From acbda29f838280ba98cf9e9e539e9d8a6e8fc6ad Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Fri, 9 Jun 2006 15:07:31 +0000
Subject: Added Om aka Graph aka god knows what

git-svn-id: http://svn.drobilla.net/lad/grauph@9 a436a847-0d15-0410-975c-d299462d15a1
---
 src/common/util/CountedPtr.h | 185 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 185 insertions(+)
 create mode 100644 src/common/util/CountedPtr.h

(limited to 'src/common/util/CountedPtr.h')

diff --git a/src/common/util/CountedPtr.h b/src/common/util/CountedPtr.h
new file mode 100644
index 00000000..f2079c7c
--- /dev/null
+++ b/src/common/util/CountedPtr.h
@@ -0,0 +1,185 @@
+/* A Reference Counting Smart Pointer.
+ * Copyright (C) 2006 Dave Robillard.
+ * 
+ * This 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.
+ * 
+ * This 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.,
+ * 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef COUNTED_PTR_H
+#define COUNTED_PTR_H
+
+#include <cassert>
+#include <cstddef>
+
+
+/** Simple reference counted pointer.
+ *
+ * Allocates one counter on the heap on initial construction.  You can safely
+ * cast a CountedPtr<X> to a CountedPtr<Y> iff Y is a base of X (eg the cast
+ * will only compile if it is a valid up-cast).
+ *
+ * It is possible for this to be a NULL pointer, and a boolean conversion
+ * operator is provided so you can test for this with "if (someCountedPtr)".
+ * Dereferencing a NULL CountedPtr will result in a failed assertion if
+ * debugging is enabled.
+ *
+ * FIXME: test this more thoroughly
+ */
+template <class T>
+class CountedPtr
+{
+public:
+	
+	// Declare some other type of CountedPtr as a friend (for casting)
+	template <class Y> friend class CountedPtr;
+
+
+	/** Allocate a new Counter (if p is non-NULL) */
+	CountedPtr(T* p)
+	: _counter(NULL)
+	{
+		if (p)
+			_counter = new Counter(p);
+	}
+
+	~CountedPtr()
+	{
+		release();
+	}
+
+	/** Copy a CountedPtr with the same type. */
+	CountedPtr(const CountedPtr& copy) 
+	: _counter(NULL)
+	{
+		assert(copy);
+		assert(this != &copy);
+		retain(copy._counter);
+	}
+	
+	/** Copy a CountedPtr to a valid base class.
+	 */
+	template <class Y>
+	CountedPtr(const CountedPtr<Y>& y)
+	: _counter(NULL)
+	{
+		assert(this != (CountedPtr*)&y);
+
+		// Fail if this is not a valid cast
+		if (y) {
+			T* const unused_variable = static_cast<Y* const>(y._counter->ptr);
+			assert(unused_variable == y._counter->ptr); // shuts up gcc
+		}
+		
+		//release();
+		retain((Counter*)y._counter);
+	}
+
+	/** Assign to the value of a CountedPtr of the same type. */
+	CountedPtr& operator=(const CountedPtr& copy)
+	{
+		if (this != &copy) {
+			release();
+			retain(copy._counter);
+		}
+		return *this;
+	}
+
+	/** Assign to the value of a CountedPtr of a different type. */
+	template <class Y>
+	CountedPtr& operator=(const CountedPtr<Y>& y)
+	{
+		if (this != (CountedPtr*)&y) {
+			release();
+			retain(y._counter);
+		}
+		return *this;
+	}
+
+	inline bool operator==(const CountedPtr& p) const
+	{
+		return (_counter == p._counter);
+	}
+
+	inline bool operator!=(const CountedPtr& p) const
+	{
+		return (_counter != p._counter);
+	}
+
+	/** Allow testing for NULL nicely like a real pointer */
+	operator bool() const
+	{
+		return (_counter && _counter->ptr);
+	}
+
+	inline T& operator*() const
+	{
+		assert(_counter);
+		assert(_counter->count > 0);
+		assert(_counter->ptr);
+		return *_counter->ptr;
+	}
+
+	inline T* operator->() const
+	{
+		assert(_counter);
+		assert(_counter->count > 0);
+		assert(_counter->ptr);
+		return _counter->ptr;
+	}
+
+	inline T* get() const { return _counter ? _counter->ptr : 0; }
+
+	bool unique() const { return (_counter ? _counter->count == 1 : true); }
+
+private:
+	/** Stored on the heap and referred to by all existing CountedPtr's to
+	 * the object */
+	struct Counter
+	{
+		Counter(T* p)
+		: ptr(p)
+		, count(1)
+		{
+			assert(p);
+		}
+		
+		T* const        ptr;
+		volatile size_t count;
+	};
+
+	/** Increment the count */
+	void retain(Counter* c) 
+	{	
+		assert(_counter == NULL || _counter == c);
+		_counter = c;
+		if (_counter)
+			++c->count;
+	}
+	
+	/** Decrement the count, delete if we're the last reference */
+	void release()
+	{	
+		if (_counter) {
+			if (--(_counter->count) == 0) {
+				delete _counter->ptr;
+				delete _counter;
+			}
+			_counter = NULL;
+		}
+	}
+	
+
+	Counter* _counter;
+};
+
+#endif // COUNTED_PTR_H
-- 
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