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1 /*
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2 * Copyright 2002-2006 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.utilities;
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26
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27 import java.util.*;
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28 import sun.jvm.hotspot.oops.*;
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29
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30 /** ReversePtrs hashtable. */
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31
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32 public class ReversePtrs {
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33 private HashMap rp;
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34
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35 public ReversePtrs() {
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36 rp = new HashMap();
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37 }
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38
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39 public void put(LivenessPathElement from, Oop to) {
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40 if (to == null) return;
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41 ArrayList al = (ArrayList) rp.get((Object) to);
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42 if (al == null) al = new ArrayList();
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43 // Inserting at the beginning is a hack to change the reported
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44 // paths from LivenessAnalysis to look more like they used to;
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45 // otherwise paths through the Finalizer queue to popular objects
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46 // seem to be preferred
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47 al.add(0, (Object) from);
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48 rp.put((Object) to, (Object) al);
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49 }
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50
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51 /** Returns an ArrayList of the incoming references to this Oop if
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52 it is alive, and null if it is dead according to the
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53 ReversePtrsAnalysis. Currently not all roots are scanned so this
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54 result is frequently inaccurate for JVM-internal objects, but is
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55 usually correct for Java-level objects. */
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56 public ArrayList/*<LivenessPathElement>*/ get(Oop obj) {
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57 return (ArrayList) rp.get((Object)obj);
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58 }
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59 }
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