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-rw-r--r--src/crepe/Asset.cpp16
-rw-r--r--src/crepe/Asset.h41
-rw-r--r--src/crepe/CMakeLists.txt2
-rw-r--r--src/crepe/ComponentManager.h5
-rw-r--r--src/crepe/ComponentManager.hpp9
-rw-r--r--src/crepe/api/Asset.cpp54
-rw-r--r--src/crepe/api/Asset.h84
-rw-r--r--src/crepe/api/CMakeLists.txt2
-rw-r--r--src/crepe/api/Config.h14
-rw-r--r--src/crepe/api/GameObject.cpp6
-rw-r--r--src/crepe/api/Script.h2
-rw-r--r--src/crepe/api/Script.hpp5
-rw-r--r--src/crepe/api/Texture.cpp2
-rw-r--r--src/crepe/facade/Sound.cpp2
-rw-r--r--src/crepe/facade/Sound.h2
-rw-r--r--src/crepe/system/AnimatorSystem.cpp5
-rw-r--r--src/crepe/system/ParticleSystem.cpp3
-rw-r--r--src/crepe/system/PhysicsSystem.cpp6
-rw-r--r--src/crepe/system/RenderSystem.cpp12
-rw-r--r--src/crepe/system/RenderSystem.h3
-rw-r--r--src/crepe/system/ScriptSystem.cpp13
-rw-r--r--src/crepe/system/ScriptSystem.h6
-rw-r--r--src/crepe/types.h9
-rw-r--r--src/crepe/util/CMakeLists.txt2
-rw-r--r--src/crepe/util/OptionalRef.h58
-rw-r--r--src/crepe/util/OptionalRef.hpp37
26 files changed, 292 insertions, 108 deletions
diff --git a/src/crepe/Asset.cpp b/src/crepe/Asset.cpp
deleted file mode 100644
index 9c41ecb..0000000
--- a/src/crepe/Asset.cpp
+++ /dev/null
@@ -1,16 +0,0 @@
-#include <filesystem>
-
-#include "Asset.h"
-
-using namespace crepe;
-using namespace std;
-
-// FIXME: restore this
-// src(std::filesystem::canonical(src))
-Asset::Asset(const std::string & src) : src(src) {
- this->file = std::ifstream(this->src, std::ios::in | std::ios::binary);
-}
-
-istream & Asset::get_stream() { return this->file; }
-
-const string & Asset::get_canonical() const { return this->src; }
diff --git a/src/crepe/Asset.h b/src/crepe/Asset.h
deleted file mode 100644
index 9051c5e..0000000
--- a/src/crepe/Asset.h
+++ /dev/null
@@ -1,41 +0,0 @@
-#pragma once
-
-#include <fstream>
-#include <iostream>
-#include <string>
-
-namespace crepe {
-
-/**
- * \brief Asset location helper
- *
- * This class is used to locate and canonicalize paths to game asset files, and should *always*
- * be used when retrieving files from disk.
