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group.hpp
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group.hpp
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#ifndef ENTT_ENTITY_GROUP_HPP
#define ENTT_ENTITY_GROUP_HPP
#include <tuple>
#include <utility>
#include <type_traits>
#include "../config/config.h"
#include "../core/type_traits.hpp"
#include "entity.hpp"
#include "fwd.hpp"
#include "sparse_set.hpp"
#include "storage.hpp"
#include "utility.hpp"
namespace entt {
/**
* @brief Group.
*
* Primary template isn't defined on purpose. All the specializations give a
* compile-time error, but for a few reasonable cases.
*/
template<typename...>
class basic_group;
/**
* @brief Non-owning group.
*
* A non-owning group returns all entities and only the entities that have at
* least the given components. Moreover, it's guaranteed that the entity list
* is tightly packed in memory for fast iterations.
*
* @b Important
*
* Iterators aren't invalidated if:
*
* * New instances of the given components are created and assigned to entities.
* * The entity currently pointed is modified (as an example, if one of the
* given components is removed from the entity to which the iterator points).
* * The entity currently pointed is destroyed.
*
* In all other cases, modifying the pools iterated by the group in any way
* invalidates all the iterators and using them results in undefined behavior.
*
* @note
* Groups share references to the underlying data structures of the registry
* that generated them. Therefore any change to the entities and to the
* components made by means of the registry are immediately reflected by all the
* groups.<br/>
* Moreover, sorting a non-owning group affects all the instances of the same
* group (it means that users don't have to call `sort` on each instance to sort
* all of them because they _share_ entities and components).
*
* @warning
* Lifetime of a group must not overcome that of the registry that generated it.
* In any other case, attempting to use a group results in undefined behavior.
*
* @tparam Entity A valid entity type (see entt_traits for more details).
* @tparam Exclude Types of components used to filter the group.
* @tparam Get Type of components observed by the group.
*/
template<typename Entity, typename... Exclude, typename... Get>
class basic_group<Entity, exclude_t<Exclude...>, get_t<Get...>> final {
/*! @brief A registry is allowed to create groups. */
friend class basic_registry<Entity>;
template<typename Component>
using storage_type = constness_as_t<typename storage_traits<Entity, std::remove_const_t<Component>>::storage_type, Component>;
class iterable_group final {
friend class basic_group<Entity, exclude_t<Exclude...>, get_t<Get...>>;
template<typename It>
class iterable_group_iterator final {
friend class iterable_group;
template<typename... Args>
iterable_group_iterator(It from, const std::tuple<storage_type<Get> *...> &args) ENTT_NOEXCEPT
: it{from},
pools{args}
{}
public:
using difference_type = std::ptrdiff_t;
using value_type = decltype(std::tuple_cat(std::tuple<Entity>{}, std::declval<basic_group>().get({})));
using pointer = void;
using reference = value_type;
using iterator_category = std::input_iterator_tag;
iterable_group_iterator & operator++() ENTT_NOEXCEPT {
return ++it, *this;
}
iterable_group_iterator operator++(int) ENTT_NOEXCEPT {
iterable_group_iterator orig = *this;
return ++(*this), orig;
}
[[nodiscard]] reference operator*() const ENTT_NOEXCEPT {
const auto entt = *it;
return std::tuple_cat(std::make_tuple(entt), get_as_tuple(*std::get<storage_type<Get> *>(pools), entt)...);
}
[[nodiscard]] bool operator==(const iterable_group_iterator &other) const ENTT_NOEXCEPT {
return other.it == it;
}
[[nodiscard]] bool operator!=(const iterable_group_iterator &other) const ENTT_NOEXCEPT {
return !(*this == other);
}
private:
It it;
const std::tuple<storage_type<Get> *...> pools;
};
iterable_group(basic_sparse_set<Entity> * const ref, const std::tuple<storage_type<Get> *...> &cpools)
: handler{ref},
pools{cpools}
{}
public:
using iterator = iterable_group_iterator<typename basic_sparse_set<Entity>::iterator>;
