在Java中，给定IP地址范围，返回覆盖范围的最小CIDR块列表 [英] In Java, given an IP Address range, return the minimum list of CIDR blocks that covers the range

问题描述

我在将IP地址范围转换为CIDR块列表时遇到了一些问题。我相信这个网站做得很好： http://ip2cidr.com/

I am having trouble with some of the logic in converting an IP Address range into a list of CIDR blocks. I do believe that this website is doing it right: http://ip2cidr.com/

我想传入一个起始IP地址和一个结束IP地址，并让java吐出所需的最小CIDR块列表，仅覆盖传入的范围，仅此而已。

I would like to pass in a starting IP address and an ending IP address and have the java spit out the minimum list of CIDR blocks required to cover only the range passed in and nothing more.

例如，如果我传入1.1.1.111的起始地址和1.1.1.120的结束地址，我希望得到回报：
1.1.1.111 / 32
1.1.1.112/29
1.1.1.120/32

For instance, if I pass in a start address of 1.1.1.111 and an end address of 1.1.1.120, I would expect to get in return: 1.1.1.111/32 1.1.1.112/29 1.1.1.120/32

（/ 32表示单个地址。）

(with the /32 indicating a single address.)

推荐答案

我的上一个答案有一些错误，当IP地址的第一个八位字节太大时就会出现这些错误。这个更好用。几乎完全取自这里： http://facedroid.blogspot.com /2010/06/ip-range-to-cidr.html

My last answer had some bugs in it that came about when the first octet of the IP address was too big. This one works better. Lifted almost entirely from here: http://facedroid.blogspot.com/2010/06/ip-range-to-cidr.html

import java.util.ArrayList;
import java.util.List;

public class RangeToCidr {
    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();     
    } 
}

这篇关于在Java中，给定IP地址范围，返回覆盖范围的最小CIDR块列表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！