Add missing file

Principal_component_analysis/include/CGAL/Subiterator.h

@@ -0,0 +1,99 @@
+// Copyright (c) 2020  GeometryFactory (France).
+// All rights reserved.
+//
+// This file is part of CGAL (www.cgal.org)
+//
+// $URL$
+// $Id$
+// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
+//
+// Author(s) : Simon Giraudot
+//
+
+#ifndef CGAL_PCA_SUBITERATOR_H
+#define CGAL_PCA_SUBITERATOR_H
+
+#include <boost/iterator/iterator_facade.hpp>
+
+namespace CGAL
+{
+
+template <typename InputIterator, typename ValueType, int Size>
+class Subiterator
+  : public boost::iterator_facade<Subiterator<InputIterator, ValueType, Size>,
+                                  ValueType,
+                                  std::input_iterator_tag>
+{
+public:
+  using Self = Subiterator<InputIterator, ValueType, Size>;
+  using Facade = boost::iterator_facade<Self, ValueType, std::input_iterator_tag>;
+
+  using Input_type = typename std::iterator_traits<InputIterator>::value_type;
+  using Output_type = ValueType;
+
+  using Converter = std::function<Output_type(const Input_type&, std::size_t)>;
+
+private:
+
+  Converter m_converter;
+  std::size_t m_next_index;
+  InputIterator m_base;
+  mutable Output_type m_current;
+
+public:
+
+  Subiterator() { }
+
+  Subiterator(InputIterator begin, const Converter& converter)
+    : m_converter(converter), m_next_index(0), m_base(begin)
+  { }
+
+  Subiterator(InputIterator end)
+    : m_next_index(0), m_base(end)
+  { }
+
+private:
+
+  friend class boost::iterator_core_access;
+
+  void increment()
+  {
+    ++ m_next_index;
+    if (m_next_index == Size)
+    {
+      ++ m_base;
+      m_next_index = 0;
+    }
+  }
+
+  bool equal(const Self& other) const
+  {
+    return this->m_base == other.m_base && this->m_next_index == other.m_next_index;
+  }
+
+  Output_type& dereference() const
+  {
+    m_current = m_converter (*m_base, m_next_index);
+    return const_cast<Output_type&>(m_current);
+  }
+};
+
+template <typename ValueType, int Size, typename InputIterator>
+Subiterator<InputIterator, ValueType, Size>
+make_subiterator (InputIterator begin,
+                  const typename Subiterator<InputIterator, ValueType, Size>::Converter& converter)
+{
+  return Subiterator<InputIterator, ValueType, Size>(begin, converter);
+}
+
+template <typename ValueType, int Size, typename InputIterator>
+Subiterator<InputIterator, ValueType, Size>
+make_subiterator (InputIterator end)
+{
+  return Subiterator<InputIterator, ValueType, Size>(end);
+}
+
+
+} // namespace CGAL
+
+#endif // CGAL_PCA_SUBITERATOR_H