10 files changed, 356 insertions, 0 deletions
diff --git a/mwe/ecs-memory-efficient/CMakeLists.txt b/mwe/ecs-memory-efficient/CMakeLists.txt
new file mode 100644
index 0000000..d072907
--- /dev/null
+++ b/mwe/ecs-memory-efficient/CMakeLists.txt
@@ -0,0 +1,17 @@
+cmake_minimum_required(VERSION 3.5)
+project(ecs-memory-efficient)
+
+# Set the C++ standard (optional, but good practice)
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED True)
+
+# Use the debug mode (otherwise breakpoints are not compiled)
+set(CMAKE_BUILD_TYPE Debug)
+
+add_executable(ecs-memory-efficient
+	src/main.cpp
+	src/ComponentManager.cpp
+	src/Components.cpp
+	src/GameObjectMax.cpp
+)
+target_include_directories(ecs-memory-efficient PRIVATE "${CMAKE_SOURCE_DIR}/inc")
diff --git a/mwe/ecs-memory-efficient/inc/ComponentManager.h b/mwe/ecs-memory-efficient/inc/ComponentManager.h
new file mode 100644
index 0000000..893aa56
--- /dev/null
+++ b/mwe/ecs-memory-efficient/inc/ComponentManager.h
@@ -0,0 +1,48 @@
+#pragma once
+
+#include "Components.h"
+#include <cstdint>
+#include <unordered_map>
+#include <vector>
+#include <typeindex>
+#include <memory>
+#include <utility>
+
+class ComponentManager {
+public:
+	static ComponentManager& GetInstance();	//Singleton
+
+	ComponentManager(const ComponentManager&) = delete;	//Singleton
+    ComponentManager(ComponentManager&&) = delete;	//Singleton
+    ComponentManager& operator=(const ComponentManager&) = delete;	//Singleton
+    ComponentManager& operator=(ComponentManager&&) = delete;	//Singleton
+
+	template <typename T, typename... Args>
+	void AddComponent(std::uint32_t id, Args&&... args);	//Add a component of a specific type
+	template <typename T>
+	void DeleteComponentsById(std::uint32_t id);	//Deletes all components of a specific type and id
+	template <typename T>
+	void DeleteComponents();	//Deletes all components of a specific type
+	void DeleteAllComponentsOfId(std::uint32_t id);	//Deletes all components of a specific id
+	void DeleteAllComponents();	//Deletes all components
+
+	template <typename T>
+    std::vector<std::reference_wrapper<T>> GetComponentsByID(std::uint32_t id) const;	//Get a vector<> of all components at specific type and id
+	template <typename T>
+	std::vector<std::pair<std::reference_wrapper<T>, std::uint32_t>> GetComponentsByType() const;	//Get a vector<> of all components of a specific type
+
+private:
+    static ComponentManager mInstance;	//Singleton
+
+    ComponentManager();	//Singleton
+
+	/*
+	 * The std::unordered_map<std::type_index, std::vector<std::vector<std::unique_ptr<Component>>>> below might seem a bit strange, let me explain this structure:
+	 * The std::unordered_map<> has a key and value. The key is a std::type_index and the value is a std::vector. So, a new std::vector will be created for each new std::type_index.
+	 * The first std::vector<> stores another vector<>. This first vector<> is to bind the entity's id to a component.
+	 * The second std::vector<> stores unique_ptrs. Each component can be gathered via an unique_ptr. This second vector<> allows multiple components of the same std::type_index for one entity (id).
