Unfortunately, the information you are asking about and in the form you are asking about is not available in the library (in its direct form).

You can query the (function) name of the decoder used by calling LibRaw:get_decoder_info() and create your own table indexed by the decoder name and containing the properties you need.

In practice, there are very few uncompressed formats now: photographers prefer to save space on flash cards and camera manufacturers follow this wish. Such uncompressed files may still present in archives, but it is hard to find an uncompressed file produced by modern camera (even if camera supports it, photographer will, most likely, switch to compressed format).

If you still want to handle uncompressed formats separately: they can be tiled/striped, so you'll need to add own code that interprets this correctly.

For uncompressed/not tiled data, data starts at libraw_internal_data.unpacker_data.data_offset and
data size is libraw_internal_data.unpacker_data.data_size
These fields are protected (in C++ terms), you may need to subclass LibRaw to access these fields.