--- jsr166/src/jsr166y/LinkedTransferQueue.java	2009/07/27 03:22:39	1.30
+++ jsr166/src/jsr166y/LinkedTransferQueue.java	2009/07/30 13:30:19	1.33
@@ -14,7 +14,6 @@ import java.util.Iterator;
 import java.util.NoSuchElementException;
 import java.util.concurrent.locks.LockSupport;
 import java.util.concurrent.atomic.AtomicReference;
-import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
 
 /**
  * An unbounded {@linkplain TransferQueue} based on linked nodes.
@@ -115,17 +114,46 @@ public class LinkedTransferQueue<E> exte
             this.isData = isData;
         }
 
-        @SuppressWarnings("rawtypes")
-        static final AtomicReferenceFieldUpdater<Node, Node>
-            nextUpdater = AtomicReferenceFieldUpdater.newUpdater
-            (Node.class, Node.class, "next");
+        // Unsafe mechanics
+
+        private static final sun.misc.Unsafe UNSAFE = getUnsafe();
+        private static final long nextOffset =
+            objectFieldOffset(UNSAFE, "next", Node.class);
 
         final boolean casNext(Node<E> cmp, Node<E> val) {
-            return nextUpdater.compareAndSet(this, cmp, val);
+            return UNSAFE.compareAndSwapObject(this, nextOffset, cmp, val);
         }
 
         final void clearNext() {
-            nextUpdater.lazySet(this, this);
+            UNSAFE.putOrderedObject(this, nextOffset, this);
+        }
+
+        /**
+         * Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
+         * Replace with a simple call to Unsafe.getUnsafe when integrating
+         * into a jdk.
+         *
+         * @return a sun.misc.Unsafe
+         */
+        private static sun.misc.Unsafe getUnsafe() {
+            try {
+                return sun.misc.Unsafe.getUnsafe();
+            } catch (SecurityException se) {
+                try {
+                    return java.security.AccessController.doPrivileged
+                        (new java.security
+                         .PrivilegedExceptionAction<sun.misc.Unsafe>() {
+                            public sun.misc.Unsafe run() throws Exception {
+                                java.lang.reflect.Field f = sun.misc
+                                    .Unsafe.class.getDeclaredField("theUnsafe");
+                                f.setAccessible(true);
+                                return (sun.misc.Unsafe) f.get(null);
+                            }});
+                } catch (java.security.PrivilegedActionException e) {
+                    throw new RuntimeException("Could not initialize intrinsics",
+                                               e.getCause());
+                }
+            }
         }
 
         private static final long serialVersionUID = -3375979862319811754L;
@@ -607,7 +635,6 @@ public class LinkedTransferQueue<E> exte
         }
     }
 
-
     public Iterator<E> iterator() {
         return new Itr();
     }
@@ -622,42 +649,39 @@ public class LinkedTransferQueue<E> exte
     class Itr implements Iterator<E> {
         Node<E> next;        // node to return next
         Node<E> pnext;       // predecessor of next
-        Node<E> snext;       // successor of next
         Node<E> curr;        // last returned node, for remove()
         Node<E> pcurr;       // predecessor of curr, for remove()
-        E nextItem;        // Cache of next item, once committed to in next
+        E nextItem;          // Cache of next item, once committed to in next
 
         Itr() {
-            findNext();
+            advance();
         }
 
         /**
-         * Ensures next points to next valid node, or null if none.
+         * Moves to next valid node and returns item to return for
+         * next(), or null if no such.
          */
-        void findNext() {
+        private E advance() {
+            pcurr = pnext;
+            curr = next;
+            E item = nextItem;
+
             for (;;) {
-                Node<E> pred = pnext;
-                Node<E> q = next;
-                if (pred == null || pred == q) {
-                    pred = traversalHead();
-                    q = pred.next;
-                }
-                if (q == null || !q.isData) {
+                pnext = next == null ? traversalHead() : next;
+                next = pnext.next;
+                if (next == pnext) {
                     next = null;
-                    return;
+                    continue;  // restart
                 }
-                Object x = q.get();
-                Node<E> s = q.next;
-                if (x != null && q != x && q != s) {
+                if (next == null)
+                    break;
+                Object x = next.get();
+                if (x != null && x != next) {
                     nextItem = (E) x;
-                    snext = s;
-                    pnext = pred;
-                    next = q;
-                    return;
+                    break;
                 }
-                pnext = q;
-                next = s;
             }
+            return item;
         }
 