+	 */
+	std::unordered_map<std::type_index, std::vector<std::vector<std::unique_ptr<Component>>>> mComponents;
+};
+
+#include "ComponentManager.hpp"
diff --git a/mwe/ecs-memory-efficient/inc/ComponentManager.hpp b/mwe/ecs-memory-efficient/inc/ComponentManager.hpp
new file mode 100644
index 0000000..53dfddd
--- /dev/null
+++ b/mwe/ecs-memory-efficient/inc/ComponentManager.hpp
@@ -0,0 +1,88 @@
+
+template <typename T, typename... Args>
+void ComponentManager::AddComponent(std::uint32_t id, Args&&... args) {
+    std::type_index type = typeid(T);	//Determine the type of T (this is used as the key of the unordered_map<>)
+
+    if (mComponents.find(type) == mComponents.end()) {	//Check if this component type is already in the unordered_map<>
+        mComponents[type] = std::vector<std::vector<std::unique_ptr<Component>>>();	//If not, create a new (empty) vector<> of vector<unique_ptr<Component>>
+    }
+
+    if (id >= mComponents[type].size()) {	//Resize the vector<> if the id is greater than the current size
+        mComponents[type].resize(id + 1);	//Initialize new slots to nullptr (resize does automatically init to nullptr)
+    }
+
+    mComponents[type][id].push_back(std::make_unique<T>(std::forward<Args>(args)...));	//Create a new component of type T using perfect forwarding and store its unique_ptr in the vector<>
+}
+
+template <typename T>
+void ComponentManager::DeleteComponentsById(std::uint32_t id) {
+	std::type_index type = typeid(T);	//Determine the type of T (this is used as the key of the unordered_map<>)
+
+	if (mComponents.find(type) != mComponents.end()) {	//Find the type (in the unordered_map<>)
+		std::vector<std::vector<std::unique_ptr<Component>>>& componentArray = mComponents[type];	//Get the correct vector<>
+
+        if (id < componentArray.size()) {	//Make sure that the id (that we are looking for) is within the boundaries of the vector<>
+            componentArray[id].clear();	//Clear the whole vector<> of this specific type and id
+        }
+	}
+}
+
+template <typename T>
+void ComponentManager::DeleteComponents() {
+	std::type_index type = typeid(T);	//Determine the type of T (this is used as the key of the unordered_map<>)
+
+	if (mComponents.find(type) != mComponents.end()) {	//Find the type (in the unordered_map<>)
+		mComponents[type].clear();	//Clear the whole vector<> of this specific type
+	}
+}
+
+template <typename T>
+std::vector<std::reference_wrapper<T>> ComponentManager::GetComponentsByID(std::uint32_t id) const {
+    std::type_index type = typeid(T);	//Determine the type of T (this is used as the key of the unordered_map<>)
+
+	std::vector<std::reference_wrapper<T>> componentVector;	//Create an empty vector<>
+
+    if (mComponents.find(type) != mComponents.end()) {	//Find the type (in the unordered_map<>)
+
+        const std::vector<std::vector<std::unique_ptr<Component>>>& componentArray = mComponents.at(type);	//Get the correct vector<>
+
+        if (id < componentArray.size()) {	//Make sure that the id (that we are looking for) is within the boundaries of the vector<>
+            for (const std::unique_ptr<Component>& componentPtr : componentArray[id]) {	//Loop trough the whole vector<>
+                T* castedComponent = static_cast<T*>(componentPtr.get());	//Cast the unique_ptr to a raw pointer
+
+                if (castedComponent) {	//Ensure that the cast was successful
+                    componentVector.push_back(*castedComponent); //Add the dereferenced raw pointer to the vector<>
+                }
+            }
+        }
+    }
+
+    return componentVector; //Return the vector<>
+}
+
+template <typename T>
