From 8ed7051d1a80c7e8b198d96575338eee6a5e2485 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Mon, 8 Sep 2014 21:28:22 +0300
Subject: [PATCH] Implement automatic resource unloading based on age

---
 source/resourcemanager.cpp | 40 +++++++++++++++++++++++++++++++++++++-
 source/resourcemanager.h   |  7 +++++++
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/source/resourcemanager.cpp b/source/resourcemanager.cpp
index cc69b895..059c2924 100644
--- a/source/resourcemanager.cpp
+++ b/source/resourcemanager.cpp
@@ -9,6 +9,9 @@ namespace GL {
 ResourceManager::ResourceManager():
 	policy(LOAD_ON_DEMAND),
 	async_loads(true),
+	frame(0),
+	max_retain_frames(0),
+	next_unload(0),
 	thread(*this)
 { }
 
@@ -30,6 +33,11 @@ void ResourceManager::set_async_loads(bool a)
 	async_loads = a;
 }
 
+void ResourceManager::set_max_retain_frames(unsigned f)
+{
+	max_retain_frames = f;
+}
+
 void ResourceManager::add_resource(Resource &r)
 {
 	insert_unique(resources, &r, ManagedResource(r));
@@ -75,6 +83,10 @@ void ResourceManager::resource_used(const Resource &r)
 	ManagedResource *managed = reinterpret_cast<ManagedResource *>(r.get_manager_data());
 	if(!managed->loaded && !managed->loader && policy!=LOAD_MANUALLY)
 		load_resource(*managed->resource);
+
+	managed->last_used = frame;
+	if(max_retain_frames && !next_unload)
+		next_unload = frame+max_retain_frames;
 }
 
 void ResourceManager::remove_resource(Resource &r)
@@ -97,6 +109,25 @@ void ResourceManager::tick()
 		queue.pop_front();
 		thread.set_resource(managed);
 	}
+
+	++frame;
+	if(frame==next_unload)
+	{
+		unsigned unload_limit = frame-max_retain_frames;
+		next_unload = 0;
+
+		for(ResourceMap::iterator i=resources.begin(); i!=resources.end(); ++i)
+			if(i->second.loaded)
+			{
+				if(i->second.last_used<=unload_limit)
+					i->second.unload();
+				else if(!next_unload || i->second.last_used<next_unload)
+					next_unload = i->second.last_used;
+			}
+
+		if(next_unload)
+			next_unload += max_retain_frames;
+	}
 }
 
 
@@ -105,7 +136,8 @@ ResourceManager::ManagedResource::ManagedResource(Resource &r):
 	collection(0),
 	io(0),
 	loader(0),
-	loaded(false)
+	loaded(false),
+	last_used(0)
 { }
 
 void ResourceManager::ManagedResource::start_loading()
@@ -129,6 +161,12 @@ void ResourceManager::ManagedResource::finish_loading()
 	io = 0;
 }
 
+void ResourceManager::ManagedResource::unload()
+{
+	resource->unload();
+	loaded = false;
+}
+
 
 ResourceManager::LoadingThread::LoadingThread(ResourceManager &m):
 	manager(m),
diff --git a/source/resourcemanager.h b/source/resourcemanager.h
index 1e3cb54f..07b0aaf0 100644
--- a/source/resourcemanager.h
+++ b/source/resourcemanager.h
@@ -29,11 +29,13 @@ private:
 		IO::Seekable *io;
 		Resource::AsyncLoader *loader;
 		bool loaded;
+		unsigned last_used;
 
 		ManagedResource(Resource &);
 
 		void start_loading();
 		void finish_loading();
+		void unload();
 	};
 
 	class LoadingThread: public Thread
@@ -76,6 +78,10 @@ private:
 	bool async_loads;
 	ResourceMap resources;
 	LoadQueue queue;
+	unsigned frame;
+	unsigned min_retain_frames;
+	unsigned max_retain_frames;
+	unsigned next_unload;
 	LoadingThread thread;
 
 public:
@@ -84,6 +90,7 @@ public:
 
 	void set_loading_policy(LoadingPolicy);
 	void set_async_loads(bool);
+	void set_max_retain_frames(unsigned);
 
 	void add_resource(Resource &);
 	void *get_data_for_resource(const Resource &);
-- 
2.43.0