feat: Waku v2 bridge

Issue #12610

vendor/github.com/anacrolix/missinggo/v2/iter/iterator.go

@@ -0,0 +1,69 @@
+package iter
+
+import "github.com/anacrolix/missinggo/slices"
+
+type Iterator interface {
+	// Advances to the next value. Returns false if there are no more values.
+	// Must be called before the first value.
+	Next() bool
+	// Returns the current value. Should panic when the iterator is in an
+	// invalid state.
+	Value() interface{}
+	// Ceases iteration prematurely. This should occur implicitly if Next
+	// returns false.
+	Stop()
+}
+
+func ToFunc(it Iterator) Func {
+	return func(cb Callback) {
+		defer it.Stop()
+		for it.Next() {
+			if !cb(it.Value()) {
+				break
+			}
+		}
+	}
+}
+
+type sliceIterator struct {
+	slice []interface{}
+	value interface{}
+	ok    bool
+}
+
+func (me *sliceIterator) Next() bool {
+	if len(me.slice) == 0 {
+		return false
+	}
+	me.value = me.slice[0]
+	me.slice = me.slice[1:]
+	me.ok = true
+	return true
+}
+
+func (me *sliceIterator) Value() interface{} {
+	if !me.ok {
+		panic("no value; call Next")
+	}
+	return me.value
+}
+
+func (me *sliceIterator) Stop() {}
+
+func Slice(a []interface{}) Iterator {
+	return &sliceIterator{
+		slice: a,
+	}
+}
+
+func StringIterator(a string) Iterator {
+	return Slice(slices.ToEmptyInterface(a))
+}
+
+func ToSlice(f Func) (ret []interface{}) {
+	f(func(v interface{}) bool {
+		ret = append(ret, v)
+		return true
+	})
+	return
+}