Storing assets as []byte requires every compiled-in asset to be copied
into writable memory at program startup. That currently takes up 1.6MB
per syncthing process. Strings stay in the RODATA section and should be
shared between processes running the same binary.
Successful LRU cache lookups modify the cache's recency list, so
RWMutex.RLock isn't enough protection.
Secondarily, multiple concurrent lookups with the same key should not
create separate rate limiters, so release the lock only when presence
of the key in the cache has been ascertained.
Co-authored-by: greatroar <@>
The previous implementation was very generic; its tests didn't cover the
actual alphabet for device IDs.
Benchmark results on amd64:
name old time/op new time/op delta
Luhnify-8 1.00µs ± 1% 0.28µs ± 4% -72.38% (p=0.000 n=9+10)
Unluhnify-8 992ns ± 2% 274ns ± 1% -72.39% (p=0.000 n=10+9)
greatroarandgreatroar <@>