001    /*
002     * Copyright 2010-2013 JetBrains s.r.o.
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    
017    package org.jetbrains.jet.lang.resolve.lazy.storage;
018    
019    import org.jetbrains.annotations.NotNull;
020    import org.jetbrains.annotations.Nullable;
021    import org.jetbrains.jet.utils.WrappedValues;
022    
023    import java.util.HashMap;
024    import java.util.Map;
025    
026    public abstract class MemoizedFunctionToNullableImpl<K, V> implements MemoizedFunctionToNullable<K, V> {
027        private final Map<K, Object> cache;
028    
029        public MemoizedFunctionToNullableImpl() {
030            this(new HashMap<K, Object>());
031        }
032    
033        public MemoizedFunctionToNullableImpl(@NotNull Map<K, Object> map) {
034            this.cache = map;
035        }
036    
037        @Nullable
038        @Override
039        public V fun(K input) {
040            Object value = cache.get(input);
041            if (value != null) return WrappedValues.unescapeNull(value);
042    
043            V typedValue = doCompute(input);
044    
045            Object oldValue = cache.put(input, WrappedValues.escapeNull(typedValue));
046            assert oldValue == null : "Race condition detected";
047    
048            return typedValue;
049        }
050    
051        @Nullable
052        protected abstract V doCompute(K input);
053    }