为什么GetDiskFreeSpaceEx(nil,userFreeBytes,totalBytes, @freeBytes) 要加个@?

Question

GetDiskFreeSpaceEx: function (Directory: PChar; var FreeAvailable,
    TotalSpace: TLargeInteger; TotalFree: PLargeInteger): Bool stdcall = nil;
你打开SysUtils.pas,就会发现如上的定义
TotalFree: PLargeInteger
PLargeInteger = ^TLargeInteger;
TLargeInteger = Int64;
你的freebytes是int64,所以传个函数用@freebytes

Answer 1

您好，请问您的这个Delphi式的定义是哪儿来得GetDiskFreeSpaceEx: function (Directory: PChar; var FreeAvailable,TotalSpace: TLargeInteger; TotalFree: PLargeInteger): Bool stdcall = nil;这是msdn的定义
BOOL GetDiskFreeSpaceEx(
  LPCTSTR lpDirectoryName,                 // pointer to the directory name
  PULARGE_INTEGER lpFreeBytesAvailableToCaller, // receives the number of bytes on
                                                // disk available to the caller
  PULARGE_INTEGER lpTotalNumberOfBytes,    // receives the number of bytes on disk
  PULARGE_INTEGER lpTotalNumberOfFreeBytes // receives the free bytes on disk
);//附我的源代码 
procedure TForm1.Button2Click(Sender: TObject);
var userFreeBytes,totalBytes,freeBytes:Int64;
begin
  if NOT GetDiskFreeSpaceEx(PChar(Edit1.Text),userFreeBytes,totalBytes,@freeBytes) then begin
    ShowMessage('操作失败');
    exit;
    end;
  Label3.Caption:='该驱动器总共容量'+Formatfloat('###,##0',totalBytes)+'字节'
    +#13+'该驱动器可用容量'+Formatfloat('###,##0',freeBytes)+'字节'
    +#13+'该驱动器可用用户容量'+Formatfloat('###,##0',userFreeBytes)+'字节';
end;您的定义是如何得知的呢，delphi中查不到呀，谢谢！

Answer 2

procedure TForm1.Button2Click(Sender: TObject);
var userFreeBytes,totalBytes,freeBytes:Int64;
begin
  if NOT GetDiskFreeSpaceEx(PChar(Edit1.Text),userFreeBytes,totalBytes,@freeBytes) then begin
    ShowMessage('操作失败');
    exit;
    end;
  Label3.Caption:='该驱动器总共容量'+Formatfloat('###,##0',totalBytes)+'字节'
    +#13+'该驱动器可用容量'+Formatfloat('###,##0',freeBytes)+'字节'
    +#13+'该驱动器可用用户容量'+Formatfloat('###,##0',userFreeBytes)+'字节';
end;