Add util::ecs::species() for iterating over all species

libs/util/include/psemek/util/ecs.hpp

@@ -3,6 +3,7 @@
 #include <psemek/util/to_string.hpp>
 #include <psemek/util/type_name.hpp>
 #include <psemek/util/function.hpp>
+#include <psemek/util/range.hpp>
 
 #include <cstdint>
 #include <typeindex>
@@ -447,6 +448,37 @@ namespace psemek::util
 			void begin(species_handle, Components const & ...) {}
 		};
 
+		struct species_iterator
+		{
+			species_iterator(ecs_detail::species_handle h)
+				: h_(h)
+			{}
+
+			species_handle operator*() const
+			{
+				return species_handle{h_};
+			}
+
+			species_iterator & operator++()
+			{
+				++h_;
+				return *this;
+			}
+
+			friend bool operator == (species_iterator const & it1, species_iterator const & it2)
+			{
+				return it1.h_ == it2.h_;
+			}
+
+			friend bool operator != (species_iterator const & it1, species_iterator const & it2)
+			{
+				return !(it1 == it2);
+			}
+
+		private:
+			ecs_detail::species_handle h_;
+		};
+
 		enum class policy
 		{
 			sparse,
@@ -456,7 +488,10 @@ namespace psemek::util
 		template <typename ... Components>
 		species_handle register_species(std::string name, policy p, Components && ... components);
 
-		ecs_detail::species_handle species_count() const { return species_.size(); }
+		util::range<species_iterator> species() const
+		{
+			return {species_iterator{0}, species_iterator{species_.size()}};
+		}
 
 		std::string_view species_name(species_handle species) const { return species_[species.value]->name(); }
 
@@ -518,7 +553,7 @@ namespace psemek::util
 	template <typename ... Components>
 	ecs::species_handle ecs::register_species(std::string name, policy p, Components && ... components)
 	{
-		auto result = species_count();
+		auto result = species_.size();
 		if (p == policy::sparse)
 			species_.push_back(std::make_unique<ecs_detail::sparse_species_impl<Components...>>(std::move(name), result, std::move(components)...));
 		else