using reverse_iterator = iterable_group_iterator<typename basic_sparse_set<Entity>::reverse_iterator>;
[[nodiscard]] iterator begin() const ENTT_NOEXCEPT {
return handler ? iterator{handler->begin(), pools} : iterator{{}, pools};
}
[[nodiscard]] iterator end() const ENTT_NOEXCEPT {
return handler ? iterator{handler->end(), pools} : iterator{{}, pools};
}
[[nodiscard]] reverse_iterator rbegin() const ENTT_NOEXCEPT {
return handler ? reverse_iterator{handler->rbegin(), pools} : reverse_iterator{{}, pools};
}
[[nodiscard]] reverse_iterator rend() const ENTT_NOEXCEPT {
return handler ? reverse_iterator{handler->rend(), pools} : reverse_iterator{{}, pools};
}
private:
basic_sparse_set<Entity> * const handler;
const std::tuple<storage_type<Get> *...> pools;
};
basic_group(basic_sparse_set<Entity> &ref, storage_type<Get> &... gpool) ENTT_NOEXCEPT
: handler{&ref},
pools{&gpool...}
{}
public:
/*! @brief Underlying entity identifier. */
using entity_type = Entity;
/*! @brief Unsigned integer type. */
using size_type = std::size_t;
/*! @brief Random access iterator type. */
using iterator = typename basic_sparse_set<Entity>::iterator;
/*! @brief Reversed iterator type. */
using reverse_iterator = typename basic_sparse_set<Entity>::reverse_iterator;
/*! @brief Default constructor to use to create empty, invalid groups. */
basic_group() ENTT_NOEXCEPT
: handler{}
{}
/**
* @brief Returns the number of entities that have the given components.
* @return Number of entities that have the given components.
*/
[[nodiscard]] size_type size() const ENTT_NOEXCEPT {
return *this ? handler->size() : size_type{};
}
/**
* @brief Returns the number of elements that a group has currently
* allocated space for.
* @return Capacity of the group.
*/
[[nodiscard]] size_type capacity() const ENTT_NOEXCEPT {
return *this ? handler->capacity() : size_type{};
}
/*! @brief Requests the removal of unused capacity. */
void shrink_to_fit() {
if(*this) {
handler->shrink_to_fit();
}
}
/**
* @brief Checks whether a group is empty.
* @return True if the group is empty, false otherwise.
*/
[[nodiscard]] bool empty() const ENTT_NOEXCEPT {
return !*this || handler->empty();
}
/**
* @brief Direct access to the list of entities.
*
* The returned pointer is such that range `[data(), data() + size())` is
* always a valid range, even if the container is empty.
*
* @return A pointer to the array of entities.
*/
[[nodiscard]] const entity_type * data() const ENTT_NOEXCEPT {
return *this ? handler->data() : nullptr;
}
/**
* @brief Returns an iterator to the first entity of the group.
*
* The returned iterator points to the first entity of the group. If the
* group is empty, the returned iterator will be equal to `end()`.
*
* @return An iterator to the first entity of the group.
*/
[[nodiscard]] iterator begin() const ENTT_NOEXCEPT {
return *this ? handler->begin() : iterator{};
}
/**
* @brief Returns an iterator that is past the last entity of the group.
*
* The returned iterator points to the entity following the last entity of
* the group. Attempting to dereference the returned iterator results in
* undefined behavior.
*
* @return An iterator to the entity following the last entity of the
* group.
*/
[[nodiscard]] iterator end() const ENTT_NOEXCEPT {
return *this ? handler->end() : iterator{};
}
/**
* @brief Returns an iterator to the first entity of the reversed group.
*
* The returned iterator points to the first entity of the reversed group.
* If the group is empty, the returned iterator will be equal to `rend()`.
*
* @return An iterator to the first entity of the reversed group.
*/
[[nodiscard]] reverse_iterator rbegin() const ENTT_NOEXCEPT {
return *this ? handler->rbegin() : reverse_iterator{};
}
/**
* @brief Returns an iterator that is past the last entity of the reversed
* group.
*
* The returned iterator points to the entity following the last entity of
* the reversed group. Attempting to dereference the returned iterator
* results in undefined behavior.
*
* @return An iterator to the entity following the last entity of the
* reversed group.
*/
[[nodiscard]] reverse_iterator rend() const ENTT_NOEXCEPT {
return *this ? handler->rend() : reverse_iterator{};
}
/**
* @brief Returns the first entity of the group, if any.
