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+#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*/