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/*
* Copyright (c) 2010-2015 Pivotal Software, Inc. All rights reserved.
*
* Licensed 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 limitations under the License. See accompanying
* LICENSE file.
*/
package com.gemstone.gemfire.internal.concurrent;
import java.util.concurrent.Semaphore;
/**
* These methods are the same ones on
* the JDK 5 version java.util.concurrent.Semaphore.
* Note that methods that take TimeUnit parameters
* have been changed to end with Ms and to
* always use milliseconds.
* @see CFactory
* @author darrel
* @deprecated use Semaphore
*/
public interface S {
/**
* Acquires a permit from this semaphore, blocking until one is
* available, or the thread is {@linkplain Thread#interrupt interrupted}.
*
*
Acquires a permit, if one is available and returns immediately,
* reducing the number of available permits by one.
*
*
If no permit is available then the current thread becomes
* disabled for thread scheduling purposes and lies dormant until
* one of two things happens:
*
* - Some other thread invokes the {@link #release()} method for this
* semaphore and the current thread is next to be assigned a permit; or
*
- Some other thread {@linkplain Thread#interrupt interrupts}
* the current thread.
*
*
* If the current thread:
*
* - has its interrupted status set on entry to this method; or
*
- is {@linkplain Thread#interrupt interrupted} while waiting
* for a permit,
*
* then {@link InterruptedException} is thrown and the current thread's
* interrupted status is cleared.
*
* @throws InterruptedException if the current thread is interrupted
*/
public void acquire() throws InterruptedException;
/**
* Acquires a permit from this semaphore, blocking until one is
* available.
*
* Acquires a permit, if one is available and returns immediately,
* reducing the number of available permits by one.
*
*
If no permit is available then the current thread becomes
* disabled for thread scheduling purposes and lies dormant until
* some other thread invokes the {@link #release()} method for this
* semaphore and the current thread is next to be assigned a permit.
*
*
If the current thread is {@linkplain Thread#interrupt interrupted}
* while waiting for a permit then it will continue to wait, but the
* time at which the thread is assigned a permit may change compared to
* the time it would have received the permit had no interruption
* occurred. When the thread does return from this method its interrupt
* status will be set.
*/
public void acquireUninterruptibly();
/**
* Acquires a permit from this semaphore, only if one is available at the
* time of invocation.
*
*
Acquires a permit, if one is available and returns immediately,
* with the value {@code true},
* reducing the number of available permits by one.
*
*
If no permit is available then this method will return
* immediately with the value {@code false}.
*
*
Even when this semaphore has been set to use a
* fair ordering policy, a call to {@code tryAcquire()} will
* immediately acquire a permit if one is available, whether or not
* other threads are currently waiting.
* This "barging" behavior can be useful in certain
* circumstances, even though it breaks fairness. If you want to honor
* the fairness setting, then use
* {@link #tryAcquireMs(long) tryAcquireMs(0) }
* which is almost equivalent (it also detects interruption).
*
* @return {@code true} if a permit was acquired and {@code false}
* otherwise
*/
public boolean tryAcquire();
/**
* Acquires a permit from this semaphore, if one becomes available
* within the given waiting time and the current thread has not
* been {@linkplain Thread#interrupt interrupted}.
*
*
Acquires a permit, if one is available and returns immediately,
* with the value {@code true},
* reducing the number of available permits by one.
*
*
If no permit is available then the current thread becomes
* disabled for thread scheduling purposes and lies dormant until
* one of three things happens:
*
* - Some other thread invokes the {@link #release()} method for this
* semaphore and the current thread is next to be assigned a permit; or
*
- Some other thread {@linkplain Thread#interrupt interrupts}
* the current thread; or
*
- The specified waiting time elapses.
*
*
* If a permit is acquired then the value {@code true} is returned.
*
*
If the current thread:
*
* - has its interrupted status set on entry to this method; or
*
- is {@linkplain Thread#interrupt interrupted} while waiting
* to acquire a permit,
*
* then {@link InterruptedException} is thrown and the current thread's
* interrupted status is cleared.
*
* If the specified waiting time elapses then the value {@code false}
* is returned. If the time is less than or equal to zero, the method
* will not wait at all.