* @return The first entity of the group if one exists, the null entity
* otherwise.
*/
[[nodiscard]] entity_type front() const {
const auto it = begin();
return it != end() ? *it : null;
}
/**
* @brief Returns the last entity of the group, if any.
* @return The last entity of the group if one exists, the null entity
* otherwise.
*/
[[nodiscard]] entity_type back() const {
const auto it = rbegin();
return it != rend() ? *it : null;
}
/**
* @brief Finds an entity.
* @param entt A valid entity identifier.
* @return An iterator to the given entity if it's found, past the end
* iterator otherwise.
*/
[[nodiscard]] iterator find(const entity_type entt) const {
const auto it = *this ? handler->find(entt) : iterator{};
return it != end() && *it == entt ? it : end();
}
/**
* @brief Returns the identifier that occupies the given position.
* @param pos Position of the element to return.
* @return The identifier that occupies the given position.
*/
[[nodiscard]] entity_type operator[](const size_type pos) const {
return begin()[pos];
}
/**
* @brief Checks if a group is properly initialized.
* @return True if the group is properly initialized, false otherwise.
*/
[[nodiscard]] explicit operator bool() const ENTT_NOEXCEPT {
return handler != nullptr;
}
/**
* @brief Checks if a group contains an entity.
* @param entt A valid entity identifier.
* @return True if the group contains the given entity, false otherwise.
*/
[[nodiscard]] bool contains(const entity_type entt) const {
return *this && handler->contains(entt);
}
/**
* @brief Returns the components assigned to the given entity.
*
* Prefer this function instead of `registry::get` during iterations. It has
* far better performance than its counterpart.
*
* @warning
* Attempting to use an invalid component type results in a compilation
* error. Attempting to use an entity that doesn't belong to the group
* results in undefined behavior.
*
* @tparam Component Types of components to get.
* @param entt A valid entity identifier.
* @return The components assigned to the entity.
*/
template<typename... Component>
[[nodiscard]] decltype(auto) get(const entity_type entt) const {
ENTT_ASSERT(contains(entt));
if constexpr(sizeof...(Component) == 0) {
return std::tuple_cat(get_as_tuple(*std::get<storage_type<Get> *>(pools), entt)...);
} else if constexpr(sizeof...(Component) == 1) {
return (std::get<storage_type<Component> *>(pools)->get(entt), ...);
} else {
return std::tuple_cat(get_as_tuple(*std::get<storage_type<Component> *>(pools), entt)...);
}
}
/**
* @brief Iterates entities and components and applies the given function
* object to them.
*
* The function object is invoked for each entity. It is provided with the
* entity itself and a set of references to non-empty components. The
* _constness_ of the components is as requested.<br/>
* The signature of the function must be equivalent to one of the following
* forms:
*
* @code{.cpp}
* void(const entity_type, Type &...);
* void(Type &...);
* @endcode
*
* @note
* Empty types aren't explicitly instantiated and therefore they are never
* returned during iterations.
*
* @tparam Func Type of the function object to invoke.
* @param func A valid function object.
*/
template<typename Func>
void each(Func func) const {
for(const auto entt: *this) {
if constexpr(is_applicable_v<Func, decltype(std::tuple_cat(std::tuple<entity_type>{}, std::declval<basic_group>().get({})))>) {
std::apply(func, std::tuple_cat(std::make_tuple(entt), get(entt)));
} else {
std::apply(func, get(entt));
}
}
}
/**
* @brief Returns an iterable object to use to _visit_ the group.
*
* The iterable object returns tuples that contain the current entity and a
* set of references to its non-empty components. The _constness_ of the
* components is as requested.
*
* @note
* Empty types aren't explicitly instantiated and therefore they are never
* returned during iterations.
*
* @return An iterable object to use to _visit_ the group.
*/
[[nodiscard]] iterable_group each() const ENTT_NOEXCEPT {
return iterable_group{handler, pools};
}
/**
* @brief Sort a group according to the given comparison function.
*
* Sort the group so that iterating it with a couple of iterators returns
* entities and components in the expected order. See `begin` and `end` for
* more details.
