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1 /*
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2 * Copyright 2000 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 package sun.jvm.hotspot.memory;
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26
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27 import java.util.*;
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28
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29 import sun.jvm.hotspot.debugger.*;
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30 import sun.jvm.hotspot.runtime.*;
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31 import sun.jvm.hotspot.types.*;
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32
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33 /** A space that supports compaction operations. This is usually, but
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34 not necessarily, a space that is normally contiguous. But, for
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35 example, a free-list-based space whose normal collection is a
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36 mark-sweep without compaction could still support compaction in
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37 full GC's. */
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38
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39 public abstract class CompactibleSpace extends Space {
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40 private static AddressField compactionTopField;
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41
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42 static {
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43 VM.registerVMInitializedObserver(new Observer() {
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44 public void update(Observable o, Object data) {
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45 initialize(VM.getVM().getTypeDataBase());
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46 }
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47 });
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48 }
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49
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50 private static synchronized void initialize(TypeDataBase db) {
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51 Type type = db.lookupType("CompactibleSpace");
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52
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53 compactionTopField = type.getAddressField("_compaction_top");
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54 }
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55
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56 public CompactibleSpace(Address addr) {
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57 super(addr);
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58 }
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59
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60 /** May be used temporarily during a compaction phase. */
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61 public Address compactionTop() {
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62 return compactionTopField.getValue(addr);
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63 }
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64 }
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