Like a FAT format but with relative indices. It should be pretty trivial pointer arithmetic.

Edit: bytell_hash_map.cpp:464 bytell_hash_map.cpp:58

Apparently there's one extra layer of indirection via a lookup table to get the final offset.

So basically the metadata byte is a bitfield union of + status flag + status code (not sure it's actually required) or offset enum. The offset enum then indexes into a look up table, the result of which is the relative offset from the current index.