*
* The comparison function object must return `true` if the first element
* is _less_ than the second one, `false` otherwise. The signature of the
* comparison function should be equivalent to one of the following:
*
* @code{.cpp}
* bool(std::tuple<Component &...>, std::tuple<Component &...>);
* bool(const Component &..., const Component &...);
* bool(const Entity, const Entity);
* @endcode
*
* Where `Component` are such that they are iterated by the group.<br/>
* Moreover, the comparison function object shall induce a
* _strict weak ordering_ on the values.
*
* The sort function oject must offer a member function template
* `operator()` that accepts three arguments:
*
* * An iterator to the first element of the range to sort.
* * An iterator past the last element of the range to sort.
* * A comparison function to use to compare the elements.
*
* @tparam Component Optional types of components to compare.
* @tparam Compare Type of comparison function object.
* @tparam Sort Type of sort function object.
* @tparam Args Types of arguments to forward to the sort function object.
* @param compare A valid comparison function object.
* @param algo A valid sort function object.
* @param args Arguments to forward to the sort function object, if any.
*/
template<typename... Component, typename Compare, typename Sort = std_sort, typename... Args>
void sort(Compare compare, Sort algo = Sort{}, Args &&... args) {
if(*this) {
if constexpr(sizeof...(Component) == 0) {
static_assert(std::is_invocable_v<Compare, const entity_type, const entity_type>, "Invalid comparison function");
handler->sort(std::move(compare), std::move(algo), std::forward<Args>(args)...);
} else if constexpr(sizeof...(Component) == 1) {
handler->sort([this, compare = std::move(compare)](const entity_type lhs, const entity_type rhs) {
return compare((std::get<storage_type<Component> *>(pools)->get(lhs), ...), (std::get<storage_type<Component> *>(pools)->get(rhs), ...));
}, std::move(algo), std::forward<Args>(args)...);
} else {
handler->sort([this, compare = std::move(compare)](const entity_type lhs, const entity_type rhs) {
return compare(std::forward_as_tuple(std::get<storage_type<Component> *>(pools)->get(lhs)...), std::forward_as_tuple(std::get<storage_type<Component> *>(pools)->get(rhs)...));
}, std::move(algo), std::forward<Args>(args)...);
}
}
}
/**
* @brief Sort the shared pool of entities according to the given component.
*
* Non-owning groups of the same type share with the registry a pool of
* entities with its own order that doesn't depend on the order of any pool
* of components. Users can order the underlying data structure so that it
* respects the order of the pool of the given component.
*
* @note
* The shared pool of entities and thus its order is affected by the changes
* to each and every pool that it tracks. Therefore changes to those pools
* can quickly ruin the order imposed to the pool of entities shared between
* the non-owning groups.
*
* @tparam Component Type of component to use to impose the order.
*/
template<typename Component>
void sort() const {
if(*this) {
handler->respect(*std::get<storage_type<Component> *>(pools));
}
}
private:
basic_sparse_set<entity_type> * const handler;
const std::tuple<storage_type<Get> *...> pools;
};
/**
* @brief Owning group.
*
* Owning groups return all entities and only the entities that have at least
* the given components. Moreover:
*
* * It's guaranteed that the entity list is tightly packed in memory for fast
* iterations.
* * It's guaranteed that the lists of owned components are tightly packed in
* memory for even faster iterations and to allow direct access.
* * They stay true to the order of the owned components and all instances have
* the same order in memory.
*
* The more types of components are owned by a group, the faster it is to
* iterate them.
*
* @b Important
*
* Iterators aren't invalidated if:
*
* * New instances of the given components are created and assigned to entities.
* * The entity currently pointed is modified (as an example, if one of the
* given components is removed from the entity to which the iterator points).
* * The entity currently pointed is destroyed.
*
* In all other cases, modifying the pools iterated by the group in any way
* invalidates all the iterators and using them results in undefined behavior.
*
* @note
* Groups share references to the underlying data structures of the registry
* that generated them. Therefore any change to the entities and to the
* components made by means of the registry are immediately reflected by all the
* groups.
* Moreover, sorting an owning group affects all the instance of the same group
* (it means that users don't have to call `sort` on each instance to sort all
* of them because they share the underlying data structure).
*
* @warning
* Lifetime of a group must not overcome that of the registry that generated it.
