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Java > Open Source Codes > org > objectweb > perseus > concurrency > pessimistic > Lock


1 /**
2  * Copyright (C) 2001-2002
3  * - France Telecom R&D
4  * - Laboratoire Logiciels, Systemes, Reseaux - UMR 5526, CNRS-INPG-UJF
5  *
6  * This library is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2 of the License, or (at your option) any later version.
10  *
11  * This library is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with this library; if not, write to the Free Software
18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19  *
20  * Release: 1.0
21  *
22  * Authors:
23  *
24  */
25
26 package org.objectweb.perseus.concurrency.pessimistic;
27
28 import org.objectweb.perseus.concurrency.api.ConcurrencyException;
29 import org.objectweb.perseus.dependency.api.DependencyGraph;
30 import org.objectweb.util.monolog.api.Logger;
31
32 /**
33  * A lock associated to an oid (see the "locks" map within the pessimistic
34  * concurrency manager).
35  * @author E. Bruneton, P. Dechamboux
36  */
37 public abstract class Lock {
38
39     protected int reservations = 0;
40     public Object JavaDoc hints;
41     public DependencyGraph dg = null;
42     public Logger logger = null;
43     public Object JavaDoc oid;
44
45     public Lock() {
46     }
47
48     public Lock(Object JavaDoc hints, DependencyGraph dg) {
49         this.hints = hints;
50         this.dg = dg;
51     }
52
53     public synchronized void reserve() {
54         reservations++;
55     }
56     
57     /**
58      * Acquires this lock in read mode for the given context. This method
59      * blocks until the lock can be acquired in read mode by this context.
60      * @param ctxt a context.
61      */
62     public abstract void readIntention(Object JavaDoc ctxt)
63             throws ConcurrencyException;
64
65     /**
66      * Acquires this lock in write mode for the given context. This method
67      * blocks until the lock can be acquired in write mode by this context.
68      * @param ctxt a context.
69      */
70     public abstract void writeIntention(Object JavaDoc ctxt)
71             throws ConcurrencyException;
72
73     /**
74      * Removes the given context from the reader and writer lists of this
75      * lock.
76      * @param ctxt a context
77      * @return true if the reader and writer list are empty, after the
78      * context has been removed from these lists. In such a case, this
79      * object can be removed from the 'locks' map.
80      */
81     public abstract boolean close(Object JavaDoc ctxt);
82
83
84     public abstract byte getMax();
85     
86 }
87
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