+std::vector<std::pair<std::reference_wrapper<T>, std::uint32_t>> ComponentManager::GetComponentsByType() const {
+    std::type_index type = typeid(T);	//Determine the type of T (this is used as the key of the unordered_map<>)
+
+    std::vector<std::pair<std::reference_wrapper<T>, std::uint32_t>> componentVector;	//Create an empty vector<>
+	std::uint32_t id = 0;	//Set the id to 0 (the id will also be stored in the returned vector<>)
+
+    if (mComponents.find(type) != mComponents.end()) {	//Find the type (in the unordered_map<>)
+
+        const std::vector<std::vector<std::unique_ptr<Component>>>& componentArray = mComponents.at(type);	//Get the correct vector<>
+
+        for (const std::vector<std::unique_ptr<Component>>& component : componentArray) {	//Loop through the whole vector<>
+            for (const std::unique_ptr<Component>& componentPtr : component) {	//Loop trough the whole vector<>
+                T* castedComponent = static_cast<T*>(componentPtr.get());	//Cast the unique_ptr to a raw pointer
+
+                if (castedComponent) {	//Ensure that the cast was successful
+                    componentVector.emplace_back(std::ref(*castedComponent), id);	//Pair the dereferenced raw pointer and the id and add it to the vector<>
+                }
+            }
+
+			++id;	//Increase the id (the id will also be stored in the returned vector<>)
+        }
+    }
+
+    return componentVector;	//Return the vector<>
+}
diff --git a/mwe/ecs-memory-efficient/inc/Components.h b/mwe/ecs-memory-efficient/inc/Components.h
new file mode 100644
index 0000000..98c5fe7
--- /dev/null
+++ b/mwe/ecs-memory-efficient/inc/Components.h
@@ -0,0 +1,33 @@
+#pragma once
+
+#include <string>
+
+class Component {
+public:
+	Component();
+
+	bool mActive;
+};
+
+class Sprite : public Component {
+public:
+	Sprite(std::string path);
+
+	std::string mPath;
+};
+
+class Rigidbody : public Component {
+public:
+	Rigidbody(int mass, int gravityScale, int bodyType);
+
+	int mMass;
+	int mGravityScale;
+	int mBodyType;
+};
+
+class Colider : public Component {
+public:
+	Colider(int size);
+
+	int mSize;
+};
diff --git a/mwe/ecs-memory-efficient/inc/GameObjectMax.h b/mwe/ecs-memory-efficient/inc/GameObjectMax.h
new file mode 100644
index 0000000..f0bcec9
--- /dev/null
+++ b/mwe/ecs-memory-efficient/inc/GameObjectMax.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+
+class GameObject {
+public:
+	GameObject(std::uint32_t id, std::string name, std::string tag, int layer);
+
+	template <typename T, typename... Args>
+	void AddComponent(Args&&... args);
+
+	std::uint32_t mId;
+	std::string mName;
+	std::string mTag;
+	bool mActive;
+	int mLayer;
+};
+
+#include "GameObjectMax.hpp"
diff --git a/mwe/ecs-memory-efficient/inc/GameObjectMax.hpp b/mwe/ecs-memory-efficient/inc/GameObjectMax.hpp
new file mode 100644
index 0000000..1e952ba
--- /dev/null
+++ b/mwe/ecs-memory-efficient/inc/GameObjectMax.hpp
@@ -0,0 +1,6 @@
+#include "ComponentManager.h"
+
+template <typename T, typename... Args>
+void GameObject::AddComponent(Args&&... args) {
+	ComponentManager::GetInstance().AddComponent<T>(mId, std::forward<Args>(args)...);
+}
diff --git a/mwe/ecs-memory-efficient/src/ComponentManager.cpp b/mwe/ecs-memory-efficient/src/ComponentManager.cpp
new file mode 100644
index 0000000..16cc2b6
--- /dev/null
+++ b/mwe/ecs-memory-efficient/src/ComponentManager.cpp
@@ -0,0 +1,21 @@
+#include "ComponentManager.h"
+
+ComponentManager ComponentManager::mInstance;
+
+ComponentManager& ComponentManager::GetInstance() {
+	return mInstance;
+}
+
+ComponentManager::ComponentManager() {}
+
+void ComponentManager::DeleteAllComponentsOfId(std::uint32_t id) {
