type
  TExactReaderDone = procedure (Sender: TExactReader) of object;
  TExactReader = class
    Buffer: TBytes;
    BufferPos, BufferSize: Cardinal;

    property OnDone: TExactReaderDone;
    procedure DataReceived(Sender: TObject; Socket: TCustomWinSocket)
    var
      DataLen: Integer;
    begin
      DataLen := Socket.ReceiveLength;
      if BufferSize < DataLen then DataLen := BufferSize;

      Socket.ReceiveBuf(@Buffer[BufferPos], DataLen);
      Inc(BufferPos, DataLen);
      Dec(BufferSize, DataLen);
      
      if BufferSize = 0 then      
        OnDone(Self);
    end;

    constructor Create(Sock: TClientSocket; Size: Cardinal; Handler: TExactReaderDone)
    begin
      BufferSize := Size;
      BufferPos := 0;
      SetLength(Buffer, BufferSize);

      OnDone := Handler;
      Sock.OnRead := DataReceived;
    end;
    destructor Destroy
    begin
      Sock.OnRead := nil;
    end;
  end;

type
  TDataStreamReceived = procedure (Sender: TDataStreamer) of object;
  TDataStreamer = class
    Buffer: TBytes;
    BufferPos, BufferSize: Cardinal;
  
    property OnReceived: TDataStreamReceived;
    procedure DataReceived(Sender: TObject; Socket: TCustomWinSocket)
    var
      DataLen: Integer;
    begin
      DataLen := Socket.ReceiveLength;
      if ((BufferPos+DataLen) >= BufferSize) or not Assigned(Buffer) then
      begin
        while (BufferPos+DataLen) >= BufferSize do BufferSize := BufferSize*2;
        SetLength(Buffer, BufferSize);
      end;
      Socket.ReceiveBuf(@Buffer[BufferPos], DataLen);
      Inc(BufferPos, DataLen);
      
      OnReceived(Self);
    end;
    
    procedure RemoveHandled(Size: Cardinal)
    begin
      MoveMemory(@Buffer[0], @Buffer[Size], BufferPos-Size);
      Dec(BufferPos, Size);
    end;
    
    constructor Create(Sock: TClientSocket)
    begin
      Buffer := nil;
      BufferPos := 0;
      BufferSize := 4*1024;
      
      Sock.OnRead := DataReceived;
    end;
    
    destructor Destroy
    begin
      Sock.OnRead := nil;
    end;
    
    function GetByte(var AtPos: Cardinal; var Data: Byte): Boolean;
    function GetWord(var AtPos: Cardinal; var Data: Word): Boolean;
    function GetDWord(var AtPos: Cardinal; var Data: DWord): Boolean;
    function GetString(var AtPos: Cardinal; var S: String): Boolean;
  end;
  
  TCommandProcessor = class
    Sock: TClientSocket;
    Streamer: TDataStreamer;

    procedure OnData(Stream: TDataStreamer)
    var
      Cmd: Word;
      Text: string;
      DataType, ValueIndex: DWord;
      I: Cardinal;
    begin
      I := 0;

      if not S.GetWord(I, Cmd) then Exit;
      case Cmd of
        $0001: begin
          if not GetString(I, Text) then Exit;
          MessageBox(0, text, 'A message', MB_OK);
        end;
        $1001: begin
          if not S.GetDWord(I, DataType) then Exit;
          if not S.GetDWord(I, ValueIndex) then Exit;
          ProcessInformationRequest(DataType, ValueIndex);
        end;
      end;

      S.RemoveHandled(I);
    end;

    constructor Create(Sock: TClientSocket)
    begin
      Streamer := TDataStreamer.Create(Sock);
      Streamer.OnReceived := OnData;
    end;
  end;