- */
-class Asset {
-public:
- /**
- * \param src Unique identifier to asset
- */
- Asset(const std::string & src);
-
-public:
- /**
- * \brief Get an input stream to the contents of this asset
- * \return Input stream with file contents
- */
- std::istream & get_stream();
- /**
- * \brief Get the canonical path to this asset
- * \return Canonical path to this asset
- */
- const std::string & get_canonical() const;
-
-private:
- //! Canonical path to asset
- const std::string src;
- //! File handle (stream)
- std::ifstream file;
-};
-
-} // namespace crepe
diff --git a/src/crepe/CMakeLists.txt b/src/crepe/CMakeLists.txt
index 3b05742..7e176e7 100644
--- a/src/crepe/CMakeLists.txt
+++ b/src/crepe/CMakeLists.txt
@@ -1,5 +1,4 @@
target_sources(crepe PUBLIC
- Asset.cpp
Particle.cpp
ComponentManager.cpp
Component.cpp
@@ -7,7 +6,6 @@ target_sources(crepe PUBLIC
)
target_sources(crepe PUBLIC FILE_SET HEADERS FILES
- Asset.h
ComponentManager.h
ComponentManager.hpp
Component.h
diff --git a/src/crepe/ComponentManager.h b/src/crepe/ComponentManager.h
index 2107453..0956d1e 100644
--- a/src/crepe/ComponentManager.h
+++ b/src/crepe/ComponentManager.h
@@ -8,6 +8,7 @@
#include "api/Vector2.h"
#include "Component.h"
+#include "types.h"
namespace crepe {
@@ -112,7 +113,7 @@ public:
* \return A vector of all components of the specific type and id
*/
template <typename T>
- std::vector<std::reference_wrapper<T>> get_components_by_id(game_object_id_t id) const;
+ RefVector<T> get_components_by_id(game_object_id_t id) const;
/**
* \brief Get all components of a specific type
*
@@ -122,7 +123,7 @@ public:
* \return A vector of all components of the specific type
*/
template <typename T>
- std::vector<std::reference_wrapper<T>> get_components_by_type() const;
+ RefVector<T> get_components_by_type() const;
private:
/**
diff --git a/src/crepe/ComponentManager.hpp b/src/crepe/ComponentManager.hpp
index be99cac..4d5eaf4 100644
--- a/src/crepe/ComponentManager.hpp
+++ b/src/crepe/ComponentManager.hpp
@@ -81,15 +81,14 @@ void ComponentManager::delete_components() {
}
template <typename T>
-std::vector<std::reference_wrapper<T>>
-ComponentManager::get_components_by_id(game_object_id_t id) const {
+RefVector<T> ComponentManager::get_components_by_id(game_object_id_t id) const {
using namespace std;
// Determine the type of T (this is used as the key of the unordered_map<>)
type_index type = typeid(T);
// Create an empty vector<>
- vector<reference_wrapper<T>> component_vector;
+ RefVector<T> component_vector;
if (this->components.find(type) == this->components.end()) return component_vector;
@@ -114,14 +113,14 @@ ComponentManager::get_components_by_id(game_object_id_t id) const {
}
template <typename T>
-std::vector<std::reference_wrapper<T>> ComponentManager::get_components_by_type() const {
+RefVector<T> ComponentManager::get_components_by_type() const {
using namespace std;
// Determine the type of T (this is used as the key of the unordered_map<>)
type_index type = typeid(T);
// Create an empty vector<>
- vector<reference_wrapper<T>> component_vector;
+ RefVector<T> component_vector;
// Find the type (in the unordered_map<>)
if (this->components.find(type) == this->components.end()) return component_vector;
diff --git a/src/crepe/api/Asset.cpp b/src/crepe/api/Asset.cpp
new file mode 100644
index 0000000..e148367
--- /dev/null
+++ b/src/crepe/api/Asset.cpp
@@ -0,0 +1,54 @@
+#include <filesystem>
+#include <stdexcept>
+#include <whereami.h>
+
+#include "api/Config.h"
+
+#include "Asset.h"
+
+using namespace crepe;
+using namespace std;
+
+Asset::Asset(const string & src) : src(find_asset(src)) {}
+Asset::Asset(const char * src) : src(find_asset(src)) {}
+
+const string & Asset::get_path() const noexcept { return this->src; }
+
+string Asset::find_asset(const string & src) const {
+ auto & cfg = Config::get_instance();
+ string & root_pattern = cfg.asset.root_pattern;
+
+ // if root_pattern is empty, find_asset must return all paths as-is
+ if (root_pattern.empty()) return src;
+
+ // absolute paths do not need to be resolved, only canonicalized
+ filesystem::path path = src;
+ if (path.is_absolute()) return filesystem::canonical(path);
+
+ // find directory matching root_pattern
+ filesystem::path root = this->whereami();
+ while (1) {
+ if (filesystem::exists(root / root_pattern)) break;
+ if (!root.has_parent_path())
+ throw runtime_error(format("Asset: Cannot find root pattern ({})", root_pattern));
+ root = root.parent_path();
+ }
+
+ // join path to root (base directory) and canonicalize
+ return filesystem::canonical(root / path);
+}
+
+string Asset::whereami() const noexcept {
+ string path;
+ size_t path_length = wai_getExecutablePath(NULL, 0, NULL);
+ path.resize(path_length + 1); // wai writes null byte
+ wai_getExecutablePath(path.data(), path_length, NULL);
+ path.resize(path_length);
+ return path;
+}
+
+bool Asset::operator==(const Asset & other) const noexcept { return this->src == other.src; }
+
+size_t std::hash<const Asset>::operator()(const Asset & asset) const noexcept {
+ return std::hash<string>{}(asset.get_path());
+};
diff --git a/src/crepe/api/Asset.h b/src/crepe/api/Asset.h
new file mode 100644
index 0000000..bfd0ac7
--- /dev/null
+++ b/src/crepe/api/Asset.h
@@ -0,0 +1,84 @@
+#pragma once
+
+#include <string>
+
+namespace crepe {
+
+/**
+ * \brief Asset location helper
+ *
+ * This class is used to locate game asset files, and should *always* be used
+ * instead of reading file paths directly.
