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package jsr166y; |
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– |
import java.util.concurrent.*; |
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import java.util.AbstractQueue; |
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import java.util.Collection; |
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import java.util.ConcurrentModificationException; |
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import java.util.Iterator; |
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import java.util.NoSuchElementException; |
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import java.util.Queue; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.locks.LockSupport; |
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/** |
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} |
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final boolean casItem(Object cmp, Object val) { |
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// assert cmp == null || cmp.getClass() != Node.class; |
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// assert cmp == null || cmp.getClass() != Node.class; |
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return UNSAFE.compareAndSwapObject(this, itemOffset, cmp, val); |
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} |
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* Tries to artificially match a data node -- used by remove. |
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*/ |
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final boolean tryMatchData() { |
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// assert isData; |
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// assert isData; |
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Object x = item; |
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if (x != null && x != this && casItem(x, null)) { |
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LockSupport.unpark(waiter); |
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@SuppressWarnings("unchecked") |
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static <E> E cast(Object item) { |
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// assert item == null || item.getClass() != Node.class; |
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// assert item == null || item.getClass() != Node.class; |
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return (E) item; |
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} |
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throw new NullPointerException(); |
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Node s = null; // the node to append, if needed |
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retry: for (;;) { // restart on append race |
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retry: |
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for (;;) { // restart on append race |
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for (Node h = head, p = h; p != null;) { // find & match first node |
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boolean isData = p.isData; |
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for (;;) { |
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Object item = s.item; |
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if (item != e) { // matched |
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// assert item != s; |
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// assert item != s; |
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s.forgetContents(); // avoid garbage |
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return this.<E>cast(item); |
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} |
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* Moves to next node after prev, or first node if prev null. |
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*/ |
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private void advance(Node prev) { |
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lastPred = lastRet; |
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lastRet = prev; |
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for (Node p = (prev == null) ? head : succ(prev); |
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p != null; p = succ(p)) { |
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Object item = p.item; |
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if (p.isData) { |
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if (item != null && item != p) { |
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nextItem = LinkedTransferQueue.this.<E>cast(item); |
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nextNode = p; |
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/* |
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* To track and avoid buildup of deleted nodes in the face |
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* of calls to both Queue.remove and Itr.remove, we must |
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* include variants of unsplice and sweep upon each |
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* advance: Upon Itr.remove, we may need to catch up links |
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* from lastPred, and upon other removes, we might need to |
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* skip ahead from stale nodes and unsplice deleted ones |
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* found while advancing. |
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*/ |
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Node r, b; // reset lastPred upon possible deletion of lastRet |
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if ((r = lastRet) != null && !r.isMatched()) |
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lastPred = r; // next lastPred is old lastRet |
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else if ((b = lastPred) == null || b.isMatched()) |
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lastPred = null; // at start of list |
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else { |
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Node s, n; // help with removal of lastPred.next |
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while ((s = b.next) != null && |
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s != b && s.isMatched() && |
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(n = s.next) != null && n != s) |
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b.casNext(s, n); |
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} |
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this.lastRet = prev; |
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for (Node p = prev, s, n;;) { |
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s = (p == null) ? head : p.next; |
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if (s == null) |
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break; |
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else if (s == p) { |
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p = null; |
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continue; |
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} |
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Object item = s.item; |
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if (s.isData) { |
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if (item != null && item != s) { |
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nextItem = LinkedTransferQueue.<E>cast(item); |
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nextNode = s; |
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return; |
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} |
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} |
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} |
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else if (item == null) |
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break; |
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// assert s.isMatched(); |
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if (p == null) |
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p = s; |
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else if ((n = s.next) == null) |
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break; |
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else if (s == n) |
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p = null; |
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else |
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p.casNext(s, n); |
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} |
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nextNode = null; |
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nextItem = null; |
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} |
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Itr() { |
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} |
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public final void remove() { |
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Node p = lastRet; |
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if (p == null) throw new IllegalStateException(); |
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if (p.tryMatchData()) |
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unsplice(lastPred, p); |
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final Node lastRet = this.lastRet; |
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if (lastRet == null) |
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throw new IllegalStateException(); |
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this.lastRet = null; |
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if (lastRet.tryMatchData()) |
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unsplice(lastPred, lastRet); |
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} |
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} |
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* Inserts the specified element at the tail of this queue. |
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* As the queue is unbounded, this method will never return {@code false}. |
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* |
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* @return {@code true} (as specified by |
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* {@link BlockingQueue#offer(Object) BlockingQueue.offer}) |
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* @return {@code true} (as specified by {@link Queue#offer}) |
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* @throws NullPointerException if the specified element is null |
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*/ |
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public boolean offer(E e) { |
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} |
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/** |
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* Returns {@code true} if this queue contains the specified element. |
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* More formally, returns {@code true} if and only if this queue contains |
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* at least one element {@code e} such that {@code o.equals(e)}. |
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* |
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* @param o object to be checked for containment in this queue |
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* @return {@code true} if this queue contains the specified element |
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*/ |
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public boolean contains(Object o) { |
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if (o == null) return false; |
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for (Node p = head; p != null; p = succ(p)) { |
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Object item = p.item; |
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if (p.isData) { |
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if (item != null && item != p && o.equals(item)) |
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return true; |
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} |
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else if (item == null) |
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break; |
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} |
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return false; |
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} |
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/** |
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* Always returns {@code Integer.MAX_VALUE} because a |
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* {@code LinkedTransferQueue} is not capacity constrained. |
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* |
