src/common/container-wrapper.hpp

   1 /*
   2  * Copyright (C) 2023 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7
   8 #ifndef LTTNG_CONTAINER_WRAPPER_H
   9 #define LTTNG_CONTAINER_WRAPPER_H
  10
  11 #include <common/macros.hpp>
  12
  13 #include <cstddef>
  14 #include <iterator>
  15
  16 namespace lttng {
  17 namespace utils {
  18
  19 /*
  20  * random_access_container_wrapper is a helper to provide an idiomatic C++ interface
  21  * from a C container API. ElementAccessorCallable and ElementCountAccessorCallable
  22  * are two functors which must be provided to allow access to the underlying elements
  23  * of the container and to its size.
  24  */
  25 template <typename ContainerType, typename ElementType, typename ContainerOperations>
  26 class random_access_container_wrapper {
  27         class _iterator : public std::iterator<std::random_access_iterator_tag, std::size_t> {
  28         public:
  29                 explicit _iterator(const random_access_container_wrapper& container,
  30                                    std::size_t start_index = 0) :
  31                         _container(container), _index(start_index)
  32                 {
  33                 }
  34
  35                 _iterator& operator++() noexcept
  36                 {
  37                         ++_index;
  38                         return *this;
  39                 }
  40
  41                 _iterator& operator--() noexcept
  42                 {
  43                         --_index;
  44                         return *this;
  45                 }
  46
  47                 _iterator& operator++(int) noexcept
  48                 {
  49                         auto this_before_increment = *this;
  50
  51                         _index++;
  52                         return this_before_increment;
  53                 }
  54
  55                 _iterator& operator--(int) noexcept
  56                 {
  57                         _index--;
  58                         return *this;
  59                 }
  60
  61                 bool operator==(const _iterator& other) const noexcept
  62                 {
  63                         return _index == other._index;
  64                 }
  65
  66                 bool operator!=(const _iterator& other) const noexcept
  67                 {
  68                         return !(*this == other);
  69                 }
  70
  71                 typename std::conditional<std::is_pointer<ElementType>::value,
  72                                           ElementType,
  73                                           ElementType&>::type
  74                 operator*() const noexcept
  75                 {
  76                         return _container[_index];
  77                 }
  78
  79         private:
  80                 const random_access_container_wrapper& _container;
  81                 std::size_t _index;
  82         };
  83
  84         using iterator = _iterator;
  85
  86 public:
  87         explicit random_access_container_wrapper(ContainerType container) : _container{ container }
  88         {
  89         }
  90
  91         iterator begin() noexcept
  92         {
  93                 return iterator(*this);
  94         }
  95
  96         iterator end() noexcept
  97         {
  98                 return iterator(*this, ContainerOperations::size(_container));
  99         }
 100
 101         std::size_t size() const noexcept
 102         {
 103                 return ContainerOperations::size(_container);
 104         }
 105
 106         typename std::conditional<std::is_pointer<ElementType>::value, ElementType, ElementType&>::type
 107         operator[](std::size_t index)
 108         {
 109                 LTTNG_ASSERT(index < ContainerOperations::size(_container));
 110                 return ContainerOperations::get(_container, index);
 111         }
 112
 113         typename std::conditional<std::is_pointer<ElementType>::value,
 114                                   const ElementType,
 115                                   const ElementType&>::type
 116         operator[](std::size_t index) const
 117         {
 118                 LTTNG_ASSERT(index < ContainerOperations::size(_container));
 119                 return ContainerOperations::get(_container, index);
 120         }
 121
 122 private:
 123         ContainerType _container;
 124 };
 125 } /* namespace utils */
 126 } /* namespace lttng */
 127
 128 #endif /* LTTNG_CONTAINER_WRAPPER_H */