include/o3tl/enumarray.hxx

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  19
  20 #ifndef INCLUDED_O3TL_ENUMARRAY_HXX
  21 #define INCLUDED_O3TL_ENUMARRAY_HXX
  22
  23 #include <iterator>
  24 #include <type_traits>
  25 #include <utility>
  26 #include <array>
  27 #include <cassert>
  28
  29 namespace o3tl {
  30
  31 template<typename EA>
  32 class enumarray_iterator;
  33 template<typename EA>
  34 class enumarray_const_iterator;
  35
  36 ///
  37 /// This is a container convenience class for arrays indexed by enum values.
  38 ///
  39 /// This assumes that the 'enum class' definition
  40 ///  - starts at zero
  41 ///  - has no holes in its sequence of values
  42 ///  - defines a value called LAST which refers to the greatest constant.
  43 ///
  44 /// \param E the 'enum class' type.
  45 /// \param V the value type to be stored in the array
  46 template<typename E, typename V>
  47 class enumarray final
  48 {
  49 public:
  50     typedef enumarray<E, V> self_type;
  51     typedef enumarray_iterator<self_type> iterator;
  52     typedef enumarray_const_iterator<self_type> const_iterator;
  53
  54     typedef V             value_type;
  55     typedef E             key_type;
  56     typedef size_t        size_type;
  57
  58     static const size_type max_index = static_cast<size_type>(E::LAST);
  59
  60     // If this ctor only had the args parameter pack, it would erroneously get picked as a better
  61     // choice than the (implicit) copy ctor (taking a const lvalue reference) when a copy is made
  62     // from a non-const lvalue enumarray; the easiest way to avoid that is the additional arg
  63     // parameter; and to keep things simple that parameter is always passed by const lvalue
  64     // reference for now even if there could be cases where passing it by rvalue reference might be
  65     // beneficial or even necessary if V is a move-only type:
  66     template<typename... T> constexpr enumarray(V const & arg, T && ...args):
  67         detail_values{arg, std::forward<T>(args)...}
  68     {
  69         static_assert(sizeof... (T) == max_index);
  70     }
  71
  72     // coverity[uninit_ctor] - by design:
  73     enumarray() {}
  74
  75     const V& operator[](E index) const
  76     {
  77         assert(index>=static_cast<E>(0) && index<=E::LAST);
  78         return detail_values[static_cast<size_type>(index)];
  79     }
  80
  81     V& operator[](E index)
  82     {
  83         assert(index>=static_cast<E>(0) && index<=E::LAST);
  84         return detail_values[static_cast<size_type>(index)];
  85     }
  86
  87     void fill(V val)
  88     { for (size_type i=0; i<=max_index; ++i) detail_values[i] = val; }
  89
  90     static size_type size()        { return max_index + 1; }
  91     iterator         begin()       { return iterator(*this, 0); }
  92     iterator         end()         { return iterator(*this, size()); }
  93     const_iterator   begin() const { return const_iterator(*this, 0); }
  94     const_iterator   end() const   { return const_iterator(*this, size()); }
  95
  96     V*               data()       { return detail_values.data(); }
  97
  98 private:
  99     std::array<V, max_index + 1> detail_values;
 100 };
 101
 102
 103 template<typename EA>
 104 class enumarray_iterator {
 105     EA*         m_buf;
 106     size_t      m_pos;
 107 public:
 108     typedef enumarray_iterator<EA>  self_type;
 109     typedef typename EA::value_type value_type;
 110     typedef typename EA::key_type   key_type;
 111     typedef std::bidirectional_iterator_tag iterator_category; //should be random access, but that would require define subtraction operators on the enums
 112     typedef
 113         typename std::make_signed<
 114             typename std::underlying_type<typename EA::key_type>::type>::type
 115         difference_type;
 116     typedef typename EA::value_type*   pointer;
 117     typedef typename EA::value_type&   reference;
 118
 119     enumarray_iterator(EA& b, size_t start_pos)
 120          : m_buf(&b), m_pos(start_pos) {}
 121     value_type& operator*()  const { return (*m_buf)[static_cast<key_type>(m_pos)]; }
 122     value_type* operator->() const { return &(operator*()); }
 123     self_type&  operator++() { ++m_pos; return *this; }
 124     bool        operator!=(self_type const & other) const { return m_buf != other.m_buf || m_pos != other.m_pos; }
 125     bool        operator==(self_type const & other) const { return m_buf == other.m_buf && m_pos == other.m_pos; }
 126 };
 127
 128 template<typename EA>
 129 class enumarray_const_iterator {
 130     EA const *  m_buf;
 131     size_t      m_pos;
 132 public:
 133     typedef enumarray_const_iterator<EA>    self_type;
 134     typedef typename EA::value_type const   value_type;
 135     typedef typename EA::key_type           key_type;
 136     typedef std::bidirectional_iterator_tag iterator_category; //should be random access, but that would require define subtraction operators on the enums
 137     typedef
 138         typename std::make_signed<
 139             typename std::underlying_type<typename EA::key_type>::type>::type
 140                                             difference_type;
 141     typedef typename EA::value_type const * pointer;
 142     typedef typename EA::value_type const & reference;
 143
 144     enumarray_const_iterator(EA const & b, size_t start_pos)
 145          : m_buf(&b), m_pos(start_pos) {}
 146     value_type& operator*()  const { return (*m_buf)[static_cast<key_type>(m_pos)]; }
 147     value_type* operator->() const { return &(operator*()); }
 148     self_type&  operator++() { ++m_pos; return *this; }
 149     bool        operator!=(self_type const & other) const { return m_buf != other.m_buf || m_pos != other.m_pos; }
 150     bool        operator==(self_type const & other) const { return m_buf == other.m_buf && m_pos == other.m_pos; }
 151 };
 152
 153 }; // namespace o3tl
 154
 155 #endif /* INCLUDED_O3TL_ENUMARRAY_HXX */
 156
 157 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */