IdIOHandlerWebsocket.pas

unit IdIOHandlerWebsocket;

{.$DEFINE DEBUG_WS}

//The WebSocket Protocol, RFC 6455
//http://datatracker.ietf.org/doc/rfc6455/?include_text=1

interface

uses
  Classes, SysUtils,
  IdIOHandlerStack, IdGlobal, IdException, IdBuffer,
  SyncObjs,
  Generics.Collections;

type
  TWSDataType      = (wdtText, wdtBinary);
  TWSDataCode      = (wdcNone, wdcContinuation, wdcText, wdcBinary, wdcClose, wdcPing, wdcPong);
  TWSExtensionBit  = (webBit1, webBit2, webBit3);
  TWSExtensionBits = set of TWSExtensionBit;

  TIdIOHandlerWebsocket   = class;
  EIdWebSocketHandleError = class(EIdSocketHandleError);

  {$if CompilerVersion >= 26}   //XE5
  TIdTextEncoding = IIdTextEncoding;
  {$ifend}

  TIdIOHandlerWebsocket = class(TIdIOHandlerStack)
  private
    FIsServerSide: Boolean;
    FBusyUpgrading: Boolean;
    FIsWebsocket: Boolean;
    FWSInputBuffer: TIdBuffer;
    FExtensionBits: TWSExtensionBits;
    FLock: TCriticalSection;
    FSelectLock: TCriticalSection;
    FCloseReason: string;
    FCloseCode: Integer;
    FClosing: Boolean;
    FLastActivityTime: TDateTime;
    FLastPingTime: TDateTime;
    class var FUseSingleWriteThread: Boolean;
    procedure SetIsWebsocket(const Value: Boolean);
  protected
    FMessageStream: TMemoryStream;
    FWriteTextToTarget: Boolean;
    FCloseCodeSend: Boolean;
    FPendingWriteCount: Integer;

    function InternalReadDataFromSource(var VBuffer: TIdBytes; ARaiseExceptionOnTimeout: Boolean): Integer;
    function ReadDataFromSource(var VBuffer: TIdBytes): Integer; override;
    function WriteDataToTarget (const ABuffer: TIdBytes; const AOffset, ALength: Integer): Integer; override;

    function ReadFrame(out aFIN, aRSV1, aRSV2, aRSV3: boolean; out aDataCode: TWSDataCode; out aData: TIdBytes): Integer;
    function ReadMessage(var aBuffer: TIdBytes; out aDataCode: TWSDataCode): Integer;

    {$if CompilerVersion >= 26}   //XE5
    function UTF8Encoding: IIdTextEncoding;
    {$else}
    function UTF8Encoding: TEncoding;
    {$ifend}
  public
    function WriteData(aData: TIdBytes; aType: TWSDataCode;
                        aFIN: boolean = true; aRSV1: boolean = false; aRSV2: boolean = false; aRSV3: boolean = false): integer;
    property BusyUpgrading : Boolean read FBusyUpgrading write FBusyUpgrading;
    property IsWebsocket   : Boolean read FIsWebsocket   write SetIsWebsocket;
    property IsServerSide  : Boolean read FIsServerSide  write FIsServerSide;
    property ClientExtensionBits : TWSExtensionBits read FExtensionBits write FExtensionBits;
  public
    class constructor Create;
    procedure  AfterConstruction;override;
    destructor Destroy; override;

    procedure Lock;
    procedure Unlock;
    function  TryLock: Boolean;

    function  HasData: Boolean;
    procedure Clear;
    function  Readable(AMSec: Integer = IdTimeoutDefault): Boolean; override;
    function  Connected: Boolean; override;

    procedure Close; override;
    property  Closing    : Boolean read FClosing;
    property  CloseCode  : Integer read FCloseCode   write FCloseCode;
    property  CloseReason: string  read FCloseReason write FCloseReason;

    //text/string writes
    procedure Write(const AOut: string; AEncoding: TIdTextEncoding = nil); overload; override;
    procedure WriteLn(const AOut: string; AEncoding: TIdTextEncoding = nil); overload; override;
    procedure WriteLnRFC(const AOut: string = ''; AEncoding: TIdTextEncoding = nil); override;
    procedure Write(AValue: TStrings; AWriteLinesCount: Boolean = False; AEncoding: TIdTextEncoding = nil); overload; override;
    procedure Write(AStream: TStream; aType: TWSDataType); overload;
    procedure WriteBufferFlush(AByteCount: Integer); override;

    procedure ReadBytes(var VBuffer: TIdBytes; AByteCount: Integer; AAppend: Boolean = True); override;

    property  LastActivityTime: TDateTime read FLastActivityTime write FLastActivityTime;
    property  LastPingTime: TDateTime read FLastPingTime write FLastPingTime;

    class property UseSingleWriteThread: Boolean read FUseSingleWriteThread write FUseSingleWriteThread;
  end;

  TThreadID = NativeUInt;

  TIdWebsocketQueueThread = class(TThread)
  private
    function GetThreadID: TThreadID;
  protected
    FLock: TCriticalSection;
    FTempThread: Integer;
    FEvent: TEvent;
    FEvents, FProcessing: TList<TThreadProcedure>;
  public
    procedure  AfterConstruction;override;
    destructor Destroy; override;

    procedure Lock;
    procedure UnLock;

    procedure ProcessQueue;
    procedure Execute; override;

    property ThreadID: TThreadID read GetThreadID;

    procedure Terminate;
    procedure QueueEvent(aEvent: TThreadProcedure);
  end;

  //http://tangentsoft.net/wskfaq/intermediate.html
  //Winsock is not threadsafe, use a single/seperate write thread and seperate read thread
  //(do not write in 2 different thread or read in 2 different threads)
  TIdWebsocketWriteThread = class(TIdWebsocketQueueThread)
  private
    class var FInstance: TIdWebsocketWriteThread;
  public
    class function  Instance: TIdWebsocketWriteThread;
    class procedure RemoveInstance;
  end;

