파일사이즈 알아내기 - in Delphi

1. 첫번째 방법

// returns file size in bytes or -1 if not found.
 function FileSize(fileName : wideString) : Int64;
 var
   sr : TSearchRec;
 begin
   if FindFirst(fileName, faAnyFile, sr ) = 0 then
      result := Int64(sr.FindData.nFileSizeHigh) shl Int64(32) + Int64(sr.FindData.nFileSizeLow)
   else
      result := -1;
 
   FindClose(sr) ;
 end;

2. 두번째 방법

function GetFileSize(AFileName: string; ASkip: boolean = false):
  Integer;
var
  f: file of Byte;
  size: Longint;
  flag: boolean;
begin
  flag := false;
  while not flag do
  begin
    Application.ProcessMessages;
    if FStopFlag then
      break;

    if FileExists(AFileName) then
    begin
      try
        size := 0;
        AssignFile(f, AFileName);
        reset(f);
        size := FileSize(f);
        CloseFile(f);
        flag := true;
      except
        on e:Exception do
        begin
          flag := ASkip;
          size := -1;
        end;
      end;
    end;
  end;
  result := size;
end;

flag 는 한번에 파일 사이즈를 못얻는 경우(파일이 오픈되었다가 close가 되지 않았을 경우 등)를 대비해 여러번 시행하기 위함임, while 문을 빼버려도 됨
3. 기타 다양한 방법들(취사 선택해서 쓰세요)

function Get_File_Size1(sFileToExamine: string; bInKBytes: Boolean): string;
{
 for some reason both methods of finding file size return
 a filesize that is slightly larger than what Windows File
 Explorer reports
}
var
  FileHandle: THandle;
  FileSize: LongWord;
  d1: Double;
  i1: Int64;
begin
  //a- Get file size
  FileHandle := CreateFile(PChar(sFileToExamine),
    GENERIC_READ,
    0, {exclusive}
    nil, {security}
    OPEN_EXISTING,
    FILE_ATTRIBUTE_NORMAL,
    0);
  FileSize   := GetFileSize(FileHandle, nil);
  Result     := IntToStr(FileSize);
  CloseHandle(FileHandle);
  //a- optionally report back in Kbytes
  if bInKbytes = True then
  begin
    if Length(Result) > 3 then
    begin
      Insert('.', Result, Length(Result) - 2);
      d1     := StrToFloat(Result);
      Result := IntToStr(round(d1)) + 'KB';
    end
    else
      Result := '1KB';
  end;
end;

{******************************************************************************
Thanks to Advanced Delphi Systems here's another method which works just as
well returning the same results
*******************************************************************************}
function Get_File_Size2(sFileToExamine: string; bInKBytes: Boolean): string;
var
  SearchRec: TSearchRec;
  sgPath: string;
  inRetval, I1: Integer;
begin
  sgPath := ExpandFileName(sFileToExamine);
  try
    inRetval := FindFirst(ExpandFileName(sFileToExamine), faAnyFile, SearchRec);
    if inRetval = 0 then
      I1 := SearchRec.Size
    else
      I1 := -1;
  finally
    SysUtils.FindClose(SearchRec);
  end;
  Result := IntToStr(I1);
end;



procedure TForm1.Button1Click(Sender: TObject);
begin
  if OpenDialog1.Execute then
    label1.Caption := Get_File_Size(Opendialog1.FileName, True);
end;

{*******************************************************************************}

function Get_File_Size3(const FileName: string): TULargeInteger;
// by nico
var
  Find: THandle;
  Data: TWin32FindData;
begin
  Result.QuadPart := -1;
  Find := FindFirstFile(PChar(FileName), Data);
  if (Find <> INVALID_HANDLE_VALUE) then
  begin
    Result.LowPart  := Data.nFileSizeLow;
    Result.HighPart := Data.nFileSizeHigh;
    Windows.FindClose(Find);
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  if (OpenDialog1.Execute) then
    ShowMessage(IntToStr(Get_File_Size3(OpenDialog1.FileName).QuadPart));
end;

{*******************************************************************************}

function Get_File_Size4(const S: string): Int64;
var
  FD: TWin32FindData;
  FH: THandle;
begin
  FH := FindFirstFile(PChar(S), FD);
  if FH = INVALID_HANDLE_VALUE then Result := 0
  else
    try
      Result := FD.nFileSizeHigh;
      Result := Result shl 32;
      Result := Result + FD.nFileSizeLow;
    finally
      CloseHandle(FH);
    end;
end;