statesystem/org.eclipse.tracecompass.statesystem.core/src/org/eclipse/tracecompass/statesystem/core/statevalue/NullStateValue.java

   1 /*******************************************************************************
   2  * Copyright (c) 2012, 2014 Ericsson
   3  * Copyright (c) 2010, 2011 École Polytechnique de Montréal
   4  * Copyright (c) 2010, 2011 Alexandre Montplaisir <alexandre.montplaisir@gmail.com>
   5  *
   6  * All rights reserved. This program and the accompanying materials are
   7  * made available under the terms of the Eclipse Public License v1.0 which
   8  * accompanies this distribution, and is available at
   9  * http://www.eclipse.org/legal/epl-v10.html
  10  *
  11  *******************************************************************************/
  12
  13 package org.eclipse.tracecompass.statesystem.core.statevalue;
  14
  15 import org.eclipse.jdt.annotation.Nullable;
  16
  17 /**
  18  * A state value that contains no particular value. It is sometimes needed over
  19  * a "null" reference, since we avoid NPE's this way.
  20  *
  21  * It can also be read either as a String ("nullValue") or an Integer (-1).
  22  *
  23  * @version 1.0
  24  * @author Alexandre Montplaisir
  25  */
  26 final class NullStateValue extends TmfStateValue {
  27
  28     private static final byte[] EMPTY_ARRAY = new byte[0];
  29     private static final String STR_VALUE = "nullValue"; //$NON-NLS-1$
  30
  31     @Override
  32     public Type getType() {
  33         return Type.NULL;
  34     }
  35
  36     @Override
  37     public boolean isNull() {
  38         return true;
  39     }
  40
  41     @Override
  42     public boolean equals(@Nullable Object object) {
  43         return (object instanceof NullStateValue);
  44     }
  45
  46     @Override
  47     public int hashCode() {
  48         return 0;
  49     }
  50
  51     @Override
  52     public String toString() {
  53         return STR_VALUE;
  54     }
  55
  56     @Override
  57     public byte[] serialize() {
  58         return EMPTY_ARRAY;
  59     }
  60
  61     // ------------------------------------------------------------------------
  62     // Unboxing methods. Null values can be unboxed into any type.
  63     // ------------------------------------------------------------------------
  64
  65     @Override
  66     public int unboxInt() {
  67         return -1;
  68     }
  69
  70     @Override
  71     public long unboxLong() {
  72         return -1;
  73     }
  74
  75     @Override
  76     public double unboxDouble() {
  77         return Double.NaN;
  78     }
  79
  80     @Override
  81     public String unboxStr() {
  82         return STR_VALUE;
  83     }
  84
  85     @Override
  86     public int compareTo(@Nullable ITmfStateValue other) {
  87         if (other == null) {
  88             throw new IllegalArgumentException();
  89         }
  90         if (other instanceof NullStateValue) {
  91             return 0;
  92         }
  93         /*
  94          * For every other state value type, we defer to how that type wants to
  95          * be compared against null values.
  96          */
  97         return -(other.compareTo(this));
  98     }
  99 }