cycle_iterator.hpp

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//=======================================================================
// Copyright (c) 2013 Piotr Wygocki
//
// Distributed under 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 PAAL_CYCLE_ITERATOR_HPP
#define PAAL_CYCLE_ITERATOR_HPP

#include "paal/utils/type_functions.hpp"

#include <boost/iterator/iterator_facade.hpp>

namespace paal {
namespace data_structures {

// could have been done by simple boost::join
// minor TODO class can specialized for randomaccess iterators

template <typename Iter>
class cycle_iterator : public boost::iterator_facade<
    cycle_iterator<Iter>, typename std::iterator_traits<Iter>::value_type,
    typename boost::forward_traversal_tag,
    typename std::iterator_traits<Iter>::reference,
    typename std::iterator_traits<Iter>::difference_type> {

    typedef std::iterator_traits<Iter> IT;
    typedef typename IT::reference ref;

  public:

    cycle_iterator(Iter start, Iter begin, Iter end)
        : m_curr(start), m_start(start), m_begin(begin), m_end(end),
          m_is_end(false) {}

    cycle_iterator() : m_is_end(true) {}

  private:
    friend class boost::iterator_core_access;
    void increment() {
        ++m_curr;

        if (m_curr == m_end) {
            m_curr = m_begin;
        }

        if (m_curr == m_start) {
            m_is_end = true;
            m_curr = m_end;
        }
    }

    bool equal(cycle_iterator ei) const {
        return (m_is_end && ei.m_is_end) || m_curr == ei.m_curr;
    }

    ref dereference() const { return *m_curr; }

    Iter m_curr;
    Iter m_start;
    Iter m_begin;
    Iter m_end;
    bool m_is_end = false;
};
}
}
#endif // PAAL_CYCLE_ITERATOR_HPP