*
* @param timeout the maximum time to wait for a permit in milliseconds
* @return {@code true} if a permit was acquired and {@code false}
* if the waiting time elapsed before a permit was acquired
* @throws InterruptedException if the current thread is interrupted
*/
public boolean tryAcquireMs(long timeout)
throws InterruptedException;
/**
* Releases a permit, returning it to the semaphore.
*
*
Releases a permit, increasing the number of available permits by
* one. If any threads are trying to acquire a permit, then one is
* selected and given the permit that was just released. That thread
* is (re)enabled for thread scheduling purposes.
*
*
There is no requirement that a thread that releases a permit must
* have acquired that permit by calling {@link #acquire()}.
* Correct usage of a semaphore is established by programming convention
* in the application.
*/
public void release();
/**
* Acquires the given number of permits from this semaphore,
* blocking until all are available,
* or the thread is {@linkplain Thread#interrupt interrupted}.
*
*
Acquires the given number of permits, if they are available,
* and returns immediately, reducing the number of available permits
* by the given amount.
*
*
If insufficient permits are available then the current thread becomes
* disabled for thread scheduling purposes and lies dormant until
* one of two things happens:
*
* - Some other thread invokes one of the {@link #release() release}
* methods for this semaphore, the current thread is next to be assigned
* permits and the number of available permits satisfies this request; or
*
- Some other thread {@linkplain Thread#interrupt interrupts}
* the current thread.
*
*
* If the current thread:
*
* - has its interrupted status set on entry to this method; or
*
- is {@linkplain Thread#interrupt interrupted} while waiting
* for a permit,
*
* then {@link InterruptedException} is thrown and the current thread's
* interrupted status is cleared.
* Any permits that were to be assigned to this thread are instead
* assigned to other threads trying to acquire permits, as if
* permits had been made available by a call to {@link #release()}.
*
* @param permits the number of permits to acquire
* @throws InterruptedException if the current thread is interrupted
* @throws IllegalArgumentException if {@code permits} is negative
*/
public void acquire(int permits) throws InterruptedException;
/**
* Acquires the given number of permits from this semaphore,
* blocking until all are available.
*
* Acquires the given number of permits, if they are available,
* and returns immediately, reducing the number of available permits
* by the given amount.
*
*
If insufficient permits are available then the current thread becomes
* disabled for thread scheduling purposes and lies dormant until
* some other thread invokes one of the {@link #release() release}
* methods for this semaphore, the current thread is next to be assigned
* permits and the number of available permits satisfies this request.
*
*
If the current thread is {@linkplain Thread#interrupt interrupted}
* while waiting for permits then it will continue to wait and its
* position in the queue is not affected. When the thread does return
* from this method its interrupt status will be set.
*
* @param permits the number of permits to acquire
* @throws IllegalArgumentException if {@code permits} is negative
*
*/
public void acquireUninterruptibly(int permits);
/**
* Acquires the given number of permits from this semaphore, only
* if all are available at the time of invocation.
*
*
Acquires the given number of permits, if they are available, and
* returns immediately, with the value {@code true},
* reducing the number of available permits by the given amount.
*
*
If insufficient permits are available then this method will return
* immediately with the value {@code false} and the number of available
* permits is unchanged.
*
*
Even when this semaphore has been set to use a fair ordering
* policy, a call to {@code tryAcquire} will
* immediately acquire a permit if one is available, whether or
* not other threads are currently waiting. This
* "barging" behavior can be useful in certain
* circumstances, even though it breaks fairness. If you want to
* honor the fairness setting, then use {@link #tryAcquireMs(int,
* long) tryAcquire(permits, 0) }
* which is almost equivalent (it also detects interruption).
*
* @param permits the number of permits to acquire
* @return {@code true} if the permits were acquired and
* {@code false} otherwise
* @throws IllegalArgumentException if {@code permits} is negative
*/
public boolean tryAcquire(int permits);
/**
* Acquires the given number of permits from this semaphore, if all
* become available within the given waiting time and the current
* thread has not been {@linkplain Thread#interrupt interrupted}.
