Delphi - 驱动程序通信，GetQueuedCompletionStatus返回空缓冲区

Question

我使用以下过程从delphi调用驱动程序

procedure TfrmReceiver.Button2Click(Sender: TObject);
label main_cleanup;
var

hr: HRESULT;
ScannerPortName:pWideChar;
msg: PSCANNER_MESSAGE;
threadId: DWORD;
context: SCANNER_THREAD_CONTEXT;
retVal: DWORD;
i,j: integer;
threads: array [0..Pred(64)] of THandle;
requestCount: DWORD;
begin
requestCount :=5;
ScannerPortName:='\ScannerPort';
hr:=FilterConnectCommunicationPort(ScannerPortName,0, Nil, 0, Nil,@hport);
if hr=s_ok then begin
showmessage('Connected');
 completion:= CreateIoCompletionPort(hport,0{nil},0,2);
 if completion=0 then begin
showmessage('Port error!');
CloseHandle(hport);
end else begin
showmessage('Ok');
 msg:= AllocMem(sizeof(SCANNER_MESSAGE));
      if msg=nil then
      begin
       showmessage('No memory!');
       exit;
      end;
       (**)
  (*  Create specified number of threads.*)
  (**)
  context.port := completion;
  for{while} i:=0 to Pred(threadCount) { i++}
  do begin
   threads[i]:= CreateThread(nil,0,@ScannerWorker,POinter(context.port),0,threadId);
if threads[i]=0{nil}then begin
      hr:= GetLastError();
ShowMessage('Thread error!');
goto main_cleanup;
end;

    for{while} j:=0 to Pred(requestCount) { j++}
    do
    begin

      (**)
      (*  Allocate the message.*)
      (**)
      msg:= AllocMem(sizeof(SCANNER_MESSAGE));
      if msg=nil then
      begin
       showmessage('No memory!');
        goto main_cleanup;
      end;
    //  ZeroMemory(@msg.FPOverlapped,sizeof(OVERLAPPED));
      //Context.Port,@message.MessageHeader,{(Ovlp)}600,@message.FPOverlapped
      hr:= FilterGetMessage(hport,@Msg^.MessageHeader,DWORD(@PSCANNER_MESSAGE(0)^.FOverlapped),@Msg^.FOverlapped);
      if hr = (ERROR_IO_PENDING)
      then begin
      ShowMessage('Err!');
        freeMem(msg);
        goto main_cleanup;
      end;
    end;
  end;
  hr:= S_OK;
 // WaitForMultipleObjects(i, @threads, TRUE, INFINITE);
  main_cleanup:
  //CloseHandle(hport);
  //CloseHandle(completion);
   end;
end else
showmessage('Not Connected'); //-->
end;

并在此函数中接收数据，但返回的缓冲区始终为空，我不知道为什么，这是应该返回缓冲区的地方，这是正确的调用来接收重叠缓冲区吗？

cResult:= GetQueuedCompletionStatus(completion,outSize,key,pOvlp,INFINITE);
        Msg := PSCANNER_MESSAGE(@PSCANNER_MESSAGE(pOvlp)^.FOverlapped);

全功能

function ScannerWorker(Context:PSCANNER_THREAD_CONTEXT): DWORD;
var
notification: PSCANNER_NOTIFICATION;
replyMessage: pSCANNER_REPLY_MESSAGE;
msg: pSCANNER_MESSAGE;
pOvlp:POverlapped;
cResult: BOOL;
outSize: cardinal;
hr: HRESULT;
key: cardinal;
sText: AnsiString;
begin

while True do begin
    (**)
    (*  Poll for messages from the filter component to scan.*)
    (**)

    cResult:= GetQueuedCompletionStatus(completion,outSize,key,pOvlp,INFINITE);
    Msg := PSCANNER_MESSAGE(@PSCANNER_MESSAGE(pOvlp)^.FOverlapped);
    If Not(cResult) Then
      begin
     // HR := HRESULT_FROM_WIN32(GetLastError());
      ShowMessage('Msg Error');
      Break;
    end;

    notification:= @msg.Notification;
   // __analysis_assume(notification.BytesToScan<=SCANNER_READ_BUFFER_SIZE);
    //cResult:= ScanBuffer(@notification^.Contents, notification^.BytesToScan);
    //replyMessage.ReplyHeader.Status:= 0;
    replyMessage.ReplyHeader.MessageId:= msg.MessageHeader.MessageId;
    replyMessage.Reply.SafeToOpen:=True;
    //WriteLN('Replying message, SafeToOpen: %d'#13#10'',replyMessage.Reply.SafeToOpen);
    hr:= FilterReplyMessage(hport,@replyMessage,sizeof(replyMessage));
    If Not(hr=s_ok) Then
      begin
     // HR := HRESULT_FROM_WIN32(GetLastError());
      ShowMessage('Msg SError');
    end;
     SetString(sText, notification.Contents, 1024);
      frmReceiver.Memo1.Lines.Add('Ok '+sText);

      HR := FilterGetMessage(hport,@Msg^.MessageHeader,DWORD(@PSCANNER_MESSAGE(0)^.FOverlapped),@Msg^.FOverlapped);
    If HR = (ERROR_IO_PENDING) Then Break;

end;
    result:= hr;
end;