* In any other case, attempting to use a group results in undefined behavior.
*
* @tparam Entity A valid entity type (see entt_traits for more details).
* @tparam Exclude Types of components used to filter the group.
* @tparam Get Types of components observed by the group.
* @tparam Owned Types of components owned by the group.
*/
template<typename Entity, typename... Exclude, typename... Get, typename... Owned>
class basic_group<Entity, exclude_t<Exclude...>, get_t<Get...>, Owned...> final {
/*! @brief A registry is allowed to create groups. */
friend class basic_registry<Entity>;
template<typename Component>
using storage_type = constness_as_t<typename storage_traits<Entity, std::remove_const_t<Component>>::storage_type, Component>;
class iterable_group final {
friend class basic_group<Entity, exclude_t<Exclude...>, get_t<Get...>, Owned...>;
template<typename, typename>
class iterable_group_iterator;
template<typename It, typename... OIt>
class iterable_group_iterator<It, type_list<OIt...>> final {
friend class iterable_group;
template<typename... Other>
iterable_group_iterator(It from, const std::tuple<Other...> &other, const std::tuple<storage_type<Get> *...> &cpools) ENTT_NOEXCEPT
: it{from},
owned{std::get<OIt>(other)...},
get{cpools}
{}
public:
using difference_type = std::ptrdiff_t;
using value_type = decltype(std::tuple_cat(std::tuple<Entity>{}, std::declval<basic_group>().get({})));
using pointer = void;
using reference = value_type;
using iterator_category = std::input_iterator_tag;
iterable_group_iterator & operator++() ENTT_NOEXCEPT {
return ++it, (++std::get<OIt>(owned), ...), *this;
}
iterable_group_iterator operator++(int) ENTT_NOEXCEPT {
iterable_group_iterator orig = *this;
return ++(*this), orig;
}
[[nodiscard]] reference operator*() const ENTT_NOEXCEPT {
return std::tuple_cat(
std::make_tuple(*it),
std::forward_as_tuple(*std::get<OIt>(owned)...),
get_as_tuple(*std::get<storage_type<Get> *>(get), *it)...
);
}
[[nodiscard]] bool operator==(const iterable_group_iterator &other) const ENTT_NOEXCEPT {
return other.it == it;
}
[[nodiscard]] bool operator!=(const iterable_group_iterator &other) const ENTT_NOEXCEPT {
return !(*this == other);
}
private:
It it;
std::tuple<OIt...> owned;
std::tuple<storage_type<Get> *...> get;
};
iterable_group(std::tuple<storage_type<Owned> *..., storage_type<Get> *...> cpools, const std::size_t * const extent)
: pools{cpools},
length{extent}
{}
public:
using iterator = iterable_group_iterator<
typename basic_sparse_set<Entity>::iterator,
type_list_cat_t<std::conditional_t<std::is_same_v<typename storage_type<Owned>::storage_category, empty_storage_tag>, type_list<>, type_list<decltype(std::declval<storage_type<Owned>>().end())>>...>
>;
using reverse_iterator = iterable_group_iterator<
typename basic_sparse_set<Entity>::reverse_iterator,
type_list_cat_t<std::conditional_t<std::is_same_v<typename storage_type<Owned>::storage_category, empty_storage_tag>, type_list<>, type_list<decltype(std::declval<storage_type<Owned>>().rbegin())>>...>
>;
[[nodiscard]] iterator begin() const ENTT_NOEXCEPT {
return length ? iterator{
std::get<0>(pools)->basic_sparse_set<Entity>::end() - *length,
std::make_tuple((std::get<storage_type<Owned> *>(pools)->end() - *length)...),
std::make_tuple(std::get<storage_type<Get> *>(pools)...)
} : iterator{{}, std::make_tuple(decltype(std::get<storage_type<Owned> *>(pools)->end()){}...), std::make_tuple(std::get<storage_type<Get> *>(pools)...)};
}
[[nodiscard]] iterator end() const ENTT_NOEXCEPT {
return length ? iterator{
std::get<0>(pools)->basic_sparse_set<Entity>::end(),
std::make_tuple((std::get<storage_type<Owned> *>(pools)->end())...),
std::make_tuple(std::get<storage_type<Get> *>(pools)...)
