/*
* Copyright 2013 The Netty Project
*
* The Netty Project licenses this file to you 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 io.netty.buffer;
import io.netty.util.IllegalReferenceCountException;
import io.netty.util.internal.PlatformDependent;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
/**
* Abstract base class for {@link ByteBuf} implementations that count references.
*/
public abstract class AbstractReferenceCountedByteBuf extends AbstractByteBuf {
private static final AtomicIntegerFieldUpdater<AbstractReferenceCountedByteBuf> refCntUpdater;
static {
AtomicIntegerFieldUpdater<AbstractReferenceCountedByteBuf> updater =
PlatformDependent.newAtomicIntegerFieldUpdater(AbstractReferenceCountedByteBuf.class, "refCnt");
if (updater == null) {
updater = AtomicIntegerFieldUpdater.newUpdater(AbstractReferenceCountedByteBuf.class, "refCnt");
}
refCntUpdater = updater;
}
private volatile int refCnt = 1;
protected AbstractReferenceCountedByteBuf(int maxCapacity) {
super(maxCapacity);
}
@Override
public final int refCnt() {
return refCnt;
}
/**
* An unsafe operation intended for use by a subclass that sets the reference count of the buffer directly
*/
protected final void setRefCnt(int refCnt) {
this.refCnt = refCnt;
}
@Override
public ByteBuf retain() {
for (;;) {
int refCnt = this.refCnt;
if (refCnt == 0) {
throw new IllegalReferenceCountException(0, 1);
}
if (refCnt == Integer.MAX_VALUE) {
throw new IllegalReferenceCountException(Integer.MAX_VALUE, 1);
}
if (refCntUpdater.compareAndSet(this, refCnt, refCnt + 1)) {
break;
}
}
return this;
}
@Override
public ByteBuf retain(int increment) {
if (increment <= 0) {
throw new IllegalArgumentException("increment: " + increment + " (expected: > 0)");
}
for (;;) {
int refCnt = this.refCnt;
if (refCnt == 0) {
throw new IllegalReferenceCountException(0, increment);
}
if (refCnt > Integer.MAX_VALUE - increment) {
throw new IllegalReferenceCountException(refCnt, increment);
}
if (refCntUpdater.compareAndSet(this, refCnt, refCnt + increment)) {
break;
}
}
return this;
}
@Override
public final boolean release() {
for (;;) {
int refCnt = this.refCnt;
if (refCnt == 0) {
throw new IllegalReferenceCountException(0, -1);
}
if (refCntUpdater.compareAndSet(this, refCnt, refCnt - 1)) {
if (refCnt == 1) {
deallocate();
return true;
}
return false;
}
}
}
@Override
public final boolean release(int decrement) {
if (decrement <= 0) {
throw new IllegalArgumentException("decrement: " + decrement + " (expected: > 0)");
}
for (;;) {
int refCnt = this.refCnt;
if (refCnt < decrement) {
throw new IllegalReferenceCountException(refCnt, -decrement);
}
if (refCntUpdater.compareAndSet(this, refCnt, refCnt - decrement)) {
if (refCnt == decrement) {
deallocate();
return true;
}
return false;
}
}
}
/**
* Called once {@link #refCnt()} is equals 0.
*/
protected abstract void deallocate();
}