  TIdBuffer_Ext = class(TIdBuffer);

//close frame codes
const
  C_FrameClose_Normal            = 1000; //1000 indicates a normal closure, meaning that the purpose for
                                         //which the connection was established has been fulfilled.
  C_FrameClose_GoingAway         = 1001; //1001 indicates that an endpoint is "going away", such as a server
                                         //going down or a browser having navigated away from a page.
  C_FrameClose_ProtocolError     = 1002; //1002 indicates that an endpoint is terminating the connection due
                                         //to a protocol error.
  C_FrameClose_UnhandledDataType = 1003; //1003 indicates that an endpoint is terminating the connection
                                         //because it has received a type of data it cannot accept (e.g., an
                                         //endpoint that understands only text data MAY send this if it
                                         //receives a binary message).
  C_FrameClose_Reserved          = 1004; //Reserved.  The specific meaning might be defined in the future.
  C_FrameClose_ReservedNoStatus  = 1005; //1005 is a reserved value and MUST NOT be set as a status code in a
                                         //Close control frame by an endpoint.  It is designated for use in
                                         //applications expecting a status code to indicate that no status
                                         //code was actually present.
  C_FrameClose_ReservedAbnormal  = 1006; //1006 is a reserved value and MUST NOT be set as a status code in a
                                         //Close control frame by an endpoint.  It is designated for use in
                                         //applications expecting a status code to indicate that the
                                         //connection was closed abnormally, e.g., without sending or
                                         //receiving a Close control frame.
  C_FrameClose_InconsistentData  = 1007; //1007 indicates that an endpoint is terminating the connection
                                         //because it has received data within a message that was not
                                         //consistent with the type of the message (e.g., non-UTF-8 [RFC3629]
                                         //data within a text message).
  C_FrameClose_PolicyError       = 1008; //1008 indicates that an endpoint is terminating the connection
                                         //because it has received a message that violates its policy.  This
                                         //is a generic status code that can be returned when there is no
                                         //other more suitable status code (e.g., 1003 or 1009) or if there
                                         //is a need to hide specific details about the policy.
  C_FrameClose_ToBigMessage      = 1009; //1009 indicates that an endpoint is terminating the connection
                                         //because it has received a message that is too big for it to process.
  C_FrameClose_MissingExtenstion = 1010; //1010 indicates that an endpoint (client) is terminating the
                                         //connection because it has expected the server to negotiate one or
                                         //more extension, but the server didn't return them in the response
                                         //message of the WebSocket handshake.  The list of extensions that
                                         //are needed SHOULD appear in the /reason/ part of the Close frame.
                                         //Note that this status code is not used by the server, because it
                                         //can fail the WebSocket handshake instead.
  C_FrameClose_UnExpectedError   = 1011; //1011 indicates that a server is terminating the connection because
                                         //it encountered an unexpected condition that prevented it from
                                         //fulfilling the request.
  C_FrameClose_ReservedTLSError  = 1015; //1015 is a reserved value and MUST NOT be set as a status code in a
                                         //Close control frame by an endpoint.  It is designated for use in
                                         //applications expecting a status code to indicate that the
                                         //connection was closed due to a failure to perform a TLS handshake
                                         //(e.g., the server certificate can't be verified).

implementation

uses
  Math, Windows,
  IdStream, IdStack, IdWinsock2, IdExceptionCore,
  IdResourceStrings, IdResourceStringsCore;

//frame codes
const
  C_FrameCode_Continuation = 0;
  C_FrameCode_Text         = 1;
  C_FrameCode_Binary       = 2;
  //3-7 are reserved for further non-control frames
  C_FrameCode_Close        = 8;
  C_FrameCode_Ping         = 9;
  C_FrameCode_Pong         = 10 {A};
  //B-F are reserved for further control frames

function BytesToStringRaw(const AValue: TIdBytes; aSize: Integer = -1): string;
var
  i: Integer;
begin
  //SetLength(Result, Length(aValue));
  for i := 0 to High(AValue) do
  begin
    if (AValue[i] = 0) and (aSize < 0) then Exit;

    if (AValue[i] < 33) or
       ( (AValue[i] > 126) and
         (AValue[i] < 161) )
    then
      Result := Result + '#' + IntToStr(AValue[i])
    else
      Result := Result + Char(AValue[i]);

    if (aSize > 0) and (i > aSize) then Break;
  end;
end;

{ TIdIOHandlerStack_Websocket }

procedure TIdIOHandlerWebsocket.AfterConstruction;
begin
  inherited;
  FMessageStream := TMemoryStream.Create;
  FWSInputBuffer := TIdBuffer.Create;
  FLock := TCriticalSection.Create;
  FSelectLock := TCriticalSection.Create;
end;

procedure TIdIOHandlerWebsocket.Clear;
begin
  FWSInputBuffer.Clear;
  InputBuffer.Clear;
  FBusyUpgrading := False;
  FIsWebsocket := False;
  FClosing := False;
  FClosing := False;
  FExtensionBits := [];
  FCloseReason := '';
  FCloseCode := 0;
  FLastActivityTime := 0;
  FLastPingTime := 0;
  FWriteTextToTarget := False;
  FCloseCodeSend := False;
  FPendingWriteCount := 0;
end;

procedure TIdIOHandlerWebsocket.Close;
var
  iaWriteBuffer: TIdBytes;
  sReason: UTF8String;
  iOptVal, iOptLen: Integer;
  bConnected: Boolean;
begin
  try
    //valid connection?
    bConnected := Opened and
                  SourceIsAvailable and
                  not ClosedGracefully;

