From ffbfe95f51058c4de3c898b1a02e2fadba2b8134 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 4 Dec 2022 22:13:56 +0200
Subject: [PATCH] Enforce correct access to buffered components

---
 source/game/accessguard.h | 16 ++++++++++++++++
 source/game/component.h   | 15 ++++++++++++++-
 source/game/system.cpp    | 12 ++++++++++++
 source/game/system.h      | 15 +++++++++++++++
 4 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/source/game/accessguard.h b/source/game/accessguard.h
index c64efe7..26bbb4e 100644
--- a/source/game/accessguard.h
+++ b/source/game/accessguard.h
@@ -6,6 +6,7 @@
 #include <string>
 #include <vector>
 #include <msp/core/noncopyable.h>
+#include <msp/debug/demangle.h>
 
 namespace Msp::Game {
 
@@ -21,6 +22,8 @@ class AccessGuard
 public:
 	struct Create { static std::string describe() { return "create"; } };
 	struct Destroy { static std::string describe() { return "destroy"; } };
+	template<typename T> struct Read { static std::string describe(); };
+	template<typename T> struct Write { static std::string describe(); };
 
 	template<typename T = void>
 	struct BlockForScope: NonCopyable
@@ -94,6 +97,19 @@ template<>
 inline void AccessGuard::unblock<void>()
 { unblock_all(); }
 
+
+template<typename T>
+inline std::string AccessGuard::Read<T>::describe()
+{
+	return "read "+Debug::demangle(typeid(T).name());
+}
+
+template<typename T>
+inline std::string AccessGuard::Write<T>::describe()
+{
+	return "write "+Debug::demangle(typeid(T).name());
+}
+
 } // namespace Msp::Game
 
 #endif
diff --git a/source/game/component.h b/source/game/component.h
index 44927ff..6406cb5 100644
--- a/source/game/component.h
+++ b/source/game/component.h
@@ -2,6 +2,7 @@
 #define MSP_GAME_COMPONENT_H_
 
 #include <msp/time/timedelta.h>
+#include "accessguard.h"
 #include "handle.h"
 
 namespace Msp::Game {
@@ -34,7 +35,7 @@ protected:
 
 	BufferedComponent(Handle<Entity> e): Component(e) { }
 
-	const T &read() const { return data[read_index]; }
+	const T &read() const;
 	T &write();
 
 public:
@@ -42,9 +43,21 @@ public:
 	virtual void commit_tick() { if(written) read_index = write_index; }
 };
 
+template<typename T>
+const T &BufferedComponent<T>::read() const
+{
+#ifdef DEBUG
+	AccessGuard::get_instance().check<AccessGuard::Read<T>>();
+#endif
+	return data[read_index];
+}
+
 template<typename T>
 T &BufferedComponent<T>::write()
 {
+#ifdef DEBUG
+	AccessGuard::get_instance().check<AccessGuard::Write<T>>();
+#endif
 	if(!written && write_index!=read_index)
 	{
 		data[write_index] = data[read_index];
diff --git a/source/game/system.cpp b/source/game/system.cpp
index 33157c3..4c1f4fb 100644
--- a/source/game/system.cpp
+++ b/source/game/system.cpp
@@ -13,15 +13,27 @@ void System::begin_tick()
 	active = this;
 
 	for(const Dependency &d: dependencies)
+	{
+#ifdef DEBUG
+		if(d.unblock)
+			d.unblock(d.flags);
+#endif
 		if(d.prepare)
 			d.prepare(stage);
+	}
 }
 
 void System::end_tick()
 {
 	for(const Dependency &d: dependencies)
+	{
 		if(d.commit)
 			d.commit(stage);
+#ifdef DEBUG
+		if(d.block)
+			d.block(d.flags);
+#endif
+	}
 
 	if(active==this)
 		active = nullptr;
diff --git a/source/game/system.h b/source/game/system.h
index 3d62c06..e3d7117 100644
--- a/source/game/system.h
+++ b/source/game/system.h
@@ -3,6 +3,7 @@
 
 #include <functional>
 #include <msp/time/timedelta.h>
+#include "accessguard.h"
 #include "component.h"
 #include "reflection.h"
 #include "stage.h"
@@ -28,6 +29,8 @@ public:
 		const Reflection::ClassBase &type;
 		void (*prepare)(Stage &) = nullptr;
 		void (*commit)(Stage &) = nullptr;
+		void (*unblock)(DependencyFlags) = nullptr;
+		void (*block)(DependencyFlags) = nullptr;
 
 		Dependency(const Reflection::ClassBase &t): type(t) { }
 	};
@@ -86,11 +89,23 @@ inline void System::declare_dependency(DependencyFlags flags)
 	Dependency &dep = (i!=dependencies.end() ? *i : dependencies.emplace_back(type));
 	dep.flags = flags;
 	if constexpr(requires(T &c) { typename T::Data; c.prepare_tick(); c.commit_tick(); })
+	{
+#ifdef DEBUG
+		dep.unblock = +[](DependencyFlags f){
+			if(f&READ_OLD) AccessGuard::get_instance().unblock<AccessGuard::Read<typename T::Data>>();
+			if(f&WRITE) AccessGuard::get_instance().unblock<AccessGuard::Write<typename T::Data>>();
+		};
+		dep.block = +[](DependencyFlags f){
+			if(f&READ_OLD) AccessGuard::get_instance().block<AccessGuard::Read<typename T::Data>>();
+			if(f&WRITE) AccessGuard::get_instance().block<AccessGuard::Write<typename T::Data>>();
+		};
+#endif
 		if(flags&WRITE)
 		{
 			dep.prepare = +[](Stage &s){ s.iterate_objects<T>([](T &c){ c.prepare_tick(); }); };
 			dep.commit = +[](Stage &s){ s.iterate_objects<T>([](T &c){ c.commit_tick(); }); };
 		}
+	}
 }
 
 } // namespace Msp::Game
-- 
2.43.0