b26a61acd1
Motivation AbstractReferenceCounted and AbstractReferenceCountedByteBuf contain duplicate logic for managing the volatile refcount in an optimized and consistent manner, which increased in complexity in #8583. It's possible to extract this into a common helper class now that all access is via an AtomicIntegerFieldUpdater. Modifications - Move duplicate logic into a shared ReferenceCountUpdater class - Incorporate some additional simplification for the most common single increment/decrement cases (fewer checks/operations) Result Less code duplication, better encapsulation of the "non-trivial" internal volatile refcount manipulation
96 lines
2.9 KiB
Java
96 lines
2.9 KiB
Java
/*
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* Copyright 2013 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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* http://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.util;
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import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
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import io.netty.util.internal.ReferenceCountUpdater;
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/**
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* Abstract base class for classes wants to implement {@link ReferenceCounted}.
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*/
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public abstract class AbstractReferenceCounted implements ReferenceCounted {
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private static final long REFCNT_FIELD_OFFSET =
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ReferenceCountUpdater.getUnsafeOffset(AbstractReferenceCounted.class, "refCnt");
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private static final AtomicIntegerFieldUpdater<AbstractReferenceCounted> AIF_UPDATER =
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AtomicIntegerFieldUpdater.newUpdater(AbstractReferenceCounted.class, "refCnt");
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private static final ReferenceCountUpdater<AbstractReferenceCounted> updater =
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new ReferenceCountUpdater<AbstractReferenceCounted>() {
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@Override
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protected AtomicIntegerFieldUpdater<AbstractReferenceCounted> updater() {
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return AIF_UPDATER;
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}
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@Override
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protected long unsafeOffset() {
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return REFCNT_FIELD_OFFSET;
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}
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};
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// Value might not equal "real" reference count, all access should be via the updater
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@SuppressWarnings("unused")
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private volatile int refCnt = updater.initialValue();
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@Override
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public int refCnt() {
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return updater.refCnt(this);
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}
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/**
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* An unsafe operation intended for use by a subclass that sets the reference count of the buffer directly
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*/
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protected final void setRefCnt(int refCnt) {
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updater.setRefCnt(this, refCnt);
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}
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@Override
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public ReferenceCounted retain() {
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return updater.retain(this);
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}
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@Override
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public ReferenceCounted retain(int increment) {
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return updater.retain(this, increment);
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}
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@Override
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public ReferenceCounted touch() {
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return touch(null);
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}
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@Override
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public boolean release() {
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return handleRelease(updater.release(this));
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}
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@Override
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public boolean release(int decrement) {
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return handleRelease(updater.release(this, decrement));
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}
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private boolean handleRelease(boolean result) {
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if (result) {
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deallocate();
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}
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return result;
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}
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/**
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* Called once {@link #refCnt()} is equals 0.
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*/
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protected abstract void deallocate();
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}
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