| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * 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 |
| * limitations under the License. |
| */ |
| |
| #ifndef _DECAF_UTIL_CONCURRENT_BLOCKINGQUEUE_H_ |
| #define _DECAF_UTIL_CONCURRENT_BLOCKINGQUEUE_H_ |
| |
| #include <decaf/util/Config.h> |
| #include <decaf/util/AbstractQueue.h> |
| |
| #include <decaf/util/concurrent/TimeUnit.h> |
| #include <decaf/lang/exceptions/InterruptedException.h> |
| |
| namespace decaf { |
| namespace util { |
| namespace concurrent { |
| |
| /** |
| * A decaf::util::Queue that additionally supports operations that wait for |
| * the queue to become non-empty when retrieving an element, and wait for space |
| * to become available in the queue when storing an element. |
| * |
| * <tt>BlockingQueue</tt> methods come in four forms, with different ways of |
| * handling operations that cannot be satisfied immediately, but may be satisfied |
| * at some point in the future: |
| * one throws an exception, the second returns a special value (either |
| * <tt>true</tt> or <tt>false</tt>, depending on the operation), the third |
| * blocks the current thread indefinitely until the operation can succeed, |
| * and the fourth blocks for only a given maximum time limit before giving |
| * up. These methods are summarized in the following table: |
| * |
| * <table BORDER CELLPADDING=3 CELLSPACING=1> |
| * <tr> |
| * <td></td> |
| * <td ALIGN=CENTER><em>Throws exception</em></td> |
| * <td ALIGN=CENTER><em>Boolean Flag</em></td> |
| * <td ALIGN=CENTER><em>Blocks</em></td> |
| * <td ALIGN=CENTER><em>Times out</em></td> |
| * </tr> |
| * <tr> |
| * <td><b>Insert</b></td> |
| * <td>{@link #add add(e)}</td> |
| * <td>{@link #offer offer(e)}</td> |
| * <td>{@link #put put(e)}</td> |
| * <td>{@link #offer(Object, long, TimeUnit) offer(e, time, unit)}</td> |
| * </tr> |
| * <tr> |
| * <td><b>Remove</b></td> |
| * <td>{@link #remove remove()}</td> |
| * <td>{@link #poll poll()}</td> |
| * <td>{@link #take take()}</td> |
| * <td>{@link #poll(long, TimeUnit) poll(time, unit)}</td> |
| * </tr> |
| * <tr> |
| * <td><b>Examine</b></td> |
| * <td>{@link #element element()}</td> |
| * <td>{@link #peek peek()}</td> |
| * <td><em>not applicable</em></td> |
| * <td><em>not applicable</em></td> |
| * </tr> |
| * </table> |
| * |
| * A <tt>BlockingQueue</tt> may be capacity bounded. At any given time it may have |
| * a <tt>remainingCapacity</tt> beyond which no additional elements can be <tt>put</tt> |
| * without blocking. A <tt>BlockingQueue</tt> without any intrinsic capacity |
| * constraints always reports a remaining capacity of <tt>Integer::MAX_VALUE</tt>. |
| * |
| * <tt>BlockingQueue</tt> implementations are designed to be used primarily for |
| * producer-consumer queues, but additionally support {@link decaf::util::Collection} |
| * interface. So, for example, it is possible to remove an arbitrary element from a |
| * queue using <tt>remove(x)</tt>. However, such operations are in general <em>not</em> |
| * performed very efficiently, and are intended for only occasional use, such as |
| * when a queued message is cancelled. |
| * |
| * <tt>BlockingQueue</tt> implementations are thread-safe. All queuing methods |
| * achieve their effects atomically using internal locks or other forms of concurrency |
| * control. However, the <em>bulk</em> Collection operations <tt>addAll</tt>, |
| * <tt>containsAll</tt>, <tt>retainAll</tt> and <tt>removeAll</tt> are <em>not</em> |
| * necessarily performed atomically unless specified otherwise in an implementation. |
| * So it is possible, for example, for <tt>addAll(c)</tt> to fail (throwing an exception) |
| * after adding only some of the elements in <tt>c</tt>. |
| * |
| * A <tt>BlockingQueue</tt> does <em>not</em> intrinsically support any kind of |
| * "close" or "shutdown" operation to indicate that no more |
| * items will be added. The needs and usage of such features tend to be |
| * implementation-dependent. For example, a common tactic is for producers to |
| * insert special <em>end-of-stream</em> or <em>poison</em> objects, that are |
| * interpreted accordingly when taken by consumers. |
| * |
| * <p> |
| * Usage example, based on a typical producer-consumer scenario. Note that a |
| * <tt>BlockingQueue</tt> can safely be used with multiple producers and multiple |
| * consumers. |
| * <pre> |
| * class Producer : public Runnable { |
| * private: |
| * |
| * BlockingQueue* queue; |
| * |
| * public: |
| * |
| * Producer( BlockingQueue* q ) : queue( q ) {} |
| * |
| * virtual void run() { |
| * try { |
| * while( true ) { queue->put( produce() ); } |
| * } catch( InterruptedException& ex ) { ... handle ...} |
| * } |
| * |
| * Object produce() { ... } |
| * } |
| * |
| * class Consumer : public Runnable { |
| * private: |
| * |
| * BlockingQueue* queue; |
| * |
| * public: |
| * |
| * Consumer( BlockingQueue* q ) : queue( q ) {} |
| * |
| * virtual void run() { |
| * try { |
| * while( true ) { consume( queue->take() ); } |
| * } catch( InterruptedException& ex ) { ... handle ...} |
| * } |
| * |
| * void consume( Object& x ) { ... } |
| * } |
| * |
| * int main( int argc, char** argv ) { |
| * |
| * BlockingQueue q = new SomeQueueImplementation(); |
| * Producer p( &q ); |
| * Consumer c1( &q ); |
| * Consumer c2( &q ); |
| * Thread t1( &p ).start(); |
| * Thread t2( &c1 ).start(); |
| * Thread t3( &c2 ).start(); |
| * } |
| * </pre> |
| * |
| * <p>Memory consistency effects: As with other concurrent collections, actions in a |
| * thread prior to placing an object into a BlockingQueue <em>happen-before</em> |
