IP to Integer

有时候我们要判断某个IP是否在某个段内，如何实现呢？ 一个简单办法就是把IP转换成Integer，然后判断整数是否在某个范围内就可以实现这个判断。

转换的算法如下：

比如我们要转换的IP为： 058.062.042.000

First Octet: 058
Second Octet: 062
Third Octet: 042
Fourth Octet: 000

计算公式如下：
(first octet * 256³) + (second octet * 256²) + (third octet * 256) + (fourth octet)
= (first octet * 16777216) + (second octet * 65536) + (third octet * 256) + (fourth octet)
= (058 * 16777216) + (062 * 65536) + (042 * 256) + (000)
= 977152512

网上有现成的服务，比如下面这个地址：

http://www.aboutmyip.com/AboutMyXApp/IP2Integer.jsp

SQL Server 的一个例子如下：

CREATE FUNCTION dbo.ipStringToInt 
( 
    @ip CHAR(15) 
) 
RETURNS INT 
AS 
BEGIN 
    DECLARE @rv INT, 
        @o1 INT, 
        @o2 INT, 
        @o3 INT, 
        @o4 INT, 
        @base INT 
 
    SELECT 
        @o1 = CONVERT(INT, PARSENAME(@ip, 4)), 
        @o2 = CONVERT(INT, PARSENAME(@ip, 3)), 
        @o3 = CONVERT(INT, PARSENAME(@ip, 2)), 
        @o4 = CONVERT(INT, PARSENAME(@ip, 1)) 
 
    IF (@o1 BETWEEN 0 AND 255) 
        AND (@o2 BETWEEN 0 AND 255) 
        AND (@o3 BETWEEN 0 AND 255) 
        AND (@o4 BETWEEN 0 AND 255) 
    BEGIN      
        SELECT @base = CASE 
            WHEN @o1 THEN 
                (@o1 * 16777216) 
            ELSE 
                -(256 - @o1) * 16777216 
            END 
     
        SET @rv = @base +  
            (@o2 * 65536) +  
            (@o3 * 256) + 
            (@o4) 
    END 
    ELSE 
        SET @rv = -1 
    RETURN @rv 
END
go

调用范例：

select dbo.ipStringToInt('058.062.042.000')

整数转换如下：

CREATE FUNCTION dbo.ipIntToString 
( 
    @ip INT 
) 
RETURNS CHAR(15) 
AS 
BEGIN 
    DECLARE @o1 INT, 
        @o2 INT, 
        @o3 INT, 
        @o4 INT 
 
    IF ABS(@ip) > 2147483647 
        RETURN '255.255.255.255' 
 
    SET @o1 = @ip / 16777216 
 
    IF @o1 = 0 
        SELECT @o1 = 255, @ip = @ip + 16777216 
 
    ELSE IF @o1 BEGIN 
        IF @ip % 16777216 = 0 
            SET @o1 = @o1 + 256 
        ELSE 
        BEGIN 
            SET @o1 = @o1 + 255 
            IF @o1 = 128 
                SET @ip = @ip + 2147483648 
            ELSE 
                SET @ip = @ip + (16777216 * (256 - @o1)) 
        END 
    END 
    ELSE 
    BEGIN 
        SET @ip = @ip - (16777216 * @o1) 
    END 
 
    SET @ip = @ip % 16777216 
    SET @o2 = @ip / 65536 
    SET @ip = @ip % 65536 
    SET @o3 = @ip / 256 
    SET @ip = @ip % 256 
    SET @o4 = @ip 
 
    RETURN 
        CONVERT(VARCHAR(4), @o1) + '.' + 
        CONVERT(VARCHAR(4), @o2) + '.' + 
        CONVERT(VARCHAR(4), @o3) + '.' + 
        CONVERT(VARCHAR(4), @o4) 
END
go

调用范例：

select dbo.ipIntToString(977152512)

C# 的例子如下：

using System;
using System.Net;

namespace ConsoleApplication1
{
    class Program
    {
        static long ToInt(string addr)
        {
            return BitConverter.ToInt32(IPAddress.Parse(addr).GetAddressBytes(), 0); 
        }

        static string ToAddr(long address)
        {
            return IPAddress.Parse(address.ToString()).ToString();
            // This also works: 
            // return new IPAddress((uint) IPAddress.HostToNetworkOrder( 
            //    (int) address)).ToString(); 
        }

        static void Main(string[] args)
        {
            Console.WriteLine(ToInt("64.233.187.99"));
            Console.WriteLine(ToAddr(1089059683)); 

            Console.ReadLine();
        }
    }
}

参考资料：

How should I store an IP address in SQL Server?
http://sqlserver2000.databases.aspfaq.com/how-should-i-store-an-ip-address-in-sql-server.html

How to convert an IPv4 address into a integer in C#?
http://stackoverflow.com/questions/461742/how-to-convert-an-ipv4-address-into-a-integer-in-c