+ */
+class Asset {
+public:
+ /**
+ * \param src Unique identifier to asset
+ */
+ Asset(const std::string & src);
+ /**
+ * \param src Unique identifier to asset
+ */
+ Asset(const char * src);
+
+public:
+ /**
+ * \brief Get the path to this asset
+ * \return path to this asset
+ */
+ const std::string & get_path() const noexcept;
+
+ /**
+ * \brief Comparison operator
+ * \param other Possibly different instance of \c Asset to test equality against
+ * \return True if \c this and \c other are equal
+ */
+ bool operator==(const Asset & other) const noexcept;
+
+private:
+ //! path to asset
+ const std::string src;
+
+private:
+ /**
+ * \brief Locate asset path, or throw exception if it cannot be found
+ *
+ * This function resolves asset locations relative to crepe::Config::root_pattern if it is
+ * set and \p src is a relative path. If \p src is an absolute path, it is canonicalized.
+ * This function only returns if the file can be found.
+ *
+ * \param src Arbitrary path to resource file
+ *
+ * \returns \p src if crepe::Config::root_pattern is empty
+ * \returns Canonical path to \p src
+ *
+ * \throws std::runtime_error if root_pattern cannot be found
+ * \throws std::filesystem::filesystem_error if the resolved path does not exist
+ * \throws std::filesystem::filesystem_error if the path cannot be canonicalized
+ */
+ std::string find_asset(const std::string & src) const;
+ /**
+ * \returns The path to the current executable
+ */
+ std::string whereami() const noexcept;
+};
+
+} // namespace crepe
+
+namespace std {
+
+//! Hash helper struct
+template <>
+struct hash<const crepe::Asset> {
+ /**
+ * \brief Hash operator for crepe::Asset
+ *
+ * This function hashes a crepe::Asset instance, allowing it to be used as a key in an \c
+ * std::unordered_map.
+ *
+ * \returns Hash value
+ */
+ size_t operator()(const crepe::Asset & asset) const noexcept;
+};
+
+} // namespace std
diff --git a/src/crepe/api/CMakeLists.txt b/src/crepe/api/CMakeLists.txt
index a185ca6..d6b6801 100644
--- a/src/crepe/api/CMakeLists.txt
+++ b/src/crepe/api/CMakeLists.txt
@@ -22,6 +22,7 @@ target_sources(crepe PUBLIC
IMouseListener.cpp
LoopManager.cpp
LoopTimer.cpp
+ Asset.cpp
EventHandler.cpp
)
@@ -56,4 +57,5 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
IMouseListener.h
LoopManager.h
LoopTimer.h
+ Asset.h
)
diff --git a/src/crepe/api/Config.h b/src/crepe/api/Config.h
index 3ab877a..13eabd1 100644
--- a/src/crepe/api/Config.h
+++ b/src/crepe/api/Config.h
@@ -62,6 +62,20 @@ public:
*/
double gravity = 1;
} physics;
+
+ //! Asset loading options
+ struct {
+ /**
+ * \brief Pattern to match for Asset base directory
+ *
+ * All non-absolute paths resolved using \c Asset will be made relative to
+ * the first parent directory relative to the calling executable where
+ * appending this pattern results in a path that exists. If this string is
+ * empty, path resolution is disabled, and Asset will return all paths
+ * as-is.
