TODO

• [x] u32 keys and values, not u64
• [ ] bloom filters on disk
• [ ] writing "flush_every"'s default should depend on the default compression.
• [ ] read cache size configurable both for page cache and for uncompressed cache
• [ ] read cache size should be in bytes, not blocks
• [ ] range queries
• [ ] cache cannot be explicitly disabled in some places
• [ ] add length to encoded bits
• [x] mmap with no compression is already multi-threaded, but the API does not reflect that
• [x] zlib bounded and unbounded performs the same in benchmarks
• [ ] remove as much as possible unsafe and unwrap
• [ ] analyze all casts from u64 to usize
  • [ ] clippy actually has a lint for it in pedantic
• [x] multi-threading
• [x] compression is all over the place
• [ ] files and imports are all over the place, reorganize
• [x] fail if keys or values are too long (> u32_max)
• [x] byte keys
  • [x] also "memchr" is very slow, better to use offsets
• [ ] indexes as separate files in this case don't need to maintain in memory while writing