+    for(auto& [type, componentArray] : mComponents) {	//Loop through all the types (in the unordered_map<>)
+        if (id < componentArray.size()) {	//Make sure that the id (that we are looking for) is within the boundaries of the vector<>
+            componentArray[id].clear();	//Clear the components at this specific id
+        }
+    }
+}
+
+void ComponentManager::DeleteAllComponents() {
+	mComponents.clear();	//Clear the whole unordered_map<>
+}
diff --git a/mwe/ecs-memory-efficient/src/Components.cpp b/mwe/ecs-memory-efficient/src/Components.cpp
new file mode 100644
index 0000000..69b5eaa
--- /dev/null
+++ b/mwe/ecs-memory-efficient/src/Components.cpp
@@ -0,0 +1,10 @@
+#include "Components.h"
+#include <iostream>
+
+Component::Component() : mActive(true) {}
+
+Sprite::Sprite(std::string path) : mPath(path) {}
+
+Rigidbody::Rigidbody(int mass, int gravityScale, int bodyType) : mMass(mass), mGravityScale(gravityScale), mBodyType(bodyType) {}
+
+Colider::Colider(int size) : mSize(size) {}
diff --git a/mwe/ecs-memory-efficient/src/GameObjectMax.cpp b/mwe/ecs-memory-efficient/src/GameObjectMax.cpp
new file mode 100644
index 0000000..62c41de
--- /dev/null
+++ b/mwe/ecs-memory-efficient/src/GameObjectMax.cpp
@@ -0,0 +1,5 @@
+#include "GameObjectMax.h"
+
+#include "ComponentManager.h"
+
+GameObject::GameObject(std::uint32_t id, std::string name, std::string tag, int layer) : mId(id), mName(name), mTag(tag), mActive(true), mLayer(layer) {}
diff --git a/mwe/ecs-memory-efficient/src/main.cpp b/mwe/ecs-memory-efficient/src/main.cpp
new file mode 100644
index 0000000..9e8fbd5
--- /dev/null
+++ b/mwe/ecs-memory-efficient/src/main.cpp
@@ -0,0 +1,108 @@
+#include <iostream>
+#include <vector>
+#include <cstdint>
+
+#include "ComponentManager.h"
+#include "GameObjectMax.h"
+#include "Components.h"
+
+int main() {
+	GameObject gameObect0(0, "Name: 0", "Tag: 0", 0);	//Entity 0
+	GameObject gameObect1(1, "Name: 1", "Tag: 1", 1);	//Entity 1
+	GameObject gameObect2(2, "Name: 2", "Tag: 2", 2);	//Entity 2
+	GameObject gameObect3(3, "Name: 3", "Tag: 3", 3);	//Entity 3
+	GameObject gameObect4(4, "Name: 4", "Tag: 4", 4);	//Entity 4
+	GameObject gameObect5(5, "Name: 5", "Tag: 5", 5);	//Entity 5
+	GameObject gameObect6(6, "Name: 6", "Tag: 6", 6);	//Entity 6
+	GameObject gameObect7(7, "Name: 7", "Tag: 7", 7);	//Entity 7
+
+	gameObect0.AddComponent<Sprite>("C:/object0");	//Add a sprite to entity0
+	gameObect0.AddComponent<Rigidbody>(1, 2, 3);	//Also add a rigidbody to entity0
+	gameObect0.AddComponent<Rigidbody>(3, 2, 1);	//Add a second rigidbody to entity0
+
+	gameObect1.AddComponent<Rigidbody>(4, 5, 6);	//Only add a rigidbody to entity1
+
+	gameObect2.AddComponent<Sprite>("C:/object2/1");	//Add four sprites to entity2
+	gameObect2.AddComponent<Sprite>("C:/object2/2");
+	gameObect2.AddComponent<Sprite>("C:/object2/3");
+	gameObect2.AddComponent<Sprite>("C:/object2/4");
+	gameObect2.AddComponent<Rigidbody>(10, 100, 500);	//Add four rigidbodies to entity2
+	gameObect2.AddComponent<Rigidbody>(10, 100, 501);
+	gameObect2.AddComponent<Rigidbody>(10, 100, 502);
+	gameObect2.AddComponent<Rigidbody>(10, 100, 500);
+	
+	//Add non components to entity3, entity4, entity5 and entity6
+
+	gameObect7.AddComponent<Sprite>("C:/object7");	//Add a sprite to entity 7
+	gameObect7.AddComponent<Colider>(30);	//Add a colder to entity 7
+
+	//The entities are now initialized
+	//Now I will demonstrate some ways of retreiving/getting components
+
+	std::cout << "Finding all sprites of entity 0" << std::endl;
+	std::vector<std::reference_wrapper<Sprite>> spriteOfEntity0 = ComponentManager::GetInstance().GetComponentsByID<Sprite>(gameObect0.mId);
