Thanks @3096 for github.com/3096/effective-guacamole -- used to dump the hash list.
Refine the FileHashRegion struct; in the savefile it's just:
u32 hash
byte[length] data
we can compute start offset (= hash offset + 4) rather than storing an extra int, simplifies things so that we can just copypaste from guac into a hash,len definition list :D