我想出了这个来计算CIDR，但我很确定它不是最快的方式：
public int MaskToCIDR(IPAddress ip)
{
return Convert
.ToString(BitConverter.ToInt32(ip.GetAddressBytes(), 0), 2)
.ToCharArray()
.Count(x => x == '1');
}
测试：
Console.WriteLine(MaskToCIDR(new IPAddress(new byte[]{255,255,255,255}))); // 32
Console.WriteLine(MaskToCIDR(new IPAddress(new byte[]{255,255,255,0}))); // 24
Console.WriteLine(MaskToCIDR(new IPAddress(new byte[]{255,255,0,0}))); // 16
Console.WriteLine(MaskToCIDR(new IPAddress(new byte[]{255,0,0,0}))); // 8
Console.WriteLine(MaskToCIDR(new IPAddress(new byte[]{0,0,0,0}))); // 0
是否有更快的方式和IPv6如何？
答案 0 :(得分：2)
您的原始代码有误 - IP地址的GetHashCode()结果赢了（或者更确切地说，不应该）告诉您有关该IP地址的任何信息。
考虑到CIDR符号子网掩码只是从高端开始设置为1的位数，您可以使用位移运算符和二进制AND运算符来快速计算。
答案 1 :(得分：0)
根据您希望处理无效网络掩码的方式，您可以获得10x-100x的速度，请参阅 - c code for valid netmask和https://superuser.com/questions/601252/is-225-225-225-128-a-valid-subnet-mask。这是我的基准测试结果（您最初的建议是花哨的，我已经尝试了好奇心的恒定时间执行）。
长话短说：使用二进制，使用常量，展开循环。 Ultra 版本可能是最好的。对于无效的网络掩码，它返回最接近的包含valid netmask。
现在IPv6怎么样？我们可能过早地优化了...我希望没有人敢用IPv6的旧式网络掩码表示法。它应该被遗忘。
11111111.11111111.11111111.11111111 (255.255.255.255)
{ ns = 625,574, cidrnet = 32, method = MaskToCIDR_Fancy }
{ ns = 61,136, cidrnet = 32, method = MaskToCIDR_Fast }
{ ns = 72,039, cidrnet = 32, method = MaskToCIDR_Constant }
{ ns = 4,710, cidrnet = 32, method = MaskToCIDR_Ultra }
{ ns = 14,250, cidrnet = 32, method = MaskToCIDR_ConstantUltra }
{ ns = 8,683, cidrnet = 32, method = MaskToCIDR_Mambo }
{ ns = 7,337, cidrnet = 32, method = MaskToCIDR_PerByte }
{ ns = 37,883, cidrnet = 32, method = MaskToCIDR_BTree }
{ ns = 2,127, cidrnet = 0, method = MaskToCIDR_Empty }
11111111.11111111.11111111.00000000 (255.255.255.0)
{ ns = 486,026, cidrnet = 24, method = MaskToCIDR_Fancy }
{ ns = 47,369, cidrnet = 24, method = MaskToCIDR_Fast }
{ ns = 69,921, cidrnet = 24, method = MaskToCIDR_Constant }
{ ns = 4,835, cidrnet = 24, method = MaskToCIDR_Ultra }
{ ns = 14,079, cidrnet = 24, method = MaskToCIDR_ConstantUltra }
{ ns = 6,663, cidrnet = 24, method = MaskToCIDR_Mambo }
{ ns = 7,336, cidrnet = 24, method = MaskToCIDR_PerByte }
{ ns = 24,911, cidrnet = 24, method = MaskToCIDR_BTree }
{ ns = 2,116, cidrnet = 0, method = MaskToCIDR_Empty }
11111111.11111111.11111110.00000000 (255.255.254.0)
{ ns = 482,456, cidrnet = 23, method = MaskToCIDR_Fancy }
{ ns = 45,700, cidrnet = 23, method = MaskToCIDR_Fast }
{ ns = 68,930, cidrnet = 23, method = MaskToCIDR_Constant }
{ ns = 4,791, cidrnet = 23, method = MaskToCIDR_Ultra }
{ ns = 14,036, cidrnet = 23, method = MaskToCIDR_ConstantUltra }
{ ns = 6,951, cidrnet = 23, method = MaskToCIDR_Mambo }
{ ns = 7,377, cidrnet = 23, method = MaskToCIDR_PerByte }
{ ns = 36,027, cidrnet = 23, method = MaskToCIDR_BTree }
{ ns = 2,115, cidrnet = 0, method = MaskToCIDR_Empty }
11111111.11111111.00000000.00000000 (255.255.0.0)
