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Adding Progress Bar To This Code...

Posted on 2003-11-04
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Last Modified: 2010-04-05
Hello,

How can I add a 'ProgressBar' to this downloader code,
http://www.scalabium.com/faq/dct0116.htm

Thx, Karamja
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Question by:Karamja
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6 Comments
 
LVL 6

Expert Comment

by:GloomyFriar
ID: 9680693
Are you sure that hte code work properly?
As I see It'll write at beginning of file something like this:

Tue Nov 04 20:38:48 2003 HTTP/1.1 200 OK
Tue Nov 04 20:38:48 2003 Date: Tue, 04 Nov 2003 18:43:05 GMT
Tue Nov 04 20:38:48 2003 Server: Apache
Tue Nov 04 20:38:48 2003 Last-Modified: Tue, 29 Jul 2003 11:37:46 GMT
Tue Nov 04 20:38:48 2003 ETag: "102db32-d343-3f265c8a"
Tue Nov 04 20:38:48 2003 Accept-Ranges: bytes
Tue Nov 04 20:38:48 2003 Content-Length: 54083
Tue Nov 04 20:38:48 2003 Connection: close
Tue Nov 04 20:38:48 2003 Content-Type: application/zip

By the way 'Content-Length' is what you are looking for - total length of the file.
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Author Comment

by:Karamja
ID: 9680913
The code does work, How would I use 'Content-Length'?
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LVL 26

Accepted Solution

by:
EddieShipman earned 375 total points
ID: 9682209
I found this post by Paul Gertzen to be more capable of adding a Progressbar...But I used a TGuage instead...

function TForm1.GetHTTP(URL: String; Stream: TMemoryStream;
                        TimeOut: Integer): Boolean;
var CS : TClientSocket;
    S : TWinSocketStream;
    ReceiveHeaders : TStringList;
    SendBufferStr : String;
    SendBuffer, ReceiveBuffer, HeaderBuffer : array[0..8192] Of Char;
    i, p : Integer;
    Domain, Page, PostStr : String;
    BytesRead, ContentLength, BytesSent, TotalBytesRead : Integer;
begin
  try
    // clear the stream
    Stream.Clear;
    CS := TClientSocket.Create(nil);
    ReceiveHeaders := TStringList.Create;
    try
      // remove http:// (if it is supplied) and split domain and page
      if Uppercase(Copy(URL,1,7)) = 'HTTP://' Then
       Delete(URL, 1, 7);
      p := Pos('/', URL);
      if p <> 0 Then
      begin
         Domain := Copy(URL,1,p-1);
         Page := Copy(URL,p, Length(URL));
      end
      else
      begin
         Domain := URL;
         Page := '/';
      end;
      CS.Host := Domain;
      CS.ClientType := ctBlocking;
      CS.Port := 80;
       SendBufferStr := 'GET '+Page+' HTTP/1.0'#13#10+
                        'Host: '+Domain+#13#10#13#10;
      FillChar(SendBuffer, SizeOf(SendBuffer), 0);
      FillChar(ReceiveBuffer, SizeOf(ReceiveBuffer), 0);
      FillChar(HeaderBuffer, SizeOf(HeaderBuffer), 0);
      StrPCopy(SendBuffer, SendBufferStr);
      CS.Open;
      S := TWinSocketStream.Create(CS.Socket, TimeOut);
      try
       // Send the request
       BytesSent := 0;
       while CS.Socket.Connected and (BytesSent < Length(SendBufferStr)) do
        BytesSent := BytesSent + S.Write(SendBuffer[BytesSent],
                                         Length(SendBufferStr)-BytesSent);
       // read headers, they will fit in first received packet (note: we may
       // get some of the data
       // too so we must look for double cr/lf which splits header from data
       BytesRead := S.Read(ReceiveBuffer, SizeOf(ReceiveBuffer));
       // Search for double cr/lf in received data
       for i := 0 to BytesRead do
       begin
         if (i < BytesRead - 3) and
            (ReceiveBuffer[i] = #13) and
            (ReceiveBuffer[i+1] = #10) and
            (ReceiveBuffer[i+2] = #13) and
            (ReceiveBuffer[i+3] = #10) then
         begin
           // move data into headerbuffer for easy conversion into stringlist
           Move(ReceiveBuffer[0], HeaderBuffer[0], i);
           ReceiveHeaders.Text := String(ReceiveBuffer);
           // write remaining data to stream (excl double cr/lf)
           Stream.Write(ReceiveBuffer[i+4], BytesRead-(i+4));
           Break;
         end;
       end;
       // setup totalbytesread (we may have read some into stream already)
       TotalBytesRead := Stream.Size;
       // now check for contentlength header
       BytesRead := 0;
       ContentLength := 0;
       for i := 0 to ReceiveHeaders.Count - 1 do
       begin
         if Copy(Uppercase(ReceiveHeaders[i]), 1, 16) = 'CONTENT-LENGTH: ' then
         begin
           ContentLength := StrToInt(Copy(Uppercase(ReceiveHeaders[i]), 17,
                                           Length(ReceiveHeaders[i])));
           Break;
         end;
       end;
       Gauge1.MaxValue := ContentLength;
       // if contentlength header does not exist then we will read until
       // receivelength = 0
       if ContentLength = 0 then
        repeat
          BytesRead := S.Read(ReceiveBuffer, SizeOf(ReceiveBuffer));
          Gauge1.Progress := BytesRead;
          Stream.Write(ReceiveBuffer, BytesRead);
        until (not CS.Socket.Connected) or (BytesRead = 0)
       else
        while CS.Socket.Connected and (TotalBytesRead < ContentLength) do
         begin
           BytesRead := S.Read(ReceiveBuffer, SizeOf(ReceiveBuffer));
           Gauge1.Progress := BytesRead;
           TotalBytesRead := TotalBytesRead + BytesRead;
           Stream.Write(ReceiveBuffer, BytesRead);
         end;
         Gauge1.Progress := TotalBytesRead;
       Result := True;
       CS.Close;
      finally
       s.Destroy;
      end;
    finally
      CS.Destroy;
      ReceiveHeaders.Destroy;
    end;
  except
   Result := False;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  Stream : TMemoryStream;
begin
  Stream := TMemoryStream.Create;
  try
    // if you don't need to post variables then just pass nil instead of post
    // you can pass variables on the url at any time
    if not GetHTTP('http://www-tcsn.experts-exchange.com/images/logo.gif', Stream, 10000) then
      ShowMessage('Download unsuccessful')
    else
      Stream.SaveToFile('c:\eelogo.gif');
  finally
    Stream.Destroy;
  end;
end;


