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authorDavid Robillard <d@drobilla.net>2007-07-24 19:26:47 +0000
committerDavid Robillard <d@drobilla.net>2007-07-24 19:26:47 +0000
commit3b4a308ff647def75e647ac8f97e1e48b57672c3 (patch)
treea33e3a5c78f2ee7f23e151f39fe17ab39b0b81c8 /raul/SRSWQueue.hpp
parentfcb302e6248527b2f1fb655f4d0a64af18f5f059 (diff)
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Consistently rename all C++ files .cpp/.hpp.
Fix (some) inclusion guard names to not clash with other libs. git-svn-id: http://svn.drobilla.net/lad/raul@613 a436a847-0d15-0410-975c-d299462d15a1
Diffstat (limited to 'raul/SRSWQueue.hpp')
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+/* This file is part of Raul.
+ * Copyright (C) 2007 Dave Robillard <http://drobilla.net>
+ *
+ * Raul 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 2 of the License, or (at your option) any later
+ * version.
+ *
+ * Raul 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 details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef RAUL_SRSW_QUEUE_HPP
+#define RAUL_SRSW_QUEUE_HPP
+
+#include <cassert>
+#include <cstdlib>
+#include <boost/utility.hpp>
+#include <raul/AtomicInt.hpp>
+
+namespace Raul {
+
+
+/** Realtime-safe single-reader single-writer queue (aka lock-free ringbuffer)
+ *
+ * Implemented as a dequeue in a fixed array. This is read/write thread-safe,
+ * pushing and popping may occur simultaneously by seperate threads, but
+ * the push and pop operations themselves are not thread-safe (ie. there can
+ * be at most 1 read and at most 1 writer thread).
+ *
+ * \ingroup raul
+ */
+template <typename T>
+class SRSWQueue : boost::noncopyable
+{
+public:
+ SRSWQueue(size_t size);
+ ~SRSWQueue();
+
+ // Any thread:
+
+ inline size_t capacity() const { return _size-1; }
+
+
+ // Write thread(s):
+
+ inline bool full() const;
+ inline bool push(const T& obj);
+
+
+ // Read thread:
+
+ inline bool empty() const;
+ inline T& front() const;
+ inline void pop();
+
+private:
+ volatile size_t _front; ///< Index to front of queue (circular)
+ volatile size_t _back; ///< Index to back of queue (one past last element) (circular)
+ const size_t _size; ///< Size of @ref _objects (you can store _size-1 objects)
+ T* const _objects; ///< Fixed array containing queued elements
+};
+
+
+template<typename T>
+SRSWQueue<T>::SRSWQueue(size_t size)
+: _front(0),
+ _back(0),
+ _size(size+1),
+ _objects((T*)calloc(_size, sizeof(T)))
+{
+ assert(size > 1);
+}
+
+
+template <typename T>
+SRSWQueue<T>::~SRSWQueue()
+{
+ free(_objects);
+}
+
+
+/** Return whether or not the queue is empty.
+ */
+template <typename T>
+inline bool
+SRSWQueue<T>::empty() const
+{
+ return (_back == _front);
+}
+
+
+/** Return whether or not the queue is full.
+ */
+template <typename T>
+inline bool
+SRSWQueue<T>::full() const
+{
+ // FIXME: uses both _front and _back - thread safe?
+ return ( ((_front - _back + _size) % _size) == 1 );
+}
+
+
+/** Return the element at the front of the queue without removing it
+ */
+template <typename T>
+inline T&
+SRSWQueue<T>::front() const
+{
+ return _objects[_front];
+}
+
+
+/** Push an item onto the back of the SRSWQueue - realtime-safe, not thread-safe.
+ *
+ * @returns true if @a elem was successfully pushed onto the queue,
+ * false otherwise (queue is full).
+ */
+template <typename T>
+inline bool
+SRSWQueue<T>::push(const T& elem)
+{
+ if (full()) {
+ return false;
+ } else {
+ _objects[_back] = elem;
+ _back = (_back + 1) % (_size);
+ return true;
+ }
+}
+
+
+/** Pop an item off the front of the queue - realtime-safe, not thread-safe.
+ *
+ * It is a fatal error to call pop() when the queue is empty.
+ *
+ * @returns the element popped.
+ */
+template <typename T>
+inline void
+SRSWQueue<T>::pop()
+{
+ assert(!empty());
+ assert(_size > 0);
+
+ _front = (_front + 1) % (_size);
+}
+
+
+} // namespace Raul
+
+#endif // RAUL_SRSW_QUEUE_HPP