Use this function to read 64 bits of big-endian data from an SDL_RWops and return in native format.
Uint64 SDL_ReadBE64(SDL_RWops * src);
the stream from which to read data
Returns 64 bits of data in the native byte order of the platform.
SDL byteswaps the data only if necessary, so the data returned will be in the native byte order.
This function is available since SDL 2.0.0.