    //no socket error? connection closed by software abort, connection reset by peer, etc
    iOptLen    := SIZE_INTEGER;
    bConnected := bConnected and
                  (IdWinsock2.getsockopt(Self.Binding.Handle, SOL_SOCKET, SO_ERROR, PAnsiChar(@iOptVal), iOptLen) = 0) and
                  (iOptVal = 0);

    if bConnected and IsWebsocket then
    begin
      //close message must be responded with a close message back
      //or initiated with a close message
      if not FCloseCodeSend then
      begin
        FCloseCodeSend  := True;

        //we initiate the close? then write reason etc
        if not Closing then
        begin
          SetLength(iaWriteBuffer, 2);
          if CloseCode < C_FrameClose_Normal then
            CloseCode := C_FrameClose_Normal;
          iaWriteBuffer[0] := Byte(CloseCode shr 8);
          iaWriteBuffer[1] := Byte(CloseCode);
          if CloseReason <> '' then
          begin
            sReason := utf8string(CloseReason);
            SetLength(iaWriteBuffer, Length(iaWriteBuffer) + Length(sReason));
            Move(sReason[1], iaWriteBuffer[2], Length(sReason));
          end;
        end
        else
        begin
          //just send normal close response back
          SetLength(iaWriteBuffer, 2);
          iaWriteBuffer[0] := Byte(C_FrameClose_Normal shr 8);
          iaWriteBuffer[1] := Byte(C_FrameClose_Normal);
        end;

        WriteData(iaWriteBuffer, wdcClose);  //send close + code back
      end;

      //we did initiate the close? then wait (a little) for close response
      if not Closing then
      begin
        FClosing := True;
        CheckForDisconnect();
        //wait till client respond with close message back
        //but a pending message can be in the buffer, so process this too
        while ReadFromSource(False{no disconnect error}, 1 * 1000, False) > 0 do ; //response within 1s?
      end;
    end;
  except
    //ignore, it's possible that the client is disconnected already (crashed etc)
  end;

  IsWebsocket   := False;
  BusyUpgrading := False;
  inherited Close;
end;

function TIdIOHandlerWebsocket.Connected: Boolean;
begin
  Lock;
  try
    Result := inherited Connected;
  finally
    Unlock;
  end;
end;

class constructor TIdIOHandlerWebsocket.Create;
begin
  //UseSingleWriteThread := True;
end;

destructor TIdIOHandlerWebsocket.Destroy;
begin
  while FPendingWriteCount > 0 do
    Sleep(1);

  FLock.Enter;
  FSelectLock.Enter;
  FLock.Free;
  FSelectLock.Free;

  FWSInputBuffer.Free;
  FMessageStream.Free;
  inherited;
end;

function TIdIOHandlerWebsocket.HasData: Boolean;
begin
  //buffered data available? (more data from previous read)
  Result := (FWSInputBuffer.Size > 0) or not InputBufferIsEmpty;
end;

function TIdIOHandlerWebsocket.InternalReadDataFromSource(
  var VBuffer: TIdBytes; ARaiseExceptionOnTimeout: Boolean): Integer;
begin
  SetLength(VBuffer, 0);

  CheckForDisconnect;
  if not Readable(ReadTimeout) or
     not Opened or
     not SourceIsAvailable then
  begin
    CheckForDisconnect; //disconnected during wait in "Readable()"?
    if not Opened then
      EIdNotConnected.Toss(RSNotConnected)
    else if not SourceIsAvailable then
      EIdClosedSocket.Toss(RSStatusDisconnected);
    GStack.CheckForSocketError(GStack.WSGetLastError); //check for socket error
    if ARaiseExceptionOnTimeout then
      EIdReadTimeout.Toss(RSIdNoDataToRead)  //exit, no data can be received
    else
      Exit(0);
  end;

  SetLength(VBuffer, RecvBufferSize);
  Result := inherited ReadDataFromSource(VBuffer);
  if Result = 0 then
  begin
    CheckForDisconnect; //disconnected in the mean time?
    GStack.CheckForSocketError(GStack.WSGetLastError); //check for socket error
    if ARaiseExceptionOnTimeout then
      EIdNoDataToRead.Toss(RSIdNoDataToRead); //nothing read? then connection is probably closed -> exit
  end;
  SetLength(VBuffer, Result);
end;

procedure TIdIOHandlerWebsocket.WriteLn(const AOut: string;
  AEncoding: TIdTextEncoding);
begin
  if UseSingleWriteThread and IsWebsocket and
     (GetCurrentThreadId <> TIdWebsocketWriteThread.Instance.ThreadID) then
  begin
    InterlockedIncrement(FPendingWriteCount);
    TIdWebsocketWriteThread.Instance.QueueEvent(
      procedure
      begin
        InterlockedDecrement(FPendingWriteCount);
        WriteLn(AOut, AEncoding);
      end)
  end
  else
  begin
    Lock;
    try
      FWriteTextToTarget := True;
      inherited WriteLn(AOut, UTF8Encoding);  //must be UTF8!
    finally
      FWriteTextToTarget := False;
      Unlock;
    end;
  end;
end;

procedure TIdIOHandlerWebsocket.WriteLnRFC(const AOut: string;
  AEncoding: TIdTextEncoding);
begin
  if UseSingleWriteThread and IsWebsocket and
     (GetCurrentThreadId <> TIdWebsocketWriteThread.Instance.ThreadID) then
  begin
    InterlockedIncrement(FPendingWriteCount);
    TIdWebsocketWriteThread.Instance.QueueEvent(
      procedure
      begin
        InterlockedDecrement(FPendingWriteCount);
        WriteLnRFC(AOut, AEncoding);
      end)
  end
  else
  begin
    Lock;
    try
      FWriteTextToTarget := True;
      inherited WriteLnRFC(AOut, UTF8Encoding);  //must be UTF8!
    finally
      FWriteTextToTarget := False;
      Unlock;
    end;
  end;
end;

procedure TIdIOHandlerWebsocket.Write(const AOut: string;
  AEncoding: TIdTextEncoding);
begin
  if UseSingleWriteThread and IsWebsocket and
     (GetCurrentThreadId <> TIdWebsocketWriteThread.Instance.ThreadID) then
  begin
    InterlockedIncrement(FPendingWriteCount);
    TIdWebsocketWriteThread.Instance.QueueEvent(
      procedure
      begin
        InterlockedDecrement(FPendingWriteCount);
        Write(AOut, AEncoding);
      end)
  end
  else
  begin
    Lock;
    try
      FWriteTextToTarget := True;
      inherited Write(AOut, UTF8Encoding);  //must be UTF8!
    finally
      FWriteTextToTarget := False;
      Unlock;
    end;
  end;
end;

procedure TIdIOHandlerWebsocket.Write(AValue: TStrings;
  AWriteLinesCount: Boolean; AEncoding: TIdTextEncoding);
begin
  if UseSingleWriteThread and IsWebsocket and
     (GetCurrentThreadId <> TIdWebsocketWriteThread.Instance.ThreadID) then
  begin
    InterlockedIncrement(FPendingWriteCount);
    TIdWebsocketWriteThread.Instance.QueueEvent(
      procedure
      begin
        InterlockedDecrement(FPendingWriteCount);
        Write(AValue, AWriteLinesCount, AEncoding);
      end)
  end
  else
  begin
    Lock;
    try
      FWriteTextToTarget := True;
      inherited Write(AValue, AWriteLinesCount, UTF8Encoding);  //must be UTF8!
    finally
      FWriteTextToTarget := False;
      Unlock;
    end;
  end;
end;

procedure TIdIOHandlerWebsocket.Write(AStream: TStream;
  aType: TWSDataType);
begin
  if UseSingleWriteThread and IsWebsocket and
     (GetCurrentThreadId <> TIdWebsocketWriteThread.Instance.ThreadID) then
  begin
    InterlockedIncrement(FPendingWriteCount);
    TIdWebsocketWriteThread.Instance.QueueEvent(
      procedure
      begin
        InterlockedDecrement(FPendingWriteCount);
        Write(AStream, aType);
      end)
  end
  else
  begin
    Lock;
    try
      FWriteTextToTarget := (aType = wdtText);
      inherited Write(AStream);
    finally
      FWriteTextToTarget := False;
      Unlock;
    end;
  end;
end;

procedure TIdIOHandlerWebsocket.WriteBufferFlush(AByteCount: Integer);
begin
  if (FWriteBuffer = nil) or (FWriteBuffer.Size <= 0) then Exit;

  if UseSingleWriteThread and IsWebsocket and
     (GetCurrentThreadId <> TIdWebsocketWriteThread.Instance.ThreadID) then
  begin
    InterlockedIncrement(FPendingWriteCount);
    TIdWebsocketWriteThread.Instance.QueueEvent(
      procedure
      begin
        InterlockedDecrement(FPendingWriteCount);
        WriteBufferFlush(AByteCount);
      end)
  end
  else
    inherited WriteBufferFlush(AByteCount);
end;

function TIdIOHandlerWebsocket.WriteDataToTarget(const ABuffer: TIdBytes;
  const AOffset, ALength: Integer): Integer;
begin
  if UseSingleWriteThread and IsWebsocket and (GetCurrentThreadId <> TIdWebsocketWriteThread.Instance.ThreadID) then
    Assert(False, 'Write done in different thread than TIdWebsocketWriteThread!');

  Lock;
  try
    Result := -1;
    if not IsWebsocket then
    begin
      {$IFDEF DEBUG_WS}
      if Debughook > 0 then
        OutputDebugString(PChar(Format('Send (non ws, TID:%d, P:%d): %s',
                                       [getcurrentthreadid, Self.Binding.PeerPort, BytesToStringRaw(ABuffer)])));
      {$ENDIF}
      Result := inherited WriteDataToTarget(ABuffer, AOffset, ALength)
    end
    else
    begin
      {$IFDEF DEBUG_WS}
      if Debughook > 0 then
        OutputDebugString(PChar(Format('Send (ws, TID:%d, P:%d): %s',
                                       [getcurrentthreadid, Self.Binding.PeerPort, BytesToStringRaw(ABuffer)])));
      {$ENDIF}
      try
        if FWriteTextToTarget then
          Result := WriteData(ABuffer, wdcText, True{send all at once},
                              webBit1 in ClientExtensionBits, webBit2 in ClientExtensionBits, webBit3 in ClientExtensionBits)
        else
          Result := WriteData(ABuffer, wdcBinary, True{send all at once},
                              webBit1 in ClientExtensionBits, webBit2 in ClientExtensionBits, webBit3 in ClientExtensionBits);
      except
        FClosedGracefully := True;
        Result := -1;
        Raise;
      end;
    end;
  finally
    Unlock;
  end;
end;

function TIdIOHandlerWebsocket.Readable(AMSec: Integer): Boolean;
begin
  if FWSInputBuffer.Size > 0 then Exit(True);

  if not FSelectLock.TryEnter then Exit(False);
  try
    Result := inherited Readable(AMSec);
  finally
    FSelectLock.Leave;
  end;
end;

