1 /*

     2  * Copyright (c) 2016, 2019, 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.internal.consumer;

    27 

    28 import jdk.jfr.internal.LongMap;

    29 

    30 /**

    31  * Holds mapping between a set of keys and their corresponding object.

    32  *

    33  * If the type is a known type, i.e. {@link RecordedThread}, an

    34  * {@link ObjectFactory} can be supplied which will instantiate a typed object.

    35  */

    36 final class ConstantMap {

    37 

    38     private static final int RESOLUTION_FINISHED = 0;

    39     private static final int RESOLUTION_STARTED = 1;

    40     public static final ConstantMap EMPTY = new ConstantMap();

    41 

    42     // A temporary placeholder, so objects can

    43     // reference themselves (directly, or indirectly),

    44     // when making a transition from numeric id references

    45     // to normal Java references.

    46     private final static class Reference {

    47         private final long key;

    48         private final ConstantMap pool;

    49 

    50         Reference(ConstantMap pool, long key) {

    51             this.pool = pool;

    52             this.key = key;

    53         }

    54 

    55         Object resolve() {

    56             return pool.get(key);

    57         }

    58 

    59         public String toString() {

    60             return "ref: " + pool.name + "[" + key + "]";

    61         }

    62     }

    63 

    64     final ObjectFactory<?> factory;

    65     final String name;

    66 

    67     private final LongMap<Object> objects;

    68 

    69     private boolean resolving;

    70     private boolean allResolved;

    71 

    72     private ConstantMap() {

    73         this(null, "<empty>");

    74         allResolved = true;

    75     }

    76 

    77     ConstantMap(ObjectFactory<?> factory, String name) {

    78         this.name = name;

    79         this.objects = new LongMap<>(2);

    80         this.factory = factory;

    81     }

    82 

    83     Object get(long id) {

    84         // fast path, all objects in pool resolved

    85         if (allResolved) {

    86             return objects.get(id);

    87         }

    88         // referenced from a pool, deal with this later

    89         if (!resolving) {

    90             return new Reference(this, id);

    91         }

    92 

    93         // should always have a value

    94         Object value = objects.get(id);

    95         if (value == null) {

    96             // unless is 0 which is used to represent null

    97             if (id == 0) {

    98                 return null;

    99             }

   100             throw new InternalError("Missing object id=" + id + " in pool " + name + ". All ids should reference object");

   101         }

   102 

   103         // id is resolved (but not the whole pool)

   104         if (objects.isSetId(id, RESOLUTION_FINISHED)) {

   105             return value;

   106         }

   107 

   108         // resolving ourself, abort to avoid infinite recursion

   109         if (objects.isSetId(id, RESOLUTION_STARTED)) {

   110             return null;

   111         }

   112 

   113         // mark id as STARTED if we should

   114         // come back during object resolution

   115         objects.setId(id, RESOLUTION_STARTED);

   116 

   117         // resolve object!

   118         Object resolved = resolve(value);

   119 

   120         // mark id as FINISHED

   121         objects.setId(id, RESOLUTION_FINISHED);

   122 

   123         // if a factory exists, convert to RecordedThread.

   124         // RecordedClass etc. and store back results

   125         if (factory != null) {

   126             Object factorized = factory.createObject(id, resolved);

   127             objects.put(id, factorized);

   128             return factorized;

   129         } else {

   130             objects.put(id, resolved);

   131             return resolved;

   132         }

   133     }

   134 

   135     private static Object resolve(Object o) {

   136         if (o instanceof Reference) {

   137             return resolve(((Reference) o).resolve());

   138         }

   139         if (o != null && o.getClass().isArray()) {

   140             final Object[] array = (Object[]) o;

   141             for (int i = 0; i < array.length; i++) {

   142                 Object element = array[i];

   143                 array[i] = resolve(element);

   144             }

   145             return array;

   146         }

   147         return o;

   148     }

   149 

   150     public void resolve() {

   151         objects.forEachKey(k -> get(k));

   152     }

   153 

   154     public void put(long key, Object value) {

   155         objects.put(key, value);

   156     }

   157 

   158     public void setResolving() {

   159         resolving = true;

   160         allResolved = false;

   161     }

   162 

   163     public void setResolved() {

   164         allResolved = true;

   165         resolving = false;

   166     }

   167 

   168     public String getName() {

   169         return name;

   170     }

   171 

   172     public Object getResolved(long id) {

   173         return objects.get(id);

   174     }

   175 

   176     public void putResolved(long id, Object object) {

   177         objects.put(id, object);

   178         objects.setId(id, RESOLUTION_FINISHED);

   179     }

   180 

   181     public void setAllResolved(boolean allResolved) {

   182         this.allResolved = allResolved;

   183     }

   184 }