+ */
+ std::string root_pattern = ".crepe-root";
+ } asset;
};
} // namespace crepe
diff --git a/src/crepe/api/GameObject.cpp b/src/crepe/api/GameObject.cpp
index 287e81d..4874426 100644
--- a/src/crepe/api/GameObject.cpp
+++ b/src/crepe/api/GameObject.cpp
@@ -23,12 +23,10 @@ void GameObject::set_parent(const GameObject & parent) {
ComponentManager & mgr = this->component_manager;
// Set parent on own Metadata component
- vector<reference_wrapper<Metadata>> this_metadata
- = mgr.get_components_by_id<Metadata>(this->id);
+ RefVector<Metadata> this_metadata = mgr.get_components_by_id<Metadata>(this->id);
this_metadata.at(0).get().parent = parent.id;
// Add own id to children list of parent's Metadata component
- vector<reference_wrapper<Metadata>> parent_metadata
- = mgr.get_components_by_id<Metadata>(parent.id);
+ RefVector<Metadata> parent_metadata = mgr.get_components_by_id<Metadata>(parent.id);
parent_metadata.at(0).get().children.push_back(this->id);
}
diff --git a/src/crepe/api/Script.h b/src/crepe/api/Script.h
index 2b70379..839d937 100644
--- a/src/crepe/api/Script.h
+++ b/src/crepe/api/Script.h
@@ -62,7 +62,7 @@ protected:
* \returns List of component references
*/
template <typename T>
- std::vector<std::reference_wrapper<T>> get_components() const;
+ RefVector<T> get_components() const;
protected:
// NOTE: Script must have a constructor without arguments so the game programmer doesn't need
diff --git a/src/crepe/api/Script.hpp b/src/crepe/api/Script.hpp
index a064a90..a85d814 100644
--- a/src/crepe/api/Script.hpp
+++ b/src/crepe/api/Script.hpp
@@ -10,7 +10,7 @@ namespace crepe {
template <typename T>
T & Script::get_component() const {
using namespace std;
- vector<reference_wrapper<T>> all_components = this->get_components<T>();
+ RefVector<T> all_components = this->get_components<T>();
if (all_components.size() < 1)
throw runtime_error(
format("Script: no component found with type = {}", typeid(T).name()));
@@ -19,9 +19,8 @@ T & Script::get_component() const {
}
template <typename T>
-std::vector<std::reference_wrapper<T>> Script::get_components() const {
+RefVector<T> Script::get_components() const {
auto & mgr = *this->component_manager_ref;
-
return mgr.get_components_by_id<T>(this->game_object_id);
}
diff --git a/src/crepe/api/Texture.cpp b/src/crepe/api/Texture.cpp
index 734a5bb..9be9421 100644
--- a/src/crepe/api/Texture.cpp
+++ b/src/crepe/api/Texture.cpp
@@ -26,7 +26,7 @@ Texture::~Texture() {
void Texture::load(unique_ptr<Asset> res) {
SDLContext & ctx = SDLContext::get_instance();
- this->texture = std::move(ctx.texture_from_path(res->get_canonical()));
+ this->texture = std::move(ctx.texture_from_path(res->get_path()));
}
int Texture::get_width() const {
diff --git a/src/crepe/facade/Sound.cpp b/src/crepe/facade/Sound.cpp
index 7aa89a9..4d3abf5 100644
--- a/src/crepe/facade/Sound.cpp
+++ b/src/crepe/facade/Sound.cpp
@@ -16,7 +16,7 @@ Sound::Sound(const char * src) {
this->load(make_unique<Asset>(src));
}
-void Sound::load(unique_ptr<Asset> res) { this->sample.load(res->get_canonical().c_str()); }
+void Sound::load(unique_ptr<Asset> res) { this->sample.load(res->get_path().c_str()); }
void Sound::play() {
SoundContext & ctx = SoundContext::get_instance();
