make lpm even faster

internal/bitset/bitset.go

@@ -90,6 +90,16 @@ func (b BitSet) Compact() BitSet {
 	return nil
 }
 
+// FirstSet returns the first bit set along with an ok code.
+func (b BitSet) FirstSet() (uint, bool) {
+	for x, word := range b {
+		if word != 0 {
+			return uint(x<<6 + bits.TrailingZeros64(word)), true
+		}
+	}
+	return 0, false
+}
+
 // NextSet returns the next bit set from the specified index,
 // including possibly the current index along with an ok code.
 func (b BitSet) NextSet(i uint) (uint, bool) {

internal/sparse/array.go

@@ -32,7 +32,7 @@ func (s *Array[T]) rank(i uint) int {
 // If the value already exists, overwrite it with val and return true.
 func (s *Array[T]) InsertAt(i uint, val T) (exists bool) {
 	// slot exists, overwrite val
-	if s.Test(i) {
+	if s.Len() != 0 && s.Test(i) {
 		s.Items[s.rank(i)] = val
 
 		return true
@@ -48,7 +48,7 @@ func (s *Array[T]) InsertAt(i uint, val T) (exists bool) {
 // DeleteAt, delete a value at i from the sparse array.
 func (s *Array[T]) DeleteAt(i uint) (T, bool) {
 	var zero T
-	if !s.Test(i) {
+	if s.Len() == 0 || !s.Test(i) {
 		return zero, false
 	}
 
@@ -68,7 +68,7 @@ func (s *Array[T]) DeleteAt(i uint) (T, bool) {
 func (s *Array[T]) Get(i uint) (val T, ok bool) {
 	var zero T
 
-	if s.Test(i) {
+	if s.Len() != 0 && s.Test(i) {
 		return s.Items[s.rank(i)], true
 	}
 

node.go

@@ -55,7 +55,7 @@ func (n *node[V]) isEmpty() bool {
 // max steps in backtracking is the stride length.
 func (n *node[V]) lpm(idx uint) (baseIdx uint, val V, ok bool) {
 	// shortcut optimization
-	minIdx, ok := n.prefixes.NextSet(0)
+	minIdx, ok := n.prefixes.FirstSet()
 	if !ok {
 		return 0, val, false
 	}
@@ -75,7 +75,7 @@ func (n *node[V]) lpm(idx uint) (baseIdx uint, val V, ok bool) {
 // lpmTest for faster lpm tests without value returns
 func (n *node[V]) lpmTest(idx uint) bool {
 	// shortcut optimization
-	minIdx, ok := n.prefixes.NextSet(0)
+	minIdx, ok := n.prefixes.FirstSet()
 	if !ok {
 		return false
 	}

table.go

@@ -581,7 +581,7 @@ func (t *Table[V]) OverlapsPrefix(pfx netip.Prefix) bool {
 	var ok bool
 	for _, octet := range octets[:lastOctetIdx] {
 		// test if any route overlaps prefix´ so far
-		if n.lpmTest(hostIndex(octet)) {
+		if n.prefixes.Len() != 0 && n.lpmTest(hostIndex(octet)) {
 			return true
 		}