Does C# support struct bit definitions?

shine pb

13y11.8kVisual Basic .NET

Does C# support struct bit definitions?.

For example is there a way to declare a structure like this in c#.net?

typedef struct

{

UINT16 SrcPort;

UINT16 DstPort;

UINT32 SeqNum;

UINT32 AckNum;

UINT16 Reserved1:4;

UINT16 HdrLength:4;

UINT16 Fin:1;

UINT16 Syn:1;

UINT16 Rst:1;

UINT16 Psh:1;

UINT16 Ack:1;

UINT16 Urg:1;

UINT16 Reserved2:2;

UINT16 Window;

UINT16 Checksum;

UINT16 UrgPtr;

} DIVERT_TCPHDR

Please help me to solve this issue? It is very urgent.

How can we set bit position in a C# Structure ?

5 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes13y ago
Try this:

using System;
using System.Runtime.InteropServices;

[StructLayout(LayoutKind.Sequential)]
public struct DIVERT_TCPHDR
{
public ushort SrcPort;
public ushort DstPort;
public uint SeqNum;
public uint AckNum;
public ushort BitField;
public ushort Window;
public ushort Checksum;
public ushort UrgPtr;

public byte Reserved1
{
get {return (byte)((BitField >> 12) & 15);}
set {BitField = (ushort)(BitField & ~(15 << 12) | (value << 12));}
}

public byte HdrLength
{
get {return (byte)((BitField >> 8) & 15);}
set {BitField = (ushort)(BitField & ~(15 << 8) | (value << 8));}
}

public byte Fin
{
get {return (byte)((BitField >> 7) & 1);}
set {BitField = (ushort)(BitField & ~(1 << 7) | (value << 7));}
}

public byte Syn
{
get {return (byte)((BitField >> 6) & 1);}
set {BitField = (ushort)(BitField & ~(1 << 6) | (value << 6));}
}

public byte Rst
{
get {return (byte)((BitField >> 5) & 1);}
set {BitField = (ushort)(BitField & ~(1 << 5) | (value << 5));}
}

public byte Psh
{
get {return (byte)((BitField >> 4) & 1);}
set {BitField = (ushort)(BitField & ~(1 << 4) | (value << 4));}
}

public byte Ack
{
get {return (byte)((BitField >> 3) & 1);}
set {BitField = (ushort)(BitField & ~(1 << 3) | (value << 3));}
}

public byte Urg
{
get {return (byte)((BitField >> 2) & 1);}
set {BitField = (ushort)(BitField & ~(1 << 2) | (value << 2));}
}

public byte Reserved2
{
get {return (byte)(BitField & 3);}
set {BitField = (ushort)((BitField & ~3) | value);}
}

}

class Test
{
static void Main()
{
DIVERT_TCPHDR hdr = new DIVERT_TCPHDR();
hdr.BitField = 0x0F94; // 00001111 10010100
PrintBitFields(hdr);
// make some changes
hdr.HdrLength = 12;
hdr.Fin = 0;
hdr.Syn = 1;
hdr.Rst = 1;
hdr.Psh = 0;
hdr.Ack = 1;
hdr.Urg = 0;
Console.WriteLine("\nAfter changes values are now\n");
PrintBitFields(hdr);
Console.ReadKey();
}

static void PrintBitFields(DIVERT_TCPHDR hdr)
{
Console.WriteLine("HdrLength = {0}", hdr.HdrLength);
Console.WriteLine("Fin = {0}", hdr.Fin);
Console.WriteLine("Syn = {0}", hdr.Syn);
Console.WriteLine("Rst = {0}", hdr.Rst);
Console.WriteLine("Psh = {0}", hdr.Psh);
Console.WriteLine("Ack = {0}", hdr.Ack);
Console.WriteLine("Urg = {0}", hdr.Urg);
}
}

The output should be:

HdrLength = 15
Fin = 1
Syn = 0
Rst = 0
Psh = 1
Ack = 0
Urg = 1

After changes values are now

HdrLength = 12
Fin = 0
Syn = 1
Rst = 1
Psh = 0
Ack = 1
Urg = 0
shine pb13y ago
I think bit positions are not possible in c# structure. It is possible in c++. My question is how we can set bit position in c# structure.Is there any ways to do it in C#?
For Example:
typedef struct
{
UINT16 SrcPort:16;
UINT16 DstPort:16;
UINT32 SeqNum:32;
UINT32 AckNum:16;
UINT16 Reserved1:4;
UINT16 HdrLength:4;
}IP_HDR

How can we create a structure like this in c# with bit positions?
Jignesh Trivedi13y ago
hi,
your question is not too much clear.
you want to set array length from out side is it correct?
you may take help from contructor.
public struct myTest
{
   public int[] b
   // Constructor:
   public myTest(int length)
   {
      b = new int[length];
   }
}
hope this will help you.
Abhishek Jain13y ago
Try something like this:

[global::System.AttributeUsage(AttributeTargets.Field, AllowMultiple = false)]
sealed class BitFieldLengthAttribute : Attribute
{
uint length;

public BitFieldLengthAttribute(uint length)
{
this.length = length;
}

public uint Length { get { return length; } }
}

struct DIVERT_TCPHDR
{
UInt16 SrcPort;
UInt16 DstPort;
UInt32 SeqNum;
UInt32 AckNum;
[BitFieldLength(4)]
UInt16 Reserved1;
[BitFieldLength(4)]
UInt16 HdrLength;
[BitFieldLength(1)]
UInt16 Fin;
[BitFieldLength(1)]
UInt16 Syn;
[BitFieldLength(1)]
UInt16 Rst;
[BitFieldLength(1)]
UInt16 Psh;
[BitFieldLength(1)]
UInt16 Ack;
[BitFieldLength(1)]
UInt16 Urg;
[BitFieldLength(2)]
UInt16 Reserved2;
UInt16 Window;
UInt16 Checksum;
UInt16 UrgPtr;
};

I have referred it from here:

http://stackoverflow.com/questions/14464/bit-fields-in-c-sharp

Regards
AJ
Iftikar Hussain13y ago
Hi,
Not clear about your query. Can you explain bit more?
You can declare structure in C#. Please refer the below link

http://www.dotnetperls.com/struct

Regards,
Iftikar