singleton_iterator.hpp

//          Copyright Morten Bendiksen 2014 - 2016.
// 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 MEDIASEQUENCER_PLUGIN_UTIL_XPATH_SINGLETON_ITERATOR
#define MEDIASEQUENCER_PLUGIN_UTIL_XPATH_SINGLETON_ITERATOR

#include <boost/iterator/iterator_facade.hpp>
#include <boost/range/iterator_range.hpp>
#include <memory>

namespace mediasequencer { namespace plugin { namespace util { namespace xpath {

// An iterator over a single node. It is given one node and the first increment
// will take it past the end.
template <typename Element>
class singleton_iterator : public boost::iterator_facade<singleton_iterator<Element>,
       Element, boost::forward_traversal_tag> {
public:
    singleton_iterator() {};

    singleton_iterator(singleton_iterator const& other)
        : context(other.context) {};


    singleton_iterator(singleton_iterator&& other)
        : context(std::move(other.context)) {};

    singleton_iterator operator=(singleton_iterator const& other) {
        context = other.context;
        return *this;
    }

    singleton_iterator operator=(singleton_iterator&& other) {
        context = std::move(other.context);
        return *this;
    }

    explicit singleton_iterator(Element&& context)
        : context(new Element(std::move(context))) {}
    explicit singleton_iterator(Element const& context)
        : context(new Element(context)) {}

private:
    friend class boost::iterator_core_access;

    void increment() {
        context.reset();
    }

    bool equal(singleton_iterator const& other) const {
        return this->context == other.context;
    }

    Element& dereference() const {
        return *context;
    }

    std::shared_ptr<Element> context;
};

template <typename Element>
boost::iterator_range
   <singleton_iterator<typename std::remove_reference<Element>::type> >
singleton(Element&& n) {
    return boost::make_iterator_range
            (singleton_iterator<typename std::remove_reference<Element>::type>(std::forward<Element>(n)),
             singleton_iterator<typename std::remove_reference<Element>::type>());

}

}}}}

#endif // MEDIASEQUENCER_PLUGIN_UTIL_XPATH_SINGLETON_ITERATOR