} : iterator{{}, std::make_tuple(decltype(std::get<storage_type<Owned> *>(pools)->end()){}...), std::make_tuple(std::get<storage_type<Get> *>(pools)...)};
}
[[nodiscard]] reverse_iterator rbegin() const ENTT_NOEXCEPT {
return length ? reverse_iterator{
std::get<0>(pools)->basic_sparse_set<Entity>::rbegin(),
std::make_tuple((std::get<storage_type<Owned> *>(pools)->rbegin())...),
std::make_tuple(std::get<storage_type<Get> *>(pools)...)
} : reverse_iterator{{}, std::make_tuple(decltype(std::get<storage_type<Owned> *>(pools)->rbegin()){}...), std::make_tuple(std::get<storage_type<Get> *>(pools)...)};
}
[[nodiscard]] reverse_iterator rend() const ENTT_NOEXCEPT {
return length ? reverse_iterator{
std::get<0>(pools)->basic_sparse_set<Entity>::rbegin() + *length,
std::make_tuple((std::get<storage_type<Owned> *>(pools)->rbegin() + *length)...),
std::make_tuple(std::get<storage_type<Get> *>(pools)...)
} : reverse_iterator{{}, std::make_tuple(decltype(std::get<storage_type<Owned> *>(pools)->rbegin()){}...), std::make_tuple(std::get<storage_type<Get> *>(pools)...)};
}
private:
const std::tuple<storage_type<Owned> *..., storage_type<Get> *...> pools;
const std::size_t * const length;
};
basic_group(const std::size_t &extent, storage_type<Owned> &... opool, storage_type<Get> &... gpool) ENTT_NOEXCEPT
: pools{&opool..., &gpool...},
length{&extent}
{}
public:
/*! @brief Underlying entity identifier. */
using entity_type = Entity;
/*! @brief Unsigned integer type. */
using size_type = std::size_t;
/*! @brief Random access iterator type. */
using iterator = typename basic_sparse_set<Entity>::iterator;
/*! @brief Reversed iterator type. */
using reverse_iterator = typename basic_sparse_set<Entity>::reverse_iterator;
/*! @brief Default constructor to use to create empty, invalid groups. */
basic_group() ENTT_NOEXCEPT
: length{}
{}
/**
* @brief Returns the number of entities that have the given components.
* @return Number of entities that have the given components.
*/
[[nodiscard]] size_type size() const ENTT_NOEXCEPT {
return *this ? *length : size_type{};
}
/**
* @brief Checks whether a group is empty.
* @return True if the group is empty, false otherwise.
*/
[[nodiscard]] bool empty() const ENTT_NOEXCEPT {
return !*this || !*length;
}
/**
* @brief Direct access to the list of components of a given pool.
*
* The returned pointer is such that range
* `[raw<Component>(), raw<Component>() + size())` is always a valid range,
* even if the container is empty.<br/>
*
* @warning
* This function is only available for owned types.
*
* @tparam Component Type of component in which one is interested.
* @return A pointer to the array of components.
*/
template<typename Component>
[[nodiscard]] Component * raw() const ENTT_NOEXCEPT {
static_assert((std::is_same_v<Component, Owned> || ...));
auto *cpool = std::get<storage_type<Component> *>(pools);
return cpool ? cpool->raw() : nullptr;
}
/**
* @brief Direct access to the list of entities.
*
* The returned pointer is such that range `[data(), data() + size())` is
* always a valid range, even if the container is empty.
*
* @return A pointer to the array of entities.
*/
[[nodiscard]] const entity_type * data() const ENTT_NOEXCEPT {
return *this ? std::get<0>(pools)->data() : nullptr;
}
/**
* @brief Returns an iterator to the first entity of the group.
*
* The returned iterator points to the first entity of the group. If the
* group is empty, the returned iterator will be equal to `end()`.
*
* @return An iterator to the first entity of the group.
*/
[[nodiscard]] iterator begin() const ENTT_NOEXCEPT {
return *this ? (std::get<0>(pools)->basic_sparse_set<entity_type>::end() - *length) : iterator{};
}
/**
* @brief Returns an iterator that is past the last entity of the group.
*
* The returned iterator points to the entity following the last entity of
* the group. Attempting to dereference the returned iterator results in
* undefined behavior.
*
* @return An iterator to the entity following the last entity of the
* group.
*/
[[nodiscard]] iterator end() const ENTT_NOEXCEPT {
return *this ? std::get<0>(pools)->basic_sparse_set<entity_type>::end() : iterator{};
}
/**
* @brief Returns an iterator to the first entity of the reversed group.
*
* The returned iterator points to the first entity of the reversed group.
* If the group is empty, the returned iterator will be equal to `rend()`.
*
* @return An iterator to the first entity of the reversed group.
*/
[[nodiscard]] reverse_iterator rbegin() const ENTT_NOEXCEPT {
return *this ? std::get<0>(pools)->basic_sparse_set<entity_type>::rbegin() : reverse_iterator{};
}
/**
* @brief Returns an iterator that is past the last entity of the reversed
* group.
*
* The returned iterator points to the entity following the last entity of
* the reversed group. Attempting to dereference the returned iterator
* results in undefined behavior.
*
* @return An iterator to the entity following the last entity of the
* reversed group.
*/
[[nodiscard]] reverse_iterator rend() const ENTT_NOEXCEPT {
return *this ? (std::get<0>(pools)->basic_sparse_set<entity_type>::rbegin() + *length) : reverse_iterator{};
}
/**
* @brief Returns the first entity of the group, if any.
* @return The first entity of the group if one exists, the null entity
* otherwise.
*/
[[nodiscard]] entity_type front() const {
const auto it = begin();
return it != end() ? *it : null;
}
/**
* @brief Returns the last entity of the group, if any.
* @return The last entity of the group if one exists, the null entity
* otherwise.
*/
[[nodiscard]] entity_type back() const {
const auto it = rbegin();
return it != rend() ? *it : null;
}
/**
* @brief Finds an entity.
* @param entt A valid entity identifier.
* @return An iterator to the given entity if it's found, past the end
* iterator otherwise.
*/
[[nodiscard]] iterator find(const entity_type entt) const {
const auto it = *this ? std::get<0>(pools)->find(entt) : iterator{};
return it != end() && it >= begin() && *it == entt ? it : end();
}
/**
* @brief Returns the identifier that occupies the given position.
* @param pos Position of the element to return.
* @return The identifier that occupies the given position.
*/
[[nodiscard]] entity_type operator[](const size_type pos) const {
return begin()[pos];
}
/**
* @brief Checks if a group is properly initialized.
* @return True if the group is properly initialized, false otherwise.
*/
[[nodiscard]] explicit operator bool() const ENTT_NOEXCEPT {
return length != nullptr;
}
/**
* @brief Checks if a group contains an entity.
* @param entt A valid entity identifier.
* @return True if the group contains the given entity, false otherwise.
*/
[[nodiscard]] bool contains(const entity_type entt) const {
return *this && std::get<0>(pools)->contains(entt) && (std::get<0>(pools)->index(entt) < (*length));
}
/**
* @brief Returns the components assigned to the given entity.
*
* Prefer this function instead of `registry::get` during iterations. It has
* far better performance than its counterpart.
*
* @warning
* Attempting to use an invalid component type results in a compilation
* error. Attempting to use an entity that doesn't belong to the group
* results in undefined behavior.
*
* @tparam Component Types of components to get.
* @param entt A valid entity identifier.
* @return The components assigned to the entity.
*/
template<typename... Component>
[[nodiscard]] decltype(auto) get(const entity_type entt) const {
ENTT_ASSERT(contains(entt));
if constexpr(sizeof...(Component) == 0) {
return std::tuple_cat(get_as_tuple(*std::get<storage_type<Owned> *>(pools), entt)..., get_as_tuple(*std::get<storage_type<Get> *>(pools), entt)...);
} else if constexpr(sizeof...(Component) == 1) {
return (std::get<storage_type<Component> *>(pools)->get(entt), ...);
} else {
return std::tuple_cat(get_as_tuple(*std::get<storage_type<Component> *>(pools), entt)...);
}
}
/**
* @brief Iterates entities and components and applies the given function
* object to them.
