[英]In C#, I have a subnet bits and need to create a Subnet Mask. How might I do this?
[英]How do I found out if a Subnet mask is valid with C#
我需要了解如何確定提供的子網掩碼示例(255.255.192.0)是否是有效的子網掩碼,如果有效則返回 true,否則返回 false,我已經在檢查該值是否超過 255 . 錯誤的子網將是 (255.64.0.0)
它在二進制中很有意義(11111111.01000000.00000000.00000000)子網不能停止擁有1,然后再次開始擁有它們。 我目前的想法涉及使用 bitshift,但我不確定如何去做。
我沒有使用任何庫,並且不允許用於此項目
我正在使用的代碼類似於
Console.WriteLine("Enter a subnet mask");
input = Console.ReadLine(); //Enters example of 255.64.0.0 which is invalid
先謝謝了,有需要可以提問
你可以這樣試試:
using System;
using System.Runtime.InteropServices;
namespace Example
{
public class Program
{
[StructLayout(LayoutKind.Explicit)]
public struct byte_array
{
[FieldOffset(0)]
public byte byte0;
[FieldOffset(1)]
public byte byte1;
[FieldOffset(2)]
public byte byte2;
[FieldOffset(3)]
public byte byte3;
[FieldOffset(0)]
public UInt32 Addr;
}
public static void Main(string[] args)
{
byte_array b_array = new byte_array();
int i;
b_array.byte3 = 255;
b_array.byte2 = 64;
b_array.byte1 = 0;
b_array.byte0 = 0;
Console.WriteLine(String.Format("{0:X4}", b_array.Addr));
for(i = 31; i >= 0; i--)
if(((1 << i) & b_array.Addr) == 0)
break;
for(; i >= 0; i--)
if(((1 << i) & b_array.Addr) != 0)
{
Console.WriteLine("Bad Mask!");
break;
}
}
}
}
我尋找了一種庫方法,但找不到。 這是我只為 IPv4 地址編寫的方法;
public static bool IsValidMask(string mask)
{
// 1) convert the address to an int32
if (!IPAddress.TryParse(mask, out var addr))
return false;
var byteVal = addr.GetAddressBytes();
if (byteVal.Length != 4)
return false;
var intVal = BitConverter.ToInt32(byteVal);
intVal = IPAddress.NetworkToHostOrder(intVal);
// A valid mask should start with ones, and end with zeros 0b111...111000...000
// 2) XOR to flip all the bits (0b000...000111...111)
var uintVal = (uint)intVal ^ uint.MaxValue;
// 3) Add 1, causing all those 1's to become 0's. (0b000...001000...000)
// An invalid address will have leading 1's that are untouched by this step. (0b101...001000...000)
var addOne = uintVal + 1;
// 4) AND the two values together, to detect if any leading 1's remain
var ret = addOne & uintVal;
return ret == 0;
}
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.