procedure TIdIOHandlerWebsocket.ReadBytes(var VBuffer: TIdBytes;
  AByteCount: Integer; AAppend: Boolean);
begin
  inherited;
  {$IFDEF DEBUG_WS}
  if IsWebsocket then  
  if Debughook > 0 then
  begin
    OutputDebugString(PChar(Format('%d Bytes read(TID:%d): %s',
                                   [AByteCount, getcurrentthreadid, BytesToStringRaw(VBuffer, AByteCount)])));
    OutputDebugString(PChar(Format('Buffer (HeadIndex:%d): %s',
                                   [TIdBuffer_Ext(InputBuffer).FHeadIndex,
                                    BytesToStringRaw(TIdBuffer_Ext(InputBuffer).FBytes,
                                    InputBuffer.Size + TIdBuffer_Ext(InputBuffer).FHeadIndex)])));
  end;
  {$ENDIF}
end;

function TIdIOHandlerWebsocket.ReadDataFromSource(
  var VBuffer: TIdBytes): Integer;
var
  wscode: TWSDataCode;
begin
  //the first time something is read AFTER upgrading, we switch to WS
  //(so partial writes can be done, till a read is done)
  if BusyUpgrading then
  begin
    BusyUpgrading := False;
    IsWebsocket   := True;
  end;

  Result := -1;
  Lock;
  try
    if not IsWebsocket then
    begin
      Result := inherited ReadDataFromSource(VBuffer);
      {$IFDEF DEBUG_WS}
      if Debughook > 0 then
        OutputDebugString(PChar(Format('Received (non ws, TID:%d, P:%d): %s',
                                       [getcurrentthreadid, Self.Binding.PeerPort, BytesToStringRaw(VBuffer, Result)])));
      {$ENDIF}
    end
    else
    begin
      try
        //we wait till we have a full message here (can be fragmented in several frames)
        Result := ReadMessage(VBuffer, wscode);

        {$IFDEF DEBUG_WS}
        if Debughook > 0 then
          OutputDebugString(PChar(Format('Received (ws, TID:%d, P:%d): %s',
                                         [getcurrentthreadid, Self.Binding.PeerPort, BytesToStringRaw(VBuffer)])));
        {$ENDIF}

        //first write the data code (text or binary, ping, pong)
        FInputBuffer.Write(LongWord(Ord(wscode)));
        //we write message size here, vbuffer is written after this. This way we can use ReadStream to get 1 single message (in case multiple messages in FInputBuffer)
        if LargeStream then
          FInputBuffer.Write(Int64(Result))
        else
          FInputBuffer.Write(LongWord(Result))
      except
        FClosedGracefully := True; //closed (but not gracefully?)
        Raise;
      end;
    end;
  finally
    Unlock;  //normal unlock (no double try finally)
  end;
end;

function TIdIOHandlerWebsocket.ReadMessage(var aBuffer: TIdBytes; out aDataCode: TWSDataCode): Integer;
var
  iReadCount: Integer;
  iaReadBuffer: TIdBytes;
  bFIN, bRSV1, bRSV2, bRSV3: boolean;
  lDataCode: TWSDataCode;
  lFirstDataCode: TWSDataCode;
//    closeCode: integer;
//    closeResult: string;
begin
  Result := 0;
  (* ...all fragments of a message are of
     the same type, as set by the first fragment's opcode.  Since
     control frames cannot be fragmented, the type for all fragments in
     a message MUST be either text, binary, or one of the reserved
     opcodes. *)
  lFirstDataCode := wdcNone;
  FMessageStream.Clear;

  repeat
    //read a single frame
    iReadCount := ReadFrame(bFIN, bRSV1, bRSV2, bRSV3, lDataCode, iaReadBuffer);
    if (iReadCount > 0) or
       (lDataCode <> wdcNone) then
    begin
      Assert(Length(iaReadBuffer) = iReadCount);

      //store client extension bits
      if Self.IsServerSide then
      begin
        ClientExtensionBits := [];
        if bRSV1 then ClientExtensionBits := ClientExtensionBits + [webBit1];
        if bRSV2 then ClientExtensionBits := ClientExtensionBits + [webBit2];
        if bRSV3 then ClientExtensionBits := ClientExtensionBits + [webBit3];
      end;

      //process frame
      case lDataCode of
        wdcText, wdcBinary:
          begin
            if lFirstDataCode <> wdcNone then
              raise EIdWebSocketHandleError.Create('Invalid frame: specified data code only allowed for the first frame. Data = ' + BytesToStringRaw(iaReadBuffer));
            lFirstDataCode := lDataCode;

            FMessageStream.Clear;
            TIdStreamHelper.Write(FMessageStream, iaReadBuffer);
          end;
        wdcContinuation:
          begin
            if not (lFirstDataCode in [wdcText, wdcBinary]) then
              raise EIdWebSocketHandleError.Create('Invalid frame continuation. Data = ' + BytesToStringRaw(iaReadBuffer));
            TIdStreamHelper.Write(FMessageStream, iaReadBuffer);
          end;
        wdcClose:
          begin
            FCloseCode := C_FrameClose_Normal;
            //"If there is a body, the first two bytes of the body MUST be a 2-byte
            // unsigned integer (in network byte order) representing a status code"
            if Length(iaReadBuffer) > 1 then
            begin
              FCloseCode := (iaReadBuffer[0] shl 8) +
                             iaReadBuffer[1];
              if Length(iaReadBuffer) > 2 then
                FCloseReason := BytesToString(iaReadBuffer, 2, Length(iaReadBuffer), UTF8Encoding);
            end;

            FClosing := True;
            Self.Close;
          end;
        //Note: control frames can be send between fragmented frames
        wdcPing:
        begin
          WriteData(iaReadBuffer, wdcPong);  //send pong + same data back
          lFirstDataCode := lDataCode;
          //bFIN := False; //ignore ping when we wait for data?
        end;
        wdcPong:
        begin
           //pong received, ignore;
          lFirstDataCode := lDataCode;
        end;
      end;
    end
    else
      Break;
  until bFIN;