*
* The function object is invoked for each entity. It is provided with the
* entity itself and a set of references to non-empty components. The
* _constness_ of the components is as requested.<br/>
* The signature of the function must be equivalent to one of the following
* forms:
*
* @code{.cpp}
* void(const entity_type, Type &...);
* void(Type &...);
* @endcode
*
* @note
* Empty types aren't explicitly instantiated and therefore they are never
* returned during iterations.
*
* @tparam Func Type of the function object to invoke.
* @param func A valid function object.
*/
template<typename Func>
void each(Func func) const {
for(auto args: each()) {
if constexpr(is_applicable_v<Func, decltype(std::tuple_cat(std::tuple<entity_type>{}, std::declval<basic_group>().get({})))>) {
std::apply(func, args);
} else {
std::apply([&func](auto, auto &&... less) { func(std::forward<decltype(less)>(less)...); }, args);
}
}
}
/**
* @brief Returns an iterable object to use to _visit_ the group.
*
* The iterable object returns tuples that contain the current entity and a
* set of references to its non-empty components. The _constness_ of the
* components is as requested.
*
* @note
* Empty types aren't explicitly instantiated and therefore they are never
* returned during iterations.
*
* @return An iterable object to use to _visit_ the group.
*/
[[nodiscard]] iterable_group each() const ENTT_NOEXCEPT {
return iterable_group{pools, length};
}
/**
* @brief Sort a group according to the given comparison function.
*
* Sort the group so that iterating it with a couple of iterators returns
* entities and components in the expected order. See `begin` and `end` for
* more details.
*
* The comparison function object must return `true` if the first element
* is _less_ than the second one, `false` otherwise. The signature of the
* comparison function should be equivalent to one of the following:
*
* @code{.cpp}
* bool(std::tuple<Component &...>, std::tuple<Component &...>);
* bool(const Component &, const Component &);
* bool(const Entity, const Entity);
* @endcode
*
* Where `Component` are either owned types or not but still such that they
* are iterated by the group.<br/>
* Moreover, the comparison function object shall induce a
* _strict weak ordering_ on the values.
*
* The sort function oject must offer a member function template
* `operator()` that accepts three arguments:
*
* * An iterator to the first element of the range to sort.
* * An iterator past the last element of the range to sort.
* * A comparison function to use to compare the elements.
*
* @tparam Component Optional types of components to compare.
* @tparam Compare Type of comparison function object.
* @tparam Sort Type of sort function object.
* @tparam Args Types of arguments to forward to the sort function object.
* @param compare A valid comparison function object.
* @param algo A valid sort function object.
* @param args Arguments to forward to the sort function object, if any.
*/
template<typename... Component, typename Compare, typename Sort = std_sort, typename... Args>
void sort(Compare compare, Sort algo = Sort{}, Args &&... args) const {
auto *cpool = std::get<0>(pools);
if constexpr(sizeof...(Component) == 0) {
static_assert(std::is_invocable_v<Compare, const entity_type, const entity_type>, "Invalid comparison function");
cpool->sort_n(*length, std::move(compare), std::move(algo), std::forward<Args>(args)...);
} else if constexpr(sizeof...(Component) == 1) {
cpool->sort_n(*length, [this, compare = std::move(compare)](const entity_type lhs, const entity_type rhs) {
return compare((std::get<storage_type<Component> *>(pools)->get(lhs), ...), (std::get<storage_type<Component> *>(pools)->get(rhs), ...));
}, std::move(algo), std::forward<Args>(args)...);
} else {
cpool->sort_n(*length, [this, compare = std::move(compare)](const entity_type lhs, const entity_type rhs) {
return compare(std::forward_as_tuple(std::get<storage_type<Component> *>(pools)->get(lhs)...), std::forward_as_tuple(std::get<storage_type<Component> *>(pools)->get(rhs)...));
}, std::move(algo), std::forward<Args>(args)...);
}
[this](auto *head, auto *... other) {
for(auto next = *length; next; --next) {
const auto pos = next - 1;
[[maybe_unused]] const auto entt = head->data()[pos];
(other->swap(other->data()[pos], entt), ...);
}
}(std::get<storage_type<Owned> *>(pools)...);
}
private:
const std::tuple<storage_type<Owned> *..., storage_type<Get> *...> pools;
const size_type * const length;
};
}
#endif