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DynamicAny.h

//
// DynamicAny.h
//
// $Id: //poco/1.3/Foundation/include/Poco/DynamicAny.h#2 $
//
// Library: Foundation
// Package: Core
// Module:  DynamicAny
//
// Definition of the DynamicAny class.
//
// Copyright (c) 2007, 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_DynamicAny_INCLUDED
#define Foundation_DynamicAny_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/DynamicAnyHolder.h"
#include <typeinfo>


namespace Poco {


00051 class Foundation_API DynamicAny
      /// DynamicAny allows to store data of different types and to convert between these types transparently.
      /// DynamicAny puts forth the best effort to provide intuitive and reasonable conversion semantics and prevent 
      /// unexpected data loss, particularly when performing narrowing or signedness conversions of numeric data types.
      ///
      /// Loss of signedness is not allowed for numeric values. This means that if an attempt is made to convert 
      /// the internal value which is a negative signed integer to an unsigned integer type storage, a RangeException is thrown. 
      /// Overflow is not allowed, so if the internal value is a larger number than the target numeric type size can accomodate, 
      /// a RangeException is thrown.
      ///
      /// Precision loss, such as in conversion from floating-point types to integers or from double to float on platforms
      /// where they differ in size (provided internal actual value fits in float min/max range), is allowed.
      /// 
      /// String truncation is allowed -- it is possible to convert between string and character when string length is 
      /// greater than 1. An empty string gets converted to the char '\0', a non-empty string is truncated to the first character. 
      ///
      /// Bolean conversion are performed as follows:
      ///
      /// A string value "false" (not case sensitive) or "0" can be converted to a boolean value false, any other string 
      /// not being false by the above criteria evaluates to true (e.g: "hi" -> true).
      /// Integer 0 values are false, everything else is true.
      /// Floating point values equal to the minimal FP representation on a given platform are false, everything else is true.
      ///
      /// A DynamicAny can be created from and converted to a value of any type for which a specialization of 
      /// DynamicAnyHolderImpl is available. For supported types, see DynamicAnyHolder documentation.
{
public:
      DynamicAny();
            /// Creates a DynamicAny holding an int with value 0.

      template <typename T> 
00082       DynamicAny(const T &val):
            _pHolder(new DynamicAnyHolderImpl<T>(val))
            /// Creates the DynamicAny from the given value.
      {
      }

      DynamicAny(const char* pVal);
            // Convenience constructor for const char* which gets mapped to a std::string internally, i.e. pVal is deep-copied.

      DynamicAny(const DynamicAny& other);
            /// Copy constructor.

      ~DynamicAny();
            /// Destroys the DynamicAny.

      void swap(DynamicAny& other);
            /// Swaps the content of the this DynamicAny with the other DynamicAny.

      template <typename T> 
00101       void convert(T& val) const
            /// Invoke this method to perform a safe conversion.
            ///
            /// Example usage:
            ///     DynamicAny any("42");
            ///     int i;
            ///     any.convert(i);
            ///
            /// Throws a RangeException if the value does not fit
            /// into the result variable.
            /// Throws a NotImplementedException if conversion is
            /// not available for the given type.
      {
            _pHolder->convert(val);
      }
      
      template <typename T> 
00118       T convert() const
            /// Invoke this method to perform a safe conversion.
            ///
            /// Example usage:
            ///     DynamicAny any("42");
            ///     int i = any.convert<int>();
            ///
            /// Throws a RangeException if the value does not fit
            /// into the result variable.
            /// Throws a NotImplementedException if conversion is
            /// not available for the given type.
      {
            T result;
            _pHolder->convert(result);
            return result;
      }
      
      template <typename T>
00136       operator T() const
            /// Safe conversion operator for implicit type
            /// conversions.
            ///
            /// Throws a RangeException if the value does not fit
            /// into the result variable.
            /// Throws a NotImplementedException if conversion is
            /// not available for the given type.
      {
            T result;
            _pHolder->convert(result);
            return result;
      }
      
      template <typename T>
00151       const T& extract() const
            /// Returns a const reference to the actual value.
            ///
            /// Must be instantiated with the exact type of
            /// the stored value, otherwise a BadCastException
            /// is thrown.
      {
            DynamicAnyHolderImpl<T>* pHolder = dynamic_cast<DynamicAnyHolderImpl<T>*>(_pHolder);
            if (pHolder)
                  return pHolder->value();
            else
                  throw BadCastException();
      }

00165       DynamicAny& operator = (const DynamicAny& other)
            /// Assignment operator
      {
            DynamicAny tmp(other);
            swap(tmp);
            return *this;
      }

      template <typename T> 
00174       DynamicAny& operator = (const T& other)
            /// Assignment operator
      {
            DynamicAny tmp(other);
            swap(tmp);
            return *this;
      }
      
      template <typename T> 
00183       bool operator == (const T& other)
            /// Equality operator
      {
            T value;
            _pHolder->convert(value);
            return value == other;
      }

00191       bool operator == (const char* other)
            /// Equality operator
      {
            std::string value;
            _pHolder->convert(value);
            return value == other;
      }

      template <typename T> 
00200       bool operator != (const T& other)
            /// Inequality operator
      {
            T value;
            _pHolder->convert(value);
            return value != other;
      }

00208       bool operator != (const char* other)
            /// Inequality operator
      {
            std::string value;
            _pHolder->convert(value);
            return value != other;
      }

    const std::type_info& type() const;
            /// Returns the type information of the stored content.
      
private:
00220       DynamicAnyHolder* _pHolder;
};


} // namespace Poco


#endif // Foundation_DynamicAny_INCLUDED

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