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Diffstat (limited to 'qpid/cpp/src/qpid/sys/BlockingQueue.h')
-rw-r--r-- | qpid/cpp/src/qpid/sys/BlockingQueue.h | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/qpid/cpp/src/qpid/sys/BlockingQueue.h b/qpid/cpp/src/qpid/sys/BlockingQueue.h new file mode 100644 index 0000000000..dd709c6bff --- /dev/null +++ b/qpid/cpp/src/qpid/sys/BlockingQueue.h @@ -0,0 +1,142 @@ +#ifndef QPID_SYS_BLOCKINGQUEUE_H +#define QPID_SYS_BLOCKINGQUEUE_H + +/* + * + * 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. + * + */ + +#include "Waitable.h" + +#include <queue> + +namespace qpid { +namespace sys { + +/** + * A simple blocking queue template + */ +template <class T> +class BlockingQueue +{ + mutable sys::Waitable lock; + std::queue<T> queue; + bool closed; + +public: + BlockingQueue() : closed(false) {} + ~BlockingQueue() { close(); } + + /** Block until there is a value to pop */ + T pop() + { + Waitable::ScopedLock l(lock); + if (!queueWait()) throw ClosedException(); + return popInternal(); + } + + /** Non-blocking pop. If there is a value set outValue and return + * true, else return false; + */ + bool tryPop(T& outValue) { + Waitable::ScopedLock l(lock); + if (queue.empty()) return false; + outValue = popInternal(); + return true; + } + + /** Non-blocking pop. If there is a value return it, else return + * valueIfEmpty. + */ + T tryPop(const T& valueIfEmpty=T()) { + T result=valueIfEmpty; + tryPop(result); + return result; + } + + /** Push a value onto the queue */ + void push(const T& t) + { + Waitable::ScopedLock l(lock); + queue.push(t); + queueNotify(0); + } + + /** + * Close the queue. Throws ClosedException in threads waiting in pop(). + * Blocks till all waiting threads have been notified. + */ + void close() + { + Waitable::ScopedLock l(lock); + if (!closed) { + closed = true; + lock.notifyAll(); + lock.waitWaiters(); // Ensure no threads are still waiting. + } + } + + /** Open a closed queue. */ + void open() { + Waitable::ScopedLock l(lock); + closed=false; + } + + bool isClosed() const { + Waitable::ScopedLock l(lock); + return closed; + } + + bool empty() const { + Waitable::ScopedLock l(lock); + return queue.empty(); + } + size_t size() const { + Waitable::ScopedLock l(lock); + return queue.size(); + } + + private: + + void queueNotify(size_t ignore) { + if (!queue.empty() && lock.hasWaiters()>ignore) + lock.notify(); // Notify another waiter. + } + + bool queueWait() { + Waitable::ScopedWait w(lock); + while (!closed && queue.empty()) + lock.wait(); + return !queue.empty(); + } + + T popInternal() { + T t=queue.front(); + queue.pop(); + queueNotify(1); + return t; + } + +}; + +}} + + + +#endif /*!QPID_SYS_BLOCKINGQUEUE_H*/ |