var got uint64
			iterator := ipIterator(tt.first, tt.last, tt.offset)

			for {
				ip := iterator()
				if !ip.IsValid() {
					break
				}
				got++
			}
			if got != tt.want {
				t.Errorf("ipIterator() = %d, want %d", got, tt.want)
			}
			// check the iterator is fully stopped
			for i := 0; i < 5; i++ {
				if ip := iterator(); ip.IsValid() {

	default:
		offset = uint64(a.rand.Int63n(int64(rangeSize)))
	}
	iterator := ipIterator(a.offsetAddress, a.lastAddress, offset)
	ip, err := a.allocateFromRange(iterator, svc)
	if err == nil {
		return ip, nil
	}
	// check the lower range
	if a.rangeOffset != 0 {
		offset = uint64(a.rand.Intn(a.rangeOffset))
		iterator = ipIterator(a.firstAddress, a.offsetAddress.Prev(), offset)

        iterator.next()
        iterator.next()

        then:
        iterator.previous() == "fuzz"
        iterator.previous() == "fizz"
        iterator.previous() == "foo"
        !iterator.hasPrevious()

        and:
        iterator.next() == "foo"
        iterator.next() == "fizz"
        iterator.next() == "fuzz"
        !iterator.hasNext()

        and:
        iterator.previous() == "fuzz"

   */
  static class IteratorWithSunJavaBug6529795<T> implements Iterator<T> {
    Iterator<T> iterator;
    boolean nextThrewException;

    IteratorWithSunJavaBug6529795(Iterator<T> iterator) {
      this.iterator = iterator;
    }

    @Override
    public boolean hasNext() {
      return iterator.hasNext();
    }

    @Override
    public T next() {
      try {

   */
  static class IteratorWithSunJavaBug6529795<T> implements Iterator<T> {
    Iterator<T> iterator;
    boolean nextThrewException;

    IteratorWithSunJavaBug6529795(Iterator<T> iterator) {
      this.iterator = iterator;
    }

    @Override
    public boolean hasNext() {
      return iterator.hasNext();
    }

    @Override
    public T next() {
      try {

      @Override
      public Iterator<T> iterator() {
        if (iterable instanceof List) {
          final List<T> list = (List<T>) iterable;
          int toSkip = Math.min(list.size(), numberToSkip);
          return list.subList(toSkip, list.size()).iterator();
        }
        final Iterator<T> iterator = iterable.iterator();

        Iterators.advance(iterator, numberToSkip);

        /*

    Map<R, V> output = new LinkedHashMap<>();
    Iterator<Entry<R, Map<C, V>>> iterator = backingMap.entrySet().iterator();
    while (iterator.hasNext()) {
      Entry<R, Map<C, V>> entry = iterator.next();
      V value = entry.getValue().remove(column);
      if (value != null) {
        output.put(entry.getKey(), value);
        if (entry.getValue().isEmpty()) {
          iterator.remove();
        }
      }
    }

        @Override
        public @Nullable Object execute(Iterator<?> iterator) {
          iterator.remove();
          return null;
        }
      };

  private static final IteratorOperation NEXT_METHOD =
      new IteratorOperation() {
        @Override
        public @Nullable Object execute(Iterator<?> iterator) {
          return iterator.next();
        }
      };

    Map<R, V> output = new LinkedHashMap<>();
    Iterator<Entry<R, Map<C, V>>> iterator = backingMap.entrySet().iterator();
    while (iterator.hasNext()) {
      Entry<R, Map<C, V>> entry = iterator.next();
      V value = entry.getValue().remove(column);
      if (value != null) {
        output.put(entry.getKey(), value);
        if (entry.getValue().isEmpty()) {
          iterator.remove();
        }
      }
    }

 public:
  typedef ParamIterator<T> iterator;

  explicit ParamGenerator(ParamGeneratorInterface<T>* impl) : impl_(impl) {}
  ParamGenerator(const ParamGenerator& other) : impl_(other.impl_) {}

  ParamGenerator& operator=(const ParamGenerator& other) {
    impl_ = other.impl_;
    return *this;
  }

  iterator begin() const { return iterator(impl_->Begin()); }
  iterator end() const { return iterator(impl_->End()); }