https://github.com/gaissmai/bart
The Balanced Routing Table is an adaptation of D. Knuth's ART algorithm and requires significantly less memory and has an even better lookup speed.
https://github.com/gaissmai/bart
art cidr cidr-lookup cidr-overlap ip ip-blacklist ip-lookup ip-routing ip-subnet ip-whitelist ipv6 longest-prefix-match
Last synced: 4 months ago
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The Balanced Routing Table is an adaptation of D. Knuth's ART algorithm and requires significantly less memory and has an even better lookup speed.
- Host: GitHub
- URL: https://github.com/gaissmai/bart
- Owner: gaissmai
- License: mit
- Created: 2024-01-28T16:41:09.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2025-06-15T21:40:55.000Z (4 months ago)
- Last Synced: 2025-06-15T23:18:56.446Z (4 months ago)
- Topics: art, cidr, cidr-lookup, cidr-overlap, ip, ip-blacklist, ip-lookup, ip-routing, ip-subnet, ip-whitelist, ipv6, longest-prefix-match
- Language: Go
- Homepage:
- Size: 4.18 MB
- Stars: 72
- Watchers: 4
- Forks: 7
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
Awesome Lists containing this project
- awesome-go - gaissmai/bart
- awesome-go - gaissmai/bart
README
# package bart
[](https://pkg.go.dev/github.com/gaissmai/bart#section-documentation)
[](https://github.com/avelino/awesome-go)
[](https://github.com/gaissmai/bart/actions/workflows/go.yml)
[](https://coveralls.io/github/gaissmai/bart)
[](https://goreportcard.com/report/github.com/gaissmai/bart)
[](https://opensource.org/licenses/MIT)
[](https://stand-with-ukraine.pp.ua)
## Overview
`package bart` provides a Balanced-Routing-Table (BART).
BART is balanced in terms of memory usage and lookup time for the longest-prefix
match.
BART is a multibit-trie with fixed stride length of 8 bits, using a fast mapping
function (taken from the ART algorithm) to map the 256 prefixes in each level
node to form a complete-binary-tree.
This complete binary tree is implemented with popcount compressed sparse arrays
together with path compression. This reduces storage consumption by almost two
orders of magnitude in comparison to ART, with even better lookup times for the
longest prefix match.
The BART algorithm is based on fixed size bit vectors and precalculated
lookup tables. The lookup is performed entirely by fast,
cache-friendly bitmask operations, which in modern CPUs are performed
by advanced bit manipulation instruction sets (POPCNT, LZCNT, TZCNT, ...).
The algorithm was specially developed so that it can always work with a fixed
length of 256 bits. This means that the bitset fit very well in a cache line and
that loops over the bitset in hot paths can be accelerated by loop unrolling, e.g.
```go
func (b *BitSet256) popcnt() (cnt int) {
cnt += bits.OnesCount64(b[0])
cnt += bits.OnesCount64(b[1])
cnt += bits.OnesCount64(b[2])
cnt += bits.OnesCount64(b[3])
return
}
```
The BART algorithm is also excellent for determining whether two tables
contain overlapping IP addresses, just in a few nanoseconds.
A `bart.Lite` wrapper is included, this is ideal for simple IP
ACLs (access-control-lists) with plain true/false results and no payload.
## Example
```golang
func ExampleLite_Contains() {
lite := new(bart.Lite)
// Insert some prefixes
prefixes := []string{
"192.168.0.0/16",
"192.168.1.0/24",
"2001:7c0:3100::/40",
"2001:7c0:3100:1::/64",
"fc00::/7",
}
for _, s := range prefixes {
pfx := netip.MustParsePrefix(s)
lite.Insert(pfx)
}
// Test some IP addresses for black/whitelist containment
ips := []string{
"192.168.1.100", // must match
"192.168.2.1", // must match
"2001:7c0:3100:1::1", // must match
"2001:7c0:3100:2::1", // must match
"fc00::1", // must match
//
"172.16.0.1", // must NOT match
"2003:dead:beef::1", // must NOT match
}
for _, s := range ips {
ip := netip.MustParseAddr(s)
ok := lite.Contains(ip)
fmt.Printf("%-20s is contained: %t\n", ip, ok)
}
// Output:
// 192.168.1.100 is contained: true
// 192.168.2.1 is contained: true
// 2001:7c0:3100:1::1 is contained: true
// 2001:7c0:3100:2::1 is contained: true
// fc00::1 is contained: true
// 172.16.0.1 is contained: false
// 2003:dead:beef::1 is contained: false
}
```
## API
From release v0.18.x on, bart requires at least go1.23, the `iter.Seq2[netip.Prefix, V]` types for iterators
are used. The lock-free versions of insert, update and delete are added, but still experimental.
