It looks like the original names of the gsf source files were chosen to sway within the old FAT 8.3 filename restrictions. Why not get away from that and make the names easier to read? e.g.
gsf_indx.c -> gsf_index.c
gsf_indx.h -> gsf_index_priv.h // Private header not to be used externally
gsf_dec -> gsf_decode
gsf_enc -> gsf_encode
gsf_ft.h -> gsf_file_table_priv.h // Private header not to be used externally
gsf.h, gsf.c, and gsf_geo.c should probably not change.
It looks like the original names of the gsf source files were chosen to sway within the old FAT 8.3 filename restrictions. Why not get away from that and make the names easier to read? e.g.
gsf.h, gsf.c, and gsf_geo.c should probably not change.