         public boolean hasNext() {
@@ -665,14 +689,9 @@ public class LinkedTransferQueue<E> exte
         }
 
         public E next() {
-            if (next == null) throw new NoSuchElementException();
-            pcurr = pnext;
-            curr = next;
-            pnext = next;
-            next = snext;
-            E x = nextItem;
-            findNext();
-            return x;
+            if (next == null) 
+                throw new NoSuchElementException();
+            return advance();
         }
 
         public void remove() {
@@ -742,32 +761,44 @@ public class LinkedTransferQueue<E> exte
      * @return the number of elements in this queue
      */
     public int size() {
-        int count = 0;
-        Node<E> h = traversalHead();
-        for (Node<E> p = h.next; p != null && p.isData; p = p.next) {
-            Object x = p.get();
-            if (x != null && x != p) {
-                if (++count == Integer.MAX_VALUE) // saturated
+        for (;;) {
+            int count = 0;
+            Node<E> pred = traversalHead();
+            for (;;) {
+                Node<E> q = pred.next;
+                if (q == pred) // restart
                     break;
+                if (q == null || !q.isData)
+                    return count;
+                Object x = q.get();
+                if (x != null && x != q) {
+                    if (++count == Integer.MAX_VALUE) // saturated
+                        return count;
+                }
+                pred = q;
             }
         }
-        return count;
     }
 
     public int getWaitingConsumerCount() {
-        int count = 0;
-        Node<E> h = traversalHead();
-        for (Node<E> p = h.next; p != null && !p.isData; p = p.next) {
-            if (p.get() == null) {
-                if (++count == Integer.MAX_VALUE)
+        // converse of size -- count valid non-data nodes
+        for (;;) {
+            int count = 0;
+            Node<E> pred = traversalHead();
+            for (;;) {
+                Node<E> q = pred.next;
+                if (q == pred) // restart
                     break;
+                if (q == null || q.isData)
+                    return count;
+                Object x = q.get();
+                if (x == null) {
+                    if (++count == Integer.MAX_VALUE) // saturated
+                        return count;
+                }
+                pred = q;
             }
         }
-        return count;
-    }
-
-    public int remainingCapacity() {
-        return Integer.MAX_VALUE;
     }
 
     public boolean remove(Object o) {
@@ -777,10 +808,10 @@ public class LinkedTransferQueue<E> exte
             Node<E> pred = traversalHead();
             for (;;) {
                 Node<E> q = pred.next;
-                if (q == null || !q.isData)
-                    return false;
                 if (q == pred) // restart
                     break;
+                if (q == null || !q.isData)
+                    return false;
                 Object x = q.get();
                 if (x != null && x != q && o.equals(x) &&
                     q.compareAndSet(x, q)) {
@@ -792,6 +823,10 @@ public class LinkedTransferQueue<E> exte
         }
     }
 
+    public int remainingCapacity() {
+        return Integer.MAX_VALUE;
+    }
+
     /**
      * Save the state to a stream (that is, serialize it).
      *
@@ -842,13 +877,15 @@ public class LinkedTransferQueue<E> exte
 
     private static final sun.misc.Unsafe UNSAFE = getUnsafe();
     private static final long headOffset =
-        objectFieldOffset("head", LinkedTransferQueue.class);
+        objectFieldOffset(UNSAFE, "head", LinkedTransferQueue.class);
     private static final long tailOffset =
-        objectFieldOffset("tail", LinkedTransferQueue.class);
+        objectFieldOffset(UNSAFE, "tail", LinkedTransferQueue.class);
     private static final long cleanMeOffset =
-        objectFieldOffset("cleanMe", LinkedTransferQueue.class);
+        objectFieldOffset(UNSAFE, "cleanMe", LinkedTransferQueue.class);
+
 
-    private static long objectFieldOffset(String field, Class<?> klazz) {
+    static long objectFieldOffset(sun.misc.Unsafe UNSAFE,
+                                  String field, Class<?> klazz) {
         try {
             return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
         } catch (NoSuchFieldException e) {