IP.java

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.Arrays;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;

class IP {

    public static void main(String[] args){
        IP.load("H:\\loveapp\\codebase\\17mon\\17monipdb.dat");

        System.out.println(Arrays.toString(IP.find("8.8.8.8")));
        System.out.println(Arrays.toString(IP.find("255.255.255.255")));
    }

    public static boolean enableFileWatch = false;

    private static int offset;
    private static int[] index = new int[256];
    private static ByteBuffer dataBuffer;
    private static ByteBuffer indexBuffer;
    private static Long lastModifyTime = 0L;
    private static File ipFile ;
    private static ReentrantLock lock = new ReentrantLock();

    public static void load(String filename) {
        ipFile = new File(filename);
        load();
        if (enableFileWatch) {
            watch();
        }
    }

    public static String[] find(String ip) {
        int ip_prefix_value = new Integer(ip.substring(0, ip.indexOf(".")));
        long ip2long_value  = ip2long(ip);
        int start = index[ip_prefix_value];
        int max_comp_len = offset - 1028;
        long index_offset = -1;
        int index_length = -1;
        byte b = 0;
        for (start = start * 8 + 1024; start < max_comp_len; start += 8) {
            if (int2long(indexBuffer.getInt(start)) >= ip2long_value) {
                index_offset = bytesToLong(b, indexBuffer.get(start + 6), indexBuffer.get(start + 5), indexBuffer.get(start + 4));
                index_length = 0xFF & indexBuffer.get(start + 7);
                break;
            }
        }

        byte[] areaBytes;
        lock.lock();
        try {
            dataBuffer.position(offset + (int) index_offset - 1024);
            areaBytes = new byte[index_length];
            dataBuffer.get(areaBytes, 0, index_length);
        } finally {
            lock.unlock();
        }

        return new String(areaBytes).split("\t");
    }

    private static void watch() {
        Executors.newScheduledThreadPool(1).scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                long time = ipFile.lastModified();
                if (time > lastModifyTime) {
                    lastModifyTime = time;
                    load();
                }
            }
        }, 1000L, 5000L, TimeUnit.MILLISECONDS);
    }

    private static void load() {
        lastModifyTime = ipFile.lastModified();
        FileInputStream fin = null;
        lock.lock();
        try {
            dataBuffer = ByteBuffer.allocate(Long.valueOf(ipFile.length()).intValue());
            fin = new FileInputStream(ipFile);
            int readBytesLength;
            byte[] chunk = new byte[4096];
            while (fin.available() > 0) {
                readBytesLength = fin.read(chunk);
                dataBuffer.put(chunk, 0, readBytesLength);
            }
            dataBuffer.position(0);
            int indexLength = dataBuffer.getInt();
            byte[] indexBytes = new byte[indexLength];
            dataBuffer.get(indexBytes, 0, indexLength - 4);
            indexBuffer = ByteBuffer.wrap(indexBytes);
            indexBuffer.order(ByteOrder.LITTLE_ENDIAN);
            offset = indexLength;

            int loop = 0;
            while (loop++ < 256) {
                index[loop - 1] = indexBuffer.getInt();
            }
            indexBuffer.order(ByteOrder.BIG_ENDIAN);
        } catch (IOException ioe) {

        } finally {
            try {
                if (fin != null) {
                    fin.close();
                }
            } catch (IOException e){}
            lock.unlock();
        }
    }

    private static long bytesToLong(byte a, byte b, byte c, byte d) {
        return int2long((((a & 0xff) << 24) | ((b & 0xff) << 16) | ((c & 0xff) << 8) | (d & 0xff)));
    }

    private static int str2Ip(String ip)  {
        String[] ss = ip.split("\\.");
        int a, b, c, d;
        a = Integer.parseInt(ss[0]);
        b = Integer.parseInt(ss[1]);
        c = Integer.parseInt(ss[2]);
        d = Integer.parseInt(ss[3]);
        return (a << 24) | (b << 16) | (c << 8) | d;
    }

    private static long ip2long(String ip)  {
        return int2long(str2Ip(ip));
    }

    private static long int2long(int i) {
        long l = i & 0x7fffffffL;
        if (i < 0) {
            l |= 0x080000000L;
        }
        return l;
    }
}