new trunk (base for 1.5)

windows build only

Foundation/include/Poco/Nullable.h

@@ -0,0 +1,179 @@
+//
+// Nullable.h
+//
+// $Id: //poco/1.4/Foundation/include/Poco/Nullable.h#1 $
+//
+// Library: Foundation
+// Package: Core
+// Module:  Nullable
+//
+// Definition of the Nullable template class.
+//
+// Copyright (c) 2010, Applied Informatics Software Engineering GmbH.
+// and Contributors.
+//
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+// 
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+//
+
+
+#ifndef Foundation_Nullable_INCLUDED
+#define Foundation_Nullable_INCLUDED
+
+
+#include "Poco/Foundation.h"
+#include "Poco/Exception.h"
+#include <algorithm>
+
+
+namespace Poco {
+
+
+template <typename C>
+class Nullable
+	/// Nullable is a simple wrapper class for value types
+	/// that allows to introduce a "null" value or state
+	/// to value objects.
+	///
+	/// The class is useful for passing parameters to functions
+	/// when parameters are optional and no default values 
+	/// should be used.
+	///
+	/// A Nullable can be default constructed. In this case, 
+	/// the Nullable will have a Null value and isNull() will
+	/// return true. Calling value() (without default value) on
+	/// a Null object will throw a NullValueException.
+	///
+	/// A Nullable can also be constructed from a value.
+	/// It is possible to assign a value to a Nullable, and
+	/// to reset a Nullable to contain a Null value by calling
+	/// clear().
+	///
+	/// For use with Nullable, the value type should support
+	/// default construction.
+{
+public:
+	Nullable(): 
+		/// Creates an empty Nullable.
+		_value(),
+		_isNull(true)
+	{
+	}
+
+	Nullable(const C& value): 
+		/// Creates a Nullable with the given value.
+		_value(value), 
+		_isNull(false)
+	{
+	}
+	
+	Nullable(const Nullable& other):
+		/// Creates a Nullable by copying another one.
+		_value(other._value),
+		_isNull(other._isNull)
+	{
+	}
+
+	~Nullable()
+		/// Destroys the Nullable.
+	{
+	}
+
+	Nullable& assign(const C& value)
+		/// Assigns a value to the Nullable.
+	{
+		_value  = value;
+		_isNull = false;
+		return *this;
+	}
+	
+	Nullable& assign(const Nullable& other)
+		/// Assigns another Nullable.
+	{
+		Nullable tmp(other);
+		swap(tmp);
+		return *this;
+	}
+	
+	Nullable& operator = (const C& value)
+	{
+		return assign(value);
+	}
+
+	Nullable& operator = (const Nullable& other)
+	{
+		return assign(other);
+	}
+
+	void swap(Nullable& other)
+	{
+		std::swap(_value, other._value);
+		std::swap(_isNull, other._isNull);
+	}
+
+	const C& value() const
+		/// Returns the Nullable's value.
+		///
+		/// Throws a NullValueException if the Nullable is empty.
+	{
+		if (!_isNull)
+			return _value;
+		else
+			throw NullValueException();
+	}
+
+	const C& value(const C& deflt) const
+		/// Returns the Nullable's value, or the
+		/// given default value if the Nullable is empty.
+	{
+		return _isNull ? deflt : _value;
+	}
+
+	bool isNull() const
+		/// Returns true iff the Nullable is empty.
+	{
+		return _isNull;
+	}
+	
+	void clear()
+		/// Clears the Nullable.
+	{
+		_isNull = true;
+	}
+
+private:
+	C _value;
+	bool _isNull;
+};
+
+
+template <typename C>
+inline void swap(Nullable<C>& n1, Nullable<C>& n2)
+{
+	n1.swap(n2);
+}
+
+
+} // namespace Poco
+
+
+#endif // Foundation_Nullable_INCLUDED