+++ /dev/null
-/* java.lang.ref.ReferenceQueue
- Copyright (C) 1999 Free Software Foundation, Inc.
-
-This file is part of GNU Classpath.
-
-GNU Classpath is free software; you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 2, or (at your option)
-any later version.
-
-GNU Classpath is distributed in the hope that it will be useful, but
-WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-General Public License for more details.
-
-You should have received a copy of the GNU General Public License
-along with GNU Classpath; see the file COPYING. If not, write to the
-Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
-02111-1307 USA.
-
-Linking this library statically or dynamically with other modules is
-making a combined work based on this library. Thus, the terms and
-conditions of the GNU General Public License cover the whole
-combination.
-
-As a special exception, the copyright holders of this library give you
-permission to link this library with independent modules to produce an
-executable, regardless of the license terms of these independent
-modules, and to copy and distribute the resulting executable under
-terms of your choice, provided that you also meet, for each linked
-independent module, the terms and conditions of the license of that
-module. An independent module is a module which is not derived from
-or based on this library. If you modify this library, you may extend
-this exception to your version of the library, but you are not
-obligated to do so. If you do not wish to do so, delete this
-exception statement from your version. */
-
-
-package java.lang.ref;
-
-/**
- * This is the queue, where references can enqueue themselve on. Each
- * reference may be registered to a queue at initialization time and
- * will be appended to the queue, when the enqueue method is called.
- *
- * The enqueue method may be automatically called by the garbage
- * collector if it detects, that the object is only reachable through
- * the Reference objects.
- *
- * @author Jochen Hoenicke
- * @see Reference#enqueue()
- */
-public class ReferenceQueue
-{
- /**
- * This is a linked list of references. If this is null, the list is
- * empty. Otherwise this points to the first reference on the queue.
- * The first reference will point to the next reference via the
- * <code>nextOnQueue</code> field. The last reference will point to
- * itself (not to null, since <code>nextOnQueue</code> is used to
- * determine if a reference is enqueued).
- */
- private Reference first;
-
- /**
- * Creates a new empty reference queue.
- */
- public ReferenceQueue()
- {
- }
-
- /**
- * Checks if there is a reference on the queue, returning it
- * immediately. The reference will be dequeued.
- *
- * @return a reference on the queue, if there is one,
- * <code>null</code> otherwise.
- */
- public synchronized Reference poll()
- {
- return dequeue();
- }
-
- /**
- * This is called by reference to enqueue itself on this queue.
- * @param ref the reference that should be enqueued.
- */
- synchronized void enqueue(Reference ref)
- {
- /* last reference will point to itself */
- ref.nextOnQueue = first == null ? ref : first;
- first = ref;
- /* this wakes only one remove thread. */
- notify();
- }
-
- /**
- * Remove a reference from the queue, if there is one.
- * @return the first element of the queue, or null if there isn't any.
- */
- private Reference dequeue()
- {
- if (first == null)
- return null;
-
- Reference result = first;
- first = (first == first.nextOnQueue) ? null : first.nextOnQueue;
- result.nextOnQueue = null;
- return result;
- }
-
- /**
- * Removes a reference from the queue, blocking for <code>timeout</code>
- * until a reference is enqueued.
- * @param timeout the timeout period in milliseconds, <code>0</code> means
- * wait forever.
- * @return the reference removed from the queue, or
- * <code>null</code> if timeout period expired.
- * @exception InterruptedException if the wait was interrupted.
- */
- public synchronized Reference remove(long timeout)
- throws InterruptedException
- {
- if (first == null)
- {
- wait(timeout);
- }
-
- return dequeue();
- }
-
-
- /**
- * Removes a reference from the queue, blocking until a reference is
- * enqueued.
- *
- * @return the reference removed from the queue.
- * @exception InterruptedException if the wait was interrupted.
- */
- public Reference remove()
- throws InterruptedException
- {
- return remove(0L);
- }
-}