Its similar to the python one that was released by cheaterskeeter. It accesses the same sof1maps repository. But its not python based and might be less confusing to understand how it works (more open-source). I am going to use this one for windows, so I thought I'd share.
For the curious minded : it uses the sp_cl_info_map command repeatedly during connect to get the mapname as early as possible. Then it saves the mapname to a small file at sofplus/data/http_tmp, this file is read by a windows batch/cmd script which then calls curl.exe (which is provided) or can be downloaded from official curl website and extracted. The file that is downloaded is a zip file, so its then extracted also by the batch/cmd script, then deleted. If the mapname.bsp already exists in your directories it doesn't download. (sofplus handles that with sp_sc_file_find).
Latest version:
