enumarray.hxx

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#ifndef INCLUDED_O3TL_ENUMARRAY_HXX
#define INCLUDED_O3TL_ENUMARRAY_HXX
 
#include <iterator>
#include <type_traits>
#include <utility>
#include <array>
#include <cassert>
 
namespace o3tl {
 
template<typename EA>
class enumarray_iterator;
template<typename EA>
class enumarray_const_iterator;
 
template<typename E, typename V>
class enumarray final
{
public:
    typedef enumarray<E, V> self_type;
    typedef enumarray_iterator<self_type> iterator;
    typedef enumarray_const_iterator<self_type> const_iterator;
 
    typedef V             value_type;
    typedef E             key_type;
    typedef size_t        size_type;
 
    static const size_type max_index = static_cast<size_type>(E::LAST);
 
    // If this ctor only had the args parameter pack, it would erroneously get picked as a better
    // choice than the (implicit) copy ctor (taking a const lvalue reference) when a copy is made
    // from a non-const lvalue enumarray; the easiest way to avoid that is the additional arg
    // parameter; and to keep things simple that parameter is always passed by const lvalue
    // reference for now even if there could be cases where passing it by rvalue reference might be
    // beneficial or even necessary if V is a move-only type:
    template<typename... T> constexpr enumarray(V const & arg, T && ...args):
        detail_values{arg, std::forward<T>(args)...}
    {
        static_assert(sizeof... (T) == max_index);
    }
 
    // coverity[uninit_ctor] - by design:
    enumarray() {}
 
    const V& operator[](E index) const
    {
        assert(index>=static_cast<E>(0) && index<=E::LAST);
        return detail_values[static_cast<size_type>(index)];
    }
 
    V& operator[](E index)
    {
        assert(index>=static_cast<E>(0) && index<=E::LAST);
        return detail_values[static_cast<size_type>(index)];
    }
 
    void fill(V val)
    { for (size_type i=0; i<=max_index; ++i) detail_values[i] = val; }
 
    static size_type size()        { return max_index + 1; }
    iterator         begin()       { return iterator(*this, 0); }
    iterator         end()         { return iterator(*this, size()); }
    const_iterator   begin() const { return const_iterator(*this, 0); }
    const_iterator   end() const   { return const_iterator(*this, size()); }
 
    V*               data()       { return detail_values.data(); }
 
private:
    std::array<V, max_index + 1> detail_values;
};
 
 
template<typename EA>
class enumarray_iterator {
    EA*         m_buf;
    size_t      m_pos;
public:
    typedef enumarray_iterator<EA>  self_type;
    typedef typename EA::value_type value_type;
    typedef typename EA::key_type   key_type;
    typedef std::bidirectional_iterator_tag iterator_category; //should be random access, but that would require define subtraction operators on the enums
    typedef
        typename std::make_signed<
            typename std::underlying_type<typename EA::key_type>::type>::type
        difference_type;
    typedef typename EA::value_type*   pointer;
    typedef typename EA::value_type&   reference;
 
    enumarray_iterator(EA& b, size_t start_pos)
         : m_buf(&b), m_pos(start_pos) {}
    value_type& operator*()  const { return (*m_buf)[static_cast<key_type>(m_pos)]; }
    value_type* operator->() const { return &(operator*()); }
    self_type&  operator++() { ++m_pos; return *this; }
    bool        operator!=(self_type const & other) const { return m_buf != other.m_buf || m_pos != other.m_pos; }
    bool        operator==(self_type const & other) const { return m_buf == other.m_buf && m_pos == other.m_pos; }
};
 
template<typename EA>
class enumarray_const_iterator {
    EA const *  m_buf;
    size_t      m_pos;
public:
    typedef enumarray_const_iterator<EA>    self_type;
    typedef typename EA::value_type const   value_type;
    typedef typename EA::key_type           key_type;
    typedef std::bidirectional_iterator_tag iterator_category; //should be random access, but that would require define subtraction operators on the enums
    typedef
        typename std::make_signed<
            typename std::underlying_type<typename EA::key_type>::type>::type
                                            difference_type;
    typedef typename EA::value_type const * pointer;
    typedef typename EA::value_type const & reference;
 
    enumarray_const_iterator(EA const & b, size_t start_pos)
         : m_buf(&b), m_pos(start_pos) {}
    value_type& operator*()  const { return (*m_buf)[static_cast<key_type>(m_pos)]; }
    value_type* operator->() const { return &(operator*()); }
    self_type&  operator++() { ++m_pos; return *this; }
    bool        operator!=(self_type const & other) const { return m_buf != other.m_buf || m_pos != other.m_pos; }
    bool        operator==(self_type const & other) const { return m_buf == other.m_buf && m_pos == other.m_pos; }
};
 
}; // namespace o3tl
 
#endif /* INCLUDED_O3TL_ENUMARRAY_HXX */
 
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