boost/geometry/iterators/ever_circling_iterator.hpp

// Boost.Geometry (aka GGL, Generic Geometry Library)

// Copyright (c) 2007-2011 Barend Gehrels, Amsterdam, the Netherlands.
// Copyright (c) 2008-2011 Bruno Lalande, Paris, France.
// Copyright (c) 2009-2011 Mateusz Loskot, London, UK.

// Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
// (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands.

// Use, modification and distribution is subject to the Boost Software License,
// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_GEOMETRY_ITERATORS_EVER_CIRCLING_ITERATOR_HPP
#define BOOST_GEOMETRY_ITERATORS_EVER_CIRCLING_ITERATOR_HPP

#include <boost/range.hpp>
#include <boost/iterator.hpp>
#include <boost/iterator/iterator_adaptor.hpp>
#include <boost/iterator/iterator_categories.hpp>

#include <boost/geometry/iterators/base.hpp>

namespace boost { namespace geometry
{

/*!
    \brief Iterator which ever circles through a range
    \tparam Iterator iterator on which this class is based on
    \ingroup iterators
    \details If the iterator arrives at range.end() it restarts from the
     beginning. So it has to be stopped in another way.
    Don't call for(....; it++) because it will turn in an endless loop
    \note Name inspired on David Bowie's
    "Chant Of The Ever Circling Skeletal Family"
*/
template <typename Iterator>
struct ever_circling_iterator :
    public detail::iterators::iterator_base
    <
        ever_circling_iterator<Iterator>,
        Iterator
    >
{
    friend class boost::iterator_core_access;

    explicit inline ever_circling_iterator(Iterator begin, Iterator end,
            bool skip_first = false)
      : m_begin(begin)
      , m_end(end)
      , m_skip_first(skip_first)
    {
        this->base_reference() = begin;
    }

    explicit inline ever_circling_iterator(Iterator begin, Iterator end, Iterator start,
            bool skip_first = false)
      : m_begin(begin)
      , m_end(end)
      , m_skip_first(skip_first)
    {
        this->base_reference() = start;
    }

    /// Navigate to a certain position, should be in [start .. end], if at end
    /// it will circle again.
    inline void moveto(Iterator it)
    {
        this->base_reference() = it;
        check_end();
    }

private:

    inline void increment(bool possibly_skip = true)
    {
        (this->base_reference())++;
        check_end(possibly_skip);
    }

    inline void check_end(bool possibly_skip = true)
    {
        if (this->base() == this->m_end)
        {
            this->base_reference() = this->m_begin;
            if (m_skip_first && possibly_skip)
            {
                increment(false);
            }
        }
    }

    Iterator m_begin;
    Iterator m_end;
    bool m_skip_first;
};



template <typename Range>
class ever_circling_range_iterator
    : public boost::iterator_adaptor
        <
            ever_circling_range_iterator<Range>,
            typename boost::range_iterator<Range>::type
        >
{
public :
    typedef typename boost::range_iterator<Range>::type iterator_type;

    explicit inline ever_circling_range_iterator(Range& range,
            bool skip_first = false)
      : m_range(range)
      , m_skip_first(skip_first)
    {
        this->base_reference() = boost::begin(m_range);
    }

    explicit inline ever_circling_range_iterator(Range& range, iterator_type start,
            bool skip_first = false)
      : m_range(range)
      , m_skip_first(skip_first)
    {
        this->base_reference() = start;
    }

    /// Navigate to a certain position, should be in [start .. end], if at end
    /// it will circle again.
    inline void moveto(iterator_type it)
    {
        this->base_reference() = it;
        check_end();
    }

private:

    friend class boost::iterator_core_access;

    inline void increment(bool possibly_skip = true)
    {
        (this->base_reference())++;
        check_end(possibly_skip);
    }

    inline void check_end(bool possibly_skip = true)
    {
        if (this->base_reference() == boost::end(m_range))
        {
            this->base_reference() = boost::begin(m_range);
            if (m_skip_first && possibly_skip)
            {
                increment(false);
            }
        }
    }

    Range& m_range;
    bool m_skip_first;
};


}} // namespace boost::geometry

#endif // BOOST_GEOMETRY_ITERATORS_EVER_CIRCLING_ITERATOR_HPP