return New(pr, func(max int, rangeSpec string, offset int) (allocator.Interface, error) {
		return allocator.NewAllocationMapWithOffset(max, rangeSpec, offset), nil
	})
}

// NewFromSnapshot allocates a PortAllocator and initializes it from a snapshot.
func NewFromSnapshot(snap *api.RangeAllocation) (*PortAllocator, error) {
	pr, err := net.ParsePortRange(snap.Range)
	if err != nil {
		return nil, err
	}
	r, err := NewInMemory(*pr)

		if err != nil {
			t.Fatal(err)
		}
		allocated = append(allocated, p)
	}

	snapshot := api.RangeAllocation{}
	if err = r.Snapshot(&snapshot); err != nil {
		t.Fatal(err)
	}

	r, err = NewFromSnapshot(&snapshot)
	if err != nil {
		t.Fatal(err)
	}

	if x := r.Free(); x != 51 {
		t.Fatalf("expected 51 free ports, got %d", x)
	}
	if x := r.Used(); x != 50 {