```golang
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.
// The Table is safe for concurrent readers but not for concurrent readers
// and/or writers. Either the update operations must be protected by an
// external lock mechanism or the various ...Persist functions must be used
// which return a modified routing table by leaving the original unchanged
// A Table must not be copied by value.
func (t *Table[V]) Contains(ip netip.Addr) bool
func (t *Table[V]) Lookup(ip netip.Addr) (val V, ok bool)
func (t *Table[V]) LookupPrefix(pfx netip.Prefix) (val V, ok bool)
func (t *Table[V]) LookupPrefixLPM(pfx netip.Prefix) (lpm netip.Prefix, val V, ok bool)
func (t *Table[V]) Insert(pfx netip.Prefix, val V)
func (t *Table[V]) Delete(pfx netip.Prefix)
func (t *Table[V]) Update(pfx netip.Prefix, cb func(val V, ok bool) V) (newVal V)
func (t *Table[V]) InsertPersist(pfx netip.Prefix, val V) *Table[V]
func (t *Table[V]) DeletePersist(pfx netip.Prefix) *Table[V]
func (t *Table[V]) UpdatePersist(pfx netip.Prefix, cb func(val V, ok bool) V) (pt *Table[V], newVal V)
func (t *Table[V]) Get(pfx netip.Prefix) (val V, ok bool)
func (t *Table[V]) GetAndDelete(pfx netip.Prefix) (val V, ok bool)
func (t *Table[V]) GetAndDeletePersist(pfx netip.Prefix) (pt *Table[V], val V, ok bool)
func (t *Table[V]) Union(o *Table[V])
func (t *Table[V]) Clone() *Table[V]
func (t *Table[V]) OverlapsPrefix(pfx netip.Prefix) bool
func (t *Table[V]) Overlaps(o *Table[V]) bool
func (t *Table[V]) Overlaps4(o *Table[V]) bool
func (t *Table[V]) Overlaps6(o *Table[V]) bool
func (t *Table[V]) Subnets(pfx netip.Prefix) iter.Seq2[netip.Prefix, V]
func (t *Table[V]) Supernets(pfx netip.Prefix) iter.Seq2[netip.Prefix, V]
func (t *Table[V]) All() iter.Seq2[netip.Prefix, V]
func (t *Table[V]) All4() iter.Seq2[netip.Prefix, V]
func (t *Table[V]) All6() iter.Seq2[netip.Prefix, V]
func (t *Table[V]) AllSorted() iter.Seq2[netip.Prefix, V]
func (t *Table[V]) AllSorted4() iter.Seq2[netip.Prefix, V]
func (t *Table[V]) AllSorted6() iter.Seq2[netip.Prefix, V]
func (t *Table[V]) Size() int
func (t *Table[V]) Size4() int
func (t *Table[V]) Size6() int
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]) DumpList4() []DumpListNode[V]
func (t *Table[V]) DumpList6() []DumpListNode[V]
```
## benchmarks
Please see the extensive [benchmarks](https://github.com/gaissmai/iprbench) comparing `bart` with other IP routing table implementations.
Just a teaser, `Contains` and `Lookup` against the Tier1 full Internet routing table with
random IP address probes:
```
goos: linux
goarch: amd64
pkg: github.com/gaissmai/bart
cpu: Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
BenchmarkFullMatch4/Contains 129756907 8.409 ns/op
BenchmarkFullMatch6/Contains 96855786 11.72 ns/op
BenchmarkFullMiss4/Contains 56269990 18.58 ns/op
BenchmarkFullMiss6/Contains 131779195 10.08 ns/op
goos: linux
goarch: amd64
pkg: github.com/gaissmai/bart
cpu: Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
BenchmarkFullMatch4/Lookup 47039798 24.44 ns/op
BenchmarkFullMatch6/Lookup 81769753 13.61 ns/op
BenchmarkFullMiss4/Lookup 51986374 22.72 ns/op
BenchmarkFullMiss6/Lookup 100000000 11.47 ns/op
```
## Compatibility Guarantees
The package is currently released as a pre-v1 version, which gives the author the freedom to break
backward compatibility to help improve the API as he learns which initial design decisions would need
to be revisited to better support the use cases that the library solves for.
These occurrences are expected to be rare in frequency and the API is already quite stable.
## CONTRIBUTION
Please open an issue for discussion before sending a pull request.
## CREDIT
Standing on the shoulders of giants.
Credits for many inspirations go to
- the clever guys at tailscale,
- to Daniel Lemire for his inspiring blog,
- to Donald E. Knuth for the **ART** routing algorithm and
- to Yoichi Hariguchi who deciphered it for us mere mortals
And last but not least to the Go team who do a wonderful job!
## LICENSE
MIT