IP段转CIDR
经常使用nginx、apache时候需要对某个ip段进行白名单或黑名单控制，而它的配置是以CIDR的方式进行的，所以此工具可以方便的做到从IP段到CIDR的转换。1
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71import java.util.ArrayList;
import java.util.List;
public class Ip2Cidr {
public static void main(String[] args) {
System.out.println(range2cidrlist("10.104.0.12","10.104.0.35"));
}
public static List<String> range2cidrlist(String startIp, String endIp) {
long start = ipToLong(startIp);
long end = ipToLong(endIp);
ArrayList<String> pairs = new ArrayList<String>();
while (end >= start) {
byte maxsize = 32;
while (maxsize > 0) {
long mask = CIDR2MASK[maxsize - 1];
long maskedBase = start & mask;
if (maskedBase != start) {
break;
}
maxsize--;
}
double x = Math.log(end - start + 1) / Math.log(2);
byte maxdiff = (byte) (32 - Math.floor(x));
if (maxsize < maxdiff) {
maxsize = maxdiff;
}
String ip = longToIP(start);
pairs.add(ip + "/" + maxsize);
start += Math.pow(2, (32 - maxsize));
}
return pairs;
}
public static final int[] CIDR2MASK = new int[] { 0x00000000, 0x80000000,
0xC0000000, 0xE0000000, 0xF0000000, 0xF8000000, 0xFC000000,
0xFE000000, 0xFF000000, 0xFF800000, 0xFFC00000, 0xFFE00000,
0xFFF00000, 0xFFF80000, 0xFFFC0000, 0xFFFE0000, 0xFFFF0000,
0xFFFF8000, 0xFFFFC000, 0xFFFFE000, 0xFFFFF000, 0xFFFFF800,
0xFFFFFC00, 0xFFFFFE00, 0xFFFFFF00, 0xFFFFFF80, 0xFFFFFFC0,
0xFFFFFFE0, 0xFFFFFFF0, 0xFFFFFFF8, 0xFFFFFFFC, 0xFFFFFFFE,
0xFFFFFFFF };
private static long ipToLong(String strIP) {
long[] ip = new long[4];
String[] ipSec = strIP.split("\\.");
for (int k = 0; k < 4; k++) {
ip[k] = Long.valueOf(ipSec[k]);
}
return (ip[0] << 24) + (ip[1] << 16) + (ip[2] << 8) + ip[3];
}
private static String longToIP(long longIP) {
StringBuffer sb = new StringBuffer("");
sb.append(String.valueOf(longIP >>> 24));
sb.append(".");
sb.append(String.valueOf((longIP & 0x00FFFFFF) >>> 16));
sb.append(".");
sb.append(String.valueOf((longIP & 0x0000FFFF) >>> 8));
sb.append(".");
sb.append(String.valueOf(longIP & 0x000000FF));
return sb.toString();
}
}
