1 /*
   2  * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.jfr.consumer;
  27 
  28 import java.util.ArrayList;
  29 import java.util.List;
  30 
  31 /**
  32  * Holds mapping between a set of keys and their corresponding object.
  33  *
  34  * If the type is a known type, i.e. {@link RecordedThread}, an
  35  * {@link ObjectFactory} can be supplied which will instantiate a typed object.
  36  */
  37 final class ConstantMap {
  38     private final static class Reference {
  39         private final long key;
  40         private final ConstantMap pool;
  41 
  42         Reference(ConstantMap pool, long key) {
  43             this.pool = pool;
  44             this.key = key;
  45         }
  46 
  47         Object resolve() {
  48             return pool.get(key);
  49         }
  50     }
  51 
  52     private final ObjectFactory<?> factory;
  53     private final LongMap<Object> objects;
  54 
  55     private LongMap<Boolean> isResolving;
  56     private boolean allResolved;
  57     private String name;
  58 
  59     ConstantMap(ObjectFactory<?> factory, String name) {
  60         this.name = name;
  61         this.objects = new LongMap<>();
  62         this.factory = factory;
  63     }
  64 
  65     Object get(long id) {
  66         // fast path, all objects in pool resolved
  67         if (allResolved) {
  68             return objects.get(id);
  69         }
  70         // referenced from a pool, deal with this later
  71         if (isResolving == null) {
  72             return new Reference(this, id);
  73         }
  74 
  75         Boolean beingResolved = isResolving.get(id);
  76 
  77         // we are resolved (but not the whole pool)
  78         if (Boolean.FALSE.equals(beingResolved)) {
  79             return objects.get(id);
  80         }
  81 
  82         // resolving ourself, abort to avoid infinite recursion
  83         if (Boolean.TRUE.equals(beingResolved)) {
  84             return null;
  85         }
  86 
  87         // resolve me!
  88         isResolving.put(id, Boolean.TRUE);
  89         Object resolved = resolve(objects.get(id));
  90         isResolving.put(id, Boolean.FALSE);
  91         if (factory != null) {
  92             Object factorized = factory.createObject(id, resolved);
  93             objects.put(id, factorized);
  94             return factorized;
  95         } else {
  96             objects.put(id, resolved);
  97             return resolved;
  98         }
  99     }
 100 
 101     private static Object resolve(Object o) {
 102         if (o instanceof Reference) {
 103             return resolve(((Reference) o).resolve());
 104         }
 105         if (o != null && o.getClass().isArray()) {
 106             final Object[] array = (Object[]) o;
 107             for (int i = 0; i < array.length; i++) {
 108                 array[i] = resolve(array[i]);
 109             }
 110             return array;
 111         }
 112         return o;
 113     }
 114 
 115     public void resolve() {
 116         List<Long> keyList = new ArrayList<>();
 117         objects.keys().forEachRemaining(keyList::add);
 118         for (Long l : keyList) {
 119             get(l);
 120         }
 121     }
 122 
 123     public void put(long key, Object value) {
 124         objects.put(key, value);
 125     }
 126 
 127     public void setIsResolving() {
 128         isResolving = new LongMap<>();
 129     }
 130 
 131     public void setResolved() {
 132         allResolved = true;
 133         isResolving = null; // pool finished, release memory
 134     }
 135 
 136     public String getName() {
 137         return name;
 138     }
 139 }