From 8b0d4b647a3ac2e21e6a8e7a902eea3ae462e213 Mon Sep 17 00:00:00 2001
From: "Matthias P. Braendli" <matthias.braendli@mpb.li>
Date: Fri, 7 Jun 2019 10:14:51 +0200
Subject: Work on STI-D/EDI input

---
 lib/ThreadsafeQueue.h | 176 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 176 insertions(+)
 create mode 100644 lib/ThreadsafeQueue.h

(limited to 'lib/ThreadsafeQueue.h')

diff --git a/lib/ThreadsafeQueue.h b/lib/ThreadsafeQueue.h
new file mode 100644
index 0000000..62f4c96
--- /dev/null
+++ b/lib/ThreadsafeQueue.h
@@ -0,0 +1,176 @@
+/*
+   Copyright (C) 2007, 2008, 2009, 2010, 2011 Her Majesty the Queen in
+   Right of Canada (Communications Research Center Canada)
+
+   Copyright (C) 2018
+   Matthias P. Braendli, matthias.braendli@mpb.li
+
+   An implementation for a threadsafe queue, depends on C++11
+
+   When creating a ThreadsafeQueue, one can specify the minimal number
+   of elements it must contain before it is possible to take one
+   element out.
+ */
+/*
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <mutex>
+#include <condition_variable>
+#include <queue>
+#include <utility>
+
+/* This queue is meant to be used by two threads. One producer
+ * that pushes elements into the queue, and one consumer that
+ * retrieves the elements.
+ *
+ * The queue can make the consumer block until an element
+ * is available, or a wakeup requested.
+ */
+
+/* Class thrown by blocking pop to tell the consumer
+ * that there's a wakeup requested. */
+class ThreadsafeQueueWakeup {};
+
+template<typename T>
+class ThreadsafeQueue
+{
+public:
+    /* Push one element into the queue, and notify another thread that
+     * might be waiting.
+     *
+     * returns the new queue size.
+     */
+    size_t push(T const& val)
+    {
+        std::unique_lock<std::mutex> lock(the_mutex);
+        the_queue.push(val);
+        size_t queue_size = the_queue.size();
+        lock.unlock();
+
+        the_rx_notification.notify_one();
+
+        return queue_size;
+    }
+
+    size_t push(T&& val)
+    {
+        std::unique_lock<std::mutex> lock(the_mutex);
+        the_queue.emplace(std::move(val));
+        size_t queue_size = the_queue.size();
+        lock.unlock();
+
+        the_rx_notification.notify_one();
+
+        return queue_size;
+    }
+
+    /* Push one element into the queue, but wait until the
+     * queue size goes below the threshold.
+     *
+     * Notify waiting thread.
+     *
+     * returns the new queue size.
+     */
+    size_t push_wait_if_full(T const& val, size_t threshold)
+    {
+        std::unique_lock<std::mutex> lock(the_mutex);
+        while (the_queue.size() >= threshold) {
+            the_tx_notification.wait(lock);
+        }
+        the_queue.push(val);
+        size_t queue_size = the_queue.size();
+        lock.unlock();
+
+        the_rx_notification.notify_one();
+
+        return queue_size;
+    }
+
+    /* Trigger a wakeup event on a blocking consumer, which
+     * will receive a ThreadsafeQueueWakeup exception.
+     */
+    void trigger_wakeup(void)
+    {
+        std::unique_lock<std::mutex> lock(the_mutex);
+        wakeup_requested = true;
+        lock.unlock();
+        the_rx_notification.notify_one();
+    }
+
+    /* Send a notification for the receiver thread */
+    void notify(void)
+    {
+        the_rx_notification.notify_one();
+    }
+
+    bool empty() const
+    {
+        std::unique_lock<std::mutex> lock(the_mutex);
+        return the_queue.empty();
+    }
+
+    size_t size() const
+    {
+        std::unique_lock<std::mutex> lock(the_mutex);
+        return the_queue.size();
+    }
+
+    bool try_pop(T& popped_value)
+    {
+        std::unique_lock<std::mutex> lock(the_mutex);
+        if (the_queue.empty()) {
+            return false;
+        }
+
+        popped_value = the_queue.front();
+        the_queue.pop();
+
+        lock.unlock();
+        the_tx_notification.notify_one();
+
+        return true;
+    }
+
+    void wait_and_pop(T& popped_value, size_t prebuffering = 1)
+    {
+        std::unique_lock<std::mutex> lock(the_mutex);
+        while (the_queue.size() < prebuffering and
+                not wakeup_requested) {
+            the_rx_notification.wait(lock);
+        }
+
+        if (wakeup_requested) {
+            wakeup_requested = false;
+            throw ThreadsafeQueueWakeup();
+        }
+        else {
+            std::swap(popped_value, the_queue.front());
+            the_queue.pop();
+
+            lock.unlock();
+            the_tx_notification.notify_one();
+        }
+    }
+
+private:
+    std::queue<T> the_queue;
+    mutable std::mutex the_mutex;
+    std::condition_variable the_rx_notification;
+    std::condition_variable the_tx_notification;
+    bool wakeup_requested = false;
+};
+
-- 
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