C++ ifstream 读取文件大小和读取所有内容

ifstream ifs(file_name, std::ios::binary|std::ios::in);
if (ifs.is_open())
{
    ifs.seekg(0,std::ios::end);
    int len = ifs.tellg();
    ifs.seekg(0,std::ios::beg);
			
    char *buff = new char[len];
			
    ifs.read(buff , len);
    delete []buff;
}