{ ns = 347,425, cidrnet = 16, method = MaskToCIDR_Fancy }
{ ns = 34,460, cidrnet = 16, method = MaskToCIDR_Fast }
{ ns = 67,445, cidrnet = 16, method = MaskToCIDR_Constant }
{ ns = 4,942, cidrnet = 16, method = MaskToCIDR_Ultra }
{ ns = 15,363, cidrnet = 16, method = MaskToCIDR_ConstantUltra }
{ ns = 6,164, cidrnet = 16, method = MaskToCIDR_Mambo }
{ ns = 7,929, cidrnet = 16, method = MaskToCIDR_PerByte }
{ ns = 22,312, cidrnet = 16, method = MaskToCIDR_BTree }
{ ns = 2,116, cidrnet = 0, method = MaskToCIDR_Empty }
11111111.00000000.00000000.00000000 (255.0.0.0)
{ ns = 198,180, cidrnet = 8, method = MaskToCIDR_Fancy }
{ ns = 20,683, cidrnet = 8, method = MaskToCIDR_Fast }
{ ns = 64,785, cidrnet = 8, method = MaskToCIDR_Constant }
{ ns = 5,138, cidrnet = 8, method = MaskToCIDR_Ultra }
{ ns = 14,058, cidrnet = 8, method = MaskToCIDR_ConstantUltra }
{ ns = 6,734, cidrnet = 8, method = MaskToCIDR_Mambo }
{ ns = 8,572, cidrnet = 8, method = MaskToCIDR_PerByte }
{ ns = 37,483, cidrnet = 8, method = MaskToCIDR_BTree }
{ ns = 2,253, cidrnet = 0, method = MaskToCIDR_Empty }
10000000.00000000.00000000.00000000 (128.0.0.0)
{ ns = 198,620, cidrnet = 1, method = MaskToCIDR_Fancy }
{ ns = 7,855, cidrnet = 1, method = MaskToCIDR_Fast }
{ ns = 62,570, cidrnet = 1, method = MaskToCIDR_Constant }
{ ns = 6,317, cidrnet = 1, method = MaskToCIDR_Ultra }
{ ns = 14,145, cidrnet = 1, method = MaskToCIDR_ConstantUltra }
{ ns = 6,399, cidrnet = 1, method = MaskToCIDR_Mambo }
{ ns = 7,413, cidrnet = 1, method = MaskToCIDR_PerByte }
{ ns = 33,861, cidrnet = 1, method = MaskToCIDR_BTree }
{ ns = 2,117, cidrnet = 0, method = MaskToCIDR_Empty }
00000000.00000000.00000000.00000000 (0.0.0.0)
{ ns = 83,629, cidrnet = 0, method = MaskToCIDR_Fancy }
{ ns = 7,348, cidrnet = 0, method = MaskToCIDR_Fast }
{ ns = 63,320, cidrnet = 0, method = MaskToCIDR_Constant }
{ ns = 4,639, cidrnet = 0, method = MaskToCIDR_Ultra }
{ ns = 14,284, cidrnet = 0, method = MaskToCIDR_ConstantUltra }
{ ns = 5,438, cidrnet = 0, method = MaskToCIDR_Mambo }
{ ns = 6,767, cidrnet = 0, method = MaskToCIDR_PerByte }
{ ns = 37,961, cidrnet = 0, method = MaskToCIDR_BTree }
{ ns = 2,118, cidrnet = 0, method = MaskToCIDR_Empty }
01101111.01101111.01101111.00000000 (111.111.111.0)
{ ns = 465,689, cidrnet = 18, method = MaskToCIDR_Fancy }
{ ns = 4,242, cidrnet = -1, method = MaskToCIDR_Fast }
{ ns = 67,996, cidrnet = -1, method = MaskToCIDR_Constant }
{ ns = 5,133, cidrnet = 24, method = MaskToCIDR_Ultra }
{ ns = 14,542, cidrnet = 18, method = MaskToCIDR_ConstantUltra }
{ ns = 6,285, cidrnet = -1, method = MaskToCIDR_Mambo }
{ ns = 7,879, cidrnet = -21, method = MaskToCIDR_PerByte }
{ ns = 40,017, cidrnet = -2, method = MaskToCIDR_BTree }
{ ns = 2,115, cidrnet = 0, method = MaskToCIDR_Empty }
00000001.00000001.00000001.00000000 (1.1.1.0)
