/*
* Copyright 2000-2009 JetBrains s.r.o.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.intellij.openapi.util;
import com.intellij.util.concurrency.JBLock;
import com.intellij.util.concurrency.JBReentrantReadWriteLock;
import com.intellij.util.concurrency.LockFactory;
public abstract class FieldCache<T, Owner,AccessorParameter,Parameter> {
private static final RecursionGuard ourGuard = RecursionManager.createGuard("fieldCache");
private final JBLock r;
private final JBLock w;
protected FieldCache() {
JBReentrantReadWriteLock ourLock = LockFactory.createReadWriteLock();
r = ourLock.readLock();
w = ourLock.writeLock();
}
public T get(AccessorParameter a, Owner owner, Parameter p) {
r.lock();
T result;
try {
result = getValue(owner, a);
}
finally {
r.unlock();
}
if (result == null) {
w.lock();
try {
result = getValue(owner, a);
if (result == null) {
RecursionGuard.StackStamp stamp = ourGuard.markStack();
result = compute(owner, p);
if (stamp.mayCacheNow()) {
putValue(result, owner, a);
}
}
}
finally {
w.unlock();
}
}
return result;
}
public final T getCached(AccessorParameter a, Owner owner) {
r.lock();
try {
return getValue(owner, a);
}
finally {
r.unlock();
}
}
public void clear(AccessorParameter a, Owner owner) {
w.lock();
try {
putValue(null, owner, a);
}
finally{
w.unlock();
}
}
protected abstract T compute(Owner owner, Parameter p);
protected abstract T getValue(Owner owner, AccessorParameter p);
protected abstract void putValue(T t, Owner owner, AccessorParameter p);
}