LRU map (cache) implementation to o3tl + tests

Change-Id: I6b1a39918e6c8c67712be2c8e9907266dcfefedb

include/o3tl/lru_map.hxx

+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ */
+
+#ifndef INCLUDED_O3TL_LRU_MAP_HXX
+#define INCLUDED_O3TL_LRU_MAP_HXX
+
+#include <list>
+#include <unordered_map>
+
+namespace o3tl
+{
+
+/** LRU map
+ *
+ * Similar to unordered_map (it actually uses it) with additionaly functionality
+ * which removes the entries that have been "least recently used" when the size
+ * hits the specified capacity.
+ *
+ * It only implements the minimal methods needed and the implementation is NOT
+ * thread safe.
+ *
+ * The implementation is as simple as possible but it still uses O(1) complexity
+ * for most of the operations with a combination unordered map and linked list.
+ *
+ **/
+template<typename Key, typename Value, class KeyHash = std::hash<Key>>
+class lru_map SAL_FINAL
+{
+private:
+    typedef typename std::pair<Key, Value> key_value_pair_t;
+    typedef std::list<key_value_pair_t> list_t;
+    typedef typename list_t::iterator list_iterator_t;
+    typedef typename list_t::const_iterator list_const_iterator_t;
+
+    typedef std::unordered_map<Key, list_iterator_t, KeyHash> map_t;
+    typedef typename map_t::iterator map_iterator_t;
+    typedef typename map_t::const_iterator map_const_iterator_t;
+
+    list_t mLruList;
+    map_t mLruMap;
+    const size_t mMaxSize;
+
+    inline void checkLRU()
+    {
+        if (mLruMap.size() > mMaxSize)
+        {
+            // remove from map
+            mLruMap.erase(mLruList.back().first);
+            // remove from list
+            mLruList.pop_back();
+        }
+    }
+public:
+    typedef list_iterator_t iterator;
+    typedef list_const_iterator_t const_iterator;
+
+    lru_map(size_t nMaxSize)
+        : mMaxSize(nMaxSize)
+    {}
+
+    void insert(key_value_pair_t& rPair)
+    {
+        map_iterator_t iterator = mLruMap.find(rPair.first);
+
+        if (iterator == mLruMap.end()) // doesn't exist -> add to queue and map
+        {
+            // add to front of the list
+            mLruList.push_front(rPair);
+            // add the list position (iterator) to the map
+            mLruMap[rPair.first] = mLruList.begin();
+            checkLRU();
+        }
+        else // already exists -> replace value
+        {
+            // replace value
+            iterator->second->second = rPair.second;
+            // bring to front of the lru list
+            mLruList.splice(mLruList.begin(), mLruList, iterator->second);
+        }
+    }
+
+    void insert(key_value_pair_t&& rPair)
+    {
+        map_iterator_t iterator = mLruMap.find(rPair.first);
+
+        if (iterator == mLruMap.end()) // doesn't exist -> add to list and map
+        {
+            // add to front of the list
+            mLruList.push_front(std::move(rPair));
+            // add the list position (iterator) to the map
+            mLruMap[rPair.first] = mLruList.begin();
+            checkLRU();
+        }
+        else // already exists -> replace value
+        {
+            // replace value
+            iterator->second->second = std::move(rPair.second);
+            // push to back of the lru list
+            mLruList.splice(mLruList.begin(), mLruList, iterator->second);
+        }
+    }
+
+    const list_const_iterator_t find(const Key& key)
+    {
+        const map_iterator_t iterator = mLruMap.find(key);
+        if (iterator == mLruMap.cend()) // can't find entry for the key
+        {
+            // return empty iterator
+            return mLruList.cend();
+        }
+        else
+        {
+            // push to back of the lru list
+            mLruList.splice(mLruList.begin(), mLruList, iterator->second);
+            return iterator->second;
+        }
+    }
+
+    const list_const_iterator_t end() const
+    {
+        return mLruList.end();
+    }
+
+    size_t size() const
+    {
+        return mLruList.size();
+    }
+};
+
+}
+
+#endif /* INCLUDED_O3TL_LRU_MAP_HXX */
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */

o3tl/CppunitTest_o3tl_tests.mk

@@ -33,6 +33,7 @@ $(eval $(call gb_CppunitTest_add_exception_objects,o3tl_tests,\
 	o3tl/qa/test-vector_pool \
 	o3tl/qa/test-sorted_vector \
 	o3tl/qa/test-typed_flags \
+	o3tl/qa/test-lru_map \
 ))
 