{ ns = 368,824, cidrnet = 3, method = MaskToCIDR_Fancy }
{ ns = 4,227, cidrnet = -1, method = MaskToCIDR_Fast }
{ ns = 67,043, cidrnet = -1, method = MaskToCIDR_Constant }
{ ns = 4,920, cidrnet = 24, method = MaskToCIDR_Ultra }
{ ns = 13,979, cidrnet = 3, method = MaskToCIDR_ConstantUltra }
{ ns = 6,134, cidrnet = -1, method = MaskToCIDR_Mambo }
{ ns = 7,611, cidrnet = -24, method = MaskToCIDR_PerByte }
{ ns = 39,957, cidrnet = -2, method = MaskToCIDR_BTree }
{ ns = 2,115, cidrnet = 0, method = MaskToCIDR_Empty }
测试代码：
public class CalculateCIDRProgram
{
private static uint[] dic = Enumerable.Range(0, 33).Select(i => i == 0 ? 0 : (uint)(~(1 << (32 - i)) + 1)).ToArray();
private static Stopwatch __watch;
public static void Main()
{
for (int i = 0; i < 33; i++)
{
byte[] intBytes = BitConverter.GetBytes(dic[i]);
if (BitConverter.IsLittleEndian)
Array.Reverse(intBytes);
Console.WriteLine($"{i}: {FormatBytes(intBytes)}");
}
__watch = Stopwatch.StartNew();
Test(IPAddress.Parse("255.255.255.255"));
Test(IPAddress.Parse("255.255.255.0"));
Test(IPAddress.Parse("255.255.254.0"));
Test(IPAddress.Parse("255.255.0.0"));
Test(IPAddress.Parse("255.0.0.0"));
Test(IPAddress.Parse("128.0.0.0"));
Test(IPAddress.Parse("0.0.0.0"));
Test(IPAddress.Parse("1.1.1.0"));
Test(IPAddress.Parse("111.111.111.0"));
}
private static void Test(IPAddress ip)
{
WriteHeader(ip);
var ipbytes = ip.GetAddressBytes();
var loops = 1000000;
//var loops = 1;
var cidrnet = null as int?;
var results = new List<object>();
__watch.Restart();
for (int i = 0; i < loops; i++)
cidrnet = MaskToCIDR_Fancy(ipbytes);
results.Add(new { ns = (1000000 * __watch.Elapsed.TotalMilliseconds / loops).ToString("0.000").PadLeft(10, ' '), cidrnet, method = nameof(MaskToCIDR_Fancy) });
__watch.Restart();
for (int i = 0; i < loops; i++)
cidrnet = MaskToCIDR_Fast(ipbytes);
results.Add(new { ns = (1000000 * __watch.Elapsed.TotalMilliseconds / loops).ToString("0.000").PadLeft(10, ' '), cidrnet, method = nameof(MaskToCIDR_Fast) });
fakeBool = true;
fakeInt = new Random().Next(33);
__watch.Restart();
for (int i = 0; i < loops; i++)
cidrnet = MaskToCIDR_Constant(ipbytes);
results.Add(new { ns = (1000000 * __watch.Elapsed.TotalMilliseconds / loops).ToString("0.000").PadLeft(10, ' '), cidrnet, method = nameof(MaskToCIDR_Constant) });
__watch.Restart();
for (int i = 0; i < loops; i++)
cidrnet = MaskToCIDR_Ultra(ipbytes);
results.Add(new { ns = (1000000 * __watch.Elapsed.TotalMilliseconds / loops).ToString("0.000").PadLeft(10, ' '), cidrnet, method = nameof(MaskToCIDR_Ultra) });
__watch.Restart();
for (int i = 0; i < loops; i++)
cidrnet = MaskToCIDR_ConstantUltra(ipbytes);
results.Add(new { ns = (1000000 * __watch.Elapsed.TotalMilliseconds / loops).ToString("0.000").PadLeft(10, ' '), cidrnet, method = nameof(MaskToCIDR_ConstantUltra) });
__watch.Restart();
for (int i = 0; i < loops; i++)
