[lNet] LHTTPClient - upload file. Buffer problem.

[Dibo]

Hi,

I'm trying to upload file with LHTTPClient. There is no demo in examples, so I'm doing the same way as with LTCPClient in this topic:
http://lazarus.firmos.at/index.php?topic=5146.0
But I have problem with buffer. Above example presents how to send large text, so we can easily offset sended chunk with String[Position] index, but how do this with file buffer? I'm not familiar with streams. This is fragment of my code:

Code: Pascal  [Select][+][-]

1. private
2.   { private declarations }
3.   FFile: TFileStream;
4.   FBuff: Pointer;
5.   FBuffReaded, FBuffSended: Integer;  
6.  
7. const
8.   ChunkSize: Longint = 8192; { copy in 8K chunks }
9.  
10. procedure TForm1.FormCreate(Sender: TObject);
11. begin
12.   FBuff := GetMem(ChunkSize);
13.   FBuffReaded := 0;
14.   FBuffSended := 0;
15. end;
16.  
17. procedure TForm1.FormDestroy(Sender: TObject);
18. begin
19.   Freemem(FBuff);
20.   FreeThenNil(FFile);
21. end;  
22.  
23. procedure TForm1.http_clientCanWrite(ASocket: TLHTTPClientSocket;
24.   var OutputEof: TWriteBlockStatus);
25. var
26.   n: Integer;
27. begin
28.   AddLog('Can write: ' + IntToStr(integer(OutputEof)));
29.  
30.   OutputEof := wsPendingData;
31.   repeat
32.     // Next chunk if whole sended
33.     if (FBuffSended>=FBuffReaded) and (FFile.Position<FFile.Size) then begin
34.       FBuffReaded := FFile.Read(FBuff^, ChunkSize);
35.       FBuffSended := 0;
36.       if (FBuffReaded=0) then Break;
37.     end;
38.    
39.     n := ASocket.Send(FBuff^, FBuffReaded);
40.     Inc(FBuffSended, n);
41.   // Loop until filled the OS send buffer or sended whole file
42.   until (n=0) or ((FBuffSended>=FBuffReaded) and (FFile.Position>=FFile.Size));
43.  
44.   if (FBuffSended>=FBuffReaded) and (FFile.Position>=FFile.Size) then
45.     OutputEof := wsDone;
46. end;
47.  

Line 39. How offset buffer (FBuff^) position to FBuffSended? Because in each loop cycle it send buffer from begining. Can I somehow strip first FBuffSended bytes from FBuff?

Regards and sorry for my English