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xenobrain/ecs1.h

Created November 1, 2023 21:37
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ecs1.h
#ifndef ENGINE_SCENE_SCENE_H
#define ENGINE_SCENE_SCENE_H
#include <scene/types.h>
#include <any>
#include <map>
#include <bitset>
#include <vector>
#include <typeindex>
namespace xc {
auto static component_id_pool = std::size_t{0};
using signature_type = std::bitset<sizeof(entity_id) << 3>;
class scene : public std::enable_shared_from_this<scene> {
public:
auto static create() -> std::shared_ptr<scene>;
~scene();
auto create_entity() -> entity_id {
auto entity = _entities++;
if (entity >= static_cast<entity_id>(_signatures.size()))
_signatures.resize(static_cast<std::size_t>(entity + 1u));
return entity;
}
auto remove_entity(entity_id entity) -> void {
_signatures[entity].reset();
}
template<class T, typename... Args> auto inline add_component(entity_id entity, Args &&... args) -> T& {
auto component_id = lookup<T>::id();
if (component_id >= _pools.size()) _pools.resize(component_id + 1);
if (!_pools[component_id].has_value()) _pools[component_id].template emplace<std::vector<T>>();
auto& pool = std::any_cast<std::vector<T>&>(_pools[component_id]);
if (entity >= pool.size()) pool.resize(_entities);
pool[entity] = T{std::forward<Args>(args)...};
_signatures.at(entity).set(component_id);
return pool[entity];
}
template<class T> auto inline remove_component(entity_id entity) -> void {
_signatures.at(entity).set(lookup<T>::id(), false);
}
template<class T> [[nodiscard]] auto inline has_component(entity_id entity) -> bool {
return _signatures.at(entity).test(lookup<T>::id());
}
template<class T> [[nodiscard]] auto inline get_component(entity_id entity) -> T& {
return std::any_cast<std::vector<T>&>(_pools[lookup<T>::id()])[entity];
}
struct view_t {
std::shared_ptr<scene> world;
std::vector<entity_id> entities;
template<class A, class F> auto each(F&& f) -> void {
for (auto entity : entities)
std::invoke(std::forward<F>(f), world->template get_component<A>(entity));
}
template<class A, class B, class F> auto each(F&& f) -> void {
for (auto entity : entities)
std::invoke(std::forward<F>(f),
world->template get_component<A>(entity),
world->template get_component<A>(entity));
}
template<class A, class B, class C, class F> auto each(F&& f) -> void {
for (auto entity : entities)
std::invoke(std::forward<F>(f),
world->template get_component<A>(entity),
world->template get_component<B>(entity),
world->template get_component<C>(entity));
}
};
template<class A> auto view() -> view_t {
auto entities = std::vector<std::size_t>{};
for (auto i = std::size_t{0u}; i < _signatures.size(); ++i) {
auto signature = _signatures[i];
auto component_id = lookup<A>::id();
if (signature.test(component_id))
entities.template emplace_back(i);
}
return view_t{shared_from_this(), std::move(entities)};
}
template<class A, class B> auto view() -> view_t {
auto entities = std::vector<std::size_t>{};
for (auto i = std::size_t{0u}; i < _signatures.size(); ++i) {
auto signature = _signatures[i];
if (signature.test(lookup<A>::id()) && signature.test(lookup<B>::id()))
entities.template emplace_back(i);
}
return view_t{shared_from_this(), std::move(entities)};
}
template<class A, class B, class C> auto view() -> view_t {
auto entities = std::vector<std::size_t>{};
for (auto i = std::size_t{0u}; i < _signatures.size(); ++i) {
auto signature = _signatures[i];
if (signature.test(lookup<A>::id()) && signature.test(lookup<B>::id()) && signature.test(lookup<C>::id()))
entities.template emplace_back(i);
}
return view_t{shared_from_this(), std::move(entities)};
}
private:
scene();
template<class T> struct lookup {
auto static id() -> std::size_t {
auto static id = component_id_pool++;
return id;
}
};
entity_id _entities = 0;
// TODO: the pools should be dense arrays-- else when we delete components a hole is left
std::vector<std::any> _pools;
std::vector<signature_type> _signatures;
};
}
#endif // ENGINE_SCENE_SCENE_H
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