uses XceedStreamingCompressionLib_TLB 

var
  xComp : TXceedStreamingCompression; 
  xBZip2 : DXceedBZip2CompressionFormat; 
  vaBytesRead : OleVariant; 
begin
  xComp := TXceedStreamingCompression.Create( self ); 
  xComp.License( 'your license key' ); 

  xBZip2 := CoXceedBZip2CompressionFormat.Create();  

  xComp.CompressionFormat := xBZip2;  

  try 
    xComp.ReadFile( 'c:\temp\source.txt', 0, 0, cfpCompress, TRUE, vaBytesRead ); 
    ShowMessage( 'Compression successful!' ); 
  except 
  on xErr : Exception do 
    ShowMessage( xErr.Message ); 
  end; 

  xComp.Free(); 

end;