io.questdb.std.WeakObjectPool Maven / Gradle / Ivy
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*
* Copyright (c) 2014-2019 Appsicle
* Copyright (c) 2019-2020 QuestDB
*
* 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.
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package io.questdb.std;
import org.jetbrains.annotations.NotNull;
import java.io.Closeable;
import java.util.ArrayDeque;
/**
* Weak object pool can be used in multi-threaded environment. While
* weak object pool is a factory of new instances, when object is popped
* out of pool there is no reference to tie this object back to pool.
*
* In multi-threaded environment weak pools must be local to thread and
* objects they create can travel between pools, e.g. one thread gets
* object from pool and last thread to finish with this object then
* returns it to its own local pool.
*/
public class WeakObjectPool implements Closeable {
private final ArrayDeque cache;
private final ObjectFactory factory;
private final int size;
public WeakObjectPool(@NotNull ObjectFactory factory, int size) {
this.cache = new ArrayDeque<>();
this.factory = factory;
this.size = size;
fill();
}
@Override
public void close() {
while (cache.size() > 0) {
Misc.free(cache.pop());
}
}
public T pop() {
final T obj = cache.poll();
return obj == null ? factory.newInstance() : obj;
}
public void push(T obj) {
assert obj != null;
obj.clear();
cache.push(obj);
}
private void fill() {
for (int i = 0; i < size; i++) {
cache.add(factory.newInstance());
}
}
}