+	for(Sprite& spriteEntity0 : spriteOfEntity0) {
+		std::cout << "Sprite of entity 0: " << spriteEntity0.mPath << std::endl;
+	}
+	std::cout << std::endl;
+
+	std::cout << "Finding all rigidbodies of entity 0" << std::endl;
+	std::vector<std::reference_wrapper<Rigidbody>> rigidbodyOfEntity0 = ComponentManager::GetInstance().GetComponentsByID<Rigidbody>(gameObect0.mId);
+	for(Rigidbody& rigidbodyEntity0 : rigidbodyOfEntity0) {
+		std::cout << "Rigidbody of entity 0: " << rigidbodyEntity0.mMass << " " << rigidbodyEntity0.mGravityScale << " " << rigidbodyEntity0.mBodyType << std::endl;
+
+		rigidbodyEntity0.mMass = 15;
+	}
+	std::cout << std::endl;
+
+	std::cout << "Finding all coliders of entity 0" << std::endl;
+	std::vector<std::reference_wrapper<Colider>> coliderOfEntity0 = ComponentManager::GetInstance().GetComponentsByID<Colider>(gameObect0.mId);
+	for(Colider& coliderEntity0 : coliderOfEntity0) {
+		std::cout << "Colider of entity 0: " << coliderEntity0.mSize << std::endl;
+	}
+	std::cout << std::endl;
+
+	std::cout << "Finding all sprites of entity 3" << std::endl;
+	std::vector<std::reference_wrapper<Sprite>> spriteOfEntity3 = ComponentManager::GetInstance().GetComponentsByID<Sprite>(gameObect3.mId);
+	for(Sprite& spriteEntity3 : spriteOfEntity3) {
+		std::cout << "Sprite of entity 3: " << spriteEntity3.mPath << std::endl;
+	}
+	std::cout << std::endl;
+
+	std::cout << "Finding all rigidbodies of entity 3" << std::endl;
+	std::vector<std::reference_wrapper<Rigidbody>> rigidbodyOfEntity3 = ComponentManager::GetInstance().GetComponentsByID<Rigidbody>(gameObect3.mId);
+	for(Rigidbody& rigidbodyEntity3 : rigidbodyOfEntity3) {
+		std::cout << "Rigidbody of entity 3: " << rigidbodyEntity3.mMass << " " << rigidbodyEntity3.mGravityScale << " " << rigidbodyEntity3.mBodyType << std::endl;
+	}
+	std::cout << std::endl;
+
+	std::cout << "Finding all sprites of all entities" << std::endl;
+	std::vector<std::pair<std::reference_wrapper<Sprite>, std::uint32_t>> sprites = ComponentManager::GetInstance().GetComponentsByType<Sprite>();
+	for(auto& [sprite, id] : sprites) {
+		std::cout << "Sprite of id: " << id << ": " << sprite.get().mPath << std::endl;
+	}
+	std::cout << std::endl;
+
+	std::cout << "Finding all coliders of all entities" << std::endl;
+	std::vector<std::pair<std::reference_wrapper<Colider>, std::uint32_t>> coliders = ComponentManager::GetInstance().GetComponentsByType<Colider>();
+	for(auto& [colider, id] : coliders) {
+		std::cout << "Colder of id: " << id << ": " << colider.get().mSize << std::endl;
+	}
+	std::cout << std::endl;
+
+	std::cout << "Finding all rigidbodies of all entities" << std::endl;
+	std::vector<std::pair<std::reference_wrapper<Rigidbody>, std::uint32_t>> rigidBodies = ComponentManager::GetInstance().GetComponentsByType<Rigidbody>();
+	for(auto& [rigidbody, id] : rigidBodies) {
+		std::cout << "Rigidbody of id: " << id << ": " << rigidbody.get().mMass << " " << rigidbody.get().mGravityScale << " " << rigidbody.get().mBodyType << std::endl;
+
+		rigidbody.get().mMass = -1;
+	}
+	std::cout << std::endl;
+
+	std::cout << "Finding all rigidbodies of all entities for the second time (after changing mMass to -1)" << std::endl;
+	std::vector<std::pair<std::reference_wrapper<Rigidbody>, std::uint32_t>> rigidBodies2 = ComponentManager::GetInstance().GetComponentsByType<Rigidbody>();
+	for(auto& [rigidbody2, id2] : rigidBodies2) {
+		std::cout << "Rigidbody of id: " << id2 << ": " << rigidbody2.get().mMass << " " << rigidbody2.get().mGravityScale << " " << rigidbody2.get().mBodyType << std::endl;
+	}
+	std::cout << std::endl;
+}