Add a view to raw vector data with DenseVector interface

dune/common/densevectorview.hh

+// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+// vi: set et ts=4 sw=2 sts=2:
+// SPDX-FileCopyrightInfo: Copyright © DUNE Project contributors, see file LICENSE.md in module root
+// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception
+#ifndef DUNE_COMMON_DENSEVECTORVIEW_HH
+#define DUNE_COMMON_DENSEVECTORVIEW_HH
+
+#include <cstddef>
+#include <vector>
+
+#include <dune/common/boundschecking.hh>
+#include <dune/common/densevector.hh>
+#include <dune/common/ftraits.hh>
+
+namespace Dune {
+
+  /** @addtogroup DenseMatVec
+      @{
+   */
+
+  /*! \file
+   * \brief This file implements a dense vector view with a dynamic size.
+   */
+
+  template< class K > class DenseVectorView;
+  template< class K >
+  struct DenseMatVecTraits< DenseVectorView< K > >
+  {
+    typedef DenseVectorView< K > derived_type;
+    typedef K value_type;
+    typedef std::size_t size_type;
+  };
+
+  template< class K >
+  struct FieldTraits< DenseVectorView< K > >
+  {
+    typedef typename FieldTraits< K >::field_type field_type;
+    typedef typename FieldTraits< K >::real_type real_type;
+  };
+
+  /** \brief Construct a vector-like view with a dynamic size.
+   *
+   * \tparam K is the field type (use float, double, complex, etc)
+   */
+  template< class K >
+  class DenseVectorView : public DenseVector< DenseVectorView< K > >
+  {
+    using Base = DenseVector< DenseVectorView< K > >;
+
+  public:
+    using size_type = typename Base::size_type ;
+    using value_type = typename Base::value_type;
+    using pointer = value_type*;
+    using reference = value_type&;
+    using const_reference = const value_type&;
+
+    constexpr DenseVectorView (pointer p, size_type s) noexcept
+      : pointer_(p)
+      , size_(s)
+    {}
+
+    template <class A, class _K = K, std::enable_if_t<not std::is_const_v<_K>,int> = 0>
+    constexpr DenseVectorView (std::vector<K,A>& v) noexcept
+      : DenseVectorView(v.data(), v.size())
+    {}
+
+    template <class A, class _K = K, std::enable_if_t<std::is_const_v<_K>,int> = 0>
+    constexpr DenseVectorView (std::vector<K,A> const& v) noexcept
+      : DenseVectorView(v.data(), v.size())
+    {}
+
+    constexpr size_type size () const { return size_; }
+
+    constexpr K& operator[] (size_type i) noexcept
+    {
+      DUNE_ASSERT_BOUNDS(i < size_);
+      return pointer_[i];
+    }
+
+    constexpr const K& operator[] (size_type i) const noexcept
+    {
+      DUNE_ASSERT_BOUNDS(i < size_);
+      return pointer_[i];
+    }
+
+  private:
+    pointer pointer_;
+    size_type size_;
+  };
+
+  template <class K>
+  DenseVectorView (K*, std::size_t)
+    -> DenseVectorView<K>;
+
+  template <class K, class A>
+  DenseVectorView (std::vector<K,A>&)
+    -> DenseVectorView<K>;
+
+  template <class K, class A>
+  DenseVectorView (std::vector<K,A> const&)
+    -> DenseVectorView<const K>;
+
+  /** @} end documentation */
+
+} // end namespace
+
+#endif