使用FILE_FLAG_NO_BUFFERING打开时,为什么写入文件会失败？

Question

我试图衡量效果FILE_FLAG_WRITE_THROUGH和FILE_FLAG_NO_BUFFERING对写入的文件中的序列,如要求另一个问题.但我发现我不能用FILE_FLAG_NO_BUFFERINGset 写一个文件.

当我使用它时,Delphi返回EWriteError消息stream read error.

使用的代码如下:

procedure TForm1.btn1Click(Sender: TObject);
var
  fsFSArquivoAAC: TFileStream;
  L, lastErr: Cardinal;
  R: WideString;
  hn: THandle;
begin
  hn := Windows.CreateFile( PChar('TesteAAC.AAC2'),
              GENERIC_READ or GENERIC_WRITE,
              FILE_SHARE_READ or FILE_SHARE_WRITE, nil, CREATE_ALWAYS,
              FILE_ATTRIBUTE_NORMAL  or FILE_FLAG_WRITE_THROUGH or FILE_FLAG_NO_BUFFERING, 0);

  lastErr := GetLastError();

  if (lastErr <> ERROR_SUCCESS) then
  begin
    if (lastErr <> ERROR_ALREADY_EXISTS ) then
    begin
      MessageDlg('Whoops, something went wrong with CreateFile!',
                  mtError, [mbOK], 0);
    end
    else
    begin
      SetLastError(ERROR_SUCCESS);
    end;

  end;

  fsFSArquivoAAC := TFileStream.Create( hn );

  try
    R := 'BatatinhaquandoNasceEspalharamapelochao';

    // write WideString
    L := Length(R);
    fsFSArquivoAAC.WriteBuffer(L, SizeOf(integer));
    if L > 0 then
      fsFSArquivoAAC.WriteBuffer(R[1], L * SizeOf(WideChar));
  finally
    fsFSArquivoAAC.Free;
  end;

如果您评论FILE_FLAG_NO_BUFFERING代码有效.为什么？

Answer 1

如果您使用FILE_FLAG_WRITE_THROUGH并且在内存中对齐缓冲区FILE_FLAG_NO_BUFFERING有各种要求,请将写入与磁盘扇区对齐,并且(我认为)以扇区大小的倍数进行写入.你似乎没有做任何这些事情.