build: add entt library

include/entt/stl/iterator.hpp

@@ -0,0 +1,110 @@
+#ifndef ENTT_STL_ITERATOR_HPP
+#define ENTT_STL_ITERATOR_HPP
+
+/*! @cond ENTT_INTERNAL */
+#if __has_include(<entt/ext/stl/iterator.hpp>)
+#    include <entt/ext/stl/iterator.hpp>
+#else
+#    include <iterator>
+#    include <version>
+#    include "../config/config.h"
+
+namespace entt::stl {
+
+using std::advance;
+using std::bidirectional_iterator_tag;
+using std::distance;
+using std::forward_iterator_tag;
+using std::input_iterator_tag;
+using std::iterator_traits;
+using std::make_reverse_iterator;
+using std::random_access_iterator_tag;
+using std::reverse_iterator;
+
+#    ifndef ENTT_FORCE_STL
+#        if defined(__cpp_lib_ranges)
+#            define ENTT_HAS_ITERATOR_CONCEPTS
+
+using std::bidirectional_iterator;
+using std::forward_iterator;
+using std::input_iterator;
+using std::input_or_output_iterator;
+using std::output_iterator;
+using std::random_access_iterator;
+using std::sentinel_for;
+
+#        endif
+#    endif
+
+#    ifndef ENTT_HAS_ITERATOR_CONCEPTS
+#        include <concepts>
+#        include <utility>
+
+namespace internal {
+
+template<typename It>
+concept has_iterator_category = requires {
+    typename std::iterator_traits<It>::iterator_category;
+};
+
+template<typename It>
+concept has_iterator_concept = has_iterator_category<It> && requires {
+    typename It::iterator_concept;
+};
+
+template<has_iterator_category It>
+struct iterator_tag {
+    using type = typename std::iterator_traits<It>::iterator_category;
+};
+
+template<has_iterator_concept It>
+struct iterator_tag<It> {
+    using type = typename It::iterator_concept;
+};
+
+template<typename It, typename Tag>
+concept has_iterator_tag = std::derived_from<typename iterator_tag<It>::type, Tag>;
+
+} // namespace internal
+
+// Bare minimum definitions to support broken platforms like PS4.
+// EnTT does not provide full featured definitions for iterator concepts.
+
+template<typename It>
+concept input_or_output_iterator = requires(It it) {
+    *it;
+    { ++it } -> std::same_as<It &>;
+    it++;
+};
+
+template<typename It>
+concept input_iterator = input_or_output_iterator<It> && internal::has_iterator_tag<It, std::input_iterator_tag>;
+
+template<typename It, typename Type>
+concept output_iterator = input_or_output_iterator<It> && requires(It it, Type &&value) {
+    *it++ = std::forward<Type>(value);
+};
+
+template<typename It>
+concept forward_iterator = input_iterator<It> && internal::has_iterator_tag<It, std::forward_iterator_tag>;
+
+template<typename It>
+concept bidirectional_iterator = forward_iterator<It> && internal::has_iterator_tag<It, std::bidirectional_iterator_tag>;
+
+template<typename It>
+concept random_access_iterator = bidirectional_iterator<It> && internal::has_iterator_tag<It, std::random_access_iterator_tag>;
+
+template<class Sentinel, typename It>
+concept sentinel_for = input_or_output_iterator<It> && requires(Sentinel sentinel, It it) {
+    { it == sentinel } -> std::same_as<bool>;
+};
+
+#    endif
+
+} // namespace entt::stl
+#endif
+/*! @endcond */
+
+#undef ENTT_HAS_ITERATOR_CONCEPTS
+
+#endif