src/common/midi_parsing/adjacent_range.h

#pragma once
#include <iterator>
#include <utility>

namespace midi_parsing {

    template <typename FwdIt> class adjacent_iterator {
    public:
        adjacent_iterator(FwdIt first, FwdIt last)
            : m_first(first), m_next(first == last ? first : std::next(first)) { }

        bool operator!=(const adjacent_iterator& other) const {
            return m_next != other.m_next; 
        }

        adjacent_iterator& operator++() {
            ++m_first;
            ++m_next;
            return *this;
        }

        typedef typename std::iterator_traits<FwdIt>::reference Ref;
        typedef std::pair<Ref, Ref> Pair;

        Pair operator*() const {
            return Pair(*m_first, *m_next); 
        }

    private:
        FwdIt m_first;
        FwdIt m_next;
    };

    template <typename FwdIt> class adjacent_range {
    public:
        adjacent_range(FwdIt first, FwdIt last)
            : m_first(first), m_last(last) { }

        adjacent_iterator<FwdIt> begin() const {
            return adjacent_iterator<FwdIt>(m_first, m_last);
        }

        adjacent_iterator<FwdIt> end() const {
            return adjacent_iterator<FwdIt>(m_last, m_last);
        }

    private:
        FwdIt m_first;
        FwdIt m_last;
    };

    template <typename C> auto make_adjacent_range(C& c) -> adjacent_range<decltype(c.begin())> {
        return adjacent_range<decltype(c.begin())>(c.begin(), c.end());
    }
}