package bart provides a Balanced-Routing-Table (BART).

BART is balanced in terms of memory consumption versus lookup time.

The lookup time is by a factor of ~2 slower on average as the routing algorithms ART, SMART, CPE, ... but reduces the memory consumption by an order of magnitude in comparison.

BART is a multibit-trie, using the baseIndex function from the ART algorithm to build the complete binary prefix tree (CBT) for each stride.

The second key factor is popcount level compression and backtracking along the CBT prefix tree in O(k).

The CBT is implemented as a bitvector, backtracking is just a matter of fast cache friendly bitmask operations.

Due to the cache locality of the popcount compressed CBT, the backtracking algorithm is as fast as possible.

... still under development, but the library is ready to use.

  import "github.com/gaissmai/bart"
  
  type Table[V any] struct {
  	// Has unexported fields.
  }
      Table is an IPv4 and IPv6 routing table with payload V. The zero value is
      ready to use.
  
  func (t *Table[V]) Insert(pfx netip.Prefix, val V)
  func (t *Table[V]) Delete(pfx netip.Prefix)
  func (t *Table[V]) Union(o *Table[V])
  func (t *Table[V]) Clone() *Table[V]
  
  func (t *Table[V]) Get(ip netip.Addr) (val V, ok bool)
  func (t *Table[V]) Lookup(ip netip.Addr) (lpm netip.Prefix, val V, ok bool)
  func (t *Table[V]) LookupShortest(ip netip.Addr) (spm netip.Prefix, val V, ok bool)

  func (t *Table[V]) Overlaps(o *Table[V]) bool
  func (t *Table[V]) OverlapsPrefix(pfx netip.Prefix) bool
  
  func (t *Table[V]) String() string
  func (t *Table[V]) Fprint(w io.Writer) error
  func (t *Table[V]) MarshalText() ([]byte, error)
  func (t *Table[V]) MarshalJSON() ([]byte, error)

  func (t *Table[V]) DumpList(is4 bool) []DumpListNode[V]

Please see the extensive benchmarks comparing bart with other IP routing table implementations.

Please open an issue for discussion before sending a pull request.

Credits for many inspirations go to the clever guys at tailscale, to Daniel Lemire for the super-fast bitset package and to Donald E. Knuth for the ART routing algorithm and all the rest of his Art and for keeping important algorithms in the public domain!

MIT