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This artifact provides a single jar that contains all classes required to use remote Jakarta Enterprise Beans and Jakarta Messaging, including
all dependencies. It is intended for use by those not using maven, maven users should just import the Jakarta Enterprise Beans and
Jakarta Messaging BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
/*
* 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.util;
import io.netty.util.concurrent.FastThreadLocal;
import io.netty.util.internal.SystemPropertyUtil;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
import java.lang.ref.WeakReference;
import java.util.Arrays;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.atomic.AtomicInteger;
/**
* Light-weight object pool based on a thread-local stack.
*
* @param the type of the pooled object
*/
public abstract class Recycler {
private static final InternalLogger logger = InternalLoggerFactory.getInstance(Recycler.class);
private static final AtomicInteger ID_GENERATOR = new AtomicInteger(Integer.MIN_VALUE);
private static final int OWN_THREAD_ID = ID_GENERATOR.getAndIncrement();
private static final int DEFAULT_MAX_CAPACITY;
private static final int INITIAL_CAPACITY;
static {
// In the future, we might have different maxCapacity for different object types.
// e.g. io.netty.recycler.maxCapacity.writeTask
// io.netty.recycler.maxCapacity.outboundBuffer
int maxCapacity = SystemPropertyUtil.getInt("io.netty.recycler.maxCapacity.default", 0);
if (maxCapacity <= 0) {
// TODO: Some arbitrary large number - should adjust as we get more production experience.
maxCapacity = 262144;
}
DEFAULT_MAX_CAPACITY = maxCapacity;
if (logger.isDebugEnabled()) {
logger.debug("-Dio.netty.recycler.maxCapacity.default: {}", DEFAULT_MAX_CAPACITY);
}
INITIAL_CAPACITY = Math.min(DEFAULT_MAX_CAPACITY, 256);
}
private final int maxCapacity;
private final FastThreadLocal> threadLocal = new FastThreadLocal>() {
@Override
protected Stack initialValue() {
return new Stack(Recycler.this, Thread.currentThread(), maxCapacity);
}
};
protected Recycler() {
this(DEFAULT_MAX_CAPACITY);
}
protected Recycler(int maxCapacity) {
this.maxCapacity = Math.max(0, maxCapacity);
}
@SuppressWarnings("unchecked")
public final T get() {
Stack stack = threadLocal.get();
DefaultHandle handle = stack.pop();
if (handle == null) {
handle = stack.newHandle();
handle.value = newObject(handle);
}
return (T) handle.value;
}
public final boolean recycle(T o, Handle handle) {
DefaultHandle h = (DefaultHandle) handle;
if (h.stack.parent != this) {
return false;
}
if (o != h.value) {
throw new IllegalArgumentException("o does not belong to handle");
}
h.recycle();
return true;
}
protected abstract T newObject(Handle handle);
final int threadLocalCapacity() {
return threadLocal.get().elements.length;
}
final int threadLocalSize() {
return threadLocal.get().size;
}
public interface Handle { }
static final class DefaultHandle implements Handle {
private int lastRecycledId;
private int recycleId;
private Stack stack;
private Object value;
DefaultHandle(Stack stack) {
this.stack = stack;
}
public void recycle() {
Thread thread = Thread.currentThread();
if (thread == stack.thread) {
stack.push(this);
return;
}
// we don't want to have a ref to the queue as the value in our weak map
// so we null it out; to ensure there are no races with restoring it later
// we impose a memory ordering here (no-op on x86)
Map, WeakOrderQueue> delayedRecycled = DELAYED_RECYCLED.get();
WeakOrderQueue queue = delayedRecycled.get(stack);
if (queue == null) {
delayedRecycled.put(stack, queue = new WeakOrderQueue(stack, thread));
}
queue.add(this);
}
}
private static final FastThreadLocal, WeakOrderQueue>> DELAYED_RECYCLED =
new FastThreadLocal, WeakOrderQueue>>() {
@Override
protected Map, WeakOrderQueue> initialValue() {
return new WeakHashMap, WeakOrderQueue>();
}
};
// a queue that makes only moderate guarantees about visibility: items are seen in the correct order,
// but we aren't absolutely guaranteed to ever see anything at all, thereby keeping the queue cheap to maintain
private static final class WeakOrderQueue {
private static final int LINK_CAPACITY = 16;
// Let Link extend AtomicInteger for intrinsics. The Link itself will be used as writerIndex.
