Class ParamIterator

tests/gtest/gtest.h:10515–10553

// and implements the const forward iterator concept.
template <typename T>
class ParamIterator {
 public:
  typedef T value_type;
  typedef const T& reference;
  typedef ptrdiff_t difference_type;

  // ParamIterator assumes ownership of the impl_ pointer.
  ParamIterator(const ParamIterator& other) : impl_(other.impl_->Clone()) {}
  ParamIterator& operator=(const ParamIterator& other) {
    if (this != &other)
      impl_.reset(other.impl_->Clone());
    return *this;
  }

  const T& operator*() const { return *impl_->Current(); }
  const T* operator->() const { return impl_->Current(); }
  // Prefix version of operator++.
  ParamIterator& operator++() {
    impl_->Advance();
    return *this;
  }
  // Postfix version of operator++.
  ParamIterator operator++(int /*unused*/) {
    ParamIteratorInterface<T>* clone = impl_->Clone();
    impl_->Advance();
    return ParamIterator(clone);
  }
  bool operator==(const ParamIterator& other) const {
    return impl_.get() == other.impl_.get() || impl_->Equals(*other.impl_);
  }
  bool operator!=(const ParamIterator& other) const {
    return !(*this == other);
  }

 private:
  friend class ParamGenerator<T>;
  explicit ParamIterator(ParamIteratorInterface<T>* impl) : impl_(impl) {}
  std::unique_ptr<ParamIteratorInterface<T> > impl_;
};

// ParamGeneratorInterface<T> is the binary interface to access generators
// defined in other translation units.