1 /*
2 * Copyright (c) 1998-2002 The Jgroup Team.
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU Lesser General Public License version 2 as
6 * published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU Lesser General Public License for more details.
12 *
13 * You should have received a copy of the GNU Lesser General Public License
14 * along with this program; if not, write to the Free Software
15 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
16 *
17 */
18
19 package jgroup.relacs.types;
20
21 import java.io.IOException;
22 import java.io.ObjectInput;
23 import java.io.ObjectOutput;
24 import java.net.InetAddress;
25 import java.net.UnknownHostException;
26
27 import jgroup.core.VMID;
28 import jgroup.util.Abort;
29 import jgroup.util.Network;
30
31 /**
32 * The <code>VMIDImpl</code> class implements the <code>VMID</code>
33 * interface to uniquely identify a Java Virtual Machine.
34 *
35 * @author Alberto Montresor
36 * @author Hein Meling
37 * @since Jgroup 0.7
38 */
39 public final class VMIDImpl
40 implements VMID
41 {
42
43 ////////////////////////////////////////////////////////////////////////////////////////////
44 // Fields
45 ////////////////////////////////////////////////////////////////////////////////////////////
46
47 private static final long serialVersionUID = 6243630502385386084L;
48
49 /** IP address of the generating host */
50 private InetAddress inetAddress;
51
52 /** Integer representation of the above IP address */
53 private int address;
54
55 /** Random number to distinguish concurrent JVMs on the same host */
56 private int hash;
57
58 /** Time when this <code>VMID</code> was generated */
59 private long time;
60
61
62 ////////////////////////////////////////////////////////////////////////////////////////////
63 // Static section
64 ////////////////////////////////////////////////////////////////////////////////////////////
65
66 /** Unique virtual machine identifier for the local host */
67 private static VMID vmid;
68
69 /*
70 * Create a virtual machine identifier for the local host.
71 */
72 static {
73 try {
74 InetAddress inetAddress = Network.getLocalHost();
75 long time = System.currentTimeMillis();
76 int hash = (new Object()).hashCode();
77 vmid = new VMIDImpl(inetAddress, time, hash);
78 } catch (Exception e) {
79 Abort.exit("Failed to generate an identifier for the virtual machine", e, 1);
80 }
81 }
82
83
84 /**
85 * Returns the <code>VMID</code> for the local Java Virtual Machine.
86 */
87 public static VMID getLocalVMID()
88 {
89 return vmid;
90 }
91
92
93 ////////////////////////////////////////////////////////////////////////////////////////////
94 // Constructors
95 ////////////////////////////////////////////////////////////////////////////////////////////
96
97 /**
98 * Public default constructor for externalization.
99 */
100 public VMIDImpl()
101 {
102 }
103
104 /**
105 * Private constructor.
106 */
107 private VMIDImpl(InetAddress inetAddress, long time, int hash)
108 {
109 this.inetAddress = inetAddress;
110 this.time = time;
111 this.hash = hash;
112 this.address = Network.translate(inetAddress);
113 }
114
115
116 ////////////////////////////////////////////////////////////////////////////////////////////
117 // Methods from the VMID interface
118 ////////////////////////////////////////////////////////////////////////////////////////////
119
120 /**
121 * Returns the address of the host in which the virtual machine
122 * identified by this <code>VMID</code> is executed.
123 */
124 public InetAddress getAddress()
125 throws UnknownHostException
126 {
127 /*
128 * If the inetAddress is null it means that this object must have
129 * been serialized, and thus we only have an integer representation
130 * of this JVMs internet address. Thus, we convert the int
131 * representation to an InetAddress representation.
132 */
133 if (inetAddress == null)
134 inetAddress = Network.translate(address);
135 return inetAddress;
136 }
137
138
139 /**
140 * Returns the time at which this <code>VMID</code> has been created.
141 */
142 public long getTime()
143 {
144 return time;
145 }
146
147
148 ////////////////////////////////////////////////////////////////////////////////////////////
149 // Methods from Object
150 ////////////////////////////////////////////////////////////////////////////////////////////
151
152 /**
153 * Returns a string representation of this object.
154 */
155 public String toString()
156 {
157 StringBuilder buf = new StringBuilder();
158 buf.append("[VMID: ");
159 buf.append(Network.translateToString(address));
160 buf.append(", ");
161 buf.append(time);
162 buf.append(", ");
163 buf.append(hash);
164 buf.append("]");
165 return buf.toString();
166 }
167
168
169 /**
170 * Returns a hashcode for the <code>VMIDImpl</code>. Two
171 * <code>VMIDImpl</code>s will have the same hashcode if they are
172 * equal with respect to their content.
173 */
174 public int hashCode()
175 {
176 return address + (int) time + hash;
177 }
178
179
180 /**
181 * Compares two objects for content equality.
182 *
183 * @param obj the object to compare with
184 * @return true if these objects are equal; false otherwise.
185 */
186 public boolean equals(Object obj)
187 {
188 if (!(obj instanceof VMIDImpl))
189 return false;
190 VMIDImpl vmid = (VMIDImpl) obj;
191 return (hash == vmid.hash && address == vmid.address && time == vmid.time);
192 }
193
194
195 ////////////////////////////////////////////////////////////////////////////////////////////
196 // Methods from Externalizable
197 ////////////////////////////////////////////////////////////////////////////////////////////
198
199 /**
200 * Write the content of this VMID on stream <tt>out</tt>. Note that
201 * the InetAddress is not serialized, because too inefficient. If
202 * requested, the InetAddress is retrieved through DNS lookup in
203 * method <tt>getAddress</tt>.
204 *
205 * @param out the stream to be written
206 */
207 public void writeExternal(ObjectOutput out)
208 throws IOException
209 {
210 out.writeInt(hash);
211 out.writeLong(time);
212 out.writeInt(address);
213 }
214
215 /**
216 * Restores the content of this object from the marshalled data contained
217 * in the specified input stream.
218 *
219 * @param in the stream to be read
220 */
221 public void readExternal(ObjectInput in)
222 throws IOException
223 {
224 hash = in.readInt();
225 time = in.readLong();
226 address = in.readInt();
227 }
228
229 } // END VMIDImpl