feat: Waku v2 bridge

Issue #12610

vendor/github.com/anacrolix/torrent/internal/limiter/limiter.go

@@ -0,0 +1,64 @@
+package limiter
+
+import "sync"
+
+type Key = interface{}
+
+// Manages resources with a limited number of concurrent slots for use for each key.
+type Instance struct {
+	SlotsPerKey int
+
+	mu sync.Mutex
+	// Limits concurrent use of a resource. Push into the channel to use a slot, and receive to free
+	// up a slot.
+	active map[Key]*activeValueType
+}
+
+type activeValueType struct {
+	ch   chan struct{}
+	refs int
+}
+
+type ActiveValueRef struct {
+	v *activeValueType
+	k Key
+	i *Instance
+}
+
+// Returns the limiting channel. Send to it to obtain a slot, and receive to release the slot.
+func (me ActiveValueRef) C() chan struct{} {
+	return me.v.ch
+}
+
+// Drop the reference to a key, this allows keys to be reclaimed when they're no longer in use.
+func (me ActiveValueRef) Drop() {
+	me.i.mu.Lock()
+	defer me.i.mu.Unlock()
+	me.v.refs--
+	if me.v.refs == 0 {
+		delete(me.i.active, me.k)
+	}
+}
+
+// Get a reference to the values for a key. You should make sure to call Drop exactly once on the
+// returned value when done.
+func (i *Instance) GetRef(key Key) ActiveValueRef {
+	i.mu.Lock()
+	defer i.mu.Unlock()
+	if i.active == nil {
+		i.active = make(map[Key]*activeValueType)
+	}
+	v, ok := i.active[key]
+	if !ok {
+		v = &activeValueType{
+			ch: make(chan struct{}, i.SlotsPerKey),
+		}
+		i.active[key] = v
+	}
+	v.refs++
+	return ActiveValueRef{
+		v: v,
+		k: key,
+		i: i,
+	}
+}