From c415a19ec3ca19801043dcb818c57fbba2ed281a Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Sat, 26 Nov 2011 00:53:55 +0000
Subject: Add missing file.

git-svn-id: http://svn.drobilla.net/lad/trunk/patchage@3636 a436a847-0d15-0410-975c-d299462d15a1
---
 src/Queue.hpp | 156 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 156 insertions(+)
 create mode 100644 src/Queue.hpp

(limited to 'src')

diff --git a/src/Queue.hpp b/src/Queue.hpp
new file mode 100644
index 0000000..c99ee54
--- /dev/null
+++ b/src/Queue.hpp
@@ -0,0 +1,156 @@
+/* This file is part of Patchage.
+ * Copyright 2007-2011 David Robillard <http://drobilla.net>
+ *
+ * Patchage 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.
+ *
+ * Patchage 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 Patchage.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef QUEUE_HPP_INCLUDED
+#define QUEUE_HPP_INCLUDED
+
+#include <cassert>
+
+#ifdef __APPLE__
+#    include <libkern/OSAtomic.h>
+#endif
+
+/**
+   Realtime-safe single-reader single-writer queue.
+
+   This is a RingBuffer but templated for fixed sized objects which makes its
+   use a bit more efficient and cleaner in C++ than a traditional byte oriented
+   ring buffer.
+*/
+template <typename T>
+class Queue
+{
+public:
+	/** @param size Size in number of elements */
+	explicit Queue(uint32_t size);
+	~Queue();
+
+	// Any thread:
+
+	inline uint32_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:
+	Queue(const Queue&);             ///< Undefined (noncopyable)
+	Queue& operator=(const Queue&);  ///< Undefined (noncopyable)
+
+	static inline void barrier() {
+#if defined(__APPLE__)
+		OSMemoryBarrier();
+#elif (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1)
+		__sync_synchronize();
+#else
+#    warning Memory barriers unsupported, possible bugs on SMP systems
+#endif
+	}
+
+	int            _front;    ///< Index to front of queue
+	int            _back;     ///< Index to back of queue (1 past last element)
+	const uint32_t _size;     ///< Size of _objects (1 more than can be stored)
+	T* const       _objects;  ///< Circular array containing queued elements
+};
+
+template<typename T>
+Queue<T>::Queue(uint32_t size)
+	: _front(0)
+	, _back(0)
+	, _size(size + 1)
+	, _objects(new T[_size])
+{
+	assert(size > 1);
+}
+
+template <typename T>
+Queue<T>::~Queue()
+{
+	delete[] _objects;
+}
+
+/** Return whether or not the queue is empty.
+ */
+template <typename T>
+inline bool
+Queue<T>::empty() const
+{
+	return (_back == _front);
+}
+
+/** Return whether or not the queue is full.
+ */
+template <typename T>
+inline bool
+Queue<T>::full() const
+{
+	return (((_front - _back + _size) % _size) == 1);
+}
+
+/** Return the element at the front of the queue without removing it
+ */
+template <typename T>
+inline T&
+Queue<T>::front() const
+{
+	return _objects[_front];
+}
+
+/** Push an item onto the back of the Queue - 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
+Queue<T>::push(const T& elem)
+{
+	if (full()) {
+		return false;
+	} else {
+		const int back = _back;
+		_objects[back] = elem;
+		barrier();
+		_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
+Queue<T>::pop()
+{
+	assert(!empty());
+	assert(_size > 0);
+
+	barrier();
+	_front = (_front + 1) % (_size);
+}
+
+#endif  // QUEUE_HPP_INCLUDED
-- 
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