根据文件路径获取剩余磁盘空间

function GetFreeSize(filePath:String):Int64;
var
  FreeBytesAvailableToCaller : TLargeInteger;
  FreeSize : TLargeInteger;
  TotalSize : TLargeInteger;
  Drive : string;
begin
  Drive := ExtractFileDrive(filePath);
  GetDiskFreeSpaceEx(PChar(Drive),
                      FreeBytesAvailableToCaller,
                      Totalsize,
                      @FreeSize );
  Result := FreeSize;
end;