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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 "qpid/sys/Waitable.h"
+
+#include <queue>
+
+namespace qpid {
+namespace sys {
+
+/**
+ * A simple blocking queue template
+ */
+template <class T>
+class BlockingQueue
+{
+ mutable sys::Waitable waitable;
+ std::queue<T> queue;
+
+public:
+ BlockingQueue() {}
+ ~BlockingQueue() { close(); }
+
+ /** Pop from the queue, block up to timeout if empty.
+ *@param result Set to value popped from queue.
+ *@param timeout Defaults to infinite.
+ *@return true if result was set, false if queue empty after timeout.
+ */
+ bool pop(T& result, Duration timeout=TIME_INFINITE) {
+ Mutex::ScopedLock l(waitable);
+ {
+ Waitable::ScopedWait w(waitable);
+ if (timeout == TIME_INFINITE) {
+ while (queue.empty()) waitable.wait();
+ } else if (timeout) {
+ AbsTime deadline(now(),timeout);
+ while (queue.empty() && deadline > now()) waitable.wait(deadline);
+ } else {
+ //ensure zero timeout pop does not miss the fact that
+ //queue is closed
+ waitable.checkException();
+ }
+ }
+ if (queue.empty()) return false;
+ result = queue.front();
+ queue.pop();
+ if (!queue.empty())
+ waitable.notify(); // Notify another waiter.
+ return true;
+ }
+
+ T pop(Duration timeout=TIME_INFINITE) {
+ T result;
+ bool ok = pop(result, timeout);
+ if (!ok)
+ throw Exception("Timed out waiting on a blocking queue");
+ return result;
+ }
+
+ /** Push a value onto the queue.
+ * Note it is not an error to push onto a closed queue.
+ */
+ void push(const T& t) {
+ Mutex::ScopedLock l(waitable);
+ queue.push(t);
+ waitable.notify(); // Notify a waiter.
+ }
+
+ /**
+ * Close the queue.
+ *@ex exception to throw to waiting threads. ClosedException by default.
+ */
+ void close(const ExceptionHolder& ex=ExceptionHolder(new ClosedException()))
+ {
+ Mutex::ScopedLock l(waitable);
+ if (!waitable.hasException()) {
+ waitable.setException(ex);
+ waitable.notifyAll();
+ waitable.waitWaiters(); // Ensure no threads are still waiting.
+ }
+ }
+
+ /** Open a closed queue. */
+ void open() {
+ Mutex::ScopedLock l(waitable);
+ waitable.resetException();
+ }
+
+ bool isClosed() const {
+ Mutex::ScopedLock l(waitable);
+ return waitable.hasException();
+ }
+
+ bool empty() const {
+ Mutex::ScopedLock l(waitable);
+ return queue.empty();
+ }
+ size_t size() const {
+ Mutex::ScopedLock l(waitable);
+ return queue.size();
+ }
+};
+
+}}
+
+
+
+#endif /*!QPID_SYS_BLOCKINGQUEUE_H*/