diff --git a/src/crepe/facade/Sound.h b/src/crepe/facade/Sound.h
index 32b6478..4c68f32 100644
--- a/src/crepe/facade/Sound.h
+++ b/src/crepe/facade/Sound.h
@@ -4,7 +4,7 @@
#include <soloud/soloud.h>
#include <soloud/soloud_wav.h>
-#include "../Asset.h"
+#include "../api/Asset.h"
namespace crepe {
diff --git a/src/crepe/system/AnimatorSystem.cpp b/src/crepe/system/AnimatorSystem.cpp
index 9d18873..676e485 100644
--- a/src/crepe/system/AnimatorSystem.cpp
+++ b/src/crepe/system/AnimatorSystem.cpp
@@ -1,6 +1,4 @@
#include <cstdint>
-#include <functional>
-#include <vector>
#include "api/Animator.h"
#include "facade/SDLContext.h"
@@ -13,8 +11,7 @@ using namespace crepe;
void AnimatorSystem::update() {
ComponentManager & mgr = this->component_manager;
- std::vector<std::reference_wrapper<Animator>> animations
- = mgr.get_components_by_type<Animator>();
+ RefVector<Animator> animations = mgr.get_components_by_type<Animator>();
uint64_t tick = SDLContext::get_instance().get_ticks();
for (Animator & a : animations) {
diff --git a/src/crepe/system/ParticleSystem.cpp b/src/crepe/system/ParticleSystem.cpp
index 7316309..fcf7522 100644
--- a/src/crepe/system/ParticleSystem.cpp
+++ b/src/crepe/system/ParticleSystem.cpp
@@ -14,8 +14,7 @@ using namespace crepe;
void ParticleSystem::update() {
// Get all emitters
ComponentManager & mgr = this->component_manager;
- std::vector<std::reference_wrapper<ParticleEmitter>> emitters
- = mgr.get_components_by_type<ParticleEmitter>();
+ RefVector<ParticleEmitter> emitters = mgr.get_components_by_type<ParticleEmitter>();
for (ParticleEmitter & emitter : emitters) {
// Get transform linked to emitter
diff --git a/src/crepe/system/PhysicsSystem.cpp b/src/crepe/system/PhysicsSystem.cpp
index 4a7dbfb..bcde431 100644
--- a/src/crepe/system/PhysicsSystem.cpp
+++ b/src/crepe/system/PhysicsSystem.cpp
@@ -12,10 +12,8 @@ using namespace crepe;
void PhysicsSystem::update() {
ComponentManager & mgr = this->component_manager;
- std::vector<std::reference_wrapper<Rigidbody>> rigidbodies
- = mgr.get_components_by_type<Rigidbody>();
- std::vector<std::reference_wrapper<Transform>> transforms
- = mgr.get_components_by_type<Transform>();
+ RefVector<Rigidbody> rigidbodies = mgr.get_components_by_type<Rigidbody>();
+ RefVector<Transform> transforms = mgr.get_components_by_type<Transform>();
double gravity = Config::get_instance().physics.gravity;
for (Rigidbody & rigidbody : rigidbodies) {
diff --git a/src/crepe/system/RenderSystem.cpp b/src/crepe/system/RenderSystem.cpp
index e379771..ad510f5 100644
--- a/src/crepe/system/RenderSystem.cpp
+++ b/src/crepe/system/RenderSystem.cpp
@@ -24,7 +24,7 @@ void RenderSystem::present_screen() { this->context.present_screen(); }
void RenderSystem::update_camera() {
ComponentManager & mgr = this->component_manager;
- std::vector<std::reference_wrapper<Camera>> cameras = mgr.get_components_by_type<Camera>();
+ RefVector<Camera> cameras = mgr.get_components_by_type<Camera>();
if (cameras.size() == 0) throw std::runtime_error("No cameras in current scene");
@@ -42,10 +42,8 @@ bool sorting_comparison(const Sprite & a, const Sprite & b) {
return false;
}
-std::vector<std::reference_wrapper<Sprite>>