*
*
Acquires the given number of permits, if they are available and
* returns immediately, with the value {@code true},
* reducing the number of available permits by the given amount.
*
*
If insufficient permits are available then
* the current thread becomes disabled for thread scheduling
* purposes and lies dormant until one of three things happens:
*
* - Some other thread invokes one of the {@link #release() release}
* methods for this semaphore, the current thread is next to be assigned
* permits and the number of available permits satisfies this request; or
*
- Some other thread {@linkplain Thread#interrupt interrupts}
* the current thread; or
*
- The specified waiting time elapses.
*
*
* If the permits are acquired then the value {@code true} is returned.
*
*
If the current thread:
*
* - has its interrupted status set on entry to this method; or
*
- is {@linkplain Thread#interrupt interrupted} while waiting
* to acquire the permits,
*
* then {@link InterruptedException} is thrown and the current thread's
* interrupted status is cleared.
* Any permits that were to be assigned to this thread, are instead
* assigned to other threads trying to acquire permits, as if
* the permits had been made available by a call to {@link #release()}.
*
* If the specified waiting time elapses then the value {@code false}
* is returned. If the time is less than or equal to zero, the method
* will not wait at all. Any permits that were to be assigned to this
* thread, are instead assigned to other threads trying to acquire
* permits, as if the permits had been made available by a call to
* {@link #release()}.
*
* @param permits the number of permits to acquire
* @param timeout the maximum time to wait for the permits in milliseconds
* @return {@code true} if all permits were acquired and {@code false}
* if the waiting time elapsed before all permits were acquired
* @throws InterruptedException if the current thread is interrupted
* @throws IllegalArgumentException if {@code permits} is negative
*/
public boolean tryAcquireMs(int permits, long timeout)
throws InterruptedException;
/**
* Releases the given number of permits, returning them to the semaphore.
*
*
Releases the given number of permits, increasing the number of
* available permits by that amount.
* If any threads are trying to acquire permits, then one
* is selected and given the permits that were just released.
* If the number of available permits satisfies that thread's request
* then that thread is (re)enabled for thread scheduling purposes;
* otherwise the thread will wait until sufficient permits are available.
* If there are still permits available
* after this thread's request has been satisfied, then those permits
* are assigned in turn to other threads trying to acquire permits.
*
*
There is no requirement that a thread that releases a permit must
* have acquired that permit by calling {@link Semaphore#acquire(int) acquire}.
* Correct usage of a semaphore is established by programming convention
* in the application.
*
* @param permits the number of permits to release
* @throws IllegalArgumentException if {@code permits} is negative
*/
public void release(int permits);
/**
* Returns the current number of permits available in this semaphore.
*
*
This method is typically used for debugging and testing purposes.
*
* @return the number of permits available in this semaphore
*/
public int availablePermits();
/**
* Acquires and returns all permits that are immediately available.
*
* @return the number of permits acquired
*/
public int drainPermits();
/**
* Returns {@code true} if this semaphore has fairness set true.
*
* @return {@code true} if this semaphore has fairness set true
*/
public boolean isFair();
/**
* Queries whether any threads are waiting to acquire. Note that
* because cancellations may occur at any time, a {@code true}
* return does not guarantee that any other thread will ever
* acquire. This method is designed primarily for use in
* monitoring of the system state.
*
* @return {@code true} if there may be other threads waiting to
* acquire the lock
*/
public boolean hasQueuedThreads();
/**
* Returns an estimate of the number of threads waiting to acquire.
* The value is only an estimate because the number of threads may
* change dynamically while this method traverses internal data
* structures. This method is designed for use in monitoring of the
* system state, not for synchronization control.
*
* @return the estimated number of threads waiting for this lock
*/
public int getQueueLength();
// /**
// * Shrinks the number of available permits by the indicated reduction.
// * This method can be useful in subclasses that use semaphores to
// * track resources that become unavailable.
// * This method differs from acquire in that it does not block
// * waiting for permits to become available.
// * @param reduction the number of permits to remove
// * @throws IllegalArgumentException if {@code reduction} is negative
// */
// public void reducePermits(int reduction);
}