u.%u",&u1,&u2,&u3,&u4)==4 && !(u1 & 0xFFFFFF00) && !(u2 & 0xFFFFFF00) && !(u3 & 0xFFFFFF00) && !(u4 & 0xFFFFFF00))
{
ip = u1<<24 | u2<<16 | u3<<8 | u4;
if (ipct>=iplist_size)
{
iplist_size += ALLOC_STEP;
iplist_new = (uint*)(iplist ? realloc(iplist,sizeof(*iplist)*iplist_size) : malloc(sizeof(*iplist)*iplist_size));
if (!iplist_new)
{
free(iplist);
fprintf(stderr,"out of memory\n");
return 100;
}
iplist = iplist_new;
}
iplist[ipct++]= ip;
}
gnu_quicksort(iplist,ipct,sizeof(*iplist),ucmp,NULL);
while(pos<ipct)
{
uchar subnet_ok=0;
uint mask,ip_start,ip_end,ip_ct,subnet_ct,pos_end;
for(zct=10, pos_end=pos+1 ; zct>=2 ; zct--)
{
mask = mask_from_bitcount(zct);
ip_start = iplist[pos] & mask;
subnet_ct = ~mask+1;
if (iplist[pos]>(ip_start+subnet_ct*PCTMULT)) continue;
ip_end = ip_start | ~mask;
for(p=pos, ip_ct=0 ; p<ipct && iplist[p]<=ip_end; p++) ip_ct++;
if (ip_ct>=(subnet_ct*PCTMULT))
{
subnet_ok=1;
pos_end = p;
break;
}
}
if (!subnet_ok) zct=0,ip_start=iplist[pos];
u1 = ip_start>>24;
u2 = (ip_start>>16) & 0xFF;
u3 = (ip_start>>8) & 0xFF;
u4 = ip_start & 0xFF;
if (zct)
printf("%u.%u.%u.%u/%u\n",u1,u2,u3,u4,32-zct);
else
printf("%u.%u.%u.%u\n",u1,u2,u3,u4);
pos = pos_end;
}
free(iplist);
return 0;
}