From 3b4a308ff647def75e647ac8f97e1e48b57672c3 Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Tue, 24 Jul 2007 19:26:47 +0000
Subject: 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
---
 raul/DoubleBuffer.hpp | 97 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100644 raul/DoubleBuffer.hpp

(limited to 'raul/DoubleBuffer.hpp')

diff --git a/raul/DoubleBuffer.hpp b/raul/DoubleBuffer.hpp
new file mode 100644
index 0000000..dd50e6a
--- /dev/null
+++ b/raul/DoubleBuffer.hpp
@@ -0,0 +1,97 @@
+/* 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_DOUBLE_BUFFER_HPP
+#define RAUL_DOUBLE_BUFFER_HPP
+
+#include <boost/utility.hpp>
+#include <raul/AtomicInt.hpp>
+#include <raul/AtomicPtr.hpp>
+
+namespace Raul {
+
+/** Double buffer.
+ *
+ * Can be thought of as a wrapper class to make a non-atomic type atomically
+ * settable (with no locking).
+ *
+ * Read/Write realtime safe, many writers safe - but set calls may fail.
+ *
+ * Space:  2*sizeof(T) + sizeof(int) + sizeof(void*)
+ */
+template<typename T>
+class DoubleBuffer : public boost::noncopyable {
+public:
+	
+	inline DoubleBuffer(T val)
+		: _state(READ_WRITE)
+	{
+		_vals[0] = val;
+		_read_val = &_vals[0];
+	}
+
+	inline T& get()
+	{
+		return *_read_val.get();
+	}
+
+	inline bool set(T new_val)
+	{
+		if (_state.compare_and_exchange(READ_WRITE, READ_LOCK)) {
+
+			// locked _vals[1] for write
+			_vals[1] = new_val;
+			_read_val = &_vals[1];
+			_state = WRITE_READ;
+			return true;
+
+			// concurrent calls here are fine.  good, actually - caught
+			// the WRITE_READ state immediately after it was set above
+
+		} else if (_state.compare_and_exchange(WRITE_READ, LOCK_READ)) {
+
+			// locked _vals[0] for write
+			_vals[0] = new_val;
+			_read_val = &_vals[0];
+			_state = READ_WRITE;
+			return true;
+
+		} else {
+
+			return false;
+
+		}
+	}
+
+private:
+	enum States {
+		// vals[0] state _ vals[1] state
+		READ_WRITE = 0,
+		READ_LOCK,
+		WRITE_READ,
+		LOCK_READ
+	};
+
+	AtomicInt    _state;
+	AtomicPtr<T> _read_val;
+	T            _vals[2];
+};
+
+
+} // namespace Raul
+
+#endif // RAUL_DOUBLE_BUFFER_HPP
-- 
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