platform/platform-impl/src/com/intellij/util/CachedValueImpl.java

   1 /*
   2  * Copyright 2000-2009 JetBrains s.r.o.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 /*
  18  * Created by IntelliJ IDEA.
  19  * User: mike
  20  * Date: Jun 6, 2002
  21  * Time: 5:41:42 PM
  22  * To change template for new class use
  23  * Code Style | Class Templates options (Tools | IDE Options).
  24  */
  25 package com.intellij.util;
  26
  27 import com.intellij.psi.util.CachedValue;
  28 import com.intellij.psi.util.CachedValueProvider;
  29 import org.jetbrains.annotations.NotNull;
  30 import org.jetbrains.annotations.Nullable;
  31
  32 public abstract class CachedValueImpl<T> extends CachedValueBase<T> implements CachedValue<T> {
  33
  34   private final CachedValueProvider<T> myProvider;
  35
  36   public CachedValueImpl(@NotNull CachedValueProvider<T> provider) {
  37     super();
  38     myProvider = provider;
  39   }
  40
  41   @Nullable
  42   public T getValue() {
  43
  44     r.lock();
  45
  46     T value;
  47     try {
  48       value = getUpToDateOrNull();
  49       if (value != null) {
  50         return value == NULL ? null : value;
  51       }
  52     } finally {
  53       r.unlock();
  54     }
  55
  56     w.lock();
  57
  58     try {
  59       value = getUpToDateOrNull();
  60       if (value != null) {
  61         return value == NULL ? null : value;
  62       }
  63
  64       CachedValueProvider.Result<T> result = myProvider.compute();
  65       value = result == null ? null : result.getValue();
  66
  67       setValue(value, result);
  68
  69       return value;
  70     }
  71     finally {
  72       w.unlock();
  73     }
  74   }
  75
  76   public CachedValueProvider<T> getValueProvider() {
  77     return myProvider;
  78   }
  79
  80 }