+++ /dev/null
-/* java.lang.ref.Reference
- 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 base class of all references. A reference allows
- * refering to an object without preventing the garbage collection to
- * collect it. The only way to get the referred object is via the
- * <code>get()</code>-method. This method will return
- * <code>null</code> if the object was collected. <br>
- *
- * A reference may be registered with a queue. When a referred
- * element gets collected the reference will be put on the queue, so
- * that you will be notified. <br>
- *
- * There are currently three types of references: soft reference,
- * weak reference and phantom reference. <br>
- *
- * Soft references will be cleared if the garbage collection is told
- * to free some memory and there are no unreferenced or weakly referenced
- * objects. It is useful for caches. <br>
- *
- * Weak references will be cleared as soon as the garbage collection
- * determines that the refered object is only weakly reachable. They
- * are useful as keys in hashtables (see <code>WeakHashtable</code>) as
- * you get notified when nobody has the key anymore.
- *
- * Phantom references don't prevent finalization. If an object is only
- * phantom reachable, it will be finalized, and the reference will be
- * enqueued, but not cleared. Since you mustn't access an finalized
- * object, the <code>get</code> method of a phantom reference will never
- * work. It is useful to keep track, when an object is finalized.
- *
- * @author Jochen Hoenicke
- * @see java.util.WeakHashtable
- */
-public abstract class Reference
-{
- /**
- * The underlying object. This field is handled in a special way by
- * the garbage collection.
- * GCJ LOCAL:
- * This is a RawData because it must be disguised from the GC.
- * END GCJ LOCAL
- */
- gnu.gcj.RawData referent;
-
- /**
- * This is like REFERENT but is not scanned by the GC. We keep a
- * copy around so that we can see when clear() has been called.
- * GCJ LOCAL:
- * This field doesn't exist in Classpath; we use it to detect
- * clearing.
- * END GCJ LOCAL
- */
- gnu.gcj.RawData copy;
-
- /**
- * The queue this reference is registered on. This is null, if this
- * wasn't registered to any queue or reference was already enqueued.
- */
- ReferenceQueue queue;
-
- /**
- * Link to the next entry on the queue. If this is null, this
- * reference is not enqueued. Otherwise it points to the next
- * reference. The last reference on a queue will point to itself
- * (not to null, that value is used to mark a not enqueued
- * reference).
- */
- Reference nextOnQueue;
-
- /**
- * This lock should be taken by the garbage collection, before
- * determining reachability. It will prevent the get()-method to
- * return the reference so that reachability doesn't change.
- */
- static Object lock = new Object();
-
- /**
- * Creates a new reference that is not registered to any queue.
- * Since it is package private, it is not possible to overload this
- * class in a different package.
- * @param referent the object we refer to.
- */
- Reference(Object ref)
- {
- create (ref);
- }
-
- /**
- * Creates a reference that is registered to a queue. Since this is
- * package private, it is not possible to overload this class in a
- * different package.
- * @param referent the object we refer to.
- * @param q the reference queue to register on.
- * @exception NullPointerException if q is null.
- */
- Reference(Object ref, ReferenceQueue q)
- {
- if (q == null)
- throw new NullPointerException();
- queue = q;
- create (ref);
- }
-
- /**
- * Notifies the VM that a new Reference has been created.
- */
- private native void create (Object o);
-
- /**
- * Returns the object, this reference refers to.
- * @return the object, this reference refers to, or null if the
- * reference was cleared.
- */
- public Object get()
- {
- synchronized(lock)
- {
- return referent;
- }
- }
-
- /**
- * Clears the reference, so that it doesn't refer to its object
- * anymore. For soft and weak references this is called by the
- * garbage collection. For phantom references you should call
- * this when enqueuing the reference.
- */
- public void clear()
- {
- referent = null;
- copy = null;
- }
-
- /**
- * Tells if the object is enqueued on a reference queue.
- * @return true if it is enqueued, false otherwise.
- */
- public boolean isEnqueued()
- {
- return nextOnQueue != null;
- }
-
- /**
- * Enqueue an object on a reference queue. This is normally executed
- * by the garbage collection.
- */
- public boolean enqueue()
- {
- if (queue != null)
- {
- queue.enqueue(this);
- queue = null;
- return true;
- }
- return false;
- }
-}
projects / msp430-gcc.git / blobdiff