  //done?
  if bFIN then
  begin
    if (lFirstDataCode in [wdcText, wdcBinary]) then
    begin
      //result
      FMessageStream.Position := 0;
      TIdStreamHelper.ReadBytes(FMessageStream, aBuffer);
      Result    := FMessageStream.Size;
      aDataCode := lFirstDataCode
    end
    else if (lFirstDataCode in [wdcPing, wdcPong]) then
    begin
      //result
      FMessageStream.Position := 0;
      TIdStreamHelper.ReadBytes(FMessageStream, aBuffer);
      SetLength(aBuffer, FMessageStream.Size);
      //dummy data: there *must* be some data read otherwise connection is closed by Indy!
      if Length(aBuffer) <= 0 then
      begin
        SetLength(aBuffer, 1);
        aBuffer[0] := Ord(lFirstDataCode);
      end;

      Result    := Length(aBuffer);
      aDataCode := lFirstDataCode
    end;
  end;
end;

procedure TIdIOHandlerWebsocket.SetIsWebsocket(const Value: Boolean);
var data: TIdBytes;
begin
  //copy websocket data which was send/received during http upgrade
  if not FIsWebsocket and Value and
     (FInputBuffer.Size > 0) then
  begin
    FInputBuffer.ExtractToBytes(data);
    FWSInputBuffer.Write(data);
  end;

  FIsWebsocket := Value;
end;

procedure TIdIOHandlerWebsocket.Lock;
begin
  FLock.Enter;
end;

function TIdIOHandlerWebsocket.TryLock: Boolean;
begin
  Result := FLock.TryEnter;
end;

procedure TIdIOHandlerWebsocket.Unlock;
begin
  FLock.Leave;
end;

{$if CompilerVersion >= 26}   //XE5
function TIdIOHandlerWebsocket.UTF8Encoding: IIdTextEncoding;
begin
  Result := IndyTextEncoding_UTF8;
end;
{$else}
function TIdIOHandlerWebsocket.UTF8Encoding: TEncoding;
begin
  Result := TIdTextEncoding.UTF8;
end;
{$ifend}

function TIdIOHandlerWebsocket.ReadFrame(out aFIN, aRSV1, aRSV2, aRSV3: boolean;
                                         out aDataCode: TWSDataCode; out aData: TIdBytes): Integer;
var
  iInputPos: NativeInt;

  function _WaitByte(ARaiseExceptionOnTimeout: Boolean): Boolean;
  var
    temp: TIdBytes;
  begin
    //if HasData then Exit(True);
    if (FWSInputBuffer.Size > 0) then Exit(True);

    Result := InternalReadDataFromSource(temp, ARaiseExceptionOnTimeout) > 0;
    if Result then
    begin
      FWSInputBuffer.Write(temp);
      {$IFDEF DEBUG_WS}
//      if debughook > 0 then
//        OutputDebugString(PChar(Format('Received (TID:%d, P:%d): %s',
//                                       [getcurrentthreadid, Self.Binding.PeerPort, BytesToStringRaw(temp)])));
//        OutputDebugString(PChar('Received: ' + BytesToStringRaw(temp)));
      {$ENDIF}
    end;
  end;

  function _GetByte: Byte;
  begin
    while FWSInputBuffer.Size <= iInputPos do
    begin
      //FWSInputBuffer.AsString;
      _WaitByte(True);
      if FWSInputBuffer.Size <= iInputPos then
        Sleep(1);
    end;

    //Self.ReadByte copies all data everytime (because the first byte must be removed) so we use index (much more efficient)
    Result := FWSInputBuffer.PeekByte(iInputPos);
    //FWSInputBuffer.AsString
    inc(iInputPos);
  end;

  function _GetBytes(aCount: Integer): TIdBytes;
  var
    temp: TIdBytes;
  begin
    while FWSInputBuffer.Size < aCount do
    begin
      InternalReadDataFromSource(temp, True); 
      FWSInputBuffer.Write(temp);
      {$IFDEF DEBUG_WS}
      if debughook > 0 then
        OutputDebugString(PChar('Received: ' + BytesToStringRaw(temp)));
      {$ENDIF}
      if FWSInputBuffer.Size < aCount then
        Sleep(1);
    end;

    FWSInputBuffer.ExtractToBytes(Result, aCount);
  end;

var
  iByte: Byte;
  i, iCode: NativeInt;
  bHasMask: boolean;
  iDataLength, iPos: Int64;
  rMask: record
    case Boolean of
      True : (MaskAsBytes: array[0..3] of Byte);
      False: (MaskAsInt  : Int32);
  end;
begin
  iInputPos := 0;
  Result := 0;
  aFIN := False; aRSV1 := False; aRSV2:= False; aRSV3:= False;
  aDataCode := wdcNone;
  SetLength(aData, 0);

  if not _WaitByte(False) then Exit;
  FLastActivityTime := Now;   //received some data

  //wait + process data
  iByte := _GetByte;
  (* 0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 (nr)
     7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0 (bit)
    +-+-+-+-+-------+-+-------------+-------------------------------+
    |F|R|R|R| opcode|M| Payload len |    Extended payload length    |
    |I|S|S|S|  (4)  |A|     (7)     |             (16/64)           |
    |N|V|V|V|       |S|             |   (if payload len==126/127)   |
    | |1|2|3|       |K|             |                               |
    +-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - + *)
  //FIN, RSV1, RSV2, RSV3: 1 bit each
  aFIN   := (iByte and (1 shl 7)) > 0;
  aRSV1  := (iByte and (1 shl 6)) > 0;
  aRSV2  := (iByte and (1 shl 5)) > 0;
  aRSV3  := (iByte and (1 shl 4)) > 0;
  //Opcode: 4 bits
  iCode  := (iByte and $0F); //clear 4 MSB's
  case iCode of
    C_FrameCode_Continuation: aDataCode := wdcContinuation;
    C_FrameCode_Text:         aDataCode := wdcText;
    C_FrameCode_Binary:       aDataCode := wdcBinary;
    C_FrameCode_Close:        aDataCode := wdcClose;
    C_FrameCode_Ping:         aDataCode := wdcPing;
    C_FrameCode_Pong:         aDataCode := wdcPong;
  else
    raise EIdException.CreateFmt('Unsupported data code: %d. Buffer = %s', [iCode, FWSInputBuffer.AsString]);
  end;