| * actions subsequent to the access or removal of that element from the |
| * BlockingQueue in another thread. |
| * |
| * @since 1.0 |
| */ |
| template< typename E > |
| class BlockingQueue : public AbstractQueue<E> { |
| public: |
| |
| virtual ~BlockingQueue() { |
| } |
| |
| using Queue<E>::offer; |
| using Queue<E>::poll; |
| |
| /** |
| * Inserts the specified element into this queue, waiting if necessary for space |
| * to become available. |
| * |
| * @param value the element to add |
| * @throws InterruptedException if interrupted while waiting |
| * @throws NullPointerException if the specified element is null |
| * @throws IllegalArgumentException if some property of the specified |
| * element prevents it from being added to this queue |
| */ |
| virtual void put(const E& value) = 0; |
| |
| /** |
| * Inserts the specified element into this queue, waiting up to the specified wait |
| * time if necessary for space to become available. |
| * |
| * @param e the element to add |
| * @param timeout how long to wait before giving up, in units of |
| * <tt>unit</tt> |
| * @param unit a <tt>TimeUnit</tt> determining how to interpret the |
| * <tt>timeout</tt> parameter |
| * |
| * @return <tt>true</tt> if successful, or <tt>false</tt> if |
| * the specified waiting time elapses before space is available |
| * |
| * @throws InterruptedException if interrupted while waiting |
| * @throws NullPointerException if the specified element is null |
| * @throws IllegalArgumentException if some property of the specified |
| * element prevents it from being added to this queue |
| */ |
| virtual bool offer(const E& e, long long timeout, const TimeUnit& unit) = 0; |
| |
| /** |
| * Retrieves and removes the head of this queue, waiting if necessary until an |
| * element becomes available. |
| * |
| * @return the head of this queue |
| * @throws InterruptedException if interrupted while waiting |
| */ |
| virtual E take() = 0; |
| |
| /** |
| * Retrieves and removes the head of this queue, waiting up to the specified |
| * wait time if necessary for an element to become available. |
| * |
| * @param result the referenced value that will be assigned the value |
| * retrieved from the Queue. Undefined if this methods returned false. |
| * @param timeout how long to wait before giving up, in units of <tt>unit</tt> |
| * @param unit a <tt>TimeUnit</tt> determining how to interpret the |
| * <tt>timeout</tt> parameter. |
| * @return <tt>true</tt> if successful or <tt>false</tt> if the specified |
| * waiting time elapses before an element is available. |
| * @throws InterruptedException if interrupted while waiting |
| */ |
| virtual bool poll(E& result, long long timeout, const TimeUnit& unit) = 0; |
| |
| /** |
| * Returns the number of additional elements that this queue can ideally |
| * (in the absence of memory or resource constraints) accept without |
| * blocking, or <tt>Integer::MAX_VALUE</tt> if there is no intrinsic |
| * limit. |
| * |
| * <p>Note that you <em>cannot</em> always tell if an attempt to insert |
| * an element will succeed by inspecting <tt>remainingCapacity</tt> |
| * because it may be the case that another thread is about to |
| * insert or remove an element. |
| * |
| * @return the remaining capacity |
| */ |
| virtual int remainingCapacity() const = 0; |
| |
| /** |
| * Removes all available elements from this queue and adds them to the given |
| * collection. This operation may be more efficient than repeatedly polling |
| * this queue. A failure encountered while attempting to add elements to |
| * collection <tt>c</tt> may result in elements being in neither, either or |
| * both collections when the associated exception is thrown. Attempts to |
| * drain a queue to itself result in <tt>IllegalArgumentException</tt>. |
| * Further, the behavior of this operation is undefined if the specified |
| * collection is modified while the operation is in progress. |
| * |
| * @param c the collection to transfer elements into |
| * @return the number of elements transferred |
| * @throws UnsupportedOperationException if addition of elements |
| * is not supported by the specified collection |
| * @throws IllegalArgumentException if the specified collection is this |
| * queue, or some property of an element of this queue prevents |
| * it from being added to the specified collection |
| */ |
| virtual int drainTo(Collection<E>& c) = 0; |
| |
| /** |
| * Removes at most the given number of available elements from |
| * this queue and adds them to the given collection. A failure |
| * encountered while attempting to add elements to |
| * collection <tt>c</tt> may result in elements being in neither, |
| * either or both collections when the associated exception is |
| * thrown. Attempts to drain a queue to itself result in |
| * <tt>IllegalArgumentException</tt>. Further, the behavior of |
| * this operation is undefined if the specified collection is |
| * modified while the operation is in progress. |
| * |
| * @param c the collection to transfer elements into |
| * @param maxElements the maximum number of elements to transfer |
| * @return the number of elements transferred |
| * @throws UnsupportedOperationException if addition of elements |
| * is not supported by the specified collection |
| * @throws IllegalArgumentException if the specified collection is this |
| * queue, or some property of an element of this queue prevents |
| * it from being added to the specified collection |
| */ |
| virtual int drainTo(Collection<E>& c, int maxElements) = 0; |
| |
| }; |
| |
| }}} |
| |
| #endif /* _DECAF_UTIL_CONCURRENT_BLOCKINGQUEUE_H_ */ |
