Added iterator_adaptor, refactored pointer_iterator (#62)

Added iterator_adaptor, refactored pointer_iterator

include/sparrow/iterator.hpp

@@ -403,48 +403,47 @@ namespace sparrow
  };
 
  /*
- * @class pointer_iterator
- * @brief iterator adaptor for pointers
+ * @class iterator_adaptor
+ * @brief generic iterator adaptor
  *
- * pointer_iterator gives an iterator API to a pointer.
- * @tparam T the pointer to adapt
+ * This class forwards the calls to its "base" iterator, i.e.
+ * the iterator it adapts. Iterator adaptor classes should
+ * inherit from this class and redefine the private methods
+ * they need only.
  */
- template <class T>
- class pointer_iterator;
-
- template <class T>
- class pointer_iterator<T*> 
- : public iterator_base<pointer_iterator<T*>, T, std::contiguous_iterator_tag>
+ template
+ <
+ class Derived,
+ class Iter,
+ class Element,
+ class IteratorConcept = typename std::iterator_traits<Iter>::iterator_category,
+ class Reference = std::iter_reference_t<Iter>,
+ class Difference = std::iter_difference_t<Iter>
+ >
+ class iterator_adaptor
+ : public iterator_base<Derived, Element, IteratorConcept, Reference, Difference>
  {
  public:
-
- using self_type = pointer_iterator<T*>;
- using base_type = iterator_base<self_type, T, std::contiguous_iterator_tag>;
- using pointer = typename base_type::pointer;
-
- pointer_iterator() = default;
- explicit pointer_iterator(pointer p)
- : p_iter(p)
- {
- }
 
- template <class Iter>
- requires std::same_as<Iter, std::remove_const_t<T>>
- pointer_iterator(const Iter& iter)
- : p_iter(iter.base())
+ using base_type = iterator_base<Derived, Element, IteratorConcept, Reference, Difference>;
+ using self_type = iterator_adaptor<Derived, Iter, Element, IteratorConcept, Reference, Difference>;
+ using reference = typename base_type::reference;
+ using difference_type = typename base_type::difference_type;
+ using iterator_type = Iter;
+
+ iterator_adaptor() = default;
+ explicit iterator_adaptor(const iterator_type& iter)
+ : p_iter(iter)
  {
  }
 
- const pointer& base() const
+ const iterator_type& base() const
  {
  return p_iter;
  }
 
  private:
 
- using reference = typename base_type::reference;
- using difference_type = typename base_type::difference_type;
-
  reference dereference() const
  {
  return *p_iter;
@@ -480,9 +479,48 @@ namespace sparrow
  return p_iter < rhs.p_iter;
  }
 
- pointer p_iter = nullptr;
+ iterator_type p_iter = {};
 
  friend class iterator_access;
  };
 
+ /*
+ * @class pointer_iterator
+ * @brief iterator adaptor for pointers
+ *
+ * pointer_iterator gives an iterator API to a pointer.
+ * @tparam T the pointer to adapt
+ */
+ template <class T>
+ class pointer_iterator;
+
+ template <class T>
+ class pointer_iterator<T*>
+ : public iterator_adaptor<pointer_iterator<T*>, T*, T, std::contiguous_iterator_tag>
+ {
+ public:
+
+ using self_type = pointer_iterator<T*>;
+ using base_type = iterator_adaptor<self_type, T*, T, std::contiguous_iterator_tag>;
+ using iterator_type = typename base_type::iterator_type;
+
+ pointer_iterator() = default;
+ explicit pointer_iterator(iterator_type p)
+ : base_type(p)
+ {
+ }
+
+ template <class U>
+ requires std::convertible_to<U*, iterator_type>
+ explicit pointer_iterator(U* u)
+ : base_type(iterator_type(u))
+ {
+ }
+ };
+
+ template <class T>
+ pointer_iterator<T*> make_pointer_iterator(T* t)
+ {
+ return pointer_iterator<T*>(t);
+ }
 }

test/test_iterator.cpp

@@ -14,6 +14,7 @@
 
 #include "doctest/doctest.h"
 
+#include <array>
 #include <cstddef>
 #include <numeric>
 
@@ -241,4 +242,28 @@ namespace sparrow
  CHECK(valid);
  }
  }
+
+ TEST_SUITE("pointer_iterator")
+ {
+ TEST_CASE("make_pointer_iterator")
+ {
+ std::array<int, 3> a = { 2, 4, 6 };
+ auto iter = make_pointer_iterator(&a[0]);
+ CHECK_EQ(*iter, a[0]);
+ ++iter;
+ CHECK_EQ(*iter, a[1]);
+ ++iter;
+ CHECK_EQ(*iter, a[2]);
+ }
+
+ TEST_CASE("const conversion")
+ {
+ std::array<int, 3> a = { 2, 4, 6 };
+ using iterator = pointer_iterator<int*>;
+ using const_iterator = pointer_iterator<const int*>;
+
+ const_iterator iter{&(a[0])};
+ CHECK_EQ(*iter, a[0]);
+ }
+ }
 }