org.eclipse.linuxtools.tmf.core/src/org/eclipse/linuxtools/tmf/core/statevalue/TmfStateValue.java

   1 /*******************************************************************************
   2  * Copyright (c) 2012 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.linuxtools.tmf.core.statevalue;
  14
  15 import org.eclipse.linuxtools.tmf.core.exceptions.StateValueTypeException;
  16
  17
  18 /**
  19  * This is the wrapper class that exposes the different types of 'state values'
  20  * available to use in the State System.
  21  *
  22  * This also defines how these values are to be stored in the History Tree. For
  23  * example, we can save numerical values as integers instead of arrays of
  24  * 1-digit characters.
  25  *
  26  * For now the two available types are either int or String.
  27  *
  28  * @author alexmont
  29  *
  30  */
  31 public abstract class TmfStateValue implements ITmfStateValue {
  32
  33     /**
  34      * Retrieve directly the value object contained within. Implementing
  35      * subclasses may limit the return type here.
  36      *
  37      * It's protected, since we do not want to expose this directly in the
  38      * public API (and require all its users to manually cast to the right
  39      * types). All accesses to the values should go through the "unbox-"
  40      * methods.
  41      *
  42      * @return The underneath object assigned to this state value.
  43      */
  44     protected abstract Object getValue();
  45
  46     /**
  47      * Specify how to "serialize" this value when writing it to a file.
  48      * Alternatively you can return "null" here if you do not need a byte-array
  49      * indirection (the getValue will get written as-in instead of the offset in
  50      * the file block)
  51      *
  52      * @return The state value in byte array form
  53      */
  54     public abstract byte[] toByteArray();
  55
  56     @Override
  57     public boolean equals(Object other) {
  58         if (this == other) {
  59             return true;
  60         }
  61         if (!(other instanceof TmfStateValue)) {
  62             return false;
  63         }
  64
  65         /* If both types are different they're necessarily not equal */
  66         if (this.getType() != ((TmfStateValue) other).getType()) {
  67             return false;
  68         }
  69
  70         /*
  71          * This checks for the case where we'd compare two null values (and so
  72          * avoid a NPE below)
  73          */
  74         if (this.isNull()) {
  75             return true;
  76         }
  77
  78         /* The two are valid and comparable, let's compare them */
  79         return this.getValue().equals(((TmfStateValue) other).getValue());
  80     }
  81
  82     @Override
  83     public int hashCode() {
  84         if (this.isNull()) {
  85             return 0;
  86         }
  87         return this.getValue().hashCode();
  88     }
  89
  90     /**
  91      * Return the max size that a variable-length state value can have when
  92      * serialized.
  93      *
  94      * @return The maximum size in bytes
  95      */
  96     public static int getStateValueMaxSize() {
  97         return Byte.MAX_VALUE;
  98     }
  99
 100     /*
 101      * Since all "null state values" are the same, we only need one copy in
 102      * memory.
 103      */
 104     private static TmfStateValue nullValue = new NullStateValue();
 105
 106     /**
 107      * Return an instance of a "null" value. Only one copy exists in memory.
 108      *
 109      * @return A null value
 110      */
 111     public final static TmfStateValue nullValue() {
 112         return nullValue;
 113     }
 114
 115     /**
 116      * Factory constructor for Integer state values
 117      *
 118      * @param intValue The integer value to contain
 119      * @return The newly-created TmfStateValue object
 120      */
 121     public static TmfStateValue newValueInt(int intValue) {
 122         if (intValue == -1) {
 123             return nullValue();
 124         }
 125         return new IntegerStateValue(intValue);
 126     }
 127
 128     /**
 129      * Factory constructor for String state values
 130      *
 131      * @param strValue The string value to contain
 132      * @return The newly-create TmfStateValue object
 133      */
 134     public static TmfStateValue newValueString(String strValue) {
 135         if (strValue == null) {
 136             return nullValue();
 137         }
 138         return new StringStateValue(strValue);
 139     }
 140
 141     @Override
 142     public int unboxInt() throws StateValueTypeException {
 143         if (this.isNull()) {
 144             /* Int value expected, return "-1" instead */
 145             return -1;
 146         }
 147
 148         if (this.getType() != 0) { /* 0 = int type */
 149             throw new StateValueTypeException();
 150         }
 151         return (Integer) this.getValue();
 152     }
 153
 154     @Override
 155     public String unboxStr() throws StateValueTypeException {
 156         if (this.isNull()) {
 157             /* String value expected, return "nullValue" instead */
 158             return "nullValue"; //$NON-NLS-1$
 159         }
 160
 161         if (this.getType() != 1) { /* 1 = string type */
 162             throw new StateValueTypeException();
 163         }
 164         return (String) this.getValue();
 165     }
 166 }