  //Mask: 1 bit
  iByte       := _GetByte;
  bHasMask    := (iByte and (1 shl 7)) > 0;
  //Length (7 bits or 7+16 bits or 7+64 bits)
  iDataLength := (iByte and $7F);  //clear 1 MSB
  //Extended payload length?
  //If 126, the following 2 bytes interpreted as a 16-bit unsigned integer are the payload length
  if (iDataLength = 126) then
  begin
    iByte       := _GetByte;
    iDataLength := (iByte shl 8); //8 MSB
    iByte       := _GetByte;
    iDataLength := iDataLength + iByte;
  end
  //If 127, the following 8 bytes interpreted as a 64-bit unsigned integer (the most significant bit MUST be 0) are the payload length
  else if (iDataLength = 127) then
  begin
    iDataLength := 0;
    for i := 7 downto 0 do  //read 8 bytes in reverse order
    begin
      iByte       := _GetByte;
      iDataLength := iDataLength +
                     (Int64(iByte) shl (8 * i)); //shift bits to left to recreate 64bit integer
    end;
    Assert(iDataLength > 0);
  end;

  //"All frames sent from client to server must have this bit set to 1"
  if IsServerSide and not bHasMask then
    raise EIdWebSocketHandleError.Create('No mask supplied: mask is required for clients when sending data to server. Buffer = ' + FWSInputBuffer.AsString)
  else if not IsServerSide and bHasMask then
    raise EIdWebSocketHandleError.Create('Mask supplied but mask is not allowed for servers when sending data to clients. Buffer = ' + FWSInputBuffer.AsString);

  //Masking-key: 0 or 4 bytes
  if bHasMask then
  begin
    rMask.MaskAsBytes[0] := _GetByte;
    rMask.MaskAsBytes[1] := _GetByte;
    rMask.MaskAsBytes[2] := _GetByte;
    rMask.MaskAsBytes[3] := _GetByte;
  end;
  //Payload data:  (x+y) bytes
  FWSInputBuffer.Remove(iInputPos);  //remove first couple of processed bytes (header)
  //simple read?
  if not bHasMask then
    aData := _GetBytes(iDataLength)
  else
  //reverse mask
  begin
    aData := _GetBytes(iDataLength);
    iPos   := 0;
    while iPos < iDataLength do
    begin
      aData[iPos] := aData[iPos] xor
                      rMask.MaskAsBytes[iPos mod 4]; //apply mask
      inc(iPos);
    end;
  end;

  Result := Length(aData);
  {$IFDEF DEBUG_WS}
  if debughook > 0 then
    OutputDebugString(PChar(Format('Received (TID:%d, P:%d, Count=%d): %s',
                                   [getcurrentthreadid, Self.Binding.PeerPort, Result, BytesToStringRaw(aData, Result)])));
  {$ENDIF}
end;

function TIdIOHandlerWebsocket.WriteData(aData: TIdBytes;
  aType: TWSDataCode; aFIN, aRSV1, aRSV2, aRSV3: boolean): integer;
var
  iByte: Byte;
  i, ioffset: NativeInt;
  iDataLength, iPos: Int64;
  rLength: Int64Rec;
  rMask: record
    case Boolean of
      True : (MaskAsBytes: array[0..3] of Byte);
      False: (MaskAsInt  : Int32);
  end;
  strmData: TMemoryStream;
  bData: TIdBytes;
begin
  Result := 0;
  Assert(Binding <> nil);

  strmData := TMemoryStream.Create;
  Lock;
  try
    FLastActivityTime := Now;   //sending some data
    (* 0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 (nr)
       7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0 (bit)
      +-+-+-+-+-------+-+-------------+-------------------------------+
      |F|R|R|R| opcode|M| Payload len |    Extended payload length    |
      |I|S|S|S|  (4)  |A|     (7)     |             (16/64)           |
      |N|V|V|V|       |S|             |   (if payload len==126/127)   |
      | |1|2|3|       |K|             |                               |
      +-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - + *)
    //FIN, RSV1, RSV2, RSV3: 1 bit each
    if aFIN  then iByte :=         (1 shl 7);
    if aRSV1 then iByte := iByte + (1 shl 6);
    if aRSV2 then iByte := iByte + (1 shl 5);
    if aRSV3 then iByte := iByte + (1 shl 4);
    //Opcode: 4 bits
    case aType of
      wdcContinuation : iByte := iByte + C_FrameCode_Continuation;
      wdcText         : iByte := iByte + C_FrameCode_Text;
      wdcBinary       : iByte := iByte + C_FrameCode_Binary;
      wdcClose        : iByte := iByte + C_FrameCode_Close;
      wdcPing         : iByte := iByte + C_FrameCode_Ping;
      wdcPong         : iByte := iByte + C_FrameCode_Pong;
    else
      raise EIdException.CreateFmt('Unsupported data code: %d', [Ord(aType)]);
    end;
    strmData.Write(iByte, SizeOf(iByte));

    iByte := 0;
    //Mask: 1 bit; Note: Clients must apply a mask
    if not IsServerSide then iByte := (1 shl 7);

