Common: Add LRUCache

common/CMakeLists.txt

@@ -67,6 +67,7 @@ target_sources(common PRIVATE
 	FileSystem.h
 	General.h
 	HashCombine.h
+	LRUCache.h
 	MemcpyFast.h
 	MemsetFast.inl
 	MD5Digest.h

common/LRUCache.h

@@ -0,0 +1,137 @@
+/*  PCSX2 - PS2 Emulator for PCs
+ *  Copyright (C) 2002-2022  PCSX2 Dev Team
+ *
+ *  PCSX2 is free software: you can redistribute it and/or modify it under the terms
+ *  of the GNU Lesser General Public License as published by the Free Software Found-
+ *  ation, either version 3 of the License, or (at your option) any later version.
+ *
+ *  PCSX2 is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ *  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ *  PURPOSE.  See the GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along with PCSX2.
+ *  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+#include <cstdint>
+#include <map>
+
+template <class K, class V>
+class LRUCache
+{
+	using CounterType = std::uint64_t;
+
+	struct Item
+	{
+		V value;
+		CounterType last_access;
+	};
+
+	using MapType = std::map<K, Item>;
+
+public:
+	LRUCache(std::size_t max_capacity = 16, bool manual_evict = false)
+		: m_max_capacity(max_capacity)
+		, m_manual_evict(manual_evict)
+	{
+	}
+	~LRUCache() = default;
+
+	std::size_t GetSize() const { return m_items.size(); }
+	std::size_t GetMaxCapacity() const { return m_max_capacity; }
+
+	void Clear() { m_items.clear(); }
+
+	void SetMaxCapacity(std::size_t capacity)
+	{
+		m_max_capacity = capacity;
+		if (m_items.size() > m_max_capacity)
+			Evict(m_items.size() - m_max_capacity);
+	}
+
+	template<typename KeyT>
+	V* Lookup(const KeyT& key)
+	{
+		auto iter = m_items.find(key);
+		if (iter == m_items.end())
+			return nullptr;
+
+		iter->second.last_access = ++m_last_counter;
+		return &iter->second.value;
+	}
+
+	V* Insert(K key, V value)
+	{
+		ShrinkForNewItem();
+
+		auto iter = m_items.find(key);
+		if (iter != m_items.end())
+		{
+			iter->second.value = std::move(value);
+			iter->second.last_access = ++m_last_counter;
+			return &iter->second.value;
+		}
+		else
+		{
+			Item it;
+			it.last_access = ++m_last_counter;
+			it.value = std::move(value);
+			auto ip = m_items.emplace(std::move(key), std::move(it));
+			return &ip.first->second.value;
+		}
+	}
+
+	void Evict(std::size_t count = 1)
+	{
+		while (m_items.size() >= count)
+		{
+			typename MapType::iterator lowest = m_items.end();
+			for (auto iter = m_items.begin(); iter != m_items.end(); ++iter)
+			{
+				if (lowest == m_items.end() || iter->second.last_access < lowest->second.last_access)
+					lowest = iter;
+			}
+			m_items.erase(lowest);
+		}
+	}
+
+	template<typename KeyT>
+	bool Remove(const KeyT& key)
+	{
+		auto iter = m_items.find(key);
+		if (iter == m_items.end())
+			return false;
+
+		m_items.erase(iter);
+		return true;
+	}
+
+	void SetManualEvict(bool block)
+	{
+		m_manual_evict = block;
+		if (!m_manual_evict)
+			ManualEvict();
+	}
+
+	void ManualEvict()
+	{
+		// evict if we went over
+		while (m_items.size() > m_max_capacity)
+			Evict(m_items.size() - (m_max_capacity - 1));
+	}
+
+private:
+	void ShrinkForNewItem()
+	{
+		if (m_items.size() < m_max_capacity)
+			return;
+
+		Evict(m_items.size() - (m_max_capacity - 1));
+	}
+
+	MapType m_items;
+	CounterType m_last_counter = 0;
+	std::size_t m_max_capacity = 0;
+	bool m_manual_evict = false;
+};

common/common.vcxproj

@@ -135,6 +135,7 @@
     <ClInclude Include="GL\StreamBuffer.h" />
     <ClInclude Include="FileSystem.h" />
     <ClInclude Include="HashCombine.h" />
+    <ClInclude Include="LRUCache.h" />
     <ClInclude Include="MD5Digest.h" />
     <ClInclude Include="ProgressCallback.h" />
     <ClInclude Include="ScopedGuard.h" />
@@ -208,4 +209,4 @@
   <ImportGroup Label="ExtensionTargets">
     <Import Project="$(VCTargetsPath)\BuildCustomizations\masm.targets" />
   </ImportGroup>
-</Project>
+</Project>

common/common.vcxproj.filters

@@ -429,6 +429,9 @@
     <ClInclude Include="StackWalker.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="LRUCache.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <Filter Include="Source Files">