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 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
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package org.apache.tomcat.jni;

Lock
Author:
Mladen Turk/** Lock
 *
 * @author Mladen Turk
 */
public class Lock {

    
Enumerated potential types for APR process locking methods

Warning : Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
         APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
/**
     * Enumerated potential types for APR process locking methods
     * <br><b>Warning :</b> Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
     *          APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
     */

    public static final int APR_LOCK_FCNTL        = 0; 
fcntl() /** fcntl() */
    public static final int APR_LOCK_FLOCK        = 1; 
flock() /** flock() */
    public static final int APR_LOCK_SYSVSEM      = 2; 
System V Semaphores /** System V Semaphores */
    public static final int APR_LOCK_PROC_PTHREAD = 3; 
POSIX pthread process-based locking /** POSIX pthread process-based locking */
    public static final int APR_LOCK_POSIXSEM     = 4; 
POSIX semaphore process-based locking /** POSIX semaphore process-based locking */
    public static final int APR_LOCK_DEFAULT      = 5; /** Use the default process lock */

    
Create and initialize a mutex that can be used to synchronize processes.

Warning : Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
         APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
Params:
fname – A file name to use if the lock mechanism requires one.  This
       argument should always be provided.  The lock code itself will
       determine if it should be used.
mech – The mechanism to use for the interprocess lock, if any; one of
           APR_LOCK_FCNTL
           APR_LOCK_FLOCK
           APR_LOCK_SYSVSEM
           APR_LOCK_POSIXSEM
           APR_LOCK_PROC_PTHREAD
           APR_LOCK_DEFAULT     pick the default mechanism for the platform
pool – the pool from which to allocate the mutex.
Throws:
Error – An error occurred
Returns:
Newly created mutex./**
     * Create and initialize a mutex that can be used to synchronize processes.
     * <br><b>Warning :</b> Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
     *          APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
     * @param fname A file name to use if the lock mechanism requires one.  This
     *        argument should always be provided.  The lock code itself will
     *        determine if it should be used.
     * @param mech The mechanism to use for the interprocess lock, if any; one of
     * <PRE>
     *            APR_LOCK_FCNTL
     *            APR_LOCK_FLOCK
     *            APR_LOCK_SYSVSEM
     *            APR_LOCK_POSIXSEM
     *            APR_LOCK_PROC_PTHREAD
     *            APR_LOCK_DEFAULT     pick the default mechanism for the platform
     * </PRE>
     * @param pool the pool from which to allocate the mutex.
     * @return Newly created mutex.
     * @throws Error An error occurred
     */
    public static native long create(String fname, int mech, long pool)
        throws Error;

    
Re-open a mutex in a child process.
This function must be called to maintain portability, even
if the underlying lock mechanism does not require it.
Params:
fname – A file name to use if the mutex mechanism requires one.  This
             argument should always be provided.  The mutex code itself will
             determine if it should be used.  This filename should be the
             same one that was passed to apr_proc_mutex_create().
pool – The pool to operate on.
Throws:
Error – An error occurred
Returns:
Newly opened mutex./**
     * Re-open a mutex in a child process.
     * This function must be called to maintain portability, even
     * if the underlying lock mechanism does not require it.
     * @param fname A file name to use if the mutex mechanism requires one.  This
     *              argument should always be provided.  The mutex code itself will
     *              determine if it should be used.  This filename should be the
     *              same one that was passed to apr_proc_mutex_create().
     * @param pool The pool to operate on.
     * @return Newly opened mutex.
     * @throws Error An error occurred
     */
    public static native long childInit(String fname, long pool)
        throws Error;

    
Acquire the lock for the given mutex. If the mutex is already locked,
the current thread will be put to sleep until the lock becomes available.
Params:
mutex – the mutex on which to acquire the lock.
Returns:
the operation status/**
     * Acquire the lock for the given mutex. If the mutex is already locked,
     * the current thread will be put to sleep until the lock becomes available.
     * @param mutex the mutex on which to acquire the lock.
     * @return the operation status
     */
    public static native int lock(long mutex);

    
Attempt to acquire the lock for the given mutex. If the mutex has already
been acquired, the call returns immediately with APR_EBUSY. Note: it
is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine
if the return value was APR_EBUSY, for portability reasons.
Params:
mutex – the mutex on which to attempt the lock acquiring.
Returns:
the operation status/**
     * Attempt to acquire the lock for the given mutex. If the mutex has already
     * been acquired, the call returns immediately with APR_EBUSY. Note: it
     * is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine
     * if the return value was APR_EBUSY, for portability reasons.
     * @param mutex the mutex on which to attempt the lock acquiring.
     * @return the operation status
     */
    public static native int trylock(long mutex);

    
Release the lock for the given mutex.
Params:
mutex – the mutex from which to release the lock.
Returns:
the operation status/**
     * Release the lock for the given mutex.
     * @param mutex the mutex from which to release the lock.
     * @return the operation status
     */
    public static native int unlock(long mutex);

    
Destroy the mutex and free the memory associated with the lock.
Params:
mutex – the mutex to destroy.
Returns:
the operation status/**
     * Destroy the mutex and free the memory associated with the lock.
     * @param mutex the mutex to destroy.
     * @return the operation status
     */
    public static native int destroy(long mutex);

    
Return the name of the lockfile for the mutex, or NULL
if the mutex doesn't use a lock file
Params:
mutex – the name of the mutex
Returns:
the name of the lock file/**
     * Return the name of the lockfile for the mutex, or NULL
     * if the mutex doesn't use a lock file
     * @param mutex the name of the mutex
     * @return the name of the lock file
     */
    public static native String lockfile(long mutex);

    
Display the name of the mutex, as it relates to the actual method used.
This matches the valid options for Apache's AcceptMutex directive
Params:
mutex – the name of the mutex
Returns:
the name of the mutex/**
     * Display the name of the mutex, as it relates to the actual method used.
     * This matches the valid options for Apache's AcceptMutex directive
     * @param mutex the name of the mutex
     * @return the name of the mutex
     */
    public static native String name(long mutex);

    
Display the name of the default mutex: APR_LOCK_DEFAULT
Returns:
the default name/**
     * Display the name of the default mutex: APR_LOCK_DEFAULT
     * @return the default name
     */
    public static native String defname();

}