-RenderSystem::sort(std::vector<std::reference_wrapper<Sprite>> & objs) const {
-
- std::vector<std::reference_wrapper<Sprite>> sorted_objs(objs);
+RefVector<Sprite> RenderSystem::sort(RefVector<Sprite> & objs) const {
+ RefVector<Sprite> sorted_objs(objs);
std::sort(sorted_objs.begin(), sorted_objs.end(), sorting_comparison);
return sorted_objs;
@@ -87,8 +85,8 @@ void RenderSystem::render_normal(const Sprite & sprite, const Transform & tm) {
void RenderSystem::render() {
ComponentManager & mgr = this->component_manager;
- vector<reference_wrapper<Sprite>> sprites = mgr.get_components_by_type<Sprite>();
- vector<reference_wrapper<Sprite>> sorted_sprites = this->sort(sprites);
+ RefVector<Sprite> sprites = mgr.get_components_by_type<Sprite>();
+ RefVector<Sprite> sorted_sprites = this->sort(sprites);
for (const Sprite & sprite : sorted_sprites) {
if (!sprite.active) continue;
diff --git a/src/crepe/system/RenderSystem.h b/src/crepe/system/RenderSystem.h
index d25a6e3..30b41cf 100644
--- a/src/crepe/system/RenderSystem.h
+++ b/src/crepe/system/RenderSystem.h
@@ -65,8 +65,7 @@ private:
* \param objs the vector that will do a sorting algorithm on
* \return returns a sorted reference vector
*/
- std::vector<std::reference_wrapper<Sprite>>
- sort(std::vector<std::reference_wrapper<Sprite>> & objs) const;
+ RefVector<Sprite> sort(RefVector<Sprite> & objs) const;
/**
* \todo Include color handling for sprites.
diff --git a/src/crepe/system/ScriptSystem.cpp b/src/crepe/system/ScriptSystem.cpp
index c4d724c..c33309c 100644
--- a/src/crepe/system/ScriptSystem.cpp
+++ b/src/crepe/system/ScriptSystem.cpp
@@ -1,6 +1,4 @@
-#include <forward_list>
#include <functional>
-#include <vector>
#include "../ComponentManager.h"
#include "../api/BehaviorScript.h"
@@ -14,7 +12,7 @@ using namespace crepe;
void ScriptSystem::update() {
dbg_trace();
- forward_list<reference_wrapper<Script>> scripts = this->get_scripts();
+ RefVector<Script> scripts = this->get_scripts();
for (auto & script_ref : scripts) {
Script & script = script_ref.get();
@@ -26,18 +24,17 @@ void ScriptSystem::update() {
}
}
-forward_list<reference_wrapper<Script>> ScriptSystem::get_scripts() const {
- forward_list<reference_wrapper<Script>> scripts = {};
+RefVector<Script> ScriptSystem::get_scripts() const {
+ RefVector<Script> scripts = {};
ComponentManager & mgr = this->component_manager;
- vector<reference_wrapper<BehaviorScript>> behavior_scripts
- = mgr.get_components_by_type<BehaviorScript>();
+ RefVector<BehaviorScript> behavior_scripts = mgr.get_components_by_type<BehaviorScript>();
for (auto behavior_script_ref : behavior_scripts) {
BehaviorScript & behavior_script = behavior_script_ref.get();
if (!behavior_script.active) continue;
Script * script = behavior_script.script.get();
if (script == nullptr) continue;
- scripts.push_front(*script);
+ scripts.push_back(*script);
}
return scripts;
diff --git a/src/crepe/system/ScriptSystem.h b/src/crepe/system/ScriptSystem.h
index deb89cb..32e1fcd 100644
--- a/src/crepe/system/ScriptSystem.h
+++ b/src/crepe/system/ScriptSystem.h
@@ -1,9 +1,9 @@
#pragma once
-#include <forward_list>
-
#include "System.h"
+#include "../types.h"
+
namespace crepe {
class Script;
@@ -33,7 +33,7 @@ private:
*
* \returns List of active \c Script instances
