116 lines
3.1 KiB
Java
116 lines
3.1 KiB
Java
/*
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* Copyright 2020 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.buffer.api.internal;
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import io.netty.buffer.api.Drop;
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import java.lang.invoke.MethodHandles;
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import java.lang.invoke.VarHandle;
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public final class ArcDrop<T> implements Drop<T> {
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private static final VarHandle COUNT;
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static {
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try {
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COUNT = MethodHandles.lookup().findVarHandle(ArcDrop.class, "count", int.class);
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} catch (Exception e) {
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throw new ExceptionInInitializerError(e);
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}
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}
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private final Drop<T> delegate;
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@SuppressWarnings("FieldMayBeFinal")
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private volatile int count;
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public ArcDrop(Drop<T> delegate) {
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this.delegate = delegate;
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count = 1;
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}
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public static <X> Drop<X> wrap(Drop<X> drop) {
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if (drop.getClass() == ArcDrop.class) {
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return drop;
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}
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return new ArcDrop<X>(drop);
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}
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public static <X> Drop<X> acquire(Drop<X> drop) {
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if (drop.getClass() == ArcDrop.class) {
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((ArcDrop<X>) drop).increment();
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return drop;
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}
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return new ArcDrop<X>(drop);
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}
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public ArcDrop<T> increment() {
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int c;
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do {
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c = count;
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checkValidState(c);
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} while (!COUNT.compareAndSet(this, c, c + 1));
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return this;
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}
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@Override
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public void drop(T obj) {
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int c;
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int n;
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do {
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c = count;
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n = c - 1;
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checkValidState(c);
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} while (!COUNT.compareAndSet(this, c, n));
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if (n == 0) {
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delegate.drop(obj);
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}
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}
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@Override
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public void attach(T obj) {
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delegate.attach(obj);
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}
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public boolean isOwned() {
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return count <= 1;
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}
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public int countBorrows() {
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return count - 1;
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}
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public Drop<T> unwrap() {
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return delegate;
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}
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@Override
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public String toString() {
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StringBuilder builder = new StringBuilder()
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.append("ArcDrop@")
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.append(Integer.toHexString(System.identityHashCode(this)))
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.append('(').append(count).append(", ");
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Drop<T> drop = this;
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while ((drop = ((ArcDrop<T>) drop).unwrap()) instanceof ArcDrop) {
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builder.append(((ArcDrop<T>) drop).count).append(", ");
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}
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return builder.append(drop).append(')').toString();
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}
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private static void checkValidState(int count) {
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if (count == 0) {
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throw new IllegalStateException("Underlying resources have already been freed.");
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}
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}
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}
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