 # vim: set noet sw=4:

o3tl/qa/test-lru_map.cxx

+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ */
+
+#include <sal/types.h>
+#include "cppunit/TestAssert.h"
+#include "cppunit/TestFixture.h"
+#include "cppunit/extensions/HelperMacros.h"
+
+#include <o3tl/lru_map.hxx>
+
+#include <boost/functional/hash.hpp>
+
+using namespace ::o3tl;
+
+class lru_map_test : public CppUnit::TestFixture
+{
+public:
+    void testBaseUsage();
+    void testReplaceKey();
+    void testReplaceValue();
+    void testLruRemoval();
+    void testCustomHash();
+
+    CPPUNIT_TEST_SUITE(lru_map_test);
+    CPPUNIT_TEST(testBaseUsage);
+    CPPUNIT_TEST(testReplaceKey);
+    CPPUNIT_TEST(testReplaceValue);
+    CPPUNIT_TEST(testLruRemoval);
+    CPPUNIT_TEST(testCustomHash);
+    CPPUNIT_TEST_SUITE_END();
+};
+
+void lru_map_test::testBaseUsage()
+{
+    o3tl::lru_map<int, int> lru(10);
+    lru.insert(std::make_pair<int, int>(1, 1));
+
+    std::pair<int, int> pair;
+    for (int i = 2; i < 7; i++)
+    {
+        pair.first = pair.second = i;
+        lru.insert(pair);
+    }
+
+    CPPUNIT_ASSERT_EQUAL(size_t(6), lru.size());
+
+    o3tl::lru_map<int, int>::const_iterator it;
+
+    it = lru.find(2);
+    CPPUNIT_ASSERT(it != lru.end());
+    CPPUNIT_ASSERT_EQUAL(2, it->second);
+
+    it = lru.find(5);
+    CPPUNIT_ASSERT(it != lru.end());
+    CPPUNIT_ASSERT_EQUAL(5, it->second);
+
+    it = lru.find(0);
+    CPPUNIT_ASSERT(it == lru.end());
+}
+
+void lru_map_test::testReplaceValue()
+{
+    o3tl::lru_map<int, int> lru(2);
+    // check if map is empty
+    CPPUNIT_ASSERT_EQUAL(size_t(0), lru.size());
+
+    // check if inserting entry with with same key replaces the value
+
+    // inserting new entry
+    lru.insert(std::make_pair<int, int>(1, 2));
+    CPPUNIT_ASSERT_EQUAL(size_t(1), lru.size());
+    CPPUNIT_ASSERT_EQUAL(2, lru.find(1)->second);
+
+    // inserting new entry with key that alreay exists
+    lru.insert(std::make_pair<int, int>(1, 4));
+    CPPUNIT_ASSERT_EQUAL(size_t(1), lru.size());
+    CPPUNIT_ASSERT_EQUAL(4, lru.find(1)->second);
+
+    // inserting new entry
+    lru.insert(std::make_pair<int, int>(2, 200));
+    CPPUNIT_ASSERT_EQUAL(size_t(2), lru.size());
+    CPPUNIT_ASSERT_EQUAL(4, lru.find(1)->second);
+    CPPUNIT_ASSERT_EQUAL(200, lru.find(2)->second);
+
+    // check if insert with same key, moves the entry back of the lru queu
+
+    // inserting new entry with key that alreay exists
+    lru.insert(std::make_pair<int, int>(1, 6));
+    // inserting new entry, lru removed
+    lru.insert(std::make_pair<int, int>(3, 300));
+
+    CPPUNIT_ASSERT_EQUAL(size_t(2), lru.size());
+    CPPUNIT_ASSERT_EQUAL(6, lru.find(1)->second);
+    CPPUNIT_ASSERT_EQUAL(300, lru.find(3)->second);
+
+}
+
+void lru_map_test::testReplaceKey()
+{
+    o3tl::lru_map<int, int> lru(2);
+
+    // inserting new entry
+    lru.insert(std::make_pair<int, int>(1, 100));
+    CPPUNIT_ASSERT_EQUAL(size_t(1), lru.size());
+    CPPUNIT_ASSERT_EQUAL(100, lru.find(1)->second);
+    CPPUNIT_ASSERT(lru.find(2) == lru.end());
+    CPPUNIT_ASSERT(lru.find(3) == lru.end());
+
+    // inserting new entry
+    lru.insert(std::make_pair<int, int>(2, 200));
+    CPPUNIT_ASSERT_EQUAL(size_t(2), lru.size());
+    CPPUNIT_ASSERT_EQUAL(100, lru.find(1)->second);
+    CPPUNIT_ASSERT_EQUAL(200, lru.find(2)->second);
+    CPPUNIT_ASSERT(lru.find(3) == lru.end());
+
+    // inserting new entry, lru entry is removed
+    lru.insert(std::make_pair<int, int>(3, 300));
+    CPPUNIT_ASSERT_EQUAL(size_t(2), lru.size());
+    CPPUNIT_ASSERT(lru.find(1) == lru.end());
+    CPPUNIT_ASSERT_EQUAL(200, lru.find(2)->second);
+    CPPUNIT_ASSERT_EQUAL(300, lru.find(3)->second);
+
+    // inserting new entry, lru entry is removed
