LocalId


1   /*
2     * JBoss, Home of Professional Open Source
3     * Copyright 2005, JBoss Inc., and individual contributors as indicated
4     * by the @authors tag. See the copyright.txt in the distribution for a
5     * full listing of individual contributors.
6     *
7     * This is free software; you can redistribute it and/or modify it
8     * under the terms of the GNU Lesser General Public License as
9     * published by the Free Software Foundation; either version 2.1 of
10    * the License, or (at your option) any later version.
11    *
12    * This software is distributed in the hope that it will be useful,
13    * but WITHOUT ANY WARRANTY; without even the implied warranty of
14    * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15    * Lesser General Public License for more details.
16    *
17    * You should have received a copy of the GNU Lesser General Public
18    * License along with this software; if not, write to the Free
19    * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20    * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21    */
22  package org.jboss.tm;
23  
24  /**
25   *  LocalId is a wrapper for a long value that identifies a transaction within 
26   *  a JBoss server. This implementation is immutable and serializable at 
27   *  runtime.
28   *
29   *  @author <a HREF="reverbel@ime.usp.br">Francisco Reverbel</a>
30   *  @version $Revision: 37459 $
31   */
32  public class LocalId
33     implements java.io.Externalizable  
34  {
35     static final long serialVersionUID = 2076780468014328911L;
36     
37     /**
38      *  Long value that identifies a transaction within a JBoss server.
39      *  This is really a sequence number generated by the XidFactory.
40      */
41     private long value;
42  
43  
44     // Static --------------------------------------------------------
45  
46     /** Number of bits in the "transaction generation" part of the local id */
47     private static final int TX_GEN_SIZE = 20;
48     
49     /** Number of bits in a long */
50     private static final int LONG_SIZE = 64;
51     
52     /** Number of bits in the "transaction number" part of the local id */
53     private static final int TX_NUM_SIZE = LONG_SIZE - TX_GEN_SIZE;
54     
55     /** Mask to extract a transaction generation from the lower part of a long */  
56     private static final long TX_GEN_MASK = (1L << TX_GEN_SIZE) - 1;
57     
58     /** Mask to extract the transaction number from a local id */  
59     private static final long TX_NUM_MASK = (1L << TX_NUM_SIZE) - 1;
60     
61     /**
62      * Assemble a local id as a long value with a generation number in its high 
63      * part (the <code>TX_GEN_SIZE</code> most significant bits) and a 
64      * transaction number in its low part (the <code>TX_NUM_SIZE</code> least 
65      * significant bits).
66      *   
67      * @param genNumber the generation number
68      * @param txNumber  the transaction number.
69      * @return a local transaction id.
70      */
71     public static long assemble(int genNumber, long txNumber)
72     {
73        return (((long) genNumber) << TX_NUM_SIZE) | (txNumber & TX_NUM_MASK);
74     }
75     
76     /**
77      * Extracts the generation number from a local id value.
78      * 
79      * @param localIdValue a local id value.
80      * @return the generation number in the <code>TX_GEN_SIZE</code> most 
81      *         significant bits of the local id.
82      */
83     public static int toGenerationNumber(long localIdValue)
84     {
85        return (int)((localIdValue >> TX_NUM_SIZE) & TX_GEN_MASK); 
86     }
87  
88     /**
89      * Extracts a transaction number from a local id value.
90      * 
91      * @param localIdValue a local id value.
92      * @return the transaction number in the <code>TX_NUM_SIZE</code> least 
93      *         significant bits of the local id.
94      */   
95     public static long toTransactionNumber(long localIdValue)
96     {
97        return localIdValue & TX_NUM_MASK;
98     }
99     
100    /**
101     * Converts a local id value into a string.
102     * 
103     * @param l  a local id value
104     * @return a string of the form "<em>gn</em>:<em>tn</em>", where 
105     *         <em>gn</em> is the generation number and <em>tn</em> is 
106     *         the transaction number.     
107     */
108    public static String   toString(long l) 
109    {
110       return "" + toGenerationNumber(l) + ":" + toTransactionNumber(l); 
111    }
112 
113    /**
114     * Copies a local id value into a byte array.
115     * 
116     * @param localIdValue a local id value
117     * @param dst the destination byte array
118     * @param dstBegin the index of the first element of <code>dst</code> that
119     *        will receive a byte of the local id.
120     */
121    public static void toByteArray(long localIdValue, byte[] dst, int dstBegin)
122    {
123       dst[dstBegin + 0] = (byte)(0xff & (localIdValue >>> 56));
124       dst[dstBegin + 1] = (byte)(0xff & (localIdValue >>> 48));
125       dst[dstBegin + 2] = (byte)(0xff & (localIdValue >>> 40));
126       dst[dstBegin + 3] = (byte)(0xff & (localIdValue >>> 32));
127       dst[dstBegin + 4] = (byte)(0xff & (localIdValue >>> 24));
128       dst[dstBegin + 5] = (byte)(0xff & (localIdValue >>> 16));
129       dst[dstBegin + 6] = (byte)(0xff & (localIdValue >>>  8));
130       dst[dstBegin + 7] = (byte)(0xff & (localIdValue >>>  0));
131    }
132 
133    /**
134     * Gets a local id value from a byte array/
135     * 
136     * @param src the source byte array
137     * @param srcBegin the index of the first element of <code>src</code> that
138     *        contains a byte of the local id.
139     * @return a local id extracted from the byte array.
140     */
141    public static long fromByteArray(byte[] src, int srcBegin) 
142    {
143       return ((long)(src[srcBegin + 0] & 0xff) << 56)
144      | ((long)(src[srcBegin + 1] & 0xff) << 48)
145      | ((long)(src[srcBegin + 2] & 0xff) << 40)
146      | ((long)(src[srcBegin + 3] & 0xff) << 32)
147      | ((long)(src[srcBegin + 4] & 0xff) << 24)
148      | ((long)(src[srcBegin + 5] & 0xff) << 16)
149      | ((long)(src[srcBegin + 6] & 0xff) << 8)
150      | ((long)(src[srcBegin + 7] & 0xff));
151    }
152 
153    // Constructors --------------------------------------------------
154 
155    /**
156     * No-arg constructor for Externalizable support.
157     */
158    public LocalId()
159    {
160    }
161    
162    /**
163     *  Create a new instance. This constructor is public <em>only</em>
164     *  to get around a class loader problem; it should be package-private.
165     */
166    public LocalId(long value)
167    {
168       this.value = value;
169    }
170 
171    public LocalId(XidImpl xid)
172    {
173       this(xid.getLocalIdValue());
174    }
175 
176    // Public --------------------------------------------------------
177 
178    public long getValue()
179    {
180       return value;
181    }
182 
183    /**
184     *  Compare for equality.
185     */
186    public boolean equals(Object   obj)
187    {
188       return (obj instanceof LocalId) ? (value == ((LocalId)obj).value) 
189                                       : false;
190    }
191 
192    public int hashCode()
193    {
194       return (int)value;
195    }
196    
197    // Externalizable implementation ---------------------------------
198    public void writeExternal(java.io.ObjectOutput   out)
199       throws java.io.IOException  
200    {
201       out.writeLong(value);
202    }
203    
204    public void readExternal(java.io.ObjectInput   in)
205       throws java.io.IOException  , ClassNotFoundException  
206    {
207       value = in.readLong();
208    }
209 
210 }
211 
212
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags