Create internal DC package

mtglib/internal/dc/addr_set.go

@@ -0,0 +1,33 @@
+package dc
+
+import "math/rand/v2"
+
+type dcAddrSet struct {
+	v4 map[int][]Addr
+	v6 map[int][]Addr
+}
+
+func (d dcAddrSet) getV4(dc int) []Addr {
+	if d.v4 == nil {
+		return nil
+	}
+	return d.get(d.v4[dc])
+}
+
+func (d dcAddrSet) getV6(dc int) []Addr {
+	if d.v6 == nil {
+		return nil
+	}
+	return d.get(d.v6[dc])
+}
+
+func (d dcAddrSet) get(addrs []Addr) []Addr {
+	otherSet := make([]Addr, 0, len(addrs))
+	otherSet = append(otherSet, addrs...)
+
+	rand.Shuffle(len(otherSet), func(i, j int) {
+		otherSet[i], otherSet[j] = otherSet[j], otherSet[i]
+	})
+
+	return otherSet
+}