+    std::pair<int, int> pair(4, 400);
+    lru.insert(pair);
+    CPPUNIT_ASSERT_EQUAL(size_t(2), lru.size());
+    CPPUNIT_ASSERT(lru.find(1) == lru.end());
+    CPPUNIT_ASSERT(lru.find(2) == lru.end());
+    CPPUNIT_ASSERT_EQUAL(300, lru.find(3)->second);
+    CPPUNIT_ASSERT_EQUAL(400, lru.find(4)->second);
+}
+
+void lru_map_test::testLruRemoval()
+{
+    o3tl::lru_map<int, int> lru(5);
+    CPPUNIT_ASSERT_EQUAL(size_t(0), lru.size());
+
+    // fill up..
+    lru.insert(std::make_pair<int, int>(1, 100));
+    lru.insert(std::make_pair<int, int>(2, 200));
+    lru.insert(std::make_pair<int, int>(3, 300));
+    lru.insert(std::make_pair<int, int>(4, 400));
+    lru.insert(std::make_pair<int, int>(5, 500));
+    CPPUNIT_ASSERT_EQUAL(size_t(5), lru.size());
+    CPPUNIT_ASSERT_EQUAL(100, lru.find(1)->second);
+    CPPUNIT_ASSERT_EQUAL(200, lru.find(2)->second);
+    CPPUNIT_ASSERT_EQUAL(300, lru.find(3)->second);
+    CPPUNIT_ASSERT_EQUAL(400, lru.find(4)->second);
+    CPPUNIT_ASSERT_EQUAL(500, lru.find(5)->second);
+
+    // add one more entry - lru entry should be removed
+    lru.insert(std::make_pair<int, int>(6, 600));
+
+    CPPUNIT_ASSERT_EQUAL(size_t(5), lru.size());
+    CPPUNIT_ASSERT_EQUAL(200, lru.find(2)->second);
+    CPPUNIT_ASSERT_EQUAL(300, lru.find(3)->second);
+    CPPUNIT_ASSERT_EQUAL(400, lru.find(4)->second);
+    CPPUNIT_ASSERT_EQUAL(500, lru.find(5)->second);
+    CPPUNIT_ASSERT_EQUAL(600, lru.find(6)->second);
+
+    // access the lru entry to put it at the back of the lru queue
+    lru.find(2);
+    // add new entry - lru entry should be removed
+    lru.insert(std::make_pair<int, int>(7, 700));
+
+    CPPUNIT_ASSERT_EQUAL(size_t(5), lru.size());
+    CPPUNIT_ASSERT_EQUAL(200, lru.find(2)->second);
+    CPPUNIT_ASSERT_EQUAL(400, lru.find(4)->second);
+    CPPUNIT_ASSERT_EQUAL(500, lru.find(5)->second);
+    CPPUNIT_ASSERT_EQUAL(600, lru.find(6)->second);
+    CPPUNIT_ASSERT_EQUAL(700, lru.find(7)->second);
+}
+
+struct TestClassKey
+{
+    int mA;
+    int mB;
+
+    TestClassKey(int a, int b)
+        : mA(a)
+        , mB(b)
+    {}
+
+    bool operator==(TestClassKey const& aOther) const
+    {
+        return mA == aOther.mA
+            && mB == aOther.mB;
+    }
+};
+
+struct TestClassKeyHashFunction
+{
+    std::size_t operator()(TestClassKey const& aKey) const
+    {
+        std::size_t seed = 0;
+        boost::hash_combine(seed, aKey.mA);
+        boost::hash_combine(seed, aKey.mB);
+        return seed;
+    }
+};
+
+void lru_map_test::testCustomHash()
+{
+    // check lru_map with custom hash function
+    o3tl::lru_map<TestClassKey, int, TestClassKeyHashFunction> lru(2);
+    CPPUNIT_ASSERT_EQUAL(size_t(0), lru.size());
+
+    lru.insert(std::make_pair<TestClassKey, int>(TestClassKey(1,1), 2));
+    CPPUNIT_ASSERT_EQUAL(size_t(1), lru.size());
+
+    lru.insert(std::make_pair<TestClassKey, int>(TestClassKey(1,1), 7));
+    CPPUNIT_ASSERT_EQUAL(size_t(1), lru.size());
+
+    lru.insert(std::make_pair<TestClassKey, int>(TestClassKey(1,2), 9));
+    CPPUNIT_ASSERT_EQUAL(size_t(2), lru.size());
+
+    CPPUNIT_ASSERT(lru.end() == lru.find(TestClassKey(0,0))); // non existent
+    CPPUNIT_ASSERT_EQUAL(7, lru.find(TestClassKey(1,1))->second);
+    CPPUNIT_ASSERT_EQUAL(9, lru.find(TestClassKey(1,2))->second);
+
+    lru.insert(std::make_pair<TestClassKey, int>(TestClassKey(2,1), 13));
+
+    CPPUNIT_ASSERT_EQUAL(size_t(2), lru.size());
+
+    CPPUNIT_ASSERT(lru.end() == lru.find(TestClassKey(1,1)));
+    CPPUNIT_ASSERT_EQUAL(9,  lru.find(TestClassKey(1,2))->second);
+    CPPUNIT_ASSERT_EQUAL(13, lru.find(TestClassKey(2,1))->second);
+}
+
+CPPUNIT_TEST_SUITE_REGISTRATION(lru_map_test);
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */