component.h

#pragma once
#include "gaia/config/config.h"
 
#include <cstdint>
#include <type_traits>
 
#include "gaia/core/hashing_policy.h"
#include "gaia/core/utility.h"
#include "gaia/ecs/id.h"
#include "gaia/mem/data_layout_policy.h"
#include "gaia/meta/type_info.h"
 
namespace gaia {
  namespace ecs {
    //----------------------------------------------------------------------
    // Component-related types
    //----------------------------------------------------------------------
 
    using ComponentVersion = uint32_t;
    using ChunkDataVersionOffset = uint8_t;
    using CompOffsetMappingIndex = uint8_t;
    using ChunkDataOffset = uint16_t;
    using ComponentLookupHash = core::direct_hash_key<uint64_t>;
    using EntitySpan = std::span<const Entity>;
    using EntitySpanMut = std::span<Entity>;
    using ComponentSpan = std::span<const Component>;
    using ChunkDataOffsetSpan = std::span<const ChunkDataOffset>;
    using SortComponentCond = core::is_smaller<Entity>;
 
    GAIA_NODISCARD constexpr bool component_uses_table_storage(Component component) noexcept {
      return component.size() != 0U && (component.storage_type() != DataStorageType::Sparse || component.soa() != 0U);
    }
 
    GAIA_NODISCARD constexpr bool component_uses_sparse_storage(Component component) noexcept {
      return component.size() != 0U && component.storage_type() == DataStorageType::Sparse && component.soa() == 0U;
    }
 
    namespace detail {
      template <typename, typename = void>
      struct auto_storage_policy_inter {
        static constexpr DataStorageType data_storage_type = DataStorageType::Table;
      };
      template <typename T>
      struct auto_storage_policy_inter<T, std::void_t<decltype(T::gaia_Data_Storage)>> {
        static constexpr DataStorageType data_storage_type = T::gaia_Data_Storage;
      };
    } // namespace detail
 
    template <typename T>
    inline constexpr DataStorageType auto_storage_policy_v = detail::auto_storage_policy_inter<T>::data_storage_type;
 
    //----------------------------------------------------------------------
    // Component verification
    //----------------------------------------------------------------------
 
    namespace detail {
      template <typename T>
      struct is_component_size_valid: std::bool_constant<sizeof(T) < Component::MaxComponentSizeInBytes> {};
 
      template <typename T>
      struct is_component_type_valid:
          std::bool_constant<
              // SoA types need to be trivial. No restrictions otherwise.
              (!mem::is_soa_layout_v<T> || std::is_trivially_copyable_v<T>)> {};
 
    } // namespace detail
 
    //----------------------------------------------------------------------
    // Component verification
    //----------------------------------------------------------------------
 
    template <typename T>
    constexpr void verify_comp() {
      using U = typename actual_type_t<T>::TypeOriginal;
 
      // Make sure we only use this for "raw" types
      static_assert(
          core::is_raw_v<U>,
          "Components have to be \"raw\" types - no arrays, no const, reference, pointer or volatile");
      static_assert(detail::is_component_type_valid<U>::value, "SoA components must be trivially copyable");
    }
 
    //----------------------------------------------------------------------
    // Component lookup hash
    //----------------------------------------------------------------------
 
    template <typename Container>
    GAIA_NODISCARD constexpr ComponentLookupHash calc_lookup_hash(Container arr) noexcept {
      constexpr auto arrSize = arr.size();
      if constexpr (arrSize == 0) {
        return {0};
      } else {
        ComponentLookupHash::Type hash = arr[0];
        core::each<arrSize - 1>([&hash, &arr](auto i) {
          hash = core::hash_combine(hash, arr[i + 1]);
        });
        return {hash};
      }
    }
 
    template <typename = void, typename...>
    constexpr ComponentLookupHash calc_lookup_hash() noexcept;
 
    template <typename T, typename... Rest>
    GAIA_NODISCARD constexpr ComponentLookupHash calc_lookup_hash() noexcept {
      if constexpr (sizeof...(Rest) == 0)
        return {meta::type_info::hash<T>()};
      else
        return {core::hash_combine(meta::type_info::hash<T>(), meta::type_info::hash<Rest>()...)};
    }
 
    template <>
    GAIA_NODISCARD constexpr ComponentLookupHash calc_lookup_hash() noexcept {
      return {0};
    }
 
    GAIA_NODISCARD inline ComponentLookupHash calc_lookup_hash(EntitySpan comps) noexcept {
      const auto compsSize = comps.size();
      if (compsSize == 0)
        return {0};
 
      auto hash = core::calculate_hash64(comps[0].value());
      GAIA_FOR2(1, compsSize) {
        hash = core::hash_combine(hash, core::calculate_hash64(comps[i].value()));
      }
      return {hash};
    }
 
    template <uint32_t MAX_COMPONENTS>
    GAIA_NODISCARD inline uint32_t comp_idx(const Entity* pComps, Entity entity) {
      // We let the compiler know the upper iteration bound at compile-time.
      // This way it can optimize better (e.g. loop unrolling, vectorization).
      GAIA_FOR(MAX_COMPONENTS) {
        if (pComps[i] == entity)
          return i;
      }
 
      GAIA_ASSERT(false);
      return BadIndex;
    }
 
    GAIA_NODISCARD inline uint32_t comp_idx(std::span<const Entity> comps, Entity entity) {
      // We let the compiler know the upper iteration bound at compile-time.
      // This way it can optimize better (e.g. loop unrolling, vectorization).
      const auto cnt = (uint32_t)comps.size();
      GAIA_FOR(cnt) {
        if (comps[i] == entity)
          return i;
      }
 
      GAIA_ASSERT(false);
      return BadIndex;
    }
  } // namespace ecs
} // namespace gaia