vector_slice.h

// ---------------------------------------------------------------------
//
// Copyright (C) 2004 - 2018 by the deal.II authors
//
// This file is part of the deal.II library.
//
// The deal.II library is free software; you can use it, redistribute
// it, and/or modify it under the terms of the GNU Lesser General
// Public License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// The full text of the license can be found in the file LICENSE at
// the top level of the deal.II distribution.
//
// ---------------------------------------------------------------------

#ifndef dealii_vector_slice_h
#define dealii_vector_slice_h

#include <deal.II/base/config.h>
#include <deal.II/base/exceptions.h>
#include <deal.II/base/array_view.h>

DEAL_II_NAMESPACE_OPEN


template <typename VectorType>
class VectorSlice
{
public:
  VectorSlice(VectorType &v);
  VectorSlice(VectorType   &v,
              unsigned int start,
              unsigned int length);

  operator ArrayView<typename VectorType::value_type *> ();

  operator ArrayView<const typename VectorType::value_type *> () const;

  unsigned int size() const;

  typename VectorType::reference operator[] (unsigned int i);

  typename VectorType::const_reference operator[] (unsigned int i) const;

  typename VectorType::iterator begin();

  typename VectorType::const_iterator begin() const;

  typename VectorType::iterator end();

  typename VectorType::const_iterator end() const;

private:
  VectorType &v;
  const unsigned int start;
  const unsigned int length;
};


template <typename VectorType>
inline
const VectorSlice<const VectorType>
make_slice (VectorType &v)
{
  const VectorSlice<const VectorType> r(v);
  return r;
}



template <typename VectorType>
inline
const VectorSlice<const VectorType>
make_slice (VectorType         &v,
            const unsigned int start,
            const unsigned int length)
{
  const VectorSlice<const VectorType> r(v, start, length);
  return r;
}




//---------------------------------------------------------------------------

template <typename VectorType>
inline
VectorSlice<VectorType>::VectorSlice(VectorType &v)
  :
  v(v), start(0), length(v.size())
{}


template <typename VectorType>
inline
VectorSlice<VectorType>::VectorSlice(VectorType   &v,
                                     unsigned int start,
                                     unsigned int length)
  :
  v(v), start(start), length(length)
{
  Assert((start+length<=v.size()),
         ExcIndexRange(length, 0, v.size()-start+1));
}


template <typename VectorType>
inline
unsigned int
VectorSlice<VectorType>::size() const
{
  return length;
}


template <typename VectorType>
VectorSlice<VectorType>::
operator ArrayView<typename VectorType::value_type *> ()
{
  return ArrayView<typename VectorType::value_type *> (&v[start], length);
}


template <typename VectorType>
VectorSlice<VectorType>::
operator ArrayView<const typename VectorType::value_type *> () const
{
  return ArrayView<const typename VectorType::value_type *> (&v[start], length);
}


template <typename VectorType>
inline
typename VectorType::reference
VectorSlice<VectorType>::operator[](unsigned int i)
{
  Assert ((i<length), ExcIndexRange(i, 0, length));

  return v[start+i];
}


template <typename VectorType>
inline
typename VectorType::const_reference
VectorSlice<VectorType>::operator[](unsigned int i) const
{
  Assert ((i<length), ExcIndexRange(i, 0, length));

  return v[start+i];
}


template <typename VectorType>
inline
typename VectorType::const_iterator
VectorSlice<VectorType>::begin() const
{
  return v.begin()+start;
}


template <typename VectorType>
inline
typename VectorType::iterator
VectorSlice<VectorType>::begin()
{
  return v.begin()+start;
}


template <typename VectorType>
inline
typename VectorType::const_iterator
VectorSlice<VectorType>::end() const
{
  return v.begin()+start+length;
}


template <typename VectorType>
inline
typename VectorType::iterator
VectorSlice<VectorType>::end()
{
  return v.begin()+start+length;
}

DEAL_II_NAMESPACE_CLOSE

#endif