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using System;
using System.Runtime.InteropServices;

namespace FpgaMeasurementInstrumentsLib
{
   /// <summary>
   /// The header for all command messages
   /// </summary>
   internal class FPGACmdMessageHeader
   {
      #region PrivateClassMembers
      private const int m_HEADER_SIZE = 1;
      private byte m_headerCmd;
      #endregion

      #region PublicFunctions

      /// <summary>
      /// Copy constructor
      /// </summary>
      /// <param name="header">The header to copy</param>
      public FPGACmdMessageHeader(FPGACmdMessageHeader header)
      {
         try
         {
            m_headerCmd = header.m_headerCmd;
         }
         catch (Exception)
         {
            throw;
         }
      }

      /// <summary>
      /// Constructor for when receiving data.
      /// Use this constructor and then parse to populate it
      /// </summary>
      public FPGACmdMessageHeader()
      {
         try
         {
            m_headerCmd = 0;
         }
         catch (Exception)
         {
            throw;
         }
      }

      /// <summary>
      /// Constructor for sending
      /// </summary>
      /// <param name="commandType">the type of the message</param>
      /// <param name="page">The page to read or write to</param>
      public FPGACmdMessageHeader(FPGACmdMsgIds commandType, FPGACmdMessage.Page page)
      {
         try
         {
            m_headerCmd = (byte)((byte)commandType | (byte)page);
         }
         catch (Exception)
         {
            throw;
         }
      }

      /// <summary>
      /// Encode the header into a byte array for sending
      /// </summary>
      /// <param name="pData">The buffer to put the message items</param>
      public void Format(IntPtr pData)
      {
         try
         {
            Marshal.StructureToPtr(m_headerCmd, pData, true);
         }
         catch (Exception)
         {
            throw;
         }
      }

      /// <summary>
      /// getter for the number of bytes in the header
      /// </summary>
      /// <returns>The header length in bytes</returns>
      public uint GetHeaderLength()
      {
         try
         {
            return m_HEADER_SIZE;
         }
         catch (Exception)
         {
            throw;
         }
      }

      /// <summary>
      /// getter for the message id
      /// </summary>
      /// <returns>The message id</returns>
      public FPGACmdMsgIds GetMessageId()
      {
         byte temp = (byte)(m_headerCmd >> 4);
         return (FPGACmdMsgIds)temp;
      }

      /// <summary>
      /// Takes an array of bytes and populates the header object
      /// </summary>
      /// <param name="pData">The header in byte form</param>
      public void Parse(IntPtr pData)
      {
         try
         {
            m_headerCmd = System.Runtime.InteropServices.Marshal.ReadByte(pData, 0);
         }
         catch (Exception)
         {
            throw;
         }
      }

      /// <summary>
      /// Creates a string version of the header members
      /// </summary>
      /// <returns>A string containning the header data</returns>
      public override string ToString()
      {
         string msg = "Header Data:\r\n";
         msg += "Command: " + m_headerCmd.ToString("X") + "\r\n";
         return msg;
      }
      #endregion
   }
}