LinkedQueue.java revision 4378
2362N/A * Copyright (c) 1999, Oracle and/or its affiliates. All rights reserved. 0N/A * Redistribution and use in source and binary forms, with or without 0N/A * modification, are permitted provided that the following conditions 0N/A * - Redistributions of source code must retain the above copyright 0N/A * notice, this list of conditions and the following disclaimer. 0N/A * - Redistributions in binary form must reproduce the above copyright 0N/A * notice, this list of conditions and the following disclaimer in the 0N/A * documentation and/or other materials provided with the distribution. 2362N/A * - Neither the name of Oracle nor the names of its 0N/A * contributors may be used to endorse or promote products derived 0N/A * from this software without specific prior written permission. 0N/A * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS 0N/A * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 0N/A * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 0N/A * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR 0N/A * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 0N/A * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 0N/A * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 0N/A * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 0N/A * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 0N/A * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 0N/A * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 4378N/A * This source code is provided to illustrate the usage of a given feature 4378N/A * or technique and has been deliberately simplified. Additional steps 4378N/A * required for a production-quality application, such as security checks, 4378N/A * input validation and proper error handling, might not be present in 0N/A Originally written by Doug Lea and released into the public domain. 0N/A This may be used for any purposes whatsoever without acknowledgment. 0N/A Thanks for the assistance and support of Sun Microsystems Labs, 0N/A and everyone contributing, testing, and using this code. 0N/A 11Jun1998 dl Create public version 0N/A 25aug1998 dl added peek 0N/A 10dec1998 dl added isEmpty 0N/A 10jun1999 bc modified for isolated use 0N/A// Original was in package EDU.oswego.cs.dl.util.concurrent; 0N/A * A linked list based channel implementation, 0N/A * adapted from the TwoLockQueue class from CPJ. 0N/A * The algorithm avoids contention between puts 0N/A * and takes when the queue is not empty. 0N/A * Normally a put and a take can proceed simultaneously. 0N/A * (Although it does not allow multiple concurrent puts or takes.) 0N/A * This class tends to perform more efficently than 0N/A * Dummy header node of list. The first actual node, if it exists, is always 0N/A * at head_.next. After each take, the old first node becomes the head. 0N/A * Helper monitor for managing access to last node, in case it is also first. 0N/A * last_ and waitingForTake_ ONLY used with synch on appendMonitor_ 0N/A * The last node of list. Put() appends to list, so modifies last_ 0N/A * The number of threads waiting for a take. 0N/A * Notifications are provided in put only if greater than zero. 0N/A * The bookkeeping is worth it here since in reasonably balanced 0N/A * usages, the notifications will hardly ever be necessary, so 0N/A * the call overhead to notify can be eliminated. 0N/A // try to extract. If fail, then enter wait-based retry loop