...find the size of a file?

最新推荐文章于 2023-05-22 13:38:14 发布

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本文介绍了使用Delphi实现获取文件大小的四种不同方法。这些方法包括使用CreateFile和GetFileSize函数、FindFirst和TSearchRec、FindFirstFile和TWin32FindData等API来获取文件的实际大小，并提供了示例代码。

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;