1 //******************************************************************************
2 //
3 // File: Channel.java
4 // Package: edu.rit.mp
5 // Unit: Class edu.rit.mp.Channel
6 //
7 // This Java source file is copyright (C) 2008 by Alan Kaminsky. All rights
8 // reserved. For further information, contact the author, Alan Kaminsky, at
9 // ark@cs.rit.edu.
10 //
11 // This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
12 // software; you can redistribute it and/or modify it under the terms of the GNU
13 // General Public License as published by the Free Software Foundation; either
14 // version 3 of the License, or (at your option) any later version.
15 //
16 // PJ is distributed in the hope that it will be useful, but WITHOUT ANY
17 // WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
18 // A PARTICULAR PURPOSE. See the GNU General Public License for more details.
19 //
20 // Linking this library statically or dynamically with other modules is making a
21 // combined work based on this library. Thus, the terms and conditions of the GNU
22 // General Public License cover the whole combination.
23 //
24 // As a special exception, the copyright holders of this library give you
25 // permission to link this library with independent modules to produce an
26 // executable, regardless of the license terms of these independent modules, and
27 // to copy and distribute the resulting executable under terms of your choice,
28 // provided that you also meet, for each linked independent module, the terms
29 // and conditions of the license of that module. An independent module is a module
30 // which is not derived from or based on this library. If you modify this library,
31 // you may extend this exception to your version of the library, but you are not
32 // obligated to do so. If you do not wish to do so, delete this exception
33 // statement from your version.
34 //
35 // A copy of the GNU General Public License is provided in the file gpl.txt. You
36 // may also obtain a copy of the GNU General Public License on the World Wide
37 // Web at http://www.gnu.org/licenses/gpl.html.
38 //
39 //******************************************************************************
40 package edu.rit.mp;
41
42 import java.io.IOException;
43 import java.io.PrintStream;
44 import java.net.InetSocketAddress;
45
46 /**
47 * Class Channel provides a channel for sending and receiving messages in the
48 * Message Protocol (MP).
49 * <P>
50 * A channel object is not constructed directly. Rather, a channel group object
51 * is used to connect a channel to another computer, accept a channel connection
52 * from another computer, or obtain a "loopback" channel within the same
53 * computer. See class {@linkplain ChannelGroup} for further information.
54 * <P>
55 * An information object may be associated with a channel. An application using
56 * MP can use the information object to hold additional data about the channel.
57 *
58 * @author Alan Kaminsky
59 * @version 13-May-2008
60 */
61 public abstract class Channel {
62
63 // Hidden data members.
64 ChannelGroup myChannelGroup;
65 IORequestList myIORequestList;
66 Object myInfo;
67
68 int myWriteState = WRITE_OPEN;
69 static final int WRITE_OPEN = 0;
70 static final int WRITE_CLOSED = 1;
71
72 int myReadState = READ_OPEN;
73 static final int READ_OPEN = 0;
74 static final int READ_CLOSED = 1;
75
76 // Hidden constructors.
77 /**
78 * Construct a new channel.
79 *
80 * @param theChannelGroup Enclosing channel group.
81 */
82 Channel(ChannelGroup theChannelGroup) {
83 myChannelGroup = theChannelGroup;
84 myIORequestList = theChannelGroup.myIORequestList;
85 }
86
87 // Exported operations.
88 /**
89 * Obtain the channel group that created this channel.
90 *
91 * @return Channel group.
92 */
93 public ChannelGroup getChannelGroup() {
94 return myChannelGroup;
95 }
96
97 /**
98 * Obtain the channel group ID of this channel's near end channel group.
99 *
100 * @return Near end channel group ID.
101 */
102 public abstract int nearEndChannelGroupId();
103
104 /**
105 * Obtain the channel group ID of this channel's far end channel group.
106 *
107 * @return Far end channel group ID.
108 */
109 public abstract int farEndChannelGroupId();
110
111 /**
112 * Obtain this channel's near end address. This is the host and port of the
113 * near end of this channel's connection.
114 *
115 * @return Near end address.
116 */
117 public abstract InetSocketAddress nearEndAddress();
118
119 /**
120 * Obtain this channel's far end address. This is the host and port of the
121 * far end of this channel's connection.
122 *
123 * @return Far end address.
124 */
125 public abstract InetSocketAddress farEndAddress();
126
127 /**
128 * Obtain this channel's information object.
129 *
130 * @return Information object, or null if none.
131 */
132 public Object info() {
133 return myInfo;
134 }
135
136 /**
137 * Set this channel's information object.
138 *
139 * @param theInfo Information object, or null if none.
140 */
141 public void info(Object theInfo) {
142 myInfo = theInfo;
143 }
144
145 /**
146 * Close this channel. Any pending send requests will fail with a
147 * {@linkplain ChannelClosedException}.
148 */
149 public void close() {
150 // To avoid deadlock, synchronize first on the channel group, then on
151 // this channel.
152 synchronized (myChannelGroup) {
153 synchronized (this) {
154 myChannelGroup.removeChannel(this);
155 myWriteState = WRITE_CLOSED;
156 myReadState = READ_CLOSED;
157 subclassClose();
158 }
159 }
160 }
161
162 /**
163 * Returns a string version of this channel.
164 *
165 * @return a {@link java.lang.String} object.
166 */
167 public String toString() {
168 return getClass().getName()
169 + "(near=" + nearEndAddress()
170 + ",far=" + farEndAddress() + ")";
171 }
172
173 /**
174 * Dump the state of this channel on the given print stream. For debugging.
175 *
176 * @param out Print stream.
177 * @param prefix String to print at the beginning of each line.
178 */
179 public void dump(PrintStream out,
180 String prefix) {
181 out.println(prefix + getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(this)));
182 out.println(prefix + "myChannelGroup = " + myChannelGroup);
183 out.println(prefix + "myIORequestList = " + myIORequestList);
184 out.println(prefix + "myInfo = " + myInfo);
185 out.println(prefix + "myWriteState = " + (myWriteState == WRITE_OPEN ? "WRITE_OPEN" : "WRITE_CLOSED"));
186 out.println(prefix + "myReadState = " + (myReadState == READ_OPEN ? "READ_OPEN" : "READ_CLOSED"));
187 out.println(prefix + "nearEndChannelGroupId() = " + nearEndChannelGroupId());
188 out.println(prefix + "farEndChannelGroupId() = " + farEndChannelGroupId());
189 out.println(prefix + "nearEndAddress() = " + nearEndAddress());
190 out.println(prefix + "farEndAddress() = " + farEndAddress());
191 }
192
193 // Hidden operations.
194 /**
195 * Start sending and receiving messages via this channel.
196 */
197 void start() {
198 }
199
200 /**
201 * Send a message via this channel. The I/O request object must be newly
202 * constructed with the message tag and source buffer fields filled in. This
203 * method is allowed to return immediately and let the message be sent in a
204 * separate thread. The calling thread should use the I/O request object to
205 * wait for the message send to complete.
206 *
207 * @param theIORequest I/O request object.
208 *
209 * @exception IOException Thrown if an I/O error occurred.
210 */
211 abstract void send(IORequest theIORequest)
212 throws IOException;
213
214 /**
215 * Perform additional close actions in a subclass.
216 */
217 void subclassClose() {
218 }
219
220 }