/interpreter/tags/at2-build190607/src/edu/vub/at/actors/net/VMAddressBook.java

 1/**
 2 * AmbientTalk/2 Project
 3 * Actorscript.java created on 2-mrt-2007 at 11:14:27
 4 * (c) Programming Technology Lab, 2006 - 2007
 5 * Authors: Tom Van Cutsem & Stijn Mostinckx
 6 * 
 7 * Permission is hereby granted, free of charge, to any person
 8 * obtaining a copy of this software and associated documentation
 9 * files (the "Software"), to deal in the Software without
10 * restriction, including without limitation the rights to use,
11 * copy, modify, merge, publish, distribute, sublicense, and/or
12 * sell copies of the Software, and to permit persons to whom the
13 * Software is furnished to do so, subject to the following
14 * conditions:
15 *
16 * The above copyright notice and this permission notice shall be
17 * included in all copies or substantial portions of the Software.
18 *
19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
20 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
21 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
22 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
23 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
24 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
25 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
26 * OTHER DEALINGS IN THE SOFTWARE.
27 */
28package edu.vub.at.actors.net;
29
30import edu.vub.at.actors.id.VirtualMachineID;
31import edu.vub.at.actors.net.comm.Address;
32import edu.vub.at.util.logging.Logging;
33
34import java.util.Hashtable;
35
36/**
37 * 
38 * The VMAddressBook encapsulates the bi-directional mapping:
39 *  AmbientTalk VM VirtualMachineID  -->  network Address
40 *  network Address      -->  AmbientTalk VM VirtualMachineID
41 *
42 * It is necessary to maintain such a mapping to correctly identify and restore
43 * the connection between AmbientTalk VMs. A network address cannot be used as
44 * a good identification key because an AmbientTalk VM may be known under different
45 * addresses as it goes offline and online.
46 * 
47 * When a new VM joins, after handshaking, an entry is added to the address book.
48 * When a VM disjoins, the entry corresponding to the address that went offline is removed.
49 * 
50 * @author elgonzal
51 * @author tvcutsem
52 */
53public class VMAddressBook {
54	
55	private final Hashtable guidToAddress_;
56	private final Hashtable addressToGuid_;
57	
58	public VMAddressBook(){
59		guidToAddress_ = new Hashtable();
60		addressToGuid_ = new Hashtable();
61	}
62	
63	public synchronized void addEntry( VirtualMachineID vmId, Address vmAddress ){
64		guidToAddress_.put(vmId, vmAddress);
65		addressToGuid_.put(vmAddress, vmId);
66	}
67
68	/**
69	 * Remove all entries that map to this VM address from the VM Address book.
70	 */
71	public synchronized void removeEntry(Address vmAddress ){
72		VirtualMachineID vmId = (VirtualMachineID) addressToGuid_.get(vmAddress);
73		Logging.VirtualMachine_LOG.debug("Removed VM binding " + vmAddress + " -> " + vmId);
74
75		guidToAddress_.remove(vmId);
76		addressToGuid_.remove(vmAddress);
77	}
78	
79	/**
80	 * Resolve a remote VM's unique identifier to a concrete network address.
81	 * @return the VM's address, or <tt>null</tt> if the VM is no longer connected.
82	 */
83	public synchronized Address getAddressOf(VirtualMachineID vmId) {
84		return (Address) guidToAddress_.get(vmId);
85	}
86
87	/**
88	 * Resolve a concrete network address to a remote VM's unique identifier.
89	 * @return the VM Id of the given address, or <tt>null</tt> if the address is no longer connected.
90	 */
91	public synchronized VirtualMachineID getGUIDOf(Address vmAddress) {
92		return (VirtualMachineID) addressToGuid_.get(vmAddress);
93	}
94
95}