Lock


1   /*
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3    *  contributor license agreements.  See the NOTICE file distributed with
4    *  this work for additional information regarding copyright ownership.
5    *  The ASF licenses this file to You under the Apache License, Version 2.0
6    *  (the "License"); you may not use this file except in compliance with
7    *  the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   *  Unless required by applicable law or agreed to in writing, software
12   *  distributed under the License is distributed on an "AS IS" BASIS,
13   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   *  See the License for the specific language governing permissions and
15   *  limitations under the License.
16   */
17  
18  package org.apache.tomcat.jni;
19  
20  /** Lock
21   *
22   * @author Mladen Turk
23   * @version $Revision: 467222 $, $Date: 2006-10-24 05:17:11 +0200 (mar., 24 oct. 2006) $
24   */
25  
26  public class Lock {
27  
28      /**
29       * Enumerated potential types for APR process locking methods
30       * <br /><b>Warning :</b> Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
31       *          APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
32       */
33  
34      public static final int APR_LOCK_FCNTL        = 0; /** fcntl() */
35      public static final int APR_LOCK_FLOCK        = 1; /** flock() */
36      public static final int APR_LOCK_SYSVSEM      = 2; /** System V Semaphores */
37      public static final int APR_LOCK_PROC_PTHREAD = 3; /** POSIX pthread process-based locking */
38      public static final int APR_LOCK_POSIXSEM     = 4; /** POSIX semaphore process-based locking */
39      public static final int APR_LOCK_DEFAULT      = 5; /** Use the default process lock */
40  
41      /**
42       * Create and initialize a mutex that can be used to synchronize processes.
43       * <br /><b>Warning :</b> Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
44       *          APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
45       * @param fname A file name to use if the lock mechanism requires one.  This
46       *        argument should always be provided.  The lock code itself will
47       *        determine if it should be used.
48       * @param mech The mechanism to use for the interprocess lock, if any; one of
49       * <PRE>
50       *            APR_LOCK_FCNTL
51       *            APR_LOCK_FLOCK
52       *            APR_LOCK_SYSVSEM
53       *            APR_LOCK_POSIXSEM
54       *            APR_LOCK_PROC_PTHREAD
55       *            APR_LOCK_DEFAULT     pick the default mechanism for the platform
56       * </PRE>
57       * @param pool the pool from which to allocate the mutex.
58       * @return Newly created mutex.
59       */
60      public static native long create(String   fname, int mech, long pool)
61          throws Error  ;
62  
63      /**
64       * Re-open a mutex in a child process.
65       * This function must be called to maintain portability, even
66       * if the underlying lock mechanism does not require it.
67       * @param fname A file name to use if the mutex mechanism requires one.  This
68       *              argument should always be provided.  The mutex code itself will
69       *              determine if it should be used.  This filename should be the
70       *              same one that was passed to apr_proc_mutex_create().
71       * @param pool The pool to operate on.
72       * @return Newly opened mutex.
73       */
74      public static native long childInit(String   fname, long pool)
75          throws Error  ;
76  
77      /**
78       * Acquire the lock for the given mutex. If the mutex is already locked,
79       * the current thread will be put to sleep until the lock becomes available.
80       * @param mutex the mutex on which to acquire the lock.
81       */
82      public static native int lock(long mutex);
83  
84      /**
85       * Attempt to acquire the lock for the given mutex. If the mutex has already
86       * been acquired, the call returns immediately with APR_EBUSY. Note: it
87       * is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine
88       * if the return value was APR_EBUSY, for portability reasons.
89       * @param mutex the mutex on which to attempt the lock acquiring.
90       */
91      public static native int trylock(long mutex);
92  
93      /**
94       * Release the lock for the given mutex.
95       * @param mutex the mutex from which to release the lock.
96       */
97      public static native int unlock(long mutex);
98  
99      /**
100      * Destroy the mutex and free the memory associated with the lock.
101      * @param mutex the mutex to destroy.
102      */
103     public static native int destroy(long mutex);
104 
105     /**
106      * Return the name of the lockfile for the mutex, or NULL
107      * if the mutex doesn't use a lock file
108      */
109     public static native String   lockfile(long mutex);
110 
111     /**
112      * Display the name of the mutex, as it relates to the actual method used.
113      * This matches the valid options for Apache's AcceptMutex directive
114      * @param mutex the name of the mutex
115      */
116     public static native String   name(long mutex);
117 
118     /**
119      * Display the name of the default mutex: APR_LOCK_DEFAULT
120      */
121     public static native String   defname();
122 
123 }
124
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