cidrnet = MaskToCIDR_Mambo(ipbytes);
results.Add(new { ns = (1000000 * __watch.Elapsed.TotalMilliseconds / loops).ToString("0.000").PadLeft(10, ' '), cidrnet, method = nameof(MaskToCIDR_Mambo) });
__watch.Restart();
for (int i = 0; i < loops; i++)
cidrnet = MaskToCIDR_PerByte(ipbytes);
results.Add(new { ns = (1000000 * __watch.Elapsed.TotalMilliseconds / loops).ToString("0.000").PadLeft(10, ' '), cidrnet, method = nameof(MaskToCIDR_PerByte) });
__watch.Restart();
for (int i = 0; i < loops; i++)
cidrnet = MaskToCIDR_BTree(ipbytes);
results.Add(new { ns = (1000000 * __watch.Elapsed.TotalMilliseconds / loops).ToString("0.000").PadLeft(10, ' '), cidrnet, method = nameof(MaskToCIDR_BTree) });
__watch.Restart();
for (int i = 0; i < loops; i++)
cidrnet = MaskToCIDR_Empty(ipbytes);
results.Add(new { ns = (1000000 * __watch.Elapsed.TotalMilliseconds / loops).ToString("0.000").PadLeft(10, ' '), cidrnet, method = nameof(MaskToCIDR_Empty) });
foreach (var result in results)
{
Console.WriteLine(result);
}
Console.WriteLine();
}
private static int fakeInt;
private static bool fakeBool;
private static int MaskToCIDR_Empty(byte[] bytes)
{
return 0;
}
private static int MaskToCIDR_BTree(byte[] bytes)
{
var addr = (uint)((bytes[0] << 24) | (bytes[1] << 16) | (bytes[2] << 8) | bytes[3]);
return Array.BinarySearch(dic, addr);
}
private static int MaskToCIDR_PerByte(byte[] bytes)
{
int b0 = bytes[0];
int b1 = bytes[1];
int b2 = bytes[2];
int b3 = bytes[3];
switch (b3)
{
case 0x00: break;
case 0xFF: return 32;
case 0xFE: return 31;
case 0xFC: return 30;
case 0xF8: return 29;
case 0xF0: return 28;
case 0xE0: return 27;
case 0xC0: return 26;
case 0x80: return 25;
default:
return ~(
(b3 & 0x01) == 0 ? 32 :
(b3 & 0x02) == 0 ? 31 :
(b3 & 0x04) == 0 ? 30 :
(b3 & 0x08) == 0 ? 29 :
(b3 & 0x10) == 0 ? 28 :
(b3 & 0x20) == 0 ? 27 :
(b3 & 0x40) == 0 ? 26 :
25
);
}
switch (b2)
{
case 0x00: break;
case 0xFF: return 24;
case 0xFE: return 23;
case 0xFC: return 22;
case 0xF8: return 21;
case 0xF0: return 20;
case 0xE0: return 19;
case 0xC0: return 18;
case 0x80: return 17;
default:
return ~(
(b2 & 0x01) == 0 ? 24 :
(b2 & 0x02) == 0 ? 23 :
(b2 & 0x04) == 0 ? 22 :
(b2 & 0x08) == 0 ? 21 :
(b2 & 0x10) == 0 ? 20 :
(b2 & 0x20) == 0 ? 19 :
(b2 & 0x40) == 0 ? 18 :
17
);
}
switch (b1)
{
case 0x00: break;
case 0xFF: return 16;
case 0xFE: return 15;
case 0xFC: return 14;
case 0xF8: return 13;
case 0xF0: return 12;
case 0xE0: return 11;
case 0xC0: return 10;
case 0x80: return 9;
default:
return ~(
(b1 & 0x01) == 0 ? 16 :
(b1 & 0x02) == 0 ? 15 :
(b1 & 0x04) == 0 ? 14 :
(b1 & 0x08) == 0 ? 13 :
(b1 & 0x10) == 0 ? 12 :
(b1 & 0x20) == 0 ? 11 :
(b1 & 0x40) == 0 ? 10 :
9
);
}
switch (b0)
{
case 0x00: break;
case 0xFF: return 8;
case 0xFE: return 7;
case 0xFC: return 6;
case 0xF8: return 5;
case 0xF0: return 4;
case 0xE0: return 3;
case 0xC0: return 2;
case 0x80: return 1;
default:
return ~(
(b0 & 0x01) == 0 ? 8 :
(b0 & 0x02) == 0 ? 7 :
(b0 & 0x04) == 0 ? 6 :
(b0 & 0x08) == 0 ? 5 :
(b0 & 0x10) == 0 ? 4 :
(b0 & 0x20) == 0 ? 3 :
(b0 & 0x40) == 0 ? 2 :
1
);
}
return 0;
}
private static int MaskToCIDR_Mambo(byte[] bytes)
{
var addr = (uint)((bytes[0] << 24) | (bytes[1] << 16) | (bytes[2] << 8) | bytes[3]);
switch (addr)
{
case 0xFFFFFFFF: return 32;
case 0xFFFFFFFE: return 31;
case 0xFFFFFFFC: return 30;
case 0xFFFFFFF8: return 29;
case 0xFFFFFFF0: return 28;
case 0xFFFFFFE0: return 27;
case 0xFFFFFFC0: return 26;
case 0xFFFFFF80: return 25;
case 0xFFFFFF00: return 24;
case 0xFFFFFE00: return 23;
case 0xFFFFFC00: return 22;
case 0xFFFFF800: return 21;
case 0xFFFFF000: return 20;
case 0xFFFFE000: return 19;
case 0xFFFFC000: return 18;
case 0xFFFF8000: return 17;
case 0xFFFF0000: return 16;
case 0xFFFE0000: return 15;
case 0xFFFC0000: return 14;
case 0xFFF80000: return 13;
case 0xFFF00000: return 12;
case 0xFFE00000: return 11;
case 0xFFC00000: return 10;
case 0xFF800000: return 9;
case 0xFF000000: return 8;
case 0xFE000000: return 7;
case 0xFC000000: return 6;
case 0xF8000000: return 5;
case 0xF0000000: return 4;
case 0xE0000000: return 3;
case 0xC0000000: return 2;
case 0x80000000: return 1;
case 0x00000000: return 0;
default:
return ~(
(addr & 0x80000000) == 0 ? 0 :
(addr & 0x40000000) == 0 ? 1 :
(addr & 0x20000000) == 0 ? 2 :
(addr & 0x10000000) == 0 ? 3 :
(addr & 0x08000000) == 0 ? 4 :
(addr & 0x04000000) == 0 ? 5 :
(addr & 0x02000000) == 0 ? 6 :
(addr & 0x01000000) == 0 ? 7 :
(addr & 0x00800000) == 0 ? 8 :
(addr & 0x00400000) == 0 ? 9 :
(addr & 0x00200000) == 0 ? 10 :
(addr & 0x00100000) == 0 ? 11 :
(addr & 0x00080000) == 0 ? 12 :
(addr & 0x00040000) == 0 ? 13 :
(addr & 0x00020000) == 0 ? 14 :
(addr & 0x00010000) == 0 ? 15 :
(addr & 0x00008000) == 0 ? 16 :
(addr & 0x00004000) == 0 ? 17 :
(addr & 0x00002000) == 0 ? 18 :
(addr & 0x00001000) == 0 ? 19 :
(addr & 0x00000800) == 0 ? 20 :
(addr & 0x00000400) == 0 ? 21 :
(addr & 0x00000200) == 0 ? 22 :
(addr & 0x00000100) == 0 ? 23 :
(addr & 0x00000080) == 0 ? 24 :
(addr & 0x00000040) == 0 ? 25 :
(addr & 0x00000020) == 0 ? 26 :
(addr & 0x00000010) == 0 ? 27 :
(addr & 0x00000008) == 0 ? 28 :
(addr & 0x00000004) == 0 ? 29 :
(addr & 0x00000002) == 0 ? 30 :
(addr & 0x00000001) == 0 ? 31 :
32);
}
}
private static int MaskToCIDR_ConstantUltra(byte[] bytes)
{
var b0 = bytes[0];
var b1 = bytes[1];
var b2 = bytes[2];
var b3 = bytes[3];
var result =
((b0 & 0x80) >> 7) +
((b0 & 0x40) >> 6) +
((b0 & 0x20) >> 5) +
((b0 & 0x10) >> 4) +
((b0 & 0x08) >> 3) +
((b0 & 0x04) >> 2) +
((b0 & 0x02) >> 1) +
(b0 & 0x01) +
((b1 & 0x80) >> 7) +
((b1 & 0x40) >> 6) +
((b1 & 0x20) >> 5) +
((b1 & 0x10) >> 4) +
((b1 & 0x08) >> 3) +
((b1 & 0x04) >> 2) +
