如何將 BlobField 欄位的值存到 Stream?

var
  oldbstrm: TBlobStream;
begin
  oldbstrm := 
    TBlobStream.Create(    {always create it}
      TBlobField(DataModule2.TableTmp.FieldByName('Abstract')),
      bmRead);                         
  try
    buflength := oldbstrm.size;
    inc(buflength);
    buffer:= AllocMem(buflength);
    try
      oldbstrm.Read(buffer^,buflength);
      {buffer^ is now loaded}
    finally
      freeMem(buffer,buflength);
    end;
  finally
    oldbstrm.free;     {always free it}
end;