@SuppressWarnings("serial")
private static final class Link extends AtomicInteger {
private final DefaultHandle[] elements = new DefaultHandle[LINK_CAPACITY];
private int readIndex;
private Link next;
}
// chain of data items
private Link head, tail;
// pointer to another queue of delayed items for the same stack
private WeakOrderQueue next;
private final WeakReference owner;
private final int id = ID_GENERATOR.getAndIncrement();
WeakOrderQueue(Stack stack, Thread thread) {
head = tail = new Link();
owner = new WeakReference(thread);
synchronized (stack) {
next = stack.head;
stack.head = this;
}
}
void add(DefaultHandle handle) {
handle.lastRecycledId = id;
Link tail = this.tail;
int writeIndex;
if ((writeIndex = tail.get()) == LINK_CAPACITY) {
this.tail = tail = tail.next = new Link();
writeIndex = tail.get();
}
tail.elements[writeIndex] = handle;
handle.stack = null;
// we lazy set to ensure that setting stack to null appears before we unnull it in the owning thread;
// this also means we guarantee visibility of an element in the queue if we see the index updated
tail.lazySet(writeIndex + 1);
}
boolean hasFinalData() {
return tail.readIndex != tail.get();
}
// transfer as many items as we can from this queue to the stack, returning true if any were transferred
@SuppressWarnings("rawtypes")
boolean transfer(Stack dst) {
Link head = this.head;
if (head == null) {
return false;
}
if (head.readIndex == LINK_CAPACITY) {
if (head.next == null) {
return false;
}
this.head = head = head.next;
}
final int srcStart = head.readIndex;
int srcEnd = head.get();
final int srcSize = srcEnd - srcStart;
if (srcSize == 0) {
return false;
}
final int dstSize = dst.size;
final int expectedCapacity = dstSize + srcSize;
if (expectedCapacity > dst.elements.length) {
final int actualCapacity = dst.increaseCapacity(expectedCapacity);
srcEnd = Math.min(srcStart + actualCapacity - dstSize, srcEnd);
}
if (srcStart != srcEnd) {
final DefaultHandle[] srcElems = head.elements;
final DefaultHandle[] dstElems = dst.elements;
int newDstSize = dstSize;
for (int i = srcStart; i < srcEnd; i++) {
DefaultHandle element = srcElems[i];
if (element.recycleId == 0) {
element.recycleId = element.lastRecycledId;
} else if (element.recycleId != element.lastRecycledId) {
throw new IllegalStateException("recycled already");
}
element.stack = dst;
dstElems[newDstSize ++] = element;
srcElems[i] = null;
}
dst.size = newDstSize;
if (srcEnd == LINK_CAPACITY && head.next != null) {
this.head = head.next;
}
head.readIndex = srcEnd;
return true;
} else {
// The destination stack is full already.
return false;
}
}
}
static final class Stack {
// we keep a queue of per-thread queues, which is appended to once only, each time a new thread other
// than the stack owner recycles: when we run out of items in our stack we iterate this collection
// to scavenge those that can be reused. this permits us to incur minimal thread synchronisation whilst
// still recycling all items.
final Recycler parent;
final Thread thread;
private DefaultHandle[] elements;
private final int maxCapacity;
private int size;
private volatile WeakOrderQueue head;
private WeakOrderQueue cursor, prev;
Stack(Recycler parent, Thread thread, int maxCapacity) {
this.parent = parent;
this.thread = thread;
this.maxCapacity = maxCapacity;
elements = new DefaultHandle[Math.min(INITIAL_CAPACITY, maxCapacity)];
}
int increaseCapacity(int expectedCapacity) {
int newCapacity = elements.length;
int maxCapacity = this.maxCapacity;
do {
newCapacity <<= 1;
} while (newCapacity < expectedCapacity && newCapacity < maxCapacity);
newCapacity = Math.min(newCapacity, maxCapacity);
if (newCapacity != elements.length) {
elements = Arrays.copyOf(elements, newCapacity);
}
return newCapacity;
}
DefaultHandle pop() {
int size = this.size;
if (size == 0) {
if (!scavenge()) {
return null;
}
size = this.size;
}
size --;
DefaultHandle ret = elements[size];
if (ret.lastRecycledId != ret.recycleId) {
throw new IllegalStateException("recycled multiple times");
}
ret.recycleId = 0;
ret.lastRecycledId = 0;
this.size = size;
return ret;
}
boolean scavenge() {
// continue an existing scavenge, if any
if (scavengeSome()) {
return true;
}
// reset our scavenge cursor
prev = null;
cursor = head;
return false;
}
boolean scavengeSome() {
WeakOrderQueue cursor = this.cursor;
if (cursor == null) {
cursor = head;
if (cursor == null) {
return false;
}
}
boolean success = false;
WeakOrderQueue prev = this.prev;
do {
if (cursor.transfer(this)) {
success = true;
break;
}
WeakOrderQueue next = cursor.next;
if (cursor.owner.get() == null) {
// If the thread associated with the queue is gone, unlink it, after
// performing a volatile read to confirm there is no data left to collect.
// We never unlink the first queue, as we don't want to synchronize on updating the head.
if (cursor.hasFinalData()) {
for (;;) {
if (cursor.transfer(this)) {
success = true;
} else {
break;
}
}
}
if (prev != null) {
prev.next = next;
}
} else {
prev = cursor;
}
cursor = next;
} while (cursor != null && !success);
this.prev = prev;
this.cursor = cursor;
return success;
}
void push(DefaultHandle item) {
if ((item.recycleId | item.lastRecycledId) != 0) {
throw new IllegalStateException("recycled already");
}
item.recycleId = item.lastRecycledId = OWN_THREAD_ID;
int size = this.size;
if (size >= maxCapacity) {
// Hit the maximum capacity - drop the possibly youngest object.
return;
}
if (size == elements.length) {
elements = Arrays.copyOf(elements, Math.min(size << 1, maxCapacity));
}
elements[size] = item;
this.size = size + 1;
}
DefaultHandle newHandle() {
return new DefaultHandle(this);
}
}
}
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