((b1 & 0x02) >> 1) +
(b1 & 0x01) +
((b2 & 0x80) >> 7) +
((b2 & 0x40) >> 6) +
((b2 & 0x20) >> 5) +
((b2 & 0x10) >> 4) +
((b2 & 0x08) >> 3) +
((b2 & 0x04) >> 2) +
((b2 & 0x02) >> 1) +
(b2 & 0x01) +
((b3 & 0x80) >> 7) +
((b3 & 0x40) >> 6) +
((b3 & 0x20) >> 5) +
((b3 & 0x10) >> 4) +
((b3 & 0x08) >> 3) +
((b3 & 0x04) >> 2) +
((b3 & 0x02) >> 1) +
(b3 & 0x01)
;
return result;
}
private static int MaskToCIDR_Ultra(byte[] bytes)
{
var b0 = bytes[0];
var b1 = bytes[1];
var b2 = bytes[2];
var b3 = bytes[3];
return
b3 != 0 ? (
(b3 & 0x01) != 0 ? 32 :
(b3 & 0x02) != 0 ? 31 :
(b3 & 0x04) != 0 ? 30 :
(b3 & 0x08) != 0 ? 29 :
(b3 & 0x10) != 0 ? 28 :
(b3 & 0x20) != 0 ? 27 :
(b3 & 0x40) != 0 ? 26 :
25) :
b2 != 0 ? (
(b2 & 0x01) != 0 ? 24 :
(b2 & 0x02) != 0 ? 23 :
(b2 & 0x04) != 0 ? 22 :
(b2 & 0x08) != 0 ? 21 :
(b2 & 0x10) != 0 ? 20 :
(b2 & 0x20) != 0 ? 19 :
(b2 & 0x40) != 0 ? 18 :
17) :
b1 != 0 ? (
(b1 & 0x01) != 0 ? 16 :
(b1 & 0x02) != 0 ? 15 :
(b1 & 0x04) != 0 ? 14 :
(b1 & 0x08) != 0 ? 13 :
(b1 & 0x10) != 0 ? 12 :
(b1 & 0x20) != 0 ? 11 :
(b1 & 0x40) != 0 ? 10 :
9) :
b0 != 0 ? (
(b0 & 0x01) != 0 ? 8 :
(b0 & 0x02) != 0 ? 7 :
(b0 & 0x04) != 0 ? 6 :
(b0 & 0x08) != 0 ? 5 :
(b0 & 0x10) != 0 ? 4 :
(b0 & 0x20) != 0 ? 3 :
(b0 & 0x40) != 0 ? 2 :
1) :
0;
}
private static int MaskToCIDR_Constant(byte[] bytes)
{
int cidrnet = 0;
var done = false;
var invalid = false;
for (var i = 0; i < bytes.Length; i++)
{
for (int v = bytes[i], j = 0; j < 8; v = v << 1, j++)
{
if ((v & 0x80) == 0)
{
fakeBool = done;
done = true;
if (fakeBool)
fakeInt++;
else
fakeInt++;
}
else
{
invalid = done;
fakeBool = true;
if (done)
fakeInt++;
else
cidrnet++;
}
}
}
if (invalid)
cidrnet = ~cidrnet;
else
fakeInt = ~fakeInt;
return cidrnet;
}
private static int MaskToCIDR_Fast(byte[] bytes)
{
int cidrnet = 0;
var zeroed = false;
for (var i = 0; i < bytes.Length; i++)
{
for (int v = bytes[i]; (v & 0xFF) != 0; v = v << 1)
{
if (zeroed)
// invalid netmask
return ~cidrnet;
if ((v & 0x80) == 0)
zeroed = true;
else
cidrnet++;
}
}
return cidrnet;
}
private static int MaskToCIDR_Fancy(byte[] bytes)
{
return Convert
.ToString(BitConverter.ToInt32(bytes, 0), 2)
.ToCharArray()
.Count(x => x == '1');
}
private static void WriteHeader(IPAddress ip)
{
var binIp = FormatBytes(ip.GetAddressBytes());
Console.WriteLine($"{binIp} ({ip})");
}
private static string FormatBytes(byte[] bytes)
{
return string.Join(".", bytes.Select(b => Convert.ToString(b, 2).PadLeft(8, '0')));
}
}
答案 2 :(得分：0)
非常简单：
int cidr = Convert.ToString(mask.Address, 2).Count( o => o == '1');
“。地址”已弃用，但仍受支持。
基于255.255.255.240的解释：
IPAddress mask = new IPAddress(new byte[] { 255, 255, 244, 240 });
// adressBinAsString = 11110000111101001111111111111111
string maskBinAsString = Convert.ToString(mask.Address, 2);
// cidr = 28
int cidr = Convert.ToString(mask.Address, 2).Count( o=> o == '1'); //