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LVL 6

Expert Comment

by:GloomyFriar
ID: 9685614
>The code does work
Here it is how it work:

HTTP/1.1 200 OK
Date: Wed, 05 Nov 2003 10:12:37 GMT
Server: Apache/1.3.28 (Unix) mod_auth_passthrough/1.6 mod_log_bytes/1.2 mod_bwlimited/1.0 PHP/4.3.2 FrontPage/5.0.2.2634 mod_ssl/2.8.15 OpenSSL/0.9.6b
Last-Modified: Mon, 17 Mar 2003 12:57:53 GMT
ETag: "2b40c5-2ca9-3e75c651"
Accept-Ranges: bytes
Content-Length: 11433
Content-Type: text/html
Connection: Close

<html>

<head>
<meta http-equiv="Content-Type"
content="text/html; charset=iso-8859-1">


'Real' page text begins from <html>. The lines before it - it's the header.
But the code puts the header in destination file. It's wrong!
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LVL 6

Expert Comment

by:GloomyFriar
ID: 9685655
So you need to extract the header firstly.
Then extract the number after 'Content-Length' - it's the full file size.
Assign the number to Max of gauge or progressbar - whatever you want (Min := 1, Position := 0).
After reading the next portion of file data add its size to Position. if intReturnCode > 0 then Position := Position + _size;

By the way, it may be so that 'Content-Length' does not appear. In such a case you cannot to show 'real'  progress.
             
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LVL 26

Expert Comment

by:EddieShipman
ID: 9686068
[quote]But the code puts the header in destination file. It's wrong![/quote]

It was not part of the requirement stated to strip out the header. It would
take only a few small changes to accomplish this with the code I posted.
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