*/
- std::forward_list<std::reference_wrapper<Script>> get_scripts() const;
+ RefVector<Script> get_scripts() const;
};
} // namespace crepe
diff --git a/src/crepe/types.h b/src/crepe/types.h
index 0d459e8..914c76c 100644
--- a/src/crepe/types.h
+++ b/src/crepe/types.h
@@ -1,9 +1,16 @@
#pragma once
#include <cstdint>
+#include <functional>
+#include <vector>
namespace crepe {
+//! GameObject ID
typedef uint32_t game_object_id_t;
-}
+//! vector of reference_wrapper
+template <typename T>
+using RefVector = std::vector<std::reference_wrapper<T>>;
+
+} // namespace crepe
diff --git a/src/crepe/util/CMakeLists.txt b/src/crepe/util/CMakeLists.txt
index 4be738a..94ed906 100644
--- a/src/crepe/util/CMakeLists.txt
+++ b/src/crepe/util/CMakeLists.txt
@@ -9,5 +9,7 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
Log.hpp
Proxy.h
Proxy.hpp
+ OptionalRef.h
+ OptionalRef.hpp
)
diff --git a/src/crepe/util/OptionalRef.h b/src/crepe/util/OptionalRef.h
new file mode 100644
index 0000000..253bc07
--- /dev/null
+++ b/src/crepe/util/OptionalRef.h
@@ -0,0 +1,58 @@
+#pragma once
+
+namespace crepe {
+
+/**
+ * \brief Optional reference utility
+ *
+ * This class doesn't need to know the full definition of \c T to be used.
+ *
+ * \tparam T Value type
+ */
+template <typename T>
+class OptionalRef {
+public:
+ //! Initialize empty (nonexistant) reference
+ OptionalRef() = default;
+ //! Initialize reference with value
+ OptionalRef(T & ref);
+ /**
+ * \brief Assign new reference
+ *
+ * \param ref Reference to assign
+ *
+ * \return Reference to this (required for operator)
+ */
+ OptionalRef<T> & operator=(T & ref);
+ /**
+ * \brief Retrieve this reference
+ *
+ * \returns Internal reference if it is set
+ *
+ * \throws std::runtime_error if this function is called while the reference it not set
+ */
+ operator T & () const;
+ /**
+ * \brief Check if this reference is not empty
+ *
+ * \returns `true` if reference is set, or `false` if it is not
+ */
+ explicit operator bool() const noexcept;
+
+ /**
+ * \brief Make this reference empty
+ */
+ void clear() noexcept;
+
+private:
+ /**
+ * \brief Reference to the value of type \c T
+ *
+ * \note This raw pointer is *not* managed, and only used as a reference!
+ */
+ T * ref = nullptr;
+};
+
+} // namespace crepe
+
+#include "OptionalRef.hpp"
diff --git a/src/crepe/util/OptionalRef.hpp b/src/crepe/util/OptionalRef.hpp
new file mode 100644
index 0000000..ae7c73e
--- /dev/null
+++ b/src/crepe/util/OptionalRef.hpp
@@ -0,0 +1,37 @@
+#pragma once
+
+#include <stdexcept>
+
+#include "OptionalRef.h"
+
+namespace crepe {
+
+template <typename T>
+OptionalRef<T>::OptionalRef(T & ref) {
+ this->ref = &ref;
+}
+
+template <typename T>
+OptionalRef<T>::operator T & () const {
+ if (this->ref == nullptr)
+ throw std::runtime_error("OptionalRef: attempt to dereference nullptr");
+ return *this->ref;
+}
+
+template <typename T>
+OptionalRef<T> & OptionalRef<T>::operator=(T & ref) {
+ this->ref = &ref;
+ return *this;
+}
+
+template <typename T>
+OptionalRef<T>::operator bool() const noexcept {
+ return this->ref != nullptr;
+}
+
+template <typename T>
+void OptionalRef<T>::clear() noexcept {
+ this->ref = nullptr;
+}
+
+} // namespace crepe