///////////////////////////////////////////////////////////////////////////////
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//

using System;
using System.Text;
using System.Runtime.InteropServices;
using Smb.Shared;


namespace Smb.Protocol
{
	[StructLayout(LayoutKind.Explicit, Pack=1, Size=37)]
	pointerfree struct SmbHeader
	{
		[FieldOffset(0)] public byte FrameLength0;
		[FieldOffset(1)] public byte FrameLength1;
		[FieldOffset(2)] public byte FrameLength2;
		[FieldOffset(3)] public byte FrameLength3;
		[FieldOffset(4)] public byte Signature0;
		[FieldOffset(5)] public byte Signature1;
		[FieldOffset(6)] public byte Signature2;
		[FieldOffset(7)] public byte Signature3;
		[FieldOffset(8)] public byte Command;
		[FieldOffset(9)] public byte ErrorClass;
		[FieldOffset(10)] public byte Error1;
		[FieldOffset(11)] public byte Error2;
		[FieldOffset(12)] public byte Error3;
		[FieldOffset(13)] public byte Flags1;
		[FieldOffset(14)] public ushort Flags2;
		[FieldOffset(16)] public ushort PidHigh;
		[FieldOffset(18)] public uint Extra0;
		[FieldOffset(22)] public uint Extra1;
		[FieldOffset(26)] public ushort ExtraReserved;
		[FieldOffset(28)] public ushort TreeId;
		[FieldOffset(30)] public ushort ProcessId;
		[FieldOffset(32)] public ushort UserId;
		[FieldOffset(34)] public ushort MuxId;		
		[FieldOffset(36)] public byte ParameterCount;
		
		// I can't believe it, but the length of this structure is 37!  THIRTY SEVEN!
		// Not only is it not aligned to any sane boundary, like 4 or 8 bytes, but it's
		// a freakin PRIME NUMBER!
		public const int SizeOf = 37;
		
		public void SetSignature()
		{
			Signature0 = SmbSignature0;
			Signature1 = SmbSignature1;
			Signature2 = SmbSignature2;
			Signature3 = SmbSignature3;	
		}
		
		public bool IsSignatureValid()
		{
			return Signature0 == SmbSignature0
				&& Signature1 == SmbSignature1
				&& Signature2 == SmbSignature2
				&& Signature3 == SmbSignature3;				
		}
		
		
		public const byte SmbSignature0 = 0xff;
		public const byte SmbSignature1 = (byte)'S';
		public const byte SmbSignature2 = (byte)'M';
		public const byte SmbSignature3 = (byte)'B';
		
		public bool IsError
		{
			get {
				return Error1 != 0 || Error2 != 0 || Error3 != 0;
			}
		}
		
		public NtStatus GetNtStatus()
		{
			if ((((SmbFlag2)Flags2) & SmbFlag2.UsingNtStatus) != 0) {
				uint code = ((uint)ErrorClass)
					| (((uint)Error1) << 8)
					| (((uint)Error2) << 16)
					| (((uint)Error3) << 24);
				return (NtStatus)unchecked((int)code);
			} else {
				return NtStatus.CodeNotMapped;
			}
		}
		
		public string! GetErrorText()
		{
			return SmbProtocol.GetErrorText(this.ErrorClass, this.Error1 | ((ushort)Error2 << 8));
		}
		
		public int SmbMessageLength
		{
			get ensures result >= 0;
			{
				return (((int)this.FrameLength1) << 16)
					| (((int)this.FrameLength2) << 8)
					| ((int)this.FrameLength3);
			}
			
			set requires value >= 0;
			{
				this.FrameLength0 = 0;
				this.FrameLength1 = (byte)((value >> 16) & 0xff);
				this.FrameLength2 = (byte)((value >> 8) & 0xff);
				this.FrameLength3 = (byte)(value & 0xff);
			}
		}
		

		public bool IsRequest
		{
			get { return (this.Flags1 & (byte)SmbFlag1.IsResponse) == 0; }
		}
		
		public bool IsResponse
		{
			get { return (this.Flags1 & (byte)SmbFlag1.IsResponse) != 0; }
		}
		
		public int TotalMessageLength
		{
			get { return this.SmbMessageLength + 4; }
			
			set
				requires value >= 4;
				{ this.SmbMessageLength = value - 4; }
		}
		
		public void Prepare(SmbCommand command, int parameterCount)
			requires parameterCount >= 0;
			requires parameterCount < 256;
		{
			this.SetSignature();
			this.Command = (byte)command;
			this.ParameterCount = (byte)parameterCount;
		}
		
		public const int FramingHeaderLength = 4;
	}
}