    //Length: 7 bits or 7+16 bits or 7+64 bits
    if Length(aData) < 126 then            //7 bit, 128
      iByte := iByte + Length(aData)
    else if Length(aData) < 1 shl 16 then  //16 bit, 65536
      iByte := iByte + 126
    else
      iByte := iByte + 127;
    strmData.Write(iByte, SizeOf(iByte));

    //Extended payload length?
    if Length(aData) >= 126 then
    begin
      //If 126, the following 2 bytes interpreted as a 16-bit unsigned integer are the payload length
      if Length(aData) < 1 shl 16 then  //16 bit, 65536
      begin
        rLength.Lo := Length(aData);
        iByte := rLength.Bytes[1];
        strmData.Write(iByte, SizeOf(iByte));
        iByte := rLength.Bytes[0];
        strmData.Write(iByte, SizeOf(iByte));
      end
      else
      //If 127, the following 8 bytes interpreted as a 64-bit unsigned integer (the most significant bit MUST be 0) are the payload length
      begin
        rLength := Int64Rec(Int64(Length(aData)));
        for i := 7 downto 0 do
        begin
          iByte := rLength.Bytes[i];
          strmData.Write(iByte, SizeOf(iByte));
        end;
      end
    end;

    //Masking-key: 0 or 4 bytes; Note: Clients must apply a mask
    if not IsServerSide then
    begin
      rMask.MaskAsInt := Random(MaxInt);
      strmData.Write(rMask.MaskAsBytes[0], SizeOf(Byte));
      strmData.Write(rMask.MaskAsBytes[1], SizeOf(Byte));
      strmData.Write(rMask.MaskAsBytes[2], SizeOf(Byte));
      strmData.Write(rMask.MaskAsBytes[3], SizeOf(Byte));
    end;

    //write header
    strmData.Position := 0;
    TIdStreamHelper.ReadBytes(strmData, bData);

    //Mask? Note: Only clients must apply a mask
    if not IsServerSide then
    begin
      iPos := 0;
      iDataLength := Length(aData);
      //in place masking
      while iPos < iDataLength do
      begin
        iByte := aData[iPos] xor rMask.MaskAsBytes[iPos mod 4]; //apply mask
        aData[iPos] := iByte;
        inc(iPos);
      end;
    end;

    AppendBytes(bData, aData);   //important: send all at once!
    ioffset := 0;
    repeat
      Result := Binding.Send(bData, ioffset);
      Inc(ioffset, Result);
    until ioffset >= Length(bData);

//    if debughook > 0 then
//      OutputDebugString(PChar(Format('Written (TID:%d, P:%d): %s',
//                                     [getcurrentthreadid, Self.Binding.PeerPort, BytesToStringRaw(bData)])));
  finally
    Unlock;
    strmData.Free;
  end;
end;

{ TIdWebsocketQueueThread }

procedure TIdWebsocketQueueThread.AfterConstruction;
begin
  inherited;
  FLock       := TCriticalSection.Create;
  FEvents     := TList<TThreadProcedure>.Create;
  FProcessing := TList<TThreadProcedure>.Create;
  FEvent      := TEvent.Create;
end;

destructor TIdWebsocketQueueThread.Destroy;
begin
  Lock;
  FEvents.Clear;
  FProcessing.Free;

  FEvent.Free;
  UnLock;
  FEvents.Free;
  FLock.Free;
  inherited;
end;

procedure TIdWebsocketQueueThread.Execute;
begin
  TThread.NameThreadForDebugging(ansistring(Self.ClassName));

  while not Terminated do
  begin
    try
      if FEvent.WaitFor(3 * 1000) = wrSignaled then
      begin
        FEvent.ResetEvent;
        ProcessQueue;
      end;

      if FProcessing.Count > 0 then
        ProcessQueue;
    except
      //continue
    end;
  end;
end;

function TIdWebsocketQueueThread.GetThreadID: TThreadID;
begin
  if FTempThread > 0 then
    Result := FTempThread
  else
    Result := inherited ThreadID;
end;

procedure TIdWebsocketQueueThread.Lock;
begin
  //System.TMonitor.Enter(FEvents);
  FLock.Enter;
end;

procedure TIdWebsocketQueueThread.ProcessQueue;
var
  proc: Classes.TThreadProcedure;
begin
  FTempThread := GetCurrentThreadId;

  Lock;
  try
    //copy
    while FEvents.Count > 0 do
    begin
      proc := FEvents.Items[0];
      FProcessing.Add(proc);
      FEvents.Delete(0);
    end;
  finally
    UnLock;
  end;

  while FProcessing.Count > 0 do
  begin
    proc := FProcessing.Items[0];
    FProcessing.Delete(0);
    proc();
  end;
end;

procedure TIdWebsocketQueueThread.QueueEvent(aEvent: TThreadProcedure);
begin
  if Terminated then Exit;

  Lock;
  try
    FEvents.Add(aEvent);
  finally
    UnLock;
  end;
  FEvent.SetEvent;
end;

procedure TIdWebsocketQueueThread.Terminate;
begin
  inherited Terminate;
  FEvent.SetEvent;
end;

procedure TIdWebsocketQueueThread.UnLock;
begin
  //System.TMonitor.Exit(FEvents);
  FLock.Leave;
end;

{ TIdWebsocketWriteThread }

class function TIdWebsocketWriteThread.Instance: TIdWebsocketWriteThread;
begin
  if FInstance = nil then
  begin
    GlobalNameSpace.BeginWrite;
    try
      if FInstance = nil then
      begin
        FInstance := Self.Create(True);
        FInstance.Start;
      end;
    finally
      GlobalNameSpace.EndWrite;
    end;
  end;
  Result := FInstance;
end;

class procedure TIdWebsocketWriteThread.RemoveInstance;
begin
  if FInstance <> nil then
  begin
    FInstance.Terminate;
    FInstance.WaitFor;
    FreeAndNil(FInstance);
  end;
end;

end.