BlockRead和BlockWrite读写文件

var  FromF, ToF: file;  NumRead, NumWritten: Integer;  Buf: array[1..2048] of Char; begin  if OpenDialog1.Execute then begin    AssignFile(FromF, OpenDialog1.FileName);    Reset(FromF, 1); { Record size = 1 }    if SaveDialog1.Execute then { Display Save dialog box}    begin      AssignFile(ToF, SaveDialog1.FileName); { Open output file }      Rewrite(ToF, 1); { Record size = 1 }      Canvas.TextOut(10, 10, 'Copying ' + IntToStr(FileSize(FromF)) + ' bytes...');      repeat        BlockRead(FromF, Buf, SizeOf(Buf), NumRead);        BlockWrite(ToF, Buf, NumRead, NumWritten);     until (NumRead = 0) or (NumWritten <> NumRead);     CloseFile(FromF);     CloseFile(ToF);   end; end; end;