System.Net.httpclient - THTTPClient z XE8

implementation
uses
  System.Threading,
  System.Net.httpclient;

procedure TForm9.AllocateFile(const sUrl, sFile: string; var iSize: Integer);
var
  oClient: THTTPClient;
  oResponse: IHTTPResponse;
  oFile : TFileStream;
begin
  oClient := THTTPClient.Create;
  try
    if not oClient.CheckDownloadResume(sUrl) then
    begin
      ShowMessage('Not support resume, parallel demo abort, use Get method'); // download direct via oClient.Get
      Abort;
    end;
    oResponse := oClient.Head(sUrl);
    oFile := TFileStream.Create(sFile, fmCreate);
    try
      iSize := oResponse.ContentLength;
      oFile.Size := iSize;
    finally
      oFile.Free;
    end;
  finally
    oClient.Free;
  end;
end;

procedure TForm9.Button1Click(Sender: TObject);
var
  iSize: Integer;
const
  csUrl = 'http://vesta.informatik.rwth-aachen.de/ftp/pub/comp/Linux/knoppix/knoppix-cd/KNOPPIX_V7.2.0bootonly-2013-06-16-EN.iso';
  csFile = 'c:\temp\temp.iso';
  ciSlice = 10;
begin
  AllocateFile(csUrl, csFile, iSize);

  TParallel.&For(0, ciSlice - 1,
     procedure (iIndex: Integer)
     var
       iPartSize, iStart, iEnd: Int64;
       oClient: THTTPClient;
       oFile: TFileStream;
       LResponse: IHTTPResponse;
     begin
       // zjisti jaký blok mám vlastně stahovat
       iPartSize := iSize div ciSlice;
       iStart := iPartSize * iIndex;
       iEnd := iPartSize * (iIndex + 1);
       if iIndex = ciSlice - 1 then  // pro poslední blok malá korekce
         iEnd := iSize;

        oClient := THTTPClient.Create;
        try
          oFile := TFileStream.Create(csFile, fmOpenWrite or fmShareDenyNone);
          try
            oFile.Seek(iStart, soBeginning); // nastav se v souboru na místo
            LResponse := oClient.GetRange(csUrl, iStart, iEnd - 1, oFile); // get it!
          finally
            oFile.Free;
          end;
        finally
          oClient.Free;
        end;
     end
  );
  ShowMessage('Downloaded!');
end;

end.